A drying crystallization system and control method

Abstract

The present application relates to the technical field of evaporator, particularly to a drying crystallization system and a control method, comprising an evaporator, the evaporator discharges condensate through a heat exchange channel, the condensate enters a cooling tank through a condensing tank and a metering tank, a plurality of control valves are used to control the flow between the condensing tank and the metering tank, the flow between the metering tank and the cooling tank, and the communication between the metering tank and compressed gas, and a plurality of liquid level sensors are used to detect the liquid level of the condensing tank and the metering tank respectively. The present application is provided with a condensing tank, a metering tank, a cooling tank and a liquid jet pump, the condensate is used to cool the compressor through the liquid jet pump, thereby saving a certain amount of water resources, the excess condensate enters the cooling tank through the condensing tank and the metering tank, and the excess condensate is used to preheat the raw liquid, thereby saving a large amount of energy.

Description

Technical Field

[0001] This invention relates to the field of evaporator technology, and in particular to a drying and crystallization system and control method. Background Technology

[0002] In current evaporation crystallization systems used for treating high-salt, high-concentration mother liquor or industrial wastewater, the condensate produced by the evaporator is typically discharged directly or transported to subsequent processes via simple pipelines. The significant amount of sensible heat carried by the condensate is not effectively utilized, and direct discharge results in substantial energy waste, increasing the additional energy consumption required for preheating the raw liquid. Furthermore, existing drying and crystallization systems cannot dynamically adjust the utilization of condensate based on its discharge. Summary of the Invention

[0003] In this section, as well as in the abstract and title of this application, some simplifications or omissions may be made to avoid obscuring the purpose of this section, the abstract, and the title of this application, and such simplifications or omissions shall not be used to limit the scope of the invention.

[0004] To address the shortcomings of existing technologies, one objective of this invention is to provide a drying and crystallization system.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a drying crystallization system, comprising, An evaporator that discharges condensate through a heat exchange channel, the condensate passing through a condensation tank and a metering tank into a cooling tank; A control valve, wherein several control valves are provided, and the control valves are provided between the condenser tank and the metering tank, between the metering tank and the cooling tank, and at the air inlet of the metering tank; A liquid level sensor, wherein several liquid level sensors are provided, and the liquid level sensors are respectively installed in the detection condensate tank and the metering tank; A control device receives a signal from the liquid level sensor and controls the control valve so that when the liquid in the metering tank reaches a high level, it is discharged to a cooling tank to heat the original liquid.

[0006] In a preferred embodiment of the drying and crystallization system of the present invention, the control valve includes a first valve, a second valve, and a third valve. The first valve is located at the liquid outlet of the condenser, the second valve is located at the air inlet of the metering tank, and the third valve is located at the liquid outlet of the metering tank.

[0007] In a preferred embodiment of the drying and crystallization system of the present invention, the liquid level sensor includes a high liquid level sensor and a low liquid level sensor. The high liquid level sensor is disposed above the inner cavity of the condenser and the metering tank, and the low liquid level sensor is disposed below the inner cavity of the metering tank. The height of the high liquid level sensor in the condenser is lower than the height of the high liquid level sensor in the metering tank.

[0008] In a preferred embodiment of the drying and crystallization system of the present invention, the liquid outlet of the condenser is connected to the compressor via a liquid injection pump.

[0009] In a preferred embodiment of the drying and crystallization system of the present invention, the air inlet of the compressor is connected to a steam pipe, and the steam pipe is connected to the steam outlet of the evaporator.

[0010] In a preferred embodiment of the drying and crystallization system of the present invention, one end of the heat exchange channel is connected to the steam outlet via a circulation pipe, and a circulation valve is provided on the circulation pipe.

[0011] In a preferred embodiment of the drying and crystallization system of the present invention, a temperature sensor is provided on the outlet of the compressor, the temperature sensor is electrically connected to the control device, and the circulation valve is electrically connected to the control device.

[0012] This invention proposes a control method for a drying and crystallization system, comprising: During cold start, soft water is added to the condensate tank until the liquid level in the condensate tank reaches the high level sensor. Then, the spray pump is started to extract the soft water from the condensate tank, completing the cold start of the spray pump.

[0013] As a preferred embodiment of the control method of the drying and crystallization system of the present invention, during cold start, when the temperature sensor detects that the temperature of the compressor outlet is less than the set value Tset, the temperature sensor sends a first signal, the control device receives the first signal and opens the self-circulation valve, so that the steam pipe, heat exchange channel and circulation pipe form a closed loop. Then the compressor is started to circulate and compress the initial gas in the evaporation chamber in the closed loop until the temperature of the circulating gas measured by the temperature sensor reaches the set value Tset. When the temperature of the circulating gas is ≥ Tset, the temperature sensor sends a second signal. The control device receives the second signal and closes the self-circulation valve, so that the steam produced in the heat exchange channel flows into the condenser and starts to circulate.

[0014] As a preferred embodiment of the control method for the drying and crystallization system described in this invention, during the circulation operation, steam condenses in the heat exchange channel to form condensate. Condensate enters the condensate tank, and the first valve is in the normally open state. The condensate in the condensate tank enters the metering tank through the first valve. When the high liquid level sensor in the metering tank detects that the liquid level in the metering tank has reached the high liquid level, the high liquid level sensor in the metering tank sends a third signal. The control device receives the third signal and closes the first valve, opens the second valve and the third valve, and the compressed gas discharges the condensate in the metering tank into the cooling tank. When the low liquid level sensor in the metering tank detects that the liquid level in the metering tank has reached a low level, the low liquid level sensor in the metering tank sends a fourth signal. The control device receives the fourth signal and opens the first valve, closes the second valve and the third valve, so that the condensate in the cooling tank can re-enter the metering tank.

[0015] As a preferred embodiment of the control method of the drying and crystallization system of the present invention, the condensate water exchanges heat with the raw liquid to be treated in a countercurrent manner in the cooling tank, so that the temperature of the raw liquid is raised from T0 to T1. When the evaporator needs to be replenished with raw liquid, the preheated raw liquid in the cooling tank is added to the evaporator.

[0016] As a preferred embodiment of the control method for the drying and crystallization system described in this invention, during cyclic operation, the compressor draws in steam through a steam pipe and compresses and heats it to the operating temperature; The compressed high-temperature steam returns to the heat exchange channel as a heat source to maintain the heat required for the evaporation of the original liquid.

[0017] The advantages of the drying and crystallization system of the present invention are as follows: By setting up a condenser, a metering tank, a cooling tank and a liquid injection pump, the condensate is used to dissipate heat from the compressor through the liquid injection pump, which saves a certain amount of water resources. The excess condensate enters the cooling tank through the condenser and metering tank, and the excess condensate is used to preheat the raw liquid, which saves a lot of energy. This invention automates the preheating of excess condensate by setting up a control device to store excess condensate and automatically use the stored condensate to preheat the raw liquid, thereby achieving automation of preheating using excess condensate. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram showing the connection between multiple control valves and control devices of the present invention.

[0020] Figure 2 This is a schematic diagram showing the connection between the circulation valve and the control device of the present invention.

[0021] Figure 3This is a schematic diagram showing the connection between the evaporator and the condenser of the present invention.

[0022] Figure 4 This is a schematic diagram showing the connection between the metering tank and the cooling tank of the present invention. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0024] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.

[0025] Reference Figure 1 This embodiment provides a drying and crystallization system, including an evaporator 100, a heat exchange channel 101, a condenser 201, a metering tank 202, a cooling tank 203, multiple control valves 204, multiple liquid level sensors 205, and a control device 300.

[0026] Several control valves 204 are provided, and the control valves 204 are provided between the condenser tank 201 and the metering tank 202, between the metering tank 202 and the cooling tank 203, and at the air inlet of the metering tank 202. Several level sensors 205 are provided, and the level sensors 205 are respectively provided in the condenser tank 201 and the metering tank 202.

[0027] In this system, the evaporator 100 discharges condensate through the heat exchange channel 101, and the condensate flows through the condenser tank 201 and the metering tank 202 into the cooling tank 203. Multiple control valves 204 are used to control the flow between the condenser tank 201 and the metering tank 202, the flow between the metering tank 202 and the cooling tank 203, and the connection between the metering tank 202 and the compressed gas. Multiple level sensors 205 are used to detect the liquid levels in the condenser tank 201 and the metering tank 202. The control device 300 receives signals from the multiple level sensors 205 and controls the multiple control valves 204 to discharge the liquid in the metering tank 202 to the cooling tank 203 to heat the original liquid when the liquid reaches a high level.

[0028] During use, steam is condensed into condensate when it passes through heat exchange channel 101. The condensate is discharged into condenser tank 201 through heat exchange channel 101. Multiple control valves 204 control the flow between condenser tank 201 and metering tank 202. Therefore, the condensate in condenser tank 201 can enter metering tank 202. When multiple level sensors 205 detect that the liquid level in metering tank 202 has reached a high level, control device 300 controls multiple control valves 204 to close the connection between condenser tank 201 and metering tank 202, connect compressed gas to metering tank 202, and connect metering tank 202 to cooling tank 203. The pressure of the compressed gas causes the liquid in metering tank 202 to be discharged into cooling tank 203, preheating the original liquid in cooling tank 203.

[0029] Reference Figure 1 , Figure 3 and Figure 4 When the level sensor 205 detects that the level of the metering tank 202 has reached a low level, the control device 300 connects the condenser tank 201 and the metering tank 202 through the control valve 204, closes the connection between the compressed gas and the metering tank 202, and closes the connection between the metering tank 202 and the cooling tank 203. The condensate in the condenser tank 201 flows back into the metering tank 202 and enters the next cycle.

[0030] The control valve 204 includes a first valve 204a, a second valve 204b, and a third valve 204c. The first valve 204a is located at the liquid outlet of the condenser 201, the second valve 204b is located at the air inlet of the metering tank 202, and the third valve 204c is located at the liquid outlet of the metering tank 202.

[0031] The condenser 201 and the metering tank 202 are connected by a connecting pipe. The first valve 204a is installed on the connecting pipe between the condenser 201 and the metering tank 202 to control the flow of liquid in the condenser 201 into the metering tank 202. The first valve 204a is in the normally open state, so the liquid levels in the condenser 201 and the metering tank 202 are the same.

[0032] The metering tank 202 is connected to the liquid inlet pipe of the condenser 201 via a constant pressure gas pipe. The second valve 204b is installed on the constant pressure gas pipe of the metering tank 202 to ensure that the pressure of the metering tank 202 and the condenser 201 is the same, so that the liquid in the condenser 201 can enter the metering tank 202. The second valve 204b is connected to the external compressed gas, so that the compressed gas can enter the metering tank 202.

[0033] The second valve 204b is a three-way valve. When the second valve 204b is open, compressed gas can enter the metering tank 401 through the second valve 204b. When the second valve 204b is closed, compressed gas cannot enter the metering tank 202 through the second valve 204b. At the same time, the constant pressure gas pipe is in the open state, so that the metering tank 202 maintains constant pressure.

[0034] The constant pressure gas pipe only "passes gas" and not "passes liquid". The constant pressure gas pipe is located above the interface of the condenser 201. The liquid level is always lower than the connection point of the constant pressure gas pipe. Therefore, water can only flow into the condenser 201 under the action of gravity and will not rush upward into the constant pressure gas pipe. The constant pressure gas pipe is used to connect the top of the metering tank 202 with the upstream of the condenser 201, so that the gas phase pressure of the two is always equal.

[0035] The metering tank 202 and the cooling tank 203 are connected by a connecting pipe. The third valve 204c is installed on the connecting pipe between the metering tank 202 and the cooling tank 203 to control the flow of liquid in the metering tank 202 into the cooling tank 203.

[0036] The liquid level sensor 205 includes a high liquid level sensor 205a and a low liquid level sensor 205b. The high liquid level sensor 205a is disposed above the inner cavity of the condenser tank 201 and the metering tank 202, and the low liquid level sensor 205b is disposed below the inner cavity of the metering tank 202. The height of the high liquid level sensor 205a in the condenser tank 201 is lower than the height of the high liquid level sensor 205a in the metering tank 202.

[0037] During use, when the high liquid level sensor 205a in the metering tank 202 detects that the liquid level in the metering tank 202 has reached the high liquid level, the high liquid level sensor 205a in the metering tank 202 sends a third signal. The control device 300 receives the third signal and closes the first valve 204a, opens the second valve 204b and the third valve 204c, and the compressed gas discharges the condensate in the metering tank 202 into the cooling tank 203. When the low liquid level sensor 205b in the metering tank 202 detects that the liquid level in the metering tank 202 has reached a low level, the low liquid level sensor 205b in the metering tank 202 sends a fourth signal. The control device 300 receives the fourth signal and opens the first valve 204a, closes the second valve 204b and the third valve 204c, so that the condensate in the cooling tank 203 re-enters the metering tank 202.

[0038] Reference Figure 2 and Figure 3 The outlet of the condenser 201 is connected to the compressor M1 via the liquid injection pump M4.

[0039] The high liquid level sensor 205a, installed in the condenser tank 201, ensures sufficient circulating liquid for the injection pump M4 during cold starts, guaranteeing its normal operation. During cold starts, because condensate cannot be generated in the heat exchange channel 101, insufficient condensate enters the condenser tank 201. The condenser tank 201 is connected to a soft water pipe to provide the necessary condensate for startup.

[0040] During cold start, soft water is pre-filled into the condenser tank 201 via a soft water pipe. This ensures the soft water level reaches the high-level sensor 205a within the condenser tank 201, guaranteeing sufficient liquid for the injection pump M4. The high-level sensor 205a in the condenser tank 201 is set at a lower height than the high-level sensor 205a in the metering tank 202, preventing the liquid level in the metering tank 202 from reaching the high-level sensor 205a and thus preventing liquid from draining from the metering tank 202.

[0041] In this process, the injection pump M4 directly injects soft water from the condenser tank 201 into the injection port of the compressor M1 at a low flow rate. The soft water instantly vaporizes within the working chamber of the compressor M1, carrying away the heat of compression and cooling the compressor M1. During the cycle, the condensate produced by the evaporator continuously flows into the condenser tank 201 through the recovery pipe, forming a stable water source. The injection pump M4 adjusts the flow rate according to the temperature of the compressor M1; when the temperature of the compressor M1 is higher than the target value, the injection volume is increased; when the temperature of the compressor M1 is lower than the target value, the injection volume is decreased.

[0042] Furthermore, the lubricating oil circuit outlet of compressor M1 is connected to the inlet of oil-cooled pump M2, and the outlet of oil-cooled pump M2 is connected to the lubricating oil circuit inlet of compressor M1.

[0043] The compressor M1 and the oil-cooled pump M2 form a closed-loop oil-cooling cycle. The compressor M1 is always in a constant temperature and constant lubrication state, without the need for additional external cooling water or refrigeration units, thus achieving self-circulating cooling.

[0044] The compressor M1 has a steam pipe M1a connected to its air inlet, and the steam pipe M1a is connected to the steam outlet of the evaporator 100.

[0045] The evaporator 100 is equipped with an evaporation chamber, and a heat exchange channel 101 is installed inside the evaporation chamber. Multiple discs are installed on the heat exchange channel 101. The hot steam in the heat exchange channel 101 heats the discs. The raw liquid is sprayed onto the discs, and the water in the raw liquid is evaporated into water vapor. The concentrated liquid falls to the bottom of the evaporator 100. Some of the raw liquid evaporates to form crystals that remain on the discs. The crystals are scraped off by a scraping device on the outer periphery of the discs.

[0046] The heat exchange channel 101 is rotatably mounted on the evaporator 100 and is driven to rotate by the reducer M5.

[0047] The water vapor formed by heat exchange of the raw liquid is discharged through the steam outlet.

[0048] The compressor M1 is used to compress the gas in the evaporation chamber. During cold start, the compressor M1 extracts and compresses the air in the evaporation chamber, circulating it through a closed loop formed by the steam pipe M1a, heat exchange channel 101, and circulation pipe 101a, allowing the system to reach the operating temperature without requiring additional hot steam feedstock. During evaporation operations, the compressor M1 extracts and compresses the steam in the evaporation chamber, thereby utilizing the heat of the steam.

[0049] One end of the heat exchange channel 101 is connected to the steam outlet through a circulation pipe 101a, and a circulation valve 101b is installed on the circulation pipe 101a.

[0050] During the cold start phase, the circulation pipe 101a is opened through the circulation valve 101b, and the compressor M1 compresses the air in the evaporation chamber and circulates through the steam pipe M1a, the heat exchange channel 101 and the circulation pipe 101a to form a closed loop until the air temperature reaches the preset value. Then, the circulation pipe 101a is cut off through the circulation valve 101b, and the steam generated in the evaporation chamber enters the heat exchange channel 101 through the steam pipe M1a, and enters the condenser tank 201 after condensation.

[0051] A temperature sensor M1b is installed at the outlet of the compressor M1. The temperature sensor M1b is electrically connected to the control device 300. The circulation valve 101b is also electrically connected to the control device 300.

[0052] Among them, the temperature sensor M1b is used to monitor the temperature at the outlet of the compressor M1. When the temperature of the temperature sensor M1b reaches the set value, the circulation valve 101b is closed, so that the steam pipe M1a, the heat exchange channel 101 and the condenser 201 form a loop, thereby enabling the compressor M1 to operate using steam.

[0053] Furthermore, a pressure sensor is installed at the outlet of compressor M1. The pressure sensor is used to monitor the pressure at the outlet of compressor M1. When the pressure at the outlet of compressor M1 is high, the pressure at the outlet of compressor M1 can be adjusted by adjusting the opening of the circulation valve 101b to prevent the compressor M1 from working under excessive load. At the same time, adjusting the pressure at the outlet of compressor M1 can also fine-tune the temperature at the outlet of compressor M1. Fine-tuning the exhaust temperature can adjust the heat source temperature without starting or stopping compressor M1 or adding or reducing external steam, thus avoiding local overheating and decomposition of the raw liquid or insufficient evaporation.

[0054] The evaporator 100 is equipped with a spray pipe inside, one end of which is connected to the raw liquid pipe via a liquid distribution pump M3. When the evaporator 100 needs to be replenished, the raw liquid is sprayed out through the raw liquid pipe, the liquid distribution pump M3, and the spray pipe to replenish the liquid.

[0055] Control of condensate water temperature.

[0056] The steam produced by the evaporator 100 is generally 100°C. After being compressed by the compressor M1, the temperature of the steam can be increased. The increase in steam temperature can be selected according to the power of the compressor M1. Increasing the power of the compressor M1 can increase the temperature of the steam after compression. In this embodiment, the compressor M1 can increase the temperature of the steam to 120°C. The 120°C steam produces condensate after heat exchange through the heat exchange channel 102. The temperature of the condensate can be calculated according to the thermal efficiency of the evaporator 100. In this embodiment, the temperature of the condensate is 80°C.

[0057] Next, we will analyze the energy-saving effect of preheating the raw liquid.

[0058] The initial temperature of the raw liquid is room temperature, i.e., 25℃, while the temperature of the condensate is 80℃. The temperature of the raw liquid after preheating can be calculated according to the formula for the efficiency η of the countercurrent heat exchanger.

[0059] The formula for the efficiency η of a counter-current heat exchanger is Formula 1: , in, This refers to the temperature at which the hot fluid (condensate) enters the heat exchanger. This refers to the temperature at which the cold fluid (raw liquid) enters the heat exchanger. The outlet temperature is the temperature of the cold fluid after it has been heated. The thermal efficiency of the heat exchanger represents the proportion of the actual temperature rise of the cold fluid to the theoretical maximum temperature rise.

[0060] When the cooling tank 203 is a plate or spiral plate heat exchanger, the heat exchanger efficiency is greater than 90%. According to Formula 1, the residual heat of the condensate can be used to preheat the original liquid from 25°C to 75–77°C.

[0061] When the cooling tank 203 is a shell-and-tube heat exchanger, the heat exchanger efficiency is about 80%. According to Formula 1, the residual heat of the condensate can be used to preheat the original liquid from 25°C to 70–72°C.

[0062] When the cooling tank 203 is a tube heat exchanger or a shell-and-tube heat exchanger, the heat exchanger efficiency is less than 70%. According to Formula 1, the residual heat of the condensate can be used to preheat the original liquid from 25°C to less than 65°C.

[0063] Reference Figure 1 This embodiment provides a control method for a drying and crystallization system, including: During cold start, soft water is added to the condenser tank 201 to bring the liquid level in the condenser tank 201 to the high liquid level sensor 205a. The spray pump M4 is then started to extract the soft water from the condenser tank 201, thus completing the cold start of the spray pump M4.

[0064] During cold start, when the temperature sensor M1b detects that the temperature at the outlet of the compressor M1 is less than the set value Tset, the temperature sensor M1b sends a first signal. The control device 300 receives the first signal and opens the self-circulation valve 101b, so that the steam pipe M1a, the heat exchange channel 101 and the circulation pipe 101a form a closed loop.

[0065] The compressor M1 is started to circulate and compress the initial gas in the evaporation chamber in a closed loop until the temperature of the circulating gas measured by the temperature sensor M1b reaches the set value Tset. When the temperature of the circulating gas is greater than or equal to Tset, the temperature sensor M1b sends a second signal. The control device 300 receives the second signal and closes the self-circulation valve 101b, so that the steam produced by the heat exchange channel 101 flows into the condenser 201 and starts to circulate.

[0066] During the cycle, steam condenses in the heat exchange channel 101 to form condensate.

[0067] Condensate enters the condensate tank 201. The first valve 204a is in the normally open state, and the condensate in the condensate tank 201 enters the metering tank 202 through the first valve 204a.

[0068] When the high liquid level sensor 205a in the metering tank 202 detects that the liquid level in the metering tank 202 has reached the high liquid level, the high liquid level sensor 205a in the metering tank 202 sends a third signal. The control device 300 receives the third signal and closes the first valve 204a, opens the second valve 204b and the third valve 204c, and the compressed gas discharges the condensate in the metering tank 202 into the cooling tank 203.

[0069] When the low liquid level sensor 205b in the metering tank 202 detects that the liquid level in the metering tank 202 has reached a low level, the low liquid level sensor 205b in the metering tank 202 sends a fourth signal. The control device 300 receives the fourth signal and opens the first valve 204a, closes the second valve 204b and the third valve 204c, so that the condensate in the cooling tank 203 re-enters the metering tank 202.

[0070] The condensate undergoes countercurrent heat exchange with the raw liquid to be treated in the cooling tank 203, raising the temperature of the raw liquid from T0 to T1.

[0071] When the evaporator 100 needs to be replenished with raw liquid, the preheated raw liquid in the cooling tank 203 is added to the evaporator 100.

[0072] During operation, compressor M1 draws in steam through steam pipe M1a and compresses and heats it to the operating temperature.

[0073] The compressed high-temperature steam returns to the heat exchange channel 101 as a heat source to maintain the heat required for the evaporation of the original liquid.

[0074] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A drying and crystallization system, characterized in that: include, Evaporator (100), the evaporator (100) discharges condensate through heat exchange channel (101), the condensate enters cooling tank (203) through condensate tank (201) and metering tank (202); The outlet of the condenser (201) is connected to the compressor (M1) via a liquid injection pump (M4); The compressor (M1) has a steam pipe (M1a) connected to its air inlet, and the steam pipe (M1a) is connected to the steam outlet of the evaporator (100). One end of the heat exchange channel (101) is connected to the steam outlet through a circulation pipe (101a), and a circulation valve (101b) is provided on the circulation pipe (101a). Control valve (204), wherein several control valves (204) are provided, and several control valves (204) are respectively located between the condenser (201) and the metering tank (202), between the metering tank (202) and the cooling tank (203), and at the air inlet of the metering tank (202); A liquid level sensor (205) is provided, and several liquid level sensors (205) are respectively installed in the detection condenser (201) and the metering tank (202); The control device (300) receives a signal from the liquid level sensor (205) and controls the control valve (204) so ​​that when the liquid in the metering tank (202) reaches a high liquid level, it is discharged to the cooling tank (203) to heat the original liquid. The liquid level sensor (205) includes a high liquid level sensor (205a) and a low liquid level sensor (205b). The high liquid level sensor (205a) is disposed above the inner cavity of the condenser (201) and the metering tank (202), and the low liquid level sensor (205b) is disposed below the inner cavity of the metering tank (202). The height of the high liquid level sensor (205a) in the condenser (201) is lower than the height of the high liquid level sensor (205a) in the metering tank (202).

2. The drying and crystallization system as described in claim 1, characterized in that: The control valve (204) includes a first valve (204a), a second valve (204b) and a third valve (204c). The first valve (204a) is located at the liquid outlet of the condenser (201), the second valve (204b) is located at the air inlet of the metering tank (202), and the third valve (204c) is located at the liquid outlet of the metering tank (202).

3. The drying and crystallization system as described in claim 2, characterized in that: A temperature sensor (M1b) is installed at the outlet of the compressor (M1), and the temperature sensor (M1b) is electrically connected to the control device (300). The circulation valve (101b) is also electrically connected to the control device (300).

4. A control method for the drying and crystallization system as described in claim 3, characterized in that, include, During cold start, soft water is added to the condenser tank (201) to bring the liquid level in the condenser tank (201) to the high liquid level sensor (205a). The injection pump (M4) is started to extract the soft water from the condenser tank (201). When the temperature sensor (M1b) detects that the temperature at the outlet of the compressor (M1) is less than the set value Tset, the temperature sensor (M1b) sends a first signal. The control device (300) receives the first signal and opens the self-circulation valve (101b) so that the steam pipe (M1a), the heat exchange channel (101) and the circulation pipe (101a) form a closed loop. Then the compressor (M1) is started to circulate and compress the initial gas in the evaporation chamber in the closed loop until the temperature of the circulating gas measured by the temperature sensor (M1b) reaches the set value Tset. When the temperature of the circulating gas is ≥ Tset, the temperature sensor (M1b) sends a second signal. The control device (300) receives the second signal and closes the self-circulation valve (101b), so that the steam produced by the heat exchange channel (101) flows into the condenser (201) and enters the circulation operation.

5. The control method for the drying and crystallization system as described in claim 4, characterized in that: During the circulation process, steam condenses in the heat exchange channel (101) to form condensate; Condensate enters the condensate tank (201), and the first valve (204a) is in the normally open state. The condensate in the condensate tank (201) enters the metering tank (202) through the first valve (204a). When the high liquid level sensor (205a) in the metering tank (202) detects that the liquid level in the metering tank (202) has reached the high liquid level, the high liquid level sensor (205a) in the metering tank (202) sends a third signal. The control device (300) receives the third signal and closes the first valve (204a), opens the second valve (204b) and the third valve (204c), and the compressed gas discharges the condensate in the metering tank (202) into the cooling tank (203). When the low liquid level sensor (205b) in the metering tank (202) detects that the liquid level in the metering tank (202) has reached a low level, the low liquid level sensor (205b) in the metering tank (202) sends a fourth signal. The control device (300) receives the fourth signal and opens the first valve (204a), closes the second valve (204b) and the third valve (204c), so that the condensate in the cooling tank (203) re-enters the metering tank (202).

6. The control method for the drying and crystallization system as described in claim 4 or 5, characterized in that: The condensate undergoes countercurrent heat exchange with the raw liquid to be treated in the cooling tank (203), raising the temperature of the raw liquid from T0 to T1; When the evaporator (100) needs to be replenished with raw liquid, the preheated raw liquid in the cooling tank (203) is added to the evaporator (100).

7. The control method for the drying and crystallization system as described in claim 6, characterized in that: During operation, the compressor (M1) draws in steam through the steam pipe (M1a) and compresses and heats it to the operating temperature; The compressed high-temperature steam returns to the heat exchange channel (101) as a heat source to maintain the heat required for the evaporation of the original liquid.

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