CO2 recovery system

Abstract

A CO2 recovery system (1) for recovering CO2 by bringing a CO2-containing gas into contact with a NaOH-containing reaction solution stored in a reaction tank (11) to generate a target product. The target product extracted from the reaction solution is adjusted on the basis of the maximum temperature of the reaction solution after NaHCO3 is generated in the reaction solution, the extraction temperature, which is the temperature of the reaction solution when the target product is extracted from the reaction tank (11), and the initial concentration of NaOH in the reaction solution.

Description

Technical Field

[0001] The present invention relates to a CO2 recovery system. Background Art

[0002] In recent years, it has been required to suppress the emission of CO2 gas, which is a greenhouse gas, and various methods for recovering CO2 gas have been studied. As a method for recovering CO2, for example, there is a method of chemically absorbing CO2 into an amine solution for recovery, but since the amine solution that absorbs CO2 cannot be used as a resource, it is necessary to separate CO2. In addition, the separation of CO2 requires heating, resulting in energy loss. In addition, there is a method of physically adsorbing CO2 on zeolite for recovery, but pressure and heating are required during adsorption, resulting in energy loss, and the zeolite that adsorbs CO2 cannot be used as a resource, so it is necessary to separate CO2.

[0003] In addition, as a method for recovering CO2, there is a method of chemically absorbing CO2 into an alkaline solution such as NaOH for recovery. For example, in the structure disclosed in Patent Document 1, the CO2 generated in the fermentation of L-glutamic acid is aerated with an aqueous NaOH solution to generate NaHCO3 or Na2CO3, thereby fixing CO2 for recovery. In addition, the structure disclosed in Patent Document 2 is also to recover CO2 from the waste gas of a power plant, a chemical plant, etc. by contacting the waste gas with an aqueous NaOH solution to generate NaHCO3 or Na2CO3. These products are useful as resources, and the recovered CO2 can be effectively reused without separating CO2. In addition, even in the case of separating CO2, citric acid can be added to the product aqueous solution, and there is no need to heat it, so there is little energy loss.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 11-243985

[0007] Patent Document 2: Japanese Patent Application No. 2009-535198 Summary of the invention

[0008] In order to utilize NaHCO3 and Na2CO3 as products more effectively as resources, it is necessary to improve the purity. However, in the configuration disclosed in Patent Documents 1 and 2, the ratio of the product varies with the CO2 concentration and reaction time in the gas containing CO2, so it is difficult to generate the products separately, and the purity of the obtained products is easy to decrease. Therefore, there is room for improvement in generating the products separately to improve the purity of the products.

[0009] The present disclosure aims to provide a CO2 recovery system capable of achieving high purity of the target product.

[0010] One embodiment of the present disclosure is a CO2 recovery system that recovers CO2 by contacting a gas containing CO2 with a reaction solution containing NaOH stored in a reaction tank to generate a target product.

[0011] The target product taken out from the reaction liquid is adjusted according to the maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid, the temperature of the reaction liquid when the target product is taken out from the reaction tank, i.e., the taking-out temperature, and the initial concentration of NaOH in the reaction liquid.

[0012] In addition, another embodiment of the present disclosure is a CO2 recovery system that recovers CO2 by contacting a gas containing CO2 with a reaction solution containing NaOH stored in a reaction tank to generate a predetermined target product.

[0013] The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is determined based on the target product taken out from the reaction solution.

[0014] The initial concentration of NaOH in the reaction solution is determined based on the target product taken out from the reaction solution and the temperature of the reaction solution when the target product is taken out from the reaction tank, that is, the taking-out temperature.

[0015] According to the CO2 recovery system of one of the above-mentioned methods, the target product taken out from the reaction liquid is adjusted by adjusting the maximum temperature of the reaction liquid after the NaHCO3 in the reaction liquid is generated, the temperature of the reaction liquid when the target product is taken out from the reaction tank, i.e., the taking-out temperature, and the initial concentration of NaOH in the reaction liquid. Therefore, it is easy to generate the products separately and to take out the desired target product with high purity.

[0016] In addition, according to the CO2 recovery system of the other embodiment, the maximum temperature of the reaction liquid after the generation of NaHCO3 is determined according to the specified target product, and the initial concentration of NaOH in the reaction liquid is determined according to the specific target product and the extraction temperature. Thus, it can become a CO2 recovery system suitable for obtaining a predetermined target product with high purity.

[0017] As described above, according to the above aspect, it is possible to provide a CO 2 recovery system that can achieve high purity of the target product.

[0018] It should be noted that the symbols in parentheses described in the claims indicate the corresponding relationship with the specific means described in the embodiments described later, and do not limit the technical scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is a schematic diagram showing the structure of the CO 2 recovery system in Embodiment 1.

[0020] Figure 2 This is a diagram showing the linear approximation of the temperature (liquid temperature) and the NaOH concentration required to generate NaHCO3 at saturated solubility.

[0021] Figure 3 This is a schematic diagram showing the correspondence between the initial concentration of NaOH and the target product in the first embodiment.

[0022] Figure 4 This is a diagram showing the linear approximation of the temperature (liquid temperature) and the NaOH concentration required to generate Na2CO3 at saturated solubility.

[0023] Figure 5 This is a schematic diagram showing the correspondence between the initial concentration of NaOH and the target product in the second embodiment.

[0024] Figure 6 This is a schematic diagram showing the correspondence between the initial concentration of NaOH and the target product in the third embodiment.

[0025] Figure 7 It is a schematic diagram showing the correspondence between the initial concentration of NaOH and the target product in the fourth embodiment.

[0026] Figure 8 It is a schematic diagram showing the correspondence between the initial concentration of NaOH and the target product in the fifth embodiment.

[0027] Fig. 9 This is a schematic diagram showing the structure of the CO2 recovery system in the sixth embodiment.

[0028] Fig.10 It is a schematic diagram showing the correspondence between the initial concentration of NaOH and the target product. DETAILED DESCRIPTION

[0029] (Implementation Method 1)

[0030] use Figure 1 to Figure 3 Embodiment 1 of the CO 2 recovery system is described.

[0031] 1-1. Target product

[0032] In the CO2 recovery system 1, the target product generated by contacting the gas containing CO2 with the reaction solution containing NaOH can be an aqueous solution or solid of NaHCO3, an aqueous solution or solid of Na2CO3, or an aqueous solution or solid of a mixture of NaHCO3 and Na2CO3, i.e., sodium sesquicarbonate. In the present embodiment 1, the target product is an aqueous solution of NaHCO3.

[0033] 1-2. Gas containing CO2

[0034] like Figure 1 As shown, the CO2 recovery system 1 of the present embodiment is configured to recover CO2 from the CO2-containing gas, i.e., the exhaust gas, emitted by the CO2 emission device 100. In this specification, "gas containing CO2" refers to a gas containing CO2 as a constituent component. The CO2-containing gas may be a gas containing only CO2 as a constituent component, or may be a gas further containing inevitable impurities. In addition, the CO2-containing gas may be a mixed gas in which CO2 and other substances are mixed as constituent components. There is no limitation on the proportion of CO2 in the mixed gas, and the main component that accounts for the largest proportion in the mixed gas may be CO2, or may be a substance other than CO2.

[0035] 1-3.CO2 emission equipment 100

[0036] Figure 1 The CO2 emission device 100 shown is not particularly limited as long as it is a device that emits gas containing CO2, and examples thereof include a device having a boiler, a fuel cell, an incinerator, a heat treatment device, etc. An exhaust pipe 20 is connected to the CO2 emission device 100, and the gas containing CO2, that is, the exhaust gas G0 is discharged through the exhaust pipe 20. The temperature of the exhaust gas G0 discharged from the CO2 emission device 100 is not particularly limited, and is preferably a high temperature, for example, it can have a temperature in the range of 100°C to 300°C. In this embodiment, the exhaust gas G0 discharged from the CO2 emission device 100 has a temperature of 140°C.

[0037] 1-4.CO2 recovery system 1

[0038] The CO 2 recovery system 1 of the present embodiment mainly includes a CO 2 recovery device 10, a gas flow path 21, a water removal filter 30, an air pump 40, a liquid temperature adjustment device 50, and a filter 60. Each of the components will be described below.

[0039] 1-5. Gas flow path 21

[0040] The gas containing CO2 is made to flow through the gas flow path 21. In the present embodiment 1, the gas flow path 21 is formed by a pipe connected to the exhaust pipe 20, and the exhaust pipe 20 is connected to the CO2 emission device 100. The gas containing CO2 flowing through the exhaust pipe 20, that is, a part of the exhaust gas G0 flows through the gas flow path 21.

[0041] It should be noted that in the present embodiment 1, considering that if the amount of gas containing CO2 that bubbles in the reaction tank 11 described later is too much, it is difficult for it to become fine bubbles in the reaction liquid, and the structure is such that only a part of the exhaust gas G0 discharged from the CO2 emission device 100 flows in the gas flow path 21, and the other exhaust gas that does not flow in the gas flow path 21 is released to the outside via the exhaust pipe 20.

[0042] 1-6. Water removal filter 30

[0043] The dewatering filter 30 is provided in the gas flow path 21 to remove moisture from the gas containing CO2 flowing in the gas flow path 21. Although not shown in the figure, the dewatering filter 30 is composed of a water separator, which includes: a water separation section for separating the water vapor contained in the gas containing CO2 as a liquid, and a gas passing section through which the gas containing CO2 after the water vapor is separated and removed passes. The separated moisture is stored in a water tank not shown in the figure and discharged appropriately. The exhaust gas passing through the gas passing section is discharged into the pipe 31 connected to the air pump 40 described later. Water is removed by the dewatering filter 30, thereby preventing water from accumulating in the air pump 40 of the rear section.

[0044] 1-7. Air pump 40

[0045] The air pump 40 is connected to the water removal filter 30 via the pipe 31 to suck the gas containing CO2. Through the suction of the air pump 40, a part of the exhaust gas flows from the exhaust pipe 20 to the gas flow path 21. The sucked gas containing CO2 is supplied to the reaction tank 11 described later via the pipe 41. The structure of the air pump 40 is not limited, and a diaphragm pump in which the gas does not directly contact the driving part of the air pump 40 is preferred.

[0046] The driving control of the air pump 40 is performed by the pump control unit 45. The pump control unit 45 changes the on and off of the suction action of the air pump 40 according to the detection result obtained by the pH sensor 13 that detects the pH of the reaction liquid in the reaction tank 11 described later. If the suction action of the air pump 40 is turned on, the gas containing CO2 in the reaction tank 11 described later begins to bubble, and if the suction action in the air pump 40 is turned off, the bubbling stops.

[0047] In addition, for controlling the flow rate of the gas containing CO2 by suction of the air pump 40, the operation of the air pump 40 can be controlled by the pump control unit 45 according to the detection result obtained by the temperature sensor 12 for detecting the temperature (liquid temperature) of the reaction liquid P in the reaction tank 11 described later. Thus, the reaction heat generated in the reaction tank 11 can be controlled by adjusting the amount of the gas containing CO2 supplied to the reaction tank 11 described later, so that the temperature of the reaction liquid P reaches a predetermined temperature. Furthermore, in the present embodiment 1, the temperature of the reaction liquid P is adjusted by the liquid temperature regulating device 50 described later while controlling the flow rate of the air pump 40. It should be noted that in order to minimize the energy required for adjusting the temperature of the reaction liquid P, the length of the pipe forming the gas flow path 21 and the heat dissipation of the pipe can be adjusted in advance according to the target value of the temperature of the reaction liquid P.

[0048] 1-8.CO2 recovery device 10

[0049] In the CO2 recovery device 10, the gas containing CO2 is brought into contact with the reaction liquid stored in the reaction tank 11 to recover CO2 from the gas containing CO2. The reaction liquid is an aqueous NaOH solution containing NaOH. It should be noted that the NaOH concentration in the reaction liquid will be described later.

[0050] The gas containing CO2 is supplied to the reaction tank 11 via the pipe 41. The front end of the pipe 41 is located near the inner bottom of the reaction tank 11, and is configured to discharge the gas containing CO2 into the reaction liquid to generate bubbles. It should be noted that the reaction tank 11 is provided with a temperature sensor 12 for detecting the temperature (liquid temperature) of the reaction liquid P and a pH sensor 13 for detecting the pH of the reaction liquid P.

[0051] The reaction tank 11 is provided with a liquid temperature regulating device 50 capable of heating or cooling the reaction liquid in the reaction tank 11. The liquid temperature regulating device 50 is connected to a liquid temperature regulating device control unit 55 for controlling the operation of the liquid temperature regulating device 50. The liquid temperature regulating device control unit 55 is configured to control the heating or cooling operation of the liquid temperature regulating device 50 according to the temperature of the reaction liquid P detected by the temperature sensor 12 provided in the reaction tank 11, that is, the liquid temperature. In addition, the pump control 45 controls the operation of the air pump 40 as described above according to the liquid temperature detected by the temperature sensor 12. In addition, the liquid temperature regulating device control unit 55 controls the operation of the liquid temperature regulating device 50, thereby being able to maintain the temperature of the reaction liquid or the product aqueous solution in the reaction tank 11 at a predetermined temperature.

[0052] 1-9. CO2 fixation reaction

[0053] By bringing the gas containing CO2 into contact with the reaction liquid (NaOH aqueous solution) containing NaOH in the reaction tank 11, the reaction of the following formula 1 is carried out in the reaction tank 11, and then the reaction of formula 2 is carried out. It should be noted that in this specification, the following formulas 1 and 2 are also referred to as CO2 fixation reactions.

[0054] 2NaOH+CO2→Na2CO3+H2O (Formula 1)

[0055] Na2CO3+CO2+H2O→2NaHCO3 (Formula 2)

[0056] exist Figure 1 In the reaction tank 11 shown, before the above reaction starts, there is a state in which NaHCO3 and Na2CO3 do not exist, but according to the progress of the above reaction, there will be a state in which Na2CO3 is generated but NaHCO3 does not exist, a state in which a part of Na2CO3 further reacts with CO2 to generate NaHCO3 and both exist at the same time, and any one of the states in which all Na2CO3 is converted into NaHCO3 and Na2CO3 disappears and NaHCO3 exists. The NaHCO3 and Na2CO3 produced by the above reaction are dissolved in the water in the reaction tank 11 to form an aqueous solution. In this specification, NaHCO3, Na2CO3 and a mixture of the two are collectively referred to as "products", and their aqueous solutions are collectively referred to as "product aqueous solutions". In addition, the substance that is desired to be obtained with high purity in the product is referred to as "target product".

[0057] In the present embodiment 1, the above reaction can be started by bubbling and contacting the gas containing CO2 supplied from the pipe 41 in the NaOH aqueous solution in the reaction tank 11. It should be noted that in order to increase the contact frequency between the gas containing CO2 and the NaOH aqueous solution, it is preferred to bubble and discharge the gas containing CO2 in the form of fine bubbles. The formation of fine bubbles can be performed by a fine bubble generator (not shown) provided at the front end of the pipe 41.

[0058] In the case where the exhaust gas discharged from the CO2 emission equipment 100 contains a substance that hinders the above-mentioned reaction in the reaction tank 11, it is preferred to set a filter (not shown) for removing the substance that hinders the above-mentioned reaction at a position upstream of the reaction tank 11, such as on the gas flow path 21, between the water removal filter 30 and the air pump 40, between the air pump 40 and the reaction tank 11, etc. It should be noted that, in the case where the exhaust gas discharged from the CO2 emission equipment 100 does not contain components other than CO2 or in the case where it is clear that the substance that hinders the above-mentioned reaction in the reaction tank 11 is not contained, it is not necessary to set the filter.

[0059] Figure 1The exhaust section 14 shown discharges the CO2-removed gas after the CO2 in the reaction tank 11 is removed from the reaction tank 11 to the filter 60. The filter 60 is a component that captures harmful components in the CO2-removed gas. The structure of the filter 60 is not limited. In the present embodiment 1, the filter 60 is configured to remove water-soluble substances in the CO2-removed gas (for example, NaOH in the reaction solution that becomes droplets due to the bubbling in the reaction tank 11 and reaches the exhaust section 14, and nitrogen oxides NO contained in the exhaust gas) by bubbling the CO2-removed gas through the water W stored in the filter 60. x The CO 2 removal gas that has passed through the filter 60 is released to the outside of the CO 2 recovery system 1 via the external release unit 61 .

[0060] The recovery of the target product can be carried out as follows. When the target product generated by the reaction of the above formula 1 and formula 2 is in an aqueous solution state, the aqueous solution of the target product is discharged to the outside and recovered in the recovery container 75 via the discharge cock 70 that can be opened and closed and is provided in the reaction tank 11. When the target product is in a solid state, the solid target product is discharged to the outside together with the aqueous solution in the reaction tank 11 and recovered in the recovery container 75 via the discharge cock 70 provided in the reaction tank 11, and then, the solid target product is recovered by separation such as filtration or centrifugation. The recovered target product can be used as a resource, for example, it can be used as a cleaning agent, a preservative, a herbicide, etc.

[0061] After the target product is recovered from the reaction tank 11, the drain cock 70 is closed and the reaction solution for the next reaction, i.e., NaOH aqueous solution, is supplied from the reaction solution supply unit (not shown) into the reaction tank 11. The drain cock 70 is normally closed when the target product is not recovered.

[0062] 1-10. Initial concentration of NaOH, maximum temperature of reaction solution, and removal temperature

[0063] The concentration of NaOH in the reaction solution stored in the reaction tank 11 before the CO2 fixation reaction starts is referred to as "NaOH initial concentration". In the first embodiment, the NaOH initial concentration is determined based on the target product taken out from the reaction solution, the maximum temperature of the reaction solution after the NaHCO3 in the reaction solution is generated, and the liquid temperature when the target product is taken out from the reaction tank 11, that is, the take-out temperature.

[0064] In the first embodiment, as described above, the target product extracted from the reaction solution is a NaHCO3 (sodium bicarbonate) aqueous solution. In addition, the initial concentration of NaOH is set to a value that is less than the NaOH concentration required to generate NaHCO3 with saturated solubility at the extraction temperature and greater than 0%, which is derived from the corresponding relationship between the temperature of the reaction solution and the NaOH concentration required to generate NaHCO3 with saturated solubility.

[0065] Regarding the correspondence between the temperature of the reaction solution and the NaOH concentration required to generate the saturated solubility of NaHCO3, first, the saturated solubility of NaHCO3 per 10°C from 0°C to 40°C is shown in the upper part of the following Table 1. Then, the NaOH concentration required to generate the saturated solubility of NaHCO3 at each temperature is calculated and shown in the lower part of the following Table 1.

[0066] [Table 1]

[0067] (Table 1)

[0068]

[0069] In addition, the first-order approximation of the temperature (liquid temperature) shown in the lower part of Table 1 and the NaOH concentration required to generate NaHCO3 with saturated solubility can be calculated according to the following formula 3: Figure 2 shown.

[0070] y=0.144x+6.82 (R 2 =0.996) (Formula 3)

[0071] (where y is the concentration of NaOH required to generate NaHCO3 at saturated solubility, and x is the liquid temperature)

[0072] In the first embodiment, the approximate formula shown in the above formula 3 is used as the correspondence between the temperature of the reaction solution and the NaOH concentration required to generate NaHCO3 with saturated solubility. And the initial NaOH concentration is less than the NaOH concentration A required to generate NaHCO3 with saturated solubility at the extraction temperature calculated according to the approximate formula 3 above, and greater than 0%, that is, Figure 3 It should be noted that the correspondence between the temperature of the reaction solution and the NaOH concentration required to generate NaHCO3 at saturated solubility is not limited, and a higher-order approximation may be used instead of the first-order approximation of the first embodiment, or it may be determined by mapping or logical expression.

[0073] In addition, the maximum temperature of the reaction liquid after the NaHCO3 in the reaction liquid is generated is set to be less than 65° C. It should be noted that the CO2 fixation reaction is an exothermic reaction, so the temperature of the reaction liquid rises during CO2 fixation, but the temperature of the reaction liquid (liquid temperature) is adjusted to less than 65° C. by the air pump 40 and the liquid temperature regulating device 50.

[0074] The liquid temperature when the target product is taken out from the reaction tank 11, that is, the take-out temperature may be in the range of a general outside air temperature, and in the first embodiment, is 0°C to 40°C.

[0075] and, Figure 3The upper limit value A of the first concentration range shown can be set to 3.86-4.57%, preferably 3.86%, when the extraction temperature is 10°C or more and less than 20°C, according to the value in the lower part of the above Table 1. In addition, the upper limit value A of the first concentration range can be set to 4.57-5.29%, preferably 4.57%, when the extraction temperature is 20°C or more and less than 30°C. In addition, the upper limit value A of the first concentration range can be set to 5.29-5.38%, preferably 5.29%, when the extraction temperature is 30°C or more and less than 40°C. It should be noted that in Figure 3 In the equation, symbol B represents the NaOH concentration required to generate Na2CO3 with saturated solubility at the extraction temperature calculated by the approximate equation of equation 4 described later.

[0076] 1-11. Start and stop of reaction

[0077] In the CO2 recovery system 1 of the present embodiment 1, the bubbling of the gas containing CO2 in the reaction tank 11 is started by starting the suction action in the air pump 40, so that the gas containing CO2 contacts the reaction solution having the initial concentration of NaOH, and the CO2 fixation reaction is started. Then, when the pH of the reaction solution in the reaction tank 11 reaches a value equivalent to the pH when the entire amount of NaOH is converted into NaHCO3 by the pH sensor 13, the suction action of the air pump 40 is turned off, the bubbling of the gas containing CO2 is stopped, and the CO2 fixation reaction is stopped. Then, the target product is taken out from the reaction tank 11 via the discharge cock 70 and recovered in the recovery container 75.

[0078] 1-12. Effects

[0079] According to the CO2 recovery system 1 of the present embodiment 1, since the maximum temperature of the reaction solution after the NaHCO3 in the reaction solution is generated is less than 65°C, and the initial concentration of NaOH is within the first concentration range described above, the NaHCO3 generated in the reaction tank 11 does not undergo thermal decomposition, does not reach supersaturation, and does not precipitate. As a result, the NaHCO3 aqueous solution as the target product can be obtained with high purity, and the target products can be easily generated respectively. In addition, since NaHCO3 is not precipitated, clogging of the unillustrated fine bubble former provided at the front end of the pipe 41 can be prevented.

[0080] In the present first embodiment, the initial concentration of NaOH is determined based on the approximate formula of the above formula 3, but the following modified forms 1-1, 1-2, and 1-3 may be used instead.

[0081] In the modification 1-1, the approximate formula of the above formula 3 is not used. According to the value of the NaOH concentration required to generate NaHCO3 with saturated solubility shown in the lower part of the above Table 1, the extraction temperature is set to be 10°C or more and less than 20°C, and the initial concentration of NaOH is Figure 3 The first concentration range shown may be greater than 0% and the upper limit A may be 3.86 to 4.57%. Preferably, the initial concentration of NaOH is greater than 0% and less than or equal to 3.86%.

[0082] In the modification 1-2, the approximate formula of the above formula 3 is not used. According to the value of the NaOH concentration required to generate NaHCO3 with saturated solubility shown in the lower part of the above Table 1, the extraction temperature is set to be 20°C or more and less than 30°C, and the initial concentration of NaOH is Figure 3 The first concentration range shown may be greater than 0% and the upper limit A may be 4.57 to 5.29%. Preferably, the initial concentration of NaOH is greater than 0% and less than 4.57%.

[0083] In variant 1-3, the approximate formula of formula 3 is not used. According to the value of NaOH concentration required to generate NaHCO3 with saturated solubility shown in the lower part of Table 1, the extraction temperature is set to be 30°C or more and less than 40°C, and the initial concentration of NaOH is Figure 3 The first concentration range shown may be greater than 0% and the upper limit A may be 5.29 to 5.38%. Preferably, the initial concentration of NaOH is greater than 0% and 5.29% or less.

[0084] In any of the above-mentioned modifications 1-1, 1-2 and 1-3, the precipitation of NaHCO 3 at the extraction temperature is suppressed, and thus the same effects as those of the first embodiment are achieved.

[0085] (Implementation Method 2)

[0086] In this second embodiment, the device is configured as follows Figure 1 The same is true for the first embodiment shown.

[0087] 2-1. Target product

[0088] The above-mentioned embodiment 1 uses the NaHCO3 aqueous solution as the target product, while the present embodiment 2 uses the sodium sesquicarbonate aqueous solution in which NaHCO3 and Na2CO3 are dissolved in water as the target product.

[0089] 2-2. Initial NaOH concentration, maximum temperature of reaction solution, and extraction temperature

[0090] In the second embodiment, the initial concentration of NaOH is derived from the correspondence between the temperature of the reaction solution and the NaOH concentration required to generate Na2CO3 with saturated solubility, and is a value less than the NaOH concentration required to generate Na2CO3 with saturated solubility at the extraction temperature and greater than 0%.

[0091] Regarding the correspondence between the temperature of the reaction solution and the NaOH concentration required to generate the saturated solubility of Na2CO3, first, the saturated solubility of Na2CO3 per 10°C from 0°C to 40°C is shown in the upper part of the following Table 2. In addition, the NaOH concentration required to generate the saturated solubility of Na2CO3 at each temperature is calculated and shown in the lower part of the following Table 2.

[0092] [Table 2]

[0093] (Table 2)

[0094]

[0095] Furthermore, the first order approximation of the temperature (liquid temperature) shown in the lower part of Table 2 and the NaOH concentration required to generate the saturated solubility of NaHCO3 can be calculated according to the following formula 4: Figure 4 shown.

[0096] y=1.112x+3.70 (R 2 =0.966) (Formula 4)

[0097] (where y is the NaOH concentration required to generate Na2CO3 at saturated solubility, and x is the liquid temperature)

[0098] In the second embodiment, the approximate formula shown in the above formula 4 is used as the correspondence between the temperature of the reaction solution and the NaOH concentration required to generate Na2CO3 with saturated solubility. And the initial NaOH concentration is the range of less than the NaOH concentration B required to generate Na2CO3 with saturated solubility at the extraction temperature calculated according to the approximate formula 4 and greater than 0%, that is, Figure 5 It should be noted that the correspondence between the temperature of the reaction solution and the NaOH concentration required to generate the saturated solubility of Na2CO3 is not limited, and a higher-order approximation may be used instead of the first-order approximation of the present embodiment 1, or it may be determined by mapping or logical expression.

[0099] Furthermore, the maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid is set to less than 65°C as in the case of Embodiment 1. In addition, the liquid temperature when the target product is taken out from the reaction tank 11, that is, the take-out temperature, is also set to 0°C to 40°C as in the case of Embodiment 1. Other configurations may be the same as in the case of Embodiment 1.

[0100] and, Figure 5 The upper limit value B of the second concentration range shown can be set to 9.43-16.22%, preferably 9.43%, when the take-out temperature is 10°C or more and less than 20°C, according to the value in the lower part of the above Table 2. In addition, the upper limit value B of the second concentration range can be set to 16.22-29.96%, preferably 16.22%, when the take-out temperature is 20°C or more and less than 30°C. In addition, the upper limit value B of the second concentration range can be set to 29.96-36.98%, preferably 29.96%, when the take-out temperature is 30°C or more and less than 40°C. It should be noted that in Figure 5 In the equation, symbol A represents the NaOH concentration required to generate NaHCO3 with saturated solubility at the extraction temperature calculated according to the approximate formula of the above formula 3.

[0101] 2-3. Start and stop of reaction

[0102] In the CO2 recovery system 1 of the second embodiment, the bubbling of the gas containing CO2 in the reaction tank 11 is started by starting the suction action in the air pump 40, so that the gas containing CO2 contacts the reaction solution having the initial concentration of NaOH, and the CO2 fixation reaction is started. Then, when the pH sensor 13 detects that the pH of the reaction solution in the reaction tank 11 reaches a pH value equivalent to the pH value when all the NaOH is consumed and the existence ratio of Na2CO3 to NaHCO3 is the desired 50:50, the suction action in the air pump 40 is turned off to stop the bubbling of the gas containing CO2, thereby stopping the CO2 fixation reaction.

[0103] 2-4. Effects

[0104] According to the CO2 recovery system 1 of the present embodiment 2, since the maximum temperature of the reaction solution after the NaHCO3 in the reaction solution is generated is less than 65°C, the NaHCO3 generated in the reaction tank 11 does not undergo thermal decomposition. In addition, since the initial concentration of NaOH is within the second concentration range mentioned above, Na2CO3 does not reach supersaturation and does not precipitate. As a result, the NaHCO3 and the sodium sesquicarbonate aqueous solution in which Na2CO3 is dissolved in water as the target product can be obtained with high purity, and the target product can be easily generated respectively. In addition, since Na2CO3 is not precipitated, the reactivity of the reaction of Na2CO3 and CO2 for generating NaHCO3 shown in the above formula 2 is prevented from decreasing, and the CO2 recovery rate is improved.

[0105] In the second embodiment, the initial concentration of NaOH is determined based on the approximate formula of the above formula 4. However, the following modified forms 2-1, 2-2, and 2-3 may be used instead.

[0106] In variation 2-1, the approximate formula of formula 4 is not used. Based on the value of NaOH concentration required to generate Na2CO3 at saturated solubility shown in the lower part of Table 2, the extraction temperature is set to be 10°C or more and less than 20°C, and the initial concentration of NaOH is Figure 5 The second concentration range shown may be greater than 0% and the upper limit value B may be 9.43 to 16.22%. The initial concentration of NaOH is preferably greater than 0% and less than or equal to 9.43%.

[0107] In the variant 2-2, the approximate formula of the above formula 4 is not used. According to the value of the NaOH concentration required to generate Na2CO3 with saturated solubility shown in the lower part of the above Table 2, the extraction temperature is set to be 20°C or more and less than 30°C, and the initial concentration of NaOH is Figure 5 The second concentration range shown may be greater than 0% and the upper limit value B may be 16.22 to 29.96%. The initial concentration of NaOH is preferably greater than 0% and 16.22% or less.

[0108] In the variant 2-3, the approximate formula of the above formula 4 is not used. According to the value of the NaOH concentration required to generate Na2CO3 with saturated solubility shown in the lower part of the above Table 2, the extraction temperature is set to be 30°C or more and less than 40°C, and the initial concentration of NaOH is Figure 5 The second concentration range shown may be greater than 0% and the upper limit value B may be 29.96 to 36.98%. The initial concentration of NaOH is preferably greater than 0% and less than or equal to 29.96%.

[0109] In any of the above-mentioned modifications 2-1, 2-2 and 2-3, the precipitation of Na 2 CO 3 at the extraction temperature can be suppressed, and the same effects as those of the second embodiment can be achieved.

[0110] (Implementation 3)

[0111] In this embodiment 3, the device is configured as Figure 1 The same is true for the embodiment 1 shown.

[0112] 3-1. Target product

[0113] In this embodiment 3, the target product is solid NaHCO3.

[0114] 3-2. Initial NaOH concentration, maximum temperature of reaction solution, and extraction temperature

[0115] In the third embodiment, the initial concentration of NaOH is higher than the concentration of NaOH required to generate NaHCO3 with saturated solubility at the removal temperature, which is derived from the correspondence between the temperature of the reaction liquid and the concentration of NaOH required to generate NaHCO3 with saturated solubility, and is lower than the concentration of NaOH required to generate Na2CO3 with saturated solubility at the removal temperature, which is derived from the correspondence between the temperature of the reaction liquid and the concentration of NaOH required to generate Na2CO3 with saturated solubility.

[0116] In the third embodiment, "the NaOH concentration required to generate NaHCO3 with saturated solubility at the extraction temperature derived from the correspondence between the temperature of the reaction liquid and the NaOH concentration required to generate NaHCO3 with saturated solubility" is the NaOH concentration A calculated based on the approximate formula of the above formula 3 in the first embodiment.

[0117] In addition, in the present third embodiment, "the NaOH concentration required to generate Na2CO3 with saturated solubility at the removal temperature, which is derived from the correspondence between the temperature of the reaction liquid and the NaOH concentration required to generate Na2CO3 with saturated solubility" is the NaOH concentration B calculated based on the approximate formula of the above formula 4 in the second embodiment.

[0118] Therefore, in the third embodiment, the initial concentration of NaOH is within the range of the concentration A of NaOH required to generate NaHCO3 with saturated solubility at the extraction temperature calculated by the approximate formula of the above formula 3, and below the concentration B of NaOH required to generate Na2CO3 with saturated solubility at the extraction temperature calculated by the approximate formula of the above formula 4, that is, Figure 6 A third concentration range is shown.

[0119] It should be noted that in the present embodiment 3, the maximum temperature of the reaction liquid after the NaHCO3 in the reaction liquid is generated is set to less than 65° C. as in the case of the embodiment 1. In addition, the liquid temperature when the target product is taken out from the reaction tank 11, that is, the take-out temperature, is also set to 0° C. to 40° C. as in the case of the embodiment 1. Other configurations may be the same as in the case of the embodiment 1.

[0120] and, Figure 6 In the third concentration range shown, when the extraction temperature is 10°C or higher and lower than 20°C, the lower limit value A can be set to 3.86 to 4.57%, preferably 3.86%, based on the value at the bottom of Table 1. In addition, the upper limit value B can be set to 9.43 to 16.22%, preferably 9.43%, based on the value at the bottom of Table 2.

[0121] In the third concentration range, when the extraction temperature is 20°C or higher and lower than 30°C, the lower limit A can be set to 4.57-5.29%, preferably 4.57%, based on the value in the lower part of Table 1. In addition, the upper limit B can be set to 16.22-29.96%, preferably 16.22%, based on the value in the lower part of Table 2.

[0122] In the third concentration range, when the extraction temperature is 30°C or higher and lower than 40°C, the lower limit A can be set to 5.29 to 5.38%, preferably 5.29%, based on the value in the lower part of Table 1. In addition, the upper limit B can be set to 29.96 to 36.98%, preferably 29.96%, based on the value in the lower part of Table 2.

[0123] 3-3. Start and stop of reaction

[0124] In the CO2 recovery system 1 of the third embodiment, the bubbling of the gas containing CO2 in the reaction tank 11 is started by starting the suction action in the air pump 40, so that the gas containing CO2 contacts the reaction solution having the initial concentration of NaOH, and the CO2 fixation reaction is started. Then, when the pH sensor 13 detects that the pH of the reaction solution in the reaction tank 11 reaches a pH value equivalent to the pH value when the entire amount of NaOH is consumed and the existence ratio of Na2CO3 to NaHCO3 is 50:50, the suction action in the air pump 40 is turned off to stop the bubbling of the gas containing CO2, thereby stopping the CO2 fixation reaction.

[0125] 3-4. Effects

[0126] According to the CO2 recovery system 1 of the present embodiment 3, since the maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, the NaHCO3 generated in the reaction tank 11 does not undergo thermal decomposition. In addition, since the initial concentration of NaOH is within the third concentration range mentioned above, Na2CO3 does not reach supersaturation and does not precipitate, but NaHCO3 reaches supersaturation and precipitates in the reaction tank 11. As a result, the product precipitated into a solid in the reaction tank 11 is only NaHCO3, so the solid NaHCO3 as the target product can be obtained with high purity, and the target products can be easily generated respectively. In addition, since Na2CO3 is not precipitated, the reactivity of the reaction of Na2CO3 and CO2 for generating NaHCO3 shown in the above formula 2 can be prevented from decreasing, thereby improving the CO2 recovery rate.

[0127] In the present embodiment 3, the initial concentration of NaOH is determined based on the approximate equations of equation 3 and equation 4 above, but alternatively, the following modified forms 3-1, 3-2, and 3-3 may be used.

[0128] In the variation 3-1, the approximation of the above formula 3 and the approximation of the above formula 4 are not used. Based on the value of the NaOH concentration A required to generate NaHCO3 with saturated solubility shown in the lower part of the above Table 1 and the value of the NaOH concentration B required to generate Na2CO3 with saturated solubility shown in the lower part of the above Table 2, the extraction temperature is set to be 10°C or more and less than 20°C, and the initial concentration of NaOH is Figure 6 In the third concentration range shown, the lower limit A can be set to 3.86 to 4.57%, and the upper limit B can be set to 9.43 to 16.22%. Furthermore, the initial concentration of NaOH can be set to 3.86% to 9.43%.

[0129] In addition, in the variation 3-2, the approximation of the above formula 3 and the approximation of the above formula 4 are not used. Based on the value of the NaOH concentration A required to generate NaHCO3 with saturated solubility shown in the lower part of the above Table 1 and the value of the NaOH concentration B required to generate Na2CO3 with saturated solubility shown in the lower part of the above Table 2, the extraction temperature is set to be greater than 20°C and less than 30°C, and the initial concentration of NaOH is Figure 6 In the third concentration range shown, the lower limit A can be set to 4.57 to 5.29%, and the upper limit B can be set to 16.22 to 29.96%. Furthermore, the initial concentration of NaOH can be set to 4.57% to 16.22%.

[0130] In addition, in the variation 3-3, the approximation of the above formula 3 and the approximation of the above formula 4 are not used. Based on the value of the NaOH concentration A required to generate NaHCO3 with saturated solubility shown in the lower part of the above Table 1 and the value of the NaOH concentration B required to generate Na2CO3 with saturated solubility shown in the lower part of the above Table 2, the extraction temperature is set to be 30°C or more and less than 40°C, and the initial concentration of NaOH is Figure 6 In the third concentration range shown, the lower limit A can be set to 5.29 to 5.38%, and the upper limit B can be set to 29.96 to 36.98%. Furthermore, the initial concentration of NaOH can be set to 5.29% to 29.96%.

[0131] In any of the above-mentioned modifications 3-1, 3-2 and 3-3, only solid NaHCO 3 can be precipitated and NaHCO 3 can be recovered at the extraction temperature, and the same effects as those in the case of the third embodiment can be achieved.

[0132] (Implementation 4)

[0133] In this embodiment 4, the device is configured as Figure 1 The same is true for the embodiment 1 shown.

[0134] 4-1. Target product

[0135] In this embodiment 4, the target product is a Na2CO3 aqueous solution or solid Na2CO3.

[0136] 4-2. Initial NaOH concentration, maximum temperature of the reaction solution, and extraction temperature

[0137] In the fourth embodiment, the initial concentration of NaOH is greater than 0%, and Figure 7 The fourth concentration range is shown.

[0138] Furthermore, in the present embodiment 4, the maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid is set to be 65°C or above. It should be noted that since the CO2 fixation reaction described above is an exothermic reaction, the temperature of the reaction liquid rises during CO2 fixation, but when the temperature of the reaction liquid (liquid temperature) is lower than 65°C, it is heated to 65°C or above by the air pump 40 and the liquid temperature regulating device 50 described above. It should be noted that the liquid temperature when the target product is taken out from the reaction tank 11, i.e., the take-out temperature, is also set to 0°C to 40°C as in the case of the embodiment 1. Other configurations may be the same as in the case of the embodiment 1.

[0139] 4-3. Start and stop of reaction

[0140] In the CO2 recovery system 1 of the present embodiment 4, the bubbling of the gas containing CO2 in the reaction tank 11 is started by starting the suction action in the air pump 40, so that the gas containing CO2 contacts the reaction solution having the initial concentration of NaOH, and the CO2 fixation reaction is started. Then, when the pH sensor 13 detects that the pH of the reaction solution in the reaction tank 11 is a state where all the NaOH is consumed, the suction action in the air pump 40 is turned off to stop the bubbling of the gas containing CO2, thereby stopping the CO2 fixation reaction.

[0141] 4-4. Effects

[0142] According to the CO2 recovery system 1 of the present embodiment 4, since the maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is above 65°C, the NaHCO3 generated in the reaction tank 11 undergoes thermal decomposition. Therefore, when the initial concentration of NaOH is the fourth concentration range mentioned above, i.e., the total range, there is a Na2CO3 aqueous solution or solid Na2CO3 as a product in the reaction tank 11, and there is no NaHCO3. As a result, Na2CO3 as a target product can be obtained with high purity, and the target products can be easily generated respectively. In addition, since there is no NaHCO3, it is possible to prevent the clogging of the unillustrated fine bubble former arranged at the front end of the pipe 41 caused by the precipitation of NaHCO3.

[0143] (Implementation method 5)

[0144] In this embodiment 5, the device is configured as Figure 1 The same is true for the embodiment 1 shown.

[0145] 5-1. Target product

[0146] In this embodiment 5, the target product is solid Na2CO3.

[0147] 5-2. Initial NaOH concentration, maximum temperature of the reaction solution, and extraction temperature

[0148] In the fifth embodiment, the initial concentration of NaOH is greater than the NaOH concentration required to generate Na2CO3 at saturated solubility at the extraction temperature, which is derived from the correspondence between the temperature of the reaction solution and the NaOH concentration required to generate Na2CO3 at saturated solubility.

[0149] In the fifth embodiment, "the NaOH concentration required to generate Na2CO3 with saturated solubility at the extraction temperature, which is derived from the correspondence between the temperature of the reaction liquid and the NaOH concentration required to generate Na2CO3 with saturated solubility" is the NaOH concentration calculated based on the approximate formula of the above formula 4 in the second embodiment.

[0150] Therefore, in the fifth embodiment, the initial concentration of NaOH is within the range of the concentration of NaOH required to generate Na2CO3 at the saturated solubility at the extraction temperature calculated by the approximate formula of the above formula 4, that is, Figure 8 The 5th concentration range is shown.

[0151] It should be noted that in the present embodiment 5, the maximum temperature of the reaction liquid after the NaHCO3 in the reaction liquid is generated is set to 65° C. or more as in the case of the embodiment 4. In addition, the liquid temperature when the target product is taken out from the reaction tank 11, that is, the take-out temperature, is also set to 0° C. to 40° C. as in the case of the embodiment 4. The other configurations may be the same as in the case of the embodiment 1.

[0152] and, Figure 8 The lower limit value B of the fifth concentration range shown can be set to 9.43-16.22% according to the value of the lower part of Table 2 when the extraction temperature is 10°C or more and less than 20°C, and is preferably 9.43%. In addition, the lower limit value B of the fifth concentration range can be set to 16.22-29.96% according to the value of the lower part of Table 2 when the extraction temperature is 20°C or more and less than 30°C, and is preferably 16.22%. In addition, the lower limit value B of the fifth concentration range can be set to 29.96-36.98% according to the value of the lower part of Table 2 when the extraction temperature is 30°C or more and less than 40°C, and is preferably 29.96%.

[0153] 5-3. Start and stop of reaction

[0154] In the CO2 recovery system 1 of the fifth embodiment, the bubbling of the gas containing CO2 in the reaction tank 11 is started by starting the suction action in the air pump 40, so that the gas containing CO2 contacts the reaction solution having the initial concentration of NaOH, and the CO2 fixation reaction is started. Then, when the pH sensor 13 detects that the pH of the reaction solution in the reaction tank 11 is a state where all the NaOH is consumed, the suction action in the air pump 40 is turned off to stop the bubbling of the gas containing CO2, thereby stopping the CO2 fixation reaction.

[0155] 5-4. Effects

[0156] According to the CO2 recovery system 1 of the fifth embodiment, since the maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid is 65°C or more, the NaHCO3 generated in the reaction tank 11 is thermally decomposed. In addition, since the initial concentration of NaOH is set to the fifth concentration range described above, Na2CO3 reaches supersaturation and precipitates in the reaction tank 11. As a result, the product precipitated as a solid in the reaction tank 11 is only Na2CO3, so by filtering or centrifuging the recovered product in the recovery container 75, the solid Na2CO3 as the target product can be obtained with high purity, and the target products can be easily generated separately.

[0157] In the fifth embodiment, the initial concentration of NaOH is determined based on the approximate formula of the above formula 4. However, the following modified forms 5-1, 5-2, and 5-3 may be used instead.

[0158] In variation 5-1, the approximate formula of formula 4 is not used. Based on the value of NaOH concentration required to generate Na2CO3 at saturated solubility shown in the lower part of Table 2, the extraction temperature is set to be 10°C or more and less than 20°C, and the initial concentration of NaOH is Figure 8 The fifth concentration range shown in FIG. 1 can be set so that the lower limit value B can be set to 9.43 to 16.22%, and the initial concentration of NaOH is preferably 9.43% or more.

[0159] In the variant 5-2, the approximate formula of the above formula 4 is not used. According to the value of the NaOH concentration required to generate Na2CO3 with saturated solubility shown in the lower part of the above Table 2, the extraction temperature is set to be 20°C or more and less than 30°C, and the initial concentration of NaOH is Figure 8 The fifth concentration range shown in FIG. 1 can be a lower limit value B of 16.22 to 29.96%, and the initial concentration of NaOH is preferably 16.22% or more.

[0160] In the modification 5-3, according to the value of NaOH concentration required to generate Na2CO3 at saturated solubility shown in the lower part of the above Table 2, the extraction temperature is set to be 30°C or higher and lower than 40°C, and the initial concentration of NaOH is Figure 8 In the fifth concentration range shown, the lower limit value B can be set to 29.96 to 36.98%, and the initial concentration of NaOH is preferably 29.96% or more.

[0161] In any of the above-mentioned modifications 5-1, 5-2 and 5-3, since the product obtained as a solid at the extraction temperature is only Na2CO3, solid Na2CO3 as the target product can be obtained with high purity, achieving the same effect as the case of embodiment 5.

[0162] (Implementation method 6)

[0163] like Fig. 9 As shown, the CO2 recovery system 1 of the sixth embodiment includes a regulator 80 and a NaOH initial concentration setting unit 81. Figure 1 The same as the embodiment 1 is shown, and the same reference numerals as those in the embodiment 1 are given and the description thereof is omitted.

[0164] 6-1. Adjustment unit 80, NaOH initial concentration setting unit 81

[0165] Fig. 9 The adjustment unit 80 shown adjusts the target product by adjusting the maximum temperature of the reaction solution after the NaHCO3 in the reaction solution is generated, the extraction temperature, and the initial concentration of NaOH in the reaction solution. In the present embodiment 6, the adjustment unit 80 adjusts the temperature (liquid temperature) of the reaction solution by adjusting the flow rate of the air pump 40 through the pump control 45 and controlling the drive of the liquid temperature adjustment device 50 through the liquid temperature adjustment device control unit 55. In addition, the initial concentration of NaOH in the reaction solution put into the reaction tank 11 is adjusted via the NaOH initial concentration setting unit 81 described later.

[0166] Fig. 9 The illustrated NaOH initial concentration setting unit 81 is configured to inject a reaction solution having an initial NaOH concentration adjusted by the adjustment unit 80 into the reaction tank 11 from a reaction solution injection unit 15 provided in the reaction tank 11 .

[0167] Furthermore, in the sixth embodiment, the adjustment unit 80 includes a selection unit 82 for selecting a target product desired by the user, and the product selected by the user via the selection unit 82 is set as the target product. Furthermore, the initial concentration of NaOH in the reaction solution and the temperature (liquid temperature) of the reaction solution are adjusted in accordance with the set target product. In addition, the correspondence between the initial concentration of NaOH and the target product can be as follows: Fig.10 shown.

[0168] 6-2. Adjustment of target product

[0169] The adjustment of the target product in the sixth embodiment is described in detail below.

[0170] In the sixth embodiment, when the user selects the NaHCO3 aqueous solution as the target product via the selection unit 82, the NaOH initial concentration is adjusted to the same first concentration range as in the first embodiment described above via the NaOH initial concentration setting unit 81, and the maximum temperature and the extraction temperature of the reaction liquid are also adjusted to the same as in the first embodiment described above via the air pump 40 and the liquid temperature regulating device 50. Thus, the NaHCO3 aqueous solution as the target product can be obtained in the same manner as in the first embodiment.

[0171] It should be noted that, similarly to the above-mentioned modifications 1-1, 1-2 and 1-3, by adjusting the initial concentration of NaOH, the maximum temperature of the reaction solution and the extraction temperature, the NaHCO3 aqueous solution as the target product can also be obtained in the same manner as in the cases of modifications 1-1, 1-2 and 1-3.

[0172] In addition, in the sixth embodiment, when the user selects the sodium sesquicarbonate aqueous solution as the target product via the selection unit 82, the initial concentration of NaOH, the maximum temperature of the reaction solution, and the extraction temperature are adjusted via the NaOH initial concentration setting unit 81, the air pump 40, and the liquid temperature adjustment device 50 in the same manner as in the second embodiment. Thus, the sodium sesquicarbonate aqueous solution as the target product can be obtained in the same manner as in the second embodiment.

[0173] In addition, in the sixth embodiment, when the user selects solid NaHCO3 as the target product via the selection unit 82, the initial concentration of NaOH, the maximum temperature of the reaction liquid, and the extraction temperature are adjusted via the NaOH initial concentration setting unit 81, the air pump 40, and the liquid temperature adjustment device 50 in the same manner as in the third embodiment. Thus, solid NaHCO3 as the target product can be obtained in the same manner as in the third embodiment.

[0174] In addition, in the sixth embodiment, when the user selects either a Na2CO3 aqueous solution or solid Na2CO3 as the target product via the selection unit 82, the initial concentration of NaOH, the maximum temperature of the reaction liquid, and the extraction temperature are adjusted via the NaOH initial concentration setting unit 81, the air pump 40, and the liquid temperature adjustment device 50 in the same manner as in the fourth embodiment. Thus, the Na2CO3 aqueous solution or solid Na2CO3 as the target product can be obtained in the same manner as in the fourth embodiment.

[0175] In addition, in the sixth embodiment, when the user selects solid Na2CO3 as the target product via the selection unit 82, the initial concentration of NaOH, the maximum temperature of the reaction liquid, and the extraction temperature are adjusted via the NaOH initial concentration setting unit 81, the air pump 40, and the liquid temperature adjustment device 50 in the same manner as in the fifth embodiment described above. Thus, solid Na2CO3 as the target product can be obtained in the same manner as in the third embodiment.

[0176] 6-3. Effects

[0177] According to the CO2 recovery system of the sixth embodiment, the target product taken out from the reaction liquid is adjusted by adjusting the maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid, the temperature of the reaction liquid when the target product is taken out from the reaction tank, i.e., the taking-out temperature, and the initial concentration of NaOH in the reaction liquid. Therefore, it is easy to generate the products separately and the desired target product can be taken out with high purity.

[0178] The present invention is not limited to the above-described embodiment and modifications, and can be applied to various embodiments without departing from the gist of the invention.

Claims

1. A CO2 recovery system (1) for recovering CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank (11) to generate a target product, The target product taken out from the reaction liquid is adjusted by adjusting the maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid, the temperature of the reaction liquid when the target product is taken out from the reaction tank, i.e., the taking-out temperature, and the initial concentration of NaOH in the reaction liquid.

2. A CO2 recovery system (1) that recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank (11) to generate a predetermined target product, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is determined based on the target product taken out from the reaction solution. The initial concentration of NaOH in the reaction solution is determined based on the target product taken out from the reaction solution and the temperature of the reaction solution when the target product is taken out from the reaction tank, that is, the taking-out temperature.

3. The CO2 recovery system according to claim 1 or 2, wherein: The target product is a NaHCO3 aqueous solution, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The removal temperature is 0°C to 40°C. The initial concentration of NaOH is less than the concentration of NaOH required to generate NaHCO3 with saturated solubility at the extraction temperature, which is derived from the correspondence between the temperature of the reaction solution and the concentration of NaOH required to generate NaHCO3 with saturated solubility, and is greater than 0%.

4. The CO2 recovery system according to claim 3, wherein: The removal temperature is above 10°C and below 20°C. The initial concentration of the NaOH is greater than 0%, and the upper limit is 3.86-4.57%.

5. The CO2 recovery system according to claim 3, wherein: The removal temperature is above 20°C and below 30°C. The initial concentration of NaOH is greater than 0%, and the upper limit is 4.57-5.29%.

6. The CO2 recovery system according to claim 3, wherein: The removal temperature is above 30°C and below 40°C. The initial concentration of NaOH is greater than 0%, and the upper limit is 5.29-5.38%.

7. The CO2 recovery system according to claim 1 or 2, wherein: The target product is a sodium sesquicarbonate aqueous solution, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The removal temperature is 0°C to 40°C. The initial concentration of NaOH is less than the concentration of NaOH required to generate Na2CO3 with saturated solubility at the extraction temperature, which is derived from the correspondence between the temperature of the reaction solution and the concentration of NaOH required to generate Na2CO3 with saturated solubility, and is greater than 0%.

8. The CO2 recovery system according to claim 7, wherein: The removal temperature is above 10°C and below 20°C. The initial concentration of NaOH is greater than 0%, and the upper limit is 9.43-16.22%.

9. The CO2 recovery system according to claim 7, wherein: The removal temperature is above 20°C and below 30°C. The initial concentration of NaOH is greater than 0%, and the upper limit is 16.22-29.96%.

10. The CO2 recovery system according to claim 7, wherein: The removal temperature is above 30°C and below 40°C. The initial concentration of NaOH is greater than 0%, and the upper limit is 29.96-36.98%.

11. The CO2 recovery system according to claim 1 or 2, wherein: The target product is solid NaHCO3, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The removal temperature is 0°C to 40°C. The initial concentration of NaOH is: greater than the NaOH concentration required to generate NaHCO3 with saturated solubility at the removal temperature, which is derived from the correspondence between the temperature of the reaction liquid and the NaOH concentration required to generate NaHCO3 with saturated solubility, and less than the NaOH concentration required to generate Na2CO3 with saturated solubility at the removal temperature, which is derived from the correspondence between the temperature of the reaction liquid and the NaOH concentration required to generate Na2CO3 with saturated solubility.

12. The CO2 recovery system according to claim 11, wherein: The removal temperature is above 10°C and below 20°C. The lower limit of the initial concentration of NaOH is 3.86 to 4.57%, and the upper limit is 9.43 to 16.22%.

13. The CO2 recovery system according to claim 11, wherein: The removal temperature is above 20°C and below 30°C. The lower limit of the initial concentration of NaOH is 4.57 to 5.29%, and the upper limit is 16.22 to 29.96%.

14. The CO2 recovery system according to claim 11, wherein: The removal temperature is above 30°C and below 40°C. The lower limit of the initial concentration of NaOH is 5.29 to 5.38%, and the upper limit is 29.96 to 36.98%.

15. The CO2 recovery system according to claim 1 or 2, wherein: The target product is at least one of a Na2CO3 aqueous solution and a solid Na2CO3, The maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid is above 65°C, The removal temperature is above 0°C. The initial concentration of NaOH in the reaction solution is greater than 0%.

16. The CO2 recovery system according to claim 1 or 2, wherein: The target product is solid Na2CO3, The maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid is above 65°C, The removal temperature is above 0°C, The initial concentration of NaOH in the reaction solution is greater than or equal to the concentration of NaOH required to generate Na2CO3 at saturated solubility at the extraction temperature, which is derived from the correspondence between the temperature of the reaction solution and the concentration of NaOH required to generate Na2CO3 at saturated solubility.

17. The CO2 recovery system according to claim 16, wherein: The removal temperature is above 10°C and below 20°C. The lower limit of the initial concentration of NaOH in the reaction solution is 9.43 to 16.22%.

18. The CO2 recovery system according to claim 16, wherein: The removal temperature is above 20°C and below 30°C. The lower limit of the initial concentration of NaOH in the reaction solution is 16.22 to 29.96%.

19. The CO2 recovery system according to claim 16, wherein: The removal temperature is above 30°C and below 40°C. The lower limit of the initial concentration of NaOH in the reaction solution is 29.96 to 36.98%.

20. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is a NaHCO3 aqueous solution, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, that is, the taking-out temperature, is 10° C. or more and less than 20° C., The initial concentration of NaOH is greater than 0%, and the upper limit is in the range of 3.86-4.57%.

21. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is a NaHCO3 aqueous solution, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, i.e., the taking-out temperature, is 20° C. or higher and lower than 30° C., The initial concentration of NaOH is greater than 0%, and the upper limit is 4.57-5.29%.

22. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is a NaHCO3 aqueous solution, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, i.e., the taking-out temperature, is 30° C. or higher and lower than 40° C., The initial concentration of NaOH is greater than 0%, and the upper limit is 5.29-5.38%.

23. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is a sodium sesquicarbonate aqueous solution, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, that is, the taking-out temperature, is 10° C. or more and less than 20° C., The initial concentration of NaOH is greater than 0%, and the upper limit is 9.43-16.22%.

24. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is a sodium sesquicarbonate aqueous solution, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, i.e., the taking-out temperature, is 20° C. or higher and lower than 30° C., The initial concentration of NaOH is greater than 0%, and the upper limit is 16.22-29.96%.

25. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is a sodium sesquicarbonate aqueous solution, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, i.e., the taking-out temperature, is 30° C. or higher and lower than 40° C., The initial concentration of NaOH is greater than 0%, and the upper limit is 29.96-36.98%.

26. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is solid NaHCO3, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, that is, the taking-out temperature, is 10° C. or more and less than 20° C., The lower limit of the initial concentration of NaOH is 3.86 to 4.57%, and the upper limit is 9.43 to 16.22%.

27. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is solid NaHCO3, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, i.e., the taking-out temperature, is 20° C. or higher and lower than 30° C., The lower limit of the initial concentration of NaOH is 4.57 to 5.29%, and the upper limit is 16.22 to 29.96%.

28. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is solid NaHCO3, The maximum temperature of the reaction solution after the generation of NaHCO3 in the reaction solution is less than 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, i.e., the taking-out temperature, is 30° C. or higher and lower than 40° C., The lower limit of the initial concentration of NaOH is 5.29 to 5.38%, and the upper limit is 29.96 to 36.98%.

29. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is at least one of a Na2CO3 aqueous solution and a solid Na2CO3, The maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid is above 65°C, The temperature of the reaction solution when the target product is taken out from the reaction vessel, i.e., the taking-out temperature, is 0° C. or higher. The initial concentration of NaOH in the reaction solution is greater than 0%.

30. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is at least one of a Na2CO3 aqueous solution and a solid Na2CO3, The maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid is above 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, that is, the taking-out temperature, is 10° C. or more and less than 20° C., The lower limit of the initial concentration of NaOH in the reaction solution is 9.43 to 16.22%.

31. A CO2 recovery system, which is a CO2 recovery system for recovering CO2 by contacting a gas containing CO2 with a reaction solution containing NaOH stored in a reaction tank to generate a target product, The target product is at least one of a Na2CO3 aqueous solution and a solid Na2CO3, The maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid is above 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, i.e., the taking-out temperature, is 20° C. or higher and lower than 30° C., The lower limit of the initial concentration of NaOH in the reaction solution is 16.22 to 29.96%.

32. A CO2 recovery system, which recovers CO2 by contacting a gas containing CO2 with a reaction liquid containing NaOH stored in a reaction tank to generate a target product, The target product is at least one of a Na2CO3 aqueous solution and a solid Na2CO3, The maximum temperature of the reaction liquid after the generation of NaHCO3 in the reaction liquid is above 65°C, The temperature of the reaction solution when the target product is taken out from the reaction tank, i.e., the taking-out temperature, is 30° C. or higher and lower than 40° C., The lower limit of the initial concentration of NaOH in the reaction solution is 29.96 to 36.98%.

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