Adsorption tower control apparatus, gas separation apparatus, control method of plurality of adsorption towers and computer program

Abstract

To provide a technique that can suppress lowering of a rate of collection of adsorbed gas, even under a situation where quantities and densities of mixed gas flowing into an adsorption tower vary.SOLUTION: An adsorption tower control apparatus, which collects specific adsorbed gas using a plurality of adsorption towers, is provided with: a control part that causes an adsorption / desorption step, in which an adsorption step is executed in an adsorption-step tower and at the same time a desorption step is executed in a desorption-step tower, to be repeatedly executed in a plurality of adsorption towers while being transferred; an information obtaining part that obtains information on a property of mixed gas and an operational condition for the adsorption-step tower; and a desorption condition determining part that determines a desorption condition in the desorption-step tower from the information on the property of mixed gas and the operation condition. The control part causes the desorption step to be executed under the desorption condition determined by the desorption condition determining part, and when integrated quantity of adsorbed gas in the adsorption-step tower reaches a predetermined integrated quantity threshold, causes the adsorption-step tower and the desorption-step tower to transfer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique for controlling a plurality of adsorption towers. [Background technology]

[0002] It is known to separate and reuse carbon dioxide (CO2) from exhaust gas from a combustion device. For example, Patent Document 1 proposes a system in which an adsorption tower containing an adsorbent adsorbs and recovers carbon dioxide in exhaust gas, and combines it with hydrogen (H2) to synthesize methane with high efficiency. Patent Document 2 also proposes a technology in which, in controlling the repeated adsorption and desorption steps in an adsorption tower, the amount of adsorption in the next adsorption step is predicted, and the desorption amount is controlled accordingly. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6791177 [Patent Document 2] Patent No. 7173088 Summary of the Invention [Problem to be solved by the invention]

[0004] However, most of the exhaust gases actually discharged from combustors have fluctuations in flow rate and concentration over time, and control technology for such fluctuations in exhaust gases was not considered in Patent Document 1. Also, in the technology described in Patent Document 2, if the prediction of the adsorption amount in the next adsorption process is incorrect, it has a large impact on the subsequent recovery rate and inventory management, and there are issues with stable operation.

[0005] This problem is not limited to methane production apparatuses that use hydrogen as a purge gas, but is a common issue with any technology that separates specific gases using an adsorbent.

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide a technology that suppresses a decrease in the recovery rate of the adsorbed gas even in situations where the amount and concentration of the mixed gas flowing into the adsorption tower fluctuates. [Means for solving the problem]

[0007] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0008] (1) According to one aspect of the present invention, there is provided an adsorption tower control device that recovers a specific adsorbed gas from a mixed gas containing the adsorbed gas by using a plurality of adsorption towers. The plurality of adsorption towers include at least an adsorption step tower in which an adsorption step is performed to which the mixed gas is supplied, and a desorption step tower in which a desorption step is performed to desorb the adsorbed gas. The adsorption tower control device includes a control unit that repeatedly executes an adsorption / desorption step in which the adsorption step is performed in the adsorption step tower and at the same time the desorption step is performed in the desorption step tower while progressing through the plurality of adsorption towers; an information acquisition unit that acquires mixed gas property information including at least one of the flow rate of the mixed gas supplied to the adsorption step tower, the concentration of the adsorbed gas in the mixed gas, the temperature of the mixed gas, and the pressure of the mixed gas, and at least one of the temperature of the adsorption step tower and the pressure in the adsorption tower; and a control unit that acquires information on the desorption step. and a desorption condition determination unit that determines desorption conditions, including at least one of the supply flow rate of purge gas to the process tower, heating of the desorption process tower, and pressure reduction inside the desorption process tower, from the mixed gas property information acquired by the information acquisition unit and the operating conditions in the adsorption process that is performed simultaneously with the desorption process, and the control unit executes the desorption process under the desorption conditions determined by the desorption condition determination unit, and transitions the adsorption process tower and the desorption process tower when the accumulated amount of the adsorbed gas in the adsorption process tower reaches a predetermined accumulated amount threshold.

[0009] According to this configuration, in one adsorption / desorption process, the desorption conditions of the desorption process tower are determined using the property information and operation conditions of the mixed gas supplied to the adsorption process tower. Also, according to this configuration, the amount of adsorbed gas adsorbed by the multiple adsorption towers in the adsorption process is approximately constant. In contrast, the time of the desorption process varies because it is the same as the time of the adsorption process performed simultaneously. In this configuration, the desorption conditions in the desorption process tower where the desorption process is performed are changed according to the flow rate of the mixed gas supplied to the adsorption process tower where the adsorption process is performed simultaneously, so that the adsorbed gas can be appropriately desorbed within the time of the desorption process. As a result, a decrease in the recovery rate of the adsorbed gas can be suppressed.

[0010] (2) In the adsorption tower control device of the above aspect, the information acquisition unit may further acquire exhaust gas property information including at least one of a flow rate of the exhaust gas discharged from the adsorption tower and a concentration of the adsorbed gas in the exhaust gas, and the control unit may calculate an integrated amount of the adsorbed gas using the mixed gas property information and the exhaust gas property information acquired by the information acquisition unit. In this way, the integrated amount of the adsorbed gas can be accurately calculated, so that the time of the adsorption / desorption process can be optimized and the recovery rate of the adsorbed gas can be improved.

[0011] (3) In the adsorption tower control device of the above aspect, the information acquisition unit may successively acquire the mixed gas property information and the operating conditions, and the desorption condition determination unit may successively determine the desorption conditions using the successively acquired mixed gas property information and the operating conditions. Here, "successively" means at regular intervals. In this way, even if the amount of mixed gas supplied to the adsorption tower varies with time, the desorption conditions can be changed at regular intervals, so that the desorption conditions can be set more appropriately and the recovery rate of the adsorbed gas can be further improved.

[0012] (4) In the adsorption tower control device of the above aspect, the information acquisition unit may sequentially acquire the mixed gas property information and the operating conditions, and the desorption condition determination unit may determine the desorption conditions using average mixed gas property information and average operating conditions obtained by time-averaging the sequentially acquired mixed gas property information and operating conditions. In this way, for example, when the fluctuation of the supplied mixed gas changes suddenly due to pulsation or the like, the mixed gas property information and the operating conditions are smoothed, so that stable desorption control can be performed.

[0013] (5) According to another aspect of the present invention, there is provided an adsorption tower control device for recovering a specific adsorbed gas from a mixed gas containing the adsorbed gas by using a plurality of adsorption towers. The plurality of adsorption towers include at least an adsorption step tower for performing an adsorption step to which the mixed gas is supplied and a desorption step tower for performing a desorption step to desorb the adsorbed gas. The adsorption tower control device includes a control unit for repeatedly executing an adsorption / desorption step in which the adsorption step tower performs the desorption step while shifting the plurality of adsorption towers, an information acquisition unit for acquiring mixed gas property information including at least one of the flow rate of the mixed gas supplied to the adsorption step tower, the concentration of the adsorbed gas in the mixed gas, the temperature of the mixed gas, and the pressure of the mixed gas, and at least one of the temperature of the adsorption step tower and the pressure inside the adsorption step tower, and a control unit for controlling the supply flow rate of a purge gas to the desorption step tower, the heating of the desorption step tower, and the reduction in pressure inside the desorption step tower. and a desorption condition determination unit that determines desorption conditions including at least one of the above from the mixed gas property information acquired by the information acquisition unit and the operation conditions in the adsorption process performed simultaneously with the desorption process, and the control unit executes the desorption process under the desorption conditions determined by the desorption condition determination unit, calculates a recovery rate of the adsorbed gas in the desorption process tower when an integrated amount of the adsorbed gas in the adsorption process tower reaches a predetermined integrated amount threshold, and shifts the adsorption process tower and the desorption process tower when the recovery rate is equal to or greater than the predetermined recovery rate threshold, and continues the adsorption and desorption process until the recovery rate is equal to or greater than the recovery rate when the recovery rate is less than the recovery rate threshold. According to this configuration, when the recovery rate of the adsorbed gas is insufficient, the adsorption process tower and the desorption process tower are not shifted and the adsorption and desorption process is continued, thereby improving the recovery rate of the adsorbed gas.

[0014] (6) According to another aspect of the present invention, there is provided a gas separation apparatus comprising: an adsorption tower control device according to the above aspect; a plurality of adsorption towers for separating a specific adsorbed gas from a mixed gas by adsorbing and desorbing the adsorbed gas in the mixed gas; a mixed gas supply unit for supplying the mixed gas to the adsorption towers; and a desorption auxiliary unit for desorbing the adsorbed gas from the adsorption towers, wherein the desorption auxiliary unit comprises at least one of a purge gas supply unit for supplying a purge gas to the adsorption towers, a heating device for heating the adsorption towers, and a decompression device for decompressing the inside of the adsorption towers.

[0015] According to this configuration, in a gas separation apparatus including an adsorption tower control device, an adsorption tower, a mixed gas supply unit, and a desorption assistance unit, it is possible to suppress a decrease in the adsorbed gas recovery rate in the adsorption tower.

[0016] The present invention can be realized in various forms, for example, in the form of an adsorption tower control device that controls a plurality of adsorption towers, a control method for a plurality of adsorption towers, a gas separation method, a hydrocarbon production method, a control method for a gas separation system, a control method for a hydrocarbon production system, computer programs that cause a computer to execute these control methods, a server device for distributing the computer program, a non-transitory storage medium on which the computer program is stored, a carbon dioxide circulation system, a fuel production system that uses hydrocarbons as fuel, etc. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic configuration of a gas separation system according to a first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram of the process switching timing of an adsorption tower in a gas separation system. [Diagram 3] FIG. 1 is an explanatory diagram of step 1 in a gas separation system. [Figure 4] FIG. 2 is an explanatory diagram showing a carbon dioxide adsorption tower model. [Diagram 5] 13 is a flowchart showing an example of a procedure for a process switching process. [Figure 6] FIG. 4 is an explanatory diagram conceptually showing a change in purge gas flow rate over time. [Figure 7] FIG. 4 is an explanatory diagram conceptually showing a change in high-temperature heat medium flow rate over time. [Figure 8] FIG. 4 is an explanatory diagram conceptually showing the time change in ON / OFF of the vacuum pump operation. [Figure 9] FIG. 4 is an explanatory diagram conceptually showing the change over time in the carbon dioxide concentration in the inflow gas and the exhaust gas. [Figure 10] FIG. 2 is an explanatory diagram conceptually showing the carbon dioxide capture results when the flow rate of the inflow gas changes over time in a gas separation system. [Figure 11] FIG. 2 is an explanatory diagram conceptually showing the change over time of desorption conditions in a gas separation system. [Figure 12] FIG. 2 is an explanatory diagram conceptually showing the energy consumption and recovery rate of a gas separation system. [Figure 13] FIG. 4 is an explanatory diagram showing a schematic configuration of a gas separation system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] First Embodiment 1 is an explanatory diagram showing a schematic configuration of a gas separation system 1 of a first embodiment. The gas separation system 1 separates and captures carbon dioxide contained in exhaust gas discharged from a combustion furnace, an internal combustion engine, or the like. The gas separation system 1 includes a plurality of adsorption towers 11, 12, 13, and 14 (when the adsorption towers 11, 12, 13, and 14 are not differentiated from one another, they may be simply referred to as adsorption towers 10), a mixed gas supply flow path 20, an exhaust gas flow path 30, a purge gas supply flow path 70 that supplies hydrogen as a purge gas, a heat medium flow path 80, a product gas flow path 60, a vacuum pump 45, and an adsorption tower control device 50.

[0019] The adsorption towers 11, 12, 13, and 14 are formed in a cylindrical shape, and adsorbents 11a, 12a, 13a, and 14a are housed therein. The adsorbents 11a, 12a, 13a, and 14a are materials having carbon dioxide occlusion performance, such as zeolite, activated carbon, and silica gel. A mixed gas supply passage 20, an exhaust gas passage 30, a purge gas supply passage 70, a product gas passage 60, and a heat medium passage 80 are connected to each of the adsorption towers 11, 12, 13, and 14. A refrigerant passage (not shown) is also formed in each of the adsorption towers 11, 12, 13, and 14.

[0020] The adsorption towers 11, 12, 13, and 14 are provided with temperature sensors 11c, 12c, 13c, and 14c and pressure sensors 11d, 12d, 13d, and 14d, respectively. When the temperature sensors 11c, 12c, 13c, and 14c are not differentiated from one another, they are also referred to as temperature sensor 10c, and when the pressure sensors 11d, 12d, 13d, and 14d are not differentiated from one another, they are also referred to as pressure sensor 10d. The temperature sensor 10c measures the temperature of the adsorbent in the adsorption tower 10, and the pressure sensor 10d measures the pressure inside the adsorption tower 10.

[0021] The mixed gas supply flow passage 20 is connected to an external exhaust gas supply device (e.g., a combustion furnace or an internal combustion engine) that discharges exhaust gas as a mixed gas containing carbon dioxide, and the exhaust gas (mixed gas) discharged by the exhaust gas supply device flows through the mixed gas supply flow passage 20. The mixed gas flowing through the mixed gas supply flow passage 20 is supplied to the adsorption towers 11, 12, 13, and 14 via mixed gas branch flow passages 21, 22, 23, and 24, respectively. The mixed gas branch flow passages 21, 22, 23, and 24 are provided with mixed gas inlet valves 21a, 22a, 23a, and 24a, respectively. The mixed gas inlet valves 21a, 22a, 23a, and 24a control the supply of the mixed gas to the inside of the adsorption towers 11, 12, 13, and 14, respectively, in response to a command from the adsorption tower control device 50. In this embodiment, an exhaust gas is exemplified as the mixed gas, but the mixed gas does not have to be an exhaust gas, and various gases containing carbon dioxide can be used.

[0022] The mixed gas supply flow path 20 is provided with a gas analyzer 20a, a flow meter 20b, a temperature sensor 20c, and a pressure sensor 20d. The gas analyzer 20a measures each component contained in the mixed gas flowing through the mixed gas supply flow path 20 and its concentration (composition). The flow meter 20b measures the flow rate of the mixed gas flowing through the mixed gas supply flow path 20. The temperature sensor 20c measures the temperature of the mixed gas flowing through the mixed gas supply flow path 20. The pressure sensor 20d measures the pressure of the mixed gas flowing through the mixed gas supply flow path 20.

[0023] The exhaust gas flow path 30 has exhaust gas branch paths 31, 32, 33, and 34. The exhaust gas branch paths 31, 32, 33, and 34 are connected to the adsorption towers 11, 12, 13, and 14, respectively, and gas from which carbon dioxide has been separated in the adsorption towers 11, 12, 13, and 14 (hereinafter referred to as exhaust gas) is discharged to the outside of the gas separation system 1 through the exhaust gas flow path 30. In this embodiment, the exhaust gas is discarded, and is therefore also referred to as "discarded gas." The exhaust gas branch paths 31, 32, 33, and 34 are provided with exhaust gas outlet valves 31a, 32a, 33a, and 34a, respectively. The exhaust gas outlet valves 31a, 32a, 33a, and 34a control the flow of exhaust gas from the adsorption towers 11, 12, 13, and 14, respectively, in response to a command from the adsorption tower control device 50.

[0024] The purge gas supply passage 70 supplies purge gas to the inside of the adsorption towers 11, 12, 13, and 14. The purge gas supply passage 70 connected to an external purge gas supply unit (e.g., a hydrogen tank) is provided with a flow rate controller 70a that adjusts the flow rate of hydrogen flowing through the purge gas supply passage 70 in response to a command from the adsorption tower controller 50. The hydrogen flowing through the purge gas supply passage 70 is supplied to the adsorption towers 11, 12, 13, and 14 via purge gas branch passages 71, 72, 73, and 74. The purge gas branch passages 71, 72, 73, and 74 are provided with purge gas inlet valves 71a, 72a, 73a, and 74a, respectively. The purge gas inlet valves 71a, 72a, 73a, and 74a each control the flow of hydrogen into the adsorption towers 11, 12, 13, and 14 in response to a command from the adsorption tower controller 50. The purge gas supply passage 70 is also called a "purge gas supply section."

[0025] The heat medium passage 80 is connected to a heat medium tank (not shown), and the heat medium flows through the heat medium passage 80. In FIG. 1, due to space limitations, a part of the heat medium passage 80 is omitted and not illustrated in a circular shape, but in reality, the heat medium passage 80 is illustrated in a circular shape and the heat medium circulates. The heat medium flowing through the heat medium passage 80 is supplied to the adsorption towers 11, 12, 13, and 14 via the heat medium distribution passages 81, 82, 83, 84, and 34. As a result, heat is input to the adsorption towers 11, 12, 13, and 14 by the heat medium. The heat medium passage 80 passes through the hydrocarbon production device 40, and heats each adsorption tower 10 using heat generated in association with the production of hydrocarbons in the hydrocarbon production device 40. In another embodiment, a heater for heating the heat medium may be provided in the heat medium passage 80, and the adsorption tower control device 50 may control the temperature of the heat medium by controlling the heater. In this embodiment, oil is used as the heat medium, but in other embodiments, water, steam, gas, etc. may be used. The heat medium passage 80 is also called a "heating device."

[0026] The heat medium distribution passages 81, 82, 83, and 84 are provided with heat medium inlet valves 81a, 82a, 83a, and 84a. The heat medium inlet valves 81a, 82a, 83a, and 84a control the flow of the heat medium to the adsorption towers 11, 12, 13, and 14, respectively, in response to a command from the adsorption tower control device 50. The adsorption towers 11, 12, 13, and 14 in this embodiment are double-shell tanks (double pipes), and the heat medium flows into the gap between the outer shell and the inner shell. As a result, heat is input into the adsorption towers 11, 12, 13, and 14 by the heat medium. In other embodiments, for example, the heat medium distribution passages 81, 82, 83, and 84 may be wound around the outer periphery of the adsorption towers 11, 12, and 13, respectively. Even in this manner, heat can be input into the adsorption towers 11, 12, and 13 by the heat medium. In another embodiment, the adsorption tower 10 may be heated using a heater (for example, an electric heating wire, hot air, light irradiation, etc.) provided in the adsorption tower 10.

[0027] As shown in FIG. 1, the product gas flow path 60 is connected to each of the adsorption towers 11, 12, 13, and 14 via product gas branch flow paths 61, 62, 63, and 64. A product gas containing carbon dioxide desorbed from the adsorbents 11a, 12a, 13a, and 14a and hydrogen as a purge gas flows through the product gas flow path 60. The product gas may contain, for example, nitrogen, oxygen, and the like. The product gas branch flow paths 61, 62, 63, and 64 are provided with product gas outlet valves 61a, 62a, 63a, and 64a. The product gas outlet valves 61a, 62a, 63a, and 64a respectively control the flow of the mixed gas from the adsorption towers 11, 12, 13, and 14 in response to a command from the adsorption tower control device 50.

[0028] The vacuum pump 45 is provided in the product gas flow path 60 between the adsorption tower 10 and the hydrocarbon production device 40. The vacuum pump 45 is driven in response to a command from the adsorption tower control device 50 to reduce the pressure inside the adsorption tower 10. The vacuum pump 45 is also referred to as a "pressure reducing device." The purge gas supply flow path 70, the heat medium flow path 80, and the vacuum pump 45 in this embodiment are each or collectively referred to as a "desorption auxiliary section."

[0029] The adsorption tower control device 50 is a computer including a ROM, a RAM, and a CPU, and performs overall control of the gas separation system 1, such as switching between the adsorption towers 11, 12, and 13 in the gas separation process described later and controlling the opening and closing of valves. The adsorption tower control device 50 controls the adsorption process and the desorption process in the adsorption tower 10. Here, the "adsorption process" refers to a process of adsorbing the adsorbed gas (carbon dioxide) to the adsorbent of the adsorption tower 10, and the "desorption process" refers to a process of desorbing the adsorbed gas (carbon dioxide) adsorbed by the adsorbent of the adsorption tower 10. The desorption process is also called a "regeneration process" because it desorbs (removes) carbon dioxide from the adsorbent to make it reusable. In the following description, the adsorption tower 10 in which the adsorption process to which the mixed gas is supplied is performed is also called an "adsorption process tower," and the adsorption tower 10 in which the desorption process to which the adsorbed gas is desorbed is also called a "desorption process tower."

[0030] The adsorption tower control device 50 functionally includes a control unit 51, an information acquisition unit 52, a desorption condition determination unit 53, and a storage unit 54. The control unit 51 cooperates with the information acquisition unit 52 and the desorption condition determination unit 53 to execute a gas separation process described later. In the gas separation process, the control unit 51 controls the above-mentioned multiple valves, the flow rate controller 70a, and the vacuum pump 45 to repeatedly execute an adsorption process and a desorption process in the adsorption tower 10. The control unit 51 repeatedly executes an adsorption / desorption process in which the adsorption process is executed in the adsorption tower and the desorption tower is executed in the desorption tower while shifting the adsorption tower and the desorption tower in the multiple adsorption towers 11, 12, 13, and 14. When the cumulative amount of the adsorbed gas supplied to the adsorption tower reaches a predetermined cumulative amount threshold, the control unit 51 shifts the adsorption tower and the desorption tower. That is, in this embodiment, the time of the adsorption / desorption process is determined according to the flow rate of the adsorbed gas supplied to the adsorption tower. Therefore, when the mixed gas supplied to the adsorption tower 10 varies over time, the time for the adsorption / desorption step also varies.

[0031] The information acquiring unit 52 acquires mixed gas property information G, which is information about the mixed gas supplied to the adsorption tower 10, and the operating conditions S of the adsorption tower 10 as an adsorption process tower. The mixed gas property information G includes any one of the flow rate of the mixed gas supplied to the adsorption tower 10, the concentration of the adsorbed gas (carbon dioxide) in the mixed gas, the temperature of the mixed gas, and the pressure of the mixed gas. Specifically, the information acquiring unit 52 uses the flow rate of the mixed gas acquired from the flowmeter 20b as the flow rate of the mixed gas, the carbon dioxide concentration in the mixed gas acquired from the gas analyzer 20a as the carbon dioxide concentration in the mixed gas, the temperature acquired from the temperature sensor 20c as the temperature of the mixed gas, and the pressure acquired from the pressure sensor 20d as the pressure of the mixed gas.

[0032] The operating condition S includes either the temperature of the adsorption tower 10 serving as an adsorption process tower or the pressure inside the adsorption tower 10. Specifically, the information acquiring unit 52 uses the temperature of the adsorbent in the adsorption tower 10 acquired from the temperature sensor 11c as the temperature of the adsorption tower 10, and uses the pressure acquired from the pressure sensor 11d as the pressure inside the adsorption tower 10.

[0033] The desorption condition determination unit 53 determines the desorption conditions, including at least one of the supply flow rate of the purge gas to the adsorption tower 10 serving as the desorption step tower, the heating of the adsorption tower, and the pressure reduction inside the adsorption tower, from the mixed gas property information G and the operation conditions S acquired by the information acquisition unit 52. Details will be described later.

[0034] The storage unit 54 stores in advance a program for implementing the gas separation process described below and a threshold value (e.g., an integrated amount threshold value Mth) used in the gas separation process. The program may be provided by a program provider via a communication network. The program may also be stored in a portable storage medium that is commercially available and in circulation. In this case, the portable storage medium may be set in an external or built-in reading device, and the program may be read and executed by the adsorption tower control device 50. As the portable storage medium, various types of storage media such as CD-ROM, DVD-ROM, flexible disk, optical disk, magneto-optical disk, IC card, USB memory device, etc. may be used. The program stored in such a storage medium is read by the reading device.

[0035] The hydrocarbon production apparatus 40 produces methane using the product gas (mixed gas of carbon dioxide and hydrogen) delivered from the adsorption towers 11, 12, 13, and 14. The produced methane is supplied to an external device such as a combustion device. A surge tank for storing the product gas may be provided between the vacuum pump 45 and the hydrocarbon production apparatus 40.

[0036] FIG. 2 is an explanatory diagram of the process switching timing of the adsorption tower 10 in the gas separation system 1 of this embodiment. In the gas separation process of this embodiment, as shown in the figure, one cycle is composed of steps 1, 2, 3, and 4, and this cycle is repeated multiple times. In each step, the adsorption step, the preheating step, the desorption step, and the cooling step are each performed in one of the four adsorption towers 11, 12, 13, and 14. Specifically, in step 1, the adsorption step is performed in the adsorption tower 11, the preheating step is performed in the adsorption tower 12, the desorption step is performed in the adsorption tower 13, and the cooling step is performed in the adsorption tower 14. That is, in step 1, the adsorption tower 11 is the "adsorption step tower" and the adsorption tower 13 is the "desorption step tower."

[0037] In step 2, an adsorption step is performed in the adsorption tower 14, a preheating step is performed in the adsorption tower 11, a desorption step is performed in the adsorption tower 12, and a cooling step is performed in the adsorption tower 13. That is, in step 2, the adsorption tower 14 is the "adsorption step tower" and the adsorption tower 12 is the "desorption step tower".

[0038] In step 3, an adsorption step is performed in the adsorption tower 13, a preheating step is performed in the adsorption tower 14, a desorption step is performed in the adsorption tower 11, and a cooling step is performed in the adsorption tower 12. That is, in step 3, the adsorption tower 13 is the "adsorption step tower" and the adsorption tower 11 is the "desorption step tower".

[0039] In step 4, the adsorption step is performed in the adsorption tower 12, the preheating step is performed in the adsorption tower 13, the desorption step is performed in the adsorption tower 14, and the cooling step is performed in the adsorption tower 11. That is, the adsorption tower 12 is the "adsorption step tower", and the adsorption tower 14 is the "desorption step tower". In this manner, in the gas separation system 1 of this embodiment, carbon dioxide in the mixed gas is adsorbed in any one of the adsorption towers, and at the same time, the adsorbed carbon dioxide is desorbed in the other adsorption tower. This makes it possible to steadily supply the mixed gas (carbon dioxide-containing gas). Each of steps 1 to 4 in this embodiment is also referred to as an "adsorption / desorption step".

[0040] Focusing on one adsorption tower 10, the adsorption process, preheating process, desorption process, and cooling process are repeated in this order. The adsorption tower 11 will be described below as an example. In the adsorption process, exhaust gas as a mixed gas is supplied to the adsorption tower 11, and a refrigerant (low-temperature heat medium) is also supplied. Note that the refrigerant is not shown in FIG. 1. By cooling the adsorption tower 11, carbon dioxide in the mixed gas is adsorbed by the adsorbent 11a. When step 1 (adsorption / desorption process) is completed, the process proceeds to the preheating process. In this embodiment, the adsorption / desorption process is completed when the accumulated amount of the adsorbed gas in the adsorption tower 11 reaches a predetermined accumulated amount threshold. For example, when the adsorption tower 11 is an adsorption tower, when the accumulated amount of the adsorbed gas in the adsorption tower 11 reaches a predetermined accumulated amount threshold, the adsorption tower 11 proceeds to the preheating process (step 2). In addition, the adsorption tower transitions to the adsorption tower 14.

[0041] In the preheating step, a heat medium is supplied to the adsorption tower 11. When the heat medium is supplied to the adsorption tower 11 and the temperature of the adsorbent 11a is raised, the carbon dioxide adsorbed in the adsorbent 11a is easily desorbed from the adsorbent 11a. When step 2 (adsorption / desorption step) is completed, the adsorption tower 11 transitions to the desorption step. Step 2 (adsorption / desorption step) is completed when the accumulated amount of the adsorbed gas in the adsorption tower 14, which is the adsorption step tower, reaches a predetermined accumulated amount threshold value.

[0042] In the desorption step, the adsorption tower 11 is supplied with a purge gas through the purge gas supply passage 70. That is, in the desorption step, the purge gas is supplied from an external purge gas supply unit (for example, a hydrogen tank). The adsorption tower 11 is heated in the preheating step, and is therefore in a state in which carbon dioxide is easily desorbed from the adsorbent 11a. When the purge gas is supplied to the adsorption tower 11, the partial pressure of carbon dioxide inside the adsorption tower 11 decreases, and the carbon dioxide adsorbed in the adsorbent 11a is desorbed from the adsorbent 11a. In this embodiment, the desorption of carbon dioxide from the adsorbent 11a is promoted by further heating with a heat medium (high-temperature heat medium) and reducing the pressure inside the adsorption tower 11 with a vacuum pump 45. When the step 3 (adsorption / desorption step) is completed, the adsorption tower 11 transitions to a cooling step. The step 3 (adsorption / desorption step) is completed when the accumulated amount of the adsorbed gas in the adsorption tower 13, which is an adsorption step tower, reaches a predetermined accumulated amount threshold value.

[0043] In the cooling step, a refrigerant (low-temperature heat medium) is supplied to the adsorption tower 11. Note that the refrigerant is not shown in FIG. 1. By cooling the adsorption tower 11, carbon dioxide in the mixed gas is easily adsorbed by the adsorbent 11a. When step 4 (adsorption / desorption step) is completed, the adsorption tower 11 transitions to the adsorption step. Step 4 (adsorption / desorption step) is completed when the accumulated amount of the adsorbed gas in the adsorption tower 12, which is the adsorption step tower, reaches a predetermined accumulated amount threshold.

[0044] In this manner, in the gas separation system 1 of this embodiment, carbon dioxide is separated from the mixed gas by a temperature pressure swing method in which the adsorption tower 10 is heated and cooled, and the inside of the adsorption tower 10 is repeatedly subjected to normal and reduced pressure to separate the gas.

[0045] Fig. 3 is an explanatory diagram of step 1 in the gas separation system 1. In the gas separation system 1, carbon dioxide is separated from the mixed gas by sequentially supplying the mixed gas to each of four adsorption towers 11, 12, 13, and 14. In Fig. 3, the flows of the mixed gas, exhaust gas, heat transfer medium, and purge gas (hydrogen) are indicated by thick solid lines.

[0046] As shown in Fig. 3, in step 1 (Fig. 2), an adsorption step is performed in the adsorption tower 11, and a mixed gas is supplied to the adsorption tower 11. Specifically, the adsorption tower control device 50 opens the mixed gas inlet valve 21a and closes the mixed gas inlet valves 22a, 23a, and 24a, and the mixed gas is supplied to the adsorption tower 11 via the mixed gas supply passage 20 and the mixed gas branch passage 21. At this time, the adsorption tower control device 50 opens the exhaust gas outlet valve 31a and closes the exhaust gas outlet valves 32a, 23a, and 24a. In addition, a refrigerant (low-temperature heat medium) is supplied to the adsorption tower 11 (the refrigerant is illustrated by the arrows with dotted hatching in Fig. 3).

[0047] In the adsorption tower 11, the carbon dioxide contained in the mixed gas is adsorbed by the adsorbent 11a, and most of the gases, such as nitrogen and moisture, that are not adsorbed by the adsorbent 11a are released as exhaust gas (also called off-gas) to the outside of the gas separation system 1, for example, into the atmosphere, via the exhaust gas distribution path 31 and the exhaust gas path 30.

[0048] A preheating step is performed in the adsorption tower 12, and a heat medium (high-temperature heat medium) is supplied to the adsorption tower 12. Specifically, the adsorption tower control device 50 drives a heat medium circulation pump (not shown), opens the heat medium inlet valves 82a and 83a, and closes the heat medium inlet valves 81a and 84a. Since the heat medium is supplied to the adsorption towers 12 and 13 via the hydrocarbon production device 40, the reaction heat of the methanation reaction in the hydrocarbon production device 40 is used for heating the preheating step and the desorption step (described later). When the heat medium is supplied to the adsorption tower 12, the adsorbent 12a is heated, and carbon dioxide adsorbed to the adsorbent 12a is easily desorbed from the adsorbent 12a.

[0049] In the adsorption tower 13, a desorption process is performed, and the adsorption tower 13 is supplied with a purge gas and a heat medium (high-temperature heat medium). The adsorption tower 13 is depressurized by the vacuum pump 45. Specifically, the adsorption tower controller 50 opens the purge gas inlet valve 73a and closes the purge gas inlet valves 71a, 72a, and 74a, and the purge gas is supplied to the adsorption tower 13 through the purge gas supply passage 70 and the purge gas branch passage 73. As described above, since the heat medium inlet valve 83a is opened, the heat medium is also supplied to the adsorption tower 13. The adsorption tower controller 50 drives the vacuum pump 45 to depressurize the adsorption tower 13. When the heat medium is supplied to the adsorption tower 13, the purge gas is supplied, and the adsorption tower 13 is depressurized, the carbon dioxide adsorbed to the adsorbent 13a is desorbed from the adsorbent 13a. The carbon dioxide desorbed from the adsorbent 13a is mixed with the purge gas (hydrogen) inside the adsorption tower 13. In step 1, the product gas outlet valve 63a is opened and the product gas outlet valves 61a, 62a, 64a are closed, and therefore the product gas discharged from the adsorption tower 13 flows into the hydrocarbon generator 40 through the product gas branch path 63 and the product gas path 60.

[0050] A cooling step is carried out in the adsorption tower 14, and a refrigerant (low-temperature heat medium) is supplied to the adsorption tower 14. By cooling the adsorption tower 14, carbon dioxide in the mixed gas is easily adsorbed by the adsorbent 14a.

[0051] Here, the effects of the mixed gas property information G and the operating conditions S on the adsorption and desorption of carbon dioxide in the adsorption tower 10 will be described. FIG. 4 is an explanatory diagram showing a carbon dioxide adsorption tower model. In FIG. 4, the adsorption tower is shown on the left, and the desorption tower is shown on the right. A typical adsorption tower will be explained. In the adsorption tower, particulate adsorbent is sealed in a cylindrical adsorption tower (a tube with a diameter D and a length L). A gas recovery device is composed of one or more adsorption towers. As shown in the figure, the inside of the tube is filled with adsorbent with a particle diameter dp, and the temperature of the side of the tube is controlled from the outside with oil. In the adsorption process, the adsorbent adsorbs CO2 contained in the inflow gas, so that the outflow gas is only N2. In the desorption process, the CO2 adsorbed on the adsorbent is desorbed by purging with H2 gas, and a mixed gas of CO2 and H2 is obtained. By repeating this adsorption and desorption, it is possible to capture CO2.

[0052] In the adsorption tower model in Figure 4, the amount of CO2 adsorbed varies with the gas composition (CO2 concentration), the temperature of the adsorbent, the gas temperature, and the gas pressure, while the adsorption time and desorption time vary with the flow rates of the inlet gas (CO2 + N2) and the purge gas (H2). The phenomenon is explained using physical equations. The temperature of the solid (adsorbent), Ts [K], is expressed by the following heat conduction equation (1).

[0053]

number

[0054] The left side of equation (1) is the time change of the solid temperature, the first term on the right side is the heat conduction, the second term is the heat exchange between the solid and the gas, and the third term is the temperature rise due to the heat of adsorption. Since the tube wall is heated by the oil, the boundary condition is T s Let (t,r=D / 2,z)=T0. Gas temperature T g [K] is expressed by the advection-diffusion equation below, equation (2).

[0055]

number

[0056] In equation (2), the left side is the time change in gas temperature, the first term on the right side is the heat transfer by advection, and the second term is the heat exchange between gas and solid. Note that because equation (1) takes into account the heat conduction phenomenon in the solid-gas composite structure, the diffusion term is ignored in equation (2). Also, the gas velocity u is a constant for only the z component. The gas flow rate is obtained by dividing the gas flow rate by the cross-sectional area of ​​the adsorption tower. CO2 concentration distribution in gas c CO2 is expressed by the advection-diffusion equation shown below in Equation (3).

[0057]

number

[0058] In the adsorption process, the CO2 concentration at the adsorption tower inlet z=0 is c CO2 becomes the CO2 concentration of the inflow gas, and CO2 flows in. In the desorption process, the CO2 concentration at the adsorption tower inlet z=0 is c CO2 becomes zero, and CO2 is desorbed as zero concentration gas flows in.

[0059] The phenomenon of CO2 adsorption into zeolite is expressed using the Linear Driving Force (LDF) model in the following equation (4). s,CO2 and the CO2 concentration outside the adsorbent c CO2 The difference between the two is the driving force, and CO2 flows into the adsorbent, increasing the amount of CO2 adsorbed, q CO2 The time constant of the adsorption rate is calculated by the following formula (5), and the CO2 concentration inside the adsorbent particle c s,CO2 is obtained from the Langmuir equation shown in the following formula (6).

[0060]

number

[0061]

number

[0062]

number

[0063] The optimal switching times for each process can be obtained by coupling the above equations (1) to (7) and solving them by numerical analysis. The important parameters in this case are G: gas properties (composition, flow rate, temperature, pressure) and S: operating conditions of the adsorption process tower (temperature, pressure). The effects of these parameters can be considered in the numerical analysis, or the optimal operating conditions for each parameter can be determined using an actual device.

[0064] G: Gas properties (composition, flow rate, temperature, pressure) and S: Adsorption process tower operating conditions (temperature, pressure) affect the above model as follows. Although this is explained as a simple trend, the actual phenomenon is complex because each physical equation is actually coupled at each point.

[0065] G: When the gas composition (concentration) increases, the amount of CO2 that the adsorbent can adsorb increases, as shown in the above formula (6). However, as shown in formulas (6) and (7), the heat of adsorption of CO2 increases the temperature of the adsorbent, which has the effect of reducing the maximum adsorption amount, and therefore the switching time between each process becomes shorter.

[0066] G: When the gas flow rate increases, the speed at which CO2 flows downstream increases according to the above formula (3), making it easier for CO2 to flow out from the outlet of the adsorption tower. In addition, the amount of CO2 flowing in per unit time increases, so the heat generated by the adsorbent increases, and the amount of CO2 adsorbed decreases as the temperature of the adsorbent rises. These effects shorten the switching time for each process.

[0067] G: When the temperature of the inlet gas increases, the temperature of the adsorbent increases, so the amount of CO2 adsorbed decreases. Therefore, the switching time of each process becomes shorter.

[0068] G: When the pressure of the inflow gas increases, the partial pressure of CO2 increases, so the same effect as when the gas composition (concentration) increases can be obtained. Therefore, the switching time for each process is shortened.

[0069] Thus, in an apparatus that repeats adsorption and desorption using an adsorbent, G: gas properties (composition, flow rate, temperature, pressure) play an important role. And, since S: adsorption step tower operating conditions (temperature, pressure) also change according to changes in G: gas properties (composition, flow rate, temperature, pressure), S: adsorption step tower operating conditions (temperature, pressure) also play an important role in the adsorption and desorption of carbon dioxide. Therefore, in the gas separation system 1 of this embodiment, the mixed gas property information G is used to determine the timing of step switching, and the mixed gas property information G and the adsorption step tower operating conditions S are used to determine the desorption conditions in the desorption step tower.

[0070] 5 is a flowchart showing an example of the procedure of the process switching process. The process switching process is started when the adsorption / desorption process is started in the adsorption tower control device 50, and is repeatedly executed while the adsorption tower control device 50 is operating. The process switching process is executed by the control unit 51, the information acquisition unit 52, and the desorption condition determination unit 53 in cooperation with each other.

[0071] First, in step S10, the control unit 51 sets time t=0. After time Δt has elapsed (step S12), the information acquisition unit 52 acquires mixed gas property information G (step S14). In FIG. 5, the mixed gas property information G at time t is written as G(t). In step S18, the information acquisition unit 52 acquires the operation conditions S of the adsorption process tower. In FIG. 5, the operation conditions at time t are written as S(t). In step S20, the control unit 51 calculates the accumulated amount M of the adsorbed gas (carbon dioxide) supplied to the adsorption process tower from the start of the adsorption / desorption process (e.g., process 1 in FIG. 2) to time t. At this time, the control unit 51 calculates the accumulated amount M of the adsorbed gas using the mixed gas property information G(t) acquired in step S14. If the accumulated amount M calculated in step S20 is greater than the accumulated amount threshold Mth (YES in step S22), the control unit 51 sends an equipment control command to switch to the next adsorption / desorption process (e.g., process 2) (step S24) and resets the time t to 0 (step S10).

[0072] On the other hand, if the accumulated amount M calculated in step S20 is equal to or less than the accumulated amount threshold value Mth (NO in step S22), the desorption condition determination unit 53 determines the desorption condition from the mixed gas property information G(t) and the operating condition S(t) acquired by the information acquisition unit 52 (step S26), and sets time t = t + Δt (step S12). In Fig. 5, the desorption condition at time t is indicated as D(G(t),S(t)).

[0073] In the adsorption tower control device 50, the desorption conditions are determined according to the time-dependent changes in the mixed gas properties and the operating conditions of the adsorption step tower, as shown in Fig. 5. The control unit 51 supplies purge gas to the desorption step tower, heats the desorption step tower, and reduces the pressure inside the desorption step tower under the determined desorption conditions. Therefore, as will be described in detail later, the desorption conditions of the desorption step tower can be changed according to the time-dependent changes in the supply of the mixed gas to the adsorption step tower, and the recovery rate of the adsorbed gas (carbon dioxide) can be improved.

[0074] In the gas separation system 1 of this embodiment, the flow rate and the like of the mixed gas (hereinafter also referred to as the "inlet gas") supplied to the adsorption tower 10 are successively acquired, and the desorption conditions are successively changed in response to fluctuations in the flow rate and the like of the mixed gas. Prior to explaining the change in the desorption conditions, the desorption conditions when the flow rate of the mixed gas supplied to the adsorption tower 10 is constant will be explained. Here, the desorption conditions are the purge gas flow rate Qp, the flow rate Qoil of the high-temperature heat medium (heat medium), and the operation ON / OFF of the vacuum pump 45.

[0075] FIG. 6 is an explanatory diagram conceptually showing the change in purge gas flow rate over time. FIG. 7 is an explanatory diagram conceptually showing the change in high-temperature heat transfer medium flow rate over time. FIG. 8 is an explanatory diagram conceptually showing the change in vacuum pump 45 ON / OFF over time. (A) of FIG. 6 to FIG. 8 shows an example where the inflow gas flow rate is Qin, and (B) of FIG. 6 to FIG. 8 shows an example where the inflow gas flow rate is 2Qin. That is, the inflow gas flow rate in the example shown in (B) is twice that in the example shown in (A).

[0076] As shown in Fig. 6, when the flow rate of the inflow gas is constant, the flow rate of the purge gas is also kept constant. The flow rate of the purge gas in the example shown in Fig. 6(B) is twice that in the example shown in Fig. 6(A). Here, in this example, the process is switched when the inflow cumulative value of the adsorbed gas (carbon dioxide) exceeds the cumulative threshold value M, so the time for one process differs depending on the flow rate of the inflow gas. In detail, the process time in the example where the flow rate of the inflow gas is 2Qp (Fig. 6(B)) is 0.5 times that of the example where the flow rate of the inflow gas is Qp (Fig. 6(A)).

[0077] As shown in FIG. 7, when the flow rate of the inflow gas is constant, the flow rate of the high-temperature heat medium is also kept constant. The flow rate of the high-temperature heat medium in the example shown in FIG. 7(B) is twice that in the example shown in FIG. 7(A). As shown in FIG. 8(A), when the flow rate of the inflow gas is Qin, the vacuum pump 45 is not operated (OFF) from the start of the process until half the process time is reached, and the vacuum pump 45 is operated after the half time. As shown in FIG. 8(B), when the flow rate of the inflow gas is 2Qin, the vacuum pump 45 is always operated (ON state). By setting the desorption conditions in this way, the recovery rate can be improved. Here, the recovery rate is the amount of adsorbed material desorbed / amount introduced.

[0078] FIG. 9 is an explanatory diagram conceptually showing the change over time in the carbon dioxide concentration in the inflow gas and the exhaust gas. FIG. 9 shows the results of a simulation using the finite element method. As with FIGS. 6 to 8, (A) shows an example where the inflow gas flow rate is Qin, and (B) shows an example where the inflow gas flow rate is 2Qin. In the example of FIG. 9(A), the recovery rate is 95%, and in the example of FIG. 9(B), the recovery rate is 99%. In this way, if the flow rate of the inflow gas is constant, a high recovery rate of 95% or more can be obtained by appropriately setting the desorption conditions.

[0079] Consider the case where the flow rate of the inflow gas is not constant but fluctuates between Qin and 2Qin. When the system is operated according to the flow rate Qin, the recovery rate decreases because the energy added in the desorption process is insufficient for the flow rate 2Qin. On the other hand, when the system is operated according to the flow rate 2Qin, the vacuum pump 45 is operated excessively for the flow rate Qin, so the energy required for desorption becomes larger than when the system is operated according to the flow rate Qin.

[0080] Therefore, in the gas separation system 1 of the present embodiment, the above-mentioned problems are overcome by operating the system as follows. (1) When the flow rate of the inflow gas is Qin, the purge gas is Qp, the high-temperature heat transfer medium (heat medium) flow rate is Qoil, and the operation of the vacuum pump 45 is turned OFF if the accumulated inflow rate of carbon dioxide is less than half the specified value, and turned ON if it is more than half the specified value. (2) When the flow rate of the inflow gas is 2Qin, the purge gas is set to 2Qp, the high-temperature heat transfer medium flow rate is set to 2Qoil, and the vacuum pump 45 is always ON. (3) When the inflow gas is 0, the purge gas is 0, the high-temperature heat transfer medium flow rate is 0, and the vacuum pump 45 is turned off. The desorption conditions (1) to (3) are changed sequentially even during the process in accordance with changes in the properties of the inflow gas. This automatically balances the time when the integrated amount M of inflowing carbon dioxide reaches the integrated amount threshold Mth and the process is switched, with the time when desorption of carbon dioxide is completed in the desorption process, achieving a high recovery rate and energy savings even when the properties of the inflow gas change.

[0081] FIG. 10 is an explanatory diagram conceptually showing the carbon dioxide capture result when the flow rate of the inflow gas changes with time in the gas separation system 1 of this embodiment. FIG. 10(A) shows the time change of the flow rate of the inflow gas, and FIG. 10(B) shows the carbon dioxide concentration in the exhaust gas at the time corresponding to FIG. 10(A). As shown in FIG. 10(A), the flow rate of the inflow gas fluctuates between Qin and 2Qin. The average value of the flow fluctuating values ​​in FIG. 10(A) is 1. The adsorption tower control device 50 of the gas separation system 1 of this embodiment controls the desorption conditions of the desorption process by D[G(t),S(t)], using the property G(t) of the introduced gas that changes with time t and the operating condition S(t) as variables. Specifically, the purge gas flow rate is set to Qp·Q(t) / Qin and the high-temperature heat transfer medium flow rate is set to Qoil·Q(t) / Qin with respect to the flow rate Q(t) of the inflow gas. Then, the amount of carbon dioxide flowing in from the start of the process is integrated to find an integrated value M, and the process is switched when M exceeds the process switching integrated amount threshold Mth. If the value of M / Mth is equal to or greater than [Qin-Q(t)] / 2Q, the pump is turned ON, and if it is less than this, the pump is turned OFF. Figure 10(B) shows the results of a simulation using the finite element method in which the desorption conditions of the desorption process are made variable by changes in the properties G(t) of the introduced gas (here, the flow rate Q) as described above, and the system is operated by successively changing the desorption conditions.

[0082] FIG. 11 is an explanatory diagram conceptually showing the time change of the desorption condition in the gas separation system 1 of this embodiment. FIG. 11(A) shows the time change of the flow rate of the mixed gas flowing into the adsorption tower 10 in which the adsorption process is being performed, and FIG. 11(B) shows the time change of the flow rate of the purge gas supplied to the adsorption tower 10 in which the desorption process is being performed at the same time. As shown in the figure, the purge gas flow rate is changed in accordance with the inflow gas flow rate at approximately the same time. In the gas separation system 1 of this embodiment, when the integrated amount of inflow carbon dioxide reaches the integrated amount threshold, the adsorption process is terminated and the next process is started. Therefore, when focusing on one adsorption tower 10, the process time may differ for each process. In such a case, the adsorption tower control device 50 sequentially changes the desorption condition in the adsorption tower 10 in which the desorption process is being performed in conjunction with the flow rate of the inflow gas in the adsorption tower 10 in which the adsorption process is being performed at the same time, so that the decrease in the amount of carbon dioxide desorbed during the desorption process can be suppressed.

[0083] In the gas separation system 1 of this embodiment, the amount of carbon dioxide adsorbed by the four adsorption towers 10 in the adsorption process is approximately constant. In contrast, the time for the desorption process varies because it is the same as the time for the adsorption process performed simultaneously. In contrast, in the gas separation system 1 of this embodiment, the desorption conditions in the adsorption towers 10 in which the desorption process is performed are changed according to the flow rate of the mixed gas supplied to the adsorption towers 10 in which the adsorption process is performed simultaneously, so that carbon dioxide can be appropriately desorbed within the time for the desorption process. As a result, the carbon dioxide recovery rate can be improved.

[0084] In determining the desorption conditions in the adsorption tower 10 in which the desorption step is performed, the operating conditions S of the adsorption tower 10 as the adsorption step tower are used as follows. Among the operating conditions S (temperature, pressure) of the adsorption process, for example, when the temperature is higher than a specified value, the adsorption capacity of the adsorbent generally decreases, although this depends on the characteristics of the adsorbent used, and the switching time of the adsorption process becomes shorter. Therefore, in order to complete the desorption process within the switching time, the desorption conditions are changed, such as by increasing the amount of purge gas, to follow the shortened switching time. And when the pressure is higher than a specified value, the carbon dioxide partial pressure increases, and although this also depends on the characteristics of the adsorbent, the adsorption capacity decreases due to the heat of adsorption caused by the increased amount of adsorption, and the switching time of the adsorption process becomes shorter. In this case, as with the temperature, the desorption conditions are changed to follow the shortened switching time.

[0085] FIG. 12 is an explanatory diagram conceptually showing the energy consumption and recovery rate of the gas separation system 1 of this embodiment. FIG. 12 shows a case where the system is operated under the desorption condition of Qin (Qin control), a case where the system is operated under the desorption condition of 2Qin, which is twice the flow rate (2Qin control), and a case where the desorption condition is changed sequentially according to the flow rate fluctuation (this embodiment) for the same inflow gas flow rate fluctuation (FIG. 10(A)). The energy consumption is shown with Qin control as the reference (1). With Qin control, a high recovery rate can be obtained when the flow rate is Qin, but when the flow rate is Qin or more, carbon dioxide flows out, so the recovery rate decreases. On the other hand, with 2Qin control, a high recovery rate can be obtained, but energy is added to desorption even when the flow rate is Qin, so the energy consumption is large. Compared to these, in this embodiment, the energy consumption can be reduced while maintaining a high recovery rate equivalent to that of 2Qin control.

[0086] As described above, according to the present embodiment 1, by sequentially changing the desorption conditions in response to fluctuations in the gas flowing into the system, it is possible to achieve energy savings while maintaining a high carbon dioxide recovery rate.

[0087] <Second embodiment> FIG. 13 is an explanatory diagram showing a schematic configuration of a gas separation system 1A of the second embodiment. In addition to the configuration of the gas separation system 1 of the first embodiment, the gas separation system 1A of this embodiment further includes exhaust gas property measurement units 31b, 32b, 33b, and 34b in the exhaust gas branch passages 31, 32, 33, and 34, respectively. When the exhaust gas property measurement units 31b, 32b, 33b, and 34b are not distinguished from each other, they are also simply called exhaust gas property measurement unit 30b. In addition, an adsorption tower control device 50A is provided instead of the adsorption tower control device 50 in the gas separation system 1. In the embodiments described below, the same components as those in the gas separation system 1 are denoted by the same reference numerals, and the preceding description is referred to.

[0088] The exhaust gas properties measuring unit 30b includes a gas analyzer, a flow meter, a temperature sensor, and a pressure sensor, and measures the properties of the exhaust gas flowing through each exhaust gas branch passage.

[0089] The adsorption tower control device 50A includes an information acquisition unit 52A instead of the information acquisition unit 52, and a control unit 51A instead of the control unit 51. The information acquisition unit 52A acquires mixed gas property information G from the gas analyzer 20a, the flow meter 20b, the temperature sensor 20c, and the pressure sensor 20d, acquires operating conditions S of the adsorption tower 10 in the adsorption process from the temperature sensor 10c and the pressure sensor 10d, and acquires exhaust gas property information OG from the exhaust gas property measurement unit 30b.

[0090] The control unit 51A calculates the amount of carbon dioxide adsorbed in the adsorption tower 10 from the supplied and discharged adsorbed gas (carbon dioxide), and switches the process when the amount of carbon dioxide adsorbed in the adsorption tower 10 reaches a set value.

[0091] According to the gas separation system 1A of the present embodiment, the adsorption tower control device 50A determines the end of the adsorption process based on the amount of carbon dioxide supplied and the amount of carbon dioxide discharged, so that the process time of the adsorption process is more appropriately controlled. As a result, the recovery rate of carbon dioxide can be further improved.

[0092] <Modifications of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit and scope of the invention. For example, the following modifications are also possible.

[0093] In the above embodiment, a gas other than hydrogen may be used as the purge gas. For example, rare gases such as helium and neon, water vapor, methane, and mixed gases containing at least one of them may be used. When a gas other than hydrogen is used as the purge gas, a hydrogen supply unit that supplies hydrogen to the hydrocarbon production apparatus 40 may be provided. However, using hydrogen as the purge gas is preferable because it allows the hydrocarbon production apparatus 40 to produce high-purity hydrocarbons.

[0094] The number of adsorption towers 10 is not limited to that in the above embodiment, and may be two or more, three or less, or five or more.

[0095] In the above embodiment, an example was shown in which the product gas flow passage 60 was connected to the hydrocarbon production apparatus 40, but the product gas flow passage 60 may also be connected to a product gas storage tank.

[0096] In the above embodiment, an example has been shown in which carbon dioxide is desorbed by flowing a purge gas, increasing the temperature of the adsorbent, and reducing the pressure inside the adsorption tower 10, that is, by performing a so-called temperature and pressure swing, but carbon dioxide may be desorbed only by flowing a purge gas. Alternatively, only the pressure reduction using a vacuum pump may be performed, or only the temperature swing may be performed. Alternatively, the supply of a purge gas, the temperature swing, and the pressure swing may be appropriately combined.

[0097] In the above embodiment, the change in flow rate is used as the fluctuation (time change) of the mixed gas supplied to the adsorption tower, but any one of the temperature, pressure, and adsorbed gas (carbon dioxide) concentration in the mixed gas may be used. Also, one or more of them may be used in combination.

[0098] In the above embodiment, the information acquisition unit may acquire the mixed gas property information and the operating conditions sequentially (at regular intervals), and the desorption condition determination unit may determine the desorption conditions using average mixed gas property information and average operating conditions obtained by time-averaging the sequentially acquired mixed gas property information and operating conditions. When the fluctuation of the supplied mixed gas changes suddenly due to pulsation or the like, the system can be operated stably by smoothing the fluctuation information by taking a time average.

[0099] In the above embodiment, an example was shown in which the timing for switching between the adsorption / desorption steps (steps 1 to 4) was determined using the integrated amount of adsorbed gas supplied from the start of the steps, but the integrated amount of the supplied mixed gas may be used as the integrated amount of the supplied adsorbed gas. Also, the integrated amount of the adsorbed gas may be calculated using mixed gas property information of the supplied mixed gas and exhaust gas property information. In this way, the switching timing can be made more appropriate, and the recovery rate of the adsorbed gas can be further improved.

[0100] The timing for switching the process may be when the concentration of the adsorbed gas contained in the exhaust gas (waste gas) of the system exceeds a certain value.

[0101] In the above embodiment, carbon dioxide (CO2) is exemplified as the adsorbed gas. However, the adsorbed gas may be, for example, water (HO), nitrogen oxides (NO X ), sulfur oxides (SO X ) or other gases.

[0102] The adsorption tower control device may control the desorption conditions when the mixed gas property information G fluctuates over time t by using control parameters for when the mixed gas property information G does not fluctuate over time t. The desorption condition D0[G0(const),S0(const)] and the switching condition M0(const) for when there is no fluctuation in the mixed gas (G0(const) and S0(const)) are first calculated, and the above parameters are sequentially changed according to the fluctuation of the inflow gas, so that the fluctuation can be tracked.

[0103] The present invention has been described above based on the embodiments and modifications, but the above-mentioned embodiments are intended to facilitate understanding of the present invention and do not limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the claims, and the present invention includes equivalents thereof. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0104] The present invention can also be realized in the following forms. [Application example 1] 1. An adsorption tower control device for recovering a specific adsorbed gas from a mixed gas containing the specific adsorbed gas by using a plurality of adsorption towers, The plurality of adsorption towers include at least an adsorption step tower in which an adsorption step is performed to which the mixed gas is supplied, and a desorption step tower in which a desorption step is performed to desorb the adsorbed gas, The adsorption tower control device includes: a control unit that repeatedly executes an adsorption / desorption process in which the adsorption process is executed in the adsorption process tower and the desorption process is executed in the desorption process tower while shifting the adsorption towers; an information acquiring unit that acquires mixed gas property information including at least one of a flow rate of the mixed gas supplied to the adsorption process tower, a concentration of the adsorbed gas in the mixed gas, a temperature of the mixed gas, and a pressure of the mixed gas, and an operating condition including at least one of a temperature of the adsorption process tower and a pressure inside the adsorption tower; a desorption condition determination unit that determines desorption conditions, including at least one of a supply flow rate of a purge gas to the desorption step tower, heating of the desorption step tower, and depressurization inside the desorption step tower, from the mixed gas property information acquired by the information acquisition unit in the adsorption step that is performed simultaneously with the desorption step and the operation conditions; Equipped with The control unit is executing the desorption step under the desorption conditions determined by the desorption condition determination unit; When an integrated amount of the adsorbed gas in the adsorption step tower reaches a predetermined integrated amount threshold, the adsorption step tower and the desorption step tower are shifted. Adsorption tower control device. [Application example 2] The adsorption tower control device according to Application Example 1, the information acquisition unit further acquires exhaust gas property information including at least one of a flow rate of the exhaust gas discharged from the adsorption process tower and a concentration of the adsorbed gas in the exhaust gas; The control unit is calculating an integrated amount of the adsorbed gas using the mixed gas property information and the exhaust gas property information acquired by the information acquisition unit; Adsorption tower control device. [Application example 3] The adsorption tower control device according to Application Example 1 or Application Example 2, The information acquisition unit sequentially acquires the mixed gas property information and the operating conditions, The desorption condition determination unit sequentially determines the desorption conditions by using the sequentially acquired mixed gas property information and operation conditions. Adsorption tower control device. [Application example 4] The adsorption tower control device according to any one of Application Examples 1 to 3, The information acquisition unit sequentially acquires the mixed gas property information and the operating conditions, the desorption condition determination unit determines the desorption conditions using average mixed gas property information and average operating conditions obtained by time-averaging the sequentially acquired mixed gas property information and operating conditions. Adsorption tower control device. [Application example 5] 1. An adsorption tower control device for recovering a specific adsorbed gas from a mixed gas containing the specific adsorbed gas by using a plurality of adsorption towers, The plurality of adsorption towers include at least an adsorption step tower in which an adsorption step is performed to which the mixed gas is supplied, and a desorption step tower in which a desorption step is performed to desorb the adsorbed gas, The adsorption tower control device includes: a control unit that repeatedly executes an adsorption / desorption process in which the adsorption process is executed in the adsorption process tower and the desorption process is executed in the desorption process tower while shifting the adsorption towers; an information acquiring unit that acquires mixed gas property information including at least one of a flow rate of the mixed gas supplied to the adsorption process tower, a concentration of the adsorbed gas in the mixed gas, a temperature of the mixed gas, and a pressure of the mixed gas, and an operating condition including at least one of a temperature of the adsorption process tower and a pressure inside the adsorption tower; a desorption condition determination unit that determines desorption conditions, including at least one of a supply flow rate of a purge gas to the desorption step tower, heating of the desorption step tower, and depressurization inside the desorption step tower, from the mixed gas property information acquired by the information acquisition unit in the adsorption step that is performed simultaneously with the desorption step and the operation conditions; Equipped with The control unit is executing the desorption step under the desorption conditions determined by the desorption condition determination unit; When an integrated amount of the adsorbed gas in the adsorption step tower reaches a predetermined integrated amount threshold, a recovery rate of the adsorbed gas in the desorption step tower is calculated, and when the recovery rate is equal to or greater than the predetermined recovery rate threshold, the adsorption step tower and the desorption step tower are shifted, and when the recovery rate is less than the recovery rate threshold, the adsorption and desorption steps are continued until the recovery rate becomes equal to or greater than the recovery rate. Adsorption tower control device. [Application Example 6] 1. A gas separation apparatus comprising: An adsorption tower control device according to any one of claims 1 to 5; a plurality of adsorption towers for separating a specific adsorbate gas from a mixed gas by adsorbing and desorbing the specific adsorbate gas in the mixed gas; a mixed gas supply unit for supplying the mixed gas to the adsorption tower; a desorption assistant section for desorbing the adsorbed gas from the adsorption tower; Equipped with The detachment assistance portion is The adsorption tower is provided with at least one of a purge gas supply unit that supplies a purge gas to the adsorption tower, a heating device that heats the adsorption tower, and a decompression device that decompresses the inside of the adsorption tower. Gas separation equipment. [Application Example 7] 1. A method for controlling a plurality of adsorption towers by an information processing device, in which a specific adsorbed gas is recovered from a mixed gas containing the adsorbed gas by using the plurality of adsorption towers, the method comprising: The plurality of adsorption towers include at least an adsorption step tower in which an adsorption step is performed to which the mixed gas is supplied, and a desorption step tower in which a desorption step is performed to desorb the adsorbed gas, The method for controlling the plurality of adsorption towers includes the steps of: a control process for repeatedly executing an adsorption / desorption process in which the adsorption process is executed in the adsorption process tower and the desorption process is executed in the desorption process tower while shifting the adsorption / desorption process in the plurality of adsorption towers; an information acquiring process for acquiring mixed gas property information including at least one of a flow rate of the mixed gas supplied to the adsorption process tower, a concentration of the adsorbed gas in the mixed gas, a temperature of the mixed gas, and a pressure of the mixed gas, and an operating condition including at least one of a temperature of the adsorption process tower and a pressure inside the adsorption tower; a desorption condition determination step of determining desorption conditions, including at least one of a supply flow rate of a purge gas to the desorption step tower, heating of the desorption step tower, and depressurization inside the desorption step tower, from the mixed gas property information acquired by the information acquisition unit in the adsorption step which is performed simultaneously with the desorption step and the operation conditions; Equipped with The control step includes: executing the desorption step under the desorption conditions determined by the desorption condition determination unit; When an integrated amount of the adsorbed gas in the adsorption step tower reaches a predetermined integrated amount threshold, the adsorption step tower and the desorption step tower are shifted. A method for controlling multiple adsorption towers. [Application Example 8] 1. A computer program for recovering a specific adsorbed gas from a mixed gas containing the specific adsorbed gas by using a plurality of adsorption towers, comprising: The plurality of adsorption towers include at least an adsorption step tower in which an adsorption step is performed to which the mixed gas is supplied, and a desorption step tower in which a desorption step is performed to desorb the adsorbed gas, The computer program includes: a control function for repeatedly executing an adsorption / desorption process in which the adsorption process is executed in the adsorption process tower and the desorption process is executed in the desorption process tower while shifting the adsorption / desorption process in the multiple adsorption towers; an information acquisition function for acquiring mixed gas property information including at least one of a flow rate of the mixed gas supplied to the adsorption process tower, a concentration of the adsorbed gas in the mixed gas, a temperature of the mixed gas, and a pressure of the mixed gas, and an operating condition including at least one of a temperature of the adsorption process tower and a pressure inside the adsorption tower; a desorption condition determination function that determines desorption conditions, including at least one of a supply flow rate of a purge gas to the desorption step tower, heating of the desorption step tower, and pressure reduction inside the desorption step tower, from the mixed gas property information acquired by the information acquisition unit in the adsorption step that is performed simultaneously with the desorption step and the operation conditions; Run the command, In the control function, executing the desorption step under the desorption conditions determined by the desorption condition determination unit; When an integrated amount of the adsorbed gas in the adsorption step tower reaches a predetermined integrated amount threshold, the adsorption step tower and the desorption step tower are shifted. Computer program. [Explanation of symbols]

[0105] 1, 1A…Gas separation system 10~14…Adsorption tower 10c…Temperature sensor 10d…Pressure sensor 11a, 12a, 13a, 14a...Adsorbent 11c…Temperature sensor 11d…Pressure sensor 20...Mixed gas supply passage 20a…Gas analyzer 20b…Flow meter 20c…Temperature sensor 20d...Pressure sensor 21...Mixed gas distribution channel 21a, 22a, 23a, 24a...Mixed gas inlet valve 30...Exhaust gas flow path 30b, 31b, 32b, 33b, 34b...Exhaust gas properties measuring section 31~34…Exhaust gas distribution channel 31a, 32a, 33a, 34a...Exhaust gas outlet valve 40...Hydrocarbon production equipment 45…Vacuum pump 50, 50A…Adsorption tower control device 51, 51A...Control unit 52, 52A...Information acquisition section 53...Desorption condition determination unit 54...Storage section 60...Product gas flow path 61~64…Product gas distribution channel 61a, 62a, 63a, 64a...Product gas outlet valve 70...Purge gas supply passage 70a...Flow rate controller 71-74: Purge gas distribution channel 71a, 72a, 73a, 74a...Purge gas inlet valve 80…Heat medium passage 81~84…Heating medium distribution channel 81a, 82a, 83a, 84a... Heat medium inlet valve

Claims

1. 1. An adsorption tower control device for recovering a specific adsorbed gas from a mixed gas containing the specific adsorbed gas by using a plurality of adsorption towers, The plurality of adsorption towers include at least an adsorption step tower in which an adsorption step is performed to which the mixed gas is supplied, and a desorption step tower in which a desorption step is performed to desorb the adsorbed gas, The adsorption tower control device includes: a control unit that repeatedly executes an adsorption / desorption process in which the adsorption process is executed in the adsorption process tower and the desorption process is executed in the desorption process tower while shifting the adsorption towers; an information acquiring unit that acquires mixed gas property information including at least one of a flow rate of the mixed gas supplied to the adsorption process tower, a concentration of the adsorbed gas in the mixed gas, a temperature of the mixed gas, and a pressure of the mixed gas, and an operating condition including at least one of a temperature of the adsorption process tower and a pressure inside the adsorption tower; a desorption condition determination unit that determines desorption conditions, including at least one of a supply flow rate of a purge gas to the desorption step tower, heating of the desorption step tower, and depressurization inside the desorption step tower, from the mixed gas property information acquired by the information acquisition unit in the adsorption step that is performed simultaneously with the desorption step and the operation conditions; Equipped with The control unit is executing the desorption step under the desorption conditions determined by the desorption condition determination unit; When an integrated amount of the adsorbed gas in the adsorption step tower reaches a predetermined integrated amount threshold, the adsorption step tower and the desorption step tower are shifted. Adsorption tower control device.

2. The adsorption tower control device according to claim 1, the information acquisition unit further acquires exhaust gas property information including at least one of a flow rate of the exhaust gas discharged from the adsorption process tower and a concentration of the adsorbed gas in the exhaust gas; The control unit is calculating an integrated amount of the adsorbed gas using the mixed gas property information and the exhaust gas property information acquired by the information acquisition unit; Adsorption tower control device.

3. The adsorption tower control device according to claim 1, The information acquisition unit sequentially acquires the mixed gas property information and the operating conditions, The desorption condition determination unit sequentially determines the desorption conditions by using the sequentially acquired mixed gas property information and operation conditions. Adsorption tower control device.

4. The adsorption tower control device according to claim 1, The information acquisition unit sequentially acquires the mixed gas property information and the operating conditions, the desorption condition determination unit determines the desorption conditions using average mixed gas property information and average operating conditions obtained by time-averaging the sequentially acquired mixed gas property information and operating conditions. Adsorption tower control device.

5. 1. An adsorption tower control device for recovering a specific adsorbed gas from a mixed gas containing the specific adsorbed gas by using a plurality of adsorption towers, The plurality of adsorption towers include at least an adsorption step tower in which an adsorption step is performed to which the mixed gas is supplied, and a desorption step tower in which a desorption step is performed to desorb the adsorbed gas, The adsorption tower control device includes: a control unit that repeatedly executes an adsorption / desorption process in which the adsorption process is executed in the adsorption process tower and the desorption process is executed in the desorption process tower while shifting the adsorption towers; an information acquiring unit that acquires mixed gas property information including at least one of a flow rate of the mixed gas supplied to the adsorption process tower, a concentration of the adsorbed gas in the mixed gas, a temperature of the mixed gas, and a pressure of the mixed gas, and an operating condition including at least one of a temperature of the adsorption process tower and a pressure inside the adsorption tower; a desorption condition determination unit that determines desorption conditions, including at least one of a supply flow rate of a purge gas to the desorption step tower, heating of the desorption step tower, and depressurization inside the desorption step tower, from the mixed gas property information acquired by the information acquisition unit in the adsorption step that is performed simultaneously with the desorption step and the operation conditions; Equipped with The control unit is executing the desorption step under the desorption conditions determined by the desorption condition determination unit; When an integrated amount of the adsorbed gas in the adsorption step tower reaches a predetermined integrated amount threshold, a recovery rate of the adsorbed gas in the desorption step tower is calculated, and when the recovery rate is equal to or greater than the predetermined recovery rate threshold, the adsorption step tower and the desorption step tower are shifted, and when the recovery rate is less than the recovery rate threshold, the adsorption and desorption steps are continued until the recovery rate becomes equal to or greater than the recovery rate. Adsorption tower control device.

6. 1. A gas separation apparatus comprising: An adsorption tower control device according to any one of claims 1 to 5; a plurality of adsorption towers for separating a specific adsorbed gas from a mixed gas by adsorbing and desorbing the specific adsorbed gas in the mixed gas; a mixed gas supply unit for supplying the mixed gas to the adsorption tower; a desorption assistant section for desorbing the adsorbed gas from the adsorption tower; Equipped with The detachment assistance portion is The adsorption tower is provided with at least one of a purge gas supply unit that supplies a purge gas to the adsorption tower, a heating device that heats the adsorption tower, and a decompression device that decompresses the inside of the adsorption tower. Gas separation equipment.

7. 1. A method for controlling a plurality of adsorption towers by an information processing device, in which a specific adsorbed gas is recovered from a mixed gas containing the adsorbed gas by using the plurality of adsorption towers, the method comprising: The plurality of adsorption towers include at least an adsorption step tower in which an adsorption step is performed to which the mixed gas is supplied, and a desorption step tower in which a desorption step is performed to desorb the adsorbed gas, The method for controlling the plurality of adsorption towers includes the steps of: a control process for repeatedly executing an adsorption / desorption process in which the adsorption process is executed in the adsorption process tower and the desorption process is executed in the desorption process tower while shifting the adsorption / desorption process in the plurality of adsorption towers; an information acquiring process for acquiring mixed gas property information including at least one of a flow rate of the mixed gas supplied to the adsorption process tower, a concentration of the adsorbed gas in the mixed gas, a temperature of the mixed gas, and a pressure of the mixed gas, and an operating condition including at least one of a temperature of the adsorption process tower and a pressure inside the adsorption tower; a desorption condition determination step of determining desorption conditions, including at least one of a supply flow rate of a purge gas to the desorption step tower, heating of the desorption step tower, and depressurization inside the desorption step tower, from the mixed gas property information acquired by the information acquisition unit in the adsorption step which is performed simultaneously with the desorption step and the operation conditions; Equipped with The control step includes: executing the desorption step under the desorption conditions determined by the desorption condition determination unit; When an integrated amount of the adsorbed gas in the adsorption step tower reaches a predetermined integrated amount threshold, the adsorption step tower and the desorption step tower are shifted. A method for controlling multiple adsorption towers.

8. 1. A computer program for recovering a specific adsorbed gas from a mixed gas containing the specific adsorbed gas by using a plurality of adsorption towers, comprising: The plurality of adsorption towers include at least an adsorption step tower in which an adsorption step is performed to which the mixed gas is supplied, and a desorption step tower in which a desorption step is performed to desorb the adsorbed gas, The computer program includes: a control function for repeatedly executing an adsorption / desorption process in which the adsorption process is executed in the adsorption process tower and the desorption process is executed in the desorption process tower while shifting the adsorption / desorption process in the multiple adsorption towers; an information acquisition function for acquiring mixed gas property information including at least one of a flow rate of the mixed gas supplied to the adsorption process tower, a concentration of the adsorbed gas in the mixed gas, a temperature of the mixed gas, and a pressure of the mixed gas, and an operating condition including at least one of a temperature of the adsorption process tower and a pressure inside the adsorption tower; a desorption condition determination function that determines desorption conditions, including at least one of a supply flow rate of a purge gas to the desorption step tower, heating of the desorption step tower, and pressure reduction inside the desorption step tower, from the mixed gas property information acquired by the information acquisition unit in the adsorption step that is performed simultaneously with the desorption step and the operation conditions; Run the command, In the control function, executing the desorption step under the desorption conditions determined by the desorption condition determination unit; When an integrated amount of the adsorbed gas in the adsorption step tower reaches a predetermined integrated amount threshold, the adsorption step tower and the desorption step tower are shifted. Computer program.

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