System and method for increasing the sodium sulfate crystallite size of coal chemical wastewater

Abstract

The application relates to the technical field of wastewater treatment, in particular to a system and method for increasing the sodium sulfate crystallization particle size of coal chemical wastewater. The system comprises an evaporator, a crystallizer connected to the downstream of the evaporator, a heat exchanger in closed loop communication with the crystallizer, a thickener, the upper part of which is in closed loop communication with the crystallizer, the thickener is internally provided with a stirrer, and a centrifugal dewatering machine connected to the bottom of the thickener. After the high-concentration brine is treated by the crystallizer, crystal slurry is obtained, when the concentration of the crystal slurry reaches a predetermined concentration, the crystal slurry is sent into the thickener, the stirrer in the thickener can prolong the residence time of the crystal slurry in the thickener, so as to increase the crystal particle size of the crystallization in the thickener. Compared with the wastewater treatment mode in the background art, in the same time, solid salt with larger particle size can be obtained, and a larger crystallizer and a circulating system are not needed, so that the feeding and equipment operation become more difficult.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and in particular to a system and method for increasing the crystal particle size of sodium sulfate in coal chemical wastewater. Background Technology

[0002] With the increasing emphasis on environmental protection, the requirements for wastewater treatment, the forms of waste disposal, and treatment standards are becoming increasingly stringent. The coal chemical, petrochemical, and pharmaceutical industries all generate wastewater during operation, and each industry has significantly different wastewater treatment methods due to variations in water quality. Coal chemical plants generate large amounts of wastewater during operation, characterized by high salinity, high COD (chemical oxygen demand), and the presence of pollutants such as ammonia nitrogen, nitrates, and silicates. The diverse range of pollutants makes treatment particularly challenging.

[0003] Wastewater enters the evaporator, and the high-concentration brine discharged after evaporation is sent to the crystallizer for further treatment. The crystallizer is heated by external steam, specifically by an external shell-and-tube forced circulation heat exchanger. The high-concentration brine enters the crystallizer via a feed pump, mixes with the crystal slurry inside the crystallizer to form a mixture, and then enters the shell-and-tube forced circulation heat exchanger for further heating. After heating, the temperature of the mixture increases, forming a crystal slurry that enters the crystallizer. Inside the crystallizer, the crystal slurry undergoes flash evaporation and continuously generates crystals. The mixture then enters a thickener to increase the salt concentration. The concentrated brine is then separated from the filtrate by a centrifugal dewatering machine to obtain solid salt. The filtrate is returned to the crystallizer, while the solid salt is collected for further processing.

[0004] Under this wastewater treatment method, the resulting solid salt particles are relatively small. Analysis revealed that extending the residence time of crystals in the crystallizer can increase the crystal growth time, resulting in crystals with a larger average particle size. However, a longer residence time means requiring a larger crystallizer and circulation system, which makes feeding and equipment operation more difficult. Summary of the Invention

[0005] This application provides a system and method for increasing the crystal size of sodium sulfate in coal chemical wastewater, in order to solve the problem in the prior art that the solid salt particle size is small and it is difficult to increase the solid salt particle size by expanding the crystallizer and circulation system.

[0006] On one hand, this application provides a system for increasing the crystal particle size of sodium sulfate in coal chemical wastewater, comprising: an evaporator configured to treat wastewater to obtain high-concentration brine; a crystallizer connected downstream of the evaporator to treat the high-concentration brine to obtain crystal slurry; a heat exchanger connected in a closed loop with the crystallizer to circulate and heat the crystal slurry; a thickener connected in a closed loop with the crystallizer at its upper part to treat the crystal slurry to obtain an upper concentrate located at the upper part and a lower concentrate located at the lower part, and to circulate a portion of the upper concentrate into the crystallizer, wherein a stirrer is provided inside the thickener to stir the crystal slurry inside the thickener; and a centrifugal dewatering machine connected to the bottom of the thickener to treat the lower concentrate to obtain solid salt.

[0007] Preferably, the bottom of the thickener is formed into a conical structure, and the lowest point of the agitator is higher than the highest point of the conical structure.

[0008] Preferably, the thickener is provided with a discharge port at the top so that a portion of the concentrated liquid at the top can be discharged from the thickener.

[0009] Preferably, the system for increasing the crystallization particle size of sodium sulfate in coal chemical wastewater also includes a concentration detector, which is installed between the crystallizer and the thickener, so as to control the opening and closing of the thickener by means of the concentration of the crystal slurry output from the crystallizer detected by the concentration detector.

[0010] Preferably, the system for increasing the crystallization particle size of sodium sulfate in coal chemical wastewater also includes a raw material tank connected between the evaporator and the crystallizer, and the raw material tank is equipped with a mixing agitator inside.

[0011] On the other hand, this application also provides a method for increasing the particle size of sodium sulfate crystals in coal chemical wastewater, comprising the following steps: S1. Use an evaporator to treat wastewater to obtain high-concentration brine; S2. Place the high-concentration brine into a crystallizer for crystallization to obtain a crystal slurry; S3. After heating the crystal slurry in a heat exchanger, it is then placed into a crystallizer to form a cycle. S4. Place the crystal slurry into the thickener and stir the crystal slurry with a stirrer. Set the speed of the stirrer to 5r / min~10r / min to obtain the upper concentrate located at the top of the thickener and the lower concentrate located at the bottom of the thickener. S5. Place a portion of the upper concentrate into a crystallizer and mix it with the high-concentration brine and crystal slurry in the crystallizer. Crystallize together in the crystallizer. Discharge the other portion of the upper concentrate from the thickener and place the lower concentrate into a centrifugal dehydrator to obtain solid salt.

[0012] Preferably, between step S3 and step S4, a step is further included: detecting the concentration of the slurry discharged from the crystallizer until the concentration reaches a predetermined concentration range.

[0013] Preferably, in step S5, the flow rate of the concentrated liquid placed in the upper part of the crystallizer is 0.5 m³. 3 / h~1m 3 / h, the flow rate of the concentrated liquid discharged from the upper part of the thickener is 2m³ / h. 3 / h~3m 3 / h.

[0014] Preferably, between step S1 and step S2, the process further includes the step of placing the high-concentration brine into the raw material tank and stirring the high-concentration brine in the raw material tank. In step S2, the high-concentration brine is introduced from the raw material tank into the crystallizer at a predetermined flow rate.

[0015] Preferably, the method for increasing the particle size of sodium sulfate crystals in coal chemical wastewater is implemented using the above-described system for increasing the particle size of sodium sulfate crystals in coal chemical wastewater.

[0016] The beneficial effects of this application are as follows: After being processed in a crystallizer, high-concentration brine yields a crystal slurry. Once the slurry reaches a predetermined concentration, it is fed into a thickener. A stirrer within the thickener prolongs the residence time of the slurry, thereby increasing the crystal particle size. Larger crystals settle to the bottom of the thickener, forming part of the lower concentrate. This lower concentrate is then dehydrated in a centrifugal dehydrator to obtain solid salt. The upper concentrate, located at the top of the thickener, contains floating salt (smaller crystals). A portion of this upper concentrate is returned to the crystallizer. Firstly, the concentration of the upper concentrate is greater than that of the mixture of high-concentration brine and crystal slurry in the crystallizer. Therefore, the reflux of the upper concentrate increases the concentration of the mixture in the crystallizer, enhancing its supersaturation and accelerating crystallization. Secondly, the floating salt in the upper concentrate promotes crystal agglomeration within the crystallizer, thus promoting crystal nucleus growth. In summary, compared with the wastewater treatment methods in the background technology, it is possible to obtain solid salt with larger particle size in the same amount of time, without the need for larger crystallizers and circulation systems, thus avoiding making feeding and equipment operation more difficult.

[0017] The method for increasing the crystal size of sodium sulfate in coal chemical wastewater provided in this application includes all the above-mentioned advantages of the system for increasing the crystal size of sodium sulfate in coal chemical wastewater in this application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the system for determining the sodium sulfate crystallization particle size in coal chemical wastewater, provided in an embodiment of this application; Figure label: 10. Evaporator; 11. First circulation pump; 20. Crystallizer; 21. Second circulation pump; 30. Heat exchanger; 40. Thickener; 41. Stirrer; 42. Discharge port; 43. Inlet valve; 44. Return valve; 50. Centrifugal dehydrator; 60. Concentration detector; 70. Raw material tank; 71. Mixing stirrer; 72. Power pump. Detailed Implementation

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

[0021] The following is combined Figure 1 This application describes a system for increasing the crystallization particle size of sodium sulfate in coal chemical wastewater, comprising: an evaporator 10 configured to treat wastewater to obtain high-concentration brine; a crystallizer 20 connected downstream of the evaporator 10 to treat the high-concentration brine to obtain crystal slurry; a heat exchanger 30 connected in a closed loop with the crystallizer 20 to circulate and heat the crystal slurry; a thickener 40 connected in a closed loop with the crystallizer 20 at its upper part to treat the crystal slurry to obtain an upper concentrate at the upper part and a lower concentrate at the lower part, and to circulate a portion of the upper concentrate back into the crystallizer 20; a stirrer 41 is provided inside the thickener 40 to stir the crystal slurry inside the thickener 40; and a centrifugal dewatering machine 50 connected to the bottom of the thickener 40 to treat the lower concentrate to obtain solid salt.

[0022] After evaporating the wastewater, the evaporator 10 produces a high-concentration brine. The high-concentration brine enters the crystallizer 20 for crystallization and is heated by an external heat exchanger 30, forming a crystal slurry within the crystallizer 20. The crystal slurry enters the thickener 40 for thickening. An agitator 41 is added to the thickener 40 to stir the crystal slurry. This process extends the residence time of the crystal slurry in the thickener 40, thereby increasing the crystal particle size. It also promotes the discharge of impurity gases from the crystal slurry, enabling the production of high-quality solid salt. Furthermore, it prevents blockage in the thickener 40, ensuring the normal operation of the thickener 40 and its downstream centrifugal dewatering machine 50. Large-diameter crystals in thickener 40 settle to the lower part of thickener 40, forming part of the lower concentrate. The lower concentrate enters centrifugal dehydrator 50 to obtain solid salt. Small-diameter floating salts are located in the upper part of thickener 40, forming part of the upper concentrate. Part of the upper concentrate is refluxed into crystallizer 20 and mixed with the high-concentration brine and crystal slurry in crystallizer 20. On the one hand, the concentration of the upper concentrate is greater than the concentration of the mixture of high-concentration brine and crystal slurry in crystallizer 20. Therefore, the reflux of the upper concentrate can increase the concentration of the mixture in crystallizer 20 and increase the supersaturation of the mixture, thereby accelerating the crystallization rate. On the other hand, the floating salts in the upper concentrate can promote the agglomeration of crystals in crystallizer 20, thereby promoting the growth of crystal nuclei in crystallizer 20. The crystals in both the thickener 40 and the crystallizer 20 have increased particle size, and the crystallization rate of the crystals in the crystallizer 20 is accelerated. Compared with the wastewater treatment methods in the prior art, larger solid salt particles can be obtained in the same amount of time, and a larger crystallizer 20 and circulation system are not required, thus avoiding making feeding and equipment operation more difficult.

[0023] In addition, the reflux of the upper concentrate allows the uncrystallized crystals in the upper concentrate to crystallize smoothly, avoiding the waste caused by the complete discharge of the upper concentrate from the thickener 40, thereby increasing the amount of solid salt finally formed.

[0024] Specifically, the evaporator 10 is also connected to a circulation pipeline, on which a first circulation pump 11 is installed. This circulation pump repeatedly circulates the high-concentration brine into the evaporator 10, where it is repeatedly evaporated to increase its concentration. Once the required number of cycles or the concentration of the high-concentration brine discharged from the evaporator 10 is reached, the brine is discharged from the evaporator 10, ending the evaporation cycle. The concentration of the high-concentration brine can be achieved by installing a concentration detector 60 on the circulation pipeline of the evaporator 10. The concentration detector 60 detects the TSS (Total Suspended Solids) of the high-concentration brine. The heat exchanger 30 can be a forced shell-and-tube heat exchanger 30 or other types of forced heat exchangers 30.

[0025] Please refer to Figure 1In some embodiments provided in this application, the bottom of the thickener 40 is formed into a conical structure, and the lowest point of the stirrer 41 is higher than the highest point of the conical structure.

[0026] Large-diameter crystals settle in the lower part of the thickener 40. Due to the conical structure at the bottom of the thickener 40, the large-diameter crystals accumulate along the inclined inner wall of the conical structure. In order to prevent the stirrer 41 from stirring the large-diameter crystals to the upper part of the thickener 40, the lowest point of the stirrer 41 is set higher than the highest point of the conical structure, so that the stirrer 41 only stirs the upper concentrate, thereby increasing the residence time of the upper concentrate in the thickener 40.

[0027] Specifically, the speed of the stirrer 41 is set to be adjustable within the range of 0 r / min to 60 r / min. The specific speed is necessary to extend the residence time of the crystal slurry in the thickener 40, while also avoiding excessive speed that could damage the crystals.

[0028] Please continue reading. Figure 1 In some embodiments provided in this application, the thickener 40 is provided with a discharge port 42 at its upper part so that a portion of the upper concentrate can be discharged from the thickener 40.

[0029] The upper concentrate in the thickener 40 contains insoluble gases and other impurities such as silica. If the insoluble gases and other impurities are returned to the crystallizer 20, it will affect the normal operation of the crystallizer 20. Therefore, it is necessary to discharge part of the upper concentrate along with the insoluble gases and other impurities mixed in it from the thickener 40 so that it will no longer flow back to the crystallizer 20, thus ensuring the normal operation of the crystallizer 20.

[0030] Specifically, a return valve 44 is installed on the connecting pipe from the thickener 40 to the crystallizer 20. The opening of the return valve 44 is adjusted according to the amount of upper concentrate that needs to be returned. The amount of upper concentrate discharged from the thickener 40 and the amount of upper concentrate returned to the crystallizer 20 are determined according to the actual situation and requirements.

[0031] Please continue reading. Figure 1 In some embodiments provided in this application, the system for increasing the crystallization particle size of sodium sulfate in coal chemical wastewater also includes a concentration detector 60, which is disposed between the crystallizer 20 and the thickener 40, so as to control the opening and closing of the thickener 40 by means of the concentration of the crystal slurry output from the crystallizer 20 detected by the concentration detector 60.

[0032] During the crystallization process, the concentration of the crystal slurry inside the crystallizer 20 gradually increases. The crystallizer 20 and the heat exchanger 30 circulate the crystal slurry. When the concentration of the crystal slurry reaches a sufficient level, the thickener 40 is turned on to introduce the crystal slurry into the thickener 40, thereby reducing the energy consumption of the thickener 40 and making full use of the crystallization function of the crystallizer 20.

[0033] Specifically, a second circulation pump 21 is installed on the pipeline connecting the outlet of the crystallizer 20 to pump the crystal slurry to the heat exchanger 30 and the thickener 40. An inlet valve 43 is installed on the connecting pipeline from the crystallizer 20 to the thickener 40. When the concentration of the crystal slurry detected by the concentration detector 60 reaches the required level, the inlet valve 43 is opened and the crystal slurry enters the thickener 40.

[0034] Please continue reading. Figure 1 In some embodiments provided in this application, the system for increasing the crystallization particle size of sodium sulfate in coal chemical wastewater also includes a raw material tank 70 connected between the evaporator 10 and the crystallizer 20, and a mixing agitator 71 is provided inside the raw material tank 70.

[0035] If a continuous flow of highly concentrated brine enters the crystallizer 20, the residence time of the brine within the crystallizer 20 will be short, resulting in poor crystallization and waste of the brine. Therefore, a raw material tank 70 is installed between the crystallizer 20 and the evaporator 10 to control the amount of highly concentrated brine entering the crystallizer 20. The highly concentrated brine entering the raw material tank 70 needs to be stirred to ensure uniform mixing of the substances inside, which is beneficial for subsequent processing in the crystallizer 20.

[0036] Specifically, a power pump 72 is installed on the connecting pipeline between the raw material tank 70 and the crystallizer 20. The power pump 72 controls the timing and amount of high-concentration brine entering the crystallizer 20. The raw material tank 70, the crystallizer 20, and the heat exchanger 30 are combined to form a crystallization system.

[0037] This application embodiment also provides a method for increasing the crystal particle size of sodium sulfate in coal chemical wastewater, including the following steps: S1. Use evaporator 10 to treat wastewater to obtain high-concentration brine; S2. Place the high-concentration brine into crystallizer 20 for crystallization to obtain crystal slurry; S3. After heating the crystal slurry in the heat exchanger 30, it is then placed in the crystallizer 20 to form a cycle. S4. Place the crystal slurry into the thickener 40 and stir the crystal slurry with the stirrer 41. Set the speed of the stirrer 41 to 5 r / min to 10 r / min to obtain the upper concentrate located at the top of the thickener 40 and the lower concentrate located at the bottom of the thickener 40. S5. A portion of the upper concentrate is placed into crystallizer 20 and mixed with the high-concentration brine and crystal slurry in crystallizer 20. The mixture crystallizes together in crystallizer 20. The other portion of the upper concentrate is discharged from thickener 40. The lower concentrate is placed into centrifugal dehydrator 50 to obtain solid salt.

[0038] In step S4, the stirring of the crystal slurry by the stirrer 41 at a speed of 5 r / min to 10 r / min extends the residence time of the crystal slurry in the thickener 40, thereby increasing the crystal particle size within the thickener 40. Stirring also promotes the removal of impurity gases from the crystal slurry, resulting in the production of high-quality solid salt. Furthermore, stirring prevents blockage within the thickener 40, ensuring the normal operation of the thickener 40 and its downstream centrifugal dehydrator 50. A portion of the upper concentrate is refluxed back into the crystallizer 20, mixing with the high-concentration brine and crystal slurry within the crystallizer 20. On one hand, the concentration of the upper concentrate is greater than the concentration of the mixture of high-concentration brine and crystal slurry within the crystallizer 20. Therefore, the reflux of the upper concentrate increases the concentration of the mixture within the crystallizer 20, enhancing its supersaturation and accelerating the crystallization rate. On the other hand, the presence of floating salt, i.e., small-diameter crystals, in the upper concentrate promotes crystal agglomeration within the crystallizer 20, thereby promoting the growth of crystal nuclei within the crystallizer 20. The crystals in both the thickener 40 and the crystallizer 20 have increased particle size, and the crystallization rate of the crystals in the crystallizer 20 is accelerated. Compared with the wastewater treatment methods in the prior art, larger solid salt particles can be obtained in the same amount of time, and a larger crystallizer 20 and circulation system are not required, thus avoiding making feeding and equipment operation more difficult.

[0039] In addition, the reflux of the upper concentrate allows the uncrystallized crystals in the upper concentrate to crystallize smoothly, avoiding the waste caused by the complete discharge of the upper concentrate from the thickener 40, thereby increasing the amount of solid salt finally formed.

[0040] Specifically, the volume of crystallizer 20 is 62.922 m³. 3 The temperature (T) is set to 150℃. In step S1, the evaporator 10 circulates the wastewater until the required number of cycles or the concentration of the high-concentration brine discharged from the evaporator 10 is reached. Then, step S2 is performed. The circulation of the evaporator 10 is achieved by setting up a circulation pipeline connecting the inlet and outlet of the evaporator 10 and installing a first circulation pump 11 on the circulation pipeline. In step S2, the temperature (T) of the crystal slurry in the crystallizer 20 is 106.7℃~108.9℃, and the total dissolved solids (TDS) is 20wt%~32wt%. In step S3, the circulation between the crystallizer 20 and the heat exchanger 30 is achieved by adding a second circulation pump 21 to the connecting pipeline between the two. The flow rate (Q) of the second circulation pump 21 is set to 4764 m³ / h. 3 The flow rate (Q) and head (H) are set to 9.33 m. In step S5, the flow rate (Q) of the concentrated liquid refluxed from the thickener 40 to the upper part of the crystallizer 20 is 0.5 m³ / h. 3 / h~1m 3 / h, T (temperature) is 105.5℃~106.5℃, TDS (total dissolved solids) is 25wt%~35wt%, and TSS (total suspended solids) is 5wt%~10wt%.

[0041] In some embodiments provided in this application, a step is further included between step S3 and step S4: detecting the concentration of the crystal slurry discharged from the crystallizer 20 until the concentration reaches a predetermined concentration range.

[0042] This step is a condition for proceeding to step S4. That is, when the concentration of the crystal slurry in the crystallizer 20 reaches a sufficient concentration, the thickener 40 is turned on to proceed to step S4, thereby reducing the energy consumption of the thickener 40 and making full use of the crystallization function of the crystallizer 20.

[0043] Specifically, in this step, the concentration is TSS (Total Suspended Solids). When this value reaches 20 wt% or higher, the conditions for crystallization and salt precipitation are met, that is, the concentration requirement is satisfied, and the thickener 40 can be started. In this step, an inlet valve 43 is installed on the pipeline from the crystallizer 20 to the thickener 40. When the concentration of the crystal slurry output by the thickener 40 meets the concentration requirement, the inlet valve 43 is opened.

[0044] In some embodiments provided in this application, in step S5, the flow rate of the upper concentrate placed in the crystallizer 20 is 0.5 m³ / s. 3 / h~1m 3 The flow rate of the concentrated liquid discharged from the upper part of the thickener 40 is 2m³ / h. 3 / h~3m 3 / h.

[0045] The upper concentrate in the thickener 40 contains insoluble gases and other impurities such as silica. If the insoluble gases and other impurities are returned to the crystallizer 20, it will affect the normal operation of the crystallizer 20. Therefore, it is necessary to discharge part of the upper concentrate along with the insoluble gases and other impurities mixed in it from the thickener 40 so that it will not flow back to the crystallizer 20, thus ensuring the normal operation of the crystallizer 20. In this step, the flow rate of the upper concentrate discharged from the thickener 40 is set to a flow rate that can avoid affecting the normal operation of the crystallizer 20, and the flow rate of the upper concentrate placed into the crystallizer 20 is set to a flow rate that can promote the growth rate and particle size of crystal nuclei in the crystallizer 20.

[0046] Specifically, the flow rate of the concentrated liquid in the upper part of the thickener 40 and crystallizer 20 is controlled by installing a return valve 44 on the connecting pipeline in the flow direction from the thickener 40 to the crystallizer 20. The opening of the return valve 44 is adjusted according to the required return flow rate of the upper concentrated liquid. The thickener 40 discharges 2m... 3 / h~3m 3The method of obtaining the upper concentrate at / h is achieved by opening a discharge port 42 on the thickener 40.

[0047] In some embodiments provided in this application, the step between step S1 and step S2 is further: placing the high-concentration brine into the raw material tank 70 and stirring the high-concentration brine in the raw material tank 70. In step S2, the high-concentration brine is introduced from the raw material tank 70 into the crystallizer 20 at a predetermined flow rate.

[0048] If step S2 is performed directly after step S1, a continuous flow of highly concentrated brine will enter the crystallizer 20. This will result in a short residence time of the highly concentrated brine in the crystallizer 20, leading to poor crystallization and waste of the highly concentrated brine. Therefore, a step of placing the highly concentrated brine into the raw material tank 70 is added between steps S1 and S2 to control the amount of highly concentrated brine entering the crystallizer 20. Stirring the highly concentrated brine in the raw material tank 70 ensures that the substances inside are mixed evenly, which is beneficial for the progress of step S2.

[0049] Specifically, the high-concentration brine in the raw material tank 70 enters the crystallizer 20 by means of a power pump 72 installed in the connecting pipeline between the two, and the power pump 72 controls the timing and amount of the high-concentration brine entering the crystallizer 20. The high-concentration brine is stirred in the raw material tank 70 by means of a mixing agitator 71 installed in the raw material tank 70.

[0050] In some embodiments provided in this application, the method for increasing the particle size of sodium sulfate crystals in coal chemical wastewater is implemented using the above-described system for increasing the particle size of sodium sulfate crystals in coal chemical wastewater.

[0051] It should be noted that the method of increasing the particle size of sodium sulfate crystals in coal chemical wastewater uses a system that increases the particle size of sodium sulfate crystals in coal chemical wastewater, which includes all the advantages of the system mentioned above, and will not be repeated here.

[0052] Example Wastewater treatment using the above systems or methods: The high-concentration brine obtained from evaporator 10 has a flow rate of Q = 11 m³ / s. 3A high-concentration brine solution with the following parameters was prepared: pH 10.5, TDS (Total Dissolved Solids) 19 wt%, suspended solids 0.07 wt%, sulfate 80000 mg / L, chloride 27000 mg / L, nitrate 7200 mg / L, and temperature T 102.7℃. The solution was placed in a raw material tank 70 and pumped to a crystallizer 20 by a power pump 72. The solution was evaporated through a heat exchanger 30 to obtain a crystal slurry with a pH 10.6 and TDS... With a total dissolved solids (TDS) of 27 wt%, suspended solids (SLS) of 21 wt%, COD (chemical oxygen demand) of 18000 mg / L, and T (temperature) of 107.2℃, once the slurry concentration reaches 20 wt%~25 wt%, open the inlet valve 43 and start the thickener 40. Control the speed of the stirrer 41 inside the thickener 40 at 6 r / min to ensure normal operation of the thickener 40. Control the opening of the return valve 44 to ensure that the flow rate of the upper concentrate returning to the crystallizer 20 is 0.5 m³ / min. 3 / h, producing stable sodium sulfate solid salt, the solid salt particle size is larger than that obtained by wastewater treatment methods in the background technology: 10% less than 20μm, 25% 20μm~40μm, 40% 40μm~100μm and 25% less than 100μm.

[0053] In the description of this application, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0054] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0055] In this application, the term "some embodiments," etc., refers to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0056] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A system for increasing the crystal particle size of sodium sulfate in coal chemical wastewater, characterized in that, include: The evaporator is designed to process wastewater to produce highly concentrated brine. A crystallizer, connected downstream of the evaporator, is capable of processing the high-concentration brine to obtain a crystal slurry; A heat exchanger is connected in a closed loop to the crystallizer to circulate and heat the crystal slurry. A thickener is connected in a closed loop with the crystallizer at its upper part to process the crystal slurry to obtain an upper concentrate located at the top and a lower concentrate located at the bottom, and to circulate a portion of the upper concentrate back into the crystallizer. The thickener is equipped with a stirrer to stir the crystal slurry inside the thickener. as well as A centrifugal dehydrator, connected to the bottom of the thickener, is used to process the lower concentrate to obtain solid salt.

2. The system for increasing the particle size of sodium sulfate crystals in coal chemical wastewater according to claim 1, characterized in that, The bottom of the thickener is formed into a conical structure, and the lowest point of the stirrer is higher than the highest point of the conical structure.

3. The system for increasing the particle size of sodium sulfate crystals in coal chemical wastewater according to claim 1, characterized in that, The thickener is provided with a discharge port at the top so that a portion of the upper concentrate can be discharged from the thickener.

4. The system for increasing the particle size of sodium sulfate crystals in coal chemical wastewater according to claim 1, characterized in that, The system for increasing the crystallization particle size of sodium sulfate in coal chemical wastewater also includes a concentration detector, which is installed between the crystallizer and the thickener, to control the opening and closing of the thickener by means of the concentration of the crystal slurry output from the crystallizer detected by the concentration detector.

5. The system for increasing the particle size of sodium sulfate crystals in coal chemical wastewater according to claim 1, characterized in that, The system for increasing the crystallization particle size of sodium sulfate in coal chemical wastewater also includes a raw material tank connected between the evaporator and the crystallizer, and the raw material tank is equipped with a mixing agitator inside.

6. A method for increasing the particle size of sodium sulfate crystals in coal chemical wastewater, characterized in that, Includes the following steps: S1. Use an evaporator to treat wastewater to obtain high-concentration brine; S2. Place the high-concentration brine into a crystallizer for crystallization to obtain a crystal slurry; S3. The slurry is heated in a heat exchanger and then placed into the crystallizer to form a cycle; S4. Place the crystal slurry into a thickener and stir the crystal slurry using a stirrer. Set the speed of the stirrer to 5 r / min to 10 r / min to obtain an upper concentrate located at the top of the thickener and a lower concentrate located at the bottom of the thickener. S5. A portion of the upper concentrate is placed into the crystallizer and mixed with the high-concentration brine and crystal slurry in the crystallizer to crystallize together in the crystallizer. The other portion of the upper concentrate is discharged from the thickener, and the lower concentrate is placed into a centrifugal dehydrator to obtain solid salt.

7. The method for increasing the particle size of sodium sulfate crystals in coal chemical wastewater according to claim 6, characterized in that, Between step S3 and step S4, there is an additional step: detecting the concentration of the slurry discharged from the crystallizer until the concentration reaches a predetermined concentration range.

8. The method for increasing the particle size of sodium sulfate crystals in coal chemical wastewater according to claim 6, characterized in that, In step S5, the flow rate of the upper concentrated liquid placed in the crystallizer is 0.5 m³ / s. 3 / h~1m 3 The flow rate of the concentrated liquid discharged from the upper part of the thickener is 2m³ / h. 3 / h~3m 3 / h.

9. The method for increasing the particle size of sodium sulfate crystals in coal chemical wastewater according to claim 6, characterized in that, Between steps S1 and S2, there is an additional step: placing the high-concentration brine into a raw material tank and stirring the high-concentration brine in the raw material tank; in step S2, introducing the high-concentration brine from the raw material tank into the crystallizer at a predetermined flow rate.

10. The method for increasing the particle size of sodium sulfate crystals in coal chemical wastewater according to claim 6, characterized in that, This is achieved using the system for increasing the particle size of sodium sulfate crystals in coal chemical wastewater according to any one of claims 1 to 5.

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