A solvent recovery system

Abstract

The present invention discloses a solvent recovery system, comprising an adsorption tank, a condenser connected to the adsorption tank, a storage tank connected to the condenser, and a steam supply unit connected to the adsorption tank, wherein a first detector is provided on the storage tank; a first pipeline is provided between the condenser and the adsorption tank, a second detector is provided on the first pipeline, the first detector and the second detector are both connected to a control unit, the first detector is used to detect the liquid level of the liquid in the storage tank and generate a liquid level signal, the second detector is used to detect the concentration of the solvent in the mixed steam flowing from the first pipeline to the condenser and generate a concentration signal, the control unit is used to receive the liquid level signal detected by the first detector and the concentration signal detected by the second detector, and control the start and stop of the steam supply unit according to the signal. The solvent recovery system of the present invention can accurately determine whether the analysis of the adsorption tank is completed, reasonably control the steam energy consumption of the system operation, reduce the interference of human factors on the solvent recovery system, and improve the automation of the system.

Description

Technical Field

[0001] The invention belongs to the technical field of solvent recovery in waste gas treatment, and in particular relates to a solvent recovery system. Background Art

[0002] In the waste gas treatment industry, a considerable number of enterprises use solvent recovery technology to treat production waste gas. When the solvent recovery technology is used to treat waste gas, online analysis is required when the adsorption equipment is saturated. The analysis method is to heat the adsorption medium (activated carbon, molecular sieve, zeolite, etc.) through a heat medium (such as steam, nitrogen), and the operator will analyze the saturated adsorption tank according to the approximate dynamic adsorption capacity and emission.

[0003] The existing solvent recovery technology in waste gas treatment has great limitations. There is no basis for judging whether the adsorption tank is completely analyzed or whether there is over-analysis. It all relies on manual experience data. For example, the analysis time generally comes from the equipment party's suggestions, the operator's experience, etc.

[0004] For example, the Chinese invention patent with announcement number CN109847525A, entitled A system and method for recovering solvents from industrial tail gas, discloses that an adsorbent that can be decomposed after heating is provided inside the tail gas adsorber, and the solvent in the absorbed tail gas can be decomposed by heating. However, there is no judgment on whether the decomposition inside the tail gas adsorber is complete. This is the same problem as the decomposition judgment of the adsorption tank in the current solvent recovery technology in the industry. There is a lack of judgment on the degree of decomposition, and the decomposition time cannot be accurately controlled, which increases the energy consumption cost of the enterprise.

[0005] Another example is the Chinese invention patent with the announcement number CN113694678A, entitled A device for dry recovery of organic solvents from waste gas. The adsorbent is heated by inert gas to facilitate more thorough vacuum desorption and increase the adsorption capacity of the adsorbent after desorption. Although the adsorption capacity of the adsorbent can be increased, it does not provide a solution for how to determine whether the desorption is complete during the desorption process and how to control the desorption time. There is also the problem of being unable to determine the degree of desorption.

[0006] However, due to environmental influences, changes in exhaust gas conditions, etc., the adsorption capacity of the adsorption tank often fluctuates, making it impossible to completely decompose the adsorption tank within the set analysis time. It is also possible that the set analysis time is too long. Desorption for too long will lead to an increase in the amount of desorption water generated by desorption, thereby increasing the company's sewage treatment costs and making it impossible to achieve accurate control of energy consumption costs. Summary of the invention

[0007] In view of this, in order to overcome the defects of the prior art, the purpose of the present invention is to provide a solvent recovery system that can accurately determine whether the analysis of the adsorption tank is completed, achieve effective analysis of the adsorption tank, and reasonably control the steam energy consumption of the system operation.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A solvent recovery system comprises an adsorption tank, a condenser connected to the adsorption tank, a storage tank connected to the condenser, and a steam supply unit connected to the adsorption tank, wherein the adsorption tank is used to adsorb the solvent in the exhaust gas, the storage tank is used to store the solvent to be recovered, and a first detector is arranged on the storage tank; a first pipeline is arranged between the condenser and the adsorption tank, and a second detector is arranged on the first pipeline, and the first detector and the second detector are both connected to a control unit, the first detector is used to detect the liquid level of the liquid in the storage tank and generate a liquid level signal, the second detector is used to detect the concentration of the solvent in the mixed steam flowing from the first pipeline to the condenser and generate a concentration signal, and the control unit is used to receive the liquid level signal detected by the first detector and the concentration signal detected by the second detector, and control the start and stop of the steam supply unit according to the liquid level signal and the concentration signal.

[0010] According to some preferred implementation aspects of the present invention, the mixed steam is generated when the adsorbent in the adsorption tank is desorbed after being saturated with adsorption, and the mixed steam includes steam and water vapor generated by thermal evaporation of the solvent adsorbed by the adsorbent in the adsorption tank.

[0011] According to some preferred implementation aspects of the present invention, the start and stop of the steam supply unit is controlled according to the liquid level signal and the concentration signal: when the second detector detects that the concentration of the solvent in the mixed steam flowing from the first pipeline to the condenser is less than or equal to 5000 mg / m³ for at least 5 consecutive minutes, and the first detector detects that the liquid level in the storage tank has passed the first stage, the second stage and the third stage, and the rising height of the liquid level of the first detector in 5 minutes is less than 10 mm, the control unit controls the steam supply unit to stop supplying steam.

[0012] According to some preferred implementation aspects of the present invention, when the liquid level in the storage tank is in the first stage, the rising rate of the liquid level in the storage tank is less than 2 mm / 5 min.

[0013] According to some preferred implementation aspects of the present invention, when the liquid level in the storage tank is in the second stage, the rising rate of the liquid level in the storage tank is greater than 10 mm / 5 min.

[0014] According to some preferred implementation aspects of the present invention, when the liquid level in the storage tank is in the third stage, the rising rate of the liquid level in the storage tank is less than 2 mm / min.

[0015] In some embodiments of the present invention, the liquid level rising rate in the storage tank is calculated by the ratio of the flow rate per unit time to the cross-sectional area of ​​the storage tank. The first stage is a slow rising stage, the second stage is a fast rising and gradually stabilizing stage, and the third stage is also a slow rising stage but the rising rate is greater than the rising rate of the first stage.

[0016] According to some preferred embodiments of the present invention, the device comprises a first adsorption tank, a second adsorption tank and an induced draft fan, a first pipe is arranged between the condenser and the second adsorption tank, a second pipe is arranged between the induced draft fan and the second adsorption tank, the first adsorption tank is connected to a third pipe, and a fourth pipe is arranged between the steam supply unit and the first adsorption tank.

[0017] According to some preferred embodiments of the present invention, the first adsorption tank is also connected to a first branch pipe, an end of the first branch pipe away from the first adsorption tank is connected to the first pipeline, a first valve is provided on the first pipeline, a second valve is provided on the first branch pipe, the first valve is located between the connection between the first pipeline and the second adsorption tank and the connection between the first branch pipe and the first pipeline, and the first valve and the second valve are both connected to the control unit.

[0018] According to some preferred implementation aspects of the present invention, the first adsorption tank is also connected to a second branch pipe, an end of the second branch pipe away from the first adsorption tank is connected to the second pipe, a third valve and a fourth valve are provided on the second pipe, a fifth valve is provided on the second branch pipe, the third valve is located at an end of the second pipe close to the induced draft fan, the fourth valve is located at an end of the second pipe close to the second adsorption tank, and the third valve, the fourth valve and the fifth valve are all connected to the control unit.

[0019] According to some preferred embodiments of the present invention, the second adsorption tank is also connected to a third branch pipe, and one end of the third branch pipe away from the second adsorption tank is connected to the third pipe, and the gas after adsorption treatment in the first adsorption tank is discharged to the outside through the third pipe, and the gas after adsorption treatment in the second adsorption tank is discharged to the outside through the third pipe and the third branch pipe.

[0020] According to some preferred embodiments of the present invention, an air outlet pipe is provided on the condenser, one end of the air outlet pipe is connected to the condenser, and the other end of the air outlet pipe is connected to the second pipe, and a first liquid outlet pipe is provided between the condenser and the storage tank, and the gas after condensation of the mixed steam entering the condenser flows from the air outlet pipe to the second pipe, and the liquid after condensation of the mixed steam entering the condenser flows from the first liquid outlet pipe to the storage tank.

[0021] According to some preferred implementation aspects of the present invention, the second adsorption tank is also communicated with a fourth branch pipe, an end of the fourth branch pipe away from the second adsorption tank is connected to the fourth pipe, the steam supply unit passes steam into the first adsorption tank through the fourth pipe, and the steam supply unit passes steam into the second adsorption tank through the fourth pipe and the fourth branch pipe; a sixth valve is provided on the fourth pipe, and a seventh valve is provided on the fourth branch pipe, the seventh valve is located between the connection between the fourth pipe and the first adsorption tank and the connection between the fourth branch pipe and the fourth pipe, and the sixth valve and the seventh valve are both connected to the control unit.

[0022] According to some preferred embodiments of the present invention, the cross-section of the storage tank is rectangular or circular.

[0023] Compared with the prior art, the benefits of the present invention are as follows: the solvent recovery system of the present invention, through the setting of the first detector on the condenser, the setting of the second detector on the first pipeline, and the setting of the control unit connected to the first detector, the second detector and each valve, adds the conditions for reaching the completion of the analysis to the control unit by analyzing the three elements of the concentration of the solvent in the desorbed mixed steam, the rising trend of the liquid level in the storage tank for recovering the solvent and the desorption time, and can judge whether the analysis in the adsorption tank is thorough. When the conditions for the completion of the analysis are reached, the control unit will be triggered to close the steam supply unit. The solvent recovery system of the present invention can accurately judge whether the analysis of the adsorption tank is completed, realize the effective analysis of the adsorption tank, reasonably control the steam energy consumption of the system operation, greatly reduce the interference of human factors on the solvent recovery system, and improve the degree of automation of the solvent recovery system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 It is a structural schematic diagram of a solvent recovery system in a preferred embodiment of the present invention;

[0026] In the attached drawings, induced draft fan-1, first adsorption tank-2, second adsorption tank-3, condenser-4, storage tank-5, first detector-6, second detector-7, first pipeline-L1, second pipeline-L2, third pipeline-L3, fourth pipeline-L4, fifth pipeline-L5, first branch pipe-L6, second branch pipe-L7, third branch pipe-L8, fourth branch pipe-L9, fifth branch pipe-L10, air outlet pipeline-G1, first liquid outlet pipeline-G2, sewage pipeline-G3, second liquid outlet pipeline-G4, first valve-F1, second valve-F2, third valve-F3, fourth valve-F4, fifth valve-F5, sixth valve-F6, seventh valve-F7. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0028] like Figure 1 As shown, a solvent recovery system of the present embodiment includes an induced draft fan 1, a condenser 4, a storage tank 5, a steam supply unit, a control unit and two adsorption tanks, namely a first adsorption tank 2 and a second adsorption tank 3, and the first adsorption tank 2 and the second adsorption tank 3 are both used for adsorbing the solvent in the exhaust gas; the cross-section of the storage tank 5 is rectangular or circular, and the cross-section of the storage tank 5 in the present embodiment is preferably rectangular, and the storage tank 5 is used for storing the solvent to be recovered.

[0029] Specifically, a first pipeline L1 is arranged between the condenser 4 and the second adsorption tank 3, a first detector 6 is arranged on the storage tank 5, and a second detector 7 is arranged on the first pipeline L1. The first detector 6 and the second detector 7 are both connected to the control unit. The first detector 6 is a liquid level detector, which is used to detect the liquid level of the liquid in the storage tank 5 and generate a liquid level signal; the second detector 7 is a concentration detector, which is used to detect the concentration of the solvent in the mixed steam flowing from the first pipeline L1 to the condenser 4 and generate a concentration signal. A first branch pipe L6 is provided between the first adsorption tank 2 and the first pipeline L1, one end of the first branch pipe L6 is connected to the first adsorption tank 2, and one end of the first branch pipe L6 away from the first adsorption tank 2 is connected to the first pipeline L1; a first valve F1 is provided on the first pipeline L1, and a second valve F2 is provided on the first branch pipe L6. The first valve F1 is located between the connection between the first pipeline L1 and the second adsorption tank 3 and the connection between the first branch pipe L6 and the first pipeline L1. The first valve F1 and the second valve F2 are both connected to the control unit, so that the control unit can control the closing and opening of the first valve F1 and the second valve F2. When only the first adsorption tank 2 is processed, the first valve F1 is closed and the second valve F2 is opened, so that the mixed steam in the first adsorption tank 2 can enter the condenser 4 through the first branch pipe L6 and the first pipeline L1. When only the second adsorption tank 3 is processed, the second valve F2 is closed and the first valve F1 is opened, so that the mixed steam in the second adsorption tank 3 can enter the condenser 4 through the first pipeline L1.

[0030] Further, a second pipe L2 is provided between the induced draft fan 1 and the second adsorption tank 3, and a second branch pipe L7 is provided between the first adsorption tank 2 and the second pipe L2. One end of the second branch pipe L7 is connected to one end of the first adsorption tank 2, and the end of the second branch pipe L7 away from the first adsorption tank 2 is connected to the second pipe L2. In addition, a third valve F3 and a fourth valve F4 are provided on the second pipe L2, and a fifth valve F5 is provided on the second branch pipe L7, wherein the third valve F3 is located at one end of the second pipe L2 close to the induced draft fan 1, and the fourth valve F4 is located at one end of the second pipe L2 close to the second adsorption tank 3; the third valve F3, the fourth valve F4 and the fifth valve F5 are all connected to the control unit, so that the control unit can control the closing and opening of the third valve F3, the fourth valve F4 and the fifth valve F5. When only the second adsorption tank 3 is processed, the fifth valve F5 is closed, and the third valve F3 and the fourth valve F4 are opened, so that the exhaust gas on the production line can enter the second adsorption tank 3 from the second pipe L2 through the induced draft fan 1 for adsorption treatment. When only the first adsorption tank 2 is being processed, the fourth valve F4 is closed, and the third valve F3 and the fifth valve F5 are opened, so that the exhaust gas on the production line can enter the first adsorption tank 2 through the second pipeline L2 and the second branch pipe L7 via the induced draft fan 1 for adsorption treatment.

[0031] An air outlet pipe G1 is provided at one end of the condenser 4, and a first liquid outlet pipe G2 is provided at the other end of the condenser 4. The end of the air outlet pipe G1 away from the condenser 4 is connected to the second pipe L2, and the end of the first liquid outlet pipe G2 away from the condenser 4 is connected to the storage tank 5; a sewage pipe G3 and a second liquid outlet pipe G4 are provided at the end of the storage tank 5 away from the condenser 4. The gas after condensation of the mixed steam entering the condenser 4 from the first adsorption tank 2 or the second adsorption tank 3 flows from the air outlet pipe G1 to the second pipe L2, and the liquid after condensation of the mixed steam entering the condenser 4 from the first adsorption tank 2 or the second adsorption tank 3 flows from the first liquid outlet pipe G2 to the storage tank 5, the pure liquid solvent flows out from the second liquid outlet pipe G4, and the steam condensate water enters the sewage treatment tank from the sewage pipe G3.

[0032] Furthermore, a third pipeline L3, a fourth pipeline L4 and a fifth pipeline L5 are also provided on the first adsorption tank 2. Among them, a third branch pipe L8 is provided between the second adsorption tank 3 and the third pipeline L3, one end of the third branch pipe L8 is connected to the second adsorption tank 3, and one end of the third branch pipe L8 away from the second adsorption tank 3 is connected to the third pipeline L3; the other end of the fourth pipeline L4 is connected to the steam supply unit, a fourth branch pipe L9 is provided between the second adsorption tank 3 and the fourth pipeline L4, one end of the fourth branch pipe L9 is connected to the second adsorption tank 3, and one end of the fourth branch pipe L9 away from the second adsorption tank 3 is connected to the fourth pipeline L4; a fifth branch pipe L10 is provided between the second adsorption tank 3 and the fifth pipeline L5, one end of the fifth branch pipe L10 is connected to the second adsorption tank 3, and one end of the fifth branch pipe L10 away from the second adsorption tank 3 is connected to the fifth pipeline L5. A sixth valve F6 is provided on the fourth pipeline L4, and a seventh valve F7 is provided on the fourth branch pipe L9. The seventh valve F7 is located between the connection between the fourth pipeline L4 and the first adsorption tank 2 and the connection between the fourth branch pipe L9 and the fourth pipeline L4. The sixth valve F6 and the seventh valve F7 are both connected to the control unit, so that the control unit can control the closing and opening of the sixth valve F6 and the seventh valve F7. In addition, valves are also provided on the third pipe L3 and the third branch pipe L8, and valves are also provided on the fifth pipe L5 and the fifth branch pipe L10 accordingly. The gas that meets the standard after adsorption treatment in the first adsorption tank 2 is discharged outward through the third pipe L3, and the gas that meets the standard after adsorption treatment in the second adsorption tank 3 is discharged outward through the third pipe L3 and the third branch pipe L8; when the first adsorption tank 2 and / or the second adsorption tank 3 are saturated with adsorption, the steam supply unit can pass steam into the first adsorption tank 2 through the fourth pipe L4 to perform desorption treatment in the first adsorption tank 2, and the steam supply unit can pass steam into the second adsorption tank 3 through the fourth pipe L4 and the fourth branch pipe L9 to perform desorption treatment in the second adsorption tank 3. In order to ensure the safety of the production line, the end of the fifth pipe L5 away from the first adsorption tank 2 is used to connect with the fire pipe to ensure that fire water can be timely passed into the first adsorption tank 2 or the second adsorption tank 3 in an emergency.

[0033] In the present embodiment, the first adsorption tank 2 and the second adsorption tank 3 are both activated carbon adsorption. When the first adsorption tank 2 and / or the second adsorption tank 3 are saturated with adsorption, they will enter the desorption process. As the desorption proceeds, the temperature in the first adsorption tank 2 and / or the second adsorption tank 3 gradually increases, and the adsorbed solvent gradually evaporates due to heat to form mixed steam with water vapor. When the mixed steam flows to the condenser 4 through the first pipeline L1, the second detector 7 can detect its concentration in real time. When the second detector 7 detects that the concentration of the solvent in the mixed steam flowing from the first pipeline L1 to the condenser 4 is less than or equal to 5000 mg / m³ for at least 5 consecutive minutes, the first detector 6 detects that the liquid level in the storage tank 5 has gone through the first stage (the liquid level in the storage tank 5 has a rising rate of less than 2 mm / 5 min), the second stage (the liquid level in the storage tank 5 has a rising rate of more than 10 mm / 5 min) and the third stage (the liquid level in the storage tank 5 has a rising rate of less than 2 mm / min), and the rising height of the liquid level of the first detector 6 in 5 minutes is less than 10 mm, when the control unit receives all these signals, it will control the steam supply unit to stop the steam supply, so that the first adsorption tank 2 and / or the second adsorption tank 3 stop desorption, and control the corresponding valve to close. This ensures that it can accurately determine whether the analysis of the first adsorption tank 2 and / or the second adsorption tank 3 is completed, which is conducive to the reasonable control of the steam energy consumption of the system operation.

[0034] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A solvent recovery system, characterized in that: The invention comprises an adsorption tank, a condenser connected to the adsorption tank, a storage tank connected to the condenser, and a steam supply unit connected to the adsorption tank, wherein the adsorption tank is used to adsorb the solvent in the exhaust gas, the storage tank is used to store the solvent to be recovered, the cross-section of the storage tank is rectangular or circular, and a first detector is arranged on the storage tank; a first pipeline is arranged between the condenser and the adsorption tank, a second detector is arranged on the first pipeline, the first detector and the second detector are both connected to a control unit, the first detector is used to detect the liquid level of the liquid in the storage tank and generate a liquid level signal, the second detector is used to detect the concentration of the solvent in the mixed steam flowing from the first pipeline to the condenser and generate a concentration signal, the mixed steam is generated when the adsorbent in the adsorption tank is desorbed after being saturated with adsorption, and the mixed steam includes the solvent adsorbed by the adsorbent in the adsorption tank The steam and water vapor generated by the heated evaporation of the agent; the control unit is used to receive the liquid level signal detected by the first detector and the concentration signal detected by the second detector, and control the start and stop of the steam supply unit according to the liquid level signal and the concentration signal: when the second detector detects that the concentration of the solvent in the mixed steam flowing from the first pipeline to the condenser is less than or equal to 5000 mg / m³ for at least 5 consecutive minutes, the first detector detects that the liquid level in the storage tank has passed the first stage, the second stage and the third stage, and the rising height of the liquid level of the first detector in 5 minutes is less than 10 mm, the control unit controls the steam supply unit to stop supplying steam; the first stage is a slow rising stage, the second stage is a fast rising and gradually stabilizing stage, and the third stage is a slow rising stage and the rising rate is greater than the rising rate of the first stage.

2. The solvent recovery system according to claim 1, characterized in that: When the liquid level of the liquid in the storage tank is in the first stage, the rising rate of the liquid level of the liquid in the storage tank is less than 2 mm / 5 min.

3. The solvent recovery system according to claim 1, characterized in that: When the liquid level of the liquid in the storage tank is in the second stage, the rising rate of the liquid level of the liquid in the storage tank is greater than 10 mm / 5 min.

4. The solvent recovery system according to claim 1, characterized in that: When the liquid level of the liquid in the storage tank is in the third stage, the rising rate of the liquid level in the storage tank is less than 2 mm / min.

5. The solvent recovery system according to claim 1, characterized in that: It includes a first adsorption tank, a second adsorption tank and an induced draft fan, a first pipe is arranged between the condenser and the second adsorption tank, a second pipe is arranged between the induced draft fan and the second adsorption tank, the first adsorption tank is connected to a third pipe, and a fourth pipe is arranged between the steam supply unit and the first adsorption tank.

6. The solvent recovery system according to claim 5, characterized in that: The first adsorption tank is also connected to a first branch pipe, and one end of the first branch pipe away from the first adsorption tank is connected to the first pipeline. A first valve is provided on the first pipeline, and a second valve is provided on the first branch pipe. The first valve is located between the connection between the first pipeline and the second adsorption tank and the connection between the first branch pipe and the first pipeline. The first valve and the second valve are both connected to the control unit.

7. The solvent recovery system according to claim 5, characterized in that: The first adsorption tank is also communicated with a second branch pipe, an end of the second branch pipe away from the first adsorption tank is connected to the second pipe, a third valve and a fourth valve are provided on the second pipe, a fifth valve is provided on the second branch pipe, the third valve is located at an end of the second pipe close to the induced draft fan, the fourth valve is located at an end of the second pipe close to the second adsorption tank, and the third valve, the fourth valve and the fifth valve are all connected to the control unit.

8. The solvent recovery system according to claim 5, characterized in that: The second adsorption tank is also connected to the third branch pipe, and the end of the third branch pipe away from the second adsorption tank is connected to the third pipe. The gas after adsorption treatment in the first adsorption tank is discharged to the outside through the third pipe, and the gas after adsorption treatment in the second adsorption tank is discharged to the outside through the third pipe and the third branch pipe.

9. The solvent recovery system according to claim 5, characterized in that: The condenser is provided with an air outlet pipe, one end of which is connected to the condenser, and the other end of which is connected to the second pipe. A first liquid outlet pipe is provided between the condenser and the storage tank. The gas after condensation of the mixed steam entering the condenser flows from the air outlet pipe to the second pipe, and the liquid after condensation of the mixed steam entering the condenser flows from the first liquid outlet pipe to the storage tank.

10. The solvent recovery system according to claim 5, characterized in that: The second adsorption tank is also communicated with a fourth branch pipe, an end of the fourth branch pipe away from the second adsorption tank is connected to the fourth pipe, the steam supply unit passes steam into the first adsorption tank through the fourth pipe, and the steam supply unit passes steam into the second adsorption tank through the fourth pipe and the fourth branch pipe; a sixth valve is provided on the fourth pipe, and a seventh valve is provided on the fourth branch pipe, the seventh valve is located between the connection between the fourth pipe and the first adsorption tank and the connection between the fourth branch pipe and the fourth pipe, and the sixth valve and the seventh valve are both connected to the control unit.

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