Gas treatment apparatus and gas treatment method

Abstract

To achieve the removal of carbon dioxide and chlorine using calcium oxide without the need for moisture supply.SOLUTION: A gas treatment apparatus 1 comprises: a plasma treatment path 10 that generates plasma in a target gas flowing through a flow path 14; and an adsorption treatment path 20 which receives the target gas in which plasma has been generated, and causes it to pass through a quicklime layer 24.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a gas treatment device and method for removing carbon dioxide and chlorine contained in a gas to be treated. [Background technology]

[0002] In recent years, various industrial sectors have been focusing on reducing carbon dioxide emissions as a measure against global warming, and carbon dioxide removal technologies have been developed for this purpose.

[0003] One such proposal is to form a steel slag powder containing calcium oxide as the main component into a porous body, add moisture to the body to promote a reaction between carbon dioxide and calcium oxide, and precipitate calcium carbonate between the slag particles in the body (Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Author: Yasue Nin (Nihon University, College of Science and Technology), "Fixation of Carbon Dioxide by Inorganic Chemical Processes", Journal of the Society of Inorganic Materials, Japan,9(299), 2002, p.192-207 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in order to allow the reaction between calcium oxide and carbon dioxide to proceed, it is necessary to continuously add sufficient moisture to the porous compact of steel slag powder with which the gas to be treated comes into contact. This method cannot be applied when it is not permitted to supply moisture, for example, in a site where a moisture supply system cannot be installed or in a site where high humidity in the gas to be treated is not desirable.

[0006] In addition, when using steel slag powder, the steel slag powder contains a large amount of silicon dioxide and the like, and the calcium oxide content is only about 40%, so this low calcium oxide content is disadvantageous for removing carbon dioxide.

[0007] The same problem occurs when removing chlorine by contacting a chlorine-containing gas to be treated with calcium hydroxide obtained by hydrating calcium oxide such as iron and steel slag powder.

[0008] In view of the above background, an object of the present invention is to realize the removal of carbon dioxide and chlorine by using calcium oxide without the need for water supply. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention employs Configuration 1, which is a gas treatment device including a plasma treatment path that generates plasma in a gas to be treated flowing through a flow path, and an adsorption treatment path into which the gas to be treated in which the plasma has been generated is introduced and passed through a quicklime layer.

[0010] According to the above configuration 1, when the gas to be treated containing at least one of carbon dioxide and chlorine to be removed is sent to the plasma treatment path, plasma is generated in the gas to be treated, and at this time, the target to be removed such as carbon dioxide is ionized or excited. The gas to be treated containing the target to be removed such as cations generated by ionization of the target to be removed such as carbon dioxide and excited carbon dioxide is passed through the quicklime layer in the adsorption treatment path. During this passage, the target to be removed such as cations generated by ionization of the target to be removed such as carbon dioxide and excited carbon dioxide is adsorbed to calcium oxide contained in the quicklime without actively supplying moisture to the quicklime layer. Therefore, it is possible to realize the removal of the target to be removed such as carbon dioxide using calcium oxide without the need to supply moisture.

[0011] In the above configuration 1, a configuration 2 can be adopted in which a plurality of the plasma processing paths and the adsorption processing paths are provided, and the plasma processing paths and the adsorption processing paths are alternately connected from the upstream side to the downstream side.

[0012] According to the above configuration 2, the target substances such as carbon dioxide can be repeatedly removed multiple times from the gas to be treated to the most upstream plasma treatment path until it is discharged from the most downstream adsorption treatment path. Therefore, the removal of the target substances such as carbon dioxide from the gas to be treated can be gradually promoted, and the final removal rate of the target substances such as carbon dioxide can be particularly increased.

[0013] In the above configuration 1 or 2, configuration 3 can be adopted in which the flow path of the plasma processing path is formed between a cylindrical electrode and an axial electrode arranged coaxially inside the cylindrical electrode, plasma is generated in the gas to be processed by applying a voltage between the cylindrical electrode and the axial electrode, and the adsorption processing path is connected to the downstream side of the flow path of the plasma processing path.

[0014] According to the above configuration 3, the gas to be treated can be turned into plasma by applying a voltage throughout the entire flow path between the cylindrical electrode and the axial electrode, and can be immediately sent to the adsorption treatment path, making it easy to ensure that the substances to be removed, such as carbon dioxide, contained in the gas to be treated, reach the quicklime layer in an ionized and excited state.

[0015] In any one of the above configurations 1 to 3, a configuration 4 can be adopted in which the quicklime used in the quicklime layer contains 93% by mass or more of calcium oxide and 2% by mass or less of carbon dioxide.

[0016] According to the above-mentioned configuration 4, the quicklime layer can be formed using special grade quicklime that is JIS compliant and has a particularly high calcium oxide content and low carbon dioxide content, so that good adsorption performance for the target to be removed, such as carbon dioxide, can be obtained while keeping down the procurement cost of quicklime.

[0017] The present invention can also be understood as essentially a method for removing a target substance such as carbon dioxide.

[0018] That is, in order to achieve the above object, the present invention employs configuration 5, which is a gas treatment method that performs a plasma treatment in which plasma is generated in a gas to be treated containing at least one of carbon dioxide and chlorine to be removed while the gas to be treated is being flowed, and an adsorption treatment in which the gas to be treated in which the plasma is generated by the plasma treatment is passed through a quicklime layer.

[0019] As in configuration 5 above, when plasma is generated in a gas to be treated that contains at least one of the targets to be removed, carbon dioxide and chlorine, the targets to be removed, such as carbon dioxide, can be ionized or excited. When the gas to be treated that contains targets to be removed, such as cations generated by ionization of the targets to be removed, such as carbon dioxide, and excited carbon dioxide, is passed through a quicklime layer, the targets to be removed, such as the cations and excited carbon dioxide, can be adsorbed by calcium oxide contained in the quicklime without actively supplying moisture to the quicklime layer. Therefore, the targets to be removed, such as carbon dioxide, can be removed using calcium oxide without the need to supply moisture.

[0020] In addition, in the above configuration 5, a configuration 6 can be adopted in which the plasma treatment and the adsorption treatment are alternately repeated multiple times from the upstream side to the downstream side.

[0021] According to the above-mentioned configuration 6, the removal of the target substances such as carbon dioxide from the gas to be treated can be advanced stepwise, and the final removal rate of the target substances such as carbon dioxide can be particularly increased.

[0022] Furthermore, in the above configurations 5 and 6, a configuration 7 can be adopted in which the plasma treatment is a process in which the gas to be treated is caused to flow in a flow path between a cylindrical electrode and an axial electrode arranged coaxially inside the cylindrical electrode and a voltage is applied between the cylindrical electrode and the axial electrode, and the adsorption treatment is a process in which the gas to be treated in which the plasma is generated is passed through a quicklime layer in a pipe connected to the downstream side of the flow path.

[0023] According to the seventh aspect, it becomes easy for the target substances to be removed, such as carbon dioxide, contained in the gas to be treated, to reach the quicklime layer in an ionized and excited state.

[0024] In addition, in any one of the above configurations 5 to 7, a configuration 8 can be adopted in which the quicklime used in the quicklime layer contains 93 mass% or more of calcium oxide and 2 mass% or less of carbon dioxide.

[0025] According to the above configuration 8, the quicklime layer is formed using special grade quicklime that complies with the JIS, so that the procurement cost of quicklime can be reduced while good adsorption performance for the object to be removed, such as carbon dioxide, can be obtained. Effect of the Invention

[0026] In this way, by adopting the above configuration 1 or 5, the present invention can realize the removal of carbon dioxide and chlorine by using calcium oxide without the need for water supply. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a vertical sectional front view showing a gas treatment device according to a first embodiment of the present invention; [Diagram 2] FIG. 11 is a front view showing a gas treatment device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, a gas treatment apparatus according to a first embodiment of the present invention will be described with reference to FIG.

[0029] The gas treatment device 1 shown in FIG. 1 is composed of one plasma treatment path 10 and one adsorption treatment path 20 continuing to the downstream side of the plasma treatment path 10.

[0030] The plasma treatment passage 10 includes a cylindrical electrode 11, an axial electrode 12 arranged coaxially with the cylindrical electrode 11 inside the cylindrical electrode 11, a plurality of insulating spacers 13 for holding the axial electrode 12 coaxially with the cylindrical electrode 11, and an inlet passage 15 for introducing the gas to be treated into a flow path 14 formed by the cylindrical electrode 11 and the axial electrode 12.

[0031] The plasma processing passage 10 is an atmospheric pressure plasma generating device that causes the gas to be processed to flow from the inlet passage 15 into the flow path 14, and applies electrical energy to the gas to be processed flowing through the flow path 14 by using an electric field generated between the cylindrical electrode 11 and the axial electrode 12, thereby stably generating plasma in the gas to be processed under atmospheric pressure, and causing the gas to be processed in which plasma has been generated to flow out of the flow path 14.

[0032] The cylindrical electrode 11 of the plasma processing passage 10 is a cathode provided in the shape of a cylindrical surface on the inner circumference of a straight tube. Hereinafter, the direction along the tube axis of the cylindrical electrode 11 is referred to as the axial direction, the direction perpendicular to the tube axis is referred to as the radial direction, and the circumferential direction around the tube axis is referred to as the circumferential direction.

[0033] The axial electrode 12 of the plasma processing passage 10 is an anode provided in the shape of a cylindrical surface on the outer periphery of a straight shaft extending in the axial direction. The axial electrode 12 faces the tubular electrode 11 in the radial direction.

[0034] It is preferable to use seamless pipes without joints as the cylindrical electrode 11 and the axial electrode 12, and the material thereof is not particularly limited. For example, they may be stainless steel pipes, or conductive resin (CFRP: Carbon Fiber Reinforced Plastics) pipes reinforced with carbon such as graphite and carbon nanotubes. Alternatively, they may be stainless steel pipes whose inner or outer circumferential surface is coated with a resin layer containing carbon such as graphite and carbon nanotubes. Note that seamless stainless steel pipes are expensive, heavy, difficult to withstand high temperatures of 400°C or more, and may be corroded by strong acids and strong alkalis, so conductive resin pipes are preferable.

[0035] The insulating spacer 13 is made of, for example, a fluororesin having excellent chemical resistance and heat resistance. The insulating spacer 13 may be, for example, substantially X-shaped or substantially Y-shaped as viewed from the axial direction in order to center it coaxially, and may be made of a frame as thin as possible so as not to impede the flow of the gas to be treated.

[0036] A flow path 14 of the plasma processing path 10 is formed by the inner circumference of the cylindrical electrode 11 and the outer circumference of the shaft-shaped electrode 12, and extends in the axial direction with an annular flow path cross section.

[0037] When a voltage of 13,000 to 25,000 V is applied between the cylindrical electrode 11 and the axial electrode 12 by an electric circuit connected to the cylindrical electrode 11 and the axial electrode 12, a discharge is generated between the cylindrical electrode 11 and the axial electrode 12. Electric energy is given to the gas to be treated flowing in the electric field of this discharge, so that plasma is generated in the gas to be treated. When plasma is generated in the gas to be treated containing carbon dioxide, the carbon dioxide is ionized and excited. It is not necessary to add a gas to the gas to be treated to facilitate the generation of plasma, and it is better not to do so in consideration of the operating costs. For example, if a rare gas such as argon (Ar) gas or helium (He) gas is added to the gas to be treated and sent to the flow path 14, plasma is easily generated, but this is not preferable because expensive gas is used.

[0038] Plasma is generated throughout the entire flow path 14 by the discharge between the cylindrical surfaces of the tubular electrode 11 and the axial electrode 12. This makes it possible to continuously process the gas to be treated by turning it into plasma all the way to the downstream end of the flow path 14 while feeding the gas to be treated into the flow path 14 and then quickly feeding it from the flow path 14 to the adsorption processing path 20.

[0039] Here, if the cylindrical electrode 11 and the axial electrode 12 have unevenness, a spark discharge will occur at that location. If a spark discharge such as a corona discharge or a glow discharge occurs, plasma will only be generated in the vicinity, and the effect of the plasma treatment will not be fully achieved. In addition, if the voltage applied between the cylindrical electrode 11 and the axial electrode 12 is too high or the distance between the cylindrical electrode 11 and the axial electrode 12 is too short, a spark discharge may occur. The voltage of 23,000 V is the upper limit for preventing a spark discharge from occurring when the distance between the cylindrical electrode 11 and the axial electrode 12 is set to 40 mm. The voltage applied between the cylindrical electrode 11 and the axial electrode 12 may be appropriately adjusted according to the dimensions of the cylindrical electrode 11 and the axial electrode 12 so that a spark discharge does not occur. If a voltage of 30,000 V or less is applied, the amount of nitrogen oxide (NOx) generated can be suppressed to a negligible level. The positions of the connection points between the cylindrical electrode 11 and the axial electrode 12 and the electric circuit are not particularly limited, but in the illustrated example, they are located near the center of the cylindrical electrode 11 and the axial electrode 12 in the axial direction.

[0040] In order to process a large amount of gas to be processed in the plasma processing path 10, for example, the inner diameter of the cylindrical electrode 11 is 100 mm, the outer diameter of the axial electrode 12 is 20 mm, and the axial length of the region where the cylindrical electrode 11 and the axial electrode 12 face each other in the radial direction is 1600 mm. These dimensions are merely examples and are not limited to these. The outer diameter of the axial electrode 12 may be 10 mm or more. On the other hand, if the inner diameter of the cylindrical electrode 11 is made too large, the distance between the cylindrical electrode 11 and the axial electrode 12 becomes long, making it difficult to generate a discharge. For this reason, it is preferable to satisfy 3≦(inner diameter of the cylindrical electrode 11 / outer diameter of the axial electrode 12)≦6, to satisfy (inner diameter of the cylindrical electrode 11-outer diameter of the axial electrode 12)≧20 mm, and to satisfy the outer diameter of the axial electrode 12≧10 mm.

[0041] Furthermore, if the cylindrical electrode 11 and the axial electrode 12 are made too long in the axial direction, it becomes difficult to hold the cylindrical electrode 11 and the axial electrode 12 concentrically in the flow path 14 with the insulating spacer 13. Therefore, it is preferable that the axial length of the flow path 14 be 500 mm or more and 2000 mm or less.

[0042] The inlet passage 15 of the plasma processing passage 10 has a guide vane portion that changes the flow of the gas to be processed toward the flow passage 14 into a spiral flow, and two or more obstacle portions that generate wake vortices in the spiral flow on the intermediate flow passage between the guide vane portion and the flow passage 14. A plasma processing passage having such an inlet passage is disclosed in detail in JP 2021-126633 A.

[0043] The gas to be treated sent into the introduction passage 15 changes into a spiral flow (spiral flow) swirling in one direction toward the downstream side in the axial direction when passing through the guide vane section, and then changes into a spiral flow including wake vortices when hitting an obstacle, and then flows into the upstream inlet of the passage 14, passing through the passage 14 in the state of a spiral flow swirling in one direction toward the downstream side in the axial direction. Due to the spiral flow and the generation of wake vortices, the gas to be treated flows a long path through the passage 14, and the probability that the molecules of the gas to be treated will be affected by the plasma increases compared to when the gas flows straight in the axial direction.

[0044] Although it is not essential to adopt such a spiral flow or wake vortexing of the gas to be treated, it is preferable to adopt it in order to increase the probability of ionization and excitation of carbon dioxide (CO2 molecules) and chlorine (Cl2) contained in the gas to be treated. The axial length of the flow path 14 is preferably 1000 mm or more in order to increase the travel distance of the spiral flow of the gas to be treated.

[0045] The adsorption processing path 20 is a pipeline formed of a connection path 21 connected to the downstream side of the flow path 14 of the plasma processing path 10, an adsorption pipe line 22 connected to the downstream side of the connection path 21, and an exhaust pipe line 23 connected to the downstream side of the adsorption pipe line 22.

[0046] The connection path 21 introduces the gas to be treated that has flowed out from the downstream side of the flow path 14 of the plasma treatment path 10 to the upstream side of the adsorption pipe line 22. The adsorption pipe line 22 has a quicklime layer 24 arranged inside a straight tube body, and breathable barriers 22a arranged respectively on the upstream and downstream sides of the quicklime layer 24. The exhaust path 23 allows the gas to be treated that has flowed out from the downstream side of the adsorption pipe line 22 to flow out of the adsorption treatment path 20.

[0047] The quicklime layer 24 is formed by randomly packing a large number of quicklime particles 24a inside the adsorption pipe 22, and randomly forming gaps 24b between the layers of quicklime 24a through which the gas to be treated passes. The quicklime layer 24 is maintained in a state in which it is formed by the upstream-side permeable barrier 22a and the downstream-side permeable barrier 22a. The permeable barrier 22a is a member that restricts the movement of the quicklime 24a while allowing the gas to be treated to pass through, and is, for example, a mesh member that does not allow the quicklime 24a to pass through.

[0048] The quicklime 24a is made by burning limestone. In general, the amount of calcium oxide (CaO) contained in quicklime is 80 mass% or more in terms of mass fraction relative to the mass of quicklime, and it contains about twice as much calcium oxide as steel slag powder. That is, quicklime generally contains calcium oxide (CaO): 80 to 98 mass%, magnesium oxide (MgO): 0.1 to 10.0 mass%, silicon dioxide (SiO2): 0.1 to 5.0 mass%, aluminum oxide (Al2O3): 0.1 to 3.0 mass%, ferric oxide (Fe2O3): 0.1 to 3.0 mass%, phosphorus pentoxide (P2O5): 0.01 to 0.50 mass%, and total sulfur (S): 0.01 to 1.00 mass%. The mass% values ​​of each component of quicklime described in this specification are values ​​obtained by a test method in accordance with JIS (Japanese Industrial Standards) R9001:2006 "Testing method for lime."

[0049] Therefore, compared to steel slag powder, quicklime 24a has superior reactivity with the objects to be removed, such as cations generated by ionization of the objects to be removed, such as carbon dioxide, electrons, and excited carbon dioxide. In other words, cations and the like are easily adsorbed to quicklime 24a. This is advantageous in suppressing the recombination of cations with the objects to be removed, such as carbon dioxide, and in capturing the objects to be removed, such as carbon dioxide, on the surface or in the pores of the quicklime. However, the adsorption here is a concept that includes chemical adsorption and physical adsorption that occur between the objects to be removed, such as cations generated by ionization of the objects to be removed, such as carbon dioxide, and excited carbon dioxide, and the surface components of quicklime 24a, and it is unclear which of chemical adsorption and physical adsorption is predominant.

[0050] It is preferable to use quicklime 24a containing 93% by mass or more of calcium oxide and 2% by mass or less of carbon dioxide. The content here is a value obtained by a test method conforming to JIS (Japanese Industrial Standards) R9001:2006 "Testing Method for Lime". As quicklime satisfying such a content, quicklime of the grade "Special" specified in JIS (Japanese Industrial Standards) R9001:2006 "Industrial Lime" is provided by various companies, and is generally distributed at low cost in Japan, which is blessed with abundant limestone resources. The quicklime 24a forming the quicklime layer 24 is replaced when the adsorption performance described above decreases over time. For example, when the generation of calcium carbonate, etc. due to the chemical adsorption of the cations, etc. and calcium oxide progresses, the pores of the quicklime 24a become more clogged, the reaction surface area decreases, and the adsorption performance described above may decrease. By adopting quicklime 24a, which has a particularly high calcium oxide content from among the JIS-compliant products that are available at low cost, it is possible to achieve both the removal performance of targets such as carbon dioxide and the like while keeping down the procurement costs of quicklime.

[0051] The above-mentioned special grade quicklime is generally provided in sizes classified by wire mesh of 2, 3, 5, and 18 mm. For example, if special grade quicklime (+18 mm size product) classified by 18 mm wire mesh and having a particle size larger than 18 mm is used as the quicklime 24a, it is easy to form gaps 24b between the quicklime 24a through which the gas to be treated flows, and since each piece of quicklime 24a contains a large amount of calcium oxide, this is advantageous for extending the periodic replacement cycle described above.

[0052] The pipe material for forming the adsorption treatment path 20 is preferably a resin pipe such as a polyvinyl chloride pipe, because it has poor reactivity with the gas to be treated and has excellent insulation. In the illustrated example, the plasma treatment path 10 and the adsorption treatment path 20 are arranged in parallel to each other to make the total axial length of the gas treatment device 1 compact, and the connection path 21 is curved to connect them, but the shape of the connection path can be changed appropriately, such as a straight pipe. In order to make the plasma-converted gas to be treated reach the adsorption treatment path as quickly as possible, it is preferable to shorten the path length from the flow path of the plasma treatment path to the quicklime layer as much as possible. In addition, the adsorption treatment path 20 is connected to the plasma treatment path 10 by the connection path 21 that is separate from the adsorption pipe 22, but the adsorption treatment path may be formed from a single pipe material without joints.

[0053] When special grade quicklime (+18 mm size) is used as the quicklime 24a, the pipe material forming the adsorption pipeline 22 can be, for example, φ45 to 100 mm and length 500 to 2000 mm in order to provide a long quicklime layer 24 while forming an appropriate gap 24b.

[0054] A blower (not shown) for feeding the gas to be treated into the inlet passage 15 of the plasma treatment passage 10 and discharging it from the exhaust passage 23 of the adsorption treatment passage 20 may be disposed upstream or downstream of this gas treatment apparatus 1. This gas treatment apparatus 1 is not limited to a particular situation in which it is used, and may be used in a site where the gas to be treated contains harmful substances such as strong acidic substances and strong alkaline substances. Considering the adverse effects of the harmful substances on the surfaces of the blower blades, etc., it is preferable to dispose the blower downstream of the gas treatment apparatus 1, since the harmful substances can be expected to be decomposed by turning the gas to be treated into plasma in the plasma treatment passage 10.

[0055] The flow rate of the gas to be treated in the flow path 14 affects the performance of converting the gas to plasma, and the flow rate of the gas to be treated in the quicklime layer 24 affects the adsorption performance by the quicklime 24a. Therefore, the flow rate should be set taking into consideration the degree of ionization required for the gas to be treated and the removal rate of the substances to be removed, such as carbon dioxide, required for the gas to be treated, and controlled by the output of the blower.

[0056] In addition, when the gas to be treated containing water vapor is fed into the plasma treatment path 10, the higher the humidity of the gas to be treated, the more likely it is that spark discharge will occur between the cylindrical electrode 11 and the axial electrode 12 in the flow path 14. If spark discharge occurs frequently in the flow path 14, nitrogen oxides are likely to be generated due to the excitation of nitrogen and oxygen contained in the gas to be treated, which is not preferable. For this reason, the humidity of the gas to be treated fed into the plasma treatment path 10 should be as low as possible, and there is no problem when a dry gas to be treated is fed. However, if the humidity of the gas to be treated becomes a problem, a steam separator (not shown) should be disposed upstream of the gas treatment device 1 to keep the humidity of the gas to be treated fed into the plasma treatment path 10 below a predetermined value, for example, below 50%. Even if the gas to be treated is dry like this, if the gas to be treated is plasma-generated, it is possible to remove the target to be removed, such as carbon dioxide, by the adsorption action of the quicklime 24a without supplying moisture to the quicklime layer 24 or using a catalyst.

[0057] This gas treatment device 1 is as described above, and includes a plasma treatment path 10 that generates plasma in the gas to be treated flowing through a flow path 14, and an adsorption treatment path 20 that introduces the gas to be treated in which plasma has been generated and passes it through a quicklime layer 24.

[0058] When the gas to be treated, which contains at least one of carbon dioxide and chlorine to be removed, is sent to the plasma treatment path 10, plasma is generated in the gas to be treated flowing through the flow path 14, and at this time, the target to be removed, such as carbon dioxide, is ionized or excited. The gas to be treated, which contains the target to be removed, such as cations generated by the ionization of the target to be removed, such as carbon dioxide, and excited carbon dioxide, flows from the flow path 14 to the adsorption treatment path 20 and is passed through the quicklime layer 24. During this passage, the target to be removed, such as cations generated by the ionization of the target to be removed, such as carbon dioxide, and excited carbon dioxide, is adsorbed by calcium oxide contained in the quicklime 24a without actively supplying moisture to the quicklime layer 24. Therefore, this gas treatment device 1 can realize the removal of the target to be removed, such as carbon dioxide, using calcium oxide without the need to supply moisture.

[0059] In addition, in this gas treatment device 1, the flow path 14 of the plasma treatment path 10 is formed between the cylindrical electrode 11 and the axial electrode 12 arranged coaxially inside the cylindrical electrode 11, and plasma is generated in the gas to be treated by applying a voltage between the cylindrical electrode 11 and the axial electrode 12, and since the adsorption treatment path 20 is connected to the downstream side of the flow path 14 of the plasma treatment path 10, the gas to be treated can be turned into plasma by applying a voltage throughout the entire flow path 14 between the cylindrical electrode 11 and the axial electrode 12, and can be immediately sent to the adsorption treatment path 20. Therefore, in this gas treatment device 1, it becomes easy to cause targets for removal such as carbon dioxide contained in the gas to be treated to reach the quicklime layer 24 in an ionized and excited state.

[0060] In addition, in this gas treatment device 1, the quicklime 24a used in the quicklime layer 24 contains 93 mass% or more of calcium oxide and 2 mass% or less of carbon dioxide, so that the quicklime layer 24 can be formed using special grade quicklime that has a particularly high calcium oxide content and a low carbon dioxide content among JIS-compliant quicklime. Therefore, this gas treatment device 1 can obtain good carbon dioxide adsorption performance while suppressing the procurement cost of the quicklime 24a.

[0061] In addition, the gas treatment method according to the first embodiment includes a plasma treatment in which plasma is generated in the gas to be treated containing at least one of carbon dioxide and chlorine to be removed while the gas to be treated is being flowed, and an adsorption treatment in which the gas to be treated in which the plasma is generated by the plasma treatment is passed through the quicklime layer 24. When plasma is generated in the gas to be treated containing the target to be removed such as carbon dioxide, the target to be removed such as carbon dioxide can be ionized or excited. When the gas to be treated containing the target to be removed such as cations generated by ionization of the target to be removed such as carbon dioxide and excited carbon dioxide is passed through the quicklime layer, the target to be removed such as the cations and excited carbon dioxide can be adsorbed by calcium oxide contained in the quicklime without actively supplying moisture to the quicklime layer. Therefore, the gas treatment method according to the first embodiment can realize the removal of carbon dioxide and chlorine using calcium oxide without the need for moisture supply.

[0062] In addition, the plasma treatment in the gas treatment method according to the first embodiment is a process in which the gas to be treated is flowed through a flow path 14 between a cylindrical electrode 11 and an axial electrode 12 arranged coaxially inside the cylindrical electrode 11, and a voltage is applied between the cylindrical electrode 11 and the axial electrode 12. The adsorption treatment is a process in which the gas to be treated in which the plasma has been generated is passed through a quicklime layer 24 in a pipe (adsorption treatment path 20) connected to the downstream side of the flow path 14, so that it becomes easy to cause the targets to be removed, such as carbon dioxide, contained in the gas to be treated to reach the quicklime layer 24 in an ionized and excited state.

[0063] Furthermore, the quicklime 24a used in the quicklime layer 24 in the gas treatment method according to the first embodiment contains 93% by mass or more of calcium oxide and 2% by mass or less of carbon dioxide. Therefore, by forming the quicklime layer 24 using special grade quicklime that complies with the JIS, the procurement cost of the quicklime 24a can be reduced, while good adsorption performance for the target to be removed, such as carbon dioxide, can be obtained.

[0064] In the first embodiment, an example was shown in which the gas treatment device has one plasma treatment path and one adsorption treatment path, which are connected in series, but it is not essential that the number of plasma treatment paths and the number of adsorption treatment paths are the same, and it is also possible to connect one or more plasma treatment paths to multiple or one adsorption treatment paths. The flow rate preferred for plasma generation and the flow rate preferred for adsorption in the quicklime layer do not necessarily match, and when the difference between these flow rates is large, it is sufficient to provide a difference in the number of plasma treatment paths and adsorption treatment paths so that an appropriate flow rate can be obtained in each treatment path. In addition, in the first embodiment, an example was shown in which the gas treatment device is configured with one set of plasma treatment path and adsorption treatment path, but it may be configured as a gas treatment device with multiple sets of plasma treatment path and adsorption treatment path in parallel to increase the treatment amount per unit time in one gas treatment device. It may also be configured as a gas treatment device with multiple sets of plasma treatment path and adsorption treatment path in series to further increase the removal rate of the target to be removed, such as carbon dioxide, in one gas treatment device. As an example, a second embodiment is shown in FIG. 2. Here, only the differences from the first embodiment will be described.

[0065] The gas treatment device according to the second embodiment has a plurality of the above-mentioned gas treatment devices 1 connected in series. In the illustrated example, the treatment path from the inlet path 31 of the most upstream gas treatment device 1 to the exhaust path 32 of the most downstream gas treatment device 1 is composed of four gas treatment devices 1. These plurality of gas treatment devices 1 are supported by a machine frame 33. By connecting these four gas treatment devices 1 in series, the gas treatment device according to the second embodiment has four plasma treatment paths and adsorption treatment paths, and these plasma treatment paths and adsorption treatment paths are alternately connected from the upstream side to the downstream side. Therefore, the gas to be treated containing the target to be removed such as carbon dioxide is fed into the inlet path 31 of the most upstream plasma treatment path, and the target to be removed such as carbon dioxide can be repeatedly removed multiple times (four times in the illustrated example) before being discharged from the exhaust path 32 of the most downstream adsorption treatment path.

[0066] Therefore, the gas treatment device according to the second embodiment can gradually remove the target substances such as carbon dioxide from the gas to be treated, and can particularly increase the final removal rate of the target substances such as carbon dioxide.

[0067] Furthermore, in the gas processing method according to the second embodiment, the plasma processing and the adsorption processing are alternately repeated multiple times from the upstream side to the downstream side, so that the removal of targets such as carbon dioxide from the treated gas can be gradually promoted, and the final removal rate of targets such as carbon dioxide can be particularly increased.

[0068] In addition, the concentration of the target substances such as carbon dioxide in the gas to be treated fed into the inlet 31 of the most upstream gas treatment device 1 is the highest, and the concentration of the target substances such as carbon dioxide in the gas to be treated fed into the gas treatment device 1 downstream is lower, so the probability that the target substances such as carbon dioxide are ionized and excited in the plasma treatment path is low, and the adsorption efficiency in the quicklime layer of the adsorption treatment path is low. Therefore, if the number of sets of plasma treatment paths and adsorption treatment paths connected in series is too large, the improvement in the removal rate of the target substances such as carbon dioxide is not worth the increase in operating costs. The number of sets of plasma treatment paths and adsorption treatment paths is preferably 3 to 4 in terms of the efficiency of improving the removal rate of the target substances such as carbon dioxide, and is preferably limited to a saturation number at which the removal rate of the target substances such as carbon dioxide does not improve at all. EXAMPLES

[0069] A test was carried out to evaluate the carbon dioxide removal performance by using a test machine of the gas treatment device according to the first embodiment (see FIG. 1).

[0070] The main specifications of the test machine are as follows: Electrical circuit specifications: 3A, 12V (power consumption: 36W), converter input 100V: output 12V Blower specifications: 1m 3 / min Cylindrical electrode 11: Carbon pipe with a diameter of 45 mm and a length of 500 mm Axial electrode 12: Carbon pipe with a diameter of 10 mm and a length of 500 mm Adsorption pipe 22: PVC pipe with diameter 45 mm and length 500 mm Quicklime 24a: Special quicklime conforming to JIS (+18mm size, manufactured by Kotegawa Sangyo)

[0071] An aluminum flexible duct was connected to the inlet 15, a blower (fan) was attached to the aluminum flexible duct, and the air in the test room in which the test machine was installed was sucked into the aluminum flexible duct, and the air was supplied to the inlet 15. Carbon dioxide adjusted with a flow regulator was introduced from a carbon dioxide cylinder (manufactured by Iwatani Gas) into the aluminum flexible duct, and the carbon dioxide concentration of the raw gas (gas to be treated sent to the inlet 15) was adjusted to the set concentration with a CO2 meter (manufactured by HORIBA, model number VA-3000). When this concentration was stabilized, the carbon dioxide concentration of the treated gas (gas to be treated exhausted from the exhaust duct 23) was measured using the above-mentioned CO2 meter, and the carbon dioxide removal rate was obtained. Four tests were performed with different set concentrations. In each test, the carbon dioxide removal rate became saturated after a certain amount of time had passed, and the removal rate did not change much, so the test was terminated at that point. The set concentrations for the four tests were 0.35%, 0.50%, 4.15%, and 4.82%, in ascending order, and are hereinafter referred to as test conditions 1 to 4. The carbon dioxide concentration in the air itself in the test room was measured using the above-mentioned CO2 meter and was found to be 0.07% (measurement time 10 minutes 15 seconds).

[0072] Under test condition 1 (carbon dioxide concentration in raw gas: 0.35%), the carbon dioxide concentration in the treated gas was 0.25% (measurement time: 10 minutes 24 seconds), and the carbon dioxide removal rate was 28.6%.

[0073] Under test condition 2 (carbon dioxide concentration in raw gas: 0.50%), the carbon dioxide concentration in the treated gas was 0.34% (measurement time 11 minutes 35 seconds), and the carbon dioxide removal rate was 32.0%.

[0074] Under test condition 3 (carbon dioxide concentration in raw gas: 4.15%), the carbon dioxide concentration in the treated gas was 2.81% (measurement time 11 minutes and 9 seconds), and the carbon dioxide removal rate was 32.3%.

[0075] Under test condition 4 (carbon dioxide concentration in raw gas: 4.82%), the carbon dioxide concentration in the treated gas was 3.30% (measurement time 11 minutes 23 seconds), and the carbon dioxide removal rate was 31.5%.

[0076] Under all test conditions 1 to 4, the carbon dioxide removal performance stabilized in about 11 minutes, and the carbon dioxide removal rate was about 30%. Based on this, if the carbon dioxide concentration of the raw gas is within the range of test conditions 1 to 4, then a gas treatment device consisting of three test devices connected in series will have a carbon dioxide removal rate of over 70%, and a gas treatment device consisting of four test devices connected in series will have a carbon dioxide removal rate of over 80%.

[0077] In addition, the changes in the composition of quicklime 24a before and after the test were analyzed using a test method based on JIS R9011:2006 "Testing methods for lime." The following analytical values ​​are mass fraction values.

[0078] The composition of the quicklime 24a sample before the test was as follows: calcium oxide: 96.14%, carbon dioxide: 0.97%, impurities (silicon dioxide, ferric oxide, aluminum oxide, etc.): 1.03%, ignition loss (loss on ignition): 1.47%.

[0079] The components of the quicklime 24a sample after the test under test condition 1 were as follows: calcium oxide: 91.54%, carbon dioxide: 1.45%, impurities (silicon dioxide, ferric oxide, aluminum oxide, etc.): 0.63%, ignition loss (loss on ignition): 6.33%.

[0080] The components of the quicklime 24a sample after the test under test condition 2 were as follows: calcium oxide: 91.30%, carbon dioxide: 1.17%, impurities (silicon dioxide, ferric oxide, aluminum oxide, etc.): 0.77%, ignition loss (loss on ignition): 6.91%.

[0081] The components of the quicklime 24a sample after the test under test condition 3 were as follows: calcium oxide: 88.19%, carbon dioxide: 2.54%, impurities (silicon dioxide, ferric oxide, aluminum oxide, etc.): 0.70%, ignition loss (loss on ignition): 9.91%.

[0082] The components of the quicklime 24a sample after the test under test condition 4 were as follows: calcium oxide: 85.58%, carbon dioxide: 3.49%, impurities (silicon dioxide, ferric oxide, aluminum oxide, etc.): 0.75%, ignition loss (loss on ignition): 12.27%.

[0083] In all test conditions, the amount of carbon dioxide contained in the quicklime 24a after the test increased compared to before the test, and the amount of calcium oxide decreased compared to before the test. From this, it is presumed that the carbon dioxide in the raw gas is physically adsorbed in the form of carbon dioxide on the surface of the quicklime 24a, or is chemically adsorbed to the calcium oxide of the quicklime 24a to become calcium carbonate. EXAMPLES

[0084] The gas treatment device according to each of the above-mentioned embodiments (see FIG. 1) is also effective for removing chlorine gas from the gas to be treated. That is, it is presumed that the chlorine gas ionized and excited by the plasma treatment of the gas to be treated is chemically adsorbed to the calcium oxide of the quicklime 24a to become calcium chloride, or is physically adsorbed in the form of chlorine gas on the surface of the quicklime 24a. Therefore, a test was conducted to evaluate the removal performance of chlorine gas using a test machine in which three gas treatment devices according to the first embodiment were connected in series.

[0085] The main specifications of the test machine are as follows: Electrical circuit specifications: 3A, 12V (power consumption: 36W) -Intake and exhaust blower specifications: 20m 3 / min Cylindrical electrode 11: Carbon pipe with a diameter of 45 mm and a length of 500 mm Axial electrode 12: Carbon pipe with a diameter of 10 mm and a length of 500 mm Adsorption pipe 22: PVC pipe with diameter 45 mm and length 500 mm Quicklime 24a: Special quicklime conforming to JIS (+18mm size, manufactured by Kotegawa Sangyo)

[0086] In the test, a vinyl chloride pipe was burned on an electric heater in a box covered with a vinyl cover to generate combustion gas containing chlorine gas. A Gastec chlorine gas detector tube 8LL (measurement range 0.02-2%) was used as a measuring device, and the maximum value of 2% was measured with this detector tube. A duct was connected to the inlet 15, an intake and exhaust blower was attached to the duct, and the air in the test room where the test machine was installed was sucked into the duct, and the air was supplied to the inlet 15. A box in which the vinyl chloride pipe was burned was connected to a duct, and the combustion gas of the vinyl chloride pipe of the intake and exhaust blower was merged with the air in the duct. The test machine was operated, and 5 minutes later, the treated gas (the gas to be treated exhausted from the exhaust path 23) was measured with the Gastec detector tube, and the measured value was 0. In other words, the chlorine gas in the combustion gas was completely removed by the test machine (removed to a concentration less than 0.02%, which is the detection limit).

[0087] It should be noted that the embodiments and examples disclosed herein are illustrative and not restrictive in all respects. Therefore, the scope of the present invention is defined by the claims, and it is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0088] 1 Gas treatment equipment 10 Plasma treatment path 11 Cylindrical electrode 12 Axial electrode 14 Flow Path 20 Adsorption processing path 22 Adsorption pipe line 24 Quicklime layer 24a quicklime

Claims

1. a plasma processing passage for generating plasma in a gas to be processed flowing through the passage; and an adsorption treatment path through which the gas to be treated in which the plasma has been generated is introduced and passed through a quicklime layer.

2. 2. The gas treatment apparatus according to claim 1, comprising a plurality of said plasma treatment paths and said adsorption treatment paths, said plasma treatment paths and said adsorption treatment paths being alternately arranged from the upstream side to the downstream side.

3. A flow path of the plasma processing path is formed between a cylindrical electrode and an axial electrode that is coaxially disposed inside the cylindrical electrode, A voltage is applied between the cylindrical electrode and the axial electrode to generate plasma in the gas to be treated, 3. The gas treatment device according to claim 1, wherein the adsorption treatment path is connected to a downstream side of a flow path of the plasma treatment path.

4. 3. The gas treatment device according to claim 1, wherein the quicklime used in the quicklime layer contains 93% by mass or more of calcium oxide and 2% by mass or less of carbon dioxide.

5. a plasma treatment for generating plasma in a gas to be treated containing at least one of carbon dioxide and chlorine to be removed while the gas is being flowed; and an adsorption treatment in which the gas to be treated from which the plasma has been generated in the plasma treatment is passed through a quicklime layer.

6. The gas processing method according to claim 5 , wherein the plasma treatment and the adsorption treatment are alternately repeated a plurality of times from the upstream side to the downstream side.

7. the plasma treatment is a treatment in which the gas to be treated is caused to flow through a flow path between a cylindrical electrode and an axial electrode coaxially disposed inside the cylindrical electrode, and a voltage is applied between the cylindrical electrode and the axial electrode; 7. The gas processing method according to claim 5, wherein the adsorption treatment is a treatment in which the gas to be processed in which the plasma has been generated is passed through a quicklime layer in a pipe connected to a downstream side of the flow path.

8. 7. The gas treatment method according to claim 5, wherein the quicklime used in the quicklime layer contains 93% by mass or more of calcium oxide and 2% by mass or less of carbon dioxide.

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