Process for producing carburised molten metal in a smelting apparatus and apparatus for performing said process

Abstract

This invention relates to a process for producing carburised molten metal in a smelting apparatus suitable for further processing and to an apparatus for performing the process.

Description

[0001] PROCESS FOR PRODUCING CARBURISED MOLTEN METAL IN A SMELTING APPARATUS AND APPARATUS FOR PERFORMING SAID PROCESS

[0002] Field of the invention

[0003] This invention relates to a process for producing carburised molten metal in a smelting apparatus and to a process for performing said process.

[0004] Background of the invention

[0005] A known process for smelting a metalliferous material is referred to hereinafter as the "HIsarna" process. The HIsarna® process (a registered trademark by Tata Steel) is associated particularly with producing molten iron from iron ore or another iron- containing material. The term "smelting" is herein understood to mean thermal processing wherein chemical reactions that reduce metal oxides take place to produce molten metal.

[0006] The process is carried out in a smelting apparatus that includes (a) a smelting vessel that includes solids injection lances and oxygen-containing gas injection lances and is adapted to contain a bath of molten metal and slag and (b) a smelt cyclone for pre-treating a metalliferous feed material that defines a cyclone chamber and includes tuyeres for injecting solid feed materials and oxygen-containing gas into the cyclone chamber and is positioned above and communicates directly with the smelting vessel. The HIsarna process and apparatus are described in international application PCT / AU99 / 00884 (WO 00 / 022176) in the name of the applicant and incorporated herein by reference.

[0007] The term "smelt cyclone" is understood herein to mean a vessel that typically defines a vertical cylindrical chamber and includes tuyeres for injecting solid feed materials and oxygen-containing gas into the chamber and is constructed so that feed materials supplied to the chamber move in a path around a vertical central axis of the chamber and can withstand high operating temperatures sufficient to at least partially melt metalliferous feed materials. A tuyere is a tube, nozzle or pipe through which a gas is blown into a furnace, hearth or vessel from the outside. Well-known examples are the tuyeres in the hearth of a blast furnace which provide the hot blast to the blast furnace.

[0008] The smelting vessel includes refractory-lined sections in a lower hearth and water cooled panels in a side wall and a roof of the vessel, and cooling water is circulated continuously through the panels in a closed circuit.

[0009] The smelting vessel also includes a forehearth connected to the smelting chamber via a connection that allows a continuous metal product outflow from the vessel. A forehearth operates as a molten-metal-filled siphon seal, naturally "spilling" excess molten metal from the smelting vessel as it is produced. This allows the molten metal level in the smelting chamber of the smelting vessel to be known and controlled to within a small tolerance - this is essential for plant safety. In one form of the HIsarna process, carbonaceous feed material (typically coal) and optionally flux (typically calcined limestone) are injected into a molten bath in the smelting vessel. The carbonaceous material is provided as a source of reductant and a source of energy. Metalliferous feed material, such as iron ore, optionally blended with flux, is injected into and heated and partially melted and partially reduced in the smelt cyclone. This molten, partly reduced metalliferous material flows downwardly from the smelt cyclone into the molten bath in the smelting vessel.

[0010] Hot reaction gases (typically CO, CO2, H2, and H2O) produced in the molten bath are partially combusted by oxygen-containing gas (typically technical-grade oxygen) in an upper part of the smelting vessel. Heat generated by the post-combustion is transferred to molten droplets in the upper section that fall back into the molten bath to maintain the temperature of the bath.

[0011] The hot, partially-combusted reaction gases flow upwardly from the smelting vessel and enter the bottom of the smelt cyclone. Oxygen-containing gas (typically technical-grade oxygen) is injected into the smelt cyclone via tuyeres that are arranged in such a way as to generate a cyclonic swirl pattern in a horizontal plane, i.e. about a vertical central axis of the chamber of the smelt cyclone. This injection of oxygencontaining gas leads to further combustion of smelting vessel gases, resulting in very hot (cyclonic) flames. Finely divided incoming metalliferous feed material is injected pneumatically into these flames via tuyeres in the smelt cyclone, resulting in rapid heating and partial melting accompanied by partial reduction. The reduction is due to both thermal decomposition of metallic oxides in the metalliferous feed material (e.g. the hematite fraction in case of ferriferous feed material) and the reducing action of CO / H2 in the reaction gases from the smelting vessel. The hot, partially melted metalliferous feed material is thrown outwards onto the walls of the smelt cyclone by cyclonic swirl action and, as described above, flows downwardly into the smelting vessel below for smelting in that vessel. Process gas, which is typically referred to as "off-gas", results from the further post-combustion of reaction gases in the smelt cyclone and is led away from an upper region of the smelt cyclone through an off-gas duct.

[0012] Conventional pig-iron has a high carbon content, typically about 3.8-4.7 wt.%. The presence of carbon in molten metal reduces the liquidus temperature of the molten metal. This carbon is important for the further processing in the LD-steelmaking process (also known as basic oxygen steelmaking (BOS)). An LD vessel (converter) is charged with molten metal resulting from the ironmaking step together with steel or iron scrap (typically about 15-30%). The required thermal energy to melt the scrap and refine the resulting melt into steel is produced during the oxidation process. A water-cooled lance with nozzles is subsequently lowered into the vessel and oxygen blown onto the melt, thereby oxidising the carbon dissolved in the melt and causing the average temperature of the melt to rise to about 1700 °C. The oxygen blowing therefore causes the scrap to melt and mixes the melt by the blowing action and the forming of CO bubbles, the carbon content of the melt to be lowered and helps to remove unwanted chemical elements such as nitrogen, silicon and phosphorus.

[0013] A problem with many of the alternatives for producing steels with a reduced carbon foot-print is that the hot metal (molten metal) that is produced by these alternatives tends to have a lower carbon content than the pig-iron that is produced in the conventional coke and coal based blast furnace process. Direct reduced iron (DRI) is produced from the direct reduction of iron ore conglomerates (mainly hematite, Fe2O3) in the form of lumps, pellets, or fines into iron by a reducing gas. Traditional DRI products that are produced on the basis of coal or natural gas still have reasonably high carbon levels of between 1.5 wt.% to 4%. However, the DRI process using hydrogen as a reducing gas produces iron with a considerably lower carbon content.

[0014] So if the molten metal from the alternative ironmaking processes such as hydrogen based DRI is to be used as input for the LD-process, then the carbon content of the molten metal needs to be increased.

[0015] Objectives of the invention

[0016] It is an object of this invention to provide a method for increasing the carbon content of a molten metal in an alternative iron-making process.

[0017] It also an object to provide a method for producing carburised molten metal from various types of metalliferous feed materials.

[0018] It is also an object to provide to provide a method for increasing the carbon content of a molten iron melt to a level comparable with blast-furnace pig iron.

[0019] Description of the invention

[0020] In a first aspect of invention is embodied in the process for producing carburised molten metal (15) in a smelting apparatus (1), with the apparatus including a smelting vessel (2) that is adapted to contain a bath of molten metal (6) and a slag layer (7), and with the process including the steps of: i. providing the bath of molten metal (6) and the slag layer (7) in the smelting vessel (2), ii. injecting pure oxygen gas (8) into the smelting vessel (2) above the slag layer (7), injecting a first stream of solid metalliferous feed material (11) into the molten metal (6) or slag layer (7) in the smelting vessel (2), and injecting solid carbon containing compounds (10) and / or carbon containing gas (9) into or above the molten metal (6) or slag layer (7) in the smelting vessel (2) for heating and melting the solid metalliferous feed material (11), for reducing any metallic oxide compounds present in the solid metalliferous feed material (11), and for carburising the molten metal (6) in the smelting vessel (2) to a desired carbon content to produce carburised molten metal (15); iii. discharging the hot and (optionally partially) combustible and reducing process gas (14) comprising CO? , CO, H2O and H2compounds in the smelting vessel upwardly out of the smelting vessel (2); iv. discharging carburised molten metal (6) with the desired carbon content from the smelting vessel (2), preferably in a continuous manner; v. discharging molten slag (7) from the smelting vessel (2), preferably separate from the carburised molten metal, preferably in a continuous manner.

[0021] Preferred embodiments are provided by the dependent claims 2 to 14.

[0022] The advantage of the inventive process is that it enables to produce carburised molten metal from various types of solid metalliferous feed materials (mfm). The mfm may be provided in a variety of forms like pellets, briquettes or agglomerates of smaller particles. The mfm needs to be of a certain mass because it has to be able to penetrate the slag layer that is floating on the molten metal in the smelting vessel. On the other hand, if the mfm is too large or heavy then it will take a lot of time for it to melt and the melt may cool too much as a result. If the mfm is propelled into the vessel by means of a solids injection lance or tuyeres then the mfm can be smaller in size than when the mfm is provided in the form of briquettes or larger agglomerates which are able to penetrate the slag layer quickly under the influence of gravity. With suitable tuyeres the mfm may be even in the form of a powder.

[0023] The process according to the invention requires the presence of a smelting vessel in which a suitable slag layer and a bath of molten metal are already present. These may be supplied from an ancillary process, for example the HIsarna process, and transferred into the smelting vessel, or they may be the result of preparatory melting and slag forming activities in the smelting vessel itself. In that case there may need to be ancillary installation available to enable these preparatory melting and slag forming activities.

[0024] In the process according to the invention mfm on the one hand and solid carbon containing compounds (ccc) or carbon containing gases (ccg), or both, on the other hand are propelled into the smelting vessel. The ccc preferably enter the slag layer and the ccg preferably stay above the slag layer. Pure oxygen gas is provided above the slag layer in the smelting vessel. The mixture of pure oxygen and carbon containing gases will, under the conditions in the vessel, reduce any remaining metallic oxide present in the mfm and may also carburise the molten metal resulting in a molten metal with a higher carbon content. The slag contains small solid carbon particles (originating from any ccc injection into the slag layer). FeO and other oxides react with the carbon thereby forming CO gas. Any excess carbon, reacts with oxygen to form CO2and CO. The hot CO2and CO gases transfer their heat to the slag. The oxygen is also used to burn any volatiles (e.g. from ccc) and the reducing gases in the smelting vessel to generate the heat required for the reduction and melting process. It is not intended that the pure oxygen reaches the liquid metal, because the contact of the oxygen with the molten metal will reduce the carbon content of the molten metal instead of increasing it. In this embodiment the smelting vessel functions as a smelting and reducing vessel. When the residence time in the vessel is longer, then the carbon content of the molten metal can be increased accordingly until the desired level is reached. After attaining the desired level of carbon in the molten metal the process is controlled in such a way that the amount of feed balances the amount of slag and carburised molten metal that is discharged from the vessel. This way a continuous process can be obtained.

[0025] In the process the oxygen supplied to the smelting vessel and to the melting cyclone (if present) is injected in the form of substantially pure oxygen. The term "pure oxygen" is here used as understood in the steel-making art. The oxygen content of this pure oxygen is above 90 vol.%, preferably above 95 vol.%, more preferably above 99 vol.%. The pure oxygen supplied to the smelting vessel and to the melting cyclone (if present) may be at low temperature, e.g. below 100°C. This is possible because contrary to prior art processes where oxygen enriched air is used, the volume of the pure oxygen gas entering the process is much smaller than the enriched air of the prior art which contains large quantities of nitrogen. The pure oxygen is preferably supplied by means of a lance or a plurality of lances. Also, the higher the purity of the oxygen supplied to the smelting vessel and to the melting cyclone (if present), the lower the chances of formation of nitrogen-oxides and the lower the thermal impact of the gas stream on the process. Any ccg that is provided into the process may also be provided by means of a lance or a plurality of lances or via tuyeres.

[0026] The means for supplying the solid carbon containing compounds (10) preferably comprises one or more of:

[0027] (i) at least one lance for pneumatically conveying solid carbon compounds in finely divided form;

[0028] (ii) at least one side-tuyere of the smelting vessel for pneumatically conveying solid carbon compounds in finely divided form;

[0029] (iii) at least one means for gravitationally dropping solid carbon compounds into the slag layer.

[0030] Solid mfm can be provided in a similar way, by means of solids injection lances, by tuyeres or just by dropping it into the slag layer.

[0031] In a preferred embodiment the first stream of solid metalliferous feed material consists mainly of solid ferriferous feed material (ffm), and wherein the bath of molten metal consists mainly of molten iron. Preferably the first stream consists of ffm, and the bath of molten metal consists of molten iron.

[0032] In an embodiment the ffm comprises one or more forms of direct reduced iron (DRI), hot briquetted iron (HBI), cold briquetted iron (CBI), solidified pig iron, ferrous scrap, optionally in combination with iron oxides or iron ore. The ffm may also comprise returns from the iron and steel production such as ferrous dusts, mill scale, steelmaking slag (e.g. EAF or BOS slag), and sludge. Preferably the ffm comprises fully reduced direct reduced iron, hot briquetted iron, cold briquetted iron, solidified pig iron, ferrous scrap and does not contain iron ore or unreduced iron oxides, the only exception being surface rust. The advantage of the latter is that the fraction of unreduced material is minimal, so that the process is effectively operated as a smelting vessel for iron as molten metal, which is then subsequently carburised to the required level. So fully reduced direct reduced iron means direct reduced iron that does not contain iron ore or unreduced iron oxides, the only exception being surface rust.

[0033] In the absence of iron oxides or iron ore in the solid ffm there is no need for reduction in the smelting vessel. This makes the process easier to control and the metallurgical process in that case is restricted to melting the solid ffm and carburising the molten iron. The amount of oxides introduced by surface rust, e.g. on scrap, is negligible.

[0034] In a particular embodiment the smelting apparatus also includes a smelt cyclone that is positioned above the smelting vessel and in open connection with the smelting vessel. This embodiment allows the combination of producing (partly) reduced hot, partially melted metalliferous feed material that flows downwardly into the smelting vessel below for smelting in that vessel. This is further reduced in the smelting vessel and the resulting iron joins the molten iron already present in the vessel.

[0035] A preferred embodiment is provided by the process wherein the smelting apparatus (1) also includes a smelt cyclone (3) that is positioned above the smelting vessel (2) in open connection with the smelting vessel (2) so as to form a single reactor therewith and wherein the process including the further steps of: i. leading the hot and (optionally partially) combustible and reducing process gas (14) resulting from one or more of a. the heating and melting the solid metalliferous feed material (11), and b. the reduction of any metallic oxide compounds present in the solid metalliferous feed material (11), and c. the carburisation of the molten metal (6) in the smelting vessel (2) to a desired carbon content, and d. the release of volatiles from injected carbon containing gas, and e. residual reducing components from excess injected carbon containing gas; upwardly out of the smelting vessel (2) through the smelt cyclone (3); ii. introducing a second stream of metalliferous feed material (11') into the smelt cyclone (3) and partially reducing said second stream of metalliferous feed material (11') in the smelt cyclone by means of the hot and (at least partially) combustible and reducing process gas (14) originating from the smelting vessel (2); iii. effecting a post-combustion of the hot and (at least partially) combustible and reducing process gas (14) in the melting cyclone (3) by supplying oxygen thereto so that said second stream of metalliferous feed material (11') is at least partly melted and at least partly reduced in the melting cyclone (3); iv. upwardly discharging an off-gas (17) from the smelt cyclone (3); v. permitting the said at least partly melted and at least partly reduced second stream of metalliferous feed material (11') to pass downwardly from the melting cyclone (3) into the smelting vessel (2); vi. effecting the final reduction and melting of the partially reduced first and second streams of metalliferous feed material (11, 11') and effecting the carburation of the molten metal to the desired carbon content to produce carburised molten metal (15) by the injected oxygen gas (8) and the injected solid carbon containing compounds (10) and / or the carbon containing gas (9).

[0036] This preferred embodiment results in an optimal balance and use of the various gas streams and material flows . The process is very flexible. This embodiment allows to start the process in conventional HIsarna-mode using only iron ore additions in the cyclone and once that conventional HIsarna-process is up and running the addition of solid mfm according to the invention can be initiated. The ratio between producing new molten metal from ore and adding solid metal to be melted can be varied over time and makes the process flexible.

[0037] In an embodiment the second stream of solid metalliferous feed material (11') comprises at most 50 wt.% fresh iron ore. Fresh iron ore in the context of this invention means iron ore that is added to the process for the first time.

[0038] In an embodiment the second stream of solid metalliferous feed material (11') comprises at most 10 wt.% fresh iron ore.

[0039] In an embodiment the second stream of metalliferous material (11') comprises no fresh iron ore.

[0040] In an embodiment the desired carbon content of the carburised molten metal is at least 3 wt.%. This amount of carbon is believed to be adequate for further processing in conventional steelmaking facilities. A preferred carbon content is at least 3.3 wt.%, more preferably of 3.5 wt.% and even more preferably 3.8 wt.%. Still more preferable is a carbon content of at least 4.0 wt.% or even 4.5 wt.%.

[0041] In an embodiment the carburised molten metal is further processed in an electric arc furnace. Such a furnace is usually used to melt scrap material. The problem with melting scrap material is that it is difficult to remove undesirable elements. By using very clean scrap (i.e. a very high iron content and very low amount of undesirable alloying elements) the impact of these undesirable elements can be mitigated by diluting the resulting melt. However, clean scrap is expensive, and the process according to the invention is able to supply a clean molten metal, such as molten iron, and therefore the impact of the undesirable elements can be mitigated by diluting the resulting melt iron in an economical way because there is no need to obtain expensive clean scrap.

[0042] In an embodiment the carburised molten metal is further processed in a reducing electric arc furnace after which it can be further refined to steel in a conventional steelmaking plant. In an embodiment the carburised molten metal is further processed in a conventional steelmaking plant, such as an LD-plant or a plant based on the Klockner Oxygen Blown Maximilianshutte (KOBM) process.

[0043] In an embodiment the second stream of solid metalliferous feed material (2) also comprises returns from the iron and steel production such as metalliferous dusts, mill scale, steelmaking slag (from BOS and / or EAF steelmaking), and sludge.

[0044] In an embodiment the carbon containing compounds comprise coal, charcoal, coke, graphite or biomass, or returns from the iron and steel production such as carbonaceous dusts.

[0045] In an embodiment the second stream of solid metalliferous feed material (2) comprises iron ore.

[0046] If present the melting cyclone 1 and the smelting vessel 2 form one entity, that is to say they are directly connected together by an opening through which both the molten iron ore and the process gas pass, without any connecting pipework because the melting cyclone 1 is placed directly on top of the smelting vessel 2.

[0047] According to a second aspect the invention is also embodied in the use of the method to produce a carburised molten metal having a carbon content of at least 3.0 wt.%, preferably wherein the carburised molten metal is carburised molten iron.

[0048] According to a third aspect the invention is also embodied in an apparatus as claimed in claim 15 to execute the process according to the invention.

[0049] Examples

[0050] The invention will be explained by means of the following, non-limiting examples.

[0051] Example 1

[0052] Smelting vessel wherein nearly all or all iron containing feeds are directly introduced into the smelting vessel 2. Such method of operation can be relevant in case the iron containing feeds primarily consist of metallic iron, such as DRI. In such situation, the smelting vessel will produce limited quantities of process gas. The carburised molten iron is suitable for further processing in a BOS-plant. The carburised molten iron contains adequate amounts of carbon to allow further processing in a BOS-plant, KOBM- plant or an EAF. The off-gas is a reducing process gas.

[0053] Example 2

[0054] A HIsarna® furnace, comprising a melting cyclone 3 and a smelting vessel 2. The melting cyclone is provided with fine iron ore and fine fresh fluxes (such as lime, limestone, dolomite). Additional fluxing is provided with fine (e.g., ground) steelmaking slags (such as LD slag) The melt flows into the smelting vessel, in which coal and / or carbon containing gases and burnt lime are injected. Oxygen is provided in both the melting cyclone 3 and smelting vessel 2 to cover the energy demand of the HIsarna furnace. Also fed into the furnace is a feed rich in metallic iron, such as DRI. Especially for DRI, introduction in the HIsarna smelting vessel will bring the advantage that the slagforming impurities in the DRI become part of HIsarna slag. The mixture of oxygen and coal and / or carbon containing gases will, under the conditions in the vessel, reduce any remaining metallic oxide present in the metalliferous feed material and carburise the molten metal resulting in a molten metal with a higher carbon content. The carburised molten iron contains adequate amounts of carbon to allow further processing in a BOS- plant. The off gas (OG) may be captured.

[0055] Brief description of the figures

[0056] The present invention is described further by way of example with reference to the accompanying and non-limiting figures, of which:

[0057] Figure 1 is a schematic diagram which illustrates an embodiment of the invention according to claim 1.

[0058] Figure 2 shows a schematic embodiment according to claim 5 and 6.

[0059] Figure 3 shows a schematic embodiment according to claim 16.

[0060] Figure 4 shows a schematic embodiment of Example 1.

[0061] Figure 5 shows a schematic embodiment of Example 2

[0062] Figure 1 shows a smelting apparatus (1) comprising a smelting vessel (2) which is more or less open at the top. An off-gas hood (not shown) may be provided to form a flue positioned above the vessel to receive gases generated in the smelting vessel, and this hood may be provided with ducts through which lances (12) can be led into the vessel. Lances (12) are shown for supplying oxygen gas (8) or ccg (9). Additional lances are shown in the side wall of the smelting vessel at different heights for ccc (10) and mfm (11). These lances are positioned such that they either propel the compounds into the slag from outside the slag (the upper set), or directly inside the slag (the lower set). Only one of each is drawn in this 2D-representation, but there may be a plurality of each, preferably more or less equally distributed along the circumference of the smelting vessel, which circumference is usually round or oval in shape to avoid sharp corners. However, less preferably, the smelting vessel may also be rectangular or polygonal with five or more faces. Optional tuyeres (13) are shown to inject ccc (10) and mfm (11) directly into the slag layer. Carburised molten metal (15) may be tapped via a taphole and slag (16). may be tapped via another taphole The very hot, combustible and reducing process gas (RPG, 14) escapes through the opening in the vessel and may be collected and led away by the off-gas hood.

[0063] Figure 2 shows a smelting apparatus (1) comprising a smelting vessel (2) provided with a smelt cyclone (3) on top of the vessel. In this smelting cyclone the very hot RPG (14) that is released in the smelting vessel is used to at least partially reduce a second stream of mfm (11') The supply of additional oxygen (8') is used to combust the RPG (14) to at least partly melt and at least partly reduce the mfm (11') in the melting cyclone 5. The resulting off-gas (OG, 17) is discharged upwardly and may be collected and led away by the off-gas hood (not drawn). The at least partly melted and at least partly reduced mfm (11') drops into the smelting vessel (2) where it can be further reduced as described in relation to figure 1.

[0064] Figure 3 shows a melting cyclone (3) to which a secondary stream of mfm (11') is supplied with a carrier gas. At the same time substantially pure oxygen (8) is supplied to the melting cyclone (3). Directly beneath the melting cyclone and in open connection with it is a smelting vessel (2). The mfm is pre-reduced in the melting cyclone and melted by a reducing process gas (14) originating from the smelting vessel (2). In this process gas a post-combustion is maintained with the oxygen in the melting cyclone (3). The pre-reduced and molten mfm trickles at a temperature of preferably 1400- 1600°C down the wall of the melting cyclone (3) directly into the smelting vessel (2). In the smelting vessel (2) there is, during operation, a bath (6) of molten metal with a slag layer (7) on top of it. Substantially pure oxygen (8) and carbon containing gas (9) may be supplied through a lance into the smelting vessel (2), and solid carbon containing compounds may be supplied via one or more lances (10, not shown) or by means of one or more tuyeres (17, not shown). The pre-reduced iron ore is finally reduced by the carbon compounds thus supplied directly into the slag layer (7), whereby a process gas comprising CO2 and CO is formed that may also contain H2O and H2from the hydrogen originating from the carbon compounds. Together with the oxygen supplied to the smelting vessel (2), the process gas is post-combusted in the smelting vessel thus generating heat. The resulting process gas (14, not shown) flows directly into the melting cyclone (3), is further post-combusted there as mentioned above, and leaves the melting cyclone. The process off-gas (17) leaves the melting cyclone at a temperature of about 1200-1800°C. The sensible heat contained in the off-gas (17) may be converted in a boiler (19) into steam with which electricity may be generated. After the boiler (19) the process gas still contains chemical energy by which electricity may also be generated. The off-gas may be dedusted after the boiler in a venturi scrubber (20) and may be processed further.

[0065] Figure 4 shows a schematic layout of a production facility starting with DRI production. The DRI is subsequently provided to the facility as described in example 1 (i.e. without the cyclone part). The resulting carburised molten metal is then supplied to either a BOS converter plant or an EAF for steelmaking or first to an EAF and then to the BOS converter for steelmaking.

[0066] Figure 5 shows a schematic layout of a production facility starting with DRI production. The DRI is subsequently provided to the facility as described in example 2 (i.e. with the cyclone part). The resulting carburised molten metal is then supplied to either a BOS converter plant or an EAF for steelmaking or first to an EAF and then to the BOS converter for steelmaking.

[0067] Important abbreviations used:

[0068] BOS: Basic Oxygen Steelmaking (also referred to as LD-process (Linz-Donawitz). ccc: solid carbon containing compounds ccg: carbon containing gas

[0069] DRI: direct reduced iron

[0070] EAF: Electric Arc Furnace ffm: solid ferriferous feed materials

[0071] KOBM: Klockner Oxygen Blowing Maximilianshuette mfm: solid metalliferous feed materials

[0072] RPG: reducing process gas

[0073] REF: reducing electric arc furnace

[0074] List of reference numbers:

[0075] 1. smelting apparatus

[0076] 2. smelting vessel

[0077] 3. smelt cyclone

[0078] 4. DRI-production apparatus

[0079] 5. Steelmaking apparatus

[0080] 6. bath of molten metal

[0081] 7. slag layer

[0082] 8. oxygen (8': second stream of oxygen)

[0083] 9. carbon containing gas

[0084] 10. solid carbon containing compounds (10'. second stream of solid carbon containing compounds)

[0085] 11. solid metalliferous feed material (11'. second stream of metalliferous feed material)

[0086] 12. lances

[0087] 13. tuyeres

[0088] 14. and reducing process gas

[0089] 15. discharge means for carburised molten metal

[0090] 16. discharge means for slag

[0091] 17. process off-gas

[0092] 18. discharge means (18) for discharging process off-gas

[0093] 19. boiler

[0094] 20. dedusting means

Claims

CLAIMS1. A process for producing carburised molten metal (15) in a smelting apparatus (1), with the apparatus including a smelting vessel (2) that is adapted to contain a bath of molten metal (6) and a slag layer (7), and with the process including the steps of: vi. providing the bath of molten metal (6) and the slag layer (7) in the smelting vessel (2), characterised in that vii. injecting pure oxygen gas (8) into the smelting vessel (2) above the slag layer (7), injecting a first stream of solid metalliferous feed material (11) into the molten metal (6) or slag layer (7) in the smelting vessel (2), and injecting solid carbon containing compounds (10) and / or carbon containing gas (9) into or above the molten metal (6) or slag layer (7) in the smelting vessel (2) for heating and melting the solid metalliferous feed material (11), for reducing any metallic oxide compounds present in the solid metalliferous feed material (11), and for carburising the molten metal (6) in the smelting vessel (2) to a desired carbon content to produce carburised molten metal (15); viii. discharging the hot and (optionally partially) combustible and reducing process gas (14) comprising CO? , CO, H2O and H2compounds in the smelting vessel upwardly out of the smelting vessel (2); ix. discharging carburised molten metal (6) with the desired carbon content from the smelting vessel (2), preferably in a continuous manner; x. discharging molten slag (7) from the smelting vessel (2), preferably separate from the carburised molten metal, preferably in a continuous manner.

2. Process according to claim 1, wherein the first stream of solid metalliferous feed material (11) consists mainly of solid ferriferous feed material, and wherein the carburised molten metal (15) comprises or consists mainly of molten iron.

3. Process according to claim 2, wherein the solid ferriferous feed material (11) comprises one or more of direct reduced iron, hot briquetted iron, cold briquetted iron, solidified pig iron, ferrous scrap, optionally in combination with iron oxides or iron ore.

4. Process according to claim 2 or 3, wherein the solid feed ferriferous material (11) consists substantially of one or more of direct fully reduced iron, hot briquetted iron, cold briquetted iron, solidified pig iron, ferrous scrap.

5. Process according to any one of claims 1 to 4, wherein the smelting apparatus (1) also includes a smelt cyclone (3) that is positioned above the smelting vessel (2) in open connection with the smelting vessel (2) so as to form a single reactor therewith.

6. Process according to claim 5, wherein the process including the further steps of: vii. leading the hot and (optionally partially) combustible and reducing process gas (14) resulting from one or more of f. the heating and melting the solid metalliferous feed material (11), and g. the reduction of any metallic oxide compounds present in the solid metalliferous feed material (11), and h. the carburisation of the molten metal (6) in the smelting vessel (2) to a desired carbon content, and i. the release of volatiles from injected carbon containing gas, and j. residual reducing components from excess injected carbon containing gas; upwardly out of the smelting vessel (2) through the smelt cyclone (3); viii. introducing a second stream of metalliferous feed material (11') into the smelt cyclone (3) and partially reducing said second stream of metalliferous feed material (11') in the smelt cyclone by means of the hot and (at least partially) combustible and reducing process gas (14) originating from the smelting vessel (2); ix. effecting a post-combustion of the hot and (at least partially) combustible and reducing process gas (14) in the melting cyclone (3) by supplying oxygen thereto so that said second stream of metalliferous feed material (11') is at least partly melted and at least partly reduced in the melting cyclone (3); x. upwardly discharging an off-gas (17) from the smelt cyclone (3); xi. permitting the said at least partly melted and at least partly reduced second stream of metalliferous feed material (11') to pass downwardly from the melting cyclone (3) into the smelting vessel (2);xii. effecting the final reduction and melting of the partially reduced first and second streams of metalliferous feed material (11, 11') and effecting the carburation of the molten metal to the desired carbon content to produce carburised molten metal (15) by the injected oxygen gas (8) and the injected solid carbon containing compounds (10) and / or the carbon containing gas (9).

7. Process according to any one of claims 1 to 6, wherein the desired carbon content of the carburised molten metal (15) is at least 3.0 wt.%.

8. Process according to any one of claims 1 to 7, wherein the carburised molten metal (15) is further processed in an electric arc furnace.

9. Process according to any one of claims 1 to 8, wherein the carburised molten metal (15) is further processed in a reducing electric arc furnace.

10. Process according to any one of claims 1 to 9, wherein the carburised molten metal (15) is further processed in a conventional steelmaking plant, such as an LD-plant or KOBM.

11. Process according to any one of claims 6 to 10, wherein the second stream of solid metalliferous feed material (11') also comprises returns from the iron and steel production such as metalliferous dusts, mill scale, steelmaking slag, and sludge.

12. Process according to any one of claims 6 to 11, wherein the carbon containing compounds (10, 10') comprises coal, charcoal, cokes, graphite or biomass, or returns from the iron and steel production such as carbonaceous dusts.

13. Process according to any one of claims 6 to 12, wherein the second stream of solid metalliferous feed material (11') comprises iron ore.

14. Process according to claim 10 wherein the carburised molten metal (15) is processed into steel.

15. Use of the process according to any one of the claims 1 to 13 to produce a carburised molten metal (15) having a carbon content of at least 3.0 wt.%, preferably wherein the carburised molten metal is carburised molten iron (15).

16. Apparatus (1) for the production of carburised molten iron (15) according to any one of claims 4 to 13, comprising a. a smelting vessel (2); b. supply means for supplying coal (10), in operation of the apparatus, into or above the molten metal (6) or into the slag layer (7) in the smelting vessel(2) above a molten bath of iron (6) in the smelting vessel (2) or into the molten metal (6); c. supply means (8) for supplying pure oxygen into the smelting vessel (2), d. discharge means for discharging carburised molten iron (15) and molten slag (16) from the smelting vessel (2), e. a smelt cyclone (3) located above and in open connection with the smelting vessel (2) so as to form a single reactor therewith, enabling combustible and reducing process gas to pass, in operation, from the smelting vessel (2) directly into the melting cyclone (3) and at least partially melted pre-reduced iron ore passing from the melting cyclone directly into the smelting vessel (2); f. supply means for supplying iron ore into the smelt cyclone (3), g. supply means for supplying oxygen into the smelt cyclone (3), h. discharge means (18) for discharging process off-gas (17) from the smelt cyclone (3), i. optionally a steam-producing boiler (19) in the discharge means for generating steam from sensible heat contained in the process off-gas (17), j. optionally dedusting means (20) downstream of the optional steamproducing boiler (19) for dedusting the process off-gas (17).

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