Hydrogencarbonate producing system and hydrogencarbonate producing method

Abstract

To provide a hydrogencarbonate producing system capable of efficiently producing hydrogencarbonate.SOLUTION: A hydrogencarbonate producing system according to the present disclosure includes: a removing device that removes acidic substances in a first exhaust gas to produce a second exhaust gas; a hydrogencarbonate producing device that reacts carbon dioxide in at least one of the first exhaust gas and the second exhaust gas with an alkaline earth compound in a reaction solution to produce hydrogencarbonate; and a pH sensor that detects pH of the reaction solution. An introduction amount of the first exhaust gas and an introduction amount of the second exhaust gas that are to be introduced into the hydrogencarbonate producing device are controlled to maintain the pH of the reaction solution detected by the pH sensor within a predetermined target pH range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to bicarbonate production systems and methods. [Background technology]

[0002] Patent Document 1 discloses a technology for recovering carbon dioxide (hereinafter also referred to as CO2) from exhaust gases from factories and the like. The captured CO2 is immobilized, for example, by reacting with alkaline earth compounds to form carbonates or bicarbonates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-051554 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have been studying the production of hydrogen carbonate by reacting CO2 in exhaust gas with an alkaline earth compound in water, and have found the following problems. If the pH of the reaction solution in which CO2 and alkaline earth compounds are reacted is too high, carbonates are more likely to be produced instead of bicarbonates, whereas if the pH of the reaction solution is too low, it is difficult to produce bicarbonates.

[0005] The present disclosure has been made in consideration of the above circumstances and provides a bicarbonate production system capable of efficiently producing bicarbonate. [Means for solving the problem]

[0006] The bicarbonate production system according to the present disclosure comprises: a removal device that removes acidic substances from the first exhaust gas to generate a second exhaust gas; a hydrogen carbonate generator that reacts carbon dioxide in at least one of the first and second exhaust gases with an alkaline earth compound in a reaction liquid to generate hydrogen carbonate; a pH sensor for detecting the pH of the reaction solution; The amount of the first exhaust gas introduced into the bicarbonate production device and the amount of the second exhaust gas introduced into the bicarbonate production device are controlled so as to maintain the pH of the reaction solution detected by the pH sensor within a predetermined target pH range.

[0007] In a bicarbonate production system according to one embodiment of the present disclosure, the amount of the first exhaust gas introduced into the bicarbonate production device before the removal of acidic substances and the amount of the second exhaust gas introduced into the bicarbonate production device after the removal of acidic substances are controlled so that the pH of the reaction solution in the bicarbonate production device, detected by a pH sensor, is maintained within a predetermined target pH range. As a result, the pH of the reaction solution can be maintained within the predetermined target pH range, and bicarbonate can be produced efficiently.

[0008] If the pH detected by the pH sensor is higher than the predetermined target pH range, the amount of the first exhaust gas introduced may be increased, and if the pH detected by the pH sensor is lower than the predetermined target pH range, the amount of the second exhaust gas introduced may be increased. The acidic substance may contain at least one of nitrogen oxides and sulfur oxides. Furthermore, the alkaline earth compound may be one contained in incineration ash, slag, or seawater.

[0009] A method for producing bicarbonate according to one embodiment of the present disclosure includes: removing acidic substances from the first flue gas to generate a second flue gas; and reacting carbon dioxide in at least one of the first and second exhaust gases with an alkaline earth compound in a reaction liquid to produce bicarbonate, Detecting the pH of the reaction solution; The amount of the first exhaust gas introduced and the amount of the second exhaust gas introduced in the step of producing hydrogen carbonate are controlled so as to maintain the detected pH of the reaction solution within a predetermined target pH range.

[0010] In a method for producing bicarbonate according to one embodiment of the present disclosure, the pH of a reaction solution in a step of producing bicarbonate is detected, and the amount of a first exhaust gas introduced before removal of acidic substances and the amount of a second exhaust gas introduced after removal of acidic substances in the step of producing bicarbonate are controlled so as to maintain the detected pH of the reaction solution within a predetermined target pH range. As a result, the pH of the reaction solution can be maintained within the predetermined target pH range, and bicarbonate can be produced efficiently. [Effects of the Invention]

[0011] According to the present disclosure, a bicarbonate production system capable of efficiently producing bicarbonate can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram showing the configuration of a bicarbonate production system according to a first embodiment. [Figure 2] 1 is a flowchart showing a bicarbonate producing method according to a first embodiment. [Figure 3] 3 is a flowchart showing a control method for controlling the pH of the reaction liquid in the bicarbonate production device 200 in step ST2 of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, specific embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments. In addition, the following description and drawings have been simplified as appropriate for clarity of explanation.

[0014] (First embodiment) <Configuration of bicarbonate generation system> First, the configuration of a bicarbonate generation system according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing the configuration of a bicarbonate generation system according to the first embodiment. In Fig. 1, thick arrows indicate gas flows, and thin arrows indicate signal flows.

[0015] As shown in FIG. 1, the bicarbonate generating system according to this embodiment includes an acidic substance remover 100, a bicarbonate generating device 200, a controller 300, a suction pump P, a three-way valve V, and a sensor S.

[0016] As shown in Fig. 1, the acidic substance removal device 100 removes acidic substances from a first exhaust gas to generate and output a second exhaust gas. The first exhaust gas is exhaust gas from, for example, a factory, which contains a higher concentration of CO2 than the atmosphere, and contains acidic substances such as nitrogen oxides (NOx) and sulfur oxides (SOx). Although not particularly limited, the acidic substance removal device 100 is, for example, a wet scrubber.

[0017] 1 , a first exhaust gas sucked by a suction pump P from a factory (not shown) is introduced into an acidic substance removal apparatus 100 via a three-way valve V. Then, a second exhaust gas from which acidic substances in the first exhaust gas have been removed by the acidic substance removal apparatus 100 is introduced into a bicarbonate production apparatus 200. On the other hand, the first exhaust gas sucked by the suction pump P is also directly introduced into the bicarbonate production apparatus 200 via the three-way valve V.

[0018] That is, the three-way valve V switches the supply destination of the first exhaust gas between the acid substance removal apparatus 100 and the bicarbonate production apparatus 200. Here, the three-way valve V may be used to change the ratio between the amount of the first exhaust gas introduced into the acid substance removal apparatus 100 and the amount of the first exhaust gas introduced into the bicarbonate production apparatus 200. With this configuration, it is possible to control the amounts of the first exhaust gas from which acid substances have not been removed and the second exhaust gas from which acid substances have been removed introduced into the bicarbonate production apparatus 200. The means for switching the supply destination of the first exhaust gas is not limited to the three-way valve shown in FIG. 1, but may be composed of, for example, two on-off valves.

[0019] 1, the controller 300 controls the amount of the first exhaust gas introduced into the bicarbonate generator 200 and the amount of the second exhaust gas introduced into the bicarbonate generator 200 so as to maintain the pH of the reaction solution in the bicarbonate generator 200, detected by the sensor S, within a predetermined target pH range. In the example shown in FIG. 1, the controller 300 controls the three-way valve V based on the pH of the reaction solution in the bicarbonate generator 200, detected by the sensor S.

[0020] Here, if the pH of the reaction solution detected by the sensor S is higher than a predetermined target pH range, carbonate rather than bicarbonate is more likely to be produced in the bicarbonate production device 200. Therefore, in order to lower the pH of the reaction solution, the controller 300 controls the three-way valve V to increase the amount of the first flue gas introduced, from which acidic substances have not been removed. For example, the controller 300 controls the three-way valve V to switch the supply destination of the first flue gas from the acidic substance removal device 100 to the bicarbonate production device 200. Alternatively, the controller 300 may control the three-way valve V to increase the proportion of the amount of the first flue gas introduced into the bicarbonate production device 200.

[0021] On the other hand, when the pH of the reaction solution detected by the sensor S is lower than a predetermined target pH range, it becomes difficult to generate bicarbonate in the bicarbonate production device 200. Therefore, in order to raise the pH of the reaction solution, the controller 300 controls the three-way valve V to increase the amount of the second exhaust gas introduced, from which acidic substances have been removed. For example, the controller 300 controls the three-way valve V to switch the supply destination of the first exhaust gas from the bicarbonate production device 200 to the acidic substance removal device 100. Alternatively, the controller 300 may control the three-way valve V to increase the proportion of the amount of the second exhaust gas introduced into the bicarbonate production device 200.

[0022] 1, the controller 300 includes a calculation unit such as a CPU (Central Processing Unit), and memories such as RAM (Random Access Memory) and ROM (Read Only Memory) that store various programs, data, etc. In other words, the controller 300 functions as a computer and executes various processes based on the various programs, etc.

[0023] The bicarbonate generator 200 receives the first and second exhaust gases and reacts CO in the first and second exhaust gases with an alkaline earth compound to generate bicarbonate. Here, the bicarbonate is a hydrogen carbonate of an alkaline earth metal, also called bicarbonate.

[0024] The alkaline earth compound may be added as it is, but it is preferable to use incineration ash, slag, seawater, or the like from the viewpoint of reducing the environmental load. Incineration ash may be used as is, or incineration ash from which compounds that interfere with CO2 fixation have been removed in advance may be used. In other words, as long as the incineration ash can fix CO2, it does not matter if it contains components other than alkaline earth compounds.

[0025] The alkaline earth compound is a compound containing an alkaline earth metal element, such as a water-soluble alkaline earth compound, including alkaline earth metal oxides, alkaline earth metal nitrates, alkaline earth metal hydroxides, and mixtures thereof.

[0026] Suitable examples of alkaline earth metals include Be, Ca, Mg, Sr, Ba, Ra, or a combination thereof. Suitable examples of alkaline earth metal oxides include CaO, MgO, SrO, BaO, or a combination thereof. Suitable examples of alkaline earth metal nitrates include Ca(NO3)2, Mg(NO3)2, Sr(NO3)2, Ba(NO3)2, or a combination thereof. Suitable examples of alkaline earth metal hydroxides include Ca(OH)2, Mg(OH)2, Sr(OH)2, Ba(OH)2, or a combination thereof. Specific examples of bicarbonates include Ca(HCO3)2, Mg(HCO3)2, Sr(HCO3)2, Ba(HCO3)2, or a combination thereof.

[0027] When water is used as a solvent and the incineration ash contains calcium oxide, for example, carbonate ions are consumed and carbonate is produced by the following reaction: If further carbonate ions are supplied, hydrogen carbonate is produced. CaO+H2O→Ca 2+ +2OH - CO2+H2O→2H + +CO3 2- Ca 2+ +CO3 2- →CaCO3 CaCO3+2H + +CO3 2- →Ca(HCO3)2

[0028] 1, the sensor S detects the pH of the reaction solution in the bicarbonate generation device 200. The sensor S is not limited in any way as long as it can detect the pH of the reaction solution in the bicarbonate generation device 200, and is, for example, a pH sensor using a glass electrode method.

[0029] The target pH range of the reaction solution is a concentration range in which bicarbonate can be efficiently produced. The target pH range of the reaction solution is not particularly limited, but is, for example, 5 to 11, preferably 6.5 to 10.5, and more preferably 7 to 9.5. Here, if the pH of the reaction solution in which CO2 and an alkaline earth compound are reacted exceeds 11, carbonate is more likely to be produced rather than bicarbonate. On the other hand, if the pH of the reaction solution is below 5, bicarbonate is less likely to be produced.

[0030] As described above, in the bicarbonate production system according to this embodiment, the amount of the first exhaust gas introduced into the bicarbonate production apparatus 200 and the amount of the second exhaust gas introduced into the bicarbonate production apparatus 200 are controlled so as to maintain the pH of the reaction solution in the bicarbonate production apparatus 200 within a predetermined target pH range. Therefore, the pH of the reaction solution can be maintained within the predetermined target pH range, and bicarbonate can be produced efficiently.

[0031] <Method for producing bicarbonate> Next, a bicarbonate production method according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a flowchart showing the bicarbonate production method according to the first embodiment. In describing Fig. 2, Fig. 1 will be referred to as appropriate.

[0032] First, as shown in FIG. 2, the acidic substance removal device 100 removes acidic substances from the first flue gas to generate a second flue gas (step ST1). Then, as shown in Fig. 2, in the bicarbonate production apparatus 200 shown in Fig. 1, the carbon dioxide and the alkaline earth compound in at least one of the first exhaust gas and the second exhaust gas are reacted in a reaction solution to produce bicarbonate (step ST2). Here, as shown in Fig. 1, the first exhaust gas from which acidic substances have not been removed and the second exhaust gas from which acidic substances have been removed can be introduced into the bicarbonate production apparatus 200.

[0033] In the bicarbonate production method of this embodiment, in step ST2, the amount of the first exhaust gas introduced into the bicarbonate production apparatus 200 and the amount of the second exhaust gas introduced into the bicarbonate production apparatus 200 are controlled so as to maintain the pH of the reaction solution in the bicarbonate production apparatus 200 within a predetermined target pH range.

[0034] FIG. 3 is a flowchart showing a control method for controlling the pH of the reaction liquid in the bicarbonate production device 200 in step ST2 of FIG. First, as shown in FIG. 3, when step ST2 is started, the pH of the reaction liquid in the bicarbonate production device 200 is detected by the sensor S (step ST21).

[0035] Next, the controller 300 determines whether the pH of the reaction solution detected by the sensor S is equal to or higher than the lower limit of a predetermined target pH range (step ST22). If the detected pH of the reaction solution is lower than the lower limit of the target pH range (NO in step ST22), it becomes difficult to generate bicarbonate in the bicarbonate production device 200. Therefore, the controller 300 controls the three-way valve V to increase the amount of the second exhaust gas introduced, from which acidic substances have been removed, in order to increase the pH of the reaction solution (step ST23). Thereafter, if step ST2 is not completed, the process returns to step ST21.

[0036] On the other hand, if the detected pH of the reaction liquid is equal to or higher than the lower limit of the target pH range (YES in step ST22), the controller 300 determines whether the detected pH of the reaction liquid is equal to or lower than the upper limit of the predetermined target pH range (step ST24).

[0037] If the detected pH of the reaction solution is higher than the upper limit of the predetermined target pH range (NO in step ST24), carbonate rather than bicarbonate is more likely to be produced in the bicarbonate production device 200. Therefore, in order to lower the pH of the reaction solution, the controller 300 controls the three-way valve V to increase the amount of the first exhaust gas introduced, from which acidic substances have not been removed (step ST25). Thereafter, if step ST2 is not completed, the process returns to step ST21.

[0038] If the detected pH of the reaction solution is equal to or lower than the upper limit of the predetermined target pH range (YES in step ST24), and step ST2 has not been completed, the process returns to step ST21. As shown in FIG. 3, the controller 300 repeatedly executes the processes of steps ST21 to ST25 described above from the start to the end of step ST2.

[0039] The determination in step ST22 and step ST23 of increasing the amount of introduced second exhaust gas are performed together. The determination in step ST24 and step ST25 of increasing the amount of introduced first exhaust gas are performed together. In Fig. 3, the determination in step ST22 is performed first for convenience, but the determination in step ST24 may be performed first, or the determinations in steps ST22 and ST24 may be performed simultaneously.

[0040] As described above, in the bicarbonate production method according to this embodiment, the amount of the first exhaust gas introduced into the bicarbonate production apparatus 200 and the amount of the second exhaust gas introduced into the bicarbonate production apparatus 200 are controlled so as to maintain the pH of the reaction solution in the bicarbonate production apparatus 200 within a predetermined target pH range. Therefore, the pH of the reaction solution can be maintained within the predetermined target pH range, and bicarbonate can be produced efficiently.

[0041] The present disclosure is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the present disclosure. This disclosure also contributes to carbon neutrality, decarbonization, and the Sustainable Development Goals (SDGs). [Explanation of symbols]

[0042] 100 Acidic substance removal equipment 200 Bicarbonate Generator 300 Controller P suction pump S sensor V Three-Way Valve

Claims

1. a removal device that removes acidic substances from the first exhaust gas to produce a second exhaust gas; a hydrogen carbonate generator that reacts carbon dioxide in at least one of the first and second exhaust gases with an alkaline earth compound in a reaction liquid to generate hydrogen carbonate; a pH sensor for detecting the pH of the reaction solution; controlling the amount of the first exhaust gas introduced into the bicarbonate production device and the amount of the second exhaust gas introduced into the bicarbonate production device so as to maintain the pH of the reaction solution detected by the pH sensor within a predetermined target pH range; Bicarbonate generation system.

2. The pH detected by the pH sensor is If the pH is higher than the predetermined target pH range, the amount of the first exhaust gas introduced is increased; If the pH is lower than the predetermined target pH range, increasing the amount of the second exhaust gas introduced. The bicarbonate generating system of claim 1 .

3. The acidic substance includes at least one of nitrogen oxides and sulfur oxides. The bicarbonate generating system according to claim 1 or 2.

4. The alkaline earth compound is contained in incineration ash, slag, or seawater. The bicarbonate generating system according to claim 1 or 2.

5. removing acidic substances from the first exhaust gas to produce a second exhaust gas; and reacting carbon dioxide in at least one of the first and second exhaust gases with an alkaline earth compound in a reaction liquid to produce bicarbonate, Detecting the pH of the reaction solution; controlling the amount of the first exhaust gas introduced and the amount of the second exhaust gas introduced in the step of producing bicarbonate so as to maintain the detected pH of the reaction solution within a predetermined target pH range; Bicarbonate production method.

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