CN120536727A - Bottom-blowing plasma-enhanced reduction method, reduction furnace, and system for recovering valuable metals - Google Patents

Abstract

The invention provides a method, a reducing furnace and a system for recovering valuable metals through bottom blowing type plasma enhanced reduction, wherein the method for recovering valuable metals through bottom blowing type plasma enhanced reduction comprises the steps of heating a lead-zinc oxide material through a reducing agent and a heating device, melting to form a high-zinc melt, wherein the heating rate of the lead-zinc oxide material is 30-50 ℃ per minute, the temperature of the high-zinc melt is 1200-1400 ℃, the reducing agent comprises a reducing plasma state substance, the reducing plasma state substance is introduced from the bottom of the lead-zinc oxide material, bottom blowing is carried out on the lead-zinc oxide material, the high-zinc melt is subjected to reduction reaction under the blowing stirring of the reducing agent to generate metal vapor, and slag-metal separation is carried out to generate an alloy phase and slag. The bottom blowing process can obviously improve the reduction rate and the reduction efficiency of the metal oxide, so that the comprehensive recovery rate of various metals such as zinc, lead, copper and the like is greatly improved.

Description

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

Technical Field

The invention belongs to the technical field of solid waste treatment, and particularly relates to a method, a reducing furnace and a system for recovering valuable metals through bottom blowing type plasma enhanced reduction.

Background

The bottom blowing plasma smelting technology utilizes the strong energy flow of the plasma and the disturbance of the bottom air flow, can quickly excite smelting reaction under high temperature and high reducing atmosphere, and is especially suitable for the treatment of nonferrous metal minerals with high viscosity, high melting point and complex components and secondary resources. The unique stirring mode and the heat energy input mode lead the raw material to have wider adaptability to the raw material, and are particularly suitable for complex raw materials which are difficult to be efficiently treated by the traditional process.

The recovery treatment of complex lead zinc ores and zinc-containing secondary resources has important significance for sustainable utilization of resources and environmental protection. However, as the raw materials contain unavoidable chlorine sources and various complex organic matters and the catalysis of heavy metals in the smelting environment, harmful substances such as dioxin and the like are generated in the high-temperature condition of traditional pyrometallurgy. Dioxins are a collective term for two types of tricyclic aromatic organic compounds, including polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). In the molecular structure of dioxin, the compound with the chlorine atoms substituted at the 2,3,7 and 8 positions has physiological toxicity, and the toxic dioxin compound is extremely stable in the environment, is difficult to degrade and is enriched in organisms through a food chain, thus the compound has serious threat to human health and ecological environment.

Therefore, although the conventional pyrometallurgy technology has a certain advantage in treating complex lead-zinc ores and zinc-containing secondary resources, the conventional pyrometallurgy technology is limited in practical application due to the generation of dioxins. Therefore, there is a need to develop new smelting techniques or to improve the prior art to reduce the production of dioxins. In the common technology, the generated dioxin is treated by utilizing the tail gas treatment and adsorption technology, the cost is high, the steps are complicated, and no smelting technology for specifically avoiding the generation of the dioxin in the pyrometallurgy process has yet appeared.

Disclosure of Invention

The invention aims to solve the technical problem that complex lead zinc ore and zinc-containing secondary resources generate dioxin in the pyrometallurgy process in the common technology, and provides a method for recovering valuable metals by bottom-blowing type plasma enhanced reduction, which comprises the following steps:

The method comprises the steps of heating a lead-zinc oxide material by a reducing agent and a heating device, and melting to form a high-zinc melt, wherein the heating rate of the lead-zinc oxide material is 30-50 ℃ per minute, and the temperature of the high-zinc melt is 1200-1400 ℃, wherein the lead-zinc oxide material comprises a lead-zinc mixed solid material which comprises complex lead-zinc ores and/or secondary zinc-containing resources, 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 performs bottom blowing on the lead-zinc oxide material;

And (3) carrying out reduction reaction on the high-zinc melt under the blowing and stirring of the reducing agent to generate metal vapor, and standing to separate slag from gold to generate alloy phase and slag.

Further, the reducing agent further comprises a non-plasma state substance, the non-plasma state substance is loaded on the plasma state substance, the non-plasma state substance comprises one or more of pulverized coal, coke powder and waste electrode particles, and the particle size of the non-plasma state substance is 0.1-5 mm;

The plasma working medium of the plasma substance comprises an excitatory working medium and a reductive working medium, wherein the excitatory working medium comprises nitrogen and argon, the reductive working medium comprises one or more of CO, H ₂、CH₄ and C powder, and the volume ratio of the reductive working medium in the plasma working medium is 5% -30%.

Furthermore, the addition amount of the reducing agent is 1.2-2.0 times of the molar amount of the reducing agent for reducing all metal oxides to be reduced in the high-zinc melt into metal simple substances.

Further, the high-zinc melt comprises, by mass, 10% -30% of lead oxide, 30% -45% of zinc oxide, 20% -30% of ferrous oxide, 25% -40% of silicon dioxide and 5% -20% of calcium oxide, wherein the calcium-silicon ratio of slag is 0.5-2.0, and the iron-silicon ratio is 0.5-1.5.

Further, the lead-zinc oxide material further comprises a lead-zinc melt, the source of the lead-zinc melt comprises one or more of lead-zinc oxide ore, secondary zinc oxide smoke dust and zinc-containing dust mud of a steel mill, the lead-zinc mixed solid material further comprises a flux, and the density of the lead-zinc mixed solid material is 2.0-6.0 g/cm ³.

Further, in the atmosphere environment formed by the reduction reaction, the molar ratio of C/O is 1.2-2.5, and the duration of the reduction reaction is 20-90 minutes.

Further, the plasma device comprises a plasma torch, and the temperature at the outlet of the nozzle of the plasma torch is 2000-3500 ℃.

The invention provides a bottom blowing type plasma reduction furnace, which is applied to the method for recovering valuable metals by the bottom blowing type plasma enhanced reduction, and comprises a molten pool mechanism and a heat supply mechanism;

the molten pool mechanism comprises a molten cavity for accommodating the high-zinc melt, wherein the top or the upper part of the side wall of the molten cavity is communicated with a melt inlet and a closed feed inlet for adding the lead-zinc oxide material into the molten cavity;

The heating mechanism comprises a plasma device and a heating device, a nozzle opening of the plasma device is positioned at the bottom of the melt cavity so as to spray the reducing plasma state substances to the lead-zinc oxide material, and the heating device is positioned at the middle part and/or the lower part of the melt cavity.

Further, the plasma device comprises 4-6 plasma torches, the power of the plasma torches is 200-500 kW, the gas flow range in the plasma torches is 5-30 m ³/h, the plasma torches are annularly and symmetrically distributed at the bottom of the melt cavity, the plasma torches comprise nozzle openings, the included angle between the axis of each nozzle opening along the length direction and the vertical direction is 15-30 degrees, and the distance between each nozzle opening and the bottom of the melt cavity in the vertical direction is 0.5-1.2m.

The invention provides a control system which comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, wherein the method for recovering valuable metals through bottom blowing type plasma enhanced reduction is realized when the processor executes the computer program.

Compared with the prior art, the invention at least comprises the following advantages:

The invention provides a method for recovering valuable metals by bottom blowing type plasma enhanced reduction, which utilizes the centralized heating of bottom blowing type reducing plasma state substances and a heating device to form strong stirring and high-temperature distribution in a furnace, thereby remarkably improving the heat transfer and mass transfer efficiency in the smelting process, realizing the uniform melting of lead-zinc oxide materials at the temperature rising rate of 30-50 ℃, and effectively avoiding the generation of dioxin, and particularly, on one hand, the temperature rising rate of 30-50 ℃ can reduce the residence time of precursor compounds at medium and low temperatures (< 850 ℃) so as to reduce the possibility of generating dioxin by reaction; on the other hand, the dioxin can be decomposed at a high temperature of above 850 ℃, the rapid temperature rise and the maintenance of a high-temperature state are helpful for promoting the decomposition of the generated dioxin, and meanwhile, the bottom blowing type plasma strengthening technology can utilize high-speed plasma jet flow and high-temperature electric arc to effectively mix lead-zinc oxide materials and high-zinc melt from the bottom, so that the uniformity of temperature distribution in the furnace is remarkably improved, and the generation of the dioxin is comprehensively and unequally avoided.

According to the bottom blowing type plasma enhanced smelting technology provided by the invention, a high-temperature reducing atmosphere and full-molten pool disturbance from bottom to top are formed by utilizing a high-heat-intensity plasma flow to quickly penetrate through a melt from the bottom, so that the reduction reaction rate of oxide difficult to reduce such as ZnO, pbO and the like is obviously improved, and meanwhile, the reduction reaction rate quickly crosses a dioxin generation temperature region (850-450 ℃) and is stably maintained in the high temperature region (more than or equal to 1250 ℃), and the generation condition of dioxin is effectively avoided. The method realizes the process control targets of green, low toxicity and low carbon emission while maintaining the high-efficiency smelting performance, and breaks through the technical bottleneck that the efficiency and the environment protection of the traditional pyrometallurgy are difficult to be achieved simultaneously.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a bottom-blowing type plasma reduction furnace according to an embodiment of the present application, wherein 1 is a melt inlet, 2 is a closed charging 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.

FIG. 2 is a graph showing the analysis of volatile components in a gas phase in example 1 of the present application.

FIG. 3 is an SEM-EDS diagram of the slag phase of example 1 of the present application.

Detailed Description

The following description of the embodiments of the present invention will be made in detail and with reference to the accompanying drawings, wherein it is apparent that the embodiments described are only some, but not all embodiments of the present invention. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.

Moreover, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the embodiments, and when the technical solutions are contradictory or cannot be implemented, it should be considered that the combination of the technical solutions does not exist, and is not within the scope of protection claimed by the present invention.

Where numerical ranges are provided in the examples, it is understood that unless otherwise stated herein, both endpoints of each numerical range and any number between the two endpoints are significant both in the numerical range. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs and to which this invention belongs, and any method, apparatus, or material of the prior art similar or identical to the methods, apparatus, or materials of the embodiments of the invention may be used to practice the invention.

With the increasing exhaustion of high-grade lead-zinc primary ore resources, the lead-zinc smelting industry faces the double challenges of diversification and complicating raw material sources. The secondary zinc-containing resources represented by complex lead zinc ores, slag, electric furnace dust and the like are widely existing in a metallurgical solid waste and renewable resource system, and the recovery treatment of the secondary zinc-containing resources has important significance for recycling of metal resources and prevention and control of environmental pollution.

However, the resources generally have the characteristics of complex metal occurrence form, accompanying a large amount of FeO/SiO ₂ impurities, znO content up to more than 30%, high melting point, high melt viscosity, limited treatment efficiency of traditional pyrogenic processes such as blast furnace zinc smelting (ISP) on the raw materials, and obvious bottlenecks especially in aspects of low ZnO activity, difficult slag-gold separation, incomplete reduction reaction and the like.

More prominently, the zinc-containing secondary resource often contains a chlorine source (such as PVC, cl-) and various organic components inevitably, and dioxin substances (PCDDs/PCDFs) with high toxicity are easily generated in a temperature region of 850-450 ℃ under the condition of high-temperature smelting environment, particularly heavy metal catalysts such as Cu, fe, zn and the like. The compounds have extremely high environmental stability, bioaccumulation, cancerogenic and mutagenic toxicological effects and the like, and are one of internationally recognized Persistent Organic Pollutants (POPs).

The traditional pyrometallurgy at present mainly depends on tail gas cooling, active carbon adsorption, catalytic decomposition and other tail end treatment means to solve the problem of dioxin, so that the method has the advantages of complex treatment flow, high investment and operation cost, easiness in generating transfer pollution and difficulty in fundamentally avoiding a dioxin generation mechanism.

Therefore, a new smelting technology for avoiding the dioxin generation window temperature zone is urgently needed from the technological sources such as heat source form, reaction atmosphere, heating rate, disturbance mode and the like.

The invention provides a method for recovering valuable metals by bottom blowing type plasma enhanced reduction, which comprises the following steps:

S1, a lead-zinc oxide material is heated by a reducing agent and a heating device 7, and is melted to form a high-zinc melt, wherein the temperature rising rate of the lead-zinc oxide material is 30-50 ℃ per minute, the temperature of the high-zinc melt is 1200-1400 ℃, the lead-zinc oxide material comprises a lead-zinc mixed solid material, the lead-zinc mixed solid material comprises zinc secondary resources, 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 subjected to bottom blowing.

The solid lead-zinc oxide material is lead-zinc mixed solid material, the lead-zinc mixed solid material comprises zinc-containing secondary resources, the zinc-containing secondary resources comprise lead-zinc oxide ore belonging to complex lead-zinc ore, mixed ore (ZnO is more than or equal to 30 percent, such as fire cloud ore and Langmuir ore), lead-zinc-copper polymetallic sulphide ore and iron-silicon-containing complex ore of oxide ore, the zinc-containing secondary resources also comprise zinc dust mud of a steel mill, lead-zinc smelting smoke dust, electronic waste, metal alloy slag, ISP zinc smelting slag, bottom blowing slag, converter slag, electric furnace dust, waste zinc alloy, zinc ash, lead storage battery slag, copper slag, metallurgical byproducts of zinc, lead and copper, renewable resources and the like, and due to the complexity and diversity of sources, quantitative chlorine sources and complex organic matters inevitably exist in the lead-zinc oxide material, and the chlorine sources react with the organic matters to generate precursors of dioxin under the temperature condition of 200-600 ℃ so as to be converted into dioxin. Therefore, the zinc-containing secondary resource is a heavy disaster area for generating dioxin in various pyrometallurgical raw materials.

The invention can be used for treating electronic waste and secondary resources containing noble metals, has remarkable effects on recycling Fe, ni, cr and rare noble metals (Au, ag, pt, pd and the like), and has important application value and development prospect in the aspects of green metallurgy and solid waste recycling.

In the invention, the bottom blowing type molten pool has stronger molten pool disturbance capability, higher thermal uniformity and reaction interface updating efficiency, obviously 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, copper and the like and the efficient treatment of complex secondary resources.

In some embodiments of the invention, the lead zinc mixed solid may further include a flux and/or a reducing agent.

In some embodiments of the invention, the density of the lead-zinc mixed solid material can be 2.0-6.0 g/cm ³, so that the lead-zinc mixed solid material can be immersed in the melt after being put into the melt, and the reduction reaction is accelerated through the heat conduction of the melt. In some embodiments, the lead-zinc mixed solid material with higher humidity or coarser granularity can be preheated or dried before feeding so as to reduce energy loss caused by water evaporation and fluctuation of the temperature of a molten pool and reduce the risk of adverse reaction of water vapor and CO.

In some embodiments of the invention, the liquid lead zinc oxide material comprises a lead zinc melt comprising a lead/zinc sulphide ore oxidation desulphurisation melt, the source of the lead zinc melt comprising one or more of lead zinc oxide ore, zinc suboxide fumes or zinc dust mud from a steelworks.

In the invention, the temperature of the high-zinc melt can be 1200-1400 ℃, namely, the high-zinc melt can be heated to 1200-1400 ℃ under the cooperative heat supply condition of the bottom blowing type plasma strengthening means and the heating device 7. Wherein, the bottom blowing type plasma strengthening means is to utilize the reducing plasma state substances to enter from the bottom of the lead-zinc oxide material and to carry out bottom blowing on the lead-zinc oxide material.

In some embodiments of the invention, the high zinc melt comprises, by mass, 10% -30% of lead oxide, 30% -50% of zinc oxide, 5% -20% of ferrous oxide, 5% -20% of silicon dioxide and 5% -20% of calcium oxide. The melting temperature of the high-zinc melt is about 1450-1500 ℃, and the viscosity of the high-zinc melt is about 1.2-1.3 Pa.s at 1250 ℃. It is emphasized that the large amount of flux (e.g., caO) introduced to reduce the melting point and viscosity forms a large amount of slag, and thus when the ZnO content is in the range of 30% -50%, the processing difficulty is significantly higher than that of a melt having a ZnO content of about 20%.

In one embodiment of the invention, the composition of the high zinc melt may include, in mass fraction, 41.7wt.% ZnO, 15.4wt.% PbO, 9.9wt.% FeO, 14.6wt.% CaO, and 8.5wt.% SiO ₂, with a melting temperature of about 1480 ℃ and a viscosity of about 1.232 Pa-s at 1250 ℃.

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

In the invention, the reducing plasma state substance can be generated by a plasma device, the plasma device can be a plasma torch, the power of the plasma torch can be 200-500 kw, and the power of the plasma torch can be 300-500 kw. When the bottom blowing type plasma reduction furnace is in operation, the plasma torch converts high-power electric energy into high-temperature and high-energy jet flow. When the excitatory working medium (N ₂, ar) and the reducing working medium (CO, H ₂、CH₄, etc.) enter the arc zone, they are rapidly heated to thousands or even thousands of degrees celsius, part of the molecules dissociate and generate a large number of reactive groups (e.g., CI, HI, etc.), which are in sufficient contact with the metal oxide particles or melt in the furnace to undergo a rapid reduction reaction, causing the metal to be released from its oxide form and to exist in the molten bath or gas phase in the form of droplets or vapors of the metal.

Compared with the traditional high-coke-ratio pyrogenic reduction, the invention can obviously reduce the solid carbon consumption, reduce the CO ₂ emission, reduce the metal content in residues by efficiently recycling volatile metals (such as zinc and lead), and is beneficial to realizing comprehensive utilization of resources and green metallurgy.

By arranging the plasma device at the furnace bottom, high-temperature plasma airflow and a reducing medium are sprayed into a molten pool from bottom to top, so that strong stirring and high-temperature area distribution is formed in the furnace, the heat transfer and mass transfer efficiency in the smelting process is remarkably improved, and the problems of uneven reaction, local nodulation, serious furnace lining loss and the like in the traditional side-blowing or top-blowing process are solved.

Compared with the side-blowing type and top-blowing type plasma strengthening technologies, the energy is concentrated in a side plasma strengthening area or a surface layer of a molten pool, uneven temperature distribution easily causes obvious temperature difference (up to 200-300 ℃) in different areas of the molten pool, the bottom reaction is insufficient, zinc vapor easily condenses on the top of the furnace to form a furnace knot, and continuous production is seriously affected. Compared with side blowing or top blowing technology, the bottom blowing plasma torch adopted by the invention realizes forced convection from bottom to top, forms a plurality of upward penetrating high-temperature jet flows at the bottom of the molten pool, greatly promotes the circulation and mixing of liquid and dissolved particles in the whole furnace, and is beneficial to rapid and uniform heat and mass transfer. The method is also based on the equalization of temperature distribution in the furnace caused by the bottom blowing type plasma technology, avoids the condition that a large amount of knots or condensates are generated on the furnace wall and the furnace top due to high temperature gradient, and reduces the difficulty of smelting operation and the damage to the furnace lining. Meanwhile, the bottom high-temperature area is relatively concentrated, and the melt is in a tumbling state, so that energy waste caused by local overheating can be reduced.

In some embodiments of the invention, the plasma working medium of the plasma state substance comprises an excitatory working medium and a reducing working medium, wherein the excitatory working medium comprises nitrogen and argon, the reducing working medium comprises one or more of CO, H ₂、CH₄ and C powder, and the reducing working medium can be quickly converted into high-temperature jet flow containing high-energy free radicals (CI, HI and the like) when being fed into the torch body or the nozzle area, so that the chemical reactivity in the furnace is greatly improved.

The invention provides a method for recovering valuable metals by bottom blowing type plasma enhanced reduction, which utilizes the bottom blowing type reducing plasma state substances and the central heating of a heating device 7 to form strong stirring and high-temperature distribution in a furnace, thereby remarkably improving the heat transfer and mass transfer efficiency in the smelting process, realizing the uniform melting of lead-zinc oxide materials at the temperature rising rate of 30-50 ℃, and effectively avoiding the generation of dioxin, and particularly, on one hand, the temperature rising rate of 30-50 ℃ can reduce the residence time of precursor compounds at medium and low temperature (< 850 ℃) so as to reduce the possibility of generating dioxin by reaction; on the other hand, the dioxin can be decomposed at a high temperature of above 850 ℃, the rapid temperature rise and the maintenance of a high-temperature state are helpful for promoting the decomposition of the generated dioxin, and meanwhile, the bottom blowing type plasma strengthening technology can utilize high-speed plasma jet flow and high-temperature electric arc to effectively mix lead-zinc oxide materials and high-zinc melt from the bottom, so that the uniformity of temperature distribution in the furnace is remarkably improved, and the generation of the dioxin is comprehensively and unequally avoided.

According to the bottom blowing type plasma enhanced smelting technology provided by the invention, a high-temperature reducing atmosphere and full-molten pool disturbance from bottom to top are formed by utilizing a high-heat-intensity plasma flow to quickly penetrate through a melt from the bottom, so that the reduction reaction rate of oxide difficult to reduce such as ZnO, pbO and the like is obviously improved, and meanwhile, the reduction reaction rate quickly crosses a dioxin generation temperature region (850-450 ℃) and is stably maintained in the high temperature region (more than or equal to 1250 ℃), and the generation condition of dioxin is effectively avoided. The method realizes the process control targets of green, low toxicity and low carbon emission while maintaining the high-efficiency smelting performance, and breaks through the technical bottleneck that the efficiency and the environment protection of the traditional pyrometallurgy are difficult to be achieved simultaneously.

Compared with the prior reducing agent bottom blowing technology, although the stirring of a molten pool can be enhanced, the prior reducing agent bottom blowing technology is limited by insufficient gas chemical energy, and is difficult to efficiently treat high-melting-point materials (such as zinc-containing solid waste is required to be more than 1300 ℃), the zinc content is high, the melt fluidity is poor, a zinc-containing silicate phase is difficult to reduce, the service life of a spray gun is short (< 72 hours), and the cost is increased due to frequent maintenance.

In the invention, the reducing agent further comprises a non-plasma state substance, the non-plasma state substance is loaded on the plasma state substance, the non-plasma state substance comprises one or more of pulverized coal, coke powder and waste electrode particles, and in some embodiments, the particle size of the non-plasma state substance can be 0.1-5 mm. The non-plasma substance is mixed with high-temperature plasma jet flow and then quickly heated to decompose, and further active reduction components such as CO, H ₂ and the like are generated.

In some embodiments of the invention the heating means 7 comprise electromagnetic induction heating means 7, in some embodiments the electromagnetic induction heating means 7 may be arranged on the side of the bath containing the lead zinc oxide material.

S2, carrying out reduction reaction on the high-zinc melt under the blowing and stirring of the reducing agent to generate metal vapor, standing, and separating slag from gold to generate alloy phase and slag.

In the invention, the standing time can be 20-30 min.

In the invention, in the atmosphere environment formed by the reduction reaction, the molar ratio of C/O is 1.2-2.5, the temperature of the high zinc melt is 1200-1400 ℃, and the duration of the reduction reaction is 30-90 min. The recovery rate of metallic zinc is more than 95% and the recovery rate of metallic lead is more than 90% after reduction smelting.

In the invention, because the high zinc melt keeps sufficient fluidity at high temperature, slag can be separated and discharged through the slag discharging port 4 at the bottom of the furnace or the lower part of the furnace body after reduction is finished, and some noble metals which are difficult to volatilize are enriched in molten metal deposited in the furnace and can be extracted through the siphon port 5 at the side surface or the upper part, thereby realizing high-efficiency separation and recovery of multiple metals.

In the present invention, the metal vapor includes zinc vapor and lead vapor. The metal zinc and the metal lead are easy to gasify at high temperature and rise to the furnace top, and a high-efficiency condensing device and a dust remover can be additionally arranged at the furnace top or an air outlet pipe to collect soot or dust formed by volatile metal vapor. The metal vapor rises to the furnace top or flue 3 along with the air flow to be trapped, and then the smoke dust or metal crystal rich in zinc and lead is obtained through condensation or dust removal process, and the noble metals (Au, ag and the like) which are difficult to volatilize are gathered in the metal liquid or alloy phase to be separated from the slag, and can be purified by means of refining or electrolysis and the like.

The invention provides a bottom blowing type plasma reduction furnace, which is applied to the method for recovering valuable metals by the bottom blowing type plasma enhanced reduction, and comprises a molten pool mechanism and a heat supply mechanism;

The molten pool mechanism comprises a molten cavity for containing the high-zinc melt, wherein the top or the upper part of the side wall of the molten cavity is communicated with a melt inlet 1 and a closed charging port 2 for adding the lead-zinc oxide material into the molten cavity, and the closed charging port 2 can be provided with a sealing valve or a screw feeder to avoid the leakage of furnace gas and environmental pollution.

The heating mechanism comprises a plasma device and a heating device 7, a nozzle opening of the plasma device 6 is positioned at the bottom of the melt cavity to spray the reducing plasma state substances to the lead-zinc oxide materials, and the heating device 7 is positioned at the middle part and/or the lower part of the melt cavity.

In the present 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 shape.

In some embodiments, the plasma torch includes a torch, and the multiple bottom-blowing torches of the present invention are distributed in a manner that helps maintain production continuity in the event of a single torch failure.

In some embodiments, the invention may be equipped with a bottom liner and cooling protection, with relatively controllable thermal stresses, relatively convenient insertion and maintenance of the lance, and longer overall maintenance cycles, thereby reducing operating and maintenance costs.

In some embodiments of the invention, the power of the plasma torch is 200-500 kW, the plasma torch is annularly and symmetrically distributed at the bottom of the melt cavity, the plasma torch comprises a nozzle opening, the nozzle opening is arranged at the end part of the spray gun, which contacts the high-zinc melt, an included angle between the axis of the nozzle opening in the length direction and the vertical direction is 15-30 degrees, and the distance between the nozzle opening and the bottom of the melt cavity in the vertical direction is 0.5-1.2m.

In some embodiments of the invention the nozzle opening may be angled 15 ° to the vertical along the longitudinal axis so that the jet penetrates the thickness of the bath and produces a wide range of stirring effects within the furnace. The insertion depth of the spray gun can be adjusted according to actual production requirements, and the spray gun is matched with a corresponding lifting or orienting mechanism, so that the optimal spraying angle and depth can be conveniently realized in different operation stages or working conditions.

In some embodiments of the invention, the plasma torch is comprised of a torch, an electrode, a cooling jacket, an insulating sheath, and the like. Inside the torch body, an excitatory working medium (e.g., N ₂, ar, etc.) is ionized by a high power arc discharge to form a stable plasma jet.

In some embodiments of the invention, the temperature at the nozzle of the plasma torch is as high as 2000-3500 ℃.

In the invention, the furnace body can be in a vertical cylindrical shape or a furnace body structure with a slightly narrow opening at the upper and lower parts, and the outside can be matched with a high-temperature-resistant steel shell so as to ensure that the furnace body can still keep stable under the conditions of high temperature and internal pressure.

In the invention, the bottom blowing type plasma reduction furnace can be lined with a furnace body refractory lining, wherein the furnace body refractory lining comprises a furnace bottom and a furnace wall lining which can adopt high-fire-resistance and slag-corrosion-resistance composite materials such as magnesia carbon bricks, corundum castable and the like, and a double-layer or multi-layer superposition structure is formed. The bottom refractory is particularly required to have high strength and excellent anti-scouring properties to withstand high-velocity gas flow from bottom to top and melt impact.

In the invention, the bottom blowing type plasma reduction furnace can comprise a cooling system, a water cooling interlayer can be arranged on the periphery of the furnace wall in the cooling system, the water temperature is controlled within the range of 30-60 ℃, and the local overheating and the damage of the furnace wall lining are avoided through circulating cooling.

In the invention, the flue 3, the slag discharging port 4 and the siphon port 5 can be arranged on the outer wall of the molten pool from top to bottom in sequence. It should be noted that, the arrangement positions of the flue 3, the slag discharging port 4 and the siphon port 5 do not need to follow the layout requirement of the same longitudinal line, and they can be flexibly and reasonably arranged in a staggered manner according to factors such as actual process requirements, furnace body structural characteristics, operation convenience and the like.

In some embodiments of the invention, the furnace roof or flue 3 port may generate high temperature dust-laden gas due to the bottom blowing process. In order to avoid environmental pollution and recover escaped valuable elements such as zinc, lead and the like, waste heat recovery equipment and a dust removal system (such as a bag-type dust collector, an electric dust collector or a washing tower) can be arranged at the rear end of the flue 3 to collect and recover metal smoke dust. In addition, in order to prevent the combustible gases such as CO, H ₂ and the like from escaping, a tight sealing and monitoring device is required to be installed between the furnace body and the ventilation system, so that the operation safety is ensured.

In the invention, the melt enhanced reduction recovery system of the bottom blowing type plasma torch can comprise a gas supply system, a power supply system, a feeding system and a powder supply system.

In some embodiments of the invention, the gas supply system may consist essentially of a gas source, a pressure regulating valve, a flow meter, a safety valve, etc., for providing the excitation gas and the reducing gas to the plasma torch, and flexibly regulating the flow of each component according to the process requirements. In some more specific embodiments of the invention, in order to ensure the stability of the atmosphere and the carbon-oxygen ratio of the molten pool, the gas supply system can adopt a multi-path parallel connection mode, and an automatic regulating and controlling device (such as an electromagnetic valve, a flowmeter and a PLC control module) is additionally arranged on each channel, so that the real-time accurate control of the carbon-oxygen ratio, the furnace pressure and the atmosphere environment is realized.

In some embodiments of the invention, the power supply system generally comprises a rectifier transformer, an inverter, a controller, etc., and is matched with the plasma torch to ensure that the high-efficiency discharge can be continuously carried out under the high-temperature high-arc field so as to maintain the stable and high-power supply driving required by the plasma torch.

In some embodiments of the invention, a feeding system can be used for feeding into the bottom-blowing type plasma reduction furnace, lead-zinc melt can be converged into the bottom-blowing type plasma reduction furnace through a melt converging inlet 1, and a closed feeding inlet 2 can be used for feeding lead-zinc mixed solid materials into the bottom-blowing type plasma reduction furnace. In some more specific embodiments of the invention, the batch or continuous feed may be carried out using a belt conveyor or a sealed feed tank.

In some embodiments of the invention, the melt-enhanced reduction recovery system of the bottom-blowing plasma torch may be equipped with a powder supply system, and powdered or granular non-plasma species may be fed into the bottom lance zone through a separate powder supply conduit to achieve a continuous and controlled feed target. In some more specific embodiments of the invention, an accurate metering device (such as a screw feeder or a weighing system) can be arranged below the storage bin, and a blower or pneumatic conveying device is utilized to convey non-plasma substances to the vicinity of a torch opening, so that the non-plasma substances are mixed with high-temperature plasma jet flow and then quickly heated and decomposed, and active reduction components such as CO, H ₂ and the like are further generated.

According to the invention, the on-line sensors such as temperature, pressure and gas components are arranged at key positions of the furnace body, and key parameters such as power supply, gas flow, charging speed and carbon-oxygen ratio are closed-loop controlled by means of a PLC or DCS system, so that the smelting process is more stable and controllable, and dynamic adjustment and optimization can be realized according to raw material components and process targets.

The melt enhanced reduction recovery system of the bottom blowing type plasma reduction furnace and the bottom blowing type plasma torch provided by the invention has the following advantages:

1. The double-energy cooperative heating and modularized furnace body is designed, the bottom blowing plasma torch and the electromagnetic induction coil are used for cooperative heating, the temperature is quickly increased to 1200-1400 ℃ within 30 minutes, the energy consumption is reduced by 25%, the furnace body adopts a double-layer fireproof lining (magnesia carbon brick and corundum) and water cooling system, and the service life is prolonged to 5 years.

2. Melt immersion reduction and dynamic heat transfer optimization, wherein solid mixed materials (density is 2.0-6.0g/cm ³) are immersed in high-zinc melt (Zn > 30%), high-heat conductivity acceleration reduction is utilized, reaction time is shortened to 30-90 minutes, zinc recovery rate is >95%, lead is >90%, and the method is suitable for high-impurity raw materials such as dust and mud in steel plants.

3. And (3) regulating and controlling the active atmosphere of the multi-medium plasma.

CO/H ₂/CH₄ and the like are used as media to spray active groups (CI, HI), and the carbon-oxygen ratio (C/O=1.2-2.5) is dynamically regulated by combining a solid reducing agent (pulverized coal/coke powder), so that the limitation of the traditional solid-gas reaction is broken through, and the reduction efficiency of the metal oxide is improved by 40%.

4. According to the invention, the plurality of plasma torches are uniformly distributed at the bottom of the furnace body, and the high-energy plasma is fully contacted with the molten material in a strong bottom-up bottom-blowing jet flow mode, so that the problems of uneven reaction, overlarge temperature gradient in the furnace, serious slag hanging and the like in the traditional side-blowing or top-blowing mode are solved.

5. The process can obviously improve the reduction rate and the reduction efficiency of the metal oxide, so that the comprehensive recovery rate of various metals such as zinc, lead, copper and the like is greatly improved. Meanwhile, the system combines measures such as powder feeding, accurate regulation and control of atmosphere, water-cooling protection of the furnace wall and the like, greatly reduces furnace lining loss and energy waste, and has the comprehensive advantages of long service life of equipment, flexible operation, high safety, environmental friendliness and the like.

6. The method is environment-friendly and full-quantification in resources, the dioxin is decomposed by the plasma at high temperature (1800 ℃), the waste gas and the waste heat are recovered and then discharged up to the standard, the slag vitrification is used for building materials (water permeable bricks), the recycling rate is more than 98%, and the carbon discharge intensity is reduced.

The invention also provides a control system which comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, and is characterized in that the method for recovering valuable metals through bottom blowing type plasma enhanced reduction is realized when the processor executes the computer program.

It should be noted that the bottom-blowing type plasma reduction furnace as described in any of the above may further include the control system.

To facilitate a further understanding of the invention by those skilled in the art, reference is now made to the accompanying drawings, in which:

Example 1

S1, firstly mixing a certain domestic lead-zinc oxide ore and lead/zinc sulfide ore oxidative desulfurization melt in proportion to obtain 2500g of lead-zinc oxide material with the main composition of PbO, feO, siO ₂, caO=23:45:11:8:8.9 (wt.%) and other oxide impurities, adding the lead-zinc oxide material into a molten pool mechanism through a sealed feed port 2, and heating by a reducing agent and a heating device 7 to form a high-zinc melt, wherein the temperature rising rate of the lead-zinc oxide material is 45 ℃ per minute, and the temperature of the high-zinc melt is 1300 ℃;

The plasma device comprises 3 plasma torches, the power of the plasma torches is 300kW, the gas flow range in the plasma torches is 20m ³/h, the plasma torches are annularly and symmetrically distributed at the bottom of a melt cavity, the plasma torches comprise nozzle openings, the included angle between the axis of each nozzle opening along the length direction and the vertical direction is 15-30 degrees, and the distance between each nozzle opening and the bottom of the melt cavity in the vertical direction is 0.7m.

In the step S1, the mixed gas of plasma state N ₂ -CO sprayed by the bottom plasma torch is used as a carrier to spray CO to the bottom of a molten pool, the spraying total amount (the molar amount of plasma state CO and the molar amount of non-plasma state CO) of the CO sprayed in the embodiment is 1.2 times of the molar amount of the reducing agent for reducing all the metal oxides to be reduced in the high-zinc melt into metal simple substances, and the volume ratio of the CO in the mixed gas of N ₂ -CO is 20%.

S2, carrying out reduction reaction on the high-zinc melt under the blowing and stirring of a reducing agent to generate metal vapor, and standing, and separating slag and gold to generate an alloy phase and slag. The duration of the reduction reaction is 20 minutes, and the molar ratio of C/O is 1.2-2.5 in the atmosphere environment formed by the reduction reaction.

According to the determination, volatile components in the gas phase are mainly zinc oxide and lead, the component analysis is shown in figure 2, silicate oxides formed by Ca, fe and Si are mainly used in the slag phase, the residual lead content in the slag phase is 0%, the zinc content is 0%, the zinc and lead recovery rate is 99%, the phase SEM-EDS chart is shown in figure 3, the formed metal phase is mainly Pb/Cu mixed phase, and the impurity (As and Sb) content in the Pb-Cu alloy phase is less than 0.05%, so that the direct refining requirement is met. The bottom blowing makes the CO bubbles fully contact with the melt, effectively reduces PbO and ZnO, and the CO energy utilization rate in the embodiment is as high as 92%.

Dioxin was not detected in the flue gas (limit of detection: 0.01ng TEQ/m ³), well below national emission standards (0.5 ng TEQ/m ³).

Example 2

Other conditions of the embodiment are unchanged, and the heating rate of the lead-zinc oxide material is only adjusted from 45 ℃ to 30 ℃ per minute.

According to measurement, volatile components in a gas phase mainly comprise zinc oxide and lead, the composition of the volatile components comprises 35% of lead, 25% of zinc and 40% of zinc oxide, a slag phase mainly comprises silicate oxide formed by Ca, fe and Si, the residual lead content in the slag phase is 0%, the zinc content is 0%, the zinc and lead recovery rate is 99%, a formed metal phase mainly comprises Pb/Cu mixed phase, and the impurity (As and Sb) content in a Pb-Cu alloy phase is less than 0.05%, so that the direct refining requirement is met. The bottom blowing makes the CO bubbles fully contact with the melt, effectively reduces PbO and ZnO, and the CO energy utilization rate in the embodiment is as high as 80%.

Dioxin was not detected in the flue gas (limit of detection: 0.01ng TEQ/m ³), well below national emission standards (0.5 ng TEQ/m ³).

Comparative example 1

In comparison with the examples, other conditions of the comparative example were unchanged, and only the bottom blowing mode was replaced with top blowing.

S1, mixing a certain domestic lead-zinc oxide ore, a high zinc lump material for fire zinc smelting and zinc oxide dust according to a proportion to obtain a lead-zinc oxide material 2500g which mainly comprises PbO, feO, siO ₂, caO=23:45:11:8:8.9 (wt.%) and the balance of impurity components such as aluminum and magnesium, wherein the lead-zinc oxide material is added into a molten pool mechanism through a sealed charging port 2, a high zinc melt is formed through heat supply of a reducing agent and a heating device 7, the heating rate of the lead-zinc oxide material is 5 ℃ per minute, and the temperature of the high zinc melt is 1300 ℃;

The plasma device comprises 3 plasma torches, the power of the plasma torches is 300kW, the gas flow range in the plasma torches is 20m ³/h, the plasma torches are annularly and symmetrically distributed at the top of a melt cavity, the plasma torches comprise nozzle openings, the included angle between the axis of the nozzle openings along the length direction and the vertical direction is 15-30 degrees, and the nozzle openings are immersed in high-zinc melt.

In the step S1, the mixed gas of plasma state N ₂ -CO sprayed by the top plasma torch is used as a carrier to spray CO to the bottom of a molten pool, the spraying total amount (the molar amount of plasma state CO and the molar amount of non-plasma state CO) of the CO sprayed in the embodiment is 1.2 times of the molar amount of the reducing agent for reducing all the metal oxides to be reduced in the high-zinc melt into metal simple substances, and the volume ratio of the CO in the mixed gas of N ₂ -CO is 20%.

S2, carrying out reduction reaction on the high-zinc melt under the blowing and stirring of the reducing agent to generate metal vapor, standing, and separating slag from gold to generate alloy phase and slag. The reduction reaction time is 40 minutes, volatile components in the gas phase are mainly zinc oxide and lead, silicate oxides formed by Ca, fe and Si are mainly used in the slag phase, the residual lead content in the slag phase is 0.89%, the zinc content is 2.7%, the zinc recovery rate is 95%, the lead recovery rate is 98%, the formed metal phase is mainly Pb/Cu mixed phase, the As content in Pb-Cu alloy is 0.3%, and an additional dearsenization process is needed. The top blowing gas floats up too fast, and the CO utilization rate is only 65%.

The concentration of dioxin in the flue gas is 1.5ng TEQ/m ³, exceeding 3 times (national limit value 0.5ng TEQ/m ³).

In the above technical solution of the present invention, the above is only a preferred embodiment of the present invention, and therefore, the patent scope of the present invention is not limited thereto, and all the equivalent structural changes made by the description of the present invention and the content of the accompanying drawings or the direct/indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims (10)

1. A method for recovering valuable metals by bottom-blowing plasma-enhanced reduction, comprising: 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-blown plasma-enhanced reduction according to claim 1, wherein the reducing agent further comprises a non-plasma substance, the non-plasma substance being supported on the plasma substance, and the non-plasma substance comprises one or more of pulverized coal, coke powder, and waste electrode particles; The plasma working medium of the reducing plasma substance includes an excitation working medium and a reducing working medium. The excitation working medium includes nitrogen and/or argon. 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-blown plasma-enhanced reduction according to claim 2, wherein 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 to elemental metal. 4. The method for recovering valuable metals by bottom-blown plasma-enhanced reduction according to claim 1, wherein the high-zinc melt comprises, by mass fraction, 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-blown plasma-enhanced reduction according to claim 4, wherein the lead-zinc oxide material further comprises a lead-zinc melt, and the source of the lead-zinc melt comprises one or more of lead-zinc oxide ore, secondary zinc oxide smoke, or zinc-containing dust from a steel mill. 6. The method for recovering valuable metals by bottom-blowing plasma-enhanced reduction according to claim 1, wherein the C/O molar ratio in the atmosphere formed by the reduction reaction is 1.2-2.5, and the reduction reaction lasts for 20-90 minutes. 7. The method for recovering valuable metals by bottom-blowing plasma-enhanced reduction according to claim 1, wherein 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 it is applied to the method for recovering valuable metals by bottom-blown plasma-enhanced reduction according to any one of claims 1 to 7, comprising 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 comprises 4 to 6 plasma torches, each having a power of 200 to 500 kW and a gas flow rate in the plasma torch of 5 to 30 m ³ /h. The plasma torches are symmetrically distributed in an annular shape at the bottom of the melt chamber, and each plasma torch comprises a nozzle opening. The angle formed between the axis of the nozzle opening along the longitudinal direction and the vertical direction is 15-30°, and the vertical distance between the nozzle opening and the bottom of the melt chamber is 0.5-1.2 m. 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.