MXPA01000804A - A direct smelting process and apparatus - Google Patents

Abstract

A process for direct smelting a metalliferous feed material is disclosed. Char and fuel gas are produced by pre-treating coal with an oxygen-containing gas. The fuel gas is used to heat an oxygen-containing gas and/or to produce an oxygen-containing gas in an oxygen plant. Metalliferous feed material, char, and the oxygen-containing gas are injected into a direct smelting vessel, and the metalliferous feed material is smelted to molten metal in the direct smelting vessel using the char as a source of energy and as a reductant.

Description

APPARATUS AND DIRECT FOUNDRY PROCESS Field of the Invention The present invention relates to a process and apparatus for producing a molten metal (such term includes metal alloys), in particular, but not exclusively, iron, from a metalliferous feedstock, such as ores or metal ores, particularly reduced ores and waste streams containing a metal, in a metallurgical vessel containing a molten bath.

Background of the Invention The present invention relates in particular to a direct casting process based on a bath of molten metal to produce a molten metal from a metalliferous feedstock. A process that produces molten metal directly from a metalliferous feedstock is generally referred to as a "direct casting process". A known direct casting process, which Ref.126863 is generally referred to as the Romelt process, is based on the use of a highly agitated slag bath, of high volume, as the means for melting the charged metal oxides at the top with respect to the metal and for the afterburning of the gaseous reaction products and the transfer of the heat when it is required to continue melting the metallic oxides. The Romelt process includes injecting the oxygen enriched air or oxygen into the slags by means of a lower row of nozzles to provide the slag agitation and the oxygen injection into the slags by means of an upper row of nozzles for promote afterburning. In the Romelt process, the metallic layer is not an important reaction medium. Another known group of direct smelting processes that are slag-based are generally described as "deep slag layers" processes. These processes, such as the DIOS and AISI processes, are based on the formation of a deep layer of slag with 3 regions, especially: an upper region of post-combustion reaction gases with injected oxygen; a lower region for melting metal oxides to metals; 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 direct casting process, which is based on a layer of molten metal as a reaction medium and is generally referred to as the Hlsmelt process, is described in International application PCT / AU96 / 00197 (WO 96/31627) on behalf of the applicant. The Hlsmelt process as described in the International application comprises: (a) forming a molten bath having a metal layer and a slag layer on the metal layer in a container; (b) inject in the bath: (i) a metalliferous feedstock, typically metal oxides; Y (ii) a solid carbonaceous material, typically mineral carbon, which acts as a reducing agent for metal oxides and a source of energy; and (c) melting the metalliferous feed material to obtain the metal in the metal layer.

The Hlsmelt process also comprises the post-combustion reaction gases, such as CO and H2, released from the bath and in the space above the bath with the oxygen-containing gas and transfer the heat generated by afterburning to the bath to contribute to the thermal energy required to melt the metalliferous feed material. The Hlsmelt process also comprises forming a transition zone above the nominal stationary surface of the bath in which there are droplets or splashes or streams of molten metal and / or ascending slags and thereafter descending, which provide an effective means for transfer to the bath of the thermal energy generated by the gases of the afterburning reaction above the bath.

Detailed description of the invention An object of the present invention is to provide a direct casting process and apparatus that can be used with a wide range of types of mineral coal, including lower grade mineral carbons. In accordance with the present invention a process was provided for the direct casting of a metalliferous feedstock which includes the steps of: (a) pre-treating the mineral coal with a gas containing oxygen and producing a carbonization and a combustible gas; (b) heating a gas containing oxygen and / or producing an oxygen-containing gas in an oxygen plant using at least part of the fuel gas produced in step (a) as an energy source; (c) injecting the metalliferous feedstock, the carbonized material produced in step (a), and the oxygen-containing gas heated or produced in step (b) in a direct casting vessel; Y (d) directly melting the metalliferous feed material to the molten metal in the direct casting vessel using the carbonized or coke material as a source of energy and as a reducing agent and afterburning the reaction gas produced in the melting process with the gas that contains oxygen.

An advantage of the process of the present invention is that the pretreatment step (a) changes the properties / composition of the mineral coal and makes it more suitable for melting the metalliferous feed material. As a consequence, the process can operate with a lower grade mineral coal at high productivity in terms of the molten metal produced in the direct casting vessel. The term "lower grade mineral coal" means mineral carbon that has low heating values and high levels of impurities relative to mineral coals for normal vapor formation and can be improved or replaced. The term "impurities" means impurities such as sulfur, alkaline substances, salts, and volatile substances. These impurities are partitioned between the coke and the fuel gas in the pretreatment step (a). As a consequence, the pretreatment step (a) leads to reduced loads of the impurities supplied to the direct casting vessel. The reduced impurity loads are an advantage because they are intended so that the rate of melting of the metalliferous metallic material can be increased and the discharge volumes of the exit gas from the container can be reduced. Both results or effects are an advantage. In addition, the process of the present invention includes the advantageous option of using the fuel gas that is produced in step (a) to heat an oxygen-containing gas, preferably air or air enriched with oxygen, which in turn is used in the direct casting container. In direct smelting processes which can operate with hot air or oxygen enriched air to burn off the reaction gases, such as the Hlsmelt process, the task of generating hot air and air enriched with oxygen is a matter of interest significant. The fuel gas produced in step (a) is very suitable as an energy source for heating the air, for example in the wind preheater, and is therefore a significant advantage of the process of the present invention on this basis. The term "metalliferous feedstock" is understood herein to mean any metal feedstock which includes metal oxides, such as ores, particularly reduced ores, and waste streams containing metals. The term "coke" is understood herein to mean a solid product remaining after at least 50% of the volatile substances / bound oxygen / moisture have been removed from the mineral coal. Preferably, step (b) includes supplying the fuel gas to a medium that supplies hot air and using the fuel gas as a source of energy to heat the air in the hot air supplying media. Preferably, the means to which a hot air jet is applied are wind preheater. Preferably, the process includes preheating the metalliferous feedstock utilizing a portion of the fuel gas produced in step (a) prior to the injection of the feedstock into the direct melt vessel. Depending on the composition, the fuel gas can also be used to partially reduce the metal feed material prior to the injection of the feed material into the direct casting vessel. Step (d) can include any direct casting process.

Preferably, step (d) includes the direct casting of the metalliferous feedstock according to the Hlsmelt process which includes: (a) forming a molten bath having a metallic layer and a slag layer on the metal layer in the direct casting vessel; (b) injecting the metal feed material and the coke into the metal layer by means of a plurality of lancets / nozzles; (c) melting the metalliferous feed material to the molten metal substantially in the metal layer; (d) causing the molten metal and slags to be projected as splashes, droplets, and streams into a space above a nominal stationary surface of the molten bath and the formation of a transition zone; Y (e) injecting the oxygen-containing gas into the direct casting vessel by means of one or more of a lancet / nozzle and then burning off the reaction gases released from the molten bath, whereby splashes, droplets, and streams of the molten metal and the slags, ascending and then descending, in the transition zone, facilitate the transfer of heat to the molten bath, and whereby the transition zone minimizes the heat loss from the container by means of the lateral wall in contact with the transition zone.

The term "immobile surface" in the context of the molten bath is here understood to mean the surface of the molten bath under the process conditions in which there is no injection of the gas / solids and hence no agitation of the bath. Preferably, the process operates at high post-combustion levels in the direct casting vessel. Preferably, the post-combustion levels are greater than 60%, where post-combustion is defined as: [CQ2j + [H20] [C02] + [H20] + [CO] + [H2] where: [C02]% by volume of C02 in the outlet gas; [H20]% by volume of H20 in the outlet gas; [CO] =% by volume of CO in the outlet gas; and [H2]% by volume of H2 in the outlet gas.

In accordance with the present invention there is also provided an apparatus for the direct casting of a metalliferous feedstock which includes: (a) a direct casting vessel for melting the metalliferous feed material; (b) a means for producing coke and a fuel gas from the mineral coal and an oxygen-containing gas; (c) a means for generating a gas containing hot oxygen using the fuel gas as a source of energy and thereafter supplying the gas containing the hot oxygen to the direct casting vessel; (d) and a means for supplying the metalliferous feed material and the coke to the direct casting vessel.

The present invention is further described by way of example with reference to the appended drawings, of which: Figure 1 is a flow chart, in a widely schematic form, of a preferred embodiment of the process and apparatus of the present invention; Y Figure 2 is a vertical section through a preferred form of a direct casting container for use in the process / apparatus illustrated in Figure 1.

The description of the preferred embodiment shown in Figure 1 is in the context of producing iron from the ore or iron ore. However, it should be noted that the preferred embodiment is equally applicable to the production of metals (including metal alloys) from another metalliferous feedstock. With reference to Figure 1, the iron ore is heated in a preheater 3 of the iron ore and supplied to a direct casting vessel 105 and melted to the molten iron in this vessel. The mineral coal, in the form of a slurry, and the oxygen, are supplied to a carbonizer 7 of the mineral coal and react and generate temperatures in the range of 800-1000 ° C. The reactions between the mineral coal (including the constituents such as the volatile substances in the mineral coal) and the oxygen, they produce coke and a combustible gas. The term "carbonization unit" is understood herein to mean any suitable apparatus in which the mineral coal and an oxygen-containing gas can be brought into contact to generate the coke and a combustible gas. The coke is discharged from the cooled, accumulated carbonizer 7, and thereafter supplied to the direct casting vessel 105 as a source of energy and as a reducing agent. At least part of the fuel gas, which is discharged from the carbonizer 7 of the mineral coal at a temperature of the order of 1000 ° C, is supplied by means of a scrubber or wet-phase scrubber (not shown) to a system 9 that provides a hot air jet, such as wind preheater, and it is burned to generate heat which heats the air to a temperature of the order of 1200 ° C. The hot air is enriched with oxygen and is supplied to the direct casting vessel 105. As described in greater detail in relation to Figure 2, the air enriched with hot oxygen post-burns the products of the reaction, such as carbon monoxide and Hydrogen, produced in the direct melting of the iron ore and the heat generated by the post-combustion contributes to maintain the temperature inside the direct casting vessel 105. Typically, the process is operated at levels of afterburning in excess of 60% . Part of the fuel gas produced in the carbonizer 7 of the mineral coal is also used to preheat the iron ore in the preheater of the ore 3 at a temperature of the order of 800 ° C. The exit gas produced in the direct casting vessel 105 is discharged at a temperature of the order of 1650 ° C, cooled to 1000 ° C, then after being burned by the addition of cold air, further cooled, and then treated, for example in the scrubber 11 of the exhaust gas, and after that it is released into the atmosphere.

Optionally, part of the outlet gas is used to preheat the iron ore in the preheater 3 of the ore. The process and apparatus described above has a number of advantages over known technology. By way of example, the known two-stage direct casting processes, which include a prereduction stage and a casting stage, focus on minimizing the total energy consumption using the exhaust gases from the casting stage as a reducing agent in the pre-reduction stage or as an energy supply for the gas containing the hot oxygen. The present invention is an alternative to these known processes and focuses on the maximization of productivity. For example, by treating the mineral coal in a separate carbonizer 7 and then injecting the coke produced in the carbonizer into the direct casting vessel 105, the load of impurities in the mineral coal that are taken in the direct casting vessel 105 is reduced. This reduces the casting issues that are related to impurities and makes it possible to increase the productivity of the direct casting vessel and reduce the volume of the exhaust gas produced in the vessel. This also makes it possible to use lower grade mineral carbons in the direct casting of the iron ore. In addition, the fuel gas produced in the carbonizer 7 is a convenient source of the flue gas for heating the air preheaters. In processes, such as the Hlsmelt process, which use air or oxygen-enriched air instead of oxygen to quench the reaction gases, the production of large volumes of hot air or air enriched with hot oxygen is a important issue. Furthermore, the process of the present invention is not limited to the extraction value of the exhaust gases generated in the melt reduction vessel 105 and this makes it possible to operate at post-combustion levels greater than 70%. The direct casting process operating in the direct casting vessel 105 can be any suitable process. The preferred direct casting process, operated in the direct casting vessel, is the Hlsmelt process as described in general terms hereinafter with reference to Figure 2 and in more detail in International application PCT / AU99 / 00538 in the name of the applicant , and the description in the patent specification related to the international application is incorporated herein for reference.

The preferred direct casting process is based on: (a) forming a molten bath having a metal layer and a slag layer on the metal layer in the direct casting vessel 105; (b) injecting the preheated iron ore and the coke into the metal layer by means of a plurality of lancets / nozzles; (c) melting the iron ore to obtain the iron melt material substantially in the metal layer; (d) causing molten iron and slag to be projected as splashes, droplets, and streams in a space above a normal motionless surface of the molten bath and form a transition zone; Y (e) injecting the enriched air with hot oxygen into the direct casting vessel 105 by means of one or more of one of the lancets / nozzles and after quench the reaction gases released from the molten bath and generate the gas phase temperatures of the order of 2000 ° C or higher in the transition zone, whereby splashes, droplets and currents of molten metal and slag, ascending and then descending, in the transition zone, facilitate the transfer of heat to the bath melted, and whereby the transition zone minimizes heat loss from the container by means of the side walls in contact with the transition zone.

The direct casting container 105 can be any suitable container. The preferred direct casting vessel is the container described in general terms thereafter with reference to Figure 2 and in greater detail in the International application PCT / AU99 / 00537 in the name of the applicant and the description in the patent specification relating to the International application is incorporated here for reference. The container 105 shown in Figure 2 has a hearth or bottom that includes a base 3 and the sides 55 formed of refractory bricks; the side walls 5 which form a generally cylindrical barrel extending upwardly from the sides 55 of the hearth or bottom and which includes an upper barrel section 51 and a lower barrel section 53; a roof 7; an outlet 9 for the exhaust gases; a refining furnace 57 for discharging the molten metal continuously; a connection 71 of the refining furnace interconnecting the home or bottom and the refining furnace 57; and a mustache 61 for unloading the molten slags. In use, under conditions of the process in a permanent state, the container 105 contains a molten iron bath and the slags which include a layer 15 of molten metal and a layer 16 of molten slags on the metal layer 15. The arrow marked by the number 17 indicates the position of the nominal immobile surface of the metallic layer 15 and the arrow marked by the number 19 indicates the position of the nominal immobile surface of the slag layer 16. The term "immobile surface" is understood to mean the surface when there is no injection of gas and solids into the container. The container 105 also includes 2 lancets / nozzles 11 for injecting the solids extending downwards and inwards at an angle of 30-60 ° with respect to the vertical through the side walls 5 and towards the slag layer 16. The position of the lancets / nozzles 11 is selected so that the lower ends are above the immobile surface 17 of the metallic layer 15 under the process conditions in the permanent state. In use, under the process conditions in a permanent state, the preheated iron ore, the coke, and the fluxes (typically lime and magnesia) entrained in a carrier gas (typically N2) are injected into the metal layer 15 by means of the lancets / nozzles 11. The moment of the solid material / carrier gas causes the solid material and the gas to penetrate the metallic layer 15. The coal partially dissolves in the metal and remains partially as solid carbon. The iron ore is melted until the metal is obtained and the foundry reaction generates the carbon monoxide gas. The gases transported to the metallic layer 15 and generated by means of the casting produce a significant flotation elevation of the molten metal, the solid carbon, and the slags (interspersed in the metallic layer 15 as a consequence of the injection of the solid / gas) from the metallic layer 15 which generates an upward movement of the splashes, the droplets and the currents of the molten metal and the slag, and these splashes, and droplets, and streams, entrain the slags because they move through the slag layer 16. The floating rise of the molten metal, solid carbon and slags produces a substantial stirring in the metallic layer 15 and the slag layer 16, with the result that the slag layer 16 expands in its volume and has a surface indicated by arrow 30. The degree of agitation is such that a reasonably uniform temperature exists in the regions of the metal and slag - typically, 1450 - 1550 ° C with a variation in temperature of no more than 30 ° in each region. In addition, the upward movement of splashes, droplets and currents of molten metal and slags, caused by the rise of floating molten metal, solid carbon, and slag, extends into the upper space 31 above the material melted in the container and: (a) forms a transition zone 23; Y (b) projects some of the molten material (predominantly slag) beyond the transition zone and over the section part 51 of the upper barrel 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 the molten metal and the slag. The container 105 further includes a lancet 13 for injecting the oxygen-enriched, hot air into the container 105. The lancet 13 is centrally located and extends vertically downward toward the container. The position of the lancet 13 and the flow velocity of the gas through the lancet 13 are selected so that under the conditions of process in a permanent state, the gas containing the oxygen penetrates the central region of the transition zone. and keep a space essentially free of metal / slag around the end of the lancet 13. In use, under the conditions of process in a permanent state, the injection of the gas containing the oxygen by means of the lancet 13 afterburning the gases of reaction CO and H2 in the transition zone 23 and in the free space 25 around the end of the lancet 13 and generates high gas phase temperatures of the order of 2000 ° C or higher in the gas space. The heat is transferred to the splashes, droplets, and up and down streams, of the molten material in the region of the gas injection and the heat is then transferred partially to the metal layer 15 when the metal / slag returns to the metal layer 15. The free space 25 is important to achieve high levels of post-combustion because it allows the entrainment of the gases in the space above the transition zone 23 towards the end region of the lancet 13 and therefore increases the exposure of the reaction gases available for afterburning. The combined effect of the position of the lancet 13, the flow velocity of the gas through the lancet 13, and the upward movement of the splashes, droplets and currents of the molten metal and the slag, is to shape the zone of transition 23 around the lower region of the lancet 13 - generally identified by the numerals 27. This shaped region provides a partial barrier for transferring the heat by radiation to the side walls 5. Also, under the conditions of process in a permanent state, the droplets, splashes and currents of the metal and the slags, ascending and descending, are an effective means for the transfer of heat from the transition zone 23 to the molten bath with the result that the temperature of the transition zone 23 in the region of the side walls 5 is of the order of 1450-1550 ° C. The container 105 is constructed with reference to the levels of the metallic layer 15, the slag layer 16, and the transition zone 23 in the container 105 when the process is operating under the conditions of the process in a permanent state and with reference to the splashes, droplets and currents of the molten metal and slags that are projected towards the upper space 31 above the transition zone 23 when the process is operating under the operating conditions in a permanent state, so that: (a) the hearth or bottom and the lower barrel section 53 of the side walls 5 which contact the metal / slag layers 15/16 are formed with bricks of refractory material (indicated by cross hatching in the Figure); (b) at least part of the lower barrel section 53 of the side walls 5 is supported by panels 8 cooled with water; and (c) the upper barrel section 51 of the side walls 5 and the roof 7 that contact the transmission zone 23 and the upper space 31, are formed of the panels 58, 59 cooled with water.

Each water-cooled panel 8, 58, 59 (not shown) in section 51 of the upper barrel of the side walls 5, has parallel upper and lower edges and parallel side bordss and is curved to define a section of the cylindrical barrel. Each panel includes a water cooling tube, internal, and an external water cooling pipe. The pipes are formed in a serpentine configuration with the horizontal sections interconnected by the curved sections. Each pipeline also includes an inlet for water and an outlet for water. The pipes are displaced vertically so that the horizontal sections of the external pipe are not immediately below the horizontal locations of the inner pipe when they are observed 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 refractory material with rams which fills in the spaces between the adjacent horizontal sections of each pipe between the pipes. Each panel also includes a support plate which forms an external surface of the panel. The water inlets and outlets for the water in 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. By way of example, although the preferred embodiment includes the supply of at least part of the fuel gas to the carbonizer 7 of the mineral coal, the present invention is not so limited and includes other options, such as the supply of the fuel gas to an oxygen plant. as a source of energy to produce oxygen.

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, property is claimed as contained in the following

Claims (8)

1. A process for directly melting a metalliferous material, which includes the steps of: (a) pre-treat the mineral coal with a gas that contains oxygen and produce a carbonization and a combustible gulf; (b) heating a gas containing oxygen and / or producing an oxygen-containing gas in an oxygen plant using at least part of the fuel gas produced in step (a) as | a source of energy; (c) injecting the target feed material; Ífero, the carbonized material produced in e. step (a), and the gas containing oxygen heated or produced in step (b) in a direct casting vessel; Y D) directly melting the metalliferous feed material to the molten metal in the direct casting vessel using the carbonized material or coke as a source of energy and as a reducing agent and afterburning the reaction gas produced in the melting process with the gas that contains oxygen.

2. The process according to claim 1, characterized in that step (b) includes heating the oxygen-containing gas by supplying a combustible gas to a medium that provides a hot air jet and using the combustible gas as a power source for heating the oxygen-containing gas in the media that provides a jet of hot air.

3. The process according to claim 2, characterized in that the means providing a hot air jet are preheating the air.

4. The process according to any of the preceding claims, characterized in that the gas containing the oxygen is air or air enriched with oxygen.

5. The process according to any of the preceding claims, characterized in that it includes preheating the metalliferous feedstock using the part of the combustible gas produced in step (a) prior to the injection of the feedstock into the casting vessel. direct

6. The process according to claim 5; characterized in that it also includes the pre-reduction of the metalliferous feed material by using part of the fuel gas produced in step (a) prior to the injection of the feed material into the direct casting vessel.

7. The process according to any of the preceding claims, characterized in that the step of direct casting (d) includes: (a) forming a molten bath having a metallic layer and a slag layer on the metal layer in the direct casting vessel; injecting the metal feed material and the coke into the metal layer by means of a plurality of lancets / nozzles; (c) melting the metalliferous feed material to the molten metal substantially in the metal layer; (d) causing the molten metal and slags to be projected as splashes, droplets, and streams into a space above a nominal stationary surface of the molten bath and the formation of a transition zone; Y (e) injecting the oxygen-containing gas into the direct casting vessel by means of one or more of a lancet / nozzle and then burning off the reaction gases released from the molten bath, whereby splashes, droplets, and streams of the molten metal and the slags, ascending and then descending, in the transition zone, facilitate the transfer of heat to the molten bath, and whereby the transition zone minimizes the heat loss from the container by means of the lateral wall in contact with the transition zone. 8 An apparatus for the direct casting of a metalliferous feed material, characterized in that it includes: (a) a direct casting vessel for the melting of the metal feed material; (b) a means for producing coke and a combustible gas from the mineral coal and a gas containing oxygen; means for generating a gas containing hot oxygen using the fuel gas as a source of energy and thereafter supplying the gas containing the oxygen calierite to the direct casting vessel; (d) and means for supplying the metalliferous feed material and coke to the direct casting vessel,