Mvr evaporation concentration crystallization system

Abstract

The utility model discloses a kind of MVR evaporation concentration crystallization systems, including one-effect evaporator, two-effect evaporator and three-effect evaporator in turn series communication along material flow direction, the air inlet of one-effect evaporator, two-effect evaporator, three-effect evaporator is communicated with compressed steam pipeline, the air inlet of two-effect evaporator is communicated with the pipeline of compressed steam pipeline and is provided with switch valve A, the secondary steam outlet of one-effect evaporator is communicated with the pipeline of compressed air inlet pipeline and is provided with switch valve B, the secondary steam outlet of one-effect evaporator is communicated with the pipeline of the air inlet of two-effect evaporator and is provided with switch valve C, the secondary steam outlet of two-effect evaporator, three-effect evaporator is communicated with compressed air inlet pipeline, change steam flow direction by switch valve A, switch valve B and switch valve C, realize the switch of multiple evaporators series connection and parallel connection in steam flow direction, so that evaporation system can be aimed at different material evaporation concentration, improve versatility.

Description

Technical Field

[0001] This utility model relates to the technical field of evaporation, concentration and crystallization equipment, specifically to an MVR evaporation, concentration and crystallization system. Background Technology

[0002] MVR, short for Mechanical Vapor Recompression, is an energy-saving technology that utilizes the secondary steam and its energy generated within the evaporation system itself. Low-grade secondary steam is upgraded to high-grade steam through the mechanical work of a compressor. This cycle continues, providing heat energy to the evaporation system and reducing the need for external energy sources. MVR technology offers advantages such as low energy waste, high thermal efficiency, and low operating costs, making it widely used in the evaporation, concentration, and crystallization of low-concentration materials.

[0003] MVR evaporation systems typically consist of multiple evaporators connected in parallel, series, or a combination of both in the steam flow direction. In a series connection, the inlet of the next evaporator is connected to the secondary steam outlet of the previous evaporator, using the secondary steam from the previous evaporator as a heat source to heat and concentrate the material. In a parallel connection, the inlets of all evaporators are connected to the outlet of a steam compressor, using high-pressure, high-temperature compressed steam from the compressor as a heat source for evaporation and concentration. However, once the existing evaporation system is built, whether in parallel or series, it cannot be changed. This results in a limited functionality of existing MVR evaporation systems, suitable only for certain low-concentration materials or a few types of low-concentration materials, and lacking versatility. Utility Model Content

[0004] In summary, in order to overcome the shortcomings of existing technologies, this utility model provides an MVR evaporation concentration and crystallization system. By setting valves on the steam pipeline and changing the direction of steam flow through the valves, it is possible to switch between series and parallel connections of multiple evaporators in the direction of steam flow. This allows the evaporation system to perform evaporation concentration on different low-concentration materials, thereby improving the versatility of the system.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: An MVR (Multi-Volume Reduction) evaporation, concentration, and crystallization system includes a first-effect evaporator, a second-effect evaporator, and a third-effect evaporator connected in series along the material flow direction. The inlet of the first-effect evaporator is connected to the outlet of a feed pump, and the inlet of the feed pump is connected to a feed balance tank. The outlet of the third-effect evaporator is connected to the inlet of a discharge pump, and the outlet of the discharge pump is connected to the discharge pipeline of the third-effect evaporator. The air inlets of the first-effect evaporator, the second-effect evaporator, and the third-effect evaporator are all connected to a compressed steam pipeline. This compressed steam pipeline is connected to the outlet of a steam compressor. A switching valve A is installed on the pipeline connecting the air inlet of the second-effect evaporator to the compressed steam pipeline. The secondary steam outlet of the first-effect evaporator is connected to the compressor inlet pipe and the inlet of the second-effect evaporator. A switching valve B is installed on the pipe connecting the secondary steam outlet of the first-effect evaporator and the compressor inlet pipe. A switching valve C is installed on the pipe connecting the secondary steam outlet of the first-effect evaporator and the inlet of the second-effect evaporator. The secondary steam outlets of both the second-effect and third-effect evaporators are connected to the compressor inlet pipe, which is connected to the inlet of the steam compressor. The compressed steam pipeline is connected to a steam source via a live steam pipeline. The non-condensable gas outlets of the first-effect evaporator, the second-effect evaporator, and the third-effect evaporator are connected to a non-condensable gas pipeline. The non-condensable gas pipeline is connected to the inlet of the condenser. The outlet of the condenser is connected to the inlet of the vacuum pump, and the outlet of the vacuum pump is used for venting.

[0006] Furthermore, the compressed air inlet pipe is connected to the air inlet of the first hydrocyclone, the air outlet of the first hydrocyclone is connected to the air inlet of the steam compressor, and the liquid outlet of the first hydrocyclone is connected to the feed inlet of the triple-effect evaporator.

[0007] Furthermore, the air inlet of the second-effect evaporator is connected to the air outlet of the second hydrocyclone, the air inlet of the second hydrocyclone is connected to the secondary steam outlet of the first-effect evaporator and the compressed steam pipeline, the switching valve A is installed on the pipeline connecting the air inlet of the second hydrocyclone and the compressed steam pipeline, the switching valve C is installed on the pipeline connecting the secondary steam outlet of the first-effect evaporator and the air inlet of the second hydrocyclone, and the liquid outlet of the second hydrocyclone is connected to the feed inlet of the third-effect evaporator.

[0008] Furthermore, the condensate outlets of the first-effect evaporator, the second-effect evaporator, the third-effect evaporator, and the condenser are all connected to the inlet of the condensate tank. The outlet of the condensate tank is connected to the inlet of the condensate pump, and the outlet of the condensate pump drains water. A condensate level gauge is installed on the condensate tank to monitor the water level inside. A condensate drain valve is installed on the outlet of the condensate pump. The condensate level gauge is electrically connected to the condensate drain valve. The condensate drain valve is adjusted by controlling the water level inside the condensate tank. The air outlet of the condensate tank is connected to the air inlet of the condenser.

[0009] Furthermore, the outlet of the condensate pump is connected to the outlet of the steam compressor via a compressor flushing pipeline. The compressor flushing pipeline is equipped with a compressor flushing valve. A compressed steam temperature sensor for monitoring the temperature of compressed steam is installed on the compressed steam pipeline. The compressed steam temperature sensor is electrically connected to the compressor flushing valve. The compressor flushing valve is adjusted by controlling the temperature of the compressed steam. The outlet of the steam compressor is connected to the inlet of the compressor drain tank. The outlet of the compressor drain tank is connected to the inlet of the compressor drain pump. The outlet of the compressor drain pump is connected to the inlet of the condensate tank.

[0010] Furthermore, a preheating system is provided between the discharge port of the feed pump and the inlet of the first-effect evaporator. The preheating system includes a primary preheater, a secondary preheater, and a tertiary preheater connected in series along the material flow direction. The inlet of the primary preheater is connected to the discharge port of the feed pump, and the discharge port of the tertiary preheater is connected to the inlet of the first-effect evaporator. The preheating medium inlet of the primary preheater is connected to the outlet of the condensate pump, and the preheating medium outlet of the primary preheater is connected to the condensate drain pipe. The preheating medium inlet of the secondary preheater is connected to the non-condensable gas pipe, and the preheating medium outlet of the secondary preheater is connected to the air inlet of the condenser. The preheating medium inlet of the tertiary preheater is connected to the live steam pipe through a steam preheating pipe. The condensate outlets of the tertiary preheater and the secondary preheater are both connected to the inlet of the condensate tank.

[0011] Furthermore, a preheating temperature sensor is installed on the pipeline connecting the outlet of the three-stage preheater and the inlet of the first-effect evaporator, and a steam preheating valve is installed on the steam preheating pipeline. The preheating temperature sensor is electrically connected to the steam preheating valve, and the steam preheating valve is adjusted by controlling the material temperature after three-stage preheating.

[0012] Furthermore, a first-effect feed valve is installed at the outlet of the feed pump, and a first-effect level gauge is installed on the first-effect evaporator to monitor the material level inside. The first-effect level gauge is electrically connected to the first-effect feed valve, and the first-effect feed valve is adjusted by controlling the material level inside the first-effect evaporator. The discharge port of the first-effect evaporator is connected to the inlet of the first-effect conveying pump. The discharge port of the first-effect conveying pump is connected to the return port of the first-effect evaporator via a first-effect return pipeline. A first-effect return valve is installed on the first-effect return pipeline. The discharge port of the first-effect conveying pump is connected to the inlet of the second-effect evaporator via a second-effect inlet pipeline. A second-effect inlet valve is installed on the second-effect inlet pipeline. The second-effect evaporator is equipped with a second-effect level gauge to monitor the material level inside. The second-effect level gauge is electrically connected to the second-effect inlet valve, and the second-effect inlet valve is adjusted by controlling the material level inside the second-effect evaporator. The discharge port of the double-effect evaporator is connected to the inlet of the double-effect conveying pump. The discharge port of the double-effect conveying pump is connected to the return port of the double-effect evaporator through the double-effect return pipeline. A double-effect return valve is installed on the double-effect return pipeline. The discharge port of the double-effect conveying pump is connected to the inlet of the triple-effect evaporator through the triple-effect feed pipeline. A triple-effect feed valve is installed on the triple-effect feed pipeline. A triple-effect level gauge is installed on the triple-effect evaporator to monitor the material level inside. The triple-effect level gauge is electrically connected to the triple-effect feed valve. The triple-effect feed valve is adjusted by controlling the material level inside the triple-effect evaporator.

[0013] Furthermore, the triple-effect discharge pipeline is connected to the return port of the triple-effect evaporator via the triple-effect return pipeline. A triple-effect return valve is installed on the triple-effect return pipeline. The triple-effect discharge pipeline is connected to the discharge pipeline. A discharge valve and a discharge flow meter are installed on the discharge pipeline. A discharge mass density meter for monitoring the discharge concentration is installed on the triple-effect discharge pipeline. The discharge mass density meter is electrically connected to the discharge valve, and the discharge valve is adjusted by controlling the discharge concentration.

[0014] Furthermore, the inlet of the feed pump is connected to the feed balance tank through a material pipeline, and a material valve is installed on the material pipeline. The inlet of the feed pump is connected to the cleaning water tank through a cleaning pipeline, and a cleaning valve is installed on the cleaning pipeline.

[0015] Furthermore, the flushing port of the first-effect evaporator is connected to the flushing tank via a first-effect flushing pipeline, and a first-effect flushing valve is installed on the first-effect flushing pipeline. The flushing port of the second-effect evaporator is connected to the flushing tank via a second-effect flushing pipeline, and a second-effect flushing valve is installed on the second-effect flushing pipeline. The flushing port of the third-effect evaporator is connected to the flushing tank via a third-effect flushing pipeline, and a third-effect flushing valve is installed on the third-effect flushing pipeline. The discharge port of the first-effect evaporator is connected to the main drain pipe via a first-effect drain pipe, and a first-effect drain valve is installed on the first-effect drain pipe. The outlet of the double-effect evaporator is connected to the main drain pipe via the double-effect drain pipe, which is equipped with a double-effect drain valve. The outlet of the triple-effect evaporator is connected to the main drain pipe via the triple-effect drain pipe, which is equipped with a triple-effect drain valve. The outlet of the condensate tank is connected to the main drain pipe via the condensate drain pipe, which is equipped with a condensate drain valve. The outlet of the feed balance tank is connected to the main drain pipe via the feed drain pipe, which is equipped with a feed drain valve.

[0016] Furthermore, the first-effect evaporator is equipped with a first-effect pressure sensor to monitor the pressure inside the first-effect evaporator, and a steam valve and a steam flow meter are installed on the live steam pipeline. The first-effect pressure sensor is electrically connected to the steam valve, and the steam valve is controlled and regulated by the pressure inside the first-effect evaporator.

[0017] Furthermore, the inlet of the first-effect conveying pump is connected to the hot cleaning water tank through a first-effect hot cleaning pipeline, and a first-effect hot cleaning valve is installed on the first-effect hot cleaning pipeline. The inlet of the second-effect conveying pump is connected to the hot cleaning water tank through a second-effect hot cleaning pipeline, and a second-effect hot cleaning valve is installed on the second-effect hot cleaning pipeline. The inlet of the discharge pump is connected to the hot cleaning water tank through a third-effect hot cleaning pipeline, and a third-effect hot cleaning valve is installed on the third-effect hot cleaning pipeline. The inlet of the feed pump is connected to the hot cleaning water tank through a feed hot cleaning pipeline, and a feed hot cleaning valve is installed on the feed hot cleaning pipeline.

[0018] Furthermore, the first-effect, second-effect, and third-effect evaporators are all centrally circulating tube evaporators, including a tank, an intermediate tube, a heating tube, an upper baffle, and a lower baffle. The lower part of the tank is equipped with an upper and lower baffle arranged vertically, and a central tube is located at the center of the lower part of the tank. The upper and lower baffles are fixedly connected to the upper and lower ends of the central tube, respectively. The upper and lower baffles and the central tube divide the inner cavity of the tank into a separation chamber, a heating chamber, and a circulation chamber. The separation chamber is the inner cavity above the upper baffle in the tank, and the heating chamber is the lower inner wall and the central circulation chamber of the tank. The cavity is formed by the outer wall of the pipe, the upper baffle, and the lower baffle. The circulation chamber is the inner cavity of the middle pipe and the inner cavity of the tank below the lower baffle. The heating chamber is equipped with a heating pipe. The upper and lower ends of the heating pipe are fixedly connected to the upper baffle and the lower baffle, respectively. The heating pipe connects the separation chamber above the upper baffle of the tank body with the circulation chamber below the lower baffle. The upper end of the separation chamber is provided with a secondary steam outlet, and the lower part of the separation chamber is provided with a feed inlet and a return outlet. The heating chamber is provided with an air inlet, a condensate outlet, and a non-condensable gas outlet that communicate with the heating chamber. The lower end of the tank body is provided with a discharge outlet.

[0019] Furthermore, the tank is equipped with a stirring device, which includes stirring blades, a stirring shaft, and a stirring power device. The stirring blades are located in the lower part of the intermediate tube, and the stirring shaft enters the tank from the lower end of the tank. Its upper end is connected to the stirring blades located in the intermediate tube, and the lower end of the stirring shaft is located on the outer side of the lower end of the tank and connected to the output shaft of the stirring power device.

[0020] Furthermore, a scraper is provided in the circulation chamber below the lower partition of the tank body. The scraper is fixedly connected to the stirring shaft and is in contact with the inner bottom surface of the tank body.

[0021] The beneficial effects of this utility model are as follows:

[0022] 1. This utility model, by installing valves on the steam pipeline and changing the steam flow direction through these valves, enables switching between series and parallel connections of multiple evaporators in the steam flow direction. When switching valve C is closed and switching valves A and B are opened, the secondary steam outlet of the first-effect evaporator is connected to the compression inlet pipeline, and the first, second, and third-effect evaporators are connected in parallel in the steam flow direction. When switching valve C is opened and switching valves A and B are closed, the secondary steam from the first-effect evaporator enters the second-effect evaporator. At this time, the first and second-effect evaporators are connected in series to form a double-effect evaporator, and the double-effect evaporator is connected in parallel with the third-effect evaporator to form a single-effect plus double-effect evaporation system. Therefore, this utility model can evaporate and concentrate different low-concentration materials, improving the system's versatility.

[0023] 2. This utility model utilizes MVR mechanical vapor recompression technology, which uses a steam compressor to compress the secondary steam generated during the evaporation process into high-temperature and high-pressure compressed steam. The compressed steam is then used to heat the material, causing it to evaporate, concentrate, and crystallize. Once the system is running stably, the live steam is only used as a supplementary heat source, which can effectively reduce the amount of live steam used and lower the cost of evaporation and concentration.

[0024] 3. The single-effect, double-effect, and triple-effect evaporators of this utility model all adopt a central circulation tube evaporator equipped with an agitator. The central circulation tube evaporator can rely on the thermal power of steam to make the material boil and circulate naturally, without the need for an additional circulation pump. In addition, the agitator installed inside the central circulation tube evaporator improves the fluidity of the material, avoids sedimentation, and reduces clogging. The central circulation tube evaporator of this utility model has a scraper fixedly connected to the stirring shaft in the circulation chamber of the tank. The scraper rotates with the stirring shaft and can scrape up the material that has settled on the bottom surface of the tank, making it less prone to sedimentation and effectively preventing clogging of the discharge port.

[0025] 4. This utility model incorporates a preheating system. The primary preheater utilizes heat from the condensate to preheat the material, while the secondary preheater utilizes heat from the non-condensable gases. This system recovers heat from both the condensate and non-condensable gases, improving heat utilization, reducing energy consumption, and lowering costs. The tertiary preheater uses live steam to preheat the material. A preheating temperature sensor is installed on the pipeline connecting the outlet of the tertiary preheater to the inlet of the first-effect evaporator. By controlling the temperature of the material after tertiary preheating and adjusting the steam preheating valve, the temperature of the material entering the first-effect evaporator can be guaranteed, thus improving the evaporation effect.

[0026] 5. The inlet of the feed pump of this utility model is connected to the cleaning water tank through a cleaning pipeline. The feed pump delivers cleaning water to the entire system, which can clean the entire system. This utility model is equipped with a rinsing tank, which uses the rinsing water in the rinsing tank to rinse the evaporator. This utility model is equipped with a hot cleaning water tank, which uses hot water to clean the system. The cleaning water tank, rinsing tank, and hot cleaning water tank can perform chemical cleaning, rinsing, and hot water rinsing on the system as needed or at regular intervals, reducing cleaning time and cleaning costs, avoiding serious scaling and blockage, and ensuring the safety and stability of the system.

[0027] 6. This invention controls the feed valve by adjusting the material level within the evaporator. When the material level is low, the opening of the feed valve is increased; when the material level is high, the opening of the feed valve is decreased, thereby controlling the feed flow rate and maintaining a constant liquid level in each evaporator. This invention monitors the slurry concentration using a discharge mass density meter and controls the opening and closing of the discharge valve based on the discharge concentration. This invention has a high degree of automation; the cooperation between the sensors and valves at various monitoring and control points enables automatic operation, automatic cleaning, and automatic discharge.

[0028] 7. This utility model has a simple structure, is easy to use, has low cost, and a high degree of automation. It can effectively realize the evaporation, concentration and crystallization of low-concentration materials. It has low evaporation energy consumption, high evaporation efficiency, low production cost and is not easy to clog pipes. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a schematic diagram of the structure of the central circulation tube evaporator of this utility model. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings.

[0031] like Figure 1As shown, an MVR evaporation concentration and crystallization system includes a feed balance tank 1 for storing low-concentration materials. The outlet of the feed balance tank 1 is connected to the inlet of a feed pump 2 via a material pipeline. A material valve 3 is installed on the material pipeline. The outlet of the feed pump 2 is connected to the inlet of a primary preheater 6. The outlet of the primary preheater 6 is connected to the inlet of a secondary preheater 11. The outlet of the secondary preheater 11 is connected to the inlet of a tertiary preheater 12. The outlet of the tertiary preheater 12 is connected to the inlet of a first-effect evaporator 20. A preheating temperature sensor 14 is installed on the pipeline connecting the outlet of the tertiary preheater 12 and the inlet of the first-effect evaporator 20. A steam preheating valve 15 is installed on the steam preheating pipeline 36. The preheating temperature sensor 14 is electrically connected to the steam preheating valve 15. The steam preheating valve 15 is adjusted by controlling the material temperature after the three-stage preheating. The feed pump 2 is equipped with a first-effect feed valve 37 at its outlet. The first-effect evaporator 20 is equipped with a first-effect level gauge 38 to monitor its internal material level. The first-effect level gauge 38 is electrically connected to the first-effect feed valve 37. The first-effect feed valve 37 is adjusted by controlling the material level inside the first-effect evaporator 20. The outlet of the first-effect evaporator 20 is connected to the inlet of the first-effect conveying pump 39. The outlet of the first-effect conveying pump 39 is connected to the return port of the first-effect evaporator 20 via a first-effect return pipeline. A first-effect return valve 4 is installed on the first-effect return pipeline. The discharge port of the first-effect conveying pump 39 is connected to the inlet of the second-effect evaporator 21 via a second-effect feed pipe. A second-effect feed valve 42 is installed on the second-effect feed pipe. A second-effect level gauge 41 is installed on the second-effect evaporator 21 to monitor the material level inside. The second-effect level gauge 41 is electrically connected to the second-effect feed valve 42. The second-effect feed valve 42 is adjusted by controlling the material level inside the second-effect evaporator 21. The discharge port of the second-effect evaporator 21 is connected to the inlet of the second-effect conveying pump 43. The discharge port of the second-effect conveying pump 43 is connected to the second-effect return pipe. The return port of the second-effect evaporator 21 is connected to the return pipe of the second-effect evaporator 22. A second-effect return valve 44 is installed on the return pipe of the second-effect evaporator 21. The outlet of the second-effect conveying pump 43 is connected to the inlet of the third-effect evaporator 22 through the third-effect inlet pipe. A third-effect inlet valve 45 is installed on the third-effect inlet pipe. A third-effect level gauge 46 is installed on the third-effect evaporator 22 to monitor the material level inside. The third-effect level gauge 46 is electrically connected to the third-effect inlet valve 45. The third-effect inlet valve 45 is adjusted by controlling the material level inside the third-effect evaporator 22. The outlet of the third-effect evaporator 22 is connected to the outlet... The inlet of the feed pump 47 and the outlet of the discharge pump 47 are connected to the triple-effect discharge pipeline. The triple-effect discharge pipeline is connected to the return port of the triple-effect evaporator 22 through the triple-effect return pipeline. A triple-effect return valve 48 is installed on the triple-effect return pipeline. The triple-effect discharge pipeline is connected to the discharge pipeline. A discharge valve 50 and a discharge flow meter are installed on the discharge pipeline. A discharge mass density meter 49 for monitoring the discharge concentration is installed on the triple-effect discharge pipeline. The discharge mass density meter 49 is electrically connected to the discharge valve 50. The discharge valve 50 is adjusted by controlling the discharge concentration.

[0032] The inlet of the first-effect evaporator 20 is connected to the compressed steam pipeline 17, which is connected to the outlet of the steam compressor 16. The secondary steam outlet of the first-effect evaporator 20 is connected to the compressed steam inlet pipeline 18 via a pipeline equipped with a switching valve B24. The secondary steam outlet of the first-effect evaporator 20 is connected to the inlet of the second hydrocyclone 26 via a pipeline equipped with a switching valve C25. The compressed steam pipeline 17 is connected to the inlet of the second hydrocyclone 26 via a pipeline equipped with a switching valve A23. The outlet of the second hydrocyclone 26 is connected to the inlet of the second-effect evaporator 21, and the outlet of the second hydrocyclone 26 is connected to the inlet of the second-effect transfer pump 43. The inlet of the second-effect evaporator 21 is connected to the compressed steam pipeline 17, and the secondary steam outlet of the second-effect evaporator 21 is connected to the compressed steam inlet pipeline 18. The inlet of the third-effect evaporator 22 is connected to the compressed steam pipeline 17, and the secondary steam outlet of the third-effect evaporator 22 is connected to the compressed steam inlet pipeline 18. The compressed steam inlet pipeline 18 is connected to the inlet of the first hydrocyclone 19, the outlet of the first hydrocyclone 19 is connected to the inlet of the steam compressor 16, and the outlet of the first hydrocyclone 19 is connected to the feed inlet of the second-effect transfer pump 43. The compressed steam pipeline 17 is connected to the steam source 13 through a live steam pipeline. A steam valve 61 and a steam flow meter are installed on the live steam pipeline. The first-effect evaporator 20 is equipped with a first-effect pressure sensor 60 to monitor the pressure inside the first-effect evaporator 20. The first-effect pressure sensor 60 is electrically connected to the steam valve 61, and the steam valve 61 is adjusted by controlling the pressure inside the first-effect evaporator 20.

[0033] The non-condensable gas outlets of the first-effect evaporator 20, the second-effect evaporator 21, and the third-effect evaporator 22 are connected to a non-condensable gas pipeline. The non-condensable gas pipeline is connected to the preheating medium inlet of the second-stage preheater 11. The preheating medium outlet of the second-stage preheater 11 is connected to the air inlet of the condenser 8. The air outlet of the condenser 8 is connected to the air inlet of the vacuum pump 7. The air outlet of the vacuum pump 7 is used for venting.

[0034] The condensate outlets of the first-effect evaporator 20, the second-effect evaporator 21, the third-effect evaporator 22, and the condenser 8 are all connected to the inlet of the condensate tank 27. The outlet of the condensate tank 27 is connected to the inlet of the condensate pump 28, the outlet of the condensate pump 28 is connected to the preheating medium inlet of the first-stage preheater 6, and the preheating medium outlet of the first-stage preheater 6 is connected to the condensate drain pipe. A condensate level gauge 29 is installed on the condensate tank 27 to monitor the water level inside the condensate tank 27. A condensate drain valve 30 is installed on the outlet of the condensate pump 28. The condensate level gauge 29 is electrically connected to the condensate drain valve 30. The condensate drain valve 30 is adjusted by controlling the water level inside the condensate tank 27. The air outlet of the condensate tank 27 is connected to the air inlet of the condenser 8. The outlet of the condensate pump 28 is connected to the outlet of the steam compressor 16 via the compressor flushing pipeline 31. The compressor flushing pipeline 31 is equipped with a compressor flushing valve 32. The compressed steam pipeline 17 is equipped with a compressed steam temperature sensor 35 for monitoring the compressed steam temperature. The compressed steam temperature sensor 35 is electrically connected to the compressor flushing valve 32. The compressor flushing valve 32 is adjusted by controlling the compressed steam temperature. The outlet of the steam compressor 16 is connected to the inlet of the compressor drain tank 33. The outlet of the compressor drain tank 33 is connected to the inlet of the compressor drain pump 34. The outlet of the compressor drain pump 34 is connected to the inlet of the condensate tank 27.

[0035] The inlet of the feed pump 2 is connected to the cleaning water tank 4 via a cleaning pipeline, and a cleaning valve 5 is installed on the cleaning pipeline. The flushing port of the first-effect evaporator 20 is connected to the flushing tank 10 via a first-effect flushing pipeline, and a first-effect flushing valve 51 is installed on the first-effect flushing pipeline. The flushing port of the second-effect evaporator 21 is connected to the flushing tank 10 via a second-effect flushing pipeline, and a second-effect flushing valve 52 is installed on the second-effect flushing pipeline. The flushing port of the third-effect evaporator 22 is connected to the flushing tank 10 via a third-effect flushing pipeline, and a third-effect flushing valve 53 is installed on the third-effect flushing pipeline. The discharge port of the first-effect evaporator 20 is connected to the main drain pipe 59 via a first-effect drain pipe, and a first-effect drain valve 54 is installed on the first-effect drain pipe. The outlet of the double-effect evaporator 21 is connected to the main drain pipe 59 through the double-effect drain pipe, and the double-effect drain pipe is equipped with a double-effect drain valve 55. The outlet of the triple-effect evaporator 22 is connected to the main drain pipe 59 through the triple-effect drain pipe, and the triple-effect drain pipe is equipped with a triple-effect drain valve 56. The outlet of the condensate tank 27 is connected to the main drain pipe 59 through the condensate drain pipe, and the condensate drain pipe is equipped with a condensate drain valve 57. The outlet of the feed balance tank 1 is connected to the main drain pipe 59 through the feed drain pipe, and the feed drain pipe is equipped with a feed drain valve 58.

[0036] The inlet of the first-effect conveying pump 39 is connected to the hot cleaning water tank 62 through a first-effect hot cleaning pipeline, and a first-effect hot cleaning valve 63 is installed on the first-effect hot cleaning pipeline. The inlet of the second-effect conveying pump 43 is connected to the hot cleaning water tank 62 through a second-effect hot cleaning pipeline, and a second-effect hot cleaning valve 64 is installed on the second-effect hot cleaning pipeline. The inlet of the discharge pump 47 is connected to the hot cleaning water tank 62 through a third-effect hot cleaning pipeline, and a third-effect hot cleaning valve 65 is installed on the third-effect hot cleaning pipeline. The inlet of the feed pump 2 is connected to the hot cleaning water tank 62 through a feed hot cleaning pipeline, and a feed hot cleaning valve 66 is installed on the feed hot cleaning pipeline.

[0037] like Figure 2 As shown, the first-effect evaporator 20, the second-effect evaporator 21, and the third-effect evaporator 22 are all centrally circulating tube evaporators, including a tank body 101, an intermediate tube 102, a heating tube 103, an upper baffle 104, and a lower baffle 105. The lower part of the tank body 101 is provided with the upper baffle 104 and the lower baffle 105 arranged vertically. The intermediate tube 102 is located at the center of the lower part of the tank body 101. The upper baffle 104 and the lower baffle 105 are fixedly connected to the upper and lower ends of the intermediate tube 102, respectively. The upper baffle 104, the lower baffle 105, and the intermediate tube 102 divide the inner cavity of the tank body 101 into a separation chamber 106, a heating chamber 107, and a circulation chamber 108. The separation chamber 106 is the inner cavity above the upper baffle 104 within the tank body 101, and the heating chamber 107 is located in the lower part of the tank body 101. The cavity is formed by the inner wall, the outer wall of the intermediate pipe 102, the upper partition 104, and the lower partition 105. The circulation chamber 108 is the inner cavity of the intermediate pipe 102 and the inner cavity of the tank 101 below the lower partition 105. The heating chamber 107 is provided with a heating pipe 103. The upper and lower ends of the heating pipe 103 are fixedly connected to the upper partition 104 and the lower partition 105, respectively. The heating pipe 103 connects the separation chamber 106 above the upper partition 104 of the tank 101 with the circulation chamber 108 below the lower partition 105. The upper end of the separation chamber 106 is provided with a secondary steam outlet. The lower part of the separation chamber 106 is provided with a feed inlet and a return outlet. The heating chamber 107 is provided with an air inlet, a condensate outlet, and a non-condensable gas outlet that communicate with the heating chamber 107. The lower end of the tank 101 is provided with a discharge outlet. A stirring device is provided on the tank body 101. The stirring device includes stirring blades 111, stirring shaft 110, and stirring power device 109. The stirring blades 111 are located in the lower part of the intermediate tube 102. The stirring shaft 110 enters the tank body 101 from the lower end, and its upper end is connected to the stirring blades 111 located in the intermediate tube 102. The lower end of the stirring shaft 110 is located on the outer side of the lower end of the tank body 101 and is connected to the output shaft of the stirring power device 109. A scraper 112 is provided in the circulation chamber 108 below the lower partition 105 in the tank body 101. The scraper 112 is fixedly connected to the stirring shaft 110 and is in contact with the inner bottom surface of the tank body 101. Example

[0038] With switching valve C25 closed and switching valves A23 and B24 opened, the secondary steam outlet of the first-effect evaporator 20 is connected to the compression inlet pipe 18. At this time, the first-effect evaporator 20, the second-effect evaporator 21, and the third-effect evaporator 22 are connected in parallel in the direction of steam flow.

[0039] When the system is initially started, since there is no material entering the first-effect evaporator 20, the second-effect evaporator 21, and the third-effect evaporator 22, no secondary steam will be generated, and there is no condensate, the steam compressor 16 cannot provide high-temperature compressed steam. At this time, the first-effect evaporator 20, the second-effect evaporator 21, and the third-effect evaporator 22 use the live steam provided by the steam source 13 as the heat source.

[0040] Start feed pump 2, open material valve 3, open first-effect feed valve 37, open steam valve 61, open steam preheating valve 15, start vacuum pump 7, vacuum pump 7 extracts negative pressure from the system, and the low-concentration material in feed balance tank 1 enters primary preheater 6 under the action of feed pump 2. Primary preheater 6 preheats the material using the heat from condensate. Since the system is initially started, no condensate is generated, therefore, primary preheater 6 cannot preheat the material at this time. The material flowing out of the outlet of primary preheater 6 enters secondary preheater 11, which preheats the material using the heat from non-condensable gases. Since the system is initially started, no non-condensable gases are generated, therefore, secondary preheater 11 cannot preheat the material at this time. The material flowing out of the outlet of secondary preheater 11 enters secondary preheater 11. Secondary preheater 11 preheats the material using the heat from non-condensable gases. The material enters the three-stage preheater 12. The live steam provided by the steam source 13 enters the three-stage preheater 12 through the pipeline. The material is preheated in the three-stage preheater 12 using live steam to reach the feed temperature. The preheated material enters the first-effect evaporator 20. The live steam provided by the steam source 13 enters the compressed steam pipeline 17 through the live steam pipeline, and then enters the first-effect evaporator 20, the second-effect evaporator 21, and the third-effect evaporator 22 through the compressed steam pipeline 17. The material is first evaporated and concentrated in the first-effect evaporator 20, then enters the second-effect evaporator 21 to be heated and evaporated and concentrated by live steam, and finally enters the third-effect evaporator 22 to be heated and evaporated and concentrated by live steam. Finally, under the action of the discharge pump 47, it is discharged through the third-effect discharge pipeline and then into the discharge pipeline. The secondary steam generated by the first-effect evaporator 20, the second-effect evaporator 21, and the third-effect evaporator 22 enters the compression inlet pipe 18, and then enters the steam compressor 16 along the compression inlet pipe 18. After being compressed, pressurized, and heated by the steam compressor 16, the secondary steam re-enters the compression steam pipe 17, and then enters the first-effect evaporator 20, the second-effect evaporator 21, and the third-effect evaporator 22 along the compression steam pipe 17, serving as a heat source to heat the material and cause the material to evaporate and concentrate.

[0041] Once the system stabilizes, the high-temperature compressed steam provided by the steam compressor 16 is sufficient to meet the material evaporation requirements. Live steam is used only as supplementary steam. The low-concentration material in the feed balance tank 1 enters the primary preheater 6 under the action of the feed pump 2. The condensate in the condensate tank 27 also enters the primary preheater 6. In the primary preheater 6, the condensate heats the material, thus preheating it for the first time. The preheated material then enters the secondary preheater 11. Non-condensable gas enters the secondary preheater 11 along the non-condensable gas pipeline. In the secondary preheater 11, the non-condensable gas heats the material. The material is preheated a second time, and then enters the tertiary preheater 12. Live steam supplied by steam source 13 enters the tertiary preheater 12, where it heats the material for a third time. After three preheatings, the material enters the first-effect evaporator 20. High-temperature compressed steam from the outlet of steam compressor 16 flows along compressed steam pipeline 17 into the first-effect evaporator 20. The material entering the first-effect evaporator 20 is heated, evaporated, and concentrated by the high-temperature compressed steam, resulting in a first increase in material concentration. Steam condenses into condensate, which enters a condensate storage tank. Secondary steam generated by the first-effect evaporator 20 enters the compressed air inlet pipe 18, opening the second-effect feed valve 42. The material, with increased concentration, enters the second-effect evaporator 21 along the second-effect feed pipe under the action of the first-effect conveying pump 39. Inside the second-effect evaporator 21, the material is reheated and concentrated by the high-temperature compressed steam entering the evaporator 21, resulting in a second increase in material concentration. The high-temperature compressed steam condenses into condensate, which enters a condensate storage tank. Secondary steam generated by the second-effect evaporator 21 then enters the compressed air inlet pipe. Pipeline 18 opens the triple-effect feed valve 45. The material, after a second concentration increase, enters the triple-effect evaporator 22 along the triple-effect feed pipeline under the action of the second-effect conveying pump 43. Inside the triple-effect evaporator 22, the material is heated, evaporated, and concentrated for the third time by the high-temperature compressed steam entering the triple-effect evaporator 22, resulting in a third concentration increase. The high-temperature compressed steam condenses into condensate, which enters the condensate storage tank. The secondary steam generated by the triple-effect evaporator 22 enters the compressed air inlet pipeline 18. The material, after a third concentration increase, enters the triple-effect discharge pipeline under the action of the discharge pump 47.

[0042] The discharge mass density meter 49 on the triple-effect discharge pipeline monitors the concentration of the material after three concentrations. When the material concentration meets the set discharge concentration, the discharge mass density meter 49 controls the discharge valve 50 to open, and the material is discharged along the discharge pipeline. When the material concentration does not reach the set discharge concentration, the material re-enters the triple-effect evaporator 22 for evaporation and concentration along the triple-effect return pipeline. After discharge, the material level in the triple-effect evaporator 22 drops, and the triple-effect level gauge controls the triple-effect feed valve 45 to open. The material in the second-effect evaporator 21 enters the triple-effect evaporator 22 along the triple-effect feed pipeline under the action of the second-effect transfer pump 43. The material level in the second-effect evaporator 21 decreases, and the second-effect level gauge controls the second-effect feed valve 42 to open. The material in the first-effect evaporator 20 enters the second-effect evaporator 21 along the second-effect feed pipeline under the action of the first-effect transfer pump 39. The material level in the first-effect evaporator 20 decreases, and the first-effect level gauge controls the first-effect feed valve 37 to open, and the feed pump 2 delivers material to the system. The interlocking of the level gauge and the feed valve ensures a constant liquid level within the system, maintaining system stability.

[0043] When the system experiences slight scaling or reaches the scheduled cleaning cycle, close the material valve 3 and the feed pump 2. After the discharge pump 47 stops discharging material, close the steam compressor 16, steam valve 61, and steam preheating valve 15 to stop supplying steam to the system. Open the cleaning valve 5, and the cleaning water in the cleaning water tank 4 enters the system under the action of the feed pump 2 to clean the pipes and evaporators in the system. Open the first-effect drain valve 54, the second-effect drain valve 55, the third-effect drain valve 56, the condensate drain valve 57, and the feed drain valve 58. The cleaning wastewater is discharged along the main sewage pipe and can enter the sewage treatment system. After cleaning, open the first-effect flushing valve 51, the second-effect flushing valve 52, and the third-effect flushing valve 53. The flushing water in the flushing tank 10 enters the first-effect evaporator 20, the second-effect evaporator 21, and the third-effect evaporator 22 respectively. Use the flushing water in the flushing tank 10 to flush the evaporators. The flushing water is discharged along the main sewage pipe 59. When hot water is needed to clean the system, open the first-effect hot cleaning valve 63, the second-effect hot cleaning valve 64, the third-effect hot cleaning valve 65, and the feed hot cleaning valve 66. The hot cleaning water in the hot cleaning water tank 62 enters the system and is used to clean the system. The cleaning wastewater is discharged along the sewage main pipe.

[0044] In this embodiment, a return gas pressure sensor 67 is installed on the compressed air intake pipe 18 to monitor its internal pressure. The pipe connecting the outlet of the condenser 8 and the inlet of the vacuum pump 7 is connected to a pressure regulating pipe, which is open to the atmosphere. A pressure regulating valve 9 is installed on the pressure regulating pipe, and the return gas pressure sensor 67 is electrically connected to the pressure regulating valve 9. The pressure regulating valve 9 is adjusted by controlling the pressure inside the compressed air intake pipe 18. The return gas pressure sensor 67 monitors the pressure inside the compressed air intake pipe 18, which reflects the vacuum level in the system. When the pressure is lower than the set value, the pressure regulating valve 9 is opened, and outside air enters the system through the pressure regulating pipe, increasing the system pressure and thus maintaining a stable system pressure. Example

[0045] Repeat Example 1, with the following differences: switch valve C25 is opened, switch valves A23 and B24 are closed, the secondary steam outlet of the first-effect evaporator 20 connects with the second hydrocyclone separator 26, and then enters the second-effect evaporator 21. At this time, the second-effect evaporator 21 uses the secondary steam flowing out of the first-effect evaporator 20 as a heat source to heat the material and evaporate and concentrate the material. At this time, the first-effect evaporator 20 and the second-effect evaporator 21 are connected in series to form a double-effect evaporator, and the double-effect evaporator is connected in parallel with the third-effect evaporator 22 to form a single-effect plus double-effect evaporation system.

[0046] It should be noted that the above-described embodiments are illustrative of the technical solutions of the present invention and not limiting thereof. Equivalent substitutions or other modifications made by those skilled in the art based on the prior art, as long as they do not exceed the concept and scope of the technical solutions of the present invention, should be included within the scope of the claims of the present invention.

Claims

1. An MVR evaporation concentration and crystallization system, characterized in that: The system includes a first-effect evaporator (20), a second-effect evaporator (21), and a third-effect evaporator (22) connected in series along the material flow direction. The inlet of the first-effect evaporator (20) is connected to the outlet of the feed pump (2), and the inlet of the feed pump (2) is connected to the feed balance tank (1). The outlet of the third-effect evaporator (22) is connected to the inlet of the discharge pump (47), and the outlet of the discharge pump (47) is connected to the third-effect discharge pipeline. The air inlet of the first-effect evaporator (20), the air inlet of the second-effect evaporator (21), and the air inlet of the third-effect evaporator (22) are all connected to the compressed steam pipeline (17). The compressed steam pipeline (17) is connected to the outlet of the steam compressor (16). A switching valve A (23) is installed on the pipeline connecting the air inlet of the second-effect evaporator (21) and the compressed steam pipeline (17). The secondary steam outlet of the first-effect evaporator (20) is connected to the compression inlet pipe (18) and the inlet of the second-effect evaporator (21). A switching valve B (24) is installed on the pipe connecting the secondary steam outlet of the first-effect evaporator (20) and the compression inlet pipe (18). A switching valve C (25) is installed on the pipe connecting the secondary steam outlet of the first-effect evaporator (20) and the inlet of the second-effect evaporator (21). The secondary steam outlets of the second-effect evaporator (21) and the third-effect evaporator (22) are both connected to the compression inlet pipe (18). The compression inlet pipe (18) is connected to the inlet of the steam compressor (16). The compressed steam pipeline (17) is connected to the steam source (13) through the live steam pipeline. The non-condensable gas outlets of the first-effect evaporator (20), the second-effect evaporator (21), and the third-effect evaporator (22) are connected to a non-condensable gas pipeline. The non-condensable gas pipeline is connected to the inlet of the condenser (8). The outlet of the condenser (8) is connected to the inlet of the vacuum pump (7). The outlet of the vacuum pump (7) is vented.

2. The MVR evaporation concentration and crystallization system according to claim 1, characterized in that: The compressed air inlet pipe (18) is connected to the air inlet of the first hydrocyclone (19), the air outlet of the first hydrocyclone (19) is connected to the air inlet of the steam compressor (16), and the liquid outlet of the first hydrocyclone (19) is connected to the feed inlet of the triple-effect evaporator (22).

3. The MVR evaporation concentration and crystallization system according to claim 1, characterized in that: The inlet of the second-effect evaporator (21) is connected to the outlet of the second hydrocyclone (26), the inlet of the second hydrocyclone (26) is connected to the secondary steam outlet of the first-effect evaporator (20) and the compressed steam pipeline (17), the switching valve A (23) is installed on the pipeline connecting the inlet of the second hydrocyclone (26) and the compressed steam pipeline (17), the switching valve C (25) is installed on the pipeline connecting the secondary steam outlet of the first-effect evaporator (20) and the inlet of the second hydrocyclone (26), and the outlet of the second hydrocyclone (26) is connected to the feed inlet of the third-effect evaporator (22).

4. The MVR evaporation concentration and crystallization system according to claim 1, characterized in that: The condensate outlets of the first-effect evaporator (20), the second-effect evaporator (21), the third-effect evaporator (22), and the condensate outlet of the condenser (8) are all connected to the inlet of the condensate tank (27). The outlet of the condensate tank (27) is connected to the inlet of the condensate pump (28), and the outlet of the condensate pump (28) drains water. A condensate level gauge (29) is installed on the condensate tank (27) to monitor the water level inside the condensate tank (27). A condensate drain valve (30) is installed on the outlet of the condensate pump (28). The condensate level gauge (29) is electrically connected to the condensate drain valve (30). The condensate drain valve (30) is adjusted by controlling the water level inside the condensate tank (27). The air outlet of the condensate tank (27) is connected to the air inlet of the condenser (8).

5. The MVR evaporation concentration and crystallization system according to claim 4, characterized in that: A preheating system is provided between the outlet of the feed pump (2) and the inlet of the first-effect evaporator (20). The preheating system includes a first-stage preheater (6), a second-stage preheater (11), and a third-stage preheater (12) connected in series along the material flow direction. The inlet of the first-stage preheater (6) is connected to the outlet of the feed pump (2), and the outlet of the third-stage preheater (12) is connected to the inlet of the first-effect evaporator (20). The preheating medium inlet of the first-stage preheater (6) is connected to the outlet of the condensate pump (28), and the preheating medium outlet of the first-stage preheater (6) is connected to the condensate drain pipe. The preheating medium inlet of the secondary preheater (11) is connected to the non-condensable gas pipeline, and the preheating medium outlet of the secondary preheater (11) is connected to the air inlet of the condenser (8). The preheating medium inlet of the tertiary preheater (12) is connected to the live steam pipeline through the steam preheating pipeline (36). The condensate outlet of the tertiary preheater (12) and the condensate outlet of the secondary preheater (11) are both connected to the water inlet of the condensate tank (27).

6. The MVR evaporation concentration and crystallization system according to claim 1, characterized in that: The triple-effect discharge pipeline is connected to the return port of the triple-effect evaporator (22) through the triple-effect return pipeline. A triple-effect return valve (48) is installed on the triple-effect return pipeline. The triple-effect discharge pipeline is connected to the discharge pipeline. A discharge valve (50) and a discharge flow meter are installed on the discharge pipeline. A discharge mass density meter (49) for monitoring the discharge concentration is installed on the triple-effect discharge pipeline. The discharge mass density meter (49) is electrically connected to the discharge valve (50). The discharge valve (50) is adjusted by controlling the discharge concentration.

7. The MVR evaporation concentration and crystallization system according to claim 1, characterized in that: The feed pump (2) is equipped with a first-effect feed valve (37) at its outlet. The first-effect evaporator (20) is equipped with a first-effect level gauge (38) to monitor the material level inside. The first-effect level gauge (38) is electrically connected to the first-effect feed valve (37). The first-effect feed valve (37) is adjusted by controlling the material level inside the first-effect evaporator (20). The outlet of the first-effect evaporator (20) is connected to the inlet of the first-effect conveying pump (39). The outlet of the first-effect conveying pump (39) is connected to the return port of the first-effect evaporator (20) through the first-effect return pipeline. A first-effect return valve (40) is installed on the first-effect return pipeline. The outlet of the first-effect conveying pump (39) is connected to the inlet of the second-effect evaporator (21) through the second-effect inlet pipeline. A second-effect inlet valve (42) is installed on the second-effect evaporator (21). A second-effect level gauge (41) is installed on the second-effect evaporator (21) to monitor the material level inside. The second-effect level gauge (41) is electrically connected to the second-effect inlet valve (42). The second-effect inlet valve (42) is adjusted by controlling the material level inside the second-effect evaporator (21). The outlet of the double-effect evaporator (21) is connected to the inlet of the double-effect conveying pump (43). The outlet of the double-effect conveying pump (43) is connected to the return port of the double-effect evaporator (21) through the double-effect return pipeline. A double-effect return valve (44) is installed on the double-effect return pipeline. The outlet of the double-effect conveying pump (43) is connected to the inlet of the triple-effect evaporator (22) through the triple-effect feed pipeline. A triple-effect feed valve (45) is installed on the triple-effect evaporator (22). A triple-effect level gauge (46) is installed on the triple-effect evaporator (22) to monitor the material level inside. The triple-effect level gauge (46) is electrically connected to the triple-effect feed valve (45). The triple-effect feed valve (45) is adjusted by controlling the material level inside the triple-effect evaporator (22).

8. The MVR evaporation concentration and crystallization system according to claim 1, characterized in that: The inlet of the feed pump (2) is connected to the feed balance tank (1) through a material pipeline, and a material valve (3) is provided on the material pipeline. The inlet of the feed pump (2) is connected to the cleaning water tank (4) through a cleaning pipeline, and a cleaning valve (5) is provided on the cleaning pipeline.

9. The MVR evaporation concentration and crystallization system according to claim 7, characterized in that: The inlet of the first-effect conveying pump (39) is connected to the hot cleaning water tank (62) through the first-effect hot cleaning pipeline. A first-effect hot cleaning valve (63) is installed on the first-effect hot cleaning pipeline. The inlet of the second-effect conveying pump (43) is connected to the hot cleaning water tank (62) through the second-effect hot cleaning pipeline. A second-effect hot cleaning valve (64) is installed on the second-effect hot cleaning pipeline. The inlet of the discharge pump (47) is connected to the hot cleaning water tank (62) through the third-effect hot cleaning pipeline. A third-effect hot cleaning valve (65) is installed on the third-effect hot cleaning pipeline. The inlet of the feed pump (2) is connected to the hot cleaning water tank (62) through the feed hot cleaning pipeline. A feed hot cleaning valve (66) is installed on the feed hot cleaning pipeline.

10. The MVR evaporation concentration and crystallization system according to claim 4 or 5, characterized in that: The flushing port of the first-effect evaporator (20) is connected to the flushing tank (10) through the first-effect flushing pipeline, and a first-effect flushing valve (51) is installed on the first-effect flushing pipeline. The flushing port of the second-effect evaporator (21) is connected to the flushing tank (10) through the second-effect flushing pipeline, and a second-effect flushing valve (52) is installed on the second-effect flushing pipeline. The flushing port of the third-effect evaporator (22) is connected to the flushing tank (10) through the third-effect flushing pipeline, and a third-effect flushing valve (53) is installed on the third-effect flushing pipeline. The discharge port of the first-effect evaporator (20) is connected to the main drain pipe (59) through the first-effect drain pipe, and a first-effect drain valve (54) is installed on the first-effect drain pipe. The outlet of the double-effect evaporator (21) is connected to the main drain pipe (59) through the double-effect drain pipe. The double-effect drain pipe is equipped with a double-effect drain valve (55). The outlet of the triple-effect evaporator (22) is connected to the main drain pipe (59) through the triple-effect drain pipe. The triple-effect drain pipe is equipped with a triple-effect drain valve (56). The outlet of the condensate tank (27) is connected to the main drain pipe (59) through the condensate drain pipe. The condensate drain pipe is equipped with a condensate drain valve (57). The outlet of the feed balance tank (1) is connected to the main drain pipe (59) through the feed drain pipe. The feed drain pipe is equipped with a feed drain valve (58).

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