Vacuum decompression desorption system for solvent recovery and working method thereof

Abstract

The application discloses a vacuum decompression desorption system for solvent recovery and a working method thereof, wherein the system comprises: a plurality of adsorption units, the gas inlets of the plurality of adsorption units being connected with a waste gas source through a plurality of pipelines; a preheating unit, which is communicated with the adsorption units, is used for heating the gas discharged from the adsorption units and returning the heated gas to the inside of the adsorption units; a vacuum decompression unit, which is connected with the gas outlets of the adsorption units; a condensation recovery unit, which is connected with the exhaust outlets of the vacuum decompression unit, is used for liquefying and recovering the gaseous solvent after desorption and discharging; and a control unit, which is electrically connected with the adsorption units, the preheating unit, the vacuum decompression unit and the condensation recovery unit. The application solves the problems of desorption fluctuation and incomplete condensation in the prior art, and improves the overall efficiency and the automation level of the solvent recovery.

Description

Technical Field

[0001] This invention relates to the technical fields of volatile organic waste gas treatment and solvent recovery, and in particular to a vacuum decompression desorption system for solvent recovery and its working method. Background Technology

[0002] In industrial production processes such as lithium battery manufacturing, chemical processing, and coating, large quantities of waste gas containing high-boiling-point organic solvents such as NMP (N-methylpyrrolidone) are generated. To reduce environmental pollution and lower costs, such waste gas typically needs to be recycled and reused. However, existing waste gas treatment technologies still have many shortcomings: On the one hand, due to the lack of efficient vacuum depressurization devices, high-temperature heating is often relied upon for desorption when treating high-temperature waste gas. This not only consumes a lot of energy, but the desorption process is also prone to low desorption efficiency and solvent loss due to drastic fluctuations in system pressure. On the other hand, conventional single-stage condensation processes often fail to condense completely when dealing with high-concentration, high-boiling-point solvents, severely limiting solvent recovery rates and making it difficult to consistently meet emission standards. Furthermore, in existing vacuum desorption systems, the vacuum depressurization unit and the vacuum suction unit are usually two independent components, resulting in redundant system structure and complex piping layout. If a suitable vacuum pump could be selected and matched to combine the two into one unit, the system structure would be effectively simplified, and equipment costs and maintenance difficulties would be reduced. Summary of the Invention

[0003] In view of this, in order to solve the above problems, the object of the present invention is to provide a vacuum depressurization desorption system for solvent recovery, comprising: The adsorption unit is provided in multiple ways, and the air inlets of the multiple adsorption units are connected to the exhaust gas source through multiple pipelines. A preheating unit, connected to the adsorption unit, is used to heat the gas discharged from the adsorption unit and return the heated gas to the interior of the adsorption unit. A vacuum decompression unit is connected to the outlet of the adsorption unit; A condensation recovery unit is connected to the exhaust port of the vacuum pressure reduction unit and is used to liquefy and recover the desorbed gaseous solvent and discharge it. The control unit is electrically connected to the adsorption unit, preheating unit, vacuum decompression unit, and condensation recovery unit.

[0004] The above-described vacuum decompression system for solvent recovery includes an adsorption unit comprising an adsorption-desorption tank and an adsorption main fan connected in sequence by pipelines. The adsorption-desorption tank contains an adsorption bed and is equipped with a pressure transmitter, a temperature transmitter, and a differential pressure transmitter. All three transmitters are electrically connected to the control unit. The adsorption-desorption tank has an independent first outlet and a second outlet. The first outlet is connected to the inlet of the adsorption main fan, and the second outlet is connected to the vacuum decompression unit.

[0005] The above-mentioned vacuum decompression desorption system for solvent recovery includes an adsorption bed filled with a plurality of adsorbents, wherein the adsorbents are one or more combinations of activated carbon, zeolite molecular sieves, or MOF molecular sieves.

[0006] The aforementioned vacuum decompression desorption system for solvent recovery further includes: a heat exchanger disposed on the cooling circuit of the adsorption-desorption tank; the high-temperature fluid side of the heat exchanger is connected to the second outlet of the adsorption-desorption tank after desorption is completed via a pipeline; and the low-temperature fluid side of the heat exchanger is connected to the inlet of the preheating unit via a pipeline.

[0007] The above-mentioned vacuum decompression desorption system for solvent recovery includes a preheating unit comprising a heating fan and a heater connected in series, wherein the outlet of the heater is connected to the inlet of the adsorption-desorption tank via a pipeline.

[0008] The above-mentioned vacuum decompression desorption system for solvent recovery includes a vacuum decompression unit comprising a vacuum buffer tank and a vacuum pump connected in sequence. The inlet of the vacuum buffer tank is connected to the second outlet of the adsorption-desorption tank via a pipeline, and the outlet of the vacuum buffer tank is connected to the inlet of the vacuum pump via a pipeline.

[0009] The above-mentioned vacuum decompression desorption system for solvent recovery includes a condensation recovery unit comprising a primary water cooler, a secondary water cooler, and a liquid storage tank. The inlet of the primary water cooler is connected to the exhaust of the vacuum pump via a pipeline, the outlet of the primary water cooler is connected to the inlet of the secondary water cooler, and the liquid outlets of the primary and secondary water coolers are connected to the liquid storage tank.

[0010] The above-mentioned working method of a vacuum depressurization desorption system for solvent recovery includes the following steps: Step S1: Adsorption saturation process. The main adsorption fan draws organic waste gas from the waste gas source and sends it into the adsorption unit. The solvent in the waste gas is captured by the adsorbent. After purification, the gas is discharged. The adsorption-desorption tank continues to operate in adsorption mode until the adsorbent in the adsorption-desorption tank reaches adsorption saturation. Step S2: Preheating and pressure building process, switch the saturated adsorption-desorption tank to desorption mode, start the preheating unit to preheat the saturated adsorbent inside the adsorption-desorption tank, and simultaneously start the vacuum pressure reduction unit to extract negative pressure from the gas inside the adsorption-desorption tank until the adsorption-desorption tank reaches the preset desorption negative pressure value and maintains the negative pressure stably. Step S3: Negative pressure constant temperature desorption process, maintaining a constant negative pressure environment inside the adsorption-desorption tank, the preheating unit continuously delivers high temperature gas flow to the adsorption-desorption tank to heat the adsorbent at a constant temperature, the organic solvent adsorbed inside the adsorbent is desorbed by heat and detaches from the adsorption bed to form a high concentration of gaseous solvent; Step S4: Two-stage condensation and recovery process. High-concentration gaseous solvent enters the vacuum decompression unit with negative pressure airflow, and is then sent to the condensation and recovery unit. It passes through the first-stage water cooler and the second-stage water cooler in sequence to condense and cool down. The gaseous solvent is completely liquefied into liquid solvent. The liquid solvent is collected in the storage tank to complete storage and recovery. Step S5: Adsorbent cooling and cycle switching process. After desorption is completed, the heating function of the preheating unit is stopped, and the adsorption bed in the adsorption-desorption tank is cooled down. The heat released during the cooling process of the adsorption bed is recovered through the heat exchanger and used to preheat the inlet gas of the other adsorption-desorption tanks in the preheating and pressure building process. After the temperature of the adsorption bed drops to room temperature and the adsorbent is regenerated, the adsorption-desorption tank is switched back to adsorption mode and enters the next round of waste gas adsorption-desorption cycle.

[0011] The positive effects of the above technical solution compared with the existing technology are: This invention provides a vacuum depressurization desorption system for solvent recovery and its operating method. The system utilizes multiple parallel adsorption units to achieve continuous and alternating adsorption and desorption of waste gas, ensuring uninterrupted system operation. A preheating unit heats the gas and returns it to the adsorption unit, providing a stable and controllable heat source for the desorption process, effectively improving solvent desorption efficiency. A direct connection between the vacuum depressurization unit and the second outlet of the adsorption unit creates a stable negative pressure desorption environment, significantly reducing the solvent's boiling point and enabling complete desorption of high-boiling-point solvents at lower temperatures. This avoids high-temperature energy consumption and prevents solvent escape caused by pressure fluctuations during desorption. A condensation recovery unit liquefies and recovers the desorbed gaseous solvent before discharge, ensuring efficient solvent recovery and compliant exhaust emissions. This solves problems such as desorption fluctuations and incomplete condensation in existing technologies, improving the overall efficiency and automation level of solvent recovery. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a vacuum decompression desorption system for solvent recovery according to the present invention.

[0013] 1. Adsorption unit; 11. Adsorption-desorption tank; 12. Adsorption bed; 13. Adsorbent; 14. Adsorption main fan; 15. Pressure transmitter; 16. Temperature transmitter; 17. Differential pressure transmitter; 18. First outlet; 19. Second outlet; 2. Waste gas source; 3. Preheating unit; 31. Heating fan; 32. Heater; 4. Vacuum pressure reduction unit; 41. Vacuum buffer tank; 42. Vacuum pump; 5. Condensation recovery unit; 51. Primary water cooler; 52. Secondary water cooler; 53. Liquid storage tank; 6. Valves. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0015] The structures, proportions, and sizes illustrated in the accompanying drawings are merely for illustrative purposes and to aid those skilled in the art in understanding and reading the invention. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0016] like Figure 1The diagram illustrates a preferred embodiment of a vacuum desorption system for solvent recovery, comprising: multiple adsorption units 1, each with its inlet connected to a waste gas source 2 via multiple pipelines; a preheating unit 3 connected to the adsorption units 1, used to heat the gas discharged from the adsorption units 1 and return the heated gas to the interior of the adsorption units 1; a vacuum desorption unit 4 connected to the outlet of the adsorption units 1, used to provide a negative pressure desorption environment for the system; a condensation recovery unit 5 connected to the exhaust port of the vacuum desorption unit 4, used to liquefy and recover the desorbed gaseous solvent and discharge it; and a control unit electrically connected to the adsorption units 1, preheating unit 3, vacuum desorption unit 4, and condensation recovery unit 5, used to regulate the temperature, pressure, and flow parameters of each unit.

[0017] In actual use, to ensure independent operation and switching of each working condition, a control valve 6 (such as a pneumatic valve or an electric valve) is installed on the pipeline between every two connected units. The valves are all electrically connected to the control unit, which automatically controls the valves' start-up, closing, and working status according to the set program, thereby realizing the automated operation of the system.

[0018] In addition to the above, the present invention also has the following embodiments: Furthermore, a vacuum depressurization desorption system for solvent recovery is provided, wherein each adsorption unit 1 includes an adsorption-desorption tank 11 and an adsorption main blower 14 connected in sequence by pipelines. The adsorption-desorption tank 11 contains an adsorption bed 12. The adsorption-desorption tank 11 is equipped with a pressure transmitter 15, a temperature transmitter 16, and a differential pressure transmitter 17, all of which are electrically connected to a control unit. The adsorption-desorption tank 11 has independent first and second outlets 18 and 19. The first outlet 18 is connected to the inlet of the adsorption main blower 14 to discharge the purified gas after adsorption. The second outlet 19 is connected to the vacuum depressurization unit 4 to discharge high-concentration gaseous solvent during the desorption process. Specifically, the pressure transmitter 15, temperature transmitter 16, and differential pressure transmitter 17 are used to collect real-time data on the pressure and temperature inside the adsorption-desorption tank 11 and the differential pressure operation data of the adsorption bed 12. When the differential pressure transmitter 17 detects that the differential pressure of the adsorption bed 12 has reached the set threshold, it indicates that the adsorbent 13 has reached the adsorption saturation state. The control unit then issues a command to switch the operating conditions, switching the adsorption unit 1 from the adsorption mode to the desorption mode.

[0019] Furthermore, a vacuum decompression desorption system for solvent recovery is provided, wherein the adsorption bed 12 is filled with a plurality of adsorbents 13, wherein the adsorbents 13 are one or more combinations of activated carbon, zeolite molecular sieves or MOF molecular sieves.

[0020] Furthermore, a vacuum depressurization desorption system for solvent recovery further includes a heat exchanger disposed on the cooling circuit of the adsorption-desorption tank 11. The high-temperature fluid side of the heat exchanger is connected via a pipeline to the second outlet 19 of the adsorption-desorption tank 11 after desorption, and the low-temperature fluid side of the heat exchanger is connected via a pipeline to the inlet of the preheating unit 3. The heat exchanger is used to recover the waste heat released during the cooling stage of the adsorption-desorption tank 11 and transfer the waste heat to the gas to be heated entering the preheating unit 3, thereby realizing the system's waste heat recovery and utilization.

[0021] Furthermore, a vacuum decompression desorption system for solvent recovery includes a preheating unit 3 comprising a heating fan 31 and a heater 32 connected in series along the gas flow direction. The outlet of the heater 32 is connected to the inlet of the adsorption-desorption tank 11 via a pipeline, for introducing hot gas into the adsorption-desorption tank 11 to heat the adsorbent 13. The heating fan 31 drives the airflow through the heater 32 to raise its temperature, and then sends the high-temperature gas into the adsorption-desorption tank 11 to heat the adsorbent 13 inside the tank.

[0022] Furthermore, a vacuum decompression desorption system for solvent recovery includes a vacuum decompression unit 4 comprising a vacuum buffer tank 41 and a vacuum pump 42 connected in sequence. The inlet of the vacuum buffer tank 41 is connected to the second outlet 19 of the adsorption-desorption tank 11 via a pipeline, and the outlet of the vacuum buffer tank 41 is connected to the inlet of the vacuum pump 42 via a pipeline. The vacuum buffer tank 41 is used to buffer system negative pressure fluctuations and prevent gaseous solvent from directly impacting the vacuum pump 42, while the vacuum pump 42 is used to provide a stable negative pressure environment for the entire desorption system.

[0023] Furthermore, a vacuum depressurization desorption system for solvent recovery includes a condensation recovery unit 5 comprising a primary water cooler 51, a secondary water cooler 52, and a storage tank 53. The inlet of the primary water cooler 51 is connected to the exhaust of the vacuum pump 42 via a pipeline, and the outlet of the primary water cooler 51 is connected to the inlet of the secondary water cooler 52. The liquid outlets of the primary and secondary water coolers 51 and 52 are both connected to the storage tank 53. The two-stage water coolers progressively cool the solvent to achieve complete liquefaction of the gaseous solvent.

[0024] A method for operating a vacuum depressurization desorption system for solvent recovery, comprising the following steps: Step S1: Adsorption saturation process. The main adsorption fan 14 draws the organic waste gas produced by the waste gas source 2 and sends it into the adsorption unit 1. The solvent in the waste gas is captured by the adsorbent 13 in the adsorption bed 12. After purification, the gas is discharged. The adsorption-desorption tank 11 continues to operate in adsorption mode until the adsorbent 13 in the adsorption-desorption tank 11 reaches the adsorption saturation state. Step S2: Preheating and pressure building process. The saturated adsorption-desorption tank 11 is switched to desorption mode. The preheating unit 3 is started to preheat the saturated adsorbent 13 inside the adsorption-desorption tank 11. At the same time, the vacuum pressure reduction unit 4 is started to extract negative pressure inside the adsorption-desorption tank 11 until the adsorption-desorption tank 11 reaches the preset desorption negative pressure value and maintains the negative pressure stably. Specifically, the mode of the adsorption-desorption tank 11 is changed by switching the valve 6 on the pipeline.

[0025] Step S3: Negative pressure constant temperature desorption process. Maintain a constant negative pressure environment inside the adsorption-desorption tank 11. The preheating unit 3 continuously delivers high temperature airflow to the adsorption-desorption tank 11 to heat the adsorbent 13 at a constant temperature. The organic solvent adsorbed inside the adsorbent 13 is desorbed by heat and detaches from the adsorption bed 12 to form a high concentration of gaseous solvent. Step S4: Two-stage condensation and recovery process. High-concentration gaseous solvent enters the vacuum decompression unit 4 with the negative pressure airflow, and is then sent to the condensation and recovery unit 5. It passes through the first-stage water cooler 51 and the second-stage water cooler 52 in sequence to condense and cool down. The gaseous solvent is completely liquefied into liquid solvent. The liquid solvent is collected in the storage tank 53 to complete the storage and recovery. Step S5: Cooling and cycle switching process of adsorbent 13. After desorption is completed, the heating function of preheating unit 3 is stopped, and the adsorption bed 12 in adsorption-desorption tank 11 is cooled down. The heat released during the cooling process of adsorption bed 12 is recovered through heat exchanger and used to preheat the intake gas of other adsorption-desorption tanks 11 in the preheating and pressure building process. After the temperature of adsorption bed 12 drops to room temperature and adsorbent 13 is regenerated, adsorption-desorption tank 11 is switched back to adsorption mode and enters the next round of waste gas adsorption-desorption cycle.

[0026] This device adjusts the preheating temperature, negative pressure, and condensation temperature according to the solvent characteristics and boiling point, and has the following embodiment: Step S1: Adsorption saturation process, waste gas containing organic solvents such as NMP is transported from waste gas source 2 to the interior of adsorption unit 1 under the traction of adsorption main fan 14. The waste gas penetrates adsorption bed 12, and the organic solvents therein are captured by adsorbent 13. The purified gas is discharged in compliance with standards. Adsorption-desorption tank 11 continues to operate in adsorption mode until sensors such as differential pressure transmitter 17 detect that the adsorbent 13 in adsorption-desorption tank 11 has reached adsorption saturation. Step S2: Preheating and pressure building process, the saturated adsorption-desorption tank 11 is switched from adsorption mode to desorption mode by switching pipeline valves. The heating fan 31 and heater 32 of preheating unit 3 are started to preheat and exchange heat with the saturated adsorbent 13 inside adsorption-desorption tank 11. The vacuum pump 42 of the vacuum decompression unit 4 is started synchronously to extract negative pressure from the gas in the adsorption-desorption tank 11 until the system reaches the preset desorption negative pressure value (e.g., the absolute pressure drops to a certain value), and maintains this negative pressure stably. The decompression environment significantly reduces the boiling point of solvents such as NMP. Step S3: Negative pressure isothermal desorption process (the negative pressure corresponding to NMP is the working negative pressure of 10kPa-80kPa, and the desorption temperature is 80-120℃). Under the constant negative pressure environment of the system, the preheating unit 3 continuously delivers high-temperature gas flow to the adsorption-desorption tank 11 to heat the adsorbent 13 at a constant temperature. The organic solvent adsorbed inside the adsorbent 13 is rapidly desorbed after being heated and detached from the adsorption bed 12 to form a high-concentration gaseous solvent. Step S4: Two-stage condensation and recovery process. The high-concentration gaseous solvent is drawn out of the adsorption-desorption tank 11 under the action of the negative pressure gas flow. It first enters the vacuum buffer tank 41 of the vacuum decompression unit 4 for pressure stabilization and buffering, and then is sent to the condensation and recovery unit 5 through the exhaust port of the vacuum pump 42. The gaseous solvent is sequentially cooled by passing through a primary water cooler 51 (cooling water temperature 15℃) and a secondary water cooler 52 (cooling water temperature -5℃). Under the effect of stepped cooling, the gaseous solvent is completely liquefied into liquid solvent, which is then collected in the storage tank 53 for storage and recovery. Non-condensable gas can be discharged to the exhaust gas main and re-enter the adsorption system. Step S5: Cooling and circulation switching process of adsorbent 13. After desorption is completed, the heating function of the preheating unit 3 is stopped, and only the heating fan 31 is kept running or cold air is introduced to cool the adsorption bed 12 (cooled to 30℃) in the adsorption-desorption tank 11 to restore it to a suitable room temperature for adsorption. During the cooling process, the waste heat released by the adsorption bed 12 is recovered through the aforementioned heat exchanger and transferred to the preheating unit 3 to preheat the intake airflow of the other adsorption-desorption tanks 11 that are currently in the preheating and pressurization process. Once the temperature sensor detects that the temperature of the adsorption bed 12 has dropped to room temperature and the adsorbent 13 has been regenerated, the control unit switches the adsorption-desorption tank 11 back to adsorption mode via the system valve, initiating the next round of waste gas adsorption-desorption cycle. Because multiple adsorption units 1 operate alternately, the system achieves continuous and uninterrupted waste gas treatment and solvent recovery.

[0027] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A vacuum depressurization desorption system for solvent recovery, characterized in that, include: The adsorption unit is provided in multiple ways, and the air inlets of the multiple adsorption units are connected to the exhaust gas source through multiple pipelines. A preheating unit, connected to the adsorption unit, is used to heat the gas discharged from the adsorption unit and return the heated gas to the interior of the adsorption unit. A vacuum decompression unit is connected to the outlet of the adsorption unit; A condensation recovery unit is connected to the exhaust port of the vacuum pressure reduction unit and is used to liquefy and recover the desorbed gaseous solvent and discharge it. The control unit is electrically connected to the adsorption unit, preheating unit, vacuum decompression unit, and condensation recovery unit.

2. The vacuum depressurization desorption system for solvent recovery according to claim 1, characterized in that, Each adsorption unit includes an adsorption-desorption tank and an adsorption main fan connected in sequence by pipelines. The adsorption-desorption tank is equipped with an adsorption bed and a pressure transmitter, a temperature transmitter, and a differential pressure transmitter. The pressure transmitter, the temperature transmitter, and the differential pressure transmitter are all electrically connected to the control unit. The adsorption-desorption tank has a first air outlet and a second air outlet that are independent of each other. The first air outlet is connected to the air inlet of the adsorption main fan, and the second air outlet is connected to the vacuum pressure reducing unit.

3. The vacuum depressurization desorption system for solvent recovery according to claim 2, characterized in that, The adsorption bed is filled with a number of adsorbents, which are one or more combinations of activated carbon, zeolite molecular sieves or MOF molecular sieves.

4. The vacuum depressurization desorption system for solvent recovery according to claim 3, characterized in that, Also includes: A heat exchanger is installed on the cooling circuit of the adsorption-desorption tank. The high-temperature fluid side of the heat exchanger is connected to the second outlet of the adsorption-desorption tank after desorption is completed via a pipeline, and the low-temperature fluid side of the heat exchanger is connected to the inlet of the preheating unit via a pipeline.

5. The vacuum depressurization desorption system for solvent recovery according to claim 4, characterized in that, The preheating unit includes a heating fan and a heater connected in series, and the outlet of the heater is connected to the inlet of the adsorption-desorption tank through a pipeline.

6. The vacuum depressurization desorption system for solvent recovery according to claim 4, characterized in that, The vacuum decompression unit includes a vacuum buffer tank and a vacuum pump connected in sequence. The inlet of the vacuum buffer tank is connected to the second outlet of the adsorption-desorption tank through a pipeline, and the outlet of the vacuum buffer tank is connected to the inlet of the vacuum pump through a pipeline.

7. The vacuum depressurization desorption system for solvent recovery according to claim 6, characterized in that, The condensation recovery unit includes a primary water cooler, a secondary water cooler, and a liquid storage tank. The air inlet of the primary water cooler is connected to the exhaust end of the vacuum pump via a pipeline. The air outlet of the primary water cooler is connected to the air inlet of the secondary water cooler. The liquid outlets of the primary water cooler and the secondary water cooler are both connected to the liquid storage tank.

8. The operating method of a vacuum depressurization desorption system for solvent recovery according to any one of claims 4 to 7, characterized in that, Includes the following steps: Step S1: Adsorption saturation process. The main adsorption fan draws organic waste gas from the waste gas source and sends it into the adsorption unit. The solvent in the waste gas is captured by the adsorbent. After purification, the gas is discharged. The adsorption-desorption tank continues to operate in adsorption mode until the adsorbent in the adsorption-desorption tank reaches adsorption saturation. Step S2: Preheating and pressure building process, switch the saturated adsorption-desorption tank to desorption mode, start the preheating unit to preheat the saturated adsorbent inside the adsorption-desorption tank, and simultaneously start the vacuum pressure reduction unit to extract negative pressure from the gas inside the adsorption-desorption tank until the adsorption-desorption tank reaches the preset desorption negative pressure value and maintains the negative pressure stably. Step S3: Negative pressure constant temperature desorption process, maintaining a constant negative pressure environment inside the adsorption-desorption tank, the preheating unit continuously delivers high temperature gas flow to the adsorption-desorption tank to heat the adsorbent at a constant temperature, the organic solvent adsorbed inside the adsorbent is desorbed by heat and detaches from the adsorption bed to form a high concentration of gaseous solvent; Step S4: Two-stage condensation and recovery process. High-concentration gaseous solvent enters the vacuum decompression unit with negative pressure airflow, and is then sent to the condensation and recovery unit. It passes through the first-stage water cooler and the second-stage water cooler in sequence to condense and cool down. The gaseous solvent is completely liquefied into liquid solvent. The liquid solvent is collected in the storage tank to complete storage and recovery. Step S5: Adsorbent cooling and cycle switching process. After desorption is completed, the heating function of the preheating unit is stopped, and the adsorption bed in the adsorption-desorption tank is cooled down. The heat released during the cooling process of the adsorption bed is recovered through the heat exchanger and used to preheat the inlet gas of the other adsorption-desorption tanks in the preheating and pressure building process. After the temperature of the adsorption bed drops to room temperature and the adsorbent is regenerated, the adsorption-desorption tank is switched back to adsorption mode and enters the next round of waste gas adsorption-desorption cycle.

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