Recovery system

Abstract

To provide a recovery system which can increase the pressure of an adsorption tower when starting an adsorption operation.SOLUTION: The recovery system comprises: a first blower which is arranged on a duct through which exhaust gas of a combustion device flows; an adsorption tower in which an adsorbent is stored and the exhaust gas is supplied by the first blower; a vacuum pump which decompresses the adsorption tower; and a switching device which switches between a first state where the first blower supplies the exhaust gas to the adsorption tower to make the adsorbent adsorb object gas and a second state where the adsorption tower is decompressed by the vacuum pump to make the adsorbent desorb the object gas, wherein the recovery system is made to be in a third state by introducing ambient air into the adsorption tower before the state changes from the second state to the first state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a recovery device for recovering a specific gas from the exhaust gas of a combustion device. [Background technology]

[0002] One technique for recovering specific gases from the exhaust gas of a combustion system involves repeatedly performing an adsorption operation, in which the exhaust gas is introduced into an adsorption tower containing an adsorbent using a blower to adsorb and separate the gas, and a desorption operation, in which the adsorption tower is depressurized using a vacuum pump to desorb the adsorbed gas. During the desorption operation, the pressure in the adsorption tower becomes negative, below atmospheric pressure, so the adsorption tower becomes negative pressure immediately after switching from the desorption operation to the adsorption operation. If a blower is installed in the duct of the combustion system, the combustion system and the adsorption tower are connected via the blower, which could reduce the pressure inside the combustion system and cause the fire to go out. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-12978 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a prior art technique in which a pressure equalization operation is performed between the desorption operation and the adsorption operation to reduce the pressure difference in the adsorption tower, but the pressure increase from a negative pressure state is insufficient.

[0005] The present invention has been made to solve this problem, and an object of the present invention is to provide a recovery device which can sufficiently increase the pressure in the adsorption column at the start of the adsorption operation. [Means for solving the problem]

[0006] A first aspect for achieving this object comprises a first blower arranged in a duct through which exhaust gas from a combustion device flows, an adsorption tower containing an adsorbent and to which exhaust gas is supplied by the first blower, a vacuum pump for depressurizing the adsorption tower, and a switching device for switching between a first state in which the first blower supplies exhaust gas to the adsorption tower and the adsorbent adsorbs the target gas, and a second state in which the adsorption tower is depressurized by the vacuum pump and the adsorbent desorbs the target gas, and the switching device introduces air into the adsorption tower to set it to a third state before changing from the second state to the first state.

[0007] In the second embodiment, in the third state of the first embodiment, the pressure in the adsorption tower into which the air has been introduced is set to 50 kPa or more.

[0008] In the third embodiment, the pressure in the adsorption tower into which the air has been introduced is increased to atmospheric pressure or higher in the first or second embodiment.

[0009] In a fourth aspect, in any one of the first to third aspects, a dehumidifying section is provided to remove water, and the air passes through the dehumidifying section and reaches the adsorbent contained in the adsorption tower.

[0010] In a fifth aspect, in the fourth aspect, the dehumidifying section is provided inside the adsorption tower and contains a dehumidifying agent that adsorbs water.

[0011] A sixth aspect is the method according to any one of the first to fifth aspects, further comprising a second blower that supplies gas to the adsorption tower.

[0012] A seventh aspect is any of the first to fifth aspects, further comprising a bypass pipe that bypasses the suction side and discharge side of the first blower, a first control valve arranged in the bypass pipe, and a first pressure gauge arranged on the suction side of the first blower, and the switching device adjusts the opening degree of the first control valve based on the pressure detected by the first pressure gauge.

[0013] An eighth aspect is any of the first to fifth aspects, further comprising a second pressure gauge arranged on the suction side of the first blower and a second control valve arranged on the discharge side of the first blower, and the switching device adjusts the opening degree of the second control valve based on the pressure detected by the second pressure gauge.

[0014] A ninth aspect is any of the first to fifth aspects, further comprising a third pressure gauge arranged on the suction side of the first blower, and the switching device adjusts the rotation speed of the first blower based on the pressure detected by the third pressure gauge. [Effects of the Invention]

[0015] According to the present invention, before the adsorption tower is depressurized by a vacuum pump and the adsorbent desorbs the target gas from a second state, to a first state, in which a first blower supplies exhaust gas to the adsorption tower and the adsorbent adsorbs the target gas, atmospheric air is introduced into the adsorption tower to create a third state, thereby enabling the pressure in the adsorption tower to be sufficiently increased immediately after the state is changed to the first state (at the start of the adsorption operation). [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a piping diagram of the recovery device according to the first embodiment. [Figure 2] 1 is a table showing the progress of time and the operations performed in the adsorption tower. [Figure 3] FIG. 10 is a piping diagram of a recovery device according to a second embodiment. [Figure 4] FIG. 11 is a piping diagram of a recovery device according to a third embodiment. [Figure 5] FIG. 10 is a piping diagram of a recovery device according to a fourth embodiment. [Figure 6] FIG. 11 is a piping diagram of a recovery device according to a fifth embodiment. [Figure 7] FIG. 13 is a piping diagram of a recovery device according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a piping diagram of a recovery system 10 according to a first embodiment. The recovery system 10 recovers a target gas from exhaust gas using pressure swing adsorption. The recovery system 10 includes adsorption towers 11, 12, and 13, and an adsorbent 14 that adsorbs the target gas is accommodated in the adsorption towers 11, 12, and 13 as a fixed bed.

[0018] The adsorbent 14 has a property that its adsorption capacity (the amount of gas adsorbed per unit of adsorbent) varies depending on the partial pressure of the target gas, and therefore the recovery device 10 can separate target gas that is easily adsorbed by the adsorbent 14 and recover a target gas (the same gas as the target gas) by increasing or decreasing the pressure of the adsorption towers 11, 12, and 13, or can separate target gas that is difficult to adsorb by the adsorbent 14 and recover a target gas (a gas different from the target gas). Examples of adsorbent 14 include activated carbon, silica gel, zeolite, molecular sieving carbon, mesoporous silica, metal-organic frameworks (MOFs), and porous coordination polymers (PCPs), and are selected appropriately depending on the target gas.

[0019] The recovery device 10 is connected to a duct 16 through which exhaust gas from a combustion device 15 flows. The combustion device 15 is a device that produces high-temperature gas for heating or simply burns gas, and examples of such a device include a boiler and an incinerator. In this embodiment, a recovery device 10 that targets carbon dioxide will be described as an example. When the combustion device 15 is operating, it supplies a substantially constant flow rate of exhaust gas to the duct 16. The duct 16 is a pipe through which the exhaust gas passes, including a flue.

[0020] A first blower 17 is disposed in the duct 16. Examples of the first blower 17 include a compressor and a blower. A buffer tank 18 is disposed in the duct 16 between the combustion device 15 and the first blower 17. The buffer tank 18 is a tank that stores exhaust gas from the combustion device 15, and reduces the effect of pressure fluctuations in the recovery device 10 on the combustion device 15.

[0021] Duct 16 downstream of first blower 17 branches into three supply pipes 19, 20, and 21, which are connected to adsorption towers 11, 12, and 13, respectively. When first blower 17 is activated, the exhaust gas flowing through duct 16 is sent to adsorption towers 11, 12, and 13 through supply pipes 19, 20, and 21.

[0022] A desorption tube 22, through which the target gas desorbed from the adsorbent 14 flows, is connected to the adsorption towers 11, 12, and 13. When a vacuum pump 23 arranged in the desorption tube 22 is activated, the pressure in the adsorption towers 11, 12, and 13 is reduced, and the target gas desorbed from the adsorbent 14 is introduced into the desorption tube 22.

[0023] A cleaning pipe 24 is connected to the adsorption towers 11, 12, and 13. A recovery tank 25 is connected to the desorption pipe 22 downstream of the vacuum pump 23 and the cleaning pipe 24. The recovery tank 25 stores the target gas desorbed from the adsorbent 14. A liquefier 26 connected to the recovery tank 25 is a device that liquefies the target gas to reduce its volume.

[0024] Of the exhaust gases sent to the adsorption towers 11, 12, and 13 through the supply pipes 19, 20, and 21, the gases that are not adsorbed by the adsorbent 14 are exhausted through a first exhaust pipe 27. Of the gases sent to the adsorption towers 11, 12, and 13 through the cleaning pipe 24, the gases that are not adsorbed by the adsorbent 14 are exhausted through a second exhaust pipe 28.

[0025] The inlet pipe 29 connected to the adsorption towers 11, 12, and 13 is a pipe through which gas flows to be introduced into the adsorption towers 11, 12, and 13 to make the pressure in the adsorption towers 11, 12, and 13 equal to or higher than atmospheric pressure. In this embodiment, the gas flowing through the inlet pipe 29 is atmospheric air. A dehumidifying unit 30 that removes water from the gas is disposed in the inlet pipe 29. The dehumidifying unit 30 removes water vapor contained in the gas that passes through the inlet pipe 29 and reaches the adsorbent 14. Examples of the dehumidifying unit 30 include a dehumidifier filled with an adsorbent (dehumidifying agent) that adsorbs water, a membrane air dryer, and a refrigerated air dryer.

[0026] The switching device 31 includes valves 32-49 and a control device (not shown). The valves 32-49 operate upon receiving electrical signals from the control device. The switching device 31 opens and closes the valves 32-49 to switch the adsorption or desorption states of the adsorption towers 11, 12, and 13. Valves 32, 33, and 34 are disposed in the supply pipes 19, 20, and 21, respectively. Valves 35, 36, and 37 are disposed in the desorption pipe 22. Valves 38, 39, and 40 are disposed in the cleaning pipe 24. Valves 41, 42, and 43 are disposed in the first exhaust pipe 27. Valves 44, 45, and 46 are disposed in the second exhaust pipe 28. Valves 47, 48, and 49 are disposed in the inlet pipe 29.

[0027] The operation of the recovery system 10 will be described with reference to Figures 1 and 2. Figure 2 is a table showing the passage of time and the operations performed in the adsorption towers 11, 12, and 13. The switching device 31 opens and closes valves 32-49 so that the operations of adsorption, cleaning, desorption, and pressure recovery are repeated in each of the adsorption towers 11, 12, and 13 in that order. In Figure 2, the adsorption tower 11 is referred to as "adsorption tower 1" or "1," the adsorption tower 12 as "adsorption tower 2" or "2," and the adsorption tower 13 as "adsorption tower 3" or "3," with 1-6 indicating the passage of time. The operations are repeated, with times 1-6 being one cycle. During the adsorption, cleaning, desorption, and pressure recovery operations, the first blower 17 and vacuum pump 23 are always operating.

[0028] At "Time 1" shown in Figure 2, an adsorption operation is performed in adsorption tower 11, a cleaning operation is performed in adsorption tower 12, and a desorption operation is performed in adsorption tower 13. During the adsorption operation, switching device 31 opens valves 32 and 41 and closes valves 33, 34, 35, 38, 44, and 47. Exhaust gas is supplied to adsorption tower 11 by first blower 17, and the pressure in adsorption tower 11 increases. The target gas (carbon dioxide) is adsorbed onto adsorbent 14 contained in adsorption tower 11, and gas not adsorbed by adsorbent 14 is discharged outside adsorption tower 11 through first exhaust pipe 27. The state in which adsorption tower 11 is pressurized during the adsorption operation and the pressure in adsorption tower 11 is higher than atmospheric pressure is referred to as the first state.

[0029] During the cleaning operation, the switching device 31 opens valves 39 and 45 and closes valves 36, 40, 42, and 48. A portion of the target gas in the recovery tank 25 is introduced into the adsorption tower 12 through the cleaning pipe 24. The gas that is not adsorbed by the adsorbent 14 is discharged out of the adsorption tower 12 through the second exhaust pipe 28 by the target gas introduced into the adsorption tower 12.

[0030] During the desorption operation, the switching device 31 opens the valve 37 and closes the valves 43, 46, and 49. The adsorption tower 13 is depressurized by the vacuum pump 23, and the pressure in the adsorption tower 13 decreases. The target gas adsorbed to the adsorbent 14 contained in the adsorption tower 13 is desorbed, and the target gas is recovered in the recovery tank 25 through the desorption tube 22. During the desorption operation, the pressure in the adsorption tower 13 is in a negative pressure state below atmospheric pressure. The state in which the adsorption tower 13 is depressurized during the desorption operation and is under negative pressure is referred to as the second state.

[0031] At "Time 2," adsorption operation continues in adsorption tower 11, desorption operation is performed in adsorption tower 12, and pressure recovery operation is performed in adsorption tower 13. During the desorption operation, switching device 31 opens valve 36 and closes valves 42, 45, and 48. Vacuum pump 23 depressurizes adsorption tower 12, and the pressure in adsorption tower 12 decreases. The target gas adsorbed by adsorbent 14 contained in adsorption tower 12 is desorbed, and the target gas passes through desorption tube 22 and is recovered in recovery tank 25.

[0032] In the prior art (Patent Document 1), an adsorption tower after a desorption operation is connected to an adsorption tower after an adsorption operation, and a pressure equalization operation is performed to reduce the pressure difference between the adsorption towers. Because the difference between the pressure in the adsorption tower 13 after the desorption operation and atmospheric pressure is large, even if the pressurized adsorption tower after the adsorption operation is connected to the adsorption tower 13, the pressure increase in the adsorption tower 13 after the pressure equalization operation is insufficient.

[0033] In contrast, during pressure recovery operation, the switching device 31 opens valve 49 and closes valves 37, 39, 40, 43, and 46. Due to the pressure difference between the negative pressure in the adsorption tower 13 and atmospheric pressure, atmospheric air is introduced into the adsorption tower 13, which is in a negative pressure state, through the inlet pipe 29. As a result, the pressure in the adsorption tower 13 reaches 50 kPa (absolute pressure) or higher, nearly equal to atmospheric pressure. The pressure recovery operation allows the pressure in the adsorption tower 13 to be higher than that achieved by the pressure equalization operation of the prior art. The state of the adsorption tower 13 during the pressure recovery operation is referred to as the third state.

[0034] During the pressure recovery operation, moisture in the atmosphere is removed by the dehumidifying section 30 disposed in the inlet pipe 29, thereby reducing the amount of water in the atmosphere that is adsorbed onto the adsorbent 14 contained in the adsorption tower 13. Since it is possible to prevent the amount of adsorption of the target gas from decreasing due to the influence of water adsorbed onto the adsorbent 14, it is possible to ensure the amount of adsorption of the target gas by the adsorbent 14.

[0035] At "time 3," adsorption operation is performed in adsorption tower 13. During adsorption operation, switching device 31 opens valves 34 and 43 and closes valves 32, 33, 37, 40, 46, and 49. Adsorption tower 13 and combustion device 15 are connected via first blower 17 disposed in duct 16, and because the pressure in adsorption tower 13, for which the pressure recovery operation has been performed, is approximately equal to atmospheric pressure, the drop in pressure inside combustion device 15 can be reduced.

[0036] Furthermore, since pressure fluctuations in the combustion device 15 can be reduced when the adsorption tower 13 and the combustion device 15 are connected via the first blower 17, it is possible to reduce the size of the buffer tank 18 that alleviates pressure fluctuations in the recovery device 10. It is also possible to omit the buffer tank 18 by setting the pressure and conditions of each part of the recovery device 10.

[0037] At "time 3", a cleaning operation is further performed in the adsorption tower 11, and a desorption operation is subsequently performed in the adsorption tower 12. The operation of the switching device 31 during the cleaning operation and desorption operation at time 3 is similar to the operation of the switching device 31 during the cleaning operation and desorption operation at time 1, and therefore a description thereof will be omitted.

[0038] As described above, in recovery device 10, before the pressure in adsorption tower 13 is reduced by vacuum pump 23 and the target gas is desorbed by adsorbent 14, and the first state is changed to the first state in which first blower 17 supplies exhaust gas to adsorption tower 13 and the target gas is adsorbed by adsorbent 14, atmospheric air is introduced into adsorption tower 13 to change to the third state, so the pressure in adsorption tower 13 rises sufficiently immediately after the change to the first state (at the start of adsorption operation). Since combustion in combustion device 15 connected to recovery device 10 is stabilized, the fire in combustion device 15 can be prevented from becoming smaller or going out.

[0039] A second embodiment will be described with reference to Figure 3. In the first embodiment, a case where the pressure in the adsorption tower 13 during the pressure recovery operation rises to approximately atmospheric pressure was described. In contrast, in the second embodiment, a case where the pressure in the adsorption tower 13 during the pressure recovery operation is further increased will be described. The same parts as those described in the first embodiment are designated by the same reference numerals, and the following description will be omitted (the same applies to Figures 4 to 7).

[0040] 3 is a piping diagram of a recovery device 50 according to the second embodiment. In the recovery device 50, dehumidifying sections 51, 52, and 53 are provided inside the adsorption towers 11, 12, and 13, respectively. The dehumidifying sections 51, 52, and 53 are filled with a dehumidifying agent that adsorbs water. Examples of the dehumidifying agent include calcium chloride and silica gel. The dehumidifying agent used has a water adsorption capacity greater than that of the adsorbent 14 at the same partial pressure.

[0041] During the pressure recovery operation, the air flowing from the inlet pipe 29 toward the adsorption towers 11, 12, and 13 passes through the dehumidifying sections 51, 52, and 53 and reaches the adsorbent 14, so that moisture in the air is adsorbed by the dehumidifying sections 51, 52, and 53. Since the amount of water in the air adsorbed by the adsorbent 14 can be reduced, the amount of target gas adsorbed by the adsorbent 14 can be ensured. Furthermore, because the dehumidifying sections 51, 52, and 53 are provided inside the adsorption towers 11, 12, and 13, the space required to provide the dehumidifying sections outside the adsorption towers 11, 12, and 13 can be saved.

[0042] The adsorbent 14 and dehumidifiers 51, 52, 53 are arranged inside the adsorption towers 11, 12, 13 so that the exhaust gas reaches the dehumidifiers 51, 52, 53 while the target gas and water vapor are sequentially adsorbed onto the adsorbent 14 during the adsorption operation. Because the water vapor concentration of the exhaust gas is low when it passes through the dehumidifiers 51, 52, 53, the water adsorbed in the dehumidifiers 51, 52, 53 during the pressure recovery operation is desorbed during the adsorption operation. Because the dehumidifiers in the dehumidifiers 51, 52, 53 are regenerated during the adsorption operation, the amount of water adsorbed by the dehumidifiers during the pressure recovery operation can be ensured.

[0043] The second blower 54 disposed in the inlet pipe 29 operates only during the pressure recovery operation. When the second blower 54 operates, the adsorption towers 11, 12, and 13 are pressurized by the gas supplied through the inlet pipe 29. As a result, the pressure in the adsorption towers 11, 12, and 13 during the pressure recovery operation becomes equal to or higher than atmospheric pressure. The pressure in the adsorption towers 11, 12, and 13 at this time can be set to approximately the same as the pressure in the adsorption towers 11, 12, and 13 during the adsorption operation, for example.

[0044] If the pressure in the adsorption tower 13, which has undergone a pressure recovery operation at time 2 (see FIG. 2), is increased by the second blower 54 to approximately the same pressure as during the adsorption operation, fluctuations in pressure on the discharge side of the first blower 17 can be reduced when the adsorption operation is performed in the adsorption tower 13 at time 3. This allows the adsorption operation to be performed in the adsorption tower 13 immediately after time 3, even when the first blower 17 is operated at a substantially constant rotation speed. Because the pressure fluctuations are small, the buffer tank 18 (see FIG. 1), which reduces pressure fluctuations, can be made smaller or omitted. This allows the space occupied by the recovery device 50 to be reduced by the space occupied by the buffer tank 18.

[0045] The concentration of the target gas in the atmosphere introduced into adsorption tower 13 during the pressure recovery operation is much lower than the concentration of the target gas in the exhaust gas, and the adsorption capacity of adsorbent 14 for components other than the target gas in the atmosphere is much smaller than the adsorption capacity of adsorbent 14 for the target gas. Therefore, even if the pressure in adsorption tower 13 during the pressure recovery operation is approximately the same as the pressure during the adsorption operation, the effect of the atmosphere introduced into adsorption tower 13 during the pressure recovery operation on the amount of adsorption of the target gas during the adsorption operation can be reduced.

[0046] A third embodiment will be described with reference to Fig. 4. In the first and second embodiments, a dehumidifying unit is provided to remove water from the air introduced during the pressure restoration operation. In contrast, in the third embodiment, a case will be described in which air whose moisture content has been reduced outside the recovery device 60 system is introduced during the pressure restoration operation.

[0047] 4 is a piping diagram of recovery device 60 in the third embodiment. In recovery device 60, an inlet pipe 29 is connected to liquefier 26, and exhaust gas from liquefier 26 is supplied to inlet pipe 29. Liquefier 26 is equipped with a dehumidifier to reduce moisture mixed in with the liquefied target gas, and the exhaust gas from liquefier 26 contains dry air in which the moisture in the atmosphere has been reduced as a result of operation of the dehumidifier. Because the dry air (atmosphere) discharged from liquefier 26 is supplied to adsorption towers 11, 12, and 13 through inlet pipe 29 during the pressure recovery operation, a dehumidification section for removing moisture from the atmosphere can be omitted.

[0048] A fourth embodiment will be described with reference to Fig. 5. In the second embodiment, the second blower 54, which sends gas to the adsorption towers 11, 12, and 13 during the pressure recovery operation, reduces pressure fluctuations on the discharge side of the first blower 17 when switching from the pressure recovery operation to the adsorption operation. In contrast, the fourth embodiment will describe a case in which a bypass pipe 71 is provided that bypasses the suction side and discharge side of the first blower 17, thereby reducing pressure fluctuations on the discharge side of the first blower 17 when switching from the pressure recovery operation to the adsorption operation.

[0049] 5 is a piping diagram of a recovery device 70 according to a fourth embodiment. The recovery device 70 includes a bypass pipe 71 that bypasses the suction side and discharge side of the first blower 17, a first control valve 72 disposed in the bypass pipe 71, and a first pressure gauge 73 disposed on the suction side of the first blower 17. The reason why the pressure on the suction side of the first blower 17 is detected by the first pressure gauge 73 is that the pressure on the suction side of the first blower 17 changes less than the pressure on the discharge side of the first blower 17, which changes significantly depending on the transition from the initial, middle, to final stages of the adsorption operation, even when the first blower 17 is operated at a constant rotation speed.

[0050] The bypass pipe 71 connects the suction side and discharge side of the first blower 17, and since the pressure on the discharge side of the first blower 17 is positive, when the first control valve 72 is open, the pressure (negative pressure) on the suction side of the first blower 17 can be made closer to atmospheric pressure.

[0051] When time 2 (see FIG. 2) changes to time 3, when time 4 changes to time 5, and when time 6 changes to time 1, one of the adsorption towers 11, 12, and 13 switches from pressure recovery operation to adsorption operation, causing fluctuations in the pressure on the discharge side of the first blower 17. As the pressure on the discharge side of the first blower 17 changes, the pressure on the suction side of the first blower 17 detected by the first pressure gauge 73 also changes.

[0052] Because the switching device 31 adjusts the opening of the first control valve 72 based on the pressure detected by the first pressure gauge 73, even when the first blower 17 is operated at a substantially constant rotation speed, it is possible to adjust the pressure on the suction side of the first blower 17 and reduce fluctuations in pressure on the discharge side of the first blower 17. Because the buffer tank 18 (see FIG. 1) that alleviates pressure fluctuations can be made smaller or eliminated, the space occupied by the recovery device 70 can be reduced.

[0053] A fifth embodiment will be described with reference to Fig. 6. In the fourth embodiment, a bypass pipe 71 is provided that bypasses the suction side and discharge side of the first fan 17, and pressure fluctuations on the discharge side of the first fan 17 are reduced when switching from pressure recovery operation to adsorption operation. In contrast, in the fifth embodiment, a second control valve 82 is provided on the discharge side of the first fan 17, and pressure fluctuations are reduced.

[0054] 6 is a piping diagram of a recovery device 80 according to the fifth embodiment. The recovery device 80 includes a second pressure gauge 81 disposed on the suction side of the first blower 17, and a second control valve 82 disposed on the discharge side of the first blower 17.

[0055] When time 2 (see Figure 2) changes to time 3, when time 4 changes to time 5, and when time 6 changes to time 1, one of the adsorption towers 11, 12, and 13 switches from pressure recovery operation to adsorption operation, causing the pressure on the discharge side of the first blower 17 to fluctuate, and accordingly, the pressure on the suction side of the first blower 17, which is connected via the first blower 17, to fluctuate.

[0056] Because the switching device 31 adjusts the opening of the second control valve 82 based on the pressure detected by the second pressure gauge 81, it is possible to reduce fluctuations in pressure on the discharge side of the first blower 17, even when the first blower 17 is operated at a substantially constant rotation speed. Because the buffer tank 18 (see FIG. 1) that reduces pressure fluctuations can be made smaller or eliminated, the space occupied by the recovery device 80 can be reduced.

[0057] A sixth embodiment will be described with reference to Fig. 7. In the first to fifth embodiments, the first fan 17 is operated at a substantially constant rotation speed. In contrast, the sixth embodiment will describe a case in which the rotation speed of the first fan 17 is adjusted to reduce fluctuations in pressure on the discharge side of the first fan 17 when switching from pressure recovery operation to adsorption operation.

[0058] 7 is a piping diagram of a recovery device 90 according to the sixth embodiment. The recovery device 90 includes a third pressure gauge 91 disposed on the suction side of the first blower 17. When time 2 (see FIG. 2) changes to time 3, when time 4 changes to time 5, or when time 6 changes to time 1, one of the adsorption towers 11, 12, and 13 switches from pressure recovery operation to adsorption operation, causing the pressure on the discharge side of the first blower 17 to fluctuate, and accordingly, the pressure on the suction side of the first blower 17 connected via the first blower 17 to fluctuate.

[0059] The switching device 31 adjusts the rotation speed of the first blower 17 based on the pressure on the suction side of the first blower 17 detected by the third pressure gauge 91. This reduces fluctuations in pressure on the discharge side of the first blower 17, making it possible to reduce the size or eliminate the buffer tank 18 (see FIG. 1) that alleviates pressure fluctuations. As a result, the space occupied by the recovery device 90 can be reduced.

[0060] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0061] For example, the piping system of the recovery device 10 is an example and can be set as appropriate. In the embodiment, the recovery device 10 is described as having three adsorption towers 11, 12, and 13, but this is not necessarily limited to this. The number of adsorption towers can be set to one or more as appropriate.

[0062] In the embodiment, the recovery device 10 is described as sequentially performing the adsorption operation, the cleaning operation, the desorption operation, and the pressure recovery operation, but this is not necessarily limited to this. For example, it is of course possible to omit the cleaning operation. By omitting the cleaning operation, it is not necessary to return a portion of the target gas recovered in the recovery tank 25 to the adsorption towers 11, 12, and 13, and therefore the recovery rate of the target gas can be improved.

[0063] In the second embodiment, the second blower 54 is disposed in the inlet pipe 29, but it is possible to omit the second blower 54. In this case, the dehumidifying units 51, 52, and 53 are provided inside the adsorption towers 11, 12, and 13, and therefore the space occupied by the dehumidifying units provided outside the adsorption towers 11, 12, and 13 can be eliminated.

[0064] In the third embodiment, a pipe for introducing air may be connected to the introduction pipe 29, or dry gas discharged from another device may be supplied to the introduction pipe 29. It is desirable to provide a dehumidifying unit in the pipe for introducing air.

[0065] In the fourth to sixth embodiments, it is of course possible to replace the dehumidifying section 30 with dehumidifying sections 51, 52, and 53 provided inside the adsorption towers 11, 12, and 13. It is also of course possible to provide a second blower 54 in the inlet pipe 29 in the fourth to sixth embodiments. [Explanation of symbols]

[0066] 10,50,60,70,80,90 Recovery device 11,12,13 Adsorption tower 14 Adsorbents 15 Combustion equipment 16 Duct 17 First Blower 23 Vacuum pump 30,51,52,53 Dehumidification section 31 Switching Device 54 Second Blower 71 Bypass pipe 72 First control valve 73 First Pressure Gauge 81 Second pressure gauge 82 Second control valve 91 Third Pressure Gauge

Claims

1. a first fan disposed in a duct through which exhaust gas from the combustion device flows; an adsorption tower containing an adsorbent and to which the exhaust gas is supplied by the first blower; a vacuum pump that depressurizes the adsorption tower; a switching device that switches between a first state in which the first blower supplies the exhaust gas to the adsorption tower and the adsorbent adsorbs the target gas, and a second state in which the adsorption tower is depressurized by the vacuum pump and the adsorbent desorbs the target gas, The switching device introduces air into the adsorption tower to set the recovery apparatus to a third state before changing from the second state to the first state.

2. 2. The recovery apparatus according to claim 1, wherein in the third state, the pressure in the adsorption tower into which the atmosphere is introduced is set to 50 kPa or more.

3. 2. The recovery apparatus according to claim 1, wherein in the third state, the pressure in the adsorption tower into which the air has been introduced is set to atmospheric pressure or higher.

4. Equipped with a dehumidifying section that removes water, 2. The recovery apparatus according to claim 1, wherein the air passes through the dehumidifying section and reaches the adsorbent contained in the adsorption tower.

5. 5. The recovery apparatus according to claim 4, wherein the dehumidifying section is provided inside the adsorption tower and includes a dehumidifying agent that adsorbs water.

6. The recovery apparatus according to claim 1 , further comprising a second blower that supplies the gas to the adsorption tower.

7. a bypass pipe that bypasses the suction side and the discharge side of the first fan; a first control valve disposed in the bypass pipe; a first pressure gauge disposed on the suction side of the first blower; The recovery device according to claim 1 , wherein the switching device adjusts the opening of the first adjustment valve based on the pressure detected by the first pressure gauge.

8. a second pressure gauge disposed on the suction side of the first blower; a second control valve disposed on the discharge side of the first blower; The recovery device according to claim 1 , wherein the switching device adjusts the opening of the second adjustment valve based on the pressure detected by the second pressure gauge.

9. a third pressure gauge disposed on the suction side of the first blower; 6. The recovery device according to claim 1, wherein the switching device adjusts the rotation speed of the first blower based on the pressure detected by the third pressure gauge.

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