Carbon dioxide capture method and carbon dioxide capture system

Abstract

To provide a carbon dioxide recovery method and a carbon dioxide recovery system capable of suppressing changes in the carbon dioxide desorption rate over time. [Solution] The carbon dioxide recovery method of the present invention is a carbon dioxide recovery method that uses multiple recovery vessels 10 containing carbon dioxide adsorbents 13 and captures carbon dioxide by repeating an adsorption step S1 in which carbon dioxide is adsorbed into each recovery vessel 10, and a desorption step S3 in which carbon dioxide is desorbed from each recovery vessel 10 in turn, wherein the adsorbents 13 are contained in multiple gas chambers 12_1, 12_2 that are separated and formed within the recovery vessel 10, and in the desorption step S3, carbon dioxide is desorbed from the adsorbents 13 in each gas chamber 12_1, 12_2 in turn with a time lag.

Description

[Technical Field]

[0001] The present invention relates to a carbon dioxide capture method and a carbon dioxide capture system. [Background technology]

[0002] Methods for separating and recovering carbon dioxide from mixed gases using adsorbents are known. Patent Document 1 discloses a method for recovering carbon dioxide by using multiple recovery vessels equipped with adsorbents and sequentially carrying out adsorption, preheating, desorption, and cooling processes. The desorbed carbon dioxide can be reacted with hydrogen to produce methane. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-163247 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when using the desorbed carbon dioxide to produce methane, it is necessary to supply hydrogen in just the right amount to allow the reaction to proceed, and therefore it is preferable that the amount of desorbed carbon dioxide does not change over time. However, in reality, the carbon dioxide desorption rate is proportional to the amount of carbon dioxide adsorbed, and therefore changes as the desorption progresses. Specifically, when carbon dioxide is desorbed sequentially from multiple recovery vessels, the desorption rate is greatest immediately after the start of carbon dioxide desorption from each recovery vessel, gradually decreases over time, and then suddenly increases again immediately after switching the recovery vessel from which carbon dioxide is desorbed. In other words, this method has the problem of large fluctuations in the carbon dioxide desorption rate.

[0005] The present invention has been made in view of the above circumstances, and provides a carbon dioxide recovery method and a carbon dioxide recovery system that can suppress the change over time in the carbon dioxide desorption rate. [Means for solving the problem]

[0006] The carbon dioxide capture method of the present invention is a carbon dioxide capture method that uses a plurality of capture vessels containing carbon dioxide adsorbents and captures carbon dioxide by repeating an adsorption step in which carbon dioxide is adsorbed into each of the capture vessels and a desorption step in which carbon dioxide is desorbed from each of the capture vessels in turn, wherein the adsorbents are contained in a plurality of gas chambers that are separated and formed within the capture vessels, and in the desorption step, carbon dioxide is desorbed from the adsorbents in each of the gas chambers in turn with a time lag. [Effects of the Invention]

[0007] The present invention can provide a carbon dioxide capture method and a carbon dioxide capture system that can suppress changes in the carbon dioxide desorption rate over time. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic diagram showing the structure of a recovery container according to the present embodiment. [Figure 2] 2 is a cross-sectional view of the collector taken along line II-II in FIG. 1. [Figure 3] 10 is a flowchart of a process performed on a collector. [Figure 4] FIG. 10 is a diagram showing the timing at which each process is performed on a plurality of collectors. [Figure 5] 4 is a graph showing the change in concentration of carbon dioxide contained in the recovered gas in the carbon dioxide recovery method according to the present embodiment. [Figure 6] FIG. 10 is a diagram showing the timing at which each process is performed on a plurality of collectors in a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings have been simplified as appropriate for clarity of explanation. Naturally, the right-handed xyz coordinate system shown in Figure 1 and other drawings is for the convenience of explaining the positional relationships of the components. Normally, the positive direction of the z axis is vertically upward, and the xy plane is the horizontal plane, which is common among the drawings. Furthermore, the multiple configuration examples described below can be implemented independently or in appropriate combination. These multiple configuration examples have different novel features. Therefore, these multiple configuration examples contribute to solving different purposes or problems and to achieving different effects.

[0010] In this embodiment, a method for capturing carbon dioxide using four capture devices will be described. First, the structure of a capture device 10 according to this embodiment will be described with reference to Figs. 1 and 2. Fig. 1 is a schematic diagram showing the structure of the capture device 10. Fig. 2 is a cross-sectional view of the capture device 10 taken along the line II-II in Fig. 1.

[0011] The collector 10 is a cylindrical container, and Fig. 1 is a cross-sectional view of the collector 10 in the zx plane. As shown in Fig. 1, the collector 10 includes an air vent 11, a first gas chamber 12_1, a second gas chamber 12_2, an adsorbent 13, a pair of valves 14_1 and 14_2, and an oil chamber 15.

[0012] The ventilation holes 11 are holes provided on the top and bottom of the collector 10. The ventilation holes 11 can be connected to, for example, an external gas introduction device or suction device, and can introduce gas from the outside or release gas to the outside.

[0013] The first gas chamber 12_1 and the second gas chamber 12_2 are chambers formed to allow gas to pass through in the vertical direction. As shown in Figures 1 and 2, the first gas chamber 12_1 and the second gas chamber 12_2 each have a shape in which two small upper and lower chambers are spatially connected by a plurality of cylindrical passages, and the adsorbent 13 is accommodated inside the passages. The first gas chamber 12_1 and the second gas chamber 12_2 are formed to be separated from each other.

[0014] The adsorbent 13 is a material for adsorbing carbon dioxide. There are no particular limitations on the adsorbent 13 as long as it is a material that can adsorb carbon dioxide, and for example, zeolite, activated carbon, silica gel, etc. These materials adsorb carbon dioxide at low temperatures and release carbon dioxide at high temperatures.

[0015] A pair of valves 14_1 are connected to the upper and lower ends of the first gas chamber 12_1, respectively, and a pair of valves 14_2 are connected to the upper and lower ends of the second gas chamber 12_2, respectively. By opening and closing the pairs of valves 14_1 and 14_2, the gas chamber 12_1 and the second gas chamber 12_2 can be opened or closed, respectively.

[0016] 1 and 2, the oil chamber 15 is a chamber provided to surround the portions of the first gas chamber 12_1 and the second gas chamber 12_2 that house the adsorbent 13. The lower and upper ends of the oil chamber 15 are connected to external oil lines, and oil is pumped from the bottom to the top of the oil chamber 15, thereby filling the oil chamber 15 with oil.

[0017] Fig. 3 is a flowchart of the processing performed on the collector 10. In the example of Fig. 3, the processing of steps S1 to S4 is repeatedly performed on the collector 10. These processing steps can be executed by, for example, a control unit (not shown). The control unit can be, for example, a computer configured to include a ROM, a RAM, and a CPU.

[0018] Step S1 is a step (adsorption step) for adsorbing carbon dioxide in the recovery vessel 10. In step S1, while low-temperature oil is being fed into the oil chamber 15, the valve pair 14_1 and the valve pair 14_2 are opened to introduce a gas containing carbon dioxide from the vent hole 11 at the lower end. The introduced gas passes through either the first gas chamber 12_1 or the second gas chamber 12_2 and is discharged from the vent hole 11 at the upper end. At this time, the carbon dioxide is adsorbed by the adsorbent 13 accommodated in the first gas chamber 12_1 or the second gas chamber 12_2.

[0019] Step S2 is a step (heating step) of heating the recovery vessel 10. In step S2, the valve pair 14_1 and the valve pair 14_2 are closed, and high-temperature oil is sent into the oil chamber 15. By heating the recovery vessel 10 in this step, it is possible to facilitate desorption of carbon dioxide from the adsorbent 13 in the next step.

[0020] Step S3 is a step (desorption step) of desorbing carbon dioxide from the recovery vessel 10. In step S3, step S3_1 of desorbing carbon dioxide from the adsorbent 13 in the first gas chamber 12_1 and step S3_2 of desorbing carbon dioxide from the adsorbent 13 in the second gas chamber 12_2 are performed in this order with a time lag.

[0021] First, in step S3_1, while high-temperature oil is being fed into the oil chamber 15, the valve pair 14_1 is opened and a vacuum pump is connected to the vent hole 11 at the lower end to reduce the pressure inside the recovery vessel 10. Also, a gas such as hydrogen is introduced through the vent hole 11 at the upper end. This causes carbon dioxide to be desorbed from the adsorbent 13 in the first gas chamber 12_1. The desorbed carbon dioxide is recovered through the vacuum pump connected to the vent hole 11 at the lower end.

[0022] Step S3_2 is started after a predetermined time has elapsed since the start of step S3_1. In step S3_2, high-temperature oil is fed into the oil chamber 15, and the valve pair 14_2 is opened while the pressure inside the recovery vessel 10 is reduced. This causes carbon dioxide to be desorbed from the adsorbent 13 in the second gas chamber 12_2. The desorbed carbon dioxide is recovered through a vacuum pump connected to the vent hole 11 at the lower end.

[0023] Step S4 is a step (cooling step) of cooling the recovery device 10. In step S4, the valve pair 14_1 and the valve pair 14_2 are closed, and low-temperature oil is sent into the oil chamber 15. By cooling the recovery device 10 in this step, it is possible to facilitate adsorption of carbon dioxide into the adsorbent 13 in the next step.

[0024] In this embodiment, any one of the collectors performs any one of steps S1 to S4, and the four collectors are caused to perform steps S1 to S4 in order. Figure 4 is a diagram showing the timing at which each process is performed on multiple collectors. In the example of Figure 4, when the first collector starts the cooling step, the second collector starts the adsorption step, the third collector starts the heating step, and the fourth collector starts the desorption step (step S3_2) from the second gas chamber.

[0025] In the example of Figure 4, steps S1, S2, S3_2, and S4 all start every 30 minutes, and steps S2, S3_1, and S3_2 all start every 15 minutes. At this time, carbon dioxide desorption from each gas chamber starts every 15 minutes. Figure 5 is a graph showing the change in carbon dioxide concentration contained in the recovered gas when carbon dioxide is desorbed under these conditions.

[0026] In Figure 5, the short dashed lines represent the change in carbon dioxide concentration contained in the gas desorbed from each second gas chamber. The concentration rises sharply immediately after desorption from the second gas chamber begins (0, 30, and 60 minutes), and then gradually decreases. The long dashed lines in the graph show the change in carbon dioxide concentration contained in the gas desorbed from each of the first gas chambers. The concentration rises sharply immediately after desorption from the first gas chamber begins (15 minutes, 45 minutes, and 75 minutes), and then gradually decreases.

[0027] If each recovery vessel has only one gas chamber as in the prior art, the concentration of carbon dioxide contained in the recovered gas will behave as shown by the dashed line. On the other hand, in this embodiment, the concentration of carbon dioxide contained in the gas recovered from the entire recovery vessel is the average of the values ​​represented by these two dashed lines, and is represented by the solid line. In the example of Figure 5, the range of change in carbon dioxide concentration represented by the solid line is 52% smaller than the range of change in carbon dioxide concentration represented by the dashed line. This is because each recovery vessel is provided with multiple gas chambers, and carbon dioxide is desorbed from each gas chamber at different times, which allows the desorption rate peaks to be dispersed.

[0028] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention.

[0029] For example, in the above embodiment, each collector is configured to have two gas chambers, but it may also be configured to have three or more gas chambers. Even in this case, by sequentially desorbing carbon dioxide from the adsorbent in each gas chamber with a time lag, it is possible to suppress the change in the carbon dioxide desorption rate over time. As an example, FIG. 6 shows the timing of performing each process on multiple collectors, each having n gas chambers. The more gas chambers each collector has, the more preferable it is, as this allows the carbon dioxide concentration peaks to be more dispersed.

[0030] In the above embodiment, the heating step and the cooling step are performed, but these steps may be omitted. In this case, the number of collectors may be two or more.

[0031] It is preferable that the carbon dioxide adsorption capacity of the adsorbents housed in each gas chamber of each recovery vessel is approximately the same, and that the carbon dioxide is desorbed from the adsorbents in each gas chamber in order at approximately the same time intervals during the desorption step. In this case, the peaks of the carbon dioxide concentration contained in the recovered gas can appear at approximately equal time intervals and with approximately the same intensity. Therefore, the change in the carbon dioxide desorption rate over time can be further suppressed. [Explanation of symbols]

[0032] 10 Recycler 11 Ventilation holes 12_1 First Gas Chamber 12_2 Second Gas Chamber 13 Adsorbent 14_1, 14_2 valve pair 15 Oil chamber

Claims

1. Using multiple recovery vessels containing carbon dioxide adsorbents, an adsorption step of adsorbing carbon dioxide in each of the collectors; a desorption step of desorbing carbon dioxide from each of the recovery devices in turn, the adsorbent is accommodated in a plurality of gas chambers formed and separated within the collector, In the desorption step, carbon dioxide is desorbed from the adsorbents in the respective gas chambers in order with a time lag. Carbon dioxide capture methods.

2. the carbon dioxide adsorption capacities of the adsorbents accommodated in each gas chamber are all substantially the same, In the desorption step, carbon dioxide is desorbed from the adsorbent in each of the gas chambers in turn at substantially equal time intervals. The carbon dioxide recovery method according to claim 1.

3. a plurality of recovery vessels each containing a carbon dioxide adsorbent in a plurality of gas chambers formed separately from each other; a control unit that repeatedly executes an adsorption step of adsorbing carbon dioxide in each of the collectors and a desorption step of desorbing carbon dioxide from each of the collectors in turn, In the desorption step, the control unit sequentially desorbs carbon dioxide from the adsorbents in the gas chambers with a time lag. Carbon dioxide capture system.

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