AU2024219865B2 - Pellet - Google Patents

Abstract

The invention relates to a process for producing a pellet and a pellet obtainable by said process. The process comprising (i) providing particulate material selected from a carbonaceous material, metal, metal ore, and mixtures thereof; and an 5 inorganic binder comprising a metal silicate, to form a mixture; (ii) compressing the mixture to form a pellet; and (iii) curing the pellet by contacting the pellet with gaseous carbon dioxide. A pellet comprising a particulate material selected from a carbonaceous material, metal, metal ore, and mixtures thereof; silica; and a metal carbonate is also described. 10

Description

Pellet Pellet

Priority Priority Cross-Reference Cross-Reference The present The presentinvention inventionclaims claimspriority prioritytotoGB GB patent patent application application 2314397.7 2314397.7 filed filed 5 5 20 September 20 September 2023, 2023, the the entire entire contents contents of which of which is hereby is hereby incorporated incorporated by reference. by reference.

Technical Field Technical Field 2024219865

Theinvention The inventionrelates relates to to the the production productionof of pellets pellets from from aa particulate particulate material andto material and to pellets pellets so produced. so produced.Typically, Typically,the thepellets pellets are are cured curedwith withcarbon carbon dioxide. dioxide.

10 10 Background Background ofof the the Invention Invention Thediscussion The discussionofofthethe background background toinvention to the the invention herein herein is intended is intended to facilitate to facilitate an an understanding understanding ofofthe theinvention. invention. However, However, it should it should be appreciated be appreciated that that the discussion the discussion is is not an acknowledgement not an acknowledgement or admission or admission thataspect that any any aspect of the of the discussion discussion was was part of part the of the

15 15 common general common general knowledge knowledge as at as atpriority the the priority date date of application. of the the application.

Theproduction The productionofofpellets pelletsfrom from particulate particulate materials, materials, such such as particulate as particulate ironiron and and otherother

metal ores metal oresisisgenerally generallyknown known in the in the art.art. For For instance, instance, pellets pellets of this of this nature nature are often are often

used in used in aa blast blast furnace furnacefor for producing producingliquid liquidiron, iron,or orin in direct direct iron iron reduction (DRI)ofofiron reduction (DRI) iron 20 20 ore to ore to generate sponge generate sponge iron. iron. TheThe pellet pellet is is designed designed to be to be sufficiently sufficiently strong strong to to allow allow thethe

pellet pellet to to be be successfully successfully transported andto transported and to be beused usedwithin withinthe theblast blastfurnace furnaceororananelectric electric arc furnace. arc Forexample, furnace. For example, when when usedused in ain a blast blast furnace, furnace, the the pellet pellet must must be able be able to retain to retain

its integrity its integritythrough through the the blast blastfurnace furnace into intothe themelting meltingfurnace, furnace, otherwise otherwise the the performance performance

of the of the blast blast furnace can be furnace can beadversely adverselyaffected. affected. 25 25 Traditionally, pellets Traditionally, pellets were were formed usingheat formed using heat processes processes producing producing so-called, so-called, hot-bonded hot-bonded

(indurated) briquettes. InIninduration (indurated) briquettes. indurationtechniques, techniques, initially, a initially, a “green” pellet is "green" pellet isformed from formed from

the combination the combinationofofparticulate particulatesubstrate substrate(particulate (particulatematerial) material)and anda abinder, binder,which whichis isthen then shapedinto shaped intoa apellet pellet(often (oftenusing using a pelletiser).AsAsused a pelletiser). used herein, herein, the the termterm “green "green pellet” pellet"

30 30 takesits takes itsusual usualmeaning meaning in art in the theand artrefers and refers to a pellet to a pellet that that does notdoes not the yet have yet required have the required strength for strength for its its end useand end use andrequires requiresfurther furthertreatment treatment or processing. or processing. The The greengreen pellets pellets

are hardened are hardenedvia viaa aseries seriesofofsteps stepsincluding includingdrying, drying,pre-heating, pre-heating,firing, firing, and andcooling coolingofofthe the greenpellets. green pellets. The Theprimary primary purpose purpose of the of the drying drying stage stage is the is the removal removal of moisture of moisture from from the pellets, the pellets, making making them morestable them more stableand andeasier easiertotohandle. handle.Removal Removal of of water water in in a a 35 35 controlled manner controlled manner prevents prevents crack crack formation formation and and maintains maintains the structural the structural integrity integrity of of the the pellet. pellet.The The temperature temperature range range of of the the drying drying stage stage is isdependent dependent on the chemical on the chemical and and physical properties of physical properties of the the green greenpellet; pellet;however, however,it it isislikely likely to to be be in in the the range rangeofof100°C 100°C to 250°C to for55to 250°C for to10 10minutes. minutes. The The pre-heating pre-heating stage stage usually usually takes takes placeplace usingusing a ramped a ramped

1

heating heating process process from around 300°C from around 300°Ctoto350°C 350°C for1010 for toto1515 minutes, minutes, to to upup to to around around 1250°C to 1350°C. 1250°C to 1350°C.The Thepre-heating pre-heatingstage stageensures ensures thatany that any metal metal hydrates hydrates or or metal metal carbonatespresent carbonates present decompose decompose to their to their anhydrous anhydrous forms. forms. Decomposition Decomposition of these of these types types of compounds of helps compounds helps to to improve improve the the structural structural integrity integrity of of the the resultant resultant pelletbybyremoving pellet removing 5 5 water and/or water and/orgas gaswhich which cancan react, react, causing causing overpressure overpressure and cracking and cracking of theofpellet the pellet during during

firing. The firing. firing stage The firing will often stage will take place often take placeatattemperatures temperatures greater greater than than 1350°C1350°C for for roughly 10toto20 roughly 10 20minutes minutes (for (for typicalcapacities typical capacitiessuch such as as 250250 to 500 to 500 tonstons per hour per hour (tph)) (tph)) 2024219865

and will and will result result in in the sintering of the sintering of the pellet, providing the pellet, the strength providing the strengthneeded neededto to render render it it suitable for suitable for its its end use.During end use. Duringthethe sintering sintering process, process, the the bonds bonds within within the pellet the pellet are are 10 10 formedbybyrecrystallisation formed recrystallisationand and bridging, bridging, creating creating ceramic ceramic bondsbonds and and the the formation formation of of macro voidswhich macro voids which allow allow forfor some some expansion expansion and stress and stress relief. relief. As used As used herein, herein, the term the term

“macrovoid" "macro void”relates relatestotovoids voidswithin withinthe thepellet pellet and andhave havea a sizeranging size ranging from from about about 50 50 um µm to about to about 11 mm mmin in diameter. diameter. TheThe void void formation formation is is particularly important particularly important where wherethe the briquette is briquette is aa metal ore briquette, metal ore briquette, as as reduction reduction of of the the metal metal(for (for instance instancethe thehematite hematitetoto

15 15 magnetiteconversion magnetite conversionin in ironore) iron ore) causes causes volume volume changes changes and stresses and stresses on the on the briquette. briquette.

As macro As macrovoid void formation formation does does not not occur occur without without firing, firing, alternative alternative methods methods are needed are needed

to prevent to disintegrationof prevent disintegration of the the pellet pellet when whenplaced placed under under internal internal stress. stress.

As noted As notedabove, above, a common a common problem problem associated associated with of with pellets pellets this of this type is type is breakage breakage of of 20 20 the agglomerate. the agglomerate.InInananattempt attemptto to overcome overcome thisthis issue, issue, particles particles areare often often bound bound together together

using using aa binder binder such suchas ascement cementor or clay clay ininthe thehope hopeof of improving improving strength strength to enable to enable further further

handling. However, handling. However, a problem a problem associated associated with with using using cementcement or clay or is clay that is itthat it increases increases

the amount the amount ofof silica in silica in the the iron iron and and slag slag produced producedatat the the end end of of thethe process. process.

25 25 Further, induration processes Further, induration processesare are uneconomical uneconomical as they as they are complex, are complex, must must be be executed executed

with care, with care, and andrequire requirethe theapplication applicationofofsignificant significantheat. heat.For Forinstance, instance,the theraw raw material material

preparationisis critical. preparation critical. The The components components of of thethe green green pellet pellet must must beappropriate be an an appropriate size size range, surfacearea, range, surface area,and and moisture moisture content content in order in order to withstand to withstand the process the process as surface as surface

chemistryplays chemistry playsa a significantrole. significant role.Moreover, Moreover, as the as the process process involves involves multiple multiple heatingheating

30 30 stages, it stages, it requires requires a a great great deal deal of of energy. energy.

As such, As such,there thereisisaaneed need fora aprocess for process of of pellet pellet production production that that is less is less energy energy intensive intensive

and more and more cost cost effective. effective. Moreover, Moreover, there there is a isneed a need for a for a process process whereisthere where there more is more flexibility ininthe flexibility thephysical physicalstate stateofofthe theparticulate particulatematerial materialused, used, and whichresults and which resultsinin the the 35 35 generation generation ofofpellets pelletshaving having comparable comparable or even or even superior superior physical physical properties properties to those to those

generatedusing generated using an an induration induration process, process, in particular in particular in terms in terms of strength, of strength, to to enable enable processing andhandling. processing and handling. The The invention invention is intended is intended to overcome to overcome or ameliorate or ameliorate at leastat least

someaspects some aspectsofof thisproblem. this problem. 2

Summary of Invention Accordingly, in a first aspect of the invention there is provided a process for producing a pellet, the process comprising: (i) providing particulate material selected from a carbonaceous material, metal, metal 5 ore, and mixtures thereof; an inorganic binder comprising a metal silicate, and an organic binder, wherein the organic binder comprises a natural polymer, a synthetic polymer, a glycerolipid, a cellulosic material, and combinations thereof, 2024219865

to form a mixture; (ii) compressing the mixture to form a pellet; and 10 (iii) curing the pellet by contacting the pellet with gaseous carbon dioxide.

The process of the invention enables the rapid production of pellets which are of sufficient strength to be handled and transported without the need for the application of heat during pellet forming (although this may optionally form part of the process). They also have 15 good water resistance and have thermal properties suitable for the end use conditions of a blast or other furnace. For some formulations of pellet, the carbon dioxide enables the production of pellets of sufficient strength without the need to apply heat, where heat would previously have been essential to the hardening process. For other formulations of pellet, the carbon dioxide acts to accelerate the hardening of pellets which can be cold- 20 formed over a greater period of time in the absence of the carbon dioxide strengthening catalyst. Therefore, the invention provides for the production of pellets in production locations where heat is not necessarily readily available, providing (in some cases) for simpler designs of the pellet manufacturing plants. Further, the generation of heat often results in production costs being incurred, and, dependent upon the source of energy 25 used to generate the heat, can result in damage to the environment by indirect carbon emissions from the energy generation. Therefore, unless care is taken to generate the heat responsibly, it’s use can be undesirable.

It should be noted that, as used in this general description, the terms 30 “strength/strengthening” and “hard/hardening” are used roughly interchangeably to indicate the provision of, and ultimate robustness of, the pellet to, transport and handling. The terms “particulate material” and “particulate substrate” are also used interchangeably to refer to the pellet feedstock.

35 Additionally, the use of carbon dioxide provides for the sequestration of this material, which is well known as a major contributor to greenhouse gas emissions. It may be that the carbon dioxide is waste carbon dioxide, for instance as produced by heavy industry,

or acts as an offset where curing is also with heating and green energy resources could not be used. The use of carbon dioxide produced by heavy industry can be particularly 2024219865

3a

beneficial wherethe beneficial where the carbon carbon dioxide dioxide is carbon is carbon dioxide dioxide produced produced by the by the iron iron or steel or steel

production industries,as production industries, asthese theseindustries industrieshave have traditionally traditionally produced produced large large amounts amounts of of wasteheat waste heatand and carbon carbon dioxide. dioxide. For instance, For instance, a typical a typical ironmaking ironmaking operation operation including including

blast blast furnace andancillary furnace and ancillaryplant plantemits emitsoff-gas off-gaswhich which is is 5 to 5 to 50%50% carbon carbon dioxide, dioxide, which which

5 5 can equate can equatetoto2000 2000 to to 20,000 20,000 tonnes tonnes per(tpd). per day day (tpd). However, However, gas flowgas flow rates rates will will vary. vary. For For instance, a mid-range instance, a blastfurnace mid-range blast furnacecan can emit emit off-gas off-gas at at 11,000 11,000 tpdtpd (or (or 3860 3860 litres litres perper

minute). Moreover, minute). Moreover, even even small small blast blast furnaces furnaces can produce can produce 2000 2000 tpd tpd dioxide carbon carbon (or dioxide (or 2024219865

701 litres per 701 litres per minute). Therefore, minute). Therefore, whilst whilst the the impact impact is much is much lower lower than,than, for instance, for instance, a a large large power station, the power station, the impact impactofofblast blastfurnace furnaceoperation operationisissignificant significant and andcan can 10 10 beneficially beneficially be decarbonised. be decarbonised. Direct Direct iron iron reduction reduction (DRI) (DRI) processes processes produce off-gas produce off-gas

comprisingaround comprising around 30% 30% carbon carbon dioxide, dioxide, even even though though some recapture some recapture is in is common common these in these systems;and systems; and electricarc electric arcfurnaces furnacesemit emit off-gas off-gas comprising comprising in the in the range range 5 to5 50% to 50% carbon carbon

dioxide. It is dioxide. It is common practice to common practice to reuse reuse the theheat heatproduced producedbyby industrial processes, industrial processes, including those described including those describedabove, above, butbut typically typically carbon carbon dioxide dioxide is either is either released released intointo the the

15 15 atmosphere, atmosphere, or or stored stored (physical (physical storage storage or chemical or chemical storage). storage). Such storage Such storage increasesincreases

the cost the cost of of iron/steel iron/steel production andwastes production and wastesa apotentially potentiallyvaluable valuable chemical chemical material, material, thethe

carbon dioxide, by carbon dioxide, locking it by locking it away without further away without further use (although the use (although the environmental environmental benefits benefits are clear). As are clear). such, finding As such, finding ways waystotouseuse thethe carbon carbon dioxide dioxide produced, produced,

sequesteringinina aproductive sequestering productiveandand beneficial beneficial wayway (as opposed (as opposed to sequestering to sequestering purely purely to to 20 20 remove the remove the carbon carbon dioxide dioxide fromfrom the atmosphere), the atmosphere), can be can be beneficial hugely hugely beneficial in reducing in reducing

scope11and scope and3 3emissions emissions from from industrial industrial production production sites sites (for (for instance instance iron iron andand steel), steel), or or fossil fuel fossil fuelpower power stations. stations. Moreover, theprocess Moreover, the processofof the the invention invention uses uses carbon carbon dioxide dioxide to to produce produce a avaluable valuableproduct product (i.e.the (i.e. the pelletfeedstock, pellet feedstock, which which in in this this case case is is often often forfor iron iron

and steel, and steel, but but also also possibly possibly for for the the mining miningindustry), industry),sequestering sequesteringthethe carbon carbon dioxide dioxide as as 25 25 a carbonate. a carbonate.Further, Further, asas the the pellets pellets produced produced are are often often intended intended for in for use useiron in iron or steel or steel

manufacture (for manufacture (for instance instance where where they they comprise comprise metallic metallic or ore or metal metal ore substrates), substrates), the the production of the production of thepellets pellets (potentially (potentially at at the the location location of of the the iron iron or or steel steel production productionsite) site) using carbondioxide using carbon dioxideresulting resultingfrom fromthe theproduction productionofof ironororsteel iron steel (such (suchas ascarbon carbondioxide dioxide foundin found in off-gas off-gas arising arising from frompower poweroror heat heat generation generation in internal in internal combustion combustion engines engines or or 30 30 induration plants induration plants at at aa mining miningsite), site), creates createsaadesirable desirablecircularity circularity in in the the process whichisis process which

environmentallyand environmentally and economically economically beneficial, beneficial, reducing reducing the the overall overall carbon carbon footprint footprint of of the the production site. production site.

As noted As notedabove, above, the the process process of of thethe invention invention provides provides for for strong strong pellets pellets which which offeroffer one one 35 35 or more or moreofofthe thebenefits benefits of of being being robust robust to transport, to transport, robust robust to handling, to handling, havinghaving good good water resistance water resistanceand and having having thermal thermal properties properties suitable suitable for the for the endconditions end use use conditions of a of a blast blast or or other furnace. Without other furnace. Without being being bound bound by theory, by theory, it is it is believed believed that that the strength the strength

can be can bederived, derived,without without thethe need need for for heat, heat, because because the carbon the carbon dioxidedioxide reacts reacts with thewith the 4

inorganic binder(a(ametal inorganic binder metal silicate) silicate) to to form form a carbonate a carbonate by anionic by anionic substitution. substitution. For For instance, wherethe instance, where theinorganic inorganicbinder binder includes includes sodium sodium silicate, silicate, the the substitution substitution reaction reaction is is

believed to believed to be: be:

5 5 Na 2SiO3.nH2O++CO2 Na2SiO3.nH2O CO2 → Na 2CO3 + Na2CO3 + SiO2 SiO2 ++ nH2O nH2O(equation (equation 1) 1)

This reaction, This reaction, aa separation separationofofsilica silica from fromsodium sodium silicateusing silicate using carbon carbon dioxide, dioxide, provides provides 2024219865

for aa pellet for pellet with with higher thermalstability higher thermal stability than pellets of than pellets of the samecomposition the same composition which which are are not curedbybycontact not cured contact with with carbon carbon dioxide. dioxide. Again, Again, without without being being bound bound by by it theory, theory, is it is 10 10 believed that believed thatthe thesilica silicahas has a greater a greater affinity affinity for for the reactive the reactive functionalities functionalities in thein the particulate particulate materials thanfor materials than for other othersilica silica groups. Resultinginina apellet groups. Resulting pelletcontaining containingbonds bonds between the between the silicaandand silica the the particulates, particulates, for instance for instance the metal/metal the metal/metal oxides inoxides the in the particulates, particulates, which wouldnot which would notbebe formed formed if the if the metal metal silicate silicate were were simply simply mixed mixed with with the the

particulate particulate without further processing. without further processing.In In essence, essence, reaction reaction withwith the carbon the carbon dioxide dioxide to to 15 15 formaametal form metalcarbonate carbonate as alternative as an an alternative to a to a dehydrated dehydrated metal silicate metal silicate allows allows for thefor the provision of provision of discrete discretesilica silicaparticles, particles,which which interact interact to form to form strong strong bonds bonds with thewith the particulate material in particulate material in the the pellet. pellet. Such Suchthat thatitit is is possible possible to to utilise utilise carbon dioxideasasa a carbon dioxide

catalyst to catalyst to cure cure a a binding systemwhich binding system which contains contains a silicatecomponent. a silicate component.

20 20 Thereaction The reactionofofthe themetal metal silicatewith silicate withcarbon carbon dioxide dioxide to to form form the the metal metal carbonate carbonate may may be partial or be partial or complete. Asthe complete. As thestrength strengthofofthe thepellet pelletis is roughly roughlyproportional proportionaltotothe thedegree degree of reaction of reactiontotoform form thethe freefree silica silica and and carbonate, carbonate, it is generally it is generally desirable desirable that the that the reaction reaction is is complete, or nearly complete, or complete.For nearly complete. Forinstance, instance, thatthe that thereaction reactionisisat atleast least 50% 50% complete, complete,

often in often inthe therange range50% 50% to to 100% complete,often 100% complete, often in in the the range range 60% to 90%, 60% to 90%,oror70% 70%toto 25 25 80%complete. 80% complete. Hardening/strengthening Hardening/strengthening of pellet of the the pellet typically typically follows follows the gas the gas penetration of the penetration of thegreen green pelletsuch pellet such that that it itwill willoften oftenbebethe the outer outer surface surface of the of the pellet pellet

whichinitially which initially hardens, hardens,with withthethe core core following following after after longer longer exposure exposure to the to the carbon carbon dioxide.ItItisisfor dioxide. forthis thisreason reason that that it it cancan often often be case be the the case that athat a partial partial reaction reaction is sufficient is sufficient

to provide to provide aa pellet pellet with with the strength required, the strength required,as asthe thehard hardexterior exteriorisissufficient sufficient to to protect protect

30 30 the interior the interior during during handling. handling.

Theparticulate The particulatematerial materialwill will generally generallycomprise comprise a carbonaceous a carbonaceous material, material, metal,metal, metal metal ore, or ore, or mixtures thereof.InInmany mixtures thereof. many cases, cases, the the particulate particulate material material willwill be be selected selected from from a a metal ore,a ametal, metal ore, metal,andand combinations combinations thereof, thereof, asapplication as the the application of carbon of carbon dioxide dioxide to to 35 35 greenpellets green pellets comprising comprisingthis thisparticulate particulatesubstrate substrate provides provides particular particular benefits benefits in terms in terms

of the of improvementsininobserved the improvements observedstrengths. strengths.TheThe metal/metal metal/metal oresores may may be further be further selectedfrom selected from metal metal residues, residues, metal metal filings, filings, metaliron metal fines, fines, oreiron ore screenings, screenings, and and collection collection

5

dusts from dusts fromfurnaces furnacesincluding includingblast blastfurnaces, furnaces,BOS, BOS, EAFEAF and and DRI.DRI. The collection The collection dustsdusts will will typically comprise typically comprise aacombination combinationof of metal metal oxides, oxides, partial partial oxides, oxides, and metal and metal fines.fines. The The particulate particulate substrate substrate isisoften often sourced sourced from the waste from the wasteproducts productsofofother otherindustrial industrial processes. Theparticulate processes. The particulatesubstrate substrate maymay comprise comprise wastewaste products products from a from singleawaste single waste 5 5 stream (in stream (in which which variation variation will will be in particle be in particle size sizeonly) only)ororwaste waste products products from from aa combinationofofwaste combination waste streams streams (in which (in which mixed mixed waste waste of of different different compositions compositions will be will be present). This is present). This is environmentally beneficialasasthe environmentally beneficial therecycling recyclingand and reuse reuse of of such such materials materials 2024219865

reduces theamount reduces the amountof of finiteresources finite resources that that maymay otherwise otherwise go togo to waste. waste.

10 10 Thecarbonaceous The carbonaceous material material maymay be coke, be coke, graphite, graphite, carbon carbon black,black, peat, peat, or coal. or coal. Often Often the the carbonaceous carbonaceous material material will will comprise comprise graphite, graphite, coke,coke, coal,coal, or a or a combination combination thereof. thereof. It It may bethe may be thecase casethat that the the carbonaceous carbonaceousmaterial material comprises comprises coke cokeand/or and/orcoal. coal. As As used used herein, the term herein, the term"coal" "coal"isisintended intendedtotoinclude include lignites,sub-bituminous lignites, sub-bituminous coal, coal, bituminous bituminous

coal, steam coal, coal and steam coal andanthracite. anthracite.Cokes Cokes have have been been found found to betoparticularly be particularly problematic problematic at at 15 15 formingpellets forming pellets and andso sothe theinvention inventionoffers offersaa particular particular benefit benefit in in the the provision provision of of stronger stronger

cokepellets. coke pellets.

Themetal The metalmay may be,be, or the or the metal metal ore contain; ore may may contain; iron, zinc, iron, zinc, nickel, nickel, copper, copper, chromium, chromium,

manganese, gold, manganese, gold, platinum, platinum, silver, silver, titanium, titanium, tin,tin, lead, lead, vanadium, vanadium, cadmium, cadmium, beryllium, beryllium,

20 20 molybdenum, molybdenum, uranium, uranium, aluminium, aluminium, or mixtures or mixtures thereof; thereof; for instance, for instance, as elemental as elemental metal metal or in or in the theform formof,of, forfor example, example, oxidesoxides or silicates. or silicates.

Often, the Often, particulate substrate the particulate substrate comprises comprises aa metal, and more metal, and moreoften oftenthe theparticulate particulate substrate comprises substrate comprises iron.The iron. The use use of of ironisisadvantageous iron advantageousdue due to the to the ready ready availability availability of of 25 25 iron iron and because it and because it can can be bereused reusedand and recycled recycled from from thethe waste waste products products of other of other processes processes totoprovide provide environmentally environmentally sustainable sustainable accessaccess to thisto this material. material. Where the Where the

particulate substrate comprises particulate substrate comprises a metal a metal ore,ore, often often the will the ore ore will be anbeiron an ore ironsuch ore as such as goethite, martite, goethite, martite, limonite, limonite, siderite, siderite, taconite, taconite, hematite hematiteorormagnetite. magnetite. Often, Often, where where the the particulate particulate substrate is aa metal substrate is ore, it metal ore, it will willbebeananiron ironore, ore,such suchas ashematite hematite or or magnetite. magnetite.

30 30 Theparticulate The particulatesubstrate substratemay may bepowder be a a powder or filings, or filings, the term the term “filings” "filings" beingbeing givengiven its its common meaning common meaning in art. in the the art. Often Often the particulate the particulate substrate substrate has ahas a particle particle diameter diameter of 4 of 4

mm mm oror less(broadest less (broadest axis). axis). Often Often the the particle particle diameter diameter will will be the be in in the range range 30 um30 toµm 4 to 4

mm, often5050 mm, often umµm to to 3 mm 3 mm or mm or 0.1 0.1tomm to 2Often, 2 mm. mm. at Often, leastat 10least 10the wt% of wt% of the particulate particulate

35 35 substrate is substrate is capable of passing capable of througha a100 passing through 100umµm sieve sieve prior prior to to forming forming into into a pellet.TheThe a pellet.

presence presence ofofa a range range of particle of particle sizes sizes within within the the sample sample improves improves the of the packing packing the of the materials within materials within thethe pellet. pellet.

6

It may It bethe may be thecase casethat thatthe theparticulate particulatematerial materialbebe added added in in an an amount amount of about of about 70 70 wt% wt% to about to 99.9wt% about 99.9 wt%of of the the mixture mixture of of step step (i),often (i), oftenabout about80 80 wt%wt% to about to about 99 wt%, 99 wt%, more more often about often 90wt% about 90 wt%to to about about 95 95 wt%. wt%. At these At these levels levels there there is aisbalance a balance between between the the need need for other for components other components andand the the desire desire to maximise to maximise the levels the levels of theofparticulate the particulate substrate substrate

5 5 as it as it isisthe thereactive reactivefeedstock feedstock that that is isthe thereason reason for for pelletisation. pelletisation.ItIt may may be be the the case case that that

the particulate the particulate material comprisesa ametal material comprises metal ore,a ametal, ore, metal, and and combinations combinations thereof, thereof, added added

in in an an amount amount ofofabout about7070 wt% wt% to about to about 99.999.9 wt%, wt%, often often about about 80 wt% 80 to wt% aboutto 99about wt%, 99 wt%, 2024219865

more often about more often about 90 90wt% wt%to to about about 95 95 wt%. wt%. It may It may be case be the the case that that the the particulate particulate material comprises material comprises a carbonaceous a carbonaceous material. material. It mayItbemay be the the case thatcase that the particulate the particulate

10 10 material is added material is in an added in an amount amount of of about about 70 70 wt%wt% to about to about 99.9 99.9 wt%, about wt%, often often 80 about wt% 80 wt%

to about to about 99 99 wt%, more often wt%, more often about about 90 90 wt% to about wt% to about 95 95 wt%. wt%.

It It may bethe may be thecase casethat thatthe theparticulate particulatematerial materialhas hasa amoisture moisture content content of of less less than than 25%, 25%,

as above as abovethese these levels, levels, dilution dilution of of thethe particulate particulate impacts impacts the ability the ability to form to form compact compact

15 15 agglomerates.Often agglomerates. Often the the moisture moisture content content will will be inbethe in range the range of about of about 1 wt% 1 towt% aboutto about 25 wt%,often 25 wt%, often from fromabout about33wt% wt%to to about about 2020 wt%, wt%, more more often often fromfrom about about 5 wt% 5 wt% to to about15 about 15wt% wt%of of thethe mixture. mixture.

The inorganic The inorganicbinder bindercomprises comprisesoneone or more or more metal metal silicates. silicates. It may It may becase be the the that casethe that the 20 20 metal silicate comprises metal silicate comprises a agroup group I or I or group group II metal II metal silicate, silicate, or or more more thanthan one group one group I I and/orgroup and/or groupIIIImetal metal silicates.Whilst silicates. Whilstother othermetal metal silicatesmay silicates maybe be successfully successfully used used as as the inorganic the inorganic binder binderof of the the invention, invention,it it has beenfound has been found thatgroup that group I and I and group group II metals II metals

are more are morereactive reactive in in the the presence presence of carbon of carbon dioxide dioxide (promoting (promoting carbonate carbonate formation) formation)

than other than othermetals. metals.As As a result, a result, “free”silicates "free" silicatesreadily readily form formwhere wherethethe metal metal silicate silicate is is a a 25 25 groupII or group or group groupIIIIsilicate, silicate, promoting promotingenhanced enhanced cross-linking cross-linking of the of the silicate silicate bonds bonds and and improving thethermal improving the thermal properties properties of pellet. of the the pellet. Some Some less less metal labile labile silicates metal silicates may may require the require the application application of of pressure andheat pressure and heatto topromote promote cross-linking. cross-linking. As As such, such, the the metal metal

silicate will silicate will often often be selectedfrom be selected from sodium sodium silicate, silicate, potassium potassium silicate silicate (e.g. (e.g. K2SiO3), K2SiO3),

calcium silicate (e.g. calcium silicate CaSiO3, Ca2SiO4), (e.g. CaSiO3, Ca2SiO4), magnesium magnesium silicate silicate (e.g. (e.g. MgSiOand MgSiO4), 4), and

30 30 combinationsthereof. combinations thereof.ItItmay maybe be thethe case case thatthat the the metal metal silicate silicate is selected is selected from from sodium sodium

silicate, potassium silicate, potassium silicate, silicate,magnesium silicate, or magnesium silicate, or combinations thereof.Where combinations thereof. Wherethethe metal metal

silicate comprises silicate calciumsilicate, comprises calcium silicate, ititmay may be presentin be present in its its natural natural mineral state, such mineral state, such as as wollastonite (i.e. wollastonite (i.e. CaSiO₃) andlarnite CaSiO3) and larnite (i.e. (i.e. Ca₂SiO₄). It will Ca2SiO4). It will not not generally generally be present as be present asaa calcined product calcined product(such (suchasasPortland Portland cement). cement). It may It may be case be the the case that that the metal the metal silicate silicate is is 35 35 selected from selected sodiumsilicate, from sodium silicate, magnesium silicate, or magnesium silicate, or combinations thereof. Sodium combinations thereof. Sodium silicate has silicate has been foundtotobebe been found particularlybeneficial particularly beneficialpossibly possiblydue due to to itsits high high ionion lability. lability.

Sodium silicateisis also Sodium silicate alsoreadily readilyavailable availableand and inexpensive. inexpensive. It may It may becase be the the that casethe that the metal silicate comprises metal silicate sodium comprises sodium silicateand silicate and magnesium magnesium silicate. silicate. It has It has been been foundfound that that

7

this combination this combination ofof alkalimetal alkali metal silicates silicates provides provides pellets pellets withwith highhigh cold cold compression compression

strength. Without strength. being bound Without being boundbybytheory, theory,asassodium sodium silicateisis more silicate morereactive reactivethan than magnesium silicate,the magnesium silicate, thesodium sodium silicateshould silicate should react react preferentiallyasasper preferentially per the the substitution substitution

reaction outlined above reaction outlined aboveininequation equation1. 1. This This should should then then allow allow the the magnesium magnesium silicate silicate to to 5 5 co-react to co-react to form formaaNa-Mg Na-Mg complex, complex, and and result result in a in a combined combined salt. salt. It is It is believed believed that that the the magnesium silicate magnesium silicate converts converts to to an an amorphous, amorphous, more reactive more reactive phase phase from itsfrom itsmore usual usual more stable, crystalline stable, crystalline phase during this phase during this process. process. 2024219865

Alternatively, it Alternatively, it may may bebe the the case case thatthat the the alkali alkali metal metal silicate silicate comprises comprises magnesium magnesium

10 10 silicate, potassium silicate, silicate, ororaacombination potassium silicate, thereof. combination thereof.

Themetal The metalsilicate silicate may maybebe in in liquidform, liquid form, powder powder form, form, or a or a combination combination thereof. thereof. When When the metal the metalsilicate silicate is is in inliquid liquidform, form,itit will be be will present in in present greater amounts greater amounts because thereisis because there

a lower a lower level level of of active active in in liquid liquid metal metal silicates silicatesthan than in in powder metalsilicates. powder metal silicates. Where Wherethe the 15 15 metal silicate is metal silicate is in in liquid liquidform, form, ititisis often oftenpresent present in inthe the range about11wt% range about wt%to to about about 6 6 wt%, often wt%, often about about 1.5 1.5 wt% to about wt% to about 5.5 5.5 wt%, wt%,often often about about 22 wt% to about wt% to about 55 wt%, wt%,often often about33wt% about wt%to to about about 4 of 4 wt% wt%theofmixture the mixture of step of step (i). (i). the Where Where metalthe metal is silicate silicate in is in powder form, powder form, it itisisoften oftenpresent present in in thethe range range about about 0.5towt% 0.5 wt% to 3.5 about about wt%,3.5 wt%, often often

about11wt% about wt%to to about about 3 wt% 3 wt% ofmixture. of the the mixture. It may It be may be the the case case that that there arethere are two or two or 20 20 more metal more metal silicatespresent. silicates present. In In thethe event event thatthat therethere areortwo are two ormetal more moresilicates metal silicates present, it may present, it bethe may be thecase casethat thatat at least least one one is is in in liquid liquidform form and and at at least leastone one is isininpowder powder

form. When form. Whentwotwo or more or more metalmetal silicates silicates are present, are present, at least at least one inone in liquid liquid form form and at and at least least one in powder one in form,itit is powder form, is often often the the case that the case that the liquid liquid and powderform and powder form are are present present

in in the the ratio ratio of offrom from 5:1 5:1 to to 1:1. 1:1. Optionally, Optionally, the the ratio ratio may be3:1, may be 3:1,optionally optionallythe theratio ratio may may 25 25 be 3:2. AsAssuch, be 3:2. such,the themetal metal silicatemay silicate maybe be present present in the in the mixture mixture in the in the range range about about 0.5 0.5

wt%totoabout wt% about6 6 wt%, wt%, often often in the in the range range about about 1 wt%1 to wt% to about about 5 wt%, 5often wt%,inoften in the the range range about1.5 about 1.5 wt% wt%toto about about 4 wt% 4 wt% of the of the mixture mixture of step of step (i). (i). AtAt these these levels,there levels, thereisissufficient sufficient metal silicate present metal silicate to ensure present to ensurethat thatbinding binding occurs, occurs, butbut thatthat the the binder binder is not is not used used in in excess, reducingthe excess, reducing theoverall overallamount amountof of particulate particulate substrate substrate available available from from the the pellet. pellet.

30 30 Optionally, it Optionally, itmay be the may be the case casethat that step step(i), (i), the the forming of the forming of the mixture, mixture, further further comprises comprises the addition the addition ofofananorganic organic binder. binder. It It hashas beenbeen foundfound thatpresence that the the presence of an of an organic organic binder, in addition binder, in to the addition to inorganic binder, the inorganic binder, enhances enhancesthethe speed speed of curing. of curing. It may It may be the be the

case that case that the the organic organic binder binder comprises comprisesa anatural naturalpolymer polymer (e.g.lignosulfonates), (e.g. lignosulfonates), aa 35 35 synthetic polymer synthetic polymer(e.g. (e.g.polyacrylics, polyacrylics,styrene-acrylate styrene-acrylatecopolymers, copolymers, polyvinyl polyvinyl alcohol, alcohol, or or a a syntheticorganic synthetic organic resin); resin); a cellulosic a cellulosic material; material; a glycerolipid a glycerolipid (e.g.di-, (e.g. mono-, mono-, di-, or tri-esters or tri-esters

of of glycerol); glycerol);aa polysaccharide; polysaccharide; or or combinations combinations thereof. As used thereof. As usedherein, herein, the theterm term “polyacrylics” takes "polyacrylics" takes its itsusual usualmeaning in the meaning in the art art and refers to and refers to aa class classof ofsynthetic syntheticpolymers polymers

8

derivedfrom derived from acrylic acrylic acid acid or its or its esters. esters. Examples Examples of polyacrylics of polyacrylics include, include, but but are not are not limited limited to, polyacrylic to, polyacrylic acid acid(PAA), (PAA), poly(methyl methacrylate) poly(methyl methacrylate) (PMMA), (PMMA), and and polyacrylamide polyacrylamide (PAM). (PAM).

As used As usedherein, herein,the theterm term"styrene-acrylate “styrene-acrylate copolymer” copolymer" takes takes its usual its usual meaning meaning in theinart the art and relates and relates to to synthetic synthetic polymers polymers formed formed by the by the copolymerization copolymerization of styrene of styrene and acrylic and acrylic

5 5 acid or acid or its its derivatives. derivatives. Examples Examplesof of styrene-acrylate styrene-acrylate copolymers copolymers include, include, but arebut not are not limited to, 2-Ethylhexyl limited to, 2-Ethylhexylacrylate acrylatestyrene styrene (2-EHA), (2-EHA), Ethyl Ethyl acrylate acrylate styrene styrene (EA), (EA), Methyl Methyl

methacrylate styrene (MMA), methacrylate styrene (MMA),and andButyl ButylAcrylate AcrylateStyrene Styrene(BA). (BA).Often, Often, thethe styrene- styrene- 2024219865

acrylate copolymerwill acrylate copolymer willcomprise comprise Ethyl Ethyl acrylate acrylate styrene styrene (EA). (EA). As used As used herein, herein, the term the term

“cellulosic material” "cellulosic material" takes takes its itsusual usual meaning in the meaning in the art art and andrefers refersto to any anymaterial materialderived derived 10 10 fromororcontaining from containing cellulose. cellulose. Cellulosic Cellulosic materials materials include include natural natural materials materials primarily primarily

composed composed of of cellulose, cellulose, butbut also also synthetic synthetic derivatives derivatives of cellulose. of cellulose. As used As used herein, herein, the the term"glycerolipid" term “glycerolipid” takes takes its its usual usual meaning meaning ininthe theart art and andrefers refers to to aa type type of of lipid lipidmolecule molecule

that consists that consists of of aa glycerol glycerolbackbone esterified with backbone esterified with one or more one or morefatty fattyacids acidsor or acyl acyl groups. groups.

15 15 It may It may bebe the the case case thatthat the the organic organic binder binder is selected is selected from a from a natural natural polymer polymer (e.g. (e.g. lignosulfonates), lignosulfonates), aa synthetic syntheticpolymer polymer (e.g. (e.g. polyacrylics, polyacrylics, styrene-acylate styrene-acylate copolymers, copolymers, a a synthetic organic synthetic organic resin resin such as polyacrylamide such as polyacrylamide resin resin or or phenol-formaldehyde phenol-formaldehyderesin resin (including resole resin, (including resole resin, which whichis is a base a base catalysed catalysed phenol-formaldehyde phenol-formaldehyde resin resin with a with a formaldehyde formaldehyde to to phenol phenol ratio ratio of of greater greater than than one,one, usually usually around around 1.5, 1.5, or or Novolac Novolac resin, resin,

20 20 whichhas which hasa aformaldehyde formaldehyde to phenol to phenol molar molar ratioratio of less of less thanthan one))one)) or polyvinyl or polyvinyl alcohol); alcohol);

a cellulosic a cellulosic material, material, such such asascellulosic cellulosic fibres, fibres, carboxymethyl carboxymethylcellulose cellulose(CMC), (CMC), hydroxyethyl cellulose(HEC), hydroxyethyl cellulose (HEC), or or hydroxyethyl hydroxyethyl methyl methyl cellulose cellulose (MHEC); (MHEC); a glycerolipid a glycerolipid

(e.g. glyceryl acetate, (e.g. glyceryl acetate, glyceryl glyceryl diacetate, diacetate, and and glyceryl glyceryl triacetate); triacetate); and/or and/or a a polysaccharide, suchas as polysaccharide, such starch starch (for (for example, example, wheat, wheat, maize,maize, barley barley andstarch, and potato potato starch, 25 25 and/or molasses) and/or or gum molasses) or (for example, gum (for example, gum Arabic, guar gum Arabic, guar gum and/or xanthan gum and/or xanthangum). gum).ItIt may may bebethe thecase case that that the the organic organic binder binder is selected is selected from from polyacrylamide polyacrylamide resin, resin, polyvinyl polyvinyl

alcohol, aa phenol alcohol, formaldehyde phenol formaldehyde resin resin (such (such as as novolac novolac or resole or resole resin), resin), a polyacrylic a polyacrylic (e.g. (e.g.

polyacrylic acid polyacrylic acid(PAA), (PAA), poly(methyl poly(methyl methacrylate) methacrylate) (PMMA, polyacrylamide(PAM)), (PMMA, polyacrylamide (PAM)),a a styrene-acrylate copolymer styrene-acrylate copolymer (e.g. (e.g. 2-Ethylhexyl 2-Ethylhexyl Acrylate Acrylate Styrene Styrene (2-EHA), (2-EHA), Ethyl Acrylate Ethyl Acrylate

30 30 Styrene (EA), Methyl Styrene (EA), Methacrylate Styrene Methyl Methacrylate Styrene (MMA), (MMA),and andButyl ButylAcrylate Acrylate Styrene Styrene(BA)), (BA)), glyceryl triacetate, glyceryl triacetate, glyceryl diacetate, cellulosic glyceryl diacetate, cellulosic fibres, fibres, carboxymethyl cellulose(CMC), carboxymethyl cellulose (CMC), hydroxyethylcellulose hydroxyethyl cellulose(HEC), (HEC),hydroxyethyl hydroxyethyl methyl methyl cellulose cellulose (MHEC), (MHEC), wheat wheat starch, starch, maizemaize

starch, barley starch, starch, potato barley starch, potato starch, starch, gum gumArabic, Arabic,guar guar gum, gum, xanthan xanthan gum, gum, and and combinations thereof. combinations thereof. It It may bethe may be thecase casethat thatthe theorganic organicbinder binderisisselected selectedfrom from 35 35 polyacrylamide resin,polyvinyl polyacrylamide resin, polyvinyl alcohol, alcohol, a phenol a phenol formaldehyde formaldehyde resin, resin, a polyacrylic, a polyacrylic, a a styrene-acrylate copolymer, styrene-acrylate copolymer, glyceryl glyceryl diacetate, diacetate, glyceryl glyceryl triacetate, triacetate, cellulosic cellulosic fibres,fibres,

carboxymethyl cellulose (CMC), carboxymethyl cellulose (CMC), hydroxyethyl hydroxyethylcellulose cellulose (HEC), (HEC),hydroxyethyl hydroxyethylmethyl methyl cellulose cellulose (MHEC), (MHEC), ororcombinations combinations thereof. thereof. It It maymay be the be the casecase that that the organic the organic binder binder is is 9

selected from selected frompolyacrylamide polyacrylamide resin, resin, polyvinyl polyvinyl alcohol, alcohol, a phenol a phenol formaldehyde formaldehyde resin, resin, glyceryl triacetate, glyceryl triacetate, polyacrylamide, polyacrylamide, ethyl ethylacrylate acrylate styrene, styrene, cellulosic cellulosic fibres, fibres, carboxymethyl carboxymethyl cellulose cellulose (CMC), (CMC), hydroxyethyl hydroxyethyl cellulose cellulose (HEC), (HEC), or combinations or combinations thereof. thereof. It It may may bebethe thecase case that that the the organic organic binder binder is selected is selected from from polyacrylamide polyacrylamide resin, resin, polyvinyl polyvinyl

5 5 alcohol, aa phenol alcohol, phenolformaldehyde formaldehyde resin, resin, cellulosic cellulosic fibres, fibres, carboxymethyl carboxymethyl cellulose cellulose (CMC), (CMC),

glyceryl triacetate, glyceryl triacetate, or or combinations thereof. combinations thereof. 2024219865

Theorganic The organicbinder binder maymay comprise comprise a cellulosic a cellulosic material, material, polyacrylamide polyacrylamide resin, polyvinyl resin, polyvinyl

alcohol, a alcohol, a phenol-formaldehyde resin, phenol-formaldehyde resin, or or a combination a combination thereof. thereof. The organic The organic binderbinder may may 10 10 comprise polyacrylamide comprise polyacrylamide resin, resin, a cellulosic a cellulosic material, material, or a combination or a combination thereof. thereof. The The organic binder organic bindermay may comprise comprise a cellulosic a cellulosic material. material.

Wherethe Where the organic organic binder binder comprises comprises a cellulosic a cellulosic material, material, it be it may maythebe thethat case case thethat the organic binder organic bindercomprises comprises carboxymethyl carboxymethyl cellulose cellulose (CMC), (CMC), cellulosic cellulosic fibres, fibres, hydroxyethyl hydroxyethyl

15 15 methylcellulose methyl cellulose(MHEC), (MHEC),or or a combination a combination thereof. thereof. It may It may becase be the the that casethe that the organic organic

binder comprises binder comprises carboxymethyl carboxymethyl cellulose cellulose (CMC)(CMC) and/or and/or hydroxyethyl hydroxyethyl methyl methyl cellulose cellulose (MHEC). (MHEC). ItItmay maybe be thethe casecase thatthat the the organic organic binder binder comprises comprises carboxymethyl carboxymethyl cellulosecellulose

(CMC). CMCisis advantageous (CMC). CMC advantageousbecause becauseitit can can be be added addedinin powder powderform formwhich whichallows allowsfor for control of the control of the overall overall moisture moisturecontent content of of thethe pellet. pellet. CMCCMC also also has ahas longa shelf-life long shelf-life in in 20 20 comparison comparison toto other other plant plant derived derived binders. binders. ThisThis is because is because otherother plant plant derived derived bindersbinders

are often are often more susceptibletotomicrobial more susceptible microbialattack attackand andsosobreak break down down more more easily. easily. Sometimes Sometimes

the organic the organic binder bindermay maybe be hydroxyethyl hydroxyethyl methyl methyl cellulose cellulose (MHEC), (MHEC), which which has has been been found found to have to haveparticularly particularlygood good adhesive adhesive qualities qualities and and helps helps to enhance to enhance the strength the strength of the of the pellet. However, pellet. However, as MHEC as MHEC is highly is highly water soluble, water soluble, this may this may affect affect the shelf theofshelf life life of the final the final

25 25 pellet, pellet, reducing reducing this this in in comparison topellets comparison to pellets containing containingCMC. CMC.

Typically, the Typically, the CMC hasanan CMC has active active polymer polymer content content of about of about 40% 40% to to 90% about about and90% a pH and a pH in in the the range of about range of about55totoabout about9,9,ororabout about 6 to 6 to about about 8 when 8 when in solution. in solution. Further, Further, the the

CMCwill CMC will often oftenbebeofofnumber number average average molecular molecular weightweight (Mn) in(M n) in the the of range range from of from about about 30 30 3,000 to about 3,000 to about70,000. 70,000. Optionally, Optionally, thethe CMCCMC willwill be be of number of number average average molecular molecular weight weight

in in the the range of from range of from about about10,000 10,000to to about about 50,000. 50,000. Without Without being being bound bound by theory, by theory, it is it is

believed that, with believed that, with lower lowernumber number average average molecular molecular weights weights of for of CMC, CMC, for instance instance in the in the

range about 10,000 range about 10,000totoabout about 50,000, 50,000, it is it is possibleto to possible prepare prepare a solution a solution of of high high concentration, concentration, which in turn which in turn can can improve improvethe thestrength strength of of thethe pellets.Any pellets. Any known known 35 35 technique, such technique, such asassize-exclusion size-exclusion chromatography chromatography(SEC), (SEC), gel permeation gel permeation chromatography (GPC),or chromatography (GPC), or light light scattering, scattering,may maybe beemployed employed to to determine determine the the number number average molecular average molecularweight weight (Mn). (Mn). The The specific specific measurement measurement conditions, conditions, including including

10

temperature,solvent, temperature, solvent, andand calibration calibration standards, standards, willwill be selected be selected basedbased on theon the chosen chosen techniqueand technique andininaccordance accordance with with appropriate appropriate industry industry standards. standards.

Polyvinyl Polyvinyl alcohol alcohol (PVA) maybebeused (PVA) may used as as an an organic organic binder binder instead instead of of or or in in addition addition toto other other

organic binders, organic binders, such suchthat thatthe theorganic organic binder binder maymay comprise comprise aboutabout 10 wt%10 towt% aboutto100 about 100 5 5 wt%, often wt%, often about about 20 20wt% wt%to to about about 90 90 wt%wt% or about or about 50 wt% 50 wt% to about to about 75PVA. 75 wt% wt% PVA. Wherethe Where the organic organic binder binder comprises comprises PVA, PVA, the the organic organic binder binder is is typically typically added inadded the in the range of about about0.01 0.01 wt%wt% to about 2.0ofwt% the of the pellet, often 0.05 about wt%0.05 wt% to 1.5 2024219865

range of to about 2.0 wt% pellet, often about to 1.5

wt%ofofthe wt% thepellet pelletor orabout about1 1wt% wt%of of thethe pellet. pellet.

Withoutbeing Without beingbound boundby by theory, theory, thethe PVAPVA is is believed believed to to provide provide good good mixing mixing of components of components

10 10 and high and highstrength strengthasasthe thepolymer polymer network network formed formed byisPVA by PVA is strong. strong. Further, Further, the process the process

of pelleting of pelletingwith with PVA PVA excludes air from excludes air the particulate from the particulate material, material,which which may reduce may reduce oxidation of the oxidation of the particulate particulate substrate substrate where wherethis thisisis metal. metal.Metal Metal oxidation oxidation is is undesirable undesirable

for the for the simple simple reason that it reason that it reduces the amount reduces the amount ofofthe themetal metal (e.g.metallic (e.g. metalliciron) iron)available available for processing for bythe processing by theend enduser. user.

15 15 PVA is typically PVA is typically commercially formed commercially formed from from polyvinyl polyvinyl acetate acetate by replacing by replacing the acetic the acetic acid acid

radical of radical of an an acetate acetate with with a a hydroxyl radical by hydroxyl radical reacting the by reacting the polyvinyl polyvinyl acetate acetate with with sodium sodium hydroxide bysaponification. hydroxide by saponification.Partially Partiallysaponified saponifiedmeans means thatthat some some of acetate of the the acetate groups groups

have beenreplaced have been replacedbyby hydroxyl hydroxyl groups groups and and thereby thereby forming forming at least at least a partially a partially saponified saponified

polyvinyl alcohol polyvinyl alcohol residue. residue. Typically, Typically,the thePVA PVA hashas a degree a degree of saponification of saponification of at of at least least

20 20 about80%, about 80%, typicallyatatleast typically leastabout about5%, 5%,at at least least about about 90%, 90%, at least at least about about 95%,95%, at least at least

about99% about 99%or or about about 100% 100% saponification. saponification. Typically, Typically, it is it is utilised utilised as aassolution a solution in water. in water.

ThePVA The PVAmay maybe be modified modified to include, to include, forfor example, example, a sodium a sodium hydroxide hydroxide content. content. Typically, Typically,

the PVA the PVAbinding bindingmaterial materialhas has an an active active polymer polymer content content of about of about 12% 12% to to about about 13% and13% and a pH a pH in in the the range rangeofofabout about4 4totoabout about 7 when 7 when in solution. in solution. Further, Further, the will the PVA PVA often will often be be 25 25 of number of averagemolecular number average molecularweight weight(Mn) (Mn)in in the the range range of of from about 15,000 from about 15,000 to to about about 150,000. Optionally,the 150,000. Optionally, thePVA PVA will will often often be be of number of number average average molecular molecular weight weight in the in the range of from range of from about about 30,000 30,000totoabout about120,000. 120,000.Without Without being being bound bound by by theory, theory, it it is is believed that, with believed that, with lower lowernumber number average average molecular molecular weights, weights, for instance for instance in the in the range range

about15,000 about 15,000toto about about 60,000, 60,000, it is it is possible possible to to prepare prepare a solution a solution of of high high concentration, concentration,

30 30 whichin which in turn turn can canimprove improve the the strength strength of of thethe pellets. pellets.

Wherethe Where the organic organic binder binder comprises comprises a polyacrylamide a polyacrylamide resin, resin, it willitoften will often be an be an anionic anionic

polyacrylamide resin polyacrylamide resin of of medium-high medium-high number number average average molecular molecular weightweight (Mn) and (Mn) and medium-high chargedensity. medium-high charge density. For Forinstance, instance, the the number averagemolecular number average molecularweight weight may may be in be in the the range range 100,000 to 2,000,000, 100,000 to 2,000,000, often often in in the therange range 500,000 500,000 to to 1,500,000. The 1,500,000. The 35 35 chargedensity charge densitywill will typically typically be in the be in range25 the range 25toto50%. 50%.AnyAny known known technique technique in the in the art art

11

may beemployed may be employedto to measure measure the the charge charge density density of the of the polymer. polymer. Suitable Suitable methods methods include, but include, butareare notnot limited limited to, potentiometric to, potentiometric titration, titration, conductometric conductometric titration,titration,

electrophoretic mobility, electrophoretic mobility, light light scattering, scattering, and andnuclear nuclear magnetic magnetic resonance resonance (NMR).(NMR). The The specific measurement specific conditions,such measurement conditions, such as as temperature, temperature, solvent, solvent, and calibration and calibration 5 5 standards, will standards, will be be selected selected based on the based on the chosen chosentechnique techniqueand and in in accordance accordance with with appropriateindustry appropriate industrystandards. standards.

Wherethe the organic organic binder binder comprises comprises aa polysaccharide, polysaccharide, this this may be starch starch or or amylase amylase 2024219865

Where may be starch. For starch. For instance, instance,itit may maybe be pregelatinised pregelatinised potato potato starch. starch. It mayItbe may beinadded added the in the amountofofabout amount about0.8 0.8wt% wt% of the of the final final pellet,often pellet, oftenabout about 0.60.6 wt%. wt%. The The usea of a use of 10 10 polysaccharideasasa acomponent polysaccharide component of the of the mixture mixture may may be desirable be desirable as polysaccharides as polysaccharides often often also function also as thickening function as thickening agents. agents.

Theorganic The organicbinder bindermay maybe be present present in the in the mixture mixture in the in the range range aboutabout 0.2towt% 0.2 wt% to 5about about 5 wt%ofofthe wt% themixture, mixture, optionally optionally inin the the range range about about 0.250.25 to about to about 0.45 0.45 wt%, wt%, optionally optionally in in the range the rangeabout about0.3 0.3totoabout about 0.40.4 wt%. wt%.

15 15 It may It bethe may be thecase casethat thatthe theorganic organic binder binder is is ofofviscosity viscosityinin the therange rangeabout about 1,000 1,000 MPa.s MPa.s

to about to 16,000 about 16,000 MPa.s, MPa.s, often often in in thethe range range about about 2,000 2,000 MPa.sMPa.s to about to about 10,000 10,000 MPa.s, MPa.s, or or in in the the range range about about 3,000 3,000 MPa.s to about MPa.s to 7,000 MPa.s. about 7,000 MPa.s. The The viscosity viscosity can can be be measured measured using standardtechniques using standard techniques known known in theinart, the such art, as such as capillary capillary viscometers, viscometers, rotational rotational

20 20 viscometers,and viscometers, andoscillatory oscillatoryrheometers. rheometers.TheThe specific specific measurement measurement conditions, conditions, including including

temperature,solvent, temperature, solvent, and and calibration calibration standards, standards, willwill be selected be selected basedbased on theon the chosen chosen techniqueand technique andininaccordance accordance with with appropriate appropriate industry industry standards. standards. Typical Typical measurement measurement

conditions include conditions include temperatures temperatures ranging ranging from from 20°C 20°C to 25°C, to 25°C, usingusing solvents solvents such such as water as water

or organic or solvents, and organic solvents, andcalibration calibration with withstandard standardviscosity viscosityreference reference materials. materials.

25 25 Themixture The mixtureofofstep step (i)(i)may may further further comprise comprise a flux a flux additive additive to promote to promote fluidity fluidity of theof the mixtureduring mixture duringsubsequent subsequent processing. processing. In instances In instances wherewhere a fluxa additive flux additive is present, is present, the the flux additive flux maybebeselected additive may selected from from silica, silica, dolomite, dolomite, fluorite,calcium fluorite, calcium oxide, oxide, magnesium magnesium

oxide, carbon, oxide, aluminium, carbon, aluminium, dunnite, dunnite, basalt,and basalt, and combinations combinations thereof. thereof. Where Where present, present, the the 30 30 flux additive flux will often additive will be present often be presentininthe therange range about about 0.5 0.5 wt% wt% to to about about 2 wt%, 2 wt%, often often about11wt% about wt%to to 1.5 1.5 wt%wt% of the of the mixture. mixture.

As noted As notedabove, above, it it may may be the be the case case that that the carbon the carbon dioxidedioxide used toused cure to thecure theispellet pellet is carbondioxide carbon dioxidegenerated generated from from one one or more or more industrial industrial processes. processes. This be This could could be termed termed 35 35 “waste”carbon "waste" carbondioxide, dioxide,or, or,when when used, used, “recycled” "recycled" carbon carbon dioxide. dioxide. As such, As such, the process the process

of the of inventionmay the invention may further further comprise comprise the step the step of capturing of capturing carboncarbon dioxidedioxide generated generated

12

fromone from oneorormore more industrialprocesses industrial processes forfor use use in in curing curing thethe pellet.TheThe pellet. step step of of curing curing thethe

pellet pellet comprises contactingthe comprises contacting thepellet pellet (the (the green greenpellet) pellet) with with gaseous carbon gaseous carbon dioxide.TheThe dioxide.

contacting will contacting will often often be placing the be placing the pellets pellets in in a a stream ofgas. stream of gas.This Thismay may be achieved be achieved by by passing passing aaflow flowofofcarbon carbondioxide dioxide over over a static a static bedbed of of thethe pellets, pellets, or or by by transporting transporting the the

5 5 pellets pellets through through aa moving moving stream stream of gas. of gas. The The gas stream gas stream may bemay be entirely almost almost entirely carbon carbon

dioxide (e.g. “pure” dioxide (e.g. or "purified" "pure" or “purified” carbon dioxide), or carbon dioxide), or it it may becarbon may be carbondioxide dioxidemixed mixed with with

an inert an inert carrier carrier gas gas such as argon such as argonorornitrogen. nitrogen.As As used used herein herein the the termterm “inert "inert carrier” carrier" is is 2024219865

intended to include intended to includeany anygas gaswhich which willnot will notreact reactwith withthe thecarbon carbon dioxide, dioxide, or or the the materials materials

in in the greenpellet. the green pellet. Typically, Typically,however, however,thethe carbon carbon dioxide dioxide will will comprise comprise in theinrange the range 10 10 about70 about 70wt% wt%to to about about 100 100 wt% wt% of theofgas thestream, gas stream, often 80 often about about 80 to99about to about 99 wt%, or wt%, or about90 about 90totoabout about9595 wt%, wt%, to maximise to maximise the contact the contact between between the reactive the reactive carbon carbon dioxide dioxide gas andthe gas and thepellets, pellets,thereby therebyensuring ensuring that that hardening hardening occurs occurs as quickly as quickly as possible, as possible, and and

that the that the time timetaken takenfor forcuring curingstep step (iii) is (iii) is minimised. minimised.OneOne advantage advantage of utilising of utilising a gasa gas streamisis that stream that the thecarbon carbondioxide dioxide supply supply is is continually continually replenished, replenished, this this would would not not occur occur

15 15 where,for where, for instance, instance,the thepellets pellets were wereplaced placedinina asealed sealed chamber chamber and and allowed allowed to react to react in in a static a static atmosphere atmosphere ofofcarbon carbon dioxide. dioxide.

It It will willoften often be be the the case that curing case that curingofofthe thepellet pelletby bycontacting contacting the the pellet pellet with with gaseous gaseous

carbon dioxideoccurs carbon dioxide occurs by by introducing introducing the the pellets pellets into into a stream a gas gas stream comprising comprising carbon carbon

20 20 dioxide at dioxide at aa flow flow rate rate in in the the range about1 1totoabout range about about 100 100 litres litres per per minute, minute, often often about about 2 2 to about to 50litres about 50 litres per per minute, minute,ororabout about 2 to 2 to about about 20 litres 20 litres perper minute. minute. At these At these rates, rates,

there is there is sufficient sufficientcarbon carbon dioxide dioxide present to ensure present to goodcontact ensure good contact with with the the pellets,without pellets, without undue unreacted undue unreacted carbon carbon dioxide dioxide passing passing beyond beyond the point the point of contact of contact (suchitthat (such that it would would

need tobe need to berecirculated recirculatedtotoavoid avoidwaste). waste). Flow Flow rates rates would would be adapted be adapted within within this range this range

25 25 for the for pellet load the pellet load being being cured, cured, pellet pelletvolume, volume, residence residence time, time, pressure used, and pressure used, and temperature,asaswould temperature, would be be understood understood by skilled by the the skilled reader. reader.

The curing The curingofofthe thepellet pelletmay may be atmospheric be at at atmospheric pressure, pressure, although although it will beoften it will often at be at slightly increased slightly increased pressure, for instance pressure, for in the instance in the range about1 1Bar range about Bartotoabout about3 3 Bar Bar (1 (1 Bar Bar = = 30 30 0.1 MPa),often 0.1 MPa), oftenabout about1.5 1.5Bar Bar toto about about 2.52.5 BarBar or or about about 1.5 1.5 Bar Bar to about to about 2 Bar. 2 Bar. At these At these

pressures carbon pressures carbon dioxide dioxide penetration penetration of the of the pellets pellets is is enhanced enhanced relative relative to atmospheric to atmospheric

pressure. Pressures pressure. Pressures would would be adapted be adapted within within this this rangerange forpellet for the the pellet load load beingbeing cured,cured,

pellet pellet volume, residencetime, volume, residence time, carbon carbon dioxide dioxide flowflow rate, rate, and and temperature, temperature, as be as would would be understood understood byby the the skilledreader. skilled reader. 35 35 Thepellets The pellets will will remain remainininthe the gas gas stream stream untiluntil the the hardening hardening reaction reaction (i.e. silicate (i.e. silicate to to carbonatetotosubsequently carbonate subsequently liberate liberate silica)has silica) has progressed progressed to the to the point point where where the pellets the pellets

are sufficiently are sufficiently strong. strong. This This would would depend depend upon upon the the load pellet pellet load being being cured, cured, pellet pellet 13

volume,pressure, volume, pressure,carbon carbon dioxide dioxide flow flow rate, rate, and and temperature, temperature, as would as would be understood be understood by by theskilled the skilledreader. reader.

Whilst the Whilst the pellets pellets can be cured can be curedatatambient ambient temperature temperature (cold-formed), (cold-formed), for for somesome 5 5 formulationsthis formulations this would wouldrequire requireanan extended extended curing curing timetime to provide to provide the desired the desired levelslevels of of strength. strength. AsAs such, such, it may it may becase be the the that casethe that stepthe of step curingofthe curing pelletthe pellet (step (step iii), iii),

additionally comprises additionally theapplication comprises the applicationofofheat heatatata atemperature temperature in the in the range range about about 50°C 50°C 2024219865

to about to about1000°C. 1000°C. Heating Heating the pellets the pellets during during contact contact with with the the gaseous gaseous carbon carbon dioxide dioxide reducesthe reduces thecuring curingtime. time. 10 10 Theterm The term"cold-formed" “cold-formed” means, means, for example, for example, without without curing, sintering, curing, sintering, or toheating or heating to above about50°C above about 50°Cororabove above about about 40°C 40°C or about or about 30°C, 30°C, such such that pellet that the the pellet wouldwould generally, if generally, if any any heat wereapplied, heat were applied,bebeheated heatedto to less less than than 50°C. 50°C. In other In other words, words, it it may may often be often be the the case casethat thatifif there there is is an application of an application of heat heat during duringpellet pellet formation, formation,only onlylow low 15 15 levels levels of of heat heat will willbe beapplied. applied. Further, Further, when thepellet when the pellet is is formed, althoughfrictional formed, although frictional heat heat may begenerated may be generatedby by anyany pressing pressing and/or and/or extrusion extrusion processes processes used, used, and theand the may binder binder may undergo exothermic undergo exothermic reactions reactions in situ, in situ, this this willsometimes will sometimes be the be the onlyonly heat heat present, present, and and

does not does notconstitute constituteheating heatingasas noted noted above above asisit not as it is not thethe application application of external of external heat. heat.

These inherent These inherent heating heating mechanisms wouldnot mechanisms would notbe beexpected expectedto to generate generate enough enoughheat heatto to 20 20 impact theformation impact the formationofofthe thepellet. pellet.The The advantage advantage of cold-forming of cold-forming is significant is significant in terms in terms

of reduction inin energy of reduction energy expenditure expenditure relative relative to induration to the the induration manufacture manufacture techniques techniques

commonlyused. commonly used.There Thereisisalso alsono noneed needfor forhigh-temperature high-temperaturefurnaces furnacestotoproduce producethe the pellet, pellet, resulting in aa simpler resulting in simplerandand moremore economically economically and environmentally and environmentally beneficial beneficial

manufacturing process. manufacturing process.

25 25 However, similarlytotothe However, similarly theuse useofofcarbon carbon dioxide dioxide from from industrial industrial processes processes as described as described

above,those above, thoseprocesses processes also also produce produce excess excess heat, heat, which which couldcould be utilised be utilised in heating in heating the the pellets pellets during during the curing step the curing step of of the the invention invention thereby therebymitigating mitigatingthe the heat heat expenditure expenditure

of the of the industrial industrial process process by engineeringthe by engineering thesystem system (for (for instance instance through through the the use use of of 30 30 heat exchangers) heat exchangers) toto reuse reuse waste waste heat heat produced produced elsewhere. elsewhere. As it As such, such, may it bemay the be the case case

that the that the application application of of heat comprisesapplication heat comprises applicationofofheat heatgenerated generated from from one one or more or more

industrial industrial processes, for instance processes, for fromthe instance from thesteel steel or or iron iron making makingindustries. industries.As As noted noted

above,it above, it may thereforebebe may therefore advantageous advantageous to heat to heat the pellets the pellets during during curing curing to a to a temperature temperature ininthe therange range about about 50°C 50°C to about to about 1000°C. 1000°C. It may It bemay be the the case case that thethat the 35 35 pellets pellets are are heated duringcuring heated during curingtotoaatemperature temperaturein in thethe range range about about 60°C60°C or about or about

100°C toabout 100°C to about900°C, 900°C, often often about about 150°C 150°C to about to about 800°C,800°C, often 200°C often about aboutto200°C about to about

600°C, oroften 600°C, or oftenabout about200°C 200°C to to about about 400°C. 400°C. It be It may maythebecase the that casethe that the pellets pellets are are heated duringcuring heated during curingtotoa atemperature temperature in the in the range range about about 400°C400°C to about to about 800°C, or 800°C or

14

about600°C about 600°Ctoto about about 800°C. 800°C. At these At these temperatures temperatures it is it is possible possible to cure to cure pellets pellets in a in a few minutes, few minutes,for forinstance instanceininabout about3030 seconds seconds to about to about 30 minutes, 30 minutes, oftenoften aboutabout 1 1 minute toabout minute to about1515 minutes minutes or about or about 2 minutes 2 minutes to about to about 10 minutes, 10 minutes, such such that that pellet pellet

formationis formation is very very rapid rapid compared comparedto to thethe longer longer curing curing times times (hours, (hours, in some in some casescases

5 5 days) that days) that can canbe beneeded needed where where heatheat is not is not usedused as part as part of the of the process. process.

Theprocess The processofofthe theinvention invention includes includes thethe step step of compressing of compressing the substrate the substrate mixture mixture to to 2024219865

form the form the pellet. pellet. This This may be via may be via any any of of aa range range of of compressive compressive techniques, techniques, such such as as passing the passing thesubstrate substratemixture mixture through through compressive compressive wheelswheels (such (such as on a as on apress), roller roller press), 10 10 compressive screws, compressive screws, hammer hammer mills,mills, a hydraulic a hydraulic press,press, a mechanical a mechanical press, press, or or pressure pressure

plates. Thepellet plates. The pelletmay maybe be formed formed by extrusion, by extrusion, such such that that therethere is a step is a step of forming of forming the the pellet pelletcomprising comprising extruding extrudingthe themixture. mixture. The extrusion process The extrusion process may take place may take place at at aa temperature temperature ininthe therange range of of about about 30°C 30°C to about to about 70°C,70°C, oftenoften in range in the the range of about of about 35°C 35°C to about to about55°C, 55°C,the the temperature temperature increases increases arising arising from from frictional frictional heat heat generated generated during during

15 15 the extrusion the extrusionprocess. process.Further Further thethe process process may may take place take place at atmospheric at atmospheric pressurepressure or or under vacuum.AsAsused under vacuum. used herein,the herein, theterm term"under “undervacuum" vacuum” takes takes itsnormal its normalmeaning meaning in in

the art, the art, in inthat thatthe theextrusion extrusionprocess process may beconducted may be conductedat at pressure pressure less less than than atmospheric atmospheric

pressure. One pressure. One method method thatthat may may be be is used used is a roller a roller pressing pressing process process (RPP), (RPP), whereinwherein the the step of step of compressing thesubstrate compressing the substrate mixture mixture comprises comprises passing passing the mixture the mixture through through a roller a roller

20 20 press configuredtotoproduce press configured produce pellets. pellets. TheThe rollers rollers exert exert continuous continuous pressure, pressure, forming forming the the substrate mixture substrate mixtureinto intopellets pelletsasasthey they pass pass through through the between the gap gap between the rollers. the rollers. This This methodallows method allows forcontinuous for continuous production production andand can can handle handle a variety a variety of materials, of materials, producing producing

pellets pellets with consistent size with consistent size and anddensity. density. Another Another method method thatbemay that may used be is used is a cold- a cold-

pressing technique(CTS), pressing technique (CTS), where where the the substrate substrate mixture mixture is placed is placed in a mould in a mould or die and or die and

25 25 subjectedto subjected to high highpressure pressureusing usinga ahydraulic hydraulic oror mechanical mechanical press. press. TheThe pressure pressure compacts compacts

the material the material into into aa solid solid pellet pelletwithout without the the use use of of heat heat ensuring thepellets ensuring the pellets are are dense denseand and cohesive. This cohesive. This method methodis is advantageous advantageous due due to toenergy its its energy efficiency, efficiency, as itas it eliminates eliminates the the need for heating. need for heating.

Whena aRPP When RPP method method is adopted, is adopted, the hydraulic the hydraulic pressure pressure applied applied in stepin(ii) stepmay (ii)often may be often be 30 30 in in the the range about5050 range about Bar Bar to to about about 300 300 Bar,Bar, often often in range in the the range about about 100 100 Bar to Bar aboutto about

250 Bar,or 250 Bar, or about about150 150 Bar Bar to to about about 200200 Bar.Bar.

Whena aCTS When CTS method method is adopted, is adopted, pressure pressure is calculated is calculated under under 6 tonnes 6 tonnes force. force. The pressure The pressure

under under 66tonnes tonnes force force willvary will vary depending depending on size on the the of size ofdie the theused die (i.e. used the (i.e.internal the internal diameterofofthe diameter thedie). die). For For instance, instance, for for aa 10 10 mm mm die, die, the the pressure pressure applied applied in step in step (ii)may (ii) may 35 35 be in the be in rangeabout the range about6000 6000 BarBar to about to about 80008000 Bar, Bar, oftenoften aboutabout 6500 6500 Bar to Bar to7500 about about 7500 Bar. For aa 16 Bar. For 16 mm mm die, die, thethe pressure pressure applied applied in step in step (ii)(ii) maymay bethe be in in the range range aboutabout 2000 2000

15

Bar to about 5000 Bar, often in the range about 2500 Bar to about 4000 Bar, often in the range 2750 Bar to 3500 Bar. For a 20 mm die, the pressure applied in step (ii) may be in the range about 800 Bar to about 3500 Bar, often in the range about 1000 Bar to about 3000 Bar, often in the range about 1500 Bar to about 2500 Bar.

5 It may be the case that, prior to step (iii) of the process according to the first aspect of the invention, the pellets are subjected to an inert atmosphere. As used herein, the term “inert atmosphere” takes its usual meaning in the art and relates to an environment that 2024219865

contains gases that are non-reactive under specific conditions, more specifically gases which will not react with the carbon dioxide, or the materials in the green pellet. 10 Incorporation of this additional step prior to step (iii) can prevent any unwanted side reactions, enhancing the quality of the resultant pellet. It may be the case that subjecting the pellets to an inert atmosphere occurs by introducing the pellets into an inert gas stream at a flow rate in the range about 1 litre to about 100 litres per minute, often about 2 litres to about 50 litres per minute, or about 2 litres to about 20 litres per minute. In 15 instances where the process comprises an additional step of subjecting the pellets to an inert atmosphere, the pellets may be heated to a temperature in the range about 50°C to about 1000°C, about 60°C, or often about 100°C to about 800°C, often about 150°C to about 700°C, or more often about 200°C to about 600°C, prior to contact with gaseous carbon dioxide. The gas used to provide the inert atmosphere may comprise nitrogen or 20 argon. It may be the case that the gas used to provide the inert atmosphere comprises nitrogen.

It may be the case that the process may further comprise the additional step (iv) of cooling the resultant pellets under an inert atmosphere. It may be the case that the inert 25 atmosphere comprises nitrogen or argon. It will often be the case that the inert atmosphere comprises nitrogen. Cooling under an inert atmosphere is advantageous, as it prevents any unwanted reactions from occurring. Processing in an inert atmosphere is frequently employed in experimental conditions due to the ease of controlling the atmosphere in small-scale reactions.

30 In a second aspect of the invention there is provided a pellet obtainable by a process according to the first aspect of the invention, and in a third aspect of the invention, a pellet comprising a particulate material selected from a carbonaceous material, metal, metal ore, and mixtures thereof; silica; and a metal carbonate, and an organic binder, wherein the organic binder comprises a natural polymer, a synthetic polymer, a 35 glycerolipid, a cellulosic material, and combinations thereof. The pellets of the second and third aspects of the invention have been found to have a unique chemical structure,

as described above. The reaction of the metal silicate with carbon dioxide provides for a metal carbonate and silica, this being believed to form bonds with the particulates, for instance with the metal/metal oxides in metal-containing particulates that would not exist in the absence of the curing in carbon dioxide. 5 Often the silica will be present as discrete particles, the surface of which is generally bonded via hydrogen bonds between hydroxyl groups present in the particulate material 2024219865

and oxide groups in the silicate, forming a composite material.

10 The volume and dimensions of the pellets will be dependent upon the end use of the pellets. For instance, pellets for steelmaking will generally be larger than pellets for DRI as in steelmaking the pellets must have sufficient mass to submerge into the molten steel. Typically pellets have an average volume in the range about 2.5 to about 25 cm3, often in the range about 3 to about 15 cm3, or about 5 to about 10 cm3. The pellets will 15 generally be sized to minimise surface area, and will often be, for instance, roughly spherical, ovoid, cylindrical or cubic structures.

Unless otherwise stated, each of the integers described may be used in combination with any other integer as would be understood by the person skilled in the art. Further, 20 although all aspects of the invention preferably "comprise" the features described in relation to that aspect, it is specifically envisaged that they may "consist" or "consist essentially" of those features outlined in the claims. In addition, all terms, unless specifically defined herein, are intended to be given their commonly understood meaning in the art. 25 Further, in the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, is to be construed as an implied statement that each intermediate value of said parameter, lying between the smaller and greater of the alternatives, is itself also 30 disclosed as a possible value for the parameter.

In addition, clearly excluded, all numerical values appearing in this application are to be understood as being modified by the term "about". The term "wt%" and analogous terms is intended to mean the percentage of the component by weight in the final pellet by 35 weight. If additives, impurities, and/or water are present in the particulate starting material in step (i), the term “wt%” includes said additives, impurities and/or water.

Brief Brief Description of the Description of the Drawings Drawings In order In order that that the the invention inventionmay maybe be more more readily readily understood, understood, it will it will be described be described further further

with reference with referenceto to the thefigures figures and andtotothe thespecific specific examples examples hereinafter. hereinafter.

5 5 Figure Figure 1 1isisaaschematic schematic diagram diagram of aoflaboratory a laboratory testtest rig rig forfor thethe process process of the of the invention invention

(iron (iron ore ore test test rig rigfrom from ITR ITR equipment, Poland); equipment, Poland); 2024219865

Figure Figure 2 2isisan anexploded exploded schematic schematic diagram diagram of theoftest therig testofrig of Figure Figure 1, focusing 1, focusing on the on the

furnace; furnace;

10 10 Figure Figure 33 is is an an XRD/SEM XRD/SEM to to show show carbonate carbonate formation formation as as a function a function of of relative%%ofof relative carbonate/silicate in the carbonate/silicate in the pellet. pellet. The Thepellet pellet on onthe theleft left of of the the image imagewas was cured cured in carbon in carbon

dioxide, and dioxide, is crystalline, and is crystalline, indicating indicatingcarbonate formation.The carbonate formation. The pelletonon pellet the the right right ofofthe the image was image was cured cured in in air,and air, and there there isisnono indicationofofcarbonate indication carbonate formation; formation;

Figure Figure 4 4isisan anoptical optical microscope microscope image image 12001200 x 1200 X 1200 pixels, pixels, 140 magnification 140 magnification showingshowing

15 15 carbonateformation carbonate formationonon thethe surface surface of of thethe leftpellet left pelletofofFigure Figure3 3after afterpartial partial curing; curing; Figure Figure 5 5isisan anoptical optical microscope microscope image image 12001200 x 1200 X 1200 pixels, pixels, 140 magnification 140 magnification showingshowing

thesurface the surfaceof of thethe left left pellet pellet of Figure of Figure 3 after 3 after curingcuring is complete; is complete;

Figure Figure 66is is aa magnified magnifiedoptical opticalmicroscope microscope image image of the of the surface surface of the of the left left pelletofoffigure pellet figure 3 showingcarbonate 3 showing carbonate formation formation on the on the surface; surface;

20 20 Figure Figure 7 7isis aa graphical graphicalrepresentation representationofof theoutcomes the outcomes of Test of Test ID No. ID No. 1 to1Test to Test ID No. ID No.

8, highlighting 8, highlighting how thecuring how the curingatmosphere atmosphereand and duration duration influence influence pellet pellet cold cold crushing crushing

strength (CCS). strength (CCS).Specifically, Specifically, Figure Figure 7(a) 7(a)is is aa graphical graphical representation representationofofTest TestIDIDNo. No. 1 1 (i.e. (i.e.cured cured under CO2)and under CO2) andTest TestIDID No. No. 2 (i.e.cured 2 (i.e. cured under under air) air) atat 200°C; 200°C; Figure7(b) Figure7(b) is ais a

graphical representation graphical representationofofTest TestIDIDNo. No.3 3(i.e. (i.e.cured curedunder under COand CO2) 2) and TestTest ID No. ID No. 4 (i.e. 4 (i.e.

25 25 cured under cured underair) air)at at 400°C; 400°C; Figure Figure 7(c) 7(c) is isa agraphical graphicalrepresentation representation of of Test Test ID ID No.No. 5 5 (i.e. (i.e.cured cured under CO2)and under CO2) andTest TestIDID No. No. 6 (i.e.cured 6 (i.e. cured under under air) air) atat 600°C; 600°C; and and Figure Figure

7(d) is 7(d) is aa graphical graphical representation of Test representation of TestID IDNo. No.7 7(i.e. (i.e. cured curedunder underCO2) CO2and ) and Test Test ID ID No. No. 88 (i.e. (i.e. cured cured under air) at under air) at 800°C; and 800°C; and

Figure Figure 8 8isis aa graphical graphicalrepresentation representationofof thecold the coldcrushing crushing strength strength (CCS) (CCS) of pellets of pellets

30 30 containing different containing different silicates/silicate silicates/silicate combinations combinations under different curing under different curing conditions. conditions. The The bar chart (i) bar chart (i) on on the the left-hand side shows left-hand side showsthe theCCS CCSof of pelletscomprising pellets comprising solid solid sodium sodium

silicate (black silicate (blackfill), fill),a combination a combinationofof liquid sodium liquid sodiumsilicate silicateand andmagnesium silicate magnesium silicate

(diagonal stripes ascending (diagonal stripes ascendingfrom from lefttotoright), left right), and andaacombination combinationof of liquidsodium liquid sodium silicate and silicate and calcium silicate (horizontal calcium silicate (horizontal stripes) stripes)when cured under when cured underair airin in an anoven ovenfor for120 120 35 35 minutes. Thebar minutes. The barchart chart(ii) (ii) on onthe theright-hand right-handside sideshows shows thethe CCSCCS of pellets of pellets comprising comprising

solid sodium solid silicate (black sodium silicate (black fill), fill), a combination a combination of ofliquid liquidsodium sodium silicate silicateand and magnesium magnesium

silicate (diagonal silicate (diagonal stripes stripes ascending fromleft ascending from left to to right), right), aa combination of liquid combination of liquid sodium sodium

silicate and silicate andcalcium calcium silicate silicate (horizontal (horizontal stripes), stripes), magnesium magnesium silicate stripes), silicate (vertical (vertical stripes), 18

and calcium and calciumsilicate silicate (diagonal (diagonal stripes stripes descending descending from from lefttotoright) left right)when when cured cured under under

CO2in CO2 in the the ITR ITRrig. rig.

Detailed Description Detailed Description 5 5 Examples Examples 2024219865

Theexamples The examples described described herein herein include include thethe formation formation of green of green ironiron ore ore pellets, pellets, which which were were

agglomerated agglomerated at at ambient ambient temperature temperature by either by either a roller-press a roller-press or a cylindrical or a cylindrical die press. die press.

10 10 As used As usedherein, herein,the theterm term “ambient "ambient temperature” temperature" takes takes its usual its usual meaning meaning in the in the art and art and refers to the refers to the temperature temperatureof of thethe airair surrounding surrounding a component a component and iswithin and is often oftenthe within the range 15°C- -25°C). range 15°C 25°C). The The green green pellets pellets werewere cured cured underunder controlled controlled conditions, conditions, including including

under under aastream streamofofCO2 COgas, 2 gas, andand various various physical physical properties properties werewere measured. measured. Specifically, Specifically,

the cold the cold crushing crushingstrength strength (CCS), (CCS), thermal thermal durability, durability, water water resistance resistance and appearance and appearance

15 15 under anoptical under an optical microscope microscopewaswas measured. measured.

Methodology Methodology

FormationofofGreen Formation Green Pellets Pellets

20 20 Formation Formation ofofthe thegreen green pelletsinvolves pellets involvesthorough thorough mixing mixing of iron of iron ore ore particles particles with with binder binder

materials to form materials to forma ablend. blend. TheThe blend blend is pressed is pressed into agglomerates into agglomerates to form to theform greenthe green

pellets. pellets.

25 25 Two methods Two methodsofofagglomeration agglomeration(both (bothconducted conducted at at ambient ambient temperature) temperature) used used in the in the examples described examples described herein herein areare (i)(i)cylindrical cylindrical test test specimens (CTS), specimens (CTS), formed formed by by a cylindrical a cylindrical

die-press, and(ii) die-press, and (ii) roller-pressed roller-pressed pellets pellets (RPP), (RPP), formed byaaroller-press. formed by roller-press.

(i) (i) CTS CTS 30 30 A measured A measured mass mass of iron of iron ore ore particles particles is is mixed mixed withwith a binder, a binder, or binders, or binders, using using a Hobart a Hobart

N50-G mixer,on N50-G mixer, onspeed speedsetting setting2,2,for for 33minutes. minutes.A Aportion portionofofthe theresulting resulting blended blended material is placed material is placedinto intoa astainless-steel stainless-steelcylindrical cylindricaldie, die,ofofheight height90 90 mm mm and internal and internal

diameter 20 diameter 20 mm, mm,so so that that thethe material material fills the fills thedie diewithout withoutcompaction. compaction.A A Baileigh Baileigh 35 35 Industrial Industrial H-Frame H-Frame 2020 Ton Ton Shop Shop Press Press (equivalent (equivalent to HSP-20A) to HSP-20A) is usedistoused pushto a push pistona piston

downinto down intothe thedye dyeand and compact compact the the material. material. The The pressure pressure is 1,873 is 1,873 Bar (i.e. Bar (i.e. 187.3187.3 mPa) mPa) calculated under calculated under 6 tonnes 6 tonnes force.force. Specifically, Specifically, pressure pressure is to is applied applied to the the piston piston until until a force a force

equivalent to equivalent to 66 Tonnes Tonnes(metric (metricTons) Tons)isismeasured. measured. Upon Upon reaching reaching this this value, value, the the pressure pressure

19

is is immediately released.The immediately released. TheBaileigh Baileighpress press isisthen then used used to to push push thethe agglomerated agglomerated pelletpellet

of material of fromthe material from thedie. die. This This process processisis repeated repeatedsosothat thata anumber number of pellets of pellets areare formed formed

fromthe from theblended blended batch batch of of material. material.

5 5 (ii) (ii) RPP RPP

Theiron The iron ore ore and andbinder binderformulation formulationwere were mixed mixed for for 3 minutes 3 minutes in ainWirtgen a Wirtgen WLM30 WLM30 paddle paddle 2024219865

mixer (highshear mixer (high shear4545 rotations rotations perper minute minute (rpm)). (rpm)). Once Once the mixing the mixing was completed, was completed, the the material was material wasremoved removed from from the the mixer mixer and samples and samples were produced were produced as as follows. follows.

10 10 Material Material was fed into was fed into aa hutt hutt roller rollerpress press at at160 160 Bar Bar gauge pressuretotoproduce gauge pressure produce ovoid ovoid roller roller

pressed pellets at pressed pellets at aa size size of of approximately 27x18x10 approximately 27x18x10 mm (4.86 mm (4.86 cm³). cm 3).

Pellets Pellets were transferredtotothe were transferred theCO2CO 2 curing curing stage stage within within 1 hour 1 hour of production. of production. The gasThe gas

stream comprised stream comprised100% 100% carbon carbon dioxide dioxide at at a flow a flow rate rate of of approximately approximately 5 litresper 5 litres per minute,at minute, at atmospheric atmospheric pressure. pressure.

15 15 Thetest The test rig rig synthesis is readily synthesis is readily scalable, scalable, for for instance instance to to recycle recycle carbon dioxide produced carbon dioxide produced as off-gas as off-gas in in industrial industrial processes by aa suitably processes by suitably engineered engineereddesign. design.

Curing of Curing of Pellets Pellets

(i) (i) Curing under Curing underananair airatmosphere atmosphere (comparative) (comparative)

20 20 To simulate To simulatetypical typicalcuring curingconditions conditions under under an air an air atmosphere, atmosphere, pellets pellets are placed are placed on a on a metal tray metal tray within within aa vented venteddrying dryingoven ovenatat a a specifiedtemperature specified temperaturefor for a specified a specified duration duration

with no with no forced forcedgas gasflow. flow.

25 25 (ii) (ii) Curing in Curing in the the presence presenceofofgaseous gaseous carbon carbon dioxide dioxide

To cure To curepellets pellets under undercarbon carbon dioxide, dioxide, a test a test rigrig isisused. used. Schematic Schematic diagrams diagrams oftest of the the test rig are rig are found in Figures found in Figures 11 and and2. 2.The Thegeneral general procedure procedure is as is as follows: follows:

30 30 500 500 ggsamples samplesof of green green pellets pellets 16 16 werewere placed placed in reactor in the the reactor 2 (such 2 (such as a retort), as a retort), on a on a

bed of ceramic bed of ceramic beads 17and beads 17 andthe thesystem systempower power modules modules 14 14 activated activated viavia thethe master master switch 4. switch 4. Gas Gasflow flowthrough throughthethe reactor reactor was was initiated initiated by process by process startstart button button 8. Heating 8. Heating

of the of the sample tothe sample to thedesired desiredtemperature temperature is carried is carried outout under under a flow a flow of Nat of N2, 2, a atrate a rate of of 5 5 l/min at I/min at atmospheric atmospheric pressure, pressure, entering entering via via gas gas inletinlet 3 exiting 3 and and exiting through through outlet outlet 18. 18. 35 35 Oncethe Once thedesired desiredtemperature temperature is attained, is attained, thethe gasgas input input is switched is switched fromfrom N2 toN CO2, 2 to CO at 25, at 5

20

l/min and I/min atmospheric pressure and atmospheric pressurevia via gas gasinlet inlet 3, 3, exiting exiting through gas outlet through gas outlet 18. The 18. The temperature temperature was was controlled controlled by by thethe heating heating system, system, comprising comprising heating heating furnace furnace 1, heater 1, heater

off button off button 5, 5, heater on button heater on button6, 6,LED LEDindicator indicator7 7(to (toindicate indicatewhether whether the the heating heating furnace furnace

1 is on 1 is on or or off), off), temperature controller 9, temperature controller 9, temperature temperature gauge gauge 10 heater 10 and and heater transformer transformer

5 5 15. The on/off 15. The on/off buttons buttons (6 (6 & 7) are & 7) are operated manually to operated manually to maintain maintain the the sample sample at at the the desired temperature. desired temperature. The The temperature temperature was held at was held at 200°C, 200°C, 400°C, 400°C, 600°C and 800°C 600°C and 800°Cfor for residence timesofof2,2,55oror1010minutes. residence times minutes. The The process process was monitored was monitored using thermocouple using thermocouple 2024219865

10, CO2signal 10, CO2 signalLED LED 11, 11, N2 N 2 signal signal LEDLED 12 gas 12 and andflow gas meter flow meter 13. As 13. Asinshown shown in 1Figures 1 Figures

and 2. and 2. 10 10 After the After prescribedCO2 the prescribed COexposure, 2 exposure, thethe samples samples were were cooledcooled under under anatmosphere an inert inert atmosphere of N of N22 to to prevent anyfurther prevent any furtherreactions. reactions.

Optical Optical Microscopy Microscopy

15 15 Imageswere Images were captured captured on Olympus on an an Olympus DSX system DSX system in field in bright brightconfiguration. field configuration. The The scale scale is is indicated indicated onon the the illustrations. illustrations.

Carbonate Formation Carbonate Formation Observations were Observations were made fromthe made from the microscopy microscopy images, images, 3-5. 3-5. 20 20 Water Resistance Water Resistance

Samples were Samples wereimmersed immersedininwater waterfor for 11 and and 55 hours hours at at ambient ambient temperature temperatureand andtested tested for compressive for strength compressive strength afterdrying. after drying.

25 25 Cold Crush Cold CrushStrength Strength (CCS) (CCS)

TheCCS The CCSvalues values described described herein herein were were determined determined usingusing standard standard methodology methodology according according

to ISO to 4700:2015 ISO 4700:2015 using using a Mecmesin a Mecmesin Omnitest Omnitest Materials Materials Tester Tester 10. Results 10. Results are presented are presented

with units with units of of either either kilonewton kilonewton (kN) (kN) or kilogram-force or kilogram-force (kgf). (kgf). As herein, As used used herein, 1 kgf =1 kgf = 0.00980665kN. 0.00980665 kN. 30 30 Thermal Properties Thermal Properties

The thermal The thermal properties properties of of the the pellets pellets were determinedusing were determined usingstandard standardmethodology methodology accordingto according to ISO ISO4696-2:2015 4696-2:2015 using using the the testtest ITR ITR rig rig shown shown in Figures in Figures 1 and 1 and 2 below. 2 below. This This ISOprovides ISO providesa amethod method for for evaluating evaluating the the degree degree of size of size degradation degradation of ores of iron iron under ores under 35 35 conditions resembling conditions resemblingthose those of of a a low-temperature low-temperature reduction reduction zone zone in a blast in a blast furnace furnace (i.e. (i.e. in in a a reducing environment reducing environment at at 550 550 °C). °C).

21

Example Example 1 1- –Sodium Sodium silicate silicate and and magnetite magnetite

Using Using the the RPP RPP methodology above,2.0 methodology above, 2.0 wt% wt%sodium sodium metasilicatewas metasilicate wasmixed mixedwith with1010kgkg 5 5 magnetite iron ore magnetite iron ore (D v90 = (Dv90 = 186 186 µm, >97wt% um, >97 wt% Fe3O4,>68 Fe3O4,>68 wt%wt% Fe) Fe) attemperature at a a temperature of of 15°C. Theresulting 15°C. The resultingsubstrate substratemixture mixture was was formed formed intointo an an agglomerate agglomerate and cured and cured at room at room

temperature (approximately temperature (approximately 20°C). 20°C). 2024219865

Theresulting The resulting pellets pellets contained contained22wt% wt% sodium sodium metasilicate. metasilicate.

Test data Test data showed showed a partialreaction a partial reaction ofof the the sodium sodium silicate silicate to to form form sodium sodium carbonate carbonate and and 10 10 silica, asasindicated silica, indicatedby byaastrength strength increase increase of of roughly roughly 50 50 kgf kgf after after curing curing for forone one hour. The hour. The

shell was shell noticeably white, was noticeably white, indicating indicating carbonate carbonateformation, formation,asas shown shown in Figures in Figures 3 5. 3 to to 5. It It wouldbebe would expected expected that that smaller smaller pellets, pellets, of amore of a size sizetypically more typically used in industrial used in industrial

processes, wouldcure processes, would cure more more quickly quickly under under these these conditions. conditions.

Example Example 2 2- –Sodium Sodium silicate,iron silicate, ironore oreand and carboxymethyl carboxymethyl cellulose cellulose

15 15 Using Using the the RPP RPP methodology above, 10 methodology above, 10 kg kg magnetite magnetiteiron iron ore ore (D80 = 500 (D80 = 500 um, µm,>97 >97wt% wt% Fe3O4) and Fe3O4) and 2.0 2.0 wt% sodium metasilicate wt% sodium metasilicate were were mixed mixed at atambient ambient temperature. temperature. 0.25 0.25 wt% wt% carboxymethylcellulose carboxymethylcellulose was was then then added added withwith mixing mixing for afor a further further 3 minutes. 3 minutes. The resulting The resulting

substrate mixture substrate mixturewas was formed formed intointo an agglomerate. an agglomerate.

Thepellets The pellets contained contained22wt% wt% silicateand silicate and0.25 0.25- – 0.5 0.5 wt% wt% carboxymethyl carboxymethyl cellulose. cellulose. CuringCuring

20 20 was facilitated under was facilitated the test under the test conditions conditions described describedininExample Example3. 3.

Example Example 3 3- –Curing Curing with with and and without without carbon carbon dioxide dioxide at aat a range range of temperatures of temperatures

In Test In Test ID IDNo. No.1 1totoTest Test IDID No.No. 8, 8, four four different different curing curing temperatures temperatures haveused: have been been used: 200°C, 400°C, 600°C 200°C, 400°C, 600°Cand and800°C. 800°C. AtAt each each temperature, temperature, curingatmospheres curing atmospheres of of airand air and CO havebeen CO2 2 have been used. used. The The air air curing curing occurred occurred in a in a drying drying oven, oven, whilewhile the curing the CO2 CO 2 curing took took

25 25 place in an place in ITR rig, an ITR rig, as as detailed detailed above. Undereach above. Under eachofof these these conditions, conditions, samples samples of pellets of pellets

werecured were curedfor fordifferent different durations: durations:2 2mins, mins,5 5mins mins andand 10 mins. 10 mins.

In Test In IDNo. Test ID No.1,1, the the green green pellets pellets were were cured cured at approximately at approximately 200°C,200°C, at atmospheric at atmospheric

pressure, in carbon pressure, in carbondioxide dioxideasasdescribed described above. above.

30 30 In Test In TestIDIDNo. No. 2, 2, a comparative a comparative test, test, the green the green pelletspellets wereatcured were cured at approximately approximately

200°C, atatmospheric 200°C, at atmospheric pressure, pressure, in in airair (i.e.inin the (i.e. theabsence absenceofof added added carbon carbon dioxide). dioxide).

22

TestID Test IDNo. No. 3 to 3 to Test Test ID No. ID No. 8 repeated 8 repeated Test IDTest No. ID No.Test 1 and 1 and Test2 ID ID No. at No. 2 at different different

temperatures,asasshown temperatures, shown in Table in Table 1 below. 1 below. The The results results are shown are shown in Table in Table 2, of 2, each each of Test Test ID No. ID No. 2, 2, Test Test ID IDNo. No.4,4,Test TestIDIDNo. No.6 6and and Test Test ID ID No.No. 8 are 8 are comparative. comparative.

5 5 Table Table 11 -– Conditions Conditionsfor forTest TestID IDNo. No.1 1totoTest TestIDIDNo. No. 8 8

Test ID Test ID No. No. Carbon Dioxide? Carbon Dioxide? Temperature Temperature 2024219865

1 1 Yes Yes 200°C 200°C 2 2 No No 200°C 200°C 3 3 Yes Yes 400°C 400°C 4 4 No No 400°C 400°C 5 5 Yes Yes 600°C 600°C 6 6 No No 600°C 600°C 7 7 Yes Yes 800°C 800°C 8 8 No No 800°C 800°C

Table Table 22 -– Influence Influenceof of curing curingatmosphere atmosphereandand duration duration on pellet on pellet coldcold crushing crushing strength strength

(CCS). (CCS).

10 10 Test ID Test ID No. No. 11 Test ID Test ID No. No. 22 Test ID Test ID No. No. 33 Test ID Test ID No. No. 44 CCS (kgf) -- CCS (kgf) CCS (kgf) -- CCS (kgf) CCS(kgf) CCS (kgf) -- CCS(kgf) CCS (kgf) -- 200°C 200°C 200°C 200°C 400°C 400°C 400°C 400°C Green Strength Green Strength 26.5 26.5 2 2 minutes minutes 148 148 6 6 135 135 14 14 5 5 minutes minutes 136 136 6 6 134 134 72 72 10 10 minutes minutes 148 148 7 7 171 171 85 85 Test ID Test ID No. No. 55 Test ID Test ID No. No. 66 Test ID Test ID No. No. 77 Test ID Test ID No. No. 88 CCS(kgf) CCS (kgf) -- CCS(kgf) CCS (kgf)-- CCS(kgf) CCS (kgf) -- CCS(kgf) CCS (kgf) -- 600°C 600°C 600°C 600°C 800°C 800°C 800°C 800°C Green Strength Green Strength 26.5 26.5 2 minutes 2 minutes 173 173 9 9 279 279 125 125 5 5 minutes minutes 212 212 126 126 260 260 100 100 10 10 minutes minutes 212 212 145 145 255 255 108 108

As can As can be beseen seenatatall all temperatures, temperatures, curing curing in in the the presence presence of of carbon carbon dioxide dioxide significantly significantly

increased thehardness increased the hardnessofofthe thepellet pelletrelative relative to to the the green greenstrength strength(Test (TestIDIDNo. No. 1,1, TestIDID Test

23

No. 3, Test No. 3, Test ID ID No. No.55and andTest Test IDID No.No. 7) 7) andand relative relative to to thethe comparative comparative teststests wherewhere the the pellets pellets are are not exposedtotocarbon not exposed carbon dioxide dioxide (Test (Test ID No. ID No. 2, Test 2, Test ID4,No. ID No. 4, ID Test Test No.ID 6 No. 6

and Test and TestID IDNo. No.8). 8).

5 5 Further, these increases Further, these increasesare areseen seen in in very very short short periods periods of time, of time, justjust two two minutes, minutes, with,with,

in in many cases,little many cases, little improvement being improvement being observed observed with with longer longer exposure exposure times,times, such that such that

exposing exposing thethe pellets pellets to carbon to carbon dioxide dioxide fora just for just a few minutes few minutes is sufficient is sufficient to provideto provide pellets pellets 2024219865

that can that be handled can be handledand and transported transported as as needed. needed. ThisThis implies implies thatthat exposing exposing pellets pellets to to CO2 CO 2 for just for just a a few minutesisissufficient few minutes sufficient to to produce producepellets pelletsstrong strong enough enough to handled to be be handled and and 10 10 transportedasasrequired transported requiredbyby the the industry. industry. This This is is vitallyimportant, vitally important,asas pelletmanufacture pellet manufacture often occurs often occursat at the theiron iron ore oremining mining siteand site and pelletsmust pellets must therefore therefore be able be able to withstand to withstand

transportation to transportation to the the ironmaking ironmaking site,which site, which can can be be a large a large distance distance away. away.

Further, whilst curing Further, whilst curing at at 200°C 200°Cprovides provides forpellets for pelletswhich which are are sufficientlystrong sufficiently strongtotomeet meet 15 15 the criteria the criteria for fortransport transport and and handling, if greater handling, if greater strength wererequired, strength were required,the thedata datashows shows that this that this can can be beobtained obtainedby by increasing increasing the the curing curing temperature, temperature, with with the the highest highest CCS CCS values observed values observed forcuring for curing at at 800°C. 800°C. Therefore, Therefore, for pellet for pellet formulations formulations with awith a greater greater

resistance to curing, resistance to curing, additional additional heat heat could could be beapplied. applied.

20 20 As this As this is is early-stage data, minor early-stage data, minorvariances variances areare reported reported which which dofollow do not not follow the the trend trend and are and arebelieved believedtotobebeexperimental experimental variance. variance. For instance, For instance, in Test in Test ID No.ID1 No. 1 and and Test Test ID No. ID No. 33the the5-minute 5-minute value value is is lower lower than than the the 2- and 2- and 10- minute 10- minute values, values, orIDTest or Test No. ID No. 2, Test 2, Test ID IDNo. No.4 4and and Test Test ID No. ID No. 6 where 6 where the initial the initial results results are lower are lower than than the the green green strength; however, strength; however, ititis is clear clear that that the overall trend the overall supportsthis trend supports this methodology methodology leading leading to to

25 25 increased strengthover increased strength overtime. time.

The outcomes The outcomesofofTest TestIDID No.No. 1 Test 1 to to Test ID No. ID No. 8, which 8, which highlight highlight how how the curing the curing atmosphere atmosphere andand duration duration influences influences pellet pellet strength strength (CCS), (CCS), are shown are shown in Figures in Figures 7(a) to7(a) to 7(d). 7(d).

30 30 Example Example 4 4- –Impact Impactof of curing curing in in carbon carbon dioxide dioxide on on water water resistance resistance

Theimpact The impactofofCO2 CO2curing curingononthe thewater water resistance resistance of of pelletswas pellets was investigated investigated on on thethe pellets pellets

of Test of ID No. Test ID No.55(10-minute (10-minute exposure exposure to carbon to carbon dioxide) dioxide) andIDTest and Test No. ID No. 6 (10-minute 6 (10-minute

35 35 exposure exposure totoair). air). The Thepellets pellets of of Test Test ID IDNo. No.5 5and and Test Test IDID No.No. 6 were 6 were thenthen measured measured for for water resistance water resistancebybyimmersion immersionforfor 1 hour. 1 hour. The The results results are are in Table in Table 3 below. 3 below.

24

Table Table 33 -– Water Waterresistance resistancetest testfor forTest TestIDIDNo. No.5 5 and and Test Test ID ID No.No. 6 6

Test ID Test ID Duration Duration of of Immersion Immersion Result CCSkgf Result CCS kgf No. No. 5 5 0 hours 0 hours 212 212 1hr 1hr 109 109 2024219865

6 6 0 hours 0 hours 145 145 1hr 1hr 58 58

5 5 As can As can be beseen, seen,despite despiteimmersion immersionin in water water forfor 1 hour, 1 hour, thethe strength strength of of thethe inventive inventive pellet pellet

(Test ID No. (Test ID No.5) 5)only onlydrops dropsbyby around around 50%, 50%, remaining remaining at avalue at a CCS CCSthat value thatenable would would enable transport, storage, transport, storage,and andhandling handling without without lossloss of integrity. of integrity. The The comparative comparative test pellet test pellet

(Test ID No. (Test ID No. 6) 6) however, however, drops drops by by roughly roughly 60%,60%, a much a much largerlarger drop drop in in relative relative strength, strength,

and to and to aa level level where thereisisaarisk where there risk of of degradation duringhandling. degradation during handling. 10 10 Example Example 5 5- –Impact Impactof of curing curing in in carbon carbon dioxide dioxide on on the the thermal thermal properties properties of of the pellets the pellets

The thermal The thermalproperties propertiesofofthe thepellets pelletsofofTest TestID IDNo. No.5 5and and Test Test IDID No. No. 6 were 6 were determined determined

15 15 in in order to confirm order to confirmthat thatthere thereisisnonoloss lossofofhot hotstrength strength forfor thethe pellets pellets cured cured in carbon in carbon

dioxide. The dioxide. Thepellets pelletswere were subjected subjected to to reduction reduction conditions conditions as per as per the the RDI RDI ISO and ISO test test and subsequentlytested subsequently testedfor forCCS. CCS.TheThe results results areare shown shown in Table in Table 4 below. 4 below.

Table Table 44 -– Thermal Thermalproperty property test test forTest for Test IDID No. No. 5 and 5 and Test Test ID No. ID No. 6 6 20 20 Test Test CCSpre-reduction CCS pre-reduction(kgf) (kgf) CCS post-reduction CCS post-reduction (kgf) (kgf) ID No. ID No. 5 5 212 212 146 146 6 6 145 145 128 128

Theseresults These resultsshow show that that whilst whilst thethe expected expected low-level low-level degradation degradation occurred occurred during during this this test (20 test – 30%), (20 - 30%),neither neither testshowed test showed a significant a significant loss loss in in pelletstrength, pellet strength, indicating indicating that that

curing in carbon curing in dioxidehas carbon dioxide hasa aminimal minimal impact impact on the on the thermal thermal properties properties of pellets. of the the pellets. 25 25

25

Example Example 6 6- -Analysis AnalysisofofMetal MetalSilicates SilicatesUnder UnderVaried Varied Curing Curing Conditions Conditions

This study This studyshows showsthethe effect effect of of curing curing in ainCO2 a CO 2 atmosphere atmosphere in the in ITRthe rig ITR for rig for 10 10 mins mins 5 5 compared compared to to curing curing in in an an airair atmosphere atmosphere in a in a drying drying oven oven formins. for 120 120 Moreover, mins. Moreover, this this study also study alsoshows showsthethe effect effect of CO of CO2 2 curing curing on different on different types types of of silicate silicate bindersbinders (and (and combinations). combinations). Pellets Pellets are are formulated formulated using using CMC combinedwith CMC combined withthe the followingmetal following metal 2024219865

silicates/metal silicate silicates/metal silicatecombinations: combinations:

10 10 • Sodiumsilicate Sodium silicate (solid) (solid) • Calcium Calcium silicate silicate (solid) (solid)

• Magnesium silicate(solid) Magnesium silicate (solid) • Magnesium silicate(solid) Magnesium silicate (solid)with withsodium sodium silicate(liquid) silicate (liquid) • Calcium Calcium silicate silicate (solid) (solid) with with sodium sodium silicate silicate (liquid) (liquid)

15 15 Details of pellet Details of pellet formulations formulationsare areshown shown in Table in Table 5. Pellets 5. Pellets were were formedformed by the CTS by the CTS

method detailed method detailed above above and and cured cured (i)150°C (i) at at 150°C under under air in air in a drying a drying oven oroven (ii) or at (ii) the at the

sametemperature same temperature under under COthe CO2 in 2 inITR therig. ITRDetails rig. Details of curing of curing conditions conditions areinshown are shown in Table 5. Table 5. 20 20 Curedpellets Cured pellets were weretested testedfor forCCS, CCS, and and thethe results results areare shown shown in Table in Table 5 and 5 and Figure Figure 8. As8. As is is evident evident from the data, from the data, the theCCS CCSofof thepellets the pelletscured cured under under CO2CO 2 for for 10 10 minsmins at 150°C at 150°C in in the ITR the ITR rig rig is is greater greater than than that that of of comparative pellets cured comparative pellets curedfor for120 120mins minsat at 150°C 150°C in the in the

drying oven. drying oven.Therefore, Therefore,this thisexample example provides provides evidence evidence for increase for the the increase in brought in CCS CCS brought 25 25 aboutbybyuse about use of of thethe process process according according to thetofirst the aspect first aspect of the of the invention, invention, and alsoand also illustrates illustratesthe thespeed speed at at which which this this benefit benefitisisattained attained(10 (10 mins mins versus 120 mins). versus 120 mins). Acceleration ofofthe Acceleration thecuring curing process process is advantageous, is advantageous, as only as it not it not only increases increases pellet pellet production efficiency, but production efficiency, but also also reduces reducesoperational operationalcosts. costs.

30 30 As can As canbebeseen seen from from the the results, results, sodium sodium silicate silicate produces produces the best-performing the best-performing pellets.pellets.

Calcium silicate and Calcium silicate andmagnesium magnesium silicate silicate perform perform poorly poorly on their on their own cured own when whenincured air. in air.

However, when However, when using using thethe process process according according to invention, to the the invention, pellets pellets formed formed with calcium with calcium

silicate and silicate and with with magnesium silicateasasthe magnesium silicate themetal metal silicateshowed silicate showed a clear a clear improvement improvement in in CCS when CCS when produced produced according according to the to the process process of the of the first first aspect aspect of the of the invention. invention. 35 35 Moreover, surprisinglymagnesium Moreover, surprisingly magnesium silicate silicate when when combined combined with with liquid liquidsilicate sodium sodium silicate produced strongpellets. produced strong pellets.

26

This study This study shows shows the the effectofofcuring effect curingatat150°C 150°Cin in a CO a CO2 2 atmosphere atmosphere inITR in the therig ITRfor rig10 for 10 minutes and minutes and curing curing at at 150°C 150°C in air in an an air atmosphere atmosphere in a drying in a drying oven oven for 120for 120 minutes minutes on on the structural the structural integrity integrity of of pellets. pellets.The The results resultsare areshown belowininTable shown below Table6.6.

5 5 As can As can be be seen seenfrom fromthe theresults resultstabulated tabulated below, below,pellets pellets produced produced according according to to the the process accordingtotothe process according thefirst first aspect aspectofofthe theinvention inventionare are cured cured in in a significantlyshorter a significantly shorter time. Shorter time. Shortercuring curingtimes timeshave have key key benefits, benefits, such such as as high high energy energy savings savings and increased and increased 2024219865

production efficiency. In production efficiency. In addition, addition, pellets pellets produced accordingtotothe produced according theprocess process according according to to

the first the first aspect of the aspect of the invention inventionhave have a lower a lower RDI%. RDI%. A lowARDI% low is RDI% a keyisindicator a key indicator of of 10 10 high-quality high-quality pellets pellets that that can withstand the can withstand the demanding demanding conditions conditions of of iron-making iron-making processes, leadingto processes, leading to improved improved efficiencyand efficiency and productivity.Pellets productivity. Pelletsfabricated fabricatedaccording accordingtoto

the process the processaccording accordingtotothe thefirst first aspect of the aspect of invention are the invention are therefore thereforeless less likely likely to to break break

downand down and have have better better structural structural integrity. integrity. Moreover, Moreover, lower lower degradation degradation is advantageous is advantageous

as it as it means means that that less less dust dust and and finesfines will will be generated be generated during during reduction, reduction, minimising minimising

15 15 material loss and material loss and reducing reducingthe therisk riskofofoperational operationalissues issuesrelated relatedtotodust dustaccumulation. accumulation.

Table Table 66 -– RDI% RDI% values values forfor Test Test ID ID No.No. 17-20 17-20

Test ID Test ID No. No.17 17 Test ID Test ID No. No.18 18 Pellet Pellet CMC (0.5%) CMC (0.5%) + + CMC (0.5%) CMC (0.5%) ++ sodium sodium Formulation Formulation sodiumsilicate sodium silicate(2%) (2%) silicate (2%) silicate (2%) Curing Curing Method Method Oven Oven ITR rig ITR rig Curing Conditions Curing Conditions air air CO2 CO2 Curing Curing 150 150 150 150 Temperature/°C Temperature/°C Curing Curing 120 120 10 10 Duration/mins Duration/mins RDI RDI %% 6.4 6.4 5.4 5.4

Test ID Test ID No. No.19 19 Test ID Test ID No. No.20 20 Pellet Pellet CMC (0.5%) CMC (0.5%) + + CMC (0.5%) CMC (0.5%) + + Formulation Formulation magnesium magnesium silicate silicate magnesium silicate magnesium silicate (2%) (2%) ++sodium sodium (2%) (2%) ++sodium sodium silicate (2.5%) silicate (2.5%) silicate (2.5%) silicate (2.5%) Curing Curing Method Method Oven Oven ITR rig ITR rig Curing Conditions Curing Conditions air air CO CO22 Curing Curing 150 150 150 150 Temperature/°C Temperature/°C Curing Curing 120 120 10 10 Duration/mins Duration/mins RDI RDI %% 61.9 61.9 19.3 19.3

20 20

27

Example Example 88 -- Comparison BetweenCMC Comparison Between CMC and and PolysaccharideBinders Polysaccharide Binders

This study This studyinvestigates investigatesthe thedifference differencebetween betweenCMC CMC and aand a polysaccharide polysaccharide when when used as used as 5 5 binders in pellets binders in pellets cured curedunder underCO2CO in2 in a process a process according according toinvention. to the the invention. A of A batch batch of pellets pellets(ID (ID No. No. 21) 21) was created and was created and cured cured according according to to test test ID ID No. No. 12, 12, but but instead instead including including a a polysaccharide in place polysaccharide in placeof of CMC CMCasasthe the binder. binder. The The polysaccharide polysaccharide was was present present 2024219865

at 0.25 at wt%.The 0.25 wt%. The polysaccharide polysaccharide usedused in this in this example example was awas a starch starch from Cargill from Cargill USA. USA.

10 10 TheCCS The CCSofof each each batch batch of pellets of pellets waswas tested, tested, and and the results the results are shown are shown in Table in Table 7. The 7. The CCSofofthe CCS thepellets pellets formulated formulated with with polysaccharide polysaccharide as aasbinder a binder are are lower lower than than that that of of the the pellets pellets formulated withCMC formulated with CMCas as a binder. a binder.

Whilst the CCS Whilst the CCSofofthe thepellets pelletswhich which comprise comprise a polysaccharide a polysaccharide binder binder are viable are viable for iron for iron

15 15 ore pellets, ore pellets, this this example illustrates that example illustrates that when thebinder when the binderisisa acellulosic cellulosic material materialsuch suchasas CMC,the CMC, theCCS CCSisisnotably notablyhigher higherwhen when formed formed using using the the process process according according toinvention. to the the invention.

Table 7: Pellet Table 7: Pellet formulations usedininExample formulations used Example5, 5, with with CCSCCS results. results.

Test Na Curing Curing Test CMC/ Polysaccharide/ Polysaccharide/ Na Curing Curing CCS/ ID CMC/ silicate/ silicate/ Duration/ Duration/ Curing Curing CCS/ ID wt% wt% method Atmos. kN No. No. wt% wt% wt% mins mins method Atmos. kN 12 0.25 - wt% 2.00 10 ITRrig ITR rig CO2 4.67 12 0.25 - 2.00 10 CO2 4.67 13 13 -- 0.25 0.25 2.00 2.00 10 10 ITRrig ITR rig CO2 CO2 3.50 3.50 20 20 It would It beappreciated would be appreciated that that the the process process and and apparatus apparatus of theofinvention the invention are capable are capable of of being implemented being implemented invariety in a a variety of ways, of ways, onlyonly a fewa of few of which which haveillustrated have been been illustrated and and describedabove. described above.

25 25 Unless the context Unless the context requires requires otherwise, otherwise, where wherethethe terms terms “comprise”, "comprise", “comprises”, "comprises", “comprised”oror"comprising" "comprised" “comprising”areare used used in this in this specification specification (including (including the the claims) claims) they they areare

to be to be interpreted interpretedasasspecifying specifying the the presence presence of the of the stated stated features, features, integers, integers, steps steps or or components, components, butbut notnot precluding precluding the presence the presence of oneoforone moreorother morefeatures, other features, integers,integers,

steps or steps or components, components, or or group group thereof. thereof.

30 30

28

Claims (27)

The claims defining the invention are as follows:

1. A process for producing a pellet, the process comprising: (i) providing particulate material selected from a carbonaceous material, metal, 5 metal ore, and mixtures thereof; an inorganic binder comprising a metal silicate, and an organic binder, wherein the organic binder comprises a natural polymer, a synthetic polymer, a glycerolipid, a cellulosic material, and 2024219865

combinations thereof, to form a mixture; (ii) compressing the mixture to form a pellet; and 10 (iii) curing the pellet by contacting the pellet with gaseous carbon dioxide.

2. A process according to claim 1, wherein the hydraulic pressure applied in step (ii) is applied using a roller pressing process (RPP) in the range 50 Bar to 300 Bar.

15 3. A process according to claim 1 or claim 2, wherein the pressure applied in step (ii) is applied using a cold-pressing technique (CTS) using a 10 mm die, wherein the pressure applied is in the range 6000 Bar to 8000 Bar calculated under 6 tonnes force; or wherein the pressure applied in step (ii) is applied using a cold-pressing technique (CTS) using a 16 mm die, wherein the pressure applied is in the range 20 2000 Bar to 5000 Bar calculated under 6 tonnes force; or wherein the pressure applied in step (ii) is applied using a cold-pressing technique (CTS) using a 20 mm die, wherein the pressure applied is in the range 800 Bar to 3500 Bar calculated under 6 tonnes force.

25 4. A process according to any preceding claim, wherein the carbon dioxide of step (iii) is carbon dioxide generated from one or more industrial processes.

5. A process according to any preceding claim, further comprising the additional step of capturing carbon dioxide generated from one or more industrial processes for use 30 in step (iii).

6. A process according to any proceeding claim, wherein step (iii) additionally comprises application of heat at a temperature in the range 50°C to 1000°C.

35 7. A process according to claim 6, wherein the application of heat comprises application of heat generated from one or more industrial processes.

8. A process according to any preceding claim, wherein curing the pellet in step (iii) takes place at atmospheric pressure.

9. A process according to any one of claims 1 to 8, wherein curing the pellet in step 5 (iii) takes place at a pressure in the range 1 Bar to 3 Bar.

10. A process according to any preceding claim, wherein the particulate material is added in an amount of about 70 wt% to about 99.9 wt% of the mixture of step (i). 2024219865

10 11. A process according to any preceding claim, wherein the particulate material comprises a metal ore, a metal, and combinations thereof, optionally wherein the particulate material comprises iron.

12. A process according to any one of claims 1 to 10, wherein the particulate material 15 comprises a carbonaceous material.

13. A process according to any preceding claim, wherein the particulate material has a moisture content of less than 25%.

20 14. A process according to any preceding claim, wherein the metal silicate is present in the mixture in the range 0.5 wt% to 5 wt% of the mixture.

15. A process according to any preceding claim, wherein the metal silicate comprises a group I or group II metal silicate, optionally wherein the metal silicate is 25 selected from sodium silicate (Na2SiO3), calcium silicate (CaSiO3, Ca2SiO4), potassium silicate (K2SiO3), magnesium silicate (MgSiO4), and combinations thereof.

16. A process according to claim 15, wherein the metal silicate is selected from sodium 30 silicate, magnesium silicate, and combinations thereof; or wherein the metal silicate is selected from potassium silicate, magnesium silicate, and combinations thereof.

17. A process according to any preceding claim, wherein the organic binder is present in the mixture in the range 0.2 wt% to 5 wt% of the mixture. 35 18. A process according to any preceding claim, wherein the organic binder comprises a polyacrylamide resin, a phenol formaldehyde resin, a polyacrylic, a styrene- acrylate polymer, cellulosic fibres, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (MHEC), glyceryl triacetate, glyceryl

diacetate, polyvinyl alcohol, and combinations thereof, preferably wherein the organic binder comprises a polyacrylamide resin, a phenol formaldehyde resin, cellulosic fibres, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (MHEC), polyvinyl alcohol, glyceryl triacetate, and 5 combinations thereof, more preferably wherein the organic binder comprises from polyacrylamide resin, cellulosic fibres, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), and combinations thereof, most preferably wherein the organic 2024219865

binder comprises carboxymethyl cellulose (CMC), cellulosic fibres, hydroxyethyl methyl cellulose (MHEC), and combinations thereof. 10 19. A process according to claim 18, wherein the organic binder comprises carboxymethyl cellulose (CMC).

20. A process according to claim 18, wherein the organic binder comprises polyvinyl 15 alcohol.

21. A process according to any preceding claim, wherein the organic binder is of viscosity in the range 3,000 to 16,000MPa-s.

20 22. A process according to any preceding claim, further comprising the addition of a flux additive to the mixture.

23. A process according to claim 22, wherein the flux additive is selected from silica, dolomite, fluorite, calcium oxide, magnesium oxide, carbon, aluminium, dunnite, 25 basalt, and combinations thereof; optionally wherein the flux additive is selected fluorite, aluminium, dunnite, basalt and combinations thereof.

24. A process according to any preceding claim, wherein curing of the pellet by contacting the pellet with gaseous carbon dioxide occurs by introducing the pellets 30 into a gas stream comprising carbon dioxide at a flow rate in the range 1 to 100 litres per minute.

25. A pellet obtainable by a process according to any preceding claim.

35 26. A pellet comprising a particulate material selected from a carbonaceous material, metal, metal ore, and mixtures thereof; silica; and a metal carbonate, and an organic binder, wherein the organic binder comprises a natural polymer, a synthetic polymer, a glycerolipid, a cellulosic material, and combinations thereof.

27. A pellet according to claim 26, wherein the metal carbonate is formed by reaction with an inorganic binder comprising a metal silicate and gaseous carbon dioxide. 2024219865