Carbon dioxide recovery device

Abstract

To efficiently recover high-concentration carbon dioxide gas from exhaust gas of a fuel cell system.SOLUTION: A carbon dioxide recovery device includes an inlet portion that introduces exhaust gas from a fuel cell system, a heat exchange portion that cools the exhaust gas by heat exchange, a first moisture absorption portion that separates condensed water from the exhaust gas, a second moisture absorption portion that absorbs humidity in the exhaust gas, a carbon dioxide recovery portion that recovers carbon dioxide from the exhaust gas, a first gas line that runs from the inlet portion through the heat exchange portion, the first moisture absorption portion, the second moisture absorption portion and the carbon dioxide recovery portion in that order before being connected to an outlet portion, and a pump provided on the first gas line.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present specification discloses a carbon dioxide gas recovery device. [Background technology]

[0002] Conventionally, this type of carbon dioxide recovery device has been proposed to include a bubbling device that dissolves carbon dioxide contained in exhaust gas emitted from a fuel cell (see, for example, Patent Document 1). Exhaust gas, which contains high-temperature steam and carbon dioxide, emitted from the fuel cell is guided to the bubbling device and bubbled into water. The water in the bubbling tank is heated by the heat of the high-temperature steam, and the carbon dioxide in the exhaust gas is dissolved in the water by the bubbling action, producing carbonated hot spring water. The carbonated hot spring water is supplied to a bathtub in the facility via a circulation pump and circulated to the bubbling device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-272693 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the carbon dioxide contained in the exhaust gas of a fuel cell is only a few percent, it is not possible to produce carbonated hot spring water with a sufficient concentration by directly supplying the exhaust gas of a fuel cell into water.

[0005] A carbon dioxide gas recovery device disclosed herein has a main object to provide a carbon dioxide gas recovery device that can efficiently recover high-concentration carbon dioxide gas from exhaust gas of a fuel cell system. [Means for solving the problem]

[0006] The carbon dioxide gas recovery device of the present disclosure employs the following means to achieve the above-mentioned main object.

[0007] The carbon dioxide gas recovery device of the present disclosure comprises: A carbon dioxide gas recovery device that recovers carbon dioxide gas contained in exhaust gas from a fuel cell system, an inlet for introducing exhaust gas from the fuel cell system; a heat exchange unit that cools the exhaust gas by heat exchange; a first moisture absorption section that separates condensed water from the exhaust gas; a second moisture absorbing section that absorbs humidity from the exhaust gas; a carbon dioxide gas recovery unit that recovers carbon dioxide gas from the exhaust gas; a first gas line extending from the inlet through the heat exchange unit, the first moisture absorption unit, the second moisture absorption unit, and the carbon dioxide gas recovery unit in this order and connected to the outlet; a pump provided in the first gas line; The gist of the project is to provide the following:

[0008] In the carbon dioxide recovery device disclosed herein, exhaust gas from a fuel cell system introduced into an inlet is cooled in a heat exchanger, condensed water produced by the cooling of the exhaust gas is separated in a first hygroscopic unit, and moisture is absorbed in a second hygroscopic unit before the gas is supplied to the carbon dioxide recovery unit. This allows the carbon dioxide recovery device to recover carbon dioxide from the exhaust gas while reducing the temperature and humidity of the exhaust gas, thereby enabling efficient recovery of high-concentration carbon dioxide. Furthermore, because the exhaust gas is cooled in the first heat exchanger and the condensed water is separated in the first hygroscopic unit, the second hygroscopic unit can reduce the humidity of the exhaust gas using a small amount of hygroscopic agent. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a carbon dioxide gas recovery device according to an embodiment of the present invention. [Figure 2] FIG. 3 is an explanatory diagram illustrating the flow of gas (exhaust gas) in an exhaust gas recovery mode. [Figure 3] FIG. 2 is an explanatory diagram illustrating the flow of gas (carbon dioxide gas) in a carbon dioxide gas desorption mode. [Figure 4]FIG. 4 is an explanatory diagram illustrating the flow of gas (purge gas) in a moisture absorbent regeneration mode. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present disclosure will be described with reference to the drawings.

[0011] FIG. 1 is a schematic diagram of a carbon dioxide gas recovery device 10 according to this embodiment. The carbon dioxide gas recovery device 10 according to this embodiment recovers carbon dioxide gas (CO2) contained in exhaust gas from a fuel cell system 1. The fuel cell system 1 includes a reformer that generates fuel gas containing hydrogen by reforming a hydrocarbon-based raw fuel gas, such as natural gas or LP gas; a fuel cell stack that generates electricity through an electrochemical reaction between the fuel gas generated in the reformer and an oxidant gas (air); and a combustor that combusts off-gas discharged from the fuel cell stack. The exhaust gas generated by combustion of the off-gas in the combustor contains water vapor and carbon dioxide gas. The carbon dioxide gas recovery device 10 according to this embodiment recovers carbon dioxide gas from the exhaust gas and supplies the recovered carbon dioxide gas to a carbon dioxide gas utilization device 100 as needed. An example of the carbon dioxide gas utilization device 100 is a carbonated spring device that generates carbonated spring water by dissolving carbon dioxide gas in hot water.

[0012] The carbon dioxide gas recovery device 10 of this embodiment includes an inlet 11 for introducing exhaust gas from the fuel cell system 1, a heat exchanger 20 for cooling the exhaust gas, a first moisture absorber 30 and a second moisture absorber 40 for absorbing moisture in the exhaust gas, a carbon dioxide gas recovery unit 50 for recovering carbon dioxide gas from the exhaust gas, a pump 60, first to fourth gas lines L1 to L4, first to sixth on-off valves V1 to V6, and a control device 70 for controlling the entire device. The heat exchanger 20, first moisture absorber 30, second moisture absorber 40, carbon dioxide gas recovery unit 50, and pump 60 are arranged in this order from the inlet 11 to the first gas line L1.

[0013] The heat exchanger 20 cools the exhaust gas. The heat exchanger 20 includes a container 21 having an internal space, an exhaust gas flow path 22 that forms part of the first gas line L1 and penetrates the internal space of the container 21, and a moisture absorbent 23 filled in the internal space of the container 21. The moisture absorbent 23 is a material with humidity control properties, such as silica gel. When the moisture absorbent 23 absorbs moisture and is purged with dry air, it releases moisture through an endothermic reaction. The heat exchanger 20 cools the exhaust gas flowing through the exhaust gas flow path 22 by the endothermic action of the moisture absorbent 23. In this embodiment, the end of the first gas line L1 is connected to the container 21 of the heat exchanger 20. The exhaust gas that has passed through the exhaust gas flow path 22, the first moisture absorbent 30, the second moisture absorbent 40, and the carbon dioxide gas recovery unit 50 of the heat exchanger 20 is introduced into the internal space of the container 21 filled with the moisture absorbent 23 as a purge gas and then discharged to the outside air.

[0014] The first moisture absorbent section 30 is configured as a moisture trap that collects and stores condensed water generated by cooling the exhaust gas in the heat exchange section 20. One end of a drain pipe 31 is connected to the bottom of the first moisture absorbent section 30, and a check valve 32 is provided at the other end of the drain pipe 31. The check valve 32 opens when the internal pressure (positive pressure) of the first moisture absorbent section 30 exceeds a set pressure. When the check valve 32 opens, the first moisture absorbent section 30 discharges the stored condensed water to the outside.

[0015] The second moisture absorbent 40 absorbs moisture from the exhaust gas that has passed through the first moisture absorbent 30. The second moisture absorbent 40 includes a container 41 having an internal space, a moisture absorbent 42 filled in the internal space of the container 41, and a heater (not shown) for heating and regenerating the moisture absorbent 42. The moisture absorbent 42 of the second moisture absorbent 40 has a higher moisture absorption capacity than the moisture absorbent 23 of the heat exchanger 20, and is regenerated by releasing the absorbed moisture when heated. For example, A-type synthetic zeolite is used as the moisture absorbent 42.

[0016] The carbon dioxide gas recovery unit 50 recovers carbon dioxide gas from the low-temperature, low-humidity exhaust gas that has passed through the heat exchange unit 20 and the first and second moisture absorption units 30, 40. The carbon dioxide gas recovery unit 50 includes a container 51 having an internal space, a carbon dioxide gas absorbent 52 filled in the internal space of the container 51, and a heater (not shown) for heating and regenerating the carbon dioxide gas absorbent 52. The carbon dioxide gas absorbent 52 selectively absorbs carbon dioxide gas contained in the exhaust gas and releases the absorbed carbon dioxide gas by heating. For example, X-type synthetic zeolite is used as the carbon dioxide gas absorbent 52. The container 51 is also configured as a storage tank for storing the carbon dioxide gas absorbed in the carbon dioxide gas absorbent 52. This allows the carbon dioxide gas recovery device 10 to have a simpler configuration and be more compact than one that requires a separate storage tank for storing the recovered carbon dioxide gas.

[0017] The pump 60 is a vacuum pump, and is arranged downstream of the carbon dioxide gas recovery unit 50 in the first gas line L1.

[0018] The second gas line L2 is a line for supplying the carbon dioxide gas recovered in the carbon dioxide gas recovery unit 50 to the carbon dioxide gas utilization device 100. The second gas line L2 branches off from the first gas line L1 at a branch point B1 downstream of the pump 60 and is connected to the carbon dioxide gas utilization device 100.

[0019] The third gas line L3 and the fourth gas line L4 are lines for supplying purging air to the second moisture absorbing section 40. The third gas line L3 branches off from the first gas line L1 at a branch point B2 between the carbon dioxide gas recovery section 50 and the pump 60 and is connected to the container 21 of the heat exchange section 20. The fourth gas line L4 branches off from the first gas line L1 at a branch point B1 and is connected to the container 41 of the second moisture absorbing section 40.

[0020] The first on-off valve V1 is arranged in the first gas line L1 downstream of the second moisture absorption section 40 and upstream of the carbon dioxide gas recovery section 50, the second on-off valve V2 is arranged in the first gas line L1 downstream of the carbon dioxide gas recovery section 50 and upstream of the pump 60 (upstream of the branch point B2), and the third on-off valve V3 is arranged in the first gas line L1 downstream of the pump 60 (downstream of the branch point B1). The fourth on-off valve V4 is arranged in the second gas line L2. The fifth on-off valve V5 is arranged in the third gas line L3. The sixth on-off valve V6 is arranged in the fourth gas line L4.

[0021] In addition, a flow meter 61 is arranged in the first gas line L1 downstream of the pump 60 and upstream of the branch point B1, and a pressure meter 62 is arranged in the first gas line L1 downstream of the first on-off valve V1 and upstream of the carbon dioxide gas recovery section 50.

[0022] Although not shown, the control device 70 is configured as a microprocessor centered around a CPU, and in addition to the CPU, is equipped with ROM, RAM, and input / output ports. Detection signals from the flow meter 61, pressure gauge 62, etc. are input to the control device 70 via the input port. In addition, the control device 70 outputs drive signals to the pump 60 and drive signals to the first to sixth on-off valves V1 to V6, etc. via the output port.

[0023] Next, a description will be given of the operation of the carbon dioxide gas recovery device 10 configured as described above. The carbon dioxide gas recovery device 10 has an exhaust gas recovery mode, a carbon dioxide gas desorption mode, and a moisture absorbent regeneration mode as its operation modes.

[0024] The exhaust gas recovery mode is a mode in which carbon dioxide gas is recovered from exhaust gas discharged from the fuel cell system 1. FIG. 2 is an explanatory diagram illustrating the flow of gas (exhaust gas) in the exhaust gas recovery mode. In the exhaust gas recovery mode, the control device 70 opens the first on-off valve V1, the second on-off valve V2, and the third on-off valve V3, closes the fourth on-off valve V4, the fifth on-off valve V5, and the sixth on-off valve V6, and operates the pump 60. Operation of the pump 60 causes exhaust gas from the fuel cell system 1 to be drawn into the inlet 11. The drawn exhaust gas flows through the first gas line L1 and passes through the heat exchanger 20 (exhaust gas flow path 22), the first moisture absorber 30, and the second moisture absorber 40 in this order before being supplied to the carbon dioxide gas recovery unit 50. That is, the introduced exhaust gas is first cooled in the heat exchanger 20. The cooled exhaust gas condenses water vapor in the exhaust gas, generating condensed water, which is then recovered in the first moisture absorber 30. The exhaust gas that has passed through the heat exchanger 20 and the first moisture absorber 30 passes through the moisture absorbent 42 of the second moisture absorber 40, where moisture is absorbed. The exhaust gas is then supplied to the carbon dioxide recovery unit 50. By lowering the temperature and humidity of the exhaust gas and then recovering carbon dioxide in the exhaust gas using the carbon dioxide absorbent 52 of the carbon dioxide recovery unit 50, carbon dioxide can be efficiently recovered using a small amount of carbon dioxide absorbent 52. The remaining exhaust gas that has passed through the carbon dioxide recovery unit 50 has its humidity reduced, and passes through the moisture absorbent 23 of the heat exchanger 20 as purge gas and is released into the atmosphere. As the exhaust gas, whose humidity has been reduced while moisture has been absorbed by the moisture absorbent 23, passes through the moisture absorbent 23, the moisture absorbent 23 undergoes an endothermic reaction and is regenerated by releasing the absorbed moisture. The heat exchanger 20 cools the exhaust gas flowing through the exhaust gas flow path 22 using the endothermic action of the moisture absorbent 23. This makes it possible to reduce the temperature and humidity of the exhaust gas in the heat exchange section 20 and the first moisture absorbent section 30 with a simple configuration, and reduces the amount of moisture absorbent 42 required in the subsequent second moisture absorbent section 40. Furthermore, because the exhaust gas whose humidity has been reduced in the first moisture absorbent section 30 and the second moisture absorbent section 40 is passed as a purge gas through the moisture absorbent 23 of the heat exchange section 20, a heater for regenerating the moisture absorbent 23 is not required, and costs can be reduced.

[0025] In the exhaust gas recovery mode, when the operation time of the pump 60 reaches a predetermined time, the control device 70 determines that the recovery of carbon dioxide gas is completed and ends the exhaust gas recovery mode. Note that, since the carbon dioxide gas absorbent 52 of this embodiment is accompanied by a rise in temperature just before the absorption of carbon dioxide gas is completed, a temperature sensor for detecting the temperature of the carbon dioxide gas absorbent 52 may be provided in the container 51 of the carbon dioxide gas recovery unit 50, and the control device 70 may determine whether the recovery of carbon dioxide gas is completed based on the detection value from the temperature sensor.

[0026] The carbon dioxide desorption mode is a mode in which the carbon dioxide gas recovered in the carbon dioxide gas recovery unit 50 is desorbed and supplied to the carbon dioxide gas utilization device 100. FIG. 3 is an explanatory diagram illustrating the flow of gas (carbon dioxide gas) in the carbon dioxide gas desorption mode. In the carbon dioxide gas desorption mode, the control device 70 first opens the second on-off valve V2 and the fifth on-off valve V5, and closes the first on-off valve V1, the third on-off valve V3, the fourth on-off valve V4, and the sixth on-off valve V6, and operates the pump 60. By operating the pump 60, exhaust gas with a low carbon dioxide concentration remaining in the container 51 of the carbon dioxide gas recovery unit 50 is purged, and the inside of the container 51 of the carbon dioxide gas recovery unit 50 is evacuated. Next, the control device 70 stops the pump 60, closes the first to sixth on-off valves V1 to V6, and operates the heater of the carbon dioxide gas recovery unit 50. When the heater is activated, the high-concentration carbon dioxide stored in the carbon dioxide recovery unit 50 (carbon dioxide absorbent 52) is released, and the pressure inside the container 51 increases. When the pressure detected by the pressure meter 62 reaches a threshold value, the control device 70 opens the second on-off valve V2 and the fourth on-off valve V4 and operates the pump 60. As a result, the high-concentration carbon dioxide released from the carbon dioxide absorbent 52 passes through the third gas line L3 and is supplied to the carbon dioxide utilization device 100 for effective utilization. In this embodiment, the carbon dioxide utilization device 100 is a carbon dioxide spring device and can generate a carbonated spring in which a high concentration of carbon dioxide is dissolved. The amount of carbon dioxide supplied is controlled by setting a target flow rate of carbon dioxide in accordance with the demands of the carbon dioxide utilization device 100 and controlling the pump 60 by feedback control so that the flow rate detected by the flow meter 61 becomes the target flow rate. The carbon dioxide recovery device 10 purges the exhaust gas remaining in the container 51 of the carbon dioxide recovery section 50 and then releases the carbon dioxide absorbed in the carbon dioxide absorbent 52, so that high-concentration carbon dioxide can be supplied immediately after starting to use the carbon dioxide.

[0027] In the carbon dioxide desorption mode, the control device 70 opens the second on-off valve V2 and the fifth on-off valve V5 and operates the pump 60 to purge the exhaust gas with a low carbon dioxide concentration remaining in the carbon dioxide recovery section 50, and then operates the heater of the carbon dioxide recovery section 50 and opens the second on-off valve V2 and the fourth on-off valve V4 to operate the pump 60 so that the carbon dioxide is supplied to the carbon dioxide utilization device 100. However, the control device 70 may operate the heater of the carbon dioxide recovery section 50 and open the second on-off valve V2 and the fourth on-off valve V4 to operate the pump 60 without purging the exhaust gas remaining in the carbon dioxide recovery section 50.

[0028] The moisture absorbent regeneration mode is a mode for releasing moisture absorbed by the moisture absorbent 42 of the second moisture absorbent unit 40 to regenerate the moisture absorbent 42. FIG. 4 is an explanatory diagram illustrating the flow of gas (purge gas) in the moisture absorbent regeneration mode. In the moisture absorbent regeneration mode, the control device 70 opens the fifth on-off valve V5 and the sixth on-off valve V6 and closes the first on-off valve V1, the second on-off valve V2, the third on-off valve V3, and the fourth on-off valve V4, operates the pump 60, and operates the heater of the second moisture absorbent unit 40. Operation of the pump 60 draws air from the atmosphere into the container 21 of the heat exchange unit 20. The drawn air passes through the moisture absorbent 23 in the container 21, where moisture contained in the air is collected. The air then passes through the third gas line L3, the pump 60, and the fourth gas line L4 in this order, and is supplied as purge air into the container 41 of the second moisture absorbent unit 40. When the heater is activated, moisture is released from the moisture absorbent 42 into the container 41 of the second moisture absorbent unit 40, and the released moisture is purged by air supplied into the container 41. As described above, the moisture in the air supplied to the container 41 of the second moisture absorbent unit 40 has been collected by the moisture absorbent 23 of the heat exchange unit 20, so the moisture absorbent 42 can be efficiently regenerated by the dry air. Furthermore, since the moisture has been collected from the air drawn into the pump 60, corrosion of the pump 60 due to moisture is prevented, and the durability of the pump 60 can be further improved. The moisture released from the second moisture absorbent unit 40 (moisture absorbent 42) and the air that has passed through the second moisture absorbent unit 40 are introduced into the first moisture absorbent unit 30 (moisture absorption trap). As described above, a drain pipe 31 is connected to the bottom of the first moisture absorbent unit 30, and the drain pipe 31 is provided with a check valve 32 that opens when positive pressure acts on the first moisture absorbent unit 30. Therefore, the moisture in the first moisture absorber 30 is released into the atmosphere together with the introduced air.

[0029] In this way, in the carbon dioxide gas recovery device 10 of this embodiment, by opening and closing the first to sixth on-off valves V1 to V6, it is possible to switch between the exhaust gas recovery mode, the carbon dioxide gas desorption mode, and the moisture absorbent regeneration mode, and to execute each mode using the single pump 60. As a result, the device can be simplified and made smaller.

[0030] In the above-described embodiment, the carbon dioxide gas recovery device 10 is provided with a single pump 60 that is shared among the exhaust recovery mode, the carbon dioxide gas desorption mode, and the moisture absorbent regeneration mode, but may be provided with two or more pumps.

[0031] In the above-described embodiment, the heat exchange section 20 cools the exhaust gas by the heat absorption action of the moisture absorbent 23, but the exhaust gas may also be cooled by heat exchange with another heat exchange medium such as cooling water.

[0032] The above describes the forms for implementing the present disclosure using embodiments, but the present disclosure is not limited to these embodiments in any way, and it goes without saying that the present disclosure can be implemented in various forms within the scope that does not deviate from the gist of the present disclosure. [Industrial Applicability]

[0033] The present disclosure is applicable to the carbon dioxide gas recovery device manufacturing industry and the like. [Explanation of symbols]

[0034] 10 Carbon dioxide gas recovery device, 11 Inlet section, 20 Heat exchange section, 21 Container, 22 Exhaust gas flow path, 23 Moisture absorbent, 30 First moisture absorption section, 40 Second moisture absorption section, 50 Carbon dioxide gas recovery section, 60 Pump, 100 Carbon dioxide gas utilization device, B1 Branch point, L1 First gas line, L2 Second gas line, L3 Third gas line, L4 Fourth gas line, V1 First on-off valve, V2 Second on-off valve, V3 Third on-off valve, V4 Fourth on-off valve, V5 Fifth on-off valve, V6 Sixth on-off valve.

Claims

1. A carbon dioxide gas recovery device that recovers carbon dioxide gas contained in exhaust gas from a fuel cell system, an inlet for introducing exhaust gas from the fuel cell system; a heat exchange unit that cools the exhaust gas by heat exchange; a first moisture absorption section that separates condensed water from the exhaust gas; a second moisture absorbing section that absorbs humidity from the exhaust gas; a carbon dioxide gas recovery unit that recovers carbon dioxide gas from the exhaust gas; a first gas line extending from the inlet through the heat exchange unit, the first moisture absorption unit, the second moisture absorption unit, and the carbon dioxide gas recovery unit in this order and connected to the outlet; a pump provided in the first gas line; A carbon dioxide recovery device equipped with:

2. The carbon dioxide gas recovery device according to claim 1, A second gas line; a first on-off valve, a second on-off valve, a third on-off valve, and a fourth on-off valve; Equipped with the pump is provided on the first gas line downstream of the carbon dioxide gas recovery unit, the second gas line branches off from the first gas line downstream of the pump and is connected to a carbon dioxide gas utilization device that utilizes carbon dioxide gas; the first on-off valve is provided in the first gas line between the second moisture absorption unit and the carbon dioxide gas recovery unit, the second on-off valve is provided in the first gas line between the carbon dioxide gas recovery unit and the pump, the third on-off valve is provided downstream of a branch point of the first gas line to the second gas line, the fourth on-off valve is provided in the second gas line, The carbon dioxide gas recovery device has operation modes including a first mode in which the pump is operated with the first on-off valve, the second on-off valve, and the third on-off valve open, and a second mode in which the carbon dioxide gas recovered in the carbon dioxide gas recovery section is released and the pump is operated with the second on-off valve and the fourth on-off valve open. Carbon dioxide recovery device.

3. The carbon dioxide gas recovery device according to claim 2, a third gas line and a fourth gas line; a fifth on-off valve and a sixth on-off valve; Equipped with the second moisture absorbing section has a moisture absorbing agent accommodated in an internal space, the third gas line branches off from the first gas line between the second on-off valve and the pump to introduce purge air; the fourth gas line branches off from the first gas line between the pump and the third on-off valve and is connected to the second moisture absorber, the first moisture absorption section stores condensed water and is released to the outside by positive pressure; The carbon dioxide gas recovery device further includes a third mode in which the moisture absorbed in the second moisture absorption unit is released and the pump is operated with the fifth on-off valve and the sixth on-off valve open. Carbon dioxide recovery device.

4. The carbon dioxide gas recovery device according to any one of claims 1 to 3, the heat exchange unit includes a container having an internal space, an exhaust gas flow path that penetrates the internal space and through which exhaust gas from the inlet flows, and a moisture absorbent that is accommodated in the internal space and absorbs ambient moisture and releases the absorbed moisture through an endothermic reaction, the first gas line is formed so that the exhaust gas that has passed through the carbon dioxide gas recovery unit passes through the moisture absorbent in the heat exchange unit. Carbon dioxide recovery device.

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