MXPA01000806A - A direct smelting process - Google Patents

Abstract

A process for direct smelting a metalliferous feed material is disclosed. The process includes the steps of partially reducing metalliferous feed material and subsantially devolatilising coal in a pre-reduction vessel and producing a partially reduced matelliferous feed material and char. The process also includes direct smelting the partially reduced matalliferous feed material to molten metal in a direct smelting vessel using the char as a source of energy and as a reductant and post-combusting reaction gas produced in the direct smetling process with pre-heated air or oxygen-enriched air to a post-combustion level of greater than 70%to generate heat required for the direct smelting reactions and to maintain the metal in a molten state.

Description

GTN ppnr.F, sn? F. rtr? mtr-.tnw DTRFICT? The present invention relates to a process for the production of molten metal (a term that includes metal alloys) in particular, but in no way means exclusively iron, from a metal feed material, such as minerals, particularly small minerals and waste streams containing metal, in a metallurgical vessel containing a liquified metal bath. The present invention relates particularly to a direct casting process based on a liquified metal bath for the production of molten metal from a metalliferous feedstock. A process that produces molten metal directly from a metalliferous feedstock is generally referred to as a "direct melting process". A known process of direct smelting, which is referred to in general as the Romelt process, is based on the use of a highly agitated slag bath, of great volume as the means for the smelting of metal oxides charged by the cap to REF: 126862 metal and for post-combustion of reaction products, gaseous and for heat transfer as required to continue the melting of metal oxides. The Romelt process includes injecting air enriched with oxygen or oxygen into the slag by means of a lower row of nozzles to provide agitation of the slag and oxygen injection into the slag by means of an upper row of nozzles to promote the post-combustion. In the Romelt process, the metal layer is not an important reaction medium. Another known group of direct smelting processes that is based on slag is generally described as "deep slag" processes. These processes, such as the DIOS or AISI processes, are based on the formation of a deep layer of slag with 3 regions, specifically: an upper region for the post-combustion of the reaction gases with injected oxygen; a lower region for the melting of metal-to-metal oxides; and an intermediate region which separates the upper and lower regions. As with the Romelt process, the metal layer below the slag layer is not an important reaction medium. Another known process of direct casting, which depends on a layer of molten metal as a reaction medium and is referred to in general as the Hlsmelt process, is described in International Application PCT / AU96 / 00197 (WO 96/31627) in the Applicant name . The Hlsmelt process, as described in the International application, comprises: (a) forming a liquified metal bath having a metal layer and a slag layer on the metal layer in a container; (b) injecting into the bath: (i) a metalliferous feedstock, typically metal oxides; and (ii) a solid carbonaceous material, typically mineral carbon, which acts as a reducer of the metal oxides and a source of energy; and (c) melting the metal-to-metal feed material in the metal layer.

The Hlsmelt process also comprises the post-combustion of reaction gases, such as CO and H2, released from the bath in the space above the bath with oxygen-containing gas and transferring the heat generated or post-combustion to the bath to contribute to the thermal energy required to melt the metal feed material. The Hlsmelt process also comprises forming a transition zone above the firm, nominal surface of the bath in which there are droplets or splashes or updrafts and therefore downwards of molten metal and / or slag which provide an effective means to transfer to the bath the thermal energy generated by the post-combustion of the reaction gases above the bath. An object of the present invention is to provide an improved direct casting process. In accordance with the present invention there is provided a process for the direct casting of a metalliferous feedstock which includes the steps of: (a) supplying the metalliferous feedstock and mineral coal to a pre-reduction vessel; (b) partially reducing the metalliferous feedstock and substantially devolatilizing the mineral coal in the pre-reduction vessel and producing a partially reduced metalliferous feedstock and coal slag. (c) supplying the partially reduced metal feed material and the coal slag produced in step (b) to a direct casting vessel; (d) supplying air or air enriched with preheated oxygen to the direct casting vessel; and (e) melt directly from the metalliferous feed material, partially reduced to molten metal in the direct casting vessel using the coal slag as a source of energy and as a reducing agent and promote afterburning of the reaction gas produced in the process Direct casting with air or air enriched with pre-heated oxygen to a post-combustion level of more than 70% to generate the heat required for direct casting reactions and to keep the metal in a molten state.

The process is particularly, although by no means exclusively, relevant for medium and highly volatile mineral coals. It is understood herein that half-volatile mineral carbons means mineral carbons containing 20-30% by weight of volatile substances. It is understood herein that highly volatile mineral coals mean mineral coals that contain more than 30% by weight of volatile substances. In the case of medium and highly volatile mineral carbons, the basis of the present invention is the realization that the substantial devolatilization of these types of mineral coal prior to the introduction of the mineral coal into a direct casting vessel makes it possible to economically operate a process Direct casting at post-combustion levels of 70% or more using air or air enriched with heated oxygen as the oxygen-containing gas for post-combustion. Preferably, step (b) produces partially reduced metalliferous feedstock having a degree of pre-reduction of less than 65%. Preferably, the concentration of oxygen in the air enriched with oxygen is less than 50 volume percent.

The term "substantially devolatilize" means the removal of at least 70 percent by weight of the volatile substances from the mineral coal. The term "post-combustion" is defined as: [CO?] + [Fí? L] [CO2] + [H2O] + [CO] + [H2] where: [CO2] =% by volume of CO2 in the malodorous gas; [H2O] =% by volume of H2O in the malodorous gas; [CO] =% by volume of CO in the malodorous gas; and [H2] =% by volume of H2 in the malodorous gas.

The term "malodorous gas" is defined herein as the gas generated by the melting and post-combustion reactions and before the optional addition of any additional carbonaceous feedstock such as natural gas in that gas. Preferably, the process includes pre-heating of air or air enriched with oxygen for passage (d) at a temperature in the range of 800-1400 ° C and then supplying air or air enriched with pre-heated oxygen to the direct casting vessel in step (d). More preferably, the temperature is in the range of 1000-1250 ° C. Preferably, the process includes the use of the malodorous gas discharged from the direct casting vessel as a source of energy for preheating the air or air enriched with oxygen before supplying the air or air enriched with oxygen pre-heated. heated to the direct casting vessel in step (d). Preferably, the process includes cooling the malodorous gas discharged from the direct casting vessel before using the malodorous gas as the energy source. Preferably, the process includes using part of the malodorous gas discharged from the pre-reduction vessel as a source of energy for preheating the air or air enriched with oxygen before supplying the air or air enriched with oxygen. heated to the direct casting vessel in step (d).

Preferentially, the process includes pre-heating the air or air enriched with oxygen in one or more of a hot blast furnace. Preferably, the process includes the pre-heating of the metalliferous feed material before the step (a) of supplying the metalliferous feed material to the pre-reduction vessel. Preferably, the process includes pre-heating the metal feed material using the malodorous gas discharged from the pre-reduction vessel. Preferably, the pre-reduction vessel is a fluidized bed. More preferably, the process includes recycling the malodorous gas discharged from the fluidized bed back into the fluidized bed. Preferably, the process includes recycling at least 70% by volume of the malodorous gas discharged from the fluidized bed back into the fluidized bed. The term "fluidized bed" is understood herein to include both types of bubbling and circulation. The combination of bubbling and circulation is also included.

The term "metalliferous feedstock" is understood herein to mean any metalliferous feedstock, which includes metal oxides, such as minerals, partially reduced minerals and waste streams containing metal. Step (e) can be any suitable direct casting process. Preferably, step (e) includes direct melting of the metalliferous feedstock, partially reduced according to the Hl sitielt process which includes: (a) forming a liquified metal bath having a metal layer and a layer slag in the metal layer in the direct casting vessel; (b) injecting the metalliferous feedstock and the coal slag into the metal layer by means of a plurality of lances / nozzles; (c) melting the metalliferous feedstock to melt the metal substantially in the metal layer; (d) cause molten metal and heel to be projected as splashes, droplets and currents in a space above a fixed, nominal surface of the molten metal bath and form a transition zone; and (e) injecting the air or air enriched with preheated oxygen into the direct casting vessel by means of one or more of a lance / nozzle and promoting the post-combustion of the reaction gases released from the molten metal bath, to that the splashes, droplets and upward and therefore downward currents of the molten metal and slag in the transition zone facilitate the transfer of heat to the molten metal bath, and because of that the transition zone minimizes the heat loss of the container by means of the side wall in contact with the transition zone.

It is understood herein that the term "metal layer" means a region or zone that is predominantly metal. Specifically, the term covers a region or zone that includes a dispersion of molten slag in a continuous volume of metal. It is understood herein that the term "fixed surface" in the context of the liquefied metal bath means the surface of the liquefied metal bath under the process conditions in which there is no injection of gas / solid materials and therefore there is no agitation of the bath. The present invention is further described by way of example with reference to the accompanying drawings, of which: Figure 1 is a flow sheet, in largely schematic form, of the process of the present invention; and Figure 2 is a vertical section through a preferred form of a direct casting container for use in the process shown in Figure 1. The description of the preferred embodiment shown in Figure 1 is in the context of iron production from the iron ore.

However, it is noted that the preferred embodiment is equally applicable for the production of metals (including metal alloys) from another metalliferous feed material.

With reference to Figure 1, the iron ore is pre-heated in the pre-heater cyclones 103, 105 at a temperature in the order of 750 ° C and transferred to a fluidized bed reactor 107 which operates at a temperature in the order of 800-1000 ° C. Mineral coal (typically, medium and / or highly volatile coal), oxygen, and a reduction gas which includes high levels of CO and H2 are also supplied to reactor 107. The pre-heated iron ore is partially reduced in the reactor 107 at a degree of pre-reduction which is preferably less than 65% and the mineral coal is substantially devolatilized and forms coal slag. The term "degree of pre-reduction" in this context means the percentage of oxygen removed presuming a starting point of Fe203 and presuming that Fe is 100% pre-reduction. The malodorous gas discharged from the reactor 107 is transferred through the pre-heater cyclones 103,105 and preheats the iron ore supplied to these cyclones. The malodorous gas is then cooled in a gas scrubber with Venturi construction 108. The malodorous gas, cooled is divided into two streams. A stream, which is at least 70% of the total volume of malodorous gas, is supplied to a CO2 gas scrubber 110, heated again and then returned as the fluidizing, reducing gas to reactor 107. The other stream is it supplies to heat the blast furnaces 109 and is used as combustion gas which heats the furnaces. The partially reduced iron ore and coal slag from reactor 107, which are typically at temperatures in the order of 600-900 ° C, and the preheated air at a temperature in the order of 1200 ° C from the furnaces 109 are supplied to a direct casting vessel 111. The partially reduced iron ore was melted to the molten iron in vessel 111 and the reaction gases, such as CO and H2 produced in the pre-reduced iron ore smelter are -burned or post-burned at a post-combustion level of at least 70%. The heat generated by the post-combustion is used to maintain the temperatures inside the container 111. A portion of the malodorous gas discharged from the container 111 is transferred by means of a gas scrubber with Venturi construction 113 to the ovens 109 and used as a gas. of combustion which contributes to heat ovens 109.

° The direct casting process operating in the direct casting vessel 111 can be any suitable process. The direct smelting process, preferred is the Hlsmelt process as described in general terms below with reference to Figure 2 and in more detail in the International application PCT / AU99 / 00583 in the name of the applicant. The description in the patent specification accommodated in the International application is incorporated herein for reciprocal reference. The preferred direct melt process is based on: (a) forming a liquified metal bath having a metal layer and a slag layer in the metal layer in the direct casting vessel 111; (b) injecting the partially reduced iron ore and coal slag (and optionally another carbonaceous material, such as coal, additional) into the metal layer by means of one or more of a lance / nozzle; (c) melting the partially reduced iron ore to melt the iron substantially in the metal layer; (d) causing the molten material to be projected as splashes, droplets, and streams in a space above a fixed, normal surface of the molten metal bath and form a transition zone; Y (e) injecting the air or air enriched with preheated oxygen into the direct casting vessel 111 by means of one or more of a lance / nozzle and the afterburning of the reaction gases released from the liquefied metal bath to a level post-combustion of greater than 70% and the generation of gas phase temperatures in the order of 2000 ° C or higher in the transition zone; due to this the splashes, droplets and rising and therefore descending currents of molten metal and slag in the transition zone facilitate the transfer of heat to the liquefied metal bath, and because of that the transition zone minimizes the heat loss of the container by means of the side walls in contact with the transition zone.

The direct casting container 111 can be any suitable container. The preferred direct casting vessel is the container described in general terms below with reference to Figure 2 and in more detail in the International application PCT / AU99 / 00573 in the name of the applicant and the description in the patent specification housed therein. the international application are incorporated herein for reciprocal reference. The container 111 shown in Figure 2 has a core including a base 3 and the sides 55 formed of the refractory bricks; the side walls 5 which generally form a cylindrical body that extends upwards from the sides 55 of the heart and which include an upper section of the cylindrical body 51 and a lower section of the cylindrical body 53; a roof 7, a mouth or outlet 9 for malodorous gases; a forehearth or furnace 57 for continually discharging the molten metal; a connection of the antecryol or refining furnace 71 interconnecting the heart and the antecryol or refining furnace 57; and a hole in the lid 61 to discharge the molten slag. In use, under conditions of the steady-state process, the container 111 contains a liquified metal bath of iron and slag which includes a layer 15 of molten metal and a layer 16 of molten slag on the metal layer 15. The arrow marked by the number 17 indicates the position of the fixed, nominal surface of the metal layer 15 and the arrow marked by the number 19 indicates the position of the fixed, nominal surface of the slag layer 16. The term "fixed surface" it is understood that means the surface when there is no injection of gas and solid materials into the container. The container 111 also includes 2 solid material injection nozzles / nozzles 11 extending downwardly and inwardly at an angle of 30-60 ° from the apex through the side walls 5 and into the slag layer 16. The position of the lances / nozzles 11 were selected so that the lower ends are above the fixed surface 17 of the metal layer 15 under the conditions of the steady-state process. In using, under the conditions of the steady-state process, the partially reduced iron ore and coal slag of the reactor 107 (and optionally another carbonaceous material, such as mineral coal), and the fluxes (typically quicklime and magnesia) introduced into a gas carrier (typically N2) are injected into the metal layer 15 by means of the lances / nozzles 11. The drive of the solid material / carrier gas causes the solid material and the gas to penetrate the metal layer 15. The carbon dissolves partially inside the metal and partially remains as solid carbon. The iron ore melts to metal and the foundry reaction generates carbon monoxide gas. The gases transported in the metal layer 15 and generated by the casting produce the buoyancy, significant lift of the molten metal, the solid carbon and the slag (introduced in the metal layer 15 as a consequence of the solid materials / the gas / injection) of the metal layer 15 which generates an upward movement of the splashes, droplets and currents of the molten metal and the slag, and these splashes and droplets and streams introduce the slag as they move through the slag layer 16. The buoyancy lift of molten metal, solid carbon and slag causes substantial agitation in the metal layer 15 and the slag layer 16, with the result that the slag layer 16 expands in volume and has a surface indicated by arrow 30. The degree of agitation is such that there is a reasonably uniform temperature in the metal and slag regions - typically, 1450 - 1550 ° C with a vari temperature of no more than 30 ° C in each region. In addition, the upward movement of splashes, droplets and streams of molten metal and slag caused by the buoyancy lift of molten metal, solid carbon, and slag extends into the upper space 31 above the molten material in the container and: (a) forms a transition zone 23; and (b) projecting some molten material (predominantly slag) beyond the transition zone and in the upper section portion of the cylindrical body 51 of the side walls 5 which is above the transition zone 23 and on the roof 7 .

Generally speaking, the slag layer 16 is a continuous volume of liquid, with gas bubbles therein, and the transition zone 23 is a continuous volume of gas with splashes, droplets and streams of molten metal and slag. The container 111 further includes a lance 13 for injecting the air or air enriched with preheated oxygen from the ovens 9 in the container 111. The lance 13 is located centrally and extends vertically downwards in the container. The position of the lance 13 and the velocity of the gas flow through the lance 13 are selected so that under the conditions of the steady-state process the oxygen-containing gas penetrates the central region of the transition zone 23 and maintains a space essentially free of metal / slag around the end of the lance 13. In use, under the conditions of the steady-state process, the injection of the oxygen-containing gas by means of the lance 13 produces the afterburning of the exhaust gases. reaction CO and H2 at a post-combustion level of more than 70% in the transition zone 23 and in the free space 25 around the end of the lance 13 and generates high gas phase temperature in the order of 2000 ° C or higher in the gas space. The heat is transferred to the splashes, droplets and upward and therefore downward currents of molten material in the region of the gas injection and the heat is then partially transferred to the metal layer 15 when the metal / slag returns to the layer of metal. 15. The clearance 25 is important to achieve high post-combustion levels because this makes it possible to entrain gases in the space above the transition zone 23 within the region of the end of the lance 13 and due to this increases the exposure of the available reaction gases to post-combustion. The combined effect of the position of the lance 13, the flow velocity of the gas through the lance 13, and the upward movement of splashes, droplets and streams of molten metal and slag is the shape of the transition zone. around the lower region of the lance 13 - generally identified by the number 27. This formed region provides a partial barrier for the transfer of heat by radiation to the side walls 5. Also, under the conditions of the steady state process, the droplets, splashes and up and down streams of metal and slag are an effective means to transfer heat from the transition zone 23 to the liquefied metal bath with the result that the temperature of the transition zone 23 in the region of the side walls 5 is in the order of 1450 ° C-1550 ° C. The container 111 is constructed with reference to the levels of the metal layer 15, the slag layer 16, and the transition zone 23 in the container 111 when the process is operable under the conditions of the steady state process and with reference to the splashes, droplets and streams of molten metal and slag projecting into the upper space 31 above the transition zone 23 when the process is operable under the conditions of steady-state operation, so that: (a) the heart and the lower section of the cylindrical body 53 of the side walls 5 contacting the metal / slag layers 15/16 are formed of bricks of refractory material (indicated by the cross-hatching in the figure); (b) at least part of the lower section of the cylindrical body 53 of the side walls 5 is supported by the water-cooled panels 8; and (c) the upper section of the cylindrical body 51 of the side walls 5 and the roof 7 that make contact with the transition zone 23 and the head space 31 are formed of water cooled panels 58, 59.

Each water-cooled panel 8, 58, 59 (not shown) in the upper section of the cylindrical body 51 of the side walls 5 has parallel upper and lower edges and parallel edges, lateral and is curved to define a section of the cylindrical body. Each panel includes an interior cooling pipe with water and an exterior cooling pipe with water. The pipes are formed in a serpentine configuration with horizontal sections interconnected by the curved sections. Each pipe also includes a water inlet and a water outlet. The pipes move vertically so that the horizontal sections of the outer pipe are not immediately behind the horizontal sections of the inner pipe when viewed from an exposed face of the panel, i.e., the face that is exposed to the interior of the container. Each panel also includes a tamped refractory material which fills the spaces between the horizontal, adjacent sections of each pipe and between the pipes. Each panel also includes a support plate which forms an outer surface of the panel. The water inlets and water outlets of the pipes are connected to a water supply circuit (not shown) which circulates the water at a high flow rate through the pipes. Many modifications can be made to the preferred embodiment, described above, without departing from the spirit and scope of the present invention.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following claims is claimed as property.

Claims (11)

1. A process for the direct casting of a metal feed material, characterized in that it includes the steps of: (a) supplying the metalliferous feed material and mineral coal to a pre-reduction vessel; (b) partially reducing the metalliferous feedstock and substantially devolatilizing the mineral coal in the pre-reduction vessel and producing a partially reduced metalliferous feedstock and coal slag; (c) supplying the partially reduced metal feed material and the coal slag produced in step (b) to a direct casting vessel; (d) using malodorous gas discharged from the pre-reduction vessel, as a source of energy and preheating the air or air enriched with oxygen and subsequently supplying the air, or the air enriched with oxygen, preheated, to the direct casting vessel; and (e) directly melting the partially reduced metal feed material to molten metal in the direct casting vessel using the coal slag as a source of energy and as a reducing agent and promoting afterburning of the direct smelting gas with the air or air enriched with oxygen, pre-heated, at a post-combustion level of more than 70%, to generate the heat required for direct casting reactions and to keep the metal in a molten state.

2. The process according to claim 1, characterized in that the concentration of oxygen in the air enriched with oxygen is less than 50 volume percent.

3. The process according to claim 1 or claim 2, characterized in that it includes preheating the air or air enriched with oxygen for passage (d) at a temperature in the order of 800-1400 ° C and then supplying the air or air enriched with oxygen, pre-heated, to the direct casting container in step (d).

4. The process according to claim 3, characterized in that the temperature is in the range of 1000-1250 ° C.

5. The process according to any of the preceding claims, characterized in that it includes using the malodorous gas discharged from the direct casting vessel, as a source of energy for pre-heating the air or air enriched with oxygen, before supplying the air or the air enriched with oxygen, heated, to the direct casting vessel in step (d).

6. The process defined in any of the preceding claims, characterized in that it includes pre-heating the air or air enriched with oxygen in one or more of a hot blast furnace.

7. The process defined in any of the preceding claims, characterized in that the pre-reduction vessel is a fluidized bed.

8. The process according to claim 7, characterized in that it includes recycling the malodorous gas discharged from the fluidized bed back into the fluidized bed.

9. The process according to claim 8, characterized in that it includes recycling at least 70% by volume of the malodorous gas discharged from the fluidized bed back into the fluidized bed.

10. The process according to any of the preceding claims, characterized in that step (e) includes: (i) forming a liquified metal bath having a metal layer and a slag layer on the metal layer in the casting vessel direct (ii) injecting the metalliferous feedstock and coal slag into the metal layer, by means of a plurality of lances / nozzles; (iii) melting the metal feed material to molten metal substantially in the metal layer; (iv) cause the molten metal and the 5 slag be projected as splashes, droplets and currents, in a space above a fixed, nominal surface, of the liquefied metal bath and form a transition zone; and (v) injecting the air or air enriched with oxygen, pre-heated, into the direct casting vessel, by means of one or more of a lance / nozzle and promoting the combustion of the released reaction gases. of the liquefied metal bath, whereby, the splashes, droplets and currents, ascending and then descending, of molten metal and The slag, in the transition zone, facilitates the transfer of heat to the liquefied metal bath, and because of that the transition zone minimizes the heat loss of the container through the 25 side wall in contact with the transition zone.

11. The process according to any of the preceding claims, characterized in that it also includes injecting mineral coal into the direct casting container, whereby the mineral coal acts as a source of energy and as a reducing agent in the container. PF.STTMF.N? F. T.? TNVFNG.TOM A process is described for the direct casting of a metal feed material. The process includes the steps of partially reducing the metalliferous feedstock and substantially devolatilizing the mineral coal in a pre-reduction vessel and producing a partially reduced metalliferous feedstock and coal slag. The process also includes the direct casting of the metalliferous feed material, partially reduced to molten metal in a direct casting vessel using the coal slag as a source of energy and as a reducing agent and promoting the post-combustion of the reaction gas. produced in the process of direct melting with air or air enriched with pre-heated oxygen to a post-combustion level greater than 70% to generate the heat required for direct casting reactions and to keep the metal in a molten state.