Carbon dioxide capture system

Abstract

To provide a carbon dioxide capture system with a more stable carbon dioxide capture rate. [Solution] The carbon dioxide recovery system 100 includes an absorption tower 110 that absorbs carbon dioxide from a gas containing carbon dioxide into an absorbent liquid containing water, an amine compound, and an organic solvent; a separation tank 120 that separates the absorbent liquid that has absorbed carbon dioxide into a concentrated phase 220 and a dilute phase 210; a regeneration tower 130 that separates carbon dioxide from the concentrated phase 220; a mixing tank 140 that mixes the dilute phase 210, the regeneration phase 230, water, an amine compound, and an organic solvent to reproduce the absorbent liquid; a composition analysis unit 171A that analyzes the composition of the dilute phase 210 and the regeneration phase 230; and an adjustment unit 171B that adjusts the amounts of the dilute phase 210, the regeneration phase 230, water, an amine compound, and an organic solvent supplied to the mixing tank 140 when the composition ratio of the dilute phase 210 falls outside the range of a first composition ratio or when the composition ratio of the regeneration phase 230 falls outside the range of a second composition ratio.

Description

Technical Field

[0001] The present invention relates to a carbon dioxide recovery system.

Background Art

[0002] Patent Document 1 discloses an absorbent that can reversibly absorb and desorb an acidic compound and contains water, an amine compound, and an organic solvent.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When constructing a carbon dioxide recovery system that separates and recovers carbon dioxide from a gas containing carbon dioxide (CO2) using an absorbent as described in Patent Document 1, the amount of carbon dioxide that can be absorbed by the absorbent from the gas containing carbon dioxide varies depending on the temperature and humidity of the gas. Also, the amounts of water, amine compound, and organic solvent that evaporate (volatilize) from the absorbent vary depending on the temperature and humidity of the gas. As a result, the composition of the absorbent circulating in the carbon dioxide recovery system varies. Therefore, there is a problem that the composition of the absorbent circulating in the carbon dioxide recovery system deviates from the optimal composition, and the recovery rate of carbon dioxide is not stable.

[0005] The present invention has been made to solve such problems, and an object thereof is to provide a carbon dioxide recovery system in which the recovery rate of carbon dioxide is more stable.

Means for Solving the Problems

[0006] The carbon dioxide recovery system according to the first aspect of the present invention is An absorption tower is provided with an absorption solution containing water, an amine compound, and an organic solvent, which separates into a concentrated phase with a high carbon dioxide content and a dilute phase with a low carbon dioxide content after absorbing carbon dioxide, and a gas containing carbon dioxide is also supplied to cause the absorption solution to absorb carbon dioxide. The absorption liquid, which has absorbed carbon dioxide, is supplied from the absorption tower, and a separation tank separates the absorption liquid into the concentrated phase and the dilute phase. The concentrated phase is supplied from the separation tank, and a regeneration tower separates carbon dioxide from the concentrated phase, A mixing tank mixes the dilute phase supplied from the separation tank, the regenerated phase which is the concentrated phase from which carbon dioxide has been separated and supplied from the regeneration tower, water, an amine compound, and an organic solvent to reproduce the absorbent liquid supplied to the absorption tower. Equipped with, A compositional analysis unit for analyzing the composition of the dilute phase and the regenerated phase supplied to the mixing tank, An adjustment unit adjusts the amounts of the dilute phase, the regenerated phase, water, amine compound, and organic solvent supplied to the mixing tank when the composition ratio of the dilute phase falls outside the range of the first composition ratio or when the composition ratio of the regenerated phase falls outside the range of the second composition ratio. To further prepare. [Effects of the Invention]

[0007] According to the carbon dioxide recovery system of the first aspect of the present invention, if the composition ratio of the dilute phase supplied to the mixing tank falls outside the range of a first composition ratio, or if the composition ratio of the regenerated phase falls outside the range of a second composition ratio, the adjustment unit adjusts the amounts of dilute phase, regenerated phase, water, amine compound, and organic solvent supplied to the mixing tank. Therefore, even if the temperature and humidity of the gas containing carbon dioxide fluctuate, the composition of the absorbent liquid circulating in the carbon dioxide recovery system can be kept close to the optimal composition. Thus, a carbon dioxide recovery system with a more stable carbon dioxide recovery rate can be provided. [Brief explanation of the drawing]

[0008] [Figure 1]This figure shows an example of a carbon dioxide capture system according to the first embodiment of the present invention. [Figure 2] A block diagram showing an example of a control device according to the first embodiment of the present invention. [Figure 3] This flowchart illustrates a method for adjusting the supply amounts of dilute phase, regenerated phase, water, amine compound, and organic solvent supplied to a mixing tank according to the first embodiment of the present invention. [Modes for carrying out the invention]

[0009] A first embodiment of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following first embodiment. Also, for clarity of explanation, the following description and drawings have been simplified as appropriate.

[0010] (First embodiment) The carbon dioxide recovery system 100 according to the first embodiment will be described below with reference to the drawings. Figure 1 is a diagram showing an example of the carbon dioxide recovery system 100 according to the first embodiment. Specifically, the carbon dioxide recovery system 100 includes an absorption tower 110, a separation tank 120, a regeneration tower 130, a mixing tank 140, valves 151-157, a pump (not shown), a sensor 160, and a control device 170. The carbon dioxide recovery system 100 separates and recovers carbon dioxide (CO2) from a gas containing carbon dioxide using an absorbent liquid containing water, an amine compound, and an organic solvent.

[0011] The amine compounds contained in the absorbent solution may contain primary amino groups, secondary amino groups (which may include amino groups in the ring structure, such as pyrrolidine), hydroxyl groups, or ether groups. For example, the amine compounds may be 2-(Ethylamino)ethanol, DL-1-Amino-2-propanol, 2-(Methylamino)ethanol, 2-(2-Aminoethoxy)ethanol, 2-Aminoethanol, DL-3-Pyrrolidinol, or Morpholine.

[0012] The organic solvent contained in the absorption solution may be, for example, Diethylene Glycol Ethyl Methyl Ether, Diethylene Glycol Dimethyl Ether, or Diethylene Glycol Monomethyl Ether.

[0013] The desired composition ratio range (optimal composition ratio range) for the absorbent solution is, for example, amine:organic solvent:water = 10-40:40-80:10-30, and the total of amine, organic solvent, and water does not exceed 100.

[0014] Furthermore, the absorbent liquid according to the first embodiment separates into two phases after absorbing carbon dioxide: a concentrated phase with a high carbon dioxide content and a dilute phase with a low carbon dioxide content. Specifically, the dilute phase becomes like an organic solvent and the concentrated phase becomes like an aqueous solution, and they separate into upper and lower halves.

[0015] The absorption tower 110 is supplied with an absorbent liquid at a constant flow rate. Specifically, a predetermined amount of absorbent liquid is supplied to the absorption tower 110 in advance, and the absorbent liquid flows from the absorption tower 110 to the separation tank 120, the regeneration tower 130, and the mixing tank 140, and then flows back into the absorption tower 110 from the mixing tank 140. In addition, a gas containing carbon dioxide is supplied to the absorption tower 110 at a constant flow rate. The ratio of the flow rate of the absorbent liquid to the flow rate of the gas containing carbon dioxide supplied to the absorption tower 110 is predetermined based on the gas-liquid contact ratio that allows the absorbent liquid to efficiently absorb carbon dioxide. The gas-liquid contact ratio is expressed, for example, as the mass ratio of the absorbent liquid to the gas containing carbon dioxide that is brought into contact. The absorbent liquid is supplied from the mixing tank 140 to the absorption tower 110 by a pump (not shown), and the flow rate of the absorbent liquid supplied to the absorption tower 110 is controlled by controlling the opening degree of a valve 151 located downstream of the pump. Similarly, a pump (not shown) supplies a gas containing carbon dioxide to the absorption tower 110, and the flow rate of the gas supplied to the absorption tower 110 is controlled by controlling the opening of a valve 151 located downstream of the pump.

[0016] The separation tank 120 is supplied with the absorption liquid that has absorbed carbon dioxide in the absorption tower 110 from the absorption tower 110. Specifically, the absorption liquid is supplied from the absorption tower 110 to the separation tank 120 by a pump (not shown), and the flow rate of the absorption liquid supplied to the separation tank 120 is controlled by controlling the opening degree of the valve 152 arranged on the downstream side of the pump. In the separation tank 120, the absorption liquid is stored for a predetermined time, and the absorption liquid that has absorbed carbon dioxide is separated into a dilute phase 210 and a concentrated phase 220 in a two-phase separation.

[0017] The concentrated phase 220 is supplied from the separation tank 120 to the regeneration tower 130. Specifically, the concentrated phase 220 is supplied from the separation tank 120 to the regeneration tower 130 by a pump (not shown), and the flow rate of the concentrated phase 220 supplied to the regeneration tower 130 is controlled by controlling the opening degree of the valve 153 arranged on the downstream side of the pump. In the regeneration tower 130, when the concentrated phase 220 is heated, carbon dioxide is separated from the concentrated phase 220, and the concentrated phase 220 becomes the regeneration phase 230. As the heating means used for the regeneration tower 130, waste heat from a thermal power plant, a chemical plant, etc., geothermal heat, and electric heat can be used. Also, for example, although the heating temperature and heating time vary depending on the properties and state of the heated material, they are 80°C to 120°C and 10 minutes to 60 minutes per liter of the absorption liquid.

[0018] The carbon dioxide separated from the concentrated phase 220 in the regeneration tower 130 is discharged from the regeneration tower 130. The carbon dioxide discharged from the regeneration tower 130 is cooled to remove moisture, and while being compressed by a compressor, it is recovered and stored in a predetermined recovery container.

[0019] In the mixing tank 140, the lean phase 210 is supplied from the separation tank 120, and the regenerated phase 230 is supplied from the regeneration tower 130. Specifically, the lean phase 210 is supplied from the separation tank 120 to the mixing tank 140 by a pump (not shown), and the flow rate of the lean phase 210 supplied to the mixing tank 140 is controlled by controlling the opening degree of a valve 155 arranged downstream of the pump. Similarly, the regenerated phase 230 is supplied from the regeneration tower 130 to the mixing tank 140 by a pump (not shown), and the flow rate of the regenerated phase 230 supplied to the mixing tank 140 is controlled by controlling the opening degree of a valve 154 arranged downstream of the pump. In addition, when the adjustment by an adjustment unit 171B described later is not performed, a lean phase 210 with a constant flow rate and a regenerated phase 230 with a constant flow rate are supplied to the mixing tank 140. Moreover, water, an amine compound, and an organic solvent (hereinafter, water, an amine compound, and an organic solvent are also collectively referred to as "single phase") are supplied to the mixing tank 140 as necessary. The single phase is supplied from a storage container storing the single phase to the mixing tank 140 by a pump (not shown), and the flow rate of the single phase supplied to the mixing tank 140 is controlled by controlling the opening degree of a valve 156 arranged downstream of the pump. In addition, when the adjustment by an adjustment unit 171B described later is not performed, a single phase with a constant flow rate is supplied to the mixing tank 140. Then, in the mixing tank 140, the lean phase 210, the regenerated phase 230, and the single phase are mixed to reproduce the absorbent liquid.

[0020] The sensor 160 measures at least the temperature and humidity of the gas containing carbon dioxide supplied to the absorption tower 110 as the state of the gas. For example, the sensor 160 is arranged in a supply pipe that supplies the gas to the absorption tower 110 and measures the temperature and humidity of the gas passing through the supply pipe.

[0021] As shown in FIG. 2, the control device 170 includes a control unit 171, a storage unit 172, and a memory 173.

[0022] The control unit 171 is a processor, or control device, that controls each component of the control device 170. The control unit 171 loads program 172A from the storage unit 172 into memory 173 and executes program 172A. In this way, the control unit 171 realizes the functions of the composition analysis unit 171A and the adjustment unit 171B.

[0023] The compositional analysis unit 171A performs compositional analysis of the dilute phase 210 separated in the flow path from the separation tank 120 to the mixing tank 140 and the regenerated phase 230 separated in the flow path from the regeneration tower 130 to the mixing tank 140. Specifically, it analyzes the compositional ratios of water, amine compounds, and organic solvents in each of the separated dilute phase 210 and regenerated phase 230.

[0024] The adjustment unit 171B adjusts the amounts of dilute phase 210, regenerated phase 230, water, amine compound, and organic solvent supplied to the mixing tank when the composition ratio of the dilute phase 210 falls outside the range of the first composition ratio or when the composition ratio of the regenerated phase 230 falls outside the range of the second composition ratio. Here, the range of the first composition ratio and the range of the second composition ratio refer to the range of composition ratios in which an optimal compositional ratio of absorbent solution is reproduced when a constant flow rate of dilute phase 210, a constant flow rate of regenerated phase 230, and a constant flow rate of single phase (water, amine compound, organic solvent) are supplied to the mixing tank 140 and the dilute phase 210, the regenerated phase 230, and the single phase are mixed in the mixing tank 140. The ranges for the first and second composition ratios are predetermined based on the results of measuring the composition ratio of the absorbent solution reproduced by supplying gases of various temperatures and humidity levels to the absorption tower 110 and mixing a constant flow rate of dilute phase 210, a constant flow rate of regenerated phase 230, and a constant flow rate of single phase in the mixing tank 140. Here, the optimal composition ratio of the absorbent solution means a composition ratio that allows the absorbent solution to stably absorb carbon dioxide from the gas at the desired absorption rate.

[0025] Furthermore, the adjustment unit 171B adjusts the amounts of dilute phase 210, regeneration phase 230, water, amine compound, and organic solvent supplied to the mixing tank when the state of the carbon dioxide-containing gas supplied to the absorption tower 110, as measured by the sensor 160, deviates from a predetermined state. Here, the state refers to, for example, at least the temperature and humidity of the gas. In other words, the adjustment unit 171B adjusts the amounts of dilute phase 210, regeneration phase 230, water, amine compound, and organic solvent supplied to the mixing tank when the temperature and humidity of the gas, as measured by the sensor 160, deviate from a predetermined temperature and humidity. The predetermined temperature and humidity may also be within a predetermined range defined by an upper limit and a lower limit. Furthermore, the predetermined temperature and humidity are the temperature and humidity at which, when the gas is supplied to the absorption tower 110, a constant flow rate of dilute phase 210, a constant flow rate of regenerating phase 230, and a constant flow rate of single phase are mixed in the mixing tank 140 to reproduce an absorbent solution with an optimal composition ratio. The predetermined temperature and humidity are determined in advance based on the results of measuring the composition ratio of the absorbent solution reproduced by supplying gases of various temperatures and humidity to the absorption tower 110 and mixing a constant flow rate of dilute phase 210, a constant flow rate of regenerating phase 230, and a constant flow rate of single phase in the mixing tank 140.

[0026] Furthermore, the adjustment unit 171B calculates the amounts (flow rates) of dilute phase 210, regenerated phase 230, water, amine compounds, and organic solvents to be supplied to the mixing tank 140, based on the composition ratios of the dilute phase 210 and the regenerated phase 230 analyzed by the composition analysis unit 171A, so that an absorption solution with the optimal composition ratio is reproduced in the mixing tank 140.Then, the adjustment unit 171B controls the opening degrees of the valves 154, 155, and 156 of the supply pipes that supply the dilute phase 210, regenerated phase 230, and single phase to the mixing tank 140 so that the flow rates determined based on the calculation results are met.

[0027] The memory unit 172 is a storage device that stores programs 172A for realizing each function of the control device 170. The memory unit 172 also stores first default value data 172B, second default value data 172C, etc.

[0028] The first set of specified value data 172B is data for a predetermined temperature and humidity of a gas containing carbon dioxide supplied to the absorption tower 110.

[0029] The second set of specified value data 172C is data relating to the range of the first composition ratio and the range of the second composition ratio. Specifically, the second set of specified value data 172C is data relating various temperatures and humidity levels of the carbon dioxide-containing gas supplied to the absorption tower 110 to the range of composition ratios of the dilute phase 210 and the regenerated phase 230, in which an absorbent liquid with the optimal composition ratio is reproduced in the mixing tank 140.

[0030] Memory 173 is a volatile memory device such as RAM, and is a storage area for temporarily holding information when the control unit 171 is operating.

[0031] In addition, the carbon dioxide capture system 100 may include a communication unit (not shown) which is a communication interface with an external network.

[0032] Next, with reference to Figure 3, an example of a method for adjusting the supply amounts of the dilute phase 210, regenerated phase 230, water, amine compound, and organic solvent supplied to the mixing tank according to the first embodiment will be described. The process shown in Figure 3 is carried out continuously while the carbon dioxide recovery system 100 is in operation.

[0033] First, the adjustment unit 171B determines whether the temperature and humidity of the gas measured by the sensor 160 have deviated from a predetermined state (step S101).

[0034] If, in step S101, the temperature and humidity of the gas are not outside the predetermined range (step S101; No), the process returns to the step before S101. In step S101, if the temperature and humidity of the gas deviate from the predetermined conditions (step S101; Yes), the composition analysis unit 171A performs a composition analysis of the dilute phase 210 separated in the flow path from the separation tank 120 to the mixing tank 140 and the regenerated phase 230 separated in the flow path from the regeneration tower 130 to the mixing tank 140 (step S102).

[0035] Next, the adjustment unit 171B determines whether the composition ratio of the dilute phase 210 has fallen outside the range of the first composition ratio, or whether the composition ratio of the regenerated phase 230 has fallen outside the range of the second composition ratio (step S103).

[0036] In step S103, if the composition ratio of the dilute phase 210 is not outside the range of the first composition ratio and the composition ratio of the regenerated phase 230 is not outside the range of the second composition ratio (step S103; No), the process returns to before step S101. In step S103, if the composition ratio of the dilute phase 210 falls outside the range of the first composition ratio, or if the composition ratio of the regenerated phase 230 falls outside the range of the second composition ratio (step S103; Yes), the adjustment unit 171B adjusts the amounts (flow rates) of the dilute phase 210, regenerated phase 230, and single phase supplied to the mixing tank 140 so that an absorbent solution with the optimal composition ratio is reproduced in the mixing tank 140, based on the composition ratios of the dilute phase 210 and the regenerated phase 230 analyzed in step S102 (step S104), and then returns to the beginning of step S101.

[0037] As described above, in the carbon dioxide recovery system 100 according to the first embodiment, if the composition ratio of the dilute phase 210 supplied to the mixing tank 140 falls outside the range of the first composition ratio, or if the composition ratio of the regenerated phase 230 falls outside the range of the second composition ratio, the adjustment unit 171B adjusts the amounts of dilute phase 210, regenerated phase 230, water, amine compound, and organic solvent supplied to the mixing tank 140. Therefore, even if the temperature and humidity of the gas containing carbon dioxide fluctuate, the composition of the absorbent liquid circulating in the carbon dioxide recovery system 100 can be kept close to the optimal composition. Thus, a carbon dioxide recovery system 100 with a more stable carbon dioxide recovery rate can be provided.

[0038] Specifically, fluctuations in the temperature and humidity of the carbon dioxide-containing gas supplied to the absorption tower 110 cause fluctuations in the amount of carbon dioxide absorbed by the absorbent, which in turn causes fluctuations in the separation ratio (volume ratio) of the dilute phase 210 and the concentrated phase 220 in the separation tank 120. This also causes fluctuations in the concentrations of amine compounds and other substances in the dilute phase 210 and concentrated phase 220 in the separation tank 120, as well as fluctuations in the evaporation (volatilization) of water, organic solvents, and amine compounds, mainly from the dilute phase 210, in the separation tank 120. Consequently, the composition of the concentrated phase 220 and dilute phase 210 in the separation tank 120 also fluctuates. Furthermore, fluctuations in the temperature and humidity of the gas cause fluctuations in the amount of water, organic solvents, and amine compounds evaporated (volatilized) from the regeneration phase 230 (concentration phase 220) in the regeneration tower 130. Therefore, the composition of the absorbent solution reproduced by mixing a fixed amount of the regenerated phase 230, dilute phase 210, and single-component phase in the mixing tank 140 may fluctuate, resulting in a composition that is not optimal. Even if the temperature and humidity of the gas do not fluctuate, evaporation (volatilization) of water, organic solvents, and amine compounds always occurs in the separation tank 120, regeneration tower 130, etc. However, fluctuations in the composition ratio of the absorbent liquid reproduced in the mixing tank 140 by mixing a fixed amount of regeneration phase 230, dilute phase 210, and single-component phase can be ignored.

[0039] In contrast, in the carbon dioxide recovery system 100 according to the first embodiment, if the composition ratio of the dilute phase 210 supplied to the mixing tank 140 falls outside the range of the first composition ratio, or if the composition ratio of the regeneration phase 230 falls outside the range of the second composition ratio, the amount (flow rate) of the dilute phase 210, regeneration phase 230, and single phase supplied to the mixing tank 140 is adjusted. This ensures that the mixing tank 140 can always reproduce an absorbent solution with the optimal composition ratio.

[0040] Furthermore, since only the concentrated phase 220 is heated in the regeneration tower 130 to recover carbon dioxide, the heating energy can be reduced compared to heating the entire absorbent liquid including the dilute phase 210, thus enabling energy-efficient recovery of carbon dioxide.

[0041] Furthermore, the temperature and humidity of the gas supplied to the absorption tower 110 are monitored, and if the temperature and humidity of the gas deviate from the predetermined temperature and humidity, the composition analysis unit 171A performs a compositional analysis of the separated dilute phase 210 and regenerated phase 230, and the adjustment unit 171B adjusts the amount (flow rate) of the dilute phase 210, regenerated phase 230, and single phase supplied to the mixing tank 140. Therefore, if the temperature and humidity of the gas do not deviate from the predetermined temperature and humidity, it is not necessary to separate the dilute phase 210 and regenerated phase 230.

[0042] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. [Explanation of Symbols]

[0043] 100 Carbon Dioxide Capture Systems 110 Absorption Towers 120 Separation tank 130 Regeneration Tower 140 Mixing tank 151-157 Valves 160 sensors 170 Control device 171 Control Unit 171A Composition Analysis Department 171B Adjustment part 172 Memory section 172B First default value data 172C Second standard value data

Claims

1. An absorption tower is provided with an absorption solution containing water, an amine compound, and an organic solvent, which separates into a concentrated phase with a high carbon dioxide content and a dilute phase with a low carbon dioxide content after absorbing carbon dioxide, and a gas containing carbon dioxide is also supplied to cause the absorption solution to absorb carbon dioxide. The absorption liquid, which has absorbed carbon dioxide, is supplied from the absorption tower, and a separation tank separates the absorption liquid into the concentrated phase and the dilute phase. The concentrated phase is supplied from the separation tank, and a regeneration tower separates carbon dioxide from the concentrated phase, A mixing tank mixes the dilute phase supplied from the separation tank, the regenerated phase which is the concentrated phase from which carbon dioxide has been separated and supplied from the regeneration tower, water, an amine compound, and an organic solvent to reproduce the absorbent liquid supplied to the absorption tower. Equipped with, A compositional analysis unit for analyzing the composition of the dilute phase and the regenerated phase supplied to the mixing tank, An adjustment unit adjusts the amounts of the dilute phase, the regenerated phase, water, amine compound, and organic solvent supplied to the mixing tank when the composition ratio of the dilute phase falls outside the range of the first composition ratio or when the composition ratio of the regenerated phase falls outside the range of the second composition ratio. Furthermore, Carbon dioxide capture system.

2. A sensor for measuring the state of the gas containing carbon dioxide supplied to the absorption tower, If the state of the gas measured by the sensor deviates from a predetermined state, the adjustment unit adjusts the amounts of the dilute phase, the regenerated phase, water, amine compound, and organic solvent supplied to the mixing tank. The carbon dioxide capture system according to claim 1.

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