Gas treatment method and gas treatment device

Abstract

Provided are a gas treatment method and a gas treatment device capable of speeding up separation and recovery of a solid matter in a method for recovering a target-substance-containing gas containing a target substance as a solid matter by ventilating the target-substance-containing gas to an absorption liquid containing a reactive substance. Specifically provided is a gas treatment method in which a target-substance-containing gas containing a target substance is ventilated to an absorption liquid containing a reactive substance, and the target substance and the reactive substance are reacted with each other to recover the target substance as a solid matter. The gas treatment method comprises: a reaction step in which the target-substance-containing gas is ventilated to the absorption liquid to cause the target substance and the reactive substance to react with each other; and a magnetic separation step in which the solid matter is magnetically separated using a magnetic substance coexisting in the absorption liquid.

Description

Gas treatment method and gas treatment device

[0001] The present invention relates to a gas treatment method and a gas treatment device for treating a gas containing a target substance.

[0002] Methods for recovering target substances such as carbon dioxide by passing a gas containing the target substance, such as carbon dioxide, through an aqueous solution and reacting it with a reactive substance in the aqueous solution have been investigated. For example, by passing a carbon dioxide-containing gas through an aqueous solution containing an amine, such as m-xylylenediamine (MXDA) or 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPDA), as the reactive substance, it is possible to selectively capture carbon dioxide as an adduct with the amine and recover it as a solid (see, for example, Non-Patent Documents 1-3). Furthermore, by heating these solids that have captured carbon dioxide, the carbon dioxide can be desorbed, allowing the carbon dioxide to be recovered as a gas, and the amine can be reused as an absorbent.

[0003] However, in this method, the solid matter that captures carbon dioxide is separated and recovered by natural settling, and speeding up the separation and recovery process remains a challenge.

[0004] Against this background, there is a demand for speeding up the separation and recovery of solids in a method in which a gas containing a target substance such as carbon dioxide is passed through an absorption liquid containing a reactive substance to recover the target substance as a solid.

[0005] "Selective Absorption of Carbon Dioxide Using m-Xylylenediamine," [online], June 6, 2017, Tokyo Chemical Industry Co., Ltd., [Retrieved November 10, 2023], Internet <URL: https: / / www.tcichemicals.com / JP / ja / product / tci-topics / ArticleHighlights_20170606> Soichi Kikkawa et al., "Direct Air Capture of CO2 Using a Liquid Amine-Solid Carbamic Acid Phase-Separation System Using Diamines Bearing an Aminocyclohexyl Group," ACS Environ. Au 2022, 2, 354-362, [online], [Retrieved November 10, 2023], Internet <URL: https: / / pubs.acs.org / doi / pdf / 10.1021 / acsenvironau.1c00065> "[Research presentation] Development of high-speed CO2 capture technology from air, surpassing existing technologies! One of the fastest in the world!" [online], May 11, 2022, Tokyo Metropolitan University, [Retrieved November 10, 2023], Internet <URL: https: / / www.tmu.ac.jp / news / topics / 31765.html>

[0006] The object of the present invention is to provide a gas treatment method and a gas treatment device that can speed up the separation and recovery of solids in a method in which a gas containing a target substance is aerated through an absorption liquid containing a reactive substance and recovered as solids.

[0007] The present invention is a gas treatment method in which a target substance-containing gas containing a target substance is passed through an absorption liquid containing a reactive substance, and the target substance is recovered as a solid by reacting the target substance with the reactive substance. The gas treatment method includes a reaction step in which the target substance-containing gas is passed through the absorption liquid, and the target substance is reacted with the reactive substance, and a magnetic separation step in which the solid is magnetically separated using a magnetic substance coexisting in the absorption liquid.

[0008] It is preferable that the gas treatment method further includes a separation and recovery step of separating and recovering the target substance and the reactive substance from the magnetically separated solid matter.

[0009] In the gas treatment method, the target substance is preferably carbon dioxide.

[0010] In the gas treatment method, the reactive substance is preferably an amine compound.

[0011] In the gas treatment method, the amine compound is preferably at least one of m-xylylenediamine, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, and monoethanolamine.

[0012] In the gas treatment method, it is preferable that the magnetic substance be made to coexist with the absorbing liquid before the target substance-containing gas is aerated through the absorbing liquid.

[0013] The present invention is a gas treatment device that passes a target substance-containing gas through an absorption liquid containing a reactive substance, causing the target substance to react with the reactive substance, thereby recovering the target substance as a solid. The gas treatment device comprises a reaction means that passes the target substance-containing gas through the absorption liquid, causing the target substance to react with the reactive substance, and a magnetic separation means that magnetically separates the solid using a magnetic substance that is coexistent in the absorption liquid.

[0014] It is preferable that the gas treatment device further comprises a separation and recovery means for separating and recovering the target substance and the reactive substance from the magnetically separated solid matter.

[0015] The present invention provides a gas treatment method and a gas treatment device that can speed up the separation and recovery of solids in a method in which a gas containing a target substance is aerated through an absorption liquid containing a reactive substance and recovered as solids.

[0016] 1 is a schematic diagram showing an example of a gas treatment device according to an embodiment of the present invention, and FIG. 2 is a photograph showing the state after solid-liquid separation for 10 seconds in Example 1, Example 2, and Comparative Example 1.

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present invention. The embodiment is an example of implementing the present invention, and the present invention is not limited to the embodiment.

[0018] An example of a gas treatment apparatus according to an embodiment of the present invention is outlined in FIG. 1, and its configuration will be described.

[0019] The gas treatment apparatus 1 shown in Figure 1 includes a reaction tank 10 as a reaction means for passing a target substance-containing gas through an absorption liquid 16 containing a reactive substance to cause a reaction between the target substance and the reactive substance, and a magnetic separation device 12 as a magnetic separation means for magnetically separating solids using a magnetic substance coexisting in the absorption liquid. The gas treatment apparatus 1 may further include a separation and recovery device 14 as a separation and recovery means for separating and recovering the target substance and reactive substances from the magnetically separated solids. The gas treatment apparatus 1 may also be an integrated apparatus in which a magnetic separation unit is provided as magnetic separation means in a part of the reaction tank 10.

[0020] The gas treatment method and the operation of the gas treatment apparatus 1 according to this embodiment will be described.

[0021] In the gas treatment device 1 of Fig. 1, the reaction tank 10 contains an absorption liquid 16, which contains a reactive substance. For example, after a magnetic substance is allowed to coexist in the absorption liquid 16, a target substance-containing gas containing the target substance is introduced, for example, from the bottom of the reaction tank 10 and aerated into the absorption liquid 16, causing the target substance to react with the reactive substance in the absorption liquid 16, resulting in a solid (reaction step). The solid contains the magnetic substance and settles or disperses in the absorption liquid 16.

[0022] For example, a target substance-containing gas containing the target substance may be aerated through the absorbing liquid 16 in the reaction tank 10, and after the target substance reacts with the reactive substance in the absorbing liquid 16, a magnetic substance may be made to coexist with the absorbing liquid 16 and mixed by, for example, stirring, to obtain a solid material containing the magnetic substance. From the viewpoint of a high recovery rate of solid materials containing the magnetic substance, it is preferable to make the magnetic substance coexist with the absorbing liquid 16 before aerating the target substance-containing gas with the absorbing liquid.

[0023] The gas from which the target substance has been removed or from which the amount of the target substance has been reduced may be discharged from the reaction vessel 10 and recovered.

[0024] The absorption liquid 16 (reaction liquid) containing the solid matter obtained in the reaction step is sent to the magnetic separation device 12, for example, through a pipe. In the magnetic separation device 12, the solid matter in the absorption liquid 16 (reaction liquid) containing the solid matter obtained in the reaction step is magnetically separated using a magnetic substance that is coexistent in the absorption liquid 16 (magnetic separation step).

[0025] The solid matter obtained by magnetic separation in the magnetic separation step may be sent to the separation and recovery device 14, for example, through a pipe or the like. In the separation and recovery device 14, the solid matter is heated, for example, so that the target substance and the reactive substance are separated and recovered from the solid matter (separation and recovery step).

[0026] In this way, a target substance, such as carbon dioxide, can be efficiently recovered from a target substance-containing gas, such as air containing carbon dioxide. In the gas treatment method and gas treatment device according to this embodiment, a key point is to have, for example, a solid magnetic substance coexist in the absorption liquid. By having a magnetic substance coexist in the absorption liquid 16, solids containing the magnetic substance can be rapidly separated by magnetic force due to the action of the magnetic substance, thereby enabling separation and recovery of solids at a higher speed (e.g., 1 / 2 to 1 / 20 of the time) compared to natural sedimentation. Furthermore, recovered reactive substances, such as amine compounds, can be reused as reactive substances. Magnetic separation using a magnetic substance can reduce the content (e.g., water content) of the absorption liquid contained in the separated solids containing the magnetic substance, thereby reducing the energy required when subsequently separating the target substance (e.g., carbon dioxide) and the reactive substance (e.g., amine compounds) by, for example, heating.

[0027] There are no particular limitations on the target substance, but examples include gases such as carbon dioxide.

[0028] The target substance-containing gas is not particularly limited as long as it contains the target substance, and examples thereof include air, combustion exhaust gas, etc. The gas treatment method and gas treatment device according to the present embodiment can be suitably used to recover carbon dioxide and the like from these target substance-containing gases.

[0029] The reactive substance is not particularly limited as long as it reacts with the target substance to form a solid, but for example, when the target substance is carbon dioxide, an amine compound capable of reacting with carbon dioxide to form carbamic acid can be used. One type of reactive substance may be used alone, or two or more types may be used in combination.

[0030] Examples of amine compounds include m-xylylenediamine (MXDA), 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPDA), 4,4'-methylenebis-(2-methylcyclohexylamine), cyclohexane-1,2-diamine, cyclohexane-1,3-diamine, cyclohexane-1,4-diamine, and monoethanolamine, with m-xylylenediamine (MXDA), 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPDA), and monoethanolamine being preferred from the standpoint of cost, ease of use, etc. The amine compounds may be used alone or in combination of two or more.

[0031] The magnetic substance is not particularly limited as long as it has magnetism. For example, magnetite (Fe ３ O ４ ), manganese zinc ferrite, iron, and other solid magnetic substances are preferred because they are easily incorporated into solid matter, and magnetite (Fe ３ O ４ The magnetic substance may be used alone or in combination of two or more kinds.

[0032] When the magnetic substance is solid, the particle size of the magnetic substance may be, for example, in the range of 50 μm to 1 mm in terms of volume average particle size.

[0033] The solvent for the absorption liquid is not particularly limited as long as it is a liquid that can be mixed with the reactive substance and has low activity or is inactive with respect to the reactive substance and the magnetic substance. For example, when the reactive substances are m-xylylenediamine (MXDA) and 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPDA), water capable of dissolving these substances can be used.

[0034] The reaction tank 10 is not particularly limited as long as it can aerate the target substance-containing gas into the absorption liquid 16, but it is preferable to provide an aeration device such as a diffuser or to use a gas-liquid mixer to increase absorption efficiency. In addition to aeration as a stirring means for agitating the absorption liquid 16 (reaction liquid), the reaction tank 10 may also be provided with, for example, a stirring device having a stirring blade and rotating the stirring blade by rotational force generated by a driving means such as a motor transmitted via a stirring shaft.

[0035] The magnetic separation device 12 is not particularly limited as long as it can magnetically separate the solids using a magnetic substance. Examples of the magnetic separation device 12 include a magnetic separation device in which a magnetic drum, made of resin or the like, with a magnet such as a neodymium magnet attached to its cylindrical surface is immersed in a tank containing an absorption liquid 16 (reaction liquid) containing the solids obtained in the reaction process and the magnetic drum is rotated around the cylindrical axis at a predetermined speed to adsorb the solids containing the magnetic substance, a magnetic separation device in which a magnetic circuit such as a neodymium magnet is fixed inside a rotating drum containing the absorption liquid 16 (reaction liquid) containing the solids obtained in the reaction process and the rotating drum outside the magnetic circuit rotates at a predetermined speed to adsorb the solids containing the magnetic substance, and similar devices using electromagnets. The magnetic separation device 12 may also be a magnetic separation tank equipped with a magnet at the bottom of the tank.

[0036] As the magnet, a neodymium magnet, an electromagnet, a ferrite magnet, or the like can be used.

[0037] The separation and recovery device 14 is a heating device that can heat, for example, solid materials when separating a target substance (e.g., carbon dioxide) from a reactive substance (e.g., an amine compound) by heating. Examples of the heating device that can be used include an electric heating device, a hot water heating device, and a device that heats by burning fuel such as gas or oil.

[0038] Before the solid material obtained by magnetic separation is heated to separate the target substance (e.g., carbon dioxide) from the reactive substance (e.g., amine compound), the solid material may be subjected to a dehydration treatment. The dehydration treatment can be performed using a dehydrator that uses compression or centrifugal force. By performing the dehydration treatment, the amount of heat required for the heating treatment can be reduced.

[0039] The reaction conditions in the reaction step, such as the reaction temperature, reaction time, and reaction pressure, may be set appropriately depending on the reactivity between the target substance and the reactive substance. For example, when the target substance is carbon dioxide and the reactive substance is an amine compound such as m-xylylenediamine or 3-aminomethyl-3,5,5-trimethylcyclohexylamine, the reaction temperature may be, for example, 0 to 50°C, and the reaction pressure may be atmospheric pressure. The contact time of the gas with the reactive substance is very short, from a few seconds to a few minutes, but if sufficient absorption efficiency is not obtained by a single contact, it is possible to configure a system in which the gas is circulated and contacted again.

[0040] The magnetic separation conditions such as temperature in the magnetic separation step may be appropriately set depending on the magnetism of the magnetic substance, etc. For example, when the magnetic substance is magnetite, the temperature may be set to, for example, 10 to 80°C.

[0041] The separation conditions such as temperature and time in the separation and recovery step may be set appropriately depending on the physical properties of the reaction product obtained by the reaction between the target substance and the reactive substance, etc. For example, when the target substance is carbon dioxide and the reactive substance is an amine compound such as m-xylylenediamine or 3-aminomethyl-3,5,5-trimethylcyclohexylamine, the heating temperature may be, for example, 100 to 150°C, the heating time may be 0.5 to 3 hours, and the heating pressure may be atmospheric pressure.

[0042] The recovered reactive substance may be reused as a reactive substance in the reaction step. For example, when the solid obtained by magnetic separation is heated to separate the target substance (e.g., carbon dioxide) and the reactive substance (e.g., an amine compound), the reactive substance is recovered in a mixed state of the reactive substance (e.g., a liquefied amine compound) and the magnetic substance. A solvent such as water can be added to this mixture of the reactive substance (e.g., the liquefied amine compound) and the magnetic substance to adjust it to a predetermined concentration, and the mixture can be reused as an absorption liquid.

[0043] This specification includes the following embodiments: (1) A gas treatment method for passing a target substance-containing gas through an absorption liquid containing a reactive substance to cause a reaction between the target substance and the reactive substance, thereby recovering the target substance as a solid, the gas treatment method including: a reaction step of passing the target substance-containing gas through the absorption liquid to cause a reaction between the target substance and the reactive substance, and a magnetic separation step of magnetically separating the solid using a magnetic substance coexisting in the absorption liquid.

[0044] (2) The gas treatment method according to (1), further comprising a separation and recovery step of separating and recovering the target substance and the reactive substance from the magnetically separated solid matter.

[0045] (3) The gas treatment method according to (1) or (2), wherein the target substance is carbon dioxide.

[0046] (4) The gas treatment method according to any one of (1) to (3), wherein the reactive substance is an amine compound.

[0047] (5) The gas treatment method according to (4), wherein the amine compound is at least one of m-xylylenediamine, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, and monoethanolamine.

[0048] (6) A method for treating a gas according to any one of (1) to (5), comprising causing the magnetic substance to coexist with the absorbing liquid before the target substance-containing gas is aerated through the absorbing liquid.

[0049] (7) A gas treatment device that passes a target substance-containing gas through an absorption liquid containing a reactive substance, causing the target substance to react with the reactive substance, thereby recovering the target substance as a solid, comprising: a reaction means that passes the target substance-containing gas through the absorption liquid, causing the target substance to react with the reactive substance; and a magnetic separation means that magnetically separates the solid using a magnetic substance that is coexistent in the absorption liquid.

[0050] (8) The gas treatment device according to (7), further comprising a separation and recovery means for separating and recovering the target substance and the reactive substance from the magnetically separated solid matter.

[0051] (9) The gas treatment device according to (7) or (8), wherein the target substance is carbon dioxide.

[0052] (10) The gas treatment device according to any one of (7) to (9), wherein the reactive substance is an amine.

[0053] (11) The gas treatment device according to (10), wherein the amine is at least one of m-xylylenediamine, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, and monoethanolamine.

[0054] (12) The gas treatment device according to any one of (7) to (11), wherein the magnetic substance is made to coexist with the absorbing liquid before the target substance-containing gas is aerated through the absorbing liquid.

[0055] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0056] Example 1 In a reaction vessel, a 7% by mass aqueous solution of 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPDA) was used as a reactive substance. Magnetite (Fe ３ O ４ ) was added, and air containing carbon dioxide, the target substance, was aerated at a liquid temperature of 20° C. After aeration for 360 minutes, a neodymium magnet was applied to the bottom of the reaction vessel to perform solid-liquid separation for 10 seconds.

[0057] Example 2 Air containing carbon dioxide as a target substance was passed through a reaction vessel containing a 7% by mass aqueous solution of 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPDA) as a reactive substance at a liquid temperature of 20°C. After passing the air for 360 minutes, magnetite (Fe) was added as a magnetic substance to a concentration of 3 g / L. ３ O ４ ) was added, and the mixture was stirred for 30 seconds to thoroughly mix, and then a neodymium magnet was applied to the bottom of the reaction vessel to effect solid-liquid separation for 10 seconds.

[0058] <Comparative Example 1> Air containing carbon dioxide, which is the target substance, was passed through a 7% by mass aqueous solution of 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPDA) as a reactive substance in a reaction vessel at a liquid temperature of 20° C. After 360 minutes of aeration, a neodymium magnet was applied to the bottom of the reaction vessel to perform solid-liquid separation for 10 seconds.

[0059] Figure 2 shows photographs of the state of the solution after 10 seconds of solid-liquid separation in Example 1, Example 2, and Comparative Example 1. In Comparative Example 1, fine particles remained suspended and the solution remained cloudy even after solid-liquid separation. However, in Example 2, although the solution remained slightly cloudy, it was confirmed that more solid matter settled. Furthermore, in Example 1, most of the solid matter settled, with only a small amount of solid matter remaining in suspension. In this way, the solid matter was able to be rapidly magnetically separated by utilizing the magnetic substance coexisting in the absorption solution.

[0060] As described above, in the examples, in a method in which a gas containing a target substance such as carbon dioxide is passed through an absorption liquid containing a reactive substance to recover the target substance as a solid, the separation and recovery of solids was able to be accelerated.

[0061] 1 Gas treatment device, 10 Reaction tank, 12 Magnetic separation device, 14 Separation and recovery device, 16 Absorption liquid

Claims

1. A gas treatment method in which a gas containing a target substance is passed through an absorption liquid containing a reactive substance, and the target substance is recovered as a solid by reacting with the reactive substance, the gas treatment method comprising: a reaction step in which the target substance-containing gas is passed through the absorption liquid, and the target substance is reacted with the reactive substance; and a magnetic separation step in which the solid is magnetically separated using a magnetic substance that is coexistent in the absorption liquid.

2. A gas treatment method according to claim 1, further comprising a separation and recovery step of separating and recovering the target substance and the reactive substance from the magnetically separated solid matter.

3. A gas treatment method according to claim 1 or 2, characterized in that the target substance is carbon dioxide.

4. A gas treatment method according to any one of claims 1 to 3, characterized in that the reactive substance is an amine compound.

5. The gas treatment method according to claim 4, wherein the amine compound is at least one of m-xylylenediamine, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, and monoethanolamine.

6. A gas treatment method according to any one of claims 1 to 5, characterized in that the magnetic substance is made to coexist with the absorption liquid before the gas containing the target substance is aerated through the absorption liquid.

7. A gas treatment device that passes a gas containing a target substance through an absorption liquid containing a reactive substance, causing the target substance to react with the reactive substance, thereby recovering the target substance as a solid, the gas treatment device comprising: a reaction means that passes the target substance-containing gas through the absorption liquid, causing the target substance to react with the reactive substance; and a magnetic separation means that magnetically separates the solid using a magnetic substance that is coexistent in the absorption liquid.

8. A gas treatment device according to claim 7, further comprising a separation and recovery means for separating and recovering the target substance and the reactive substance from the magnetically separated solid matter.

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