CO2 capture equipment

Abstract

To provide a CO2 recovery device capable of estimating the production state of product materials at high precision and having an excellent CO2 exhaust suppression effect.SOLUTION: A CO2 recovery device 1 comprises a reaction tank 10, a weight increase amount detection unit 20 and a production state estimation unit 30. The reaction tank 10 brings a CO2 gas into contact with a prescribed amount of NaOH aqueous solution having a known NaOH concentration. The weight increase amount detection unit 20 detects the weight increase amount of an aqueous solution L in the reaction tank 10 increased by bringing the CO2 gas into contact with the NaOH aqueous solution in the reaction tank 10. The production state estimation unit 30 estimates the production state of product materials in the reaction tank 10 based on the weight increase amount detected by the weight increase amount detection unit 20.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a CO2 recovery device. [Background technology]

[0002] In recent years, there has been a demand for reducing CO2 emissions as a greenhouse gas, and various CO2 gas capture devices have been developed. For example, one CO2 capture device recovers CO2 from exhaust gas containing CO2, such as that from a power generation boiler, by reacting the exhaust gas with an aqueous NaOH solution stored in a reaction vessel to produce NaHCO3 or Na2CO3. The NaHCO3, Na2CO3, and mixtures thereof produced by the CO2 capture device can be used as resources. However, because these products have different uses, it is necessary to manage the production status of these products when recovering them. However, because NaHCO3 and Na2CO3 are produced as aqueous solutions in the reaction vessel, it is difficult to directly detect the production status of NaHCO3 and Na2CO3. Therefore, the production status of NaHCO3 and Na2CO3 has been estimated based on the pH of the aqueous solution, which changes depending on the progress of the reaction in the reaction vessel. For example, Patent Document 1 discloses a configuration in which a phenolphthalein solution of a predetermined concentration is dropped into the reaction tank, and the pH of the aqueous solution is detected based on a change in the hue of the aqueous solution, thereby detecting the production state of NaHCO3 and Na2CO3. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-248224 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the configuration disclosed in Patent Document 1 requires image processing technology to accurately detect the hue change of the aqueous solution in the reaction vessel, which requires a camera and a computing device. Furthermore, if electricity generated using fossil fuels is used to drive these components, the entire system is equivalent to emitting CO2 generated for the purpose of generating the electricity. As a result, the overall CO2 emission reduction effect of the system is reduced. Furthermore, if the CO2 emissions from the power generation exceed the amount of CO2 captured by the CO2 capture device, the system as a whole will not be able to achieve CO2 emission reduction. In particular, as the system becomes larger, the device for detecting the hue change of the aqueous solution in the reaction vessel also becomes larger, which increases power consumption and makes CO2 emission reduction even more difficult. Furthermore, depending on the progress of the reaction in the reaction vessel, the distribution of products and the concentration of the NaOH aqueous solution may become uneven, resulting in pH variations within the reaction vessel. Furthermore, when measuring the hue change of an aqueous solution using a phenolphthalein solution, variations in the amount of phenolphthalein solution added significantly affect the pH variation, potentially reducing detection accuracy. Furthermore, when NaHCO3 and Na2CO3 are used as resources, phenolphthalein becomes an impurity, and it becomes necessary to remove phenolphthalein or its products.

[0005] Another option is to use a pH meter to measure the pH of the aqueous solution in the reaction tank and estimate the amount of NaHCO3 and Na2CO3 produced. In this case, too, electricity is required to operate the pH meter. If electricity generated using fossil fuels is used, the CO2 emission reduction effect of the entire system will be reduced, as in the case described above. If the CO2 emissions from the electricity generated by this electricity exceed the amount of CO2 captured by the CO2 capture device, the CO2 emission reduction effect of the entire system will not be achieved. Furthermore, the pH meter requires periodic maintenance, which is time-consuming if used over the long term.

[0006] The present invention has been made in view of the above problems, and aims to provide a CO2 recovery device that can estimate the state of product production with high accuracy and has an excellent effect of suppressing CO2 emissions. [Means for solving the problem]

[0007] One aspect of the present invention is a reaction vessel in which CO gas is brought into contact with a predetermined amount of NaOH aqueous solution having a known NaOH concentration; a weight increase detector for detecting an increase in weight of the aqueous solution L in the reaction tank caused by contacting the NaOH aqueous solution with the CO gas in the reaction tank; an estimation unit that estimates a production state of a product in the reaction tank based on the weight increase detected by the weight increase detection unit. 、 the production state estimation unit estimates the production state based on a result of comparing the weight increase amount with a preset reference value; the reference value is a value in a range exceeding a first threshold value and less than a second threshold value, The first threshold is the temperature at which the total amount of NaOH present in the reaction vessel is reduced to CO 2 reacts with Na 2 CO 3 CO used when generated 2 is the total weight of The second threshold is the temperature at which the total amount of NaOH present in the reaction vessel is reduced to CO 2 reacts with Na 2 CO 3 After the Na 2 CO 3 The total amount of CO 2 reacts with NaHCO 3 CO used when generated 2 is the total weight of As the above product, Na 2 CO 3 and NaHCO 3 and a mixture of the above is removed. Located in the CO2 capture unit. [Effects of the Invention]

[0008] In the CO2 capture device, Na2CO3 is first produced in the reaction vessel by the reaction of CO2 with NaOH. After the entire amount of NaOH present in the reaction vessel reacts with CO2, the resulting Na2CO3 reacts with CO2 to produce NaHCO3. Since the CO2 capture device uses a predetermined amount of NaOH aqueous solution with a known NaOH concentration, the total amount of NaOH in the reaction vessel is determined. Therefore, by detecting the weight gain of the aqueous solution in the reaction vessel, i.e., the amount of CO2 captured, the progress of the reaction in the reaction vessel can be accurately determined without measuring the pH in the reaction vessel. Therefore, even if pH measurements using a pH meter produce variations, the product production status in the reaction vessel can be estimated with high accuracy without being affected by such variations. Furthermore, since the weight gain can be easily detected using a power-free or energy-saving weighing scale, the weight gain detector can be driven with little or no power consumption, resulting in a CO2 capture device with excellent CO2 emission reduction effects. Furthermore, weighing scales have a simpler structure than pH measuring instruments, requiring less maintenance.

[0009] As described above, according to the above-described embodiment, it is possible to provide a CO2 recovery device that can estimate the state of product production with high accuracy and has an excellent effect of suppressing CO2 emissions. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing the configuration of a CO2 recovery device according to a first embodiment. [Figure 2] FIG. 2A is a cross-sectional schematic diagram of a main body and a reaction vessel, and FIG. 2B is a perspective schematic diagram of the main body and the reaction vessel in the first embodiment. [Figure 3] (a) A conceptual diagram showing the change in pH of the aqueous solution in the reaction tank, (b) A conceptual diagram showing the change in the weight gain of the aqueous solution, (c) A conceptual diagram showing the change in the amount of NaOH afterimage in the aqueous solution, (d) A conceptual diagram showing the change in the amount of Na2CO3 produced, and (e) A conceptual diagram showing the change in the amount of NaHCO3 produced, in embodiment 1. [Figure 4]FIG. 2 is a flow chart showing a usage mode in the first embodiment. [Figure 5] FIG. 10 is another flow chart showing a usage mode in the first embodiment. [Figure 6] 1 is a cross-sectional conceptual diagram of the main body and reaction vessel in variant form 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Embodiment 1) An embodiment of a CO2 recovery system will be described with reference to FIGS. The CO2 recovery device 1 of the first embodiment includes a reaction vessel 10, a weight increase detection unit 20, and a production state estimation unit 30, as shown in FIG. In the reaction vessel 10, CO2 gas is brought into contact with a predetermined amount of an aqueous NaOH solution having a known NaOH concentration. The weight increase detection unit 20 detects the weight increase of the aqueous solution L in the reaction vessel 10 that increases as a result of bringing the NaOH aqueous solution into contact with CO 2 gas in the reaction vessel 10. The production state estimation unit 30 estimates the production state of the product in the reaction vessel 10 based on the weight increase detected by the weight increase detection unit 20.

[0012] The CO2 recovery device 1 of this embodiment will be described in detail below. As shown in Figures 2(a) and 2(b), the CO2 recovery device 1 has a main body 40. The main body 40 has a side portion 40c standing in the height direction Z, an upper portion 40a located above the side portion 40c, and a lower portion 40b located below the side portion 40c, which are configured to form a roughly U-shape. Two through-holes 43 are formed in the upper portion 40a, and the reaction vessel 10 is placed on the lower portion 40b.

[0013] As shown in Figures 2(a) and 2(b), the reaction vessel 10 is placed on a weighing scale 21 (described below) that is provided on the lower part 40b of the main body 40. In Figure 2(b), the width direction is designated X, the front-rear direction is designated Y, and the height direction is designated Z. In this embodiment, the upper part 40a of the main body 40 is slidable in the height direction Z, and the lower part 40b of the main body 40 is slidable in the front-rear direction Y, making it easy to remove and install the reaction vessel 10.

[0014] As shown in FIGS. 2(a) and 2(b), a CO2 gas supply unit 41 and a CO2 removal gas discharge unit 42 are inserted into two through-holes 43 in the upper portion 40a of the main body 40. The CO2 gas supply unit 41 supplies CO2 gas into the reaction vessel 10 (described below), and the CO2 removal gas discharge unit 42 discharges the CO2 removal gas from the reaction vessel 10. In this specification, "CO2 gas" refers to a gas containing CO2 as a constituent component. The CO2 gas may be a gas containing only CO2 as a constituent component, or may further contain unavoidable impurities. Furthermore, the CO2 gas may be a mixed gas containing CO2 and other substances as constituent components. The proportion of CO2 in the mixed gas is not limited, and the predominant component in the mixed gas may be CO2 or a substance other than CO2.

[0015] As shown in FIG. 2(a), the CO2 gas supply unit 41 and the CO2 removal gas discharge unit 42 are both detachably attached to the top of the reaction vessel 10 so that their respective tips are located inside the reaction vessel 10. In this embodiment, the CO2 gas supply unit 41 and the CO2 removal gas discharge unit 42 are loosely fitted into through-holes 43 in the upper portion 40a. This allows the upper portion 40a to be configured so as not to generate resistance to movement of the CO2 gas supply unit 41 and the CO2 removal gas discharge unit 42. Furthermore, in this embodiment, the CO2 gas supply unit 41 and the CO2 removal gas discharge unit 42 are made of highly flexible resin piping, and are configured so as to easily follow even slight movement of the reaction vessel 10 so as not to generate resistance.

[0016] As shown in FIG. 1, the weight gain detection unit 20 is provided in the lower portion 40b of the main body 40. The weight gain detection unit 20 is configured to detect the weight gain of the aqueous solution L in the reaction vessel 10 that increases when CO2 gas is brought into contact with the NaOH aqueous solution in the reaction vessel 10. The weight gain detection unit 20 includes a weigh scale 21, a memory unit 22, and a calculation unit 23. The configuration of the weigh scale 21 is not limited, but it is preferable that it consumes little power, and more preferably that it can be operated without electricity. For example, the weigh scale 21 can be a platform scale that operates without electricity or a power-saving digital platform scale.

[0017] 1, the weight increase detection unit 20 can measure the total weight of the reaction vessel 10, the weight of the CO2 gas supply unit 41 connected to the reaction vessel 10, the weight of the CO2 removal gas discharge unit 42, and the weight of the aqueous solution L in the reaction vessel 10 using a weigh scale 21. Alternatively, of the total weight, the weight of the reaction vessel 10, the weight of the CO2 gas supply unit 41 connected to the reaction vessel 10, and the weight of the CO2 removal gas discharge unit 42 may be preset as constant weights, and the weigh scale 21 may always detect a value obtained by subtracting the constant weights from the measured value.

[0018] In this embodiment, the weight increase detection unit 20 includes a weigh scale 21, a memory unit 22, and a calculation unit 23. The memory unit 22 is composed of a storage medium capable of storing the total weight measured by the weigh scale 21 and can store the initial weight described above. The calculation unit 23 is composed of a computing device and calculates the weight increase by subtracting the initial weight stored in the memory unit 22 from the total weight obtained by the weigh scale 21 after contacting CO2 gas with the NaOH aqueous solution in the reaction vessel 10. Note that if the total weight is measured while CO2 gas is being supplied by the weigh scale 21 from the CO2 gas supply unit 41, the calculation unit 23 can calculate the weight increase by subtracting the pressurized weight, which is the weight equivalent to the amount of air pressurized from the CO2 gas supply unit 41, from the total weight, along with the initial weight. Furthermore, in this embodiment, the weight increase detection unit 20 includes a weight display unit 24. The weight display unit 24 may display the total weight measured by the weigh scale 21 or the weight increase calculated by the calculation unit 23. In this embodiment, the weight increase calculated by the calculation unit 23 is displayed.

[0019] The production state estimation unit 30 shown in FIG. 1 is composed of a calculation device, and estimates the production state of the product in the reaction vessel 10 based on the weight increase detected by the weight increase detection unit 20. Here, "product in the reaction vessel 10" is a general term that includes Na2CO3 and NaHCO3 that are produced by bringing CO2 gas into contact with an aqueous NaOH solution in the reaction vessel 10. All of the products are dissolved in water in the reaction vessel 10 and are in the form of an aqueous solution. Furthermore, the "product production state" refers to the following five states of the aqueous solution L in the reaction vessel 10, and the aqueous solution L in the reaction vessel 10 is in one of these five states: (1) Initial state where NaOH is present but Na2CO3 and NaHCO3 are not present (2) The first state is when NaOH and Na2CO3 coexist and NaHCO3 does not exist. (3) A second state in which NaOH is absent, Na2CO3 is present, and NaHCO3 is absent. (4) The third state is when NaOH is not present and Na2CO3 and NaHCO3 coexist. (5) The fourth state is when NaOH and Na2CO3 are absent but NaHCO3 is present.

[0020] The reaction in the reaction vessel 10 shown in Figure 1 and the pH of the aqueous solution L in the reaction vessel 10 are described below. In the reaction vessel 10, the reactions of the following formulas 1 and 2 occur due to the supply of CO2 gas. 2NaOH+CO2→ Na2CO3+H2O (Formula 1) Na2CO3+CO2+H2O→ 2NaHCO3 (formula 2)

[0021] First, before the reaction starts, the reaction tank 10 is charged with an aqueous NaOH solution, and therefore the pH of the aqueous solution L in the reaction tank 10 is high, at about 14, as shown in Figure 3(a). Therefore, after the CO2 gas supply start time T0, only the reaction of the above formula 1 proceeds.

[0022] After time T0, as the reaction of Equation 1 progresses, the NaOH in the aqueous solution is consumed as shown in Figure 3(c), and the pH gradually decreases as shown in Figure 3(a). As a result, CO2 is fixed in the aqueous solution as Na2CO3, and the amount of Na2CO3 produced gradually increases as shown in Figure 3(d). As a result, the weight of the aqueous solution also gradually increases as shown in Figure 3(b).

[0023] Then, as shown in Figure 3(c), at time T1, all of the NaOH in the aqueous solution L reacts with CO2, disappearing from the solution L, and the pH drops to approximately 12 as shown in Figure 3(a). Then, as shown in Figure 3(b), the weight gain of the aqueous solution reaches R1, and the amount of Na2CO3 produced reaches a maximum as shown in Figure 3(d).

[0024] After time T1, the supply of CO2 gas continues, causing the reaction of formula 2 to proceed. As a result, Na2CO3 in the aqueous solution L is gradually consumed as shown in Figure 3(d), and the pH further decreases as shown in Figure 3(a). As a result, in the reaction tank 10, CO2 reacted with Na2CO3 is taken into the aqueous solution L as Na2CO3, and the amount of NaHCO3 produced begins to increase as shown in Figure 3(e). As a result, the weight of the aqueous solution L further increases as shown in Figure 3(b).

[0025] Then, at time T2, as shown in Figure 3(d), all of the Na2CO3 in the solution reacts with CO2, resulting in the disappearance of Na2CO3 from solution L, and the pH drops to approximately 8.5 as shown in Figure 3(a). Then, as shown in Figure 3(b), the weight gain of solution L reaches R2, and the amount of NaHCO3 produced reaches a maximum as shown in Figure 3(d). If the supply of CO2 gas continues after time T2, CO2 gas dissolves into solution L as H2CO3, causing the pH to further decrease as shown in Figure 3(a) and the weight of solution L to further increase as shown in Figure 3(b), but the amount of NaHCO3 produced remains at its maximum as shown in Figure 3(e).

[0026] From the above, the following correspondence relationship is established between the weight increase of the aqueous solution L in the reaction vessel 10 and the state of the product in the aqueous solution L. (1) At time T0 before the start of the reaction shown in FIG. 3(a), that is, when the weight increase of the aqueous solution L is 0, the initial state is one in which NaOH is present but Na2CO3 and NaHCO3 are not present. (2) In the first section I from time T0 to before T1, that is, when the weight increase of the aqueous solution L is greater than 0 and less than R1, the first state is reached in which NaOH and Na2CO3 coexist and NaHCO3 does not exist. (3) At time T1, that is, when the weight increase of the aqueous solution is R1, the second state is reached in which there is no NaOH, there is Na2CO3, and there is no NaHCO3. (4) In the second section II after time T1 and before time T2, that is, when the weight increase of the aqueous solution L is greater than R1 and less than R2, NaOH is not present, and a third state is reached in which Na2CO3 and NaHCO3 coexist. (5) At time T2 and in the third section III after T2, that is, when the weight increase of the aqueous solution L is equal to or greater than R2, the fourth state is reached in which NaOH and Na2CO3 are absent but NaHCO3 is present.

[0027] The NaOH concentration of the initial NaOH aqueous solution introduced into the reaction vessel 10 and the amount of the introduced aqueous solution are known. Therefore, based on the above equation (1), the weight increase R1 of the aqueous solution L, which corresponds to the amount of CO2 recovered when all of the NaOH in the reaction vessel 10 has converted to Na2CO3 and disappeared, is necessarily determined from the NaOH concentration and the amount of the introduced aqueous solution. Similarly, the weight increase R2 of the aqueous solution L, which corresponds to the amount of CO2 recovered when all of the Na2CO3 in the reaction vessel 10 has converted to NaHCO3 and disappeared, is also necessarily determined from the NaOH concentration and the amount of the introduced aqueous solution. For example, when 20 L of an aqueous NaOH solution with a 5% NaOH concentration is introduced into the reaction vessel 10, the weight of NaOH contained therein is 952 g, so the weight increase R1 is necessarily determined to be 524 g, and the weight increase R2 is necessarily determined to be 1047 g.

[0028] The production state estimation unit 30 shown in Figure 1 estimates the production state of the product in the reaction tank 10 by detecting the weight increase of the aqueous solution L using the above-mentioned correspondence between the weight increase of the aqueous solution L and the production state of the product in the reaction tank 10.

[0029] The production state estimation unit 30 can set a value within a range R from a first threshold value R1 to a second threshold value R2 shown in FIG. 3(b) as the reference value for the weight increase of the aqueous solution L. For example, when a first reference value R1 and a second reference value R2 are set as the reference values, the production state estimation unit 30 compares the weight increase detected by the weight increase detection unit 20 with the reference values ​​R1 and R2, and if the weight increase does not reach the reference value R1, it estimates that the aqueous solution L in the reaction tank 10 is in a first state. If the weight increase reaches the reference value R1, it estimates that the aqueous solution L in the reaction tank 10 is in a second state. If the weight increase exceeds the reference value R1 but does not reach the second threshold value R2, it estimates that the aqueous solution L in the reaction tank 10 is in a third state. If the weight increase reaches the second threshold value R2, it estimates that the aqueous solution L in the reaction tank 10 is in a fourth state. Also, when the weight increase exceeds the reference value R2, the aqueous solution L in the reaction tank 10 is estimated to be in the fourth state. The reference value may be any value within the range R, and R3 shown in FIG. 3(b) may be used as the reference value.

[0030] 1, the CO2 recovery device 1 includes a determination unit 35. The determination unit 35 determines whether or not the product can be extracted based on the estimation result of the production state estimation unit 30. In determining whether or not the product can be extracted by the determination unit 35, the estimation result of the production state estimation unit 30 and whether or not the product can be extracted can be set in any desired combination.

[0031] For example, the determination unit 35 can determine that the product cannot be extracted when the estimation result of the production state estimation unit 30 indicates that the product exists in the initial state or the first state, and can determine that the product can be extracted when the estimation result indicates that the product exists in the second state, the third state, or the fourth state. This can prevent NaOH from being present in the aqueous solution L of the product.

[0032] Alternatively, the determination unit 35 may determine that extraction of the product is not permitted when the estimation result of the production state estimation unit 30 indicates that the state of existence of the product is other than the fourth state, and may determine that extraction of the product is permitted when the estimation result indicates that the state of existence of the product is the fourth state. This allows only NaHCO to be obtained as the product.

[0033] Next, a usage mode of the CO2 recovery device 1 of this embodiment will be described with reference to the flow chart shown in FIG. First, in step S1 shown in Fig. 4, a predetermined amount of NaOH aqueous solution with a known NaOH concentration is introduced into the reaction tank 10. In this embodiment, 20 L of NaOH aqueous solution with a NaOH concentration of 5% is used. Next, in step S2 of Fig. 4, a first reference value R1 and a second reference value R2 are set.

[0034] 3(b) to 3(e), the first reference value R1 is a value corresponding to the total weight of CO2 used when all of the NaOH present in the reaction tank 10 reacts with CO2 to produce Na2CO3, and can be calculated from the NaOH concentration of the aqueous NaOH solution and the amount of the solution added. In this embodiment, the first reference value R1 calculated from the NaOH concentration of the aqueous NaOH solution and the amount of the solution added is 524 g.

[0035] 3(b) to 3(e), the second reference value R2 is a value equivalent to the total weight of CO2 used when all of the NaOH present in the reaction tank 10 reacts with CO2 to produce Na2CO3 and then all of the Na2CO3 further reacts with CO2 to produce NaHCO3, and can be calculated from the NaOH concentration of the aqueous NaOH solution and the amount of the solution added. In this embodiment, the second reference value R2 calculated from the NaOH concentration of the aqueous NaOH solution and the amount of the solution added is 1047 g.

[0036] 4, the total weight of the reaction tank 10, CO2 gas supply unit 41, CO2 removal gas discharge unit 42, and aqueous solution L in the reaction tank 10 before the CO2 gas is brought into contact with the NaOH aqueous solution is measured using the weight scale 21, and the measured value is stored as the initial weight in the memory unit 22. Thereafter, in step S4, CO2 gas is bubbled from the CO2 gas supply unit 41 into the NaOH aqueous solution in the reaction tank 10 to bring them into contact with each other.

[0037] 4, the weight increase detection unit 20 detects the weight increase of the aqueous solution L in the reaction tank 10. The weight increase is detected by the calculation unit 23 as a value calculated by subtracting the initial weight and the air pressurization of the CO2 gas supplied from the CO2 gas supply unit 41 into the reaction tank 10 from the total weight of the reaction tank 10, the CO2 gas supply unit 41, the CO2 removal gas discharge unit 42, and the aqueous solution L in the reaction tank 10 measured by the weighing scale 21.

[0038] Next, in step S6 of Fig. 4, a target product to be recovered in this flow is selected. In this flow, the target product is either Na2CO3 (sodium carbonate), a mixture of Na2CO3 and NaHCO3 (sodium sesquicarbonate), or NaHCO3 (sodium bicarbonate).

[0039] In step S6 of Fig. 4, if Na2CO3 (sodium carbonate) is selected as the target product, the process proceeds to P = a. Then, in step S71, the production state estimation unit 30 compares the weight increase detected by the weight increase detection unit 20 with a first reference value R1, and determines whether the weight increase has reached the first reference value R1. If it is determined in step S71 that the weight increase has not reached the first reference value R1, the process proceeds to No in step S71. Then, in step S8, the production state estimation unit 30 estimates that the production state of the product in the reaction tank 10 is the first state, and the determination unit 35 determines that the product cannot be removed, and the process returns to step S5.

[0040] 4, when it is determined that the weight increase has reached the first reference value R1, the process proceeds to Yes in step S71. Then, in step S9, the production state estimation unit 30 estimates that the production state of the product in the reaction tank 10 is the second state, and the determination unit 35 determines that the product can be removed, and the process proceeds to step S10.

[0041] 4, the supply of CO2 gas from the CO2 gas supply unit 41 is stopped to stop the bubbling of CO2 gas, and in step S11 the reaction vessel 10 is removed from the main body 40. Then, in step S12, the aqueous solution L containing the product in the reaction vessel 10 is recovered, and the aqueous solution L is dehydrated and dried to recover the target product. Then, this flow ends.

[0042] In step S6 of FIG. 4, if a mixture of Na2CO3 and NaHCO3 (sodium sesquicarbonate) is selected as the target product, the process proceeds to P=b. Then, in step S72, the production state estimation unit 30 compares the weight increase detected by the weight increase detection unit 20 with the first reference value R1 and the second reference value R2 to determine whether the weight increase exceeds the first reference value R1 and is less than the second reference value R2. If it is determined in step S72 that the weight increase does not exceed the first reference value R1 and is not less than the second reference value R2, the process proceeds to No in step S72, and the above-mentioned steps S8 and onward are performed. Note that since the weight increase increases over time from 0, in step S72, the process does not actually determine whether the weight increase is less than the second reference value R2, but only whether it exceeds the first reference value R1.

[0043] On the other hand, in step S72 shown in FIG. 4, if it is determined that the weight increase exceeds the first reference value R1 and is less than the second reference value R2, the process proceeds to Yes in step S72, and the above-mentioned step S9 and subsequent steps are performed, the target product is recovered, and this flow ends.

[0044] 4, if NaHCO3 (baking soda) is selected as the target product, the process proceeds to P=c. Then, in step S73, the production state estimation unit 30 compares the weight increase detected by the weight increase detection unit 20 with the second reference value R2, and determines whether the weight increase is equal to or greater than the second reference value R2. If it is determined in step S73 that the weight increase is not equal to or greater than the second reference value R2, the process proceeds to No in step S723, and the above-mentioned steps S8 and onward are performed.

[0045] On the other hand, in step S73 shown in FIG. 4, if it is determined that the weight increase is equal to or greater than the second reference value R2, the process proceeds to Yes in step S73, and the above-mentioned steps S9 and onward are carried out, the target product is recovered, and this flow ends.

[0046] As a result, the target product of high purity can be recovered with high accuracy by this flow.

[0047] If the weight increase of the aqueous solution L in the reaction vessel 10 is greater than the second reference value R2, the amount of NaHCO3 produced reaches its maximum, and CO2 gas dissolves in the aqueous solution L as H2CO3, resulting in the aqueous solution L containing carbon dioxide. That is, the weight increase greater than the second reference value R2 corresponds to the amount of CO2 dissolved as H2CO3. In order to prevent carbon dioxide from being contained in the target product when the target product is sodium bicarbonate, the process may proceed to step S9 when the weight increase reaches R2 (when weight increase = R2). In this way, high-purity sodium bicarbonate can be extracted with higher accuracy.

[0048] Furthermore, when the target product is sodium sesquicarbonate and it is desired to set the ratio of Na2CO3 to NaHCO3 to a predetermined ratio (x:y), a third reference value R3 is set as a reference value between the first threshold value R1 and the second threshold value R2, corresponding to the ratio (x:y), as shown in Figures 3(b), 3(d), and 3(e). Then, instead of step S72 shown in Figure 4, it may be determined whether the increase in weight of the aqueous solution L in the reaction tank 10 has reached the third reference value R3, as in step S721 shown in Figure 5. This makes it possible to obtain sodium sesquicarbonate having a ratio of Na2CO3 to NaHCO3 of the predetermined ratio (x:y).

[0049] Next, the effects of the CO2 recovery device 1 of this embodiment will be described in detail. In the CO2 recovery system 1 of this embodiment, Na2CO3 is first produced in the reaction tank 10 by the reaction of CO2 with NaOH. After the entire amount of NaOH present in the reaction tank 10 reacts with CO2, the produced Na2CO3 reacts with CO2 to produce NaHCO3. Since the CO2 recovery system 1 uses a predetermined amount of NaOH aqueous solution with a known NaOH concentration, the total amount of NaOH in the reaction tank 10 is determined. Therefore, by detecting the weight increase of the aqueous solution L in the reaction tank 10, i.e., the amount of CO2 recovered, the progress of the reaction in the reaction tank 10 can be accurately determined without measuring the pH in the reaction tank 10. Therefore, even if pH variations occur in measurements using a pH meter, the state of product production in the reaction tank 10 can be estimated with high accuracy without being affected by such variations. Furthermore, weighing scale 21 for detecting the weight increase can be a weighing scale that does not consume power or a power-saving weighing scale, so that weight increase detection unit 20 can be driven without consuming power or with little power consumption, resulting in a CO2 recovery device 1 that is excellent in reducing CO2 emissions. Furthermore, weighing scale 21 has a simpler structure than a pH measuring device, so maintenance work is less necessary.

[0050] In this embodiment, a determination unit 35 is provided that determines whether or not the product can be extracted based on the estimation result of the production state estimation unit 30. This allows the target product to be extracted in a highly pure state.

[0051] In this embodiment, the production state estimation unit 30 estimates the production state based on the result of comparing the weight increase amount with preset reference values ​​R1 and R2, thereby enabling the production state of the product to be estimated with higher accuracy.

[0052] In addition, in this embodiment, the reference value is set to R1 (first reference value), which is a value equivalent to the total weight of CO2 used when all of the NaOH present in the reaction tank 10 reacts with CO2 to produce Na2CO3, so that Na2CO3 is extracted as the target product. This allows sodium carbonate (Na2CO3), which is a valuable resource, to be extracted in a highly pure state.

[0053] Furthermore, in this embodiment, the reference value is set to R2 (second reference value), which corresponds to the total weight of CO2 used when NaHCO3 is produced by further reacting all of the NaOH present in the reaction tank 10 with CO2 to produce NaHCO3. This allows sodium bicarbonate (NaHCO3), a valuable resource, to be extracted in a highly pure state.

[0054] In this embodiment, the reference values ​​are set to a value greater than a first threshold value R1 and less than a second threshold value R2, with the first threshold value R1 being set to a value equivalent to the total weight of CO2 used when all of the NaOH present in the reaction vessel 10 reacts with CO2 to produce Na2CO3, and the second threshold value R2 being set to a value equivalent to the total weight of CO2 used when all of the NaOH present in the reaction vessel 10 reacts with CO2 to produce Na2CO3 and then all of the Na2CO3 further reacts with CO2 to produce NaHCO3, thereby allowing a mixture of Na2CO3 and NaHCO3 to be extracted as the target product. This allows sodium sesquicarbonate (a mixture of Na2CO3 and NaHCO3), a valuable resource, to be extracted in a highly pure state.

[0055] In this embodiment, the CO2 gas supply unit 41 and the CO2 removal gas discharge unit 42 are detachably attached to the upper part 11 of the reaction vessel 10, so that the weighing scale 21 measures the weight including the CO2 gas supply unit 41 and the CO2 removal gas discharge unit 42. Alternatively, a first modified embodiment shown in FIG. 6 may be used. In the first modified embodiment, the CO2 gas supply unit 41 comprises a first pipe 411, a second pipe 412, and a relay pipe 413. The first pipe 411 is fixed to the upper part 40a of the main body 40. The second pipe 412 is fixed to the upper part 11 of the reaction vessel 10. The relay pipe 413 is provided between the first pipe 411 and the second pipe 412 to connect them. The relay pipe 413 is made of flexible resin and is a hollow, bellows-shaped pipe. The connection between the relay pipe 413 and the first pipe 411 is detachably configured by detachment mechanisms 411a, 413a, which allow easy attachment and detachment from each other. Similarly, the connecting portion between relay pipe 413 and second pipe 412 is also configured to be detachable by detachment mechanisms 412b and 413b that allow them to be easily detached from each other.

[0056] 6, the CO2 removal gas discharge unit 42 also includes a first pipe 421, a second pipe 422, and a relay pipe 423. As with the CO2 gas supply unit 41, the first pipe 421 is fixed to the upper portion 40a of the main body 40. The second pipe 422 is fixed to the upper portion 11 of the reaction vessel 10. The relay pipe 423 is provided between the first pipe 421 and the second pipe 422 to connect them. Like the relay pipe 413, the relay pipe 423 is also made of flexible resin and is a bellows-shaped hollow pipe. The connection between the relay pipe 423 and the first pipe 421 is detachably configured by detachable mechanisms 421a and 423a, which allow easy attachment and detachment from each other. Similarly, the connection between the relay pipe 423 and the second pipe 422 is detachably configured by detachable mechanisms 422b and 423b, which allow easy attachment and detachment from each other. As a result, even if the reaction vessel 10 moves relative to the upper part 40a of the main body 40, the relay pipes 413, 423 deform accordingly, preventing pressure from being applied to the weighing scale 21 from the CO2 gas supply unit 41 and the CO2 removal gas discharge unit 42 via the reaction vessel 10. As a result, the influence of movement of the reaction vessel 10 relative to the upper part 40a of the main body 40 on weight changes during measurement by the weighing scale 21 can be suppressed. In this way, the weighing scale 21 does not measure the weights of the objects above the relay pipes 413, 423, namely, the first piping 411, the detachment mechanisms 411a, 413a, the first piping 421, and the detachment mechanisms 421a, 423a.

[0057] As described above, according to the above-described embodiment, it is possible to provide a CO2 recovery device that can estimate the state of product production with high accuracy and has an excellent effect of suppressing CO2 emissions.

[0058] The present invention is not limited to the above-described embodiment and modified forms, and can be applied to various embodiments without departing from the spirit of the present invention. [Explanation of symbols]

[0059] 1: CO2 recovery device, 10: reaction tank, 20: weight increase amount detection unit, 21: weight scale, 30: production state estimation unit, 35: determination unit, 41: CO2 gas supply unit, 42: CO2 removed gas discharge unit

Claims

1. Add a predetermined amount of NaOH solution with a known NaOH concentration to CO ２ a reaction vessel for contacting the gas; In the reaction vessel, the NaOH aqueous solution is ２ a weight increase detector that detects an increase in weight of the aqueous solution L in the reaction tank due to contact with the gas; a production state estimation unit that estimates a production state of a product in the reaction tank based on the weight increase detected by the weight increase detection unit, the production state estimation unit estimates the production state based on a result of comparing the weight increase amount with a preset reference value; the reference value is a value in a range exceeding a first threshold value and less than a second threshold value, the first threshold value is a value corresponding to the total weight of CO 2 used when the entire amount of NaOH present in the reaction tank reacts with CO 2 to produce Na 2 CO 3 , the second threshold value is a value corresponding to the total weight of CO 2 used when, after all of the NaOH present in the reaction tank has reacted with CO 2 to produce Na 2 CO 3 , all of the Na 2 CO 3 further reacts with CO 2 to produce NaHCO 3 ; A CO 3 extractor configured to extract a mixture of Na 2 CO 3 and NaHCO 3 as the product. ２ Recovery device.

2. The CO 2 system according to claim 1 , further comprising a determination unit that determines whether or not the product can be extracted based on the estimation result of the production state estimation unit. ２ Recovery device.

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