Method, reduction furnace and system for recovering valuable metals through bottom blowing type plasma enhanced reduction

Abstract

The invention provides a method, a reduction furnace and a system for recovering valuable metals through bottom blowing type plasma enhanced reduction, and the method comprises the following steps: a lead-zinc oxide material is molten to form a high-zinc melt through heat supply of a reducing agent and a heating device, the temperature rise rate of the lead-zinc oxide material is 30-50 DEG C / min, and the temperature rise rate of the lead-zinc oxide material is 30-50 DEG C / min; the temperature of the high-zinc melt is 1200 to 1400 DEG C; the reducing agent comprises a reducing plasma state substance, and the reducing plasma state substance is introduced from the bottom of the lead-zinc oxide material and is used for carrying out bottom blowing on the lead-zinc oxide material; and the high-zinc melt is subjected to a reduction reaction under blowing and stirring of a reducing agent to generate metal steam, slag and metal are separated, and an alloy phase and slag are generated. According to the bottom blowing type process, the reduction rate and the reduction efficiency of the metal oxide can be remarkably improved, and the comprehensive recovery rate of various metals such as zinc, lead and copper is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste treatment, and in particular relates to a method, a reduction furnace and a system for recovering valuable metals by bottom-blowing plasma-enhanced reduction. Background Art

[0002] Bottom-blowing plasma smelting technology utilizes the high energy flow of plasma and the turbulent flow of bottom air to rapidly stimulate smelting reactions in a high-temperature, highly reducing atmosphere. It is particularly suitable for processing nonferrous minerals and secondary resources with high viscosity, high melting points, and complex compositions. Its unique stirring and heat input methods make it adaptable to a wide range of raw materials, making it particularly suitable for complex raw materials that are difficult to process efficiently using traditional processes.

[0003] The recycling and treatment of complex lead-zinc ores and zinc-containing secondary resources is of great significance for sustainable resource utilization and environmental protection. However, due to the unavoidable presence of chlorine sources and diverse, complex organic matter in the raw materials, coupled with the catalytic effect of heavy metals in the smelting environment, the high temperatures of traditional pyrometallurgical smelting can produce hazardous substances such as dioxins. Dioxins are a general term for two types of tricyclic aromatic organic compounds, including polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Dioxin molecules in which chlorine atoms simultaneously replace positions 2, 3, 7, and 8 are physiologically toxic. These 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, while traditional pyrometallurgical smelting technology offers certain advantages in processing complex lead-zinc ores and zinc-containing secondary resources, its practical application is hampered by the generation of dioxins. Therefore, there is a need to develop new smelting technologies or improve existing ones to reduce dioxin generation. Commonly used technologies typically utilize tail gas treatment and adsorption techniques to treat generated dioxins, but these are costly and complex. No specific smelting technology has yet emerged to prevent dioxin generation during pyrometallurgical smelting. Summary of the Invention

[0005] Aiming to solve the technical problem of dioxin generation during the pyrometallurgical smelting of complex lead-zinc ores and zinc-containing secondary resources in the above-mentioned conventional technologies, the present invention provides a bottom-blown plasma-enhanced reduction and recovery method for valuable metals, comprising:

[0006] The lead-zinc oxide material is melted by a reducing agent and heat provided by a heating device to form a high-zinc melt. The heating rate of the lead-zinc oxide material is 30-50°C / min, and the temperature of the high-zinc melt is 1200-1400°C. The lead-zinc oxide material includes a lead-zinc mixed solid material, and the lead-zinc mixed solid material includes a complex lead-zinc ore and / or a zinc-containing secondary resource. The reducing agent includes a reducing plasma-state substance, and the reducing plasma-state substance is introduced from the bottom of the lead-zinc oxide material to perform bottom blowing on the lead-zinc oxide material.

[0007] The high-zinc melt undergoes a reduction reaction under the spraying and stirring of the reducing agent to generate metal vapor. After standing, the slag and gold are separated to generate an alloy phase and slag.

[0008] Furthermore, the reducing agent further includes a non-plasma substance, the non-plasma substance is loaded on the plasma substance, the non-plasma substance includes one or more of pulverized coal, coke powder, and waste electrode particles, and the particle size of the non-plasma substance is 0.1 to 5 mm;

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

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

[0011] Furthermore, the composition of the high-zinc melt includes, by mass fraction, 10% to 30% lead oxide, 30% to 45% zinc oxide, 20% to 30% ferrous oxide, 25% to 40% silicon dioxide, and 5% to 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 further comprises a lead-zinc melt, the source of which comprises one or more of lead-zinc oxide ore, secondary zinc oxide smoke, or zinc-containing dust from a steel mill; the lead-zinc mixed solid material further comprises a flux, and the density of the lead-zinc mixed solid material is 2.0 to 6.0 g / cm 3 .

[0013] Furthermore, in the atmosphere formed during the reduction reaction, the C / O molar ratio is 1.2-2.5, and the reduction reaction lasts for 20 to 90 minutes.

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

[0015] The present invention provides a bottom-blown plasma reduction furnace, which is applied to the bottom-blown plasma enhanced reduction and recovery of valuable metals method as described above, comprising a molten pool mechanism and a heat supply mechanism;

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

[0017] The heat supply 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 substance toward 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, the power of the plasma torches is 200 to 500 kW, and the gas flow rate in the plasma torches is in the range of 5 to 30 m 3 / h, the plasma torch is symmetrically distributed in a ring shape at the bottom of the melt chamber, the plasma torch includes a nozzle port, the angle between the axis of the nozzle port along the length direction and the vertical direction is 15-30°, and the distance between the nozzle port and the bottom of the melt chamber in the vertical direction is 0.5-1.2m.

[0019] 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. The control system is characterized in that when the processor executes the computer program, the method for bottom-blowing plasma-enhanced reduction and recovery of valuable metals as described in any one of the above items is implemented.

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

[0021] The present invention provides a method for recovering valuable metals by bottom-blowing plasma-enhanced reduction. By utilizing bottom-blown reducing plasma and centralized heat supply from a heating device, intense stirring and high-temperature zone distribution are generated within a furnace, significantly improving heat and mass transfer efficiency during the smelting process. Uniform melting of lead-zinc oxide materials is achieved at a heating rate of 30-50°C, effectively avoiding the generation of dioxins. Specifically, the heating rate of 30-50°C can reduce the time that precursor compounds remain at medium-low temperatures (less than 850°C), thereby reducing the possibility of dioxin generation through reactions. Furthermore, dioxins can be decomposed at temperatures above 850°C, and rapid heating and maintenance of the high temperature state help promote the decomposition of generated dioxins. Furthermore, because the bottom-blowing plasma-enhanced technology can effectively mix the lead-zinc oxide materials and the high-zinc melt from the bottom using a high-speed plasma jet and a high-temperature arc, the uniformity of the temperature distribution within the furnace is significantly improved, completely avoiding the generation of dioxins.

[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 furnace bottom, creating a bottom-up high-temperature reducing atmosphere and full-melt pool disturbance. This not only significantly increases the reduction reaction rate of difficult-to-reduced oxides such as ZnO and PbO, but also rapidly transcends the dioxin formation temperature range (850-450°C) and stably maintains the high-temperature range (≥1250°C), effectively avoiding the conditions for dioxin formation. While maintaining efficient smelting performance, it achieves the process control goals of green, low-toxicity, and low-carbon emissions, breaking through the technical bottleneck of traditional pyrometallurgical smelting, which is difficult to achieve both efficiency and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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.

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

[0025] Figure 2 This is an analysis chart of volatile components in the gas phase in Example 1 of the present application.

[0026] Figure 3 This is the SEM-EDS image of the slag phase in Example 1 of the present application. DETAILED DESCRIPTION

[0027] 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.

[0028] 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.

[0029] 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.

[0030] With the increasing depletion of high-grade primary lead and zinc ore resources, the lead and zinc smelting industry faces the dual challenges of diversifying and increasing the complexity of raw material sources. Zinc-containing secondary resources, such as complex lead and zinc ores, smelting slag, and electric furnace dust, are widely present in the metallurgical solid waste and renewable resource system. Their recovery and processing are of great significance to the recycling of metal resources and the prevention and control of environmental pollution.

[0031] However, this type of resource generally has 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 such 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 inevitably contain chlorine sources (such as PVC and Cl-) and various organic components. High-temperature smelting environments, especially in the presence of heavy metal catalysts such as Cu, Fe, and Zn, can easily generate highly toxic dioxins (PCDDs / PCDFs) in the 850-450°C temperature range. These compounds are known to be highly environmentally stable, bioaccumulative, and have toxic effects such as carcinogenicity and mutagenicity, making them internationally recognized persistent organic pollutants (POPs).

[0033] Currently, traditional pyrometallurgical smelting still mainly relies on end-of-pipe treatment measures such as tail gas cooling, activated carbon adsorption, and catalytic decomposition to deal with the dioxin problem. Not only are the treatment processes complicated and the investment and operating costs high, but they are also prone to transfer pollution and it is difficult to fundamentally avoid the dioxin generation mechanism.

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

[0035] The present invention provides a method for recovering valuable metals by bottom-blowing plasma-enhanced reduction, comprising:

[0036] S1. The lead-zinc oxide material is melted by the reducing agent and the heat provided by the heating device 7 to form a high-zinc melt. The heating rate of the lead-zinc oxide material is 30-50°C / min, and the temperature of the high-zinc melt is 1200-1400°C. The lead-zinc oxide material includes a lead-zinc mixed solid material, and the lead-zinc mixed solid material includes a zinc-containing secondary resource. The reducing agent includes a reducing plasma-state substance, and the reducing plasma-state substance is introduced from the bottom of the lead-zinc oxide material and bottom-blown into the lead-zinc oxide material.

[0037] In the present invention, the solid lead-zinc oxide material is a lead-zinc mixed solid material, which includes zinc-containing secondary resources, including lead-zinc oxide ores, mixed ores (ZnO ≥ 30%, such as Huoshaoyun Mine and Lanping Mine), lead-zinc-copper polymetallic sulfide ores, oxide ores, and complex minerals containing high iron and silicon. Zinc-containing secondary resources also include zinc-containing dust and mud from steel mills, lead-zinc smelting smoke, electronic waste, metal alloy slag, ISP zinc smelting slag, bottom-blown slag, converter slag, electric furnace dust, waste zinc alloy, zinc ash, lead-acid battery slag, copper slag, and metallurgical byproducts and renewable resources containing zinc, lead, and copper. Due to the complexity and diversity of sources, the lead-zinc oxide material inevitably contains a certain amount of chlorine source and complex organic matter. Under temperature conditions of 200-600°C, the chlorine source reacts with the organic matter to form dioxin precursors, which are then converted into dioxins. Therefore, zinc-containing secondary resources are the most serious source of dioxin generation among various pyrometallurgical raw materials.

[0038] It should be noted that the present invention can also be used for the treatment of electronic waste and secondary resources containing 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 the present invention, the bottom blowing type has stronger melt pool disturbance ability, 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, and is particularly suitable for the joint recovery of multi-metal oxides such as zinc, lead and copper and the efficient treatment of complex secondary resources.

[0040] In some embodiments of the present invention, the lead-zinc mixed solid material may further include a flux and / or a 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 / cm 3 , so that the lead-zinc mixture solid material can be immersed in the melt after being added, accelerating the reduction reaction through heat conduction from the melt. In some embodiments, the lead-zinc mixture solid material with high humidity or coarse particle size can be preheated or dried before adding to reduce energy loss and fluctuations in the melt pool temperature caused by water evaporation, and reduce 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 a lead-zinc melt, which includes an oxidative desulfurization melt of a lead / zinc sulfide ore, and the source of the lead-zinc melt includes one or more of lead-zinc oxide ore, secondary zinc oxide smoke, or zinc-containing dust from a steel plant.

[0043] In the present 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 conditions of coordinated heating by the bottom-blowing plasma enhancement means and the heating device 7. The bottom-blowing plasma enhancement means uses reducing plasma to be introduced from the bottom of the lead-zinc oxide material and bottom-blown the lead-zinc oxide material.

[0044] In some embodiments of the present invention, the composition of the high-zinc melt includes, by mass, 10% to 30% lead oxide, 30% to 50% zinc oxide, 5% to 20% ferrous oxide, 5% to 20% silicon dioxide, and 5% to 20% calcium oxide. The high-zinc melt of this composition has a melting temperature of approximately 1450 to 1500°C and a viscosity of approximately 1.2 to 1.3 Pa·s at 1250°C. 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% to 50%, the processing difficulty is significantly higher than that of a melt with a ZnO content of approximately 20%.

[0045] In a specific embodiment of the present invention, the composition of the high-zinc melt may include, by mass fraction, 1.7 wt.% ZnO, 15.4 wt.% PbO, 9.9 wt.% FeO, 14.6 wt.% CaO, and 8.5 wt.% SiO2. The high-zinc melt has a melting temperature of approximately 1480°C and a viscosity of approximately 1.232 Pa·s at 1250°C.

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

[0047] In the present invention, the reducing plasma substance can be generated by a plasma device, which can be a plasma torch. The power of the plasma torch can be 200 to 500 kW, and for example, the power of the plasma torch can be 300 to 500 kW. When the bottom-blown plasma reduction furnace is in operation, the plasma torch converts high-power electrical energy into a high-temperature, high-energy jet. When the excitation working medium (N2, Ar) and the reducing working medium (CO, H2, CH4, etc.) enter the arc zone, they are rapidly heated to thousands or even tens of thousands of degrees Celsius. Some molecules dissociate and produce a large number of active groups (such as CI, HI, etc.). These active groups fully contact the metal oxide particles or melt in the furnace, undergoing a rapid reduction reaction, releasing the metal from its oxide form and existing in the molten pool or gas phase in the form of metal droplets or vapor.

[0048] Compared with traditional high-coke ratio pyroreduction, the plasma smelting method of the present invention can significantly reduce solid carbon consumption, reduce CO2 emissions, and reduce the metal content in the residue by efficiently recovering volatile metals (such as zinc and lead), 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 sprayed into the molten pool from bottom to top, thereby forming strong stirring and high-temperature zone distribution in the furnace, significantly improving the heat and mass transfer efficiency during the smelting process, and solving the problems of uneven reaction, local nodules, and severe furnace lining loss in traditional side-blowing or top-blowing processes.

[0050] In comparison, the energy of side-blowing and top-blowing plasma strengthening technologies is concentrated in the side plasma strengthening area or the surface of the molten pool. The uneven temperature distribution can easily lead to significant temperature differences in different areas of the molten pool (up to 200-300°C), insufficient bottom reaction, and zinc vapor easily condenses on the top of the furnace to form furnace lumps, which seriously affects continuous production. Compared with the side-blowing or top-blowing processes, the bottom-blowing plasma torch used in the present invention realizes forced convection from bottom to top, forming multiple upward-penetrating high-temperature jets at the bottom of the molten pool, greatly promoting the circulation and mixing of liquid and dissolved particles in the entire furnace, and facilitating rapid and uniform heat and mass transfer. It is also based on the balanced temperature distribution in the furnace brought about by the bottom-blowing plasma technology, which avoids the occurrence of a large number of nodules or condensates on the furnace wall and top due to high temperature gradients, reducing the difficulty of smelting operations and damage to the furnace lining. At the same time, since the high-temperature area at the bottom is relatively concentrated and the melt is in a churning state, the energy waste caused by local overheating can be 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 body or nozzle area, it can be rapidly converted into a high-temperature jet containing high-energy free radicals (CI, HI, etc.), greatly improving the chemical reaction activity in the furnace.

[0052] The present invention provides a method for recovering valuable metals by bottom-blowing plasma-enhanced reduction. By utilizing bottom-blown reducing plasma and centralized heat supply from a heating device 7, intense stirring and a high-temperature zone distribution are generated within the furnace, significantly improving the heat and mass transfer efficiency during the smelting process. Uniform melting of the lead-zinc oxide material is achieved at a heating rate of 30 to 50°C, effectively avoiding the generation of dioxins. Specifically, the heating rate of 30 to 50°C can reduce the time that the precursor compound remains at a medium-low temperature (less than 850°C), thereby reducing the possibility of dioxin generation by the reaction. Furthermore, dioxins can be decomposed at temperatures above 850°C, and rapidly heating and maintaining the high temperature helps promote the decomposition of generated dioxins. Furthermore, because the bottom-blowing plasma-enhanced technology can effectively mix the lead-zinc oxide material and the high-zinc melt from the bottom using a high-speed plasma jet and a high-temperature arc, the uniformity of the temperature distribution within the furnace is significantly improved, completely avoiding the generation of dioxins.

[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 furnace bottom, creating a bottom-up high-temperature reducing atmosphere and full-melt pool disturbance. This not only significantly increases the reduction reaction rate of difficult-to-reduced oxides such as ZnO and PbO, but also rapidly transcends the dioxin formation temperature range (850-450°C) and stably maintains the high-temperature range (≥1250°C), effectively avoiding the conditions for dioxin formation. While maintaining efficient smelting performance, it achieves the process control goals of green, low-toxicity, and low-carbon emissions, breaking through the technical bottleneck of traditional pyrometallurgical smelting, which is difficult to achieve both efficiency and environmental protection.

[0054] In comparison, although the existing reducing agent bottom blowing technology can enhance the stirring of the molten pool, it is limited by the insufficient chemical energy of the gas and is difficult to efficiently process high-melting-point materials (such as zinc-containing solid waste requires >1300°C). The zinc content is high and the melt fluidity is poor, forming a zinc-containing silicate phase that is difficult to reduce. In addition, the spray gun has a short life (<72 hours), and frequent maintenance leads to rising costs.

[0055] In the present invention, the reducing agent further comprises a non-plasma substance, which is supported on the plasma substance. The non-plasma substance includes one or more of pulverized coal, coke powder, and spent electrode particles. In some embodiments, the particle size of the non-plasma substance can be 0.1 to 5 mm. After mixing with the high-temperature plasma jet, the non-plasma substance rapidly decomposes at elevated temperatures, further generating active reducing species 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 can be arranged on the side of the molten pool containing the lead-zinc oxide material.

[0057] S2. The high-zinc melt undergoes a reduction reaction under the spraying and stirring of the reducing agent to generate metal vapor. After standing, the slag and gold are separated to generate an alloy phase and slag.

[0058] In the present invention, the standing time may be 20 to 30 minutes.

[0059] In the present invention, the reduction reaction is performed in an atmosphere having a C / O molar ratio of 1.2-2.5, a temperature of the high-zinc melt of 1200-1400°C, and a reduction reaction duration of 30-90 minutes. After reduction smelting, the recovery rate of metallic zinc is greater than 95%, and the recovery rate of metallic lead is greater than 90%.

[0060] In the present 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 the reduction is completed; while some less volatile or precious metals are enriched in the molten metal deposited in the furnace and can be extracted through the siphon port 5 on the side or the upper part, thereby achieving efficient separation and recovery of multiple metals.

[0061] In the present invention, metal vapor includes zinc vapor and lead vapor. Metallic zinc and lead easily vaporize at high temperatures and rise to the furnace roof. A high-efficiency condensing device and dust collector can be installed at the furnace roof or exhaust pipe to collect the soot or dust formed by the volatile metal vapor. Specifically, the metal vapor rises with the airflow to the furnace roof or flue 3 where it is captured. After condensation or dust removal, zinc- and lead-rich soot or metal crystals are obtained. Precious metals (such as Au and Ag) that are difficult to volatilize accumulate in the molten metal or alloy phase, separated from the slag, and can subsequently be purified through refining or electrolysis.

[0062] The present invention provides a bottom-blown plasma reduction furnace, which is applied to the bottom-blown plasma enhanced reduction and recovery of valuable metals method as described above, comprising a molten pool mechanism and a heat supply mechanism;

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

[0064] The heat supply 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 substance toward the lead-zinc oxide material; the heating device 7 is located in the middle and / or lower part of the melt chamber.

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

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

[0067] In some embodiments, the present invention can be equipped with a bottom lining and cooling protection, thermal stress is relatively controllable, insertion and maintenance of the spray gun are relatively convenient, and the overall maintenance cycle is longer, thereby reducing operation 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 shape at the bottom of the melt chamber, and the plasma torch includes a nozzle port, which is arranged at the end of the spray gun contacting the high-zinc melt, and the angle between the axis of the nozzle port along the length direction and the vertical direction is 15-30°, and the vertical distance between the nozzle port and the bottom of the melt chamber is 0.5-1.2m.

[0069] In some embodiments of the present invention, the longitudinal axis of the nozzle opening may be angled at 15° with the vertical axis to allow the jet to penetrate the molten pool and produce a wide-area stirring effect within the furnace. The lance insertion depth can be adjusted according to actual production needs, and combined with appropriate lifting or directional mechanisms, the optimal spray angle and depth can be achieved under different operating stages or conditions.

[0070] In some embodiments of the present invention, a plasma torch is composed of a spray gun, an electrode, a cooling water jacket, an insulating jacket, etc. Inside the torch, a high-power arc discharge ionizes an exciting 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 nozzle of the plasma torch is as high as 2000-3500°C.

[0072] In the present invention, the furnace body can be in the shape of a vertical cylinder or a furnace body structure with slightly narrow openings at the top and bottom, and the exterior can be matched 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 the present 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 linings can be made of highly refractory and slag-resistant composite materials such as magnesia carbon bricks and corundum castables, forming a double-layer or multi-layer stacked structure. The bottom refractory material must particularly possess high strength and excellent erosion resistance to withstand the impact of high-speed airflow and melt from bottom to top.

[0074] In the present invention, the bottom-blown plasma reduction furnace may include a cooling system, in which a water-cooling interlayer may be provided on the periphery of the furnace wall, and the water temperature is controlled within the range of 30 to 60° C., thereby avoiding local overheating and damage to the furnace wall lining through circulating cooling.

[0075] In the present invention, the flue 3, slag discharge port 4, and siphon port 5 can be sequentially provided on the outer wall of the molten pool from top to bottom. It should be noted that the flue 3, slag discharge port 4, and siphon port 5 do not need to be arranged in the same vertical line. They can be flexibly and reasonably arranged in a staggered manner based on actual process requirements, furnace structural characteristics, and operational convenience.

[0076] In some embodiments of the present invention, during the bottom-blowing smelting process, high-temperature dust-laden gas is generated at the furnace top or flue 3. 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, an electrostatic precipitator, or a scrubber) can be installed at the rear end of the flue 3 to capture and recover the metal fume. In addition, 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 safe operation.

[0077] In the present invention, the melt-enhanced reduction 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 be primarily composed of a gas source, a pressure regulating valve, a flow meter, and a safety valve, and is 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, to ensure the stability of the molten pool atmosphere and carbon-oxygen ratio, the gas supply system may adopt a multi-channel parallel connection method, and automatic control devices (such as solenoid valves, flow meters, and PLC control modules) may be installed on each channel to achieve real-time and precise control of the carbon-oxygen ratio, furnace pressure, and atmosphere.

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

[0080] In some embodiments of the present invention, a feeding system can be used to feed the bottom-blown plasma reduction furnace. A lead-zinc melt can be introduced into the bottom-blown plasma reduction furnace through a melt inlet 1. A lead-zinc mixed solid material can be introduced into the bottom-blown plasma reduction furnace through a sealed feeding port 2. In 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 a bottom-blown plasma torch can be equipped with a powder supply system. Powdered or granular non-plasma materials can be fed into the bottom spray gun area through an independent powder supply pipeline to achieve continuous and controllable feeding. In more specific embodiments of the present invention, a precise metering device (such as a screw feeder or weighing system) can be installed below the storage bin. A blower or pneumatic conveying device can be used to transport the non-plasma materials to the vicinity of the torch nozzle. After mixing with the high-temperature plasma jet, the materials are rapidly heated and decomposed to further generate active reducing species such as CO and H2.

[0082] In the present invention, online sensors such as temperature, pressure, and gas composition can be arranged at key positions of the furnace body, and closed-loop control of key parameters such as power supply power, gas flow, feeding speed, and carbon-oxygen ratio can be performed with the help of a PLC or DCS system, making the smelting process more stable and controllable, and enabling dynamic adjustment and optimization according to the raw material composition and process objectives.

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

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

[0085] 2. Melt immersion reduction and dynamic heat transfer optimization, solid mixed materials (density 2.0-6.0g / cm 3 ) is immersed in a high-zinc melt (Zn>30%), and the high thermal conductivity of the melt is used to accelerate the reduction, shortening the reaction time to 30-90 minutes, with a zinc recovery rate of>95% and lead>90%, which is suitable for high-impurity raw materials such as steel mill dust and mud.

[0086] 3. Control of multi-media plasma active atmosphere.

[0087] By using CO / H2 / CH4 as the medium to inject active groups (CⅠ, HⅠ), and combining with solid reducing agents (pulverized coal / coke powder) to dynamically adjust the carbon-oxygen ratio (C / O=1.2-2.5), the limitations of traditional solid-gas reactions can be broken through, and the metal oxide reduction efficiency can be increased by 40%.

[0088] 4. The present invention evenly distributes multiple plasma torches at the bottom of the furnace body, and uses a strong bottom-blowing jet from bottom to top to fully contact the high-energy plasma with the molten material, thereby overcoming the problems of uneven reaction, excessive temperature gradient in the furnace, and severe slag in traditional side-blowing or top-blowing modes.

[0089] 5. The process of this invention significantly improves the reduction rate and efficiency of metal oxides, significantly increasing the comprehensive recovery rate of various metals such as zinc, lead, and copper. Furthermore, the system combines powder feeding, precise atmosphere control, and water-cooled furnace wall protection to significantly reduce furnace lining wear and energy waste, offering comprehensive advantages such as long equipment life, flexible operation, high safety, and environmental friendliness.

[0090] 6. Environmentally friendly and fully resource-efficient, the plasma high temperature (>1800°C) decomposes dioxins, and the waste heat of the exhaust gas is recovered and discharged in compliance with standards; the slag is vitrified and used for building materials (permeable bricks), with a resource utilization rate of >98% and reduced carbon emission intensity.

[0091] The present invention also provides a control system, which includes a memory, a processor, and a computer program stored in the memory and runnable on the processor. The control system is characterized in that when the processor executes the computer program, it implements the bottom-blowing plasma-enhanced reduction and recovery of valuable metals method as described in any one of the above items.

[0092] It should be noted that any of the above-mentioned bottom-blown plasma reduction furnaces may further include the control system.

[0093] In order to facilitate those skilled in the art to further understand the present invention, examples are given below:

[0094] Example 1

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

[0096] The plasma device includes three plasma torches with a power of 300kW and a gas flow range of 20m 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 axis of the nozzle along the length direction forms an angle of 15-30° with the vertical direction, and the distance between the nozzle and the bottom of the melt chamber in the vertical direction is 0.7m.

[0097] In step S1, CO is sprayed toward the bottom of the molten pool using the plasma-state N2-CO mixed gas blown by the bottom plasma torch as a carrier; in this embodiment, the total amount of CO injected (the molar amount of plasma-state CO + the molar amount of non-plasma-state CO) is 1.2 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the high-zinc melt into metal elements, and the volume proportion 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 stagnant conditions, the slag and metal separate, forming an alloy phase and slag. The reduction reaction lasts 20 minutes, and the atmosphere created by the reduction reaction has a C / O molar ratio of 1.2-2.5.

[0099] The volatile components in the gas phase are mainly zinc oxide and lead. The composition analysis is as follows: Figure 2 As shown, the slag phase is mainly composed of silicate oxides formed by Ca, Fe, and Si. The remaining lead content in the slag phase is 0%, the zinc content is 0%, and the recovery rate of zinc and lead is 99%. The SEM-EDS image of the phase is shown in Figure 3 As shown, the formed metal phase is primarily a Pb\Cu mixed phase, and the impurity (As, Sb) content in the Pb-Cu alloy phase is less than 0.05%, meeting the requirements for direct refining. Bottom injection ensures full contact between CO bubbles and the melt, effectively reducing PbO and ZnO. In this example, the CO energy utilization rate reaches 92%.

[0100] No dioxins were detected in the flue gas (detection limit: 0.01ng TEQ / m 3 ), far below the national emission standard (0.5ngTEQ / m 3 ).

[0101] Example 2

[0102] In this embodiment, other conditions remain unchanged, and only the heating rate of the lead-zinc oxide material is adjusted from 45°C / min to 30°C / min.

[0103] Measurements show that the volatile components in the gas phase are primarily zinc oxide and lead, with a composition of 35% lead, 25% zinc, and 40% zinc oxide. The slag phase primarily consists of silicate oxides formed by Ca, Fe, and Si, with a residual lead content of 0% and zinc content of 0%, resulting in a zinc and lead recovery rate of 99%. The formed metal phase is primarily a Pb / Cu mixed phase, with the impurity (As, Sb) content of the Pb-Cu alloy phase less than 0.05%, meeting direct refining requirements. Bottom injection ensures full contact between CO bubbles and the melt, effectively reducing PbO and ZnO. In this embodiment, the CO energy utilization rate reaches 80%.

[0104] No dioxins were detected in the flue gas (detection limit: 0.01ng TEQ / m 3 ), far below the national emission standard (0.5ngTEQ / m 3 ).

[0105] Comparative Example 1

[0106] Compared with the embodiment, other conditions in this comparative example remain unchanged, and only the bottom blowing method is replaced by top blowing.

[0107] S1. First, a domestic lead-zinc oxide ore, a high-zinc block material from pyrometallurgical zinc smelting, and zinc oxide dust are mixed in proportion to obtain 2500g of a lead-zinc oxide material having a main composition of PbO:ZnO:FeO:SiO2:CaO = 23:45:11:8:8.9 (wt.%), with the remainder being impurities such as aluminum and magnesium. The lead-zinc oxide material is added to the molten pool mechanism through a closed feed port 2, and a high-zinc melt is formed by heat supplied by a reducing agent and a heating device 7. The heating rate of the lead-zinc oxide material is 5°C / min, and the temperature of the high-zinc melt is 1300°C.

[0108] The plasma device includes three plasma torches with a power of 300kW and a gas flow range of 20m 3 / h, the plasma torch is symmetrically distributed in a ring shape on the top of the melt chamber, the plasma torch includes a nozzle port, the axis of the nozzle port along the length direction forms an angle of 15-30 degrees with the vertical direction, and the nozzle port is immersed in the high zinc melt.

[0109] In step S1, CO is sprayed toward the bottom of the molten pool using the plasma-state N2-CO mixed gas blown by the top plasma torch as a carrier; in this embodiment, the total amount of CO injected (the molar amount of plasma-state CO + the molar amount of non-plasma-state CO) is 1.2 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the high-zinc melt into metal elements, and the volume proportion 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 standing, the slag and metal separate to form an alloy phase and slag. The reduction reaction lasts 40 minutes. The volatile components in the gas phase are mainly zinc oxide and lead, and the slag phase is mainly composed of silicate oxides formed by Ca, Fe, and Si. The remaining lead content in the slag phase is 0.89%, the zinc content is 2.7%, the zinc recovery rate reaches 95%, and the lead recovery rate reaches 98%. The formed metal phase is mainly a Pb\Cu mixed phase. The As content in the Pb-Cu alloy reaches 0.3%, requiring an additional dearsenicization process. The top-injected gas rises too quickly, and the CO utilization rate is only 65%.

[0111] The dioxin concentration in the flue gas is 1.5ng TEQ / m 3 , 3 times higher than the national limit (0.5ng TEQ / m 3 ).

[0112] 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 bottom-blowing plasma-enhanced reduction, characterized in that: include: The lead-zinc oxide material is melted by a reducing agent and heat provided by a heating device to form a high-zinc melt. The heating rate of the lead-zinc oxide material is 30-50°C / min, and the temperature of the high-zinc melt is 1200-1400°C. The lead-zinc oxide material includes a lead-zinc mixed solid material, and the lead-zinc mixed solid material includes a zinc-containing secondary resource. The reducing agent includes a reducing plasma-state substance, and the reducing plasma-state substance is introduced from the bottom of the lead-zinc oxide material to perform bottom blowing on the lead-zinc oxide material. The high-zinc melt undergoes a reduction reaction under the spraying and stirring of the reducing agent to generate metal vapor. After standing, the slag and gold are separated to generate an alloy phase and slag.

2. The method for recovering valuable metals by bottom-blowing plasma-enhanced reduction according to claim 1, characterized in that: The reducing agent further includes a non-plasma substance, the non-plasma substance is loaded on the plasma substance, and the non-plasma substance includes one or more of pulverized coal, coke powder, and waste electrode particles; The plasma working medium of the reducing plasma state substance 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 volume proportion of the reducing working medium in the plasma working medium is 5% to 30%.

3. The method for recovering valuable metals by bottom-blowing plasma-enhanced reduction according to claim 2, characterized in that: The amount of the reducing agent added is 1.2 to 2.0 times the molar amount of the reducing agent required to reduce all the metal oxides to be reduced in the high-zinc melt into metal elements.

4. The method for recovering valuable metals by bottom-blowing plasma-enhanced reduction according to claim 1, characterized in that: Calculated by mass fraction, the composition of the high-zinc melt includes: 10% to 30% lead oxide, 30% to 50% zinc oxide, 5% to 20% ferrous oxide, 5% to 20% silicon dioxide, and 5% to 20% calcium oxide.

5. The method for recovering valuable metals by bottom-blowing plasma-enhanced reduction according to claim 4, characterized in that: The lead-zinc oxide material also includes a lead-zinc melt, and the source of the lead-zinc melt includes one or more of lead-zinc oxide ore, secondary zinc oxide smoke or zinc-containing dust in a steel plant.

6. The method for recovering valuable metals by bottom-blowing plasma-enhanced reduction 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 reduction reaction lasts for 20 to 90 minutes.

7. The method for recovering valuable metals by bottom-blowing plasma-enhanced reduction according to claim 1, characterized in that: The plasma device comprises a plasma torch, and the temperature at the nozzle outlet of the plasma torch is 2000-3500°C.

8. A bottom-blown plasma reduction furnace, characterized in that: The method for bottom-blown plasma-enhanced reduction and recovery of valuable metals as claimed in any one of claims 1 to 7 comprises a molten pool mechanism and a heat supply mechanism; The molten pool mechanism includes a melt cavity to accommodate the high-zinc melt; the top or upper side wall of the melt cavity is connected to a melt inlet and a sealed feeding port to add the lead-zinc oxide material into the melt cavity; The heat supply 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 substance toward the lead-zinc oxide material; the heating device is located in the middle and / or lower part of the melt chamber.

9. The bottom-blown plasma reduction furnace according to claim 8, characterized in that: The plasma device includes 4 to 6 plasma torches, the power of the plasma torches is 200 to 500 kW, and the gas flow rate in the plasma torches is in the range of 5 to 30 m 3 / h, the plasma torch is symmetrically distributed in a ring shape at the bottom of the melt chamber, the plasma torch includes a nozzle port, the angle between the axis of the nozzle port along the length direction and the vertical direction is 15-30°, and the distance between the nozzle port and the bottom of the melt chamber in the vertical direction is 0.5-1.2m.

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 bottom-blowing plasma-enhanced reduction is implemented as described in any one of claims 1 to 7.

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