A system and method for the resource-based treatment of complex polluting chemical waste salt

Abstract

This invention relates to a resource-based treatment system and method for compound-polluting chemical waste salt, aiming to solve the technical problems of high energy consumption, incomplete treatment, high cost, and complex processes in existing treatment methods for compound-polluting chemical waste salt. The system includes a pyrolysis unit and a separation and purification unit. The pyrolysis unit includes a crushing and screening device, a first preheating device, a second preheating device, and a microwave pyrolysis device. The separation and purification unit receives the purified salt output from the microwave pyrolysis device and performs separation and purification. The method includes: 1. Crushing and screening the compound-polluting chemical waste salt to obtain particulate material; 2. Preheating and pyrolyzing the particulate material to obtain purified salt and VOCs-containing waste gas; 3. The VOCs-containing waste gas is purified by passing through a flue gas filter and a catalyst packing section before being output. The purified salt is purified and separated by the separation and purification unit to obtain refined first salt and refined second salt.

Description

Technical Field

[0001] This invention relates to the reprocessing of chemical waste salt, specifically to a resource-based treatment system and method for compound-polluted chemical waste salt. Background Technology

[0002] Composite polluting chemical waste salts are hazardous wastes, characterized by high sodium content, strong mobility, and composite pollution of heavy metals and organic matter. Furthermore, their large generation volume and high treatment costs pose significant challenges to safe landfilling or high-value utilization after solidification and stabilization pretreatment: (1) Safe landfilling carries substantial potential environmental risks; (2) Removal of organic matter and heavy metals is extremely difficult, and improper high-temperature heat treatment can easily lead to secondary toxic and harmful pollution such as dioxins; (3) Sodium salts have low value, and the refining technologies for sodium chloride and sodium sulfate are still immature, making large-scale targeted high-value conversion a global challenge. Therefore, large-scale high-value utilization of composite polluting chemical waste salts presents new challenges to technological innovation in the existing solid waste recycling technology system.

[0003] To address the environmental problems caused by waste salt and the resulting issues affecting the healthy development of the industry, exploring its large-scale, high-value utilization has become a research hotspot both domestically and internationally. Developed countries have very little research on waste salt, and in engineering, it is generally disposed of by dumping into the sea. my country is currently in a leading position in the research and treatment of waste salt, and the following development trends are emerging: (1) Waste salt landfill disposal is developing towards large-scale, high-value utilization and resource-based harmlessness; (2) Pyrolysis removal of organic pollutants, crystallization and salt purification, and preparation of caustic soda have become research hotspots; (3) Microwave pyrolysis treatment of waste salt has attracted attention.

[0004] Chinese Patent Publication No. CN110642270A discloses a method for refining industrial waste salt. This method involves pretreatment with a mixture of industrial waste salt and a washing agent to obtain pretreated salt and filtrate. Refined crystalline salt is then obtained through oxidation, adsorption, and evaporation crystallization, solving some of the waste salt resource utilization problems. However, the treated salt still has a high organic content and generates a large amount of polluted wastewater. Chinese Patent Publication No. CN110201975A discloses a method for treating industrial hazardous waste salt using drying, primary carbonization, and deep carbonization. The primary carbonization and deep carbonization temperatures are 400–500℃ and 500–700℃, respectively, with carbonization times of 2–4 hours for both. The treated salt can be used for ion-exchange membrane electrolysis to produce alkali, but this method has a long calcination time, high energy consumption, and high cost, making it suitable only for waste salt with extremely high organic content. Chinese Patent Publication No. CN112974487A discloses a device and method for the harmless treatment of waste salt containing organic matter. It employs crushing, preheating, microwave pyrolysis, tail gas treatment, dissolution filtration, and evaporation to achieve the harmless treatment and refining of waste salt. However, the tail gas generated by the crushing, preheating, and microwave pyrolysis devices all needs to be collected and then purified through a series of interconnected components: a secondary combustion chamber, a quench tower, a dry reactor, a bag filter, a desulfurization and denitrification device, an exhaust fan, and a chimney. This tail gas treatment process is complex and has high operating costs. In summary, achieving deep purification and high-value utilization of chemically polluted waste salt is a significant requirement for ecological environment management and sustainable development. Therefore, there is an urgent need to develop an efficient and low-cost integrated process system for waste salt treatment and reuse to achieve efficient removal of organic matter from waste salt, maximize resource utilization of waste salt, and ultimately achieve near-zero emissions of waste salt. Summary of the Invention

[0005] To address the technical problems of existing methods for treating compound polluting chemical waste salt, such as high energy consumption, incomplete treatment, high cost, and complex processes, this invention proposes a resource-based treatment system and method for compound polluting chemical waste salt.

[0006] The technical solution provided by this invention is as follows:

[0007] A composite polluting chemical waste salt resource utilization treatment system is characterized by including a pyrolysis unit and a separation and purification unit.

[0008] The pyrolysis unit includes a crushing and screening device, a first preheating device, a second preheating device, and a microwave pyrolysis device arranged sequentially according to the processing order of compound polluting chemical waste salt.

[0009] The first preheating device includes a first preheating device air inlet and a first preheating device air outlet, and the second preheating device includes a second preheating device air inlet and a second preheating device air outlet.

[0010] The microwave pyrolysis device includes an outer wall, a thermal insulation material layer disposed on the outer side of the outer wall, and multiple microwave generators penetrating the outer wall and the thermal insulation material layer;

[0011] The microwave pyrolysis device is divided into a pyrolysis section and a waste gas treatment section. The pyrolysis section is equipped with a microwave pyrolysis device feed inlet, a microwave pyrolysis device air inlet, and a microwave pyrolysis device discharge outlet that penetrate the outer wall and the insulation material layer.

[0012] The exhaust gas treatment section is provided with a flue gas filter and a catalyst filling section in sequence along the exhaust gas discharge direction of the pyrolysis section. The catalyst filling section is used to fill the catalyst and catalyze the combustion and degradation of the exhaust gas under the assistance of microwave generated by the microwave generator. The microwave pyrolysis device outlet is provided on the side of the catalyst filling section away from the flue gas filter for outputting microwave pyrolysis exhaust gas.

[0013] The separation and purification unit is used to receive the purified salt output from the outlet of the microwave pyrolysis device and to separate and purify it.

[0014] Furthermore, the outlet of the microwave pyrolysis device is connected to the inlet of the first preheating device and the inlet of the second preheating device, respectively.

[0015] The first preheating device has a first preheating material chamber for transferring compound polluting chemical waste salt;

[0016] The air inlet and air outlet of the first preheating device are both connected to the first preheating material chamber; the air outlet of the first preheating device is connected to the air inlet of the microwave pyrolysis device.

[0017] The second preheating device has a preheating partition cavity and a second preheating material cavity. The air inlet of the second preheating device is connected to the preheating partition cavity. The microwave pyrolysis tail gas in the preheating partition cavity and the composite polluted chemical waste salt in the second preheating material cavity exchange heat through the side wall of the preheating partition cavity to achieve preheating.

[0018] The second preheating device outlet includes a preheating partition cavity outlet and a second preheating material cavity outlet that communicates with the second preheating material cavity. The second preheating material cavity outlet is connected to the microwave pyrolysis device inlet. The preheating partition cavity outlet is in communication with the external environment.

[0019] Furthermore, the separation and purification unit includes a dissolution and purification device, a separation device, and a concentration and crystallization device;

[0020] The inlet of the dissolving and purifying device is connected to the outlet of the microwave pyrolysis device, and the outlet of the dissolving and purifying device is connected to the separation device. The dissolving and purifying device is used to dissolve and remove impurities from the purified salt and output it from the outlet of the dissolving and purifying device. After filtration, a mixed salt solution is obtained and output to the separation device.

[0021] The concentration and crystallization apparatus includes a first salt concentration and crystallization apparatus and a second salt concentration and crystallization apparatus;

[0022] The separation device includes a heat pump freezing crystallization device and a membrane salt separation device;

[0023] The heat pump refrigeration crystallization device includes a circulating pump, an evaporator, a compressor, a condenser, a throttle valve, a discharge pump, a hydrocyclone, a crystallizer, a forced circulation pump, a solvent, and a heat exchanger.

[0024] The upper part of the crystallizer is provided with a crystallizer cryogenic supernatant outlet and a crystallizer circulation inlet. The crystallizer has a conical bottom, and the lower end of the conical bottom is provided with a crystallizer circulation outlet.

[0025] The circulating pump is used to pump the received mixed salt solution into the first inlet of the evaporator, and the first outlet of the evaporator is connected to the circulating inlet of the crystallizer;

[0026] The circulation outlet of the crystallizer is connected to the inlet of the circulation pump via a connecting pipe. The connecting pipe has a mixed salt solution inlet and a crystallized salt outlet. The crystallized salt outlet is located upstream of the mixed salt solution inlet and is connected to the outlet pump inlet.

[0027] The discharge pump outlet is connected to the hydrocyclone inlet; the hydrocyclone overflow port is connected to the mixed salt solution inlet; the bottom outlet of the hydrocyclone is connected to the first inlet of the solvent; the first outlet of the solvent is connected to the inlet of the forced circulation pump; the outlet of the forced circulation pump is connected to the first inlet of the heat exchanger; the first outlet of the heat exchanger is connected to the second inlet of the solvent; the second outlet of the solvent is connected to the first salt concentration and crystallization device; the second outlet of the heat exchanger is connected to the first inlet of the condenser; the second inlet of the heat exchanger is connected to the first outlet of the condenser.

[0028] The second outlet of the evaporator is connected to the compressor, and through the compressor, it is connected to the second inlet of the condenser; the second outlet of the condenser is connected to the second inlet of the evaporator through a throttle valve.

[0029] The outlet of the supernatant from the crystallizer is connected to the membrane separation device.

[0030] Furthermore, the outer wall of the evaporator has an evaporator annular cavity that communicates with both the second outlet and the second inlet of the evaporator. The evaporator annular cavity is filled with a low-temperature, low-pressure wet refrigerant, which is used to exchange heat with the mixed salt solution and then be converted into a medium-temperature, low-pressure gaseous refrigerant. The compressor is used to convert the medium-temperature, low-pressure gaseous refrigerant into a high-temperature, high-pressure gaseous refrigerant.

[0031] The outer wall of the condenser has a condenser annular cavity that communicates with both the second inlet and the second outlet of the condenser. The condenser annular cavity is used to receive high-temperature and high-pressure gaseous refrigerant and cool it down to convert it into medium-temperature and high-pressure liquid refrigerant. The throttling valve is used to convert the medium-temperature and high-pressure liquid refrigerant into low-temperature and low-pressure wet refrigerant and re-enter it into the evaporator annular cavity.

[0032] The low-temperature, low-pressure wet refrigerant has a temperature range of -22℃ to -28℃ and a pressure of 0.8-1.2 kg / cm³. 2The temperature of the medium-temperature, low-pressure gaseous refrigerant is -25℃ to 30℃, and the pressure is 0.8-1.2 kg / cm³. 2 The temperature of the high-temperature, high-pressure gaseous refrigerant is 70–90℃, and the pressure is 7–10 kg / cm³. 2 The temperature of the medium-temperature, high-pressure liquid refrigerant is -25℃ to 30℃, and the pressure is 7 to 10 kg / cm³. 2 ;

[0033] The outer wall of the heat exchanger has a heat exchanger annular cavity communicating with the second inlet and the second outlet of the heat exchanger. The heat exchanger annular cavity contains a coolant, which is used to circulate within the condenser and the heat exchanger annular cavity to achieve heat exchange.

[0034] Furthermore, the dissolution and purification device is also provided with an adsorbent material inlet for adding adsorbent material into the dissolution and purification device;

[0035] The adsorbent material is activated carbon, resin, metal-organic framework material, or micelles.

[0036] Furthermore, the membrane separation device is provided with an ultrafiltration membrane and a nanofiltration membrane sequentially along the transport direction of the supernatant in the crystallizer;

[0037] The nanofiltration permeate obtained by the nanofiltration membrane is output as a second salt solution to the second salt concentration and crystallization device.

[0038] Furthermore, the crushing and screening device is a crusher with screening function;

[0039] The first preheating device and the first preheating device are rotary kilns or tunnel kilns.

[0040] A method for the resource recovery and treatment of compound polluting chemical waste salts, characterized by the use of the aforementioned compound polluting chemical waste salt resource recovery and treatment system, comprising the following steps:

[0041] S1. Add the composite polluting chemical waste salt to the crushing and screening device for crushing and screening to obtain granular material of composite polluting chemical waste salt with a diameter of 0.5-1.5mm;

[0042] S2. The granular material is added from the feed inlet of the first preheating device for primary preheating, raising the temperature to 200-250℃. The primary preheated granular material is added from the feed inlet of the second preheating device for secondary preheating, raising the temperature to 300-500℃. The secondary preheated granular material enters the pyrolysis section from the feed inlet of the microwave pyrolysis device. Under the microwave irradiation generated by the microwave generator with a power of 50-75kW, the secondary preheated granular material is heated to 600-750℃, producing purified salt and VOCs-containing waste gas.

[0043] S3. The VOCs-containing waste gas is purified by passing through a flue gas filter and a catalyst filling section to obtain microwave pyrolysis tail gas, which is then output from the outlet of the microwave pyrolysis device.

[0044] The purified salt is output to the separation and purification unit for purification and separation to obtain refined first salt and refined second salt.

[0045] Furthermore, in step S3, the purified salt is output to the separation and purification unit for purification and salt separation, specifically as follows:

[0046] S3.1 Add the purified salt to the dissolving and purifying device, add water and adsorbent material to dissolve and purify, and obtain a purified salt solution; the purified salt solution is output from the outlet of the dissolving and purifying device and filtered to obtain a mixed salt solution;

[0047] S3.2 The mixed salt solution enters the evaporator through the circulation pump. After exchanging heat with the low-temperature and low-pressure wet refrigerant, the mixed salt solution enters the crystallization tank through the first outlet of the evaporator and the circulation inlet of the crystallization tank to crystallize and form hydrated salt crystals. The mixed salt solution containing hydrated salt enters the circulation pump through the circulation outlet of the crystallization tank, and then enters the crystallization tank through the evaporator for circulating crystallization. In the crystallization tank, the upper layer is the supernatant of mixed salt, and the bottom of the cone-shaped tank has hydrated salt precipitate.

[0048] When the crystallization content of the mixed salt solution containing hydrated salt in the crystallizer reaches 10% to 15%, the discharge pump and hydrocyclone are turned on. The hydrated salt solution output from the circulation outlet of the crystallizer is then fed into the dissolver through the discharge pump and hydrocyclone. The solution at the bottom of the hydrocyclone is then fed into the dissolver and output to the heat exchanger. Heat exchange is carried out in the heat exchanger to achieve preheating. The solution is then fed into the dissolver through the forced circulation pump and circulated for preheating until the solution in the dissolver reaches the preset temperature. Finally, the solution is output to the first salt concentration and crystallization device through the first outlet of the dissolver.

[0049] When the crystallization content of the mixed salt solution containing hydrated salt in the crystallizer is less than 10%, turn off the discharge pump and hydrocyclone, and continue the circulation crystallization.

[0050] The mixed salt supernatant enters the membrane salt separation unit through the outlet of the crystallization tank. After impurity removal by the ultrafiltration membrane, the ultrafiltration concentrate is returned to the dissolution and purification unit for further treatment. The ultrafiltration permeate is output to the nanofiltration membrane. After salt separation by the nanofiltration membrane, the nanofiltration permeate is the second salt solution, which is output to the second salt concentration and crystallization unit. The nanofiltration concentrate is the third salt solution, which is combined with the mixed salt solution and participates in the circulating crystallization through the circulation pump.

[0051] S3.3 The first salt solution and the second salt solution are evaporated and concentrated in the first salt concentration and crystallization device and evaporated and crystallized in the second salt concentration and crystallization device, respectively, to obtain refined first salt and refined second salt.

[0052] Further, in step S3, obtaining purified microwave pyrolysis tail gas and outputting it from the outlet of the microwave pyrolysis device specifically involves:

[0053] The purified microwave pyrolysis tail gas enters from the inlet of the first preheating device and the inlet of the second preheating device, respectively, and is used to exchange heat with the particulate material and the particulate material that has been preheated once.

[0054] The beneficial effects of this invention are:

[0055] 1. The composite pollution chemical waste salt resource utilization treatment system provided by this invention directly transmits materials to the microwave pyrolysis device through a preheating device. The microwave pyrolysis device, by setting up a waste gas treatment section, utilizes the high efficiency, uniformity, and easy temperature control of microwave heating, as well as the significant synergistic effect of microwave irradiation on the catalytic cracking of organic matter, to achieve deep purification of VOCs waste gas generated in the microwave pyrolysis device, meeting the emission standards. It fully utilizes the heat of the waste gas itself and the synergistic effect of microwave irradiation, greatly simplifies the process flow, reduces the investment in waste gas treatment equipment, and makes the device highly integrated, small in size, and low in cost.

[0056] 2. This invention outputs the high-temperature exhaust gas processed by the microwave pyrolysis device to the first preheating device and the second preheating device. At the same time, the exhaust gas newly generated during the preheating process of the first and second preheating devices is input into the air inlet of the microwave pyrolysis device, processed in the exhaust gas treatment section, and then output to the first and second preheating devices. This cycle is repeated, which on the one hand realizes the recycling of heat, reduces energy consumption, and lowers costs; on the other hand, realizes the recycling treatment of exhaust gas, and finally discharges exhaust gas that meets the standards.

[0057] 3. This invention utilizes carbon materials generated from the microwave pyrolysis of organic matter in waste salt to achieve in-situ self-purification of heavy metal ions and residual small molecule organic matter during the salt dissolution process, thereby reducing the amount of adsorption material used.

[0058] 4. The various devices in the pyrolysis unit and separation and purification unit of this invention are tightly connected, and the technology applied in each link is reasonable, which ensures the stable operation of the system and makes it easy to automate. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of an embodiment of the composite pollution chemical waste salt resource utilization treatment system of the present invention;

[0060] Figure 2 This is a schematic diagram of the pyrolysis unit in an embodiment of the present invention;

[0061] Figure 3 This is a schematic diagram of the separation device and the concentration and crystallization device in an embodiment of the present invention.

[0062] The attached figures are labeled as follows:

[0063] 1- Crushing and screening device; 2- Feed inlet of the first preheating device; 3- First preheating device; 4- Air outlet of the first preheating device; 5- Insulation material layer; 6- Air inlet of the first preheating device; 7- Motor; 8- Discharge outlet of the first preheating device; 9- Feed inlet of the second preheating device; 10- Air inlet of the second preheating device; 11- Discharge outlet of the second preheating device; 12- Air outlet of the preheating partition cavity; 13- Air outlet of the second preheating material cavity; 14- Feed inlet of the microwave pyrolysis device; 15- Microwave pyrolysis device; 16- Microwave generator; 17- Air inlet of the microwave pyrolysis device; 18- Microwave pyrolysis device 19-Catalyst packing section; 20-Flue gas filter; 21-Microwave pyrolysis device outlet; 22-Dissolution and purification device; 23-Crystallization tank; 24-First salt concentration and crystallization device; 25-Membrane salt separation device; 26-Second salt concentration and crystallization device; 27-Crystallization tank frozen supernatant outlet; 28-Crystallization tank circulation inlet; 29-Crystallization tank circulation outlet; 30-Condenser; 31-Throttle valve; 32-Evaporator; 33-Compressor; 34-Circulation pump; 35-Discharge pump; 36-Hydrocyclone; 37-Forced circulation pump; 38-Dissolver; 39-Heat exchanger. Detailed Implementation

[0064] See Figure 1 This embodiment provides a resource recovery system for chemical waste salts with complex pollution. The system includes a pyrolysis unit and a separation and purification unit; see [link to documentation]. Figure 2 The pyrolysis unit includes a crushing and screening device 1, a first preheating device 3, a second preheating device, and a microwave pyrolysis device 15, arranged sequentially according to the processing order of compound polluting chemical waste salt. Specifically, the discharge port of the crushing and screening device 1 is connected to the inlet 2 of the first preheating device, the discharge port 8 of the first preheating device is connected to the inlet 9 of the second preheating device, and the discharge port 11 of the second preheating device is connected to the inlet 14 of the microwave pyrolysis device. The crushing and screening device 1 is a crusher with screening function. It can be understood that the first preheating device 3 and the second preheating device are rotary kilns or tunnel kilns with heat exchange function.

[0065] The first preheating device 3 includes a first preheating device air inlet 6, a first preheating device air outlet 4, an outer wall of the first preheating device 3, and a thermal insulation material layer 5 disposed on the outer side of the outer wall of the first preheating device 3. The second preheating device includes a second preheating device air inlet 10, a second preheating device air outlet, an outer wall of the second preheating device, and a thermal insulation material layer 5 disposed on the outer side of the outer wall of the second preheating device. Both the first preheating device 3 and the second preheating device are driven by a motor 7 to realize the transmission of composite polluting chemical waste salt.

[0066] The microwave pyrolysis device 15 includes an outer wall, a thermal insulation material layer 5 disposed on the outer side of the outer wall, and multiple microwave generators 16 penetrating the outer wall and the thermal insulation material layer 5; the microwave pyrolysis device 15 also uses a motor 7 to drive the transfer of composite polluting chemical waste salt.

[0067] The microwave pyrolysis device 15 is internally divided into a pyrolysis section and a waste gas treatment section. The pyrolysis section is provided with a microwave pyrolysis device inlet 14, a microwave pyrolysis device air inlet 17, and a microwave pyrolysis device outlet 21 that penetrate the outer wall and the insulation material layer 5. The waste gas treatment section is provided with a flue gas filter 20 and a catalyst filling section 19 in sequence along the exhaust gas discharge direction of the pyrolysis section. The flue gas filter 20 is a high-temperature flue gas filter that can be used to withstand high temperatures. The catalyst filling section 19 is used to fill the catalyst and catalyze the combustion and degradation of the waste gas under the assistance of microwaves generated by the microwave generator 16. The side of the catalyst filling section 19 away from the high-temperature flue gas filter is provided with a microwave pyrolysis device outlet 18 for outputting microwave pyrolysis exhaust gas.

[0068] The microwave pyrolysis device's outlet 18 is connected to the first preheating device's inlet 6 and the second preheating device's inlet 10, respectively. The first preheating device 3 has a first preheating material chamber for transporting composite polluting chemical waste salt. Both the first preheating device's inlet 6 and outlet 4 communicate with the first preheating material chamber. The first preheating device's outlet 4 is connected to the microwave pyrolysis device's inlet 17. The second preheating device has a preheating partition cavity and a second preheating material chamber. The second preheating material chamber is used for transporting composite polluting chemical waste salt. The preheating partition cavity can be an annular cavity in the outer wall of the second preheating device, or it can be a cavity formed in the part of the drive motor 7 that contacts the material. The device receives purified microwave pyrolysis tail gas output from the microwave pyrolysis device outlet 18, or it can be any other purified microwave pyrolysis tail gas container capable of indirect, non-contact heat exchange with the material; the second preheating device inlet 10 is connected to the preheating partition cavity, and the microwave pyrolysis tail gas in the preheating partition cavity and the composite polluted chemical waste salt in the second preheating material cavity exchange heat through the side wall of the preheating partition cavity to achieve preheating; the second preheating device outlet includes a preheating partition cavity outlet 12 and a second preheating material cavity outlet 13 connected to the second preheating material cavity, and the second preheating material cavity outlet 13 is connected to the microwave pyrolysis device inlet 17; the preheating partition cavity outlet 12 is connected to the external environment.

[0069] The separation and purification unit includes a dissolution and purification device 22, a separation device, and a concentration and crystallization device. The concentration and crystallization device includes a first salt concentration and crystallization device 24 and a second salt concentration and crystallization device 26. The inlet of the dissolution and purification device 22 is connected to the outlet 21 of the microwave pyrolysis device, and the outlet of the dissolution and purification device 22 is connected to the separation device. After the purified salt is cooled to below 100°C, the dissolution and purification device 22 dissolves the purified salt, removes impurities, and outputs it from the outlet of the dissolution and purification device 22. After filtration, a mixed salt solution and solid residue are obtained. The mixed salt solution is output to the separation device, and the solid residue can be... Recycling through heat treatment; it is understood that the purified salt contains carbon materials generated during the microwave pyrolysis of organic matter. During the dissolution process of the purified salt, the carbon materials can achieve in-situ self-purification of the solution, adsorbing heavy metals and residual organic matter; preferably, the dissolution and purification device 22 can also be provided with an adsorbent material inlet for adding adsorbent materials and reagents to the dissolution and purification device 22 to remove heavy metal ions, residual small molecule organic matter, scale ions and insoluble impurities, adjust pH, and achieve further purification; the adsorbent material is activated carbon, resin, metal-organic framework material or micelles.

[0070] See Figure 3 The separation device includes a heat pump freezing crystallization device and a membrane salt separation device 25. The heat pump freezing crystallization device includes a circulation pump 34, an evaporator 32, a compressor 33, a condenser 30, a throttle valve 31, a discharge pump 35, a hydrocyclone 36, a crystallizer 23, a forced circulation pump 37, a dissolver 38, and a heat exchanger 39. The upper part of the crystallizer 23 is provided with a crystallizer freezing supernatant outlet 27 and a crystallizer circulation inlet 28. The crystallizer 23 has a conical bottom, and the lower end of the conical bottom is provided with a crystallizer circulation outlet 29. The circulation pump 34 is used to pump the mixed salt solution into the first inlet of the evaporator, and the first outlet of the evaporator is connected to the crystallizer circulation inlet 28.

[0071] The crystallizer circulation outlet 29 is connected to the circulation pump inlet via a connecting pipe. The connecting pipe has a mixed salt solution inlet and a crystallized salt outlet located upstream of the mixed salt solution inlet. The crystallized salt outlet is connected to the discharge pump inlet. The discharge pump outlet is connected to the hydrocyclone inlet. The hydrocyclone overflow outlet is connected to the mixed salt solution inlet, and after merging with the mixed salt solution, it enters the crystallization cycle. The bottom outlet of the hydrocyclone is connected to the first inlet of the solvent. The first outlet of the solvent is connected to the forced circulation pump inlet. The forced circulation pump outlet is connected to the first inlet of the heat exchanger. The first outlet of the heat exchanger is connected to the second inlet of the solvent. The second outlet of the solvent is connected to the first salt concentration crystallization device 24. The second outlet of the heat exchanger is connected to the first inlet of the condenser. The second inlet of the heat exchanger is connected to the first outlet of the condenser.

[0072] The second outlet of the evaporator is connected to the compressor 33, and through the compressor 33, it is connected to the second inlet of the condenser. The second outlet of the condenser is connected to the second inlet of the evaporator through a throttle valve 31. The outer wall of the evaporator 32 has an evaporator annular cavity that communicates with both the second outlet and the second inlet of the evaporator. A low-temperature, low-pressure wet refrigerant is placed in the evaporator annular cavity to exchange heat with the mixed salt solution and then be converted into a medium-temperature, low-pressure gaseous refrigerant. The compressor 33 is used to convert the medium-temperature, low-pressure gaseous refrigerant into a high-temperature, high-pressure gaseous refrigerant. The outer wall of the condenser 30 has a condenser annular cavity that communicates with both the second inlet and the second outlet of the condenser. The condenser annular cavity receives the high-temperature, high-pressure gaseous refrigerant and cools it down to convert it into a medium-temperature, high-pressure liquid refrigerant. The throttle valve 31 is used to convert the medium-temperature, high-pressure liquid refrigerant into a low-temperature, low-pressure wet refrigerant that re-enters the evaporator annular cavity. The temperature of the low-temperature, low-pressure wet refrigerant is -25℃, and its pressure is 1 kg / cm³. 2 The temperature of the medium-temperature, low-pressure gaseous refrigerant is -25℃ to 30℃, and the pressure is 1 kg / cm³. 2 The temperature of the high-temperature, high-pressure gaseous refrigerant is 70–90℃, and the pressure is 7–10 kg / cm³. 2 The temperature of the medium-temperature, high-pressure liquid refrigerant is -25℃ to 30℃, and the pressure is 7 to 10 kg / cm³. 2 The outer wall of the heat exchanger has a heat exchanger annular cavity that communicates with the second inlet and the second outlet of the heat exchanger. The heat exchanger annular cavity contains a coolant, which is used to circulate within the condenser and the heat exchanger annular cavity to achieve heat exchange.

[0073] The outlet 27 of the supernatant of the crystallizer is connected to the membrane salt separation device 25. The membrane salt separation device 25 is equipped with an ultrafiltration membrane and a nanofiltration membrane in sequence along the supernatant transport direction of the crystallizer. The nanofiltration permeate obtained by the nanofiltration membrane is the second salt solution and is output to the second salt concentration and crystallization device 26. The second salt is obtained by concentration and crystallization.

[0074] Different concentration-crystallization processes are selected for different salt solutions to obtain refined salt. For example, sodium sulfate solution is crystallized by MVR forced circulation evaporation, while sodium chloride solution can be concentrated by MVR falling film evaporation followed by MVR forced circulation evaporation. When there is surplus steam, the evaporation concentration-evaporation crystallization device can also be a multi-effect evaporator or a single-effect evaporation concentration / crystallization device.

[0075] The above-mentioned complex pollution chemical waste salt resource utilization treatment system includes the following steps:

[0076] S1. Add the composite polluting chemical waste salt to the crushing and screening device 1 for crushing and screening to obtain granular material of composite polluting chemical waste salt with a diameter of 0.5-1.5mm.

[0077] S2. The granular material is added from the feed inlet 2 of the first preheating device for primary preheating, and the temperature is raised to 200-250℃. The granular material that has been preheated once is added from the feed inlet 9 of the second preheating device for secondary preheating, and the temperature is raised to 300-500℃. The granular material that has been preheated twice enters the pyrolysis section from the feed inlet 14 of the microwave pyrolysis device. Under the microwave irradiation generated by the microwave generator 16 with a power of 50-75kW, the granular material that has been preheated twice is raised to 600-750℃, producing purified salt and VOCs-containing waste gas.

[0078] S3. The VOC-containing waste gas is purified by passing it through a high-temperature flue gas filter and catalyst filling section 19, resulting in purified microwave pyrolysis tail gas, which is output from the microwave pyrolysis device outlet 18. The output purified microwave pyrolysis tail gas enters from the first preheating device inlet 6 and the second preheating device inlet 10, respectively. In the first preheating device 3, the purified microwave pyrolysis tail gas directly contacts and exchanges heat with the particulate material. During the heating of the particulate material, a first preheated tail gas containing harmful components is generated. The first preheated tail gas enters the microwave pyrolysis device 15 through the microwave pyrolysis inlet, participates in pyrolysis in the microwave pyrolysis section, and is then treated in the waste gas treatment section to obtain purified microwave pyrolysis tail gas for reuse. In the second preheating device... The purified microwave pyrolysis tail gas does not directly contact the preheated particulate material. Instead, it enters the preheating partition chamber and exchanges heat with the material through the partition. After heat exchange with the preheated particulate material, the purified microwave pyrolysis tail gas in the preheating partition chamber can be directly discharged. In the second preheating chamber, the material will also generate a second preheating tail gas containing harmful components during the second preheating. The second preheating tail gas enters the microwave pyrolysis device 15 through the microwave pyrolysis inlet and participates in pyrolysis in the microwave pyrolysis section. After treatment in the waste gas treatment section, the purified microwave pyrolysis tail gas is obtained again for reuse. In this way, the purification treatment of each tail gas and the recycling of energy are realized, reducing costs and simplifying the treatment process of harmful tail gas.

[0079] The purified salt is then fed to a separation and purification unit for further purification and separation, yielding refined first salt and refined second salt, specifically:

[0080] S3.1 Add purified salt to the dissolving and purifying device 22, add water and adsorbent material to dissolve and purify, and obtain purified salt solution; the purified salt solution is output from the outlet end of the dissolving and purifying device 22 and filtered to obtain mixed salt solution;

[0081] S3.2 The mixed salt solution enters the evaporator 32 via the circulation pump 34. Salts whose solubility is sensitive to temperature crystallize and precipitate as the solution temperature decreases. Specifically, after exchanging heat with the low-temperature, low-pressure wet refrigerant, the mixed salt solution enters the crystallizer 23 through the first outlet of the evaporator and the circulation inlet 28 of the crystallizer to crystallize and form hydrated salt crystals. The mixed salt solution containing hydrated salts enters the evaporator 32 and the crystallizer 23 through the circulation outlet 29 of the crystallizer and the circulation pump 34 for circulating crystallization. In the crystallizer 23, the upper layer is the mixed salt supernatant, and the bottom of the cone-shaped container contains hydrated salt crystals.

[0082] The crystallization content of the mixed salt solution containing hydrated salts in crystallization tank 23 is between 10% and 15%. The discharge pump 35 and hydrocyclone 36 are turned on, and the hydrated salt solution output from the crystallization tank circulation outlet 29 passes through the discharge pump 35 and hydrocyclone 36, then the solution at the bottom of the hydrocyclone is fed into the dissolver 38. From the dissolver 38, the solution is output to the heat exchanger 39 for preheating through heat exchange. It then enters the dissolver 38 via the forced circulation pump 37, circulating and preheating until the solution in the dissolver 38 reaches the preset temperature. Finally, it is output to the first salt concentration and crystallization device 24 through the second outlet of the dissolver. A salt leg can also be installed at the conical bottom, further increasing the crystallization content in the salt leg to 15%–20%. The salt leg outlet is connected to the discharge pump 35. It is worth noting that when the crystallization content of the mixed salt solution containing hydrated salts in crystallization tank 23 is less than 10%, the freezing crystallization discharge pump 35 is turned off, meaning only freezing crystallization is circulated, and no solution is discharged. The mixed salt supernatant enters the membrane salt separation device 25 through the crystallization tank's frozen supernatant outlet 27. After impurity removal by the ultrafiltration membrane, the obtained ultrafiltration concentrate is returned to the dissolution and purification device 22 for further treatment. The ultrafiltration permeate is output to the nanofiltration membrane. After salt separation by the nanofiltration membrane, the obtained nanofiltration permeate is the second salt solution, which is output to the second salt concentration and crystallization device 26. The nanofiltration concentrate is the third salt solution, which is combined with the mixed salt solution and participates in the circulating crystallization through the circulation pump 34.

[0083] S3.3 The first salt solution and the second salt solution are evaporated and concentrated and evaporated and crystallized in the first salt concentration and crystallization device 24 and the second salt concentration and crystallization device 26, respectively, to obtain refined first salt and refined second salt.

Claims

1. A composite contaminated chemical waste salt resourceful treatment system, characterized in that: The system comprises a pyrolysis unit and a separation and purification unit. The pyrolysis unit comprises a crushing and screening device (1), a first preheating device (3), a second preheating device and a microwave pyrolysis device (15) arranged in sequence according to the processing sequence of the composite contaminated chemical waste salt. The first preheating device (3) comprises a first preheating device air inlet (6) and a first preheating device air outlet (4), and the second preheating device comprises a second preheating device air inlet (10) and a second preheating device air outlet. The microwave pyrolysis device (15) comprises an outer wall, a heat preservation material layer (5) arranged outside the outer wall, and a plurality of microwave generators (16) penetrating through the outer wall and the heat preservation material layer (5). The microwave pyrolysis device (15) is internally divided into a pyrolysis section and a waste gas treatment section, and the pyrolysis section is provided with a microwave pyrolysis device feed inlet (14), a microwave pyrolysis device air inlet (17) and a microwave pyrolysis device discharge outlet (21) penetrating through the outer wall and the heat preservation material layer (5). The waste gas treatment section is provided with a flue gas filter screen (20) and a catalyst filling section (19) in sequence along the direction of tail gas discharge of the pyrolysis section, and the catalyst filling section (19) is used for filling catalyst and catalyzing waste gas combustion degradation under the assistance of microwaves generated by the microwave generator (16). The catalyst filling section (19) is provided with a microwave pyrolysis device air outlet (18) away from the flue gas filter screen (20) side, which is used for outputting microwave pyrolysis tail gas. The separation and purification unit is used for receiving purified salt output by the microwave pyrolysis device discharge outlet (21) and performing separation and purification. The microwave pyrolysis device air outlet (18) is connected with the first preheating device air inlet (6) and the second preheating device air inlet (10) respectively. The first preheating device (3) has a first preheating material cavity inside, which is used for transmitting the composite contaminated chemical waste salt. The first preheating device air inlet (6) and the first preheating device air outlet (4) are both communicated with the first preheating material cavity, and the first preheating device air outlet (4) is connected with the microwave pyrolysis device air inlet (17). The second preheating device has a preheating interwall cavity and a second preheating material cavity, the second preheating device air inlet (10) is communicated with the preheating interwall cavity, and the microwave pyrolysis tail gas in the preheating interwall cavity and the composite contaminated chemical waste salt in the second preheating material cavity exchange heat through the side wall of the preheating interwall cavity to realize preheating. The second preheating device air outlet comprises a preheating interwall cavity air outlet (12) and a second preheating material cavity air outlet (13) communicated with the second preheating material cavity, the second preheating material cavity air outlet (13) is connected with the microwave pyrolysis device air inlet (17), and the preheating interwall cavity air outlet (12) is communicated with the external environment.

2. The composite contaminated chemical waste salt resource processing system according to claim 1, characterized in that: The separation and purification unit comprises a dissolution and purification device (22), a separation device and a concentration and crystallization device. The inlet end of the dissolution and purification device (22) is connected with the microwave pyrolysis device discharge outlet (21), the outlet end of the dissolution and purification device (22) is connected with the separation device, the dissolution and purification device (22) is used for dissolving and purifying the purified salt, removing impurities, and then outputting from the outlet end of the dissolution and purification device (22), and obtaining a mixed salt solution after filtration and outputting to the separation device. The concentration and crystallization device comprises a first salt concentration and crystallization device (24) and a second salt concentration and crystallization device (26); The separation device comprises a heat pump freezing and crystallization device and a membrane method salt separation device (25); The heat pump freezing and crystallization device comprises a circulating pump (34), an evaporator (32), a compressor (33), a condenser (30), a throttling valve (31), a discharge pump (35), a cyclone (36), a crystallization tank (23), a forced circulation pump (37), a dissolver (38) and a heat exchanger (39); The upper part of the crystallization tank (23) is provided with a crystallization tank freezing supernatant outlet (27) and a crystallization tank circulating inlet (28), and the crystallization tank (23) has a conical cylinder-shaped bottom, and the lower end of the conical cylinder-shaped bottom is provided with a crystallization tank circulating outlet (29); The circulating pump (34) is used for pumping the received mixed salt solution into the first inlet of the evaporator, and the first outlet of the evaporator is connected with the crystallization tank circulating inlet (28); The crystallization tank circulating outlet (29) is connected with the inlet of the circulating pump through a connecting pipe, and the connecting pipe is provided with a mixed salt solution feeding port and a crystalline salt discharge port, the crystalline salt discharge port is located upstream of the mixed salt solution feeding port and is connected with the inlet of the discharge pump; The outlet of the discharge pump is connected with the inlet of the cyclone, the overflow port of the cyclone is connected with the mixed salt solution feeding port, the bottom outlet of the cyclone is connected with the first inlet of the dissolver, the first outlet of the dissolver is connected with the inlet of the forced circulation pump, the outlet of the forced circulation pump is connected with the first inlet of the heat exchanger, the first outlet of the heat exchanger is connected with the second inlet of the dissolver, the second outlet of the dissolver is connected with the first salt concentration and crystallization device (24), the second outlet of the heat exchanger is connected with the first inlet of the condenser, and the second inlet of the heat exchanger is connected with the first outlet of the condenser; The second outlet of the evaporator is connected with the compressor (33) and is connected with the second inlet of the condenser through the compressor (33); the second outlet of the condenser is connected with the second inlet of the evaporator through the throttling valve (31); The crystallization tank freezing supernatant outlet (27) is connected with the membrane method salt separation device (25).

3. The composite contaminated chemical industrial waste salt resource utilization treatment system according to claim 2, characterized in that: The outer wall of the evaporator (32) has an evaporator annular cavity which is communicated with the second outlet and the second inlet of the evaporator, and the evaporator annular cavity is provided with low-temperature and low-pressure wet refrigerant which is used for being converted into medium-temperature and low-pressure gaseous refrigerant after heat exchange with the mixed salt solution; The compressor (33) is used for converting the medium-temperature and low-pressure gaseous refrigerant into high-temperature and high-pressure gaseous refrigerant; The outer wall of the condenser (30) has a condenser annular cavity which is communicated with the second inlet and the second outlet of the condenser, and the condenser annular cavity is used for receiving the high-temperature and high-pressure gaseous refrigerant and converting it into medium-temperature and high-pressure liquid refrigerant; the throttling valve (31) is used for converting the medium-temperature and high-pressure liquid refrigerant into low-temperature and low-pressure wet refrigerant which is input into the evaporator annular cavity again; The temperature of the low-temperature and low-pressure wet refrigerant is -22℃ to -28℃, and the pressure is 0.8-1.2 kg / cm 2 The temperature of the medium-temperature and low-pressure gaseous refrigerant is -25℃ to 30℃, and the pressure is 0.8-1.2 kg / cm 2 The temperature of the high-temperature and high-pressure gaseous refrigerant is 70-90℃, and the pressure is 7-10 kg / cm 2 The temperature of the medium-temperature and high-pressure liquid refrigerant is -25℃ to 30℃, and the pressure is 7-10 kg / cm 2 ​ The outer wall of the heat exchanger has a heat exchanger annular cavity which is communicated with the second inlet and the second outlet of the heat exchanger, and the heat exchanger annular cavity has cooling liquid which is used for realizing heat exchange inside the condenser and in the heat exchanger annular cavity.

4. The composite contaminated chemical industrial waste salt resource utilization treatment system according to claim 3, characterized in that: The dissolving and purifying device (22) is further provided with an adsorbing material adding port for adding adsorbing material into the dissolving and purifying device (22); The adsorbing material is activated carbon, resin, metal organic framework material or micelle.

5. The composite contaminated chemical industrial waste salt resource utilization treatment system according to claim 4, characterized in that: The membrane method salt separation device (25) is provided with ultrafiltration membrane and nanofiltration membrane in sequence along the transmission direction of supernatant in the crystallization tank (23); The nanofiltration product water obtained by nanofiltration membrane filtration is output as a second salt solution to the second salt concentration and crystallization device (26).

6. The composite contaminated chemical industrial waste salt resource utilization treatment system according to claim 5, characterized in that: The crushing and screening device (1) is a crusher with screening function; The first preheating device (3) and the second preheating device are rotary kiln or tunnel kiln.

7. A method for recycling a complex contaminated chemical salt waste, characterized in that, The composite contaminated chemical industrial waste salt resource utilization treatment system according to claim 6 comprises the following steps: S1, the composite contaminated chemical industrial waste salt is added into the crushing and screening device (1) for crushing and screening to obtain granular material of the composite contaminated chemical industrial waste salt with a diameter of 0.5-1.5 mm; S2, the granular material is added into the first preheating device (3) for primary preheating to a temperature of 200-250℃, and the primary preheated granular material is added into the second preheating device for secondary preheating to a temperature of 300-500℃; the secondary preheated granular material is fed into the pyrolysis section from the microwave pyrolysis device feed port (14) and heated to a temperature of 600-750℃ under microwave irradiation generated by the microwave generator (16) with a power of 50-75 kW, to generate purified salt and VOCs-containing waste gas; S3, the VOCs-containing waste gas is treated by the flue gas filter screen (20) and the catalyst filling section (19) to realize waste gas purification, to obtain microwave pyrolysis tail gas and output the microwave pyrolysis tail gas from the microwave pyrolysis device gas outlet (18); The purified salt is output to the separation and purification unit for purification and salt separation to obtain refined first salt and refined second salt.

8. The composite contaminated chemical industrial waste salt resource utilization treatment method according to claim 7, characterized in that: In step S3, the purified salt is output to the separation and purification unit for purification and salt separation, specifically as follows: S3.1, the purified salt is added into the dissolving and purifying device (22) for dissolving and purifying by adding water and adsorbing material to obtain a purified salt solution; the purified salt solution is output from the outlet end of the dissolving and purifying device (22) and filtered to obtain a mixed salt solution; S3.2, the mixed salt solution is fed into the evaporator (32) by the circulating pump (34), and the mixed salt solution exchanges heat with low-temperature and low-pressure wet refrigerant and is then fed into the crystallization tank (23) through the evaporator first outlet and the crystallization tank circulating inlet (28) to form hydrated salt crystals by crystallization; the mixed salt solution containing hydrated salt is fed into the circulating pump (34) through the crystallization tank circulating outlet (29), and then fed into the crystallization tank (23) through the circulating pump (34) and the evaporator (32) to perform cyclic crystallization; in the crystallization tank (23), the upper layer is supernatant of the mixed salt, and the conical bottom is settled with hydrated salt precipitate. When the crystallization content of the mixed salt solution containing hydrated salt in the crystallization tank (23) reaches 10%-15%, the discharge pump (35) and the cyclone (36) are opened, the hydrated salt solution output from the crystallization tank circulation outlet (29) is output through the discharge pump (35) and the cyclone (36), and then the solution at the bottom of the cyclone is input into the dissolver (38), output from the dissolver (38) to the heat exchanger (39), and preheated by heat exchange in the heat exchanger (39), and then input into the dissolver (38) through the forced circulation pump (37) to realize preheating and circulation until the solution in the dissolver (38) reaches the preset temperature, and then output through the second outlet of the dissolver to the first salt concentration and crystallization device (24); When the crystallization content of the mixed salt solution containing hydrated salt in the crystallization tank (23) is less than 10%, the discharge pump (35) and the cyclone (36) are closed, and the crystallization is continued to circulate; The supernatant of the mixed salt is input into the membrane method salt separation device (25) through the crystallization tank frozen supernatant outlet (27), and the ultrafiltration concentrated water obtained after the ultrafiltration membrane removes impurities is returned to the dissolving and purifying device (22) for further treatment, and the ultrafiltration water is output to the nanofiltration membrane, and the nanofiltration water obtained after the nanofiltration membrane separates the salt is the second salt solution, and the second salt solution is output to the second salt concentration and crystallization device (26); the nanofiltration concentrated water is the third salt solution, and the third salt solution is combined into the mixed salt solution to participate in the circulating crystallization through the circulating pump (34); S3.3, the first salt solution and the second salt solution are evaporated and concentrated and evaporated and crystallized in the first salt concentration and crystallization device (24) and the second salt concentration and crystallization device (26) respectively, and refined first salt and refined second salt are obtained.

9. The composite pollution chemical waste salt resource utilization treatment method according to claim 7, characterized in that: In step S3, the purified microwave pyrolysis tail gas is obtained and output from the microwave pyrolysis device gas outlet (18), which is specifically: The purified microwave pyrolysis tail gas is respectively input from the first preheating device gas inlet (6) and the second preheating device gas inlet (10) to exchange heat with the particulate material and the once preheated particulate material.

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