WO2018154499A1

WO2018154499A1 - Production of form coke

Info

Publication number: WO2018154499A1
Application number: PCT/IB2018/051135
Authority: WO
Inventors: Grant Christopher PIO; Pieter Willem Schalk PEENS; Johan Andries PEENS; Richard A. Wolfe
Original assignee: Afri Eco Trade Pty Ltd
Current assignee: Afri Eco Trade Pty Ltd
Priority date: 2017-02-24
Filing date: 2018-02-23
Publication date: 2018-08-30
Anticipated expiration: 2019-08-24
Also published as: ZA201801284B

Abstract

A process (10) for the manufacture of form coke includes briquetting (22) an admixture of particulate hard coking coal (HCC), particulate semi-soft coking coal (SSCC), a particulate carbon-containing filler other than hard coking coal or semi-soft coking coal, and a binder to form briquettes. The hard coking coal has a particle size distribution with a D90 value of no more than 500 µm, the semi-soft coking coal has a particle size distribution with a D90 value of no more than 500 µm, and the carbon-containing filler has a particle size distribution with a D90 value of no more than 500 µm. The hard coking coal makes up at most 30% by mass of the admixture and the carbon-containing filler makes up at least 10% by mass of the admixture. The briquettes are carbonised (24) at a temperature of at least 900°C to provide form coke.

Description

PRODUCTION OF FORM COKE

THIS INVENTION relates to the production of form coke. In particular, the invention relates to a process for the manufacture of form coke, and to form coke briquettes.

One of the major difficulties and financial limitations to making a quality coke in a conventional coke battery is that very high quality and expensive metallurgical grade coals are required. The supply of such coals in many places is limited. Furthermore, the construction of coke batteries is capital intensive.

A process for manufacturing form coke that uses lower quality coal as raw material, while still providing a coke product of acceptable quality, would be desirable. It would be an additional benefit if such a process can make use of a tunnel kiln.

According to one aspect of the invention, there is provided a process for the manufacture of form coke, the process including

briquetting an admixture of particulate hard coking coal (HCC), particulate semi-soft coking coal (SSCC), a particulate carbon-containing filler other than hard coking coal or semi-soft coking coal, and a binder to form briquettes, wherein the hard coking coal has a particle size distribution with a D90 value of no more than 500 μιη, the semi-soft coking coal has a particle size distribution with a D90 value of no more than 500 μιη, and the carbon-containing filler has a particle size distribution with a D90 value of no more than 500 μιη, and wherein the hard coking coal makes up at most 30% by mass of the admixture and the carbon-containing filler makes up at least 10% by mass of the admixture; and

carbonising the briquettes at a temperature of at least 900°C to provide form coke.

In this specification, the term "hard coking coal" is intended to refer to a coal with a maximum vitrinite reflectance (Ro%) greater than 0.95, as determined using the ISO 7404- 5:2009 testing procedure and a minimum fluidity of at least 300 dial divisions per minute (DDPM) on a Gieseler Plastometer, using the ISO 10329:2009 testing procedure, whereas the term "semi- soft coking coal" is intended to refer to a coal with a maximum vitrinite reflectance (Ro%) of less than 1.0, as determined using the ISO 7404-5:2009 testing procedure and a maximum fluidity of less than 300 dial divisions per minute (DDPM) on a Gieseler Plastometer, using the ISO 10329:2009 testing procedure. The semi-soft coking coal is thus a high volatile coal.

The hard coking coal may have a free swelling index (FSI), according to the ASTM D720 testing procedure, of at least 5, preferably at least 7, more preferably at least 8, e.g. 8.5.

The hard coking coal may have a volatile content of less than about 30% by mass.

The semi-soft coking coal may have a volatile content of at least about 28% by mass, typically at least about 30% by mass, e.g. about 35% by mass.

The semi-soft coking may have a volatile content of less than about 38% by mass, typically less than about 37% by mass.

Preferably, the hard coking coal has a D90 value of no more than about 400 μιη, more preferably no more than about 350 μιη, most preferably no more than about 300 μιη, e.g. about 250 μιη.

Preferably, the semi-soft coking coal has a D90 value of no more than about 400 μιη, more preferably no more than about 350 μιη, most preferably no more than about 300 μιη, e.g. about 250 μιη.

Preferably, the carbon-containing filler has a D90 value of no more than about 400 μιη, more preferably no more than about 350 μιη, most preferably no more than about 300 μιη, e.g. about 250 μιη.

Preferably, the hard coking coal makes up no more than about 20% by mass of the admixture, more preferably no more than about 15% by mass of the admixture, most preferably no more than about 13% by mass of the admixture, e.g. about 10% by mass of the admixture. Preferably, the hard coking coal makes up at least about 2% by mass of the admixture, more preferably at least about 4% by mass of the admixture, most preferably at least about 5% by mass of the admixture.

Preferably, the carbon-containing filler makes up at least about 15% by mass of the admixture, more preferably at least about 20% by mass of the admixture, most preferably at least about 25% by mass of the admixture, e.g. about 30% by mass of the admixture.

Preferably, the carbon-containing filler makes up no more than about 50% by mass of the admixture, more preferably no more than about 40% by mass of the admixture, most preferably no more than about 35% by mass of the admixture.

Preferably, the semi-soft coking coal makes up between about 40% by mass of the admixture and about 90% by mass of the admixture, more preferably between about 50% by mass of the admixture and about 80% by mass of the admixture, most preferably between about 55% by mass of the admixture and about 70% by mass of the admixture, e.g. about 60% by mass of the admixture.

The admixture may include water.

Preferably, the admixture includes no more than about 15% by mass water, more preferably no more than about 10% by mass water, most preferably no more than about 8% by mass water, e.g. about 7.5% by mass water.

Although it is in principle possible for the admixture to be substantially free of water, water is typically introduced into the admixture as part of the binder. Typically, the admixture will thus include at least about 1% by mass water.

Preferably, the binder makes up at least about 3% by mass of the admixture, more preferably at least about 5% by mass of the admixture, most preferably at least about 6% by mass of the admixture, e.g. about 6.5% by mass of the admixture. Typically, the binder does not make up more than 15% by mass of the admixture, preferably no more than about 12% by mass of the admixture, more preferably no more than about 11% by mass of the admixture.

The binder may be a hydrocarbonaceous substance. In one embodiment of the invention, the binder is tar.

Typically, the tar is introduced into the admixture in the form of a water and tar emulsion, e.g. in the form of SS60, which is an ionic stable grade bitumen emulsion which has a binder content (i.e. tar content) of 60 - 62% by mass. SS60 is freely commercially available, e.g. in 200L drums from Deuces Bitumen Supplies (Pty) Ltd of 12 Jordaan Street, Lilivale, Benoni, Johannesburg, South Africa.

Preferably, the tar is even further diluted with water before being introduced into the admixture. Thus, the tar may be introduced as a tar and water emulsion or mixture which includes between about 20% by mass and about 3% by mass tar, more preferably between about 15% by mass and about 4% by mass tar, most preferably between about 10% by mass and about 5% by mass tar, e.g. about 5.8% by mass tar.

The carbon-containing filler is typically a low volatile or devolatilised carbon- containing material. Examples of suitable carbon-containing filler include charcoal, carbon black, char fines, bio-char, coke fines, anthracite, fine waste coking coal, low volatile coal and pitch coke.

Preferably, the carbon-containing filler has a volatile content of less than about 25% by mass, more preferably less than about 20% by mass, most preferably less than about 15% by mass, e.g. about 12% by mass.

Typically, the briquetting takes place at a briquetting pressure of between about 100 bar and about 700 bar. Preferably, the briquettes are carbonised in a carboniser at a temperature of at least about 900°C, more preferably at least about 1000°C, most preferably at least about 1050°C, e.g. about 1100°C.

Preferably, the briquettes are carbonised at a temperature of less than about 1250°C, more preferably less than about 1200°C, most preferably less than about 1150°C.

During carbonisation, the briquettes release volatile materials that are combusted, providing the heat for carbonisation. As the admixture from which the briquettes are formed includes an unusually high concentration of a relatively high volatile coal (i.e. a semi- soft coking coal), significant quantities of volatile materials are released and combusted, which may require steps to prevent the carbonisation temperature from becoming too high, thereby preventing damage to the carboniser and preventing the coal (carbon) in the briquettes from burning. Such steps may include limiting ingress of air into the carboniser, introducing an inert gas (such as N₂) into the carboniser, and cooling a gas product from the carboniser and recycling of the cooled gas product from the carboniser back to the carboniser.

Thus, in one embodiment of the invention, the briquettes are carbonised in a carboniser at a temperature of at least 900°C but less than 1250°C, the process including the step of preventing the carbonisation temperature from becoming too high as a result of combustion of volatile materials released from the briquettes, thereby preventing damage to the carboniser and preventing the coal (carbon) in the briquettes from burning, said step of preventing the carbonisation temperature from becoming too high being selected from the group of process steps consisting of limiting ingress of air into the carboniser, introducing an inert gas into the carboniser, cooling a gas product from the carboniser and recycling of the cooled gas product from the carboniser back to the carboniser, and combinations of two or more of these process steps.

Preferably, the briquettes are carbonised in a continuous carboniser, such as a continuous tunnel kiln or a rotary hearth furnace, although it is possible to carbonise the briquettes on a batch basis, e.g. in a batch coke battery. In one embodiment of the invention, the briquettes are carbonised in a continuous tunnel kiln.

In the continuous tunnel kiln, the briquettes may be kept in a carbonisation temperature range of 900°C to 1250°C for a period of at least about 30 minutes, more preferably at least about 1 hour, most preferably at least about 2 hours, e.g. about 3 - 10 hours.

Typically, in the continuous tunnel kiln, the briquettes are kept in a carbonisation temperature range of 900°C to 1250°C for a period of no more than about 12 hours, preferably no more than about 10 hours.

When the briquettes are carbonised in a continuous tunnel kiln, the briquettes may be transported through the continuous tunnel kiln as one or more shallow beds of briquettes, with the or each bed having a thickness of at most about 200cm, preferably at most about 160cm, more preferably at most about 130cm, most preferably at most about 120cm.

The or each bed typically is also heated from below by the volatile gasses, released from the briquettes, being combusted inside the continuous tunnel kiln.

In one embodiment of the invention, the briquettes are transported through the continuous tunnel kiln on a plurality of trolleys arranged in series, with each trolley defining a raised platform with a bed of briquettes on the platform, and with gas flow paths being defined below the raised platform through which hot gas can flow to heat the platform, and hence the bed of briquettes, also from below.

The process of the invention may include comminuting or milling two or more of the hard coking coal, semi-soft coking coal and the carbon-containing filler together for purposes of forming said admixture. Preferably, all three of the hard coking coal, the semi-soft coking coal and the carbon-containing filler are milled together to form said admixture. This may be the case even when one or more of the hard coking coal, semi-soft coking coal and the carbon-containing filler is/are already of a sufficiently small particle size, as the milling also acts to thoroughly admix the hard coking coal, semi-soft coking coal and the carbon-containing filler together. In one embodiment of the invention, the semi-soft coking coal is coal supplied by the Grootegeluk mine in South Africa and the hard coking coal is coal supplied by Oaky Mine in Australia or Vale Mine in Tete, Mozambique.

The process of the invention typically includes withdrawing product gas from the carboniser. Typically, the product gas still includes volatile gasses than can be combusted. The process may thus include combusting the withdrawn product gas to generate heat or power.

The inventors have surprisingly found that by using sufficiently fine particulate material in the admixture, combined with a sufficiently high briquetting pressure, form coke briquettes are produced that have a desirably high Coke Strength After Reaction (CSR) and a desirably low Coke Reactivity Index (CRI), as determined in accordance with ASTM D5341- 99(2004), making the form coke suitable for use at least in a ferrochrome smelter, even when using hard coking coal, semi-soft coking coal, carbon-containing filler and a binder in the mass ranges in the admixture as hereinbefore described. Noticeably, this is possible even with the low binder concentration and the low hard coking coal concentration in the admixture, as set out hereinbefore.

The particle sizes (sufficiently fine), admixture composition and the briquetting pressure (sufficiently high) may thus be selected to provide form coke with a CSR of at least about 35, preferably at least about 40, more preferably at least about 43, e.g. about 45.

The particle sizes (sufficiently fine), admixture composition and the briquetting pressure (sufficiently high) may be selected to provide form coke with a CRI of no more than about 55, preferably no more than about 53, more preferably no more than about 50, most preferably no more than about 45, e.g. about 43.

Surprisingly, as a result of the briquetting of the admixture, it has been found that external layers of the briquettes formed during carbonisation are denser and stronger than centres of the briquettes. This physical relationship has proven to be a technical advantage when the form coke briquettes are used in an alloy smelter or steel furnace due to the fact that the briquettes penetrate deeper into the bed of the furnace due to the slower initial reaction because of the more dense and less reactive outer surface (in effect, due to a lower CRI). Once the form coke briquettes penetrate deeper into the furnace bed and the outer layers have been reacted, the more reactive inner centres or cores of the briquettes are exposed.

The particle size (sufficiently fine) and the briquetting pressure (sufficiently high) may be selected to provide form coke briquettes with an individual briquette density of at least about 950 kg/m³, preferably at least about 1000 kg/m³, more preferably at least about 1100 kg/m³, most preferably at least about 1200 kg/m³, e.g. about 1210 kg/m³. As will be appreciated by those skilled in the art, the form coke briquettes produced by the method of the invention may thus have an individual briquette density which is easily 20% higher than that of commercially marketed lump coke.

The briquettes may have a maximum dimension of no more than about 85 mm, preferably no more than about 70 mm, more preferably no more than about 65 mm, most preferably no more than about 60 mm, e.g. about 55 mm. A more rounded or oval shape is preferred, to avoid sharp corners or edges that can wear easily.

Preferably, the briquettes are uniform in shape and size.

The invention extends to form coke manufactured by the process of the invention.

According to another aspect of the invention, there is provided form coke briquettes, the briquettes being formed from carbonisation of an admixture of particulate hard coking coal, particulate semi-soft coking coal, a particulate carbon-containing filler and a binder, the admixture being characterised in that the hard coking coal has a particle size distribution with a D90 value of no more than 500 μιη, the semi-soft coking coal has a particle size distribution with a D90 value of no more than 500 μιη, and the carbon-containing filler has a particle size distribution with a D90 value of no more than 500 μιη, and in that the hard coking coal makes up at most 30% by mass of the admixture and the carbon-containing filler makes up at least 10% by mass of the admixture, the form coke briquettes having a Coke Strength After Reaction (CSR) of at least 35 and a Coke Reactivity Index (CRI) of no more than 55, as determined in accordance with ASTM D5341-99(2004).

The form coke briquettes may have an individual briquette density as hereinbefore described.

The admixture, the hard coking coal, the semi-soft coking coal, the carbon- containing filler and the binder may be as hereinbefore described.

The form coke briquettes may be as hereinbefore described.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which

Figure 1 shows a process in accordance with the invention for the manufacture of form coke; and

Figure 2 shows a graph of temperature in the vicinity of a batch of briquettes being carbonised, in accordance with the process of Figure 1, as they are moving through a tunnel kiln.

Referring to Figure 1 of the drawings, reference numeral 10 generally indicates a process in accordance with the invention for the manufacture of form coke. The process 10 generally includes a stockpile 12 of hard coking coal lumps, a stockpile 14 of semi-soft coking coal lumps, a stockpile 16 of particulate carbon-containing filler in the form of char, a comminution stage 18, a supply 20 of a binder, a briquetting stage 22, a trolley and rail facility 23 which includes trolleys 32 and pairs of rails 33, 34 and 36, and a tunnel kiln 24 with a product gas withdrawal line 38.

Conveyors 26 lead from the stockpiles 12, 14, 16 to the comminution stage 18. A conveyor 28 leads from the comminution stage 18 to the briquetting stage 22 and a binder feed line 21 leads from the binder supply 20 to the conveyor 28. A conveyor 30 leads from the briquetting stage 22 to one of the trolleys 32. The trolley 32 can be moved sideways, supported on the pair of rails 34 on a bogie (not shown) for displacement from the pair of rails 33 to a pair of rails 36 which runs through the tunnel kiln 24.

In order to manufacture form coke, i.e. coke briquettes, hard coking coal lumps from the stockpile 12, semi-soft coking coal lumps from the stockpile 14, and char from the stock pile 16 are conveyed by means of the conveyors 26 to the comminution stage 18, in a desired ratio of hard coking coal:semi-soft coking coal:char.

The hard coking coal in the embodiment illustrated in Figure 1 of the drawings was obtained from Oaky Mine, has a maximum vitrinite reflectance (Ro%) of 1.62, a maximum fluidity of about 740 DDPM, a free swelling index of about 8.5 and a volatile matter content of 22.4% by mass.

The semi-soft coking coal, in the embodiment illustrated in Figure 1 of the drawings, was obtained from Grootegeluk Mine and has a volatile matter content of about 36% by mass, a maximum fluidity of about 12 DDPM, and a free swelling index of about 5.0.

The carbon-containing filler, i.e. char, has a volatile matter content of about 10%. The char in the stockpile 16 is in the form of char fines.

In the comminution stage 18, the lumpy hard coking coal and the lumpy semi-soft coking coal are milled together with the char fines to provide an admixture wherein the hard coking coal has a particle size distribution with a D90 value of about 250 μιη, the semi-soft coking coal has a particle size distribution with a D90 value of about 250 μιη, and also the char fines have a particle size distribution with a D90 value of about 250 μιη. The lumpy hard coking coal, lumpy semi-soft coking coal and char fines are fed to the comminution stage so that the admixture produced by the comminution stage comprises about 10% by mass of hard coking coal fines, about 60% by mass of semi-soft coking coal fines, and about 30% by mass of carbon- containing filler, i.e. char fines, all intimately mixed. Any suitable conventional comminution technology and classification technology may be employed in the comminution stage 18. For example, the comminution stage 18 may employ a hammer mill in series with a pendular mill, or a roller mill, or a ball mill or similar with air classification.

From the comminution stage 18, the admixture is conveyed by means of the conveyor 28 to the briquetting stage 22. On the way to the briquetting stage 22, the admixture is wetted once or twice with binder from the binder supply 20, using the binder feed line 21. In the embodiment of the invention illustrated in Figure 1 of the drawings, the binder is an emulsion of tar and water, produced by diluting SS60 tar emulsion further with water to produce a diluted tar and water emulsion containing about 5.8% by mass tar. The diluted tar and water emulsion is added to the admixture at a mass ratio of diluted tar emulsion:admixture of about 8:92, so that the wetted admixture which is fed to the briquetting stage 22 has a tar content of about 0.45% by mass and a water content of about 7.55% by mass. Any suitable technology may be employed to add the diluted tar emulsion to the admixture, e.g. a pump and spray nozzles injecting the emulsion into a double shaft mixer (not shown).

Although not shown in Figure 1, it may be advantageous to allow the wetted admixture to mature for a period, e.g. at least 12h, or at least 16h, or at least 20h, or at least 24h, before briquetting the wetted admixture.

In the briquetting stage 22, the admixture is briquetted to form green briquettes, using conventional briquetting technology (i.e. a conventional briquetting machine) and applying a briquetting pressure of about 250 bar. The green briquettes are transported by means of the conveyor 30 from the briquetting stage 22 onto one of the trolleys 32 (also known as a kiln car) and dumped onto the trolley 32 to form a shallow bed 40 with a substantially homogenous thickness of about 100 cm. The trolley 32 is similar to conventional trolleys or kiln cars used in tunnel kilns for baking tiles and other ceramic artefacts. The trolley 32 thus has a raised rectangular platform of refractory material on which the bed of briquettes is supported, with a gas flow path being defined below the raised platform through which hot gas generated in the tunnel kiln 24 can flow, to heat the platform and the bed of briquettes from below. End walls 38 of refractory material are provided on shorter sides of the platform of the trolley 32, with the ends walls 38 joining a floor of the platform with a large radius. Opposed longitudinal sides of the platform are open. The gas flow paths underneath the platform are parallel to the end walls 38.

A trolley 32 with a fresh load of green briquettes from the conveyor 30 is first displaced along the pair of rails 33 towards the intersecting rails 34, and then sideways on a bogie along the rails 34 to intercept the rails 36 (alternatively, rotating tracks can be used). Thereafter, the trolley 32 is pushed along the rails 36 to enter the tunnel kiln 24, with the end walls 38 of the platform of the trolley 32 being adjacent and close to side walls of the tunnel kiln 24 and with an open side of the platform leading and an opposed open side of the platform trailing. A roof of the tunnel kiln 24 is about 150 cm above the bed of green briquettes on the trolley 32. The tunnel kiln 24 has a width of about 3.5 m and a length of about 96 m and the trolley 32 travels in start- stop fashion through the tunnel kiln 24 over a period of about 10-20 hours typically.

In order to ensure that the process 10 is a continuous process, another, empty trolley 32 is then positioned at the discharge of the conveyor 30 so that it can also be filled with green briquettes.

Loaded trolleys 32 are thus fed, one after the other, in series to form a train of trolleys or kiln cars, into the tunnel kiln 24 and pushed by means of a hydraulic ram (not shown), acting on the rearmost trolley 32 in the train, half a trolley length at a time, through the tunnel kiln 24.

In the tunnel kiln 24, the green briquettes supported on the trolleys 32 are carbonised at a temperature of about 1100°C. Referring to Figure 2 of the drawings, the temperature of the environment surrounding one of the trolleys 32 moving through the tunnel kiln 24 is graphically illustrated as a function of time, and hence as a function of position inside the tunnel kiln 24. As can be noted, the temperature rises rapidly as the trolley 32 enters the tunnel kiln 24 and then moves deeper into the tunnel kiln 24, until the temperature reaches the carbonisation temperature of about 1100°C. The carbonisation temperature is achieved by combusting the volatile matter given off by the green briquettes at the elevated temperature inside the tunnel kiln 24. The temperature remains at the carbonisation temperature of about 1100°C as long as sufficient volatile matter is given off by the green briquettes to sustain combustion and as long as sufficient oxygen is available for combustion. Thereafter, the temperature starts dropping as the trolley 32 moves towards an outlet end of the tunnel kiln 24. Naturally, in order to start up the tunnel kiln 24, it is necessary first to supply heat to the tunnel kiln 24. This is done, in conventional fashion, using oil burners extending through the roof of the tunnel kiln 24.

It is to be noted that Figure 2 shows a graph, obtained during a trial, for briquettes that are travelling unusually slowly through the tunnel kiln 24, and that are in the carbonisation temperature range of about 900°C to 1250°C for an unusually long period of time.

In order to ensure that temperatures inside the tunnel kiln 24 do not become too high, it is typically necessary to take one or more steps to control the temperature, bearing in mind the relatively high volatile matter content of the green briquettes, compared to good quality hard coking coal lumps. The simplest of such steps is to control the ingress of air into the tunnel kiln 24, at an inlet end of the tunnel kiln 24 where the trolleys 32 are pushed into the tunnel kiln 24, and at the outlet end of the tunnel kiln 36.

Gas produced inside the tunnel kiln 24 as a result of the combustion of the volatile matter given off by the green briquettes being carbonised is withdrawn from the tunnel kiln by means of the product gas withdrawal line 38. The product gas is only partially combusted and still contains combustible volatile matter. The product gas is thus typically further combusted to generate heat or power, before the gas is discharged to atmosphere through a stack. If necessary, the gas is cleaned prior to discharge, and waste heat may be recovered from the gas before it is discharged to atmosphere.

When a trolley 32 exits the tunnel kiln 24, the hot carbonised briquettes are pushed off the trolley over one of the open longitudinal sides or ends of the platform of the trolley 32, preferably using a mechanical pusher, and allowed to cool, with the trolley 32 being returned along rails (not shown) back to the rails 33 to be refilled with green briquettes supplied by the conveyor 30. If desired, the hot briquettes may be quenched, e.g. with water. The briquettes are then stockpiled (not shown). The process 10, as illustrated, provides form coke in the form of carbonised briquettes with a density of about 1200kg/m³, a Coke Strength After Reaction (CSR) of about 45 and a Coke Reactivity Index (CRI) of about 42.

The process 10, as illustrated, advantageously allows the production of high quality form coke without the necessity to use 100% high quality metallurgical grade coals. Instead, an admixture of hard coking coal, semi-soft coking coal and carbon-containing filler is carbonised. The carbonisation allows the hard coking coal, with a higher fluidity, to melt and to form a carbon bond with the semi-soft coking coal and with the carbon-containing filler, providing a strong and hard coke briquette. The briquettes are substantially homogenous in size and shape and have individual densities which are higher than that of conventional coke lumps made in commercially active coke batteries. As will be appreciated, the high density coke briquettes allow for larger amounts of carbon to be introduced into steel furnaces or the like, thus increasing efficiency and production. The briquetted coke not only provides for a higher density, but also provides for a less reactive surface that allows deeper penetration into the bed of a furnace before a more reactive core of the briquette is exposed.

Advantageously, the briquetted coke produced by the process 10, as illustrated, generates less fines during handling and processing in a furnace, than commercially available lump coke. Any fines that are generated can be recycled and formed again into coke briquettes again, using the process of the invention.

Claims

Claims:

1. A process for the manufacture of form coke, the process including

2. The process of claim 1, wherein the hard coking coal has a free swelling index (FSI), according to the ASTM D720 testing procedure, of at least 5, and/or wherein the hard coking coal has a volatile content of less than 30% by mass, and/or wherein the semi-soft coking coal has a volatile content of at least 28% by mass, and/or wherein the semi-soft coking has a volatile content of less than 38% by mass.

3. The process of claim 1 or claim 2, wherein the hard coking coal has a D90 value of no more than 400 μιη, and/or wherein the semi-soft coking coal has a D90 value of no more than 400 μιη, and/or wherein the carbon-containing filler has a D90 value of no more than 400 μιη, and wherein the hard coking coal makes up no more than 20% by mass of the admixture.

4. The process of any of claims 1 to 3, wherein the hard coking coal makes up at least 2% by mass of the admixture, and/or wherein the carbon-containing filler makes up at least 15% by mass of the admixture and/or wherein the semi-soft coking coal makes up between 40% by mass of the admixture and 90% by mass of the admixture.

5. The process of any of claims 1 to 4, wherein the carbon-containing filler makes up no more than 50% by mass of the admixture and/or wherein the admixture includes water in a concentration of no more than 15% by mass.

6. The process of any of claims 1 to 5, wherein the binder makes up at least 3% by mass of the admixture but no more than 15% by mass of the admixture, and/or wherein the binder is a hydrocarbonaceous substance.

7. The process of any of claims 1 to 6, wherein the binder is tar, which is introduced into the admixture in the form of a water and tar emulsion.

8. The process of any of claims 1 to 7, wherein the carbon-containing filler is a low volatile or devolatilised carbon-containing material with a volatile content of less than 25% by mass.

9. The process of any of claims 1 to 8, wherein the briquettes are carbonised in a carboniser at a temperature of at least 900°C but less than 1250°C, the process including the step of preventing the carbonisation temperature from becoming too high as a result of combustion of volatile materials released from the briquettes, thereby preventing damage to the carboniser and preventing the coal (carbon) in the briquettes from burning, said step of preventing the carbonisation temperature from becoming too high being selected from the group of process steps consisting of limiting ingress of air into the carboniser, introducing an inert gas into the carboniser, cooling a gas product from the carboniser and recycling of the cooled gas product from the carboniser back to the carboniser, and combinations of two or more of these process steps.

10. The process of any of claims 1 to 9, wherein the briquettes are carbonised in a continuous carboniser.

11. The process of claim 10, wherein the continuous carboniser is a continuous tunnel kiln, the briquettes being kept in a carbonisation temperature range of 900°C to 1250°C for a period of at least 30 minutes but no more than 12 hours.

12. The process of claim 11, wherein the briquettes are transported through the continuous tunnel kiln as one or more shallow beds of briquettes, with the or each bed having a thickness of at most 200cm, and with the or each bed also being heated from below by volatile gasses, released from the briquettes, being combusted inside the continuous tunnel kiln.

13. The process of claim 11 or claim 12, wherein the briquettes are transported through the continuous tunnel kiln on a plurality of trolleys arranged in series, with each trolley defining a raised platform with a bed of briquettes on the platform, and with gas flow paths being defined below the raised platform through which hot gas can flow to heat the platform, and hence the bed of briquettes, also from below.

14. The process of any of claims 1 to 13, which includes comminuting or milling all three of the hard coking coal, the semi-soft coking coal and the carbon-containing filler together to form said admixture.

15. The process of any of claims 1 to 14, wherein the particle sizes are selected sufficiently fine, an admixture composition is selected within the limits set out in claim 1, and a briquetting pressure is selected sufficiently high to provide form coke with a Coke Strength After Reaction (CSR) of at least 35, as determined in accordance with ASTM D5341-99(2004).

16. The process of any of claims 1 to 15, wherein the particle sizes are selected sufficiently fine, an admixture composition is selected within the limits set out in claim 1, and a briquetting pressure is selected sufficiently high to provide form coke with a Coke Reactivity Index (CRI) of no more than 55, as determined in accordance with ASTM D5341-99(2004).

17. The process of any of claims 1 to 16, wherein the particle sizes are selected sufficiently fine and a briquetting pressure is selected sufficiently high to provide form coke briquettes with a density of at least 950 kg/m³.

18. Form coke briquettes, the briquettes being formed from carbonisation of an admixture of particulate hard coking coal, particulate semi-soft coking coal, a particulate carbon- containing filler and a binder, the admixture being characterised in that the hard coking coal has a particle size distribution with a D90 value of no more than 500 μιη, the semi-soft coking coal has a particle size distribution with a D90 value of no more than 500 μιη, and the carbon- containing filler has a particle size distribution with a D90 value of no more than 500 μιη, and in that the hard coking coal makes up at most 30% by mass of the admixture and the carbon- containing filler makes up at least 10% by mass of the admixture, the form coke briquettes having a Coke Strength After Reaction (CSR) of at least 35 and a Coke Reactivity Index (CRI) of no more than 55, as determined in accordance with ASTM D5341-99(2004).

19. The form coke briquettes of claim 18, which have an individual briquette density of at least 950 kg/m³, and/or which are uniform in shape and size.

20. The form coke briquettes of claim 18 or claim 19, which have an individual briquette density of at least 1100 kg/m³ and/or which have a maximum dimension of no more than 85 mm.

21. Form coke when manufactured by the process of any of claims 1 to 17.