Device and method for extracting sodium chloride from sodium sulfate frozen crystallization mother liquor of coking wastewater

Abstract

This invention relates to the field of coking wastewater treatment technology, specifically to an apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater. The apparatus includes an evaporation crystallization chamber, with an electrically heated base fixedly installed at the bottom. Three sets of support rollers are movably installed inside the evaporation crystallization chamber. The apparatus and method for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater involves introducing the denitrification mother liquor into the evaporation crystallization chamber through an inlet pipe, allowing the mother liquor to fall into the evaporation zone. The electrically heated base heats the mother liquor in the evaporation zone, causing sodium chloride to evaporate and crystallize. Simultaneously, a drive motor is activated to rotate the conveyor belt and conveyor filter plates, discharging the crystallized sodium chloride. This maintains a balance between the amount of sodium chloride discharged from the evaporation zone and the inflow and outflow of the denitrification mother liquor, ensuring a continuous flow of sodium chloride crystallization in the evaporation zone. This allows for uninterrupted crystallization extraction of sodium chloride from the denitrification mother liquor.

Description

Technical Field

[0001] This invention relates to the field of coking wastewater treatment technology, specifically to an apparatus and method for extracting sodium chloride from sodium sulfate freeze crystallization mother liquor in coking wastewater. Background Technology

[0002] Coking wastewater mainly originates from the primary cooling of coke oven gas, production water used in the coking process, and steam condensate wastewater. Coking wastewater has high pollutant concentrations and is difficult to degrade. The presence of nitrogen in the wastewater leads to an excess of nitrogen source required for biological purification, making it difficult to meet treatment standards. The wastewater is highly hazardous, containing not only excessive nitrogen but also phenols, cyanides, oils, ammonia, and large amounts of inorganic salts. Polycyclic aromatic hydrocarbons (PAHs) in coking wastewater are not only difficult to degrade but are also often potent carcinogens, causing serious environmental pollution and directly threatening human health. With increasing environmental protection efforts and the deepening of sustainable development concepts, the requirements for zero wastewater discharge are becoming increasingly stringent. Before being discharged, coking wastewater requires multiple treatment processes, including the treatment of sodium sulfate and sodium chloride in the wastewater.

[0003] Currently, the main method for extracting sodium sulfate and sodium chloride from coking wastewater is crystallization, which includes the following steps: Pre-treatment with activated carbon for decolorization to remove insoluble impurities, including soluble substances such as Ca2+, Mg2+, and silicate ions; After pre-treatment, the wastewater is successively fed into electrodialysis and mechanical vapor recompression units for concentration, aiming to bring the sodium sulfate and sodium chloride content close to saturation based on the initial composition of the wastewater; The concentrated wastewater is then fed into a crystallizer for cooling and crystallization to obtain Glauber's salt, which is directly collected, washed, and dried to obtain anhydrous sodium sulfate; The concentrated denitrification mother liquor undergoes two-stage evaporation crystallization, and the sodium chloride product is directly collected. Sodium chloride is mainly extracted from the mother liquor of sodium sulfate cryogenic crystallization by evaporation. Currently, common evaporation crystallization devices typically use an evaporator-type evaporation structure to evaporate and crystallize sodium chloride. However, the crystallization process involves introducing the concentrated denitrification mother liquor into the evaporator for evaporation and crystallization. After crystallization, the system is shut down and the crystallized sodium chloride is discharged. Then, the mother liquor is added back in, and the process is repeated to extract sodium chloride from the mother liquor. Although this method can extract sodium chloride from the mother liquor, each evaporation and crystallization cycle is independent. Before and after evaporation and crystallization, the mother liquor needs to be added and the sodium chloride crystals need to be removed, which prevents continuous extraction and results in low extraction efficiency. Therefore, we propose a device and method for extracting sodium chloride from the mother liquor of sodium sulfate cryogenic crystallization in coking wastewater to solve the above-mentioned problems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an apparatus and method for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater, thus solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater, comprising an evaporation crystallization chamber, an electrically heated base fixedly installed at the bottom of the evaporation crystallization chamber, three sets of support rollers movably installed inside the evaporation crystallization chamber, and a conveyor filter belt movably fitted around the support rollers, with several conveyor filter plates fixedly connected to the outside of the conveyor filter belt, a drive motor fixedly installed on the front of the evaporation crystallization chamber to provide power for the rotation of the conveyor filter belt, the drive motor driving the support rollers on the output shaft to rotate, thereby driving the conveyor filter belt and the conveyor filter plates to rotate, and the sodium chloride crystallized in the evaporation zone can be discharged along the inclined section through filtration by the conveyor filter plates, the evaporation crystallization chamber having an evaporation zone located below the conveyor filter belt, and an inclined section cooperating with the conveyor filter belt, and a condenser plate fixedly installed on the top of the evaporation crystallization chamber, and the condenser plate A liquid collecting pipe is fixedly installed on one side of the bottom, and a liquid collecting tank is fixedly installed on the back of the evaporation crystallization chamber. A guide pipe is fixedly connected to the top of the liquid collecting tank. The gas produced by evaporation and crystallization rises and condenses after encountering the bottom of the condensing plate. It then flows into the liquid collecting pipe along the bottom of the condensing plate and enters the liquid collecting tank through the guide pipe. The reflux pump can reintroduce the condensed liquid into the evaporation crystallization chamber for evaporation and crystallization, thereby extracting sodium chloride from the denitrification mother liquor multiple times. A reflux pump is fixedly installed on the top of the liquid collecting tank, and a reflux pipe is fixedly connected to the outlet of the reflux pump. An inlet pipe is fixedly connected to the end of the reflux pipe away from the reflux pump. The denitrification mother liquor is introduced into the evaporation zone along the inlet pipe. The drive motor drives the conveyor belt and conveyor filter plate to rotate. At the same time, the evaporation zone is heated by the electric heating base to keep the sodium chloride discharge in the evaporation zone balanced with the denitrification mother liquor inlet and evaporation. This allows for continuous crystallization and extraction of sodium chloride from the denitrification mother liquor.

[0006] Preferably, the output shaft of the drive motor is fixedly connected to any one of the support rollers. The three sets of support rollers are distributed in a triangle inside the evaporation crystallization chamber. The length of the support rollers is the same as the width of the conveyor filter belt and the interior of the evaporation crystallization chamber. This limits the width of the support rollers and the conveyor filter belt, ensuring that the support rollers can drive the conveyor filter belt to rotate stably. At the same time, it ensures that the conveyor filter plate outside the conveyor filter belt can completely discharge the sodium chloride crystallized in the evaporation zone when rotating, thus ensuring the sodium chloride discharge effect.

[0007] Preferably, the bottom end of the conveyor filter plate at the bottom of the conveyor filter belt abuts against the bottom of the inside of the evaporation crystallization chamber, ensuring that when the conveyor filter belt drives the conveyor filter plate to rotate, the conveyor filter plate can completely discharge the sodium chloride crystallized in the evaporation zone, avoiding the accumulation of the crystallized sodium chloride in the evaporation zone. An extension plate is fixedly installed on the upper edge of the inclined section of the evaporation crystallization chamber, and the sodium chloride discharged along the inclined section of the evaporation crystallization chamber can be conducted and discharged along the extension plate, which facilitates the collection of the crystallized sodium chloride.

[0008] Preferably, the area of ​​the top of the electric heating base is the same as the area of ​​the evaporation zone. The electric heating base can heat the evaporation zone, ensuring that the electric heating base can completely heat the entire evaporation zone, thus ensuring the evaporation crystallization effect and speed.

[0009] Preferably, the end of the condenser plate near the liquid inlet pipe is tilted downwards at an angle of 10-30°. This tilting arrangement facilitates the flow of liquid condensed at the bottom of the condenser plate into the liquid collection pipe for easy collection. The condenser plate is embedded with serpentine water-cooling pipes to extend the residence time of the coolant within the condenser plate, thus improving the cooling effect. A chiller is installed on the back of the evaporation crystallization chamber, with its outlet and inlet fixedly connected to both ends of the water-cooling pipes. The chiller cools the coolant in the water-cooling pipes and circulates the coolant within the pipes, thereby cooling the condenser plate.

[0010] Preferably, the liquid collecting pipe is located at the bottom of the condenser plate near the liquid inlet pipe. By setting the liquid collecting pipe at a low position on the condenser plate, condensed liquid can be collected through the liquid collecting pipe. One end of the liquid collecting pipe is fixedly connected to the guide pipe. The bottom of the condenser plate is provided with evenly distributed guide grooves. When liquid condenses at the bottom of the condenser plate, it is guided through the guide grooves and can be directed into the liquid collecting pipe to prevent the liquid from falling off midway.

[0011] Preferably, the width of the condenser plate is the same as the width of the evaporation crystallization chamber, and the length of the condenser plate is not less than the length of the evaporation zone, so as to ensure that the gas evaporated in the evaporation zone can fully contact the condenser plate and ensure the condensation effect.

[0012] Preferably, the bottom end of the inlet pipe is provided with several evenly distributed nozzles. The denitrification mother liquor is dispersed by the nozzles, allowing the mother liquor to enter the evaporation zone at multiple points and ensuring even distribution. An inlet pump and a pipeline solenoid valve are fixedly installed on the inlet pipe.

[0013] Preferably, the front of the evaporation crystallization chamber is fixedly connected to a connecting pipe, and a liquid level sensor is threadedly connected inside the connecting pipe. The liquid level sensor can detect the liquid level inside the connecting pipe. Detecting the liquid level inside the connecting pipe by the liquid level sensor can detect the liquid level in the evaporation zone, thus preventing the liquid level from exceeding the height of the bottom of the conveyor filter belt and preventing sodium chloride crystallization from entering the conveyor filter belt and affecting its rotation.

[0014] A method for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater includes the following operational steps:

[0015] S1. Connect one end of the inlet pipe to the denitrification mother liquor storage equipment, start the inlet pump and pipeline solenoid valve, and introduce the denitrification mother liquor into the evaporation crystallization chamber along the inlet pipe and the nozzle at the bottom, so that the denitrification mother liquor falls into the evaporation zone. Since the connecting pipe is connected to the evaporation crystallization chamber, the denitrification mother liquor can enter the inside of the connecting pipe. The liquid level inside the connecting pipe is detected by the liquid level sensor, thereby realizing the detection of the liquid level in the evaporation zone and preventing the liquid level from exceeding the bottom height of the conveyor filter belt.

[0016] S2. Start the electric heating base to heat the denitrification mother liquor in the evaporation zone, so that the denitrification mother liquor evaporates. When the sodium chloride concentration of the denitrification mother liquor in the evaporation zone increases, crystallization begins. Start the drive motor to drive the support roller on the output shaft, as well as the conveyor filter belt and conveyor filter plate to rotate. The crystallized sodium chloride is filtered through the conveyor filter plate and discharged along the inclined section on the evaporation crystallization chamber.

[0017] S3. Based on the crystallization rate, control the rotation speed of the conveyor filter belt, the heating temperature of the electric heating base, and the flow rate of the denitrification mother liquor introduced into the inlet pipe to make the evaporation rate of the denitrification mother liquor, the inlet flow rate of the denitrification mother liquor, and the outlet rate of sodium chloride in the evaporation zone tend to be balanced, so that the concentration of the denitrification mother liquor in the evaporation zone remains stable, ensuring that sodium chloride is always crystallized out, and realizing the uninterrupted crystallization extraction of sodium chloride.

[0018] S4. During evaporation and crystallization, start the chiller. The chiller drives the coolant in the water-cooled pipe to flow and circulate the coolant inside the water-cooled pipe. The gas rising during evaporation condenses at the bottom of the condenser plate and is guided into the collection pipe along the guide groove at the bottom of the condenser plate. It then enters the collection tank along the guide pipe. After the denitrification mother liquor has undergone one evaporation and crystallization, start the reflux pump and guide the condensed liquid back into the evaporation and crystallization chamber along the reflux pipe for another evaporation and crystallization.

[0019] This invention provides an apparatus and method for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater, which has the following beneficial effects:

[0020] 1. The apparatus and method for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater involves introducing the denitrification mother liquor into the evaporation crystallization chamber through the inlet pipe, allowing the mother liquor to fall into the evaporation zone. The mother liquor in the evaporation zone is heated by an electric heating base, causing sodium chloride to evaporate and crystallize. Simultaneously, a drive motor is started to rotate the conveyor belt and conveyor filter plate, discharging the crystallized sodium chloride. This ensures that the amount of sodium chloride discharged from the evaporation zone is balanced with the amount of denitrification mother liquor entering and the amount of evaporation, so that a certain amount of sodium chloride is always crystallized in the evaporation zone. This allows for continuous crystallization extraction of sodium chloride from the denitrification mother liquor, improving extraction efficiency.

[0021] 2. The apparatus and method for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater utilizes a chiller to cool the coolant in the water-cooled pipes and circulate the coolant within the pipes, thereby cooling the condenser plate. The gas produced by evaporation and crystallization rises and condenses at the bottom of the condenser plate, flowing down the bottom of the condenser plate into the collection pipe. The condensate then enters the collection tank through a guide pipe. A reflux pump operates to reintroduce the condensed liquid into the evaporation and crystallization chamber for further evaporation and crystallization, thus extracting sodium chloride from the denitrification mother liquor multiple times and improving the sodium chloride extraction efficiency.

[0022] 3. The apparatus and method for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater, by setting a connecting pipe on the evaporation crystallization chamber and a liquid level sensor on the connecting pipe, the liquid level inside the connecting pipe is detected by the liquid level sensor, thereby realizing the detection of the liquid level in the evaporation zone, preventing the liquid level from exceeding the height of the bottom of the conveyor filter belt, preventing sodium chloride crystallization from entering the conveyor filter belt and affecting the rotation of the conveyor filter belt, and at the same time, preventing the impact on the amount of sodium chloride extracted. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall assembled structure of the present invention;

[0024] Figure 2 This is a schematic diagram of the overall rear structure of the present invention;

[0025] Figure 3 This is a front view of the internal structure of the evaporation and crystallization chamber of the present invention;

[0026] Figure 4 This is a schematic diagram of the cross-section of the connecting pipe of the present invention;

[0027] Figure 5 This is a schematic diagram of the structure of the water-cooling pipe of the present invention;

[0028] Figure 6 This is a schematic diagram of the bottom structure of the condenser plate of the present invention.

[0029] In the diagram: 1. Evaporation and crystallization chamber; 2. Support roller; 3. Conveyor filter belt; 4. Conveyor filter plate; 5. Drive motor; 6. Evaporation zone; 7. Electric heating base; 8. Extension plate; 9. Condensation plate; 10. Water-cooled pipe; 11. Chiller; 12. Liquid collection pipe; 13. Guide channel; 14. Guide pipe; 15. Liquid collection tank; 16. Return pump; 17. Return pipe; 18. Liquid inlet pipe; 19. Liquid inlet pump; 20. Pipeline solenoid valve; 21. Connecting pipe; 22. Liquid level sensor. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0031] Please see Figure 1 and 2 This invention provides a technical solution: an apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater, comprising an evaporation crystallization chamber 1, an electric heating base 7 fixedly installed at the bottom of the evaporation crystallization chamber 1, three sets of support rollers 2 movably installed inside the evaporation crystallization chamber 1, and a conveyor filter belt 3 movably fitted outside the support rollers 2, with several conveyor filter plates 4 fixedly connected to the outside of the conveyor filter belt 3, and a drive motor 5 fixedly installed on the front of the evaporation crystallization chamber 1 to provide power for the rotation of the conveyor filter belt 3. The drive motor 5 drives the support rollers 2 on the output shaft to rotate, thereby driving the conveyor filter belt 3 and the conveyor filter plates 4 to rotate. The sodium chloride crystallized in the evaporation zone 6 can be discharged along the inclined section through the conveyor filter plates 4. The evaporation crystallization chamber 1 has an evaporation zone 6 located below the conveyor filter belt 3, and the evaporation crystallization chamber 1 has an inclined section that cooperates with the conveyor filter belt 3. A condenser plate 9 is fixedly installed on the top of the evaporation crystallization chamber 1, and a collection pipe 12 is fixedly installed on one side of the bottom of the condenser plate 9. A collection tank 15 is fixedly installed on the back of the crystallization chamber 1, and a guide pipe 14 is fixedly connected to the top of the collection tank 15. The gas evaporated and crystallized rises and condenses upon encountering the bottom of the condenser plate 9, then flows along the bottom of the condenser plate 9 into the collection pipe 12, and enters the collection tank 15 through the guide pipe 14. The reflux pump 16 can reintroduce the condensed liquid into the evaporation and crystallization chamber 1 for evaporation and crystallization, thereby extracting sodium chloride from the denitrification mother liquor multiple times. The reflux pump 16 is fixedly installed on the top of the collection tank 15. Furthermore, the outlet end of the reflux pump 16 is fixedly connected to a reflux pipe 17, and the end of the reflux pipe 17 away from the reflux pump 16 is fixedly connected to an inlet pipe 18. The denitrification mother liquor is introduced into the evaporation zone 6 along the inlet pipe 18, and the conveying filter belt 3 and the conveying filter plate 4 are driven to rotate by the drive motor 5. At the same time, the evaporation zone 6 is heated by the electric heating base 7, so that the amount of sodium chloride discharged in the evaporation zone 6 is balanced with the amount of denitrification mother liquor entering and the amount of evaporation, which can realize the continuous crystallization extraction of sodium chloride in the denitrification mother liquor.

[0032] Please see Figure 3 , 56. The output shaft of the drive motor 5 is fixedly connected to any one of the support rollers 2. The three sets of support rollers 2 are distributed in a triangle inside the evaporation crystallization chamber 1. The length of the support rollers 2 is the same as the width of the conveyor filter belt 3 and the inside of the evaporation crystallization chamber 1. The width of the support rollers 2 and the conveyor filter belt 3 is limited to ensure that the support rollers 2 can drive the conveyor filter belt 3 to rotate stably. At the same time, it ensures that the conveyor filter plate 4 outside the conveyor filter belt 3 can completely discharge the sodium chloride crystallized in the evaporation zone 6 when rotating, thus ensuring the sodium chloride discharge effect. The drive motor 5 is model Y100L-2 and is equipped with a reducer.

[0033] The bottom end of the conveyor filter plate 4 at the bottom of the conveyor filter belt 3 abuts against the bottom of the inner side of the evaporation crystallization chamber 1, ensuring that when the conveyor filter belt 3 drives the conveyor filter plate 4 to rotate, the conveyor filter plate 4 can completely discharge the sodium chloride crystallized in the evaporation zone 6, avoiding the accumulation of the crystallized sodium chloride in the evaporation zone 6. An extension plate 8 is fixedly installed on the upper edge of the inclined section of the evaporation crystallization chamber 1. The sodium chloride discharged along the inclined section of the evaporation crystallization chamber 1 can be conducted and discharged along the extension plate 8, which facilitates the collection of the crystallized sodium chloride.

[0034] The area of ​​the top of the electric heating base 7 is the same as the area of ​​the evaporation zone 6. The electric heating base 7 can heat the evaporation zone 6, ensuring that the electric heating base 7 can completely heat the entire evaporation zone 6, thus ensuring the evaporation crystallization effect and speed. The electric heating base 7 is manufactured by Zhenjiang Runlu Electric Heating Appliance Co., Ltd.

[0035] The end of the condenser plate 9 near the liquid inlet pipe 18 is tilted downwards at an angle of 10-30°. This tilting of the condenser plate 9 facilitates the flow of liquid condensed at the bottom of the condenser plate 9 into the liquid collection pipe 12 for easy collection. Water-cooled pipes 10 are embedded in the condenser plate 9 in a serpentine pattern, which prolongs the residence time of the coolant in the water-cooled pipes 10 inside the condenser plate 9 and improves the cooling effect. A chiller 11 is installed on the back of the evaporation crystallization chamber 1, and the outlet and inlet of the chiller 11 are fixedly connected to both ends of the water-cooled pipes 10, respectively. The chiller 11 cools the coolant in the water-cooled pipes 10 and drives the coolant to circulate in the water-cooled pipes 10, thereby cooling the condenser plate 9. The chiller 11 is model HC360.

[0036] Please see Figure 2The liquid collecting pipe 12 is located at the bottom of the condenser plate 9, near the end of the liquid inlet pipe 18. Positioning the liquid collecting pipe 12 at the low end of the condenser plate 9 allows for the collection of condensed liquid. One end of the liquid collecting pipe 12 is fixedly connected to the guide pipe 14. The bottom of the condenser plate 9 has evenly distributed guide grooves 13. When liquid condenses at the bottom of the condenser plate 9, it is guided through the guide grooves 13 into the liquid collecting pipe 12, preventing the liquid from falling off midway. The width of the condenser plate 9 is the same as the width of the evaporation and crystallization chamber 1, and the length of the condenser plate 9 is... The length of the condenser plate 9 is not less than that of the evaporation zone 6. The length of the condenser plate 9 is 5-10 cm longer than that of the evaporation zone 6. The distance between the two ends of the condenser plate 9 and the ends of the evaporation zone 6 is 3-5 cm. This ensures that the gas evaporated in the evaporation zone 6 can be in complete contact with the condenser plate 9 to ensure the condensation effect. The bottom end of the liquid inlet pipe 18 is provided with several evenly distributed nozzles. The denitrification mother liquor is dispersed through the nozzles, so that the mother liquor can enter the evaporation zone 6 at multiple points and can be evenly distributed. The liquid inlet pipe 18 is fixedly installed with a liquid inlet pump 19 and a pipeline solenoid valve 20.

[0037] Please see Figure 4 An evaporation crystallization chamber 1 is fixedly connected to a connecting pipe 21 on its front side, and a liquid level sensor 22 is threadedly connected inside the connecting pipe 21. The liquid level sensor 22 can detect the liquid level inside the connecting pipe 21. By detecting the liquid level inside the connecting pipe 21 through the liquid level sensor 22, the liquid level in the evaporation zone 6 is detected, so as to prevent the liquid level from exceeding the height of the bottom of the conveyor filter belt 3, and to prevent sodium chloride crystallization from entering the conveyor filter belt 3 and affecting the rotation of the conveyor filter belt 3. The liquid level sensor 22 is manufactured by Tianchang Instrument and Cable Factory.

[0038] A method for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater includes the following operational steps:

[0039] S1. Connect one end of the inlet pipe 18 to the denitrification mother liquor storage equipment, start the inlet pump 19 and the pipeline solenoid valve 20, and introduce the denitrification mother liquor into the evaporation crystallization chamber 1 along the inlet pipe 18 and the nozzle at the bottom, so that the denitrification mother liquor falls into the evaporation zone 6. Since the connecting pipe 21 is connected to the evaporation crystallization chamber 1, the denitrification mother liquor can enter the connecting pipe 21. The liquid level inside the connecting pipe 21 is detected by the liquid level sensor 22, thereby realizing the detection of the liquid level in the evaporation zone 6 and preventing the liquid level from exceeding the bottom height of the conveying filter belt 3.

[0040] S2. Start the electric heating base 7 to heat the denitrification mother liquor in the evaporation zone 6, so that the denitrification mother liquor evaporates. When the sodium chloride concentration of the denitrification mother liquor in the evaporation zone 6 increases, crystallization begins. Start the drive motor 5 to drive the support roller 2 on the output shaft, as well as the conveying filter belt 3 and the conveying filter plate 4 to rotate. The crystallized sodium chloride is filtered through the conveying filter plate 4 and discharged along the inclined section on the evaporation crystallization chamber 1.

[0041] S3. Based on the crystallization rate, the rotation speed of the conveyor filter belt 3, the heating temperature of the electric heating base 7, and the flow rate of the denitrification mother liquor introduced into the inlet pipe 18 are controlled to make the evaporation rate of the denitrification mother liquor, the inlet flow rate of the denitrification mother liquor, and the outlet rate of sodium chloride in the evaporation zone 6 tend to be balanced, so that the concentration of the denitrification mother liquor in the evaporation zone 6 remains stable, ensuring that sodium chloride is always crystallized out, and realizing the uninterrupted crystallization extraction of sodium chloride.

[0042] S4. During evaporation and crystallization, the chiller 11 is started. The chiller 11 drives the coolant in the water-cooled pipe 10 to flow and circulate the coolant inside the water-cooled pipe 10. The gas rising during evaporation condenses at the bottom of the condenser plate 9 and is guided into the liquid collection pipe 12 along the guide groove 13 at the bottom of the condenser plate 9. It then enters the liquid collection tank 15 along the guide pipe 14. After the denitrification mother liquor has undergone one evaporation and crystallization, the reflux pump 16 is started to guide the condensed liquid into the evaporation and crystallization chamber 1 again along the reflux pipe 17 for another evaporation and crystallization.

[0043] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Moreover, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater, comprising an evaporation crystallization chamber (1), characterized in that: An electric heating base (7) is fixedly installed at the bottom of the evaporation crystallization chamber (1). Three sets of support rollers (2) are movably installed inside the evaporation crystallization chamber (1), and a conveyor filter belt (3) is movably fitted on the outside of the support rollers (2). Several conveyor filter plates (4) are fixedly connected to the outside of the conveyor filter belt (3). A drive motor (5) that can provide power for the rotation of the conveyor filter belt (3) is fixedly installed on the front of the evaporation crystallization chamber (1). An evaporation zone (6) located below the conveyor filter belt (3) is provided inside the evaporation crystallization chamber (1), and an evaporation zone (6) is provided inside the evaporation crystallization chamber (1) with... The inclined section of the conveyor filter belt (3) is fixedly installed on the top of the evaporation crystallization chamber (1), and a liquid collection pipe (12) is fixedly installed on one side of the bottom of the evaporation crystallization chamber (1). A liquid collection tank (15) is fixedly installed on the back of the evaporation crystallization chamber (1), and a guide pipe (14) is fixedly connected to the top of the liquid collection tank (15). A return pump (16) is fixedly installed on the top of the liquid collection tank (15), and a return pipe (17) is fixedly connected to the outlet end of the return pump (16). An inlet pipe (18) is fixedly connected to the end of the return pipe (17) away from the return pump (16). The condenser plate (9) is inclined downward at one end near the liquid inlet pipe (18) with an inclination angle of 10-30°. The condenser plate (9) is inlaid with water-cooling pipes (10) arranged in a serpentine pattern. A chiller (11) is provided on the back of the evaporation crystallization chamber (1), and the outlet and inlet of the chiller (11) are fixedly connected to both ends of the water-cooling pipe (10).

2. The apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater according to claim 1, characterized in that: The output shaft of the drive motor (5) is fixedly connected to any of the support rollers (2). The three sets of support rollers (2) are distributed in a triangle inside the evaporation crystallization chamber (1). The length of the support rollers (2) is the same as the width of the conveying filter belt (3) and the inside of the evaporation crystallization chamber (1).

3. The apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater according to claim 1, characterized in that: The bottom end of the bottom conveying filter plate (4) of the conveying filter belt (3) abuts against the bottom of the inner side of the evaporation crystallization chamber (1), and an extension plate (8) is fixedly installed on the upper edge of the inclined section of the evaporation crystallization chamber (1).

4. The apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater according to claim 1, characterized in that: The area of ​​the top of the electric heating base (7) is the same as the area of ​​the evaporation zone (6).

5. The apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater according to claim 1, characterized in that: The liquid collecting pipe (12) is located at the bottom of the condensing plate (9) near the end of the liquid inlet pipe (18). One end of the liquid collecting pipe (12) is fixedly connected to the guide pipe (14). The bottom of the condensing plate (9) is provided with evenly distributed guide grooves (13).

6. The apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater according to claim 5, characterized in that: The width of the condenser plate (9) is the same as the width of the evaporation crystallization chamber (1), and the length of the condenser plate (9) is not less than the length of the evaporation zone (6).

7. The apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater according to claim 1, characterized in that: The bottom end of the inlet pipe (18) is provided with several evenly distributed nozzles, and an inlet pump (19) and a pipeline solenoid valve (20) are fixedly installed on the inlet pipe (18).

8. The apparatus for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater according to claim 1, characterized in that: The front of the evaporation crystallization chamber (1) is fixedly connected to a connecting pipe (21), and the internal thread of the connecting pipe (21) is connected to a liquid level sensor (22) for detecting the liquid level inside the connecting pipe (21).

9. A method for extracting sodium chloride from sodium sulfate cryogenic crystallization mother liquor in coking wastewater using the apparatus according to any one of claims 1-8, characterized in that, The following steps are included: S1. Connect one end of the inlet pipe (18) to the denitrification mother liquor storage equipment, start the inlet pump (19) and the pipeline solenoid valve (20), and introduce the denitrification mother liquor into the evaporation crystallization chamber (1) along the inlet pipe (18) and the nozzle at the bottom, so that the denitrification mother liquor falls into the evaporation zone (6). Since the connecting pipe (21) is connected to the evaporation crystallization chamber (1), the denitrification mother liquor can enter the connecting pipe (21). The liquid level inside the connecting pipe (21) is detected by the liquid level sensor (22), thereby realizing the detection of the liquid level in the evaporation zone (6) and preventing the liquid level from exceeding the bottom height of the conveying filter belt (3). S2. Start the electric heating base (7) to heat the denitrification mother liquor in the evaporation zone (6) to evaporate the denitrification mother liquor. When the sodium chloride concentration in the denitrification mother liquor in the evaporation zone (6) increases, crystallization begins. Start the drive motor (5) to drive the support roller (2) on the output shaft and the conveying filter belt (3) and conveying filter plate (4) to rotate. Filter the crystallized sodium chloride through the conveying filter plate (4) and discharge the crystallized sodium chloride along the inclined section on the evaporation crystallization chamber (1). S3. Based on the crystallization rate, control the rotation speed of the conveying filter belt (3), the heating temperature of the electric heating base (7), and the flow rate of the denitrification mother liquor introduced into the inlet pipe (18) so that the evaporation rate of the denitrification mother liquor, the inlet flow rate of the denitrification mother liquor and the discharge rate of sodium chloride in the evaporation zone (6) tend to be balanced, so that the concentration of the denitrification mother liquor in the evaporation zone (6) remains stable, and sodium chloride is always crystallized out to achieve uninterrupted crystallization extraction of sodium chloride. S4. During evaporation and crystallization, start the chiller (11). The chiller (11) drives the coolant in the water-cooled pipe (10) to flow and circulate the coolant inside the water-cooled pipe (10). The gas rising during evaporation condenses at the bottom of the condenser plate (9) and is guided into the collection pipe (12) along the guide groove (13) at the bottom of the condenser plate (9). It then enters the collection tank (15) along the guide pipe (14). After the denitrification mother liquor has undergone one evaporation and crystallization, start the reflux pump (16) and guide the condensed liquid into the evaporation and crystallization chamber (1) again along the reflux pipe (17) for another evaporation and crystallization.

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