Hot-process evaporative crystallization treatment system and method for high-salinity wastewater of evaporation pond in coal chemical industry

Abstract

The invention relates to the technical field of wastewater treatment, in particular to a hot-process evaporative crystallization treatment system and method for high-salinity wastewater of a coal chemical industry evaporation pond, and the hot-process evaporative crystallization treatment system comprises a pre-precipitation module, an MVR evaporation module, a sedimentation module and a drying module; wastewater is preheated by a non-condensable gas preheater and a distilled water preheater, the preheated wastewater enters a crystallization separator and a forced circulation heater and is evaporated in the crystallization separator to form carnallite mother liquor, the carnallite mother liquor enters a settling tank for settling separation to generate thick slurry, and the thick slurry firstly enters a filter press for water removal and then enters the forced circulation heater for water removal. And drying in a drying machine to form solid carnallite. When the device is used, the treatment processes are effectively communicated and mutually coordinated, the concentration reduction capacity is improved, the impact load is dealt with, the drying reduction is realized, the energy consumption is reduced, the foaming influence of organic matters is reduced, the content of the organic matters in distilled water is reduced, the scaling influence of substances such as calcium and magnesium is reduced, and the long-term stable operation of the system is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a thermal evaporation and crystallization treatment system and method for high-salt wastewater from coal chemical evaporation ponds. Background Technology

[0002] High-salinity wastewater from the coal chemical industry, after membrane treatment, is the most critical and difficult-to-treat end-of-pipe wastewater in the process of achieving "near-zero discharge." Its significant characteristics include high salinity, high hardness, and high levels of pollutants. Total dissolved solids (TDS) typically reach 30,000-100,000 mg / L or even higher, with Cl- being the main ionic component. - SO4 2- Na + K + The high salinity renders membrane treatment unsuitable, necessitating forced separation methods such as thermal evaporation. After membrane concentration, the wastewater contains calcium... 2+ and Mg 2+ The wastewater contains recalcitrant organic compounds such as phenols and heterocyclic compounds, leaving behind a concentrated solution containing almost all impurities, making it difficult to treat. Existing technologies for treating coal chemical wastewater typically employ a concentration-reduction + centrifugal separation process. Concentration-reduction includes multi-effect evaporation (MED), mechanical vapor recompression (MVR), and a combination of MED and MVR processes. Centrifugal separation involves forced circulation crystallization followed by solid-liquid separation to obtain solid impurities.

[0003] However, during the implementation of the process, the treatment processes are relatively independent and lack synchronization and coordination, which may lead to unstable operation after changes in water quality. On the one hand, as temperature and concentration further increase, Ca... 2+ and Mg 2+ Calcium sulfate (CaSO4) scale, calcium carbonate (CaCO3) scale, and silica scale (SiO2) are easily formed on the surface of heat exchange tubes. Organic matter can also form viscous scale, which greatly reduces heat exchange efficiency. Moreover, scale can clog heat exchange tubes, requiring frequent maintenance and descaling, thus reducing production efficiency. On the other hand, organic matter can easily cause serious foam entrainment problems during evaporation, leading to a decrease in evaporation efficiency and even problems such as uncontrolled foam and foam leakage from the evaporation equipment. In addition, centrifugal separation becomes difficult, and a large amount of crystalline salt remaining in the evaporation system can clog the pipes. Summary of the Invention

[0004] The purpose of this invention is to provide a thermal evaporation and crystallization treatment system and method for high-salt wastewater from coal chemical evaporation ponds, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A thermal evaporation crystallization treatment system for high-salt wastewater from a coal chemical evaporation pond includes a pre-precipitation module. The pre-precipitation module is sequentially connected to a feed balance tank, a non-condensable gas preheater, and a distilled water preheater. The non-condensable gas preheater and the distilled water preheater preheat the wastewater twice, making full use of thermal energy and reducing thermal energy waste. The distilled water preheater is connected to a crystallization separator. The crystallization separator is connected to a forced circulation heater via a forced circulation pump. The forced circulation heater heats the wastewater, and the crystallization separator evaporates the wastewater to increase its concentration. The water vapor generated by evaporation is then recycled by a steam compressor, saving water resources. The forced circulation heater has a gas inlet and a distilled water outlet connected to a steam compressor and a distilled water tank, respectively. The steam compressor and the non-condensable gas preheater are connected to the gas outlet of the forced circulation heater, respectively. The gas outlet of the crystallizer is connected to the gas inlet of the forced circulation heater. The distilled water inlet of the distilled water preheater is connected to the distilled water tank. The distilled water can be stored for backup or used in other equipment, reducing the waste of distilled water. The crystallization separator is sequentially connected to a flocculation reaction tank, a clarification tank, and a settling tank. The settling tank is connected to the crystallization separator through a mother liquor circulation module, and the clarification tank is connected to the mother liquor circulation module. The settling tank separates wastewater and sediment, and the mother liquor circulation module can fully settle the mother liquor without additional treatment steps, thus simplifying the mother liquor treatment process. The settling tank is connected to a buffer tank, which is connected to a dryer via a filter press. The buffer tank is connected to a pre-sedimentation module to collect sediment, which can delay the scaling cycle in the forced circulation heater and improve wastewater treatment efficiency.

[0006] Furthermore, the pre-precipitation module includes a dosing reaction tank, an equalization tank, an inclined tube sedimentation tank, and a pre-concentrator connected in sequence. This allows for the early separation of some precipitates, eliminating the basis for the formation of calcium carbonate and magnesium hydroxide scale, extending the scaling cycle of the forced circulation heater, and eliminating the need for frequent shutdowns to clean the forced circulation heater. The precipitate outlet of the inclined tube sedimentation tank is connected to a buffer tank, allowing for subsequent drying of the precipitate.

[0007] Furthermore, a feed pump is installed between the feed balance tank and the wastewater inlet of the non-condensable gas preheater, a vacuum pump is connected to the gas outlet of the non-condensable gas preheater, a discharge pump is installed between the crystallizer and the flocculation reaction tank, a thickening pump is installed between the settling tank and the buffer tank, the thickening pump is linked to the liquid level of the buffer tank, and a drying feed pump is installed between the buffer tank and the filter press.

[0008] Furthermore, a distilled water pump is installed between the distilled water tank and the distilled water preheater. The distilled water tank is equipped with a distilled water level gauge. The distilled water pump is equipped with a frequency converter that is electrically connected to the distilled water level gauge, which automatically maintains the set liquid level value. It can reserve water for the steam generator and discharge excess distilled water for use.

[0009] Furthermore, the distilled water tank is connected to a steam generator via a purifier. The steam generator is connected to a steam compressor. The purifier purifies the distilled water, which can ensure stable operation of the steam generator, prevent scale buildup in the steam generator, and extend its service life.

[0010] Furthermore, a secondary separator is installed between the crystallizer and the forced circulation heater, and a negative pressure pump is installed between the secondary separator and the crystallizer. The secondary separator purifies the water vapor, which can ensure the stable operation of the steam compressor and reduce the failure rate.

[0011] Furthermore, the crystallizer is equipped with a slurry leg structure and a demister. The slurry leg structure can obtain larger crystal particles. A densitometer is installed on the circulation pipeline of the crystallizer to detect the density of the high-salt mother liquor. A level gauge and a wastewater thermometer are installed on the crystallizer to measure the level and temperature of the high-salt mother liquor, ensuring the continuous and stable operation of the crystallizer.

[0012] Furthermore, the mother liquor circulation module includes a mother liquor tank and a mother liquor pump connected to the mother liquor tank. The mother liquor pump is linked to the liquid level of the mother liquor tank. The inlet of the mother liquor pump is connected to the clarification tank and the settling tank, and the outlet of the mother liquor pump is connected to the settling tank and the crystallizer. A densitometer is installed in the outlet direction of the mother liquor pump, and a mother liquor reflux self-control valve linked to the densitometer is installed in the settling tank, which can automatically maintain the liquid level of the mother liquor tank and maintain automated operation.

[0013] Furthermore, the feed balance tank is equipped with a feed automatic control valve linked to the liquid level of the crystallizer; the outlet of the crystallizer is equipped with a discharge automatic control valve linked to the wastewater density; the fresh steam inlet of the crystallizer is equipped with a fresh steam automatic control valve linked to the wastewater temperature; a non-condensable gas automatic control valve linked to the pressure of the forced circulation heater is installed between the non-condensable gas preheater and the forced circulation heater; and a settling tank is equipped with a settling discharge automatic control valve, which is linked to the density in the settling tank.

[0014] A method for thermal evaporation and crystallization treatment of high-salt wastewater from coal chemical evaporation ponds includes the following steps: S1: Wastewater is first treated by sedimentation and then preheated by a non-condensable gas preheater and a distilled water preheater. The preheated wastewater enters a crystallizer and a forced circulation heater and evaporates in the crystallizer to form mixed salt mother liquor. S2: The mixed salt mother liquor enters the settling tank for settling and separation, producing a concentrated slurry; S3: The concentrated slurry first enters the filter press to remove water, and then enters the dryer to dry it to form solid impurities and salts; S4: Mixed salts are stabilized and then utilized as resources.

[0015] Compared with the prior art, the beneficial effects of the present invention are: (1) The wastewater treated in the equalization tank is sent to the inclined tube sedimentation tank for solid-liquid separation to reduce the salt content in the wastewater. The wastewater circulates in the forced circulation heater and crystallizer. The wastewater flows at high speed in the forced circulation heater and the wastewater temperature rises by about 2°C. No phase change will occur. Therefore, the scaling cycle of the forced circulation heater can be effectively extended, blockage can be prevented, and the wastewater treatment efficiency can be improved.

[0016] (2) The water vapor generated by the evaporation of wastewater in the crystallizer is processed by the wire mesh demister and the secondary separator in sequence to obtain high-quality water vapor, thereby reducing the organic content in the distilled water, realizing the treatment and control of foam, and preventing foam leakage.

[0017] (3) By combining MVR, settling tank and dryer, the wastewater treatment process is connected and coordinated. The MVR evaporation part concentrates and reduces the amount of wastewater, the solid-liquid settling part focuses on the sedimentation of the mother liquor of mixed salts by its own gravity, and the supernatant returns to the crystallizer for further evaporation. The dryer part focuses on drying and reducing the amount of wastewater. The three combined processes connect the treatment process, improve the wastewater treatment's ability to resist shock loads, and ensure long-term stable operation.

[0018] (4) The steam heated by the steam compressor enters the forced circulation heater to heat the wastewater. When the pressure in the forced circulation heater is too high, the excess steam enters the non-condensable gas preheater to preheat the wastewater. The distilled water produced by the forced circulation heater enters the distilled water preheater to preheat the wastewater, making full use of the heat energy. The crystallizer provides secondary steam to the steam compressor, realizing recycling. The whole process only requires a small amount of fresh steam to be added, reducing the energy consumption of wastewater treatment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the thermal evaporation and crystallization treatment system for high-salt wastewater according to the present invention.

[0020] In the diagram: 101, Feed balance tank; 102, Feed pump; 103, Non-condensable gas preheater; 104, Distilled water preheater; 105, Distilled water tank; 106, Distilled water pump; 107, Forced circulation heater; 108, Crystallizer separator; 109, Forced circulation pump; 110, Steam compressor; 111, Secondary separator; 112, Discharge pump; 113, Vacuum pump; 114, Steam generator. ; 115. Negative pressure pump; 116. Purifier; 117. Dosing reaction tank; 118. Equalization tank; 119. Inclined tube sedimentation tank; 120. Pre-concentrator; 201. Settling tank; 202. Mother liquor tank; 203. Mother liquor pump; 204. Flocculation reaction tank; 205. Clarifying tank; 301. Concentrated slurry pump; 302. Buffer tank; 303. Drying feed pump; 304. Dryer; 305. Filter press. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 Please see Figure 1 The present invention provides a technical solution: A thermal evaporation crystallization treatment system for high-salt wastewater from a coal chemical evaporation pond includes a pre-precipitation module. The pre-precipitation module removes or converts ions generated by scale in advance, thus alleviating the scaling inside the forced circulation heater 107 from the source. For example, for common substances such as calcium and magnesium, sodium hydroxide and sodium carbonate are added to reduce the subsequent wastewater treatment load. The pre-sedimentation module is sequentially connected to a feed balance tank 101, a non-condensable gas preheater 103, and a distilled water preheater 104. The distilled water preheater 104 is connected to a crystallizer 108. The crystallizer 108 is connected to a forced circulation heater 107 via a forced circulation pump 109. The forced circulation heater 107 heats the wastewater. The non-condensable gas preheater 103, the distilled water preheater 104, and the forced circulation heater 107 have a double-layer structure, with the wastewater and the heating medium flowing independently. The feed balance tank 101 buffers fluctuations in the influent flow rate to avoid subsequent evaporation instability caused by water quality and quantity impacts, ensuring stable suction pressure of the feed pump 102 and reducing wastewater impact load. The non-condensable gas preheater 103 recovers the latent heat of water vapor entrained in the non-condensable gas, reducing heat loss during non-condensable gas discharge. The gas inlet and distilled water outlet of the forced circulation heater 107 are respectively connected to the steam compressor 110 and the distilled water tank 105. The steam compressor 110 and the non-condensable gas preheater 103 are respectively connected to the gas outlet of the forced circulation heater 107. The gas outlet of the crystallizer 108 is connected to the gas inlet of the forced circulation heater 107. The distilled water inlet of the distilled water preheater 104 is connected to the distilled water tank 105. The steam compressor 110 compresses and raises the temperature and pressure of the secondary steam (low pressure and low temperature) generated by the crystallizer 108, converting it into high-temperature and high-pressure steam, which is then introduced into the forced circulation heater 107 as a heating medium to release latent heat, thereby realizing the recycling of steam and reducing the demand for fresh steam. The crystallization separator 108 is sequentially connected to a flocculation reaction tank 204, a clarification tank 205, and a settling tank 201. Flocculants can be added to the flocculation reaction tank 204 to form large flocs, ensuring good separation of sediment and water in the clarification tank 205. The settling tank 201 is connected to the crystallization separator 108 through a mother liquor circulation module, and the clarification tank 205 is connected to the mother liquor circulation module. The settling tank 201 separates wastewater and sediment. The wastewater generated by the clarification tank 205 and the settling tank 201 can be sent to the settling tank 201 (high concentration) or the crystallization separator 108 (low concentration) according to its concentration. The settling tank 201 is connected to a buffer tank 302, which is connected to a dryer 304 via a filter press 305. The buffer tank 302 stores the concentrated slurry delivered by the settling tank 201, balancing the flow rate of the concentrated slurry with the feed demand of the dryer 304, and avoiding uneven drying caused by fluctuations in the feed of the dryer 304. The buffer tank 302 is equipped with a liquid level sensor that is linked to the concentrated slurry pump 301. The buffer tank 302 is connected to the pre-sedimentation module to collect the sediment, which facilitates the drying of the sediment.

[0023] In this embodiment, the pre-precipitation module includes a dosing reaction tank 117, an equalization tank 118, an inclined tube sedimentation tank 119, and a pre-concentrator 120 connected in sequence. The dosing reaction tank 117 adds reagents to the equalization tank 118 to achieve a chemical reaction of hardness ions. Wastewater flows into the inclined tube sedimentation tank 119 for solid-liquid separation. The pre-concentrator 120 concentrates the wastewater to reduce the water content of high-salt wastewater, reduce wastewater from subsequent evaporation and crystallization, and improve wastewater treatment efficiency. The sediment outlet of the inclined tube sedimentation tank 119 is connected to the buffer tank 302, or the sediment outlet of the inclined tube sedimentation tank 119 can be connected to the settling tank 201. The concentration of sediment is determined according to the sediment concentration. If the sediment concentration is high, it is sent to the buffer tank 302; if the sediment concentration is high, it is sent to the settling tank 201.

[0024] In this embodiment, a feed pump 102 is installed between the feed balance tank 101 and the wastewater inlet of the non-condensable gas preheater 103. The feed pump 102 feeds the wastewater sequentially into the non-condensable gas preheater 103 and the distilled water preheater 104. The forced circulation pump 109 feeds the wastewater in the distilled water preheater 104 into the crystallizer 108. When the wastewater circulates between the crystallizer 108 and the forced circulation heater 107, the automatic control valves of the relevant pipelines are closed. A vacuum pump 113 is connected to the gas outlet of the non-condensable gas preheater 103. The vacuum pump 113 draws non-condensable gas and water vapor from the forced circulation heater 107. A discharge pump 112 is installed between the crystallizer 108 and the flocculation reaction tank 204. The discharge pump 112 sends the high-salt mother liquor with the required density in the crystallizer 108 to the flocculation reaction tank 204. A thickening pump 301 is installed between the settling tank 201 and the buffer tank 302. The thickening pump 301 is linked to the liquid level of the buffer tank 302. When the liquid level of the thickening liquid in the buffer tank 302 reaches the required level, the thickening pump 301 stops working. A drying feed pump 303 is installed between the buffer tank 302 and the filter press 305.

[0025] In this embodiment, a distilled water pump 106 is installed between the distilled water tank 105 and the distilled water preheater 104. The distilled water tank 105 is equipped with a distilled water level gauge. The distilled water pump 106 is equipped with a frequency converter electrically connected to the distilled water level gauge. When the water level in the distilled water tank 105 exceeds the threshold, the distilled water pump 106 discharges distilled water. When the water level in the distilled water tank 105 is lower than the threshold, the distilled water pump 106 stops working to maintain the water level in the distilled water tank 105, so that the steam generator 114 can always have water available. The distilled water tank 105 is connected to the steam generator 114 via the purifier 116. The purifier 116 includes a security filter, an activated carbon adsorber, a membrane separator, etc., to remove suspended solids, organic matter and some salt to prevent clogging of the steam generator 114 and affecting the steam quality. The steam generator 114 is connected to the steam compressor 110 to provide fresh and pure water steam to the steam compressor 110.

[0026] In this embodiment, a secondary separator 111 is installed between the crystallizer 108 and the forced circulation heater 107. The crystallizer 108 is equipped with a slurry leg structure and a demister. The crystallizer 108 can also be equipped with a scraper to clean the crystallized salt on the inner wall of the crystallizer 108. The scraper can also agitate the wastewater to improve the crystallization efficiency. A densitometer is installed on the circulation pipeline of the crystallizer 108. A level gauge and a wastewater thermometer are also installed on the crystallizer 108. Organic matter in the crystallizer 108 forms foam, which is then carried by secondary steam and intercepted by the demister of the crystallizer 108. The remaining foam is then intercepted by the secondary separator 111 and returned to the crystallizer 108. A negative pressure pump 115 is installed between the secondary separator 111 and the crystallizer 108. The negative pressure pump 115 maintains a negative pressure environment in the crystallizer 108 and the forced circulation heater 107, lowers the boiling point of water, avoids rapid scaling of calcium and magnesium due to high temperature, and extracts non-condensable gases from the system to ensure heat exchange efficiency.

[0027] In this embodiment, the mother liquor circulation module includes a mother liquor tank 202 and a mother liquor pump 203 connected to the mother liquor tank 202. The mother liquor tank 202 is equipped with a level gauge, and the mother liquor pump 203 is equipped with a frequency converter. The mother liquor pump 203 is linked to the level of the mother liquor tank 202. Through frequency converter control, the mother liquor pump 203 automatically maintains a set level value. The inlet of the mother liquor pump 203 is connected to the clarification tank 205 and the settling tank 201, and the outlet of the mother liquor pump 203 is connected to the settling tank 201 and the crystallizer 108. A densitometer is installed in the liquid outlet direction of pump 203, and a mother liquor reflux control valve is installed in settling tank 201. The online densitometer after mother liquor pump 203 is interlocked with the mother liquor reflux control valve. When the mother liquor density reaches the set value, the direction of crystallizer 108 is closed and the direction of settling tank 201 is opened, and the mother liquor returns to settling tank 201 to continue settling. When the mother liquor density is lower than the set value, the direction of crystallizer 108 is opened and the direction of settling tank 201 is closed, and the mother liquor returns to crystallizer 108 to continue evaporation.

[0028] In this embodiment, the feed balance tank 101 is equipped with a feed self-control valve that is linked to the liquid level of the crystallizer 108, which can automatically replenish wastewater to the crystallizer 108 and control the liquid level in the crystallizer 108. The discharge port of the crystallizer 108 is equipped with a discharge automatic control valve that is linked to the wastewater density. When the wastewater density reaches the set value, the discharge automatic control valve opens; when the wastewater density is lower than the set value, it closes, and the wastewater is in a reflux state to continue evaporation. The fresh steam inlet of the crystallizer 108 is equipped with a fresh steam automatic control valve that is linked to the wastewater temperature. The fresh steam automatic control valve will automatically open and maintain the temperature value set by the crystallizer 108. A non-condensable gas automatic control valve that is linked to the pressure of the forced circulation heater 107 is installed between the non-condensable gas preheater 103 and the forced circulation heater 107. The non-condensable gas automatic control valve will automatically open to discharge non-condensable gas and maintain the pressure of the forced circulation heater 107 stable. The settling tank 201 is equipped with a settling discharge automatic control valve and a density meter. The settling discharge automatic control valve is linked to the density in the settling tank 201. It opens when the wastewater density reaches the set value and closes when the wastewater density is lower than the set value.

[0029] Specifically, this embodiment provides a method for thermal evaporation and crystallization treatment of high-salt wastewater from coal chemical evaporation ponds, including the following steps: S1: Wastewater enters equalization tank 118. Chemical dosing tank 117 adds chemicals to equalization tank 118, causing some substances in wastewater to precipitate. The precipitate and wastewater enter inclined tube sedimentation tank 119 for solid-liquid separation. The solid is pumped into buffer tank 302, and the wastewater passes through pre-concentrator 120 to reduce some of the water content. Next, the wastewater enters the feed balance tank 101. The feed pump 102 draws the wastewater and preheats it through the non-condensable gas preheater 103 and the distilled water preheater 104. The preheated wastewater enters the crystallization separator 108 through the forced circulation pump 109. Steam generator 114 draws distilled water from distilled water tank 105 and heats it to generate fresh steam. The fresh steam enters steam compressor 110, which sends the steam into forced circulation heater 107. Forced circulation pump 109 sends wastewater into forced circulation heater 107 for heating and returns it to crystallizer 108. Negative pressure pump 115 maintains negative pressure in crystallizer 108, and the wastewater evaporates and crystallizes in crystallizer 108. The secondary steam generated by the crystallizer 108 is sent to the forced circulation heater 107 and the steam compressor 110 after passing through the secondary separator 111. At this time, the power of the steam compressor 110 can be reduced. The steam compressor 110 heats the secondary steam and sends it to the forced circulation heater 107 to heat the wastewater. Distilled water in forced circulation heater 107 flows to distilled water tank 105, and distilled water pump 106 sends distilled water to distilled water preheater 104 to preheat wastewater according to the water level in distilled water tank 105. When the internal pressure of the forced circulation heater 107 is greater than the threshold, the non-condensable gas and water vapor in the forced circulation heater 107 are extracted by the vacuum pump 113 and sent to the non-condensable gas preheater 103, which preheats the wastewater.

[0030] S2: An online density meter is installed in the circulation pipeline of the forced circulation heater 107 and the crystallizer 108. The high and low values ​​of the wastewater density are preset. When the wastewater density reaches the standard, the discharge control valve of the crystallizer 108 is opened. When the wastewater density is lower than the low density value, the discharge control valve and the discharge pump 112 are closed. The discharge pump 112 transports the wastewater to the flocculation reaction tank 204. Flocculant is added to the flocculation reaction tank 204 and mixed evenly with the wastewater. The wastewater flows into the clarification tank 205 for solid-liquid separation. Flocculated solids and some wastewater enter the settling tank 201. The wastewater in the upper layer of the clarifier 205 flows into the mother liquor tank 202. Flocculated solids and wastewater separate into layers in the settling tank 201. The upper layer of wastewater also flows into the mother liquor tank 202. When the wastewater concentration in the mother liquor tank 202 is high, the mother liquor pump 203 sends the wastewater to the settling tank 201. When the wastewater concentration in the mother liquor tank 202 is low, the mother liquor pump 203 sends the wastewater to the crystallizer 108.

[0031] S3: After the density of the wastewater in the settling tank 201 is detected by the densitometer to meet the standard, the settling discharge control valve is automatically opened. The slurry pump 301 draws the slurry (wastewater) in the settling tank 201 and sends it to the buffer tank 302. When the level gauge on the buffer tank 302 detects that the slurry level is met, the drying feed pump 303 sends the slurry to the filter press 305 to remove part of the wastewater in the slurry. The wastewater flows back to the buffer tank 302. Alternatively, an additional pipeline can be set to send the wastewater into the flocculation reaction tank 204 or the settling tank 201. The concentrated slurry processed by filter press 305 is sent to dryer 304. The dryer 304 is heated by steam, and the concentrated slurry is dried to form solid impurities.

[0032] S4: After stabilization treatment, the mixed salts are utilized for resource recovery. The goal of stabilization treatment is to reduce the leaching risk of salt ions and heavy metals, improve the physical strength of the mixed salts to facilitate subsequent resource recovery, and inhibit the volatilization of organic matter. The core treatment path is solidification / stabilization, which involves treating the mixed salts through chemical bonding, physical encapsulation, and other methods.

[0033] Example 2 Please see Figure 1 This embodiment is designed to treat wastewater with low TDS (e.g., TDS less than 30,000). Since its salt content is relatively low and scale formation is minimal, the number of wastewater treatment steps can be reduced.

[0034] Wastewater is fed into the feed balance tank 101 and the feed pump 102 is turned on. At this time, the feed control valve is interlocked with the liquid level of the crystallizer 108 and the feed begins. When the crystallizer 108 reaches the low liquid level setting, the forced circulation pump 109 and the discharge pump 112 are turned on. When the crystallizer 108 reaches the set working liquid level, the feed control valve automatically closes and enters the automatic mode.

[0035] Open the hand valves before and after the fresh steam pressure reducing valve on the fresh steam pipe below the forced circulation heater 107 to start feeding fresh steam (provided by the steam generator 114) into the forced circulation heater 107 and begin preheating. When the liquid phase temperature of the crystallizer 108 reaches the set evaporation temperature, the fresh steam pressure reducing valve will automatically close and enter automatic mode.

[0036] Steam is condensed into distilled water. When the distilled water tank 105 reaches the working liquid level setting, the distilled water pump 106 is automatically turned on, and the water flow rate is adjusted by frequency conversion to automatically maintain the current working liquid level.

[0037] Prepare to start the steam compressor 110. Start the vacuum pump 113. The shell-side pressure of the forced circulation heater 107 is interlocked with the non-condensable gas automatic control valve. When the shell-side pressure is higher than the set condensing pressure, the non-condensable gas automatic control valve will automatically open to discharge gas, and when it is lower than the set value, it will automatically close.

[0038] After the material undergoes evaporation and crystallization, its density is measured. The online density meter on the circulation pipeline of the crystallizer 108 is set with high and low values. When the online density meter reaches the set high density value, the discharge automatic control valve is opened and the material is discharged into the settling tank 201. When the online density meter reaches the set low density value, the discharge automatic control valve is closed. Only after the high and low density values ​​are set and the operation is stable can the discharge automatic control valve and the online density meter be put into automatic mode.

[0039] After discharge, the mixed salt mother liquor flows through the flocculation reaction tank 204 and the clarification tank 205 without the addition of reagents. The mixed salt mother liquor settles and separates in the settling tank 201. The supernatant overflows into the mother liquor tank 202, and the lower layer of concentrated slurry is prepared for drying treatment.

[0040] The mother liquor pump 203 is automatically controlled. When the mother liquor tank 202 reaches the minimum liquid level, the mother liquor pump 203 automatically starts; when the liquid level in the mother liquor tank 202 reaches the high liquid level setting, the mother liquor pump 203 shuts off. The online density meter downstream of the mother liquor pump 203 is interlocked with the mother liquor reflux automatic control valve. When the mother liquor density reaches the set value, the directional valve of the crystallizer 108 is closed and the directional valve of the settling tank 201 is opened, allowing the mother liquor to return to the settling tank 201 for further settling. When the mother liquor density is lower than the set value, the valve is closed, the directional valve of the crystallizer 108 is opened and the directional valve of the settling tank 201 is closed, allowing the mother liquor to return to the crystallizer 108 for further evaporation.

[0041] The online density meter in the settling tank 201 is set with high and low values. When the online density meter reaches the set high density value, the settling discharge automatic control valve of the settling tank 201 is opened. When the online density meter reaches the set low density value, it is closed. After the high and low density values ​​are set and the operation is stable, the settling discharge automatic control valve of the settling tank 201 and the online density meter can be put into automatic mode.

[0042] When the buffer tank 302 reaches the working liquid level setting, the thick slurry pump 301 automatically starts, and the frequency converter adjusts the water flow rate to automatically maintain the current working liquid level.

[0043] The drying feed pump 303 can directly transport the concentrated slurry to the dryer 304, and input steam to heat the dryer 304. After the concentrated slurry is dried, it forms solid impurities.

[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. A coal chemical evaporation pond high-salinity wastewater heat evaporation crystallization treatment system, characterized in that, The pre-sedimentation module is sequentially connected with a feed balance tank, a non-condensable gas preheater and a distilled water preheater, the distilled water preheater is connected with a crystallization separator, the crystallization separator is connected with a forced circulation heater through a forced circulation pump, and the forced circulation heater heats wastewater; The gas inlet and distilled water outlet of the forced circulation heater are respectively connected with a steam compressor and a distilled water tank, the steam compressor and the non-condensable gas preheater are respectively connected with the gas outlet of the forced circulation heater, the gas outlet of the crystallization separator is connected with the gas inlet of the forced circulation heater, and the distilled water inlet of the distilled water preheater is connected with the distilled water tank; The crystallization separator is sequentially connected with a flocculation reaction tank, a clarifier and a settling tank, the settling tank is communicated with the crystallization separator through a mother liquor circulation module, the clarifier is communicated with the mother liquor circulation module, and the settling tank separates wastewater and precipitates; The settling tank is communicated with a buffer tank, the buffer tank is connected with a drying machine through a filter press, and the buffer tank is communicated with the pre-sedimentation module to take precipitates.

2. The coal chemical evaporation pond high-salinity wastewater thermal evaporation crystallization treatment system according to claim 1, characterized in that: The pre-sedimentation module comprises a dosing reaction tank, an adjusting tank, an inclined tube sedimentation tank and a pre-concentrator which are sequentially connected, and the precipitate outlet of the inclined tube sedimentation tank is communicated with the buffer tank.

3. The coal chemical evaporation pond high-salinity wastewater thermal evaporation crystallization treatment system according to claim 1, characterized in that: A feed pump is arranged between the feed balance tank and the wastewater inlet of the non-condensable gas preheater, a vacuum pump is connected with the gas outlet of the non-condensable gas preheater, a discharge pump is arranged between the crystallization separator and the flocculation reaction tank, a thick slurry pump is arranged between the settling tank and the buffer tank, the thick slurry pump is linked with the liquid level of the buffer tank, and a drying feed pump is arranged between the buffer tank and the filter press.

4. The coal chemical evaporation pond high-salinity wastewater thermal evaporation crystallization treatment system according to claim 1, characterized in that: A distilled water pump is arranged between the distilled water tank and the distilled water preheater, a distilled water liquid level meter is arranged on the distilled water tank, and the distilled water pump is provided with a frequency converter which is electrically connected with the distilled water liquid level meter.

5. The coal chemical evaporation pond high-salinity wastewater thermal evaporation crystallization treatment system according to claim 1, characterized in that: The distilled water tank is connected with a steam generator through a purifier, and the steam generator is communicated with the steam compressor.

6. The coal chemical evaporation pond high-salinity wastewater thermal evaporation crystallization treatment system according to claim 1, characterized in that: A secondary separator is arranged between the crystallization separator and the forced circulation heater, and a negative pressure pump is arranged between the secondary separator and the crystallization separator.

7. The coal chemical evaporation pond high-salinity wastewater thermal evaporation crystallization treatment system according to claim 1, characterized in that: A elutriation leg structure and a defoamer are arranged in the crystallization separator, a density meter is arranged on the circulating pipeline of the crystallization separator, and a liquid level meter and a wastewater temperature meter are arranged on the crystallization separator.

8. The coal chemical evaporation pond high-salinity wastewater thermal evaporation crystallization treatment system according to claim 1, characterized in that: The mother liquor circulation module comprises a mother liquor tank and a mother liquor pump connected with the mother liquor tank, the mother liquor pump is linked with the liquid level of the mother liquor tank, the inlet of the mother liquor pump is communicated with the clarifier and the settling tank, the outlet of the mother liquor pump is communicated with the settling tank and the crystallization separator, a density meter is arranged on the outlet of the mother liquor pump, and a mother liquor backflow automatic control valve linked with the density meter is arranged on the settling tank.

9. The coal chemical evaporation pond high-salinity wastewater thermal evaporation crystallization treatment system according to claim 1, characterized in that: A feed automatic control valve linked with the liquid level of the crystallization separator is arranged on the feed balance tank, a discharge automatic control valve linked with the density of wastewater is arranged on the discharge port of the crystallization separator, a fresh steam automatic control valve linked with the temperature of wastewater is arranged on the fresh steam inlet of the crystallization separator, a non-condensable gas automatic control valve linked with the pressure of the forced circulation heater is arranged between the non-condensable gas preheater and the forced circulation heater, a settling discharge automatic control valve is arranged on the settling tank, and the settling discharge automatic control valve is linked with the density in the settling tank.

10. A treatment method based on the coal chemical evaporation pond high-salinity wastewater thermal evaporation crystallization treatment system according to any one of claims 1-9, characterized in that, The method comprises the following steps: S1: the wastewater is first treated by sedimentation, and then preheated by the non-condensable gas preheater and the distilled water preheater, and the preheated wastewater enters the crystallization separator and the forced circulation heater and is evaporated in the crystallization separator to form a mother liquor of miscellaneous salt; S2: the mother liquor of miscellaneous salt enters the sedimentation tank for sedimentation separation to produce thick slurry; S3: the thick slurry first enters the filter press to remove water, and then enters the drying machine to be dried to form solid miscellaneous salt.

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