Gas recovery apparatus and gas recovery method

Abstract

The present invention provides a gas recovery apparatus and a gas recovery method that can reduce variations in the concentration of recovered gases. [Solution] The gas recovery device comprises an adsorption tower filled with an adsorbent that adsorbs specific gas components contained in the raw gas; a vacuum pump that desorbs and sucks up desorbed gas containing gas components from the adsorbent by reducing the pressure in the adsorption tower; an exhaust pipe including a first branch pipe and a second branch pipe downstream of the vacuum pump; a first valve disposed between the vacuum pump and the first branch pipe for opening and closing the first branch pipe; a second valve disposed between the vacuum pump and the second branch pipe for opening and closing the second branch pipe; a pressure gauge for detecting the pressure inside the adsorption tower; and a control device that switches from a state where the first valve is open and the second valve is closed to a state where the first valve is closed and the second valve is open, based on the pressure detected by the pressure gauge.

Description

Technical Field

[0001] The present invention relates to a gas recovery device and a gas recovery method for recovering gas contained in a raw material gas.

Background Art

[0002] Regarding the technology of separating and recovering gas contained in a raw material gas by the pressure swing adsorption method, there is a prior art disclosed in Patent Document 1 in which the time zone for sucking the gas desorbed by depressurizing the inside of the adsorption tower with a vacuum pump is divided into a plurality of time zones, and the gas is recovered separately for each time zone.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the prior art, the time for sucking with a vacuum pump is measured and divided into a plurality of time zones, and the gas is recovered separately for each time zone. Therefore, due to the temperature of the environment where the device is installed, the deterioration of the adsorbent, etc., the adsorption amount and the suction amount of the vacuum pump change, and the concentration of the recovered gas is likely to vary.

[0005] The present invention has been made to solve this problem, and an object thereof is to provide a gas recovery device and a gas recovery method capable of reducing variations in the concentration of the recovered gas.

Means for Solving the Problems

[0006] A first embodiment for achieving this objective is a gas recovery apparatus for separating gas components from a raw gas by a pressure swing adsorption method, comprising: an adsorption tower filled with an adsorbent that adsorbs specific gas components contained in a raw gas; a vacuum pump that depressurizes the adsorption tower to desorb and suck up desorbed gas containing gas components from the adsorbent; an exhaust pipe including a first branch pipe and a second branch pipe downstream of the vacuum pump; a first valve disposed between the vacuum pump and the first branch pipe for opening and closing the first branch pipe; and a second valve disposed between the vacuum pump and the second branch pipe for opening and closing the second branch pipe, comprising: a pressure gauge for detecting the pressure inside the adsorption tower; and a control device that, based on the pressure detected by the pressure gauge, switches from a state in which the first valve is open and the second valve is closed to a state in which the first valve is closed and the second valve is open.

[0007] A second embodiment is a gas recovery apparatus for separating gas components from a raw gas by a pressure swing adsorption method, comprising: an adsorption tower filled with an adsorbent that adsorbs specific gas components contained in a raw gas; a vacuum pump that desorbs and sucks up desorbed gas containing gas components from the adsorbent by reducing the pressure of the adsorption tower; an exhaust pipe including a first branch pipe and a second branch pipe downstream of the vacuum pump; a first valve disposed between the vacuum pump and the first branch pipe for opening and closing the first branch pipe; and a second valve disposed between the vacuum pump and the second branch pipe for opening and closing the second branch pipe, comprising: a concentration meter for detecting the concentration of gas components in a pipe connecting the adsorption tower and the vacuum pump, or the concentration of gas components in the exhaust pipe; and a control device that switches from a state in which the first valve is open and the second valve is closed to a state in which the first valve is closed and the second valve is open based on the concentration detected by the concentration meter.

[0008] A third embodiment is provided in the second embodiment with a pressure gauge for detecting the pressure inside the adsorption tower, and the control device calculates the partial pressure of the gas components based on the pressure and concentration detected by the pressure gauge, and switches the opening and closing of the first valve and the second valve based on the partial pressure.

[0009] In the fourth embodiment, in the third embodiment, the control device switches to a state in which the first valve is closed and the second valve is open when the partial pressure is between 10 kPa and 60 kPa.

[0010] The fifth embodiment is that, in any of the first to fourth embodiments, the adsorbent exhibits adsorption-desorption behavior represented by a sigmoid-type adsorption-desorption isotherm.

[0011] The sixth aspect is that, in any of the first to fifth aspects, the adsorbent exhibits adsorption / desorption behavior of type IV or type V according to the IUPAC classification of adsorption / desorption isotherms.

[0012] The seventh aspect is that, in any of the first to sixth aspects, the adsorption tower includes a plurality of adsorption towers connected in parallel to one another, and comprises a pipe for supplying the desorption gas from one adsorption tower to another adsorption tower as a cleaning gas.

[0013] The eighth aspect is that, in any of the first to seventh aspects, the control device switches from a state in which the first valve is open and the second valve is closed to a state in which the first valve is closed and the second valve is open, based on the adsorption / desorption isotherm of the adsorbent.

[0014] The ninth aspect is a method for separating gas components from a raw material gas by pressure swing adsorption, comprising: an adsorption step of adsorbing a specific gas component onto an adsorbent packed in an adsorption tower; a desorption step of depressurizing the adsorption tower to desorb the gas component adsorbed by the adsorbent; and a transfer step of transferring the desorbed gas containing the gas component to an exhaust pipe including a first branch pipe and a second branch pipe downstream of the vacuum pump using a vacuum pump connected to the adsorption tower, wherein in the transfer step, the transfer is switched from a state in which the desorbed gas is transferred to the first branch pipe to a state in which the desorbed gas is transferred to the second branch pipe, based on the pressure in the adsorption tower, the concentration of the gas component in the pipe connecting the adsorption tower and the vacuum pump, or the concentration of the gas component in the exhaust pipe. [Effects of the Invention]

[0015] According to the present invention, based on the pressure of the adsorption tower and the concentration of the gas components, the control device switches from a state where the first valve is open and the second valve is closed to a state where the first valve is closed and the second valve is open. This makes the device less susceptible to the effects of the temperature of the environment in which it is installed and the deterioration of the adsorbent, thereby reducing variations in the concentration of the recovered gas. [Brief explanation of the drawing]

[0016] [Figure 1] This is a piping diagram of the gas recovery device in the first embodiment. [Figure 2] This is an example of an adsorption / desorption isotherm. [Figure 3] This is a piping diagram of the gas recovery system in the second embodiment. [Modes for carrying out the invention]

[0017] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1 is a piping diagram of the gas recovery device 10 in the first embodiment. The gas recovery device 10 is a device that separates specific gas components contained in the raw material gas using a pressure swing adsorption method.

[0018] Examples of raw material gases include exhaust gas containing carbon dioxide, moisture, nitrogen oxides, etc., air, petroleum cracking gas, coke oven gas, and anaerobic digester gas. Examples of exhaust gases include those emitted from power plants, factories, waste treatment facilities, natural gas fields, and oil fields. Examples of gases separated and recovered from the raw material gases vary depending on the type of raw material gas, but examples include carbon dioxide, nitrogen, oxygen, hydrogen, and methane. The gas recovery device 10 can separate and recover specific gas components from the raw material gas, or separate specific gas components from the raw material gas and recover the gases other than the separated gas components.

[0019] The gas recovery device 10 is equipped with adsorption towers 11 and 12. Adsorbents 13 that adsorb specific gas components are contained in the adsorption towers 11 and 12 as stationary layers. The adsorbent 13 is appropriately selected depending on the type of raw gas and gas components. Examples of adsorbents 13 include activated carbon, silica gel, zeolite, molecular sieving carbon, mesoporous silica, metal-organic frameworks (MOFs), and porous coordination polymers (PCPs). There are no restrictions on the type of adsorbent 13, but examples of zeolites include FAU type, MFI type, GME type, PHI type, and CHA type, and examples of MOFs include gate-type MOFs such as ELM-11 and MIL-53(AL).

[0020] A supply pipe 14 for supplying raw material gas to the adsorption towers 11, 12 is connected to the adsorption towers 11, 12. The supply pipe 14 is a bifurcated pipe, and the bifurcated portions are respectively connected to the inlets of the adsorption towers 11, 12. A pressurizing device 15 for pressurizing the raw material gas and sending it to the adsorption towers 11, 12 is arranged in the supply pipe 14. Examples of the pressurizing device 15 include a compressor and a blower. The pressurizing device 15 introduces the pressurized raw material gas into the adsorption towers 11, 12. Among the raw material gas introduced from the supply pipe 14 into the adsorption towers 11, 12, specific gas components are adsorbed by the adsorbent 13.

[0021] The discharge pipe 16 has bifurcated portions respectively connected to the outlets of the adsorption towers 11, 12. The gas that the adsorbent 13 did not adsorb (unadsorbed gas) is discharged from the adsorption towers 11, 12 through the discharge pipe 16. Thereby, the gas components adsorbed by the adsorbent 13 (adsorbed gas) can be separated from the raw material gas.

[0022] The desorption pipe 17 has bifurcated portions respectively connected to the outlets of the adsorption towers 11, 12. A vacuum pump 18 is connected downstream of the desorption pipe 17. The vacuum pump 18 decompresses the adsorption towers 11, 12, desorbs the adsorbed gas from the adsorbent 13, and desorbs and sucks the desorbed gas containing the adsorbed gas from the adsorbent 13. An exhaust pipe 19 connected downstream of the vacuum pump 18 includes a first branch pipe 20 and a second branch pipe 21. A first tank 22 is connected downstream of the first branch pipe 20, and a second tank 23 is connected downstream of the second branch pipe​​​​​​​A pressure gauge 35 located in the adsorption tower 11 detects the pressure in the adsorption tower 11, and a pressure gauge 36 located in the adsorption tower 12 detects the pressure in the adsorption tower 12. A concentration meter 37 is located in the exhaust pipe 19 between the point where the first branch pipe 20 and the second branch pipe 21 branch off and the vacuum pump 18. The concentration meter 37 detects the concentration of gas components in the exhaust pipe 19.

[0025] The control device 40 is a device for controlling the opening and closing of the control valves 25-32. The control device 40 includes a central processing unit (CPU) 41 and a memory device 42. The memory device 42 stores programs for opening and closing the control valves 25-32 and adsorption / desorption isotherms 43 (see Figure 2). Based on the programs stored in the memory device 42, the CPU 41 acquires detection results from the pressure gauges 35, 36 and the concentration meter 37 and executes the process of opening and closing the control valves 25-32. The control valves 25-32 operate by receiving electrical signals from the control device 40.

[0026] Figure 2 shows an example of an adsorption / desorption isotherm 43, which is the carbon dioxide isotherm when the adsorbent 13 is a GME-type zeolite. The adsorption / desorption isotherm 43 is a plot of the measured results, where the amount of adsorption was measured while the pressure was changed, the partial pressure of carbon dioxide was plotted on the horizontal axis, and the amount of carbon dioxide adsorbed by the adsorbent 13 was plotted on the vertical axis. The adsorption-side isotherm 44 is the isotherm when the pressure is increased, and the desorption-side isotherm 45 is the isotherm when the pressure is decreased.

[0027] The adsorption-desorption isotherm 43 shows a discrepancy (hysteresis) between the adsorption-side isotherm 44 and the desorption-side isotherm 45. The adsorbent 13 exhibits adsorption-desorption behavior of type IV or V according to the International Union of Pure and Applied Chemistry (IUPAC) classification of adsorption-desorption isotherms. Furthermore, the adsorption-desorption isotherm 43 shows a sigmoid type isotherm, with the adsorption amount on the adsorption-side isotherm 44 rapidly increasing from approximately 0 kPa to approximately 40 kPa, and the adsorption amount on the desorption-side isotherm 45 rapidly decreasing from approximately 20 kPa to approximately 0 kPa. In particular, the adsorption-side isotherm 44 shows two-stage adsorption behavior with a boundary between approximately 10 kPa and approximately 20 kPa. This is due to the influence of pores present in the adsorbent 13.

[0028] Let's return to Figure 1 for explanation. The control device 40 carries out the adsorption process in one of the adsorption towers 11 and 12, while simultaneously carrying out the desorption process in the other of the adsorption towers 11 and 12, so that the adsorption and desorption processes are repeated in each of the adsorption towers 11 and 12. The control device 40 opens and closes the control valves 25-32 to separate the unadsorbed gas from the raw material gas and recover it in the first tank 22, and separate the adsorbed gas from the raw material gas and recover it in the second tank 23. The pressurizer 15 and vacuum pump 18 operate continuously while the unadsorbed gas and adsorbed gas are being recovered.

[0029] The control device 40 opens control valves 25, 27, 30, and 31 and closes the other control valves in order to allow the adsorption process to proceed in the adsorption tower 11 and the desorption process to proceed in the adsorption tower 12. In the adsorption process, when the raw material gas is introduced from the supply pipe 14 to the adsorption tower 11 at a predetermined pressure through control valve 25, the adsorbent 13 sequentially adsorbs the gas components, and the adsorption zone (the part where adsorption is progressing) that has formed near the inlet of the adsorption tower 11 moves to the outlet of the adsorption tower 11. The gas that was not adsorbed by the adsorbent 13 (unadsorbed gas) is released outside the gas recovery device 10 system through the discharge pipe 16 via control valve 27.

[0030] On the other hand, during the desorption process, the adsorption tower 12 is depressurized by the vacuum pump 18, so the desorption of adsorbed gas from the adsorbent 13 proceeds. As the pressure inside the adsorption tower 12 decreases, the amount of adsorbed gas desorbed increases. In the case of carbon dioxide as the adsorbed gas, even if the pressure inside the adsorption tower 12 decreases and the partial pressure of carbon dioxide drops from 100 kPa to about 40 kPa, the amount of adsorbed gas desorbed from the adsorbent 13 increases only slightly (see Figure 2).

[0031] Until the partial pressure of carbon dioxide drops to about 20 kPa, the desorbed gas containing the adsorbed gas is discharged from the desorbing pipe 17 to the exhaust pipe 19 through the control valve 30 by the vacuum pump 18, and then recovered in the first tank 22 through the control valve 31. This allows for a lower concentration of adsorbed gas in the desorbed gas recovered in the first tank 22 and a higher concentration of gas that was not adsorbed by the adsorbent 13 (unadsorbed gas), thus enabling the recovery of a high concentration of unadsorbed gas in the first tank 22. It is, of course, possible to release the unadsorbed gas into the atmosphere or use it for specific purposes without recovering it in the first tank 22.

[0032] When the partial pressure of carbon dioxide drops to approximately 20 kPa (see Figure 2), the amount of adsorbed gas desorbed by the adsorbent 13 increases rapidly. The control device 40 acquires the pressure detected by the pressure gauge 36, and when it determines that the pressure in the adsorption tower 12 has fallen below the threshold pressure (for example, the pressure in the adsorption tower 12 when the partial pressure of carbon dioxide is 20 kPa), it closes the control valve 31 and opens the control valve 32. The desorbed gas containing the adsorbed gas is discharged into the exhaust pipe 19 by the vacuum pump 18 and recovered in the second tank 23 through the control valve 32. Because the concentration of adsorbed gas and the concentration of unadsorbed gas in the desorbed gas recovered in the second tank 23 can be increased, a high concentration of adsorbed gas can be recovered in the second tank 23.

[0033] The number of gas molecules adsorbed by the adsorbent 13 depends on the pressure of the adsorption tower 12 filled with the adsorbent 13. Therefore, by detecting the pressure of the adsorption tower 12 with the control valve 31 open and the control valve 32 closed, and switching to a state where the control valve 31 is closed and the control valve 32 is opened when the pressure of the adsorption tower 12 falls below the threshold pressure, the concentration of the gas recovered in the first tank 22 and the second tank 23 becomes less susceptible to the temperature of the environment in which the gas recovery device 10 is installed and the deterioration of the adsorbent 13. As a result, variations in the concentration of the gas recovered in the first tank 22 and the second tank 23 can be reduced.

[0034] When using an adsorbent 13 that exhibits adsorption behavior represented by a sigmoid-type adsorption-side isotherm 44, the amount of adsorption increases sharply at a certain threshold pressure. Therefore, by setting the pressure of the adsorption tower 11 to a pressure exceeding that threshold pressure (for example, the pressure inside the adsorption tower 11 where the partial pressure of carbon dioxide inside the adsorption tower 11 is 60 kPa), the amount of adsorption of the adsorbent 13 can be secured (see Figure 2). Since the amount of adsorption of the adsorbent 13 can be secured without inputting excessive energy into the pressurizing device 15 to pressurize the inside of the adsorption tower 11 to a pressure far exceeding the threshold pressure, the energy consumed by the pressurizing device 15 can be reduced.

[0035] When using an adsorbent 13 that exhibits adsorption behavior represented by a sigmoid-type desorption-side isotherm 45, the amount of adsorption decreases sharply at a certain threshold pressure (for example, the pressure inside the adsorption tower 12 where the partial pressure of carbon dioxide inside the adsorption tower 12 is 20 kPa) (see Figure 2). Therefore, by switching from a state where control valve 31 is open and control valve 32 is closed to a state where control valve 31 is closed and control valve 32 is open around that threshold pressure, the concentration of adsorbed gas in the desorbed gas recovered in the first tank 22 can be reduced. Furthermore, since the concentration of unadsorbed gas in the desorbed gas recovered in the second tank 23 can also be reduced, high concentrations of unadsorbed gas and high concentrations of adsorbed gas can be recovered.

[0036] When using adsorbent 13 that exhibits adsorption / desorption behavior of type IV or V according to the IUPAC classification of adsorption / desorption isotherms, a phenomenon is observed where the adsorption and desorption processes do not coincide. Because adsorbent 13 exhibits desorption behavior in which the amount of adsorbed decreases sharply at a certain threshold pressure, by switching from a state where control valve 31 is open and control valve 32 is closed to a state where control valve 31 is closed and control valve 32 is open around that threshold pressure, the concentration of unadsorbed gas in the desorbed gas recovered in the first tank 22 can be increased. Furthermore, the concentration of adsorbed gas in the desorbed gas recovered in the second tank 23 can be increased.

[0037] By separating specific gas components using the adsorbent 13 which exhibits a characteristic adsorption / desorption isotherm 43, it is expected that high concentrations of unadsorbed gas and adsorbed gas can be separated even without the washing step described in the second embodiment (see Figure 3). By omitting the washing step, it becomes unnecessary to return some of the adsorbed gas to the adsorption towers 11 and 12, thus reducing the cost of recovering the adsorbed gas.

[0038] Instead of switching the opening and closing of the control valves 31 and 32 based on the pressure detected by the pressure gauges 35 and 36, the control device 40 may also switch the opening and closing of the control valves 31 and 32 based on the concentration of a specific gas component (adsorbed gas) detected by the concentration meter 37. During the desorption process, the adsorption tower 12 is depressurized by the vacuum pump 18, so the desorption of adsorbed gas from the adsorbent 13 progresses, and as the pressure inside the adsorption tower 12 decreases, the concentration of adsorbed gas in the exhaust pipe 19 increases.

[0039] The control device 40 acquires the concentration of the adsorbed gas detected by the concentration meter 37, and when it determines that the concentration of the adsorbed gas has risen above a threshold (for example, the concentration at which the partial pressure of carbon dioxide in the adsorption tower 12 becomes 20 kPa), it closes control valve 31 and opens control valve 32. The desorbed gas containing the adsorbed gas is discharged into the exhaust pipe 19 by the vacuum pump 18 and recovered in the second tank 23 through control valve 32. This makes it possible to increase the concentration of unadsorbed gas in the desorbed gas recovered in the first tank 22 and increase the concentration of adsorbed gas in the desorbed gas recovered in the second tank 23. Since control valves 31 and 32 are switched according to the concentration of adsorbed gas in the exhaust pipe 19, variations in the concentration of the gas recovered in the first tank 22 and the second tank 23 can be reduced.

[0040] Instead of switching the opening and closing of the control valves 31 and 32 based on the pressure detected by the pressure gauges 35 and 36, or switching the opening and closing of the control valves 31 and 32 based on the concentration of the adsorbed gas detected by the concentration meter 37, the control device 40 may calculate the partial pressure of the adsorbed gas in the adsorption tower 12 based on the pressure detected by the pressure gauges 35 and 36 and the concentration of the adsorbed gas detected by the concentration meter 37.

[0041] When the control device 40 determines that the calculated partial pressure of the adsorbed gas in the adsorption tower 12 has fallen below the threshold pressure (e.g., 20 kPa) calculated using the adsorption / desorption isotherm 43, it closes control valve 31 and opens control valve 32. The desorbed gas, including the adsorbed gas, is discharged to the exhaust pipe 19 by the vacuum pump 18 and collected in the second tank 23 through control valve 32. This allows for a higher concentration of unadsorbed gas in the desorbed gas collected in the first tank 22 and a higher concentration of adsorbed gas in the desorbed gas collected in the second tank 23. The partial pressure of the adsorbed gas in the adsorption tower 12 is calculated based on the pressure detected by pressure gauges 35 and 36 and the concentration of the adsorbed gas detected by the concentration meter 37, and control valves 31 and 32 are switched accordingly, further reducing variations in the concentration of the gas collected in the first tank 22 and the second tank 23.

[0042] A second embodiment will be described with reference to Figure 3. In the second embodiment, the gas recovery device 50 is added to the gas recovery device 10 of the first embodiment by adding a second branch pipe 21 and a cleaning pipe 51 that connects the second tank 23 to the adsorption towers 11 and 12. The cleaning pipe 51 is connected to the second tank 21, and its branched portions are connected to the inlets of the adsorption towers 11 and 12, respectively. Control valves 52 and 53 are located at the branched portions of the cleaning pipe 51 for each of the adsorption towers 11 and 12.

[0043] The control device 40 carries out the adsorption process and the cleaning process in one of the adsorption towers 11 and 12, while simultaneously carrying out the desorption process in the other of the adsorption towers 11 and 12. The control device 40 executes the process so that the adsorption process, cleaning process, and desorption process are repeated in order in each of the adsorption towers 11 and 12.

[0044] After the adsorption process is completed in the adsorption tower 11, the control device 40 closes the control valve 25 and opens the control valve 33 for the cleaning process. Since the supply of raw material gas from the pressurizer 15 has stopped, the pressure in the adsorption tower 11 drops to near atmospheric pressure when the control valve 33 is opened, because the control valve 27 is open. The adsorbed gas in the second tank 23 is introduced into the adsorption tower 11 from the cleaning pipe 51 through the control valve 52 as cleaning gas. Impurities other than the adsorbed gas in the adsorption tower 11 are pushed out by the cleaning gas (adsorbed gas) and released from the discharge pipe 16 through the control valve 27. This makes it possible to increase the concentration of adsorbed gas in the adsorption tower 11. As a result, a high concentration of adsorbed gas can be recovered in the desorption process.

[0045] Although the present invention has been described above based on embodiments, it can be easily inferred that the present invention is not limited in any way to the above embodiments, and that various improvements and modifications are possible without departing from the spirit of the present invention.

[0046] For example, the piping system of the gas recovery device 10 is just one example and can be configured as appropriate. In this embodiment, a gas recovery device 10 equipped with two adsorption towers 11 and 12 has been described, but it is not necessarily limited to this. The number of adsorption towers can be set to one or more as appropriate.

[0047] In the first embodiment, it is naturally possible to reduce the pressure inside the adsorption towers 11 and 12 before depressurizing them with the vacuum pump 18 after the adsorption process. To do this, the pressure inside the adsorption towers 11 and 12 is reduced through the control valves 27 and 28. Since part of the desorption process can be performed without operating the vacuum pump 18, the energy required to operate the vacuum pump 18 can be reduced accordingly.

[0048] In the second embodiment, a case in which the cleaning pipe 51 is connected to the second tank 23 was described, but this is not necessarily the only case. Instead of connecting the cleaning pipe 51 to the second tank 23, it is certainly possible to provide a cleaning pipe 51 that is branched from the second branch pipe 21.

[0049] In this embodiment, we have described a case where unadsorbed gas is recovered in the first tank 22 and adsorbed gas is recovered in the second tank 23, but this is not necessarily the only case. If it is not necessary to recover either the unadsorbed gas or the adsorbed gas, it is naturally possible to omit the tank for the gas that does not need to be recovered.

[0050] In this embodiment, the case in which the concentration meter 37 is located in the exhaust pipe 19 has been described, but it is not necessarily limited to this. The concentration meter 37, which can detect the concentration of adsorbed gas under reduced pressure, can be located in the desorption pipe 17. [Explanation of symbols]

[0051] 10.50 Gas recovery device 11,12 Adsorption tower 13 Adsorbent 17. Desorption tube (a tube connecting the adsorption tower and the vacuum pump) 18 Vacuum pump 19 Exhaust pipe 20 First branch pipe 21. Second branch pipe 31 Control valve (first valve) 32 Control valve (second valve) 35,36 Pressure gauge 37 Densitometer 40 Control device 43 Adsorption / desorption isotherm 51. Washing pipe (pipe that supplies desorption gas)

Claims

1. An adsorption tower filled with an adsorbent that adsorbs specific gaseous components contained in the raw gas, A vacuum pump that desorbs and sucks the desorbed gas containing the gas component from the adsorbent by reducing the pressure of the adsorption tower, An exhaust pipe including a first branch pipe and a second branch pipe downstream of the vacuum pump, A first valve is positioned between the vacuum pump and the first branch pipe and opens and closes the first branch pipe, A gas recovery apparatus comprising a second valve disposed between the vacuum pump and the second branch pipe for opening and closing the second branch pipe, for separating the gas components from the raw material gas by a pressure swing adsorption method, A pressure gauge for detecting the pressure inside the adsorption tower, A gas recovery apparatus comprising: a control device that switches from a state in which the first valve is open and the second valve is closed to a state in which the first valve is closed and the second valve is open, based on the pressure detected by the pressure gauge.

2. An adsorption tower filled with an adsorbent that adsorbs specific gaseous components contained in the raw gas, A vacuum pump that desorbs and sucks the desorbed gas containing the gas component from the adsorbent by reducing the pressure of the adsorption tower, An exhaust pipe including a first branch pipe and a second branch pipe downstream of the vacuum pump, A first valve is positioned between the vacuum pump and the first branch pipe and opens and closes the first branch pipe, A gas recovery apparatus comprising a second valve disposed between the vacuum pump and the second branch pipe for opening and closing the second branch pipe, for separating the gas components from the raw material gas by a pressure swing adsorption method, A concentration meter for detecting the concentration of the gas component in the pipe connecting the adsorption tower and the vacuum pump, or the concentration of the gas component in the exhaust pipe, A gas recovery apparatus comprising: a control device that switches from a state in which the first valve is open and the second valve is closed to a state in which the first valve is closed and the second valve is open, based on the concentration detected by the concentration meter.

3. The adsorption tower is equipped with a pressure gauge for detecting the pressure inside the tower. The gas recovery apparatus according to claim 2, wherein the control device calculates the partial pressure of the gas component based on the pressure detected by the pressure gauge and the concentration, and switches the opening and closing of the first valve and the second valve based on the partial pressure.

4. The gas recovery apparatus according to claim 3, wherein the control device switches to a state in which the first valve is closed and the second valve is opened when the partial pressure is between 10 kPa and 60 kPa.

5. The gas recovery apparatus according to any one of claims 1 to 4, wherein the adsorbent exhibits adsorption and desorption behavior represented by a sigmoid-type adsorption / desorption isotherm.

6. The gas recovery apparatus according to any one of claims 1 to 4, wherein the adsorbent exhibits adsorption-desorption behavior of type IV or type V according to the IUPAC classification of adsorption-desorption isotherms.

7. The adsorption tower includes a plurality of adsorption towers connected in parallel to each other. A gas recovery apparatus according to any one of claims 1 to 4, comprising a pipe for supplying the desorbed gas from one adsorption tower to another adsorption tower as a cleaning gas.

8. The gas recovery apparatus according to any one of claims 1 to 4, wherein the control device switches from a state in which the first valve is open and the second valve is closed to a state in which the first valve is closed and the second valve is open, based on the adsorption / desorption isotherm of the adsorbent.

9. An adsorption process in which a specific gas component is adsorbed onto an adsorbent packed in an adsorption tower, A desorption step is performed by reducing the pressure of the adsorption tower and desorbing the gas component that has been adsorbed by the adsorbent, A method for separating gas components from a raw material gas by pressure swing adsorption, comprising: a transfer step of transferring the desorbed gas containing the gas components to an exhaust pipe including a first branch pipe and a second branch pipe downstream of the vacuum pump using a vacuum pump connected to the adsorption tower; A gas recovery method in which, during the transfer process, the system switches from a state in which the desorbed gas is transferred to the first branch pipe to a state in which the desorbed gas is transferred to the second branch pipe, based on the pressure in the adsorption tower, the concentration of the gas component in the pipe connecting the adsorption tower and the vacuum pump, or the concentration of the gas component in the exhaust pipe.

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