JP5534865B2 - Gas separation method and gas separation apparatus by pressure swing adsorption method - Google Patents

Description

  The present invention relates to a gas separation method for adsorbing and separating a specific gas component from a mixed gas by a pressure swing adsorption method, and a gas separation apparatus used for the method.

Conventionally, a pressure swing adsorption method has been widely used as a method for separating a mixed gas. This method uses an adsorbent that has an adsorptive power for one or more gas components in a mixed gas, introduces the mixed gas into an adsorption tower packed with the adsorbent, and contacts the adsorbent. An adsorption process for adsorbing components to the adsorbent and a desorption process for desorbing and separating the adsorbed gas components from the adsorbent by lowering the pressure in the tower are repeated.
This pressure swing adsorption method is used in various fields as a method for separating a mixed gas, but is usually used as a method for producing a high purity gas by separating a specific gas component from the mixed gas. Often. Examples of the high purity gas that is adsorbed and separated (manufactured) from the mixed gas by the pressure swing adsorption method include hydrogen, oxygen, carbon dioxide, and carbon monoxide.

In the mixed gas separation method by this pressure swing adsorption method, the adsorbent temperature rises due to the reaction heat (adsorption heat) generated in the adsorption step. There is a problem that the adsorption capacity of the adsorbent decreases due to this temperature rise. On the other hand, in the desorption process, there is a problem that an endothermic reaction occurs, the adsorbent temperature decreases, and the desorption amount decreases. In order to deal with such problems, the conventional method employs a purification process in which the heat of adsorption is released to the outside in the purge process following the adsorption process, and the heat is effectively utilized. It wasn't.
On the other hand, a physical adsorption process using temperature change is known. In this process, adsorption is performed by applying cold from outside to lower the temperature to promote adsorption, and desorption by applying heat from outside during desorption. And the adsorption and desorption of gas are performed by repeatedly giving and receiving heat. However, this process adds heat from the outside and is not energy efficient.

  On the other hand, in Patent Document 1, in order to suppress the temperature rise in the adsorption process and the temperature drop in the desorption process, volatilization is performed in each of the two adsorption towers in which the adsorption process and the desorption process are alternately performed. A heat exchange chamber containing a volatile liquid is provided, and the top and bottom of both heat exchange chambers are connected by conduits to suppress the temperature rise by evaporation of the volatile liquid during adsorption, and the volatile liquid is removed during desorption. A technique that suppresses the temperature drop by condensation is shown.

JP-A-2-26611

  The technology of Patent Document 1 uses the evaporation and condensation of volatile liquids to suppress the temperature rise during heat absorption and the temperature drop during desorption. Therefore, it does not effectively use the heat of adsorption generated during the adsorption or the cold generated during the desorption, and has no viewpoint of effectively using the heat.

  Accordingly, an object of the present invention is to increase the efficiency of adsorbent use and efficiently perform gas separation by effectively using the heat of adsorption generated during adsorption and the cold generated during desorption in gas separation by the pressure swing adsorption method. It is an object of the present invention to provide a method and apparatus capable of performing the above.

The gist of the present invention for solving the above problems is as follows.
[1] One or more gases in a mixed gas by a pressure swing adsorption method using two adsorption towers (A) and (B) in which an adsorbent is filled and an adsorption step and a desorption step are alternately performed. A gas separation method for adsorbing and separating components,
The heat medium heat-exchanged with the adsorbent in each adsorption tower (A), (B) is circulated between both adsorption towers (A), (B), and the heat of adsorption generated in the adsorption process by the circulating heat medium. Is applied to the adsorbent in the desorption process and the cold heat generated in the desorption process is recovered to cool the adsorbent in the adsorption process .
The heat medium is water or an aqueous solution, and the heat medium passes through a heat exchange channel provided along the flow direction of the raw material gas inside each of the adsorption towers (A) and (B). In the adsorption tower in the adsorption process, the heat exchange channel flows in the direction opposite to the flow direction of the raw material gas, and in the adsorption tower in the desorption process, the heat exchange channel is fed in the raw material. A gas separation method by a pressure swing adsorption method, wherein the gas flows in the same direction as the gas flow direction (however, the raw material gas flow direction in the adsorption step) .

[2] It has two adsorption towers (A) and (B) that are filled with an adsorbent and alternately perform an adsorption process and a desorption process, and one or more gases in a mixed gas by a pressure swing adsorption method A gas separation device that adsorbs and separates components,
In each of the adsorption towers (A) and (B), heat exchange channels (1a) and (1b) for passing the heat medium are provided along the raw material gas flow direction, and both adsorption towers (A ), (B) the ends of the heat exchange channels (1a), (1b) on the source gas inlet side are connected by a conduit (2), and the heat exchange channels (1a), By connecting the ends of (1b) with the conduit (3), a circulation path for circulating the heat medium is formed between the adsorption towers (A) and (B), and the heat medium is circulated in the circulation path. A gas separation apparatus using a pressure swing adsorption method, comprising a pump mechanism for circulating in such a manner that the forward and reverse directions can be switched.

  According to the present invention, the heat of adsorption in the adsorption process and the cold heat generated in the desorption process are recovered by the heat medium, and the heat energy in the apparatus that has been conventionally discarded can be effectively utilized in both processes. Effective utilization can improve the utilization efficiency of the adsorbent, and gas separation can be performed with high energy efficiency. In addition, since the amount of gas adsorption is increased, there is an effect that the equipment can be made compact as compared with the prior art.

1 shows an embodiment of the gas separation method and apparatus of the present invention, and is an explanatory view showing a state in which the adsorption tower A is in the adsorption process and the adsorption tower B is in the desorption process. 1 shows an embodiment of the gas separation method and apparatus of the present invention, and is an explanatory view showing a state in which the adsorption tower A is in the desorption process and the adsorption tower B is in the adsorption process A graph showing the adsorption characteristics of a comparative example and an example of the present invention when a pressure change of 700 torr to 100 torr is applied in the adsorption step and the desorption step in the case of performing adsorption of CO ₂ using the zeolite-based adsorbent x.

FIG. 1 and FIG. 2 show an embodiment of the gas separation method and apparatus of the present invention, and are explanatory views schematically showing a state in which an adsorption tower is longitudinally sectioned.
The gas separation device of the present invention includes two adsorption towers A and B in which an adsorbent is filled and an adsorption process and a desorption process are alternately performed, and one or more in a mixed gas by a pressure swing adsorption method. Adsorbs and separates gas components. FIG. 1 shows a state in which the adsorption tower A is in the adsorption process and the adsorption tower B is in the desorption process, and FIG. 2 shows a state in which the adsorption tower A is in the desorption process and the adsorption tower B is in the adsorption process. .

Partition plates 4 and 5 (dispersion plates) that allow gas to pass through are provided at the upper and lower positions inside the adsorption towers A and B, and the adsorbent x is filled between the partition plates 4 and 5. Thus, a gas adsorption unit 6 (gas adsorption region) is configured.
A space below the partition plate 5 is a raw material gas inflow portion 7 (raw material gas inflow region), and a raw material gas supply pipe 8 having an on-off valve 9 is connected to the raw material gas inflow portion 7. The space above the partition plate 4 is a gas outflow portion 10 (gas outflow region). The gas outflow portion 10 includes a concentrated gas outlet pipe 11 having an on-off valve 12, an on-off valve 14, and a pump 15. The product gas lead-out pipes 13 provided with are respectively connected.
The partition walls 4 and 5 are formed of a perforated plate (for example, a metal mesh or punching metal) having a small hole through which the gas can pass while holding the granular adsorbent in the gas adsorbing portion 6. Is done.

Inside each of the adsorption towers A and B (inside the gas adsorption unit 6), heat exchange channels 1a and 1b for allowing the heat medium e to pass therethrough are provided along the raw material gas flow direction. The heat exchange channels 1a and 1b can be provided in any way, but both the adsorption process and the desorption process are more reactive near the source gas inlet (source gas inflow portion 7), so heat exchange is efficient. Therefore, it is preferable to provide it along the raw material gas flow direction as in this embodiment. The heat exchange channels 1a and 1b may have any specific structure such as a tubular shape or a jacket shape using a plate.
Moreover, each heat exchange flow path 1a, 1b may be configured by a single continuous flow path, or may be configured by a plurality of parallel flow paths, and the plurality of flow paths are merged at both ends thereof. It is good also as such a structure. In any case, each of the heat exchange channels 1a and 1b has two end portions that serve as inlets and outlets of the heat medium, and each of the heat exchange channels 1a and 1b is arranged in parallel as described above. In the case of being constituted by a flow path, end portions serving as the inlet / outlet of the heat medium are provided in the flow path after merging at both ends.

One end of the heat exchange channels 1a, 1b is connected by a conduit 2, the other end is connected by a conduit 3, and a circulation path for circulating a heat medium e between both adsorption towers A, B. Is formed. In the present embodiment, the end portions of the heat exchange channels 1a and 1b on the raw material gas inlet (raw material gas inflow portion 7) side of both adsorption towers A and B are connected by the conduit 2, and the concentrated gas outlet (gas outflow portion). 10) The ends of the heat exchange channels 1a and 1b on the side are connected by a conduit 3, so that the heat medium between the adsorption towers A and B is connected by the heat exchange channels 1a and 1b and the conduits 2 and 3. A circulation path for circulating e is formed.
Further, a pump mechanism 16 is provided for circulating the heat medium e in the circulation path so that the forward and reverse directions can be switched. The pump mechanism 16 branches from a pump 17 having an inlet-side conduit 170 and an outlet-side (discharge-side) conduit 171 and a position near the adsorption tower A of the conduits 2 and 3, and is connected to the inlet-side conduit 170. Branch pipes 200 and 300, branch pipes 201 and 301 branched from the positions near the adsorption tower B of the conduits 2 and 3, respectively, and connected to the outlet conduit 171, and the above branch pipes 200, 201, and 300 , 301 are provided with on-off valves 18, 19, 20, 21, etc., respectively.

Hereinafter, the gas separation method of the present invention will be described.
In the gas separation method of the present invention, the adsorption step and the desorption step are alternately performed by the two adsorption towers A and B, and one or more gas components in the mixed gas are adsorbed and separated by the pressure swing adsorption method. However, the heat medium e heat-exchanged with the adsorbent x in each of the adsorption towers A and B is circulated between the adsorption towers A and B, and the heat of adsorption generated in the adsorption process is recovered by the circulating heat medium e. The adsorbent x in the desorption process is applied to the adsorbent x, and the cold heat generated in the desorption process is recovered to cool the adsorbent x in the adsorption process. As described above, the adsorption heat generated in the adsorption process and the cold heat generated in the desorption process are recovered by the heat medium e, and the heat energy in the apparatus is effectively utilized by mutually effectively using both of the processes. The utilization efficiency of the agent can be improved, and gas separation can be performed with high energy efficiency.
As the heat medium e, any fluid such as water, an aqueous solution, a liquid such as oil, a gas such as steam, or other special heat medium can be used, but water or an aqueous solution is used from the viewpoint of handling and equipment costs. It is preferable.

The open / close valves 9, 12, 14, and 18 to 21 shown in FIGS. 1 and 2 indicate that the white ones are open and the ones that are black are closed.
As shown in FIG. 1, when the adsorption tower A is in the adsorption process and the adsorption tower B is in the desorption process, the raw material gas (mixed gas) is introduced into the gas inflow portion 7 through the raw material gas supply pipe 8 in the adsorption tower A. The The raw material gas introduced into the gas inflow portion 7 flows into the gas adsorbing portion 6 through the partition plate 5, where a specific gas component in the raw material gas is adsorbed by the adsorbent x, and a non-adsorbed component is present in the gas phase. Concentrated. The concentrated gas flows out to the gas outflow portion 10 through the partition plate 4 and is then discharged through the concentrated gas outlet pipe 11. On the other hand, in the adsorption tower B, the inside of the tower is depressurized by the pump 15, and the adsorbed gas component is desorbed from the adsorbent x, and this gas (product gas) passes through the gas outflow part 10 to the product gas outlet pipe 13. It is discharged through.

  When the pump mechanism 16 is driven, the heat medium e circulates in the circulation path between the adsorption towers A and B, and passes through the heat exchange flow paths 1a and 1b in the adsorption towers A and B. In the case of FIG. 1, the on-off valves 20 and 21 of the branch pipes 300 and 301 constituting the pump mechanism 16 are closed, and the on-off valves 18 and 19 of the branch pipes 200 and 201 are open. Drive. As a result, the heat medium e flows in the heat exchange flow path 1a in the opposite direction to the flow direction of the raw material gas in the adsorption tower A in the adsorption process, and in the heat exchange flow path 1b in the adsorption tower B in the desorption process. In the same direction as the raw material gas flow direction (however, the raw material gas flow direction in the adsorption step).

In the gas adsorption section 6 of the adsorption tower A in the adsorption process, the adsorption reaction is faster toward the side closer to the raw material gas inlet (raw material gas inflow section 7). It can be efficiently recovered with the heat medium e flowing through. This heat medium e flows through the conduit 2 to the heat exchange channel 1b of the adsorption tower B in the desorption process.
In the gas adsorption part 6 of the adsorption tower B in the desorption process, the endothermic reaction is larger toward the side closer to the raw material gas inlet (raw material gas inflow part 7), so the heat recovered by the heat medium e in the adsorption process is used here as the adsorbent. By giving to x, the desorption amount can be increased. The heat medium e flowing through the heat exchange flow path 1b collects the cold heat generated in the desorption process, and then flows through the conduit 3 to the heat exchange flow path 1a of the adsorption tower A, so that the adsorbent x in the adsorption process. The amount of adsorption is increased by cooling.

Next, as shown in FIG. 2, when the adsorption tower A is switched to the desorption process and the adsorption tower B is switched to the adsorption process, gas adsorption / separation similar to that described above is performed in each of the adsorption towers A and B. In this case, the pump 17 is driven while the on-off valves 20 and 21 of the branch pipes 300 and 301 constituting the pump mechanism 16 are open and the on-off valves 18 and 19 of the branch pipes 200 and 201 are closed. Thus, the heat medium e flows in the heat exchange flow path 1b in the adsorption tower B in the adsorption process in the direction opposite to the flow direction of the raw material gas, and in the adsorption tower A in the desorption process, the heat medium e flows in the heat exchange flow path 1a. In the same direction as the raw material gas flow direction (however, the raw material gas flow direction in the adsorption step), and heat exchange can be performed efficiently as in the case of FIG.
As described above, the adsorption process and the desorption process are alternately repeated in the two adsorption towers A and B, and the circulation of the heat medium e between the adsorption towers A and B is switched in the forward and reverse directions each time.

FIG. 3 shows an adsorption process in a case where CO ₂ is adsorbed and separated from a raw material gas (a gas containing CO ₂ such as combustion exhaust gas) using a zeolite-based adsorbent according to the conventional method and the present invention method. It shows the amount of adsorption when a pressure change of 700 torr to 100 torr is given in the desorption process. In the figure, the lines (i) and (ii) show the adsorption characteristics of the comparative example (conventional method), and (i) shows the adsorption characteristics when the adsorbent temperature in the adsorption process / desorption process is 10 ° C. (Ii) is an adsorption characteristic when the adsorbent temperature in the adsorption step / desorption step is 30 ° C., and the adsorption amount is about 40 Nml / g in both cases. On the other hand, by performing heat separation at about 20 ° C. with a heat medium according to the method of the present invention and performing gas separation, adsorption characteristics as indicated by the line (iii) can be obtained, which is a comparative example (conventional method). Compared with this, the amount of adsorption increases by about 1.7 times, so that the energy efficiency can be improved by 40% or more.

A, B Adsorption tower 1a, 1b Heat exchange flow path 2, 3 Conduit 4, 5 Partition plate 6 Gas adsorption part 7 Raw material gas inflow part 8 Raw material gas supply pipe 9 Open / close valve 10 Gas outflow part 11 Concentrated gas outlet pipe 12 Open / close Valve 13 Product gas outlet pipe 14 Open / close valve 15 Pump 16 Pump mechanism 17 Pump 18, 19, 20, 21 Open / close valve 170 Inlet pipe 171 Outlet pipe 200, 201, 300, 301 Branch pipe x Adsorbent e Heat medium

Claims (2)

Adsorbs one or more gas components in the mixed gas by pressure swing adsorption method using two adsorption towers (A) and (B) in which the adsorbent is filled and the adsorption process and desorption process are performed alternately. A gas separation method for separating,
The heat medium heat-exchanged with the adsorbent in each adsorption tower (A), (B) is circulated between both adsorption towers (A), (B), and the heat of adsorption generated in the adsorption process by the circulating heat medium. Is applied to the adsorbent in the desorption process and the cold heat generated in the desorption process is recovered to cool the adsorbent in the adsorption process .
The heat medium is water or an aqueous solution, and the heat medium passes through a heat exchange channel provided along the flow direction of the raw material gas inside each of the adsorption towers (A) and (B). In the adsorption tower in the adsorption process, the heat exchange channel flows in the direction opposite to the flow direction of the raw material gas, and in the adsorption tower in the desorption process, the heat exchange channel is fed in the raw material. A gas separation method by a pressure swing adsorption method, wherein the gas flows in the same direction as the gas flow direction (however, the raw material gas flow direction in the adsorption step) . It is equipped with two adsorption towers (A) and (B) that are filled with an adsorbent and alternately perform adsorption and desorption, and adsorb one or more gas components in the mixed gas by pressure swing adsorption. A gas separation device for separation,
In each of the adsorption towers (A) and (B), heat exchange channels (1a) and (1b) for passing the heat medium are provided along the raw material gas flow direction, and both adsorption towers (A ), (B) the ends of the heat exchange channels (1a), (1b) on the source gas inlet side are connected by a conduit (2), and the heat exchange channels (1a), By connecting the ends of (1b) with the conduit (3), a circulation path for circulating the heat medium is formed between the adsorption towers (A) and (B), and the heat medium is circulated in the circulation path. A gas separation apparatus using a pressure swing adsorption method, comprising a pump mechanism for circulating in such a manner that the forward and reverse directions can be switched.

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