AU2005248040A1 - A direct reduction process - Google Patents

Description

WO 2005/116274 PCT/EP2005/005465 A DIRECT REDUCTION PROCESS 5 The present invention relates to a direct reduction process for a metalliferous feed ma terial, particularly, although by no means exclusively, to a direct reduction process for an iron-containing feed material, such as iron ore. The present invention also relates to a process for reducing a metalliferous feed mate 10 rial that comprises a direct reduction process for partially reducing metalliferous feed material in the solid state and a smelting process for melting and further reducing the partially reduced metalliferous feed material to a molten metal. The present invention was made during the course of an on-going research project car 15 ried out by the applicant to develop the so called "CIRCOFER technology" for the direct reduction of iron ore. CIRCOFER technology is a direct reduction process that is capable of reducing iron ore in the solid state to a metallisation of 50% or higher. 20 CIRCOFER technology is based on the use of fluidised beds. The main feed materials to the fluidised beds are fluidising gas, metal oxides (typically iron ore fines), solid car bonaceous material (typically coal) and oxygen-containing gas (typically oxygen gas). The main product produced in the fluidised beds is metallised metal oxides, i.e. metal 25 oxides that have been at least partially reduced. One of the findings of the applicant in the research project is that it is possible to oper ate the process with relatively fine feed materials and minimise carry-over of iron units in an off-gas stream from the process and minimise undesirable accretions of materials, 30 such as metal oxide fines, on exposed surfaces in the fluidised bed apparatus that are capable of disrupting the process. High carry-over of iron units in off-gas streams and undesirable accretions on exposed apparatus surfaces are significant issues for com- WO 2005/116274 PCT/EP2005/005465 -2 mercialisation of the CIRCOFER technology, particularly with metal oxide feed materi als that are relatively brittle. The applicant has found that it is possible to achieve controlled agglomeration of parti 5 cles and minimise undesirable accretions of materials, such as metal oxides, by provid ing a carbon-rich zone in a fluidised bed, passing metalliferous material through the zone, and injecting oxygen into the zone and oxidising smaller particles, including smaller metallised particles. 10 According to the present invention there is provided a direct reduction process for a solid metalliferous material having a particle size distribution that at least in part comprises micron sized particles, which process comprises supplying the metalliferous material, a solid carbonaceous material, an oxygen-containing gas, and a fluidising gas into a fluidised bed in a vessel and maintaining the fluidised bed in the vessel, at least 15 partially reducing metalliferous material in the vessel, and discharging a product stream that comprises the at least partially reduced metalliferous material from the vessel, which process is characterised by: (a) establishing and maintaining a carbon-rich zone within the fluidised bed; (b) passing metalliferous material, including metallised material (which term includes partially metallised material), through the carbon-rich zone; and 20 (c) injecting the oxygen-containing gas into the carbon-rich zone and oxidising metalli sed material, solid carbonaceous material and other oxidisable solids and gases and causing controlled agglomeration of particles. The term "carbon-rich" zone is understood herein to mean a region in the fluidised bed 25 in which there is a relatively large amount of carbon-containing material in relation to the amount of metalliferous material than there is in other regions of the fluidised bed. The applicant does not have a totally clear understanding at this stage of the mecha nism or mechanisms that enables controlled agglomeration of metalliferous material to 30 be achieved. Nevertheless, without wishing to be bound by the following comments, in the research project the applicant observed that the agglomerates that formed com prise smaller particles, particularly fines, adhered to each other and to larger particles. The applicant speculates that the conditions in the carbon-rich zone, and more particu- WO 2005/116274 PCT/EP2005/005465 -3 larly a hot zone within the carbon-rich zone, are such that (a) micron sized partially and completely reduced, i.e. metallised, iron ore particles react with oxygen and generate heat and the resultant oxidised particles become sticky (b) fine coal particles react with oxygen and oxidise and the resultant ash becomes sticky; and (c) fine iron ore particles 5 become sticky as a consequence of being heated. The applicant also speculates that these smaller sticky particles, adhere to larger particles that have a higher heat sink capacity, with the overall beneficial result that there is a reduction in the proportion of smaller particles in the vessel that can adhere to apparatus surfaces and be carried out from the vessel in an off-gas stream. 10 Preferably the process comprises supplying the metalliferous material in the form of fines. In the case of reducing metalliferous material in the form of iron ore fines, preferably 15 the fines are sized at minus 6 mm. Preferably the fines have an average particle size in the range of 0.1 to 0.8 mm. One of the advantages of the process is that it can accept a substantial amount of met 20 alliferous feed material with a grain size of less than 100 microns without a significant amount of this material exiting the process entrained in off-gas. This is believed to be due to an agglomeration mechanism operating within the fluidised bed that promotes a desirable level of agglomeration between particles of feed materials, particularly sub 100 micron particles, without appearing to promote uncontrolled agglomeration capable 25 of interrupting operation of the fluidised bed. Similarly, friable ores that have a ten dency to break down during processing and to thereby increase the proportion of parti cles in the fluidised bed with a size of less than 100 microns may be processed without significant loss of feed material in process off-gas. 30 Preferably the process comprises supplying the metalliferous material with a selected maximum particle size and controlling agglomeration so that 90% of the particles di scharged from the process as a product stream do not exceed the maximum selected feed size.

WO 2005/116274 PCT/EP2005/005465 -4 Preferably the process comprises supplying the metalliferous material with a selected maximum particle size and controlling agglomeration so that no more than 30%, prefe rably no more than 20%, and more preferably no more than 10% by weight of the total 5 weight of iron units discharged from the process is carried off in an off-gas stream from the process. Preferably the process comprises controlling agglomeration by adjusting the feed rates of any one or more of the metalliferous material, the carbonaceous material, the reacti 10 on temperature and the oxygen-containing gas. More preferably the process comprises controlling agglomeration by adjusting the feed rate of the carbonaceous material. 15 The process has considerable advantages. By way of example, it has hitherto been thought that CIRCOFER technology requires amounts of carbon that are at least 20-30% by weight of the total weight of solids in a fluidized bed to prevent uncontrolled agglomeration leading to undesirable accretions 20 on exposed surfaces of fluidized bed apparatus that disrupts the process. The applicant has found that it is possible to operate the process with minimal undesir able accretions and with desirable controlled agglomeration with relatively low levels, typically 5-30%, of carbonaceous material. Low levels of carbonaceous material 25 means that it is possible to produce a solids product stream with low levels of char and the product stream can be supplied into smelters with minimal downstream processing. In addition, controlled agglomeration of metalliferous material fines into larger particles that become part of the solid products stream rather than being carried out of the proc 30 ess as entrained solids in an off-gas stream means that there is higher recovery from the process and less downstream treatment of off-gas required. This is a particularly important benefit for iron ores that tend to be brittle and would break down into micron sized particles in the course of materials handling prior to being supplied to the vessel WO 2005/116274 PCT/EP2005/005465 -5 and during the course of being processed in the vessel. Such brittle ores include ores mined in Western Australia, such as Brockman and Mara Maba ores. On current indications, typically the process can reduce minus 3mm iron ore fines with 5 the following results. At least 90% by weight of the iron ore fines supplied to the process being metallised to some extent and discharged as part of a solids product stream, with less than 50% of the fines being greater than 2mm. 10 SIn the range of 5-30% by weight of the solids product stream comprising carbon. Less than 20% by weight of the iron ore fines supplied to the process being discharged from the process with off-gas. 15 Preferably the process comprises injecting the oxygen-containing gas into a central region of the vessel, ie a region that is located inwardly of a side wall of the vessel. Preferably the process comprises injecting the oxygen-containing gas so that there is a downward flow of the gas in the vessel. 20 Preferably the process comprises injecting the oxygen-containing gas with a downward flow in a range of plus or minus 40 degrees to the vertical. More preferably the process comprises injecting the oxygen with a downward flow in a 25 range of plus or minus 15 degrees to the vertical. Preferably the process comprises injecting the oxygen-containing gas via at least one lance having a lance tip with an outlet positioned in the vessel inwardly of the side wall of the vessel in the central region of the vessel. 30 Preferably the lance tip is directed downwardly. More preferably the lance tip is directed vertically downwardly.

WO 2005/116274 PCT/EP2005/005465 -6 The position of the lance and, more particularly, the height of the outlet of the lance tip, is determined by reference to factors, such as the oxygen-containing gas injection velo city, the vessel pressure, the selection and amounts of the other feed materials to the 5 vessel, and the fluidised bed density. Preferably the process comprises water-cooling the lance tip to minimise the possibility of accretions forming on the lance tip that could block the injection of the oxygen containing gas. 10 Preferably the process comprises water cooling an outer surface of the lance. Preferably the process comprises injecting the oxygen-containing gas through a central pipe of the lance. 15 Preferably the process comprises injecting the oxygen-containing gas with sufficient velocity to form a substantially solids-free zone in the region of the outlet of the lance tip to minimise the formation of accretions that could block the injection of the oxygen containing gas. 20 Preferably the oxygen is injected with a velocity in the range 50-300 m/s. Preferably the process comprises injecting nitrogen and/or steam and/or other suitable shrouding gas and shrouding the region of the outlet of the lance tip to minimise oxida 25 tion of metal that could result in accretions forming on the lance tip that could block the injection of the oxygen-containing gas. Preferably the process comprises injecting the shrouding gas into the vessel at a velo city that is at least 60% of the velocity of the oxygen-containing gas. 30 In one embodiment the process comprises establishing reaction zones in a fluidised bed and moving solids (including metalliferous and carbonaceous materials) and fluidis ing gas within the bed so that the solids pass through the reaction zones.

WO 2005/116274 PCT/EP2005/005465 -7 The reaction zones may be contiguous. One reaction zone is the carbon-rich zone described above. 5 The other reaction zone is a metal-rich zone in which metalliferous material, such as iron ore, is reduced in a solid state. The term "metal-rich" zone is understood herein to mean a region in the fluidised bed in 10 which there is a relatively large amount of metalliferous material in relation to the amount of carbon-containing material than there is in other regions of the fluidised bed. The metal-rich zone is located in a lower section of the fluidised bed and the carbon rich zone is located above the metal-rich zone. 15 The zones may be contiguous. The fluidised bed comprises upward and downward movement of solids through the zones. 20 Preferably the process comprises supplying the metalliferous material, the carbonace ous material, the oxygen-containing gas, and the fluidising gas to the fluidised bed and maintaining the fluidised bed with (a) a downward flow of the oxygen-containing gas, (b) an upward flow of solids and fluidising gas countercurrent to the downward flow of 25 the oxygen-containing gas, and (c) a downward flow of solids outwardly of the upward flow of solids and fluidising gas. In the fluidised bed described in the preceding paragraph, solids in the upward and downward flows of solids are heated by heat generated by reactions between the oxy 30 gen-containing gas, the carbonaceous material and other oxidisable materials (such as CO, volatiles, and H 2 ) in the carbon-rich zone. The solids in the downward flow of so lids transfer heat to the metal-rich zone.

WO 2005/116274 PCT/EP2005/005465 -8 In addition, the upward and downward flows of solids shield the side wall of the vessel from radiant heat generated by reactions between the oxygen-containing gas and the solid carbonaceous material and other oxidisable solids and gases in the fluidised bed. 5 Preferably the carbonaceous material is coal. In such a situation, the process devolati lises the coal to char and at least part of the char reacts with oxygen and forms CO in the fluidised bed. Coal volatiles also decompose to gases such as CO and H 2 , which in turn may further react with oxygen in the fluidised bed. 10 Preferably the fluidising gas comprises a reducing gas, such as CO and H 2 . Preferably the process comprises selecting the amount of H 2 in the fluidising gas to be at least 15% by volume of the total volume of CO and H 2 in the gas. 15 Preferably the process comprises discharging the product stream comprising at least partially reduced metalliferous material from the lower section of the vessel. Preferably the product stream also comprises other solids (for example char). 20 Preferably the process comprises separating at least a portion of the other solids from the product stream. Preferably the process comprises returning at least a portion of the other solids to the vessel. 25 Preferably the process comprises discharging an off-gas stream containing entrained solids from an upper section of the vessel. Preferably the process comprises separating at least a portion of the entrained solids 30 from the off-gas stream.

WO 2005/116274 PCT/EP2005/005465 -9 Preferably the process comprises maintaining a circulating fluidised bed by separating entrained solids from the off-gas stream and returning at least a portion of the separa ted solids to the vessel. 5 Preferably the process comprises returning solids separated from the off-gas to the lower section of the fluidised bed. Preferably the process comprises preheating metalliferous feed material with the off gas from the vessel. 10 Preferably the process comprises treating the off-gas after the preheating step and re turning at least a portion of the treated off-gas to the vessel as the fluidising gas. Preferably the off-gas treatment comprises one or more of (a) solids removal, (b) coo 15 ling, (c) H 2 0 removal; (d) CO2 removal, (e) compression, and (f) reheating. Preferably the off-gas treatment comprises returning solids to vessel. The process may be operated to produce a product stream ranging from low to high 20 metallisation depending on the downstream requirements for the at least partially redu ced metalliferous material. The metallisation may range from 30 to in excess of 80%. In situations in which metallisation greater than 50% is required, preferably the process comprises operating with reducing gas in the fluidising gas. One option for the fluidi sing gas in this instance is treated off-gas from the vessel. In situations in which metal 25 lisation less than 50% is required, it is envisaged that it will not be necessary to operate with reducing gas in the fluidising gas and sufficient reductant can be obtained via solid carbonaceous material supplied to the process. The oxygen-containing gas may be any suitable gas. 30 Preferably the oxygen-containing gas comprises at least 90% by volume oxygen.

WO 2005/116274 PCT/EP2005/005465 -10 The present invention is described further with reference to the accompany drawing which is a diagram of an apparatus for direct reduction of a metalliferous material by one embodiment of a process in accordance with the present invention which illustrates the reaction zones formed by the process within the vessel shown in the Figure. 5 The following description is in the context of direct reduction of metalliferous material in the form of iron ore in the solid state. The present invention is not so limited and ex tends to direct reduction of other iron-containing materials (such as ilmenite) and more generally to other metalliferous materials. 10 The following description is also in the context of direct reduction of iron ore with coal as a solid carbonaceous material, oxygen as an oxygen-containing gas, and recycled off-gas containing a mixture of CO and H 2 as a fluidising gas. The present invention is not so limited and extends to the use of any other suitable solid carbonaceous material, 15 oxygen-containing gas, and fluidising gas. With reference to the Figure, solid feed materials, namely iron ore (typically fines sized to less than 6 mm) and coal, oxygen and fluidising gas are supplied to the vessel 3 shown in the Figure and establish a fluidised bed in the vessel. 20 The solid feed materials are supplied to the vessel via a solids delivery device such as a screw feed or a solids injection lance 5 that extends through a side wall 7 of the ves sel. 25 The oxygen is injected into the vessel via a lance 9 that has a lance tip 11 with an out let that directs the oxygen downwardly in a central region of the vessel, ie spaced in wardly from the side wall 7 of the vessel. The lance tip is directed downward in the vessel. The fluidising gas is injected via a series of tuyeres or nozzles (not shown) in a base 13 of the vessel. 30 The above-described supply of solids and gases produces the following reactions in the vessel.

WO 2005/116274 PCT/EP2005/005465 -11 Devolatilisation of coal fines to char and decomposition of coal volatiles to gaseous products (such as CO and H 2 ) and reaction of at least part of the char with oxygen to form CO. 5 Direct reduction of iron ore to at least partially reduced iron by the CO, H 2 , which reac tions produce CO2 and H 2 0. Reaction of CO2 with carbon to form CO (Boudouard reaction). 10 Oxidation of solids and gases, such as partially reduced iron ore particles, char, coal volatiles, CO, and H 2 (injected as a part of the fluidising gas or produced through de composition of coal volatiles) with oxygen which generates heat that assists with main taining the reactions described in the preceding dot points and which also contributes to a desirable controlled agglomeration of the smaller reduced ore particles to form lar 15 ger reduced ore particles. The relative densities of the solids and the above-described injection of the solids and the gases, including the locations of the solids/gas injection, results in the formation of reaction zones in the vessel. The zones may be contiguous. 20 One reaction zone is a carbon-rich zone 17 in the region of the lance tip 11 of the lance 9, i.e. in an intermediate section of the vessel in terms of height. In this zone the pre dominant reactions are oxidising reactions involving combustion of metallised material, char, coal volatiles, CO, and H 2 with oxygen which generate heat, particularly in a hot 25 zone 51 in the immediate vicinity of the lance tip 11. The other reaction zone is a metal-rich zone 19 in a lower section of the vessel in which (a) coal is devolatilised and forms char and coal volatiles and (b) iron ore fines are at least partially reduced and thereby metallised by CO and H 2 . 30 The above-described supply of solids and gases produces an upward flow of fluidising gas and entrained solids in the central region of the vessel. Increasingly, as the solids move upwardly, the solids disengage from the upward stream of fluidising gas and flow WO 2005/116274 PCT/EP2005/005465 -12 downwardly in an annular region between the central region and the side wall of the vessel. Recirculated solids are either entrained again in the upward stream of fluidis ing gas or are discharged from the vessel. The movement of solids transports the sol ids through the hot zone 51 and the smaller particles, particularly metallised micron 5 sized particles become sticky and adhere to other particles, particularly larger particles. As is indicated above, this agglomeration of smaller particles provides substantial ad vantages. The upward stream of fluidising gas and entrained solids in the central region of the 10 vessel 3 is countercurrent to the downward flow of oxygen gas and is believed to result in the entrainment of some of the solids in the oxygen gas. The interaction of the counter current flows of fluidising gas and oxygen is believed to limit the extent to which solids entrained in or passing through the oxygen flow can contact vessel surfaces and cause accretions. The formation of accretions is believed to be further limited due to 15 the central location of the flow of oxygen gas within the vessel. The above-described downward flow of solids in the annular region between the central region and the side wall facilitates transfer of heat from the carbon-rich zone to the metal-rich zone. 20 In addition, the downward flow of solids partially shields the side wall from direct expo sure to radiant heat from the central region of the vessel. The above-described process also produces a stream of off-gas and entrained solids 25 that is discharged from the vessel via an outlet 27 in an upper section of the vessel. The off-gas stream is processed by separating solids from the off-gas and returning the separated solids to the vessel via a solids return leg 29. Thereafter, the off-gas is treated by a series of steps including (a) removal of solids, (b) cooling the off-gas, (c) 30 H 2 0 removal, (d) CO 2 removal, (e) compression, and (f) reheating. The treated off-gas is thereafter returned to the vessel as part of the fluidising gas.

WO 2005/116274 PCT/EP2005/005465 -13 The above-described process produces a stream of solids, including at least partially reduced iron ore and char, that is discharged from the vessel via an outlet 25 in the base of the vessel. 5 The solids stream may be processed by separating the at least partially reduced iron ore and at least part of the other solids. The other solids, predominantly char, may be returned to the vessel as a part of the solids feed for the process. The at least partially reduced iron ore is further processed as required. By way of example, the at least par tially reduced iron ore may be supplied to a molten bath-based smelting vessel and 10 smelted to molten iron, for example by a process such as the so called "Hlsmelt proc ess". As is indicated above, the present invention was made during the course of an on going research project carried out by the applicant to develop CIRCOFER technology 15 for the direct reduction of iron ore. The research project included a series of pilot plant runs on 350mm diameter and 700mm diameter pilot plant set-ups of the applicant. The following discussion focuses on research work on the 700 mm diameter vessel pilot plant. 20 The pilot plant comprises an apparatus of the type shown in Figure 1 and 2. The pilot plant was operated as a circulating fluidised bed at atmospheric pressure. The vessel has a height of 10.7 m. An upper section of the vessel has a height of approximately 8.9 m and an internal diameter of 700 mm. A lower section of the vessel has a height 25 of approximately 1.8m and an internal diameter of 500 mm. This height of 1.8 m inclu des the height of a fluidising grate and a transition section between the 500 mm diame ter and the 700 mm diameter sections. The vessel is refractory lined. Off-gas from the vessel was processed to remove entrained solids by passing the off 30 gas successively through 3 cyclones connected in series. The first cyclone (cyclone 1) received off-gas directly from the vessel. Solids separated in the cyclone were re turned to the vessel via a seal pot that provided for pressure sealing. The second cyc lone (cyclone 2) received off-gas from cyclone 1. Solids separated in the cyclone were WO 2005/116274 PCT/EP2005/005465 -14 returned to the vessel via a direct return of solids (i.e. no seal pot). The third cyclone (cyclone 3) received off-gas from the second 2. Solids separated by cyclone 3 were not returned to the vessel. 5 After solids separation by the three cyclones, the off-gas was further treated by a radial flow scrubber, which further removed solids from the off-gas. These solids were con centrated by a thickener and then passed through a drum filter to produce thickener sludge. 10 Off-gas leaving the radial flow scrubber was then treated by a tube cooler that operated to dewater the off-gas by cooling it to within the range 10-30 0 C. Following treatment by the tube cooler, the off-gas was combusted. The fluidised bed was fluidised by air during the initial stages of testing and was later 15 fluidised by a mixture of nitrogen and hydrogen gas. As there were no provisions for processing and recycling the process off-gas, e.g. CO 2 removal and compression, it was not possible for it to be returned to the vessel as fluidising gas. In this regard, hydrogen gas was used to simulate the effect of using processed off-gas as fluidising gas. 20 In summary, the research work demonstrated the following: The concept of a coal based fluidised bed reduction process with oxygen injection, pro ducing a reduced product with metallisation levels of up to 78%. 25 Injecting oxygen into/or close to a fluidised bed with up to 42% metallic iron in the bed appears to be feasible without the formation of accretions. The concept of simultaneously reducing iron ore and partially burning coal for energy in 30 a single bed vessel appears to be feasible, at metallic iron loadings up to 48% in the product.

WO 2005/116274 PCT/EP2005/005465 -15 The position of the oxygen lance in the vessel is important because of the desirability of transferring the heat of oxidation back into the bed while minimising the level of iron re oxidation. The 4-m position is about right for the conditions tested. 5 High phosphorus Brockman iron ore was successfully fluidised and reduced without excessive dust make. (Brockman ore is a friable West Australian iron ore made avail able by Hamersley Iron Pty Ltd, Perth, Western Australia.) Objectives of the experimental program: 10 The primary objective was to achieve stable operation for a significant amount of time with high phosphorus Brockman ore (-3mm) and Blair Athol coal. The plan was to operate with low iron ore feed (up to 20% in product discharge) for two 15 days with the oxygen lance in a low position (1.9-m above the distributor plate (not shown in the Figure) of the vessel. The aim was then to operate for three days with high ore feed (up to 70% in the product) with the oxygen lance in an upper position (3.8-m above the distributor plate). 20 Start-up: The campaign started on the 9 th of December 2003 at 0600 hrs with a gradual heat up of the 700-mm vessel (hereinafter also referred to as a "CFB") using alumina as the bed material. Once the target temperature was reached, coal and oxygen were intro 25 duced into the vessel at 1550 hrs. The oxygen rate was increased up to 105 Nm 3 /hr while the coal rate was in the range 300-450 kg/hr. Operation with coal and oxygen 10/12/03 - 11/12/03 30 Operation with coal, air and oxygen was conducted on 10/12/03. The operation was very smooth with the system stabilising fairly quickly and the vessel maintaining its temperature of 900-930 0 C without any problems.

WO 2005/116274 PCT/EP2005/005465 -16 The standard operating conditions during this period were as follows. CFB temperature: 9300C bottom and 9000C top Fluidising gas flowrate: 140Nm 3 /hr (N 2 ) and 300Nm 3 /hr (air) 5 Pressure drop CFB: 80-140 mbar Oxygen flowrate: up to 100 Nm 3 /hr

N

2 shield gas flowrate: 30 Nm 3 /hr Coal Feed Rate: 340-450 kg/hr 10 A summary of the results is as follows: Bed Discharge Rate: 100-160 kg/hr Cyclone 3 Discharge: 10-14 kg/hr Offgas Analysis 15 CO/CO2 12.8/8.7 = 1.47 %H2 7.6

%CH

4 0.7 The discharge product was clean with only some small +2mm pieces which looked like residual refractory material. The dust make was reasonably low with <10% of the dis charge reporting to the final cyclone discharge. 20 Operation with Iron Ore (10-140 kg/hr), Coal and Oxygen (lance 2-m height) 10/12/03 12/12/03 10/12/03 2200 - 11/12/03 0600: Iron Ore at 10 kq/hr 25 Iron ore (<3-mm) was introduced into the feed system at 2200 on 10/12/03 at a rate of 10 kg-hr. Hydrogen was also introduced into the fluidising gas at a rate of 20 Nm 3 /hr to simulate use of processed off-gas as fluidising gas. The operation was smooth with the bed AP being maintained at about 100-120 mbar and the temperature profile having a 30 range of only 1000 between the bottom and the top of the bed.

WO 2005/116274 PCT/EP2005/005465 -17 The product appeared fine without any signs of accretions or agglomerates. However, on screening the product (at 2mm) some larger scale type material was found but this was only a very small proportion of the overall product. The scale appeared to be 5 made up of ash/char and probably formed on the walls of the vessel or distributor plate in the vessel. The standard operating conditions and results during this period were as follows. 10 CFB temperatures: 9300C bottom and 9000C top Fluidising gas flowrate: 350 Nm 3 /hr (N 2 ) and 20 Nm 3 /hr (H 2 ) Pressure drop CFB: 100-130 mbar Oxygen flowrate: 100-115 Nm 3 /hr

N

2 shield gas flowrate: 30 Nm 3 /hr 15 Coal Feed Rate: 280-360 kg/hr Iron Ore Feed Rate: 10 kg/hr A summary of the results is as follows: 20 Bed Discharge Rate: 125 kg/hr Cyclone Discharge: 15 kg/hr Offgas Analysis CO/CO2 10.3/9.7 = 1.06 %H2 9.2

%CH

4 2.0 25 11/12/13 0600 - 11/12/03 1200: Iron Ore at 20 kq/hr The iron ore feed rate was increased up to 20 kg/hr at 0600 on 11/12/03 until 1200 11/12/03 and the hydrogen gas rate was also increased up to 40 Nm 3 /hr. The operation 30 continued to be smooth without any disruptions. The vessel bed pressure was being WO 2005/116274 PCT/EP2005/005465 -18 maintained at about 80-100 mbar and the temperature profile had a range of only 100C between the bottom and the top of the bed. The appearance of the product continued to be good without any signs of accretions or 5 agglomerates. As before the only exception to this was the odd piece of scale type material, which appeared to be composed of ash/char. The standard operating conditions and results during this period were as follows. 10 CFB temperatures: 9520C bottom and 9401C top Fluidising gas flowrate: 350 Nm 3 /hr (N 2 ) and 40 Nm 3 /hr Pressure drop CFB: 80-100 mbar Oxygen flowrate: 112 Nm 3 /hr

N

2 shield gas flowrate: 30 Nm 3 /hr 15 Coal Feed Rate: 430 kg/hr Iron Ore Feed Rate: 20 kg/hr A summary of the results is as follows: 20 Bed Discharge Rate: 125 kg/hr Cyclone 3 Discharge: 15 kg/hr Offgas Analysis CO/CO2 11.5/9.6 = 1.2 %H2 14.1

%CH

4 2.6 25 Product Analysis: (0900 11/12/03) Mass % Fe(T) Fe 2 Feo % Met. Magnetic 9 58.2 15.5 42.35 72.8 Non-Magnetic 91 1.74 WO 2005/116274 PCT/EP2005/005465 -19 11/12/03 1200 - 12/12/03 0600: Iron Ore at 40 kq/hr Summary: 5 The iron ore feed rate was increased up to 40 kg/hr at 1200 on 11/12/03 and operated with this rate until 0600 12/12/03, while the hydrogen gas rate was maintained at 40 Nm 3 /hr and the coal rate was around 360-420 kg/hr. The operation continued to be smooth without any disruptions and the iron product discharge was highly metallised. Dust make was also low with less than 10% of the total discharge coming from the final 10 cyclone (i.e. cyclone 3). The vessel bed AP was being maintained at about 90-135 mbar and the temperature profile had a range of less than 100C between the bottom and the top of the bed. Results 15 The appearance of the product continued to be good without any signs of accretions or agglomerates. The standard operating conditions and results during this period were as follows. 20 CFB temperatures: 9530C bottom and 9410C top Fluidising gas flowrate: 370 Nm 3 /hr (N 2 ) and 40 Nm 3 /hr (H 2 ) Pressure drop CFB: 98-130 mbar Oxygen flowrate: 113 Nm 3 /hr 25 N 2 shield gas flowrate: 30 Nm 3 /hr Coal Feed Rate: 426 kg/hr Iron Ore Feed Rate: 40 kg/hr A summary of the results is as follows: 30 Bed Discharge Rate: 190-210 kg/hr Cyclone 3 Discharge: 15-20 kg/hr Offgas Analysis WO 2005/116274 PCT/EP2005/005465 -20

CO/CO

2 9.9/11.4 = 0.87

%H

2 12.9

%CH

4 2.9 Product Analysis: (11/12/03) Mass % Fe(T) Fe2+ Fe o % Met. %Fe ° in Prod 1500 Magnetic 30 74.38 14.59 57.44 77.2 25.8 11/12/03 Non- 70 4.95 magnetic 1900 Magnetic 34.8 71.56 19.33 50.75 70.9 26.8 11/12/03 Non- 65.2 2.98 magnetic 2300 Magnetic 27.4 66.4 20.22 45.66 68.8 21.1 11/12/03 Non- 72.6 4.03 magnetic 0200 Magnetic 24.6 67.1 22.1 42.53 63.4 19.7 12/12/03 Non- 75.4 4.3 magnetic 0600 Magnetic 19.6 68.86 22.55 43.48 61.8 15.7 12/12/03 Non- 80.4 2.73 magnetic I I The high metallisation achieved (70-77%) indicates that the oxygen lance (even at its 1.9-m position) did not penetrate too far to the bottom of the bed and that there was good segregation within the bed. The lower part of the bed is iron rich. The higher part of the bed is carbon rich and this is interacting with the oxygen lance to generate heat 10 and this heat is then transferred back into the bed by the recirculation of the solids to the lower parts of the bed. The low CO/CO 2 ratio in the off-gas indicates achievement of high post combustion, with the energy levels being transferred back into the bed, while maintaining high metallisation levels in the product discharge.

WO 2005/116274 PCT/EP2005/005465 -21 The iron levels in the product and the degree of metallisation indicates that the 700-mm vessel can be operated in gasification mode with up to 20-25% metallic iron content without any problems with accretions. This is a significant achievement. 5 Oxygqen Lance Inspection (12/12/03) The lance was taken out of the 700-mm vessel and inspected on 12/12/03. In summary, the lance was clean. The water cooled pipe as well as the nozzle tip had 10 no evidence of any buildup of material. The lance was repositioned in the vessel at a higher position i.e. 3.8-m above the dis tributor plate. The vessel was restarted with coal and oxygen and then once stabilised iron ore and hydrogen. 15 Operation with Iron Ore (110-200 kg/hr), Coal and Oxygqen (lance 4-m height) 13/12/03 - 16/12/03 13/12/03 0600 - 13/12/03 1200: Iron Ore at 110 kq/hr 20 Summary: The iron ore feed rate was increased stepwise up to 110 kg/hr at 0625 on 13/12/03 and operated with this rate until 1200 13/12/03 while the hydrogen gas rate was also in 25 creased stepwise up to 110 Nm 3 /hr over a 2 hr period. The coal rate was around 360 400 kg/hr. The operation continued to be smooth without any disruptions and the iron product discharge from the vessel was up to 78% metallised. Dust make was also low with <10% of the total discharge coming from the final cyclone (i.e. cyclone 3). The vessel bed AP was being maintained at about 90-135 mbar and the temperature profile 30 had a range of less than 50C between the bottom and the top of the bed. Increasing the lance height from 1.9m to 3.8m did not seem to impact on the bed tem perature profile. In fact, the temperature spread was less than 50C from top to bottom.

WO 2005/116274 PCT/EP2005/005465 - 22 Results: The appearance of the product continued to be good without any signs of accretions or 5 agglomerates. The standard operating conditions and results during this period were as follows. CFB temperatures: 953 0 C bottom and 9510C top Fluidising gas flowrate CFB 10 Nm 3 /hr (N 2 ) at 8600C, 110 Nm 3 /hr (N 2 ) at 7400C, 180 10 Nm 3 /hr (N 2 ) at 680oC, and 110 Nm 3 /hr (H 2 ) at 8600C Pressure drop CFB: 80-100 mbar Oxygen flowrate: 110 Nm 3 /hr

N

2 shield gas flowrate: 30-40 Nm 3 /hr Coal Feed Rate: 360-400 kg/hr 15 Iron Ore Feed Rate: 110 kg/hr A summary of the results is as follows: Bed Discharge Rate: 162 kg/hr 20 Cyclone 3 Discharge: 16 kg/hr Offgas Analysis CO/CO2 10.9/9.6 = 1.14 %H2 19.6

%CH

4 2.3 Product Analysis: (13/12/03) 25 Mass Fe(T) Fe * Feo %Met. % 1200 Magnetic 37.8 76.42 14.98 59.33 77.6 13/12/03 Non- 62.2 2.66 magnetic WO 2005/116274 PCT/EP2005/005465 - 23 With the higher oxygen lance position the uniform bed temperature profile of the lower lance was maintained. This indicates that even with the oxygen lance at the 3.8m posi tion the solids recirculation profile is such that enough heat is transferred back into the 5 bottom of the bed. The temperature profile in the vessel and the cyclones indicated that there was proba bly no increase in dust make with the increase in iron ore feed rate up to 110 kg/hr. The discharge from the final cyclone relative to the vessel also did not change signifi 10 cantly. This suggests that either the iron ore is not breaking down as much as predicted or that any fines generated are re-agglomerated in the high temperature region of the oxygen lance. 13/12/03 1200 - 16/12/03 0500: Iron Ore at 120 - 230 kq/hr 15 Summary: For the first period of this operation from 17:00 13/12/03 to 12:00 15/12/03 the opera tion rate was approximately 120 kg/h iron ore feed. This included a period of distur 20 bance where there was no feed. The final period operated at approximately 230 kg/h iron ore feed. The operation with 230 kg/hr iron ore feed rate was smooth without any disruptions and the iron product discharge from the CFB ranged from 48% to 78% metallised. Dust 25 make was also low at <10% of the total discharge, coming from cyclone 3. The vessel bed AP was being maintained at about 80-100 mbar and the temperature profile range had now increased to about 20 0 C between the bottom and the top of the bed. Operating the vessel at the higher iron ore feed rate of 200 kg/hr increased the range of 30 the CFB temperature profile with the bottom part of the bed now being up to 20C00 colder than the middle of the bed. The metallisation levels were also lower at the higher iron ore feed rates but they were still in the 60-80% metallisation range.

WO 2005/116274 PCT/EP2005/005465 -24 Results: The appearance of the product continued to be good without any signs of accretions or agglomerates. 5 The standard operating conditions and results during this period were as follows. CFB temperatures: 9470C bottom and 9600C top FB gas heater temperature: 7400C and 6150C main heater 10 Fluidising gas flowrate CFB: 20 Nm 3 /hr (N 2 ) at 8400C, 100 20 Nm 3 /hr (N 2 ) at 74000, 185 20 Nm 3 /hr (N 2 ) at 615 0 C, and 140 Nm 3 /hr (H 2 ) @ 8400C Pressure drop CFB: 83-96 mbar Oxygen flowrate: 113 Nm 3 /hr

N

2 shield gas flowrate: 30-40 Nm 3 /hr 15 Coal Feed Rate: 380 kg/hr Iron Ore Feed Rate: 200 kg/hr A summary of the results is as follows: 20 Bed Discharge Rate: 227-286 kg/hr Cyclone 3 Discharge: 18-24 kg/hr Offgas Analysis (0400 hrs 15/12/03)

CO/CO

2 11/10.4 = 1.06 %H2 16.5

%CH

4 1.4 WO 2005/116274 PCT/EP2005/005465 - 25 Product Analysis: (13-15/12/03) Mass C (T) Fe(T) Fe" Feo % % Met. 1700 Magnetic 40.2 - 75.55 22.1 51.37 68.0 13/12/03 Non- 59.8 - 8.11 magnetic 2000 Magnetic 54.2 1.8 78.35 15.33 61.18 78.1 13/12/03 Non- 45.8 80.3 5.03 magnetic 1700 Cyclone 3 12.89 2.73 2.47 19.2 13/12/03 discharge 2000 Cyclone 3 15.74 3.12 6.67 42.4 13/12/03 Discharge 0200 Magnetic 51.3 - 78.85 19.6 58.87 74.7 15/12/03 Non- 48.7 - 7.29 magnetic 0500 Magnetic 57.2 - 77.44 17.27 57.65 74.4 15/12/03 Non- 42.8 - 4.55 magnetic 0700 Magnetic 62.8 0.9 76.93 17.38 58.43 75.9 15/12/03 Non- 37.2 72.5 11.25 magnetic 0200 Cyclone 3 20.29 7.77 5.38 26.5 15/12/03 Discharge 0500 Cyclone 3 21.73 7.69 6.28 28.9 15/12/03 Discharge 12:00 Magnetic 59.2 - 76.9 18.1 56.6 73.6 15/12/03 Non- 40.8 - 31.0 4.7 22.0 70.9 Magnetic 16:00 Magnetic 62.7 1.9 73.6 32.5 36.0 48.9 15/12/03 Non- 37.3 53.6 27.6 8.4 13.2 48.0 Magnetic 22:00 Magnetic 59.6 - 71.5 28.0 39.0 54.5 15/12/03 Non- 40.4 - 20.4 3.9 11.0 54.0 Magnetic 02:00 Magnetic 53.3 - 74.1 26.8 43.5 58.7 16.12.03 Non- 46.7 - 13.7 3.7 2.8 20.1 Magnetic 04:00 Magnetic 62.7 1.6 74.4 29.5 40.0 53.8 16/12/03 Non- 37.3 63.8 16.8 5.7 5.4 32.2 Magnetic WO 2005/116274 PCT/EP2005/005465 - 26 At the high iron ore feed rates (200 kg/hr) the discharge from the vessel increased sig nificantly while the discharge from the final cyclone only increased slightly. However, the discharge from the final cyclone relative to the vessel did not seem to change. It was further observed that the amount of fines <0.1mm in the discharge was lower than 5 the amount of fines <0.1mm in the feed. This suggests that either the iron ore is not breaking down as much as predicted or that any fines generated are re-agglomerated in the high temperature region of the oxygen lance. The temperature profile through the cyclones also supports this since there were no significant increases in tempera tures through the cyclone system at the higher iron ore feed rates. The product metal 10 lisation levels were maintained in the range of 68-78% during the high iron ore feed rates while the product discharge had up to 48% metallic iron. Oxygen Lance and Vessel Inspection (16/12/03 and 19/12/03) 15 The lance was taken out of the 700-mm vessel and inspected on 16/12/03. In sum mary, the lance was fairly clean. The water cooled pipe had a thin coating of material while the nozzle tip was relatively clean. The nature of the build up (flaky and thin) suggested that this would not lead to any operational problems. 20 Iron Distribution & Agglomeration Analysis of the Brockman ore sample used as feed to the fluidised bed indicated a fines content of approximately 10.6% sub 45 micron. These units were expected to appear as output from cyclone 3 or as thickener sludge. Due to the friable nature of Brockman 25 Ore, it was expected that additional fines would be produced during processing. It was therefore expected that the percentage of iron units exiting the system through cyclone 3 would exceed 10.6%. It was observed that approximately 7% of the iron units input to the fluidised bed were 30 discharged through cyclone 3, either as direct output from cyclone 3 (approximately 4%) or as output from the radial flow scrubber (approximately 3%). Analysis of the main product output from the fluidised bed indicated that an agglomeration mechanism was present within the process. This mechanism appeared to be primarily smaller par- WO 2005/116274 PCT/EP2005/005465 -27 ticles, typically sub 100 micron particles, agglomerating to each other and to larger par ticles. Many modifications may be made to the embodiments of the present invention shown 5 in the Figure without departing from the spirit and scope of the invention.

Claims (44)

1. A direct reduction process for a solid metalliferous material having a particle size distribution that at least in part comprises micron sized particles, which process com 5 prises supplying the metalliferous material, a solid carbonaceous material, an oxygen containing gas, and a fluidising gas into a fluidised bed in a vessel and maintaining the fluidised bed in the vessel, at least partially reducing metalliferous material in the ves sel, and discharging a product stream that comprises the at least partially reduced met alliferous material from the vessel, and 10 which process is characterised by (a) establishing and maintaining a carbon-rich zone within the fluidised bed; 15 (b) passing metalliferous material, including metallised material, through the car bon-rich zone; and (c) injecting the oxygen-containing gas into the carbon-rich zone and oxidising met allised material, solid carbonaceous material and other oxidisable solids and gases and 20 causing controlled agglomeration of particles.

2. Process according to claim 1, characterized by supplying the metalliferous ma terial in the form of fines. 25

3. Process according to claim 2 wherein the metalliferous material is in the form of iron ore fines, characterized in that the fines are sized at minus 6 mm.

4. Process according to claim 2 or 3, characterized in that the fines have an aver age particle size in the range of 0.1 to 0.8 mm. 30

5. Process according to any of the preceding claims, characterized by supplying the metalliferous material with a selected maximum particle size and controlling ag- WO 2005/116274 PCT/EP2005/005465 -29 glomeration so that 90% of the particles discharged from the process as a product stream do not exceed the maximum selected feed size.

6. Process according to any of the preceding claims, characterized by supplying 5 the metalliferous material with a selected maximum particle size and controlling ag glomeration so that no more than 30%, preferably no more than 20%, and more pref erably no more than 10% by weight of the total weight of iron units discharged from the process is carried off in an off-gas stream from the process. 10

7. Process according to any of the preceding claims, characterized by controlling agglomeration by adjusting the feed rates of any one or more of the metalliferous mate rial, the carbonaceous material, the reaction temperature and the oxygen-containing gas. 15

8. Process according to any of the preceding claims, characterized by injecting the oxygen-containing gas into a central region of the vessel, i.e. a region that is lo cated inwardly of a side wall of the vessel.

9. Process according to claim 8, characterized by injecting the oxygen-containing 20 gas so that there is a downward flow of the gas in the vessel.

10. Process according to claim 9, characterized by injecting the oxygen-containing gas with a downward flow in a range of plus or minus 40 degrees to the vertical, pref erably in a range of plus or minus 15 degrees to the vertical 25

11. Process according to any of the preceding claims, characterized by injecting the oxygen-containing gas via at least one lance having a lance tip with an outlet posi tioned in the vessel inwardly of the side wall of the vessel in the central region of the vessel. 30

12. Process according to claim 11, characterized in that the lance tip is directed downwardly, more preferably vertically downwardly. WO 2005/116274 PCT/EP2005/005465 - 30

13. Process according to claim 11 or 12, characterized in that the position of the lance and, more particularly, the height of the outlet of the lance tip, is determined by reference to factors, such as the oxygen-containing gas injection velocity, the vessel pressure, the selection and amounts of the other feed materials to the vessel, and the 5 fluidised bed density.

14. Process according to any of claims 11 to 13, characterized by water-cooling the lance tip to minimise the possibility of accretions forming on the lance tip that could block the injection of the oxygen-containing gas. 10

15. Process according to any of claims 11 to 14, characterized by water cooling an outer surface of the lance.

16. Process according to any of claims 11 to 15, characterized by injecting the oxy 15 gen-containing gas through a central pipe of the lance.

17. Process according to any of the preceding claims, characterized by injecting the oxygen-containing gas with sufficient velocity to form a substantially solids-free zone in the region of the outlet of the lance tip to minimise the formation of accretions 20 that could block the injection of the oxygen-containing gas.

18. Process according to claim 17, characterized in that the oxygen is injected with a velocity in the range 50-300 m/s. 25

19. Process according to any of the preceding claims, characterized by injecting nitrogen and/or steam and/or other suitable shrouding gas and shrouding the region of the outlet of the lance tip.

20. Process according to claim 19, characterized by injecting the shrouding gas 30 into the vessel at a velocity that is at least 60% of the velocity of the oxygen-containing gas. WO 2005/116274 PCT/EP2005/005465 -31

21. Process according to any of the preceding claims, characterized by establish ing reaction zones in a fluidised bed and moving solids and fluidising gas within the bed so that the solids pass through the reaction zones. 5

22. Process according to claim 21, characterized in that the reaction zones may be contiguous.

23. Process according to claim 20 or 21, characterized in that one reaction zone is the carbon-rich zone and that the other reaction zone is a metal-rich zone in which 10 metalliferous material, such as iron ore, is reduced in a solid state.

24. Process according to claim 23, characterized in that the metal-rich zone is lo cated in a lower section of the fluidised bed and the carbon-rich zone is located above the metal-rich zone. 15

25. Process according to any of the preceding claims, characterized in that the fluidised bed comprises upward and downward movement of solids through the zones.

26. Process according to any of the preceding claims, characterized by supplying 20 the metalliferous material, the carbonaceous material, the oxygen-containing gas, and the fluidising gas to the fluidised bed and maintaining the fluidised bed with (a) a downward flow of the oxygen-containing gas, (b) an upward flow of solids and fluidising gas countercurrent to the downward flow of the oxygen-containing gas, and (c) a downward flow of solids outwardly of the upward flow of solids and fluidising gas. 25

27. Process according to claim 26, characterized in that solids in the upward and downward flows of solids are heated by heat generated by reactions between the oxy gen-containing gas, the carbonaceous material and other oxidisable materials (such as CO, volatiles, and H 2 ) in the carbon-rich zone, wherein the solids in the downward flow 30 of solids transfer heat to the metal-rich zone.

28. Process according to claim 26 or 27, characterized in that the upward and downward flows of solids shield the side wall of the vessel from radiant heat generated WO 2005/116274 PCT/EP2005/005465 - 32 by reactions between the oxygen-containing gas and the solid carbonaceous material and other oxidisable solids and gases in the fluidised bed.

29. Process according to any of the preceding claims, characterized in that the 5 carbonaceous material is coal.

30. Process according to any of the preceding claims, characterized in that the fluidising gas comprises a reducing gas, such as CO and H 2 . 10

31. Process according to claim 30, characterized by selecting the amount of H 2 in the fluidising gas to be at least 15% by volume of the total volume of CO and H 2 in the gas.

32. Process according to any of the preceding claims, characterized by discharging 15 the product stream comprising at least partially reduced metalliferous material from the lower section of the vessel.

33. Process according to any of the preceding claims wherein the product stream also comprises other solids, characterized by separating at least a portion of the other 20 solids from the product stream.

34. Process according to claim 33, characterized by returning at least a portion of the other solids to the vessel. 25

35. Process according to any of the preceding claims, characterized by discharging an off-gas stream containing entrained solids from an upper section of the vessel.

36. Process according to claim 35, characterized by separating at least a portion of the entrained solids from the off-gas stream. 30

37. Process according to claim 35 or 36, characterized by maintaining a circulating fluidised bed by separating entrained solids from the off-gas stream and returning at least a portion of the separated solids to the vessel. WO 2005/116274 PCT/EP2005/005465 - 33

38. Process according to any of claims 35 to 37, characterized by returning solids separated from the off-gas to the lower section of the fluidised bed. 5

39. Process according to any of the preceding claims, characterized by preheating metalliferous feed material with the off-gas from the vessel.

40. Process according to claim 39, characterized by treating the off-gas after the preheating step and returning at least a portion of the treated off-gas to the vessel as 10 the fluidising gas.

41. Process according to claim 40, characterized in that the off-gas treatment com prises one or more of (a) solids removal, (b) cooling, (c) H 2 0 removal; (d) CO 2 removal, (e) compression, and (f) reheating. 15

42. Process according to claim 40 or 41, characterized in that the off-gas treat ment comprises returning solids to vessel.

43. Process according to any of the preceding claims with a metallisation greater 20 than 50%, characterized by operating with reducing gas in the fluidising gas

44. Process according to any of the preceding claims, characterized in that the oxygen-containing gas comprises at least 90% by volume oxygen.