MXPA00002928A - Direct smelting process for producing metals from metal oxides - Google Patents

Abstract

A molten bath-based direct smelting process for producing metals from metal oxides (including partially reduced metal oxides) is disclosed. The process includes causing upward movement of splashes, droplets, and streams of molten material from a metal layer (15) of the molten bath which:(i) promotes strong mixing of metal in a slag layer (16) of the molten bath so that the slag layer (16) is maintained in a strongly reducing condition leading to FeO levels below 8 wt%based on the total weight of the slag in the slag layer (16);and (ii) extends into a space above a nominal quiescent surface of the molten bath to form a transition zone (23).

Description

DIRECT FOUNDRY PROCESS TO PRODUCE METALS FROM METALLIC OXIDES / DESCRIPTION OF THE INVENTION The present invention relates to a process for producing molten metal (a term which includes metal alloys), in particular, though by no means exclusively, iron, from metalliferous feedstock, such as ores, partially reduced ores and water stream. waste containing metal, in a metallurgical vessel containing a molten bath. The present invention relates particularly to a direct casting process based on molten metal bath to produce molten metal from a metalliferous feedstock. The process used most widely to produce molten metal is based on the use of a blast furnace. The solid material is loaded in the upper part of the furnace and the molten iron is poured from the ground. The solid material includes iron ore (in sintered form, from lumps or grit), coke, and flows and forms a permeable load that moves downward. Preheated air is injected into the bottom of the oven, which can be enriched with oxygen, and moves up through the permeable bed and generates REF .: 33154 carbon monoxide and heat by coke combustion. The result of these reactions is to produce molten iron and slag. A process that produces iron by reduction of iron ore below the melting point of the iron produced is generally classified as a "direct reduction process", and the product is referred to as DRI. The FIOR process (fluid iron ore reduction) is an example of a direct reduction process. The process reduces iron ore fines as the fines are fed by gravity through each reactor in a series of fluid bed reactors. The fines are reduced by compressed reducing gas that enters the lower bottom of the reactor in the series, and flows countercurrent to the downward movement of the fines. Other direct reduction processes include vat furnace-based processes, processes based on static vat furnace, rotating earth based processes, rotary kiln-based processes and retort-based processes. The COREX process produces cast iron directly from coal without the requirement of a blast furnace. The process includes a 2-stage operation in which: (a) DRI is produced in a vat furnace from a permeable bed of iron ore (in the form of lumps or grit), coal and fluxes; and (b) the DRI is then loaded without cooling in a connected melting gasifier. The partial combustion of coal in the fluidized bed of the melting gasifier produces a reducing gas for the shaft furnace. Another known group of processes for producing molten iron is based on cyclonic converters in which the iron ore is melted by combustion of oxygen and reducing gas in an upper melting cyclone and melted in a melter containing a cast iron bath. The lower melter generates the reducing gas for the upper melting cyclone. A process that produces molten metal directly from ore is generally referred to as a "direct casting process". A known group of direct smelting processes is based on the use of electric furnaces as the main source of energy for smelting reactions. Another known direct casting process, which is generally referred to as the Romelt process, is based on the use of a large volume of a highly agitated slag bath as the means to melt metal oxides charged by the top to metal and combustion Subsequent gaseous reaction product- and heat transfer as required to continue the melting of metal oxides. The Romelt process involves injecting air enriched with oxygen or oxygen into the slag by means of a row of lower nozzles to provide slag agitation and oxygen injection into the slag by means of an upper row of nozzles to promote combustion later. In the Romelt process, the metal layer is not an important reaction medium. Another known group of direct smelting processes that are based on slag are generally described as "deep slag" processes. These processes, such as the DIOS and AISI processes, are based on the formation of a deep layer of slag with three regions, specifically: an upper region for reaction gases subjected to subsequent combustion with injected oxygen, a lower region for oxide smelting. metal to metal; 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 which is generally referred to as the Hlsmelt process, is described in the 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 bath of molten iron and slag in a container; (b) injecting into the bath: (i) a metalliferous feedstock, typically metal oxides; and (ii) carbonaceous solid material typically carbon, which acts as a reducer of the metal oxides and a source of energy; and (c) melting the metal-to-metal feedstock in the metal layer. The Hlsmelt process also comprises post-combustion reaction gases, such as CO and H2, released from the bath in the space above the bath containing oxygen-containing gas and transferring the heat generated by subsequent combustion, to the bath to contribute thermal energy needed to melt metalliferous feed materials. The Hlsmelt process also comprises forming a transition zone above the nominal quiescent surface of the bath, in which there are ascending and subsequently descending droplets or splashes or streams of molten metal and / or slag which provide an effective means of transfer to the bath of the thermal energy generated by the post-combustion reaction gases, above the bath. The Hlsmelt process, as described in the international application, is characterized in that a transition zone is formed by injecting a carrier gas and a metalliferous feed material and / or a solid carbonaceous material and / or other solid material into the bath through of a section of the side of the container that is in contact with the bath and / or from the top of the bath so that the carrier gas and the solid material penetrate the bath and cause the molten material and / or the slag to be projected into the bath. of space above the surface of the bathroom. The Hlsmelt process, as described in the international application, is an improvement on the previous forms of the Hlsmelt process, which forms the transition zone by injection in the lower part of the gas and / or carbonaceous material inside the bath, which causes droplets and splashes and currents, and molten metal and slag that project from the bathroom. An object of the present invention is to provide an improved direct casting process for producing metals from metal oxides (including partially reduced metal oxides). According to the present invention, there is provided a direct casting process for producing metals from metal oxides (including partially reduced metal oxides) which includes the steps of: (a) forming a molten bath having a metallic layer and a layer of slag on the metal layer, in a metallurgical vessel; (b) injecting a metalliferous feedstock into the metallic layer via one or more of a lance / nozzle and melting the metalliferous material to metal in the metallic layer; (c) injecting a solid carbonaceous material into the metal layer by means of one or more nozzles / nozzles in an amount that is sufficient such that the level of carbon dissolved in the metal is at least 3% by weight based on in the total weight of coal and metal; (d) causing upward movement of splashes, droplets and molten material streams from the molten bath metal layer, which: (i) promotes strong mixing of the metal in the slag layer of the molten bath so that the layer of slag is maintained in a strongly reducing condition leading to FeO levels of less than 8% based on the total slag weight in the slag layer; and (ii) extends the space above the nominal quiescent surface of the molten bath to form a transition zone; and (e) injecting an oxygen-containing gas into the container by means of one or more of a lance / nozzle for post-combustion reaction gases released from the molten bath, whereby splashes, droplets and ascending melt streams and subsequently downwards in the transition zone facilitate the transfer of heat to the molten bath, and so the transition zone minimizes heat loss from the container and the side walls in contact with the transition zone. Typically, the molten metal is a major part and the slag is the remaining part of the molten material in the splashes, droplets and streams of molten material of the metal layer. Typically, splashes, droplets and streams of molten material entrain additional molten material (particularly slag) as they move upward. In addition, increasingly, splashes, droplets and streams of molten material lose momentum and fall downward toward the metal layer. In view of the higher density of the metal compared to the slag, the relative amount of metal in the molten material in the splashes, droplets and currents decreases with the distance from the metal layer to the point where the transition zone may include small, if any, of metal. The upward movement of the splashes, droplets and streams of molten material from the metal layer ensure that there is strong mixing of the metal in the slag layer. The injection of solid carbonaceous material into the metallic layer ensures that there are high levels of dissolved carbon in the metal that is mixed in the slag layer. As a consequence of the carbon dissolved in the metal in the slag layer and the strong mixing of the metal in the slag layer, the slag layer desirably has low levels (ie less than 8% by weight) of FeO in the slag layer. human waste. It is understood herein that the term "smelting" means a term processing wherein chemical reactions that reduce the metal oxides to produce liquid metal take place. It is understood that the term "metallic layer" herein means that region of the bath that is predominantly metal. Specifically, the term encompasses a region or zone that includes a dispersion of molten slag in a continuous volume of metal. It is understood that the term "slag layer" herein means that region of the bath that is predominantly slag. Specifically, the term encompasses a region or zone that includes a dispersion of molten metal in a continuous volume of slag. The term "quiescent surface" in the context of molten bath is understood to mean the surface of the molten bath under process conditions in which there is no gas / solids injection and therefore no agitation of the bath. The space above the nominal quiescent surface of the molten bath is referred to below as the "upper space". It is preferred that the level of carbon dissolved in the metal be greater than 4% by weight. It is preferred that the FeO concentration in the slag layer be less than 6% by weight, and more preferably less than 5% by weight. It is preferred that the process further comprises selecting the amount of solid carbonaceous material injected into the metal layer which must be greater than that required to melt the metalliferous feed and to generate heat and maintain such reaction rates so that the powder entrained in the the gaseous discharge left by the container contains at least some excess carbon. It is preferred that the concentration of solid carbon in the gaseous discharge powder of the container is in the range of 5 to 90% by weight (more preferably 20 to 50% by weight) of the weight of the powder in the gas discharge, a dust generation rate of 10-50 g / nm3 in the gas discharge. Preferably, step (e) of the process operates at high levels of primary back combustion. The term "primary post combustion" means: [CQ21 JH2OI [C02] + [H, 0] + [CO] + [H2] where : [C02] = volume in% of C02 in the gas discharge; [H20] = volume, in% of H20 in the gas discharge; [CO] = volume, in% CO in the gas discharge; and [H2} = volume, in% of H2 in the gas discharge. More particularly, the term "primary rear combustion" also means the subsequent combustion which results from the melting process in the absence of any addition of supplementary carbonaceous material for other purposes.

In some instances, a supplemental source of solid or gaseous carbonaceous material (such as coal or natural gas) can be injected into the gaseous discharge of the vessel in order to capture the thermal energy in the form of chemical energy. An example of such supplementary injection of carbonaceous material is the injection of natural gas which pyrolyses and converts, and therefore cools, the gas discharge and at the same time enriches its fuel value. The supplementary carbonaceous material may be added in the upper reaches of the vessel or in the gas discharge pipe after the gas discharge has left the vessel. The addition of supplemental carbonaceous material can be used to decrease primary back combustion in a manner which is virtually independent of the main melting process in the vessel. The process of the present invention can operate at a primary back combustion greater than 40%. Preferably, the process operates at a primary back combustion greater than 50%. More preferably, the process operates at a primary back combustion greater than 60%. The transition zone formed in stage (d) (ii) above is important for three reasons.

First, splashes, droplets and upward and downward currents of molten material are an effective means of transferring to the molten bath the heat generated by subsequent combustion of the reaction gases in the upper space above the nominal quiescent surface of the bath . Secondly, the molten material and particularly the slag in the transition zone is an effective means for minimizing heat losses by radiation via the side walls of the container. Third, carbon containing dust in the transition zone reduces radiation heat losses to the side walls of the container. A fundamental difference between the process of the present invention and the processes of the prior art is that, in the process of the present invention, the main foundry reaction is the metal layer, and the main gas oxidation region (i.e. the generation of heat) are separated from the metal layer and, more particularly, are in the transition zone, and these regions are spatially well separated and the heat transfer is via the physical movement of the molten material between the two regions. Preferably, the upward movement of the splashes, droplets and streams of molten material, particularly slag, which form the transition zone, is generated by injecting the metalliferous feed material and / or the carbonaceous material into a carrier gas through an or more than one spears / nozzles that extend downwards towards the metallic layer. More preferably, as indicated in the above, one or more of a lances / nozzles extend towards the side walls of the container and are inclined inwardly and downwardly towards the metal layer. This injection of solid material towards, and subsequently through the metallic layer, has the following consequences. (a) the moment of the solid material / carrier gas causes the solid material and the gas to penetrate the metallic layer; (b) the carbonaceous material, typically coal, is devolatilized and therefore produces gas in the metal layer; (c) coal dissolves predominantly in the metal and remains partially as a solid; (d) the metalliferous material is molten to metal by the coal derived from the injected coal as described in subsection (c) and the foundry reaction generates gaseous carbon monoxide; AND (e) gases transported in the metallic layer and generated via devolatilization and melting produce a significant upward flotation of the molten material, specifically molten metal (which includes dissolved carbon) and molten slag (which is extracted within the layer metal from the top of the metal layer and as a consequence of solid / gas injection), and the solid carbon from the metal layer resulting in an upward movement of splashes, droplets and streams of molten material, and These splashes, droplets and streams carry additional slag as they move through the slag layer. Another option, although by no means the only one, is to generate an upward movement of splashes, droplets and streams of molten material to inject the metalliferous feed material and the carbonaceous material by means of one or more nozzles at the bottom of the vessel or at the bottom of the vessel. side walls of the container that make contact with the metal layer. The injection of metal feed material and carbonaceous material can be through equal or separate lances and / or nozzles.

It is preferred that the injection of the carrier gas and the carbonaceous material and / or the metalliferous feed and / or other solid material within the bath be sufficient to project splashes, droplets and streams of molten material into the space above the bath, in a manner similar to source. Preferably, the metallurgical vessel includes: (a) the lances / nozzles described above for injecting oxygen containing gas and lances / nozzles to inject solid materials, such as metalliferous material, carbonaceous material (typically carbon) and fluxes, into the container; (b) discharge orifices for discharging molten material and slag from the container; and (c) one or more gas discharge outlets. The metalliferous feedstock may be in any suitable form, for example, it may be in the form of ores, partially reduced ores, DRI (direct reduced iron), iron carbide, rolling scale, blast furnace dust, fine sintered, powder BOF or a mixture of such materials. In the case of partially reduced ores, the degree of prior reduction can vary from relatively low levels (for example to FeO) to relatively high levels (for example 70 to 95% metallization). In this regard, the process also includes partially reducing metal ores and subsequently injecting the partially reduced ores in the metal layer. The metal feed material can be pre-heated. The carrier gas can be any suitable carrier gas. It is preferred that the carrier gas is an oxygen deficient gas. It is preferred that the carrier gas comprises nitrogen. The oxygen-containing gas can be oxygen, air or air enriched with oxygen containing up to 40% oxygen by volume. It is preferred that the gas containing oxygen be air. It is particularly preferred that the air is preheated. The present invention is further described by way of example with reference to the accompanying drawing which is a vertical section through a metallurgical vessel schematically illustrating a preferred embodiment of the process of the present invention. The following description is in the context of casting an iron ore to produce cast iron and it is understood that the present invention is not limited to this application and that it is applicable to any suitable metal ore and / or concentrate -including metal ore. partially reduced and waste materials. The container shown in Figure 1 has a base 3, side walls 5 which form a generally cylindrical barrel, a roof 7, an upper outlet 9 for gas discharge and discharge orifices (not shown) for discharging metal and slag. The base 3 and the lower section 8 of the side walls 5 are formed of refractory material. The roof 7 and an upper section 10 of the side walls 5 are formed of panels cooled with water. The panels are described in detail in the Australian Provisional Application PP4426 of the applicant, and the description of that application is incorporated herein by cross reference. When used, the container contains a molten iron and slag bath including a layer 15 of molten metal and a layer 16 of molten slag on the metal layer 15. The arrow indicated by the number 17 indicates the position of the nominal quiescent surface of the metal layer 15 and the arrow with the number 19 indicates the position of the nominal quiescent surface of the slag layer 16. It is understood that the term "quiescent surface" means a surface where there is no injection of gas or solids into the container.

The container also includes nozzles / nozzles 11 for injection of solids extending downward and inward, through the side walls 5 within the layer 16 of slag. The position of the nozzles / nozzles 11 is selected such that the lower ends are above the quiescent surface 17 of the metal layer 15. When it's used, the iron ore, the solid carbonaceous material (typically coal) and fluxes (typically lime and magnesia) are entrained in the carrier gas (typically N2) and injected into the metallic layer 15 via the nozzles / nozzles 11. The moment of solid material / carrier gas causes the solid material and gas to penetrate the metal layer 15. The carbon is devolatilized and therefore produces gas in the metal layer 15. The coal partially dissolves in the metal and remains partially as solid carbon. The iron ore melts to metal and the melting reaction generates gaseous carbon monoxide gas. The gases transported within the metal layer 15 and generated via devolatilization and melting produce a significant upward flotation effect of the molten metal, solid carbon and molten slag (extracted within the metal layer 15 from the top, the layer 15 of metal as a consequence of the injection of solids / gas) from the metal layer 15 which generates an upward movement of splashes, droplets and streams of molten material and solid carbon, and these splashes and droplets and streams entrain slags as they move through layer 16 of slag. The upward flotation of the molten material and the solid carbon causes substantial agitation in the metallic layer 15 and the slag layer 16, with the result that the slag layer 16 expands in volume and has a surface indicated by the arrow 30. The degree of agitation is such that the metallic layer 15 and the slag layer 16 are each substantially homogeneous to the extent that there are reasonably uniform temperatures throughout each region - typically 1450 - 1550 ° C - and reasonably uniform compositions throughout. each region. In addition, the upward movement of splashes, droplets and streams of molten material caused by the upward floatation of the molten metal, solid carbon and slag extends into the upper space 31 above the molten material in the container and forms an area of the molten material. of Transition. In general terms, slag layer 16 is a liquid continuous volume, with gas and metal bubbles (typically in the form of droplets) therein, and the transition zone 23 is a continuous volume of gas with splashes, droplets and streams of molten material (which is at least predominantly slag at this stage) therein.

The substantial agitation of the metallic layer 15 and the slag layer 16 caused by the upward float discussed above ensures that there is strong mixing of the metal in the slag layer 16. The deliberate injection of solid carbonaceous material into the metal layer 15 ensures that there are high levels of dissolved carbon in the metal and that they are mixed in the slag layer. As a consequence of the carbon dissolved in the metal in the slag layer and the strong mixing of the metal in the slag layer, the slag layer desirably has low levels (typically less than 8% by weight) of FeO in the slag. . The container further includes a lance 13 for injecting an oxygen-containing gas which is centrally located and extends vertically downward within the container. The position of the lance 13 and the gas flow rate through the lance 13 are selected so that 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. The injection of the oxygen-containing gas via the lance 13 subsequent to the combustion reaction gases CO and H2 in the transition zone 23 and in the free space around the end of the lance 13 and generates high 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 molten material in the gas injection region and the heat is then partially transferred to the metal layer when the metal / slag returns to the metal layer 15. The free space 25 is important to obtain high levels of post-combustion material, ie, greater than 40%, because it allows the entrainment of gases in the space above the transition zone 23 within the end region. of the lance 13 and in this way increases the exposure of available reaction gases for subsequent combustion. The combined effect of the position of the lance 13, rate of gas flow through the lance 13 and the upward movement of the splashes, droplets and streams of molten material conform to the transition zone 23 around the lower region of the lance 13 -identified generally with the number 27. This shaped region provides a partial barrier to heat transfer by radiation to the side walls. In addition, splashes, droplets and up and down streams of molten material are an effective means of transferring 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 walls 5 laterals is of the order of 1450 ° C-1550 ° C.

The preferred embodiment of the process of the present invention includes selecting the amount of solid carbonaceous material added to the bath which must be greater than that required to melt the iron ore introduced into the bath so that the solid carbon in the form of soot or coal be carried through the bathroom and into transition zone 23. As a result, the carbon is present in a significant amount in the powder of the gas discharge from the vessel. The carbon may also be present in small amounts in the slag which is discharged from the container. It is preferred that the solid carbonaceous material injected into the metal layer 15 be sufficient to maintain: (a) a concentration of at least 3% by weight of carbon in the metal in the bath; (b) FeO levels less than 8% by weight of the slag in the slag layer 16, and in the transition zone 23; and (c) at least 5% carbon in the powder entrained in the gas discharge from the container. The advantages of operating with the method of the present invention with an excess of carbon are two. First, as indicated above the high levels of dissolved carbon in the metal in the bath and the strong mixing of the metal in the slag layer 16 ensures that the slag layer is maintained in a strongly reduced condition by virtue of mixing the slag-metal . The slag with a low FeO content that is obtained in this way avoids the operational problems associated with a potentially rapid and uncontrolled reaction between the high slag of FeO and a carbon-rich metal. Secondly, the bath is kept close to saturation with respect to the dissolved carbon and the carbon content of the metal does not need to be controlled explicitly. The loss of carbon from the metal is a serious problem from the operating point of view of a plant since the metal liquids (for the iron-carbon system) change significantly on both sides of the eutectic condition. The presence of excess carbon in the bath means that the system corrects itself to a certain degree, with more time for corrective action available to the operator in the event of alterations in the process. The degree of subsequent combustion that is obtained in the container is effectively controlled by the amount of excess carbon that is transported from the container as a powder in the gas discharge. This results in the unused carbon being transported from the container which can be recycled to the container.

The applicant has carried out extensive work on pilot plants in the container shown in the figure and described above, and in accordance with the process conditions described above. The work in the pilot plant evaluated the recipient and the investigated process under a wide range of different: (a) feeding materials; (b) solids and gas injection rates; (c) slag relationships. metal; (d) operating temperatures; and (e) device distributions. Table 1 below indicates the relevant data during stable operating conditions for part of the work of the pilot plant.

Iron ore is purchased from Hamersley as a normal fine sent directly as ore and contains 64.6% iron, 4.21% Si02 and 2.78% Al203, on a dry basis. An anthracite coal is used as both reducing agent and a source of carbon and hydrogen to subject it to combustion and energy supply for the process. The coal has a calorific value of 30.7 MJ / kg, an ash content of 10%, and a volatile level of 9.5%. Other characteristics include 79.82% of total coal, 1.8% of H20, 1.59% of N2, 3.09% of 02 and 3.09% of H2.

The process is operated to maintain a slag basicity of 1.3 (ratio of CaO / SiO2) using a combination of lime and magnesia fluxes. Magnesia contributes MgO, thereby reducing the corrosive condition of the slag to refractory objects by maintaining appropriate levels of MgO in the slag. Under stable operating conditions, relatively low heat losses of 8 PM are recorded. The productivity is 6.1 t / h of hot metal. The solids injection rates are 9.7 t / h of ore fines and 6.1 t / h of coal along with 1.4 t / h of fluxes. A coal rate of 100 kg of carbon / t of hot metal is obtained. The results of operation under these conditions produce a powder carbon level of 25% by weight and a FeO in the slag of 4% by weight, and a carbon bath of 4% by weight. Many modifications can be made to the preferred embodiments of the processes of the present invention as 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 the conventional one for the manufacture of the objects or products to which it refers.

Claims (10)

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

1. A direct casting process for producing metals from metal oxides (including partially reduced metal oxides), characterized in that it includes the steps of: (a) forming a molten bath having a metallic layer and a slag layer on the metal layer , in a metallurgical vessel; (b) injecting a metalliferous feedstock into the metallic layer via one or more of a lance / nozzle and melting the metalliferous material to metal at least predominantly in the metallic layer; (c) injecting a solid carbonaceous material into the metal layer by means of one or more nozzles / nozzles in an amount that is sufficient such that the level of carbon dissolved in the metal is at least 3% by weight based on in the total weight of coal and metal; (d) causing upward movement of splashes, droplets and molten material streams from the molten bath metal layer, which: (i) promotes strong mixing of the metal in the slag layer of the molten bath so that the layer of slag is maintained in a strongly reducing condition leading to FeO levels 10 less than 8% by weight based on the total weight of the slag in the slag layer; and (ii) extends the space above the nominal quiescent surface of the bathroom 15 melted to form a transition zone; and (e) injecting an oxygen-containing gas into the container by means of one or more of a lance / nozzle for subsequent reaction gases 20 to the combustion released from the molten bath, whereby splashes, droplets and currents of molten material ascending and subsequently descending in the transition zone facilitate heat transfer 25 to the molten bath, and so the transition zone minimizes heat loss from the container and to the side walls in contact with the transition zone.

2. The process according to claim 1, characterized in that the level of carbon dissolved in the metal is greater than 4% by weight.

3. The process according to claim 1 or claim 2, characterized in that the concentration of FeO in the slag in the slag layer is below 6% by weight.

4. The process according to claim 3, characterized in that the concentration of FeO is less than 5% by weight.

5. The process according to any of the preceding claims, characterized in that it includes selecting the amount of solid carbonaceous material injected into the metallic layer to be such that the dust entrained in the gaseous discharge leaving the container contains at least a little of coal.

6. The process according to claim 5, characterized in that the concentration of the solid carbon in the powder of the gas discharge of the container is in the range of 5 to 90% by weight of the weight of the powder in the gas discharge, which corresponds to a Dust generation rate of 10-50 g / NM3 of the gas discharge.

7. The process according to any of the preceding claims, characterized in that it includes operating the process at primary rear combustion levels greater than 40%.

8. The process according to claim 7, characterized in that it includes operating the process at primary rear combustion levels greater than 50%.

9. The process according to any of the preceding claims, characterized in that step (d) includes injecting metalliferous feedstock and the carbonaceous material into a carrier gas through one or more of a lance / nozzle extending downward toward the metallic layer and therefore generate an upward movement of splashes, droplets and streams of molten material within the space above the nominal quiescent surface to form the transition zone.

10. The process according to any of claims 1 to 8, characterized in that step (d) includes injecting the metalliferous feed material and the carbonaceous material via one or more nozzles at the bottom of the container or on the side walls of the container which make contact with the metallic layer and in this way cause an upward movement of splashes, droplets and streams of molten material within the space above the nominal quiescent surface to form a transition zone.