Gas treatment apparatus and gas treatment method

Abstract

The aim is to suppress fluctuations in the water content of the treatment solution while ensuring a reduction in the regeneration temperature of the treatment solution. [Solution] The gas treatment apparatus 10 comprises an absorber 21 that brings a gas to be treated containing an acidic compound into contact with a treatment liquid to absorb the acidic compound into the treatment liquid; a first regenerator 22 into which a portion of the treatment liquid that has absorbed the acidic compound is introduced and the introduced treatment liquid is heated to separate the acidic compound from the treatment liquid; a second regenerator 23 connected in parallel with the first regenerator 22 into which a portion of the treatment liquid that has absorbed the acidic compound is introduced and the introduced treatment liquid is heated to separate the acidic compound from the treatment liquid; an introduction means 43 for introducing a separation-promoting gas that promotes the separation of acidic compounds from the treatment liquid into the first regenerator; and a connection path 44 for introducing a gas containing the separation-promoting gas discharged from the first regenerator 22 into the second regenerator 23.

Description

[Technical Field]

[0001] The present invention relates to a gas treatment apparatus and a gas treatment method. [Background technology]

[0002] In recent years, carbon dioxide is considered to have a significant impact on global warming. As an effective measure against this global warming problem, carbon dioxide separation and recovery technology is attracting attention. There are various methods for separating and recovering CO2 from CO2 emission sources such as power plants and steel mills, but when the scale is large and the emitted CO2 is close to atmospheric pressure, the chemical absorption method is suitable. In this chemical absorption method, acidic CO2 is absorbed into an alkaline aqueous solution (treatment solution), such as an amine aqueous solution, and this CO2-absorbing treatment solution is heated. This causes the CO2 in the treatment solution to be released from the treatment solution (called the regeneration process), and the separated CO2 is recovered.

[0003] In this type of amine absorption method, heating is required to release the CO2 from the absorbed treatment solution, thus requiring a large amount of thermal energy. Furthermore, temperatures of 100°C or higher are required during heating. This is a factor that increases the cost required for CO2 separation and recovery.

[0004] Therefore, Patent Documents 1 and 2 below disclose gas treatment devices that achieve energy saving by using a treatment liquid that can be regenerated at low temperatures. Patent Document 1 discloses that a regeneration temperature of 100°C or less can be achieved by using a treatment liquid that separates into two phases, a phase with a high CO2 content and a phase with a low CO2 content, by the absorption of CO2. The treatment liquid is an alkaline liquid containing water, an amine compound, and an organic solvent. Patent Document 2 discloses that the regeneration temperature can be further reduced by supplying a separation-promoting gas, which is a gas that is almost insoluble in the treatment liquid and consists of a hydrocarbon gas such as methane gas, hydrogen gas, or oxygen gas, during the regeneration process.

[0005] Furthermore, Patent Document 3 discloses a gas treatment apparatus equipped with a cleaning unit for cleaning components of the treatment liquid accompanying the gas to be treated.

[0006] Furthermore, Patent Document 4 discloses a gas treatment device in which multiple regenerators are provided, and each regenerator is connected to a supply source of separation-promoting gas. In this gas treatment device, multiple regenerators are connected in parallel to an absorber, while heaters provided in each regenerator are connected to which a heat source fluid for heating the processing liquid flows sequentially. This increases the efficiency of heat utilization.

[0007] In Patent Documents 1-2 and 4, a separation-accelerating gas is used in the regenerator, so a predetermined regeneration rate can be achieved even when the processing liquid is heated at a lower temperature. Furthermore, the effect is further improved when a processing liquid is used that is separated into two phases, a phase with a high CO2 content and a phase with a low CO2 content, due to CO2 absorption. In addition, in a gas treatment device equipped with a washing unit that washes the components of the processing liquid entrained in the gas to be treated, as in Patent Document 3, the components of the processing liquid can be recovered, thus preventing these components from being discharged outside the gas treatment device. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 6906761 [Patent Document 2] Patent No. 6906766 [Patent Document 3] Patent No. 5968159 [Patent Document 4] Japanese Patent Publication No. 2024-24388 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, in gas treatment devices equipped with a cleaning unit, as described in Patent Document 3, cleaning water may mix with the treatment liquid, which could lead to the treatment liquid being diluted.

[0010] As described in Patent Document 4, when multiple regenerators are provided and the heat source fluid is configured to flow sequentially through each heater, the efficiency of heat utilization from the heat source fluid can be increased. However, in Patent Document 4, since the separation-promoting gas is introduced separately (or in parallel) to multiple regenerators provided in parallel with the absorber, if the regeneration temperature in each regenerator is to be lowered by a predetermined temperature, the total amount of separation-promoting gas supplied may become large.

[0011] Therefore, the present invention has been made in view of the above-mentioned prior art, and its objective is to reduce the total amount of separation-accelerating gas supplied compared to the case in which separation-accelerating gas is introduced separately to multiple regenerators, while also achieving the effect of reducing the regeneration temperature of the processed liquid. [Means for solving the problem]

[0012] To achieve the above objective, the gas treatment apparatus according to the present invention comprises: an absorber that brings a gas to be treated containing an acidic compound that produces acid when dissolved in water into contact with a treatment liquid, thereby absorbing the acidic compound contained in the gas to be treated into the treatment liquid; a first regenerator into which a portion of the treatment liquid that has absorbed the acidic compound in the absorber is introduced, and the introduced treatment liquid is heated to separate the acidic compound from the treatment liquid; a second regenerator connected in parallel with the first regenerator, into which a portion of the treatment liquid that has absorbed the acidic compound in the absorber is introduced, and the introduced treatment liquid is heated to separate the acidic compound from the treatment liquid; an introduction means for introducing a separation-promoting gas that promotes the separation of the acidic compound from the treatment liquid into the first regenerator; and a connecting path for introducing a gas containing the separation-promoting gas discharged from the first regenerator into the second regenerator.

[0013] In the aforementioned gas treatment apparatus, separation-accelerating gas is introduced into the first regenerator, thereby lowering the regeneration temperature of the treatment liquid in the first regenerator. On the other hand, gas containing the separation-accelerating gas that has passed through the first regenerator is introduced into the second regenerator. Since this gas also contains gas components released from the treatment liquid in the first regenerator, the effect of lowering the regeneration temperature in the second regenerator is lower than that of the first regenerator. However, because it also contains separation-accelerating gas, the gas that has flowed out of the first regenerator is introduced into the second regenerator, thereby lowering the regeneration temperature of the treatment liquid in the second regenerator, although not to the same extent as in the first regenerator. Therefore, the effect of lowering the regeneration temperature of the treatment liquid can be achieved in both the first and second regenerators.

[0014] Furthermore, since the separation-accelerating gas used to lower the regeneration temperature in the first regenerator is also used in the second regenerator, the total supply of separation-accelerating gas can be prevented from becoming excessive. In addition, since the regeneration temperature of the processed liquid in the first regenerator can be lowered to that of the processed liquid in the second regenerator, the degree of freedom in selecting the heat source for heating the processed liquid in the first regenerator can be greatly increased.

[0015] The gas treatment apparatus may further include a heat supply means for supplying heat from within the gas treatment apparatus to the first regenerator.

[0016] In this configuration, the heat within the gas treatment device can be effectively utilized, thereby reducing the total energy consumption. Consequently, the separation of acidic compounds becomes more energy-efficient. Specifically, the reduction in the regeneration temperature in the first regenerator is accelerated, allowing the excess heat within the gas treatment device to be used for regenerating the treatment liquid in the first regenerator. Therefore, the total energy consumption can be reduced. The gas treatment device is equipped with a first regenerator and a second regenerator, but the separation-accelerating gas is first introduced into the first regenerator, and then this separation-accelerating gas is also introduced into the second regenerator. By adopting this configuration, the regeneration temperature of the treatment liquid, particularly in the first regenerator, can be reduced, thus effectively utilizing the heat within the gas treatment device and reducing the total energy consumption.

[0017] The absorber and the first regenerator may be thermally connected to each other such that heat of the absorber is transferred to the first regenerator.

[0018] In this aspect, since the heat of the absorber can be effectively utilized, the total amount of energy can be reduced. Therefore, it is possible to separate the acidic compound with less energy. That is, since the decrease in the regeneration temperature in the first regenerator is promoted, it is possible to use the heat of the absorber for the regeneration of the treatment liquid in the first regenerator. Therefore, the total amount of energy can be reduced.

[0019] The treatment liquid may contain water and a non-aqueous component. In this case, the gas treatment device may include a cleaning unit that is disposed in at least one of the absorber or the second regenerator and washes the treatment liquid so that the non-aqueous component scattered from the treatment liquid is recovered.

[0020] In this aspect, the non-aqueous component scattered from the treatment liquid can be recovered in the treatment liquid in the cleaning unit disposed in the absorber or the second regenerator. Therefore, it is possible to suppress the non-aqueous component from being discharged from the gas treatment device.

[0021] The gas treatment device may further include an adjustment means for adjusting the water content rate of the treatment liquid to a water content rate within a predetermined range.

[0022] In this aspect, the water content rate in the treatment liquid may change due to the introduction of the separation promoting gas into the first regenerator and the washing of the treatment liquid with water in the cleaning unit. However, since the water content rate of the treatment liquid is adjusted by the adjustment means, it is possible to prevent the separation ability of the acidic compound by the treatment liquid from deteriorating and to suppress an increase in the energy unit.

[0023] The gas treatment apparatus may further include a heat exchanger that exchanges heat between the heat of the treatment liquid flowing from the absorber to the first regenerator and the second regenerator and the heat of the treatment liquid flowing from the second regenerator to the absorber. In this case, the flow path of the treatment liquid from the first regenerator to the absorber may be configured to return the treatment liquid from the first regenerator to the absorber without passing through the heat exchanger.

[0024] In this embodiment, the processing liquid heated in the second regenerator can heat the processing liquid introduced from the absorber to the first and second regenerators, thus contributing to a reduction in the energy required for the regeneration of the processing liquid in the first and second regenerators. On the other hand, since the temperature of the processing liquid heated in the first regenerator is relatively low, it is possible to suppress the decrease in the temperature of the processing liquid introduced from the absorber to the first and second regenerators by the processing liquid moving from the first regenerator to the absorber.

[0025] The introduction means may be configured to introduce the separation-promoting gas having a water content of 3% by volume or less. In this embodiment, when the first regenerator and the second regenerator are connected in parallel to the absorber, the effect of reducing the energy required to regenerate the processed liquid can be effectively realized.

[0026] The gas treatment method according to the present invention involves bringing a gas to be treated containing an acidic compound that produces acid when dissolved in water into contact with a treatment liquid in an absorber, thereby absorbing the acidic compound contained in the gas to be treated into the treatment liquid; introducing a portion of the treatment liquid discharged from the absorber and a separation-promoting gas that promotes the separation of the acidic compound from the treatment liquid into a first regenerator; in the first regenerator, heating the treatment liquid that has absorbed the acidic compound in the presence of the separation-promoting gas to separate the acidic compound from the treatment liquid; introducing a portion of the treatment liquid discharged from the absorber and a gas containing the separation-promoting gas discharged from the first regenerator into a second regenerator; and in the second regenerator, heating the treatment liquid that has absorbed the acidic compound in the presence of the gas containing the separation-promoting gas to separate the acidic compound from the treatment liquid.

[0027] In the gas treatment method described above, heat from within the gas treatment apparatus comprising the absorber, the first regenerator, and the second regenerator may be supplied to the first regenerator.

[0028] In the gas treatment method using the gas treatment apparatus described above, the heat exchanger may be used to exchange heat between the heat of the treatment liquid flowing from the absorber to the first regenerator and the second regenerator and the heat of the treatment liquid flowing from the second regenerator to the absorber, and the treatment liquid flowing from the first regenerator to the absorber may be returned to the absorber without passing through the heat exchanger. [Effects of the Invention]

[0029] As described above, according to the present invention, compared to the case in which separation-accelerating gas is introduced separately to multiple regenerators, it is possible to reduce the total amount of separation-accelerating gas supplied while ensuring the effect of reducing the regeneration temperature of the processed liquid. [Brief explanation of the drawing]

[0030] [Figure 1] This diagram schematically shows the configuration of the gas treatment apparatus according to the first embodiment. [Figure 2] This diagram schematically shows the configuration of the gas treatment apparatus according to the second embodiment. [Figure 3] This figure schematically shows the configuration of a gas treatment apparatus according to the first modified example of the second embodiment. [Figure 4] This figure schematically shows the configuration of a gas treatment apparatus according to a second modified example of the second embodiment. [Figure 5] This figure schematically shows the configuration of a gas treatment apparatus according to a third modified example of the second embodiment. [Figure 6] This diagram schematically shows the configuration of the gas treatment apparatus according to the third embodiment. [Figure 7] This diagram schematically shows the configuration of the gas treatment apparatus according to the fourth embodiment. [Figure 8] This figure schematically shows the configuration of a gas treatment apparatus according to the first modified example of the fourth embodiment. [Figure 9]This figure schematically shows the configuration of a gas treatment apparatus according to a second modified example of the fourth embodiment. [Figure 10] This figure schematically shows the configuration of a gas treatment apparatus according to a third modified example of the fourth embodiment. [Figure 11] This diagram schematically shows the configuration of the gas treatment apparatus according to the fifth embodiment. [Figure 12] This figure schematically shows the configuration of a gas treatment apparatus according to the first modified example of the fifth embodiment. [Figure 13] This diagram illustrates the comparison of the energy required for heating. [Figure 14] This diagram illustrates the comparison of evaporation rates of amine compounds. [Modes for carrying out the invention]

[0031] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[0032] (First Embodiment) As shown in Figure 1, the gas treatment apparatus 10 according to this embodiment is used to separate acidic compounds from a gas to be treated that contains acidic compounds using a treatment liquid. The gas treatment apparatus 10 of this embodiment targets carbon dioxide as an acidic compound. However, the acidic compound separated by the gas treatment apparatus 10 is not particularly limited as long as its aqueous solution becomes acidic, and examples include carbon dioxide and sulfur compounds. Examples of gases to be treated that contain acidic compounds include industrial exhaust gas, process gas produced during purification, and natural gas.

[0033] The gas treatment device 10 includes an absorber 21, a first regenerator 22, a second regenerator 23, a supply channel 25, a return channel 26, and a heat exchanger 28.

[0034] The feed channel 25 extracts the processed liquid (rich liquid) from the absorber 21 and introduces it into the first regenerator 22 and the second regenerator 23. The feed channel 25 includes a main channel 25a connected to the absorber 21, a first branch channel 25b connected to the main channel 25a and the first regenerator 22, and a second branch channel 25c connected to the main channel 25a and the second regenerator 23, branching off from the first branch channel 25b. In other words, the second regenerator 23 is connected to the absorber 21 in parallel with the first regenerator 22. The main channel 25a is connected to the lower end or near the lower end of the absorber 21. That is, the feed channel 25 is connected to a position where the processed liquid accumulated in the absorber 21 can be extracted.

[0035] The main channel 25a is equipped with a pump 25d for sending the processed liquid from the absorber 21 to the first regenerator 22 and the second regenerator 23. The first branch channel 25b is equipped with a cooler 25e for cooling the processed liquid flowing through the first branch channel 25b, and the second branch channel 25c is equipped with a heater 25f for heating the processed liquid flowing through the second branch channel 25c. The pump 25d, cooler 25e, and heater 25f are optional.

[0036] The return channel 26 includes a first return channel 26a for extracting the processed liquid (lean liquid) from the first regenerator 22, a second return channel 26b for extracting the processed liquid (lean liquid) from the second regenerator 23, and a confluence channel 26c where the first return channel 26a and the second return channel 26b merge and are connected to the absorber 21. The confluence channel 26c is connected to the upper end or near the upper end of the absorber 21. In other words, the return channel 26 is connected to a position where the processed liquid returned from the first regenerator 22 and the second regenerator 23 can flow down from above. Pumps 26d and 26e are provided in the first return channel 26a and the second return channel 26b, respectively.

[0037] The heat exchanger 28 is connected to the feed channel 25 and the return channel 26, and facilitates heat exchange between the processed liquid flowing through the feed channel 25 and the processed liquid flowing through the return channel 26. Specifically, the heat exchanger 28 is connected to the main channel 25a of the feed channel 25 and to the second return channel 26b of the return channel 26. In other words, the flow path of the processed liquid from the second regenerator 23 to the absorber 21 passes through the heat exchanger 28. On the other hand, the flow path of the processed liquid from the first regenerator 22 to the absorber 21 is configured to return the processed liquid from the first regenerator 22 to the absorber 21 without passing through the heat exchanger 28. Note that the heat exchanger 28 can be omitted.

[0038] The absorber 21 is connected to an inlet passage 31 for taking in the gas to be treated and a gas discharge passage 32 for discharging the treated gas. The inlet passage 31 is connected to the lower end of the absorber 21, and the gas discharge passage 32 is connected to the upper end of the absorber 21.

[0039] The gas discharge passage 32 is equipped with an absorption-side condenser 34, which cools the treated gas (the gas remaining after the acidic compounds have been absorbed into the processing liquid) and separates moisture from the cooled gas, and an absorption-side washing section 35, which is a washing section that washes the treated gas with water. The absorption-side condenser 34 separates moisture by condensing the water vapor contained in the processed gas by cooling it. The absorption-side washing section 35 recovers non-aqueous components such as amine compounds released from the processing liquid into the washing water by bringing the treated gas into contact with the washing water. The washing water from which the non-aqueous components have been recovered is returned to the absorption-side condenser 34, and the treated gas from which the non-aqueous components have been removed is discharged from the gas treatment device 10. Note that the absorption-side condenser 34 is optional. The absorption-side washing section 35 is also optional.

[0040] The absorber 21 brings the gas to be treated into contact with the treatment liquid, thereby absorbing acidic compounds in the gas into the treatment liquid, and then discharges the gas from which the acidic compounds have been removed. The absorption of acidic compounds in the absorber 21 is an exothermic reaction. The heat of this reaction generated in the absorber 21 raises the temperature of the gas to be treated and the treatment liquid. The absorber 21 is provided with a cooling unit 36 ​​to cool the treatment liquid inside the absorber 21, but the cooling unit 36 ​​is optional.

[0041] The first regenerator 22 is connected to the first branch channel 25b of the supply channel 25 and the first return channel 26a of the return channel 26. The first branch channel 25b is connected to the area from the top to the center of the first regenerator 22. The first return channel 26a is connected to the lower end or near the lower end of the first regenerator 22.

[0042] The second regenerator 23 is connected to the second branch channel 25c of the supply channel 25 and the second return channel 26b of the return channel 26. The second branch channel 25c is connected to the upper to central area of ​​the second regenerator 23. The second return channel 26b is connected to the lower end or near the lower end of the second regenerator 23.

[0043] The first regenerator 22 and the second regenerator 23 are configured to store the treated liquid that has absorbed the acidic compound, and to regenerate the stored treated liquid by heating it. For this reason, the first regenerator 22 and the second regenerator 23 each have heaters 40 and 41.

[0044] The heater (first heater 40) of the first regenerator 22 is configured to heat the processing liquid of the first regenerator 22 using the heat of a heat source fluid. However, the first heater 40 is not limited to a configuration that heats the processing liquid using a heat source fluid, but may also be configured to heat the processing liquid using a heater or the like. In Figure 1, the first heater 40 is located outside the main body of the first regenerator 22 and is configured to heat the processing liquid drawn out from the main body. However, the first heater 40 may also be located inside the main body of the first regenerator 22 and is configured to heat the processing liquid within the main body. Here, the heat source fluid used in the first heater 40 may be a fluid heated outside the gas processing device 10. For example, when the gas processing device 10 is combined with a reactor (not shown) to form a single reactor, the heat source fluid may be a fluid heated by the heat generated in this reactor. Examples of such reactors include a methanation reactor.

[0045] The heater (second heater 41) of the second regenerator 23 is configured to heat the processing liquid of the second regenerator 23 with the heat of a heat source fluid. However, the second heater 41 is not limited to a configuration that heats the processing liquid using a heat source fluid, but may also be configured to heat the processing liquid with a heater or the like. In Figure 1, the second heater 41 is located outside the main body of the second regenerator 23 and is configured to heat the processing liquid drawn out from the main body. However, the second heater 41 may also be located inside the main body of the second regenerator 23 and is configured to heat the processing liquid within the main body. Here, the heat source fluid used in the second heater 41 may be a fluid heated outside the gas processing device 10. For example, when the gas processing device 10 is combined with a reactor (not shown) to form a single reactor, the heat source fluid may be a fluid heated by the heat generated in this reactor. Examples of such reactors include a methanation reactor.

[0046] When the processing solution is heated, acidic compounds are released from it. This release of acidic compounds from the processing solution is an endothermic reaction. In the first regenerator 22 and the second regenerator 23, when the processing solution is heated, not only are acidic compounds released, but the water in the processing solution also evaporates.

[0047] The gas treatment apparatus 10 further comprises an introduction means 43 and a connecting passage 44. The introduction means 43 is for supplying a gas to promote the separation of acidic compounds (hereinafter referred to as separation-promoting gas) to the first regenerator 22, and has an introduction passage 43a connected to the first regenerator 22. The introduction passage 43a is connected to the lower end or near the lower end of the first regenerator 22.

[0048] The connecting passage 44 is a flow path for guiding the gas and separation-promoting gas released from the processing liquid within the first regenerator 22 to the second regenerator 23. One end of the connecting passage 44 is connected to the upper end or near the upper end of the first regenerator 22, and the other end of the connecting passage 44 is connected to the lower end or near the lower end of the second regenerator 23.

[0049] A supply line 45 is connected to the second regenerator 23. The supply line 45 supplies gas containing acidic compounds obtained in the first regenerator 22 and the second regenerator 23 to the demand side.

[0050] The supply path 45 is equipped with a regeneration condenser 46 and a regeneration cleaning unit 47. The regeneration condenser 46 cools the mixed gas of acidic compound gas evaporated from the processing liquid and water vapor. As the mixed gas cools, the water vapor condenses, allowing the regeneration condenser 46 to separate the water vapor. The separated water vapor is returned to the second regenerator 23.

[0051] The regeneration-side cleaning unit 47 is a cleaning unit located in the second regenerator 23. By bringing the mixed gas into contact with the rinse water, it recovers non-aqueous components such as amine compounds released from the processing liquid into the rinse water. The rinse water from which the non-aqueous components have been recovered is returned to the regeneration-side condenser 46. The gas from which the water vapor and non-aqueous components have been recovered is sent to the demand side.

[0052] The separation-accelerating gas supplied to the first regenerator 22 by the introduction means 43 is a gas that is almost insoluble in the processing liquid. In other words, the separation-accelerating gas is almost not absorbed by the processing liquid. Therefore, by introducing the separation-accelerating gas into the first regenerator 22, the partial pressure of carbon dioxide inside the regenerator 22 can be lowered, thereby promoting the separation of carbon dioxide from the processing liquid. Examples of separation-accelerating gases include hydrocarbon gases such as hydrogen gas, oxygen gas, and methane gas, but in this embodiment, hydrogen gas is used. Note that water vapor may also be used as the separation-accelerating gas. Water vapor can dissolve in the processing liquid, but it can lower the partial pressure of carbon dioxide.

[0053] When the separation-accelerating gas is almost insoluble in the processing solution, "almost insoluble in the processing solution" may mean that its solubility in the processing solution is below a predetermined value. The separation-accelerating gas can be, for example, a gas that follows Henry's Law and has a solubility of 1 mol or less per 100 g of processing solution under conditions of 0°C and 100 kPa. Note that the solubility of oxygen in water is 1.3 × 10⁻⁶. -4 The solubility of methane in water, measured in mol / 100g, is 8 × 10⁻⁶. -4 The solubility of hydrogen in water, measured in mol / 100g, is 9.5 × 10⁻⁶. -5 The concentration is mol / 100g. In contrast, the solubility of ammonia in water is 6 mol / 100g, so ammonia does not qualify as a separation-accelerating gas.

[0054] In this embodiment, as the treatment liquid (absorbent) used in the gas treatment apparatus 10, an absorbent capable of reversibly absorbing and desorbing an acidic compound is used. The treatment liquid is, for example, an alkaline absorbent containing water, an amine compound, and an organic solvent. The amine compound may be 30 wt%, the organic solvent may be 60 wt%, and water may be 10 wt%. The treatment liquid preferably undergoes phase separation by absorbing an acidic compound that generates an acid upon dissolution in water, but is not limited thereto. For example, a treatment liquid that is an aqueous solution of an amine compound without using an organic solvent may also be used. Further, the treatment liquid may be an amine compound, an organic solvent, an ionic liquid, a mixture thereof, an aqueous solution, or the like. That is, the treatment liquid may contain water and a non-aqueous component.

[0055] Examples of the amine compound include 2-aminoethanol (MEA: solubility parameter = 14.3 (cal / cm 3 )) 1 / 2 ), 2-(2-aminoethoxy)ethanol (AEE: solubility parameter = 12.7 (cal / cm 3 )) 1 / 2 ) and other primary amines, such as 2-(methylamino)ethanol (MAE), 2-(ethylamino)ethanol (EAE), 2-(butylamino)ethanol (BAE) and other secondary amines, and such as triethanolamine (TEA), N-methyldiethanolamine (MDEA), tetramethylethylenediamine (TEMED), pentamethyldiethylenetriamine (PMDETA), hexamethyltriethylenetetramine, bis(2-dimethylaminoethyl)ether and other tertiary amines.

[0056] Examples of the organic solvent include 1-butanol (solubility parameter = 11.3 (cal / cm 3 )) 1 / 2 ), 1-pentanol (solubility parameter = 11. (cal / cm 3 )) 1 / 2 ), octanol, diethylene glycol diethyl ether (DEGDEE), diethylene glycol dimethyl ether (DEGDME), etc., and a plurality of types may be mixed and used.

[0057] When the solubility parameters of the amine compound and the organic solvent fall within a predetermined range, the treatment solution is separated into two phases by absorption of the acidic compound: a phase with a high concentration of the acidic compound and a phase with a low concentration of the acidic compound. Here, the solubility parameter is given by the following equation (1).

[0058]

number

[0059] ΔH is the latent heat of vaporization of moles, R is the gas constant, T is the absolute temperature, and V is the molar volume.

[0060] [Table 1]

[0061] As shown in Table 1, in an absorbent containing water, an amine compound, and an organic solvent, the value obtained by subtracting the solubility parameter of the organic solvent from the solubility parameter of the amine compound is 1.1 (cal / cm³). 3 ) 1 / 2 More than 4.2(cal / cm 3 ) 1 / 2By selecting the following combination of amine compounds and organic solvents, the absorption of acidic compounds results in two-phase separation into a phase with a high concentration of acidic compounds and a phase with a low concentration of acidic compounds. If the difference in solubility parameters is less than the lower limit, the treatment solution may not separate into two phases even if it absorbs acidic compounds. On the other hand, if the difference in solubility parameters exceeds the upper limit, the treatment solution may separate into two phases before absorbing acidic compounds, and in the step of contacting the treatment solution with the gas to be treated containing acidic compounds, the contact state between the treatment solution and the gas to be treated may become non-uniform, potentially reducing the absorption efficiency. In Table 1, "Good" means that there was a single liquid phase before carbon dioxide absorption and that it separated into two liquid phases after carbon dioxide absorption. Also, in Table 1, "Not Miscible" means that there was a two-liquid phase state before carbon dioxide absorption and that a single liquid phase was not formed. Also, in Table 1, "Not Separated" means that there was a single liquid phase even after carbon dioxide absorption.

[0062] It is desirable to set the absorption conditions in absorber 21 to a region where the processed liquid separates into two phases and a large amount of carbon dioxide dissolves, and to set the regeneration conditions in regenerator 22 to a region where the processed liquid does not separate into two phases and not much carbon dioxide dissolves. In other words, the absorption conditions and regeneration conditions are adjusted according to the partial pressure of carbon dioxide, the absorption temperature, and the regeneration temperature. This makes the processed liquid more prone to phase separation, making it possible to keep the temperature difference between the regeneration temperature and the absorption temperature lower. That is, it is possible to keep the temperature difference between the regeneration temperature and the absorption temperature low because the degree of carbon dioxide absorption changes with temperature, which changes the ease of phase separation and thus shifts the equilibrium of the carbon dioxide absorption concentration. In addition, by supplying a separation-promoting gas to the first regenerator 22, the temperature at which a predetermined regeneration rate can be achieved for the processed liquid (regeneration temperature) can be kept lower.

[0063] Here, a gas treatment method using the gas treatment apparatus 10 according to the first embodiment will be described. The gas treatment method includes an absorption step, a first regeneration step, and a second regeneration step.

[0064] The absorption process involves bringing the gas to be treated into contact with the treatment liquid in the absorber 21. The gas to be treated, containing at least carbon dioxide (an acidic compound), is supplied to the absorber 21 through the inlet passage 31. The treatment liquid is also introduced into the absorber 21 through the return passage 26. The treatment liquid comes into contact with the acidic compound contained in the gas to be treated and absorbs the acidic compound. The treatment liquid that has absorbed the acidic compound is stored in the absorber 21. If a phase-separating treatment liquid is used, the treatment liquid that comes into contact with the acidic compound undergoes phase separation into a first phase portion with a high acidic compound content and a second phase portion with a low acidic compound content.

[0065] The processed liquid stored in the absorber 21 is sent to the first regenerator 22 and the second regenerator 23 through the feed channel 25. At this time, the processed liquid flowing through the feed channel 25 is heated in the heat exchanger 28 by the processed liquid flowing through the second return channel 26b of the return channel 26. This heated processed liquid is then divided, and a portion of it is introduced into the first regenerator 22.

[0066] At this time, the first branch channel 25b and the second branch channel 25c are set so that the flow rate of the processing liquid introduced into the first regenerator 22 is less than the flow rate of the processing liquid introduced into the second regenerator 23. Therefore, a smaller flow rate of processing liquid is introduced into the first regenerator 22 than into the second regenerator 23. Consequently, the amount of acidic compounds in the first regenerator 22 is less than the amount of acidic compounds in the second regenerator 23.

[0067] In the first regenerator 22, the processing liquid is heated by the first heater 40, and a separation-accelerating gas is introduced by the introduction means 43. Therefore, in the first regenerator 22, acidic compounds are separated from the processing liquid in the presence of the separation-accelerating gas (first regeneration step). In other words, if the number of moles of separation-accelerating gas (or separation-accelerating gas consisting of water vapor) that is almost insoluble in the processing liquid is greater than the number of moles of carbon dioxide (acidic compounds) separated from the processing liquid in the first regenerator 22, the partial pressure of carbon dioxide gas in the first regenerator 22 will be lower, making it easier to expel carbon dioxide (acidic compounds) from the processing liquid. Therefore, the regeneration temperature of the processing liquid in the first regenerator 22 can be kept low.

[0068] The gas containing acidic compounds separated from the processing liquid is introduced into the second regenerator 23 through the connecting channel 44, along with the separation-promoting gas. In addition, a portion of the processing liquid that has been heated in the heat exchanger 28 and then diverted is also introduced into the second regenerator 23 through the second branch channel 25c.

[0069] In the second regenerator 23, the processing liquid is heated by the second heater 41 in the presence of gas introduced through the connection passage 44. This separates the acidic compounds from the processing liquid (second regeneration step). In the second regenerator 23, the ratio of moles of separation-promoting gas to moles of carbon dioxide (acidic compounds) is smaller compared to the first regenerator 22, but the effect of lowering the regeneration temperature due to the presence of the separation-promoting gas can still be exerted in the second regenerator 23.

[0070] The processed liquid in the first regenerator 22 flows through the first return channel 26a and the confluence channel 26c and is returned to the absorber 21. The processed liquid in the second regenerator 23 flows through the second return channel 26b and the confluence channel 26c and is returned to the absorber 21. The processed liquid flowing through the second return channel 26b heats the processed liquid flowing through the main channel 25a of the feed channel 25 in the heat exchanger 28. On the other hand, the processed liquid flowing through the first return channel 26a is at a relatively low temperature and is returned to the absorber 21 without passing through the heat exchanger 28.

[0071] In the first regenerator 22 and the second regenerator 23, a mixed gas containing water vapor evaporated from the processing liquid and acidic compounds separated from the processing liquid is discharged from the second regenerator 23 to the supply channel 45. In the supply channel 45, the water vapor condenses in the regeneration-side condenser 46 and is returned to the second regenerator 23. The gas, after the water vapor has been removed, comes into contact with rinse water in the regeneration-side washing section 47. This recovers non-aqueous components such as amines released from the processing liquid into the rinse water. This rinse water is returned to the regeneration-side condenser 46. The gas from which water vapor and non-aqueous components have been removed (for example, gas containing carbon dioxide and hydrogen) is sent to the gas consumer.

[0072] As explained above, in this embodiment, since separation-accelerating gas is introduced into the first regenerator 22, the regeneration temperature of the processed liquid can be reduced in the first regenerator 22. On the other hand, gas containing the separation-accelerating gas that has passed through the first regenerator 22 is introduced into the second regenerator 23. Since this gas also contains gas components released from the processed liquid in the first regenerator 22, the effect of reducing the regeneration temperature in the second regenerator 23 is lower than that of the first regenerator 22. However, since separation-accelerating gas is also included, the gas that has flowed out of the first regenerator 22 is introduced into the second regenerator 23, so the regeneration temperature of the processed liquid can be reduced in the second regenerator 23 as well, although not to the same extent as in the first regenerator 22. Therefore, the effect of reducing the regeneration temperature of the processed liquid can be exerted in both the first regenerator 22 and the second regenerator 23.

[0073] Furthermore, since the separation-accelerating gas used to lower the regeneration temperature in the first regenerator 22 is also used in the second regenerator 23, the total supply of separation-accelerating gas can be prevented from becoming excessive. In addition, since the regeneration temperature of the processed liquid in the first regenerator 22 can be lowered to that of the processed liquid in the second regenerator 23, the degree of freedom in selecting the heat source for heating the processed liquid in the first regenerator 22 can be greatly increased.

[0074] Furthermore, in this embodiment, since the absorber 21 or the second regenerator 23 is provided with cleaning units 35 and 47, non-aqueous components scattered from the processing liquid can be recovered into the processing liquid by the absorption-side cleaning unit 35 and the regeneration-side cleaning unit 47. Therefore, it is possible to suppress the discharge of non-aqueous components from the gas processing device 10.

[0075] Furthermore, in this embodiment, the heat exchanger 28 can heat the processing liquid introduced from the absorber 21 to the first regenerator 22 and the second regenerator 23 using the processing liquid heated in the second regenerator 23. This contributes to reducing the energy required for the regeneration of the processing liquid in the first regenerator 22 and the second regenerator 23. On the other hand, since the temperature of the processing liquid heated in the first regenerator 22 is relatively low, it does not pass through the heat exchanger 28. Therefore, it is possible to suppress the decrease in the temperature of the processing liquid introduced from the absorber 21 to the first regenerator 22 and the second regenerator 23 due to the processing liquid moving from the first regenerator 22 to the absorber 21.

[0076] (Second Embodiment) As shown in Figure 2, in the second embodiment, a heat supply means 50 is provided for supplying heat from the gas treatment device 10 to the first regenerator 22. Here, the same reference numerals are used for the same components as in the first embodiment, and their detailed descriptions are omitted.

[0077] The heat supply means 50 is provided to utilize unused heat within the gas processing apparatus 10 to heat the processing liquid in the first regenerator 22. For example, the heat supply means 50 shown in Figure 2 is configured to supply heat from the absorber 21 to the first regenerator 22. That is, the heat supply means 50 includes a circulation path 51 containing a fluid for transporting heat, and a pump 52 for circulating the fluid. The circulation path 51 includes a heat absorption section 51a that receives heat from within the gas processing apparatus 10 to raise the temperature of the fluid, and a heat dissipation section 51b that releases the heat from the heated fluid.

[0078] The heat-absorbing section 51a shown in Figure 2 is thermally connected to the absorber 21. That is, the heat-absorbing section 51a is located inside the absorber 21 and consists of a heat exchange section such as a heat transfer tube that generates heat exchange between the processing liquid inside the absorber 21 and the fluid in the circulation path 51, thereby raising the temperature of the fluid.

[0079] The heat dissipation unit 51b is thermally connected to the first regenerator 22. Specifically, the heat dissipation unit 51b shown in Figure 2 is configured to be placed in the first heater 40 and heat the processing liquid in the first regenerator 22. That is, the fluid circulating in the circulation path 51 is used as a heat source fluid to heat the processing liquid in the first heater 40, and the heat dissipation unit 51b functions as the first heater 40 that heats the processing liquid in the first regenerator 22.

[0080] The flow rate of the separation-accelerating gas supplied to the first regenerator 22 by the introduction means 43 is adjusted by the flow rate adjustment unit 53. The flow rate adjustment unit 53 is composed of, for example, a valve located in the introduction passage 43a of the introduction means 43. The flow rate adjustment unit 53 is configured to adjust the flow rate of the separation-accelerating gas so that the ratio of the number of moles of acidic compounds (e.g., carbon dioxide) separated from the processing liquid introduced into the first regenerator 22 to the number of moles of separation-accelerating gas (e.g., hydrogen) (stripping ratio = hydrogen / carbon dioxide) falls within a predetermined range.

[0081] Furthermore, the first branch channel 25b and the second branch channel 25c are configured such that the flow rate of the processing liquid introduced into the first regenerator 22 is less than the flow rate of the processing liquid introduced into the second regenerator 23. As a result, the flow rate of the processing liquid introduced into the first regenerator 22 is suppressed, and the number of moles of acidic compounds separated from the processing liquid in the first regenerator 22 is also suppressed. This prevents the flow rate of the separation-promoting gas from becoming too large when the flow rate adjustment unit 53 adjusts the flow rate of the separation-promoting gas so that the stripping ratio becomes a predetermined ratio.

[0082] By adjusting the flow rate of the separation-promoting gas so that the stripping ratio is a predetermined ratio, the regeneration temperature in the first regenerator 22 can be kept low. In other words, even if the temperature of the processing liquid in the first regenerator 22 is lower than the temperature of the processing liquid in the absorber 21, it is possible to desorb acidic compounds from the processing liquid in the first regenerator 22. Therefore, the first heater 40 can be set to heat the processing liquid in the first regenerator 22 to a temperature lower than the temperature of the processing liquid in the absorber 21. For this reason, as described above, the heat dissipation section 51b of the circulation path 51 is placed in the first heater 40, and the processing liquid in the first regenerator 22 is heated by the heat dissipation section 51b, but the amount of heating at that time may be an amount of heating that makes the temperature in the first regenerator 22 lower than the temperature in the absorber 21.

[0083] Here, we present an example of the results of a specific simulation. The simulation compares seven conditions, Conditions 1 to 7, as shown in Table 2.

[0084] [Table 2]

[0085] As shown in Table 2, under conditions 1, 2, 4, and 6, the processing liquid discharged from the absorber 21 is introduced only into the first regenerator 22 and not into the second regenerator 23. On the other hand, under conditions 3, 5, and 7, the processing liquid discharged from the absorber 21 is distributed to the first regenerator 22 and the second regenerator 23 in a ratio of 15:85. Furthermore, under condition 1, the water content of the separation-accelerating gas is set to 10 vol%; under conditions 2 and 3, it is set to 5 vol%; under conditions 4 and 5, it is set to 3 vol%; and under conditions 6 and 7, it is set to 0 vol%. Under these conditions, the stripping ratio is set to 4, and the amine loss is constant under conditions 2 and 3, constant under conditions 4 and 5, and constant under conditions 6 and 7.

[0086] Calculating with the absorber 21 temperature at 50°C, under conditions 1, 2, 4, and 6, the temperature of the first regenerator 22 is 65°C, while under conditions 3, 5, and 7, the temperature of the first regenerator 22 is 45°C and the temperature of the second regenerator 23 is 68.5°C. Therefore, it can be seen that when a separation-accelerating gas is introduced under conditions where the stripping ratio is, for example, 4, the processing liquid will be regenerated in the first regenerator 22 even if the temperature inside the first regenerator 22 is lower than the temperature inside the absorber 21. In other words, by keeping the flow rate of the processing liquid distributed to the first regenerator 22 lower than the flow rate of the processing liquid distributed to the second regenerator 23, it is possible to suppress the flow rate of the separation-accelerating gas required to keep the stripping ratio in the first regenerator 22 within a predetermined range, and by keeping the regeneration temperature in the first regenerator 22 low, the heat inside the gas treatment device 10 can be utilized for the regeneration of the processing liquid. Furthermore, the conditions under which the processing solution can be regenerated at a temperature lower than that in the absorber 21 are not limited to the condition where the stripping ratio is 4.

[0087] Therefore, according to this embodiment, the heat within the gas treatment device 10 can be effectively utilized, thus reducing the total energy consumption. This makes it possible to separate acidic compounds with less energy. Specifically, since the regeneration temperature in the first regenerator 22 is reduced, the excess heat within the gas treatment device 10 can be used for regenerating the treatment liquid in the first regenerator 22. Therefore, the total energy consumption can be reduced.

[0088] Furthermore, since the flow rate adjustment unit 53 provided in the introduction passage 43a can adjust the flow rate of the separation-promoting gas so that the stripping ratio falls within a predetermined range, the regeneration temperature can be effectively reduced.

[0089] In Figure 2, the heat absorption section 51a of the circulation path 51 is composed of a heat exchange section such as a heat transfer tube located inside the absorber 21, but it is not limited to this. For example, as shown in Figure 3, the heat absorption section 51a may be composed of a heat exchange section (or heat exchange jacket) such as a heat transfer tube located outside the absorber 21 so as to be thermally connected to the outer circumferential surface of the absorber 21.

[0090] In Figure 2, the heat dissipation section 51b of the circulation path 51 is provided to function as a first heater 40 located on the outside of the main body of the first regenerator 22, but it is not limited to this. For example, as shown in Figure 4, the heat dissipation section 51b of the circulation path 51 may be provided to function as a first heater 40 located inside the first regenerator 22. Also, as shown in Figure 5, the heat dissipation section 51b may be configured to function as a first heater 40 thermally connected to the outer circumferential surface of the main body of the first regenerator 22.

[0091] The other configurations, functions, and effects will not be described here, but the description of the first embodiment can be applied to the second embodiment.

[0092] (Third embodiment) As shown in Figure 6, in the third embodiment, the absorber 21 and the first regenerator 22 are in thermal contact. Note that the same reference numerals are used for the same components as in the first embodiment, and their detailed descriptions are omitted.

[0093] The absorber 21 and the first regenerator 22 can be configured as an integrated heat exchange device 55 using a double-tube heat exchanger, a shell-and-tube heat exchanger with bundled double tubes, a plate heat exchanger, or the like. In Figure 6, an example is shown in which the outer tube of the heat exchange device 55 constitutes the absorber 21, and the inner tube of the heat exchange device 55 constitutes the first regenerator 22.

[0094] In the third embodiment, the introduction means 43 also includes a flow rate adjustment unit 53 that adjusts the flow rate of the separation-promoting gas supplied to the first regenerator 22. This flow rate adjustment unit 53 is configured to adjust the flow rate of the separation-promoting gas so that the stripping ratio (= hydrogen / carbon dioxide ratio) falls within a predetermined range.

[0095] Furthermore, the first branch channel 25b and the second branch channel 25c are configured such that the flow rate of the processed liquid introduced into the first regenerator 22 is less than the flow rate of the processed liquid introduced into the second regenerator 23.

[0096] By adjusting the flow rate of the separation-promoting gas so that the stripping ratio is a predetermined ratio, the temperature of the processing liquid in the first regenerator 22 can be set lower than the temperature of the processing liquid in the absorber 21. Therefore, it becomes possible to desorb acidic compounds from the processing liquid in the first regenerator 22 by utilizing the heat from the absorber 21.

[0097] Therefore, according to this embodiment, the heat from the absorber 21 can be effectively utilized, thus reducing the total energy consumption. Consequently, separation of acidic compounds becomes more energy-efficient. In other words, the reduction in the regeneration temperature in the first regenerator 22 is promoted, making it possible to utilize the heat from the absorber 21 for regenerating the processed liquid in the first regenerator 22. Consequently, the total energy consumption can be reduced.

[0098] The other configurations, functions, and effects will not be described here, but the description of the first embodiment can be applied to the second embodiment.

[0099] (Fourth Embodiment) In the second and third embodiments, the heat from the absorber 21 is used to regenerate the processing liquid in the first regenerator 22. In contrast, in the fourth embodiment, as shown in Figure 7, the heat from the processing liquid (lean liquid) flowing through the return channel 26 is used to regenerate the processing liquid in the first regenerator 22. Here, the same reference numerals are used for the same components as in the first embodiment, and their detailed descriptions are omitted.

[0100] The heat absorption section 51a of the circulation path 51 is located in the confluence passage 26c of the return passage 26. That is, the heat absorption section 51a is configured to heat the fluid flowing through the circulation path 51 with the heat of the processed liquid (heat in the gas processing device 10) that is returned to the absorber 21. The fluid heated in the heat absorption section 51a then heats the processed liquid in the first regenerator 22 in the heat dissipation section 51b.

[0101] In Figure 7, the heat absorption section 51a is located in the confluence channel 26c of the return channel 26. Alternatively, the heat absorption section 51a may be located in the second return channel 26b of the return channel 26. In that case, it is preferable that the heat absorption section 51a be located downstream of the heat exchanger 28 in the second return channel 26b.

[0102] In the configuration where the heat absorption section 51a receives heat from the processing liquid returned to the absorber 21, the heat dissipation section 51b may be thermally connected to the outer surface of the first regenerator 22, as shown in Figure 8.

[0103] Furthermore, in Figure 7, the circulation path 51 is provided with a heat absorption section 51a that heats the fluid flowing through the circulation path 51 with the processing liquid flowing through the confluence passage 26c, and the heat dissipation section 51b heats the processing liquid in the first regenerator 22 with the heat from the fluid heated by the heat absorption section 51a. In other words, Figure 7 shows an example in which a fluid other than the processing liquid is sealed in the circulation path 51. Alternatively, Figure 9 shows a configuration in which the fluid flowing through the circulation path 51 is the processing liquid. That is, since the temperature of the processing liquid flowing through the confluence passage 26c is higher than the temperature of the processing liquid in the first regenerator 22, the processing liquid flowing through the confluence passage 26c is used as a heat source for the processing liquid in the first regenerator 22. For this reason, the circulation path 51 is connected to the confluence passage 26c of the return passage 26 so that the processing liquid in the confluence passage 26c flows into the circulation path 51. In this configuration, the processing liquid from the first regenerator 22 is heated in the confluence channel 26c, so the confluence channel 26c functions as a heat absorption section 51a that heats the fluid in the circulation path 51 using the heat in the gas treatment device 10. The fluid (processing liquid) heated in the heat absorption section 51a is introduced into the first heater 40, which heats the processing liquid inside the first heater 40. The first heater 40 functions as a heat dissipation section 51b. The fluid (processing liquid) heated in the first heater 40 then flows through the circulation path 51 and is introduced into the absorber 21. The confluence channel 26c, which functions as a heat absorption section 51a, passes outside the absorber 12.

[0104] Instead of Figure 9, the heat dissipation section 51b may be located inside the first regenerator 22, as shown in Figure 10. In this case, the processing liquid flowing through the merging channel 26c of the return channel 26 merges with the circulation channel 51. This processing liquid is introduced into the heat dissipation section 51b inside the first regenerator 22, where it is heated. After passing through the heat dissipation section 51b, the processing liquid is returned to the absorber 12.

[0105] The other configurations, functions, and effects will not be described here, but the descriptions of the first to third embodiments can be applied to the fourth embodiment.

[0106] (Fifth embodiment) As shown in Figure 11, in the fifth embodiment, an adjustment means 57 is provided for adjusting the water content of the processing liquid to a predetermined range. Here, the same reference numerals are used for the same components as in the first embodiment, and their detailed descriptions are omitted.

[0107] The adjustment means 57 is configured to adjust the amount of water introduced into the processing solution so that the water content of the processing solution falls within a predetermined range. In other words, since fluctuations in the water content of the processing solution affect the ability of the processing solution to separate acidic compounds, the adjustment means 57 is provided to keep the water content of the processing solution within a predetermined range.

[0108] The adjustment means 57 may include, for example, a flow rate adjustment unit 57a located in the inlet passage 31 connected to the absorber 21. The adjustment means 57 may also include a flow rate adjustment unit 53 located in the inlet passage 43a of the introduction means 43. The adjustment means 57 may also include a flow rate adjustment unit 57b located in the water replenishment passage 59a for replenishing water, which is part of the replenishment unit 59 for replenishing the processing liquid in the gas processing device 10. The replenishment unit 59 may also include a replenishment unit 59b for replenishing amine compounds in the processing liquid and a replenishment unit 59c for replenishing organic solvents in the processing liquid. The adjustment means 57 may also include a flow rate adjustment unit 57c located in the piping that supplies wash water to the absorption-side washing unit 35. The adjustment means 57 may also include a flow rate adjustment unit 57d located in the piping that supplies wash water to the regeneration-side washing unit 47. Any of the flow rate adjustment units 53, 57a to 57d may be omitted. The flow rate adjustment units 53, 57a to 57d may include valves or the like.

[0109] A portion of the processing liquid in the gas processing device 10 may be taken to measure its water content, and the amount of water brought in may be adjusted by the adjustment means 57 according to the measurement result. The water content of the processing liquid is adjusted to a range of, for example, 5% to 20%, preferably 8% to 15%, and more preferably 8% to 12%.

[0110] To reduce the amount of moisture introduced, a cooler 61 may be provided in the inlet passage 31, as shown in Figure 12. By cooling the gas to be treated introduced into the absorber 21, the amount of water vapor in the gas to be treated can be reduced. Alternatively, or in conjunction with this, a cooler 62 may be provided in the introduction passage 43a of the separation-accelerating gas. By cooling the separation-accelerating gas introduced into the first regenerator 22, the amount of water vapor in the separation-accelerating gas can be reduced.

[0111] Here, we will explain the amount of energy required to heat the treatment solution in order to obtain a predetermined regeneration rate for each of the conditions 1 to 7 shown in Table 2.

[0112] As shown in Figure 13, compared to Condition 1, where the water content of the separation-accelerating gas is 10% by volume, the amount of energy required increases for Conditions 2 to 7, where the water content of the separation-accelerating gas is 0 to 5% by volume. This is because when the water content of the separation-accelerating gas is low, the amount of water carried in by the separation-accelerating gas decreases. In other words, since the adjustment means 57 operates the system so that the water content of the processing liquid falls within a predetermined range, if the amount of water carried in by the separation-accelerating gas is small, water will be introduced through the water replenishment section, etc. As a result, the amount of liquid water increases, which increases the amount of energy required for the evaporation of water in the first regenerator 22 and the second regenerator 23. Furthermore, comparing Conditions 2 and 3, where the water content of the separation-accelerating gas is 5% by volume, it can be seen that Condition 3, in which the processing liquid is distributed to both the first regenerator 22 and the second regenerator 23, requires more energy than Condition 2, in which the processing liquid is introduced only to the first regenerator 22.

[0113] On the other hand, comparing conditions 4 and 5, where the water content of the separation-accelerating gas is 3 volume%, it can be seen that distributing the processed liquid to the first regenerator 22 and the second regenerator 23 requires less energy than introducing the processed liquid only to the first regenerator 22. This trend is also observed in conditions 6 and 7, where the water content of the separation-accelerating gas is 0 volume%. In other words, a similar trend is observed when the separation-accelerating gas contains 3 volume% or less of water, or when the separation-accelerating gas contains no water. This is presumed to be because, when the water content of the separation-accelerating gas is 3 volume% or less, evaporation of water is more dominant than condensation in the first regenerator 22, but when the water content of the separation-accelerating gas is 5 volume% or more, condensation of water is more dominant than evaporation. From these results, it can be seen that if the water content of the separation-accelerating gas is 3 volume% or less, the effect of reducing the required energy by distributing the processed liquid to the first regenerator 22 and the second regenerator 23 is realized.

[0114] Furthermore, as shown in Figure 14, under conditions 2 to 7, where the water content of the separation-accelerating gas is 0 to 5 volume%, the amount of amine evaporation is kept lower compared to condition 1, where the water content of the separation-accelerating gas is 10 volume%. Moreover, under conditions 2 to 7, the amount of amine evaporation decreases as the water content of the separation-accelerating gas decreases. In other words, when the water content of the separation-accelerating gas is low and the amount of water brought in by the separation-accelerating gas decreases, the amount of water used for washing by the washing unit increases, thus reducing the amount of amine discharged to the outside of the gas treatment device 10. Therefore, the amount of amine replenishment can be reduced, which also contributes to reducing running costs.

[0115] Therefore, according to this embodiment, the water content in the processing liquid may change due to the introduction of the separation-promoting gas into the first regenerator 22, and due to the washing of the processing liquid with water in at least one of the absorption-side washing section 35 and the regeneration-side washing section 47. However, since the water content of the processing liquid is adjusted by the adjustment means 57, it is possible to prevent deterioration of the separation ability of acidic compounds by the processing liquid and to suppress an increase in energy intensity.

[0116] The other configurations, functions, and effects will not be described here, but the description of the first embodiment can be applied to the second embodiment.

[0117] (Other embodiments) It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The present invention is not limited to the embodiments described above, and various modifications and improvements are possible without departing from its spirit. [Explanation of Symbols]

[0118] 10: Gas treatment equipment 21: Absorber 22:First regenerator 23:Second regenerator 28: Heat exchanger 35: Absorption side cleaning section 43: Introduction methods 44: Connecting path 47: Regeneration side cleaning unit 50: Heat supply means 57: Adjustment means

Claims

1. An absorber that brings a gas to be treated containing an acidic compound that produces acid upon dissolution in water into contact with a treatment liquid, thereby absorbing the acidic compound contained in the gas to be treated into the treatment liquid. A first regenerator is provided in which a portion of the processing liquid that has absorbed the acidic compound in the absorber is introduced, and the introduced processing liquid is heated to separate the acidic compound from the processing liquid. A second regenerator is connected in parallel with the first regenerator, into which a portion of the processing liquid that has absorbed the acidic compound in the absorber is introduced, and the introduced processing liquid is heated to separate the acidic compound from the processing liquid. An introduction means for introducing a separation-promoting gas that promotes the separation of the acidic compound from the processing liquid into the first regenerator, A connecting path for introducing the gas containing the separation-promoting gas discharged from the first regenerator into the second regenerator, Equipped with, Gas treatment device.

2. The system further comprises a heat supply means for supplying heat from within the gas treatment apparatus to the first regenerator. The gas treatment apparatus according to claim 1.

3. The absorber and the first regenerator are thermally connected to each other so that the heat from the absorber is transferred to the first regenerator. The gas treatment apparatus according to claim 1.

4. The aforementioned processing liquid contains water and non-aqueous components. The absorber or the second regenerator is further provided with a washing unit that washes the processing liquid with water to recover non-aqueous components scattered from the processing liquid. A gas treatment apparatus according to any one of claims 1 to 3.

5. The system further includes an adjustment means for adjusting the water content of the processing liquid to a predetermined range. The gas treatment apparatus according to claim 4.

6. The system further comprises a heat exchanger that exchanges heat between the heat of the processing liquid flowing from the absorber to the first regenerator and the second regenerator and the heat of the processing liquid flowing from the second regenerator to the absorber. The flow path of the processing liquid from the first regenerator to the absorber is configured to return the processing liquid from the first regenerator to the absorber without passing through the heat exchanger. A gas treatment apparatus according to any one of claims 1 to 3.

7. The introduction means is configured to introduce the separation-promoting gas having a water content of 3% by volume or less. A gas treatment apparatus according to any one of claims 1 to 3.

8. In the absorber, the gas to be treated, which contains an acidic compound that produces acid when dissolved in water, and the treatment liquid are brought into contact with each other, and the acidic compound contained in the gas to be treated is absorbed into the treatment liquid. A portion of the processing liquid discharged from the absorber and a separation-promoting gas that promotes the separation of the acidic compound from the processing liquid are introduced into the first regenerator. In the first regenerator, the treatment liquid that has absorbed the acidic compound is heated in the presence of the separation-promoting gas to separate the acidic compound from the treatment liquid. A portion of the processing liquid discharged from the absorber and the gas containing the separation-promoting gas discharged from the first regenerator are introduced into the second regenerator. In the second regenerator, the treatment liquid that has absorbed the acidic compound is heated in the presence of the gas containing the separation-promoting gas to separate the acidic compound from the treatment liquid. Gas treatment method.

9. The heat from within the gas treatment apparatus, which comprises the absorber, the first regenerator, and the second regenerator, is supplied to the first regenerator. The gas treatment method according to claim 8.

10. A gas treatment method using the gas treatment apparatus described in claim 6, In the heat exchanger, heat is exchanged between the heat of the processing liquid flowing from the absorber to the first regenerator and the second regenerator and the heat of the processing liquid flowing from the second regenerator to the absorber. The processing liquid flowing from the first regenerator toward the absorber is returned to the absorber without passing through the heat exchanger. Gas treatment method.

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