Method, strengthening furnace and system for recovering valuable metal through top-blown plasma reduction

Abstract

The invention provides a method, a strengthening furnace and a system for recovering valuable metals through top-blown plasma reduction, and the method comprises the following steps: mixing and melting a lead-zinc-containing material and a flux in a plasma strengthening furnace to obtain a lead-zinc melt, and the plasma strengthening furnace comprises a plasma generation device; the lead-zinc melt is subjected to a reduction reaction under stirring of plasma-state substances blown by a plasma generation device, a metal phase, a gas phase and reducing slag are obtained, and plasma working media of the plasma-state substances comprise carbon powder and CO. A plasma strengthening means is utilized to cooperate with a molten pool smelting technology to treat the lead-zinc melt in a targeted mode, the chemical reaction process is strengthened, reaction barriers are reduced, and the reduction process of valuable metal in the lead-zinc melt is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of valuable metal recovery, and in particular relates to a method for recovering valuable metals by top-blown plasma reduction, a plasma enhanced furnace, and a control system. Background Art

[0002] During the smelting process of polymetallic ores, the multimetallic materials undergo a desulfurization-melting process, where they are synergistically interfused into a melt in the form of metal oxides. The metal oxide melt is then subjected to a reduction smelting process to recover the metals. Modern enhanced metallurgy technology promotes oxygen-enriched melt-enhanced metallurgy. Metal sulfide ores undergo oxidation-desulfurization smelting to form a high-temperature melt, which flows directly into a reduction smelting furnace. Reducing agents and fluxes reduce the molten metals to pure metals. However, high-grade, high-zinc oxides containing lead, zinc, and copper are currently scarce, and many of the metal elements exist as compounds, making complete separation difficult. This results in a complex raw material composition and the coexistence of multiple metals in the molten pool smelting process.

[0003] In the industrial lead and zinc smelting process, reducing agents such as coke and lump coal float on the surface of the molten pool due to their lower specific gravity than the melt, making it difficult for them to be absorbed into the pool and effectively participate in the reduction reaction. To enhance the melt's ability to capture the reducing agent, top-blowing carbon powder is a common method for enhancing reduction. However, top-blowing carbon powder into the molten pool can easily lead to localized accumulation of carbon powder in the melt, forming a core of undissolved carbon particles. These undissolved carbon particles react with oxygen in the melt to generate large amounts of CO gas. This gas is encapsulated by the slag and is difficult to escape, hindering the merging and collapse of bubbles, ultimately resulting in the continuous formation of foamy slag. The formation of foamy slag can easily deteriorate furnace conditions and cause furnace failure.

[0004] Based on this, it is necessary to provide a method, an enhanced furnace and a system for top-blown plasma reduction and recovery of valuable metals to solve the technical problems existing in the above-mentioned common technologies. Summary of the Invention

[0005] The present invention aims to solve the technical problem that top-blown carbon powder-enhanced reduction in the above-mentioned conventional technology during molten pool zinc smelting leads to the formation of foamy slag and deterioration of furnace conditions. The present invention provides a method for recovering valuable metals by top-blown plasma reduction, comprising: mixing and melting lead-zinc-containing materials with flux in a plasma-enhanced furnace to obtain a lead-zinc melt, wherein the plasma-enhanced furnace includes a plasma generator;

[0006] The lead-zinc melt undergoes a reduction reaction under the stirring of the plasma-state material sprayed by the plasma generator to obtain a metal phase, a gas phase and reduced slag, and the plasma working medium of the plasma-state material includes carbon powder.

[0007] Furthermore, the amount of the carbon powder added is 1.2-2 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements.

[0008] Furthermore, the plasma working medium includes a reducing gas, which includes CO; the plasma working medium also includes a shielding gas, which includes N2 and / or Ar; and the volume ratio of the reducing gas to the shielding gas is 1:5 to 10.

[0009] Furthermore, in the case where the plasma working medium includes the carbon powder and the CO, the added amount of the carbon powder and the CO is 1.0-2.0 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements.

[0010] Furthermore, the temperature of the reduction reaction is 1100-1400° C., and the duration of the reduction reaction is 30 min-60 min.

[0011] Furthermore, the composition of the lead-zinc melt includes, by mass fraction, 5-30% zinc, 5-20% lead, 0-10% copper, 8-40% FeO, 12-30% SiO2, and 5-20% CaO; the calcium-silicon ratio of the lead-zinc melt is 1.0-2.0, and the iron-silicon ratio is 0.2-1.0.

[0012] The present invention provides a plasma enhanced furnace for use in any of the above methods for recovering valuable metals by top-blown plasma reduction, comprising a molten pool and a plasma generating device:

[0013] A melt cavity is formed inside the molten pool to accommodate the lead-zinc melt; a melt inlet is provided on the outer wall of the molten pool and is connected to the melt cavity to inject the lead-zinc melt into the melt cavity; a flue, a slag discharge port and a siphon port are provided on the outer wall of the molten pool from top to bottom; and a sealed feeding port is provided on the upper part of the molten pool;

[0014] The nozzle of the plasma generating device is vertically connected to the top of the melt chamber in a liftable manner so as to spray and reduce the lead-zinc melt from the top.

[0015] Furthermore, the plasma generating device is a non-transferred arc plasma torch, and the power of the non-transferred arc plasma torch is 50 to 150 kW.

[0016] Furthermore, the plasma enhanced furnace also includes a thermocouple temperature measuring device, a plasma torch voltage control device and an electromagnetic induction heating device that are communicatively connected to each other, so as to maintain the temperature inside the plasma enhanced furnace at the temperature of the reduction reaction.

[0017] The present invention provides a control system, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method for recovering valuable metals by top-blown plasma reduction as described in any one of the above items is implemented.

[0018] Compared with the prior art, the present invention has at least the following advantages:

[0019] The present invention provides a method for recovering valuable metals by top-blowing plasma reduction, which utilizes plasma enhancement means in conjunction with molten pool smelting technology to specifically treat a lead-zinc melt: a plasma generator generates plasma-state carbon powder, which is sprayed into the lead-zinc melt in the form of an airflow. On the one hand, pyrolysis and gasification reactions occur on the surface of carbon powder particles in the high-temperature plasma, generating active groups (such as CⅠ, CⅡ, and other free radicals) with highly reactive carbon. After entering the lead-zinc melt, the active carbon groups can rapidly diffuse and dissolve in the melt due to their high energy and activity, significantly reducing the dissolution activation energy of carbon in the melt, increasing the solubility of carbon, thereby strengthening the chemical reaction process and lowering the reaction barrier. On the other hand, under the agitation of the plasma-state material, the heat and mass transfer effects of the lead-zinc melt are optimized, and the solubility of the carbon powder in the lead-zinc melt is significantly optimized, further promoting the reduction process of the valuable metals in the lead-zinc melt. In comparison, in commonly used technologies, the carbon powder reducing agent sprayed in the form of top blowing often floats on the surface of the lead-zinc melt and cannot be immersed in the melt. Undissolved carbon particles form obvious inclusions in the lead-zinc melt, and the gas generated by the reaction of local carbon particles continues to accumulate in the melt, producing foamy slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0021] Figure 1 This is a schematic diagram of the structure of a plasma enhanced furnace according to an embodiment of the present invention, wherein 1-melt inlet; 2-sealed charging port; 3-plasma generator; 4-flue; 5-siphon port; 6-electromagnetic induction heating device; 7-sealed feeding port; 8-slag discharge port; 9-siphon charging port;

[0022] Figure 2 The scanning electron microscope image and EDS test result image of the melt quenching phase during the reduction reaction in Example 2 of the present invention are shown;

[0023] Figure 3Graphs showing EDS detection results of the reduced slag phase produced by the reduction reaction in Example 3 of the present invention and graphs showing detection results of the metal phase in the reduced slag;

[0024] Figure 4 is a scanning electron microscope image of the metal phase in Example 3 of the present invention;

[0025] Figure 5 This is an electron microscope image of the slag phase of the reduced slag obtained after the reduction reaction in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] Moreover, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] When numerical ranges are given in the examples, it should be understood that unless otherwise specified herein, both endpoints of each numerical range and any value between the two endpoints may be used. Unless otherwise defined, all technical and scientific terms used herein are consistent with the prior art as understood by those skilled in the art and the description of the present invention. Any prior art methods, devices, and materials similar or equivalent to those in the examples of the present invention may also be used to implement the present invention.

[0029] The present invention provides a method for recovering valuable metals by top-blown plasma reduction, comprising:

[0030] S1. The lead-zinc material is mixed with a flux and melted in a plasma enhanced furnace to obtain a lead-zinc melt, wherein the plasma enhanced furnace includes a plasma generator 3.

[0031] The top-blown plasma reduction method for recovering valuable metals provided by the present invention can be applied to thinner molten pools. In a low-viscosity, thin molten pool, the lead-zinc melt can be fully infiltrated and uniformly reacted under the agitation of the top-blown plasma material.

[0032] In the present invention, the viscosity of the lead-zinc melt can be 0.1 Pa·s to 1.0 Pa·s. Within this range, the melt has good fluidity, is conducive to the penetration of plasma gas flow, and ensures uniform reaction on the surface and deep layers of the molten pool.

[0033] In the present invention, the composition of the lead-zinc melt, by mass fraction, includes: 5% to 30% zinc, 5% to 20% lead, 0% to 10% copper, 8% to 40% FeO, 12% to 30% SiO2, and 5% to 20% CaO. In some specific embodiments, the composition of the lead-zinc melt, by mass fraction, includes: 15% to 30% zinc, 10% to 20% lead, 5% to 20% FeO, 10% to 25% SiO2, and 5% to 15% CaO. In some more specific embodiments, the composition of the lead-zinc melt, by mass fraction, includes: 20% to 30% zinc, 10% to 20% lead, 8% to 15% FeO, 12% to 20% SiO2, and 5% to 17% CaO.

[0034] In some embodiments, the lead-zinc melt has a calcium-silicon ratio of 1.0-2.0 and an iron-silicon ratio of 0.2-1.0.

[0035] In the present invention, the source of the lead-zinc material may include Xinjiang Huoshaoyun minerals, and may also include materials with higher reaction activity, such as simple lead-zinc alloys, etc., and may also include lead-zinc sulfide ores (such as sphalerite, lead ore), zinc, lead oxide ores, single-component minerals, etc.

[0036] In the present invention, the lead-zinc material may also include a zinc-containing melt. In some embodiments, the zinc-containing melt may comprise, by mass fraction, 5% to 30% zinc, 5% to 20% lead, less than 30% iron, and less than 30% silicon.

[0037] In the present invention, the lead-zinc-containing material may also include lead-zinc-copper-containing solid oxides, such as lead-zinc oxide ore.

[0038] In some embodiments, when the lead-zinc material is a zinc-containing melt, the lead-zinc material can flow into the plasma enhanced furnace from the melt inlet 1, and the flux can be added into the plasma enhanced furnace from the closed charging port 2; when the lead-zinc material is a lead-zinc-copper solid oxide, the lead-zinc material can be added into the plasma enhanced furnace together with the flux from the closed charging port 2; when the lead-zinc material includes a zinc-containing melt and a lead-zinc-copper solid oxide, the zinc-containing melt can flow into the plasma enhanced furnace from the melt inlet 1, and the lead-zinc-copper solid oxide can be added into the plasma enhanced furnace together with the flux from the closed charging port 2.

[0039] In the present invention, the type of flux may include limestone.

[0040] The present invention configures a plasma generator 3 in a plasma-enhanced furnace, and cooperates with the molten pool smelting technology to specifically treat low-viscosity lead-zinc melt: the plasma generator 3 generates high-temperature plasma, which is sprayed into the lead-zinc melt in the form of a high-speed airflow. On the one hand, the plasma-state reducing atmosphere acts as a reducing agent to undergo a reduction reaction with the oxides in the lead-zinc melt, providing activating groups for the reduction reaction. On the other hand, under the agitation of the plasma-state gas, the heat and mass transfer effects of the lead-zinc melt are optimized, thereby promoting the reduction process of the valuable metals in the lead-zinc melt.

[0041] In the present invention, the plasma generating device 3 may be a non-transferred arc plasma torch, and the power of the non-transferred arc plasma torch may be 50 kW to 150 kW. In some embodiments, the plasma generating device may include 1 to 3 plasma torches.

[0042] In the present invention, the flow rate of plasma-state substances in a single plasma torch can be 10-30 cubic meters per hour.

[0043] In a non-transferred arc plasma torch, the anode also serves as the torch nozzle. This design enables the plasma torch to produce a directed plasma jet.

[0044] It should be noted that the temperature at the nozzle outlet of the plasma generator can be 2000-3500°C.

[0045] The working principle of the non-transferred arc plasma torch is as follows:

[0046] Arc Generation: In a non-transferred arc plasma torch, an arc with high current density and continuous operation is established. This arc is ignited by applying a high voltage between electrodes and igniting it with the help of a high-frequency oscillator.

[0047] Plasma formation: When an arc is generated, it heats the plasma working medium, ionizing it and forming a plasma gas. Plasma gas is an electrically neutral gas mixture composed of positive and negative ions, electrons, and neutral particles. It has an extremely high temperature and high energy density.

[0048] Generation of plasma jet: After being stabilized by an external medium (such as a magnetic field, airflow, etc.), the plasma gas is compressed and accelerated to form a very fast plasma flow, namely a plasma jet. The plasma jet will be ejected outward from the nozzle to stir and reduce the melt.

[0049] In some embodiments, the non-transferred arc plasma torch may include a cathode, an anode, a water inlet assembly, a water outlet assembly, a circulating water control assembly, a power control assembly, and a cooling water assembly, wherein the cooling water assembly may cool the cathode and anode to prevent high-temperature ablation of the electrodes.

[0050] In some embodiments, the non-transferred arc plasma torch may be configured in a rectangular shape.

[0051] In some embodiments, the plasma generator 3 is vertically connected to the top of the molten pool in a liftable manner and lowered below the surface of the molten pool. For example, an electric lift device can be provided between the plasma generator 3 and the top of the molten pool to achieve a liftable connection between the plasma generator 3 and the top of the molten pool.

[0052] By means of the liftable arrangement of the plasma generator 3, a certain distance can be maintained between the nozzle and the surface of the lead-zinc melt during the process of forming a melt by electromagnetic induction-assisted heating of the material to protect the plasma spray gun; after a melt with good fluidity is formed, the height of the plasma torch can be lowered, and the front end can be immersed in the molten pool for spraying, thereby stirring the molten pool, enhancing mass transfer, and increasing the residence time of the reducing agent in the melt; as the reaction proceeds and the height of the melt changes, the height can be further adjusted by the lifting device; it should be noted that the front end includes a nozzle and a cooling water jacket.

[0053] S2. The lead-zinc melt undergoes a reduction reaction under the stirring of the plasma-state material sprayed by the plasma generating device 3, including the metal phase, gas phase and reduced slag, and the plasma working medium of the plasma-state material includes carbon powder.

[0054] There are two situations in the present invention. The first is that the plasma working medium is only carbon powder. In this case, the amount of carbon powder added can be 1.2-2 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements. Due to the activation of carbon powder by plasma technology, the amount of carbon powder added within this range can ensure the reduction effect of valuable metal oxides in the lead-zinc melt while avoiding the generation of foamy slag, thereby ensuring smooth operation of the furnace.

[0055] The second scenario is that the plasma working medium includes carbon powder and CO. In this scenario, the addition of CO enhances plasma reduction, reduces foamy slag formation, and improves reduction efficiency. When the plasma working medium includes the carbon powder and CO, the amount of the carbon powder and CO added is 1.0-2.0 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt to elemental metals; the amount of carbon powder added can be 0.5-1.0 times the molar amount of the reducing agent required to reduce all the metal compounds to be reduced in the lead-zinc melt to elemental metals, and the amount of CO added can be 0.5-1.0 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt to elemental metals.

[0056] With the increasing emphasis on environmental protection and resource utilization, the lead and zinc smelting industry is facing stricter environmental regulations and energy efficiency standards. Reducing the use of carbon powder, CO and other agents is a key measure to avoid environmental risks. In addition, global lead and zinc mineral resources are becoming increasingly scarce. Improving the comprehensive utilization rate of resources and realizing the resource utilization of waste have become inevitable choices for the sustainable development of the industry. Reducing the use of carbon-containing reducing agents such as carbon powder and CO can reduce raw material consumption, increase metal recovery rate and alleviate resource pressure.

[0057] In the present invention, when the plasma working medium only includes carbon powder, the amount of carbon powder added can be 1.2-1.5 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements. The demand for carbon powder in the present application is significantly reduced: due to the pyrolysis and gasification reactions on the surface of the carbon powder particles in the high-temperature plasma, active groups with highly reactive carbon (such as CⅠ, CⅡ· and other free radicals) are generated. After the active carbon groups enter the lead-zinc melt, based on their high energy and high activity, the carbon powder can quickly diffuse and dissolve in the melt, significantly reducing the dissolution activation energy of carbon in the melt, increasing the solubility of carbon, and thereby strengthening the chemical reaction process and reducing the reaction barrier. In comparison, referring to Comparative Example 3, other conditions are the same, and only whether the reducing agent is plasmatized is used as a variable to achieve the same reduction effect. The carbon powder demand in the present application is only three-fifths of the carbon powder demand in the conventional technology, and the time is greatly shortened.

[0058] In the present invention, when the plasma working medium only includes carbon powder and CO, the amount of carbon powder added can be 0.5 to 0.7 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt to the metal element, and the amount of CO added can be 0.5 to 0.7 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt to the metal element. For example, when the amount of carbon powder added is 0.7 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt to the metal element, the amount of CO added can be 0.5 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt to the metal element.

[0059] Because CO is added in the form of a plasma in this application, CO can absorb energy through rotation, vibration, dissociation, ionization, and other methods when interacting with high-energy electrons in the plasma torch, forming excited species such as CO, CI, CII, and OII. This significantly enhances the reduction effect of the lead-zinc melt and significantly reduces the CO requirement. Referring to Example 3 and Comparative Example 5 of this application, it can be seen that under the condition that other conditions are the same and the only variable is whether the reducing agent is in a plasma state, the CO requirement in this application is only one-fifth of the CO requirement in conventional techniques to achieve the same reduction effect.

[0060] It should be noted that the reason why the amount of carbon powder and CO added in this application is significantly reduced is not only due to the activation effect of plasma technology on reducing groups, but also due to the strong heat supplementation ability of plasma technology.

[0061] In some embodiments, the plasma state gas further includes a plasma state protective atmosphere, wherein the plasma working medium of the plasma state protective atmosphere includes a protective gas, and the protective gas includes N2 and / or Ar.

[0062] In some embodiments, the volume ratio of the reducing gas serving as the plasma working medium to the shielding gas serving as the plasma working medium may be 1:5-10.

[0063] In some embodiments, the plasma generating device 3 may include a gas distribution system; a certain proportion of reducing gas and protective gas can be mixed through the gas distribution system, and then arc ionization is used to generate plasma gas, and the lead-zinc melt undergoes a reduction reaction under the stirring of the plasma gas.

[0064] In some embodiments, the plasma generating device 3 may include a DC power supply, which generates a high-voltage current. The reducing gas and the protective gas are instantly broken down by the arc between the cathode and anode to generate a high-temperature plasma gas. The nozzle sprays a high-speed airflow into the lead-zinc melt and provides high temperature and activation groups.

[0065] In the present invention, the temperature of the reduction reaction can be 1100-1400°C, and the duration of the reduction reaction can be 30-60 minutes. By setting the temperature of the reduction reaction, when the reduction reaction temperature is higher than 1400°C, the high temperature causes the valuable metal elements in the melt to volatilize and wastes heat resources. When the reduction reaction temperature is lower than 1100°C, the melt in the furnace partially solidifies and even causes the furnace to die. Furthermore, in the present invention, due to the improvement in reduction efficiency achieved by plasma enhancement, the present invention can complete the reduction of metal oxides and the separation of slag and gold within 30-60 minutes.

[0066] In the present invention, the products of the reduction reaction include a metal phase, a gas phase, and reduced slag. The liquid metal phase is discharged through a siphon port 5 for further clarification and separation, the reduced slag flows out through a slag discharge port 8, and the zinc vapor enters a zinc rain condenser or a vapor deposition chamber through a flue 4 for direct recovery of metallic zinc. In some embodiments, the gas phase is a volatile gas phase component, including lead vapor and zinc oxide.

[0067] like Figure 1 As shown, in the present invention, the plasma enhanced furnace may include a molten pool and a plasma generating device 3:

[0068] A melt cavity is formed inside the molten pool to accommodate the lead-zinc melt; a melt inlet 1 connected to the melt cavity is provided on the outer wall of the molten pool to introduce the lead-zinc melt into the melt cavity; a flue 4, a slag discharge port 8, and a siphon port 5 are also provided on the outer wall of the molten pool from top to bottom; a sealed feeding port 2 is also provided at the top of the molten pool to feed the flux into the plasma enhanced furnace; the nozzle of the plasma generator 3 is located in the melt cavity to spray and reduce the lead-zinc melt.

[0069] In the present invention, the flue 4, the slag discharge port 8 and the siphon port 5 do not need to be arranged on a longitudinal line.

[0070] In the present invention, the flue 4 and the siphon port 5 can be arranged at the end of the melt away from the confluence port.

[0071] In the present invention, the plasma generating device 3 is a non-transferred arc plasma torch, and the power of the non-transferred arc plasma torch is 100-300 kw.

[0072] In the present invention, the outer wall of the molten pool may be provided with a siphon feeding port 9 to feed the lead-zinc melt into the plasma enhanced furnace.

[0073] In some embodiments, adaptive large-scale production can be achieved by regulating plasma power, adjusting the number of plasma torches, adjusting the powder feeding amount, and adjusting the furnace volume.

[0074] In some specific embodiments, the method for recovering valuable metals by top-blown plasma reduction comprises the steps of:

[0075] S1'. The lead-zinc melt after desulfurization in the previous step is sealed and flows into the plasma enhanced furnace through the melt confluence inlet 1 and the melt siphon feeding port 9; the flux and the lead-zinc-copper solid oxide are added to the plasma enhanced furnace through the closed feeding port 2, and the material is heated to 1300±50℃ using the bottom electromagnetic induction heating device 6.

[0076] S2 '. A reducing gas, carbon monoxide, and a protective gas, nitrogen are mixed through a gas distribution system, a plasma torch generates an arc, and the mixed gas is ionized to produce a plasma gas, which undergoes a reduction reaction with the lead-zinc melt; the volume ratio of nitrogen and carbon monoxide is 10:1 to 5:1; after ionization, the carbon monoxide plasma acts as a reducing agent and reacts with the oxides in the lead-zinc melt to undergo a reduction reaction, and lead and zinc are volatilized to the gas phase for recovery, and iron is reduced to liquid iron and discharged through the siphon port 5. Impurities in the ore and the remaining oxide slag phase are molten and float on the surface, and the slag discharge port 8 is discharged.

[0077] In some specific embodiments, the method for recovering valuable metals by top-blown plasma reduction can be applied in a laboratory, comprising the steps of:

[0078] S1". Start the nitrogen generator and CO controller, add lead-zinc materials into the crucible, close the chamber, open the vent valve, start the nitrogen purge device, keep the atmosphere in the plasma furnace in an inert state, start the electromagnetic induction heating device, and heat the furnace to 1100-1400℃.

[0079] S2". The plasma gun advance distance is controlled according to the temperature of the melt in the crucible. The lead-zinc material is heated by the induction coil and melted to form a lead-zinc melt. The lead-zinc melt is then subjected to enhanced reduction injection by a CO plasma torch to produce alloys such as lead, copper, antimony, bismuth, gold, and silver. Impurities such as gangue in the melt form a reduction slag.

[0080] The present invention utilizes CO plasma blowing to enhance molten pool blowing, stirs the molten pool, and strengthens mass transfer and heat transfer, so that the reduced gaseous products in the lead-zinc melt can escape quickly, and the metal phase after reduction is strengthened to aggregate and settle, thereby forming a good separation between slag and metal.

[0081] Compared to traditional solid-state carbon-based reduction and gas injection reduction, the present invention provides a top-blown plasma reduction method for recovering valuable metals. This method fully utilizes plasma-enhanced chemical reactions and the sensible heat of high-temperature liquid melts to explore and optimize the process, laying the foundation for subsequent continuous and large-scale production. This method rapidly recovers valuable metals from slag, and compared to traditional pulverized coal injection, coke filter layer reduction, and gas-solid reduction, the post-reduction slag contains lower valuable metal content and achieves a higher overall recovery rate.

[0082] The present invention provides a plasma enhanced furnace for use in any of the above methods for recovering valuable metals by top-blown plasma reduction, comprising a molten pool and a plasma generator 3:

[0083] A melt cavity is formed inside the molten pool to accommodate the lead-zinc melt; a melt inlet 1 connected to the melt cavity is provided on the outer wall of the molten pool to introduce the lead-zinc melt into the melt cavity; a flue 4, a slag discharge port 8, and a siphon port 5 are also provided on the outer wall of the molten pool from top to bottom; a sealed feeding port 2 is also provided at the top of the molten pool to feed the flux into the plasma enhanced furnace; the nozzle of the plasma generator 3 is located in the melt cavity to spray and reduce the lead-zinc melt.

[0084] In the present invention, the plasma generating device 3 is a non-transferred arc plasma torch, and the power of the non-transferred arc plasma torch is 50-150 kW.

[0085] In the present invention, the plasma generating device 3 is vertically connected to the top of the molten pool in a liftable manner.

[0086] In some embodiments, the plasma enhancement furnace may also include a furnace cover, which may be located at the top of the molten pool. An electric lifting device may be provided between the plasma generator and the furnace cover to achieve a liftable connection between the plasma generator 3 and the top of the molten pool.

[0087] In the present invention, the plasma enhanced furnace further comprises a thermocouple temperature measuring device, a plasma torch voltage control device and an electromagnetic induction heating device which are communicatively connected to each other, so as to maintain the temperature inside the plasma enhanced furnace at the temperature of the reduction reaction.

[0088] In some embodiments of the present invention, the electromagnetic induction heating device 6 includes an electromagnetic induction coil and a thermocouple temperature measuring device to detect the temperature within the furnace. The thermocouple temperature measuring device sends instructions to the electromagnetic induction heating device 6, which uses the electromagnetic induction coil to maintain the reduction furnace temperature. An electromagnetic induction coil can be installed at the bottom of the molten pool in the plasma-enhanced furnace. The electromagnetic induction coil can be used to preheat the lead-zinc melt and prevent it from solidifying during the plasma-enhanced stage.

[0089] The present invention also provides a control system, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method for recovering valuable metals by top-blown plasma reduction as described in any one of the above items is implemented.

[0090] It should be noted that the plasma enhancement furnace may include the control system.

[0091] In order to facilitate those skilled in the art to further understand the present invention, examples are given below:

[0092] Example 1

[0093] S1. A domestic lead-zinc oxide ore and limestone were mixed in appropriate proportions and fed into a plasma-enhanced furnace through a sealed feed port to produce a lead-zinc melt. The composition (by mass fraction) of the lead-zinc melt was: Zn 28.98%, Pb 14.17%, FeO 9.96%, SiO 17.9%, and CaO 10.82%.

[0094] S2. Start the DC power supply control system and cooling water circulation system and spray plasma-state carbon powder into the lead-zinc melt. The amount of carbon powder added is 1.5 times the molar amount of reducing agent required to completely reduce the metal oxides to elemental metal in the lead-zinc melt. Use a plasma torch and electromagnetic induction heating device to heat the melt to form a molten pool. Control the reduction temperature of the lead-zinc melt to 1300±50°C.

[0095] S3. The reduction time is 40 minutes, and the carbon powder is completely dissolved in the melt. It has good solubility in the lead-zinc melt. The lead-zinc melt undergoes reduction reaction to obtain a metal phase, a gas phase, and a reduced slag. The volatile components of the gas phase are mainly Pb and ZnO, and the reduced slag phase is mainly composed of silicate oxides formed by Ca, Fe, and Si. The Zn content in the reduced slag phase is 2.7%, and the Pb content is 0.89%. The precipitated metal phase is mainly Cu.

[0096] Example 2

[0097] Compared with Example 1, only the amount of carbon powder added was adjusted.

[0098] S1. A domestic lead-zinc oxide ore and limestone were mixed in appropriate proportions and fed into a plasma-enhanced furnace through a sealed feed port to produce a lead-zinc melt. The melt's composition (by mass) was: Zn 28.98%, Pb 14.17%, FeO 9.96%, SiO2 17.9%, and CaO 10.82%.

[0099] S2. Start the DC power supply control system and cooling water circulation system, spraying plasma-state carbon powder into the lead-zinc melt. The amount of carbon powder added is twice the theoretical amount required for reduction. Use a plasma torch and electromagnetic induction heating device to heat the melt to form a molten pool, and control the melt reduction temperature to 1300±50℃.

[0100] S3. The reduction time was 40 minutes, during which the carbon powder completely dissolved in the melt, showing good solubility. The melt underwent a reduction reaction, yielding a metal phase, a vapor phase, and a reduced slag. The volatile components of the vapor phase were primarily lead (Pb), zinc (Zn), and zinc oxide (ZnO). The reduced slag phase was primarily composed of silicate oxides formed by calcium, iron, and silicon (Ca), with a Zn content of 1.71% and a lead content of 0%. The precipitated metal phase was primarily composed of copper (Cu) and lead (Pb).

[0101] The increase in the injection amount of carbon powder promotes the strengthening of the reducing atmosphere in the system, the increase in the metal reduction degree, and the generation of elemental Zn. Figure 2 This is a scanning electron microscope image of the melt quenching phase during the reduction process. It can be seen that C has been completely dissolved in the melt and has good solubility in the melt.

[0102] Example 3

[0103] Compared with Example 1, other conditions remain unchanged, and only carbon powder is added to the lead-zinc melt in the form of plasma together with CO.

[0104] S1. A domestic lead-zinc oxide ore and limestone were mixed in appropriate proportions and fed into a plasma-enhanced furnace through a sealed feed port to produce a lead-zinc melt. The melt's composition (by mass) was: Zn 28.98%, Pb 14.17%, FeO 9.96%, SiO2 17.9%, and CaO 10.82%.

[0105] S2. Start the DC power supply control system and cooling water circulation system, adjust the power and air flow of the plasma torch, and spray plasma carbon powder and plasma carbon monoxide into the lead-zinc melt. The amount of carbon powder added is 0.7 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt to elemental metal. The amount of CO added is 0.5 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt to elemental metal. The volume ratio of nitrogen to CO is 10:1. Use the plasma torch and electromagnetic induction heating device to heat the melt to form a molten pool, and control the melt reduction temperature to 1300±50°C.

[0106] S3. The reduction reaction lasted 40 minutes, and the melt underwent a reduction reaction to produce a metal phase, a gas phase, and a reduced slag. The volatile components of the gas phase were primarily Pb and Zn. The reduced slag phase was primarily composed of silicate oxides formed by Ca, Fe, and Si, with a Zn content of 1.93% and a Pb content of 0.52%. After a certain amount of molten iron was reduced, the precipitated metal phase was primarily composed of Cu, Pb, and Fe.

[0107] Figure 3 The scanning electron microscope image of the molten slag phase after reduction and its EDS test results are shown in Figure 2. Figure 4 The scanning electron micrograph of the metal phase shows a predominantly FeCu alloy. This indicates that, compared to Example 1, the synergistic effect of CO and carbon powder as reducing agents significantly reduces the amount of reducing agent required to achieve the same reduction effect as in Example 1, significantly enhancing the system's reducing capacity and verifying the plasma-enhanced CO's role in promoting the reduction effect.

[0108] Comparative Example 1

[0109] Compared with Example 1, this comparative example eliminates the step of plasmatizing the carbon powder, and adds the carbon powder into the lead-zinc melt by ordinary blowing.

[0110] S1. A domestic lead-zinc oxide ore and limestone were mixed in appropriate proportions and fed into a medium-frequency melting furnace through a sealed feed port to produce a lead-zinc melt. The melt had the following composition (by mass): Zn 28.98%, Pb 14.17%, FeO 9.96%, SiO2 17.9%, and CaO 10.82%.

[0111] S2. Start the DC power supply control system and the cooling water circulation system, and use a top-blowing pipe to spray carbon powder into the melt. The amount of carbon powder added is 1.5 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements. Use medium-frequency heating to form a molten pool, and control the melt reduction temperature to 1300±50℃.

[0112] S3. The reduction reaction lasted 40 minutes, and the melt underwent a reduction reaction to produce a metal phase, a gas phase, and reduced slag. Volatile components in the gas phase were primarily Pb and ZnO, while the slag phase was primarily composed of silicate oxides formed from Ca, Zn, Pb, Fe, and Si. The Zn content in the slag phase was 15.46%, and the Pb content was 2.78%. The precipitated metal phase was primarily Cu and Pb. Compared to Example 1, the reduction effect in Comparative Example 1 was significantly reduced, accompanied by the appearance of foamy slag.

[0113] Comparative Example 2

[0114] Compared with Example 2, this comparative example eliminates the step of plasmatizing the carbon powder, and adds the carbon powder into the lead-zinc melt by ordinary blowing.

[0115] S1. A domestic lead-zinc oxide ore and limestone were mixed in appropriate proportions and fed into a plasma-enhanced furnace through a sealed feed port to produce a lead-zinc melt. The melt had the following composition (by mass): Zn 28.98%, Pb 14.17%, FeO 9.96%, SiO2 17.9%, and CaO 10.82%.

[0116] S2. Start the DC power supply control system and cooling water circulation system, and use a top-blowing nozzle to spray carbon powder into the melt. The amount of carbon powder added is twice the amount required for theoretical reduction. Use medium-frequency heating to form a molten pool, and control the melt reduction temperature to 1300±50℃.

[0117] S3. The reduction reaction lasted 40 minutes, and the melt was reduced to a metal phase, a gas phase, and reduced slag. The volatile components of the gas phase were primarily Pb, Zn, and ZnO. The slag phase was primarily composed of silicate oxides formed by Ca, Fe, and Si. The Zn content in the slag phase was 10.75% and the Pb content was 0.98%. The precipitated metal phase was primarily Cu and Pb.

[0118] Compared with Example 2, the reduction effect is significantly reduced, and foamy slag appears. Figure 5 This is an electron microscope image of the slag phase after reduction, in which a large number of carbon particles were observed to be aggregated and included in the slag phase.

[0119] Comparative Example 3

[0120] Compared with Comparative Example 2, the amount of carbon powder added in this comparative example is adjusted to ensure complete reduction of the valuable metal oxides in the lead-zinc melt, and the required reduction time is adaptively adjusted.

[0121] S1. A domestic lead-zinc oxide ore and limestone were mixed in appropriate proportions and fed into a plasma-enhanced furnace through a sealed feed port to produce a lead-zinc melt. The melt had the following composition (by mass): Zn 28.98%, Pb 14.17%, FeO 9.96%, SiO2 17.9%, and CaO 10.82%.

[0122] S2. Start the DC power supply control system and cooling water circulation system, and use a top-blowing nozzle to spray carbon powder into the melt. The amount of carbon powder added is 2.5 times the amount required for theoretical reduction. Use medium-frequency heating to form a molten pool, and control the melt reduction temperature to 1300±50℃.

[0123] S3. The reduction reaction lasted 150 minutes, and the melt was reduced to a metal phase, a gas phase, and reduced slag. Volatile components in the gas phase were primarily Pb, Zn, and ZnO. The slag phase was primarily composed of silicate oxides formed by Ca, Fe, and Si, with a Zn content of 1.71% and a Pb content of 0%. The precipitated metal phase was primarily Cu and Pb.

[0124] Compared with Comparative Example 2, the time of this comparative example is greatly increased, and the amount of carbon powder used is greatly increased to achieve complete reduction of valuable metals such as lead, zinc, and copper.

[0125] Comparative Example 4

[0126] Compared with Example 3, other conditions in this comparative example remain unchanged, only the plasma step is eliminated, and carbon powder and CO are added to the lead-zinc melt in the form of ordinary top blowing.

[0127] S1. A domestic lead-zinc oxide ore and limestone were mixed in appropriate proportions and fed into a plasma-enhanced furnace through a sealed feed port to produce a lead-zinc melt. The melt had the following composition (by mass): Zn 28.98%, Pb 14.17%, FeO 9.96%, SiO2 17.9%, and CaO 10.82%.

[0128] S2. Start the DC power supply control system and the cooling water circulation system, and use a top-blowing nozzle to spray carbon powder and CO into the melt. The amount of carbon powder added is 0.7 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements, and the amount of CO added is 0.5 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements. The volume ratio of nitrogen to CO is 10:1. Medium-frequency heating is used to form a molten pool, and the melt reduction temperature is controlled to 1300±50℃.

[0129] S3. The reduction reaction lasted 40 minutes, and the melt was reduced to a metal phase, a gas phase, and reduced slag. The volatile components of the gas phase were primarily Pb, Zn, and ZnO. The slag phase was primarily composed of silicate oxides formed from Ca, Zn, Fe, and Si, with a Zn content of 14.34% and a Pb content of 1.36%. The precipitated metal phase was primarily composed of Cu and Pb.

[0130] Compared with Example 3, the reduction effect of this comparative example is poor under the condition of not using plasma enhancement; and this comparative example does not produce a significant enhanced reduction effect compared with Comparative Example 1.

[0131] Comparative Example 5

[0132] Compared with Comparative Example 4, the amount of CO added in this comparative example is adjusted to ensure complete reduction of the valuable metal oxides in the lead-zinc melt; the required reduction time is adaptively adjusted.

[0133] S1. A domestic lead-zinc oxide ore and limestone were mixed in appropriate proportions and fed into a plasma-enhanced furnace through a sealed feed port to produce a lead-zinc melt. The melt had the following composition (by mass): Zn 28.98%, Pb 14.17%, FeO 9.96%, SiO2 17.9%, and CaO 10.82%.

[0134] S2. Start the DC power supply control system and the cooling water circulation system, and use a top-blowing nozzle to spray carbon powder and CO into the melt. The amount of carbon powder added is 0.7 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements, and the amount of CO added is 2.5 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements. The volume ratio of nitrogen to CO is 10:1. Medium-frequency heating is used to form a molten pool, and the melt reduction temperature is controlled to 1300±50℃.

[0135] S3. The reduction reaction lasted 120 minutes, and the melt was reduced to a metal phase, a gas phase, and reduced slag. Volatile components in the gas phase were primarily Pb and Zn. The slag phase was primarily composed of silicate oxides formed by Ca, Fe, and Si, with a Zn content of 0% and a Pb content of 0%. The precipitated metal phase was primarily composed of Cu, Pb, and Fe.

[0136] The above technical solutions of the present invention are only preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention's description and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for recovering valuable metals by top-blown plasma reduction, characterized in that: include: The lead-zinc material is mixed with a flux and melted in a plasma enhanced furnace to obtain a lead-zinc melt, wherein the plasma enhanced furnace includes a plasma generating device; The lead-zinc melt undergoes a reduction reaction under the stirring of the plasma-state material sprayed by the plasma generator to obtain a metal phase, a gas phase and reduced slag, and the plasma working medium of the plasma-state material includes carbon powder.

2. The method for recovering valuable metals by top-blown plasma reduction according to claim 1, characterized in that: The amount of the carbon powder added is 1.2-2.0 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements.

3. The method for recovering valuable metals by top-blown plasma reduction according to claim 1, characterized in that: The plasma working medium further includes a reducing gas, which includes CO; the plasma working medium further includes a shielding gas, which includes N2 and / or Ar; the volume ratio of the reducing gas to the shielding gas is 1:5-10.

4. The method for recovering valuable metals by top-blown plasma reduction according to claim 3, characterized in that: When the plasma working medium includes the carbon powder and the CO, the added amount of the carbon powder and the CO is 1.0-2.0 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the lead-zinc melt into metal elements.

5. The method for recovering valuable metals by top-blown plasma reduction according to claim 1, characterized in that: The temperature of the reduction reaction is 1100-1400° C., and the duration of the reduction reaction is 30-60 minutes.

6. The method for recovering valuable metals by top-blown plasma reduction according to claim 1, characterized in that: The composition of the lead-zinc melt includes, by mass fraction, 5-30% zinc, 5-20% lead, 0-10% copper, 8-40% FeO, 12-30% SiO2, and 5-20% CaO; the calcium-silicon ratio of the lead-zinc melt is 1.0-2.0, and the iron-silicon ratio is 0.2-1.

0.

7. A plasma enhanced furnace, characterized in that: The method for recovering valuable metals by top-blown plasma reduction as claimed in any one of claims 1 to 6 comprises a molten pool and a plasma generating device: A melt cavity is formed inside the molten pool to accommodate the lead-zinc melt; a melt inlet is provided on the outer wall of the molten pool and is connected to the melt cavity to inject the lead-zinc melt into the melt cavity; a flue, a slag discharge port and a siphon port are provided on the outer wall of the molten pool from top to bottom; and a sealed feeding port is provided on the upper part of the molten pool; The nozzle of the plasma generating device is vertically connected to the top of the melt chamber in a liftable manner so as to spray and reduce the lead-zinc melt from the top.

8. The plasma enhancement furnace according to claim 7, characterized in that: The plasma generating device is a non-transferred arc plasma torch, and the power of the non-transferred arc plasma torch is 50-150 kW.

9. The plasma enhancement furnace according to claim 7, characterized in that: The plasma enhanced furnace further comprises a thermocouple temperature measuring device, a plasma torch voltage control device and an electromagnetic induction heating device which are communicatively connected to each other, so as to maintain the temperature inside the plasma enhanced furnace at the temperature of the reduction reaction.

10. A control system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the method for recovering valuable metals by top-blown plasma reduction according to any one of claims 1 to 6 is implemented.

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