JP4189344B2 - Carbon dioxide separation and recovery system - Google Patents

Description

  The present invention relates to a carbon dioxide separation and recovery system for recovering carbon dioxide from a raw material gas such as exhaust gas containing carbon dioxide.

  Carbon dioxide is one of the gases caused by the global warming phenomenon specially mentioned in the Kyoto Protocol, and it has been proposed to regulate emissions of artificially generated carbon dioxide. For this reason, it is desired to separate and recover carbon dioxide from a source gas such as carbon dioxide-containing exhaust gas with high efficiency and low cost.

  There are two types of carbon dioxide gas separation methods whose main purpose is the separation and recovery of a specific component gas and those whose main purpose is gas purification by removing the specific component gas.

  Conventionally, as the former carbon dioxide separation and recovery technology, an absorption method, a pressure swing adsorption method (hereinafter referred to as “PSA method”), a membrane separation method, and the like are known. Among them, the adsorption method is known as a method having an excellent separation performance because it uses a solid adsorbent having a large carbon dioxide adsorption capacity and high adsorption selectivity with respect to a carrier gas component such as coexisting air.

When the PSA method is applied to the recovery of carbon dioxide, the carbon dioxide is adsorbed by flowing the raw material gas to one of the pair of adsorption / desorption towers filled with the adsorbent under high pressure in the adsorption step. In the desorption step, the other adsorption / desorption tower is set to a low pressure, and the carbon dioxide adsorbed in the adsorption step is desorbed and collected by the adsorbent. In other words, this PSA method utilizes the characteristics that when the adsorbent adsorbs carbon dioxide, it shifts to a low pressure to cause a pressure difference, and desorbs carbon dioxide and restores its own carbon dioxide adsorption. It is a thing.
In the two-column PSA carbon dioxide recovery system, the adsorption and desorption steps under high pressure and the desorption step under low pressure are alternately carried out by pressure swinging the two adsorption / desorption towers. Separation and recovery.

  Desorption by pressure swing is performed under “depressurization from pressurization to normal pressure” or “depressurization from normal pressure or pressurization to suction by vacuum pump” and is called “one cycle” with adsorption step and desorption step. Is done.

  One method for increasing the carbon dioxide concentration in the recovered product gas is to adsorb a part of the gas discharged from the adsorption / desorption tower (hereinafter referred to as “concentrated gas”) in which the desorption step is performed. Supplied to the absorption / desorption tower. This process is called “concentration reflux” and is supplied in the same direction as the flow of the raw material gas in the other adsorption / desorption tower in which the adsorption step is performed.

  One technique for increasing the recovery rate of carbon dioxide is the adsorption / desorption step in which a part of the gas discharged from the adsorption / desorption tower in which the adsorption step is performed (hereinafter referred to as “purified gas”) is desorbed. Feed to desorption tower. This process is called "refining reflux" and is supplied in the same direction as the concentrated gas discharge direction in the adsorption / desorption tower in which the desorption step is performed.

  In the PSA method described above, in the adsorption / desorption tower where the adsorption step is performed, the raw material gas is introduced, the purified gas is discharged on one end side, the concentrated reflux is performed on the other end side, and in the adsorption / desorption tower where the desorption step is performed. Purification reflux is performed on one end side, and concentrated gas is discharged on the other end side.

However, this PSA method is not always satisfactory in terms of adsorption effect or recovery efficiency.
For this reason, Patent Document 1 discloses a method for improving the separation and recovery characteristics of carbon dioxide by using multiple stages of absorption / desorption towers using the PSA method. However, this method has a problem of increasing the complexity and cost of the system because the adsorption / desorption towers are multistage.
On the other hand, various developments have been carried out for the purpose of improving the adsorption effect or the recovery efficiency compared to the PSA method described above. The DRIFFPSA method (Dual Reflux Intermediate Feed PSA): (Referred to as “feed PSA process”).

  A carbon dioxide separation and recovery system using the intermediate supply PSA method generally has the following configuration. The pair of absorption / desorption towers (first and second absorption / desorption towers) are each filled with an adsorbent. Gas introduction pipes (first and second gas introduction pipes) for supplying a source gas containing carbon dioxide in a switchable manner are respectively connected to the middle of the respective adsorption / desorption towers. That is, in each of the adsorption / desorption towers, a region toward the one end side with the gas supply pipe connecting portion as a boundary adsorbs the carbon dioxide in the concentrated gas at a purification region for purifying the source gas, and a region toward the other end side. It functions as a concentrated region for the purpose. The purified gas reflux pipe is connected to one end side of each of the adsorption / desorption towers, and a part of the purified gas is refluxed between the adsorption / desorption towers through the reflux pipe. The concentrated gas reflux pipe is connected to the other end of each of the adsorption / desorption towers, and a part of the carbon dioxide enriched gas is refluxed between the adsorption / desorption towers through the reflux pipe. For example, a vacuum pump is connected to the bottom of each of the adsorption / desorption towers, and reduces the pressure in the adsorption / desorption towers in the desorption step.

  In such a carbon dioxide separation and recovery system, the raw material gas containing carbon dioxide is supplied to the purification region of the first adsorption / desorption tower through a first gas introduction pipe, for example, in a certain time unit, and the purified gas is discharged and decompressed. The concentrated gas is discharged from the concentrated region of the second absorption / desorption tower placed underneath. At this time, for example, purification reflux from the purification region of the first absorption / desorption column to the purification region of the second absorption / desorption column, and concentration region of the first absorption / desorption column from the concentration region of the second absorption / desorption column Is concentrated and refluxed as a unidirectional gas flow, and the desorption effect by purification reflux is promoted, and the concentrated gas generation effect by concentration reflux is promoted. Therefore, by continuously performing the operation of switching and supplying the raw material gas containing carbon dioxide to the first gas introduction pipe or the second gas introduction pipe, the adsorption step under normal pressure and the desorption step under reduced pressure are continuously performed. It is possible to continuously recover the product gas.

  By the way, the adsorbent used in the ordinary PSA method and the intermediate supply PSA method has a large difference in the amount of equilibrium adsorption due to pressure change, that is, has a large inclination of the adsorption isotherm, in order to exhibit high adsorption / desorption properties. desirable. As a carbon dioxide adsorbent, a zeolite-based adsorbent is known. Although this zeolite-based adsorbent exhibits high absorption / desorption at low concentrations, the adsorption isotherm decreases at a high concentration because the slope of the adsorption isotherm becomes gentle.

In the conventional carbon dioxide separation and recovery system using the intermediate supply PSA method, if the above-mentioned zeolite-based adsorbent is used, the high concentration of carbon dioxide in the product gas and the high recovery of the product gas are restricted due to its properties. There was a problem.
JP-A-5-228326

  The present invention provides a carbon dioxide separation and recovery system capable of efficiently separating and recovering carbon dioxide as compared with a conventional carbon dioxide separation and recovery system using an intermediate supply PSA method. That is, the present invention is based on the use of the raw material gas having the same carbon dioxide concentration as in the conventional carbon dioxide separation and recovery system, the same reflux conditions and the switching conditions of the raw material gas, etc. 1) Product gas containing the same concentration of carbon dioxide To improve the recovery rate, 2) increase the concentration of carbon dioxide in the product gas when recovering the product gas at the same recovery rate as the conventional carbon dioxide separation and recovery system, and 3) the conventional The recovery rate can be improved and the concentration can be increased as compared with the carbon dioxide separation and recovery system.

  The present invention can improve the above-mentioned 1) to 3) as compared with the conventional carbon dioxide separation and recovery system using the intermediate supply PSA method, and further, the carbon dioxide in the raw material gas according to the user's request. A carbon dioxide separation and recovery system capable of performing a separation and recovery operation is provided.

According to the present invention, in a carbon dioxide separation and recovery system using an intermediate supply PSA method,
At least a pair of absorption / desorption towers filled with an adsorbent,
Switchable gas introduction pipes connected to the middle of each of the adsorption / desorption towers for supplying a raw material gas containing carbon dioxide,
Purified gas reflux means for refluxing part of the purified gas to each other at one end of each of the adsorption / desorption towers;
A concentrated gas reflux means for refluxing part of the carbon dioxide concentrated gas at the other end of each of the adsorption / desorption towers;
A region toward one end with the gas introduction pipe connecting portion in each of the adsorption / desorption towers as a boundary is a purification region, and a region toward the other end is a concentration region, and the temperature of the concentration region is higher than that of the purification region. And a carbon dioxide separation and recovery system characterized by comprising a temperature control means.

  The middle where the gas introduction pipe is located is an arbitrary position excluding both ends that can form the purification region on one end side of the pair of absorption / desorption towers and the concentration region on the other end side.

According to the present invention, in the carbon dioxide separation and recovery system using the intermediate supply PSA method,
At least a pair of absorption / desorption towers filled with an adsorbent,
A switchable gas introduction pipe connected to each of the adsorption / desorption towers for supplying a raw material gas containing carbon dioxide,
Purified gas reflux means for refluxing part of the purified gas to each other at one end of each of the adsorption / desorption towers;
A concentrated gas reflux means for refluxing part of the carbon dioxide concentrated gas at the other end of each of the adsorption / desorption towers;
Temperature control means for controlling the temperature of each of the adsorption / desorption towers,
The gas introduction pipe is branched into a plurality of pipes, the branch pipes are connected to a plurality of positions in the height direction of the respective suction / desorption towers, and the temperature control means is capable of switching between cooling and heating. A carbon dioxide separation and recovery system is provided, wherein a plurality of carbon dioxide separation / recovery systems are arranged corresponding to the areas of the respective adsorption / desorption towers located between the branch pipes.

  According to the present invention, it is possible to improve 1) to 3) as compared with the conventional carbon dioxide separation and recovery system using the intermediate supply PSA method, and to reduce the emission of carbon dioxide to the atmosphere. It is possible to provide a carbon dioxide separation and recovery system that can contribute to prevention of global warming and can effectively use the recovered carbon dioxide as a soft drink, a digestive agent, or the like, or liquefy it as a cooling medium for a refrigerator.

Hereinafter, a carbon dioxide separation and recovery system according to the present invention will be described in detail with reference to the drawings.
(First embodiment)
1 and 2 are schematic views showing a carbon dioxide separation and recovery system using the intermediate supply PSA method according to the first embodiment. In particular, FIG. 1 shows the open / close state of each valve during the adsorption step by the first adsorption / desorption tower and the desorption step by the second adsorption / desorption tower, and FIG. 2 shows the desorption step by the first adsorption / desorption tower, The open / close state of each valve during the adsorption step by the desorption tower is shown. In FIGS. 1 and 2, the open valve is outlined and the closed valve is black.
The pair of absorption / desorption towers (first and second absorption / desorption towers) 1 and 2 are provided with mesh portions 3 and 4 for smooth gas introduction in the middle. On the upper side of the first and second adsorption / desorption towers 1 and 2 with the mesh portions 3 and 4 as boundaries, purification regions 5 and 6 for purifying the raw material gas are formed. Concentrated regions 7 and 8 for adsorbing carbon dioxide in the concentrated gas are formed on the lower side of the first and second adsorption / desorption towers 1 and 2 with the mesh portions 3 and 4 as a boundary. Yes. Each of the regions 5 to 9 is filled with the same kind of adsorbent, for example, a zeolite adsorbent.

  The gas ports 9 and 10 are attached to the first and second absorption / desorption towers 1 and 2 corresponding to the mesh portions 3 and 4, respectively. First and second gas introduction pipes 12 and 13 branched from the gas introduction pipe 11 are connected to the gas ports 9 and 10, respectively. These first and second gas introduction pipes 12 and 13 are respectively provided with valves 14 and 15, and the supply gas source switching including carbon dioxide is switched by opening and closing these valves 14 and 15 at desired time intervals. Is made.

The upper ends of the first and second adsorption / desorption towers 1 and 2 where the purification regions 5 and 6 are located are connected to each other by a pipe 16. Two pipes 17 and 18 are interposed in the pipe 16. One end of the pipe 19 is connected to the pipe 16 part between the upper end of the first suction / desorption tower 1 and the valve 17, and the other end is connected to the pipe 16 part between the upper end of the second suction / desorption tower 2 and the valve 18. ing. Two valves 20 and 21 are interposed in the pipe 19. A pipe 22 for discharging the purified gas is branched from a pipe 16 portion between the valves 17 and 18. A valve 23 is interposed in the pipe 22. The pipe 24 is branched from a pipe 22 portion between the branch point and the valve 23, and the other end is connected to the pipe 19 between the valves 20 and 21. A refined reflux needle valve 25 is interposed in the pipe 24. A purified gas reflux means is constituted by such a pipe, a valve, and a purified reflux needle valve.
In the purified gas recirculation means, as shown in FIG. 1, the three valves 17, 21, 23 are opened, the valves 18, 20 are closed, and the opening degree of the purified recirculation needle valve 25 is adjusted, whereby the first suction valve 25 is closed. The purified gas passes from the upper end of the desorption tower 1 through the pipe 16, the valve 17 and the pipe 22, and most of the purified gas is discharged to the atmosphere from the other end of the pipe 22 as indicated by the arrow, and the purified reflux needle valve 25 Part of the narrowed purified gas flows to the upper end of the second adsorption / desorption tower 2 through the pipe 24, the pipe 19 part in which the valve 21 is interposed, and the pipe 16, and is returned to the inside.
On the other hand, in the purified gas reflux means, as shown in FIG. 2, the three valves 18, 21, 23 are opened, the two valves 17, 21 are closed, and the opening degree of the purified reflux needle valve 25 is adjusted. Purified gas passes from the upper end of the second absorption / desorption tower 2 through the pipe 16, the valve 18 and the pipe 22, and most of the purified gas is discharged to the atmosphere from the other end of the pipe 22 as indicated by the arrow. Part of the purified gas throttled by the valve 25 flows to the upper end of the first suction / desorption tower 1 via the pipe 24, the pipe 19 and the pipe 16 provided with the valve 20, and is refluxed therein.
Lower ends of the first and second adsorption / desorption towers 1 and 2 where the enrichment regions 7 and 8 are located are connected to each other by a pipe 26. Two pipes 27 and 28 are interposed in the pipe 26. The pipe 29 has one end connected to the pipe 26 portion between the lower end of the first suction / desorption tower 1 and the valve 27, and the other end connected to the pipe 26 portion between the lower end of the second suction / desorption tower 2 and the valve 28. Has been. Two valves 30 and 31 are interposed in the pipe 29. A pipe 32 for discharging the concentrated gas is branched from a pipe 29 portion between the two valves 30 and 31. A pump 33 and a valve 34, which are pressure control means, are sequentially inserted in the pipe 32 from the branch point side. The pump 33 is preferably a vacuum pump in terms of system characteristics. The pipe 35 is branched from a pipe 32 portion between the pump 33 and the valve 34, and the other end is connected to a pipe 26 portion between the two valves 27 and 28. Concentrated reflux buffer tank 36, pressurizing pump 37, and concentrated reflux needle valve 38 are interposed in this piping 35 from the branching side of piping 32 between pump 33 and valve 34. Concentrated gas recirculation means is constituted by such a pipe, valve, concentration recirculation needle valve, concentration recirculation buffer tank and pressurizing pump.
In the concentrated gas reflux means, as shown in FIG. 1, the valves 27, 31, and 34 are opened, the valves 28 and 30 are closed, the opening degree of the concentrated reflux needle valve 38 is adjusted, a vacuum pump 33, a pressure pump 37 is operated, the concentrated gas passes from the lower end of the second adsorption / desorption tower 2 through the pipe 26, the pipe 29 and the pipe 32 provided with the valve 31, and most of the pipe as shown by the arrows. 32 is recovered as product gas from the other end, and part of the concentrated gas throttled by the concentrated reflux needle valve 38 is routed through the piping 35, the concentrated reflux buffer tank 36, and the piping 26 in which the valve 27 is interposed. It flows to the lower end of the first suction / desorption tower 1 and is refluxed therein.
On the other hand, in the concentrated gas reflux means, as shown in FIG. 2, the three valves 28, 30, 34 are opened, the valves 27, 31 are closed, the opening degree of the concentrated reflux needle valve 38 is adjusted, and the vacuum pump 33, By starting the pressurizing pump 37, the concentrated gas passes from the lower end of the first suction / desorption tower 1 through the piping 26, the piping 29 and the piping 32 having the valve 30 interposed, and most of them are indicated by arrows. In addition, the product gas is recovered from the other end of the pipe 32 as product gas, and a part of the concentrated gas throttled by the concentrated reflux needle valve 38 is part of the pipe 26 in which the pipe 35, the concentrated reflux buffer tank 36 and the valve 28 are interposed. And then flows to the lower end of the second adsorption / desorption tower 2 and is refluxed therein.
The first temperature control member, for example, tubes 39 and 40 through which room-temperature water such as tap water is circulated are arranged on the purification regions 5 and 6 side of the first and second adsorption / desorption towers 1 and 2, and the purification is performed. Regions 5 and 6 are held at room temperature. The second temperature control member, for example, the ribbon heaters 41 and 42 are arranged on the concentration regions 7 and 8 side of the first and second adsorption / desorption towers 1 and 2 and heats the concentration regions 7 and 8. ing. Such tubes 39 and 40 and ribbon heaters 41 and 42 constitute a temperature control means. The temperature difference between the purification regions 5 and 6 and the concentration regions 7 and 8 of the first and second adsorption / desorption towers 1 and 2 by the temperature control means is determined by the characteristics of the adsorbent used. For example, in the case of a zeolitic adsorbent, it is desirable that the refining regions 5 and 6 be at room temperature, and the concentrating regions 7 and 8 be 30 ° C. higher than that. In particular, the purification regions 5 and 6 are desirably made as low as possible from the viewpoint of increasing the amount of adsorption of carbon dioxide having a relatively low concentration in the raw material gas. However, maintaining excessive cooling or warming is not efficient because of increased energy costs.

Next, carbon dioxide adsorption and desorption operations of the carbon dioxide separation and recovery system shown in FIGS. 1 and 2 will be described.
(1) Adsorption step by the first absorption / desorption tower 1 and desorption step by the second absorption / desorption tower 2 First, as shown in FIG. 1, the valves 14, 17, 21, 23, 27, 31, and 34 are opened and the valves are opened. Close 15, 18, 20, 28, 30. Further, the tap water is circulated through the tubes 39 and 40 to keep the purification regions 5 and 6 of the first and second adsorption / desorption towers 1 and 2 at room temperature, respectively, and the ribbon heaters 41 and 42 are energized to supply the first. 1. The concentration regions 7 and 8 of the second absorption / desorption towers 1 and 2 are heated to 60 ° C., for example. As a result, the zeolite-based adsorbent filled in the purification regions 5 and 6 is held near normal temperature, and the zeolite-based adsorbent filled in the concentration regions 7 and 8 is held near 60 ° C., for example.

  In this state, when source gas containing carbon dioxide (for example, exhaust gas containing carbon dioxide) is supplied to the gas introduction pipe 11 as shown in FIG. 1, the source gas is branched into the first gas introduction pipe 12, the opened valve 14, and the gas. Carbon dioxide is adsorbed while it is introduced into the mesh part 3 of the first adsorption / desorption tower 1 through the port 9 and ascends the purification region 5 filled with the zeolite adsorbent. The carrier gas with a reduced amount of carbon dioxide is released from the pipe 22 to the atmosphere. On the other hand, when the vacuum pump 33 is started, gas is sucked from the lower end of the second suction / desorption tower 2 through the pipes 26, 29, and 32, and the concentration region 8 is depressurized, so that the concentration region 8 is filled. Carbon dioxide adsorbed in the adsorption step is desorbed from the zeolite-based adsorbent, and the produced concentrated gas is recovered through the pipe 32.

  In the adsorption step, the zeolitic adsorbent packed in the purification region 5 of the first adsorption / desorption tower 1 is held near normal temperature by the tube 39 through which tap water is circulated. High adsorbability with respect to carbon dioxide is expressed, and carbon dioxide is adsorbed efficiently. On the other hand, the zeolitic adsorbent filled in the concentration region 8 of the second adsorption / desorption tower 2 in the desorption step is heated and held near, for example, 60 ° C. by the ribbon heater 42, so that the pressure changes. It exhibits the property that the difference in equilibrium adsorption amount is large, that is, the slope of the adsorption isotherm is large (high adsorption / desorption properties). As a result, by reducing the pressure in the concentration region 8, the carbon dioxide adsorbed in the adsorption step is efficiently desorbed from the heated zeolite-based adsorbent, and the concentrated gas having a high carbon dioxide concentration is recovered.

  The purified gas in the first adsorption / desorption tower 1 is partially passed through the pipes 24, 19, and 16 in accordance with the opening of the purified reflux needle valve 25 as described in the purified gas reflux means. Reflux to the purification zone 6 of the desorption tower 2 On the other hand, the concentrated gas in the second suction / desorption tower 2 is partially passed through the pipes 35 and 26 according to the opening degree of the concentrated reflux needle valve 38 as described in the concentrated gas reflux means. It is refluxed to the concentration region 7 of the desorption tower 1. The concentrated reflux is temporarily stored in the buffer tank 36, and the fixed amount is returned to the concentrated region 7 of the first suction / desorption tower 1 by starting the pressurizing pump 37.

  That is, the purification reflux from the purification region 5 of the first adsorption / desorption tower 1 to the purification region 6 of the second adsorption / desorption tower 2, and the concentration region 8 of the second adsorption / desorption tower 2 from the first adsorption / desorption tower 2. A unidirectional gas flow of concentration reflux to the concentration region 7 of the desorption tower 1 occurs. In this unidirectional gas flow, the carbon dioxide already adsorbed from the zeolite adsorbent packed in the purification region 6 and the concentration region 8 of the second adsorption / desorption tower 2 where the desorption step is performed by the purification reflux. Desorption is promoted. Further, carbon dioxide in the concentrated gas is adsorbed by the zeolitic adsorbent packed in the concentration region 7 of the first adsorption / desorption tower 1 where the adsorption step is performed by the concentration reflux, and the concentration of the concentrated gas is increased. Is promoted.

By the temperature control between the purification regions 5 and 6 and the concentration regions 7 and 8 of the first and second adsorption / desorption towers 1 and 2, and the interaction between the purification reflux and the concentration reflux, the adsorption, In the desorption step, carbon dioxide in the raw material gas can be efficiently adsorbed in the purification region 5 of the first adsorption / desorption column 1, and the concentrated gas can be further concentrated in the concentration region 7. The concentrated gas having a higher carbon dioxide concentration can be recovered by efficiently desorbing the carbon dioxide adsorbed in the adsorption step in the concentration region 8.
(2) Desorption step by the first absorption / desorption tower 1, adsorption step by the second absorption / desorption tower 2 Maintaining room temperature by the tubes 39 and 40 through which tap water is circulated, and heating by the ribbon heaters 41 and 42 were continued. In the state, the opening / closing state of the valve is switched in a certain time unit to switch the absorption / desorption by the first and second absorption / desorption towers 1 and 2. That is, as shown in FIG. 2, the valves 15, 18, 20, 23, 28, 30, 32 are opened and the valves 14, 17, 21, 27, 31 are closed.
In this state, when a source gas containing carbon dioxide is supplied to the gas introduction pipe 11 as shown in FIG. 2, the source gas passes through the second gas introduction pipe 13, the opened valve 15, and the gas port 10, and the second adsorption / desorption tower 2. The carbon dioxide is adsorbed while ascending the purification region 6 filled with the zeolite adsorbent. On the other hand, when the vacuum pump 33 is started, gas is sucked from the lower end of the first suction / desorption tower 1 through the pipes 26, 29, 32, and the concentration region 7 is depressurized, so that the concentration region 7 is filled. Carbon dioxide that has already been adsorbed from the zeolite-based adsorbent is desorbed, and the produced concentrated gas is discharged through the pipe 32.

  In the adsorption step, the zeolitic adsorbent packed in the purification region 6 of the second adsorption / desorption tower 2 has a high adsorptivity to a low concentration of carbon dioxide by the zeolitic adsorbent as described in the above (1). And carbon dioxide is adsorbed efficiently. On the other hand, in the desorption step, the carbon dioxide already adsorbed from the zeolitic adsorbent filled in the concentration region 7 of the first adsorption / desorption tower 1 is efficiently desorbed in the same manner as described in (1) above. A concentrated gas with a high carbon concentration is recovered.

  The purified gas in the second adsorption / desorption tower 2 is partially routed through the pipes 24, 19, 16 in accordance with the opening of the purified reflux needle valve 25 as described in the purified gas reflux means. Reflux to the purification zone 5 of the desorption tower 1 On the other hand, the concentrated gas in the first suction / desorption tower 1 is partially passed through the pipes 35 and 26 according to the opening of the concentrated reflux needle valve 38 as described in the concentrated gas reflux means. The mixture is refluxed to the concentration region 8 of the desorption tower 2. The concentrated reflux is temporarily stored in the buffer tank 36, and the fixed amount is returned to the concentrated region 8 of the second suction / desorption tower 2 by starting the pressurizing pump 37.

  That is, the purification reflux from the purification region 6 of the second adsorption / desorption tower 2 to the purification region 5 of the first adsorption / desorption tower 1, and the concentration of the second adsorption / desorption tower 1 from the concentration region 7 of the second adsorption / desorption tower 1 are performed. A gas flow in a single direction of concentration and reflux to the concentration region 8 of the desorption column 2 is generated, and the desorption step is performed by the purification and reflux in the same manner as described in the above (1). In the concentration region 8 of the second adsorption / desorption tower 2 where the desorption of carbon dioxide already adsorbed from the zeolite-based adsorbent packed in the purification region 5 and the concentration region 7 is promoted and the adsorption step is performed by the concentration reflux. The carbon dioxide in the concentrated gas is adsorbed by the zeolite-based adsorbent filled in the catalyst, and the concentration of the concentrated gas is increased.

By the temperature control between the purification regions 5 and 6 and the concentration regions 7 and 8 of the first and second adsorption / desorption towers 1 and 2, and the interaction between the purification reflux and the concentration reflux, the adsorption, In the desorption step, carbon dioxide in the raw material gas can be efficiently adsorbed in the purification region 6 of the second adsorption / desorption column 2, and the concentrated gas can be further concentrated in the concentration region 8, and the first adsorption / desorption column 1 can be concentrated. The concentrated gas having a higher carbon dioxide concentration can be recovered by efficiently desorbing the carbon dioxide already adsorbed in the region 7.
Therefore, according to the carbon dioxide separation and recovery system according to the first embodiment, the zeolite adsorption between the purification regions 5 and 6 and the concentration regions 7 and 8 of the first and second adsorption / desorption towers 1 and 2 is performed. By giving a temperature difference corresponding to the absorption and desorption properties of carbon dioxide by the material and continuously performing the operations (1) and (2) and the switching operation, it is possible to efficiently perform the adsorption step under normal pressure. Adsorption, high concentration of carbon dioxide in the concentrated gas, and efficient desorption in the desorption step under reduced pressure can be performed continuously.

As a result, the following effects were obtained under the use of the raw material gas having the same carbon dioxide concentration as in the conventional carbon dioxide separation and recovery system using the intermediate supply PSA method, the same reflux conditions, and the raw material gas switching conditions. Can be achieved.
1) When recovering a product gas containing carbon dioxide having the same concentration as a conventional carbon dioxide separation and recovery system, the recovery rate can be improved.

  2) When the product gas is recovered at the same recovery rate as that of the conventional carbon dioxide separation and recovery system, the concentration of carbon dioxide in the product gas can be increased.

  3) A higher recovery rate and higher concentration can be achieved than the conventional carbon dioxide separation and recovery system.

  In addition, it can contribute to the prevention of global warming by reducing the discharge of carbon dioxide into the atmosphere.

(Second Embodiment)
The carbon dioxide separation and recovery system using the intermediate supply PSA method according to the second embodiment has a multistage gas gas introduction pipe shown in FIG. 3 and temperature control corresponding to the adsorbent filling region of the raw gas pipe. Except for the arrangement of the means, it has a structure substantially similar to that shown in FIGS. 4 is an enlarged view of a main part of FIG. 3 and 4, the same members as those in FIGS. 1 and 2 described above are denoted by the same reference numerals, and the description thereof is omitted.
In the first absorption / desorption tower 1, a plurality of, for example, nine mesh portions 3a to 3i for smooth gas introduction are respectively provided at equal intervals in the height direction, for example. Between the mesh parts 3a to 3i, the first adsorbing / desorbing tower 1 located on the upper side of the mesh part 3a and on the lower side of the mesh part 3i has 10 adsorbent filling regions 51a to 51a filled with an adsorbent. 51j are formed. The adsorbents are all of the same type of zeolite.
The plurality of gas ports 9a to 9i are attached to the first suction / desorption tower 1 corresponding to the mesh portions 3a to 3i. A plurality of first gas introduction pipes 12a to 12i branched from the gas introduction pipe 11 are connected to the gas ports 9a to 9i, respectively. Valves 14a to 14i are interposed in the first gas introduction pipes 12a to 12i, respectively.
For example, ten tubes 52a to 52j circulated so as to be able to switch between room temperature water and hot water (for example, hot water of 60 ° C.) such as tap water are used as the adsorbent of the first adsorption / desorption tower 1 as shown in FIG. It is arranged corresponding to each of the filling regions 51a to 51j. In FIG. 4, the tubes 52f to 52j are not shown, but the following description will be made assuming that these tubes are provided for convenience.
Although the second absorption / desorption tower is not shown, the second absorption / desorption tower has the same structure as the first absorption / desorption tower 1.
Such adsorbing / desorbing tower (for example, the first adsorbing / desorbing tower 1) is partitioned by a plurality of mesh portions 3a-3i, and a plurality of adsorbent filling regions 51a-51j filled with adsorbent are respectively arranged in the height direction. By forming a gas introduction pipe (for example, the first gas introduction pipes 12a to 12i) branched into a plurality of gas ports 9a to 9i that are formed and communicated with the mesh portions 3a to 3i, a user's request is met. Accordingly, the volume of the purification region and the concentration region described above can be changed, and the separation and recovery operation of carbon dioxide in the raw material gas can be executed.

That is, for example, when performing an operation for suppressing the release of carbon dioxide to the atmosphere as much as possible, the valve 14g of the lower gas introduction pipe (for example, 12g) among the first gas introduction pipes 12a to 12i is selectively selected. Open, normal temperature water is circulated through the tubes 52a to 52g above the gas introduction pipe 12g, and hot water is circulated through the tubes 52h to 52j below it. According to such usage, the adsorbent filling regions 51a to 51g of the first adsorption / desorption tower 1 corresponding to the tubes 52a to 52g are used as the purification region, and the adsorbent of the first adsorption / desorption tower 1 corresponding to the tubes 52h to 52j. The filling regions 51h to 51j can be the concentration region. That is, the volume of the purification region can be effectively increased as compared with the volume of the concentration region. As a result, by introducing the raw material gas into the first adsorption / desorption tower 1 through the gas introduction pipe 12g, the carbon dioxide in the raw material gas can be sufficiently adsorbed, so that the amount of carbon dioxide is reduced as much as possible. Can be released to the atmosphere from the pipe 22 shown in FIG.
On the other hand, when increasing the concentration of carbon dioxide in the product gas, the valve 14c of the upper gas introduction pipe (for example, 12c) among the first gas introduction pipes 12a to 12i is selectively opened, The normal temperature water is circulated through the tubes 52a to 52c above the one gas introduction pipe 12c, and the hot water is circulated through the tubes 52d to 52j below it. With such a usage pattern, the adsorbent filling regions 51a to 51c of the first adsorption / desorption tower 1 corresponding to the tubes 52a to 52c are purified, and the adsorbent of the first adsorption / desorption tower 1 corresponding to the tubes 52d to 52j. The filling regions 51h to 51j can be the concentration region. That is, the volume of the concentration region can be effectively increased as compared with the volume of the purification region. As a result, for example, the concentrated gas desorbed in the desorption step in the second adsorption / desorption tower is concentrated and refluxed to the first adsorption / desorption tower 1 so that the concentrated gas is adsorbed more efficiently in the first adsorption / desorption tower 1. Therefore, the product gas having a higher carbon dioxide concentration can be recovered from the pipe 32 shown in FIG.
In the second embodiment described above, the first absorption / desorption tower 1 has been described as an example. However, the same operation is performed for the second absorption / desorption tower 2.

  Therefore, according to the carbon dioxide separation and recovery system according to the second embodiment, as in the carbon dioxide separation and recovery system of the first embodiment described above, efficient adsorption in the adsorption step under normal pressure, and high carbon dioxide concentration gas. Since the efficient desorption in the desorption step under concentration and reduced pressure can be performed continuously, the effects 1) to 3) described above can be achieved, and the emission of carbon dioxide to the atmosphere can be reduced to reduce the earth. Can contribute to the prevention of global warming.

  In addition, it is possible to execute a separation and recovery operation of carbon dioxide in the raw material gas according to the user's request such as suppressing the release of carbon dioxide into the atmosphere as much as possible and increasing the concentration of carbon dioxide in the product gas.

(Third embodiment)
The carbon dioxide separation and recovery system using the intermediate supply PSA method according to the third embodiment performs automatic switching for performing selection of opening of valves of a plurality of gas introduction pipes according to the carbon dioxide concentration of the raw material gas shown in FIG. Except for the addition of a control device, it has a structure substantially similar to that shown in FIGS. In FIG. 5, the same members as those shown in FIGS.
The automatic switching control device 101 includes a processing circuit 102, a touch panel 103, and a temperature management circuit 104.
The processing circuit 102 is connected through a signal line 106 to a concentration meter 105 that measures the concentration of carbon dioxide in the raw material gas supplied to the gas introduction pipe 11. The processing circuit 102 is connected to the touch panel 103 through a signal line 107. Further, the processing circuit 102 supplies the valves 14a to 14i of the plurality of first gas introduction pipes 12a to 12i branched from the gas introduction pipe 11 through the multicore signal line 108 and the single signal lines 108a, 108b, 108c. It is connected. In FIG. 5, the first gas introduction pipes 12a to 12c and 12f to 12i and the valves 14a to 12c and 12f to 14 are not shown. Will be described. In such a connection, a control signal that determines which of the valves 14 a to 14 i is selected from the touch panel 103 according to the concentration of the raw material gas is input to the processing circuit 102 in advance. When a detection signal from the densitometer 105 is output to the processing circuit 102 by this setting, a signal for selecting one of the valves 14a to 14i is output from the processing circuit 102, and the valve is opened. The

  The processing circuit 102 is connected to the temperature management circuit 104 through a signal line 109. The temperature management circuit 104 passes through the multi-core signal line 110 and the single signal lines 110a, 110b, 110c... To the adsorbent filling regions 51a to 51j of the first adsorption / desorption tower 1 partitioned by the mesh portions 3a to 3i. It connects to the switching member (not shown) for switching supply of the normal temperature water and warm water (for example, 55 degreeC warm water) to the corresponding tubes 52a-52j. In FIG. 5, the mesh portions 3a to 3b, 3f to 3i, the adsorbent filling regions 51a to 51c, 51f to 51j, and the tubes 52a to 52c, 52f to 52 are not shown. A description will be given assuming that there are a mesh portion, an adsorbent filling region, and a tube. In such a connection, when a control signal based on a detection signal from the densitometer 105 is output from the processing circuit 102 to the temperature management circuit 104, the switching member of each of the tubes 52a to 52j is output from the temperature management circuit 104. A signal for switching to either room temperature water or warm water is output (not shown).

Further, the processing circuit 102 is connected to the purified reflux needle valve 25 and the concentrated reflux needle valve 38 through a multi-core signal line 111 and single signal lines 111a and 111b therefrom. In such a connection, the processing circuit 102 is preliminarily input with control conditions relating to the carbon dioxide concentration and the recovery amount in the product gas from the touch panel 104, and based on these control conditions, the purification reflux needle valve 25 and the concentration reflux needle. A signal for adjusting the opening of the valve 38 is output.
Although the second absorption / desorption tower is not shown, the second absorption / desorption tower has the same structure as the first absorption / desorption tower 1 and is connected to the automatic switching control device. The
In such a carbon dioxide separation and recovery system according to the third embodiment, when a raw material gas containing carbon dioxide is supplied to the gas introduction pipe 11, the concentration of carbon dioxide in the raw material gas is detected by the concentration meter 105, and this detection is performed. The signal is output to the processing circuit 102 of the control panel 101 through the signal line 106. In response to the input of the detection signal, the processing circuit 102 outputs a signal for selecting one of the valves 14a to 14i of the first gas introduction pipes 12a to 12i, for example, the valve 14e, and opens the valve 14e. At the same time, a control signal based on the detection signal from the densitometer 105 is output from the processing circuit 102 to the temperature management circuit 104. In response to the input of this control signal, the temperature management circuit 104 outputs a signal for switching to a switching member (not shown) of the tubes 52a to 52j corresponding to the adsorbent filling regions 51a to 51j of the first adsorption / desorption tower 1. The normal temperature water is circulated through the tubes 52a to 52e above the one gas introduction pipe 12e, and the hot water is circulated through the tubes 52f to 52j below it.
By such a usage pattern, the adsorbent filling regions 51a to 51e of the first adsorption / desorption tower 1 corresponding to the tubes 52a to 52e are purified regions maintained at room temperature, and the first adsorption / desorption corresponding to the tubes 52f to 52j. The adsorbent filling regions 51f to 51j of the tower 1 can be heated regions. That is, the volumes of the purification region and the concentration region can be automatically increased or decreased in accordance with the concentration of carbon dioxide in the raw material gas.
Specifically, when the carbon dioxide concentration in the raw material gas is low, the low-position valve among the valves 14a to 14i of the first gas introduction pipes 12a to 12i is automatically opened by a detection signal from the concentration meter 105. For example, tap water is circulated through the tube above the first introduction pipe, and the volume is effectively increased with the adsorbent filling area above the connection position (mesh portion) of the first introduction pipe as a purification area. Thus, the low concentration carbon dioxide in the raw material gas can be adsorbed sufficiently efficiently in the first adsorption / desorption tower 1.

On the other hand, when the carbon dioxide concentration in the raw material gas is high, the valve at the higher position among the valves 14a to 14i of the first gas introduction pipes 12a to 12i is automatically opened by the detection signal from the concentration meter 105, and the first 1 For example, tap water is circulated through the tube above the introduction pipe, and the volume of the adsorbent filling area above the connection position (mesh part) of the first introduction pipe is effectively reduced to reduce the volume thereof. By effectively increasing the volume, the high concentration of carbon dioxide in the raw material gas can be adsorbed sufficiently efficiently in the first adsorption / desorption tower 1, and at the same time, the concentration of carbon dioxide in the concentrated gas can be increased by increasing the volume of the concentration region. High concentration is achieved, and higher concentration product gas can be recovered.
Further, the control circuit outputs control signals from the processing circuit 102 to the purified reflux needle valve 25 and the concentrated reflux needle valve 38, and adjusts the opening of the control signal to thereby adjust the carbon dioxide concentration and the recovered amount of the recovered product gas. Can be controlled.
Therefore, according to the third embodiment, as in the carbon dioxide separation and recovery system of the first embodiment described above, efficient adsorption in the adsorption step under normal pressure, higher concentration of carbon dioxide in the concentrated gas, and desorption under reduced pressure. Since efficient desorption at the step can be performed continuously, as in the carbon dioxide separation and recovery system of the first embodiment described above, efficient adsorption at the adsorption step under normal pressure, and carbon dioxide in the concentrated gas Since it is possible to continuously perform efficient desorption in the desorption step under high concentration and reduced pressure, the above-mentioned effects 1) to 3) can be achieved, and emission of carbon dioxide into the atmosphere can be reduced. It can contribute to the prevention of global warming.

  In addition, since the volume of the purification region and the concentration region can be automatically increased or decreased in accordance with the concentration of carbon dioxide in the raw material gas, the above-mentioned 1) to ˜depending on the concentration of carbon dioxide in the raw material gas. The effect of 3) can be achieved.

In the first to third embodiments described above, in order to provide a pressure difference between the adsorption step and the desorption step, normal pressure source gas is supplied from the gas introduction pipe to the adsorption / desorption tower in which the adsorption step is performed. Although the inside of the suction / desorption tower which is supplied and desorbed is evacuated by a vacuum pump to reduce the pressure, it is not limited to such a form. For example, a pressurized source gas is supplied from a gas introduction pipe to an adsorption / desorption tower in which an adsorption step is performed, and the pressure in the adsorption / desorption step is set to normal pressure in the adsorption / desorption tower in which the desorption step is performed. A difference may be imparted.
In the second and third embodiments described above, a room temperature water or a tube through which hot water is circulated is used as the temperature control means arranged corresponding to the plurality of adsorbent packed regions of the adsorption / desorption tower. Corresponding to a plurality of adsorbent filling regions, the temperature control means may be configured by juxtaposing a tube through which normal temperature water as the first temperature management member is circulated and a heater as the second temperature management member.

The carbon dioxide separation and recovery system using the intermediate supply PSA method according to the first embodiment of the present invention (the open / close state of each valve at the time of the adsorption step by the first adsorption / desorption tower and the desorption step by the second adsorption / desorption tower is also shown. ) Is a schematic diagram showing. The carbon dioxide separation and recovery system using the intermediate supply PSA method according to the first embodiment of the present invention (denoting the open / close state of each valve during the desorption step by the first adsorption / desorption tower and the adsorption step by the second adsorption / desorption tower) ) Is a schematic diagram showing. Schematic which shows the 1st absorption / desorption tower part of the carbon dioxide separation-and-recovery system which concerns on 2nd Embodiment of this invention. FIG. 4 is an enlarged schematic view illustrating a main part of FIG. 3 in detail. Schematic which shows the principal part of the carbon dioxide separation-and-recovery system using the intermediate supply PSA method which concerns on 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st absorption / desorption tower, 2 ... 2nd absorption / desorption tower, 5, 6 ... Purification area | region, 7, 8 ... Concentration area | region, 11 ... Gas introduction piping, 12, 12a-12i ... 1st gas introduction piping, DESCRIPTION OF SYMBOLS 13 ... 2nd gas introduction piping, 14, 14a-14i, 15 ... Valve, 25 ... Refinement | purification reflux needle valve, 33 ... Vacuum pump, 35 ... Pressurization pump, 38 ... Concentration reflux needle valve, 39, 40, 52a ˜52I, tube, 41, 42, ribbon heater, 51a-51i, adsorbent filling region, 101, automatic switching control device, 102, processing circuit, 103, touch panel, 104, temperature management circuit.

Claims (3)

In the carbon dioxide separation and recovery system using the bi-directional reflux feed gas intermediate supply pressure swing adsorption method,
At least a pair of absorption / desorption towers filled with an adsorbent,
Switchable gas introduction pipes connected to the middle of each of the adsorption / desorption towers for supplying a raw material gas containing carbon dioxide,
Purified gas reflux means for refluxing part of the purified gas to each other at one end of each of the adsorption / desorption towers;
A concentrated gas reflux means for refluxing part of the carbon dioxide concentrated gas at the other end of each of the adsorption / desorption towers;
A region toward one end with the gas introduction pipe connecting portion in each of the adsorption / desorption towers as a boundary is a purification region, and a region toward the other end is a concentration region, and the temperature of the concentration region is higher than that of the purification region. A carbon dioxide separation and recovery system comprising a temperature control means for the purpose. In the carbon dioxide separation and recovery system using the bi-directional reflux feed gas intermediate supply pressure swing adsorption method,
At least a pair of absorption / desorption towers filled with an adsorbent,
A switchable gas introduction pipe connected to each of the adsorption / desorption towers for supplying a raw material gas containing carbon dioxide,
Purified gas reflux means for refluxing part of the purified gas to each other at one end of each of the adsorption / desorption towers;
A concentrated gas reflux means for refluxing part of the carbon dioxide concentrated gas at the other end of each of the adsorption / desorption towers;
Temperature control means for controlling the temperature of each of the adsorption / desorption towers,
The gas introduction pipe is branched into a plurality of pipes, the branch pipes are connected to a plurality of positions in the height direction of the respective suction / desorption towers, and the temperature control means is capable of switching between cooling and heating. A carbon dioxide separation / recovery system, wherein a plurality of carbon dioxide separation / recovery systems are arranged corresponding to the areas of the adsorption / desorption towers located between the branch pipes.   The apparatus further comprises an automatic switching control device for automatically switching supply of the source gas to each branch pipe and cooling / heating of the plurality of temperature control means according to the concentration of the source gas. The carbon dioxide separation and recovery system according to claim 2.

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