Environment-friendly smelting system for waste circuit board

Abstract

This invention provides an environmentally friendly smelting system for waste circuit boards, which maintains high production capacity while meeting environmental protection requirements for production and processing. It utilizes an environmentally friendly smelting furnace to process waste circuit boards. Waste circuit boards, along with auxiliary materials, are continuously fed into the furnace cavity from the top inlet. Combustion air is blown in from the bottom air inlet, and the fuel undergoes high-temperature combustion near the air inlet, forming a high-temperature smelting zone. In the charge column zone, the charge undergoes preheating, pyrolysis, sintering, and melting reactions sequentially from top to bottom. After being reduced and melted, the metal in the smelting zone undergoes vertical movement from top to bottom, during which metal droplets aggregate and grow, separating from the slag, thus completing the separation and recovery of the metal.

Description

Technical Field

[0001] This utility model relates to the field of pyrometallurgical smelting technology for solid waste and hazardous waste, specifically to an environmentally friendly smelting system for waste circuit boards. Background Technology

[0002] Common sources of circuit boards in daily life include discarded household appliances, base stations, car motherboards, computer motherboards, and other electronic devices. After dismantling and pre-processing, the electronic components have been removed from these waste circuit boards, leaving only bare boards in sheet or block form. As waste rich in precious metals such as copper, tin, gold, and silver, the extraction of these metals through resource recovery methods can yield significant resource benefits and generate substantial profits.

[0003] The main methods for treating waste circuit boards currently include physical-mechanical treatment, pyrometallurgical treatment, chemical treatment, and biological treatment technologies. Among these, pyrometallurgical treatment is the most common method. Pyrometallurgical treatment typically involves feeding sheet or block-shaped circuit boards into a combustion furnace to burn off the organic matter and recover the remaining metals. However, the large-scale circuit board combustion furnaces used in existing pyrometallurgical technologies are usually open-top furnaces. The circuit boards are mixed with coal or coke and then fed into the furnace chamber. An ignition device inside the furnace allows the mixture to burn with an open flame, and then a gas collection hood at the top directs the high-temperature flue gas into a downstream flue gas treatment system. However, most existing incinerators are open-type incinerators, resulting in heat loss into the environment, leading to high heat loss and failing to meet the environmental protection requirements for current equipment use. Summary of the Invention

[0004] To address the issues of high heat loss and non-compliance with environmental protection requirements in existing pyrometallurgical waste circuit board processing systems, this invention provides an environmentally friendly waste circuit board smelting system that maintains high production capacity while meeting environmental protection requirements for production and processing.

[0005] The structure of this utility model is as follows: an environmentally friendly smelting system for waste circuit boards, comprising: an incineration device and a flue gas treatment system, characterized in that: the incineration device is based on an environmentally friendly smelting furnace; a secondary combustion chamber and a waste heat recovery device are provided between the incineration device and the flue gas treatment system;

[0006] The environmentally friendly smelting furnace includes: a furnace body and a bottom bed arranged from top to bottom, wherein the bottom bed is a movable bottom bed and is movably installed below the furnace body;

[0007] The inner cavity of the environmentally friendly smelting furnace is arranged from top to bottom as a feeding port, a material column area, a smelting area, and a layered area; air inlets are evenly arranged on the side wall of the smelting area, and the air inlets are connected to an external air supply device;

[0008] A flue gas outlet is provided on the upper side of the furnace body, and the flue gas outlet is connected to the secondary combustion chamber; the flue gas outlet of the secondary combustion chamber is connected to the waste heat recovery equipment, the waste heat recovery equipment is connected to the flue gas treatment system, and the flue gas treatment system is connected to the chimney;

[0009] The flue gas treatment system includes: an SNCR denitrification structure, a quench tower, a bag filter, a wet acid removal device, and an SGH heat exchanger connected in sequence.

[0010] Its further features are:

[0011] The base bed includes: a bed frame and rollers disposed at the bottom of the bed frame; the top of the bed frame has a groove as a layered area;

[0012] The furnace body is mounted on top of the base bed based on the mounting base. A channel for the base bed is provided within the inner cavity of the mounting base, forming a U-shaped cross-section in the vertical direction. A channel opening, adapted to the dimensions of the furnace body's inner cavity, is opened above the channel at a corresponding position to connect the furnace body's inner cavity and the layered areas of the base bed. The base bed is movably disposed within the channel. A guide block is provided at the top of the inner cavity of the mounting base, with its length aligned with the sliding direction of the base bed. A guide groove is provided above the base bed, and the dimensions of the guide block and the guide groove are adapted to each other.

[0013] A settling chamber is provided between the environmentally friendly smelting furnace and the secondary combustion chamber;

[0014] The wet deacidification equipment includes a primary precooling tower and a secondary alkaline washing tower connected in sequence. The flue gas inlet of the primary precooling tower is connected to the bag filter, and the flue gas outlet of the secondary alkaline washing tower is connected to the SGH heat exchanger.

[0015] A Venturi flue is provided between the quench tower and the bag filter, and the inner wall of the Venturi flue is provided with a dry powder and activated carbon powder injection device.

[0016] An induced draft fan is installed at the tail end of the flue gas treatment system;

[0017] The waste heat recovery equipment is based on a waste heat boiler, and the hot gas inlet of the SGH heat exchanger is connected to the steam outlet of the waste heat boiler.

[0018] The SNCR denitrification structure is installed in the 850℃~1100℃ range of the waste heat boiler.

[0019] This application provides an environmentally friendly smelting system for waste circuit boards. The system uses an environmentally friendly smelting furnace to process waste circuit boards. Waste circuit boards, along with auxiliary materials, are continuously fed into the furnace cavity from the top inlet. Combustion air is blown in from the bottom air inlet, and the fuel undergoes high-temperature combustion near the air inlet, forming a high-temperature smelting zone. The furnace charge in the charge column undergoes preheating, pyrolysis, sintering, and melting reactions sequentially from top to bottom. After being reduced and melted, the metal in the smelting zone undergoes a vertical downward movement, during which metal droplets aggregate and grow, separating from the slag, thus completing the metal separation process. Separation and recycling; Based on the environmentally friendly smelting furnace, waste circuit boards are processed. Due to the presence of mixed materials accumulated in the material column area, the heat generated in the lower smelting zone can be fully utilized, effectively reducing the heat emitted into the environment, reducing heat loss while meeting environmental protection requirements; The flue gas generated in the smelting furnace is sent to the secondary combustion chamber for high-temperature treatment, which can effectively decompose organic matter and carbon monoxide. The high-temperature flue gas generated in the secondary combustion chamber is then sent to the subsequent flue gas treatment system after heat recovery by the waste heat recovery equipment, further reducing system energy consumption and making the equipment more compliant with environmental protection requirements. Attached Figure Description

[0020] Figure 1 A schematic diagram of an environmentally friendly smelting system for waste circuit boards;

[0021] Figure 2 This is a schematic diagram of the structure of an environmentally friendly smelting furnace;

[0022] Figure 3 This is a schematic diagram of the process of changing the movable subbed. Detailed Implementation

[0023] This application includes an environmentally friendly smelting system for waste circuit boards, comprising: an incineration device and a flue gas treatment system. In this application, the incineration device is based on an environmentally friendly smelting furnace 1.

[0024] In existing technologies, environmentally friendly smelting furnaces are typically used in non-ferrous metal smelting. This application utilizes an environmentally friendly smelting furnace to recover metals from waste circuit boards based on pyrometallurgical smelting. In the high-temperature smelting furnace, organic components such as resin boards in the waste circuit boards are decomposed. Under the heating and reduction smelting action of carbon-based fuels, the metals are melted, and metal oxides or metal salts are reduced to elemental metals, accumulating as molten metal at the bottom of the furnace and finally collected after being discharged from the furnace. The molten metal is then sold to downstream refining industries based on its metal content. The smelting process of waste circuit boards using an environmentally friendly smelting furnace can effectively reduce energy consumption, increase reaction speed, and improve metal recovery efficiency.

[0025] The main components of waste circuit boards are copper and resin-bonded glass fiber. Resin-bonded glass fiber is primarily composed of silicon dioxide, which is one of the slagging agents that form glassy slag (composite silicates). Therefore, the amount of silicon-based auxiliary materials added to the furnace can be reduced or almost eliminated. Waste circuit boards also contain rare and precious metals such as gold and silver. Copper is a good collector of gold and silver; most of these rare and precious metals melt into the copper molten metal, forming copper alloys. Once a certain content is reached, these alloys can also be used for valuation.

[0026] like Figure 1 As shown, a secondary combustion chamber 3 and a waste heat recovery device 4 are installed between the incineration equipment and the flue gas treatment system. The processes used in the system of this application include: an oxygen-enriched environmentally friendly smelting furnace, a settling chamber, a secondary combustion chamber, a waste heat boiler, SNCR denitrification, flue gas quenching, dry powder / activated carbon injection, bag filter dust collection, two-stage wet scrubbing, and SGH flue gas heating.

[0027] A flue gas outlet 108 is provided on the upper side of the smelting furnace body 101, which connects to the secondary combustion chamber 3. The exhaust port of the secondary combustion chamber 3 connects to the waste heat recovery equipment 4, which in turn connects to the flue gas treatment system, which in turn connects to the chimney 13. A settling chamber 2 is provided between the environmentally friendly smelting furnace 1 and the secondary combustion chamber 3. The flue gas treatment system includes: an SNCR denitrification structure 5, a quench tower 6, a bag filter 8, a wet acid removal device, and an SGH heat exchanger 11, all connected in sequence. The wet acid removal device includes: a primary precooling tower 9 and a secondary alkaline scrubbing tower 10, connected in sequence. The flue gas inlet of the primary precooling tower 9 connects to the bag filter 8, and the exhaust port of the secondary alkaline scrubbing tower 10 connects to the SGH heat exchanger 11.

[0028] like Figure 2 As shown, the furnace body 101 of the environmentally friendly smelting furnace 1 is provided with a re-insulated and refractory bottom bed 107 on the upper part; the top of the furnace body 101 is provided with a feeding port 102, and the inner cavity of the furnace body consists of the following from top to bottom: a material column area 103, a smelting area 104 and a layered area 105; air inlets 106 are evenly provided on the inner cavity side wall of the smelting area 104, and the air inlets 106 are connected to an external air supply device to provide oxygen-enriched air to the smelting furnace.

[0029] In practical applications, the same environmentally friendly smelting furnace 1 may be used to process circuit board waste from different users. Typically, before processing circuit board waste from different users using existing incinerators with fixed bottom beds, it is necessary to shut down the furnace and clean the residual metal from the layered areas 105, chutes, and other structures in the bottom bed before restarting the furnace to process another batch of materials. However, each shutdown and restart consumes a significant amount of time. In this application, the bottom bed 107 is set as a movable bottom bed, movably installed at the bottom of the furnace body 101. The layered areas 105, chutes, and other structures are located within the bottom bed 107. After processing each batch of waste, the movable bottom bed is directly replaced, effectively improving the system's utilization efficiency.

[0030] The base bed 107 includes a bed body 1071 and rollers 1072 disposed at the bottom of the bed body 1071, which allow the bed body 1071 to be flexibly repositioned. The top of the bed body 1071 is slotted as a layering area 105, and the size and shape of the specific layering area 105 are adapted to the internal cavity of the furnace body 101.

[0031] The furnace body 101 is mounted on top of the base bed 107 based on the mounting base 109. The mounting base 109 has a channel 1092 in its inner cavity that allows the base bed 107 to pass through, forming a U-shaped structure in the vertical direction. Above the channel 1092, at a corresponding position to the inner cavity of the furnace body 101, a channel opening 1094 adapted to the size of the inner cavity of the furnace body 101 is opened to connect the inner cavity of the furnace body 101 and the layered area 105 opened on the top of the base bed 107; the base bed 107 is movably disposed in the channel 1092.

[0032] A guide block 1091 is provided at the top of the channel 1092. The length direction of the guide block 1091 is set along the sliding direction of the base bed 107. A guide groove 1073 is opened above the base bed 107. The dimensions of the guide block and the guide groove are adapted to each other. Each time the movable base bed 107 is replaced, the guide groove 1073 above the base bed 107 is aligned with the guide block 1091 in the channel 1092, so that the guide block 1091 extends into the guide groove 1073, pushing the base bed 107 to slide in the channel 1092, guiding the position of the base bed 107, and ensuring that the groove opened on the base bed 107 can be aligned with the channel opening 1094, and then aligned with the inner cavity of the furnace.

[0033] like Figure 3 As shown, when the base bed 107 needs to be replaced, the movable base bed 1 used for the previous batch of waste is pushed forward along the channel 1092 away from the bottom of the mounting base 109, while the movable base bed 2 used this time is pushed along the channel 1092 to the bottom of the furnace cavity, thus quickly completing the base bed replacement. In practice, after repositioning the movable base bed and the mounting base, it is sealed with fire putty or high-temperature resistant flexible insulation material, and resealing is performed each time the base bed is replaced.

[0034] In practice, fuel is first placed at the bottom of the smelting chamber and ignited. Then, waste circuit boards are mixed with a certain amount of carbon-based fuel and fed into the environmentally friendly smelting furnace 1 from top to bottom through the feeding port 102. At the same time, an appropriate amount of flux such as limestone is added. Depending on the iron and silicon content in the raw materials, an appropriate amount of iron- and silicon-containing waste is added as needed to form slag. Finally, the copper-based metal is reduced and periodically discharged, while molten glass slag is generated. After water quenching, it is packaged and subsequently utilized as a resource. The specific water quenching structure is based on existing technology.

[0035] The operation of this environmentally friendly smelting furnace 1 requires the gradual addition of raw materials and carbon-based fuels in batches, which are then stacked into pillars inside the furnace. The raw materials and carbon-based fuels are buffered in a buffer bin and fed into the furnace via conveyor belts when needed. The circuit boards are in block and sheet form, mixed with coke to form a mixture. Gaps exist between the block-shaped mixtures. Large quantities of the mixture accumulate in the pillar area 103. The mixture in the lower smelting zone 104 is burned at high temperature with the aid of oxygen-enriched air introduced through the air inlet 106. The carbon reacts with oxygen to provide heat, forming a molten pool. During the smelting process, elemental copper or other metals, or their oxides, react with carbon.

[0036] In this process, metal oxides or salts react with carbon to reduce them to elemental metals. The reduced and melted metal undergoes a vertical downward motion, during which the metal droplets coalesce and grow. In the stratification zone 105, they separate from the slag. The liquid metal and slag are discharged from their respective chutes (not marked in the diagram). The resulting metal enters the ingot casting machine, is cooled, and then transported, stored, and sold to downstream refining processes. The resulting slag is water-quenched to become vitrified slag, meeting product standards and potentially suitable for comprehensive utilization. The temperature at the top of the feed column is controlled at 300-400 degrees Celsius. Specific temperatures and stratification times are adjusted based on existing smelting technology and actual needs. The system itself can produce matte or black copper with a copper content of 70-80%. By adding an electric heating forebed and other existing technologies, even higher copper content crude copper can be discharged.

[0037] As the flue gas generated during combustion flows upward through the smelting furnace, it pyrolyzes and preheats the cold material accumulated in the charge column 103, ensuring full utilization of the heat generated by combustion. Because the flue gas contains a large amount of dust, it is sent to the settling chamber 2 through the flue gas outlet 108 to separate large dust particles. The collected dust is then returned to the furnace for further processing. The dust-removed flue gas enters the downstream secondary combustion chamber 3.

[0038] Waste circuit boards contain a large amount of organic matter and halogens, and the combustion process produces dioxins. Therefore, this system is equipped with a secondary combustion chamber to ensure the "3T+E" high-temperature decomposition of harmful substances. A secondary combustion chamber 3 is located downstream of the environmentally friendly smelting furnace. Based on the "3T+E" incineration theory, which ensures sufficient temperature (>1100℃), sufficient residence time (>2s at 1100℃), sufficient disturbance, and sufficient excess oxygen, the system fully decomposes organic matter and harmful pollutants in the flue gas at high temperatures. An emergency exhaust chimney is installed at the top of the secondary combustion chamber, equipped with pressure interlock control. It automatically opens in case of abnormal furnace pressure or emergency, ensuring operational safety.

[0039] After being decomposed at high temperature in the secondary combustion chamber, the flue gas enters the downstream waste heat boiler 4. The waste heat boiler 4 uses a membrane wall waste heat recovery boiler to recover waste heat from the high-temperature flue gas at the outlet of the secondary combustion chamber 3. The generated steam is used for downstream flue gas heating, system heat tracing, etc., and all steam condensate is recovered and recycled.

[0040] The high-temperature section of the environmentally friendly smelting furnace 1 has a high temperature and a long residence time, resulting in the generation of a certain amount of NOx in the exhaust gas. This system uses SNCR denitrification to control nitrogen oxides and ensure that the exhaust gas meets standards. The SNCR process is employed, with an SNCR denitrification device 5 installed in the 4850℃~1100℃ zone of the waste heat boiler. This device removes most of the nitrogen oxides from the flue gas by injecting a certain concentration of denitrification reducing agent into the boiler.

[0041] After being cooled by the waste heat boiler 5, the flue gas enters the downstream quench tower 6. A spray system 61 is installed at the top of the quench tower 6 to spray a certain amount of quenching water. The spray system 61 can rapidly reduce the flue gas temperature from 500~550℃ to 190~200℃ within 1 second, avoiding the temperature range of dioxin regeneration reaction, thereby inhibiting dioxin regeneration and reducing the concentration of dioxins in the tail gas. The atomizing medium of the quench system is designed to meet the requirements of recycled water recirculation. The recycled water is mainly the water reused from the wastewater treatment system and can be switched between tap water and recycled water as needed. The specific application method is based on existing technology. An ash hopper 63 is installed at the bottom of the quench tower 6, from which the fly ash that settles during the quenching process is discharged. To avoid the inability to spray water for cooling in time in case of power outages or other emergencies, an emergency water tank (not marked in the figure) can also be installed to supply water for emergency cooling using compressed air.

[0042] A Venturi flue 7 is installed downstream of the quench tower 6 to increase the flue gas velocity. A dry powder injection device 71 is installed inside the Venturi flue 7, injecting an appropriate amount of dry powder and a certain amount of activated carbon powder into this section. The dry powder is used for pre-coating the bag filter as needed. The high-speed flue gas, carrying the dry powder and activated carbon powder, reaches the downstream bag filter 8, forming a filter cake on the surface of the filter bags. The filter cake protects the bags from clogging and also serves as a substrate for the even distribution of activated carbon powder, adsorbing dioxins and heavy metals in the flue gas to ensure that the exhaust gas ultimately meets emission standards. The bag filter 8 captures most of the dust in the flue gas, which is collected in the dust collector hopper 81 and discharged through the ash conveying equipment.

[0043] In addition, the waste circuit boards have a high content of Br bromide. Based on the operating experience of similar projects, this system has set up a wet deacidification section in the flue gas treatment. The sodium alkali method is used to make the final sodium bromide available for resource utilization, thereby reducing the disposal cost of secondary waste salt.

[0044] The flue gas from the bag filter outlet enters the wet acid removal equipment, which consists of two stages: a primary precooling tower 9 and a secondary alkaline scrubbing tower 10. The primary precooling tower 9 is equipped with a circulating spray system 91. The flue gas first enters the primary precooling tower 9 and undergoes circulating spraying at the tower inlet. The flue gas temperature is reduced to approximately 70°C due to heat absorption from water evaporation. Simultaneously, the multi-layer circulating alkaline solution within the primary tower neutralizes the flue gas, effectively removing most of the acidic pollutants. The flue gas after primary precooling and scrubbing then enters the secondary alkaline scrubbing tower 10.

[0045] The secondary alkaline scrubbing tower 10 is equipped with a packing layer 1001, an alkaline spraying device 1002, and a demister 1003. The packing layer 1001 specifically includes a sieve plate and packing material. Through a large amount of circulating alkaline spraying and washing, it achieves deep purification of flue gas pollutants. At the same time, in conjunction with the efficient demisting of the top demister 1003, it can enable the exhaust gas emissions to meet stricter emission standards.

[0046] A steam-to-flue gas heat exchanger 11 is installed downstream of the wet process. The steam-to-flue gas heat exchanger 11 is connected to the steam discharge port of the waste heat boiler. The steam from the waste heat boiler 4 is used by the steam in the steam exchanger to reheat the exhaust gas, ensuring that it is unsaturated with moisture and reducing the amount of white smoke emitted from the chimney.

[0047] The induced draft fan 12 is located at the end of the flue gas treatment system, ensuring the entire system is under negative pressure and effectively preventing the leakage of incompletely purified flue gas. The final exhaust gas temperature is >130℃, and the water vapor content in the flue gas is in a super-unsaturated state, effectively reducing the "white smoke" phenomenon at the chimney outlet. The treated flue gas that meets the standards is finally discharged into the chimney via the induced draft fan.

[0048] Compared with other waste circuit board treatment methods, the metal recovery rate of the technical solution of this application is higher when using the technical solution of this application, and the copper content in the waste residue is <0.8%; the single system has a large capacity, which can reach 30~70t / d; the environmental protection effect is good: the waste residue discharged by this system is general solid waste and does not need to be landfilled, and the exhaust gas emission meets the requirements of national standard GB18484-2020.

Claims

1. An environmentally friendly smelting system for waste circuit boards, comprising: An incineration device and a flue gas treatment system, characterized in that: the incineration device is based on an environmentally friendly smelting furnace; a secondary combustion chamber and a waste heat recovery device are provided between the incineration device and the flue gas treatment system; The environmentally friendly smelting furnace includes: a furnace body and a bottom bed arranged from top to bottom, wherein the bottom bed is a movable bottom bed and is movably installed below the furnace body; The inner cavity of the environmentally friendly smelting furnace is arranged from top to bottom as a feeding port, a material column area, a smelting area, and a layered area; air inlets are evenly arranged on the side wall of the smelting area, and the air inlets are connected to an external air supply device; A flue gas outlet is provided on the upper side of the furnace body, and the flue gas outlet is connected to the secondary combustion chamber; the flue gas outlet of the secondary combustion chamber is connected to the waste heat recovery equipment, the waste heat recovery equipment is connected to the flue gas treatment system, and the flue gas treatment system is connected to the chimney; The flue gas treatment system includes: an SNCR denitrification structure, a quench tower, a bag filter, a wet acid removal device, and an SGH heat exchanger connected in sequence.

2. The waste circuit board environmental protection smelting system according to claim 1, characterized in that: The base bed includes: a bed frame and rollers disposed at the bottom of the bed frame; the top of the bed frame is slotted as a layered area.

3. The waste circuit board environmental protection smelting system according to claim 2, characterized in that: The furnace body is mounted above the base bed based on the mounting base. The mounting base has a channel through which the base bed passes, forming a U-shaped cross-section in the vertical direction. Above the channel, at a corresponding position to the inner cavity of the furnace body, a channel opening adapted to the size of the inner cavity of the furnace body is opened to connect the layered areas of the inner cavity of the furnace body and the base bed. The base bed is movably disposed in the channel. A guide block is provided at the top of the inner cavity of the mounting base. The length direction of the guide block is set along the sliding direction of the base bed. A guide groove is opened above the base bed. The size of the guide block and the guide groove are adapted to each other.

4. The environmentally friendly smelting system for waste circuit boards according to claim 1, characterized in that: A settling chamber is provided between the environmentally friendly smelting furnace and the secondary combustion chamber.

5. The waste circuit board environmental smelting system according to claim 1, characterized in that: The wet acid removal equipment includes a primary precooling tower and a secondary alkaline washing tower connected in sequence. The flue gas inlet of the primary precooling tower is connected to the bag filter, and the flue gas outlet of the secondary alkaline washing tower is connected to the SGH heat exchanger.

6. The waste circuit board environmental protection smelting system according to claim 1, characterized in that: A Venturi flue is provided between the quench tower and the bag filter, and the inner wall of the Venturi flue is provided with a dry powder and activated carbon powder injection device.

7. The environmentally friendly smelting system for waste circuit boards according to claim 1, characterized in that: An induced draft fan is installed at the tail end of the flue gas treatment system.

8. The waste circuit board environmental protection smelting system according to claim 1, characterized in that: The waste heat recovery equipment is based on a waste heat boiler, and the hot gas inlet of the SGH heat exchanger is connected to the steam outlet of the waste heat boiler.

9. The waste circuit board environmental protection smelting system according to claim 8, characterized in that: The SNCR denitrification structure is installed in the 850℃~1100℃ range of the waste heat boiler.

Images