Gas recovery device and gas recovery method

Abstract

The present invention provides a gas recovery device (10) and a gas recovery method that can reduce variation in the concentration of recovered gas. This gas recovery device comprises: adsorption towers (11, 12) filled with an adsorbent (13) for adsorbing a specific gas component contained in a feedstock gas; a vacuum pump (18) for depressurizing the adsorption towers to desorb and suction a desorbed gas containing the gas component from the adsorbent; an exhaust pipe (19) including a first branch pipe (20) and a second branch pipe (21) downstream of the vacuum pump; a first valve (31) for opening and closing the first branch pipe; a second valve (32) for opening and closing the second branch pipe; pressure gauges (35, 36) for detecting the respective pressures in the adsorption towers; and a control device (40) for switching, on the basis of the pressures detected by the pressure gauges, 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.

Description

Gas recovery device and gas recovery method

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

[0002] Regarding the technology of separating and recovering the gas contained in the raw material gas by the pressure swing adsorption method, Patent Document 1 discloses a prior art in which the time zone for sucking the gas desorbed by depressurizing 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.

[0003] Japanese Patent Application Laid-Open No. 2018-114464

[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.

[0006] A first aspect for achieving this object is an adsorption tower filled with an adsorbent that adsorbs a specific gas component contained in a raw material gas, a vacuum pump that desorbs and sucks a desorbed gas containing the gas component by depressurizing 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. A gas recovery device that separates a gas component from a raw material gas by the pressure swing adsorption method, comprising a pressure gauge for detecting the pressure inside the adsorption tower, and a control device for switching 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.

[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 embodiment is that, in any of the first to fifth embodiments, 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 desorbed 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.

[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.

[0016] This is a piping diagram of the gas recovery system in the first embodiment. This is an example of an adsorption / desorption isotherm. This is a piping diagram of the gas recovery system in the second embodiment.

[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 according to 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 materials such as ELM-11 and MIL-53 (AL).

[0020] A supply pipe 14 is connected to the adsorption towers 11 and 12 to supply raw material gas to the adsorption towers 11 and 12. The supply pipe 14 is a pipe that branches into two, and the branched parts are connected to the inlets of the adsorption towers 11 and 12, respectively. A pressurizing device 15 is located in the supply pipe 14 to pressurize the raw material gas and send it to the adsorption towers 11 and 12. The pressurizing device 15 may be a compressor or a blower. The pressurizing device 15 introduces the pressurized raw material gas into the adsorption towers 11 and 12. Certain gas components of the raw material gas introduced into the adsorption towers 11 and 12 from the supply pipe 14 are adsorbed by the adsorbent 13.

[0021] The discharge pipe 16 has branched sections that are connected to the outlets of the adsorption towers 11 and 12, respectively. Gas that was not adsorbed by the adsorbent 13 (unadsorbed gas) is released from the discharge pipe 16 to the outside of the adsorption towers 11 and 12. This allows the gas components that have been adsorbed by the adsorbent 13 (adsorbed gas) to be separated from the raw material gas.

[0022] The branched portions of the desorption pipe 17 are connected to the outlets of the adsorption towers 11 and 12, respectively. A vacuum pump 18 is connected downstream of the desorption pipe 17. The vacuum pump 18 depressurizes the adsorption towers 11 and 12, desorbs the adsorbed gas from the adsorbent 13, and desorbs and sucks out the desorbed gas containing the adsorbed gas from the adsorbent 13. The 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 21.

[0023] Control valves 25 and 26 are located in the branched portions of the supply pipe 14 for each adsorption tower 11 and 12. Control valves 27 and 28 are located in the branched portions of the discharge pipe 16 for each adsorption tower 11 and 12. Control valves 29 and 30 are located in the branched portions of the desorption pipe 17 for each adsorption tower 11 and 12. Control valve 31 (first valve) is located in the first branch pipe 20, and control valve 32 (second valve) is located in the second branch pipe 21.

[0024] 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 storage device 42. The storage 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 storage 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 by changing the pressure, 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 to 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 in the adsorption tower 12 filled with the adsorbent 13. Therefore, by detecting the pressure in 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 in 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 the control valve 31 is open and the control valve 32 is closed to a state where the control valve 31 is closed and the 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 an adsorbent 13 that 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 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. 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 the control valves 31 and 32 are switched according to the concentration of the 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 containing the adsorbed gas is discharged to 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. Based on the pressure detected by pressure gauges 35 and 36 and the concentration of adsorbed gas detected by the concentration meter 37, the partial pressure of the adsorbed gas in the adsorption tower 12 is calculated, and control valves 31 and 32 are switched accordingly, further reducing variations in the concentration of the gas recovered 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 and 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 on one of the adsorption towers 11 and 12, while simultaneously carrying out the desorption process on 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 on each of the adsorption towers 11 and 12.

[0044] After the adsorption process ends in the adsorption tower 11, the control device 40 closes the regulating valve 25 and opens the regulating valve 33 for the cleaning process. Since the regulating valve 27 is open, the pressure in the adsorption tower 11 where the supply of the raw material gas by the pressurizing device 15 has stopped drops to near atmospheric pressure when the regulating valve 33 is opened. The adsorption gas in the second tank 23 is introduced as a cleaning gas from the cleaning pipe 51 through the regulating valve 52 into the adsorption tower 11, and the impurities other than the adsorption gas in the adsorption tower 11 are pushed out by the cleaning gas (adsorption gas) and discharged from the discharge pipe 16 through the regulating valve 27. As a result, the concentration of the adsorption gas in the adsorption tower 11 can be increased. Consequently, a high-concentration adsorption gas can be recovered in the desorption process.

[0045] As described above, the present invention has been described based on the embodiments. However, it is easily conceivable that the present invention is not limited to the above embodiments at all, and various improvements and modifications can be made without departing from the spirit of the present invention.

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

[0047] In the first embodiment, after the adsorption process, it is of course possible to reduce the pressure in the adsorption towers 11 and 12 before depressurizing the adsorption towers 11 and 12 with the vacuum pump 18. To do so, the pressure in the adsorption towers 11 and 12 is reduced through the regulating valves 27 and 28. Since a part of the desorption process can be carried out without operating the vacuum pump 18, the energy for operating the vacuum pump 18 can be reduced accordingly.

[0048] In the second embodiment, the case where the cleaning pipe 51 is connected to the second tank 23 has been described, but it is not necessarily limited to this. Instead of connecting the cleaning pipe 51 to the second tank 23, it is of course possible to provide a cleaning pipe 51 branched from the second branch pipe 21.

[0049] In this embodiment, we have described a case in which 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.

[0051] 10, 50 Gas recovery device 11, 12 Adsorption tower 13 Adsorbent 17 Desorption pipe (pipe connecting the adsorption tower and 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 Concentration meter 40 Control device 43 Adsorption / desorption isotherm 51 Washing pipe (pipe supplying desorbed gas)

Claims

1. A gas recovery apparatus for separating the 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 out a desorbed gas containing the 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, the gas recovery apparatus comprising: a pressure gauge for detecting the pressure inside the adsorption tower; 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 pressure detected by the pressure gauge.

2. A gas recovery apparatus for separating the 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 out a desorbed gas containing the 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, wherein the gas recovery apparatus comprises: a concentration meter for detecting the concentration of the gas components in a pipe connecting the adsorption tower and the vacuum pump, or the concentration of the 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.

3. The gas recovery apparatus according to claim 2, comprising a pressure gauge for detecting the pressure inside the adsorption tower, 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 gas recovery apparatus according to any one of claims 1 to 4, wherein the adsorption tower includes a plurality of adsorption towers connected in parallel to each other, and comprises 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. A method for separating a gas component from a raw material gas by a pressure swing adsorption method, 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 method 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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