Resourceful treatment and cyclic utilization system for sodium chloride and sodium sulfate waste salt

Abstract

The invention relates to a resourceful treatment and cyclic utilization system for sodium chloride and sodium sulfate waste salt. The resourceful treatment and cyclic utilization system comprises a pretreatment module, a dissolution and preliminary separation module, a first purification module, a second purification module, a wastewater treatment module and an energy recovery module, the pretreatment module is connected with the dissolution and preliminary separation module and conveys a pretreated waste salt solution into the dissolution and preliminary separation module; the dissolution and preliminary separation module dissolves the pretreated waste salt in water, sodium sulfate is preliminarily crystallized and separated according to the solubility difference of sodium chloride and sodium sulfate at different temperatures, and sodium chloride is kept in a dissolved state; the first purification module is used for purifying and drying the sodium chloride solution; the second purification module is used for purifying, purifying and drying sodium sulfate; the wastewater treatment module is used for treating wastewater generated by the first purification module and the second purification module; the energy recovery module is used for recovering heat generated by the dissolution and preliminary separation module, the first purification module and the second purification module.

Description

Technical Field

[0001] This invention relates to the fields of environmental protection and resource recycling technology, specifically to a resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salts. Background Technology

[0002] Sodium chloride and sodium sulfate are widely used as important raw materials or production byproducts in many industrial sectors such as chemical, pharmaceutical, food processing, textile, and leather industries. However, waste salt containing sodium chloride and sodium sulfate generated during the production process is often accompanied by various impurities, including heavy metals, organic matter, calcium and magnesium ions. Improper handling of this waste not only results in a huge waste of resources but may also cause irreversible damage to the environment, especially soil, water sources, and air quality. Waste salt is highly toxic, difficult to degrade, and often has an irritating odor. Although it is not listed separately in the hazardous waste list, the 2016 National Hazardous Waste List officially included distillation and reaction residues and cleaning waste liquids from various production processes as hazardous waste. Therefore, industrial waste salt is managed as hazardous waste in various regions. Currently, traditional waste salt treatment methods, such as landfill and incineration, have drawbacks such as low resource recovery rates, high risk of secondary pollution, and high energy consumption. They can no longer meet the increasingly stringent environmental standards and the demands for resource recycling. Innovative technologies are urgently needed to improve the resource utilization efficiency and environmental performance of waste salt.

[0003] Patent No. ZL201911218752.4 discloses a method and equipment for the resource-based treatment of industrial waste salt. The method includes the following steps: industrial waste salt is sequentially dissolved, chemically pre-treated, deeply treated, concentrated and reduced in organic matter, adsorbed and oxidized decolorized, and crystallized by multi-effect evaporation to obtain sodium sulfate, sodium chloride, and sodium nitrate crystals, respectively. The method also includes determining the content of sodium chloride, sodium nitrate, and sodium sulfate in the industrial waste salt as a reference for the crystallization order of each salt during multi-effect evaporation crystallization. If the content of each component in the industrial waste salt changes, the crystallization order of sodium chloride, sodium nitrate, and sodium sulfate changes. The concentration and reduction of organic matter refers to the removal of organic matter from the degassed salt solution through a separation membrane to obtain a purified salt solution and a concentrate. The adsorption and oxidation decolorization refers to the purification of the salt solution after adsorption by a stacked packing material. The solution is then thoroughly mixed with an oxidant to remove the chromophores and some organic matter. The multi-effect evaporation crystallization refers to the process where the mother liquor obtained after the salt solution, following adsorption and oxidation decolorization, undergoes three stages of evaporation (first-effect, second-effect, third-effect, and fourth-effect) to crystallize into sodium sulfate, sodium chloride, and sodium nitrate, respectively. The first-effect evaporation temperature is 110-120℃, the second-effect evaporation temperature is 100-110℃, the third-effect evaporation temperature is 85-95℃, and the fourth-effect evaporation temperature is 75-85℃. The crystallization temperature of sodium sulfate is 75-85℃, sodium chloride is 60-70℃, and sodium nitrate is 45-55℃. The concentrated solution is washed with condensate generated during multi-effect evaporation crystallization, and the condensate is then recycled to the dissolution step to dissolve the industrial salt. This patent does not cover the subsequent recycling of sodium chloride and sodium sulfate.

[0004] Patent application number 202010450363.0 discloses a zero-discharge system and method for salt separation in wet desulfurization wastewater, comprising: a pretreatment system for removing suspended solids, organic matter, and heavy metal ions from wastewater to obtain a pretreated clarified wastewater; a membrane concentration system connected to the outlet of the pretreated wastewater in the pretreatment system for separating sodium sulfate and sodium chloride to obtain a salt solution mainly composed of sodium sulfate and a salt solution mainly composed of sodium chloride; and a salt production system connected to the outlet of the salt solution in the membrane concentration system for obtaining sodium sulfate from the sodium sulfate-dominant salt solution and / or obtaining sodium chloride from the sodium chloride-dominant salt solution. This patent does not cover the subsequent recycling of sodium chloride and sodium sulfate. Summary of the Invention

[0005] This invention addresses one or more technical problems existing in the prior art by providing a resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salts. It aims to solve the problem of separating and recycling sodium chloride and sodium sulfate from industrial waste salts, reducing environmental pollution and achieving efficient resource recovery. This invention belongs to the field of environmental protection and resource recycling technology, and is particularly suitable for the treatment of sodium chloride and sodium sulfate waste salts in industries such as chemical, pharmaceutical, food processing, and wastewater treatment.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt, comprising a pretreatment module, a dissolution and preliminary separation module, a first purification module, a second purification module, a wastewater treatment module and an energy recovery module;

[0007] The pretreatment module is connected to the dissolution and preliminary separation module and transports the pretreated waste salt solution to the dissolution and preliminary separation module;

[0008] The dissolution and preliminary separation module dissolves the pretreated waste salt in water to form a saturated solution. Based on the difference in solubility of sodium chloride and sodium sulfate at different temperatures, sodium sulfate is initially crystallized and separated, while sodium chloride remains dissolved. The first purification module is used to remove impurities, purify, and dry the sodium chloride solution. The second purification module is used to remove impurities, purify, and dry the sodium sulfate solution.

[0009] The wastewater treatment module is used to treat the wastewater generated by the first purification module and the second purification module; the energy recovery module is used to recover the heat generated by the dissolution and preliminary separation module, the first purification module and the second purification module.

[0010] The beneficial effects of this invention are as follows: The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salts of this invention, by setting up a pretreatment module, a dissolution and preliminary separation module, a first purification module, a second purification module, a wastewater treatment module, and an energy recovery module, can achieve efficient separation and purification of sodium chloride and sodium sulfate, with a resource recovery rate of over 95%; the wastewater treatment module can perform deep treatment on the wastewater generated after purification, achieving zero discharge; the energy recovery module can improve the overall energy utilization efficiency of the system, reducing operating costs by 30% compared to traditional methods; the purified sodium chloride and sodium sulfate products can be recycled, reducing resource waste, promoting the realization of a circular economy and sustainable development, and conforming to the development direction of green industry and low-carbon economy.

[0011] Based on the above technical solution, the present invention can be further improved as follows.

[0012] Furthermore, the wastewater treatment module includes a Fenton reactor, a photocatalytic oxidation reactor, an aerobic bioreactor, a microfiltration membrane, and an ultrafiltration membrane. The wastewater pipes of the first purification module and the second purification module are both connected to the Fenton reactor. The bottom of the Fenton reactor is connected to the photocatalytic oxidation reactor, and the bottom of the photocatalytic oxidation reactor is connected to the aerobic bioreactor. The aerobic bioreactor is sequentially connected to the microfiltration membrane and the ultrafiltration membrane.

[0013] The beneficial effects of adopting the above-mentioned further scheme are: using a Fenton reactor, H2O2 and Fe can be added... 2+ Catalysts initiate the Fenton reaction, decomposing organic matter and improving treatment efficiency. Aerobic bioreactors can enhance system bioactivity by introducing well-acclimated microbial communities, and promote biodegradation by controlling suitable temperature, pH, and dissolved oxygen.

[0014] Furthermore, the dissolution and preliminary separation module includes an activated carbon adsorber, a cooling crystallizer, a first centrifuge, a dissolution tank, and a solution buffer tank. The pretreatment module is connected to the activated carbon adsorber and transports the pretreated waste salt solution to the activated carbon adsorber. The activated carbon adsorber is connected to the cooling crystallizer and sprays the waste salt solution adsorbed by the activated carbon into the cooling crystallizer. Sodium sulfate is initially crystallized and separated in the cooling crystallizer. After centrifugation by the first centrifuge, the sodium chloride solution enters the solution buffer tank and is transported to the first purification module for purification. The sodium sulfate crystals enter the dissolution tank for redissolution and are transported to the second purification module for purification.

[0015] Furthermore, the energy recovery module includes a first heat exchanger, which is installed at the outlet of the dissolving tank.

[0016] The beneficial effects of adopting the above-mentioned further scheme are: the first heat exchanger can capture the high-temperature waste heat generated during the dissolution process in the dissolving tank, and use the recovered heat to preheat the raw materials to be dissolved or to assist other low-heat-demand processes.

[0017] Furthermore, the dissolving tank is equipped with a first temperature sensor and a concentration detection sensor. A solvent delivery pipeline is connected to the dissolving tank, and a flow regulating valve is provided on the solvent delivery pipeline. The concentration detection sensor is electrically connected to the flow regulating valve and is used to adjust the opening degree of the flow regulating valve.

[0018] The beneficial effect of adopting the above-mentioned further solution is that the amount of solvent added can be automatically adjusted by the concentration detection sensor and the flow regulating valve to ensure the best dissolution efficiency.

[0019] Furthermore, the first purification module includes a nanofiltration device, a membrane separation device, a multi-effect evaporator, and a first drying device. The solution buffer tank is connected to the nanofiltration device via a first solution pump and delivers the sodium chloride solution to the nanofiltration device. The outlet of the nanofiltration device is connected to the inlet of the membrane separation device, the outlet of the membrane separation device is connected to the inlet of the multi-effect evaporator, and the outlet of the multi-effect evaporator is connected to the inlet of the first drying device. After the sodium chloride solution is purified by passing through the nanofiltration device, the membrane separation device, and the multi-effect evaporator in sequence, it enters the first drying device for drying to obtain the sodium chloride product. The wastewater outlet of the multi-effect evaporator is connected to the wastewater treatment module.

[0020] Furthermore, the energy recovery module includes a second heat exchanger and a turbocharger recovery device. The second heat exchanger is installed at the discharge port of the first drying equipment, and the turbocharger recovery device is installed on the membrane separation equipment and uses the pressure difference of the membrane separation equipment to convert it into electrical energy for recovery.

[0021] The beneficial effects of adopting the above-mentioned further scheme are as follows: By setting up a second heat exchanger and a turbocharger recovery device, the second heat exchanger can recover the steam or hot air emitted by the first drying equipment during the drying process and convert it into electrical and thermal energy. Specifically, the high-temperature hot air discharged from the first drying equipment passes through the second heat exchanger, where the thermal energy is transferred to the working medium. The working medium is heated and converted into steam, which drives the ORC generator to generate electricity. The steam generated is then condensed, and the released thermal energy is stored in a thermal energy storage tank for subsequent use.

[0022] Furthermore, the second purification module includes an electrodialysis module, an MVR module, and a second drying device. The dissolving tank is connected to the electrodialysis module via a second solution pump, which delivers the dissolved sodium sulfate solution to the electrodialysis module. The outlet of the electrodialysis module is connected to the inlet of the MVR module. The sodium sulfate solution is purified sequentially through the electrodialysis module and the MVR module before entering the second drying device for drying to obtain the sodium sulfate product. The wastewater outlet of the MVR module is connected to the wastewater treatment module.

[0023] Furthermore, the energy recovery module includes a third heat exchanger, which is installed at the discharge port of the second drying device.

[0024] The beneficial effects of adopting the above-mentioned further scheme are: the third heat exchanger can recover the steam or hot air emitted by the second drying equipment during the drying process and convert it into electrical and thermal energy. Specifically, the high-temperature hot air discharged from the second drying equipment passes through the third heat exchanger, where the thermal energy is transferred to the working medium. The working medium is heated and converted into steam, which drives the ORC generator to generate electricity. The steam generated is then condensed, and the released thermal energy is stored in a thermal energy storage tank for subsequent use.

[0025] Furthermore, the pretreatment module includes a filter screen, a water washing tank, a second centrifuge, a third solution pump, an acid washing tank, a fourth solution pump, an alkaline washing tank, and a fifth solution pump. Sodium chloride and sodium sulfate waste salts are conveyed to the filter screen for filtration and then enter the water washing tank for water washing. The waste salts after water washing enter the second centrifuge for centrifugation, and the resulting waste salt solution is then pumped into the acid washing tank by the third solution pump for acid washing, then into the alkaline washing tank by the fourth solution pump for alkaline washing, and finally into the dissolution and preliminary separation module by the fifth solution pump for preliminary separation. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the preprocessing module of the present invention;

[0027] Figure 2 This is a partial structural diagram of the first purification module and the second purification module of the present invention. Figure 1 ;

[0028] Figure 3 This is a partial structural diagram of the first purification module and the second purification module of the present invention. Figure 2 ;

[0029] Figure 4 This is a schematic diagram of the wastewater treatment module of the present invention;

[0030] Figure 5 This is a block diagram of the resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salts of the present invention.

[0031] The attached diagram lists the components represented by each number as follows:

[0032] 1. Conveyor; 2. Filter screen; 3. Washing tank; 4. Second centrifuge; 5. Third solution pump; 6. Acid washing tank; 7. Alkali washing tank; 8. Activated carbon adsorber; 9. Cooling crystallizer; 10. First centrifuge; 11. Dissolving tank; 12. Solution buffer tank; 13. First solution pump; 14. Second solution pump; 15. Electrodialysis module; 16. MVR module; 17. Nanofiltration equipment; 18. Membrane separation equipment; 19. Multi-effect evaporation equipment; 20. First drying equipment; 21. Second drying equipment; 22. Mixer; 23. Biological treatment tank; 24. Fenton reactor; 25. Photocatalytic oxidation reactor; 26. Aerobic bioreactor; 27. Microfiltration membrane; 28. Ultrafiltration membrane; 29. ​​Fourth solution pump; 30. Fifth solution pump. Detailed Implementation

[0033] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0034] like Figures 1-5As shown, this embodiment of a resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt includes a pretreatment module, a dissolution and preliminary separation module, a first purification module, a second purification module, a wastewater treatment module, and an energy recovery module.

[0035] The pretreatment module is connected to the dissolution and preliminary separation module and transports the pretreated waste salt solution to the dissolution and preliminary separation module;

[0036] The dissolution and preliminary separation module dissolves the pretreated waste salt in water to form a saturated solution. Based on the difference in solubility of sodium chloride and sodium sulfate at different temperatures, sodium sulfate is initially crystallized and separated, while sodium chloride remains dissolved. The first purification module is used to remove impurities, purify, and dry the sodium chloride solution. The second purification module is used to remove impurities, purify, and dry the sodium sulfate solution.

[0037] The wastewater treatment module is used to treat the wastewater generated by the first purification module and the second purification module; the energy recovery module is used to recover the heat generated by the dissolution and preliminary separation module, the first purification module and the second purification module.

[0038] This embodiment of a resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt aims to solve the problems of low treatment efficiency, low resource recovery rate, and serious environmental pollution in existing technologies. By proposing a high-efficiency and environmentally friendly resource-based treatment and recycling system, it achieves efficient separation, purification, and resource utilization of sodium chloride and sodium sulfate in waste salt, while reducing energy consumption and environmental pollution during the treatment process, and improving the overall system's economy and environmental friendliness.

[0039] like Figure 4 As shown, the wastewater treatment module in this embodiment includes a Fenton reactor 24, a photocatalytic oxidation reactor 25, an aerobic bioreactor 26, a microfiltration membrane 27, and an ultrafiltration membrane 28. The wastewater pipes of both the first and second purification modules are connected to the Fenton reactor 24. The bottom of the Fenton reactor 24 is connected to the photocatalytic oxidation reactor 25, and the bottom of the photocatalytic oxidation reactor 25 is connected to the aerobic bioreactor 26. The aerobic bioreactor 26 is sequentially connected to the microfiltration membrane 27 and the ultrafiltration membrane 28. Using the Fenton reactor, H2O2 and Fe can be added... 2+ The catalyst initiates the Fenton reaction, decomposing organic matter and improving treatment efficiency. The aerobic bioreactor can enhance system biological activity by introducing well-acclimated microbial communities and promote biodegradation by controlling suitable temperature, pH, and dissolved oxygen. The wastewater treatment module utilizes advanced treatment technologies such as biological treatment, chemical precipitation, and reverse osmosis to process wastewater generated throughout the system, achieving water resource recycling and recovering some usable salts and chemicals.

[0040] The wastewater treatment module in this embodiment treats the wastewater generated by the two purification modules. Specifically, it targets industrial wastewater that is difficult to degrade, has high organic content, and is difficult to treat with conventional biological methods. It employs an integrated advanced oxidation-biological enhancement-membrane filtration process to achieve highly efficient wastewater purification. The Fenton reactor 24 and photocatalytic oxidation reactor 25 in the wastewater treatment module primarily aim to degrade recalcitrant organic matter and toxic substances in the water, improving the wastewater's biodegradability. This is achieved by adding H2O2 and Fe2O3. + The catalyst initiates the Fenton reaction, decomposing organic matter. Then, ultraviolet or visible light excites TiO2 to generate hydroxyl radicals, enhancing the oxidation effect. The aerobic bioreactor 26 primarily aims to utilize microorganisms to degrade residual organic matter, improving treatment efficiency. This is achieved by introducing well-acclimated microbial communities to enhance system biological activity. Appropriate temperature, pH, and dissolved oxygen are controlled to promote biodegradation. The microfiltration membrane 27 and ultrafiltration membrane 28 primarily perform solid-liquid separation, retaining suspended solids and microorganisms, removing color, bacteria, and viruses, ensuring effluent quality. Wastewater from the Fenton reactor 24, photocatalytic oxidation reactor 25, and aerobic bioreactor 26 enters the microfiltration membrane to remove large particles. It then passes through the ultrafiltration membrane to ensure clear and transparent effluent. The wastewater treatment module features: flexibility: adjusting oxidant dosage and microbial population according to water quality, resulting in strong adaptability; high efficiency: combining multiple technologies to ensure thorough treatment and stable effluent; and economic efficiency: optimizing operating parameters to reduce reagent consumption and lower costs.

[0041] like Figure 2 As shown, the dissolution and preliminary separation module in this embodiment includes an activated carbon adsorber 8, a cooling crystallizer 9, a first centrifuge 10, a dissolution tank 11, and a solution buffer tank 12. The pretreatment module is connected to the activated carbon adsorber 8 and transports the pretreated waste salt solution to the activated carbon adsorber 8. The activated carbon adsorber 8 is connected to the cooling crystallizer 9 and sprays the waste salt solution from the activated carbon adsorber 8 into the cooling crystallizer 9. Sodium sulfate is initially crystallized and separated in the cooling crystallizer 9. After centrifugation by the first centrifuge 10, the sodium chloride solution enters the solution buffer tank 12 and is transported to the first purification module for purification. The sodium sulfate crystals enter the dissolution tank 11 for redissolution and are transported to the second purification module for purification. The dissolution and preliminary separation module utilizes the difference in solubility to dissolve the pretreated waste salt in water to form a saturated solution. Based on the difference in solubility of sodium chloride and sodium sulfate at different temperatures, the preliminary clean separation of sodium sulfate is achieved through precise temperature control. At a specific temperature, sodium sulfate crystallizes out, while sodium chloride remains dissolved, thus achieving preliminary separation.

[0042] In one specific embodiment, the energy recovery module includes a first heat exchanger installed at the outlet of the dissolving tank 11. The first heat exchanger can capture the high-temperature waste heat generated during the dissolving process in the dissolving tank and use the recovered heat to preheat the raw materials to be dissolved or to assist other low-heat-requirement processes.

[0043] Optionally, the dissolving tank 11 is equipped with a first temperature sensor and a concentration detection sensor. A solvent delivery pipe is connected to the dissolving tank 11, and a flow regulating valve is installed on the solvent delivery pipe. The concentration detection sensor is electrically connected to the flow regulating valve and is used to adjust the opening of the flow regulating valve. The amount of solvent added can be automatically adjusted through the concentration detection sensor and the flow regulating valve to ensure optimal dissolution efficiency.

[0044] Optionally, this embodiment can integrate an intelligent control module, employing technologies such as the Internet of Things and big data analytics to monitor the entire system's operational status in real time. By optimizing control parameters through algorithms, it achieves efficient and stable system operation. A fault early warning system can also be established to promptly detect and address potential equipment failures, reducing downtime and improving system efficiency. The intelligent control module enables data acquisition and analysis, process optimization, and predictive maintenance. This includes: real-time monitoring: collecting data from various sensors, including key parameters such as temperature, humidity, and flow rate; intelligent diagnostics: using AI algorithms to analyze data in real time and identify abnormal conditions; dynamic adjustment: automatically adjusting equipment operating parameters, such as temperature and pressure, based on real-time data; energy management: intelligently scheduling energy use to improve energy efficiency; fault early warning: predicting potential equipment problems and scheduling maintenance in advance to reduce downtime; lifespan prediction: assessing equipment health status and extending service life. Ultimately, this leads to efficiency improvements: automated and intelligent operation significantly improves processing efficiency and product quality; cost savings: refined energy management reduces waste and lowers operating costs; and environmental friendliness: reducing energy consumption and emissions, aligning with green production principles.

[0045] like Figure 2 As shown, the first purification module in this embodiment includes a nanofiltration device 17, a membrane separation device 18, a multi-effect evaporator 19, and a first drying device 20. The solution buffer tank 12 is connected to the nanofiltration device 17 via a first solution pump 13 and delivers the sodium chloride solution to the nanofiltration device 17. The outlet of the nanofiltration device 17 is connected to the inlet of the membrane separation device 18, the outlet of the membrane separation device 18 is connected to the inlet of the multi-effect evaporator 19, and the outlet of the multi-effect evaporator 19 is connected to the inlet of the first drying device 20. The sodium chloride solution is purified sequentially by passing through the nanofiltration device 17, the membrane separation device 18, and the multi-effect evaporator 19, and then enters the first drying device 20 for drying to obtain the sodium chloride product. The wastewater outlet of the multi-effect evaporator 19 is connected to the wastewater treatment module.

[0046] Specifically, the energy recovery module includes a second heat exchanger and a turbocharger recovery device. The second heat exchanger is installed at the exhaust port of the first drying device 20, and the turbocharger recovery device is installed on the membrane separation device 18 and utilizes the pressure difference of the membrane separation device 18 to convert it into electrical energy for recovery. By setting up the second heat exchanger and the turbocharger recovery device, the second heat exchanger can recover the steam or hot air emitted by the first drying device during the drying process and convert it into electrical and thermal energy. That is, the high-temperature hot air discharged from the first drying device passes through the second heat exchanger, and the thermal energy is transferred to the working medium inside the second heat exchanger. The working medium is heated and converted into steam, which drives the ORC generator to generate electricity. The steam after power generation is condensed, and the released thermal energy is stored in a thermal energy storage tank for subsequent use.

[0047] like Figure 2 As shown, the second purification module in this embodiment includes an electrodialysis module 15, an MVR module 16, and a second drying device 21. The dissolving tank 11 is connected to the electrodialysis module 15 via a second solution pump 14, which delivers the dissolved sodium sulfate solution to the electrodialysis module 15. The outlet of the electrodialysis module 15 is connected to the inlet of the MVR module 16. The sodium sulfate solution is purified by passing through the electrodialysis module 15 and the MVR module 16 in sequence, and then enters the second drying device 21 for drying to obtain the sodium sulfate product. The wastewater outlet of the MVR module 16 is connected to the wastewater treatment module.

[0048] Furthermore, such as Figure 3 As shown, in this embodiment, the wastewater outlets of the MVR module 16 and the multi-effect evaporator 19 are connected to the mixer 22 via pipelines, and the mixer 22 is connected to the biological treatment tank 23 via pipelines. The wastewater discharged from the biological treatment tank 23 is connected to the wastewater treatment module.

[0049] The two purification modules utilize nanofiltration and reverse osmosis membrane separation technologies to remove organic matter, colloids, and some inorganic impurities from the solution, improving the purity of sodium sulfate and sodium chloride. Further chemical methods such as ion exchange, precipitation, and extraction can be used to remove residual trace impurities, ensuring high product purity. Electrochemical methods, such as electrolysis and electrodialysis, can also be used to remove impurities that are difficult to remove by physical or chemical methods, further enhancing the purification effect.

[0050] Specifically, the energy recovery module includes a third heat exchanger, which is installed at the exhaust port of the second drying device 21. The third heat exchanger can recover the steam or hot air emitted by the second drying device during the drying process, converting it into electrical and thermal energy. That is, the high-temperature hot air discharged from the second drying device passes through the third heat exchanger, where the thermal energy is transferred to the working medium. The working medium is heated and converted into steam, which drives the ORC generator to generate electricity. The steam generated is then condensed, and the released thermal energy is stored in a thermal energy storage tank for subsequent use.

[0051] This embodiment integrates combined heat and power (CHP) technology into heat-consuming processes such as dissolution and drying by incorporating an energy recovery module. This allows for the recovery and reuse of generated heat, reducing energy consumption. Furthermore, it optimizes electrical energy usage by reducing unnecessary energy consumption through system design improvements. Additionally, it considers introducing energy recovery in high-energy-consuming processes such as membrane separation to improve energy efficiency. The heat exchanger can utilize waste heat generated during system operation to preheat incoming waste salt solutions or during the drying process, further enhancing energy utilization.

[0052] The energy recovery module in this embodiment focuses on high-heat-consuming processes such as dissolution and drying. By integrating combined heat and power (CHP) technology, it achieves effective recovery and utilization of heat energy. This technology not only reduces energy consumption but also improves energy self-sufficiency through thermal power generation, creating a green and sustainable production model. Heat recovery in the dissolution process primarily recovers waste heat emitted during dissolution for subsequent processes or facilities. A heat exchanger is installed at the outlet of the dissolution tank to capture the high-temperature waste heat generated during dissolution. The recovered heat is used to preheat raw materials to be dissolved or to assist other low-heat-demand processes. Heat recovery and CHP in the drying process recover steam or hot air emitted during drying, converting it into electricity and heat. The high-temperature hot air discharged from the dryer passes through a heat exchanger, transferring the heat energy to the working medium. The working medium is heated and converted into steam, driving an ORC generator to generate electricity. The steam after power generation is condensed, and the released heat energy is stored in a thermal energy storage tank for subsequent use. The heat energy recovered from the dissolution and drying processes is integrated to form a unified thermal energy supply network. Flexible scheduling based on the thermal energy demand of different seasons and time periods improves system energy efficiency. The main features are as follows: Energy self-sufficiency: Through combined heat and power (CHP), both electricity and heat are provided, reducing dependence on external energy sources. Cost savings: Reduced heat consumption costs improve the economic efficiency of the entire production system. Environmental protection and emission reduction: Reduced use of fossil fuels and lower emissions of greenhouse gases such as CO2 align with green production principles.

[0053] Specifically, the focus is on the integrated application of power optimization and energy recovery technologies, aiming to reduce unnecessary power consumption, especially by introducing energy recovery mechanisms in high-energy-consuming processes such as membrane separation, to improve overall power utilization efficiency. Through precise control and intelligent scheduling, refined energy management is achieved. Power optimization reduces unnecessary power consumption and optimizes system energy efficiency. A smart grid management system is introduced to control variable frequency motors and equipment, monitoring power consumption in real time and adjusting accordingly. Variable frequency motors are used to automatically adjust power based on load. In high-energy-consuming processes such as membrane separation, energy is recovered and reused. The pressure difference generated during membrane separation is converted into electrical energy through a turbocharging recovery system. The recovered electrical energy is used in membrane systems or other low-demand equipment. Power optimization and energy recovery are integrated to form a closed-loop energy management system. Intelligent control strategies are implemented to dynamically adjust power allocation. System performance is regularly evaluated, and equipment and strategies are optimized and upgraded. Key features include: Improved energy efficiency: Significantly reduced energy consumption in membrane separation, improving overall power utilization efficiency. Cost savings: Reduced electricity expenses, resulting in a significant decrease in long-term operating costs. Environmentally friendly: Reduces greenhouse gas emissions and aligns with green production goals.

[0054] The energy recovery module focuses on precisely capturing the waste heat generated during system operation through a waste heat recovery device. This waste heat is then efficiently used to preheat newly introduced waste salt solutions or to enhance the drying process, significantly improving energy utilization, achieving secondary energy use, and reducing energy loss. The waste heat recovery and preheating of newly introduced waste salt solutions directly utilizes waste heat from the waste salt treatment process to preheat the newly introduced solutions, improving efficiency. Waste heat is captured at heat exchange points installed in the waste salt treatment system. This heat energy is used to preheat newly input waste salt solutions, saving heating costs. Waste heat-enhanced drying improves drying efficiency, accelerates moisture evaporation, and speeds up processing. The integrated heat recovery system within the drying tower directly utilizes waste heat to increase drying temperature, accelerating moisture evaporation, improving drying efficiency, and reducing energy consumption. Key features include: Improved energy efficiency: Effectively utilizing waste heat reduces additional energy consumption and improves overall energy efficiency. Cost savings: Significantly reduces heating and drying costs, making long-term operation more economical. Environmental protection and emission reduction: Reduces the use of fossil fuels, lowers carbon emissions, and meets green production standards.

[0055] like Figure 1As shown, the pretreatment module in this embodiment includes a filter screen 2, a washing tank 3, a second centrifuge 4, a third solution pump 5, an acid washing tank 6, a fourth solution pump 29, an alkaline washing tank 7, and a fifth solution pump 30. Waste sodium chloride and sodium sulfate are conveyed to the filter screen 2 via a conveyor 1 for filtration and then enter the washing tank 3 for washing. The washed waste salt is centrifuged in the second centrifuge 4, and the resulting waste salt solution is pumped through the third solution pump 5 into the acid washing tank 6 for acid washing. It is then pumped through the fourth solution pump 29 into the alkaline washing tank 7 for alkaline washing. Finally, it enters the dissolution and preliminary separation module via the fifth solution pump 30 for preliminary separation. The pretreatment module utilizes the filter screen and washing tank, employing mechanical screening and washing technology to effectively remove large particulate impurities and surface deposits from the waste salt. Through chemical methods such as acid washing, alkaline washing, and oxidation-reduction, heavy metals, organic matter, and some inorganic impurities in the waste salt are removed, improving the efficiency and purity of subsequent treatment. The waste sodium chloride and sodium sulfate can be conveyed to the filter screen 2 via the conveyor 1 for filtration.

[0056] This embodiment can also include resource recovery and productization modules, which can convert purified sodium chloride and sodium sulfate into high value-added products, such as those used in food processing, pharmaceuticals, and chemical raw materials, according to market demand.

[0057] The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salts in this embodiment, by setting up a pretreatment module, a dissolution and preliminary separation module, a first purification module, a second purification module, a wastewater treatment module, and an energy recovery module, can achieve efficient separation and purification of sodium chloride and sodium sulfate, with a resource recovery rate of over 95%. The wastewater treatment module can perform deep treatment on the wastewater generated after purification, achieving zero discharge. The energy recovery module can improve the overall energy utilization efficiency of the system, reducing operating costs by 30% compared to traditional methods. The purified sodium chloride and sodium sulfate products can be recycled, reducing resource waste, promoting the realization of a circular economy and sustainable development, and conforming to the development direction of green industry and low-carbon economy.

[0058] Test case

[0059] In a large chemical enterprise, the system of this invention was used to treat a mixed waste salt of sodium chloride and sodium sulfate with an annual output of 5,000 tons. Through pretreatment, dissolution and preliminary separation, purification, and resource utilization steps, 3,200 tons of high-purity sodium sulfate and 1,600 tons of high-purity sodium chloride were finally obtained, with a resource recovery rate as high as 96%. The system's operating cost was reduced by 30% compared to traditional methods, achieving a dual improvement in economic and environmental benefits. Simultaneously, the wastewater, after deep treatment, met zero-discharge standards, demonstrating the significant environmental advantages of this invention. Furthermore, through the integration of combined heat and power (CHP) technology, the system's energy utilization efficiency was improved by 20%, further reducing operating costs and enhancing overall economic and environmental performance.

[0060] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0061] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0062] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0063] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0064] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0065] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salts, characterized in that, It includes a pretreatment module, a dissolution and preliminary separation module, a first purification module, a second purification module, a wastewater treatment module, and an energy recovery module; The pretreatment module is connected to the dissolution and preliminary separation module and transports the pretreated waste salt solution to the dissolution and preliminary separation module; The dissolution and preliminary separation module dissolves the pretreated waste salt in water to form a saturated solution. Based on the difference in solubility of sodium chloride and sodium sulfate at different temperatures, sodium sulfate is initially crystallized and separated, while sodium chloride remains dissolved. The first purification module is used to remove impurities, purify, and dry the sodium chloride solution. The second purification module is used to remove impurities, purify, and dry the sodium sulfate solution. The wastewater treatment module is used to treat the wastewater generated by the first purification module and the second purification module; The energy recovery module is used to recover the heat generated by the dissolution and preliminary separation module, the first purification module, and the second purification module.

2. The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt according to claim 1, characterized in that, The wastewater treatment module includes a Fenton reactor, a photocatalytic oxidation reactor, an aerobic bioreactor, a microfiltration membrane, and an ultrafiltration membrane. The wastewater pipes of the first purification module and the second purification module are both connected to the Fenton reactor. The bottom of the Fenton reactor is connected to the photocatalytic oxidation reactor, and the bottom of the photocatalytic oxidation reactor is connected to the aerobic bioreactor. The aerobic bioreactor is connected to the microfiltration membrane and the ultrafiltration membrane in sequence.

3. The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt according to claim 1, characterized in that, The dissolution and preliminary separation module includes an activated carbon adsorber, a cooling crystallizer, a first centrifuge, a dissolution tank, and a solution buffer tank. The pretreatment module is connected to the activated carbon adsorber and transports the pretreated waste salt solution to the activated carbon adsorber. The activated carbon adsorber is connected to the cooling crystallizer and sprays the waste salt solution adsorbed by the activated carbon into the cooling crystallizer. Sodium sulfate is initially crystallized and separated in the cooling crystallizer. After centrifugation by the first centrifuge, the sodium chloride solution enters the solution buffer tank and is transported to the first purification module for purification. The sodium sulfate crystals enter the dissolution tank for redissolution and are transported to the second purification module for purification.

4. The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt according to claim 3, characterized in that, The energy recovery module includes a first heat exchanger, which is installed at the outlet of the dissolving tank.

5. The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt according to claim 3, characterized in that, The dissolving tank is equipped with a first temperature sensor and a concentration detection sensor. A solvent delivery pipeline is connected to the dissolving tank. A flow regulating valve is installed on the solvent delivery pipeline. The concentration detection sensor is electrically connected to the flow regulating valve and is used to adjust the opening degree of the flow regulating valve.

6. The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt according to claim 3, characterized in that, The first purification module includes a nanofiltration device, a membrane separation device, a multi-effect evaporator, and a first drying device. The solution buffer tank is connected to the nanofiltration device via a first solution pump and delivers the sodium chloride solution to the nanofiltration device. The outlet of the nanofiltration device is connected to the inlet of the membrane separation device, the outlet of the membrane separation device is connected to the inlet of the multi-effect evaporator, and the outlet of the multi-effect evaporator is connected to the inlet of the first drying device. The sodium chloride solution is purified sequentially by passing through the nanofiltration device, the membrane separation device, and the multi-effect evaporator before entering the first drying device for drying to obtain the sodium chloride product. The wastewater outlet of the multi-effect evaporator is connected to the wastewater treatment module.

7. The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt according to claim 6, characterized in that, The energy recovery module includes a second heat exchanger and a turbocharged recovery device. The second heat exchanger is installed at the discharge port of the first drying equipment, and the turbocharged recovery device is installed on the membrane separation equipment and uses the pressure difference of the membrane separation equipment to convert it into electrical energy for recovery.

8. The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt according to claim 3, characterized in that, The second purification module includes an electrodialysis module, an MVR module, and a second drying device. The dissolving tank is connected to the electrodialysis module via a second solution pump, which delivers the dissolved sodium sulfate solution to the electrodialysis module. The outlet of the electrodialysis module is connected to the inlet of the MVR module. The sodium sulfate solution is purified sequentially through the electrodialysis module and the MVR module before entering the second drying device for drying to obtain the sodium sulfate product. The wastewater outlet of the MVR module is connected to the wastewater treatment module.

9. The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt according to claim 8, characterized in that, The energy recovery module includes a third heat exchanger, which is installed at the discharge port of the second drying device.

10. The resource-based treatment and recycling system for sodium chloride and sodium sulfate waste salt according to claim 1, characterized in that, The pretreatment module includes a filter screen, a washing tank, a second centrifuge, a third solution pump, an acid washing tank, a fourth solution pump, an alkaline washing tank, and a fifth solution pump. Waste salts of sodium chloride and sodium sulfate are conveyed to the filter screen for filtration and then enter the washing tank for washing. The washed waste salts are centrifuged in the second centrifuge, and the resulting waste salt solution is pumped into the acid washing tank by the third solution pump for acid washing. Then, it is pumped into the alkaline washing tank by the fourth solution pump for alkaline washing. Finally, it is pumped into the dissolution and preliminary separation module by the fifth solution pump for preliminary separation.

Images