OA22006A - Exothermic Iron Compounds For Producing Iron Oxide Pellets. - Google Patents

Abstract

There is provided a method of producing iron oxide pellets having a target internai energymeasured as a target beat of magnetite équivalent (HME). An iron oxide is reduced into an exothermic iron compound having a lower oxidation number. The exothermic iron compound is magnetite, wustite, and/or metallic iron and is mixed with iron ore, a binder and optionally a Carbon material selected from coke breeze, anthracite and biomass. The iron ore comprises magnetite and/or hematite and/or goethite. The mixture contains at least 1 wt. % of the exothermic iron compound and from 0 to 0.8 wt. % of total carbon. The mixture contains a sufficient amount of magnetite, wustite, and/or metallic iron to maintain the target HME calculated as follows : <img file="OA22006A_A0001.tif"/> where CM stands for carbon material, CV stands for calorific value, wus is wustite, mag is magnetite, and Fcmetai is metallic iron; The iron pellets are formed from the mixture, dried and subjected to an induration process.

Description

EXOTHERMIC IRON COMPOUNDS FOR PRODUCING IRON OXIDE PELLETS CROSS-REFERENCE TO A RELATED APPLICATION

This disclosure daims priority from U.S. Provisional Application No. 63/514,923 filed July 21,2023, which is incorporated herein by référencé in its entirety.

TECHNICAL F1ELD

This disclosure relates to the field of iron oxide pellets and methods of making same.

BACKGROUND OF THE ART

Iron oxide pellets (or pellets), referred to as greenballs before they are dried and indurated, are produced in a generally spherical form (5-20 mm of diameter) by rolling finely ground iron ore w'ith suitable additives and a binder. Pellets are utilized as feedstock for direct réduction (DR) or blast fumace (BF) iron making operations. To obtain suffïcient internai energy to facilitate the induration of a greenball into a pellet of acceptable quality, coke breeze is traditionally included in the greenball mix. The inclusion of coke breeze leads to a significant production of carbon dioxide during the fonnation of the pellet, particularly at the induration step. Accordingly, improvemcnts in the pelletizing process are desired, particularly a réduction in the production of carbon dioxide while maintaining suffïcient internai energy in the iron oxide pellets.

SUMMARY

In one aspect, there is provided a method of producing iron oxide pellets having a target internai energy measured as a target heat of magnetite équivalent (HME), the method comprising:

reducing an iron oxide into an exothemiic iron compound having a lower oxidation number, wherein the exothermic iron compound is magnetite, wustite, and/or metallic iron;

mixing the exothermic iron compound, with iron ore, a binder and a carbon material selected from coke breeze, anthracite, and biomass, wherein the iron ore comprises magnetite and hématite, wherein the exothermic iron compound is présent in a concentration of at least 1 wt. %, wherein a total carbon concentration in the mixture is in the range of from 0 to 0.8 wt. %, and wherein the mixture contains a suffïcient amount of magnetite, wustite, and/or metallic iron to maintain the target HME calculated as follows :

-1 22006

CV of CM CV of ivus target HME = —— ----(wt. % of CM) + wt. % of mag -I------- (wt. % of wus)

CV of mag CV of mag । CV of

CV of mag

(. Wt. % of F6métal) wherein CM stands for carbon material, CV stands for calorific value, wus is wustite, ma is magnetite, and Fcinetai is metallic iron;

forming iron pellets from the mixture;

drying the iron pellets; and subjecting the iron pellets to an induration process.

In some embodiments, the iron oxide is hématite. In some embodiments, the step of reducing is a hydrogen réduction. In some embodiments, the hydrogen réduction is supplied energy from hydroelectric energy. In some embodiments, the step of reducing is performed in a green hydrogen based fluidized bed réduction reactor.

In some embodiments, the concentration of the total carbon is less than 0.1 wt. %.

In some embodiments, the carbon material is coke breeze, preferably the concentration of the coke breeze in the mixture is less than 0.1 wt. %.

In some embodiments, the mixing comprises grinding and/or bail milling.

In some embodiments, the method further comprises, after the mixing and before the forming, breaking lumps in the mixture.

In some embodiments, the method further comprises, before the forming, filtering the mixture to exclude particles larger than 200 μηι.

In some embodiments, the binder is bentonite and/or an organic binder.

In some embodiments, the mixture further comprises an additive selected from limestone and dolomite.

-222006

In some embodiments, the concentration of the magnetite in the mixture is from 10 to 80 wt. % or is from 35 to 45 wt. %.

In some embodiments, the mixture is in the form of a slurry.

In some embodiments, the exothermic iron compound is provided in powder form.

There is also provided an iron oxide pellet obtained or obtainable from the method of the présent disclosure.

Many further features and combinations thereof conceming the présent improvements will appear to those skilled in the ait following a reading of the instant disclosure.

DETAILED DESCRIPTION

The présent disclosure provides the use of exothermic iron compounds as a substitute for carbon materials (t.e. coke breeze, anthracite and/or biomass) in the production of iron oxide pellets. The term “biomass” as used herein refers to the charcoal-like material obtained by buming organic matter such as biowaste from the agriculture or forestry industries. In some embodiments, the term biomass can be defïned as consisting of carbon and ashes. The term “coke breeze”, in some embodiments, refers to the residue obtained from the screening of heat treated coke, and has a size of less than one-half inch. The addition of exothermic iron compounds allows to reduce or eliminate the concentration of carbon materials in iron oxide pellets and to reduce the resulting CO2 émissions while maintaining a target internai energy of the iron oxide pellets. Depending on the pellets’ Chemical and mineralogical composition, the target internai energy will vary.

Iron oxide pellets are produced by mixing iron ore with a binder and optionally additives. Traditionally, after selecting the target internai energy, an amount of carbon material such as coke breeze is added in the mixture to hâve the resulting iron oxide pellets reach the target internai energy. However, this addition of carbon material (e.g. coke breeze) leads to undesirable CO2 émissions during the pelletizing process. To reduce or eliminate the carbon content, exothermic iron compounds which include magnetite, wustite, and/or metallic iron are provided instead ofthe carbon material and preferably completel y replace the carbon material addition. The term “exothermic iron compounds” is defïned herein to mean magnetite, wustite, and/or metallic iron. In some embodiments, the exothermic iron compounds are provided in powder form. The powder may hâve a particle size of less

-322006 than 2 mm. The pairticle size can Lie measured by image analysis (e.g. microscopy. laser diffraction, dynamic light scattering) or other suitable means.

Traditionally, coke breeze is included in the mixture to produce pellets in a concentration of 1.1 to 1.6 wt. % (e.g. about 1.4 wt. %). The use ofthe exothermic iron compounds allows for the réduction of coke breeze concentration or other carbon materials to up to 0.8 wt. %, up to 0.7 wt. %, up to 0.6 wt. %, up to 0.5 wt. %, up to 0.4 wt. %, up to 0.3 wt. %. up to 0.2 wt.% or to less than 0.1 wt. %. In some embodiments, no coke breeze is added in the mixture and therefore the exothermic iron compounds completely replace the coke breeze. More generally when considering carbon materials, reference can be made to the carbon concentration ralher than the coke breeze concentration. Accordingly, the concentration of elemental carbon in the mixture is up to up to 0.8 wt. %, up to 0.7 wt. %, up to 0.6 wt. %, up to 0.5 wt. %, up to 0.4 wt. %, up to 0.3 wt. %, up to 0.2 wt.% or to less than (). 1 wt. %. To achieve the réduction in carbon content, the exothennic iron compounds are included in the mixture in a concentration of at least 1 wt. %, at least 1.5 wt. %, at least 2 wt. %, from 1 to 12 wt. %, from 2 to 10 wt. %, or from 3 to 8 wt. %.

The iron ore as used herein contaîns hématite and magnetite and can contain goethite. The target internai energy for the iron oxide pellets is calculated as a target heat of magnetite équivalent (HME). The équation is as follows:

CV of CM target HME = ——-----(wt. % of CM) + wt. % of mag + cl/ of mag

CV of wus _f---- (wt. % of wus)

CV of mag

C^ °f ^^emetal CV of mag (wt. % of Fe_metal)

Where CM = carbon material, CV = calorific value, wus = wustite and mag = magnetite, or alternatively

CV of coke CV of wus target HME = ——-----(wt. % of coke) + wt. % of mag -I------- (wt. % of wus)

CV of mag CV of mag । CI/ of Fe_metal CV of mag (wt. % of Fe_metal)

The équation is such that when the wt. % of carbon material or coke breeze is 0, the concentration of the exothermic iron compounds is increased to maintain the target HME at the same value or in some cases the HME can be increased. The concentration of magnetite is in the range of

-422006

Irom 10 to 80 wt. % to obtain a useful iron oxide pellet, and în some cases in the range of 30 to 50 wt. % or 35 to 45 wt. %. The calorific values of coke breeze, magnetite, wustite, and metallic iron are measurable values that may not necessarily be constant. They can be measured with a calorimeter. In some embodiments. the calorific value of magnetite is from 490 MJ kg to 520 MJ/kg or about 495 MJ/kg. In some embodiments. the calorific value of wustite is from 2040 to 2060 MJ/kg or about 2051 MJ/kg, and the calorie value of metallic iron is from 7350 to 7370 kj/kg or about 7360 kJ/kg.

The exothermic iron compounds are obtained by performing a réduction on an iron oxide to reduce the oxidation nuinber of thaï iron oxide. The iron oxide that is reduced to obtain the exothermic iron compounds is preferably hématite. The réduction reaction can for example be a hydrogen réduction. In one embodiment, the réduction is performed on a green hydrogen based fluidized bed réduction reactor. The advantage of producing the exothermic iron compounds is that the oxidation level and other physico-chemical properties of the obtained exothermic iron compounds can be controlled in order to a target internai energy in order to replace coke breeze in the iron oxide pellet production process. It is preferred to produce the exothermic iron compounds on site because reduced iron is not completely stable and will revert back to its oxidized form. Accordingly, in some embodiments, there is a minimal delay between the time the exothermic iron compound ts produced and when the exothermic iron compound is mixed with the iron ore and the binder to produce the iron oxide pellets. This minimal delay can be defined as same day, less than 5 h, less than 2 h or less than 1 h. An important advantage of using a hydrogen réduction as opposed to réductions fueled by hydrocarbons is the absence of carbon dioxide émissions. The hydrogen réduction can preferably be fueled by green energy for example hydroelectric energy, wind turbine energy and the like. This allows the internai energy process of iron oxide pellet making to be free of carbon dioxide émissions and can be generally considered carbon free. In some embodiments, an advantage of hydrogen réduction is that it allows to supply hydrogen to different areas.

In the process of making iron oxide pellets, the mixture is kept as a slurry and dewatered before the agglomération step where a binder is added. Examples of binders that can be included in the dewatered mixture are bentonite and/or organic binders (that are substitutes to bentonite). These organic binders include a variety ofcarbon-based polymeric or fibrous compounds. Limestone and/or dolomite are optional additives that can be included in the mixture and additives that can be processed by grinding and/or bail mîlling, for example wet bail milling. Optionally, after the grinding and/or

-522006 bail inilling, the mixture can be treated so as lo break the lumps formed (if any). Filtration is used to remove the water from the slurry mixture.

The pellets are formed by shaping into spherical shapes (i.e. the material is agglomerated into green balls). Prcfcrably, the mixture is First filtered to exclude particles larger than 200 pm. The balls formed are then conveyed to be subjected to the induration process. Induration is a process of drying and firing (cooking), and cooling the pellets. The induration process can be subdivided into steps of évaporation, calcination, combustion, fusion, and oxidation of the varions compounds with the objective of achieving target physical and metallurgical properties. The final product is fired pellets, and the off gascs during the induration process are exhausted through a stack on each induration machine.

The use of coke breeze is the largest emîtter of CO; équivalent at the Iron Ore Company (IOC) of Canada. The coke breeze is used as an internai energy source in iron ore pelletizing which contribuas to enhancing product quality and reducing fuel consumption (i.e. heavy fuel oil) which complétés the iron ore induration process. Iron ore pellets require thermal energy to complété ail the necessary drying, calcination, combustion, fusion, and sintering reactions. The présent disclosure replaces at least a portion ofthe coke breeze with an exothermic iron compound in order to reduce the CO; émissions while maintaining similar properties for the pellets. The exothermic iron compound (i.e. magnetite, wustite, and/or metallic iron) provides the thermal energy required while reducing or avoiding CO; émissions without diluting the iron content ofthe iron ore pellets.

Claims (10)

1. WHAT IS CLAIMED IS:

   1. A method of producing iron oxide pellets having a target internai energy measured as a target heat of magnetite équivalent (HME), the method comprising:

   reducing an iron oxide into an exothermic iron compound having a lower oxidation number, wherein the exothermic iron compound is magnetite, wustite, and/or metallic iron;

   mixing the exothermic iron compound, with iron ore, a binder and a carbon material selected from coke breeze, anthracite, and biomass, wherein the iron ore comprises magnetite and hématite, wherein the exothermic iron compound is présent in a concentration of at least I wt, %, wherein a total carbon concentration in the mixture is in the range of from 0 to 0.8 wt. %, and wherein the mixture contains a sufficient amount of magnetite, wustite, and/or metallic iron to maintain the target HME calculated as follows :

   CVofCM target HME = ——----(wt. % of CM) + wt. % of mag

   CV of mag ^ΰ

   CV of wus _z CV of Fe_metal + 7777-7---- (vvt. % of wus) + ------ (wt.% of Fe_metal)

   CV of mag CV of mag

   Wherein CM stands for carbon material, CV stands for calorific value, wus is wustite, mag is magnetite, and Fe_mt._ta] is metallic iron;

   forming iron pellets from the mixture;

   drying the iron pellets; and subjecting the iron pellets to an induration process.
2. 2. The method of claim 1, wherein the iron oxide is hématite.
3. 3. The method ol claim 1 or 2, wherein the step of reducing is a hydrogen réduction supplied energy from hydroelectric energy.
4. 4. The method of any one of claims 1 to 3, wherein the concentration of the total carbon is less than 0.1 wt. %.
5. 5. The method of any one of claims 1 to 4, wherein the carbon material is coke breeze and the concentration of the coke breeze in the mixture is less than 0.1 wt. %.
6. 6. The method of any one of claims 1 to 5, further comprising, before the forming, filtering the mixture to exclude particles larger than 200 pm.

   - 7 22006
7. 7. The method ot any one of daims 1 to 6, wherein the binder is bentonite andor an organic binder and/or wherein the mixture further comprises an additive sdected from limestone and dolomite.
8. 8. The method of any one of daims 1 to 7, wherein the concentration of the magnetite in the 5 mixture is from 10 to 80 wl. %.
9. 9. The method of any one of daims 1 to 8, wherein the mixture is in the form of a slurry.
10. 10. The method of any one of daims 1 to 9, wherein the exothennic iron compound is provided in powder form.