Title of Invention

A PROCESS FOR THE RECOVERY OF COBALT PRODUCT FROM A MOLTEN SLAG

Abstract

ABSTRACT 2208/MAS/96 A process for the recovery of cobalt product from a molten alag The process for the recovery of cobalt product from a molten slag having :obalt- and iron-containing constituents, uses a top-submerged lancing njection furnace system. The slag is smelted in a furnace of the system by: 'i) charging carbon-containing reductant to the molten slag in the furnace o as to generate a reducing region at or adjacent to a top surface of the slag; and ii) injecting free-oxygen-containing gas and combustion fuel into the slag by i top-submerged lance of the furnace system to generate a combustion region jetween the top and a bottom surface of the slag. The process enables control )ver the iron content of the product, by adjusting the proximity of the :ombustion region to the slag/metal interface.

Full Text

RECOVERY OF COBALT FROM SLAG This invention relates to a process for the recovery of cobalt from cobalt containing slags. Cobalt containing slags suitable for the recovery of cobalt metal usually have quite low levels of cobalt but relatively high levels of iron, and significant levels of other metals, all mostly present as solutions of oxides in iron-calcium-silicate slags. The level of cobalt may be less than 1%, while the iron content may be up to 50% or higher. Other metals which may be present include copper, nickel and bismuth. Suitable slags for the recovery of cobalt, both for conventional processes and for the present invention, include those from a converting furnace and/or an electric, reverberatory or flash furnace used to process nickel or copper concentrates or mattes. Previously used processes for the recovery of cobalt from slags are -limited in their utility. A disadvantage of these processes is an inability to control the level of production achieved simultaneously with control of the grade of metal recovered. Because of this disadvantage, the known processes are operated so as to limit the level of metal recovery, so as to avoid a resultant metal product having an excessive iron content. Thus, for example, in the use of an electric furnace for recovery of cobalt from slag, enabling recovery of a metal product with only about 3 to 6% Co, constituents in the slag containing cobalt and also those containing iron are reduced at the top surface of the slag, by coke used as a reductant, by the following overall reactions: CoO(s) + C(c) = Co(m) + CO (1) FeO(s) + C(c) =Fe(m) + CO (2) where (s) denotes a constituent of the slag, (m) denotes a constituent of the metal product and C(c) denotes free-carbon of the reductant which, in this case is coke. The levels of cobalt and iron in the slag are controlled under prevailing reduction conditions, by the equilibrium point for the reaction: CoO(s) + Fe(m) = Co(m) + FeO(s) (3) The low density of the coke causes it to float at the upper surface of the slag. Thus, strongly reducing conditions prevail at the upper surface where the slag is in contact with the coke, and reduction by the overall reactions (1) and (2) occurs at that surface; with carbon monoxide being an intermediary in the overall reduction reactions (1) and (2). Once cobalt and iron metal is formed, it settles through the slag to form a metal phase on the bottom of the furnace. The opportunity for reaction (3) is limited to contact between the slag and settling the droplets of iron metal, and surface to surface contact between the slag and the metal phase. However, there is little opportunity for controlling the relative rates of reactions (1) and (2) and, hence, the iron content of metal product comprising the metal phase produced. The overall conditions are such that there is scope only for gross control over the iron content of the metal product. Such inadequate control is possible in a continuous operation by Dalancing the rates of feeding slag and coke or, in a batch operation, by the ime allowed for reduction. The present invention is directed to providing a process for the recovery )f cobalt frorn slags. The process of the invention, at least in a preferred form, enables improved control over the iron content of metal produced. In the process of the invention, cobalt is recovered from a molten slag laving cobalt- and iron-containing constituents, using a top-submerged lancing ijection furnace system. In the process, the s'ag is smelted in a furnace of the ystem by: ) charging carbon-containing reductant to the molten slag so as to enerate a reducing region at or adjacent to a top surface of the slag; and (ii) injecting free-oxygen-containing gas and combustion fuel into the slag by a top-submerged lance of the furnace system to generate a combustion region between the top and a bottom surface of the slag. In the process, there may be a single combustion region in which the free-oxygen containing gas and fuel is injected. Alternatively, there may be two or more combustion regions into each of which free-oxygen containing gas and fuel is injected by a respective top-submerged lance of the furnace system. The carbon-containing reductant can comprise any suitable carbon source. It may comprise a suitable fluid, carbon-containing material, such as fuel oil. natural gas, LPG and/or town gas. However, it preferably is a material containing free-carbon, such as coal or coke, in lump and/or particulate form. Coal is the most preferred reductant for use in the invention, as coal provides a significantly enhanced rate of reduction compared with other carbon-containing reductants. When the carbon-containing reductant is fluid or of relatively fine particulate form, it can be injected, such as by at least one top-blowing lance, or at least one top submerged lance other than the lance or lances providing injected free-oxygen containing gas and fuel. Particularly in such case, reducing conditions can prevail over substantially the entire top surface of the slag, although the reducing region then will principally be located at the or each site of reductant injection. Where the reductant is coal or coke, it preferably is in lump form and may simply be fed to the furnace system via a suitable feed chute or the like. Particularly in the latter case, the reductant will float on the top surface of the slag, tending to provide similar reducing conditions over that surface. The slag present at the commencement of an operating cycle can comprise a heel of molten slag from a preceding cycle, or it can be provided from fresh particulate or molten slag feed material to be smelted. In the case of fresh slag feed material, the slag can be charged to the furnace of the system from another furnace, such as an electric furnace, a flash smelting furnace or a converter, in which it has been produced or melted. Alternatively, the slag can be feed material which is charged to the furnace of the system in particulate and/or lump form and melted therein, using the or each lance providing free-oxygen containing gas to achieve combustion of the fuel supplied to the or each combustion zone. The temperature of the slag during smelting preferably is from 1200°C to 1500°C. To maintain a required temperature level, the free-oxygen containing gas and fuel can be supplied throughout a cycle of operation, or they can be supplied intermittently as required. The fuel can comprise at least one of a suitable fuel oil, natural gas, LPG, particulate coal and particulate coke. The fuel and free-oxygen containing gas preferably pass through a respective passage of the or each lance. If necessary, the fuel is supplied with an entraining, inert carrier gas. The free-oxygen containing gas and fuel are supplied such that, in the or each combustion region, substantially all free-oxygen is consumed in combustion of the fuel. To ensure this, free-oxygen content of the gas is not in excess of stoichiometric requirements for combustion of the fuel, and desirably is below stoichiometric requirements. The free-oxygen-containing gas may be air, oxygen-enriched air, or any other suitable gas containing free-oxygen. In the process of the invention, cobalt metal and iron metal are produced in the reducing region by reactions (1) and (2). However, in the combustion region, another significant reaction occurs, namely: 4FeO(s) + 02 = 4FeO,.5(s) (4) This reaction (4) is possible since, although free-oxygen does not exceed and desirably is below stoichiometric requirements for combustion of the fuel, the relative rates of combustion and reaction of combustion gasses with the slag are such that not all free-oxygen is consumed by combustion of the fuel. As a consequence of this, and of excess of fuel, a minor proportion of the fuel remains in the gas as CO gas which is able to be finally burnt in an afterburning or post-combustion region above the slag bath. Also, due to agitation of the slag resulting from the top-submerged injection, the FeC15(s) resulting from reaction (4) is distributed throughout the Thus, while reaction (7) results in some re-oxidation of cobalt metal, the overall effect of reactions (5) to (7) is to ensure a greater retention of iron in the slag as oxide, relative to retention of cobalt in the slag. Also, oxidation reactions (6) and (7) are found to be able to be enhanced or retarded, relative to reaction (4), depending on the proximity of the lance tip and, hence, the combustion region to the interface between the slag and metal phase. The oxidation reactions are enhanced by lowering the lance tip nearer to the interface, and retarded by raising the lance tip towards the upper surface of the slag. Thus, in addition to reactions (4) to (7) enhancing production of cobalt metal relative to iron metal at a given lance tip height within the slag, an operator is able to adjust the ratio of cobalt metal and iron metal by raising or lowering the lance as required to control the overall state of reduction reactions involved. The operator therefore is able to improve and control the level of reduction of cobalt and iron achieved, and thereby optimise the process for recovery of cobalt with a required iron content. A cobalt containing slag for use in the invention typically will contain constituents of other metals, in addition to iron. The other metals include nickel, copper and bismuth. The non-ferrous metals will tend to be reduced along with cobalt and iron and, to the extent that this is the case, they generally also will report in the metal phase, such as is the case of nickel and copper. However, some non-ferrous metals will report in the smelting off-gases from which they can be recovered, and bismuth is an example of such metal. The process of the invention can be conducted as a continuous or a batch operation. In each case, the process enables the relative rates of reactions (1) and (2) at the upper surface of the slag to be optimised by the choice of reductant, and also by adjustment of the level at which the tip of the or each lance provides top-submerged injection of free-oxygen containing gas. As indicated, selection of the lance tip level allows the production of cobalt metal with a controlled level of iron metal. In a continuous operation, there typically is a continuous feed to the furnace system of slag to be smelted, reductant and free-oxygen containing gas, while there also may be continuous or intermittent supply of fuel. Additionally, the furnace system can be continuously or intermittently tapped, at respective locations, for discharge of metal product and discardable slag. In a batch operation, the molten metal product may be retained in the furnace system, after tapping off the slag, thereby preventing accumulation of iron oxide in the slag to a level tending to reverse reaction (6). Alternatively, at least until the iron content of the slag approaches such level, the molten metal product can be tapped from the furnace system, with a heal of slag being retained for processing of a next batch of slag to be smelted. The slag, if of an appropi.cnc uuinpusiuun, may De smelted without addition of other slag forming material. However, if necessary, slag forming compounds such as SiOz Al203 CaO and/or MgO can be added. In addition to the improved control in recovery of cobalt from a slag provided by the process of the present invention, the process also provides other advantages over previously known processes. The top-submerged lancing system required by the invention is one which has a very low capital investment requirement compared with the electric or smelting furnace of the known processes. The capital investment can be significantly less, in some instances up to an order of magnitude less than, that for the known processes. Also, the process of the invention preferably is able to be operated with low-cost reductant comprising coal, with this resulting in lower operating costs and enhanced reaction rates compared with reliance in the known processes on electricity or coke. Indeed, the known processes are unable to utilise coal as a reductant since, unlike the furnace system of the invention, the furnaces of the known processes are unable to accommodate the large volume of furnace off-gases which results from use of coal. While the process of the invention enables avoidance of a furnace as required by the known processes, it can enable use of such furnace, if available. Thus, as indicated above, the slag to be smelted can be supplied to the furnace of the system used in the process of the invention from another furnace, such as an electric furnace, a flash smelting furnace or a converter. Additionally, if required, slag discharged from the furnace system of the invention can be passed to another furnace, such as an electric furnace, a bath smelting furnace (such as a top-submerged lancing reactor or Noranda reactor), a suspension smelting furnace (such as an Outukumpu smelting furnace), or a converter, for further treatment such as for additional smelting for recovery of its remaining iron content. The process can be operated to produce a sulphidised metal product, if required. This can be achieved by adding, and smelting the slag in the presence of, a sulphide such as FeS, pyrite, pyrrhotite or other concentrate including FeS, FeS2 or other metal sulphides such as a copper concentrate, or sulphates such as CaS04, or a sulphidising agent such as sulphur, in each case to react with the metal product to generate a sulphide phase (matte). This variant of the process can have advantages, as the lower liquidus temperature of the matte enables use of lower smelting temperatures. Also, the matte can be a preferred product for down-stream processing for recovery of cobalt metal or other products. Whether used to produce a metal product or a matte, the process of the invention can accommodate a limited addition of cobalt-containing or other metal-containing secondary material, reverts or scrap to the slag to enable additional metal to be taken-up in the metal product or matte. Additionally, or alternatively, some ores or concentrates can be charged to the furnace of the system for smelting with the slag, such as to produce a metal product of a composition suitable for production of a required alloy, although it generally is not desirable that cobalt-containing ore or concentrate be used for this purpose. In the process of the invention, it is highly desirable that the ratio of free-oxygen to fuel supplied by top-submerged injection to the or each combustion zone provides a substoichiometric level of oxygen. In that ratio, the level of free oxygen can be from 80% to 95% of stoichiometric requirements for full combustion of the fuel. However, the actual level can vary, depending on the mode of operation in use of the process. The process can be operated in one stage producing a single cobalt-containing product, or in two stages. In the latter case, the process may utilise a first stage operated at a higher substoichiometric level of free-oxygen, usually in excess of about 85% such as about 90% of the stoichiometric level, to produce for example a copper-rich metal product containing a minor proportion of recovered cobalt. The process then may utilise a second stage, after separation of the copper-rich metal, which is operated at a lower substoichiometric level of free-oxygen such as from about 85% down to 60%, or lower, of the stoichiometric level, to produce iron-rich metal product containing the balance of recovered cobalt. In the process of the invention, the principal heat energy source is provided, at the or each combustion zone, by combustion of injected fuel by free-oxygen provided by the top-submerged injection; However, carbon monoxide generated by this combustion by reaction (5) and, principally, by •reactions (1) and (2), as well as any hydrogen generated, discharges from the ^slag to a furnace space of the top-submerged lancing injection furnace system. This gas can be combusted above the slag by free-oxygen blown into the furnace space and heat energy from such post-combustion or after-burning supplements heat energy is taken up by the slag. The take-up of heat energy from post-combustion can increase the operating temperature to a required level and/or reduce the level of free-oxygen and fuel consumed as a consequence of the top submerged injection Free-oxygen for post-combustion or after-burning can be supplied by any suitable means. It may be blown into the furnace space, above the slag, by a top blowing lance; that is, by a lance which does not provide for top-submerged injection. However, a lance which does provide top-submerged injection of free-oxygen containing gas and fuel into the slag also can be used to blow free-oxygen into the furnace space above the slag. In the latter case, the top-submerged injection lance may be of a form disclosed in our Australian patent specification 64QS55 (corresponding to US 5251879) or our Australian patent specification 647669 (corresponding to US 5308043) the disclosures of which are incorporated herein and to be read as part of the present disclosure. A lance of the form discicsec r: those specifications has a shroud, disposed around an upper part thereof, through which a lance cooling gas is able to be passed for discharge into the furnace space. In use of a lance of that form in the present invention, the cooling gas is or includes free-oxygen, which provides for post-combustion or after burning above the slag. Otherwise, the top-submerged injecting lance or lances can be of any suitable form. Accordingly the present invention provides a process for the recovery of cobalt product from a molten slag having cobalt and iron-containing constituents, using a top-submerged lancing injection furnace system, wherein the slag is smelted in a furnace of the system by; (i) charging carbon-containing reductant to the molten slag in the furnace so as to generate a reducing region at or adjacent to a top surface of the slag; and (ii) injecting free-oxygen-containing gas and combustion fuel into the slag by a top-submerged lance of the furnace system to generate a combustion region between the top and a bottom surface of the slag. The invention will now be described more in detail with reference to the accompanying drawings, in which; Figure 1 is a schematic, sectional representation of a top-submerged lancing injection furnace system according to the invention; Figure 2 is a flow-chart depicting operation with the system of Figure 1 in a single stage process; and Figure 3 is a flow-chart depicting operation with the system of Figure 1 in a two stage process. With reference to Figure 1, the system 10 shown therein includes a furnace 12 and a top-submerged injecting lance 14. Furnace 12 is of a suitable refractory material and, in use, holds molten cobalt-containing slag 16 from a furnace used to process nickel or copper concentrate or matte, and which additionally contains iron with copper and/or nickel. Adjacent to its base, furnace 12 has a taphole 18 for tapping molten metal 20 (and/or matte), and a taphole 22 for tapping slag 16. Furnace 12 also has an off-take flue 24 through which fume and off-gases can be discharged for subsequent processing. Also, in a roof-portion below flue 24, furnace 12 has a feed port 26, with a feed-control device 26a, by which reductant such as coal and, if required, flux material is able to be charged into the furnace. Adjacent port 26, furnace 12 additionally has an opening 28 through which lance 14 extends and, while not shown, system 12 further includes means by which lance 14 is able to be raised and lowered. With establishment of a sufficient depth of slag 16 in,-furnace 12, injection via lance 14 is commenced. In an initial stage, lance 14 is positioned so that its lower discharge end is above the slag, to cause splashing of the slag 16 and formation of a coating 30 on the outer surface of lance 12. The cooling effect of gas passing through lance 14 freezes coating 30 so as to protect the lance from corrosion by molten slag 16. Lance 14 then is positioned so that its lower end is at a required level below the slag surface, to enable top-submerged injection in the slag 16. Despite the lower end of the lance 14 being in the molten slag 16, coating 30 is able to be maintained by the cooling effect of gas passing through lance 14. With lance 14 positioned for top-submerged injection, fuel such as oil and free-oxygen containing gas such as air is supplied to the upper end thereof from suitable sources (not shown) for injection within the slag 16. Also, reductant such as coal and, if required, suitable flux material is charged via port 26 onto slag 16. The top-submerged injection establishes substantial turbulence within slag 16, as depicted by arrows A and splashing of slag 16, and a combustion and oxidising zone 32 at the lower end of lance 14 in which the fuel is substantially fully combusted. Flux material, if required, melts and combines with slag 16 to achieve and/or maintain a suitable level of slag basicity and/or fluidity. The reductant, preferably in lump form, floats on the top of slag 16 and establishes an upper smelting and reducing zone 34, above the combustion zone 32. In zone 34, the reductant reduces metal species in the slag 16 to the metal, by reactions (1) and (2) in the case of cobalt and iron. The turbulence resulting from submerged injection circulates fresh slag to zone 34 to maintain such reduction. Also, as indicated herein, reactions (3) to (7) occur to varying degrees within slag 16, but with the conditions favouring reduction of cobalt species to the metal to a substantially greater extent, relative to reduction of iron species to the metal, than is possible with conventionally processes. Droplets of the molten metals settle through slag 16 to establish a layer of molten metal 20 below slag 16, in a quiescent zone at the base of furnace 12. Carbon monoxide and hydrogen produced during the smelting and combustion operation is evolved from slag 16 into the furnace space above the slag. These gases, and any entrained carbon dust, can be subjected to post-combustion or after-burning in zone 36 of that space. For this, free-oxygen containing gas such as air can be supplied to zone 36 by a lance (not shown) extending laterally through an upper portion of furnace 12. Alternatively, lance 14 can be of the form of Australian patent specification 640955 or 647669, which has a shroud which terminates in or adjacent to zone 36, with the free-oxygen containing gas for post-combustion being discharged within furnace 12, above slag 16, via the lower end of the shroud. On completion of the smelting of slag 16, or at an intermediate stage, molten metal 20 is tapped from furnace 12 via taphole 18. Also, on completion or at a convenient intermediate stage of smelting, slag 16 can be tapped from furnace 12 via taphole 22. The operation may be continuous, with continuous or periodic charging of fresh slag, or it may be batchwise. In the latter case a heel of slag 16 preferably is retained in furnace 12 to facilitate commencement of a next cycle of operation with a fresh charge of slag. Example 1 Using a system as described for system 12 of Figure 1, 400 kg of copper converter slag was charged to furnace 12 and smelted in a single stage to produce Cu-Fe-Co-Fe alloy. The initial slag contained 3.3% Cu, 0.9% Ni, 0.6% Co, 53% Fe, 20% Si02 and other incidental constituents. The slag was melted, and then reduced at about 1280°C over a period of 90 minutes, generally as depicted by Figure 2. Over that period coarse coal was used as reductant and charged at a rate of about 50 kg/h, while light fuel oil and air was injected into - the molten slag at injection rates sufficient to maintain an operating temperature of about 1280°C. The fuel to air ratio was such as to provide oxygen sufficient for 85% of stoichiometric requirements for combustion of the fuel. The alloy metal produced during the 90 minute smelting period contained 35% Cu, 11.6% Ni, 6.1% Co and 38.9% Fe. The resultant slag contained 0.42% Cu, 0.01% Ni and 0.08% Co, indicating a very substantial recovery of cobalt, and an attainment of an alloy having a high Co/Fe ratio relative to conventional processes. The ratio is very significantly enhanced relative to that for the initial slag, while the alloy was suitable for processing for cobalt recovery. The resultant slag was suitable for disposal or use for a variety of purposes. Example 2 Again using a system as described for system 12 of Figure 1, 500 kg of initial slag similar to that used in Example 1 was charged to furnace 12 and smelted in a two stage process to produce an alloy product in the first stage, and a sulphidised matte product in the second stage. The first stage procedure was similar to that used in Example 1, but fuel oil and air were charged by top-submerged lance injection to maintain the free-oxygen at a sub-stoichiometric level in excess of 85% of stoichiometric requirements, and a melt temperature of from 1250 to 1400°C, generally about 1350°C. Molten alloy produced in the first stage was tapped from the furnace before the second stage. Depending on the actual level of free-oxygen, the duration of the smelting and the rate of addition of coarse coal reductant, the alloy contained from 4-15% Co, 30-70% Fe, 1-25% Cu and 1-25% Ni. The slag resulting from the first stage was retained in the furnace and subjected to second stage smelting. Before or during the second stage, a sulphidising agent was supplied to the furnace to result in metal produced being provided as a sulphide matte phase. The sulphidising agent was selected from sulphidic copper concentrate, pyrite, pyrrhotite, sulphur, or a mixture of a sulphate sucfj as gypsum with carbon and oxidic or metallic iron. Otherwise, the procedure was as for the first stage but with the lance fired at less than 85% stoichiometry, and maintenance of a bath temperature of from 1200 to 1350°C. On completion of the second stage reduction, most of the resultant slag was tapped from the furnace, to leave a sulphidised matte phased produced in the second stage and a heel of the slag. Depending on the level of free-oxygen at which the lance was fired, the duration of smelting, the rate of addition of lump coal reductant, the composition of the slag at the commencement of the second stage, and the level of Co recovery sought, the matte produced has a metal content comprising 4-25% Co, 20-60% Fe, 1-25% Cu and 1-25% Ni. After tapping the slag from the second stage, the matte was upgraded in the same furnace. The upgrading was performed by blowing the heel of slag with the lance, while supplying fluxes such as silica to the slag. The blowing, from above the surface of the slag rather than top-submerged injection, was without addition of reductant, and resulted in oxidation of iron in the matte to increase the level of FeO and FeOi 5 in the slag. The upgraded matte, depending on the composition of the initial matte and the duration of blowing, had a metal content of 10-25% Co, 10-50% Fe, 5-25% Cu and 5-25% Ni. The alloy produced by the single stage process or the first stage of a two stage process, as well as the sulphidised matte product, are suitable for sale to Co refineries, or to be refined, for the recovery of Co, as well as other metals including Cu and Ni, as the metal. In relation to examples 1 and 2, or variation between the flow-charts of Figures 2 and 3, it is to be appreciated that the opportunity for and benefit of a two-stage process tends to arise when Cu and/or Ni levels in the slag are high relative to the Co level. r ' . , - .. .. ■ . J3u and Ni are reduced more readily from slag than is Co. Thus, by having a less strongly reducing first stage and a more strongly reducing second stage, as determined by the level of free-oxygen in each stage, more Cu and/or Ni can be reduced in the first stage relative to Co, enabling higher recovery of Co relative to Cu and/or Ni in the second stage. In addition to benefits detailed herein, the process of the invention has a number of other practical benefits. These include: (a) An ability to use a wider range of cobalt-containing slags - an electric furnace process is limited to slags with a high electrical resistance and which are electrically conducting or which can be fluxed so as to be electrically conducting; (b) the alloy product is able to be suphidised; (c) the slags able to be used can have a relatively high magnesium content, as the process of the invention is able to accommodate operating temperatures of about 1500°C necessitated by such slags. Those skilled in the art will appreciate that there may be many variations and modifications of the configuration described herein which are within the scope of the present invention. Claims: 1. A process for the recovery of cobalt product from a molten slag having cobalt- and iron-containing constituents, using a top-submerged lancing injection furnace system, wherein the slag is smelted in a furnace of the system by: (i) charging carbon-containing reductant to the molten slag in the furnace so as to generate a reducing region at or adjacent to a top surface of the slag; and (ii) injecting free-oxygen-containing gas and combustion fuel into the slag by a top-submerged lance of the furnace system to generate a combustion region between the top and a bottom surface of the slag. 2. The process of claim 1, wherein there is a single combustion region in which the free-oxygen-containing gas and fuel is injected. 3. The process of claim 1, wherein there are at least two combustion regions into each of which free-oxygen-containing gas and fuel is injected by a respective top-submerged lance of the furnace system. 4. The process of any one of claims 1 to 3, wherein the carbon-containing reductant is a fluid reductant selected from the group comprising fuel oil, natural gas, town gas, liquefied petroleum gas and mixtures thereof. 5. The process of claim 4, wherein the reductant is charged to the furnace by injection from above the slag. 6. The process of any one of claims 1 to 3, wherein the carbon-containing reductant is selected from coal, coke and mixtures thereof in a form selected from lump, particulate material and mixtures thereof. 7. The process of claim 6, wherein the reductant is in the form of particulate material and is charged to the furnace by injection from above the slaq. 8. The process of claim 6 or claim 7, wherein the carbon-containing reductant is coal. 9. The process of claim 5 or claim 7, wherein the reductant is injected onto the slag by at least one top-blowing lance. 10. The process of claim 5 or claim 7, wherein the reductant is injected into the slag by at least one top-submerged lance which is other than the lance providing free-oxygen-containing gas and fuel. 11. The process of any one of claims 1 to 10, wherein the slag present at the commencement of an operating cycle of the smelting comprises a heel of molten slag from a preceding cycle. 12. The process of any one of claims 1 to 10, wherein the slag present at the commencement of an operating cycle, is fresh slag feed material which is charged to the furnace of the system from another furnace. 13. The process of claim 12, wherein the slag feed material is charged from a furnace selected from an electric furnace, a bath smelting reactor, a suspension smelting furnace, a flash smelting furnace and a converter, in which the slag has been produced or melted. 14. The process of any one of claims 1 to 12, wherein the slag is charged to the furnace of the system in particulate, lump, or particulate and lump form, and is melted therein using the or each lance providing free-oxygen-containing gas and fuel. 15. The process of any one of claims 1 to 14, wherein the temperature of the slag during smelting thereof is from 1200°C to 1500°C. 16. The process of any one of claims 1 to 15, wherein the fuel is selected from the group comprising fuel oil, natural gas, liquefied petroleum gas, particulate coal, particulate coke and mixtures thereof. 17. The process of any one of claims 1 to 16, wherein the free-oxygen-containing gas and fuel pass through respective passages of the top-submerged lance, and the fuel is supplied through its passage of the lance with an entraining carrier gas. 18. The process according to any one of claims 1 to 17, wherein the free-oxygen-containing gas and fuel are injected at respective feed rates providing for consumption of substantially all of the free-oxygen in combustion of the fuel. 19. The process of claim 18, wherein the free-oxygen-containing gas is injected at below stoichiometric requirements for combustion of the fuel. 20. The process of any one of claims 1 to 19, wherein the free-oxygen-containing gas is selected from the group comprising air, oxygen-enriched air and oxygen. 21. The process of any one of claims 1 to 20, wherein the cobalt product substantially comprises cobalt metal and iron metal. 22. The process of claim 21, wherein cobalt metal and iron metal are produced in the reducing region by the overall reactions: CoO(s) + C(c) = Co(m) + CO (1) FeO(s) + C(c) =Fe(m) + CO (2) where (s) denotes a constituent of the slag, (m) denotes metal of the product and C(c) denotes fee-carbon of the reductant, and wherein the levels of cobalt and iron in the slag are controlled by the equilibrium point for the reaction: CoO(s) + Fe(m) = Co(m) + FeO(s) (3), with carbon monoxide operating as an intermediary in the overall reactions (1) and (2). 23. The process according to claim 22, wherein the reaction: 4FeO(s) + 02 = 4Fe015(s) (4) occurs in the combustion region. 24. The process of claim 23, wherein the slag is agitated by the top- submerged injection whereby FeO-, 5(s) resulting from said reaction (4) is distributed throughout the slag resulting in the reactions: 2Fe015(s) + C = 2FeO(s) + CO (5) Fe(m) + 2Fe01.5(s) = 3FeO(s) (6) Co(m) + 2Fe015(s) = CoO(s) + 2FeO(s).... (7) whereby there is greater retention of iron in the slag as oxide, relative to retention of cobalt in the slag. 25. The process of any one of claims 1 to 24, wherein retention of iron in the slag as oxide relative to cobalt in the slag as oxide is adjusted by variation in the proximity of the combustion region to the interface between the slag and metal phase. 26. The process of any one of claims 1 to 20, wherein the slag is smelted in the presence of a sulphidising agent, whereby the cobalt produce comprises a matte. 27. The process of claim 26, wherein the sulphidising agent is elemental sulphur. 28. The process of claim 26, wherein the sulphidising agent is a compound if sulphur selected from the group comprising sulphides and sulphates. 29. The process of any one of claims 1 to 28, wherein carbon monoxide is generated during the smelting and discharges from the slag into a reaction space above the slag, and wherein free-oxygen-containing gas is blown into the reactor space whereby the carbon monoxide is post-combusted above the slag to provide heat energy to the slag. 30. The process of claim 29, wherein hydrogen is generated during the smelting and discharges from the slag into a reaction space above the slag, and wherein free-oxygen-containing gas is blown into the reactor space whereby the hydrogen is post-combusted above the slag to provide heat energy to the slag. 31. A process for the recovery of cobalt product from a molten slag substantially as herein described with refere¬ nce to the accompanying drawings.

Documents:

2208-mas-1996 abstract-duplicate.pdf

2208-mas-1996 abstract.pdf

2208-mas-1996 claims-duplicate.pdf

2208-mas-1996 claims.pdf

2208-mas-1996 correspondence-others.pdf

2208-mas-1996 correspondence-po.pdf

2208-mas-1996 description (complete)-duplicate.pdf

2208-mas-1996 description (complete).pdf

2208-mas-1996 drawings.pdf

2208-mas-1996 form-2.pdf

2208-mas-1996 form-26.pdf

2208-mas-1996 form-4.pdf

2208-mas-1996 form-6.pdf

2208-mas-1996 petition.pdf