Method for recovering valuable metals by bottom-blown plasma-enhanced reduction, reduction furnace and system

Abstract

The application provides a method for recovering valuable metals by bottom blowing plasma enhanced reduction, a reduction furnace and a system, wherein the method for recovering valuable metals by bottom blowing plasma enhanced reduction comprises the following steps: lead-zinc oxide materials are heated by a reducing agent and a heating device, and high-zinc melt is formed by melting, the temperature increasing rate of the lead-zinc oxide materials is 30-50 DEG C / min, and the temperature of the high-zinc melt is 1200-1400 DEG C; the reducing agent comprises a reducing plasma state substance, the reducing plasma state substance is introduced from the bottom of the lead-zinc oxide materials, and the lead-zinc oxide materials are subjected to bottom blowing; the high-zinc melt is subjected to reduction reaction to generate metal vapor under the stirring of the reducing agent, slag and metal are separated, an alloy phase and slag are generated. The bottom blowing process can significantly improve the reduction rate and the reduction efficiency of metal oxides, and the comprehensive recovery rate of zinc, lead, copper and other metals is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment technology, specifically relating to a method, reduction furnace and system for bottom-blown plasma enhanced reduction and recovery of valuable metals. Background Technology

[0002] Bottom-blown plasma smelting technology utilizes the strong energy flow of plasma and bottom airflow disturbance to rapidly initiate smelting reactions under high temperature and high reducing atmosphere. It is particularly suitable for processing non-ferrous metal minerals and secondary resources with high viscosity, high melting point, and complex composition. Its unique stirring and heat input methods make it adaptable to a wide range of raw materials, especially suitable for complex raw materials that are difficult to process efficiently using traditional processes.

[0003] The recovery and treatment of complex lead-zinc ores and zinc-containing secondary resources are of great significance for the sustainable utilization of resources and environmental protection. However, due to the unavoidable chlorine source and diverse and complex organic matter in the raw materials, coupled with the catalytic effect of heavy metals in the smelting environment, harmful substances such as dioxins will be generated under the high-temperature conditions of traditional pyrometallurgical processes. Dioxins are a collective term for two classes of tricyclic aromatic organic compounds, including polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). In the molecular structure of dioxins, compounds in which chlorine atoms are simultaneously substituted at positions 2, 3, 7, and 8 are physiologically toxic. Toxic dioxin compounds are extremely stable in the environment, difficult to degrade, and accumulate in organisms through the food chain, posing a serious threat to human health and the ecological environment.

[0004] Therefore, although traditional pyrometallurgical techniques have certain advantages in processing complex lead-zinc ores and zinc-containing secondary resources, their practical application is limited by dioxin formation. Thus, it is necessary to develop new smelting technologies or improve existing ones to reduce dioxin generation. Commonly used technologies typically employ tail gas treatment and adsorption techniques to treat existing dioxins, which are costly and complex, and no smelting technology specifically designed to avoid dioxin formation during pyrometallurgical processes has yet emerged. Summary of the Invention

[0005] To address the technical problem of dioxin generation in the pyrometallurgical process of complex lead-zinc ores and zinc-containing secondary resources, as described above, this invention provides a bottom-blown plasma-enhanced reduction method for recovering valuable metals, comprising:

[0006] Lead-zinc oxide is heated by a reducing agent and a heating device to melt and form a high-zinc melt. The heating rate of the lead-zinc oxide is 30-50℃ / min, and the temperature of the high-zinc melt is 1200-1400℃. The lead-zinc oxide includes a lead-zinc mixed solid material, which includes complex lead-zinc ore and / or zinc-containing secondary resources. The reducing agent includes a reducing plasma-state substance, which is introduced from the bottom of the lead-zinc oxide and bottom-blown.

[0007] The high-zinc melt undergoes a reduction reaction under the blowing and stirring of the reducing agent to generate metal vapor. After settling, the slag and metal separate, forming an alloy phase and slag.

[0008] Furthermore, the reducing agent also includes a non-plasma-state substance, which is loaded onto the plasma-state substance. The non-plasma-state substance includes one or more of pulverized coal, coke powder, and waste electrode particles, and the particle size of the non-plasma-state substance is 0.1 to 5 mm.

[0009] The plasma working medium of the plasma-state material includes an excitation working medium and a reducing working medium. The excitation working medium includes nitrogen and argon, and the reducing working medium includes one or more of CO, H2, CH4, and C powder. The volume percentage of the reducing working medium in the plasma working medium is 5% to 30%.

[0010] Furthermore, the amount of reducing agent added is 1.2 to 2.0 times the molar amount of reducing agent used to completely reduce all the metal oxides to be reduced in the high-zinc melt to elemental metal.

[0011] Furthermore, by mass fraction, the composition of the high-zinc melt includes: 10%–30% lead oxide, 30%–45% zinc oxide, 20%–30% ferrous oxide, 25%–40% silicon dioxide, and 5%–20% calcium oxide; the calcium-silicon ratio of the slag is 0.5–2.0, and the iron-silicon ratio is 0.5–1.5.

[0012] Furthermore, the lead-zinc oxide material also includes lead-zinc melt, the source of which includes one or more of lead-zinc oxide ore, secondary zinc oxide dust, or zinc-containing dust and sludge from steel plants; the lead-zinc mixed solid material also includes flux, and the density of the lead-zinc mixed solid material is 2.0–6.0 g / cm³. 3 .

[0013] Furthermore, in the atmosphere in which the reduction reaction is formed, the C / O molar ratio is 1.2-2.5, and the duration of the reduction reaction is 20-90 minutes.

[0014] Furthermore, the plasma device includes a plasma torch, the temperature at the nozzle outlet of the plasma torch being 2000-3500°C.

[0015] This invention provides a bottom-blown plasma reduction furnace, which is applied to the bottom-blown plasma enhanced reduction and recovery of valuable metals as described in any of the above methods, including a molten pool mechanism and a heating mechanism;

[0016] The molten pool mechanism includes a molten cavity to contain the high-zinc molten metal; the top or upper side wall of the molten cavity is connected to a molten inlet and a sealed feed port to add the lead-zinc oxide material into the molten cavity;

[0017] The heating mechanism includes a plasma device and a heating device. The nozzle of the plasma device is located at the bottom of the melt chamber to spray the reducing plasma material onto the lead-zinc oxide material. The heating device is located in the middle and / or lower part of the melt chamber.

[0018] Furthermore, the plasma device includes 4 to 6 plasma torches, each with a power of 200 to 500 kW and a gas flow rate within the plasma torch ranging from 5 to 30 m³ / h. 3 / h, the plasma torch is symmetrically distributed in a ring at the bottom of the melt chamber, the plasma torch includes a nozzle, the angle between the axis of the nozzle along the length direction and the vertical direction is 15-30°, and the vertical distance between the nozzle and the bottom of the melt chamber is 0.5-1.2m.

[0019] The present invention provides a control system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor, when executing the computer program, implements the method for bottom-blown plasma-enhanced reduction and recovery of valuable metals as described in any of the preceding claims.

[0020] Compared with the prior art, the present invention has at least the following advantages:

[0021] This invention provides a bottom-blown plasma-enhanced reduction and recovery method for valuable metals. Utilizing the reducing plasma state of the bottom-blown material and the centralized heating of the heating device, a strong stirring and high-temperature zone distribution are formed within the furnace, significantly improving the heat and mass transfer efficiency during the smelting process. A heating rate of 30–50°C achieves uniform melting of lead-zinc oxide materials, effectively avoiding dioxin formation. Specifically: firstly, the 30–50°C heating rate reduces the residence time of precursor compounds at medium to low temperatures (<850°C), thereby reducing the possibility of dioxin formation; secondly, dioxins decompose at temperatures above 850°C, and rapid heating and maintaining a high temperature helps promote the decomposition of already formed dioxins; simultaneously, because the bottom-blown plasma-enhanced technology can effectively mix the lead-zinc oxide materials and high-zinc melt from the bottom using a high-speed plasma jet and a high-temperature electric arc, the uniformity of the temperature distribution within the furnace is significantly improved, completely avoiding dioxin formation.

[0022] The bottom-blown plasma-enhanced smelting technology provided by this invention utilizes a high-intensity plasma flow to rapidly penetrate the melt from the bottom of the furnace, forming a high-temperature reducing atmosphere and full-melt pool disturbance from bottom to top. This not only significantly improves the reduction reaction rate of difficult-to-reduce oxides such as ZnO and PbO, but also rapidly crosses the dioxin formation temperature range (850–450°C) and stably maintains it in the high-temperature range (≥1250°C), effectively avoiding the conditions for dioxin formation. While maintaining high-efficiency smelting performance, it achieves the process control goals of being green, low-toxicity, and low-carbon, breaking through the technical bottleneck of traditional pyrometallurgical processes where "efficiency and environmental protection are difficult to achieve simultaneously." Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of a bottom-blown plasma reduction furnace in one embodiment of this application, wherein 1 is the melt inlet, 2 is the sealed feed port, 3 is the flue, 4 is the slag discharge port, 5 is the siphon port, 6 is the plasma device, and 7 is the heating device.

[0025] Figure 2 This is a chromatogram of volatile components in the gas phase in Example 1 of this application.

[0026] Figure 3 This is a SEM-EDS image of the slag phase in Example 1 of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0029] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.

[0030] With the increasing depletion of high-grade primary lead-zinc ore resources, the lead-zinc smelting industry faces the dual challenges of diversified and complex raw material sources. Zinc-containing secondary resources, represented by complex lead-zinc ores, smelting slag, and electric furnace dust, are widely present in the metallurgical solid waste and renewable resource system. Their recycling and treatment are of great significance for the circular utilization of metal resources and the prevention and control of environmental pollution.

[0031] However, these resources generally have the following characteristics: complex metal occurrence forms, accompanied by a large amount of FeO / SiO2 impurities, ZnO content as high as 30% or more, high melting point, and high melt viscosity. Traditional pyrometallurgical processes such as blast furnace zinc smelting (ISP) have limited efficiency in processing these raw materials, especially in terms of low ZnO activity, difficulty in slag-metal separation, and incomplete reduction reaction.

[0032] More notably, zinc-containing secondary resources often inevitably contain chlorine sources (such as PVC and Cl-) and various organic components. Under high-temperature smelting environments, especially in the presence of heavy metal catalysts such as Cu, Fe, and Zn, they readily generate highly toxic dioxin-like substances (PCDDs / PCDFs) in the temperature range of 850–450℃. These compounds exhibit extremely high environmental stability, bioaccumulation, and carcinogenic and mutagenic toxicological effects, and are among the internationally recognized persistent organic pollutants (POPs).

[0033] Currently, traditional pyrometallurgical processes still mainly rely on end-of-pipe treatment methods such as tail gas cooling, activated carbon adsorption, and catalytic decomposition to deal with dioxin problems. These methods are not only complex and costly to invest in and operate, but also prone to causing pollution transfer, making it difficult to fundamentally avoid the dioxin formation mechanism.

[0034] Therefore, there is an urgent need for a new smelting technology that avoids the dioxin formation window temperature range by starting from the process source, such as the form of heat source, reaction atmosphere, heating rate, and disturbance method.

[0035] This invention provides a method for bottom-blown plasma-enhanced reduction and recovery of valuable metals, comprising:

[0036] S1. Lead-zinc oxide material is heated by a reducing agent and heating device 7 to melt and form a high-zinc melt. The heating rate of the lead-zinc oxide material is 30-50℃ / min, and the temperature of the high-zinc melt is 1200-1400℃. The lead-zinc oxide material includes a lead-zinc mixed solid material, which includes zinc-containing secondary resources. The reducing agent includes a reducing plasma state substance, which is introduced from the bottom of the lead-zinc oxide material and performs bottom blowing on the lead-zinc oxide material.

[0037] In this invention, the solid lead-zinc oxide material is a lead-zinc mixed solid material, which includes zinc-containing secondary resources. These include lead-zinc oxide ores, mixed ores (ZnO≥30%, such as Huoshaoyun Mine and Lanping Mine) belonging to complex lead-zinc mines, lead-zinc-copper polymetallic sulfide ores, and complex minerals containing high-iron and silicon oxides. Zinc-containing secondary resources also include zinc-containing dust and sludge from steel plants, lead-zinc smelting fumes, electronic waste, metal alloy slag, ISP zinc smelting slag, bottom-blown slag, converter slag, electric furnace dust, waste zinc alloys, zinc ash, lead-acid battery slag, and copper slag; metallurgical by-products and recycled resources containing zinc, lead, and copper, etc. Due to the complexity and diversity of their sources, lead-zinc oxide materials inevitably contain a certain amount of chlorine sources and complex organic matter. Under temperature conditions of 200–600°C, chlorine sources will react with organic matter to generate dioxin precursors, which will then be converted into dioxins. Therefore, zinc-containing secondary resources are a major source of dioxin formation in various pyrometallurgical raw materials.

[0038] It should be noted that this invention can also be used for the secondary resource treatment of electronic waste and precious metals. It has significant effects on the recovery of Fe, Ni, Cr and rare precious metals (Au, Ag, Pt, Pd, etc.), and has important application value and development prospects in green metallurgy and solid waste resource utilization.

[0039] In this invention, the bottom-blowing method has stronger molten pool disturbance capability, higher thermal uniformity and reaction interface renewal efficiency, which significantly improves the adaptability and reduction reaction rate of high ZnO, high FeO and high viscosity melts. It is particularly suitable for the joint recovery of multi-metal oxides such as zinc, lead and copper and the efficient processing of complex secondary resources.

[0040] In some embodiments of the present invention, the lead-zinc mixed solid may further include flux and / or reducing agent.

[0041] In some embodiments of the present invention, the density of the lead-zinc mixed solid material can be 2.0–6.0 g / cm³. 3 This allows the lead-zinc mixture to be submerged in the melt after being added, accelerating the reduction reaction through heat conduction within the melt. In some embodiments, lead-zinc mixtures with high moisture content or coarse particle size can be preheated or dried before addition to reduce energy loss due to moisture evaporation and fluctuations in the molten pool temperature, as well as lower the risk of adverse reactions between water vapor and CO.

[0042] In some embodiments of the present invention, the liquid lead-zinc oxide material includes lead-zinc melt, which includes lead / zinc sulfide ore oxidation and desulfurization melt. The source of the lead-zinc melt includes one or more of lead-zinc oxide ore, secondary zinc oxide dust, or zinc-containing dust and sludge from steel plants.

[0043] In this invention, the temperature of the high-zinc melt can be 1200–1400°C, that is, the high-zinc melt can be heated to 1200–1400°C under the synergistic heating conditions of the bottom-blown plasma strengthening method and the heating device 7. The bottom-blown plasma strengthening method utilizes a reducing plasma state substance introduced from the bottom of the lead-zinc oxide material to perform bottom blowing on the lead-zinc oxide material.

[0044] In some embodiments of the present invention, the high-zinc melt comprises, by mass fraction: 10%–30% lead oxide, 30%–50% zinc oxide, 5%–20% ferrous oxide, 5%–20% silicon dioxide, and 5%–20% calcium oxide. The melting temperature of this high-zinc melt is approximately 1450–1500°C, and its viscosity at 1250°C is approximately 1.2–1.3 Pa·s. It should be emphasized that the large amount of flux (such as CaO) introduced to lower the melting point and viscosity will form a large amount of slag. Therefore, when the ZnO content is in the range of 30%–50%, the processing difficulty is significantly higher than that of a melt with a ZnO content of approximately 20%.

[0045] In one specific embodiment of the present invention, the composition of the high-zinc melt, by mass fraction, may include: ZnO 41.7 wt.%, PbO 15.4 wt.%, FeO 9.9 wt.%, CaO 14.6 wt.%, SiO2 8.5 wt.%; the melting temperature of the high-zinc melt is about 1480°C, and the viscosity at 1250°C is about 1.232 Pa·s.

[0046] In this invention, the calcium-silicon ratio of the high-zinc melt can be controlled to be 0.5-2.0, and the iron-silicon ratio to be 0.5-1.5.

[0047] In this invention, the reducing plasma can be generated by a plasma device, which can be a plasma torch with a power of 200–500 kW. For example, the power of the plasma torch can be 300–500 kW. During operation, the bottom-blown plasma reduction furnace converts high-power electrical energy into a high-temperature, high-energy jet. When the activating working medium (N2, Ar) and the reducing working medium (CO, H2, CH4, etc.) enter the arc zone, they are rapidly heated to thousands of degrees Celsius. Some molecules dissociate and generate a large number of active groups (such as Cl, HI, etc.). These active groups come into full contact with the metal oxide particles or melt in the furnace, resulting in a rapid reduction reaction. This releases the metal from its oxide form, which then exists as metal droplets or vapor in the molten pool or gas phase.

[0048] Compared with traditional high coke ratio pyrometallurgical reduction, plasma smelting can significantly reduce solid carbon consumption and CO2 emissions. Furthermore, by efficiently recovering volatile metals (such as zinc and lead), it can reduce the metal content in the residue, which is conducive to the comprehensive utilization of resources and green metallurgy.

[0049] By arranging a plasma device at the bottom of the furnace, high-temperature plasma gas flow and reducing medium are injected into the molten pool from bottom to top, thereby forming strong stirring and high-temperature zone distribution in the furnace, which significantly improves the heat and mass transfer efficiency in the smelting process and solves the problems of uneven reaction, local nodule formation and serious furnace lining wear that exist in traditional side-blowing or top-blowing processes.

[0050] In contrast, side-blown and top-blown plasma strengthening technologies concentrate energy in the side plasma strengthening area or the surface of the molten pool. Uneven temperature distribution easily leads to significant temperature differences (up to 200-300°C) between different areas of the molten pool, insufficient bottom reaction, and zinc vapor condensation at the furnace top, forming furnace slag, severely impacting continuous production. Compared to side-blown or top-blown processes, the bottom-blown plasma torch used in this invention achieves forced convection from bottom to top, forming multiple upward-penetrating high-temperature jets at the bottom of the molten pool. This greatly promotes the circulation and mixing of liquid and dissolved particles throughout the furnace, facilitating rapid and uniform heat and mass transfer. The uniform temperature distribution within the furnace, also due to the bottom-blown plasma technology, avoids the formation of large amounts of slag or condensate on the furnace walls and top due to high-temperature gradients, reducing the difficulty of smelting operations and minimizing damage to the furnace lining. Simultaneously, because the high-temperature zone at the bottom is relatively concentrated and the melt is in a turbulent state, energy waste caused by localized overheating is reduced.

[0051] In some embodiments of the present invention, the plasma working medium of the plasma-state material includes an excitation working medium and a reduction working medium. The excitation working medium includes nitrogen and argon, and the reduction working medium includes one or more of CO, H2, CH4, and C powder. When the reduction working medium is fed into the torch or nozzle area, it can be rapidly converted into a high-temperature jet containing high-energy free radicals (CI, HI, etc.), which greatly improves the chemical reaction activity in the furnace.

[0052] This invention provides a bottom-blown plasma-enhanced reduction and recovery method for valuable metals. Utilizing the reducing plasma state of the bottom-blown material and the centralized heating of the heating device 7, a strong stirring and high-temperature zone distribution are formed within the furnace, significantly improving the heat and mass transfer efficiency during the smelting process. A heating rate of 30–50°C achieves uniform melting of lead-zinc oxide materials, effectively avoiding dioxin formation. Specifically: firstly, the 30–50°C heating rate reduces the residence time of precursor compounds at medium to low temperatures (<850°C), thereby reducing the possibility of dioxin formation; secondly, dioxins decompose at temperatures above 850°C, and rapid heating and maintaining a high temperature helps promote the decomposition of already formed dioxins; simultaneously, because the bottom-blown plasma-enhanced technology can effectively mix the lead-zinc oxide materials and high-zinc melt from the bottom using a high-speed plasma jet and a high-temperature electric arc, the uniformity of the temperature distribution within the furnace is significantly improved, completely avoiding dioxin formation.

[0053] The bottom-blown plasma-enhanced smelting technology provided by this invention utilizes a high-intensity plasma flow to rapidly penetrate the melt from the bottom of the furnace, forming a high-temperature reducing atmosphere and full-melt pool disturbance from bottom to top. This not only significantly improves the reduction reaction rate of difficult-to-reduce oxides such as ZnO and PbO, but also rapidly crosses the dioxin formation temperature range (850–450°C) and stably maintains it in the high-temperature range (≥1250°C), effectively avoiding the conditions for dioxin formation. While maintaining high-efficiency smelting performance, it achieves the process control goals of being green, low-toxicity, and low-carbon, breaking through the technical bottleneck of traditional pyrometallurgical processes where "efficiency and environmental protection are difficult to achieve simultaneously."

[0054] In comparison, while existing reducing agent bottom blowing technology can enhance molten pool stirring, it is limited by insufficient gas chemical energy, making it difficult to efficiently process high-melting-point materials (such as zinc-containing solid waste requiring >1300℃). The high zinc content results in poor melt fluidity, making it difficult to reduce the zinc-containing silicate phase. Furthermore, the short lifespan of the spray gun (<72 hours) and frequent maintenance lead to increased costs.

[0055] In this invention, the reducing agent also includes a non-plasma-state substance, which is loaded onto the plasma-state substance. The non-plasma-state substance includes one or more of pulverized coal, coke powder, and waste electrode particles. In some embodiments, the particle size of the non-plasma-state substance can be 0.1–5 mm. After mixing with the high-temperature plasma jet, the non-plasma-state substance is rapidly heated and decomposed, further generating active reducing components such as CO and H2.

[0056] In some embodiments of the present invention, the heating device 7 includes an electromagnetic induction heating device 7; in some embodiments, the electromagnetic induction heating device 7 may be disposed on the side of the molten pool containing lead-zinc oxide material.

[0057] S2. The high-zinc melt undergoes a reduction reaction under the blowing and stirring of the reducing agent to generate metal vapor. After settling, the slag and metal separate, forming an alloy phase and slag.

[0058] In this invention, the settling time can be 20 to 30 minutes.

[0059] In this invention, the C / O molar ratio is 1.2-2.5 in the atmosphere in which the reduction reaction occurs, the temperature of the high-zinc melt is 1200-1400°C, and the duration of the reduction reaction is 30-90 minutes. After reduction smelting, the recovery rate of metallic zinc is >95%, and the recovery rate of metallic lead is >90%.

[0060] In this invention, since the high-zinc melt maintains sufficient fluidity at high temperatures, the slag can be separated and discharged through the slag discharge port 4 at the bottom of the furnace or the lower part of the furnace body after reduction; while some less volatile or precious metals are enriched in the molten metal deposited in the furnace, which can be extracted through the siphon port 5 on the side or top, thereby achieving efficient separation and recovery of multiple metals.

[0061] In this invention, the metal vapor includes zinc vapor and lead vapor. Zinc and lead readily vaporize at high temperatures and rise to the furnace top. High-efficiency condensation devices and dust collectors can be installed at the furnace top or exhaust pipe to collect the soot or dust formed by the volatile metal vapors. In other words, the metal vapor rises with the airflow to the furnace top or flue and is captured. After condensation or dust removal, zinc- and lead-rich soot or metal crystals are obtained. Non-volatile precious metals (Au, Ag, etc.) accumulate in the molten metal or alloy phase, separating from the slag, and can be further purified through refining or electrolysis.

[0062] This invention provides a bottom-blown plasma reduction furnace, which is applied to the bottom-blown plasma enhanced reduction and recovery of valuable metals as described in any of the above methods, including a molten pool mechanism and a heating mechanism;

[0063] The molten pool mechanism includes a molten cavity to contain the high-zinc molten material; the top or upper side wall of the molten cavity is connected to a molten inlet 1 and a sealed feed port 2 to add the lead-zinc oxide material into the molten cavity; the sealed feed port 2 may be equipped with a sealing valve or a screw feeder to prevent furnace gas leakage and environmental pollution.

[0064] The heating mechanism includes a plasma device and a heating device 7. The nozzle of the plasma device 6 is located at the bottom of the melt chamber to spray the reducing plasma material onto the lead-zinc oxide material. The heating device 7 is located in the middle and / or lower part of the melt chamber.

[0065] In this invention, the plasma device 6 may include 4 to 6 plasma torches, and in some embodiments, the plasma torches may be symmetrically distributed in a ring.

[0066] In some embodiments, the plasma torch includes a spray gun, and the distribution of multiple bottom-blowing spray guns in this invention helps to maintain production continuity in the event of a failure of a single spray gun.

[0067] In some embodiments, the present invention may be equipped with a bottom liner and cooling protection, making thermal stress relatively controllable, and making the insertion and maintenance of the spray gun relatively convenient, resulting in a longer overall maintenance cycle and thus reducing operating and maintenance costs.

[0068] In some embodiments of the present invention, the power of the plasma torch is 200-500kW; the plasma torch is symmetrically distributed in a ring at the bottom of the melt chamber, the plasma torch includes a nozzle orifice, the nozzle orifice is disposed at the end of the spray gun that contacts the high zinc melt, the angle between the axis of the nozzle orifice along the length direction and the vertical direction is 15-30°, and the vertical distance between the nozzle orifice and the bottom of the melt chamber is 0.5-1.2m.

[0069] In some embodiments of the present invention, the angle between the axis of the nozzle orifice along its length and the vertical direction can be 15°, so that the jet penetrates the thickness of the molten pool and produces a large-scale stirring effect in the furnace. The insertion depth of the spray gun can be adjusted according to actual production needs, and with the corresponding lifting or directional mechanism, it is convenient to achieve the best spraying angle and depth under different operating stages or conditions.

[0070] In some embodiments of the present invention, the plasma torch is composed of components such as a spray gun, electrodes, a cooling water jacket, and an insulating sheath. Inside the torch body, a high-power electric arc discharge ionizes the excitation working medium (e.g., N2, Ar, etc.) to form a stable plasma jet.

[0071] In some embodiments of the present invention, the temperature at the plasma torch nozzle is as high as 2000-3500°C.

[0072] In this invention, the furnace body can be a vertical cylindrical shape or a furnace body structure with a slightly narrow opening at the top and bottom. It can be fitted with a high-temperature resistant steel shell to ensure that the furnace body can remain stable under high temperature and internal pressure conditions.

[0073] In this invention, the bottom-blown plasma reduction furnace can be lined with a furnace body refractory lining. The furnace body refractory lining includes: the furnace bottom and furnace wall lining, which can be made of high-refractory and slag-erosion-resistant composite materials such as magnesia-carbon bricks and corundum castables, forming a double-layer or multi-layer stacked structure. The bottom refractory material especially needs to have high strength and excellent erosion resistance to withstand the impact of high-speed airflow and molten material from bottom to top.

[0074] In this invention, the bottom-blown plasma reduction furnace may include a cooling system. A water-cooled jacket may be provided around the furnace wall in the cooling system, and the water temperature is controlled within the range of 30 to 60°C. Local overheating and damage to the furnace wall lining are avoided through circulating cooling.

[0075] In this invention, a flue 3, a slag discharge port 4, and a siphon port 5 can be sequentially opened from top to bottom on the outer wall of the molten pool. It should be noted that the positions of the flue 3, slag discharge port 4, and siphon port 5 do not need to follow the layout requirement of being on the same vertical line. They can be flexibly and reasonably arranged in a staggered layout according to actual process requirements, furnace structure characteristics, and ease of operation.

[0076] In some embodiments of the present invention, high-temperature dust-laden gas is generated at the furnace top or flue 3 during the bottom-blown smelting process. To avoid environmental pollution and recover valuable elements such as zinc and lead that escape, waste heat recovery equipment and a dust removal system (such as a bag filter, electrostatic precipitator, or scrubbing tower) can be installed at the rear end of flue 3 to capture and recover the metal fumes. Furthermore, to prevent the escape of combustible gases such as CO and H2, a tight seal and monitoring device must be installed between the furnace body and the ventilation system to ensure operational safety.

[0077] In this invention, the melt enhancement reduction and recovery system of the bottom-blown plasma torch may include a gas supply system, a power supply system, a feeding system, and a powder supply system.

[0078] In some embodiments of the present invention, the gas supply system may mainly consist of a gas source, pressure regulating valve, flow meter, and safety valve, used to provide excitation gas and reducing gas to the plasma torch, and flexibly adjust the flow rate of each component according to process requirements. In some more specific embodiments of the present invention, in order to ensure the stability of the molten pool atmosphere and carbon-oxygen ratio, the gas supply system may adopt a multi-channel parallel connection, and automatic control devices (such as solenoid valves, flow meters, and PLC control modules) may be installed on each channel, thereby realizing real-time and precise control of carbon-oxygen ratio, furnace pressure, and atmosphere environment.

[0079] In some embodiments of the present invention, the power supply system typically includes a rectifier transformer, an inverter, a controller, and other components, and is matched with the plasma torch to ensure continuous and efficient discharge under high temperature and high arc field conditions, so as to maintain the stable and high-power power supply required by the plasma torch.

[0080] In some embodiments of the present invention, a feeding system can be used to feed materials into the bottom-blown plasma reduction furnace. Lead-zinc molten material can be fed into the bottom-blown plasma reduction furnace through the melt inlet 1, or a lead-zinc mixed solid material can be added into the bottom-blown plasma reduction furnace through the sealed feeding port 2. In some more specific embodiments of the present invention, a belt conveyor or a sealed feeding tank can be used for batch or continuous feeding.

[0081] In some embodiments of the present invention, the melt-enhanced reduction and recovery system of the bottom-blown plasma torch can be equipped with a powder supply system. Powdered or granular non-plasma substances can be fed into the bottom spray gun area through an independent powder supply pipe to achieve continuous and controllable feeding. In some more specific embodiments of the present invention, a precise metering device (such as a screw feeder or weighing system) can be configured below the storage silo, and a blower or pneumatic conveying equipment can be used to transport the non-plasma substances to the vicinity of the torch nozzle. After mixing with the high-temperature plasma jet, the substances are rapidly heated and decomposed to further generate active reducing components such as CO and H2.

[0082] In this invention, online sensors for temperature, pressure, and gas composition can be placed at key locations in the furnace body. With the help of a PLC or DCS system, key parameters such as power supply, gas flow rate, feeding speed, and carbon-oxygen ratio can be controlled in a closed loop, making the smelting process more stable and controllable. Dynamic adjustment and optimization can also be achieved based on the raw material composition and process objectives.

[0083] The bottom-blown plasma reduction furnace and the melt-enhanced reduction and recovery system of the bottom-blown plasma torch provided by this invention have the following advantages:

[0084] 1. Dual-energy synergistic heating and modular furnace design: Through bottom-blown plasma torch and electromagnetic induction coil synergistic heating, the temperature can be rapidly raised to 1200-1400℃ in 30 minutes, reducing energy consumption by 25%; the furnace body adopts double-layer refractory lining (magnesia-carbon brick + corundum) and water cooling system, extending its service life to 5 years.

[0085] 2. Optimization of melt immersion reduction and dynamic heat transfer for solid mixtures (density 2.0-6.0 g / cm³). 3 Immersed in a high-zinc melt (Zn > 30%), the high thermal conductivity of the melt accelerates the reduction, shortening the reaction time to 30-90 minutes. The zinc recovery rate is > 95%, and the lead recovery rate is > 90%. It is suitable for high-impurity raw materials such as dust and sludge from steel plants.

[0086] 3. Multi-medium plasma active atmosphere control.

[0087] By using CO / H2 / CH4 as a medium to inject active groups (CI, HI), and combining solid reducing agents (pulverized coal / coke powder) to dynamically adjust the carbon-oxygen ratio (C / O = 1.2-2.5), the traditional solid-gas reaction limitation is broken, and the reduction efficiency of metal oxides is improved by 40%.

[0088] 4. This invention overcomes the problems of uneven reaction, excessive temperature gradient in the furnace and serious slag buildup in traditional side-blowing or top-blowing modes by uniformly distributing multiple plasma torches at the bottom of the furnace body and using a powerful bottom-blowing jet to fully contact high-energy plasma with molten materials.

[0089] 5. The process of this invention can significantly improve the reduction rate and efficiency of metal oxides, thereby greatly enhancing the comprehensive recovery rate of various metals such as zinc, lead, and copper. Simultaneously, the system, combined with measures such as powder feeding, precise atmosphere control, and water-cooled furnace wall protection, greatly reduces furnace lining wear and energy waste, offering comprehensive advantages such as long equipment service life, flexible operation, high safety, and environmental friendliness.

[0090] 6. Environmentally friendly and resource-efficient: Dioxins are decomposed by plasma at high temperatures (>1800℃), and waste heat is recovered from the exhaust gas before being discharged in compliance with standards; the slag is vitrified and used in building materials (permeable bricks), with a resource utilization rate of >98% and a reduction in carbon emission intensity.

[0091] The present invention also provides a control system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, when the processor executes the computer program, it implements the method for bottom-blown plasma-enhanced reduction and recovery of valuable metals as described in any of the preceding claims.

[0092] It should be noted that the bottom-blown plasma reduction furnace described above may also include the control system.

[0093] To facilitate a further understanding of the present invention by those skilled in the art, the following examples are provided:

[0094] Example 1

[0095] S1. First, a certain domestic lead-zinc oxide ore and lead / zinc sulfide ore desulfurization melt are mixed in proportion to obtain 2500g of lead-zinc oxide material with the main composition of PbO:ZnO:FeO:SiO2:CaO=23:45:11:8:8.9 (wt.%), the remainder being other oxide impurities. The lead-zinc oxide material is added into the molten pool mechanism through the sealed feeding port 2, and a high-zinc melt is formed by the heating of the reducing agent and the heating device 7. The heating rate of the lead-zinc oxide material is 45℃ / min, and the temperature of the high-zinc melt is 1300℃.

[0096] The plasma device consists of three plasma torches, each with a power of 300 kW and a gas flow rate of 20 m³ / s. 3 / h, the plasma torch is symmetrically distributed in a ring at the bottom of the melt chamber. The plasma torch includes a nozzle orifice. The angle between the axis of the nozzle orifice along its length and the vertical direction is 15-30°. The vertical distance between the nozzle orifice and the bottom of the melt chamber is 0.7m.

[0097] In step S1, CO is injected into the bottom of the molten pool using plasma-state N2-CO mixed gas sprayed from the bottom plasma torch as a carrier. In this embodiment, the total amount of CO injected (molar amount of plasma-state CO + molar amount of non-plasma-state CO) is 1.2 times the molar amount of reducing agent used to reduce all the metal oxides to be reduced in the high-zinc melt to elemental metal. The volume ratio of CO in the N2-CO mixed gas is 20%.

[0098] S2. The high-zinc melt undergoes a reduction reaction under the agitation of a reducing agent to generate metal vapor. After settling, the slag and metal separate, forming an alloy phase and slag. The reduction reaction lasts for 20 minutes, and the C / O molar ratio in the atmosphere formed during the reduction reaction is 1.2-2.5.

[0099] The volatile components in the gas phase were determined to be mainly zinc oxide and lead, and their component analysis is as follows: Figure 2 As shown, the slag phase mainly consists of silicate oxides formed by Ca, Fe, and Si. The remaining lead and zinc content in the slag phase is 0%, and the zinc and lead recovery rates reach 99%. Its phase SEM-EDS diagram is shown below. Figure 3 As shown, the main metallic phase is a Pb / Cu mixed phase, and the impurity (As, Sb) content in the Pb-Cu alloy phase is <0.05%, meeting the requirements for direct refining. Bottom blowing ensures full contact between CO bubbles and the melt, effectively reducing PbO and ZnO. In this embodiment, the CO energy utilization rate is as high as 92%.

[0100] Dioxins were not detected in the flue gas (detection limit: 0.01 ng TEQ / m³). 3 This is far below the national emission standard (0.5 ng TEQ / m³). 3 ).

[0101] Example 2

[0102] In this embodiment, all other conditions remain unchanged, except that the heating rate of the lead-zinc oxide material is adjusted from 45℃ / min to 30℃ / min.

[0103] Analysis revealed that the volatile components in the gas phase were mainly zinc oxide and lead, comprising 35% lead, 25% zinc, and 40% zinc oxide. The slag phase consisted primarily of silicate oxides formed from Ca, Fe, and Si, with 0% residual lead and 0% residual zinc, achieving a zinc and lead recovery rate of 99%. The formed metallic phase was mainly a Pb / Cu mixed phase, with impurities (As and Sb) in the Pb-Cu alloy phase less than 0.05%, meeting the requirements for direct refining. Bottom blowing ensured sufficient contact between CO bubbles and the melt, effectively reducing PbO and ZnO. In this embodiment, the CO energy utilization rate reached as high as 80%.

[0104] Dioxins were not detected in the flue gas (detection limit: 0.01 ng TEQ / m³). 3 This is far below the national emission standard (0.5 ng TEQ / m³). 3 ).

[0105] Comparative Example 1

[0106] Compared to the embodiment, this comparative example retains all other conditions except that the bottom blowing method is replaced with top blowing.

[0107] S1. First, a certain domestic lead-zinc oxide ore, high-zinc lumps from pyrometallurgical zinc refining, and zinc oxide dust are mixed in a certain proportion to obtain 2500g of lead-zinc oxide material with the main composition of PbO:ZnO:FeO:SiO2:CaO=23:45:11:8:8.9 (wt.%). The remainder consists of impurities such as aluminum and magnesium. The lead-zinc oxide material is added into the molten pool mechanism through the sealed feeding port 2. It is heated by the reducing agent and the heating device 7 to form a high-zinc melt. The heating rate of the lead-zinc oxide material is 5℃ / min, and the temperature of the high-zinc melt is 1300℃.

[0108] The plasma device consists of three plasma torches, each with a power of 300 kW and a gas flow rate of 20 m³ / s. 3 / h, the plasma torch is symmetrically distributed in a ring at the top of the melt chamber. The plasma torch includes a nozzle orifice. The angle between the axis of the nozzle orifice along the length direction and the vertical direction is 15-30°. The nozzle orifice is immersed in the high zinc melt.

[0109] In step S1, CO is injected into the bottom of the molten pool using the plasma-state N2-CO mixed gas sprayed from the top plasma torch as a carrier. In this embodiment, the total amount of CO injected (molar amount of plasma-state CO + molar amount of non-plasma-state CO) is 1.2 times the molar amount of reducing agent required to reduce all the metal oxides to be reduced in the high-zinc melt to elemental metal. The volume percentage of CO in the N2-CO mixed gas is 20%.

[0110] S2. The high-zinc melt undergoes a reduction reaction under the agitation of the reducing agent to generate metal vapor. After settling, the slag and metal separate, forming an alloy phase and slag. The reduction reaction lasts for 40 minutes. Analysis shows that the volatile components in the vapor phase are mainly zinc oxide and lead, while the slag phase mainly consists of silicate oxides formed from Ca, Fe, and Si. The remaining lead content in the slag phase is 0.89%, and the zinc content is 2.7%, with a zinc recovery rate of 95% and a lead recovery rate of 98%. The formed metallic phase is mainly a Pb / Cu mixed phase, with an As content of 0.3% in the Pb-Cu alloy, requiring an additional arsenic removal process. The top-blown gas rises too quickly, resulting in a CO utilization rate of only 65%.

[0111] The concentration of dioxins in the flue gas was 1.5 ng TEQ / m³. 3 Exceeded the standard by 3 times (national limit 0.5ng TEQ / m³). 3 ).

[0112] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for bottom-blown plasma-enhanced reduction and recovery of valuable metals, characterized in that, include: Lead-zinc oxide is heated by a reducing agent and a heating device to melt and form a high-zinc melt. The heating rate of the lead-zinc oxide is 30-50℃ / min, and the temperature of the high-zinc melt is 1200-1400℃. The lead-zinc oxide includes a lead-zinc mixed solid material, which includes zinc-containing secondary resources. The reducing agent includes a reducing plasma-state substance, which is introduced from the bottom of the lead-zinc oxide and bottom-blown. The zinc-containing secondary resource contains a chlorine source and organic components; The lead-zinc oxide material comprises, by mass fraction: 10%~30% lead oxide, 30%~50% zinc oxide, 5%~20% ferrous oxide, 5%~20% silicon dioxide, and 5%~20% calcium oxide; The plasma working medium of the reducing plasma state material includes an excitation working medium and a reducing working medium. The excitation working medium includes nitrogen and / or argon, and the reducing working medium includes one or more of CO, H2, CH4, and C powder. The high-zinc melt undergoes a reduction reaction under the blowing and stirring of the reducing agent to generate metal vapor. After settling, the slag and metal separate, forming an alloy phase and slag.

2. The method for bottom-blown plasma-enhanced reduction and recovery of valuable metals according to claim 1, characterized in that, The reducing agent also includes a non-plasma-state substance, which is loaded onto the plasma-state substance. The non-plasma-state substance includes one or more of pulverized coal, coke powder, and waste electrode particles. The volume percentage of the reducing working medium in the plasma working medium is 5% to 30%.

3. The method for bottom-blown plasma-enhanced reduction and recovery of valuable metals according to claim 2, characterized in that, The amount of reducing agent added is 1.2 to 2.0 times the molar amount of reducing agent required to completely reduce all the metal oxides to be reduced in the lead-zinc oxide material to elemental metal.

4. The method for bottom-blown plasma-enhanced reduction and recovery of valuable metals according to claim 1, characterized in that, The lead-zinc oxide material also includes lead-zinc melt, the source of which includes one or more of lead-zinc oxide ore, secondary zinc oxide dust, or zinc-containing dust and sludge from steel plants.

5. The method for bottom-blown plasma-enhanced reduction and recovery of valuable metals according to claim 1, characterized in that, In the atmosphere formed by the reduction reaction, the C / O molar ratio is 1.2-2.5, and the duration of the reduction reaction is 20-90 minutes.

6. The method for bottom-blown plasma-enhanced reduction and recovery of valuable metals according to claim 1, characterized in that, The plasma device includes a plasma torch, the temperature of which is 2000-3500°C at the nozzle exit of the plasma torch.

7. A control system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method for bottom-blown plasma-enhanced reduction and recovery of valuable metals as described in any one of claims 1-6.

Images