Efficient salt separation resourceful treatment system for salt-containing wastewater in coal chemical industry

Abstract

The invention relates to the technical field of industrial salt-containing wastewater environment-friendly treatment, in particular to a coal chemical salt-containing wastewater efficient salt separation resourceful treatment system which comprises a homogeneous regulation unit, an impurity removal pretreatment unit, a removal module, a mirabilite freezing crystallization separation unit, a crystallization separation module, a mother liquor drying unit and a mixed salt redissolution unit. The removal module comprises a primary organic matter removal unit, an evaporation and concentration unit and a secondary organic matter removal unit; the crystallization separation module comprises a sodium sulfate crystallization separation unit, a sodium chloride crystallization separation unit and a mixed salt crystallization separation unit. The system adopts a low-temperature freezing crystallization method to preferentially separate out mirabilite, effectively improves the recovery rate and quality of a system byproduct sodium sulfate salt, reduces the transportation and disposal cost of carnallite, improves the degradation and removal rate of organic matters, and reduces the equipment investment.

Description

Technical Field

[0001] This invention relates to the field of environmental protection treatment technology for industrial saline wastewater, specifically a high-efficiency salt separation and resource utilization system for coal chemical saline wastewater. Background Technology

[0002] Regions in my country rich in coal resources generally suffer from water scarcity and fragile ecological environments. Meanwhile, coal chemical production enterprises consume huge amounts of water and discharge huge amounts of wastewater. Their rapid development can easily lead to regional water supply and demand imbalances and environmental damage, affecting the normal development of local industry and agriculture. Implementing reasonable treatment and recycling of coal chemical wastewater can effectively reduce the pollution and damage of wastewater to the environment and alleviate the thorny problems of severe water shortage.

[0003] In existing conventional processes, the removal rate of organic impurities in saline wastewater is not ideal, and the recovery rate and quality of by-product sodium sulfate are low, resulting in a high rate of mixed salts, which increases the cost of transporting and disposing of mixed salts. At the same time, the equipment investment is high and the operating energy consumption is high. Summary of the Invention

[0004] The purpose of this invention is to provide a high-efficiency salt separation and resource utilization system for coal chemical saline wastewater, to solve the problems mentioned in the background art, such as the unsatisfactory removal rate of organic impurities in saline wastewater, the low recovery rate and quality of by-product sodium sulfate, resulting in a high rate of mixed salts, increased costs for transporting and disposing of mixed salts, high equipment investment, and high operating energy consumption. This solution uses a low-temperature freeze crystallization method to preferentially separate Glauber's salt, effectively improving the recovery rate and quality of by-product sodium sulfate, reducing the costs of transporting and disposing of mixed salts, improving the degradation and removal rate of organic matter, and reducing equipment investment.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a high-efficiency salt separation and resource utilization treatment system for saline wastewater from coal chemical industry. This system includes a homogenization and conditioning unit, a pretreatment unit for impurity removal, a removal module, a sodium sulfate freezing and crystallization separation unit, a crystallization separation module, a mother liquor drying unit, and a mixed salt re-dissolution unit. The removal module includes a primary organic matter removal unit, an evaporation and concentration unit, and a secondary organic matter removal unit. The crystallization separation module includes a sodium sulfate crystallization separation unit, a sodium chloride crystallization separation unit, and a mixed salt crystallization separation unit. The functions of each unit are as follows: The homogenization adjustment unit is used to fully mix the saline wastewater with the liquid after the mixed salt resolution unit to achieve homogenization and uniformity, thereby reducing the impact load of incoming water. The impurity removal pretreatment unit is used to remove hardness, silicon, and suspended solids from homogeneous and uniform saline wastewater, including chemical and physical methods to remove impurities from saline wastewater. The primary organic matter removal unit is used to perform room temperature advanced oxidation degradation COD treatment on the feed liquid after hardening, silicon removal and suspended solids removal. Ozone catalytic oxidation technology is used to initially degrade and remove organic impurities in the wastewater. The evaporation and concentration unit is used to remove impurities and preliminarily remove organic matter from saline wastewater. It achieves high-rate concentration through a thermal evaporation process, in which secondary steam is reused as product water to reduce energy consumption. The secondary organic matter removal unit is used to treat the COD of the high-temperature concentrated brine after it has been enriched by high-temperature advanced oxidation degradation, and to deeply degrade and remove organic impurities from the high-temperature concentrated brine wastewater. The Glauber's salt freeze crystallization separation unit is used to further pre-cool the high-temperature concentrated brine wastewater after evaporation and concentration to remove organic matter, and obtain solid Glauber's salt through freeze crystallization separation. The mother liquor is discharged to the sodium chloride crystallization separation unit, where Glauber's salt is preferentially separated from the concentrated brine wastewater through low-temperature crystallization, thereby improving the quality of the final sodium sulfate. The sodium sulfate crystallization separation unit is used to melt and recrystallize Glauber's salt, and after separation, anhydrous sodium sulfate and Glauber's salt mother liquor are obtained; The sodium chloride crystallization separation unit is used to crystallize and separate the mother liquor discharged from the Glauber's salt freezing crystallization separation unit by heating to obtain sodium chloride by-product salt. The quality of the crystallized salt is improved by controlling the concentration of the discharged salt, and the mother liquor is discharged to the mixed salt crystallization separation unit. The mixed salt crystallization separation unit is used to further evaporate and crystallize the mother liquor discharged from the sodium sulfate crystallization separation unit and the sodium chloride crystallization separation unit to obtain mixed salt. The mixed salt enters the mixed salt redissolution unit through a solid conveyor, and the mother liquor is discharged to the mother liquor drying unit. The mother liquor drying unit is used to dry the mother liquor discharged from the mixed salt crystallization and separation unit to obtain mixed salts, and some of the mixed salts are added back to the mixed salt reconstitution unit. The mixed salt re-dissolving unit is used to redissolve the obtained mixed salt and mix it with the feed liquid in the homogenization adjustment unit to improve the recovery rate of by-product salts in the system and reduce the impurity salt rate in the system.

[0006] Preferably, the homogenization and conditioning unit includes a conditioning tank, an aeration pipeline, and a blower. The conditioning tank is equipped with an aeration pipeline, the input end of which is connected to the output end of the blower. The blower and the aeration pipeline are used to stir the saline wastewater and the mixed salt resolution solution to ensure thorough mixing.

[0007] Preferably, the impurity removal pretreatment unit includes a chemical dosing reaction tank, a first agitator, a high-density sedimentation tank, a media filter, a pretreatment product water tank, and several sets of first feed pumps. Both the chemical dosing reaction tank and the high-density sedimentation tank are equipped with first agitators. A media filter is installed between the high-density sedimentation tank and the pretreatment product water tank. A set of first feed pumps is installed between the chemical dosing reaction tank and the high-density sedimentation tank, and between the high-density sedimentation tank and the media filter. The output end of the media filter is connected to the input end of the pretreatment product water tank. Lime slurry and soda ash are added stepwise to the chemical dosing reaction tank to remove calcium and magnesium hardness from the wastewater. Aluminum or magnesium agents are added to remove silicon. In the high-density sedimentation tank, coagulants and flocculants are added sequentially to remove colloidal suspended solids from the saline wastewater through coagulation and sedimentation. The coagulation and sedimentation process also has a certain removal effect on organic matter in the saline wastewater. The product water from the high-density sedimentation tank is pumped into the media filter by the first feed pumps and finally enters the pretreatment product water tank.

[0008] Preferably, the primary organic matter removal unit includes an ozone generator, a catalytic oxidation reactor, and a tail gas destroyer. The output end of the ozone generator is connected to the input end of the catalytic oxidation reactor, and the output end of the catalytic oxidation reactor is connected to the input end of the tail gas destroyer to improve ozone utilization. The catalyst uses spherical γ-Al2O3 as a carrier, and the organic matter degradation and removal rate of saline wastewater in this unit is 40%-50%.

[0009] Preferably, the evaporation and concentration unit includes an evaporation feed tank, a preheater, a degasser, and an evaporator. The feed tank is equipped with a dedicated water pump for conveying sulfuric acid, and the output end of the dedicated water pump is connected to the input end of the feed tank. The input end of the evaporation feed tank is connected to the input end of the preheater, the output end of the preheater is connected to the input end of the degasser, and the output end of the degasser is connected to the input end of the evaporator. The wastewater in the feed tank is adjusted to pH 5-6. The saline wastewater is then heated to 85℃-90℃ by the preheater. The degasser removes dissolved oxygen, carbon dioxide, and non-condensable gases from the saline wastewater. Finally, the wastewater is evaporated and concentrated by the evaporator.

[0010] Preferably, the secondary organic matter removal unit includes an intermediate water tank and a heterogeneous Fenton oxidation reactor. The heterogeneous Fenton oxidation reactor is a fixed-bed type and includes a multi-stage catalyst bed for staged catalytic reaction and a multi-stage hydrogen peroxide dosing pipeline system for adding hydrogen peroxide. The multi-stage catalyst bed is installed inside the heterogeneous Fenton oxidation reactor. The input end of the heterogeneous Fenton oxidation reactor is connected to the multi-stage hydrogen peroxide dosing pipeline system. The output end of the intermediate water tank is connected to the input end of the heterogeneous Fenton oxidation reactor. This improves the efficiency of organic matter oxidation and degradation removal. It uses a non-ferrous metal catalyst, and the reaction process does not require acid-base adjustment, produces no iron sludge, has a fast reaction rate, consumes less oxidant, and has a high organic matter degradation removal rate of 50%-80%. During the reaction, the high temperature (60℃-80℃) of the concentrated brine is a necessary condition and does not require additional heating, providing external conditions for system thermal activation, which is conducive to the generation of more oxidizing hydroxyl radicals and their action on the rapid degradation and removal of organic matter.

[0011] Preferably, the Glauber's salt freeze crystallization separation unit includes a precooler, a freeze crystallizer, a first centrifugal dehydrator, and a first mother liquor discharge pump. The output end of the precooler is connected to the input end of the freeze crystallizer, the output end of the freeze crystallizer is connected to the input end of the first centrifugal dehydrator, and the input end of the first mother liquor discharge pump is connected to the output end of the first centrifugal dehydrator. The high-temperature concentrated brine after evaporation and concentration to remove organic matter first enters the precooler and is cooled to the freeze crystallization temperature. The operating temperature is controlled, and then it is pumped into the freeze crystallizer to reach the required Glauber's salt crystallization precipitation point. A large amount of Glauber's salt is generated and grows in the freeze crystallizer. After reaching a certain solid content, the concentrated slurry is pumped into the first Glauber's salt centrifugal dehydrator for solid-liquid separation. The Glauber's salt is transported to the next stage, and the centrifugal mother liquor is transported to the sodium chloride crystallization separation unit via the first mother liquor discharge pump.

[0012] Preferably, the sodium sulfate crystallization separation unit, the sodium chloride crystallization separation unit, and the mixed salt crystallization separation unit all include crystallization separation equipment. The crystallization separation equipment includes a heater, a crystallizer, a second centrifugal dehydrator, and a second mother liquor discharge pump. The output end of the heater is connected to the input end of the crystallizer, the output end of the crystallizer is connected to the input end of the second centrifugal dehydrator, and the input end of the second mother liquor discharge pump is connected to the output end of the second centrifugal dehydrator.

[0013] Preferably, the sodium sulfate crystallization separation unit further includes several sets of first solid conveyors, remelting tanks, and dryers. The output end of the first solid conveyor is connected to the input end of the remelting tank, the output end of the remelting tank is connected to the input end of the crystallization separation equipment, and the output end of the crystallization separation equipment is connected to the input end of the dryer through the first solid conveyor. Glauber's salt is conveyed to the remelting tank via the first solid conveyor to prepare a sodium sulfate aqueous solution. After the liquid is heated to the boiling point by the heater, it is evaporated and concentrated in the crystallizer. When the concentration of the liquid reaches the sodium sulfate saturation precipitation point, a large amount of sodium sulfate is generated and grows in the crystallizer. After reaching a certain solid content, the concentrated slurry is pumped into the second centrifugal dehydrator for solid-liquid separation. The wet sodium sulfate salt is conveyed to the dryer via the first solid conveyor for further dehydration and drying to form sodium sulfate by-product salt. The centrifugal mother liquor is conveyed to the mixed salt crystallization separation unit via the second mother liquor discharge pump.

[0014] Preferably, the sodium chloride crystallization separation unit includes a heater, a crystallizer, a centrifugal dehydrator, and a mother liquor discharge pump. The sodium sulfate centrifugal mother liquor is transported to the sodium chloride crystallization separation unit via the mother liquor discharge pump. The liquid is first heated by the heater to reach the boiling point, and then evaporated and concentrated in the crystallizer. When the concentration of the liquid reaches the sodium chloride saturation precipitation point, a large amount of sodium chloride is generated and grows in the crystallizer. After reaching a certain solid content, the concentrated slurry is pumped to the sodium chloride centrifugal dehydrator for solid-liquid separation. The sodium chloride is then transported to the next stage. The centrifugal mother liquor is transported to the mixed salt crystallization separation unit via the mother liquor discharge pump.

[0015] Preferably, the mixed salt crystallization separation unit includes a heater, a crystallizer, a centrifugal dehydrator, and a mother liquor discharge pump. The centrifugal mother liquors of sodium chloride and sodium sulfate are jointly transported to the mixed salt crystallization separation unit via the mother liquor discharge pump. The liquid is first heated to the boiling point by the heater, and then evaporated and concentrated in the crystallizer. When the concentration of the liquid reaches the saturation precipitation point of the mixed salt, a large amount of mixed salt is generated and grows in the crystallizer. After reaching a certain solid content, the concentrated slurry is pumped to the mixed salt centrifugal dehydrator for solid-liquid separation. The mixed salt solids are transported to the mixed salt reconstitution unit via a solid conveyor, and the centrifugal mother liquor is transported to the mother liquor drying unit via the mother liquor discharge pump.

[0016] Preferably, the mother liquor drying unit includes a vacuum drum dryer and a second solid conveyor. The output end of the vacuum drum dryer is connected to the input end of the second solid conveyor. The mixed salt centrifugal mother liquor is transported to the vacuum drum dryer by the mother liquor discharge pump. Under negative pressure and low temperature, the water is continuously evaporated to obtain solid mixed salt, which is then transported to the next stage by the second solid conveyor and finally packaged into mixed salt for external disposal.

[0017] Preferably, the mixed salt remelting unit includes a salt dissolving tank, a second stirrer, a third solid conveyor, and a second liquid conveying pump. The second stirrer is installed inside the salt dissolving tank. The output end of the salt dissolving tank is connected to the input end of the third solid conveyor and the second liquid conveying pump. Mixed salts are added to the salt dissolving tank, and system recycled water or feed saline wastewater is used as a solvent. The salts are melted by the second stirrer, and the melted liquid is pumped into the homogenization and conditioning unit for use by the second liquid conveying pump.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. Low-temperature freeze crystallization method is used to preferentially separate Glauber's salt, which effectively improves the recovery rate and quality of sodium sulfate by-product of the system. The sodium sulfate recovery rate reaches more than 98%, and the purity reaches more than 99%. 2. The addition of a mixed salt resolution unit significantly reduces the mixed salt rate of the system to below 5%, thereby reducing the cost of transporting and disposing of mixed salts. 3. The synergistic effect of two advanced oxidation technologies in removing organic impurities from saline wastewater extends the stable operating time of the system to more than six months, and the purity of the by-product sodium sulfate and sodium chloride is greater than 99%. 4. The heterogeneous Fenton oxidation technology is adopted, which utilizes the catalytic effect of non-ferrous metal catalysts and the activation effect of high temperature heat energy of concentrated brine to increase the amount of hydroxyl radicals generated in the system and improve the organic matter degradation and removal rate to 50%-80%. At the same time, the system influent does not require acid or alkali adjustment, no iron sludge is generated, and the oxidant consumption is low. 5. The use of evaporation concentrate for secondary organic matter removal significantly reduces the processing scale of the oxidation reactor and reduces equipment investment. The use of thermal evaporation achieves high-rate concentration of saline wastewater, making the system more stable and durable, and reducing energy consumption. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 1 One embodiment provided by the present invention: A high-efficiency salt separation and resource utilization system for saline wastewater from coal chemical industry is disclosed. The system includes a homogenization and conditioning unit, a pretreatment unit for impurity removal, a removal module, a sodium sulfate freezing and crystallization separation unit, a crystallization separation module, a mother liquor drying unit, and a mixed salt re-dissolution unit. The removal module includes a primary organic matter removal unit, an evaporation and concentration unit, and a secondary organic matter removal unit. The crystallization separation module includes a sodium sulfate crystallization separation unit, a sodium chloride crystallization separation unit, and a mixed salt crystallization separation unit. The functions of each unit are as follows: The homogenization adjustment unit is used to fully mix the saline wastewater with the liquid after the mixed salt resolution unit to achieve homogenization and uniformity, thereby reducing the impact load of incoming water. The impurity removal pretreatment unit is used to remove hardness, silicon, and suspended solids from homogeneous and uniform saline wastewater, including chemical and physical methods to remove impurities from saline wastewater. The primary organic matter removal unit is used to perform room temperature advanced oxidation degradation COD treatment on the feed liquid after hardening, silicon removal and suspended solids removal. Ozone catalytic oxidation technology is used to initially degrade and remove organic impurities in the wastewater. The evaporation and concentration unit is used to remove impurities and preliminarily remove organic matter from saline wastewater. It achieves high-rate concentration through a thermal evaporation process, in which secondary steam is reused as product water to reduce energy consumption. The secondary organic matter removal unit is used to treat the COD of the high-temperature concentrated brine after it has been enriched by high-temperature advanced oxidation degradation, and to deeply degrade and remove organic impurities from the high-temperature concentrated brine wastewater. The Glauber's salt freeze crystallization separation unit is used to further pre-cool the high-temperature concentrated brine wastewater after evaporation and concentration to remove organic matter, and obtain solid Glauber's salt through freeze crystallization separation. The mother liquor is discharged to the sodium chloride crystallization separation unit, where Glauber's salt is preferentially separated from the concentrated brine wastewater through low-temperature crystallization, thereby improving the quality of the final sodium sulfate. The sodium sulfate crystallization separation unit is used to melt and recrystallize Glauber's salt, and after separation, anhydrous sodium sulfate and Glauber's salt mother liquor are obtained; The sodium chloride crystallization separation unit is used to crystallize and separate the mother liquor discharged from the Glauber's salt freezing crystallization separation unit by heating to obtain sodium chloride by-product salt. The quality of the crystallized salt is improved by controlling the concentration of the discharged salt, and the mother liquor is discharged to the mixed salt crystallization separation unit. The mixed salt crystallization separation unit is used to further evaporate and crystallize the mother liquor discharged from the sodium sulfate crystallization separation unit and the sodium chloride crystallization separation unit to obtain mixed salt. The mixed salt enters the mixed salt redissolution unit through a solid conveyor, and the mother liquor is discharged to the mother liquor drying unit. The mother liquor drying unit is used to dry the mother liquor discharged from the mixed salt crystallization and separation unit to obtain mixed salts, and some of the mixed salts are added back to the mixed salt reconstitution unit. The mixed salt re-dissolving unit is used to redissolve the obtained mixed salt and mix it with the feed liquid in the homogenization adjustment unit to improve the recovery rate of by-product salts in the system and reduce the impurity salt rate in the system. In this embodiment, the homogenization and conditioning unit includes a conditioning tank, an aeration pipeline, and a blower. The conditioning tank is equipped with an aeration pipeline, the input end of which is connected to the output end of the blower. The blower and the aeration pipeline are used to stir the saline wastewater and the mixed salt resolution solution to ensure thorough mixing. The saline wastewater in the conditioning tank has a TDS of 20000mg / L-40000mg / L, a suspended solids content of 100mg / L-500mg / L, a total hardness of 500mg / L-1000mg / L, a total silicon content of 150mg / L-250mg / L, and an organic matter content of 500mg / L-1000mg / L. In this embodiment, the impurity removal pretreatment unit includes a dosing reaction tank, a first stirrer, a high-density sedimentation tank, a media filter, a pretreated water tank, and several sets of first feed pumps. The dosing reaction tank and the high-density sedimentation tank are both equipped with first stirrers. A media filter is installed between the high-density sedimentation tank and the pretreated water tank. A set of first feed pumps is installed between the dosing reaction tank and the high-density sedimentation tank, and another set of first feed pumps is installed between the high-density sedimentation tank and the media filter. The output end of the media filter is connected to the input end of the pretreated water tank. Lime slurry and... are added stepwise to the dosing reaction tank. Soda ash is used to remove calcium and magnesium hardness from wastewater. Aluminum or magnesium agents are added to remove silicon. In a high-density sedimentation tank, coagulants and flocculants are added sequentially to remove colloidal suspended solids from saline wastewater through coagulation and sedimentation. The coagulation and sedimentation process also has a certain removal effect on organic matter in saline wastewater. The permeate from the high-density sedimentation tank is pumped into a media filter by the first feed pump and finally enters the pretreatment permeate tank to further reduce the content of colloidal suspended solids in the wastewater. The water quality indicators in the pretreatment permeate tank can meet the following requirements: suspended solids content is less than 5 mg / L, total hardness is less than 120 mg / L, total silicon content is less than 20 mg / L, and organic matter removal rate is 15%-25%. In this embodiment, the primary organic matter removal unit includes an ozone generator, a catalytic oxidation reactor, and a tail gas destroyer. The output end of the ozone generator is connected to the input end of the catalytic oxidation reactor, and the output end of the catalytic oxidation reactor is connected to the input end of the tail gas destroyer to improve ozone utilization. The catalyst uses spherical γ-Al2O3 as a carrier with a particle size of 3mm-5mm and is loaded with one or more metal oxides of Mn, Cu, Ce, and Ni. The organic matter degradation and removal rate of saline wastewater in this unit is 40%-50%. In this embodiment, the evaporation and concentration unit includes an evaporation feed tank, a preheater, a degasser, and an evaporator. The feed tank is equipped with a dedicated water pump for conveying sulfuric acid, and the output end of the dedicated water pump is connected to the input end of the feed tank. The input end of the evaporation feed tank is connected to the input end of the preheater, the output end of the preheater is connected to the input end of the degasser, and the output end of the degasser is connected to the input end of the evaporator. The wastewater in the feed tank is adjusted to pH 5-6 to remove alkalinity from the saline wastewater. The saline wastewater is then heated to 85℃-90℃ by the preheater. The degasser removes dissolved oxygen, carbon dioxide, and non-condensable gases from the saline wastewater. A vertical falling film tubular evaporator is used, coupled with multi-effect or MVR energy-saving technology and salt-based anti-scaling technology. In this embodiment, the secondary organic matter removal unit includes an intermediate water tank and a heterogeneous Fenton oxidation reactor. The heterogeneous Fenton oxidation reactor is a fixed-bed type and includes a multi-stage catalyst bed for staged catalytic reaction and a multi-stage hydrogen peroxide dosing pipeline system for adding hydrogen peroxide. The multi-stage catalyst bed is installed inside the heterogeneous Fenton oxidation reactor. The input end of the heterogeneous Fenton oxidation reactor is connected to the multi-stage hydrogen peroxide dosing pipeline system, and the output end of the intermediate water tank is connected to the input end of the heterogeneous Fenton oxidation reactor, thereby improving the efficiency of organic matter removal. The organic matter oxidation and degradation removal efficiency adopts non-ferrous metal catalysts, such as those composed of one or more of the metal elements Cu, Co, and Ni. The hydrogen peroxide concentration is 27.5% or 30%. The reaction process does not require acid or alkali adjustment, does not produce iron sludge, has a fast reaction rate, low oxidant consumption, and a high organic matter degradation and removal rate of 50%-80%. During the reaction process, the high temperature (60℃-80℃) of concentrated brine is a necessary condition and does not require additional heating. It provides external conditions for system thermal activation, which is conducive to the generation of more oxidizing hydroxyl radicals and their action on the rapid degradation and removal of organic matter. In this embodiment, the Glauber's salt freeze crystallization separation unit includes a precooler, a freeze crystallizer, a first centrifugal dehydrator, and a first mother liquor discharge pump. The output end of the precooler is connected to the input end of the freeze crystallizer, the output end of the freeze crystallizer is connected to the input end of the first centrifugal dehydrator, and the input end of the first mother liquor discharge pump is connected to the output end of the first centrifugal dehydrator. The high-temperature concentrated brine, after deep removal of organic matter through evaporation and concentration, first enters the precooler and is cooled to the freeze crystallization temperature. The operating temperature is controlled before it is pumped into the freeze crystallizer to achieve the desired temperature. The required crystallization point for Glauber's salt is reached by the formation and growth of a large amount of Glauber's salt in a freeze crystallizer. Once a certain solid content is reached, the concentrated slurry is pumped into the first centrifugal dehydrator for solid-liquid separation. The Glauber's salt is then transported to the next stage. The centrifugal mother liquor is pumped to the sodium chloride crystallization separation unit via the first mother liquor discharge pump. The freeze crystallizer is of the DTB type, with the operating temperature controlled at -5℃ to 0℃. The freeze crystallization method is used to preferentially separate Glauber's salt, effectively overcoming the shortcomings of the traditional high-temperature thermal crystallization method for preferentially separating anhydrous sodium sulfate, such as the low yield and poor quality of by-product sodium sulfate. In this embodiment, the sodium sulfate crystallization separation unit, the sodium chloride crystallization separation unit, and the mixed salt crystallization separation unit all include crystallization separation equipment. The crystallization separation equipment includes a heater, a crystallizer, a second centrifugal dehydrator, and a second mother liquor discharge pump. The output end of the heater is connected to the input end of the crystallizer, the output end of the crystallizer is connected to the input end of the second centrifugal dehydrator, and the input end of the second mother liquor discharge pump is connected to the output end of the second centrifugal dehydrator. The sodium sulfate crystallization separation unit also includes several sets of first solid conveyors, reconstitution tanks, and dryers. The output end of the first solid conveyor is connected to the input end of the reconstitution tank, the output end of the reconstitution tank is connected to the input end of the crystallization separation equipment, and the output end of the crystallization separation equipment is connected to the input end of the dryer via the first solid conveyor. Glauber's salt is conveyed to the reconstitution tank via the first solid conveyor to prepare a sodium sulfate aqueous solution. After the solution is heated to its boiling point by a heater, it is evaporated and concentrated in the crystallizer. When the concentration of the solution reaches the sodium sulfate concentration... After the saturation precipitation point, a large amount of sodium sulfate is generated and grows in the crystallizer. After reaching a certain solid content, the concentrated slurry is pumped into the second centrifugal dehydrator for solid-liquid separation. The wet sodium sulfate salt is transported to the dryer by the first solid conveyor for further dehydration and drying to form sodium sulfate by-product salt. The centrifugal mother liquor is transported to the mixed salt crystallization separation unit by the second mother liquor discharge pump. The sodium sulfate salt obtained in this unit has a purity of over 99%, which meets the Class I Grade 1 requirements of "Industrial Anhydrous Sodium Sulfate" (GB / T6009-2014). The sodium sulfate recovery rate of the system reaches over 98%. The sodium chloride crystallization separation unit includes a heater, a crystallizer, a centrifugal dehydrator, and a mother liquor discharge pump. The sodium sulfate centrifugal mother liquor is pumped to the sodium chloride crystallization separation unit via the mother liquor discharge pump. The liquid is first heated to the boiling point by the heater, and then evaporated and concentrated in the crystallizer. When the concentration of the liquid reaches the sodium chloride saturation precipitation point, a large amount of sodium chloride is generated and grows in the crystallizer. After reaching a certain solid content, the concentrated slurry is pumped to the sodium chloride centrifugal dehydrator for solid-liquid separation. The sodium chloride is then transported to the next stage. The centrifugal mother liquor is pumped to the mixed salt crystallization separation unit via the mother liquor discharge pump. The sodium chloride salt obtained in this unit has a purity of over 99%, which meets the requirements of Grade I refined industrial salt (GB / T5462-2015) for industrial dry salt. The mixed salt crystallization separation unit includes a heater, a crystallizer, a centrifugal dehydrator, and a mother liquor discharge pump. The centrifugal mother liquors of sodium chloride and sodium sulfate are jointly transported to the mixed salt crystallization separation unit via the mother liquor discharge pump. The liquid is first heated to the boiling point by the heater, and then evaporated and concentrated in the crystallizer. When the concentration of the liquid reaches the saturation precipitation point of the mixed salt, a large amount of mixed salt is generated and grows in the crystallizer. After reaching a certain solid content, the concentrated slurry is pumped to the mixed salt centrifugal dehydrator for solid-liquid separation. The mixed salt solids are transported to the mixed salt reconstitution unit via a solid conveyor, and the centrifugal mother liquor is transported to the mother liquor drying unit via the mother liquor discharge pump. In this embodiment, the mother liquor drying unit includes a vacuum drum dryer and a second solid conveyor. The output end of the vacuum drum dryer is connected to the input end of the second solid conveyor. The mixed salt centrifugal mother liquor is transported to the vacuum drum dryer by the mother liquor discharge pump. Under negative pressure and low temperature, the water is continuously evaporated to obtain solid mixed salt, which is then transported to the next stage by the second solid conveyor. Finally, it is packaged into mixed salt for external disposal. When the incoming water quality is better, that is, when the quality of mixed salt is better, some of the mixed salt is transported to the mixed salt re-dissolution unit via the second solid conveyor to reduce the mixed salt rate of the system. Finally, the mixed salt rate of the system is controlled below 5%. The organic impurities enriched in the system are mainly carried out with the mixed salt and transported for external disposal. In this embodiment, the mixed salt remelting unit includes a salt dissolving tank, a second stirrer, a third solid conveyor, and a second liquid conveying pump. The second stirrer is installed inside the salt dissolving tank. The output end of the salt dissolving tank is connected to the input end of the third solid conveyor and the second liquid conveying pump. Impurities are added to the salt dissolving tank, and the system's recycled water or feed saline wastewater is used as a solvent. The impurities are melted by the second stirrer, and the melted liquid is pumped into the homogenization and conditioning unit for use by the second liquid conveying pump. Due to the mixed salt remelting unit, the amount of impurities generated in the system is greatly reduced, and the cost of transporting and disposing of them is reduced. At the same time, the overall effective recovery rate of salt in saline wastewater is also increased.

[0022] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A high-efficiency salt separation and resource utilization system for saline wastewater from coal chemical industry, characterized in that, include: The unit includes a homogenization adjustment unit, a pretreatment unit for impurity removal, a removal module, a Glauber's salt freezing and crystallization separation unit, a crystallization separation module, a mother liquor drying unit, and a mixed salt reconstitution unit. The homogenization adjustment unit is used to fully and evenly mix the saline wastewater with the liquid after the mixed salt resolution unit; The impurity removal pretreatment unit is used to remove hardness, silicon, and suspended solids from homogeneous and uniform saline wastewater, including chemical and physical methods to remove impurities from saline wastewater. The removal module is used to perform preliminary removal of organic matter from saline wastewater, high-temperature concentration, and deep degradation to remove organic matter. After high-temperature concentration, the saline wastewater becomes high-temperature concentrated brine wastewater. The Glauber's salt freeze crystallization separation unit is used to further pre-cool and lower the temperature of high-temperature concentrated brine wastewater after evaporation and concentration to remove organic matter, and obtain solid Glauber's salt through freeze crystallization separation. The mother liquor is discharged to the crystallization separation module. The crystallization separation module is used to separate anhydrous sodium sulfate, mother liquor, sodium chloride by-product salt, and mixed salt from saline wastewater. The mother liquor drying unit receives the mother liquor from the crystallization separation module, and obtains mixed salts through drying treatment. Some of the mixed salts are then added back to the mixed salt reconstitution unit. The mixed salt re-dissolving unit is used to redissolve the obtained mixed salt and then mix it with the feed liquid in the homogenization adjustment unit.

2. The efficient salt separation and resource utilization system for saline wastewater from coal chemical industry according to claim 1, characterized in that: The removal module includes a primary organic matter removal unit, an evaporation and concentration unit, and a secondary organic matter removal unit; The primary organic matter removal unit is used to perform room temperature advanced oxidation degradation COD treatment on the feed liquid after hardening, silicon removal and suspended solids removal, and uses ozone catalytic oxidation technology to preliminarily degrade and remove organic impurities in saline wastewater. The evaporation and concentration unit is used to remove impurities and preliminarily remove organic matter from saline wastewater, and achieves high-rate concentration through a thermal evaporation process. The secondary organic matter removal unit is used to treat the COD of the high-temperature concentrated brine after it has been enriched by advanced oxidation at high temperature, and to deeply degrade and remove organic impurities from the high-temperature concentrated brine wastewater.

3. The efficient salt separation and resource utilization system for saline wastewater from coal chemical industry according to claim 1, characterized in that: The crystallization separation module includes a sodium sulfate crystallization separation unit, a sodium chloride crystallization separation unit, and a mixed salt crystallization separation unit; The sodium sulfate crystallization separation unit is used to melt and recrystallize Glauber's salt, and after separation, anhydrous sodium sulfate and mother liquor are obtained; The sodium chloride crystallization separation unit is used to crystallize and separate the mother liquor discharged from the Glauber's salt freezing crystallization separation unit by heating to obtain sodium chloride by-product salt. The quality of the crystallized salt is improved by controlling the concentration of the discharged salt, and the mother liquor is discharged to the mixed salt crystallization separation unit. The mixed salt crystallization separation unit is used to continue evaporating and crystallizing the mother liquor discharged from the sodium sulfate crystallization separation unit and the sodium chloride crystallization separation unit to obtain mixed salt. The mixed salt enters the mixed salt reconstitution unit through a solid conveyor, and the mother liquor is discharged to the mother liquor drying unit.

4. The efficient salt separation and resource utilization system for coal chemical saline wastewater according to claim 1, characterized in that: The homogenization adjustment unit includes an adjustment tank, an aeration pipeline, and a blower. The adjustment tank is equipped with an aeration pipeline, and the input end of the aeration pipeline is connected to the output end of the blower.

5. The efficient salt separation and resource utilization system for saline wastewater from coal chemical industry according to claim 1, characterized in that: The impurity removal pretreatment unit includes a chemical dosing reaction tank, a first agitator, a high-density sedimentation tank, a media filter, a pretreated water tank, and several sets of first feed pumps. The chemical dosing reaction tank and the high-density sedimentation tank are each equipped with a first agitator. A media filter is installed between the high-density sedimentation tank and the pretreated water tank. A set of first feed pumps is installed between the chemical dosing reaction tank and the high-density sedimentation tank. A set of first feed pumps is installed between the high-density sedimentation tank and the media filter. The output end of the media filter is connected to the input end of the pretreated water tank.

6. The efficient salt separation and resource utilization system for coal chemical saline wastewater according to claim 2, characterized in that: The primary organic matter removal unit includes an ozone generator, a catalytic oxidation reactor, and an exhaust gas destroyer. The output end of the ozone generator is connected to the input end of the catalytic oxidation reactor, and the output end of the catalytic oxidation reactor is connected to the input end of the exhaust gas destroyer. The evaporation and concentration unit includes an evaporation feed tank, a preheater, a degasser, and an evaporator. The feed tank is equipped with a dedicated water pump for conveying sulfuric acid, and the output end of the dedicated water pump is connected to the input end of the feed tank. The input end of the evaporation feed tank is connected to the input end of the preheater, the output end of the preheater is connected to the input end of the degasser, and the output end of the degasser is connected to the input end of the evaporator. The secondary organic matter removal unit includes an intermediate water tank and a heterogeneous Fenton oxidation reactor. The heterogeneous Fenton oxidation reactor is a fixed-bed type and includes a multi-stage catalyst bed for staged catalytic reaction and a multi-stage hydrogen peroxide dosing pipeline system for adding hydrogen peroxide. The multi-stage catalyst bed is installed inside the heterogeneous Fenton oxidation reactor. The input end of the heterogeneous Fenton oxidation reactor is connected to the multi-stage hydrogen peroxide dosing pipeline system, and the output end of the intermediate water tank is connected to the input end of the heterogeneous Fenton oxidation reactor.

7. The efficient salt separation and resource utilization system for coal chemical saline wastewater according to claim 1, characterized in that: The Glauber's salt freeze crystallization separation unit includes a precooler, a freeze crystallizer, a first centrifugal dehydrator, and a first mother liquor discharge pump. The output end of the precooler is connected to the input end of the freeze crystallizer, the output end of the freeze crystallizer is connected to the input end of the first centrifugal dehydrator, and the input end of the first mother liquor discharge pump is connected to the output end of the first centrifugal dehydrator.

8. The efficient salt separation and resource utilization system for saline wastewater from coal chemical industry according to claim 1, characterized in that: The sodium sulfate crystallization separation unit, the sodium chloride crystallization separation unit, and the mixed salt crystallization separation unit all include crystallization separation equipment; The sodium sulfate crystallization separation unit also includes several sets of first solid conveyors, remelting tanks, and dryers. The output end of the first solid conveyor is connected to the input end of the remelting tank, the output end of the remelting tank is connected to the input end of the crystallization separation equipment, and the output end of the crystallization separation equipment is connected to the input end of the dryer through the first solid conveyor. The crystallization separation equipment includes a heater, a crystallizer, a second centrifugal dehydrator, and a second mother liquor discharge pump. The output end of the heater is connected to the input end of the crystallizer, the output end of the crystallizer is connected to the input end of the second centrifugal dehydrator, and the input end of the second mother liquor discharge pump is connected to the output end of the second centrifugal dehydrator.

9. The efficient salt separation and resource utilization system for saline wastewater from coal chemical industry according to claim 1, characterized in that: The mother liquor drying unit includes a vacuum drum dryer and a second solid conveyor, with the output end of the vacuum drum dryer connected to the input end of the second solid conveyor.

10. The efficient salt separation and resource utilization system for saline wastewater from coal chemical industry according to claim 1, characterized in that: The salt reconstitution unit includes a salt dissolving tank, a second stirrer, a third solid conveyor, and a second liquid conveying pump. The second stirrer is installed inside the salt dissolving tank, and the output end of the salt dissolving tank is connected to the input end of the third solid conveyor and the second liquid conveying pump, respectively.

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