Evaporative crystallization and purification treatment system for high-salinity wastewater

Abstract

The utility model discloses an evaporative crystallization purification treatment system for high-salinity wastewater, which is suitable for treating high-salinity and high-hardness wastewater represented by desulfurization wastewater in a power plant, and is also suitable for removing sulfate radicals in calcium chloride and sodium chloride systems represented by polycrystalline silicon production wastewater. The seed crystal feeding device, the seed crystal recovery device and the mother liquor separation device are additionally arranged on the basis of a traditional evaporative crystallization system, the seed crystal concentration in the system is maintained through feeding during starting and maintaining scale resistance during normal operation, and self-circulation of the seed crystal is achieved through seed crystal recovery; secondary separation of the seed crystal is realized through the mother liquor separation device, so that the purity of subsequent crystallized salt is ensured.

Description

Technical Field

[0001] This utility model belongs to the field of high-salt wastewater evaporation, crystallization and purification, and particularly relates to a high-salt wastewater evaporation, crystallization and purification treatment system. Background Technology

[0002] Resource utilization of high-salinity wastewater is currently a hot research topic. Through advanced technologies, the salt and organic matter in high-salinity wastewater can be transformed into valuable resources. For example, waste salt can be purified to meet industrial salt recycling standards and then reused in industrial production; or it can be processed into fertilizers, building materials, etc. These resource utilization approaches not only reduce wastewater discharge and treatment costs but also achieve resource recycling and sustainable economic development.

[0003] For the treatment of high-salinity and high-hardness wastewater, a series of effective processes are needed to reduce its salinity and hardness to ensure that the wastewater meets discharge standards or reuse requirements. Chemical softening is the main form of chemical precipitation. Chemical precipitation is a process based on the solubility product principle, where unwanted components in water are converted into insoluble compounds by appropriate reagents. The most commonly used method in water treatment is the crystallization precipitation of calcium and magnesium ions.

[0004] Chemical softening typically uses agents such as lime, soda ash, and sodium hydroxide. Depending on the quality of the raw water and the desired quality of the treated water, one or more agents can be used simultaneously. Examples include the lime method, sodium hydroxide method, lime-soda ash method, and sodium hydroxide-soda ash method.

[0005] The advantages of chemical softening and hardening are that the process is mature and the operation is simple. The disadvantages are that the cost of adding chemicals is high and the amount of sludge produced is large and needs to be properly treated.

[0006] For high-hardness wastewater, especially high-salt, high-hardness wastewater with calcium ion concentrations above 2000 mg / L, direct chemical softening treatment is costly.

[0007] High-salt, high-hardness wastewater, such as desulfurization wastewater from power plants, is saturated with calcium sulfate. During evaporation, calcium sulfate continuously accumulates, and excess calcium sulfate tends to grow on the pipe and tank walls, affecting heat transfer, reducing evaporation intensity, and increasing the viscosity of the liquid, making long-term stable system operation impossible. Traditional dual-alkali chemical hardening methods require large amounts of reagents and incur high sludge disposal costs. Utility Model Content

[0008] The purpose of this invention is to provide a high-salt wastewater evaporation crystallization purification treatment system, which is suitable for the treatment of high-salt and high-hardness wastewater, such as power plant desulfurization wastewater. By adding seed crystals to prevent scale buildup, the system slows down the scaling of the evaporation crystallization system, extends the equipment cleaning cycle, and reduces the pretreatment softening cost, thereby solving the technical problems of traditional dual-alkali chemical hardening methods, which require large amounts of reagents and have high sludge disposal costs.

[0009] To solve the above-mentioned technical problems, the specific technical solution of this utility model is as follows:

[0010] A high-salt wastewater evaporation crystallization purification treatment system includes a seed crystal addition device, a raw water tank, an evaporation crystallization device, a seed crystal recovery device, a mother liquor separation device, a centrifuge device, a mother liquor tank, and a packaging device.

[0011] The seed crystal addition device is used for seed crystal addition during the system startup phase and is connected to the original water tank.

[0012] The raw water tank is used for feeding the buffer system and establishes the seed crystal concentration during the start-up phase. It is connected to the evaporation and crystallization device.

[0013] The evaporation and crystallization device is used for the evaporation and crystallization of materials, and its discharge pump is connected to the seed crystal recovery device.

[0014] The supernatant of the seed crystal recovery device is connected to the evaporation crystallization device, and the discharge of the seed crystal recovery device is connected to the mother liquor separation device.

[0015] The supernatant of the mother liquor separation device is connected to the mother liquor tank, and the discharge is connected to the centrifuge device.

[0016] The centrifuge device is used for solid-liquid separation of crystalline salt. The crystalline salt in the centrifuge device is connected to the packaging device, and the centrifuged mother liquor is connected to the mother liquor tank.

[0017] The mother liquor tank is used to collect centrifuged mother liquor and supernatant from the mother liquor separation device, and its discharge is connected to the evaporation and crystallization device.

[0018] Furthermore, the seed crystal addition device includes a seed crystal silo, a seed crystal quantitative addition device, and a stirring device. The seed crystal silo is connected to the seed crystal quantitative addition device, the seed crystal quantitative addition device is connected to the raw water tank, and the stirring device is connected to the raw water tank.

[0019] Furthermore, the seed crystal recovery device includes a discharge pump, a high-efficiency hydrocyclone, and a sight glass. The discharge pump is connected to the high-efficiency hydrocyclone, the upper outlet of the high-efficiency hydrocyclone is connected to the sight glass, and the lower outlet of the high-efficiency hydrocyclone is connected to the mother liquor separator device.

[0020] This utility model provides a high-salt wastewater evaporation crystallization purification system, which has the following advantages:

[0021] This invention presents a high-salt wastewater evaporation crystallization purification system specifically designed for the treatment of high-salt, high-hardness wastewater. Based on a traditional evaporation crystallization system, it adds a seed crystal addition device, a seed crystal recovery device, and a mother liquor separator. The seed crystals participate in the system circulation, preventing calcium sulfate crystal growth on the heat exchange wall and thus mitigating scaling. Compared to traditional chemical softening processes, this invention achieves long-term stable operation of the evaporator without chemical softening, significantly reducing the costs of evaporation crystallization agents and sludge disposal. The system has demonstrated excellent operational feedback and significant economic value. Compared to the seed crystal method for anti-scaling in the salt chemical industry, this invention employs a two-stage seed crystal recovery and separation process tailored to different water qualities, effectively ensuring the purity of the subsequently crystallized salt, facilitating the maintenance of the system's seed crystal concentration, and extending the equipment's stable operating time. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a high-salt wastewater evaporation crystallization purification treatment system according to the present invention;

[0023] Figure 2 This is a schematic diagram of the treatment process for sulfate removal in a calcium chloride and sodium chloride system, represented by polycrystalline silicon wastewater, according to this utility model. Detailed Implementation

[0024] To better understand the purpose, structure, and function of this utility model, the following description, in conjunction with the accompanying drawings, provides a more detailed account of a high-salt wastewater evaporation crystallization purification system.

[0025] like Figure 1 As shown, a high-salt wastewater evaporation crystallization purification treatment system consists of a raw water tank, a seed crystal addition device, an evaporation crystallization device, a seed crystal recovery device, a mother liquor separation device, a centrifuge device, a mother liquor tank, and a packaging device.

[0026] The seed crystal addition device is used for seed crystal addition during the system startup phase and is connected to the original water tank.

[0027] The raw water tank is used for feeding the buffer system and establishes the seed crystal concentration during the start-up phase. It is connected to the evaporation and crystallization device.

[0028] The evaporation and crystallization device is used for the evaporation and crystallization of materials, and its discharge pump is connected to the seed crystal recovery device.

[0029] The seed crystal recovery device is used for the primary separation and recovery of seed crystals in the discharge of the evaporation crystallization device. The discharge of the evaporation crystallization device is connected to the seed crystal recovery device through a discharge pump.

[0030] The mother liquor separation device is used for secondary separation of the discharged material to purify the discharged material and obtain crystalline salt with higher purity. Its supernatant is connected to the mother liquor tank and its discharge port is connected to the centrifuge.

[0031] The centrifuge device is used for solid-liquid separation of crystalline salt. The crystalline salt in the centrifuge device is connected to the packaging device, and the centrifuged mother liquor is connected to the mother liquor tank.

[0032] The mother liquor tank is used to collect centrifuged mother liquor and supernatant from the mother liquor separation device, and its discharge is connected to the evaporation and crystallization device.

[0033] like Figure 1 As shown, a seed crystal addition device, a seed crystal recovery device, and a mother liquor separator are added to the traditional evaporation crystallization system. The seed crystals are used to participate in the system circulation to prevent calcium sulfate crystals from growing on the heat exchange wall, thereby alleviating the tendency to scale.

[0034] The seed crystal dosing device is used to add seed crystals into the system during the equipment start-up phase. The appropriate amount of seed crystals to be added is calculated based on the inflow water volume and water quality, and the addition is quantitative.

[0035] The seed crystal recovery device is used to recover calcium sulfate from the system output during normal system operation. The seed crystal recovery device enables the reuse of seed crystals without the need for continuous seed crystal addition, and at the same time, it performs a one-time separation and purification of the material by seed crystals.

[0036] The mother liquor separation device is used for secondary separation and purification of the material system to achieve the purification process of the material, so that the output does not contain calcium sulfate crystals, thus ensuring the purity of the subsequent crystallized salt.

[0037] The high-salt wastewater evaporation crystallization purification system proposed in this invention is also applicable to the removal of sulfate ions in calcium chloride and sodium chloride systems, represented by polysilicon wastewater.

[0038] like Figure 2 As shown, the system consists of a raw water tank, a seed crystal addition device, a multi-effect sodium chloride concentration device, an inter-effect pump, a seed crystal recovery device, a mother liquor separation device, a sodium chloride crystallizer, a sodium chloride centrifuge, a mother liquor tank, a calcium chloride crystallizer, and a calcium chloride flake forming machine.

[0039] The seed crystal addition device is used for seed crystal addition during the system startup phase and is connected to the original water tank.

[0040] The raw water tank is used for feeding the buffer system and establishes the seed crystal concentration during the start-up phase. It is connected to the multi-effect sodium chloride concentration device.

[0041] The multi-effect sodium chloride concentration device is used for the evaporation and concentration of materials, and its inter-effect pump is connected to the seed crystal recovery device.

[0042] The seed crystal recovery device is used for the primary separation and recovery of seed crystals in the discharge of the multi-effect sodium chloride concentration device. The discharge of the multi-effect sodium chloride concentration device is connected to the seed crystal recovery device through an inter-effect pump.

[0043] The mother liquor separation device is used for secondary separation of the discharged material to purify the discharged material and obtain a mother liquor with higher purity. Its supernatant is connected to the mother liquor tank, and its discharge port is connected to the sodium chloride crystallizer.

[0044] The sodium chloride crystallizer is used for further evaporation and crystallization of sodium chloride mother liquor, and its outlet is connected to a sodium chloride centrifuge.

[0045] The sodium chloride centrifuge is used for solid-liquid separation of crystalline salt, with the crystalline salt connected to the packaging device and the centrifuged mother liquor connected to the mother liquor tank.

[0046] The mother liquor tank is used to collect centrifuged mother liquor and supernatant from the mother liquor separation device, and its discharge is connected to the calcium chloride crystallizer.

[0047] The calcium chloride crystallizer is used for concentrating the mother liquor of sodium chloride crystallization, and its discharge is connected to the calcium chloride flake machine.

[0048] The calcium chloride flake machine is used for cooling and crystallizing calcium chloride mother liquor to form flakes, and its discharge is connected to the packaging machine.

[0049] like Figure 2 As shown, a seed crystal addition device, a seed crystal recovery device, and a mother liquor separation device are added to the conventional zero-discharge treatment system for sodium chloride and calcium chloride wastewater to solve the scaling problem in the system under high sulfate conditions.

[0050] The seed crystal dosing device is used to add seed crystals into the system during the equipment start-up phase. The appropriate amount of seed crystals to be added is calculated based on the inflow water volume and water quality, and the addition is quantitative.

[0051] The seed crystal recovery device is used to recover calcium sulfate from the system output during normal system operation. The recovery device enables the reuse of seed crystals without the need for continuous seed crystal addition. At the same time, it performs a primary separation and purification of the material entering the sodium chloride evaporation and crystallization system.

[0052] The mother liquor separation device is used to perform secondary separation and purification of the materials from the seed crystal recovery device, so that the output does not contain calcium sulfate crystals, thus ensuring the purity of the subsequent crystallized salt.

[0053] The principle of calcium sulfate seed crystal anti-scaling is based on selective crystallization. When wastewater contains a large amount of salt or total dissolved solids (TDS), these substances easily adhere to the surface of heat exchange tubes and form scale during evaporation in the evaporator. By adding a certain amount of calcium sulfate or calcium chloride as seed crystals to the wastewater, the affinity of the crystal surface (similar to scale) for scale can be utilized, reducing the supersaturation of calcium sulfate in the wastewater. In this way, calcium sulfate molecules precipitated from the wastewater will preferentially adhere to the suspended seed crystals rather than deposit on the inner wall of the heating tubes, thus achieving the purpose of scale prevention.

[0054] The following is a specific implementation method. During the system startup phase, a certain amount of calcium sulfate seed crystals needs to be added externally. Generally, the gypsum concentration in the evaporation crystallization device is controlled at 20-30 g / L. The calcium sulfate concentration in the system is maintained by quantitatively discharging the gypsum mother liquor. The seed crystal concentration in the feed water tank is maintained during the startup phase by a seed crystal addition device installed in the system. The feed water tank and the evaporation crystallization device are connected by a feed pump.

[0055] The material and seed crystals enter the evaporation and crystallization device. As the water evaporates continuously, the material is continuously concentrated to a saturated state. At the same time, the calcium and sulfate ions in the material are also concentrated to supersaturation and precipitate out. The evaporation and crystallization device is connected to the seed crystal recovery device via a discharge pump.

[0056] As the discharge pump discharges the system concentrate or solid-containing mother liquor from the equipment, the crystal concentration within the system decreases. By installing a seed crystal recovery device, the difference in particle size is utilized to recover and recycle the seed crystals, thus maintaining the system's crystal concentration. The seed crystals in the seed crystal recovery device are connected to the evaporator via pipelines through the pressure head provided by the discharge pump.

[0057] The crystal recovery device can only recover most of the calcium sulfate seed crystals, leaving a certain amount of calcium sulfate residue in the discharged mother liquor. If this residue is not recovered, it will cause scaling in the subsequent evaporator and reduce the purity of the crystalline salt. By adding a mother liquor separation device to the circulation pipe or discharge pipe of the evaporator crystallizer, a quantitative amount of gypsum mother liquor can be discharged. The mother liquor separation device controls the gypsum content within the evaporator crystallizer and simultaneously purifies the discharged gypsum mother liquor.

[0058] After primary separation in the seed crystal recovery unit, the material enters a subsequent mother liquor separation unit for secondary separation to further purify the material. The secondary separator utilizes a mother liquor separation device, and the separation effect is controlled by designing an appropriate jacket ring cross-sectional area and mother liquor discharge rate. The seed crystal recovery unit is connected to the mother liquor separation unit via pipeline.

[0059] The mother liquor separation device utilizes the difference in particle size between salt and gypsum for separation. The average particle size of gypsum in the mother liquor differs from that of sodium chloride and other similar substances by 20 to 50 times, a significant difference. As the salt slurry slowly rises within the jacket of the mother liquor separator, the free settling velocity of the salt crystals in the slurry exceeds the rising velocity, causing the salt crystals to gradually settle, exit the jacket, and enter the circulation pipe to continue circulating the salt slurry. Meanwhile, the free settling velocity of the gypsum crystals is lower than their rising velocity, so they are discharged from the system along with the mother liquor. The mother liquor separation device is connected to a centrifuge via pipeline.

[0060] The mother liquor from the separation unit enters the subsequent thickening centrifuge unit to obtain pure crystalline salt, which then enters the drying and packaging unit. The centrifuged mother liquor enters the mother liquor tank, is returned to the crystallizer, and a small amount is discharged to the subsequent mother liquor drying system. The centrifuge's liquid is connected to the mother liquor tank via pipeline, and the centrifuged crystalline salt is conveyed to the subsequent drying unit via a conveyor, where it falls by gravity into the crystalline salt packaging buffer hopper.

[0061] It is used to remove sulfate ions in calcium chloride and sodium chloride systems, represented by polysilicon wastewater, to obtain sodium chloride crystalline salt and calcium chloride dihydrate crystalline salt.

[0062] Figure 2 Technology and Figure 1 The seed crystal feeding devices are the same for the process; the difference lies in the location of the seed crystal recovery device. Figure 2 The seed crystal recovery device is located in the intermediate section between the material concentration and crystallization stages. The inter-stage pump of the multi-effect sodium chloride concentration unit is connected to the seed crystal recovery device. The seed crystals participate in the circulation between the sodium chloride concentration stages, without affecting the purity of the sodium chloride crystallized salt.

[0063] The material is pumped from the raw water tank to the evaporation crystallization unit via a raw water pump. After preheating, degassing, heating, flash evaporation, and concentration, it is discharged into the evaporation crystallization unit via an inter-stage pump. The seed crystal addition device is connected to the raw water tank via a conveying device, and the raw water tank is connected to the sodium chloride concentration system via a raw water pump.

[0064] The sodium chloride concentration system and the seed crystal recovery unit are connected via an inter-effect pump. The material first passes through the seed crystal recovery unit, where the seed crystals are separated from the material using density differences. After the primary separation, the material enters a subsequent mother liquor separator for secondary separation, further purifying the material. The seed crystal recovery unit and the mother liquor separator are connected via pipelines, and the seed crystals from the seed crystal recovery unit are connected to the sodium chloride concentration system via pipelines using the residual pressure of the inter-effect pump.

[0065] The secondary separator employs a mother liquor separation device, and the separation effect is controlled by designing an appropriate jacket ring cross-sectional area and mother liquor discharge rate. The mother liquor after secondary separation is connected to a sodium chloride crystallizer via a transfer pump.

[0066] The material enters the sodium chloride evaporator crystallizer for further concentration and crystallization. The solid-containing material is pumped into a thickening and centrifugal device for solid-liquid separation to obtain wet sodium chloride salt. The wet sodium chloride salt is conveyed by belt to the drying and packaging system to meet external sales standards. The sodium chloride crystallizer and centrifuge are connected by a discharge pump, the centrifuge and sodium chloride crystallizer drying are connected by a conveyor system, and the sodium chloride crystallizer and packaging device are connected by gravity pipelines.

[0067] The mother liquor from the sodium chloride centrifugation process enters the mother liquor tank. A portion is returned to the sodium chloride evaporation and crystallization unit, while the remainder enters the calcium chloride crystallization system. The centrifuge mother liquor is connected to the mother liquor tank via pipelines, and the mother liquor tank is connected to the sodium chloride crystallizer and the calcium chloride crystallizer via a discharge pump.

[0068] After multi-stage preheating, the material enters a calcium chloride evaporator for further concentration. Once the designed concentration is reached, it is pumped to a cooling and flaking machine. An external circulating cooling water system cools and crystallizes the material to obtain calcium chloride dihydrate, which is then packaged and sold via a packaging system. The sodium chloride crystallizer is connected to the calcium chloride flaking machine via a discharge pump, and the calcium chloride flaking machine is connected to the calcium chloride packaging system via a soft cloth bag pipe.

[0069] This invention presents an evaporation crystallization purification system for high-salt wastewater, specifically designed for the treatment of high-salt, high-hardness wastewater. Compared to traditional chemical softening processes, this invention achieves long-term stable operation of the evaporator without the need for chemical softening, significantly reducing the costs of evaporation crystallization agents and sludge disposal. The system has demonstrated excellent operational feedback and significant economic value. Compared to the seed crystal method for scale prevention in the salt chemical industry, this invention employs a two-stage seed crystal recovery and separation process tailored to different water qualities, effectively ensuring the purity of the subsequently crystallized salt, facilitating the maintenance of the system's seed crystal concentration, and extending the equipment's stable operating time.

[0070] It is understood that this utility model has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this utility model. Furthermore, under the teachings of this utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this utility model.

Claims

1. A high-salinity wastewater evaporation crystallization purification treatment system, characterized in that, The system comprises a seed adding device, a raw water tank, an evaporation crystallization device, a seed recovery device, a mother liquor separation device, a centrifugal device, a mother liquor tank and a packing device. The seed adding device is used for seed adding in the system starting stage and is communicated with the raw water tank. The raw water tank is used for buffering the system feed and establishing the feed seed concentration in the starting stage and is communicated with the evaporation crystallization device. The evaporation crystallization device is used for evaporation and crystallization of the material, and the discharge pump thereof is communicated with the seed recovery device. The supernatant of the seed recovery device is communicated with the evaporation crystallization device, and the discharge thereof is communicated with the mother liquor separation device. The supernatant of the mother liquor separation device is communicated with the mother liquor tank, and the discharge thereof is communicated with the centrifugal device. The centrifugal device is used for solid-liquid separation of the crystalline salt, and the crystalline salt in the centrifugal device is communicated with the packing device, and the centrifugal mother liquor is communicated with the mother liquor tank. The mother liquor tank is used for collecting the centrifugal mother liquor and the supernatant of the mother liquor separation device, and the discharge thereof is communicated with the evaporation crystallization device.

2. The high-salinity wastewater evaporative crystallization purification treatment system of claim 1, wherein, The seed adding device comprises a seed bin, a seed quantitative adding device and a stirring device.

3. The high-salinity wastewater evaporative crystallization purification treatment system of claim 1, wherein, The seed recovery device comprises a discharge pump, a high-efficiency cyclone and a sight glass. The discharge pump is communicated with the high-efficiency cyclone, the upper outlet of the high-efficiency cyclone is communicated with the sight glass, and the lower outlet of the high-efficiency cyclone is communicated with the mother liquor separator device.

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