Sectional melting recovery method and system for waste electronic products

Abstract

The invention discloses a segmented melting recovery method and system for waste electronic products, and relates to the technical field of solid waste resource utilization and environment-friendly treatment. Performing high-pressure steam cleaning and desorption; softening, melting and separating plastic packaging and an insulating layer; melting and separating the welding flux and the low-melting-point alloy; recovering the residual metal frame and the high-melting-point element; comprehensive utilization and environmental protection control are achieved, aiming at the structural characteristics of the waste electronic products, the method does not depend on strong mechanical crushing, avoids acid-base chemical leaching as much as possible and is mainly achieved through a high-pressure steam segmented melting and physical separation method, the environmental risk is controlled, meanwhile, the separation purity and recovery efficiency of plastic, solder and metal are improved, and the method is suitable for industrial production. And step-by-step physical separation of the plastic packaging layer, the insulating layer, the welding flux and the metal framework is realized through step-by-step heating, step-by-step melting and step-by-step discharging of the melt, so that dust and secondary pollution are reduced.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and environmental protection treatment technology, specifically to a method and system for the segmented melting and recycling of waste electronic products. Background Technology

[0002] With the rapid pace of technological advancements in electronic products such as mobile phones, computers, tablets, and routers, a large amount of discarded electronic products are entering the recycling system. These electronic wastes typically contain various alloy metals, copper foil, solder, and precious metals, as well as large amounts of plastics, epoxy resin encapsulation materials and insulating sheaths, adhesives, flame retardants, and other organic matter. There are two main categories of existing treatment routes for discarded electronic products: one is the mechanical crushing plus physical sorting plus smelting / hydrometallurgical route, and the other is the comprehensive crushing plus steam cleaning plus plastic softening plus circuit board thermal melting separation route. Route 1 involves coarsely crushing or even finely pulverizing the discarded electronic products, and then recovering some metals through magnetic separation, eddy current separation, and specific gravity separation. Afterward, the metals are extracted through pyrometallurgical or hydrometallurgical processes such as acid leaching and cyanidation. Route 2 is more suitable for larger discarded household appliances such as televisions, refrigerators, and washing machines. It involves first crushing the whole product, then cleaning and softening the light components and plastics, and then thermally melting the circuit boards. This method is more effective for cleaning and removing plastics from large-sized casings and circuit boards. However, Route 1 generates a large amount of dust and heavy metal particles during the crushing process, making dust control difficult and requiring complex exhaust gas and wastewater treatment systems, resulting in high operating costs. Hydrometallurgy introduces chemical agents such as acids and alkalis, posing a high risk of secondary pollution. Route 2 has significant problems for small, highly integrated waste electronic products (such as smartphone motherboards, tablet / laptop motherboards, router boards, small appliance control boards, modular electronic components, etc.): tiny components, thin wires, and multilayer boards are easily crushed into fine particles, and metals, plastics, and glass fibers are highly mixed, significantly increasing the difficulty of subsequent separation and generating a large amount of high-value-added metal fine powder, which is not conducive to the recovery of high-value metals and reduces economic efficiency. In order to avoid over-crushing, the crushing intensity is reduced, but it is difficult to balance equipment adaptability and processing efficiency. The process flow of multiple devices connected in series is long, the interfaces are complex, and the system investment is high. It is neither economical nor friendly to small electronic products. In addition, many current electronic waste treatment processes still rely heavily on hydrometallurgical solutions such as acids and alkalis, which brings pressure on secondary pollution control and contradicts the current policy orientation of pollution reduction, carbon reduction and green recycling. Summary of the Invention

[0003] This invention provides a method and system for the segmented melting and recycling of waste electronic products, proposing a recycling technology path that achieves segmented phase change and segmented emission within the same closed pressure reactor. This effectively solves the problems mentioned in the background art, such as the difficulty of dust control, high operating costs, high risk of secondary pollution, easy crushing of micro-components, fine wires, and multilayer boards into fine particles, significantly increasing the difficulty of subsequent separation, hindering the recovery of high-value metals, reducing economic efficiency, and the long process flow and complex interfaces of multiple connected devices, resulting in high system investment and being neither economical nor suitable for small electronic products.

[0004] To achieve the above objectives, this invention provides a segmented melting and recycling method and system for waste electronic products. In the same sealed pressure reactor, waste electronic products are segmented, heated, melted, and separated using a heat carrier medium. This causes different materials to undergo phase changes at different stages and are discharged in segments, achieving resource-based treatment and recycling of waste electronic products. The method includes the following steps: Step S1, preprocessing and sorting; Step S2: Introduce a humid heat medium into the reactor to clean and preheat the waste electronic products. Step S3: Adjust the temperature and pressure inside the reactor to soften and de-stick the plastic materials, insulating materials and / or packaging materials in the waste electronic products and form a mobile phase, which is then discharged through the first melt discharge port located at the bottom of the reactor and collected separately. Step S4: Without replacing the reactor, continue to increase the temperature and pressure inside the reactor to melt the solder or low-melting-point alloy material in the waste electronic products, and discharge it through the second melt discharge port located at the bottom of the reactor and spatially isolated from the first melt discharge port and collect it separately. S5, separate and recycle the remaining metal frame and high-melting-point components; Step S6: Comprehensive utilization and environmental control; In stages S3 and S4, the atmosphere inside the reactor is adjusted by introducing steam and / or inert gas to ensure that the oxygen volume fraction inside the reactor does not exceed a preset threshold. A first melt collection chamber and a second melt collection chamber, which are isolated from each other, are set at the bottom of the reactor and are respectively connected to the corresponding discharge channels. The opening sequence of the first melt discharge port and the second melt discharge port is linked and controlled to achieve segmented melting, segmented discharge and non-mixing recycling of the plastic phase and the solder phase.

[0005] According to the above technical solution, S2 uses a humid heat medium to clean and preheat waste electronic products in order to remove surface contaminants and make the material uniformly heated. S3 adjusts the temperature and pressure inside the reactor to soften and de-stick the plastic materials, insulating materials and / or packaging materials in the waste electronic products, forming a flowable or peelable phase. The phase material is discharged and collected separately through the first melt discharge channel and the first melt discharge port set in the reactor. The operating conditions are to keep the temperature inside the reactor in the range of 150–230℃ and the pressure inside the reactor in the operating window of 0.5–1.6MPa. S4 continues to increase the temperature and pressure inside the reactor without replacing it, causing the solder or low-melting-point alloy material in the waste electronic products to melt. The solder melt is discharged and collected separately through a second melt discharge channel and a second melt discharge port that are spatially separated from the first melt discharge port. The operating conditions are to keep the temperature inside the reactor in the range of 230–320°C and the pressure inside the reactor in the operating window of 1.6–3.5 MPa.

[0006] According to the above technical solution, the humid heat medium is saturated steam, superheated steam, or a combination thereof, and the temperature inside the reactor is the saturation temperature at the corresponding operating pressure or a temperature with a preset superheat based on the saturation temperature.

[0007] According to the above technical solution, the inert gas is selected from one or more of nitrogen, carbon dioxide, and argon. In the second and third stages, the oxygen volume fraction in the reactor is controlled within the range of 0.1–5%, preferably not higher than 3%.

[0008] According to the above technical solution, the reactor is provided with a multi-layer support structure for carrying waste electronic products, and at least two melt collection areas isolated from each other are provided below the support structure, which are respectively connected to the first melt discharge channel and the second melt discharge channel; The supporting structure is a multi-layer perforated support tray with a tray hole diameter of 2–20 mm. The tray is horizontal or has an inclination angle of 1–10° to guide the molten material to flow in a directional manner.

[0009] According to the above technical solution, the opening of the first melt discharge port and the second melt discharge port is automatically controlled based on at least one criterion of temperature, pressure, melt flowability, melt level and / or physical property parameters. The solder or low-melting-point alloy material includes tin-based solder, tin-lead solder, tin-silver-copper solder, bismuth-based solder, or combinations thereof.

[0010] According to the above technical solution, the plastic material, insulating material or encapsulation material includes PVC, PE, PP, ABS, epoxy resin encapsulation material and combinations thereof; The epoxy resin encapsulation material undergoes a softening, thermal debonding, or partial thermal decomposition process in the second stage to reduce its interfacial adhesion with the metal or glass fiber substrate, rather than complete thermal decomposition.

[0011] According to the above technical solution, the heat carrier medium is at least one of steam, heat transfer oil, organic high-boiling-point liquid, or humid hot gas containing water vapor. The heat carrier medium can use different media or combinations of media at different stages to achieve the softening or melting of plastic materials and solder materials in different temperature zones and their segmented discharge.

[0012] According to the above technical solution, the plastic phase discharged from the first melt discharge port is degassed, filtered and molded to form a recycled plastic product; The molten solder discharged from the second melt outlet is cooled, deslag-removed, and graded to form recycled metal products; The waste electronic products include waste circuit boards, electronic components of small household appliances, electronic modules of communication equipment, or combinations thereof.

[0013] According to the above technical solution, a segmented melting and recycling system includes: A sealed pressure reactor, wherein the reactor is provided with a multi-layer support structure, a first melt discharge channel and a second melt discharge channel; The humid heat medium supply unit and the inert gas supply unit are respectively connected to the reactor; The segmented melt collection unit corresponds to the first melt discharge port and the second melt discharge port, respectively; The control unit is used to control the temperature, pressure, oxygen volume fraction, and opening sequence of the first and second melt discharge ports within the reactor.

[0014] Compared with existing technologies, this invention can achieve the step-by-step separation of plastic layers, solder metal and metal skeleton without deep crushing of waste electronic products. It can reduce the loss of dust and fine metal particles, reduce the risk of solder oxidation and secondary pollution, and facilitate the improvement of plastic recycling purity and solder recycling quality, thus having good prospects for industrial application.

[0015] 1. Targeting the structural characteristics of waste electronic products, this method does not rely on strong mechanical crushing, minimizes acid and alkali chemical leaching, and mainly relies on high-pressure steam staged melting and physical separation. While controlling environmental risks, it improves the separation purity and recycling efficiency of plastics, solders, and metals. It is particularly suitable for small and medium-sized electronic products such as mobile phones and computer motherboards. Without relying on strong mechanical crushing and chemical leaching agents, it achieves the step-by-step physical separation of plastic encapsulation layer, insulation layer, solder, and metal skeleton through staged heating, staged melting, and staged discharge of melt, reducing dust and secondary pollution. By integrating high-pressure steam cleaning, plastic melting, and solder melting into a single closed high-pressure reactor system, the energy loss and cross-contamination caused by multiple devices connected in series are reduced. The system has a compact structure and simplified operation process, complementing existing waste appliance and waste plastic treatment routes. While existing systems are suitable for large appliances, large casings, and large circuit boards, this system focuses on waste electronic product modules, boards, and highly integrated small circuit boards, extending and supplementing the field of refined, small-scale, and high-value-added metal recycling.

[0016] 2. By adopting a disassembly and modular feeding method, the circuit board and module structure are kept as intact as possible. Only necessary size adaptation is performed to avoid fine fragmentation, which greatly reduces the amount of heavy metal dust generated, improves operational safety and environmental friendliness. The plastic melt and solder melt are separated in two different temperature and pressure sections, and the discharge is completed in stages in time and space to avoid mixing of plastic and solder. This is conducive to the high purity and classified recycling of recycled plastic and solder metal, and increases the added value of materials. Compared to the traditional approach of connecting multiple devices in series, this method reduces the number of devices and floor space by performing high-pressure steam cleaning, plastic melting, and solder melting in the same reactor in stages. It is suitable for processing small and medium-sized, highly integrated electronic components such as mobile phone motherboards, laptop motherboards, and router boards. The reaction process takes place in a closed reactor, and the temperature, pressure, and oxygen content are monitored and interlocked. Through condensate recovery, wastewater, and exhaust gas treatment units, it can better meet environmental emission requirements. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0018] In the attached diagram: Figure 1 This is a process flow diagram of the recycling method of the present invention; Figure 2 It is a process flow diagram of the traditional crushing and humidification metallurgical route; Figure 3 This is a schematic diagram of the composition of the recycling system of the present invention; Figure 4 This is a schematic diagram of the composition of the high-pressure steam segmented melting reactor of the present invention; The diagram is labeled as follows: 1. Feeding and pretreatment unit; 2. High-pressure steam segmented melting reactor; 3. Steam generation and atmosphere control unit; 4. Plastic melt collection and regeneration unit; 5. Solder melt collection and metal separation unit; 6. Condensation and wastewater treatment unit; 7. Waste gas purification unit one; 8. Waste gas purification unit two. 201. Outer shell of the vessel; 202. Tray; 203. Steam nozzle; 204. Plastic melting outlet; 205. Solder melting outlet; 206. Feeding pipeline. Detailed Implementation

[0019] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0020] Example 1: As Figure 1 As shown, this invention provides a technical solution: a method for the segmented melting and recycling of waste electronic products. This method utilizes high-pressure steam to physically melt and separate waste electronic products in segments, achieving resource recovery from waste electronic products. The method includes the following steps: Step S1, preprocessing and sorting; Step S2, high-pressure steam cleaning and desorption; Step S3: Softening, melting and separation of the plastic encapsulation and insulating layer; Step S4: Melting and separation of solder and low-melting-point alloy; Step S5: Recycle the remaining metal frame and high-melting-point components; Step S6: Comprehensive utilization and environmental control; Explanation of the state of the humid heat medium (steam) The "high-pressure steam / humid heat medium" referred to in this invention includes saturated steam, superheated steam, or a combination of both. The system can adopt a control method that uses pressure as the main control variable and temperature as the corresponding saturation temperature or a superheated temperature ΔT based on the saturation temperature, or it can adopt a control method that uses temperature as the main control variable and pressure is maintained within the operating window by a back pressure valve. The above description aims to illustrate that the key to this invention does not rely on a fixed "temperature-pressure" combination, but rather on achieving rapid, uniform, and controllable heat transfer and phase regulation through a humid heat medium within a closed vessel, thereby supporting the process objectives of segmented softening / de-viscosity and segmented melting discharge.

[0021] Description of phase changes in encapsulation materials Waste electronic products contain thermoplastics, thermosetting resins (such as epoxy encapsulation / solder resist materials), and composite materials. The "softening, de-adhesion, and formation of a flowable or peelable phase" referred to in this invention includes: the softening and flowability of thermoplastic materials; and the process by which thermosetting encapsulation materials undergo glass transition, interfacial de-adhesion, and the formation of a peelable adhesive phase / thermally softened phase, or undergo slight pyrolysis under a certain temperature and pressure atmosphere, resulting in a significant decrease in their interfacial adhesion to the metal or glass fiber substrate. It should be understood that this invention does not require the thermosetting material to undergo complete melting or complete thermal decomposition, but emphasizes the formation of a "separable phase" in the second stage to achieve efficient desorption and separation from the substrate.

[0022] Explanation of the mechanism of segmented melting and segmented discharge This invention utilizes segmented temperature and pressure zones within a single sealed pressure reactor to allow different components in waste electronic products to sequentially enter separable phases based on their thermal response differences. In the second stage, plastic / insulating / encapsulating materials are preferentially softened and de-adhesive, converging along a flow guide structure and discharged through a first discharge channel. Subsequently, in the third stage, the temperature is further increased, causing solder or low-melting-point alloys to enter a molten flow state and converge along an independent channel, being discharged through a second discharge channel. Because the first and second discharge channels are spatially isolated within the reactor, and with the coordination of discharge timing, liquid level / temperature criteria, and valve interlocking control, segmented recycling where the plastic phase and molten metal do not mix can be achieved under the same reactor conditions. This significantly improves recycling purity and reduces the burden of subsequent sorting.

[0023] Synergistic effect of humid heat medium and inert atmosphere The humid heat medium, with its high heat transfer coefficient and strong permeability within a closed reactor, can rapidly and uniformly heat multi-layered stacked electronic product materials, reducing the risk of localized overheating and coking. Inert gas or a controlled low-oxygen atmosphere can inhibit the oxidation and combustion of organic matter, reducing the tendency for secondary pollution from flue gas and lowering the probability of solder oxidation into metallic slag, thus facilitating the acquisition of higher-purity solder recycling products. The synergy of these two factors results in more stable phase transitions, more controllable emissions, and higher system safety.

[0024] Internal support and flow guiding structure of the reactor The reactor interior is equipped with a multi-layer support structure for holding waste electronic products, preferably a detachable multi-layer perforated support tray or grid shelf, to achieve the following: (1) The humid heat medium and the inert gas can penetrate the material layer from multiple directions to achieve uniform heat transfer; (2) The softened phase / colloidal phase / molten plastic generated in the second stage (S3) can pass through the filter pores and converge downwards under the action of gravity; (3) The solid skeleton (such as copper foil, fiberglass board, steel parts, etc.) is effectively supported to prevent sinking and blocking the discharge channel.

[0025] The carrier tray can be equipped with an inclination angle or guide ribs to direct the flow phase to a designated collection cavity area, reducing retention and adhesion.

[0026] 6. Segmented melt collection chamber and dual discharge channels The lower part of the reactor is provided with at least two isolated melt collection chambers, forming a "plastic phase collection chamber" and a "solder melt collection chamber" respectively. An isolation baffle / flow-blocking structure or a stepped flow-guiding structure is provided between the two to suppress backflow and mixing.

[0027] The plastic phase collection chamber is connected to the first melt discharge port through the first melt discharge channel; the solder melt collection chamber is connected to the second melt discharge port through the second melt discharge channel. The first discharge channel and the second discharge channel are arranged separately in the internal space of the reactor and can be equipped with check valves, temperature barriers or heat insulation sections to reduce secondary disturbance to the plastic phase residue during the third stage heating process and further improve the purity of the staged recovery.

[0028] Temperature-pressure-oxygen content coordinated control The system control unit is used for closed-loop regulation of the temperature, pressure, oxygen volume fraction, and steam / inert gas supply within the reactor. Preferably, the reactor is equipped with temperature sensors, pressure sensors, and oxygen content sensors. The control unit executes the following control logic based on a preset segmented process curve: (1) First stage (S2): Establish stable pressure and wet heat flow to achieve uniform preheating and cleaning; (2) Second stage (S3): Adjust the temperature / pressure to the point where the plastic phase and the encapsulation material enter the softening and de-adhesion range, and maintain a low oxygen threshold; (3) Third stage (S4): After the second stage is completed and emission verification is performed, continue to heat up to the solder melting zone and maintain a low oxygen threshold.

[0029] The low oxygen threshold can be set to ≤5%, preferably ≤3% or ≤2%, to suppress oxidation reaction and combustion risk.

[0030] Dual emission port interlock control and criteria The first and second melt discharge ports are interlocked to ensure a "plastic phase first, solder phase later" sequence: when the second stage reaches the softening / flowing phase formation conditions and the liquid level, flowability, or temperature of the plastic phase collection chamber meets the discharge criteria, the first discharge port is opened for discharge. After discharge, a discharge confirmation step is initiated (e.g., the liquid level falls below the threshold, the discharge channel temperature drops, or the flow rate becomes zero), before the third stage is allowed to proceed and the second discharge port is opened. This interlocking strategy prevents plastic residue from being trapped or causing mixing during the third stage solder melt discharge.

[0031] Safety Interlocks and Abnormal Handling When excessive oxygen content, excessive pressure, abnormal temperature rise, or a tendency for the discharge channel to become blocked are detected, the control unit executes safety interlock strategies, including: automatically cutting off the heating / steam supply, increasing inert gas replacement, opening the safety pressure relief valve, prohibiting the discharge valve from opening, or switching to a cooling and pressure-maintaining mode, in order to reduce the risk of accidents and protect the safety of equipment and personnel.

[0032] Inserted paragraph: Exhaust gas and condensate treatment and resource recycling After the humid heat medium exchanges heat with the material inside the reactor, it forms exhaust gas and condensate. The system can be equipped with condensation and gas-liquid separation units to condense and recover water vapor and condensable components carried in the exhaust gas, and further purify it through demisting, filtration, or adsorption. The condensate can be sent to a wastewater treatment or circulating water system; the exhaust gas, after meeting emission requirements, can be discharged or reused in the preheating unit. Through gas-liquid separation and purification reuse, the risk of odor and secondary pollution can be reduced, and the efficiency of energy and water resource utilization can be improved.

[0033] Principles for setting segmented temperature and pressure parameters The temperature and pressure settings for the second and third stages are not limited to a single fixed point, but are determined based on the principle of "achieving the target phase change while maintaining stable heat transfer and safety boundaries." Specifically, the second stage aims to induce the plastic / insulating / encapsulating materials into a softening, de-sticking, or separable phase; the third stage aims to induce the solder or low-melting-point alloy to melt and flow stably. The system can employ either pressure-based or temperature-based control strategies, and achieve stable control within the operating window through back pressure valves, steam flow regulation, and inert gas replacement. Those skilled in the art can select appropriate temperature and pressure curves based on different categories of waste electronic products, solder types, and material loading quantities, while adhering to the above principles.

[0034] Example 2: Based on the above technical solution, S1, collect waste electronic products, including waste smartphone motherboards; The motherboards of discarded smartphones are pre-processed by manual disassembly, removing the battery, screen, and large metal casing, leaving only the motherboard and a few small modules. Furthermore, during the pretreatment process, the waste smartphone motherboards need to be purged, cleaned, and dried. After treatment, they are framed and placed into the subsequent reaction vessel. The specific material to be placed into the reaction vessel is the smartphone motherboard, which includes multilayer boards and small components. The smartphone motherboard weighs 100 kg. Based on the above technical solution, in step S2, the pre-treated waste smartphone motherboards are placed on multi-layer perforated support trays inside the high-pressure steam segmented melting reactor. Multi-layer stacking can be used to achieve a loading rate of 60% for the reactor. After placing the discarded smartphone motherboard into the reactor, close the lid and introduce saturated steam to bring the reactor to the first set condition, as follows: Temperature T1: 120℃, pressure P1: 0.5MPa, holding time: 20min; During this stage, high-pressure steam primarily removes surface oil, flux residue, and dust, and softens some low-melting-point adhesives and thin-film substances. Simultaneously, the condensate flow carries away the desorbed contaminants. The resulting condensate is collected by a condensation device and enters the wastewater treatment unit after the COD of the condensate drops below 1000 mg / L. The wastewater treatment unit performs oil-water separation, sedimentation filtration and biochemical treatment, and discharges the wastewater after it meets the treatment standards.

[0035] Based on the above technical solution, in step S3, after completing step S2, the reactor is kept in a sealed state, and the temperature continues to rise within the same reactor to enter the second stage of heat treatment conditions, as follows: Temperature T2: 190℃, pressure P2: 1.5MPa, mainly high-pressure steam, inert gas can be added to control oxygen volume fraction ≤3%, nitrogen is selected as the inert gas, and the holding time is 30min; During this stage, the plastic encapsulation, some potting compound, and cable insulation layer of the waste smartphone motherboard soften and melt significantly. Through the holes on the tray and the flow guiding structure set inside the reactor, the softened and melted plastic flows downward under the action of gravity and a small pressure difference, and enters the plastic melt collection chamber. The plastic melt is discharged through the first set of melt discharge ports under liquid level control. After vacuum degassing and filtration, it is cooled and granulated to serve as a raw material for recycled plastics.

[0036] Based on the above technical solution, in step S4, after the plastic melt is discharged, the waste smartphone motherboards still remaining on the tray are heated to the third stage conditions in the same reactor, as follows: Temperature T3: 260℃, pressure P3: 2.5MPa, atmosphere: a mixture of high-pressure steam and nitrogen to ensure that the oxygen volume fraction in the reactor is ≤1.5%, and the holding time is 30min; During this stage, the solder and lead-tin solder alloy on the circuit board reach a molten state and flow down from the metal connection parts. Some aluminum alloy and zinc alloy components will also partially melt and loosen, which is conducive to subsequent separation. The molten solder is guided to the solder melt collection tank through the second set of melt guide channels and discharge ports arranged inside. The segmented cooling structure can be set according to density and cooling rate to achieve the initial differentiation of different alloy components such as tin-rich phase and lead-rich phase.

[0037] Based on the above technical solution, S5, after step S4 is completed, stop the steam supply, cool down and depressurize, reduce the temperature of the reactor to a safe opening temperature, not higher than 80°C, open the reactor lid, and take out the remaining materials on the support tray, mainly including residual copper foil, connector metal parts, iron parts, and high melting point components. The residues were then subjected to further physical sorting, specifically magnetic separation and eddy current separation to distinguish between ferromagnetic metals and non-ferrous metals. Statistical analysis of the sieve results showed that the copper content increased to over 80%. The high-metal-content material was then sent to pyrometallurgical refining for further purification.

[0038] Based on the above technical solution, in S6, the steam condensate generated in each stage is recovered by the condenser and recycled as boiler makeup water to reduce the consumption of fresh water. The condensate containing organic matter is discharged in compliance with standards after oil-water separation, sedimentation, filtration, and necessary biological treatment. A small amount of non-condensable gas generated at the top of the reactor and the tail of the system is introduced into the exhaust gas purification unit to meet the emission standards. The non-condensable gas is organic vapor. The exhaust gas purification unit includes condensation and adsorption. Throughout the recycling process, compared to the traditional crushing and humidification metallurgical route, such as Figure 2 As shown, this method does not introduce strong acid, strong alkali solutions, or cyanide hydrometallurgical reagents throughout the process. It mainly relies on high-pressure steam and physical segmented melting to achieve separation and recovery, which helps to reduce the risk of secondary pollution.

[0039] This embodiment uses waste circuit boards (PCBs) as the processing target. After pretreatment, obviously non-target large components (such as heat sinks and casings) are removed from the waste circuit boards, and their dimensions are adjusted to fit the filling space of the multi-layer support trays inside the reactor. The material is dispersed and laid on three layers of perforated support trays, with tray perforations of 5–12 mm in diameter and trays tilted at a 2–6° angle to facilitate flow. The filling amount is 30–55% (preferably about 40–50%) of the effective volume of the reactor, ensuring that the humid and hot medium can penetrate the material layer.

[0040] The filled tray assembly is placed into a sealed pressure reactor, the reactor door is closed, and inert gas purging is performed to reduce the oxygen volume fraction inside the reactor to a preset threshold (e.g., ≤3%). Then, the process is operated in stages: First stage (S2) (wet heat cleaning and uniform preheating): Wet heat medium is introduced to make the pressure inside the vessel enter the first operating window and maintain it for a certain time, so that oil / dust and other contaminants on the surface of the material are peeled off and carried out with the condensate, while uniform preheating is achieved at the same time. • Second stage (S3) (Softening and de-adhesion of plastic / encapsulation materials and first discharge): Adjust the temperature and pressure to enter the second operating window, causing the plastic, insulating layer or encapsulation material to soften and de-adhere, forming a flowable or peelable phase. The softened phase collects along the guide structure into the plastic phase collection chamber. When the liquid level / temperature or discharge flow rate in the first collection chamber meets the discharge criteria, the first melt discharge port is opened for discharge and collected separately. After the discharge is completed, discharge confirmation is performed (liquid level drops, flow rate is zero or discharge port temperature drops below the threshold). • Third stage (S4) (solder melting and second discharge): After the discharge is confirmed, continue to heat up and pressurize to enter the third operating window, so that the solder enters a stable molten flow state and gathers into the solder melt collection chamber; when the second collection chamber meets the discharge criteria, open the second melt discharge port to discharge the solder melt and collect it separately.

[0041] In this embodiment, the solder system is Sn-Ag-Cu (SAC) type lead-free solder. Through "segmented operation in the same reactor + dual collection chambers / dual discharge ports + discharge interlock" control, a recycled product in which the plastic phase and solder do not mix can be obtained; the solid skeleton (such as fiberglass board / copper foil) can be taken out as solid residue from the solid discharge end of the reactor after the third stage and enter the subsequent metal sorting process.

[0042] Tests showed that the impurity content of the recycled plastic product obtained from the first melt discharge port was no higher than 5%, and the mass proportion of solder components entering the plastic phase was no higher than 2%; the proportion of non-metallic inclusions in the recycled solder metal product obtained from the second melt discharge port was no higher than 3%. This indicates that the present invention can achieve high-purity separation of plastic materials and solder materials.

[0043] Example 3: Based on the above technical solution, S1, collect waste electronic products, including computer motherboards and router boards; Pre-processing of computer motherboards and router boards involves manual disassembly to remove batteries, screens, and large metal casings, leaving only the motherboard and a few small modules. Furthermore, during the pretreatment process, the computer motherboard and router board need to be purged, cleaned, and dried. After treatment, they are framed and placed into the subsequent reaction vessel. The material is a mixture of computer motherboard and router board, with 70 kg of computer motherboard and 30 kg of router board.

[0044] Based on the above technical solution, in step S2, the pre-treated computer motherboard and router board are placed on a multi-layer perforated support tray inside the high-pressure steam segmented melting reactor. The multi-layer stacking method can be adopted to achieve a loading rate of 60% for the reactor. After inserting the computer motherboard and router board, close the lid of the reactor and introduce saturated steam to bring the reactor to the first set condition, as follows: Temperature T1: 120℃, pressure P1: 0.5MPa, holding time: 25min; During this stage, high-pressure steam primarily removes surface oil, flux residue, and dust, and softens some low-melting-point adhesives and thin-film substances. Simultaneously, the condensate flow carries away the desorbed contaminants. The resulting condensate is collected by a condensation device and enters the wastewater treatment unit after the COD of the condensate drops below 1000 mg / L. The wastewater treatment unit performs oil-water separation, sedimentation filtration and biochemical treatment, and discharges the wastewater after it meets the treatment standards.

[0045] Based on the above technical solution, in step S3, after completing step S2, the reactor is kept in a sealed state, and the temperature continues to rise within the same reactor to enter the second stage of heat treatment conditions, as follows: Temperature T2: 200℃, pressure P2: 1.5MPa, mainly high-pressure steam, inert gas can be added to control oxygen volume fraction ≤3%, nitrogen is selected as the inert gas, and the holding time is 40min; During this stage, the plastic encapsulation, some potting compound, and cable insulation of the computer motherboard and router boards soften and melt significantly. Through the holes on the tray and the flow guiding structure set inside the reactor, the softened and melted plastic flows downward under the action of gravity and a small pressure difference, and enters the plastic melt collection chamber. The plastic melt is discharged through the first set of melt discharge ports under liquid level control. After vacuum degassing and filtration, it is cooled and granulated to serve as a raw material for recycled plastics.

[0046] Based on the above technical solution, in step S4, after the plastic melt is discharged, the computer motherboard and router board still remaining on the tray are heated to the third stage condition in the same reactor, as follows: Temperature T3: 270℃, pressure P3: 2.5MPa, atmosphere: a mixture of high-pressure steam and nitrogen to ensure that the oxygen volume fraction in the reactor is ≤1.5%, and the holding time is 20min; During this stage, the solder and lead-tin solder alloy on the circuit board reach a molten state and flow down from the metal connection parts. Some aluminum alloy and zinc alloy components will also partially melt and loosen, which is conducive to subsequent separation. The molten solder is guided to the solder melt collection tank through the second set of melt guide channels and discharge ports arranged inside. The segmented cooling structure can be set according to density and cooling rate to achieve the initial differentiation of different alloy components such as tin-rich phase and lead-rich phase.

[0047] Based on the above technical solution, S5, after step S4 is completed, stop the steam supply, cool down and depressurize, reduce the temperature of the reactor to a safe opening temperature, not higher than 80°C, open the reactor lid, and take out the remaining materials on the support tray, mainly including residual copper foil, connector metal parts, iron parts, and high melting point components. The residues were then subjected to further physical sorting, specifically magnetic separation and eddy current separation to distinguish between ferromagnetic metals and non-ferrous metals. Statistical analysis of the sieve results showed that the copper content increased to over 80%. The high-metal-content material was then sent to pyrometallurgical refining for further purification.

[0048] Based on the above technical solution, in S6, the steam condensate generated in each stage is recovered by the condenser and recycled as boiler makeup water to reduce the consumption of fresh water. The condensate containing organic matter is discharged in compliance with standards after oil-water separation, sedimentation, filtration, and necessary biological treatment. A small amount of non-condensable gas generated at the top of the reactor and the tail of the system is introduced into the exhaust gas purification unit to meet the emission standards. The non-condensable gas is organic vapor. The exhaust gas purification unit includes condensation and adsorption. Throughout the recycling process, compared to the traditional crushing and humidification metallurgical route, such as Figure 2 As shown, this method does not introduce strong acid, strong alkali solutions, or cyanide hydrometallurgical reagents throughout the process. It mainly relies on high-pressure steam and physical segmented melting to achieve separation and recovery, which helps to reduce the risk of secondary pollution. As can be seen from Examples 1 and 2, Examples 1 and 2 respectively process waste smartphone motherboards, computer motherboards and router boards. In the specific processing, the parameters of the cleaning section, plastic melting section and solder melting section are optimized to adapt to different board thicknesses and solder types, so as to stably separate different waste electronic products. like Figure 3-4 As shown, a segmented melting and recycling system for waste electronic products achieves segmented continuous processing of cleaning, plastic melting, and solder melting through an integrated high-pressure steam reactor. The temperature, time, and pressure can be adjusted according to different types of waste electronic products. It includes a feeding and pretreatment unit, a high-pressure steam segmented melting reactor, a steam generation and atmosphere control unit, a plastic melt collection and regeneration unit, a solder melt collection and metal separation unit, a condensation and wastewater treatment unit, an exhaust gas purification unit one, and an exhaust gas purification unit two.

[0049] Based on the above technical solution, the feeding and pre-treatment unit includes a disassembly workbench, a conveying device, and a pre-cleaning and drying device, which are used to disassemble waste electronic products, remove batteries and large shells, form electronic product modules of suitable size, and convey them to the loading port of the high-pressure steam reactor. The high-pressure steam staged melting reactor is a vertical, closed pressure vessel, and its internal components include the following: The vessel features a multi-layer perforated support tray structure, an internal guide plate, and segmented melt collection chambers. The segmented melt collection chambers include a plastic melt collection chamber and a solder melt collection chamber. It also includes multiple steam injection ports, an inert gas inlet, a first melt discharge port, and a second melt discharge port. The first melt discharge port corresponds to the plastic melt collection chamber, and the second melt discharge port corresponds to the solder melt collection chamber. A jacketed heating system is also provided on the outside of the vessel to regulate the heating rate in conjunction with the steam supply. The steam generation and atmosphere control unit includes a steam boiler, superheater, pressure regulating valve, flow meter and steam delivery pipeline. It is equipped with an inert gas inlet pipeline. The oxygen volume fraction in the reactor is regulated by the flow control valve and mixer to ensure that the oxygen content is controlled within the set safe range during the plastic melting and solder melting stages. The plastic melt collection and recycling unit is connected to the first melt discharge port and includes a plastic melt buffer tank, a vacuum degassing device, and a filtration, cooling and pelletizing device for preparing recycled plastic pellets.

[0050] Based on the above technical solution, the solder melt collection and metal separation unit is connected to the second melt discharge port, including a solder melt collection tank and a segmented cooling tank, which are used to initially separate alloys of different components by utilizing the difference in density and freezing point, and the interface is connected to the downstream metal refining equipment. The condensation and wastewater treatment unit is used to treat the condensate from the top of the reactor and the condensate containing oil and organic matter, including a condenser, an oil-water separator, a sedimentation and filtration device, and a biological treatment unit; The condenser is used to condense steam into liquid, the oil-water separator and sedimentation filter are used to separate suspended solids and oil phase, and the biological treatment unit is used to further reduce the concentration of organic matter to achieve emission standards. The exhaust gas purification unit treats small amounts of uncondensed organic vapors and other volatile components, including a condenser, activated carbon adsorption device, and catalytic oxidation device. The second exhaust gas purification unit is equipped with temperature, pressure, oxygen content, steam flow, and liquid level sensors. The PLC controls the temperature, pressure, time, steam and inert gas flow, and melt discharge sequence of the three stages in a coordinated manner. It also has safety interlock protection functions for over-temperature, over-pressure, and excessive oxygen content.

[0051] In the above embodiments, using high-pressure steam as a humid heat medium to heat and clean waste electronic products is only a preferred solution. Those skilled in the art will understand that the heating medium used to achieve the segmented softening, segmented melting, and phase regulation in this invention is not limited to steam. It can also be a heat carrier medium with similar heat transfer and temperature control capabilities, such as heat transfer oil, organic high-boiling-point liquid, or water-containing humid heat gas. As long as the heating medium can soften or melt the plastic material and solder material in different temperature zones under controlled oxygen content, and achieve segmented discharge and separate collection through different melt discharge channels, it belongs to the equivalent alternative of this invention and should be considered to fall within the protection scope of this invention.

[0052] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of staged smelting recycling of waste electronic products, characterized by: In the same sealed pressure reactor, the waste electronic products are subjected to segmented heating, melting and separation by using a heat carrier medium in a physical manner, so that different materials change phase in different stages and are discharged in segments, thereby realizing the recycling of waste electronic products, including the following steps: Step S1, pretreatment and sorting; Step S2, introducing a wet heat medium into the reactor to clean and preheat the waste electronic products; Step S3, adjusting the temperature and pressure in the reactor to make the plastic material, insulating material and / or packaging material in the waste electronic products soften, lose adhesion and form a flowable phase, and then discharging and collecting the phase through a first melt discharge port arranged at the lower part of the reactor; Step S4, without replacing the reactor, continuously increasing the temperature and pressure in the reactor to make the solder or low-melting-point alloy material in the waste electronic products melt, and then discharging and collecting the solder melt through a second melt discharge port arranged at the lower part of the reactor and spaced from the first melt discharge port; S5, separating and recycling the remaining metal frame and high-melting-point elements; Step S6, comprehensive utilization and environmental protection control; In the S3 and S4 stages, the oxygen volume fraction in the reactor is not higher than a preset threshold by introducing steam and / or inert gas into the reactor to adjust the atmosphere in the reactor, the first melt collection cavity and the second melt collection cavity are arranged at the lower part of the reactor and are isolated from each other, are respectively communicated with the corresponding discharge channels, and the opening time sequence of the first melt discharge port and the second melt discharge port is controlled in linkage, so that the plastic phase and the solder phase are subjected to segmented melting, segmented discharging and mutual non-mixing recycling.

2. A method of fractional melting recycling of waste electronic products according to claim 1, characterized in that: The S2 cleans and preheats the waste electronic products by using a wet heat medium to remove surface contaminants and make the whole material evenly heated; S3 adjusts the temperature and pressure in the reactor to make the plastic material, insulating material and / or packaging material in the waste electronic products soften, lose adhesion, form a flowable phase or a peelable phase, and then discharges and collects the phase through a first melt discharge channel and a first melt discharge port arranged in the reactor, and the operating conditions are that the temperature in the reactor is in the range of 150-230℃, and the pressure in the reactor is in the operating window of 0.5-1.6MPa; S4, without replacing the reactor, continuously increasing the temperature and pressure in the reactor to make the solder or low-melting-point alloy material in the waste electronic products melt, and then discharging and collecting the solder melt through a second melt discharge channel and a second melt discharge port arranged separately from the first melt discharge port, and the operating conditions are that the temperature in the reactor is in the range of 230-320℃, and the pressure in the reactor is in the operating window of 1.6-3.5MPa.

3. A method of fractional melting recycling of waste electronic products according to claim 2, characterized in that: The wet heat medium is saturated steam, superheated steam or a combination thereof, and the temperature in the reactor is the saturation temperature under the corresponding operating pressure or a temperature with a preset superheat degree based on the saturation temperature.

4. A method of fractional melting of waste electronic products according to claim 1, characterized in that: The inert gas is selected from one or more of nitrogen, carbon dioxide and argon, and the oxygen volume fraction in the reactor in the second and third stages is controlled in the range of 0.1-5%, preferably not higher than 3%.

5. A method for the fractional melting recycling of waste electronic products according to claim 1, characterized in that: The reactor is provided with a multi-layer support structure for carrying waste electronic products, and at least two isolated melt collection areas are provided below the support structure, which are respectively connected to the first melt discharge channel and the second melt discharge channel. The supporting structure is a multi-layer perforated support tray with a tray hole diameter of 2–20 mm. The tray is horizontal or has an inclination angle of 1–10° to guide the molten material to flow in a directional manner.

6. A method of fractional melting recycling of waste electronic products as claimed in claim 1 wherein: The opening of the first melt discharge port and the second melt discharge port is automatically controlled based on at least one criterion of temperature, pressure, melt flowability, melt level and / or physical property parameters; The solder or low-melting-point alloy material includes tin-based solder, tin-lead solder, tin-silver-copper solder, bismuth-based solder, or combinations thereof.

7. A method of fractional melting recycling of waste electronic products as claimed in claim 2, wherein: The plastic material, insulating material, or encapsulation material includes PVC, PE, PP, ABS, epoxy resin encapsulation material, and combinations thereof; The epoxy resin encapsulation material undergoes a softening, thermal debonding, or partial thermal decomposition process in the second stage to reduce its interfacial adhesion with the metal or glass fiber substrate, rather than complete thermal decomposition.

8. A method of fractional melting recycling of waste electronic products as claimed in claim 1 wherein: The plastic phase discharged from the first melt discharge port is degassed, filtered, and molded to form recycled plastic products. The molten solder discharged from the second melt outlet is cooled, deslag-removed, and graded to form recycled metal products; The waste electronic products include waste circuit boards, electronic components of small household appliances, electronic modules of communication equipment, or combinations thereof.

9. A method of fractional melting recycling of waste electronic products as claimed in claim 1 wherein: The heat carrier medium is at least one of steam, heat transfer oil, organic high-boiling-point liquid, or humid hot gas containing water vapor. The heat carrier medium can use different media or combinations of media at different stages to achieve the softening or melting of plastic materials and solder materials in different temperature zones and their segmented discharge.

10. A staged smelting recovery system for carrying out the method of any one of claims 1 - 9, characterized in that, include: A sealed pressure reactor, wherein the reactor is provided with a multi-layer support structure, a first melt discharge channel and a second melt discharge channel; The humid heat medium supply unit and the inert gas supply unit are respectively connected to the reactor; The segmented melt collection unit corresponds to the first melt discharge port and the second melt discharge port, respectively; The control unit is used to control the temperature, pressure, oxygen volume fraction, and opening sequence of the first and second melt discharge ports in the reactor. The control unit communicates with temperature sensors, pressure sensors, oxygen volume fraction sensors, and liquid level sensors to perform closed-loop regulation and safety interlock control of the process.

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