Carbon dioxide recovery control device, carbon dioxide recovery device, hydrocarbon production device, carbon dioxide recovery method, and program

Abstract

To provide a carbon dioxide recovery control device suppressing a variation in carbon dioxide concentration in a recovery gas containing carbon dioxide recovered from a mixed gas containing carbon dioxide using an adsorption tower.SOLUTION: A carbon dioxide recovery control device includes: a step control part for repeatedly performing a first step of performing an adsorption step of supplying a mixed gas to a first adsorption tower and at the same time performing a desorption step of supplying hydrogen to a second adsorption tower, and a second step of performing an adsorption step of supplying the mixed gas to a second adsorption tower and at the same time performing a desorption step of supplying hydrogen to the first adsorption tower; a breakthrough time prediction part for predicting breakthrough time at a predetermined prediction time in the adsorption tower where the adsorption step is performed; and a hydrogen flow rate determination part for determining a hydrogen flow rate flowing in the desorption step according to a predicted breakthrough time. The step control part switches between the first step and the second step based on carbon dioxide breakthrough information.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a technique for recovering carbon dioxide from a mixed gas containing carbon dioxide using an adsorption tower.

Background Art

[0002] Conventionally, a technique has been proposed for removing impurities contained in a gas or liquid using an adsorption device filled with an adsorbent (see, for example, Patent Document 1). Patent Document 1 describes an adsorption device that uses two towers filled with an adsorbent to alternately perform an impurity adsorption step and a desorption (regeneration) step. In this adsorption device, when the flow rate of the inflowing gas decreases below the design value in the adsorption step, the time of the adsorption step is extended until the total flow rate of the inflowing gas reaches the design value, and the regeneration step is operated as designed. Thus, even when the flow rate of the inflowing gas decreases, the performance of the adsorption tower can be utilized to the maximum extent, and it is described that the energy efficiency of impurity separation is increased.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, according to the technique described in Patent Document 1, when the flow rate of the inflowing gas decreases, the adsorption step is extended and the desorption step remains as it is. Therefore, in the adsorption tower performing the desorption step, a waiting time occurs. When using the technique described in Patent Document 1 to separate and recover carbon dioxide from a mixed gas containing carbon dioxide, for example, since carbon dioxide comes out of the adsorption tower in the desorption step, no carbon dioxide comes out during the waiting period. That is, the concentration of carbon dioxide coming out of the adsorption tower fluctuates.

[0005] A hydrocarbon synthesis apparatus for hydrocarbonating carbon dioxide recovered by an adsorption tower may be connected downstream of the adsorption tower. In such a configuration, when the concentration of carbon dioxide fluctuates, if the carbon dioxide supplied to the hydrocarbon synthesis apparatus is excessive, there is a risk of deactivation of the hydrocarbon catalyst. On the other hand, if the hydrogen supplied to the hydrocarbon synthesis apparatus is excessive, there is a risk of a decrease in the purity of the hydrocarbon obtained from the hydrocarbon synthesis apparatus.

[0006] Therefore, in a carbon dioxide separation and recovery apparatus that separates and recovers carbon dioxide from a mixed gas containing carbon dioxide using an adsorption tower, a technique for suppressing fluctuations in the concentration of the recovered carbon dioxide is desired.

[0007] The present invention has been made to solve the above-described problems, and an object thereof is to provide a technique for suppressing fluctuations in the carbon dioxide concentration in a recovered gas containing carbon dioxide recovered using an adsorption tower from a mixed gas containing carbon dioxide.

Means for Solving the Problems

[0008] The present invention has been made to solve at least a part of the above-described problems and can be realized in the following forms.

[0009] (1) According to one aspect of the present invention, there is provided a carbon dioxide recovery control device that performs carbon dioxide recovery control for recovering carbon dioxide from a mixed gas containing carbon dioxide using a plurality of adsorption towers including at least a first adsorption tower and a second adsorption tower. This carbon dioxide recovery control device includes a first step of causing the adsorption tower to execute an adsorption step of supplying the mixed gas to the first adsorption tower and simultaneously causing the second adsorption tower to execute a desorption step of supplying hydrogen to the second adsorption tower; a second step of causing the second adsorption tower to execute an adsorption step of supplying the mixed gas to the second adsorption tower and simultaneously causing the first adsorption tower to execute a desorption step of supplying hydrogen to the first adsorption tower; a process control unit that repeatedly executes the steps; a breakthrough time prediction unit that predicts a breakthrough time, which is the time from a predetermined prediction time until carbon dioxide leaks out of the adsorption tower in the adsorption tower where the adsorption step is being executed; and a hydrogen flow rate determination unit that determines a hydrogen flow rate for controlling the flow rate of hydrogen flowing through the adsorption tower in the desorption step that is being executed simultaneously according to the breakthrough time predicted by the breakthrough time prediction unit. The process control unit controls the flow rate of hydrogen flowing through the adsorption tower in which the desorption step is being executed to be the hydrogen flow rate determined by the hydrogen flow rate determination unit, obtains carbon dioxide breakthrough information, which is information regarding the breakthrough of carbon dioxide in the adsorption tower in which the adsorption step is being executed, and switches between the first step and the second step when carbon dioxide breakthrough occurs or immediately before carbon dioxide breakthrough occurs based on the carbon dioxide breakthrough information.

[0010] According to this configuration, the first step and the second step are each performed until carbon dioxide breaks through or immediately before it breaks through in the adsorption step. Therefore, the periods of the first step and the second step vary according to the flow rate of the mixed gas supplied to the adsorption tower and the carbon dioxide concentration in the mixed gas. In the adsorption step, since the mixed gas is supplied until carbon dioxide breaks through or immediately before it breaks through, the adsorption amount of carbon dioxide is substantially the full amount (maximum adsorption amount). On the other hand, if the hydrogen flow rate is kept constant in the desorption step, the total amount of hydrogen supplied to the adsorption tower during the entire desorption step fluctuates, resulting in an excess or deficiency of hydrogen. However, according to this configuration, since the hydrogen flow rate supplied in the desorption step that is performed simultaneously with (equal in period to) the adsorption step is determined according to the breakthrough time, the amount of hydrogen supplied to the adsorption tower during the entire desorption step can be appropriately controlled according to the variation in the length of the desorption step. As a result, fluctuations in the carbon dioxide concentration in the recovered gas containing carbon dioxide recovered using the adsorption tower from the mixed gas containing carbon dioxide can be suppressed.

[0011] (2) In the carbon dioxide recovery control device of the above aspect, the breakthrough time prediction unit predicts the breakthrough time at each predetermined time, and the hydrogen flow rate determination unit updates the hydrogen flow rate at each predetermined time according to the predicted breakthrough time. When the predetermined time is dt, the prediction time is n (n is an integer of 1 or more), and the breakthrough time predicted at the prediction time n is t(n), the hydrogen flow rate determination unit determines the relationship between the breakthrough time t(n) predicted at the prediction time n and the breakthrough time t(n - 1) predicted at the prediction time (n - 1). In the case of the first relationship, the hydrogen flow rate at the prediction time n is decreased from the hydrogen flow rate at the prediction time (n - 1). In the case of the second relationship, the hydrogen flow rate at the prediction time n is increased from the hydrogen flow rate at the prediction time (n - 1). In the case of the third relationship, the hydrogen flow rate at the prediction time n is made the same as the hydrogen flow rate at the prediction time (n - 1). The first relationship may be t(n - 1) < t(n) + dt, the second relationship may be t(n - 1) > t(n) + dt, and the third relationship may be t(n - 1) = t(n) + dt.

[0012] According to this configuration, during one adsorption process, the breakthrough time is predicted moment by moment, and according to the breakthrough time, the hydrogen flow rate is updated moment by moment. Therefore, the hydrogen flow rate can be changed with higher accuracy. Further, when the relationship between the breakthrough times predicted at the current prediction time and the prediction time one hour before is the first relationship, since the length of the adsorption process predicted at the current time is longer than the length of the adsorption process predicted at the prediction time one hour before, by reducing the hydrogen flow rate, the total amount of hydrogen supplied in the desorption process can be made appropriate. When the relationship between the breakthrough times predicted at the current prediction time and the prediction time one hour before is the second relationship, since the length of the adsorption process predicted at the current time is shorter than the length of the adsorption process predicted at the prediction time one hour before, by increasing the hydrogen flow rate, the total amount of hydrogen supplied in the desorption process can be made appropriate. When the relationship between the breakthrough times predicted at the current prediction time and the prediction time one hour before is the third relationship, since the length of the adsorption process predicted at the prediction time one hour before is equal (unchanged) to the length of the adsorption process predicted at the current time, by maintaining the hydrogen flow rate, the total amount of hydrogen supplied in the desorption process can be made appropriate. That is, by updating the hydrogen flow rate in this way, the supply amount of hydrogen can be made more accurately appropriate, and the variation in the carbon dioxide concentration in the recovered gas can be further suppressed.

[0013] (3) The carbon dioxide recovery control device according to the above aspect, wherein the hydrogen flow rate determination unit acquires the amount of hydrogen that has flowed through the adsorption tower from the start of the desorption process to the prediction time and the total amount of hydrogen that can flow through the adsorption tower during the entire period of the desorption process, and the hydrogen flow rate to be passed through the adsorption tower during the desorption process after the prediction time may be determined by the following formula (1). mf(n)=(ma - mp) / t(n)… (1) However, mf(n): the hydrogen flow rate to be passed through the adsorption tower during the desorption process after the prediction time n; mp: the amount of hydrogen passed through the adsorption tower from the start of the desorption process to the prediction time n; ma: the total amount of hydrogen that can be passed through the adsorption tower during the entire desorption process; t(n): the breakthrough time predicted at the prediction time n

[0014] According to this configuration, during the desorption process of the adsorption tower, by using the actually supplied amount of hydrogen, the hydrogen flow rate in the remaining desorption process can be determined, so that the calculation accuracy of the appropriate hydrogen flow rate can be improved.

[0015] (4) The carbon dioxide recovery control device of the above form, wherein the breakthrough time prediction unit, in the adsorption process, acquires the total amount of the mixed gas that has flowed into the adsorption tower until the prediction time, the amount of the mixed gas that can be processed in the adsorption process, and the rated mixed gas flow rate which is the flow rate of the mixed gas predetermined for each supply source of the mixed gas, and may predict the breakthrough time according to the following formula (2). t(n)=(qc-q(n)) / qf … (2) However, t(n): the breakthrough time predicted at the prediction time n; qc: the amount of the mixed gas that can be processed in the adsorption process; q(n): the total amount of the mixed gas that has flowed in until the prediction time n; qf: the rated mixed gas flow rate According to this configuration, the breakthrough time can be easily predicted.

[0016] (5) The carbon dioxide recovery control device of the above form, wherein the breakthrough time prediction unit acquires the flow rate of the mixed gas flowing into the adsorption tower, the temperature of the mixed gas, and the concentration of carbon dioxide in the mixed gas, calculates the total amount of carbon dioxide that has flowed in until the prediction time in the adsorption process by using the flow rate of the mixed gas and the concentration of carbon dioxide in the mixed gas, calculates the saturated adsorption amount of carbon dioxide in the adsorption process by using the temperature of the mixed gas at the prediction time and the concentration of carbon dioxide in the mixed gas, acquires the rated carbon dioxide flow rate which is the flow rate of carbon dioxide predetermined for each supply source of the mixed gas, and may predict the breakthrough time according to the following formula (3). t(n) = (Ca - C(n)) / Cf … (3) However, t(n): breakthrough time predicted at prediction time n; Ca: saturated adsorption amount of carbon dioxide; C(n): total amount of carbon dioxide that has flowed in up to prediction time n; Cf: rated carbon dioxide flow rate

[0017] According to this configuration, since the breakthrough time can be predicted using the saturated adsorption amount of carbon dioxide that varies according to the temperature of the mixed gas and the carbon dioxide concentration in the mixed gas, the prediction accuracy of the breakthrough time can be improved.

[0018] (6) According to another aspect of the present invention, a carbon dioxide recovery device is provided. This carbon dioxide recovery device includes the carbon dioxide recovery control device of the above aspect, an adsorption tower capable of separating carbon dioxide from a mixed gas containing carbon dioxide, including a plurality of adsorption towers including at least a first adsorption tower and a second adsorption tower, a mixed gas supply unit capable of supplying the mixed gas to the plurality of adsorption towers, and a hydrogen supply unit capable of supplying hydrogen to the plurality of adsorption towers. According to this configuration, fluctuations in the carbon dioxide concentration in the recovered gas containing carbon dioxide recovered using the adsorption tower from the mixed gas containing carbon dioxide can be suppressed.

[0019] (7) According to another aspect of the present invention, a hydrocarbon production device is provided. This hydrocarbon production device includes the carbon dioxide recovery device of the above aspect, and a hydrocarbon production unit having a hydrocarbonation catalyst inside and generating a hydrocarbon compound using the recovered gas containing carbon dioxide and hydrogen flowing out from the carbon dioxide recovery device. According to this configuration, since fluctuations in the carbon dioxide concentration in the recovered gas containing carbon dioxide recovered using the adsorption tower from the mixed gas containing carbon dioxide can be suppressed, deactivation of the hydrocarbonation catalyst in the hydrocarbon production unit can be suppressed. Also, the methane purity of the gas generated by the hydrocarbon production unit can be improved.

[0020] Note that the present invention can be implemented in various forms. For example, it can be realized in the form of a carbon dioxide recovery method, a program for controlling a carbon dioxide recovery device, a carbon dioxide recovery system, a hydrocarbon production system, a methane production system, a method for controlling these devices and systems, a program for controlling these devices and systems, a server device for distributing these programs, a non-transitory storage medium storing the program, and the like.

Brief Description of the Drawings

[0021]

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Modes for Carrying Out the Invention

[0022] <First Embodiment> FIG. 1 is an explanatory diagram showing a schematic configuration of a hydrocarbon production apparatus 100 according to the first embodiment. The hydrocarbon production apparatus 100 is an apparatus for producing a hydrocarbon compound using a mixed gas of carbon dioxide (CO 2 ) and hydrogen (H 2 ), and includes a carbon dioxide recovery apparatus 200 and a hydrocarbon generation unit 60. Specifically, in the hydrocarbon production apparatus 100, the carbon dioxide recovery apparatus 200 recovers carbon dioxide from a mixed gas containing carbon dioxide, and uses the recovered carbon dioxide to generate a hydrocarbon. In the present embodiment, an example of generating methane (CH 4 ) as the hydrocarbon is shown. However, hydrocarbon compounds other than methane (CH 4 ), for example, compounds composed of carbon and hydrogen such as ethane and propane, or compounds mainly composed of carbon and hydrogen such as methanol may be generated.

[0023] The hydrocarbon generation unit 60 has a hydrocarbonation catalyst inside, and uses the recovered gas (containing carbon dioxide and hydrogen) supplied from the carbon dioxide recovery apparatus 200 and hydrogen supplied from an external hydrogen supply source to generate methane, and is configured to be able to supply a gas mainly composed of methane (hereinafter, also referred to as "product gas") to the outside. The hydrocarbon generation unit 60 is connected to the carbon dioxide recovery apparatus 200 via a recovered gas flow path 72 and is connected to an external hydrogen supply source via a hydrogen flow path 62. A flow rate controller 62a for adjusting the flow rate of hydrogen flowing through the hydrogen flow path 62 is provided in the hydrogen flow path 62. The hydrogen flow rate in the flow rate controller 62a is preset. Further, the hydrocarbon generation unit 60 is connected to a product gas flow path 63. For example, by connecting a storage tank to the other end of the product gas flow path 63, the product gas can be stored in the storage tank. In the present embodiment, as will be described later, in the carbon dioxide recovery apparatus 200, fluctuations in the flow rate and concentration of the recovered gas can be suppressed, so that the hydrocarbon generation unit 60 can supply a product gas with a high methane purity to the outside.

[0024] The carbon dioxide recovery device 200 recovers carbon dioxide from a mixed gas containing carbon dioxide using an adsorption tower. In the present embodiment, an example of the mixed gas containing carbon dioxide is exhaust gas discharged from a combustion furnace, an internal combustion engine, or the like. The carbon dioxide recovery device 200 includes a plurality of adsorption towers (first adsorption tower 11 and second adsorption tower 12), an exhaust gas flow path 20, an off-gas flow path 25, a hydrogen flow path 30, a recovered gas flow path 40, a recovered gas tank 70, and a carbon dioxide recovery control device 50. In the following description, when the first adsorption tower 11 and the second adsorption tower 12 are not distinguished, they are simply referred to as the adsorption tower 10. In the carbon dioxide recovery device 200, carbon dioxide adsorbed on the adsorption tower 10 is desorbed using hydrogen as a purge gas.

[0025] The first adsorption tower 11 and the second adsorption tower 12 are each formed in a cylindrical shape, and adsorbents 11a and 12a are respectively accommodated inside. The adsorbents 11a and 12a are materials having carbon dioxide occlusion performance, such as zeolite, activated carbon, silica gel, and the like. An exhaust gas flow path 20, a hydrogen flow path 30, and a recovered gas flow path 40 are connected to each of the first adsorption tower 11 and the second adsorption tower 12.

[0026] The exhaust gas flow path 20 is connected to an external exhaust gas supply device that discharges exhaust gas containing carbon dioxide, such as a combustion furnace or an internal combustion engine, and the exhaust gas discharged by the exhaust gas supply device flows therethrough. The exhaust gas flowing through the exhaust gas flow path 20 is supplied to the first adsorption tower 11 and the second adsorption tower 12 via exhaust gas diversion paths 21 and 22. Exhaust gas inlet valves 21a and 22a are respectively provided in the exhaust gas diversion paths 21 and 22. Each of the exhaust gas inlet valves 21a and 22a controls the supply of exhaust gas into the first adsorption tower 11 and the second adsorption tower 12 in accordance with a command from the carbon dioxide recovery control device 50 described later. In the present embodiment, exhaust gas is exemplified as the mixed gas containing carbon dioxide, but the mixed gas containing carbon dioxide may not be exhaust gas. The exhaust gas flow path 20, the exhaust gas diversion paths 21 and 22, and the exhaust gas inlet valves 21a and 22a in the present embodiment are collectively referred to as the "mixed gas supply unit".

[0027] The off-gas flow path 25 is connected to the first adsorption tower 11 via the off-gas diversion path 23 and to the second adsorption tower 12 via the off-gas diversion path 24. Carbon dioxide contained in the exhaust gas is trapped by the adsorbent, and the off-gas containing nitrogen etc. that was not trapped by the adsorbent flows through the off-gas flow path 25. The off-gas is discharged to the outside of the carbon dioxide recovery device 200, for example, to the atmosphere. The off-gas flow path 25 is connected to the off-gas diversion paths 23 and 24 via a three-way valve 25a, and controls the discharge of off-gas from the first adsorption tower 11 and the second adsorption tower 12 according to the command of the carbon dioxide recovery control device 50 described later.

[0028] Temperature sensors 84 and 85 are provided in the off-gas diversion path 23 and the off-gas diversion path 24 respectively. The temperature sensors 84 and 85 detect the temperature of the off-gas discharged from the first adsorption tower 11 and the second adsorption tower 12 respectively, and output the detection results to the carbon dioxide recovery control device 50.

[0029] The hydrogen flow path 30 is connected to an external hydrogen supply source that supplies hydrogen as a purge gas inside the first adsorption tower 11 and the second adsorption tower 12. A flow controller 30a for adjusting the flow rate of hydrogen flowing through the hydrogen flow path 30 is provided in the hydrogen flow path 30 according to the command of the carbon dioxide recovery control device 50. The hydrogen flowing through the hydrogen flow path 30 is supplied to the first adsorption tower 11 and the second adsorption tower 12 via the hydrogen diversion paths 31 and 32. Hydrogen inlet valves 31a and 32a are provided in the hydrogen diversion paths 31 and 32 respectively. Each of the hydrogen inlet valves 31a and 32a controls the flow of hydrogen into the first adsorption tower 11 and the second adsorption tower 12 according to the command of the carbon dioxide recovery control device 50. The hydrogen flow path 30, the flow controller 30a, the hydrogen diversion paths 31 and 32, and the hydrogen inlet valves 31a and 32a in this embodiment are collectively referred to as the "hydrogen supply unit".

[0030] The recovered gas flow path 40 is connected to each of the first adsorption tower 11 and the second adsorption tower 12 via recovered gas branch flow paths 41 and 42. A recovered gas, which is a mixed gas of carbon dioxide desorbed from the adsorbents 11a and 12a and hydrogen supplied to the first adsorption tower 11 and the second adsorption tower 12 as purge gas, flows through the recovered gas flow path 40. Recovered gas outlet valves 41a and 42a are provided in the recovered gas branch flow paths 41 and 42. Each of the recovered gas outlet valves 41a and 42a controls the flow of the recovered gas from the first adsorption tower 11 and the second adsorption tower 12 according to a command from the carbon dioxide recovery control device 50.

[0031] The recovered gas tank 70 is connected to the recovered gas flow path 40 and temporarily stores the recovered gas flowing through the recovered gas flow path 40. Further, the recovered gas tank 70 is connected to the hydrocarbon generation unit 60 via a recovered gas flow path 72 and supplies the recovered gas to the hydrocarbon generation unit 60.

[0032] The flow meter 81 is provided at a position upstream of the position where the exhaust gas branch flow path 21 connects in the exhaust gas flow path 20. The flow meter 81 detects the flow rate of the exhaust gas flowing through the exhaust gas flow path 20. The flow meter 81 outputs the detected exhaust gas flow rate to the carbon dioxide recovery control device 50.

[0033] The carbon dioxide recovery control device 50 is a computer (information processing device) including a ROM, a RAM, and a CPU, and performs overall control of the carbon dioxide recovery device 200, such as switching between the first adsorption tower 11 and the second adsorption tower 12 and opening / closing control of valves in the process control unit described later. Further, the carbon dioxide recovery control device 50 determines the flow rate of hydrogen supplied to the adsorption tower 10 (described later).

[0034] The carbon dioxide recovery control device 50 includes a process control unit 51, a breakthrough time prediction unit 52, a hydrogen flow rate determination unit 53, and a storage unit 54.

[0035] The carbon dioxide recovery control device 50 executes a first step of causing the adsorption tower 11 to execute an adsorption step of supplying exhaust gas and simultaneously causing the desorption tower 12 to execute a desorption step of supplying hydrogen, and a second step of causing the adsorption tower 12 to execute an adsorption step of supplying exhaust gas and simultaneously causing the desorption tower 11 to execute a desorption step of supplying hydrogen, and repeatedly executes carbon dioxide recovery control. In each adsorption tower 10, the adsorption step and the desorption step are alternately repeated, whereby carbon dioxide is recovered from the exhaust gas. The carbon dioxide recovery control device 50 switches the steps in conjunction with the breakthrough of carbon dioxide in the adsorption tower 10 in which the adsorption step is being performed (to be described in detail later). In the present embodiment, the adsorption step is a step of supplying exhaust gas to the adsorption tower 10, and the desorption step is a step of supplying hydrogen to the adsorption tower 10.

[0036] The process control unit 51 cooperates with the breakthrough time prediction unit 52 and the hydrogen flow rate determination unit 53 to execute the carbon dioxide recovery control described later. The process control unit 51 controls the exhaust gas inlet valves 21a, 22a, the three-way valve 25a, the flow controller 30a, the hydrogen inlet valves 31a, 32a, and the recovered gas outlet valves 41a, 42a described above, so as to repeatedly execute the adsorption step and the desorption step in the adsorption tower 10.

[0037] The breakthrough time prediction unit 52 predicts the breakthrough time, which is the time from a predetermined prediction time until carbon dioxide leaks out of the adsorption tower 10 in the adsorption tower 10 in which the adsorption step is being executed. In the present embodiment, the breakthrough time prediction unit 52 acquires the exhaust gas flow rate measured by the flow meter 81 provided in the exhaust gas flow path 20, and calculates the remaining adsorption period (the time until breakthrough) based on the total exhaust gas flow rate that can be separated by the adsorption tower (to be described in detail later). In the present embodiment, the breakthrough time prediction unit 52 predicts the breakthrough time a plurality of times while the adsorption step is being executed. That is, the prediction time, which is the time at which the breakthrough time is predicted, is set at a predetermined interval.

[0038] The hydrogen flow rate determination unit 53 determines the hydrogen flow rate for controlling the flow rate of hydrogen to be passed through the adsorption tower 10 in the desorption process that is executed simultaneously with the adsorption process for which the breakthrough time has been predicted, according to the breakthrough time predicted by the breakthrough time prediction unit 52 (to be described in detail later).

[0039] The storage unit 54 stores the rated exhaust gas flow rate 55 and the treatable exhaust gas amount 56. The rated exhaust gas flow rate 55 is the flow rate of exhaust gas predetermined for each exhaust gas supply source, and a value specific to the exhaust gas supply device connected to the hydrocarbon production apparatus 100 has been input in advance by the user or the like. The treatable exhaust gas amount 56 is the total amount of exhaust gas that the adsorption tower 10 can treat, and is predetermined for each adsorption tower 10 according to, for example, the capacity of the adsorption tower 10, the type of adsorbent, the filling rate of the adsorbent, etc. The treatable exhaust gas amount 56 may be input by the user, similar to the rated exhaust gas flow rate 55, or may be stored in advance during the manufacture of the hydrocarbon production apparatus 100.

[0040] FIG. 2 is an explanatory diagram of the switching timing of the adsorption tower 10 in the carbon dioxide recovery apparatus 200 of the present embodiment. In the carbon dioxide recovery control of the present embodiment, as shown in the figure, the first step and the second step are taken as one cycle, and this cycle is repeated a plurality of times. In each step, each of the adsorption step and the desorption step (hydrogen supply) is executed in one of the two adsorption towers (the first adsorption tower 11 and the second adsorption tower 12). Specifically, in the first step, the adsorption step is executed in the first adsorption tower 11, and the desorption step is executed in the second adsorption tower 12. In the second step, the desorption step is executed in the first adsorption tower 11, and the adsorption step is executed in the second adsorption tower 12. In the carbon dioxide recovery apparatus 200 of the present embodiment, in this way, while carbon dioxide in the exhaust gas is adsorbed in one adsorption tower 10, the adsorbed carbon dioxide is desorbed in the other adsorption tower 10. Thereby, it is possible to constantly supply a carbon dioxide-containing gas (exhaust gas).

[0041] Focusing on one adsorption tower 10, the adsorption process and the desorption process are repeated. In Fig. 2, the sequential numbers N of the repeated processes are listed in order from 0. Hereinafter, taking the first adsorption tower 11 as an example, an explanation will be given. In the adsorption process, exhaust gas is supplied to the first adsorption tower 11 (the first step). Immediately before carbon dioxide breaks through in the first adsorption tower 11, the process shifts to the desorption process (the second step). In the desorption process, hydrogen as a purge gas is supplied to the first adsorption tower 11. When hydrogen as a purge gas is supplied to the first adsorption tower 11, the partial pressure of carbon dioxide inside the first adsorption tower 11 decreases, so the carbon dioxide adsorbed on the adsorbent 11a desorbs from the adsorbent 11a. Immediately before carbon dioxide breaks through in the second adsorption tower 12 in the second step, the first adsorption tower 11 shifts to the adsorption process (the first step).

[0042] Thus, in the carbon dioxide recovery device 200 of the present embodiment, immediately before carbon dioxide breaks through in the adsorption tower 10 where the adsorption process is being performed, the switching between the first step and the second step is carried out. Therefore, as shown in the figure, the lengths of a plurality of first steps and a plurality of second steps may be different from each other. However, the lengths of the adsorption process and the desorption process in the first step are the same, and the lengths of the adsorption process and the desorption process in the second step are the same. The switching between the first step and the second step will be described in detail later.

[0043] Fig. 3 is an explanatory diagram of the first step of carbon dioxide recovery control in the carbon dioxide recovery device 200. Fig. 4 is an explanatory diagram of the second step of carbon dioxide recovery control in the carbon dioxide recovery device 200. As described above, in the carbon dioxide recovery device 200, carbon dioxide is recovered from the exhaust gas by sequentially supplying the exhaust gas to each of the two adsorption towers 10 (the first adsorption tower 11 and the second adsorption tower 12). Each of the first adsorption tower 11 and the second adsorption tower 12 functions as an adsorption tower in which carbon dioxide is adsorbed on the adsorbent and a desorption tower in which the carbon dioxide adsorbed on the adsorbent is desorbed.

[0044] The first adsorption tower 11 functions as an adsorption tower in the first step shown in FIG. 3 and functions as a desorption tower in the second step shown in FIG. 4. In FIGS. 3 and 4, the flows of the exhaust gas, hydrogen, and the recovered gas are indicated by thick solid lines. As shown in FIG. 3, the exhaust gas is supplied to the first adsorption tower 11 that functions as an adsorption tower. Hydrogen is supplied to the second adsorption tower 12 that functions as a desorption tower, and the carbon dioxide desorbed from the adsorbent is discharged as a recovered gas together with hydrogen.

[0045] In the first step shown in FIG. 3, the exhaust gas is supplied to the first adsorption tower 11 using the exhaust gas flow path 20 (adsorption step). Specifically, the carbon dioxide recovery control device 50 opens the exhaust gas inlet valve 21a and controls each valve so that the off-gas shunt flow path 23 and the off-gas flow path 25 are connected via the three-way valve 25a. Thereby, the exhaust gas flowing through the exhaust gas flow path 20 is supplied to the first adsorption tower 11 via the exhaust gas shunt flow path 21. In the first adsorption tower 11, the carbon dioxide contained in the exhaust gas is trapped by the adsorbent 11a, and nitrogen, moisture, etc. that are not trapped by the adsorbent 11a are discharged to the outside of the carbon dioxide recovery device 200, for example, the atmosphere, as off-gas via the off-gas shunt flow path 23 and the off-gas flow path 25.

[0046] In the first step, simultaneously with the above adsorption step, a desorption step is performed in the second adsorption tower 12. In the desorption step, hydrogen is supplied to the second adsorption tower 12 using the hydrogen flow path 30. Specifically, the carbon dioxide recovery control device 50 opens the hydrogen inlet valve 32a and closes the hydrogen inlet valve 31a. Then, it opens the recovered gas outlet valve 42a and closes the recovered gas outlet valve 41a. The flow controller 30a controls the hydrogen flow rate according to the command of the carbon dioxide recovery control device 50 so that the hydrogen flow rate determined by the hydrogen flow rate determination unit 53 is achieved. As will be described in detail later, in the carbon dioxide recovery control device 50, since the hydrogen flow rate determined by the hydrogen flow rate determination unit 53 changes from moment to moment, the hydrogen flow rate supplied to the second adsorption tower 12 also changes from moment to moment. When hydrogen is supplied to the second adsorption tower 12, the partial pressure of carbon dioxide inside the second adsorption tower 12 decreases, so the carbon dioxide adsorbed on the adsorbent 12a is desorbed from the adsorbent 12a. The desorbed carbon dioxide flows into the recovered gas diversion path 42 together with hydrogen, flows through the recovered gas flow path 40, and flows into the recovered gas tank 70. In the desorption step, when hydrogen is supplied to the second adsorption tower 12, the adsorbent 12a is cooled and becomes capable of adsorbing carbon dioxide.

[0047] As shown in FIG. 4, in the second step, contrary to the first step, an adsorption step is performed in the second adsorption tower 12 and a desorption step is performed in the first adsorption tower 11. Specifically, the carbon dioxide recovery control device 50 opens the exhaust gas inlet valve 22a and controls each valve so that the off-gas diversion path 24 and the off-gas discharge path 25 are connected via the three-way valve 25a. Thereby, the exhaust gas flowing through the exhaust gas flow path 20 is supplied to the second adsorption tower 12 via the exhaust gas diversion path 22. In the second adsorption tower 12, the carbon dioxide contained in the exhaust gas is trapped by the adsorbent 12a, and nitrogen, moisture, etc. that are not trapped by the adsorbent 12a are discharged to the outside of the carbon dioxide recovery device 200 as off-gas via the off-gas diversion path 24 and the off-gas flow path 25.

[0048] In the second step, simultaneously with the above adsorption step, a desorption step is executed in the first adsorption tower 11. In the desorption step, hydrogen is supplied to the first adsorption tower 11 using the hydrogen flow path 30. Specifically, the carbon dioxide recovery control device 50 opens the hydrogen inlet valve 31a and closes the hydrogen inlet valve 32a. Then, it opens the recovered gas outlet valve 41a and closes the recovered gas outlet valve 42a. The flow controller 30a controls the flow rate of hydrogen according to the command of the carbon dioxide recovery control device 50 so that the hydrogen flow rate determined by the hydrogen flow rate determination unit 53 is achieved. When hydrogen is supplied to the first adsorption tower 11, the carbon dioxide adsorbed on the adsorbent 11a desorbs from the adsorbent 11a, flows into the recovered gas diversion path 41 together with hydrogen, flows through the recovered gas flow path 40, and flows into the recovered gas tank 70.

[0049] FIG. 5 is a flowchart of carbon dioxide recovery control in the carbon dioxide recovery device 200. The carbon dioxide recovery control starts when the hydrocarbon production device 100 is started and an instruction to start carbon dioxide recovery is input, and is repeatedly executed until an end instruction is input. The carbon dioxide recovery control is executed by the cooperation of the process control unit 51, the breakthrough time prediction unit 52, and the hydrogen flow rate determination unit 53.

[0050] In step S10, the process control unit 51 sets the process serial number N (FIG. 2) to N = 0, and in step S11, sets the predicted time n in each adsorption step to n = 0.

[0051] In step S20, the process control unit 51 causes an adsorption step to be executed in one of the adsorption towers 10. Here, the exhaust gas discharged from the exhaust gas supply device is supplied to the adsorption tower 10 as it is without the flow rate being adjusted. That is, when the flow rate of the exhaust gas discharged from the exhaust gas supply device fluctuates, the flow rate of the exhaust gas flowing into the adsorption tower 10 also fluctuates. When N = 2m (m is an integer greater than or equal to 0), in step S20, an adsorption step is executed in the first adsorption tower 11, and when N = 2m + 1 (m is an integer greater than or equal to 0), in step S20, an adsorption step is executed in the second adsorption tower 12. That is, when N = 0, in step S20, an adsorption step is executed in the first adsorption tower 11.

[0052] In step S12, the process control unit 51 causes the other adsorption tower 10 to execute the desorption process. When N = 2m (m is an integer of 0 or more), in step S12, the desorption process is executed in the second adsorption tower 12. When N = 2m + 1 (m is an integer of 0 or more), in step S12, the desorption process is executed in the first adsorption tower 11. At this time, the process control unit 51 controls the flow controller 30a to supply hydrogen with a hydrogen flow rate mf(n). In this way, when N = 2m (m is an integer of 0 or more), the first process is executed (FIGS. 2 and 3), and when N = 2m + 1 (m is an integer of 0 or more), the second process is executed (FIGS. 2 and 4). When N = 0, in step S12, the desorption process is executed in the second adsorption tower 12. When the prediction time n = 0, the hydrogen flow rate mf(n) is set in advance as the initial value of the hydrogen flow rate (hydrogen flow rate mf(0)), and the process control unit 51 supplies hydrogen so as to obtain the preset hydrogen flow rate mf(0). As the hydrogen flow rate mf(0), for example, when exhaust gas is supplied from the exhaust gas supply device at a predetermined flow rate and carbon dioxide is adsorbed up to the maximum adsorption amount in the adsorption tower 10, the flow rate of hydrogen for desorbing all the carbon dioxide in the time required to adsorb the maximum adsorption amount of carbon dioxide is set.

[0053] In step S13, the process control unit 51 determines whether it is immediately before the breakthrough of carbon dioxide for the adsorption tower 10 in which the adsorption tower process is being performed. In the present embodiment, the breakthrough of carbon dioxide is determined based on the off-gas temperature at the outlet of the adsorption tower 10 detected by the temperature sensor 84 or the temperature sensor 85. Since the adsorption reaction in which carbon dioxide is adsorbed by the adsorbent is an exothermic reaction, the temperature of the off-gas rises as the adsorption amount of carbon dioxide increases. Therefore, by monitoring the temperature of the off-gas, the breakthrough of carbon dioxide can be determined. In the present embodiment, experimentally, the relationship between the breakthrough of carbon dioxide and the off-gas temperature is examined in advance, and the off-gas temperature immediately before the breakthrough of carbon dioxide is set as a threshold value. When the off-gas temperature detected by the temperature sensor 84 or the temperature sensor 85 exceeds the threshold value, it is determined that it is immediately before the breakthrough of carbon dioxide. Note that "immediately before the breakthrough" is set, for example, within 5 minutes before the breakthrough time. The off-gas temperature in the present embodiment is also referred to as "carbon dioxide breakthrough information".

[0054] In step S13, when it is determined that carbon dioxide has not broken through (step S13: NO), the process proceeds to step S14. Specifically, when the off-gas temperature detected by the temperature sensor 84 or the temperature sensor 85 is lower than the threshold value, it is determined that carbon dioxide has not broken through.

[0055] In step S14, the process control unit 51 determines whether the time dt has elapsed since the start of one process. Until the time dt elapses, steps S13 and S14 are repeated, and if it becomes immediately before the breakthrough of carbon dioxide during the process, the process is switched (step S16). The time dt is an interval for predicting the breakthrough time described later, and in the present embodiment, it is set to, for example, 1 minute. The time dt can be arbitrarily set.

[0056] In step S14, when the time dt has elapsed (step S14: YES), the process control unit 51 sets the prediction time n = n + 1 (step S15). In the first step S14, the prediction time n is updated to 1.

[0057] In step S30, the breakthrough time prediction unit 52 predicts the breakthrough time t(n), which is the time until carbon dioxide breaks through at the prediction time n = n (current time). In the first step S30, the breakthrough time t(1) at the prediction time n = 1 is predicted. The prediction process of the breakthrough time t(n) will be described in detail later.

[0058] In step S40, the hydrogen flow rate determination unit 53 determines the hydrogen flow rate mf(n) according to the breakthrough time t(n), and returns to steps S12 and S20. In the first step S40, the hydrogen flow rate mf(1) is determined. That is, the hydrogen flow rate is updated from the initial value mf(0) of the hydrogen flow rate to mf(1). The determination process of the hydrogen flow rate mf(n) will be described in detail later.

[0059] In step S12, the process control unit 51 adjusts the hydrogen flow rate so that it becomes the hydrogen flow rate mf(n) determined in the most recently executed step S40. That is, in the second step S12, the process control unit 51 adjusts the hydrogen flow rate so that it becomes the hydrogen flow rate mf(1). In step S20, the exhaust gas discharged from the exhaust gas supply device is supplied to the adsorption tower 10 as it is without the flow rate being adjusted.

[0060] In this way, while the first step is being performed, the carbon dioxide recovery control device 50 predicts the breakthrough time t(n) of carbon dioxide in the first adsorption tower 11 every time dt, updates the hydrogen flow rate mf(n) according to the prediction result, and supplies hydrogen to the second adsorption tower 12 so that it becomes the updated hydrogen flow rate mf(n). On the other hand, regardless of the predicted breakthrough time, the process is switched immediately before carbon dioxide breaks through in the first adsorption tower 11 using the temperature at the off-gas outlet of the first adsorption tower 11. Also in the second step, similar to the first step, while the second step is being performed, the carbon dioxide recovery control device 50 predicts the breakthrough time t(n) of carbon dioxide in the second adsorption tower 12 every time dt, updates the hydrogen flow rate mf(n) according to the prediction result, and supplies hydrogen to the first adsorption tower 11 so that it becomes the updated hydrogen flow rate mf(n).

[0061] In step S13, when it is determined that it is immediately before the breakthrough of carbon dioxide (step S13: YES), the process proceeds to step S16, and the process control unit 51 switches the process, sets N = N + 1, returns to step S11, and resets the prediction time n = 0 (step S11). That is, when the process is switched, it is reset to the prediction time n = 0, and as time elapses in the running process (the first process or the second process), the hydrogen flow rate mf(n) is updated. When N = 0, the first process is being executed as described above. When N = N + 1, N becomes 1, and the process is switched to the second process. When the first process is being executed, in step 16, the process is switched to the second process. When the second process is being executed, in step S16, the process is switched to the first process.

[0062] (Breakthrough time prediction process) FIG. 6 is a flowchart showing the flow of the breakthrough time prediction process S30 in the first embodiment. FIG. 7 is an explanatory diagram for explaining the breakthrough time prediction process.

[0063] In step S31, the breakthrough time prediction unit 52 acquires the total exhaust gas amount q(n) [L]. The total exhaust gas amount q(n) is the total amount of exhaust gas that has flowed in from the start of the adsorption process to the prediction time n. As shown in FIGS. 7(b) and 7(c), the total amount of exhaust gas that has flowed in by the prediction time n changes as the prediction time increases. The breakthrough time prediction unit 52 can acquire the total exhaust gas amount q(n) by calculating the integrated value of the measured value [L / s] of the exhaust gas flow rate input from the flow meter 81 every second.

[0064] In step S32, the breakthrough time prediction unit 52 acquires the processable exhaust gas volume qc [L]. The processable exhaust gas volume qc is the total volume of exhaust gas that the adsorption tower 10 can process in the adsorption process, and is determined in advance for each adsorption tower 10 according to the capacity of the adsorption tower 10, the type of adsorbent, the filling rate of the adsorbent, etc. As shown in Fig. 7(a), the processable exhaust gas volume qc is the total volume of exhaust gas that has flowed through the adsorption tower 10 until the adsorbent is saturated with carbon dioxide. In this embodiment, as described above, the processable exhaust gas volume 56 is stored in advance in the storage unit 54, and the breakthrough time prediction unit 52 acquires the processable exhaust gas volume 56 from the storage unit 54.

[0065] In step S33, the breakthrough time prediction unit 52 acquires the rated exhaust gas volume qf [L / s]. The rated exhaust gas volume qf is the exhaust gas flow rate determined in advance for each exhaust gas supply source, and as described above, the rated exhaust gas flow rate 55 is stored in advance in the storage unit 54. The breakthrough time prediction unit 52 acquires the rated exhaust gas flow rate 55 from the storage unit 54.

[0066] In step S34, the breakthrough time prediction unit 52 calculates the breakthrough time t(n) using the following formula (2). t(n)=(qc - q(n)) / qf … (2) However, t(n): breakthrough time predicted at prediction time n, qc: processable exhaust gas volume in the adsorption process, q(n): total volume of exhaust gas that has flowed in until prediction time n, qf: rated exhaust gas flow rate

[0067] In formula (2), qc - q(n) corresponds to the processable exhaust gas volume (L) during the remaining adsorption process period at prediction time n (Figs. 7(b) and (c)). Therefore, the breakthrough time t(n) at prediction time n can be obtained by formula (2). As shown in the figure, as time passes, the processable exhaust gas volume at prediction time n changes (decreases), so the predicted breakthrough time t(n) becomes shorter as time passes. However, due to fluctuations in the exhaust gas flow rate, the increase amount of q(n) also fluctuates, so the decrease amount of the processable exhaust gas volume (qc - q(n)) at prediction time n also fluctuates, and the decrease amount of the breakthrough time t(n) also fluctuates.

[0068] (Hydrogen flow rate determination process) FIG. 8 is a flowchart showing the flow of the hydrogen flow rate determination process S40 in the first embodiment.

[0069] As shown in FIG. 8, in step S41, the hydrogen flow rate determination unit 53 determines the relationship between the breakthrough time t(n) predicted at the prediction time n and the breakthrough time t(n−1) predicted at the prediction time (n−1) one time step before (before time dt).

[0070] When the relationship between the breakthrough time t(n) and the breakthrough time t(n−1) is t(n−1)<t(n)+dt … (First relationship) the process proceeds to step S42, and the hydrogen flow rate mf(n) is decreased from the hydrogen flow rate mf(n−1) set one time step before.

[0071] For example, using the amount of exhaust gas (qc - q(n)) that can be processed at the prediction time n, the amount of carbon dioxide adsorbed on the adsorbent of the adsorption tower 10 until carbon dioxide breaks through is calculated, and the amount of hydrogen that is neither excessive nor insufficient to desorb the calculated carbon dioxide is divided by the breakthrough time t(n) to obtain the hydrogen flow rate mf(n).

[0072] The case where the relationship between the breakthrough time t(n) at the prediction time n and the breakthrough time t(n - 1) at the previous prediction time (n - 1) is the first relationship means that the exhaust gas flow rate flowing into the adsorption tower 10 has become less than at the prediction time (n - 1). That is, the time from the start of the process (the first process or the second process) until carbon dioxide breaks through (the time of the adsorption process) has become longer than the predicted time (the time of the adsorption process) at the prediction time (n - 1), and it is predicted that the time of the ongoing process (the first process or the second process) will become longer. In each process, the desorption process is executed simultaneously with the adsorption process and has the same period, so it is predicted that the desorption process will also become longer as the adsorption process becomes longer. Therefore, by making the hydrogen flow rate mf(n) at the prediction time n less than the hydrogen flow rate mf(n - 1) at the prediction time (n - 1), it is possible to suppress the amount of hydrogen supplied in the desorption process from becoming excessive. As a result, fluctuations in the carbon dioxide concentration in the recovered gas can be suppressed.

[0073] When the relationship between the breakthrough time t(n) and the breakthrough time t(n - 1) is t(n - 1)>t(n)+dt … (Second relationship) in this case, proceed to step S43 and increase the hydrogen flow rate mf(n) from the hydrogen flow rate mf(n - 1) set one time step before.

[0074] The hydrogen flow rate mf(n) can be obtained in the same manner as in the case where the relationship between the breakthrough time t(n) and the breakthrough time t(n - 1) is the first relationship.

[0075] The case where the relationship between the breakthrough time t(n) and the breakthrough time t(n - 1) is the second relationship means that the exhaust gas flow rate flowing into the adsorption tower 10 is greater than at the prediction time (n - 1). That is, the time from the start of the process (the first process or the second process) until carbon dioxide breaks through (the time of the adsorption process) is shorter than the time predicted at the prediction time (n - 1) (the time of the adsorption process), and it is predicted that the time of the process being executed (the first process or the second process) will be shortened. In each process, the desorption process is executed simultaneously with the adsorption process and has the same period, so it is predicted that the desorption process will also be shortened when the adsorption process is shortened. Therefore, by making the hydrogen flow rate mf(n) at the prediction time n greater than the hydrogen flow rate mf(n - 1) at the prediction time (n - 1), it is possible to suppress the shortage of the amount of hydrogen supplied in the desorption process. Therefore, in the desorption process, the amount of carbon dioxide remaining in the adsorption tower 10 without being desorbed can be reduced. As a result, fluctuations in the carbon dioxide concentration in the recovered gas can be suppressed.

[0076] When the relationship between the breakthrough time t(n) and the breakthrough time t(n - 1) is t(n - 1)=t(n)+dt … (the third relationship) then, proceed to step S44 and set the hydrogen flow rate mf(n) to be the same as the hydrogen flow rate mf(n - 1) set one time step before.

[0077] The case where the relationship between the breakthrough time t(n) and the breakthrough time t(n - 1) is the third relationship means that the exhaust gas flow rate flowing into the adsorption tower 10 is the same (unchanged) as that at the prediction time (n - 1). That is, it is the case where the time from the start of the process (the first process or the second process) until carbon dioxide breaks through (the time of the adsorption process) is the same as the predicted time (the time of the adsorption process) at the prediction time (n - 1), and it is predicted that the time of the ongoing process (the first process or the second process) does not change. In each process, the desorption process is carried out simultaneously with the adsorption process and the periods are equal, so it is predicted that the desorption process also does not change. Therefore, by making the hydrogen flow rate mf(n) at the prediction time n the same as the hydrogen flow rate mf(n - 1) at the prediction time (n - 1), fluctuations in the carbon dioxide concentration in the recovered gas can be suppressed.

[0078] FIG. 9 is an explanatory diagram showing an example of the relationship between the breakthrough time t(n) and the hydrogen flow rate mf(n) in the first embodiment. In this example, the initial value of the breakthrough time t(n) is set to 30 [min], the initial value of the hydrogen flow rate mf(n) is set to x1 [L / min], and dt is set to 1 [min].

[0079] The relationship between the breakthrough time t(n) and the breakthrough time t(n - 1) and the hydrogen flow rate mf(n) at each prediction time shown in FIG. 9 will be described. At the prediction time n = 1, the breakthrough time t(1) = 29 and the breakthrough time t(0) = 30, and since dt = 1, t(1) = t(0) + dt That is. The relationship between the breakthrough time t(n) and the breakthrough time t(n - 1) is the third relationship. Therefore, mf(1) = mf(0) That is, mf(1) = x1 is set. That is, mf(n) at the prediction time n maintains the hydrogen flow rate mf(n - 1) at the prediction time (n - 1).

[0080] At the prediction time n = 2, the breakthrough time t(2) = 28.5 and the breakthrough time t(1) = 29, and since dt = 1, t(1) < t(2) + dt That is, the relationship between the breakthrough time t(n) and the breakthrough time t(n - 1) is the first relationship. Therefore, mf(2) = x2 (x2 < x1) is set. That is, mf(n) at the prediction time n is made lower than the hydrogen flow rate mf(n - 1) at the prediction time (n - 1).

[0081] At the prediction time n = 3, the breakthrough time t(3) = 26, the breakthrough time t(2) = 28.5, and dt = 1. Therefore, t(2) > t(3) + dt That is, the relationship between the breakthrough time t(n) and the breakthrough time t(n - 1) is the second relationship. Therefore, mf(3) = x3 (x3 > x2) is set. That is, mf(n) at the prediction time n is made higher than the hydrogen flow rate mf(n - 1) at the prediction time (n - 1).

[0082] The program for realizing the above carbon dioxide recovery control may be stored in advance in the carbon dioxide recovery control device 50. Also, the program may be provided from the program provider side via a communication network. Further, the program may be stored in a commercially available and circulating portable storage medium. In this case, this portable storage medium may be set in an external or built-in reading device, and the program may be read and executed by the carbon dioxide recovery 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, and USB memory device can be used. The program stored in such a storage medium is read by the reading device.

[0083] As described above, according to the carbon dioxide recovery apparatus 200 of the present embodiment, in the first step or the second step, the adsorption step and the desorption step are executed simultaneously. That is, in each adsorption tower 10, while the adsorption step is being performed in one adsorption tower 10, the desorption step is being performed in the other adsorption tower 10, and there is no waiting period in the step being executed (the first step or the second step). Further, in the carbon dioxide recovery apparatus 200, the breakthrough time, which is the time until carbon dioxide breaks through in the adsorption tower 10 where the adsorption step is being executed, is predicted moment by moment, and according to the prediction result, the hydrogen flow rate in the adsorption tower 10 where the desorption step is being performed is updated moment by moment. Since the breakthrough time t(n) is calculated based on the exhaust gas flow rate, it can be said that the hydrogen flow rate flowing through the adsorption tower 10 functioning as the desorption tower is varied according to the variation in the exhaust gas flow rate flowing into the adsorption tower 10 functioning as the adsorption tower. Here, since the hydrogen flow rate is decreased when the exhaust gas flow rate increases and the hydrogen flow rate is increased when the exhaust gas flow rate decreases, an excess or deficiency of hydrogen in the desorption step can be suppressed. As a result, variations in the carbon dioxide concentration and the flow rate of the recovered gas can be suppressed.

[0084] According to the carbon dioxide recovery apparatus 200 of the present embodiment, the switching between the first step and the second step is performed immediately before carbon dioxide breaks through in the adsorption tower 10 functioning as the adsorption tower. Therefore, the amount of carbon dioxide that is not adsorbed by the adsorbent and is discharged as off-gas can be suppressed. That is, the recovery rate of carbon dioxide from the exhaust gas by the carbon dioxide recovery apparatus 200 can be improved.

[0085] According to the hydrocarbon production apparatus 100 of the present embodiment, as described above, fluctuations in the carbon dioxide concentration and fluctuations in the flow rate of the recovered gas in the carbon dioxide recovery apparatus 200 can be suppressed. Therefore, in the hydrocarbon generation unit 60 that generates a product gas mainly composed of methane using the recovered gas, a decrease in the methane purity of the product gas due to fluctuations in the flow rate and concentration of the recovered gas can be suppressed. In addition, deactivation of the hydrocarbonation catalyst in the hydrocarbon generation unit 60 due to fluctuations in the exhaust gas flow rate can be suppressed. Therefore, in the product gas generated in the hydrocarbon production apparatus 100, a decrease in the methane purity due to fluctuations in the flow rate of the exhaust gas supplied to the hydrocarbon production apparatus 100 can be suppressed.

[0086] <Second Embodiment> FIG. 10 is an explanatory diagram showing a schematic configuration of a hydrocarbon production apparatus 100A according to the second embodiment. The hydrocarbon production apparatus 100A according to the second embodiment has a carbon dioxide recovery apparatus 200A instead of the carbon dioxide recovery apparatus 200 in the configuration of the first embodiment. In the embodiments described below, the same components as those of the hydrocarbon production apparatus 100 are denoted by the same reference numerals, and reference is made to the previous description.

[0087] The carbon dioxide recovery apparatus 200A includes a carbon dioxide concentration sensor 82 and a temperature sensor 83 in addition to the configuration of the carbon dioxide recovery apparatus 200 of the first embodiment. The carbon dioxide concentration sensor 82 and the temperature sensor 83 are provided in the exhaust gas flow path 20, and detect the carbon dioxide concentration and the exhaust gas temperature in the exhaust gas, respectively, and output the detection results to the carbon dioxide recovery control device 50.

[0088] Further, the carbon dioxide recovery apparatus 200A of the present embodiment has a carbon dioxide recovery control device 50A instead of the carbon dioxide recovery control device 50. In the carbon dioxide recovery control device 50A, the method for predicting the breakthrough time in the breakthrough time prediction unit 52 and the method for calculating the hydrogen flow rate in the hydrogen flow rate determination unit 53 are different from those in the first embodiment. Further, in the storage unit 54, instead of the rated exhaust gas flow rate 55 and the treatable exhaust gas amount 56 in the first embodiment, a rated carbon dioxide flow rate 57 and a saturation adsorption amount map 58 are stored. The rated carbon dioxide flow rate 57 is the flow rate of carbon dioxide supplied from the exhaust gas supply device, and is determined in advance for each exhaust gas supply device. In the present embodiment, as the rated carbon dioxide flow rate 57, a value specific to the exhaust gas supply device connected to the hydrocarbon production apparatus 100 is input in advance by the user or the like. The saturation adsorption amount map 58 is a map showing the relationship between the carbon dioxide adsorption capacity of the adsorption tower 10, the exhaust gas temperature, and the carbon dioxide concentration. In the embodiment, the relationship between the carbon dioxide adsorption capacity (maximum adsorption amount) in the adsorption tower 10, the exhaust gas temperature, and the carbon dioxide concentration is experimentally investigated in advance, and the result is input to the storage unit 54 by the user or the like as a map showing the result. Further, it may be stored in advance at the time of manufacturing the hydrocarbon production apparatus 100A.

[0089] (Breakthrough Time Prediction Process) FIG. 11 is a flowchart showing the flow of the breakthrough time prediction process in the second embodiment.

[0090] In step S31A, the breakthrough time prediction unit 52 calculates the total amount of carbon dioxide C(n) [L]. The total amount of carbon dioxide C(n) is the total amount of carbon dioxide that has flowed in from the start of the adsorption process to the prediction time n. The breakthrough time prediction unit 52 calculates the carbon dioxide flow rate [L / s] every second using the measured value [L / s] of the exhaust gas flow rate input from the flow meter 81 every second and the measured value of the carbon dioxide concentration input from the carbon dioxide concentration sensor 82 every second, and calculates the integrated value of the carbon dioxide flow rate [L / s], whereby the total amount of carbon dioxide C(n) can be obtained.

[0091] In step S32A, the breakthrough time prediction unit 52 acquires the saturated adsorption amount Ca [L]. The saturated adsorption amount Ca is the total amount of carbon dioxide (maximum adsorption amount) that the adsorption tower 10 can adsorb in the adsorption process, and can be obtained from the saturated adsorption amount map 58 stored in the storage unit 54 using the exhaust gas temperature (acquired from the temperature sensor 83) and the carbon dioxide concentration (acquired from the carbon dioxide concentration sensor 82) at the prediction time n.

[0092] In step S33A, the breakthrough time prediction unit 52 acquires the rated carbon dioxide flow rate Cf [L / s]. The rated carbon dioxide flow rate Cf is the carbon dioxide flow rate determined in advance for each exhaust gas supply source, and as described above, is stored in the storage unit 54 in advance as the rated carbon dioxide flow rate 57. The breakthrough time prediction unit 52 acquires the rated carbon dioxide flow rate 57 from the storage unit 54.

[0093] In step S34A, the breakthrough time prediction unit 52 calculates the breakthrough time t(n) using the following formula (3). t(n)=(Ca-C(n)) / Cf … (3) However, t(n): breakthrough time predicted at the prediction time n; Ca: saturated adsorption amount; C(n): total amount of carbon dioxide that has flowed in up to the prediction time n; Cf: rated carbon dioxide flow rate

[0094] In formula (3), Ca - C(n) corresponds to the amount of carbon dioxide (L) that can be adsorbed during the remaining adsorption process at the prediction time n. Therefore, the breakthrough time t(n) at the prediction time n can be obtained using formula (3). As time passes, the amount of carbon dioxide that can be adsorbed at the prediction time n changes (decreases), so the predicted breakthrough time t(n) becomes shorter as time passes. However, due to fluctuations in the carbon dioxide flow rate, the increase amount of C(n) also fluctuates, so the decrease amount of the amount of carbon dioxide that can be adsorbed (Ca - C(n)) at the prediction time n also fluctuates, and the decrease amount of the breakthrough time t(n) also fluctuates.

[0095] In this embodiment, the breakthrough time t(n) is predicted using the flow rate, temperature, and carbon dioxide concentration of the exhaust gas. Since the adsorption amount of carbon dioxide in the adsorption tower 10 varies depending on the flow rate, temperature, and carbon dioxide concentration of the exhaust gas, the breakthrough time can be predicted more accurately than in the first embodiment.

[0096] (Hydrogen flow rate determination process) In the second embodiment, the hydrogen flow rate determination unit 53 calculates the hydrogen flow rate mf(n) according to the following formula (1).

[0097] mf(n)=(ma - mp) / t(n)… (1) However, mp: the amount of hydrogen that has flowed through the adsorption tower from the start of the desorption process to the prediction time n, ma: the total amount of hydrogen that can flow through the adsorption tower during the entire desorption process, t(n): the breakthrough time at the prediction time n

[0098] The amount of hydrogen mp [L] that has flowed through the adsorption tower from the start of the desorption process to the prediction time n can be obtained by integrating the hydrogen flow rate [L / s] input from the flow controller 30a every second.

[0099] In this embodiment, the total amount of hydrogen ma that can flow through the adsorption tower during the entire desorption process is obtained as follows. In the adsorption process performed before the current desorption process, the total amount of carbon dioxide adsorbed in the adsorption tower 10 is predicted using the exhaust gas flow rate input from the flow meter 81, the carbon dioxide concentration input from the carbon dioxide concentration sensor 82, the temperature input from the temperature sensor 83, and the saturated adsorption amount map 58. Then, the amount of hydrogen required to desorb all the predicted carbon dioxide adsorption amount is calculated and set as the total hydrogen amount ma [L]. The total hydrogen amount ma does not change even when n is incremented.

[0100] The breakthrough time t(n) is the breakthrough time calculated at the prediction time n as described above.

[0101] When the temperature and carbon dioxide concentration of the exhaust gas flowing into the adsorption tower 10 change, the saturated adsorption amount of carbon dioxide changes. Specifically, the lower the temperature of the exhaust gas, the larger the saturated adsorption amount, and the higher the carbon dioxide concentration in the exhaust gas, the larger the saturated adsorption amount. In this embodiment, the hydrogen flow rate mf(n) is calculated using the total amount of hydrogen ma corresponding to the carbon dioxide adsorption amount calculated using the carbon dioxide concentration and exhaust gas temperature in the exhaust gas. Therefore, in order to desorb the carbon dioxide adsorbed inside the adsorption tower 10, the hydrogen flow rate mf(n) can be set to a more appropriate (neither excessive nor insufficient) amount. As a result, fluctuations in the flow rate and concentration of the recovered gas can be further suppressed. And the methane purity of the product gas can be further improved.

[0102] <Modification Example of this Embodiment> The present invention is not limited to the above-described embodiments, and can be implemented in various aspects without departing from the gist thereof. For example, the following modifications are possible. Also, in the above embodiment, a part of the configuration realized by hardware may be replaced with software, or conversely, a part of the configuration realized by software may be replaced with hardware.

[0103] ·In the above embodiment, in one adsorption step, an example was shown in which the breakthrough time t(n) was predicted and the hydrogen flow rate mf(n) was updated multiple times. However, in one adsorption step, the breakthrough time may be predicted only once, and the hydrogen flow rate may be determined based on the predicted breakthrough time. For example, at the start of the adsorption step, the breakthrough time may be predicted using the exhaust gas flow rate, and the hydrogen flow rate may be determined according to the predicted breakthrough time. By doing so, compared with the case where the hydrogen flow rate is not changed or the hydrogen flow rate is changed to a predetermined value regardless of the breakthrough time, fluctuations in the flow rate of the recovered gas and the concentration of carbon dioxide can be suppressed. In particular, when the fluctuation of the exhaust gas flow rate is relatively gentle, the fluctuations in the flow rate and concentration of the recovered gas can be appropriately suppressed.

[0104] ·In the above embodiment, when predicting the breakthrough time t(n) multiple times in one adsorption process, an example of the method for determining the hydrogen flow rate mf(n) based on the relationship between the breakthrough time t(n) and the breakthrough time t(n - 1) was shown. However, the method for determining the hydrogen flow rate mf(n) is not limited to the above embodiment. For example, when t(n - 1) < t(n) + dt, the hydrogen flow rate mf(n) may be decreased from the hydrogen flow rate mf(n - 1), and when t(n - 1) ≥ t(n) + dt, the hydrogen flow rate mf(n) may be maintained (the same as the hydrogen flow rate mf(n - 1)). Even in this case, at least an excessive supply of hydrogen to the adsorption tower 10 can be suppressed.

[0105] ·The method for calculating the breakthrough time is not limited to the above embodiment. For example, the breakthrough time may be obtained using a map or relational expression showing the relationship between the exhaust gas flow rate and the breakthrough time. The breakthrough time may be obtained using a map or relational expression showing the relationship between the exhaust gas flow rate, the carbon dioxide concentration in the exhaust gas, the exhaust gas temperature, and the breakthrough time. Alternatively, it may be obtained by simulation.

[0106] The method for determining the hydrogen flow rate is not limited to the above embodiment. For example, in the formula (1) shown in the second embodiment, the total amount of hydrogen ma may be a fixed value. Specifically, assuming that the same amount of carbon dioxide is adsorbed in each process, the amount of hydrogen required to separate the amount of carbon dioxide may be used as the total amount of hydrogen ma.

[0107] · In the above-described embodiment, an example in which the temperature of the off-gas is used as carbon dioxide breakthrough information, which is information regarding the breakthrough of carbon dioxide, has been shown. However, the breakthrough of carbon dioxide may be predicted using other information. For example, the carbon dioxide concentration in the off-gas may be used as the carbon dioxide breakthrough information. Specifically, carbon dioxide concentration sensors may be provided in the off-gas diversion passages 23 and 24, and the outflow of carbon dioxide may be detected based on the carbon dioxide concentration in the off-gas. Further, the exhaust gas flow rate and the off-gas flow rate may be used as the carbon dioxide breakthrough information. Specifically, flow meters may be provided in the off-gas diversion passages 23 and 24, and the outflow of carbon dioxide may be detected from the difference between the flow rate of the exhaust gas flowing into the adsorption tower 10 and the flow rate of the gas (off-gas) flowing out from the adsorption tower 10.

[0108] · In the above-described embodiment, an example in which the first step and the second step are switched immediately before carbon dioxide breaks through has been shown. However, the first step and the second step may be switched when carbon dioxide breaks through. Switching the steps immediately before breakthrough is preferable because the carbon dioxide recovery efficiency from the exhaust gas can be improved.

[0109] · In the above-described embodiment, an example in which the carbon dioxide recovery apparatus includes two adsorption towers has been shown. However, a configuration including three or more adsorption towers may be employed.

[0110] · In the above-described embodiment, an example in which a plurality of cycles are repeatedly executed with one adsorption tower having an adsorption step and a desorption step as one cycle has been shown. However, another step may be further executed. For example, one cycle may include an adsorption step, a desorption step, and a cooling step, or one cycle may include an adsorption step, a preheating step, a desorption step, and a cooling step.

[0111] · The carbon dioxide recovery apparatus according to the above-described embodiment may further be configured to include a temperature adjustment unit (e.g., a heater, a heat medium, etc.) for adjusting the temperature of the adsorption tower.

[0112] ·In the above embodiment, an example of carbon dioxide recovery control was shown. However, the procedure for hydrocarbon recovery control can be variously modified, and the processing content in each step may be added / omitted / changed, or the execution order of the steps may be changed.

[0113] ·In the above embodiment, a hydrocarbon production apparatus including a carbon dioxide recovery apparatus and a hydrocarbon generation unit was exemplified, but it may be configured as a single carbon dioxide recovery apparatus or as a single carbon dioxide recovery control apparatus.

[0114] The present invention has been described based on the embodiments and modification examples above. However, the embodiments in the above-described modes are for facilitating the understanding of the present invention and do not limit the present invention. The present invention can be changed and improved without departing from the gist and scope of the claims, and equivalents thereof are included in the present invention. Also, if the technical features are not described as essential in this specification, they can be deleted as appropriate.

Explanation of Reference Numerals

[0115] 10... Adsorption tower 11... First adsorption tower 11a, 12a... Adsorbents 12... Second adsorption tower 20... Exhaust gas flow path 21, 22... Exhaust gas diversion paths 21a... Exhaust gas inlet valve 22a... Exhaust gas inlet valve 23, 24... Off-gas diversion paths 25... Off-gas flow path 25a... Three-way valve 30... Hydrogen flow path 30a... Flow controller 31, 32... Hydrogen diversion paths 31a, 32a... Hydrogen inlet valves 40... Recovered gas flow path 41, 42... Recovered gas diversion paths 41a, 42a... Recovered gas outlet valves 50, 50A... Carbon dioxide recovery control apparatuses 51... Process control unit 52…Breakthrough time prediction unit 53…Hydrogen flow rate determination unit 54…Memory unit 55…Rated exhaust gas flow rate 56…Processable exhaust gas amount 57…Rated carbon dioxide flow rate 58…Saturation adsorption amount map 60…Hydrocarbon generation unit 62…Hydrogen flow path 62a…Flow controller 63…Product gas flow path 70…Recovery gas tank 72…Recovery gas flow path 81…Flow meter 82…Carbon dioxide concentration sensor 83…Temperature sensor 84…Temperature sensor 85…Temperature sensor 100, 100A…Hydrocarbon production device 200, 200A…Carbon dioxide recovery device

Claims

1. A carbon dioxide recovery control device that performs carbon dioxide recovery control to recover carbon dioxide from a mixed gas containing carbon dioxide using a plurality of adsorption towers including at least a first adsorption tower and a second adsorption tower, a first step of performing an adsorption step of supplying the mixed gas to the first adsorption tower and simultaneously performing a desorption step of supplying hydrogen to the second adsorption tower; and a second step of performing an adsorption step of supplying the mixed gas to the second adsorption tower and simultaneously performing a desorption step of supplying hydrogen to the first adsorption tower, and a process control unit that repeatedly executes the steps; a breakthrough time prediction unit that predicts a breakthrough time, which is the time from a predetermined prediction time until carbon dioxide leaks out of the adsorption tower, in the adsorption tower in which the adsorption step is being performed; a hydrogen flow rate determination unit that determines a hydrogen flow rate for controlling the flow rate of hydrogen flowing through the adsorption tower in the desorption step that is being executed simultaneously according to the breakthrough time predicted by the breakthrough time prediction unit; comprising the process control unit controls the flow rate of hydrogen flowing through the adsorption tower in which the desorption step is being executed so as to be the hydrogen flow rate determined by the hydrogen flow rate determination unit, acquires carbon dioxide breakthrough information, which is information regarding breakthrough of carbon dioxide in the adsorption tower in which the adsorption step is being executed, and based on the carbon dioxide breakthrough information, switches between the first step and the second step when breakthrough of carbon dioxide occurs or immediately before breakthrough of carbon dioxide occurs, carbon dioxide recovery control device.

2. The carbon dioxide recovery control device according to claim 1, wherein the breakthrough time prediction unit predicts the breakthrough time at predetermined time intervals, the hydrogen flow rate determination unit updates the hydrogen flow rate at predetermined time intervals according to the predicted breakthrough time, when the predetermined time is dt, the prediction time is n (n is an integer of 1 or more), and the breakthrough time predicted at the prediction time n is t(n), the hydrogen flow rate determination unit When the relationship between the breakthrough time t(n) predicted at the prediction time n and the breakthrough time t(n−1) predicted at the prediction time (n−1) is the first relationship, the hydrogen flow rate at the prediction time n is decreased from the hydrogen flow rate at the prediction time (n−1); when the relationship is the second relationship, the hydrogen flow rate at the prediction time n is increased from the hydrogen flow rate at the prediction time (n−1); and when the relationship is the third relationship, the hydrogen flow rate at the prediction time n is made the same as the hydrogen flow rate at the prediction time (n−1). The first relationship is t(n−1) < t(n) + dt. The second relationship is t(n−1) > t(n) + dt. The third relationship is t(n−1) = t(n) + dt. Carbon dioxide recovery control device.

3. The carbon dioxide recovery control device according to claim 1, wherein the hydrogen flow rate determination unit acquires the amount of hydrogen that has flowed through the adsorption tower from the start of the desorption process to the prediction time and the total amount of hydrogen that can flow through the adsorption tower during the entire period of the desorption process, and determines the hydrogen flow rate to be passed through the adsorption tower during the desorption process after the prediction time by the following formula (1). Carbon dioxide recovery control device. mf(n) = (ma − mp) / t(n)… (1) where mf(n): hydrogen flow rate to be passed through the adsorption tower during the desorption process after the prediction time n; mp: amount of hydrogen that has flowed through the adsorption tower from the start of the desorption process to the prediction time n; ma: total amount of hydrogen that can flow through the adsorption tower during the entire period of the desorption process; t(n): breakthrough time predicted at the prediction time n

4. The carbon dioxide recovery control device according to any one of claims 1 to 3, wherein the breakthrough time prediction unit in the adsorption process, acquires the total amount of the mixed gas that has flowed into the adsorption tower by the prediction time, the amount of the mixed gas that can be processed in the adsorption process, and the rated mixed gas flow rate which is the flow rate of the mixed gas predetermined for each supply source of the mixed gas, and predicts the breakthrough time by the following formula (2). Carbon dioxide recovery control device. t(n) = (qc − q(n)) / qf… (2) where t(n): breakthrough time predicted at the prediction time n; qc: amount of the mixed gas that can be processed in the adsorption process; q(n): total amount of the mixed gas that has flowed in by the prediction time n; qf: rated mixed gas flow rate

5. The carbon dioxide recovery control device according to any one of claims 1 to 3, wherein the breakthrough time prediction unit Obtain the flow rate of the mixed gas flowing into the adsorption tower, the temperature of the mixed gas, and the concentration of carbon dioxide in the mixed gas. In the adsorption step, calculate the total amount of carbon dioxide that has flowed in up to the prediction time using the flow rate of the mixed gas and the concentration of carbon dioxide in the mixed gas. In the adsorption step, calculate the saturated adsorption amount of carbon dioxide using the temperature of the mixed gas at the prediction time and the concentration of carbon dioxide in the mixed gas. Obtain the rated carbon dioxide flow rate, which is the carbon dioxide flow rate predetermined for each supply source of the mixed gas. Predict the breakthrough time according to the following formula (3). Carbon dioxide recovery control device. t(n) = (Ca - C(n)) / Cf... (3) However, t(n): breakthrough time predicted at prediction time n, Ca: saturated adsorption amount of carbon dioxide, C(n): total amount of carbon dioxide that has flowed in up to prediction time n, Cf: rated carbon dioxide flow rate

6. A carbon dioxide recovery device, The carbon dioxide recovery control device according to any one of Claims 1 to 5, An adsorption tower capable of separating carbon dioxide from a mixed gas containing carbon dioxide, including a plurality of adsorption towers including at least a first adsorption tower and a second adsorption tower, A mixed gas supply unit capable of supplying the mixed gas to the plurality of adsorption towers, A hydrogen supply unit capable of supplying hydrogen to the plurality of adsorption towers, A carbon dioxide recovery device comprising the above.

7. A hydrocarbon production device, The carbon dioxide recovery device according to Claim 6, A hydrocarbon production unit having a hydrocarbon reforming catalyst inside and generating a hydrocarbon compound using a recovered gas containing carbon dioxide and hydrogen flowing out from the carbon dioxide recovery device. A hydrocarbon production device.

8. A carbon dioxide recovery method for recovering carbon dioxide from a mixed gas containing carbon dioxide using a plurality of adsorption towers including at least a first adsorption tower and a second adsorption tower, A first step of performing an adsorption step of supplying the mixed gas to the first adsorption tower and simultaneously performing a desorption step of supplying hydrogen to the second adsorption tower, and a second step of performing an adsorption step of supplying the mixed gas to the second adsorption tower and simultaneously performing a desorption step of supplying hydrogen to the first adsorption tower, and repeating these steps, In the adsorption tower in which the adsorption step is being performed, predict the breakthrough time, which is the time from a predetermined prediction time until carbon dioxide leaks out of the adsorption tower. Determine a hydrogen flow rate for controlling the flow rate of hydrogen to be passed through the adsorption tower in the desorption process that is being executed simultaneously according to the predicted breakthrough time, Control the flow rate of hydrogen to be passed through the adsorption tower in which the desorption process is being executed so as to be the determined hydrogen flow rate, Obtain carbon dioxide breakthrough information, which is information regarding the breakthrough of carbon dioxide in the adsorption tower in which the adsorption process is being executed, and based on the carbon dioxide breakthrough information, switch the first step and the second step when the breakthrough of carbon dioxide occurs or immediately before the breakthrough of carbon dioxide occurs, Carbon dioxide recovery method.

9. A program for controlling a carbon dioxide recovery apparatus that recovers carbon dioxide from a mixed gas containing carbon dioxide using a plurality of adsorption towers including at least a first adsorption tower and a second adsorption tower, the program causing a computer to execute a first step of simultaneously executing an adsorption step of supplying the mixed gas to the first adsorption tower and a desorption step of supplying hydrogen to the second adsorption tower, and a second step of simultaneously executing an adsorption step of supplying the mixed gas to the second adsorption tower and a desorption step of supplying hydrogen to the first adsorption tower, and repeatedly execute the steps, a breakthrough time prediction function for predicting a breakthrough time, which is the time from a predetermined prediction time until carbon dioxide leaks out of the adsorption tower in the adsorption tower in which the adsorption process is being executed, a hydrogen flow rate determination function for determining a hydrogen flow rate for controlling the flow rate of hydrogen to be passed through the adsorption tower in the desorption process that is being executed simultaneously according to the breakthrough time predicted by the breakthrough time prediction function, be realized, In the process control function, control the flow rate of hydrogen to be passed through the adsorption tower in which the desorption process is being executed so as to be the hydrogen flow rate determined by the hydrogen flow rate determination function, obtain carbon dioxide breakthrough information, which is information regarding the breakthrough of carbon dioxide in the adsorption tower in which the adsorption process is being executed, and based on the carbon dioxide breakthrough information, switch the first step and the second step when the breakthrough of carbon dioxide occurs or immediately before the breakthrough of carbon dioxide occurs, Program.

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