Recycling and reusing method of nonferrous metal waste

Abstract

The invention belongs to the technical field of resource recycling, and particularly relates to a non-ferrous metal waste recycling method which comprises the following steps: step 1, selective gasification separation: converting first target metals such as zinc, lead, indium and germanium into gaseous compounds to escape through vulcanization or chlorination atmosphere at the temperature lower than the melting point of matrix metals; 2, multi-stage fractional condensation, wherein selective condensation and enrichment of gaseous metal compounds with different boiling points are achieved through a gradient temperature interval; step 3, selective infiltration separation: heating in a second reaction zone to melt second target metals such as tin, and separating the second target metals from the solid-phase copper matrix through gravity seepage or centrifugal separation; and fourthly, base metal refining is conducted, specifically, the purified copper base is subjected to melting refining, and high-purity metal is obtained. By means of the process, multi-component valuable metal in the complex non-ferrous metal waste can be graded, accurately and efficiently recycled, the resource utilization rate is remarkably increased, and environmental pollution is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of resource recycling, and particularly relates to a recycling method of non-ferrous metal waste. BACKGROUND

[0002] Global industrialization deepening and natural resource tension drive the demand for non-ferrous metals to rise, and the difficulty of primary mineral exploitation and environmental cost increase synchronously. Recycling non-ferrous metals from industrial waste, waste slag and scrap products is a key measure to alleviate resource constraints, ensure industry chain safety and promote circular economy, so developing efficient, environmentally friendly and economical recycling technology has become a core issue in the field of metallurgical engineering and environmental science.

[0003] In the prior art, pyrometallurgical high-temperature smelting process has long dominated, which has the advantages of large processing capacity, fast reaction rate and wide adaptability of raw materials. The process adds pretreated waste, slagging agent and reducing agent into a high-temperature smelting furnace, melts the metal components at a high temperature of 1200 DEG C or above, and realizes the preliminary separation of target metals and impurities by using the differences in density, melting point and chemical affinity of various components, effectively solving the recycling problem of early large quantities of single-component industrial waste and laying the technical foundation for resource recycling.

[0004] With the fine demand of downstream, non-ferrous metal waste shows the characteristics of "multiple symbiosis, low grade and high value", and traditional pyrometallurgy shows principle bottleneck. High-temperature smelting is a non-selective physical and chemical reaction environment, which can realize macroscopic separation of main metals, but will lead to oxidation, volatilization or entering of associated valuable metals (such as indium, germanium, noble metals, etc.) into the slag; when adjusting process parameters to optimize main metal recovery rate, the recovery efficiency of associated metals will be further sacrificed. Although multi-stage dust removal and slag secondary enrichment are used to remedy, the process is prolonged, energy and material consumption is increased, and associated metals are highly diluted and passivated, so the recovery rate and economy are not good, forming a technical bottleneck of "trade-off".

[0005] Therefore, the application provides a recycling method of non-ferrous metal waste. SUMMARY

[0006] In order to make up for the deficiencies of the prior art and solve at least one technical problem in the background art.

[0007] The technical scheme adopted by the application to solve the technical problem is that the application provides a recycling method of non-ferrous metal waste, which comprises the following steps:

[0008] Step one, selective gasification separation step: the non-ferrous metal waste is placed in the first reaction zone of a multi-zone temperature control reactor, and is subjected to heat preservation treatment at a first preset temperature and a first preset reaction atmosphere for a first preset time, so that at least one first target valuable metal component in the waste reacts with the first preset reaction atmosphere, is converted into a gaseous metal compound, and escapes from the solid waste, forming a mixed gas stream rich in the gaseous metal compound and a solid residue material after preliminary purification; the set value of the first preset temperature is lower than the melting point of the base metal in the non-ferrous metal waste;

[0009] Step two, fractional condensation enrichment step: the mixed gas stream is introduced into a multi-stage fractional condensation system, and by setting a gradient temperature interval from high temperature to low temperature in the multi-stage fractional condensation system, the gaseous metal compounds with different boiling points in the mixed gas stream are selectively condensed into solid or liquid concentrates in the corresponding temperature interval, thereby realizing the separation and enrichment of multiple first target valuable metal components;

[0010] Step three, selective infiltration separation step: the solid residue material is transferred from the first reaction zone to the second reaction zone of the multi-zone temperature control reactor, and is subjected to heat preservation treatment at a second preset temperature and a second preset inert atmosphere for a second preset time, so that at least one second target valuable metal component in the solid residue material melts to form a liquid phase, while the base metal and other high-melting-point components remain in a solid phase; the set value of the second preset temperature is higher than the melting point of the second target valuable metal component but lower than the melting point of the base metal; the liquid phase is separated from the solid phase of the base metal by a solid-liquid separation device, to obtain a liquid alloy rich in the second target valuable metal component and a solid phase base metal after secondary purification;

[0011] Step four, base metal refining step: the solid phase base metal after secondary purification is transferred to the third reaction zone of the multi-zone temperature control reactor, and is melted and refined under a third preset temperature and a third preset refining atmosphere, to remove residual impurity elements, and finally obtain a high-purity target base metal.

[0012] Further, in the step one, the non-ferrous metal waste is electronic waste broken pieces or alloy chips containing copper as the base metal and associated with zinc, lead, tin, indium, germanium and other valuable metal elements. The first target valuable metal component is zinc, lead, indium and germanium. The value range of the first preset temperature is 650-850°C.

[0013] As a preferred embodiment of the present application, the first preset reaction atmosphere is a sulfidizing atmosphere. Specifically, the sulfidizing atmosphere is composed of 5% to 15% by volume of sulfur dioxide, 5% to 20% by volume of carbon monoxide, and the balance of nitrogen. Under this atmosphere, the elements of zinc, lead, indium, etc. in the first target valuable metal component react in situ with the sulfur component in the atmosphere to generate corresponding gaseous metal sulfides, such as zinc sulfide (ZnS) and lead sulfide (PbS). The first preset duration is 60 minutes to 120 minutes to ensure sufficient progress of the sulfidation reaction.

[0014] Further, the first reaction zone of the multi-zone temperature-controlled reactor has an inner wall composed of a nickel-chromium-molybdenum-based high-temperature corrosion-resistant alloy, the chemical composition of which includes: chromium content of 20-23wt%, molybdenum content of 15-17wt%, iron content less than 5wt%, tungsten content of 3.0-4.5wt%, and the balance of nickel. The reaction zone is equipped with an array of quartz infrared heating modules, and the power of each zone is adjusted by a central process controller (CPC) to control the uniformity of the temperature field in the reaction zone, with a temperature control accuracy of ±5℃. The first preset reaction atmosphere is uniformly introduced through an annular porous ceramic gas distributor arranged at the bottom of the reaction zone.

[0015] In the second step, the multi-stage fractional condensation system is composed of at least three condensation chambers connected in series. The operating temperature of the first condensation chamber is maintained at 700℃ to 800℃, which is used to selectively condense and collect lead sulfide (PbS) and other high-boiling sulfides in the exhaust gas stream. The operating temperature of the second condensation chamber is maintained at 500℃ to 650℃, which is used to condense and collect indium sulfide (In2S3) and germanium sulfide (GeS2). The operating temperature of the third condensation chamber is maintained at 300℃ to 450℃, which is used to condense and collect zinc sulfide (ZnS). Each condensation chamber is provided with a collection bin at the bottom with a gas lock valve, which is used to periodically discharge the collected metal sulfide concentrate without damaging the negative pressure of the system. A bag-type dust collector and an activated carbon adsorption tower are connected at the end of the system to capture the escaping dust and adsorb the residual sulfur dioxide in the treated tail gas.

[0016] Further, in the third step, the second target valuable metal component is tin. After the solid-phase residual material is treated in step one, it is mainly composed of a copper matrix and a tin component. The value of the second preset temperature ranges from 900℃ to 1050℃. This temperature is higher than the liquidus temperature of the low-melting eutectic phase in copper-tin alloy, but significantly lower than the melting point of pure copper (1083℃).

[0017] Specifically, the second preset inert atmosphere is nitrogen gas with purity not less than 99.99%, and the flow rate is set to 5-10 standard cubic meters per hour to form a micro-positive pressure environment in the second reaction zone, so as to prevent air from entering and the material from being oxidized. The solid-liquid separation device is a porous graphite crucible structure integrated at the bottom of the second reaction zone. The pore size of the graphite crucible is 0.5-1.5 mm, which allows the molten tin-rich liquid alloy to flow through under the action of gravity at the second preset temperature, and the solid-phase copper matrix with a size much larger than the pore size is intercepted in the upper part of the crucible. The liquid alloy under the flow is collected in the graphite condensing mold below the crucible, and forms a tin-copper alloy ingot after cooling.

[0018] In the fourth step, the main component of the solid-phase matrix metal after secondary purification is copper, and the purity has been significantly improved. The third reaction zone is an induction melting furnace structure. The third preset temperature is set to 1200-1300°C to ensure that the solid-phase matrix metal is completely melted. The third preset refining atmosphere is a controlled oxidizing atmosphere, which is realized by blowing air or oxygen-enriched air into the copper melt at a flow rate of 0.5-1.5 standard cubic meters per minute. This process aims to oxidize trace amounts of impurity elements such as iron and sulfur in the copper melt and combine them with a small amount of pre-added silica-based slagging agent to form low-density slag that floats on the surface of the copper liquid. After the refining process is completed, the surface slag is removed by a slag skimming robot, and then the high-purity copper liquid is poured into a continuous casting system to prepare standard copper ingots or billets.

[0019] As another embodiment of the present application, the first preset reaction atmosphere in the first step is a chlorinating atmosphere. Specifically, the chlorinating atmosphere is composed of 2%-8% chlorine gas by volume and the balance of nitrogen gas. Under this atmosphere, zinc, lead, indium, germanium, and other elements in the first target valuable metal component undergo in-situ chlorination reaction to generate corresponding gaseous metal chlorides, such as germanium tetrachloride (GeCl4), indium trichloride (InCl3), lead dichloride (PbCl2), and zinc dichloride (ZnCl2). Since the boiling points of these metal chlorides are generally lower than those of their corresponding sulfides, the first preset temperature can be adjusted to the range of 400-600°C, thereby achieving gasification separation at a lower energy consumption level.

[0020] Accordingly, in the embodiment of chlorination atmosphere, the temperature gradient of the multi-stage condensing system of step two is also adjusted. The first condensing chamber is maintained at 350-450℃ for condensing and collecting lead chloride and zinc chloride. The second condensing chamber is maintained at 150-250℃ for condensing and collecting indium trichloride. The third condensing chamber is maintained at 50-80℃ for condensing and collecting germanium tetrachloride by using a refrigeration unit. The exhaust gas of the system needs to be treated by an alkali spray washing tower to completely absorb the unreacted chlorine and hydrogen chloride gas that may be formed, ensuring that the emission meets the standards.

[0021] As another embodiment of the present application, the solid-liquid separation device in step three adopts a centrifugal separation mechanism. Specifically, the second reaction zone is designed as a cylindrical furnace body that can rotate at high speed. After the solid residue is heated and the second target valuable metal component (e.g., tin) forms a liquid phase, a driving motor is started to rotate the cylindrical furnace body at a speed of 300-500 rpm. Since the density of the liquid phase is usually different from that of the solid phase, under the action of the centrifugal force field, the phase with a larger density (usually the solid copper matrix) is thrown to the inner wall of the furnace body, while the liquid phase with a smaller density is squeezed to the center area. By setting an overflow port or a bottom center liquid discharge pipe in the center of the furnace body, the enriched liquid alloy can be discharged, thereby achieving efficient solid-liquid separation. This method is particularly suitable for processing material systems with a significant difference in density between the liquid phase and the solid phase.

[0022] The beneficial effects of the present application are as follows:

[0023] The application relates to a recycling method of non-ferrous metal waste, which realizes programmed and classified recovery of various valuable metal components in complex waste through an integrated, multi-region and multi-stage control process. The core creativity is embodied in that a traditional pyrometallurgical technical paradigm of “overall melting and macroscopic phase separation” is completely abandoned, and a new strategy of “step-by-step unlocking and accurate separation” based on the differences in physical and chemical properties of various metal components at different temperatures and atmospheres is adopted. First, under mild conditions far below the melting point of the base metal, the valuable metal components with high volatility or high reactivity are converted into a gas phase by using a specific reaction atmosphere, so that they are “steamed out” from the solid phase matrix with high selectivity, thereby avoiding the risk of being oxidized, diluted or irreversibly combined with the slag in the high-temperature molten pool. Secondly, for the valuable metal components with medium melting point, the application creates a “solid-liquid coexistence” window in which only the component is melted while the base metal is still solid by using precise temperature zone control, and then realizes the accurate separation of the component from the solid phase matrix by physical methods such as gravity seepage or centrifugal force field. Finally, only after most of the valuable associated elements have been pre-separated and purified, the highly purified base metal is subjected to final melting and refining. This “easy first, difficult later and divide and rule” process design not only enables each valuable metal to be efficiently recovered under its optimal thermodynamic and kinetic conditions, significantly improving the total value of resource recovery, but also greatly reduces the slag production and dust treatment load of the subsequent refining steps, showing significant energy-saving and environmental protection benefits. The new technical system constructed by the application provides a non-obvious and systematic solution to the resource recovery problem of multi-element symbiotic complex non-ferrous metal waste. BRIEF DESCRIPTION OF DRAWINGS

[0024] The application will be further described below with reference to the drawings.

[0025] Figure 1 is a flowchart of the recycling method of non-ferrous metal waste of the application;

[0026] Figure 2 is a block diagram of the overall structure of the system for executing the method in the embodiment of the application;

[0027] Figure 3 is a structural diagram of the selective gasification separation and fractional condensation enrichment step in the embodiment of the application;

[0028] Figure 4 is a structural diagram of the selective melting and seepage separation step in the embodiment of the application using gravity seepage.

[0029] In the figure: 100, multi-zone temperature control reactor; 110, first reaction zone; 111, central process controller; 112, annular porous ceramic gas distributor; 120, second reaction zone; 130, third reaction zone; 200, multi-stage fractional condensation system; 210, first condensation chamber; 220, second condensation chamber; 230, third condensation chamber; 240, bag-type dust collector; 250, activated carbon adsorption tower; 310, porous graphite crucible; 320, graphite condensation mold; 410, slagging mechanical arm; 420, continuous casting system. DETAILED DESCRIPTION

[0030] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in conjunction with specific embodiments.

[0031] Referring to Figure 1 the flowchart and Figure 2 the overall system structure block diagram, the present application discloses an integrated multi-stage recovery method, which realizes programmed and high-selectivity separation and enrichment of multiple valuable elements in complex non-ferrous metal waste through the cooperative work of a multi-zone temperature control reactor 100 and a multi-stage fractional condensation system 200. The core technical logic of this method lies in the use of a step-by-step processing strategy combining "low-temperature gasification-fractional condensation" and "medium-temperature infiltration-solid-liquid separation" based on the physical and chemical property differences of each metal component in the waste at different temperatures and specific reaction atmospheres, ultimately achieving high-purity recovery of base metals.

[0032] In a specific embodiment, the non-ferrous metal waste is a metal mixture obtained by mechanical crushing and physical sorting of waste printed circuit boards (WPCB), and its typical chemical composition is about 82.5% copper (Cu), 5.2% tin (Sn), 4.8% zinc (Zn), 3.1% lead (Pb), 0.12% indium (In), 0.08% germanium (Ge), and a small amount of other metals and non-metallic inclusions, by weight percentage. The execution of this method relies on a set of precisely controlled continuous or semi-continuous processing systems, which mainly consist of a feeding unit, a multi-zone temperature control reactor 100, a multi-stage fractional condensation system 200, a material transport mechanism, and a tail gas treatment unit.

[0033] First, step one, selective gasification separation step, is performed. This step is completed in the first reaction zone 110 of the multi-zone temperature control reactor 100, and the equipment structure is shown in detail in Figure 3The non-ferrous metal scraps to be treated are fed into the first reaction zone 110 by a double-valve airlock screw feeder in a quantitative and continuous manner. The main body of the reaction zone is a horizontally arranged tube furnace, the inner wall of which is integrally cast from a specially designed nickel-chromium-molybdenum-based high-temperature corrosion-resistant alloy (e.g., UNS N10276 or similar grade). The chemical composition of the alloy is precisely designed, with a chromium content of 21.5 wt%, a molybdenum content of 16.0 wt%, an iron content strictly controlled below 4.5 wt%, and a tungsten content of 3.8 wt%, with the balance being nickel. This material ratio ensures that the inner wall of the reactor maintains excellent structural integrity and creep resistance at high temperatures up to 900°C and in a strongly corrosive atmosphere (such as a sulfidizing or chloridizing atmosphere).

[0034] The heating system of the first reaction zone 110 is composed of multiple groups of quartz infrared heating module arrays surrounding the outer wall of the furnace tube. The power output of each group of heating modules is independently controlled by a central process controller (CPC) 111 using a proportional-integral-derivative (PID) algorithm. The CPC 111 collects temperature signals from multiple S-type (platinum-rhodium 10-platinum) thermocouples arranged at different positions within the reaction zone in real time, and performs real-time modeling and dynamic adjustment of the temperature field in the furnace through complex algorithm models, thereby achieving highly uniform control of the axial and radial temperature distribution of the entire reaction zone up to several meters long, ensuring that the temperature fluctuations at any point are accurately controlled within ±5°C of the set value.

[0035] In this embodiment, the first preset temperature is set to 780°C. This temperature is selected after rigorous thermodynamic calculations and dynamic experimental verification, and its value is significantly lower than the melting point of the base metal copper in the waste (1083.4°C), but is sufficient to drive the target valuable metal components to undergo efficient chemical conversion with a specific atmosphere. The first preset reaction atmosphere is an artificially prepared sulfidizing atmosphere, which is accurately metered and mixed by multiple mass flow controllers (MFCs). Specifically, the atmosphere is composed of 10% by volume of sulfur dioxide (SO2), 15% by volume of carbon monoxide (CO), and 75% by volume of high-purity nitrogen (N2). After preheating to 600°C, the mixed gas is uniformly introduced into the furnace through the annular porous ceramic gas distributor 112 arranged at the bottom of the first reaction zone 110 in the form of a uniform surface flow. The micrometer-scale pore structure of the porous ceramic divides the gas flow into countless small bubbles, greatly increasing the gas-solid contact specific surface area and thereby intensifying the mass transfer process.

[0036] When the waste enters the reaction zone at 780°C and contacts the above-mentioned sulfidizing atmosphere, the first target valuable metal components contained in the waste, such as zinc, lead, indium and germanium, will undergo in-situ chemical conversion due to their higher sulfidizing reactivity than copper in the environment where both sulfur potential and oxygen potential are controlled. For example, zinc oxide (ZnO), metallic lead (Pb), indium oxide (In2O3) and other components in the waste will react with the active sulfur components in the atmosphere to form corresponding metal sulfides. At a temperature of 780°C, the generated zinc sulfide (ZnS, sublimation point about 1185°C, but its gas phase migration can be promoted in the presence of CO), lead sulfide (PbS, boiling point 1114°C, but it already has a significant vapor pressure at this temperature), indium sulfide (In2S3) and germanium sulfide (GeS2) all exhibit sufficiently high volatility and can escape from the solid waste matrix in the form of gaseous molecules. These gaseous metal sulfides, together with nitrogen gas as the carrier gas, form a mixed gas stream rich in valuable metal components, which is led out from the end of the first reaction zone 110. The first preset duration of this process is set to 90 minutes to ensure the depth and completeness of the sulfidization and gasification process. After this step, the solid phase material remaining in the first reaction zone 110 is mainly composed of a copper matrix, tin and a small amount of impurities that have not been completely gasified, which we call solid residue.

[0037] Next, step two, the fractional condensation enrichment step, is performed. The high-temperature mixed gas stream led out from the first reaction zone 110 is directly introduced into a multi-stage fractional condensation system 200 through a pipeline also made of nickel-chromium-molybdenum alloy and fully heated (maintained above 850°C to prevent premature condensation). The structure of this system is also embodied in Figure 3 The system is composed of three cyclone condensation chambers connected in series, with the same structure but decreasing operating temperatures, namely the first condensation chamber 210, the second condensation chamber 220 and the third condensation chamber 230.

[0038] Specifically, the mixed gas stream first enters the first condensation chamber 210 tangentially. High-temperature heat conduction oil is circulated in the jacket of the condensation chamber, and by precisely controlling the flow and temperature of the heat conduction oil, the internal operating temperature is stably maintained at 750°C. According to the condensation temperature (i.e. vapor pressure-temperature curve) of each metal sulfide, at this temperature range, the PbS vapor with the highest boiling point first reaches its saturation point and selectively sublimates into solid particles. Under the action of cyclone centrifugal force, these PbS particles are efficiently thrown to the wall and settle at the bottom. The bottom of the first condensation chamber 210 is connected to a collection bin with a double airlock valve structure, which can realize quasi-continuous discharge operation, i.e. under the condition of not breaking the negative pressure (about -500 Pa) of the whole system, the enriched high-purity lead sulfide concentrate can be periodically discharged.

[0039] After the first stage condensation, most of the lead sulfide in the gas stream has been removed. The remaining gas stream temperature drops slightly and then enters the second condensation chamber 220. The operating temperature of this condensation chamber is controlled at 580°C. At this temperature, the indium sulfide (In2S3) and germanium sulfide (GeS2) vapor in the gas stream reach supersaturation state one after another and sublimate. Again by the cyclone separation principle, the sulfide mixture rich in indium and germanium is collected in the collection bin at the bottom of the condensation chamber.

[0040] Finally, the gas stream enters the third condensation chamber 230, which is controlled at an operating temperature of 400°C. This temperature is lower than the condensation point of zinc sulfide, so the remaining main valuable component, zinc sulfide (ZnS), in the gas stream is effectively condensed and collected at this point. Through the fine control of the three-stage temperature gradient, not only is the total capture of multiple first target valuable metal components achieved, but more importantly, the preliminary separation and enrichment among them are completed at the same time, and the obtained concentrates at each stage can be directly used as high-quality raw materials for subsequent wet refining or electrolytic purification.

[0041] The tail gas discharged from the third condensation chamber 230 has a temperature below 400°C, and may still contain a small amount of uncondensed sulfide dust and unreacted SO2 and CO. Therefore, the tail gas needs to be treated by subsequent purification. First, the tail gas passes through a high-efficiency bag-type dust collector 240, which uses polytetrafluoroethylene (PTFE) coated filter material and can capture ultra-fine dust with a particle size of 0.1 microns or more. Subsequently, the cleaned gas enters an activated carbon adsorption tower 250 filled with modified activated carbon for deep adsorption to remove residual sulfur dioxide. The final treated tail gas is mainly composed of nitrogen and carbon monoxide, and the carbon monoxide can be selectively recovered for use as fuel or reducing agent, or converted to carbon dioxide by catalytic oxidation and then discharged to meet the emission standards.

[0042] While steps one and two are being completed, the system performs step three, the selective infiltration separation step, in parallel. The solid residue remaining in the first reaction zone 110 is smoothly transported to the adjacent second reaction zone 120 by a push rod type transport mechanism made of silicon carbide ceramic built into the multi-zone temperature-controlled reactor 100. The structure of the second reaction zone 120 is shown in Figure 4 The heating method of this reaction zone also uses infrared heating modules, but its core component is a specially designed porous graphite crucible 310.

[0043] The second preset temperature within the second reaction zone 120 is precisely controlled at 980°C. This temperature setting is crucial to this step; it is higher than the melting point (231.9°C) of the second target valuable metal component in the waste—tin (Sn), and also higher than the liquidus temperature of a low-melting-point eutectic phase in the copper-tin binary alloy system, but clearly lower than the melting point (1083.4°C) of the base metal, pure copper. Therefore, under the holding temperature of 980°C, the tin component in the solid residual material will react with some copper to form a low-melting-point copper-tin alloy phase, which will completely melt into a liquid state. Meanwhile, the majority of the copper matrix and other higher-melting-point impurities will remain in a solid state, forming a mixed system in which solid and liquid coexist.

[0044] To prevent undesirable oxidation reactions of the material at this high temperature, high-purity nitrogen (99.999% purity) is continuously introduced into the second reaction zone 120 as a second preset inert atmosphere. The nitrogen flow rate is set to 8 standard cubic meters per hour, creating a slightly positive pressure environment (approximately +50 Pa) within the furnace, effectively isolating it from external air intrusion. The second preset duration for the material, i.e., the holding time, is set to 45 minutes to ensure complete melting of the tin and homogenization of the liquid phase.

[0045] Solid-liquid separation is achieved using gravity. For example... Figure 4 As shown, the bottom of the porous graphite crucible 310 is designed with a dense array of micropores. The pore size of these micropores is precisely machined and controlled to be within 0.8 mm. At 980°C, the molten tin-rich liquid copper-tin alloy, due to its excellent fluidity, will drip downwards through these micropores under its own gravity. The solid copper matrix framework, with a size much larger than 0.8 mm, is effectively retained in the upper part of the crucible 310. This melt-diffusion separation method based on size sieving and gravity-driven processes is gentle and has extremely high separation efficiency. The liquid alloy dripping from the bottom of the crucible is directly collected in a graphite cooling mold 320 below. After cooling, a tin-rich tin-copper alloy ingot is obtained, which can be sold directly as a high-value-added solder or raw material for bronze alloys.

[0046] Finally, step four, the base metal refining step, is performed. After step three, the solid material retained in the upper part of the porous graphite crucible 310 is the solid base metal that has undergone secondary purification. At this point, its copper content has been greatly increased. This material is then conveyed to the third reaction zone 130 of the multi-zone temperature-controlled reactor 100 via the next step of the conveying mechanism. The third reaction zone 130 is essentially a medium-frequency coreless induction melting furnace. Its furnace body is constructed of high-purity magnesium oxide refractory material and surrounded by water-cooled induction coils.

[0047] In this reaction zone, the third preset temperature is set to 1250℃. After the induction heating system is started, a strong alternating electromagnetic field generates a large eddy current in the solid copper block, which rapidly heats up and completely melts in a short time to form a copper liquid pool. Subsequently, the refining process is entered. At this time, the third preset refining atmosphere is a controlled oxidizing atmosphere. Specifically, dry air is blown into the copper melt at a flow rate of 1.0 standard cubic meters per minute through a quartz oxygen blowing pipe. The oxygen in the air will selectively oxidize the impurity elements (such as trace amounts of iron, sulfur, etc.) in the melt that have a higher oxygen affinity than copper, generating oxides (such as FeO, SO2). At the same time as the oxygen is blown, a small amount of a slag forming agent mainly composed of silicon dioxide is added to the surface of the melt pool. The generated metal oxides such as FeO will combine with SiO2 to form low-density silicate slag and stably float on the surface of the copper liquid. After about 20 minutes of refining, the surface slag layer is completely removed by a slag skimming mechanical arm 410 controlled by a preset program.

[0048] After the slag is removed, the copper liquid in the furnace has reached a very high purity. Subsequently, the induction furnace body is tilted, and the high-purity copper liquid enters a set of continuous casting system 420 through the runner, and is finally cast into electrolytic copper ingots or copper billets of specific specifications that meet international standards, realizing the final productization of the base metal recovery.

[0049] As another embodiment of the present application, the first preset reaction atmosphere in step one can be replaced by a chlorinating atmosphere. In this case, the atmosphere is composed of 5% chlorine gas (Cl2) and 95% nitrogen gas. Since the chlorides of the target metals (such as GeCl4, InCl3, PbCl2, ZnCl2) generally have lower boiling points than their sulfides, the first preset temperature can be significantly reduced to the level of 500℃, which brings significant energy saving benefits. Accordingly, the temperature range of the multi-stage fractional condensation system in step two must also be adjusted. The operating temperature of the first condensation chamber can be set to 400℃, which is used to preferentially condense and collect lead chloride and zinc chloride with relatively high boiling points. The operating temperature of the second condensation chamber is set to 200℃, which is used to condense and collect indium trichloride. For germanium tetrachloride, which has an extremely low boiling point (only 84.6℃), an additional set of deep refrigeration unit is required in the third condensation chamber to maintain its operating temperature at around 60℃, to ensure its effective capture. In addition, since chlorine gas is used, the tail gas treatment system of this embodiment must add an alkaline (such as sodium hydroxide solution) spray washing tower to completely absorb and treat any unreacted chlorine gas and possible hydrogen chloride gas, to ensure the absolute safety and compliance of the emissions.

[0050] As another embodiment of the present application, the solid-liquid separation device in step three can use centrifugal separation mechanism to replace gravity percolation. In this design, the second reaction zone 120 is constructed as a cylindrical furnace body which can be driven by a high-power motor to rotate at high speed. When the internal solid-phase residual material is heated to 980°C to form a solid-liquid coexisting system, the motor is started to rotate the furnace body at a speed of 400 revolutions per minute. Due to the significant difference in density between the solid-phase copper matrix (density about 8.9 g / cm3) and the liquid-phase tin-rich copper-tin alloy (density about 7.5-8.0 g / cm3), under the action of strong centrifugal force, the solid-phase copper with greater density will be tightly thrown to and attached to the inner wall of the furnace body, while the liquid phase with smaller density will be forced to gather in the central area of the furnace body. By setting an overflow port above the central axis of the furnace body, or opening a liquid discharge channel in the center of the furnace bottom which can be controlled by a valve, the separated and enriched liquid alloy can be efficiently discharged. This centrifugal separation method is particularly suitable for situations with large density difference between solid and liquid phases and high processing capacity requirements, and its separation speed is much faster than gravity percolation.

[0051] Example 1

[0052] Take 1000 kg of non-ferrous metal waste with the above-mentioned components and process it using the sulfidizing atmosphere-gravity percolation technology path of the present application. Step one: the temperature of the first reaction zone 110 is set to 780°C, the reaction atmosphere is 10% SO2+15% CO+75% N2, and the material residence time is 90 minutes. Step two: the temperatures of each stage of the multi-stage fractional condensing system 200 are set to 750°C, 580°C and 400°C respectively. Step three: the temperature of the second reaction zone 120 is set to 980°C, the inert atmosphere is N2, and the material residence time is 45 minutes. Step four: the smelting temperature of the third reaction zone 130 is 1250°C, and the air refining is 20 minutes. After material balance calculation, the following products are obtained:

[0053] The lead sulfide concentrate 35.2 kg is collected in the first condensing chamber 210, and the Pb content is detected to be 85.1%, which is equivalent to 29.95 kg of recovered lead.

[0054] The indium-germanium mixed sulfide concentrate 2.1 kg is collected in the second condensing chamber 220, and the In content is detected to be 45.2% and the Ge content is 27.8%, which is equivalent to 0.95 kg of recovered indium and 0.58 kg of recovered germanium.

[0055] The zinc sulfide concentrate 70.1 kg is collected in the third condensing chamber 230, and the Zn content is detected to be 67.0%, which is equivalent to 46.97 kg of recovered zinc.

[0056] The tin-copper alloy ingot 63.5 kg was collected in the graphite condensing mold 320 below the second reaction zone 120, and the Sn content was 81.2% and the Cu content was 18.8% by detection, which was equivalent to 51.56 kg of recovered tin.

[0057] The high-purity copper ingot 816.1 kg was finally obtained in the third reaction zone 130, and the Cu content reached 99.97% by detection.

[0058] Comparative Example 1

[0059] 1000 kg of non-ferrous metal waste with the same composition and mass as in Example 1 was treated by using a traditional pyrometallurgical process. The waste was directly added to a small Kaldo furnace, and the temperature was raised to 1300°C for oxidative smelting. In this process, a large amount of zinc was volatilized into the dust, and part of the lead and tin were oxidized into the slag. Part of the zinc oxide and lead oxide can be captured through the dust recovery system, but most of the rare metals such as indium and germanium are lost in the dust or slag, which are difficult to effectively recover. The crude copper obtained needs to be further electrolytic refined to reach a higher purity. The following results were obtained by statistics:

[0060] Zinc 15.8 kg was recovered from the dust.

[0061] The total lead recovery from the slag and dust was 11.2 kg.

[0062] Most of the tin entered the slag, and only about 9.4 kg was recovered.

[0063] Indium and germanium could not be effectively recovered, and the recovery rate was less than 10%.

[0064] The crude copper obtained was about 830 kg with a purity of about 98.5%, which needed to be further refined.

[0065] Hazardous solid waste slag rich in various heavy metal elements was generated, about 110 kg.

[0066] Performance comparison

[0067] Indicator item Example 1 (method of the present invention) Comparative Example 1 (conventional pyrometallurgical smelting) Copper (Cu) recovery rate 98.92% (into high-purity copper ingot) About 97% (into crude copper) Tin (Sn) recovery rate 99.15% 18.08% Zinc (Zn) recovery rate 97.85% 32.92% Lead (Pb) recovery rate 96.61% 36.13% Indium (In) recovery rate 79.17% <10% Germanium (Ge) recovery rate 72.50% <10% Final copper product purity 99.97% 98.5% (crude copper) Amount of hazardous slag produced About 5 kg (refining slag) About 110 kg Overall energy consumption (estimated) Lower (stepwise low-temperature treatment) Higher (overall high-temperature melting)

[0068] Through the detailed description and data comparison of the above examples and comparative examples, it can be clearly seen that, compared with the prior art, the recycling method of non-ferrous metal waste provided by the present application, through the innovative process path of "step-by-step unlocking and precise separation", significantly improves the recovery rate of tin, zinc, lead and other conventional associated metals, and revolutionarily realizes the efficient enrichment and recovery of indium, germanium and other high-value rare metals, greatly improving the comprehensive utilization value of the waste. At the same time, due to its staged and low-temperature operation characteristics, the energy consumption and the amount of hazardous waste are significantly reduced, which shows excellent economic and environmental benefits.

[0069] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for recycling non-ferrous scrap material, characterized by, The method comprises the following steps: Step one, selective gasification separation step: the non-ferrous metal waste is placed in the first reaction zone (110) of a multi-zone temperature control reactor (100), and is subjected to heat preservation treatment at a first preset temperature and a first preset reaction atmosphere for a first preset time, so that at least one first target valuable metal component in the waste reacts with the first preset reaction atmosphere, is converted into a gaseous metal compound, and escapes from the solid waste, forming a mixed gas stream rich in the gaseous metal compound and a solid residue material after preliminary purification; the set value of the first preset temperature is lower than the melting point of the base metal in the non-ferrous metal waste; Step two, fractional condensation enrichment step: the mixed gas stream is introduced into a multi-stage fractional condensation system (200), and by setting a gradient temperature interval from high temperature to low temperature in the multi-stage fractional condensation system (200), the gaseous metal compounds with different boiling points in the mixed gas stream are selectively condensed into solid or liquid concentrates in the corresponding temperature interval, thereby realizing the separation and enrichment of multiple first target valuable metal components; Step three, selective infiltration separation step: the solid residue material is transferred from the first reaction zone (110) to the second reaction zone (120) of the multi-zone temperature control reactor (100), and is subjected to heat preservation treatment at a second preset temperature and a second preset inert atmosphere for a second preset time, so that at least one second target valuable metal component in the solid residue material melts to form a liquid phase, while the base metal and other high-melting-point components remain in a solid phase; the set value of the second preset temperature is higher than the melting point of the second target valuable metal component but lower than the melting point of the base metal; the liquid phase is separated from the solid phase of the base metal by a solid-liquid separation device, to obtain a liquid alloy rich in the second target valuable metal component and a solid phase base metal after secondary purification; Step four, base metal refining step: the solid phase base metal after secondary purification is transferred to the third reaction zone (130) of the multi-zone temperature control reactor (100), and is melted and refined under a third preset temperature and a third preset refining atmosphere, to remove residual impurity elements, and finally obtain a high-purity target base metal.

2. The method for recycling non-ferrous scrap material according to claim 1, wherein In the step one, the non-ferrous metal waste is electronic waste crushed material or alloy chips containing copper as the base metal and associated with valuable metal elements of zinc, lead, tin, indium, and germanium; the first target valuable metal component is zinc, lead, indium, and germanium; the value range of the first preset temperature is 650-850°C.

3. The method of claim 2, wherein, The first preset reaction atmosphere is a sulfidizing atmosphere composed of 5% to 15% by volume of sulfur dioxide, 5% to 20% by volume of carbon monoxide, and the balance of nitrogen; under the sulfidizing atmosphere, zinc, lead, indium, and germanium in the first target valuable metal component undergo in-situ sulfidation reactions to generate corresponding gaseous metal sulfides; the first preset time length is 60 minutes to 120 minutes.

4. The method of claim 2, wherein, The first preset reaction atmosphere is a chlorinating atmosphere composed of 2% to 8% by volume of chlorine and the balance of nitrogen; under the chlorinating atmosphere, zinc, lead, indium, and germanium in the first target valuable metal component undergo in-situ chlorination reactions to generate corresponding gaseous metal chlorides; accordingly, the numerical range of the first preset temperature is adjusted to 400°C to 600°C.

5. The method according to claim 1 or 3, characterized in that, In the second step, the multi-stage fractional condensing system (200) is composed of at least three condensing chambers connected in series, including a first condensing chamber (210), a second condensing chamber (220), and a third condensing chamber (230); the operating temperature of the first condensing chamber (210) is maintained at 700°C to 800°C for condensing and collecting lead sulfide; the operating temperature of the second condensing chamber (220) is maintained at 500°C to 650°C for condensing and collecting indium sulfide and germanium sulfide; the operating temperature of the third condensing chamber (230) is maintained at 300°C to 450°C for condensing and collecting zinc sulfide; each condensing chamber is provided with a collection bin at the bottom with a gas lock valve; the end of the multi-stage fractional condensing system (200) is connected to a bag-type dust collector (240) and an activated carbon adsorption tower (250) for capturing escaping dust and adsorbing and treating tail gas.

6. The method of claim 1, wherein, In the third step, the second target valuable metal component is tin; the numerical range of the second preset temperature is 900°C to 1050°C; the second preset inert atmosphere is nitrogen with a purity of not less than 99.99%, and the flow rate is set to form a micro-positive pressure environment in the second reaction zone (120).

7. The method of claim 6, wherein, The solid-liquid separation device in the third step is a porous graphite crucible (310) structure integrated at the bottom of the second reaction zone (120); the pore size of the porous graphite crucible (310) is 0.5 mm to 1.5 mm; under the second preset temperature, the molten liquid alloy rich in the second target valuable metal component seeps through the pores of the porous graphite crucible (310) due to gravity, while the solid-phase matrix metal is trapped in the upper part of the porous graphite crucible (310); the seeped liquid alloy is collected in a graphite condensing mold (320) arranged below the crucible.

8. The method of claim 6, wherein, The solid-liquid separation device in step three adopts centrifugal separation mechanism; the second reaction zone (120) is a cylindrical furnace body that can rotate at high speed; after the liquid phase is formed in the solid-phase residual material, a driving motor is started to make the cylindrical furnace body rotate at a speed of 300 to 500 revolutions per minute, and by using the density difference between the liquid phase and the solid-phase substrate metal, the phase with larger density is thrown to the inner wall of the furnace body under the action of centrifugal force field, while the phase with smaller density is extruded to the central area, and the liquid phase is discharged through the liquid discharge structure arranged in the central area of the furnace body.

9. The method of claim 1, wherein, In step four, the third reaction zone (130) is an induction melting furnace structure; the third preset temperature is set to 1200 to 1300 DEG C; the third preset refining atmosphere is an oxidizing atmosphere, which is realized by blowing air or oxygen-enriched air into the molten substrate metal melt; the refining process further includes adding a silica-based slagging agent into the melt, and after the refining process is completed, the surface slag is removed by a slagging mechanical arm (410), and then the high-purity substrate metal liquid is poured into a continuous casting system (420).

10. The method of claim 1, wherein, The first reaction zone (110) of the multi-zone temperature control reactor (100) is composed of a nickel-chromium-molybdenum-based high-temperature corrosion-resistant alloy, and the chemical composition of the alloy includes: the chromium content is 20-23wt%, the molybdenum content is 15-17wt%, the iron content is less than 5wt%, the tungsten content is 3.0-4.5wt%, and the balance is nickel; the first reaction zone (110) is provided with a quartz infrared heating module array, and the array is adjusted in power by a central process controller (111) to control the uniformity of the temperature field in the reaction zone, and the temperature control precision reaches ±5 DEG C; the first preset reaction atmosphere is uniformly introduced through the annular porous ceramic gas distributor (112) arranged at the bottom of the first reaction zone (110).

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