Carbon dioxide separation and recovery apparatus

Abstract

To provide a carbon dioxide separation and recovery apparatus capable of reducing overall energy consumption while maintaining the recovery amount of carbon dioxide.SOLUTION: In an absorption unit 20, carbon dioxide in the carbon dioxide-containing gas G is absorbed into an absorption liquid A containing an alkaline aqueous solution. In a desorption unit 30, the absorption liquid A', after absorbing the carbon dioxide, is heated to desorb the carbon dioxide from the absorption liquid A'. A circulation unit 40 circulates the absorption liquid A and absorption liquid A' between the absorption unit 20 and the desorption unit 30. In a fixation unit 50 connected to the absorption unit 20, the carbon dioxide-containing gas G' that has passed through the absorption unit 20 is brought into contact with a fixation material 54 to fix the carbon dioxide contained in the carbon dioxide-containing gas G'.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus for separating, capturing, and immobilizing carbon dioxide contained in a carbon dioxide-containing gas (for example, exhaust gas from a cement plant). [Background technology]

[0002] BACKGROUND ART Various techniques are known for immobilizing carbon dioxide contained in exhaust gases and reducing the amount of carbon dioxide emitted into the atmosphere.

[0003] For example, in the device described in Patent Document 1, carbon dioxide contained in gas is absorbed using an absorbing liquid containing alkanolamine, and the absorbing liquid that has absorbed the carbon dioxide is heated to recover the carbon dioxide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-184080 Summary of the Invention [Problem to be solved by the invention]

[0005] However, this device has the problem that a large amount of heat energy is required to increase the carbon dioxide recovery rate.In addition, the carbon dioxide recovery process generates waste liquid with a pH that does not meet emission standards or that contains a large amount of nitrogen, which means that energy and resources are consumed in treating the waste liquid.

[0006] An object of the present invention is to provide a carbon dioxide separation and capture device that can reduce overall energy consumption while maintaining the amount of carbon dioxide captured. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention relates to a carbon dioxide separation and capture device comprising: an absorption unit that brings a carbon dioxide-containing gas into contact with an absorption liquid containing an alkaline aqueous solution to absorb the carbon dioxide contained in the gas; a desorption unit that heats the absorption liquid after absorbing the carbon dioxide to desorb the carbon dioxide from the absorption liquid; a circulation unit that circulates the absorption liquid between the absorption unit and the desorption unit; and a fixation unit that is connected to the absorption unit and brings the carbon dioxide-containing gas that has passed through the absorption unit into contact with a fixation material to fix the carbon dioxide contained in the carbon dioxide-containing gas.

[0008] According to the carbon dioxide separation and capture apparatus of the present invention, in addition to a method of chemically absorbing carbon dioxide from a carbon dioxide-containing gas, carbon dioxide contained in the gas is absorbed by a method of bringing the carbon dioxide gas into contact with a fixation material and fixing the carbon dioxide to the fixation material. This makes it possible to reduce the heating in the desorption section compared to existing methods. Therefore, according to this apparatus, it is possible to reduce the consumption of thermal energy required for capture while maintaining a high carbon dioxide capture rate.

[0009] The fixing material is preferably a calcium-containing material.

[0010] Furthermore, it is preferable that the fixation section fixes carbon dioxide in a wet manner, and it is preferable that the liquid used in the fixation section includes at least one of the liquids produced in the absorption section, the desorption section, the circulation section, and the supply section.

[0011] The term "wet method" means, for example, that when the fixing material comes into contact with a carbon dioxide-containing gas, it combines with a liquid and takes on a liquid, muddy, paste-like, surface-wet, or other form. In the present invention, by using a calcium-containing material as the fixing material, the carbon dioxide contained in the gas is fixed to the calcium in the fixing material, thereby reducing the carbon dioxide content of the gas. Furthermore, in the present invention, by contacting the calcium-containing material with carbon dioxide in a wet method, calcium ions are eluted from the calcium-containing material throughout the liquid, expanding the area of ​​contact with the carbon dioxide in the gas, thereby increasing the amount of carbon dioxide fixed and enabling the carbon dioxide to be fixed uniformly. Furthermore, by using waste liquid generated before the fixing unit in the fixing unit, the energy consumption required for treating the waste liquid can be avoided.

[0012] The carbon dioxide separation and capture system preferably includes a raw material supply unit in the fixation unit that supplies fixation material with reduced carbon dioxide fixation capacity to a raw material mill in the cement production process.

[0013] According to the carbon dioxide separation and capture device of the present invention, the carbon dioxide fixation material with reduced carbon dioxide fixation capacity can be used in cement production, thereby avoiding the energy consumption for disposal.

[0014] It is also preferable that at least one type of waste liquid generated in the absorption section, the desorption section, the circulation section, and the supply section that supplies the carbon dioxide-containing gas to the absorption section used in the fixing section is used in the fixing section.

[0015] According to the carbon dioxide separation and capture apparatus of the present invention, the waste liquid that cannot be discharged as it is can be used to fix the carbon dioxide contained in the gas. [Effects of the Invention]

[0016] As described above, according to the present invention, it is possible to provide an apparatus that can recover and fix carbon dioxide contained in exhaust gas and treat waste liquid and waste materials in an energy-saving manner. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of a carbon dioxide separation and capture device according to one embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing a location where waste liquid is generated and how the waste liquid and fixing material are reused after use, according to one embodiment of the present invention. [Figure 3] FIG. 1 is a diagram showing the thermal energy required for the amount of carbon dioxide recovered in a chemical absorption method, which is one embodiment for carrying out the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Details and other features of the present invention will now be described with reference to the drawings.

[0019] FIG. 1 is a schematic diagram of a carbon dioxide separation and capture apparatus, which is one embodiment for carrying out the present invention.

[0020] (composition) As shown in FIG. 1, a carbon dioxide separation and capture apparatus 1 according to one embodiment of the present invention includes a supply unit 10, an absorption unit 20, a desorption unit 30, a circulation unit 40, and a fixation unit 50. The supply unit 10 cools carbon dioxide-containing gas G generated from a kiln O or the like in a cement factory to near room temperature. The absorption unit 20 contacts the gas G supplied from the supply unit 10 with an absorption solution A containing an alkaline aqueous solution to absorb carbon dioxide into the absorption solution A. The desorption unit 30 heats the absorption solution A' that has absorbed the gas G in the absorption unit 20 to desorb and capture carbon dioxide from the absorption solution A'. The circulation unit 40 circulates the absorption solutions A and A' between the absorption unit 20 and the desorption unit 30. The fixation unit 50 is installed so as to be connected to the ceiling of the absorption unit 20. The fixation unit 50 wet-contacts the carbon dioxide contained in the gas G' that was not completely captured by the absorption solution A with a fixation material 54, thereby fixating the carbon dioxide contained in the gas G' to the fixation material.

[0021] The supply unit 10 is a section that performs pretreatment to facilitate absorption of carbon dioxide contained in the gas G by the absorption liquid A before supplying the gas G to the absorption unit 20. The supply unit 10 includes a circulation path 11, a pump 12, a cooler 13, packing materials 14, and a sprayer 15. The circulation path 11 circulates a cleaning liquid for cleaning the gas between the lower and upper parts of the supply unit 10. The pump 12 sends the cleaning liquid from the lower part to the upper part of the supply unit 10 through the circulation path 11. The cooler 13 cools the cleaning liquid. The packing materials 14 increase the contact area when the gas G and the cleaning liquid come into contact with each other, thereby more effectively cleaning the gas G. The sprayer 15 sprays the cleaning liquid sent to the upper part of the supply unit 10 toward the bottom part of the supply unit 10. Note that although the liquid used in the circulation path 11 is referred to as a cleaning liquid here, it may also be a cooling liquid for cooling the gas G.

[0022] The absorbing unit 20 has, for example, a substantially cylindrical hollow space defined by a substantially cylindrical body and a ceiling and a bottom that close the upper and lower ends of the substantially cylindrical body, respectively. The absorbing unit 20 is connected to the supply unit 10 by a supply path 16 that connects the upper part of the supply unit 10 with the lower part of the absorbing unit 20. An absorbing liquid A is stored in the lower space of the absorbing unit 20. A filler 21a is filled in the space above the lower space of the absorbing unit 20. Here, the absorbing liquid is, for example, an alkaline aqueous solution containing an alkaline compound having an affinity for carbon dioxide, such as monoethanolamine or alkanolamine, as an absorbent.

[0023] A circulation path 23 is connected to a first section, which is an intermediate section of the absorbing section 20. The circulation path 23 collects moisture from the gas vapor and sends it to a second section of the absorbing section 20 above the first section by a pump 24. The collected moisture is then cooled by a cooler 25 and sprayed downward by a sprayer 22b. A sprayer 22a is provided below the first section, and sprays moisture sent through a circulation section 40 (described later) downward. The top and bottom of the first section are filled with packing materials 21b and 21a, respectively. Furthermore, a supply path 26, which communicates with the bottom of the fixing section 50, is connected to the ceiling of the absorbing section 20.

[0024] The detachment section 30 is provided opposite the absorption section 20. Similar to the absorption section 20, the detachment section 30 has a substantially cylindrical hollow space defined by a substantially cylindrical body and a ceiling section and a bottom section that close the upper and lower ends of the substantially cylindrical body, respectively.

[0025] The desorption section 30 is connected to the absorption section 20 through the circulation section 40. The desorption section 30 is provided with sprayers 32a, 32b in a first section, which is an intermediate section thereof, and in a second section above the first section, respectively. Fillers 31a and 31b are filled in the spaces below the sprayers 32a and 32b, respectively. Absorption liquid A' that has absorbed carbon dioxide in the absorption section 20 is stored in the lower space of the desorption section 30. A boiler 34 is provided in the circulation path 33 in the lower part of the desorption section 30 to heat the absorption liquid A' and desorb carbon dioxide from the absorption liquid A'.

[0026] The gas-liquid separator 38 is provided in the middle of the circulation path extending from the ceiling of the desorption section 30 to a second location below the ceiling. In addition, the circulation path 35 is provided with a cooler 36 for cooling the vapor upstream of the gas-liquid separator 38, and a pump 37 for sending the liquid to the desorption section 30 downstream of the gas-liquid separator 38.

[0027] The circulation section 40 is composed of a first return path 41 that connects the lower part of the absorbing section 20 and the sprayer 32a of the desorbing section 30, a second return path 44 that connects the lower part of the desorbing section 30 and the sprayer 22a of the absorbing section 20, and a heat exchanger 43. A pump 42 is provided in the first return path 41. A pump 45 is provided in the second return path 44. Note that the first return path 41 and the second return path 44 are not particularly limited in their connection points to the absorbing section 20 and the desorbing section 30, respectively, as long as they separately connect the absorbing section 20 and the desorbing section 30, respectively, and enable the exchange of the absorption liquid.

[0028] The fixed section 50 is connected to the absorption section 20 via the supply path 26. The fixed section 50 includes a gas inlet 51, a fixing material 54 with which the gas G' comes into contact, and a liquid 55. The fixed section 50 also includes a liquid inlet / outlet 56, an exhaust gas outlet 57, and a fixing material inlet / outlet 58. The fixing material 54 may be any calcium-containing material, such as a material containing calcium oxide or calcium hydroxide, a hardened cement-containing body, concrete waste, or sludge generated during the concrete manufacturing process. The gas inlet 51 is provided with an air diffuser 53 and a flow rate adjuster 52 for adjusting the supply rate of the gas G'. The air diffuser 53 includes a porous structure and releases the introduced gas G' as fine bubbles. One or more air diffusers 53 are disposed within the fixed section 50. The porous structure of the air diffuser 53 is formed from a porous material containing numerous pores.

[0029] (function) Gas G is introduced from the kiln 0 into the supply section 10. This gas G is cooled in the supply section so that it becomes easier to absorb. The gas G is supplied to the absorption section 20 through a supply path 16. The gas G comes into gas-liquid contact with the absorbing liquid A in the absorption section 20, and the carbon dioxide contained in the gas G is absorbed by the absorbing liquid A. The absorbing liquid A' that has absorbed the carbon dioxide is sent to the heat exchanger 43 by the pump 42 in the first flow passage, where it is heated and then supplied into the desorption section 30.

[0030] This absorption liquid A' is stored in the lower part of the desorption section 30 and heated by a boiler 34. When the temperature of the absorption liquid A' is raised to 115°C to 121°C or higher depending on the type of absorption liquid A', the carbon dioxide contained in the absorption liquid A' is desorbed as carbon dioxide gas. This gas containing carbon dioxide rises inside the desorption section 30 and passes through the packings 31a and 31b twice, and only the gas portion of the liquid is recovered by a gas-liquid separator 38 as a gas containing high-purity carbon dioxide.

[0031] On the other hand, the absorbent A from which carbon dioxide has been desorbed and regenerated is sent by the pump 45 to the heat exchanger 43, where it is cooled and then supplied from above into the absorption section 20, where it absorbs carbon dioxide from the gas G again.

[0032] The gas G′ from which most of the carbon dioxide has been removed rises within the absorption section 20 and is introduced into the fixed section 50 via the supply path 26 .

[0033] When the gas G' comes into contact with the fixing material 54 contained in the fixing part 50, the carbon dioxide contained in the gas G' is fixed to the fixing material 54. Here, the carbon dioxide may be fixed to the fixing material 54 in a wet state or in a dry state. The wet state means that, for example, when the fixing material comes into contact with the carbon dioxide-containing gas, it is combined with a liquid and takes on a liquid, mud, paste, surface-wet state, or other form. The dry state means a state other than the above-mentioned wet state.

[0034] After carbon dioxide is fixed in the fixing material 54, the gas G'' is discharged into the atmosphere from the exhaust gas outlet 57 of the fixing part 50. The gas G'' satisfies the standard value for carbon dioxide content in final exhaust gas set by the emission operator.

[0035] The second embodiment of the present invention will be described below with reference to Fig. 2. Note that the same parts as those in the first embodiment will be omitted.

[0036] (composition) As shown in FIG. 2, waste liquids are generated at multiple locations during the absorption, desorption, and recovery of carbon dioxide contained in gas G. Waste liquid W1 is condensed water generated in the process of sending gas G from kiln 0 to supply section 10, and has a low pH and contains nitrogen components such as NOx. Waste liquid W2 is an excess of the cleaning liquid circulating through supply section 10, and has a high pH and contains nitrogen components such as NOx. Waste liquid W3 is generated from desorption section 30 or circulation section 40, and has a high pH and contains nitrogen components such as amines. Waste liquid W4 is condensed water contained in the outlet gas of absorption section 20. These waste liquids W1 to W4 can each be used as liquid 55 in the fixed section.

[0037] A raw material supply unit 60 is attached to the upper part of the fixing unit 50, and supplies the fixing material 54 and liquid 55, whose fixing capacity has decreased due to progress in carbonation to the extent that the standard for carbon dioxide content in final exhaust gas set by the emission business operator can no longer be met, to the raw material mill 100 in the cement manufacturing process. Note that the fixing material 54 with a reduced fixing capacity refers to a material whose fixing capacity has decreased to, for example, 0.3 to 0.4, where the fixing capacity in the initial state is 1.

[0038] The raw material supply section 60 includes a liquid supply path 61 through which the liquid 55 flows, a fixing material supply path 62 through which the fixing material 54 flows, and a material supply port 63 for supplying the liquid 55 and the fixing material 54 to the raw material mill 100 in the cement manufacturing process.

[0039] (function) A liquid 55 containing the fixation material 54 and the waste liquids W1 to W4, which have had their carbon dioxide sufficiently fixed and whose carbon dioxide fixation capacity has decreased, is supplied to the raw material mill 100 of the cement manufacturing equipment through the raw material supply unit 60. The fixation material 54 and the like pulverized in the raw material mill 100 are fired in the firing furnace 200 at a high temperature of up to 1450°C. Since the liquid 55 evaporates during this process, separate treatment of the waste liquids W1 to W4 is not required. After being fired in the firing furnace 200, the fixation material 54 can be used as cement.

[0040] Furthermore, in the carbon dioxide separation and capture system of the present invention, the amount of carbon dioxide captured from the gas G in the absorption section 20 and the desorption section 30 can be adjusted by adjusting the circulation rate and / or heating temperature of the absorption solution A' supplied to the boiler 34. This makes it possible to reduce the amount of energy required to heat the absorption solution A', as shown in Fig. 3 .

[0041] For example, as shown in FIG. 3, suppose that the amount of carbon dioxide recovered from gas G in the absorption section 20 and desorption section 30 is limited to 80% of the carbon dioxide contained in gas G, while 10% of the carbon dioxide contained in gas G is immobilized and recovered by the fixation section 50. In this case, the energy required to heat the absorption solution A' can be reduced to 0.76, assuming that the energy required to immobilize and recover 90% of the carbon dioxide contained in gas G using only the absorption section 20 and desorption section 30 is 1. This value can be calculated using the formula E = (hg - hl) × s. The symbols used above have the following meanings: E: heating energy per hour (kJ / h), hg: specific enthalpy of saturated steam (kJ / kg), hl: specific enthalpy of saturated water (kJ / kg), and s: steam supply rate per hour (kg / h).

[0042] Furthermore, as shown in Figure 2, wastewater is generated from various locations in carbon dioxide chemical absorption facilities. This wastewater may have a pH that does not meet discharge standards or may contain large amounts of nitrogen. Treating this wastewater requires neutralization and denitrification, which requires direct or indirect energy consumption for transporting the wastewater, operating treatment equipment, and using chemicals.

[0043] On the other hand, in the present invention, the waste liquid is used as liquid 55 in fixation section 50 and is used as a material for carbon dioxide fixation. After use, the waste liquid is treated in the cement manufacturing process, which avoids the energy consumption required in conventional chemical absorption facilities.

[0044] As described above, the carbon dioxide separation and capture device of the present invention not only makes it possible to reduce the consumption of thermal energy required for capture while maintaining a high recovery rate of carbon dioxide contained in gas, but also makes it possible to avoid the separate consumption of energy for treating waste liquids, etc. by using the waste liquid and waste materials generated in the carbon dioxide separation and capture process as raw materials for cement production. [Explanation of symbols]

[0045] 0. Kiln 1. Carbon dioxide separation and capture equipment 10‥Supply section 20. Absorption section 30. Detachment part 40‥Circulation section 50‥Fixed part 100...Raw material mill 200...Firing furnace 11,23,33,35‥Circulation path 12, 24, 37, 42, 45... Pump 13,25,36‥Cooler 14,21a,21b,31a,31b‥Filling material 15,22a,22b,32a,32b‥Scatterer 16,26‥Supply route 34. Boiler 38‥Gas-liquid separator 41. First return path 43‥Heat exchanger 44...Second return path 51 Gas inlet 52‥Flow rate adjustment device 53‥Air diffuser 54‥Fixed material 55‥Liquid 56‥Liquid inlet / outlet 57. Exhaust gas outlet 58‥Fixed material inlet / outlet 60‥Raw material supply department 61‥Liquid supply path 62‥Fixed material supply route 63‥Material supply port W1, W2, W3, W4...waste liquid A, A'...Absorption liquid G, G', G''...gas

Claims

1. an absorption unit that brings a carbon dioxide-containing gas into contact with an absorption liquid containing an alkaline aqueous solution to absorb carbon dioxide contained in the carbon dioxide-containing gas; a desorption section that heats the absorption liquid after absorbing carbon dioxide and desorbs carbon dioxide from the absorption liquid; a circulation section that circulates the absorption liquid between the absorption section and the desorption section; a fixing section connected to the absorption section, which brings the carbon dioxide-containing gas that has passed through the absorption section into contact with a fixing material to fix the carbon dioxide contained in the carbon dioxide-containing gas; A carbon dioxide separation and capture device comprising:

2. The carbon dioxide separation and capture system according to claim 1, The fixing material is calcium-containing. Carbon dioxide capture and separation equipment.

3. The carbon dioxide separation and capture system according to claim 1 or 2, The fixing unit fixes carbon dioxide in a wet manner. Carbon dioxide capture and separation equipment.

4. The carbon dioxide separation and capture system according to claim 1 or 2, a raw material supply unit that supplies the fixed material whose carbon dioxide fixation capacity has decreased in the fixation unit to a raw material mill in a cement manufacturing process; Carbon dioxide capture and separation equipment.

5. The carbon dioxide separation and capture system according to claim 1 or 2, The waste liquid generated in at least one of the absorption section, the desorption section, the circulation section, and the supply section for supplying the carbon dioxide-containing gas is used in the fixing section. Carbon dioxide capture and separation equipment.

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