System and method for separating sodium chloride and potassium chloride

Abstract

The invention provides a sodium chloride and potassium chloride separation system and method. The separation system comprises an evaporative crystallization module, a cooling crystallization module and a drying module which are arranged in sequence, wherein the drying module is connected with the evaporative crystallization module and the cooling crystallization module; the evaporative crystallization module is used for sequentially carrying out evaporative concentration treatment and first solid-liquid separation treatment on the high-salinity wastewater to obtain first mother liquor and crude sodium chloride; the cooling crystallization module is used for sequentially carrying out cooling crystallization treatment and second solid-liquid separation treatment on the first mother liquor to obtain second mother liquor and crude potassium chloride; a solvent conveying unit arranged in the cooling crystallization module is configured to add an organic solvent into the first mother liquor according to a preset adding proportion when the first mother liquor is cooled to a first preset temperature range; and the drying module is used for drying the crude sodium chloride and the crude potassium chloride to obtain a sodium chloride product and a potassium chloride product. The sodium chloride and potassium chloride separation system and method provided by the invention can improve the recovery rate and purity of sodium chloride and potassium chloride.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a system and method for separating sodium chloride and potassium chloride. Background Art

[0002] At present, my country's steel industry produces a large amount of coking wastewater and cold rolling wastewater, which have the characteristics of high salt content and high COD. In order to improve the utilization rate of water resources, more and more steel companies use a series of deep treatment technologies to treat these wastewaters and strive to achieve zero wastewater discharge.

[0003] The wastewater zero discharge technology mainly involves concentrating and evaporating and crystallizing these wastewaters, and reusing the steam generated during the evaporation and crystallization process after condensation, and purifying and separating the dissolved salts (such as sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, etc.) in the wastewater as much as possible during the evaporation and crystallization process to generate finished salts that can be used for industrial production. In the evaporation and crystallization process, in addition to the finished salts, some concentrated mother liquors are also produced, which can be converted into solid impure salts through drying and incineration.

[0004] However, when separating and treating high-salinity wastewater generated in the process of zero wastewater discharge, the main technical difficulties include the difficulty of separation and recovery, low purity of separated salts, low salt recovery rate and high energy consumption of incineration. Therefore, how to separate and recover high-salinity wastewater, improve salt purity and salt recovery rate and reduce energy consumption has become one of the technical problems that technicians in this field need to solve urgently. Summary of the invention

[0005] The object of the present invention is to provide a sodium chloride and potassium chloride separation system and method to solve one or more of the problems existing in the prior art, such as the difficulty in separating and recovering high-salt wastewater generated by zero wastewater discharge, the low purity of separated salts, the low salt recovery rate and the high energy consumption of incineration.

[0006] To achieve the above object, the present invention is implemented by the following technical scheme: a separation system of sodium chloride and potassium chloride, the separation system comprising an evaporation crystallization module and a cooling crystallization module arranged in sequence and a drying module connected to the evaporation crystallization module and the cooling crystallization module, wherein the cooling crystallization module is provided with a solvent delivery unit; the evaporation crystallization module is configured to sequentially perform evaporation concentration treatment and a first solid-liquid separation treatment on high-salt wastewater containing sodium chloride and potassium chloride to obtain a first mother liquor and a crude sodium chloride; the cooling crystallization module is configured to sequentially perform cooling crystallization treatment and a second solid-liquid separation treatment on the first mother liquor to obtain a second mother liquor and a crude potassium chloride; the solvent delivery unit is configured to add an organic solvent to the first mother liquor according to a preset addition ratio when the first mother liquor is cooled to a first preset temperature range; the drying module is configured to dry the crude sodium chloride and the crude potassium chloride to obtain product sodium chloride and product potassium chloride.

[0007] Optionally, the evaporation crystallization module includes an evaporation concentration unit and a first solid-liquid separation unit which are arranged in sequence; the evaporation concentration unit is configured to perform the evaporation concentration treatment on the high-salt wastewater to obtain a first concentrated liquid; the first solid-liquid separation unit is configured to perform the first solid-liquid separation treatment on the first concentrated liquid to obtain the first mother liquor and the crude sodium chloride.

[0008] Optionally, the evaporation and concentration unit includes a raw water pump, a preheater, a heater, an evaporator and a circulating pump which are arranged in sequence, the circulating pump is connected to the heater, and the evaporator is connected to the first solid-liquid separation unit; the raw water pump is used to transport the high-salt wastewater to the preheater; the evaporator is used to boil and evaporate the high-salt wastewater to obtain the first concentrated liquid and secondary steam; the circulating pump is used to drive the high-salt wastewater to circulate between the evaporator, the circulating pump and the heater.

[0009] Optionally, the evaporator is connected to a vacuum system and a compressor for recovering and increasing the thermal energy of the secondary steam; the exhaust port of the compressor is connected to the steam inlet of the heater, and the steam outlet of the heater is connected to the condensate inlet of the preheater.

[0010] Optionally, the cooling crystallization module includes a first insulation unit, a cooling crystallization unit, and a second solid-liquid separation unit, which are arranged in sequence, and a solvent delivery unit connected to the cooling crystallization unit; the first insulation unit is used to receive the first mother liquor and control its temperature within a second preset temperature range; the cooling crystallization unit is configured to cool the received first mother liquor, and when the first mother liquor is cooled to a third preset temperature range, stop cooling to obtain a second concentrated liquid; the solvent delivery unit is configured to add the organic solvent to the first mother liquor according to the preset addition ratio when the first mother liquor in the cooling crystallization unit is cooled to the first preset temperature range; the second solid-liquid separation unit is configured to perform the second solid-liquid separation process on the second concentrated liquid to obtain the second mother liquor and the crude potassium chloride.

[0011] Optionally, the first preset temperature range includes 55°C-65°C, the second preset temperature range includes 90°C-100°C, and the third preset temperature range includes 35°C-45°C.

[0012] Optionally, the second solid-liquid separation unit is connected to the evaporation crystallization module; the second solid-liquid separation unit is further configured to transport the second mother liquor to the evaporation crystallization module.

[0013] Optionally, the drying module comprises a drum blade dryer.

[0014] To achieve the above object, the present invention also provides a method for separating sodium chloride and potassium chloride, using any of the above-mentioned sodium chloride and potassium chloride separation systems to treat high-salt wastewater containing sodium chloride and potassium chloride, the separation method comprising:

[0015] The high-salt wastewater is subjected to evaporation concentration treatment and first solid-liquid separation treatment in sequence to obtain a first mother liquor and crude sodium chloride;

[0016] The first mother liquor is subjected to a cooling crystallization treatment and a second solid-liquid separation treatment in sequence, and when the first mother liquor is cooled to a first preset temperature range, an organic solvent is added to the first mother liquor according to a preset addition ratio to obtain a second mother liquor and crude potassium chloride;

[0017] The crude sodium chloride and the crude potassium chloride are dried to obtain product sodium chloride and product potassium chloride.

[0018] Optionally, the separation method further comprises:

[0019] The second mother liquor is transported to the evaporation crystallization module of the separation system.

[0020] Compared with the prior art, the sodium chloride and potassium chloride separation system and method provided by the present invention have the following beneficial effects:

[0021] The present invention provides a separation system for sodium chloride and potassium chloride, wherein the separation system comprises an evaporation crystallization module and a cooling crystallization module which are arranged in sequence, and a drying module which is connected to the evaporation crystallization module and the cooling crystallization module, wherein a solvent conveying unit is arranged in the cooling crystallization module; the evaporation crystallization module is configured to sequentially perform evaporation concentration treatment and a first solid-liquid separation treatment on high-salinity wastewater containing sodium chloride and potassium chloride to obtain a first mother liquor and a crude sodium chloride; the cooling crystallization module is configured to sequentially perform cooling crystallization treatment and a second solid-liquid separation treatment on the first mother liquor to obtain a second mother liquor and a crude potassium chloride; the solvent conveying unit is configured to, when the first mother liquor is cooled to a first preset temperature range, add an organic solvent to the first mother liquor according to a preset addition ratio; the drying module is configured to perform drying treatment on the crude sodium chloride and the crude potassium chloride to obtain product sodium chloride and product potassium chloride. Thus, the separation system of sodium chloride and potassium chloride provided by the present invention first carries out evaporation and concentration treatment on the high-salt wastewater containing sodium chloride and potassium chloride through the evaporation crystallization module, which can reduce the amount of wastewater and increase the salt concentration in the wastewater; then the high-salt wastewater is subjected to the first solid-liquid separation treatment, and more crude sodium chloride can be separated, so that the recovery rate of sodium chloride can be improved, and the potassium chloride concentration in the first mother liquor can also be improved, which lays a good foundation for improving the recovery rate of potassium chloride. Further, the first mother liquor is first subjected to the cooling crystallization treatment by the cooling crystallization module, and the crude potassium chloride in the first mother liquor can be separated; in addition, in the process of cooling crystallization treatment of the first mother liquor, when the first mother liquor is cooled to the first preset temperature range, the solvent delivery unit provided in the cooling crystallization module is added to the first mother liquor according to the preset addition ratio. Organic solvent (such as anhydrous methanol) can be added to the first mother liquor, which can reduce the solubility of potassium chloride in water, and lays a good foundation for separating more crude potassium chloride. The first mother liquor is subjected to the second solid-liquid separation treatment by the cooling crystallization module, and more crude potassium chloride can be separated, so that the recovery rate of potassium chloride can be improved. Finally, the obtained crude sodium chloride and crude potassium chloride are dried by a drying module to remove moisture and organic matter that may be enriched in the crystals, thereby obtaining dry and higher purity product sodium chloride and product potassium chloride.

[0022] Further, the cooling crystallization module includes a first insulation unit, a cooling crystallization unit, and a second solid-liquid separation unit, which are sequentially arranged, and the solvent delivery unit connected to the cooling crystallization unit; the first insulation unit is used to receive the first mother liquor and control its temperature within a second preset temperature range; the cooling crystallization unit is configured to cool the received first mother liquor, and when the first mother liquor is cooled to a third preset temperature range, stop cooling to obtain a second concentrated solution; the solvent delivery unit is configured to add the organic solvent to the first mother liquor according to the preset addition ratio when the first mother liquor in the cooling crystallization unit is cooled to the first preset temperature range; the second solid-liquid separation unit is configured to perform the second solid-liquid separation process on the second concentrated solution to obtain the second mother liquor and the crude potassium chloride. Thus, the separation system of sodium chloride and potassium chloride provided by the present invention receives the first mother liquor through the first insulation unit and controls its temperature within a second preset temperature range, which can ensure that the temperature of the first mother liquor output by the evaporation crystallization module is maintained within a stable range, thereby improving the recovery rate and purity of potassium chloride. Next, the cooling crystallization unit is used to cool the first mother liquor and the terminal temperature of the cooling crystallization is precisely controlled, so that high-purity potassium chloride crystals can be precipitated to obtain a second concentrated solution; and during the cooling crystallization process, the solvent delivery unit is used to add an organic solvent according to a preset addition ratio, so that the solubility of potassium chloride can be reduced, so that more potassium chloride crystals can be precipitated. Finally, the second concentrated solution is subjected to a second solid-liquid separation process by the second solid-liquid separation unit, so that more crude potassium chloride can be separated, thereby improving the recovery rate of potassium chloride.

[0023] Furthermore, the second solid-liquid separation unit is connected to the evaporation crystallization module; the second solid-liquid separation unit is further configured to transport the second mother liquor to the evaporation crystallization module. Thus, the sodium chloride and potassium chloride separation system provided by the present invention can increase the potassium chloride concentration in the high-salinity wastewater by connecting the second solid-liquid separation unit to the evaporation crystallization module so that the second mother liquor is transported to the evaporation crystallization module and mixed with the high-salinity wastewater, thereby improving the recovery rate of potassium chloride.

[0024] Since the method for separating sodium chloride and potassium chloride provided by the present invention and the system for separating sodium chloride and potassium chloride provided by the present invention belong to the same inventive concept, the method for separating sodium chloride and potassium chloride provided by the present invention at least has all the advantages of the system for separating sodium chloride and potassium chloride provided by the present invention. For the advantages of the method for separating sodium chloride and potassium chloride provided by the present invention, please refer to the relevant description on the beneficial effects of the system for separating sodium chloride and potassium chloride provided by the present invention, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1A structural block diagram of a sodium chloride and potassium chloride separation system provided in Example 1 of the present invention;

[0026] Figure 2 A process flow chart of a sodium chloride and potassium chloride separation system provided in Example 1 of the present invention;

[0027] Figure 3 A schematic flow chart of a method for separating sodium chloride and potassium chloride provided in Example 2 of the present invention;

[0028] The following are the descriptions of the reference numerals:

[0029] 1-evaporation crystallization module, 11-evaporation concentration unit, 111-raw water pump, 112-preheater, 1121-wastewater inlet, 1122-wastewater outlet, 1123-condensed water inlet, 1124-condensed water outlet, 113-heater, 1131-water inlet, 1132-water outlet, 1133-steam inlet, 1134-steam outlet, 114-evaporator, 1141-vacuum system, 1142-compressor, 11421-air intake, 11422-exhaust outlet, 1 15-circulation pump, 12-first solid-liquid separation unit, 121-first centrifuge, 2-cooling crystallization module, 21-solvent delivery unit, 211-solvent pump, 212-solvent storage tank, 22-first insulation unit, 221-first mother liquor insulation tank, 23-cooling crystallization unit, 231-cooling crystallizer, 24-second solid-liquid separation unit, 241-second centrifuge, 25-second insulation unit, 251-second mother liquor insulation tank, 3-drying module, 31-drum scraper dryer. DETAILED DESCRIPTION

[0030] The following is a further detailed description of the sodium chloride and potassium chloride separation system and method proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, which are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purposes, features and advantages of the present invention more obvious and easy to understand, please refer to the accompanying drawings. It should be noted that the structures, proportions, sizes, etc. illustrated in the accompanying drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Any modification of the structure, change of the proportional relationship or adjustment of the size, in the case of the same or similar effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical content disclosed by the present invention. The specific design features of the present invention disclosed herein include, for example, specific dimensions, directions, positions and shapes, which will be determined in part by the specific environment to be applied and used. And, in the embodiments described below, sometimes the same figure mark is used to represent the same part or part with the same function between different drawings, and its repeated description is omitted.

[0031] It should be understood that, unless otherwise stated or obvious from the context, as used herein, the term "about" is understood to be within the normal tolerance range in the art, such as within 2 standard deviations of the mean. "About" can be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05% or 0.01% of the value. Unless otherwise clear from the context, all numerical values ​​provided herein are modified by the term "about".

[0032] Embodiment 1

[0033] This embodiment provides a separation system of sodium chloride and potassium chloride. Figure 1 and Figure 2 , Figure 1 A block diagram of a system for separating sodium chloride and potassium chloride provided in this embodiment; Figure 2 The process flow chart of the separation system of sodium chloride and potassium chloride provided in this embodiment. Figure 1 and Figure 2It can be seen that the separation system includes an evaporation crystallization module 1 and a cooling crystallization module 2 which are arranged in sequence, and a drying module 3 which is connected to both the evaporation crystallization module 1 and the cooling crystallization module 2, wherein the cooling crystallization module 2 is provided with a solvent delivery unit 21; the evaporation crystallization module 1 is configured to sequentially perform an evaporation concentration treatment and a first solid-liquid separation treatment on the high-salt wastewater containing sodium chloride and potassium chloride to obtain a first mother liquor and a crude sodium chloride; the cooling crystallization module 2 is configured to sequentially perform a cooling crystallization treatment and a second solid-liquid separation treatment on the first mother liquor to obtain a second mother liquor and a crude potassium chloride; the solvent delivery unit 21 is configured to add an organic solvent to the first mother liquor according to a preset addition ratio when the first mother liquor is cooled to a first preset temperature range; the drying module 3 is configured to dry the crude sodium chloride and the crude potassium chloride to obtain product sodium chloride and product potassium chloride.

[0034] Thus, the separation system of sodium chloride and potassium chloride provided in the present embodiment, by evaporation and crystallization module 1, high-salt wastewater containing sodium chloride and potassium chloride is first subjected to evaporation and concentration treatment, which can reduce the amount of wastewater and improve the salt concentration in the wastewater; then the high-salt wastewater is subjected to the first solid-liquid separation treatment, more crude sodium chloride can be separated, so that the recovery rate of sodium chloride can be improved, and the potassium chloride concentration in the first mother liquor can also be improved, which lays a good foundation for improving the recovery rate of potassium chloride. Further, the first mother liquor is first subjected to cooling and crystallization treatment by cooling and crystallization module 2, and the crude potassium chloride in the first mother liquor can be separated; in addition, in the process of cooling and crystallization treatment of the first mother liquor, when the first mother liquor is cooled to the first preset temperature range, an organic solvent (such as anhydrous methanol) is added to the first mother liquor according to a preset addition ratio by the solvent delivery unit 21 provided in the cooling and crystallization module 2, which can reduce the solubility of potassium chloride in water, which lays a good foundation for separating more crude potassium chloride. The first mother liquor is subjected to a second solid-liquid separation treatment through the cooling crystallization module 2, so that more crude potassium chloride can be separated, thereby improving the recovery rate of potassium chloride. Finally, the crude sodium chloride and crude potassium chloride obtained are dried through the drying module 3 to remove moisture and organic matter that may be enriched in the crystals, thereby obtaining dry and higher purity product sodium chloride and product potassium chloride.

[0035] It should be noted that, as can be understood by those skilled in the art, the high-salt wastewater may include, but is not limited to, the mother liquor produced by zero-discharge treatment of coking wastewater and cold rolling wastewater in the steel industry. The mother liquor is difficult to handle, has a high salt content and a high COD, and the salts contained mainly include sodium ions, potassium ions, chloride ions, sulfate ions and nitrate ions. Exemplarily, the sodium ion concentration in the high-salt wastewater is about 120,000 mg / L, the potassium ion concentration is about 70,000 mg / L, the chloride ion concentration is about 150,000 mg / L, and the sulfate ion concentration is not higher than 20,000 mg / L. In addition, in order to ensure the purity and yield of the potassium chloride product obtained by treating the high-salt wastewater using the sodium chloride and potassium chloride separation system provided by the present invention, the ratio of the sodium ion concentration to the potassium ion concentration in the high-salt wastewater is preferably in the range of 1:1 to 2:1.

[0036] Preferably, the evaporation crystallization module 1 includes an evaporation concentration unit 11 and a first solid-liquid separation unit 12 which are arranged in sequence; the evaporation concentration unit 11 is configured to perform the evaporation concentration treatment on the high-salt wastewater to obtain a first concentrated solution; the first solid-liquid separation unit 12 is configured to perform the first solid-liquid separation treatment on the first concentrated solution to obtain the first mother liquor and the crude sodium chloride. Thus, by performing the evaporation concentration treatment on the high-salt wastewater through the evaporation concentration unit 11, the water in the high-salt wastewater can be evaporated, thereby reducing the treatment amount of the high-salt wastewater and increasing the salt concentration in the high-salt wastewater, laying a good foundation for improving the recovery rate of sodium chloride and potassium chloride; by performing the first solid-liquid separation treatment on the first concentrated solution obtained after the evaporation concentration treatment through the first solid-liquid separation unit 12, the crude sodium chloride can be separated.

[0037] It should be noted that, in one exemplary embodiment, when the volume of the first concentrated liquid reaches 45%-55% of the initial volume of the high-salinity wastewater, the high-salinity wastewater stops evaporating and concentrating. Exemplarily, the initial steam of the evaporator 114 can be low-pressure steam at 180°C-200°C, and the evaporation temperature of the evaporator 114 is preferably 90°C-100°C. The first solid-liquid separation unit 12 includes a first centrifuge 121.

[0038] Preferably, the evaporation concentration unit 11 comprises a raw water pump 111, a preheater 112, a heater 113, an evaporator 114 and a circulation pump 115 which are arranged in sequence, the circulation pump 115 is connected to the heater 113, and the evaporator 114 is connected to the first solid-liquid separation unit 12; the raw water pump 111 is used to transport the high-salt wastewater to the preheater 112; the evaporator 114 is used to boil and evaporate the high-salt wastewater to obtain the first concentrated liquid and secondary steam; the circulation pump 115 is used to drive the high-salt wastewater to circulate between the evaporator 114, the circulation pump 115 and the heater 113. Thus, the high-salt wastewater is transported to the preheater 112 for preheating by the raw water pump 111, and then the high-salt wastewater is circulated and heated by the heater 113 in combination with the circulation pump 115, so that the evaporation efficiency of the evaporator 114 can be improved.

[0039] For example, in one exemplary embodiment, the circulation pump 115 is a forced circulation pump, the head of the circulation pump 115 is 5 meters, the circulation volume is 500 times the flow rate of high-salt wastewater, and the operating frequency is 40 Hz; the heater 113 is a shell and tube heat exchanger.

[0040] Furthermore, the evaporator 114 is connected with a vacuum system 1141 and a compressor 1142 for recovering and increasing the heat energy of the secondary steam; the exhaust port 11422 of the compressor 1142 is connected to the steam inlet 1133 of the heater 113, and the steam outlet 1134 of the heater 113 is connected to the condensed water inlet 1123 of the preheater 112. Thus, the vacuum system 1141 can control the negative pressure state in the evaporator 114, so that the high-salt wastewater can boil at a lower temperature, thereby further improving the evaporation efficiency of the evaporator 114 and reducing energy consumption. The heat energy of the secondary steam generated by the evaporator 114 is increased by the compressor 1142, and the high-salt wastewater can be heated again by transporting the secondary steam with increased heat energy to the heater 113. The heated high-salt wastewater enters the evaporator 114 to continue evaporating and generate secondary steam, thereby achieving a continuous evaporation state. Such a configuration can make full use of the waste heat of steam, effectively improve thermal efficiency and save energy. At the same time, the condensed water condensed by the heater 113 can be recovered through the preheater 112, and the waste heat of the condensed water can be used to preheat the high-salt wastewater, thereby improving energy utilization and reducing system operating costs.

[0041] Exemplarily, the vacuum system 1141 controls the pressure in the evaporator 114 to -0.02 MPa to -0.03 MPa. A water spray device (not shown) is provided at the outlet of the compressor 1142, and the water spray device is used to cool the compressor 1142 to ensure that the outlet temperature of the compressor 1142 is not higher than 120°C when the compressor 1142 is in operation.

[0042] In order to facilitate the understanding of the present invention, the evaporation and concentration process of the high-salt wastewater is exemplarily described below:

[0043] First, the high-salt wastewater is continuously transported to the preheater 112 through the raw water pump 111, and the high-salt wastewater enters from the wastewater inlet 1121 of the preheater 112, and is output from the wastewater outlet 1122 of the preheater 112 to the water inlet 1131 of the heater 113 after preheating. Then, the high-salt wastewater is heated by the heater 113 and output from the water outlet 1132 of the heater 113 to the evaporator 114 for evaporation and concentration treatment, and the high-salt wastewater is driven by the forced circulation pump to circulate between the evaporator 114, the forced circulation pump and the heater 113. At the same time, the secondary steam continuously generated in the evaporator 114 is output from the steam outlet of the evaporator 114 to the air intake 11421 of the compressor 1142, and after the heat energy is increased by the compressor 1142, it is output from the exhaust port 11422 of the compressor 1142 to the steam inlet 1133 of the heater 113. Next, the secondary steam is condensed by the heater 113 to generate condensed water, and the condensed water in the heater 113 is output from the steam outlet 1134 of the heater 113 to the condensed water inlet 1123 of the preheater 112 after heat exchange with the high-salt wastewater, and the high-salt wastewater is preheated by recovering the waste heat of the condensed water by the preheater 112. Finally, the condensed water is discharged from the condensed water outlet 1124 of the preheater 112.

[0044] Preferably, the cooling crystallization module 2 includes a first heat preservation unit 22, a cooling crystallization unit 23, and a second solid-liquid separation unit 24, which are sequentially arranged, and the solvent delivery unit 21 connected to the cooling crystallization unit 23; the first heat preservation unit 22 is used to receive the first mother liquor and control its temperature within a second preset temperature range; the cooling crystallization unit 23 is configured to cool the received first mother liquor, and when the first mother liquor is cooled to a third preset temperature range, stop cooling to obtain a second concentrated solution; the solvent delivery unit 21 is configured to add the organic solvent to the first mother liquor according to the preset addition ratio when the first mother liquor in the cooling crystallization unit 23 is cooled to the first preset temperature range; the second solid-liquid separation unit 24 is configured to perform the second solid-liquid separation process on the second concentrated solution to obtain the second mother liquor and the crude potassium chloride. Thus, by receiving the first mother liquor through the first heat preservation unit 22 and controlling its temperature within the second preset temperature range, it is possible to ensure that the temperature of the first mother liquor output by the evaporation crystallization module 1 is maintained within a stable range, thereby improving the recovery rate and purity of potassium chloride. Next, the cooling crystallization unit 23 is used to cool the first mother liquor and accurately control the terminal temperature of the cooling crystallization, so that high-purity potassium chloride crystals can be precipitated to obtain a second concentrated solution; and during the cooling crystallization process, the solvent delivery unit 21 is used to add an organic solvent according to a preset addition ratio, so that the solubility of potassium chloride can be reduced, so that more potassium chloride crystals can be precipitated. Finally, the second concentrated solution is subjected to a second solid-liquid separation process by the second solid-liquid separation unit 24, so that more crude potassium chloride can be separated, thereby improving the recovery rate of potassium chloride.

[0045] Exemplarily, the first insulation unit 22 includes a first mother liquor insulation tank 221, and the control temperature range of the first mother liquor insulation tank 221 is 90°C-100°C. The cooling crystallization unit 23 includes a cooling crystallizer 231, and a frame agitator (not shown in the figure) is arranged in the cooling crystallizer 231, and the stirring rate is 305 rpm. The frame agitator can effectively stir the solution and scrape off the sediment on the container wall and the bottom. The solvent delivery unit 21 includes a solvent pump 211 for delivering the organic solvent and a solvent storage tank 212 for storing the organic solvent. The second solid-liquid separation unit 24 includes a second centrifuge 241.

[0046] Preferably, the first preset temperature range includes 55°C-65°C, the second preset temperature range includes 90°C-100°C, and the third preset temperature range includes 35°C-45°C.

[0047] It should be noted that the present invention does not impose too many restrictions on the type of the organic solvent and the preset addition ratio. For example, in one exemplary embodiment, the organic solvent is anhydrous methanol, and the first heat preservation unit 22 delivers 1 ton of the first mother liquor to the cooling crystallization unit 23, and the solvent delivery unit 21 adds 100 liters of anhydrous methanol to the first mother liquor.

[0048] Furthermore, the second solid-liquid separation unit 24 is connected to a second heat preservation unit 25, and the second heat preservation unit 25 is used to receive the second mother liquid and control its temperature within a fourth preset temperature range. Thus, the temperature of the second mother liquid can be prevented from decreasing, thereby preventing the precipitation of crystals from causing pipeline blockage.

[0049] Exemplarily, the second heat preservation unit 25 includes a second mother liquid heat preservation tank 251, and the fourth preset temperature range is 35°C-45°C.

[0050] Preferably, the second solid-liquid separation unit 24 is connected to the evaporation crystallization module 1; the second solid-liquid separation unit 24 is further configured to transport the second mother liquor to the evaporation crystallization module 1. Thus, by connecting the second solid-liquid separation unit 24 to the evaporation crystallization module 1 so that the second mother liquor is transported to the evaporation crystallization module 1 and mixed with the high-salinity wastewater, the concentration of potassium chloride in the high-salinity wastewater can be increased, thereby improving the recovery rate of potassium chloride.

[0051] Exemplarily, the second mother liquor insulation tank 251 is connected to the evaporator 114 so that the second mother liquor in the second mother liquor insulation tank 251 is transported to the evaporator 114 to be mixed with the high-salt wastewater.

[0052] Furthermore, the drying module 3 includes a drum blade dryer 31. Thus, the drum blade dryer 31 is used to dry the crude sodium chloride obtained by the evaporation crystallization module 1 and the crude potassium chloride obtained by the cooling crystallization module 2, thereby removing moisture and obtaining dry salt.

[0053] It should be noted that the drum scraper dryer 31 is an internal heating conduction type drying device with a single drum, double drum or multi-drum structure. The wet material obtains heat on the outer wall of the drum by heat conduction, thereby removing moisture to achieve the required moisture content. The heat is transferred from the inner wall of the drum to the outer wall of the drum, and then passes through the material film coated on the outer wall of the drum. This heat transfer method has a high thermal efficiency.

[0054] For example, in one exemplary embodiment, the drum scraper dryer 31 is heated by blast furnace waste heat tail gas at 800°C to 1000°C generated by a steel plant. Thus, energy can be saved and wastewater treatment costs can be reduced; moreover, through high-temperature treatment, the light yellow organic matter enriched in the crude sodium chloride and crude potassium chloride can be evaporated, thereby improving the purity of the product sodium chloride and product potassium chloride.

[0055] It should be noted that the material of the pipes and equipment in the sodium chloride and potassium chloride separation system provided by the present invention should be TA2 or above grade materials to ensure the corrosion resistance and long-term reliability of the pipes and equipment.

[0056] Embodiment 2

[0057] This embodiment provides a method for separating sodium chloride and potassium chloride, and uses the sodium chloride and potassium chloride separation system described in any of the above embodiments to treat high-salt wastewater containing sodium chloride and potassium chloride. Figure 3 , Figure 3 The schematic diagram of the process for separating sodium chloride and potassium chloride provided in this embodiment. Figure 3 It can be seen that the separation method comprises:

[0058] S100: performing evaporation concentration treatment and first solid-liquid separation treatment on the high-salt wastewater in sequence to obtain a first mother liquor and crude sodium chloride;

[0059] S200: performing a cooling crystallization process and a second solid-liquid separation process on the first mother liquor in sequence, and when the first mother liquor is cooled to a first preset temperature range, adding an organic solvent to the first mother liquor according to a preset addition ratio to obtain a second mother liquor and crude potassium chloride;

[0060] S300: Drying the crude sodium chloride and the crude potassium chloride to obtain product sodium chloride and product potassium chloride.

[0061] Since the method for separating sodium chloride and potassium chloride provided in this embodiment and the system for separating sodium chloride and potassium chloride provided in any of the above-mentioned embodiments belong to the same inventive concept, the method for separating sodium chloride and potassium chloride provided in this embodiment at least has all the advantages of the separation systems for sodium chloride and potassium chloride provided in the above-mentioned embodiments. For the advantages of the method for separating sodium chloride and potassium chloride provided in this embodiment, please refer to the relevant description of the beneficial effects of the separation systems for sodium chloride and potassium chloride provided in the above-mentioned embodiments, which will not be repeated here.

[0062] Preferably, the separation method further comprises:

[0063] S400: transporting the second mother liquor to the evaporation crystallization module 1 of the separation system. Thus, by transporting the second mother liquor rich in potassium chloride to the evaporation crystallization module 1, the potassium chloride concentration of the high-salt wastewater in the evaporation crystallization module 1 can be increased, thereby improving the recovery rate of potassium chloride.

[0064] For example, in one exemplary embodiment, the sodium ion concentration in the high-salt wastewater is about 120,000 mg / L, the potassium ion concentration is about 60,000 mg / L, the chloride ion concentration is about 190,000 mg / L, the sulfate ion concentration is not higher than 1,000 mg / L, and the COD concentration is about 32,000 mg / L. If the sodium chloride and potassium chloride separation method provided by the present invention is used to treat each ton of the high-salt wastewater, about 200 kg of product sodium chloride with a purity of 88% and about 50 kg of product potassium chloride with a purity of 90% can be obtained; in addition, about 500 liters of condensed water can be obtained, and the COD concentration of the condensed water is not higher than 50 mg / L, and the TDS is about 100 mg / L, which meets the use conditions of industrial circulating cooling water and can be recycled after cooling, thereby saving resources.

[0065] In order to make the present invention more easily understood, the present invention will be described below with reference to two specific examples of separating and treating high-salt wastewater using the method for separating sodium chloride and potassium chloride provided by the present invention.

[0066] Example 1: The sodium ion concentration in a stream of high-salt wastewater is about 120,000 mg / L, the potassium ion concentration is about 70,000 mg / L, the chloride ion concentration is about 150,000 mg / L, the sulfate ion concentration is not higher than 20,000 mg / L, and the high-salt wastewater contains some organic matter, and the water sample is yellow.

[0067] First, the high-salinity wastewater is transported to the TA2 material evaporator 114 through the raw water pump 111 for evaporation and concentration. When the volume of the first concentrated liquid reaches 50% of the initial volume of the high-salinity wastewater, the evaporation and concentration is stopped. The first concentrated liquid is then transported to the first centrifuge 121 for the first solid-liquid separation process to obtain the first mother liquor and crude sodium chloride.

[0068] Then, after the first mother liquor enters the first insulation tank, it is transported to the cooling crystallizer 231 through a centrifugal pump for cooling and crystallization. When the first mother liquor is cooled to 60°C, anhydrous methanol is added to the cooling crystallizer 231 according to a preset addition ratio through the solvent pump 211 to reduce the solubility of potassium chloride in water, thereby obtaining more potassium chloride crystals. When the first mother liquor continues to cool to 40°C, the cooling is stopped to obtain a second concentrated solution. The second concentrated solution is then transported to the second centrifuge 241 for a second solid-liquid separation process to obtain a second mother liquor and crude potassium chloride.

[0069] Finally, the crude sodium chloride and crude potassium chloride are subjected to high-temperature drying treatment using a drum scraper dryer 31 to obtain product sodium chloride and product potassium chloride. At the same time, the second mother liquor is transported to the evaporator 114 to be mixed with the high-salt wastewater.

[0070] Thus, if the separation method of sodium chloride and potassium chloride provided by the present invention is used for treatment, about 200 kg of product sodium chloride and about 50 kg of product potassium chloride can be obtained per ton of the high-salt wastewater; in addition, about 500 liters of condensed water can be obtained, the COD concentration of the condensed water is not higher than 50 mg / L, and the TDS is not higher than 100 mg / L, which meets the use conditions of industrial circulating cooling water and can be recycled after cooling, thereby saving resources. In the obtained product sodium chloride, sodium ions are about 323.828 mg / g, potassium ions are about 42.057 mg / g, chloride ions are about 557.89 mg / g, and sulfate ions are about 0.27 mg / g, and the purity of the product sodium chloride can reach 88%; in the obtained product potassium chloride, sodium ions are about 24.703 mg / g, potassium ions are about 451.233 mg / g, chloride ions are about 457.73 mg / g, and sulfate ions are about 1.22 mg / g, and the purity of the product potassium chloride can reach 90%.

[0071] If anhydrous methanol is not added to the cooling crystallizer 231, the product sodium chloride obtained after separation and treatment of each ton of the high-salt wastewater is about 200 kg and the product potassium chloride is about 25 kg.

[0072] Example 2: The sodium ion concentration in another stream of high-salt wastewater is about 115,000 mg / L, the potassium ion concentration is about 61,450 mg / L, the chloride ion concentration is about 197,000 mg / L, the sulfate ion concentration is not higher than 20,000 mg / L, and the high-salt wastewater contains some organic matter, and the water sample is yellow.

[0073] First, the high-salinity wastewater is transported to the TA2 material evaporator 114 through the raw water pump 111 for evaporation and concentration. When the volume of the first concentrated liquid reaches 50% of the initial volume of the high-salinity wastewater, the evaporation and concentration is stopped. The first concentrated liquid is then transported to the first centrifuge 121 for the first solid-liquid separation process to obtain the first mother liquor and crude sodium chloride.

[0074] Then, after the first mother liquor enters the first insulation tank, it is transported to the cooling crystallizer 231 through a centrifugal pump for cooling and crystallization. When the first mother liquor is cooled to 60°C, anhydrous methanol is added to the cooling crystallizer 231 according to a preset addition ratio through the solvent pump 211 to reduce the solubility of potassium chloride in water, thereby obtaining more potassium chloride crystals. When the first mother liquor continues to cool to 40°C, the cooling is stopped to obtain a second concentrated solution. The second concentrated solution is then transported to the second centrifuge 241 for a second solid-liquid separation process to obtain a second mother liquor and crude potassium chloride.

[0075] Finally, the crude sodium chloride and crude potassium chloride are subjected to high-temperature drying treatment using a drum scraper dryer 31 to obtain product sodium chloride and product potassium chloride. At the same time, the second mother liquor is transported to the evaporator 114 to be mixed with the high-salt wastewater.

[0076] Thus, if the separation method of sodium chloride and potassium chloride provided by the present invention is used for treatment, about 192 kg of product sodium chloride and about 48.5 kg of product potassium chloride can be obtained per ton of the high-salt wastewater; in addition, about 500 liters of condensed water can be obtained, the COD concentration of the condensed water is not higher than 50 mg / L, and the TDS is not higher than 100 mg / L, which meets the use conditions of industrial circulating cooling water and can be recycled after cooling, thereby saving resources. In the obtained product sodium chloride, the sodium ion is about 355.478 mg / g, the potassium ion is about 37.577 mg / g, the chloride ion is about 594.14 mg / g, and the sulfate ion is about 1.23 mg / g, and the purity of the product sodium chloride can reach 90%; in the obtained product potassium chloride, the sodium ion is about 38.551 mg / g, the potassium ion is about 436.194 mg / g, the chloride ion is about 460.22 mg / g, and the sulfate ion is about 0.92 mg / g, and the purity of the product potassium chloride can reach 91%.

[0077] If anhydrous methanol is not added to the cooling crystallizer 231, the product sodium chloride obtained after separation and treatment of each ton of the high-salt wastewater is about 192 kg and the product potassium chloride is about 23.8 kg.

[0078] Therefore, by using the method for separating sodium chloride and potassium chloride provided by the present invention to separate and treat high-salt wastewater, and by adding anhydrous methanol for cooling and crystallization treatment, the recovery rate of potassium chloride can be significantly improved.

[0079] In summary, the sodium chloride and potassium chloride separation system and method provided by the present invention have the following advantages: the sodium chloride and potassium chloride separation system provided by the present invention, the separation system comprises an evaporation crystallization module and a cooling crystallization module arranged in sequence and a drying module connected to the evaporation crystallization module and the cooling crystallization module, and the cooling crystallization module is provided with a solvent delivery unit; the evaporation crystallization module is configured to sequentially perform evaporation concentration treatment and a first solid-liquid separation treatment on high-salt wastewater containing sodium chloride and potassium chloride to obtain a first mother liquor and a crude sodium chloride; the cooling crystallization module is configured to sequentially perform cooling crystallization treatment and a second solid-liquid separation treatment on the first mother liquor to obtain a second mother liquor and a crude potassium chloride; the solvent delivery unit is configured to add an organic solvent to the first mother liquor according to a preset addition ratio when the first mother liquor is cooled to a first preset temperature range; the drying module is configured to dry the crude sodium chloride and the crude potassium chloride to obtain product sodium chloride and product potassium chloride. Thus, the separation system of sodium chloride and potassium chloride provided by the present invention first carries out evaporation and concentration treatment on the high-salt wastewater containing sodium chloride and potassium chloride through the evaporation crystallization module, which can reduce the amount of wastewater and increase the salt concentration in the wastewater; then the high-salt wastewater is subjected to the first solid-liquid separation treatment, and more crude sodium chloride can be separated, so that the recovery rate of sodium chloride can be improved, and the potassium chloride concentration in the first mother liquor can also be improved, which lays a good foundation for improving the recovery rate of potassium chloride. Further, the first mother liquor is first subjected to the cooling crystallization treatment by the cooling crystallization module, and the crude potassium chloride in the first mother liquor can be separated; in addition, in the process of cooling crystallization treatment of the first mother liquor, when the first mother liquor is cooled to the first preset temperature range, the solvent delivery unit provided in the cooling crystallization module is added to the first mother liquor according to the preset addition ratio. Organic solvent (such as anhydrous methanol) can be added to the first mother liquor, which can reduce the solubility of potassium chloride in water, and lays a good foundation for separating more crude potassium chloride. The first mother liquor is subjected to the second solid-liquid separation treatment by the cooling crystallization module, and more crude potassium chloride can be separated, so that the recovery rate of potassium chloride can be improved. Finally, the obtained crude sodium chloride and crude potassium chloride are dried by a drying module to remove moisture and organic matter that may be enriched in the crystals, thereby obtaining dry and higher purity product sodium chloride and product potassium chloride.

[0080] Further, the cooling crystallization module includes a first insulation unit, a cooling crystallization unit, and a second solid-liquid separation unit, which are sequentially arranged, and the solvent delivery unit connected to the cooling crystallization unit; the first insulation unit is used to receive the first mother liquor and control its temperature within a second preset temperature range; the cooling crystallization unit is configured to cool the received first mother liquor, and when the first mother liquor is cooled to a third preset temperature range, stop cooling to obtain a second concentrated solution; the solvent delivery unit is configured to add the organic solvent to the first mother liquor according to the preset addition ratio when the first mother liquor in the cooling crystallization unit is cooled to the first preset temperature range; the second solid-liquid separation unit is configured to perform the second solid-liquid separation process on the second concentrated solution to obtain the second mother liquor and the crude potassium chloride. Thus, the separation system of sodium chloride and potassium chloride provided by the present invention receives the first mother liquor through the first insulation unit and controls its temperature within a second preset temperature range, which can ensure that the temperature of the first mother liquor output by the evaporation crystallization module is maintained within a stable range, thereby improving the recovery rate and purity of potassium chloride. Next, the cooling crystallization unit is used to cool the first mother liquor and the terminal temperature of the cooling crystallization is precisely controlled, so that high-purity potassium chloride crystals can be precipitated to obtain a second concentrated solution; and during the cooling crystallization process, the solvent delivery unit is used to add an organic solvent according to a preset addition ratio, so that the solubility of potassium chloride can be reduced, so that more potassium chloride crystals can be precipitated. Finally, the second concentrated solution is subjected to a second solid-liquid separation process by the second solid-liquid separation unit, so that more crude potassium chloride can be separated, thereby improving the recovery rate of potassium chloride.

[0081] Furthermore, the second solid-liquid separation unit is connected to the evaporation crystallization module; the second solid-liquid separation unit is further configured to transport the second mother liquor to the evaporation crystallization module. Thus, the sodium chloride and potassium chloride separation system provided by the present invention can increase the potassium chloride concentration in the high-salinity wastewater by connecting the second solid-liquid separation unit to the evaporation crystallization module so that the second mother liquor is transported to the evaporation crystallization module and mixed with the high-salinity wastewater, thereby improving the recovery rate of potassium chloride.

[0082] Since the method for separating sodium chloride and potassium chloride provided by the present invention and the system for separating sodium chloride and potassium chloride provided by the present invention belong to the same inventive concept, the method for separating sodium chloride and potassium chloride provided by the present invention at least has all the advantages of the system for separating sodium chloride and potassium chloride provided by the present invention. For the advantages of the method for separating sodium chloride and potassium chloride provided by the present invention, please refer to the relevant description on the beneficial effects of the system for separating sodium chloride and potassium chloride provided by the present invention, which will not be repeated here.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A separation system for sodium chloride and potassium chloride, characterized in that: The separation system comprises an evaporation crystallization module and a cooling crystallization module which are arranged in sequence, and a drying module which is connected to both the evaporation crystallization module and the cooling crystallization module, wherein a solvent delivery unit is arranged in the cooling crystallization module; The evaporation crystallization module is configured to sequentially perform evaporation concentration treatment and a first solid-liquid separation treatment on the high-salt wastewater containing sodium chloride and potassium chloride to obtain a first mother liquor and a crude sodium chloride; The cooling crystallization module is configured to sequentially perform cooling crystallization treatment and second solid-liquid separation treatment on the first mother liquor to obtain a second mother liquor and crude potassium chloride; The solvent delivery unit is configured to add an organic solvent to the first mother liquid according to a preset addition ratio when the first mother liquid is cooled to a first preset temperature range; The drying module is configured to dry the crude sodium chloride and the crude potassium chloride to obtain product sodium chloride and product potassium chloride.

2. The separation system of sodium chloride and potassium chloride as claimed in claim 1, characterized in that The evaporation crystallization module comprises an evaporation concentration unit and a first solid-liquid separation unit which are arranged in sequence; The evaporation and concentration unit is configured to perform the evaporation and concentration treatment on the high-salinity wastewater to obtain a first concentrated solution; The first solid-liquid separation unit is configured to perform the first solid-liquid separation process on the first concentrated liquid to obtain the first mother liquid and the crude sodium chloride.

3. The separation system of sodium chloride and potassium chloride as claimed in claim 2, characterized in that The evaporation concentration unit comprises a raw water pump, a preheater, a heater, an evaporator and a circulation pump which are arranged in sequence, the circulation pump is connected to the heater, and the evaporator is connected to the first solid-liquid separation unit; The raw water pump is used to transport the high-salt wastewater to the preheater; The evaporator is used to boil and evaporate the high-salt wastewater to obtain the first concentrated liquid and secondary steam; The circulation pump is used to drive the high-salt wastewater to circulate between the evaporator, the circulation pump and the heater.

4. The separation system of sodium chloride and potassium chloride as claimed in claim 3, characterized in that The evaporator is connected to a vacuum system and a compressor for recovering and increasing the thermal energy of the secondary steam; the exhaust port of the compressor is connected to the steam inlet of the heater, and the steam outlet of the heater is connected to the condensed water inlet of the preheater.

5. The separation system of sodium chloride and potassium chloride as claimed in claim 1, characterized in that, The cooling crystallization module comprises a first heat preservation unit, a cooling crystallization unit, a second solid-liquid separation unit, and a solvent delivery unit connected to the cooling crystallization unit. The first heat preservation unit is used to receive the first mother liquid and control the temperature of the first mother liquid within a second preset temperature range; The cooling crystallization unit is configured to cool the received first mother liquid, and when the first mother liquid is cooled to a third preset temperature range, stop cooling to obtain a second concentrated liquid; The solvent delivery unit is configured to add the organic solvent to the first mother liquid according to the preset addition ratio when the first mother liquid in the cooling crystallization unit is cooled to the first preset temperature range; The second solid-liquid separation unit is configured to perform the second solid-liquid separation process on the second concentrated liquid to obtain the second mother liquor and the crude potassium chloride.

6. The separation system of sodium chloride and potassium chloride as claimed in claim 5, characterized in that: The first preset temperature range includes 55°C-65°C, the second preset temperature range includes 90°C-100°C, and the third preset temperature range includes 35°C-45°C.

7. The separation system of sodium chloride and potassium chloride as claimed in claim 5, characterized in that: The second solid-liquid separation unit is connected to the evaporation crystallization module; The second solid-liquid separation unit is further configured to transport the second mother liquid to the evaporation crystallization module.

8. The separation system of sodium chloride and potassium chloride as claimed in claim 1, characterized in that, The drying module comprises a drum blade dryer.

9. A method for separating sodium chloride and potassium chloride, characterized in that: A sodium chloride and potassium chloride separation system as claimed in any one of claims 1 to 8 is used to treat high-salt wastewater containing sodium chloride and potassium chloride, wherein the separation method comprises: The high-salt wastewater is subjected to evaporation concentration treatment and first solid-liquid separation treatment in sequence to obtain a first mother liquor and crude sodium chloride; The first mother liquor is subjected to a cooling crystallization treatment and a second solid-liquid separation treatment in sequence, and when the first mother liquor is cooled to a first preset temperature range, an organic solvent is added to the first mother liquor according to a preset addition ratio to obtain a second mother liquor and crude potassium chloride; The crude sodium chloride and the crude potassium chloride are dried to obtain product sodium chloride and product potassium chloride.

10. The method for separating sodium chloride and potassium chloride as claimed in claim 9, wherein: The separation method further comprises: The second mother liquor is transported to the evaporation crystallization module of the separation system.

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