Carbon dioxide adsorption and desorption method and device

Abstract

The invention provides a carbon dioxide adsorption and desorption method and device. The method and the device can separate carbon dioxide from exhaust gas containing carbon dioxide and can easily regenerate adsorption liquid. In the adsorption tank (2), an exhaust gas containing carbon dioxide is brought into contact with an adsorption liquid to obtain a metal carbonate aqueous solution. The aqueous metal carbonate solution is transferred to a desorption tank (3). In a state in which the desorption tank (3) is depressurized, the metal carbonate aqueous solution is irradiated with ultrasonic waves, and carbon dioxide is desorbed from the metal carbonate aqueous solution, thereby regenerating the adsorbed solution. And transferring the regenerated adsorption liquid to the adsorption tank.

Description

Technical Field

[0001] The invention relates to a method and a device for adsorbing and desorbing carbon dioxide. Background Art

[0002] In recent years, in order to curb global warming, it is necessary to reduce the emission of carbon dioxide, which is a greenhouse gas. In particular, a large amount of exhaust gas is generated in thermal power plants, steel mills, etc., and various methods have been studied.

[0003] In order to reduce the emission of the above-mentioned carbon dioxide, for example, the following carbon dioxide adsorption and desorption method has been proposed (for example, refer to Patent Document 1), which comprises the following steps: a step of contacting exhaust gas containing carbon dioxide with an adsorption liquid composed of an aqueous sodium hydroxide solution in an adsorption tank to obtain an aqueous sodium carbonate solution; a step of transferring the aqueous sodium carbonate solution from the adsorption tank to a desorption tank; a step of desorbing carbon dioxide from the aqueous sodium carbonate solution in the desorption tank to regenerate the adsorption liquid; and a step of transferring the regenerated adsorption liquid from the desorption tank to the adsorption tank.

[0004] According to the invention described in Patent Document 1, after the above-mentioned adsorption liquid adsorbs carbon dioxide in the above-mentioned adsorption tank to obtain a sodium carbonate aqueous solution, carbon dioxide is desorbed from the sodium carbonate aqueous solution in the above-mentioned desorption tank, thereby being able to efficiently separate only carbon dioxide from the above-mentioned exhaust gas containing carbon dioxide, and further, the adsorption liquid regenerated by the desorption of carbon dioxide can be reused for the adsorption of carbon dioxide in the above-mentioned adsorption tank.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2005-262051 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, in the method described in Patent Document 1, hydrogen chloride is used when desorbing carbon dioxide from the sodium carbonate aqueous solution in the desorption tank, so that after desorption of carbon dioxide, a sodium chloride aqueous solution is generated as shown in the following formula.

[0010] Na2CO3+2HCl→CO2+2NaCl+H2O

[0011] In order to regenerate the sodium chloride aqueous solution into the sodium hydroxide aqueous solution, the sodium chloride aqueous solution must be treated using a bipolar electrodialysis device, and further, by-produced hydrogen and chlorine must be treated using the bipolar electrodialysis device to regenerate hydrogen chloride, which has the problem of complicated operations.

[0012] The present invention aims to solve the above-mentioned problems and to provide a method and an apparatus for use therein which can efficiently separate only carbon dioxide from exhaust gas containing carbon dioxide and can easily regenerate an adsorption liquid after desorption of carbon dioxide.

[0013] Means for solving problems

[0014] In order to achieve the above-mentioned purpose, the carbon dioxide adsorption and desorption method of the present invention includes the following steps: a step of contacting exhaust gas containing carbon dioxide with an adsorption liquid composed of an aqueous solution of a hydroxide of a metal capable of generating carbonate in an adsorption tank to obtain an aqueous solution of a metal carbonate; a step of transferring the aqueous solution of the metal carbonate from the adsorption tank to a desorption tank; a step of desorbing carbon dioxide from the aqueous solution of the metal carbonate in the desorption tank to regenerate the adsorption liquid; and a step of transferring the regenerated adsorption liquid from the desorption tank to the adsorption tank. The carbon dioxide adsorption and desorption method is characterized in that the step of desorbing carbon dioxide from the aqueous solution of the metal carbonate to regenerate the adsorption liquid is carried out in the following manner: depressurizing the desorption tank and irradiating the aqueous solution of the metal carbonate contained in the depressurized desorption tank with ultrasonic waves.

[0015] In the carbon dioxide adsorption and desorption method of the present invention, in the above-mentioned adsorption tank, exhaust gas containing carbon dioxide is brought into contact with the above-mentioned adsorption liquid composed of an aqueous solution of a metal hydroxide capable of generating carbonate, thereby allowing the adsorption liquid to adsorb carbon dioxide and generate an aqueous solution of metal carbonate.

[0016] It should be noted that, in the present invention, the term "metal carbonate" includes metal carbonates and metal hydrogen carbonates.

[0017] Next, the metal carbonate aqueous solution is transferred from the adsorption tank to the desorption tank. Then, the desorption tank is depressurized, and the metal carbonate aqueous solution contained in the depressurized desorption tank is irradiated with ultrasonic waves, thereby desorbing carbon dioxide from the metal carbonate aqueous solution and regenerating the adsorption liquid. The regenerated adsorption liquid is transferred to the adsorption tank and used again for adsorption of carbon dioxide.

[0018] According to the carbon dioxide adsorption and desorption method of the present invention, carbon dioxide can be desorbed from the metal carbonate aqueous solution, thereby regenerating the adsorption liquid, simply by depressurizing the above-mentioned desorption tank and irradiating the above-mentioned metal carbonate aqueous solution contained in the depressurized desorption tank with ultrasonic waves. Therefore, only carbon dioxide can be effectively separated from the exhaust gas containing carbon dioxide, and the adsorption liquid can be easily regenerated after the desorption of carbon dioxide.

[0019] The carbon dioxide adsorption and desorption method of the present invention can be implemented by the following carbon dioxide adsorption and desorption device, which comprises: an adsorption tank, which is equipped with an adsorption liquid supply mechanism for supplying an adsorption liquid and an exhaust gas supply mechanism for supplying an exhaust gas containing carbon dioxide, wherein the adsorption liquid is composed of an aqueous hydroxide solution of a metal that can generate carbonate, and in the adsorption tank, the adsorption liquid is brought into contact with the exhaust gas to obtain a metal carbonate aqueous solution; a metal carbonate aqueous solution transfer mechanism, which transfers the metal carbonate aqueous solution from the adsorption tank to the desorption tank; a desorption tank, which is equipped with an ultrasonic irradiation mechanism and a decompression mechanism, in which carbon dioxide is desorbed from the metal carbonate aqueous solution to regenerate the adsorption liquid; a carbon dioxide removal mechanism, which removes carbon dioxide from the desorption tank; and an adsorption liquid transfer mechanism, which transfers the regenerated adsorption liquid from the desorption tank to the adsorption tank.

[0020] In the carbon dioxide adsorption and desorption device of the present invention, it is preferable that the adsorption tank is a part of a conduit for conveying exhaust gas from a source of exhaust gas containing carbon dioxide to an exhaust gas treatment device.

[0021] Furthermore, in the carbon dioxide adsorption and desorption device of the present invention, it is preferable that the conduit is a pipe connecting a source of exhaust gas containing the carbon dioxide and the exhaust gas treatment device.

[0022] Brief description of the attached figure

[0023] Figure 1 This is a system configuration diagram showing an example of the configuration of an apparatus used in the carbon dioxide adsorption and desorption method of the present invention.

[0024] Figure 2 is a flow chart showing the carbon dioxide adsorption and desorption method of the present invention.

[0025] Figure 3 This is a system configuration diagram showing an example of the configuration of an apparatus used in the carbon dioxide adsorption and desorption method of the present invention. DETAILED DESCRIPTION

[0026] Next, embodiments of the present invention will be described in further detail with reference to the accompanying drawings.

[0027] The carbon dioxide adsorption and desorption method of this embodiment can be performed, for example, Figure 1 The carbon dioxide adsorption and desorption device 1 shown is implemented.

[0028] like Figure 1As shown, the carbon dioxide adsorption and desorption device 1 of this embodiment includes an adsorption tank 2 and a desorption tank 3. The adsorption tank 2 includes an adsorption liquid conduit 4 and an exhaust gas supply conduit 5. The adsorption liquid conduit 4 supplies an aqueous hydroxide solution of a metal capable of generating carbonate as the adsorption liquid; and the exhaust gas supply conduit 5 supplies exhaust gas containing carbon dioxide. The adsorption tank 2 stores a metal carbonate aqueous solution 6 generated by the adsorption of carbon dioxide by the adsorption liquid. In addition, the adsorption tank 2 includes a metal carbonate aqueous solution transfer conduit 7 for transferring the metal carbonate aqueous solution 6 to the desorption tank 3, and the metal carbonate aqueous solution transfer conduit 7 is connected to the desorption tank 3 via a first transfer pump 8.

[0029] The desorption tank 3 is provided with an ultrasonic oscillator device 9 on the outside of the bottom surface, and the ultrasonic oscillator device 9 irradiates ultrasonic waves to the metal carbonate aqueous solution 6 contained in the desorption tank 3. On the other hand, the desorption tank 3 is provided with a vacuum pump 10 for decompressing the upper space of the metal carbonate aqueous solution 6 and a carbon dioxide transfer conduit 11 for sucking carbon dioxide desorbed from the metal carbonate aqueous solution 6 and transferring it to the outside. The carbon dioxide transfer conduit 11 is provided with a suction pump 12 in the middle. In addition, the desorption tank 3 is provided with an adsorption liquid transfer conduit 13, and the adsorption liquid transfer conduit 13 transfers the adsorption liquid 6a regenerated by desorbing carbon dioxide from the metal carbonate aqueous solution 6 to the adsorption tank 2, and the adsorption liquid transfer conduit 13 is connected to the adsorption tank 2 via a second transfer pump 14.

[0030] Next, refer to Figure 2 Yes Figure 1 The carbon dioxide adsorption and desorption method of the present embodiment of the carbon dioxide adsorption and desorption device 1 shown will be described.

[0031] In the carbon dioxide adsorption and desorption method of the present embodiment, first, an aqueous solution of a hydroxide of a metal capable of generating carbonate is supplied as an adsorption liquid to the adsorption tank 2 through the adsorption liquid conduit 4 (step 1 / STEP1). At the same time, exhaust gas containing carbon dioxide is supplied to the adsorption tank 2 from the exhaust gas supply conduit 5 (step 2 / STEP2), and the adsorption liquid and the exhaust gas are brought into gas-liquid contact in the adsorption tank 2 (step 3 / STEP3).

[0032] As the aqueous hydroxide solution of the metal that can generate carbonate, any aqueous hydroxide solution of the metal that can react with carbon dioxide to generate carbonate can be used, for example, aqueous hydroxide solutions of metals such as sodium, potassium, calcium, and magnesium can be used, and preferably sodium hydroxide aqueous solution is used. Hereinafter, in this embodiment, the case where sodium hydroxide aqueous solution is used as the above-mentioned adsorption liquid is described as an example.

[0033] The sodium hydroxide aqueous solution can be prepared by commercially available sodium hydroxide crystals, or by electrolyzing a sodium chloride aqueous solution.

[0034] The gas-liquid contact between the adsorbent and the waste gas can be carried out in the following ways: Figure 1 As shown, the above-mentioned exhaust gas is brought into contact with the sodium hydroxide aqueous solution in the adsorption tank 2, or the above-mentioned exhaust gas is bubbled in the sodium hydroxide aqueous solution stored in the adsorption tank 2.

[0035] When the exhaust gas is brought into contact with the sodium hydroxide aqueous solution in the adsorption tank 2, a shelf may be provided in the adsorption tank 2, and a filler for a distillation tower may be arranged on the shelf to increase the contact area between the exhaust gas and the sodium hydroxide aqueous solution. In addition, two or more of the above methods may be combined to bring the adsorbent into gas-liquid contact with the exhaust gas.

[0036] As a result of the gas-liquid contact, the sodium hydroxide aqueous solution as the adsorption liquid reacts with carbon dioxide, whereby carbon dioxide is adsorbed by the sodium hydroxide aqueous solution, and an aqueous solution 6 containing sodium carbonate or sodium bicarbonate can be obtained (step 4 / STEP4). It should be noted that, in the present embodiment, for convenience, the aqueous solution 6 containing sodium carbonate or sodium bicarbonate is collectively referred to as sodium carbonate aqueous solution 6.

[0037] The end point of the reaction of generating the sodium carbonate aqueous solution 6 can be detected by the change of the liquid property of the liquid stored in the adsorption tank 2 from a strong base to an acid. The change of the liquid property can be detected by a pH meter (not shown) provided in the adsorption tank 2.

[0038] Next, the first transfer pump 8 is operated to transfer the sodium carbonate aqueous solution 6 produced in the adsorption tank 2 to the desorption tank 3 through the metal carbonate aqueous solution transfer conduit 7. The first transfer pump 8 is stopped after a predetermined amount of the sodium carbonate aqueous solution 6 in the adsorption tank 2 is transferred to the desorption tank 3.

[0039] Next, the upper space of the desorption tank 3 is depressurized to 5-50 kPa by a vacuum pump 10. When the pressure in the desorption tank 3 is depressurized to the above-mentioned pressure range, an ultrasonic vibrator device 9 is used to generate a pressure of 70-120 W / m 2 And preferably 75 to 114 m 2 The output of irradiates the metal carbonate aqueous solution 6 contained in the desorption tank 3 with ultrasonic waves having a frequency of 100 to 300 kHz (step 5 / STEP5), thereby desorbing carbon dioxide from the metal carbonate aqueous solution 6 (step 6 / STEP6).

[0040] The vacuum pump 10 is operated after the first transfer pump 8 is stopped, and stops when the pressure in the upper space of the desorption tank 3 reaches the above range. The suction pump 12 is operated after the ultrasonic oscillator device 9 irradiates the metal carbonate aqueous solution 6 with ultrasonic waves, and stops when the reaction of carbon dioxide desorption is reached to an end point.

[0041] The vacuum pump 10 and the suction pump 12 may be any pumps as long as they can reduce the pressure in the desorption tank 3, and may be vacuum generating devices such as ejectors and aspirators.

[0042] As a modified example of the carbon dioxide adsorption and desorption method, the decompression of the desorption tank 3 by the vacuum pump 10 in step 5 and the desorption of carbon dioxide by the suction pump 12 in step 6 may be performed by a single pump.

[0043] The end point of the reaction of desorbing carbon dioxide from the sodium carbonate aqueous solution 6 can be detected by the change of the liquid property of the liquid stored in the desorption tank 3 from acidic to alkaline. The change of the liquid property can be detected by a pH meter (not shown) provided in the desorption tank 3.

[0044] Next, the suction pump 12 is operated to take out the carbon dioxide from the desorption tank 3 through the carbon dioxide transfer conduit 11 and store it separately (step 7 / STEP 7).

[0045] The sodium carbonate aqueous solution 6 in the desorption tank 3 is converted into a sodium hydroxide aqueous solution by desorption of carbon dioxide, thereby regenerating the adsorption liquid 6a (step 8 / STEP8).

[0046] Next, by operating the second transfer pump 14, the regenerated adsorbent 6a is transferred to the adsorption tank 2 via the adsorbent delivery conduit 13, and the adsorbent 6a can be used again for gas-liquid contact with the exhaust gas containing carbon dioxide. The second transfer pump 14 stops after a predetermined amount of the adsorbent 6a in the desorption tank 3 is transferred to the adsorption tank 2.

[0047] Next, refer to Figure 3 ,illustrate Figure 1 Other forms of the carbon dioxide adsorption and desorption device 1 shown. Figure 3 As shown, it can be Figure 1 The adsorption tank 2 in the carbon dioxide adsorption and desorption device 1 shown is configured as a part of a conduit for transporting exhaust gas from a source 15 of exhaust gas containing carbon dioxide to an exhaust gas treatment device 17, and the above-mentioned conduit can be configured as a pipe 16 connecting the source of exhaust gas containing carbon dioxide and the above-mentioned exhaust gas treatment device.

[0048] As the generation source 15 of the exhaust gas containing carbon dioxide, for example, there can be cited a thermal power plant, an iron and steel plant, etc. In addition, as the exhaust gas treatment device 17, for example, there can be cited a device having a neutralization mechanism for neutralizing nitrogen oxides, sulfur oxides, etc. contained in the exhaust gas, a bag filter for removing fly ash contained in the exhaust gas, etc.

[0049] By providing a portion of a conduit, such as a pipe 16, for conveying exhaust gas from a source 15 of exhaust gas containing carbon dioxide to an exhaust gas treatment device 17 as an adsorption tank 2, the above-mentioned gas-liquid contact can be performed without providing an adsorption tank 2, and the device structure can be simplified.

[0050] Regarding the gas-liquid contact between the adsorption liquid and the exhaust gas in the above-mentioned pipeline 16, the adsorption liquid supply mechanism 4 can be connected to the downstream side of the pipeline 16 and the metal carbonate aqueous solution transfer mechanism 7 can be connected to the upstream side of the pipeline 16, so that the convection contact between the adsorption liquid and the exhaust gas can be achieved, so that the metal carbonate aqueous solution 6 after adsorbing carbon dioxide can be efficiently transferred to the desorption tank 3.

[0051] Explanation of symbols

[0052] 1...carbon dioxide adsorption and desorption device, 2...adsorption tank, 3...desorption tank, 4...adsorption liquid supply mechanism, 5...exhaust gas supply mechanism, 6...metal carbonate aqueous solution, 6a...adsorption liquid, 7, 8...metal carbonate aqueous solution transfer mechanism, 9...ultrasonic irradiation mechanism, 10...pressure reduction mechanism, 11, 12...carbon dioxide extraction mechanism, 13, 14...adsorption liquid transfer mechanism.

Claims

1. A method for adsorbing and desorbing carbon dioxide, comprising the following steps: a step of contacting exhaust gas containing carbon dioxide with an adsorption solution consisting of an aqueous solution of a hydroxide of a metal capable of generating carbonate in an adsorption tank to obtain an aqueous solution of a metal carbonate; a step of transferring the aqueous solution of the metal carbonate from the adsorption tank to a desorption tank; a step of desorbing carbon dioxide from the aqueous solution of the metal carbonate in the desorption tank to regenerate the adsorption solution; and a step of transferring the regenerated adsorption solution from the desorption tank to the adsorption tank. The carbon dioxide adsorption and desorption method is characterized in that The step of desorbing carbon dioxide from the metal carbonate aqueous solution to regenerate the adsorbent is performed by reducing the pressure in the desorption tank and irradiating the metal carbonate aqueous solution contained in the depressurized desorption tank with ultrasonic waves.

2. A carbon dioxide adsorption and desorption device, characterized in that: have: An adsorption tank, comprising an adsorption liquid supply mechanism for supplying an adsorption liquid and an exhaust gas supply mechanism for supplying exhaust gas containing carbon dioxide, wherein the adsorption liquid is composed of an aqueous hydroxide solution of a metal capable of generating carbonate, and in the adsorption tank, the exhaust gas is adsorbed by the adsorption liquid to obtain an aqueous solution of a metal carbonate; a metal carbonate aqueous solution transfer mechanism for transferring the metal carbonate aqueous solution from the adsorption tank to the desorption tank; a desorption tank having an ultrasonic irradiation mechanism and a decompression mechanism, in which carbon dioxide is desorbed from the metal carbonate aqueous solution to regenerate the adsorbent; a carbon dioxide removal mechanism that removes carbon dioxide from the desorption tank; and The adsorption liquid transfer mechanism transfers the regenerated adsorption liquid from the desorption tank to the adsorption tank.

3. The carbon dioxide adsorption and desorption device according to claim 2, characterized in that: The adsorption tank is a part of a conduit for conveying exhaust gas from a source of exhaust gas containing carbon dioxide to an exhaust gas treatment device.

4. The carbon dioxide adsorption and desorption device according to claim 3, characterized in that: The conduit is a pipe connecting a source of the exhaust gas containing the carbon dioxide and the exhaust gas treatment device.

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