Method for carbothermic smelting of a metal-containing feedstock using hot oxidizing gas

Abstract

The present invention relates to a method of smelting a metalliferous feed material. More particularly, the present invention relates to a method of smelting composite agglomerates comprising a metalliferous feed material, a reducing agent and a fluxing agent using a hot oxidising gas. According to a first aspect of the invention, there is provided a method of carbothermic smelting of a metalliferous feed material using an oxidising gas, comprising the steps of: (i) feeding composite agglomerates into a reactor to create a packed bed within the reactor; wherein the agglomerates comprise a metalliferous feed material, a reducing agent and a fluxing agent; (ii) heating and smelting the agglomerates using a hot oxidising gas, wherein the hot oxidising gas enters the reactor and passes through the packed bed to form a molten material comprising an intermediate slag component and a partially reduced metalliferous component; (iii) introducing the molten material into an electric slag cleaning furnace; (iv) adding additional reducing agent to the molten material in the electric slag cleaning furnace to form a liquid metal product, a liquid slag product and a CO-containing gas; and (v) combusting the CO-containing gas with preheated air to form a hot oxidising gas enriched in oxygen which then enters the reactor in step (ii); wherein the temperature of the hot oxidising gas entering the reactor is controlled to be above 1400°C, and wherein the oxygen content of the hot oxidising gas is controlled to be between 0% and 20%.

Description

Technical Field

[0001] This invention relates to a method for smelting metal-containing raw materials. More specifically, this invention relates to a method for smelting composite agglomerates containing metal-containing raw materials, reducing agents, and fluxing agents using a thermal oxidizing gas. Background Technology

[0002] Pre-reduction of agglomerated metal-containing feedstocks prior to carbothermal smelting in an electric furnace is a well-known process in the art. The interest in such processes stems from the proven metallurgical and electrical efficiency of agglomerated feedstocks during carbothermal smelting (allowing for more precise quality control, i.e., control of mechanical and chemical properties), which are preheated and pre-reduced before carbothermal smelting. This is demonstrated, for example, by US 4571259, which discloses a method for pre-reducing and preheating feedstocks introduced into a reactor using a depleted plasma-heated gas stream to produce molten metal.

[0003] Against this backdrop, the most prominent are those pre-reduction treatment methods that include direct reduction or solid-state reduction. As an alternative, WO 2020 / 229994 discloses a method for smelting a metallic feedstock containing a reducing agent, wherein the pre-reduction includes not only heating and solid-state reduction, but also smelting the feedstock using hot reducing gas from a gasifier, and then allowing the product to flow into an electric furnace for final slag removal.

[0004] To further improve metallurgical and electrical efficiency, it is known to use agglomerates of products from solid oxidation processes (e.g., sintering in air) as raw materials for the aforementioned solid reduction.

[0005] However, utilizing solid-state oxidation prior to pre-reduction still has a fundamental drawback: material transfer between pretreatment steps and / or between pretreatment and carbothermal melting steps is only feasible in the solid state, resulting in material cooling during transport. This cooling reduces the unit energy consumption (SEC) of the entire process, as any subsequent step requires reheating the feedstock to at least compensate for the heat lost during transfer.

[0006] Therefore, the known process routes have shortcomings in SEC, which are attributed to the disadvantages associated with solid pre-oxidation, or the limitations of pre-oxidation, coupled with the increased consumption of reducing agents due to the requirement of pre-reduction to achieve feasible metallurgical and energy efficiency in electric furnace smelting.

[0007] NL2023109B1 teaches the use of the heat and reducing properties of carbon monoxide (CO) waste gas from a reduction furnace to smelt metallic raw materials to form liquid metal and slag products. This invention utilizes CO waste gas in a dual manner: first, as a reducing agent passing through the agglomerate bed to partially reduce the metallic particles in the solid state; second, as fuel combined with oxygen in the furnace burner to heat the furnace's refractory material, thereby reaching the high temperatures required to melt the agglomerates. However, despite this dual use of CO gas as both fuel and reducing gas, the invention remains limited by solid-state reduction and requires a significant input of electrical energy into the furnace to achieve a feasible degree of metallization.

[0008] In addition to the known drawbacks of upstream carbothermic smelting processes mentioned above, the final exhaust gases from electric furnaces are typically combusted and released into the environment to avoid emitting CO-rich gases. Essentially, this combustion results in low chemical energy utilization efficiency due to the loss of high-energy chemical products to non-productive combustion. The application of furnace exhaust gases in metallurgical processes is limited, and to date, no other applications have been observed besides preheating and / or solid-state pre-reduction of metallic raw materials.

[0009] A recent exception is the premelting of complex agglomerates using combustion furnace gas, which is oxidizing, as described in WO 2020 / 229994. This disclosure excludes the use of reducing agents, meaning that no reduction of metal oxides occurs. Only the premelting of the ore is achieved.

[0010] Purpose of the invention Therefore, the object of the present invention is to provide a new method for carbothermal smelting of metal-containing raw materials, which at least partially overcomes the above-mentioned disadvantages and limitations, and / or will provide beneficial improvements to existing carbothermal smelting methods for metal-containing raw materials. Summary of the Invention

[0011] For the purposes of this specification, it should be understood that the term "partial reduction" refers to the degree of reduction of a metal-containing feedstock, where the degree of reduction is insufficient to produce a viable amount of the target element metal, and therefore further and / or final reduction is required to achieve a conversion suitable for industrial use or downstream processing.

[0012] It should be understood that the term "carbothermic reduction" refers to the reduction of oxides containing metal raw materials using carbon (C) as a reducing agent.

[0013] According to the present invention, the term "smelting" includes the melting and reduction of metal-containing raw materials.

[0014] According to a first aspect of the present invention, a method for carbothermic smelting of a metal-containing raw material using an oxidizing gas is provided, comprising the following steps: (i) The composite agglomerates are fed into the reactor to create a packed bed within the reactor; wherein the agglomerates contain a metal-containing raw material, a reducing agent and a flux; (ii) The agglomerates are heated and smelted with a thermal oxidizing gas, wherein the thermal oxidizing gas enters a reactor and passes through a packed bed to form a molten material comprising intermediate slag components and partially reduced metallic components; (iii) Introduce the molten material into the electric furnace slag cleaning furnace; (iv) Adding additional reducing agent to the molten material in the electric furnace slag cleaning furnace to form liquid metal product, liquid slag product, and CO-containing gas; and (v) Combust CO-containing gas with preheated air to form oxygen-rich thermal oxidizing gas, which is then introduced into the reactor in step (ii); wherein the temperature of the thermal oxidizing gas entering the reactor is controlled above 1400°C, and the oxygen content of the thermal oxidizing gas is controlled to be 0% to 20%.

[0015] In embodiments of the present invention, the metal-containing raw material may be any material comprising a metal, a metal oxide, a metal carbonate, or any metal composition, wherein the metal is selected from the group consisting of manganese (Mn), chromium (Cr), vanadium (V), titanium (Ti), nickel (Ni), iron (Fe), and combinations thereof.

[0016] The metal-containing raw material can be a fine-grained metal-containing raw material, wherein the fine-grained refers to a particle size of less than or equal to 6 mm. Preferably, the fine-grained metal-containing raw material has a particle size of less than 100 μm at 80% sieve particle size (P80).

[0017] In embodiments of the present invention, the reducing agent may be selected from the group consisting of anthracite, coke, char, charcoal, and combinations thereof. Preferably, the reducing agent may be anthracite.

[0018] In a preferred embodiment of the invention, the stoichiometric carbon content of the reducing agent is 105% to 220% relative to the complex agglomerates.

[0019] In embodiments of the present invention, the flux can be selected from the group consisting of limestone, quartz, dolomite, and combinations thereof. Preferably, the flux can be a combination of limestone and quartz.

[0020] In an embodiment of the present invention, the composite agglomerate can be produced before feeding the composite agglomerate, wherein the composite agglomerate can be produced at a production facility.

[0021] In embodiments of the present invention, the composite aggregate may include a binder, wherein the binder may be selected from the group consisting of bentonite, cement, sodium silicate, molasses, and combinations thereof.

[0022] In a preferred embodiment of the invention, the diameter of the composite agglomerates is 15 mm to 40 mm. In embodiments of the invention, the packed bed can provide a fluid-permeable interface located downstream of the region where the agglomerates are fed into the reactor to allow thermal oxidizing gases to pass through. Preferably, the fluid-permeable interface can be located in the operative base region of the packed bed suspended in the reactor.

[0023] In an embodiment of the present invention, the filling bed can be suspended at the side wall position where the side wall position changes.

[0024] In an alternative embodiment of the invention, the packed bed can be suspended in the reactor by means of an obstruction located operably downstream of the area where the agglomerates are fed into the reactor. This obstruction can be a bed of permeable refractory material.

[0025] Those skilled in the art should understand that, in the context of this invention, thermal oxidizing gas should be understood as a gas in which the mass percentage of CO2+O2 is greater than the mass percentage of CO+H2, and the temperature of the gas is high enough to heat and melt the composite agglomerate according to its composition.

[0026] In embodiments of the present invention, as described above, the thermal oxidizing gas is a combustion product containing CO gas, which is a product of a reduction reaction that occurs during the formation of molten material and liquid metal product in the reactor and slag cleaning furnace, respectively.

[0027] In an embodiment of the invention, the oxygen enrichment of the thermal oxidizing gas is carried out in the combustion step (v). Depending on the type of metal-containing feedstock introduced into the reactor, the composition of the thermal oxidizing gas is controlled to have an oxygen content of 0% to 20%.

[0028] In a preferred embodiment of the present invention, the oxygen content of the thermal oxidizing gas can be from 5% to 18%.

[0029] In a preferred embodiment of the present invention, the oxygen content of the thermal oxidizing gas can be 10% to 15%.

[0030] In an embodiment of the present invention, the thermal oxidizing gas is introduced in the opposite direction to the direction in which the composite agglomerates enter the reactor.

[0031] According to the present invention, in step (ii), when entering the reactor, depending on the type of metal-containing raw material fed into the reactor, the temperature of the hot oxidizing gas entering the reactor and passing through the packed bed is controlled at 1400°C or higher, preferably 1600°C to 1750°C.

[0032] In a preferred embodiment of the present invention, the hot oxidizing gas entering the reactor is fed at a rate of 1 m / s to 4 m / s.

[0033] In embodiments of the present invention, a combustion chamber may be provided for burning CO-containing gas to form thermal oxidizing gas.

[0034] Those skilled in the art will understand that the slag cleaning step can be carried out in a separate slag cleaning furnace that is in fluid communication with the reactor.

[0035] In embodiments of the present invention, additional reducing agents and additional fluxes may be added to the slag cleaning furnace as needed for additional smelting and conditioning.

[0036] In an embodiment of the present invention, the slag cleaning furnace may be provided with at least one electrode for providing electrical energy to the molten material and adding an additional reducing agent to the molten material in the slag cleaning furnace to allow the partially reduced metal components to undergo final reduction, thereby forming the final liquid metal product and the liquid slag product.

[0037] In embodiments of the present invention, the operation mode of the slag cleaning furnace can be selected as a combination of open-bath mode and partially open-bath mode.

[0038] In embodiments of the present invention, additional reducing agent may be injected into the slag cleaning furnace.

[0039] In embodiments of the present invention, the additional reducing agent may be selected from the group consisting of anthracite, coke, coke, coal, and combinations thereof. Preferably, the additional reducing agent may be anthracite.

[0040] In embodiments of the present invention, additional ore can be added to the slag cleaning furnace as needed for additional smelting and conditioning.

[0041] In embodiments of the present invention, the temperature of the slag cleaning furnace can be controlled to allow the first target metal in the metal-containing raw material to be selectively metallized and enter the liquid metal product, while allowing the non-target metal to enter the liquid slag product.

[0042] It should be understood that the liquid slag product or part of the liquid slag product as described above can constitute the metal-containing raw material in the subsequent process, wherein the subsequent process is the process according to the present invention, and the operating temperature in the slag cleaning furnace of the subsequent process can be controlled to selectively metallize the second target metal in the metal-containing raw material, such that the second target metal enters the liquid metal product of the subsequent process, while the remaining part enters the liquid slag product of the subsequent process.

[0043] In embodiments of the present invention, the liquid slag product can be used for further hydrometallurgical and / or pyrometallurgical processing.

[0044] Those skilled in the art will understand that this invention deviates from conventional teachings that thermally oxidizing gases are unsuitable for heating and melting complex agglomerates because the Boudouard reaction consumes reducing agents and gases containing O2 and CO2 have high oxidation potentials. Based on conventional teachings, knowledge, and methods, those skilled in the art have turned to using reducing gases (e.g., CO-containing gases) to induce solid-state and / or direct reduction of agglomerates at temperatures below 600°C, thereby achieving a pre-reduction purpose.

[0045] However, most unexpectedly, the present invention provides the ability to melt complex agglomerates using thermal oxidizing gases as defined herein and operating at temperatures above 1400°C.

[0046] This higher temperature is achieved by burning CO-containing gas with preheated air to form a thermal oxidizing gas, which is then enriched with oxygen as described herein. The combustion of CO-containing gas (so-called process exhaust gas) releases more chemical energy usable for smelting compared to conventional low-temperature reducing gases known and taught in the art.

[0047] Utilizing temperatures exceeding 1400°C significantly reduces downstream energy consumption in the slag cleaning furnace because the chemical energy obtained by burning CO-containing gas (process waste gas) to generate a thermal oxidizing gas (which is subsequently oxygen-enriched) is far greater than the chemical energy of conventional reducing gases (approximately three times higher). This overcomes the drawbacks associated with solid-state and / or direct reduction used for pre-reduction, as the temperature reaches levels capable of melting agglomerates, allowing pre-reduction of the agglomerates to occur in a molten state.

[0048] In step (ii), as the thermal oxidizing gas passes through the packed bed, a protective molten layer forms around the end region of the agglomerates. This protective molten layer allows pre-reduction of the metal-containing material to occur within the protective molten layer of the agglomerates, where the agglomerates are also melted and reduced. By doing so, although minimal oxidation occurs to the reducing agent inside the agglomerates, the higher temperature of the thermal oxidizing gas allows for heating, melting, and a greater degree of reduction of the metal-containing material, as opposed to pre-reduction in the solid state.

[0049] As is well known and practiced in the art, the Budoar reaction consumes the reducing agent contained in the agglomerates when they are melted at a slow rate. However, according to the present invention, the agglomerates are melted at an extremely fast rate due to the high temperature of the thermal oxidizing gas and the aforementioned protective molten layer, which mitigates the effects of the Budoar reaction and preserves the reducing agent within the agglomerates.

[0050] It should be understood that, in the context of this invention, the effects of the Budoar reaction are mitigated rather than eliminated. The partial oxidation of the reducing agent in the aggregates is an acceptable trade-off compared to the large amount of chemical energy available using a thermal oxidizing gas (and the associated barriers of using a reducing gas at lower temperatures).

[0051] In this way, the present invention allows the reduction of metal-containing raw materials in the molten state using thermal oxidizing gases, which is the opposite of solid-state and / or direct reduction using reducing gases. This not only reduces the energy consumption of the slag cleaning furnace, but also provides a greater degree of reduction of metal-containing raw materials in the molten state.

[0052] The above-described features, characteristics, and advantages of the present invention, as well as other features, characteristics, and advantages, will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrate the principles of the invention by way of example. These descriptions are given for illustrative purposes only and do not limit the scope of the invention. Attached Figure Description

[0053] The invention will now be further described by way of example only, with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of a method for carbothermal smelting of metal-containing raw materials using thermal oxidizing gas according to the present invention; Figure 2 For example Figure 1 The cross-sectional side view of the reactor and slag cleaning furnace shown; and Figure 3 This is a cross-sectional side view of the reactor, illustrating the invention as follows: Figure 1 The process shown includes the retention of the reducing agent and the flow of oxygen-rich thermal oxidizing gas.

[0054] The subject matter disclosed herein will be described more fully below with reference to the accompanying drawings of preferred embodiments of the invention, in which representative embodiments are shown. However, the subject matter disclosed herein may be embodied in different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided to make this disclosure exhaustive and complete, and to fully communicate the scope of these embodiments to those skilled in the art. Detailed Implementation

[0055] The following is for reference. Figures 1 to 3 The preferred embodiments of the present invention will be described in more detail below.

[0056] In the accompanying drawings, the method of carbothermic smelting of metal-containing raw materials using oxidizing gas according to the present invention is generally indicated by drawing number 10.

[0057] Figure 1 A schematic flow diagram of method 10 is shown. The agglomerate feed A, containing a metal-containing raw material, reducing agent, and flux, prepared at preparation facility 100, is fed into reactor 12.1 (in... Figure 2 (shown in more detail below) to 12.n, and forming a portion of the fluid-permeable packed bed of agglomerates 14 in each corresponding reactor 12.1 to 12.n (in Figure 2 The reactor mentioned in section 12.1 is shown.

[0058] It should be understood that binders or adhesives may be suitably selected, and depending on the metal-containing raw material being processed, the size of the agglomerates used in method 10, and / or the required stacking height of the agglomerate bed 14 in reactors 12.1 to 12.n, binders or adhesives may or may not be used.

[0059] The agglomerates in the packed bed 14 are melted by suspending the agglomerates by obstruction 20 and then by passing the thermal oxidizing gas in the opposite direction through the packed bed 14. In an embodiment of the invention, the thermal oxidizing gas is generated in combustion chambers 32.1 to 32.n and then enriched with oxygen such that its composition is 0% to 20%, depending on the type of metal-containing feedstock introduced into the reactor.

[0060] The thermal oxidizing gas is fed into the packed bed 14 at an operable downstream position 24, and enters reactors 12.1 to 12.n in the opposite direction to the direction in which the agglomerates are fed into reactor 12.1, thereby permeating through the packed bed 14 at a temperature sufficient to melt the agglomerates. The temperature of the thermal oxidizing gas entering reactors 12.1 to 12.n is controlled above 1400°C, preferably above 1600°C, depending on the type of metal-containing feedstock used. In this way, the pressure drop of the thermal oxidizing gas through the fluid-permeable interface 16 and the packed bed 14 is minimized, typically to about 5 kPa to 10 kPa. After passing through the packed bed 14 containing the agglomerates, the temperature of the thermal oxidizing gas is typically below 800°C.

[0061] In reactors 12.1 to 12.n, the agglomerates are melted to form a molten material comprising intermediate slag components and partially reduced metal-containing components.

[0062] refer to Figure 3The hot oxidizing gas is passed through the packed bed 14, allowing a protective molten layer to form around the end region of the agglomerates. This protective molten layer allows for pre-reduction of the metal-containing raw material within it. During the formation of the protective molten layer, minimal oxidation of the reducing agent within the agglomerates does occur. However, the high temperature of the hot oxidizing gas entering reactors 12.1 to 12.n allows for rapid melting of the agglomerates, thus mitigating the effects of the Budoal reaction. Therefore, partial oxidation of the reducing agent within the agglomerates is advantageous by retaining it.

[0063] Therefore, the fluid-permeable interface 16 formed in the operable lower region 22 of the packed bed 14 allows: (i) Thermal oxidizing gas passes through it and enters the packed bed 14; and (ii) The molten material flows out and leaves the packed bed 14.

[0064] By controlling the viscosity of the liquid intermediate slag components, whether through the addition of flux to the agglomerates and / or through the self-melting effect of the metal-containing raw materials, the C molten material can be guided into the electric furnace slag cleaning furnace 26 (in Figure 1 In the example shown, a closed submerged arc furnace is used, in which additional reducing agent, flux or ore is added to the molten material within the furnace 26.

[0065] like Figure 2 As shown, furnace 26 is configured to be in fluid flow communication with reactor 12.1, thereby minimizing heat loss during the transfer of fluid materials. An additional reducing agent (granular anthracite), combined with electrical energy input into the molten material using the submerged electrodes 28 of furnace 26, promotes and allows the formation of liquid metal products, liquid slag products, and CO-containing gas. While the liquid metal products and liquid slag products are necessarily in liquid form when contained in furnace 26, those skilled in the art will understand that solid particles may still be present.

[0066] In embodiments of the invention, the liquid metal product and the liquid slag product are formed in furnace 26 by open-pool melting due to the electrochemical reaction between an additional reducing agent in the molten material and the partially reduced metal-containing raw material. This reduction of the partially reduced metal-containing raw material, as part of the molten material, allows for a much higher level of metallization compared to conventional melting known in the art.

[0067] The liquid metal product and / or liquid slag product can then be discharged from the furnace 26 in a manner known in the art. Further processing of the liquid metal product and / or liquid slag product can then be performed as needed.

[0068] Importantly, CO-containing gas E is captured from furnace 26 and sent to cooler 30. The cooled gas is then sent to combustion chambers F 32.1 to 32.n, where it is burned with preheated air to form thermal oxidizing gas. This thermal oxidizing gas is then enriched with oxygen and subsequently introduced into method 10, which allows it to enter reactors 12.1 to 12.n and pass through the packed bed as described above.

[0069] The fundamental advantage of process 10 of this invention is that it allows: i) Before smelting in furnace 26, the metal-containing raw materials in the agglomerate are pre-melted and partially reduced by using hot oxidizing gas in reactors 12.1 to 12.n, thereby achieving high SEC efficiency; ii) Energy loss is reduced by allowing molten material to be transferred from reactors 12.1 to 12.n to furnace 26; and iii) Introducing CO-containing gas into process 10 by burning CO-containing gas to generate a thermal oxidizing gas suitable for melting agglomerates in reactors 12.1 to 12.n, while allowing a very high degree of process control to achieve high metallurgical and energy (electrical and chemical energy) efficiency.

[0070] As an example, when subjected to thermal oxidizing gases, the melting of agglomerates and the viscosity of the resulting molten material are controlled by many physical and chemical properties of the agglomerate components. By adding a suitable flux to the agglomerates, the melting temperature of the gangue material and the viscosity of the resulting liquid phase can be reduced, thereby reducing the viscosity of the molten material.

[0071] When method 10 includes preparation facility 100, method 10 allows control over the composition of the agglomerates, thereby controlling the melting of the agglomerates and the viscosity of the resulting molten material. This change in melting and the viscosity of the resulting fluid material can in turn affect the melting rate of the agglomerate components, the degree of reduction of the metal-containing raw materials in reactors 12.1 to 12.n, and the ease with which the molten material flows to furnace 26.

[0072] To illustrate this point, if necessary, by adding fluxes (such as limestone or dolomite and quartz) to lower the melting temperature of the gangue material in the agglomerates and reduce the viscosity of the molten material, the melting rate of the gangue material in the agglomerates can be increased at thermal oxidizing gas temperatures above 1400°C. Therefore, the molten material will penetrate through the packed bed 14 at a higher rate. This results in a shorter residence time of the agglomerates in the packed bed 14, thereby reducing the degree of oxidation of the metallic feedstock in reactors 12.1 to 12.n.

[0073] Importantly, method 10 further allows for control: i) Add additional reducing agent D to furnace 26; and ii) The degree of combustion of the CO-containing gas in the combustion chambers 32.1 to 32.n is such that the CO2+O2 content of the thermal oxidizing gas is greater than its CO+H2 content, which is sufficient to produce a partially reduced metal-containing component (e.g., O2 between 0% and 20%) from the agglomerates, and the temperature is sufficient to heat and melt the agglomerates while retaining the reducing agent in the agglomerates so that reduction can occur within the protective molten layer.

[0074] Meanwhile, method 10 allows control over the following additions: i) Adding additional reducing agent, flux, and ore to the molten material in the furnace 26 itself; and ii) Inputting electrical energy into the molten material in furnace 26; by: i) Ensure the target CO content of CO-containing gas and the required degree of metallization for liquid metal products; ii) Bring furnace 26 to operating temperature to form liquid metal products and liquid slag products suitable for discharge of G from furnace 26; and iii) Adjust the composition of the liquid slag product to be compatible with the refractory lining 34 of the furnace 26 and / or the refractory lining of the pipes 36 used to introduce molten material from reactors 12.1 to 12.n into the furnace 26.

[0075] As described above, by utilizing the significantly higher chemical energy provided by thermal oxidizing gases, rather than using reducing gases, the applicant unexpectedly discovered that the method of the present invention allows agglomerates to be simultaneously melted and partially reduced, thereby allowing the transfer of molten material between furnaces prior to carbothermic melting. In doing so, the metallurgical and energy efficiency of the carbothermic melting process in furnace 26 is improved. Previously, those skilled in the art considered it impossible to reduce metal-containing raw materials in this manner for a variety of reasons, including the following.

[0076] The metal-containing raw material (which includes a carbon-containing reducing agent) is heated using the hot oxidizing gas after combustion. This heating is limited to 600°C because the carbon-containing reducing agent is known to be consumed by the Budoar reaction. Therefore, since the smelting of metal oxides typically requires temperatures of 1400°C to 1600°C, most of the carbon-containing reducing agent in the metal-containing raw material is expected to be consumed by the CO2 in the hot oxidizing gas after combustion. This situation is best illustrated in WO2017 / 089651, which discloses a method for preheating and smelting manganese ore sinter, wherein the preheating is limited by the Budoar reaction and the water-gas shift reaction. Therefore, the preheating temperature in the pretreatment chamber can only reach a maximum of 700°C.

[0077] It is generally accepted by those skilled in the art that the smelting of metal oxides (including the melting and reduction of metal oxides) cannot be carried out using oxidizing gases, let alone gases with high oxidation potentials, such as oxygen-containing gases. The known view is that, thermodynamically, the reduction of metal oxides is only possible when the partial pressures of O2 and CO2 are very low, several orders of magnitude lower than those contained in the thermal oxidizing gases after combustion.

[0078] Furthermore, those skilled in the art should understand that the reduction of chromium and manganese metal oxides requires a significant amount of energy, as does the energy required to melt them. It is generally accepted that the energy obtained from thermal reducing gases is insufficient to smelt ores such as chromium and manganese.

[0079] Furthermore, commercially developed pretreatment methods are limited to solid-state operation. The smelted material needs to continuously flow to a slag cleaning furnace for final reduction of the metal oxides. It is known that the slag produced from smelting chromium refractory ore has high viscosity, making continuous flow difficult.

[0080] Furthermore, it is known that chromium refractory ore is smelted at temperatures above 1700°C, and it is generally accepted that chromium ore can only be smelted by using electrical energy to generate a high-temperature electric arc.

[0081] By using the process inputs for the packed bed 14 listed in Table 1 below, the applicant was able to obtain the results listed in Table 2 from the packed bed 14 and the slag cleaning furnace 26; Table 2 depicts the high chromium recovery achieved without generating the high-energy-consuming electric arc as described above.

[0082] Table 1. Process input variables for packed bed 14

[0083] Table 2 shows the results based on the packed bed 14 and slag cleaning furnace 26 in Table 1.

[0084] In view of the above, the applicant believes that the method of the present invention provides significant advantages over the currently used technology.

[0085] This specification is presented by way of example only and is intended to provide a description that is most useful and readily understood in terms of the principles and concepts of the invention. In this respect, no attempt is made to show structural details of the invention and / or the devices used therein, except as necessary for a basic understanding of the invention.

Claims

1. A method for carbothermic smelting of metal-containing raw materials using oxidizing gas, comprising the following steps: (i) The composite agglomerates are fed into a reactor to create a packed bed within the reactor; wherein the agglomerates contain a metal-containing raw material, a reducing agent, and a flux; (ii) The agglomerates are heated and smelted with a thermal oxidizing gas, wherein the thermal oxidizing gas enters the reactor and passes through the packed bed to form a molten material comprising intermediate slag components and partially reduced metallic components; (iii) Introduce the molten material into an electric furnace slag cleaning furnace; (iv) Adding additional reducing agent to the molten material in the electric furnace slag cleaning furnace to form a liquid metal product, a liquid slag product, and CO-containing gas; and (v) The CO-containing gas is burned with preheated air to form an oxygen-rich thermal oxidizing gas, which is then fed into the reactor in step (ii); wherein the temperature of the thermal oxidizing gas entering the reactor is controlled above 1400°C, and the oxygen content of the thermal oxidizing gas is controlled to be between 0% and 20%.

2. The method according to claim 1, wherein, The metal-containing raw material is any material comprising a metal, a metal oxide, a metal carbonate, or any metal composition, wherein the metal is selected from the group consisting of manganese (Mn), chromium (Cr), vanadium (V), titanium (Ti), nickel (Ni), iron (Fe), and combinations thereof.

3. The method according to claim 1 or claim 2, wherein, The metal-containing raw material is a fine-grained metal-containing raw material with a particle size of less than or equal to 6 mm.

4. The method according to claim 3, wherein, The fine-grained metal-containing raw material has a particle size of less than 100 μm at 80% sieve size (P80).

5. The method according to claim 1, wherein, The reducing agent is selected from the group consisting of anthracite, coke, coke, charcoal, and combinations thereof.

6. The method according to claim 1 or claim 5, wherein the stoichiometric carbon content of the reducing agent is 105% to 220% relative to the complex agglomerates.

7. The method according to claim 1, wherein, The flux is selected from the group consisting of limestone, quartz, dolomite and combinations thereof.

8. The method according to claim 1, wherein, The complex agglomerates are produced at a production facility before being fed into the feedstock.

9. The method according to claim 1 or claim 8, wherein, The composite aggregate contains a binder, wherein the binder is selected from the group consisting of bentonite, cement, sodium silicate, molasses, and combinations thereof.

10. The method according to any one of claims 1, 8, or 9, wherein, The diameter of the composite aggregate is 15 mm to 40 mm.

11. The method according to claim 1, wherein, The packed bed provides a fluid-permeable interface that can be located operably downstream of the region into which the agglomerates are fed into the reactor, allowing the thermal oxidizing gas to pass through it.

12. The method according to claim 1, wherein, The thermal oxidizing gas is the combustion product of the CO-containing gas, which in turn is the product of the reduction reaction that occurs during the formation of the molten material and the liquid metal product in the reactor and the slag cleaning furnace, respectively.

13. The method according to claim 1 or claim 12, wherein, The oxygen content of the thermal oxidizing gas is 5% to 18%.

14. The method according to claim 1 or claim 13, wherein, The oxygen content of the thermal oxidizing gas is 10% to 15%.

15. The method according to any one of claims 1, 12, or 13, wherein, The thermal oxidizing gas is introduced in the opposite direction to the direction in which the composite agglomerates enter the reactor.

16. The method according to claim 1 or any one of claims 12 to 15, in step (ii), when entering the reactor, depending on the type of metal-containing raw material fed into the reactor, the temperature of the thermal oxidizing gas entering the reactor and passing through the packed bed is controlled to be between 1600°C and 1750°C.

17. The method according to claim 1 or any one of claims 12 to 16, wherein, The thermal oxidizing gas entering the reactor is fed at a rate of 1 m / s to 4 m / s.

18. The method according to claim 1, wherein, The slag cleaning furnace is equipped with at least one electrode for providing electrical energy to the molten material and adding additional reducing agent to the molten material in the slag cleaning furnace to allow the partially reduced metal components to undergo final reduction, thereby forming the final liquid metal product and the liquid slag product.

19. The method according to claim 1 or claim 18, wherein, The slag cleaning furnace is selected from a combination of open pool mode and partially open pool mode.

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