KR20170137302A - Apparatus for carbon dioxide in biogas fixing reaction - Google Patents

Abstract

The present invention relates to a method for recycling biogas in the entirety thereof, which recovers high-purity methane from biogas, and synthesizes by-product carbon dioxide into calcium carbonate; and to a system for the same. Specifically, the method comprises: a first isolation step for isolating methane from biogas containing methane and carbon dioxide by using a separation film; and a second isolation step for removing carbon dioxide from a methane-carbon gas mixture containing methane that had not been isolated in the first isolation step by using the fixation of carbon dioxide, thereby reisolating methane. By using, as energy sources, the high-purity methane primarily isolated in the first isolation step, and the unreacted methane secondarily isolated in the second isolation step, the method and the system for recycling biogas in the entirety thereof according to the present invention can recover high-purity methane from biogas, and at the same time, can produce calcium carbonate widely utilized as a chemical raw material.

Description

TECHNICAL FIELD [0001] The present invention relates to a biogas fixing reaction apparatus,

The present invention relates to an apparatus for fixing carbon dioxide in biogas.

Interest in using biogas has been amplified as a means to overcome the crisis caused by depletion of fossil fuels and price fluctuations. Currently, biogas generated from a biogas generation facility is used as a heat source, or only a gas is used to generate electricity, by removing heavy impurities from the biogas.

Especially, in case of small and medium sized landfills, there is not enough technology to utilize gas of biogas generation facilities such as simple incineration of biogas generated due to insufficient economic efficiency or spreading to the atmosphere.

In the case of biogas, the methane contained in the gas is about 50 ~ 75% of the global warming gas. It is possible to produce high concentration methane by separating the carbon dioxide, and it is possible to supply the distant gas to the power generation, boiler, business fuel, automobile and city gas. This is easy. One of the main components of biogas, carbon dioxide, is also the cause of global warming, and more than 70% of it is concentrated as a raw material for chemical products.

Commercialization techniques for biomethane solidification include pressure swing adsorption, water scrubbing, methanol scrubbing, polyethylene glycol scrubbing, and membrane separation. The absorption process mainly uses a water scrubbing process, which depends on the type of the absorption liquid, the gas-liquid contact area, and the temperature of the gas and the water. In addition, the purified methane gas is saturated with water, requiring a post-treatment process for removing moisture. The adsorption process is a technology for selectively separating specific components of the mixed gas by using the difference in the adsorption equilibrium amount caused by the pressure cycling between the adsorbent and the mixed gas. It primarily adsorbs carbon dioxide at high pressure and purifies methane, do. Since the adsorption process is in abnormal condition, it is difficult to predict and design various operating parameters during the operation stage and it is necessary to pretreat water according to the adsorbent. Compared with the understanding, the separation membrane process is energy-saving because it does not require the energy required for the phase change and can be operated only by the minimum driving force required for the membrane process, and there is no phase change. In addition, there is an advantage that the equipment is compact because it is mostly composed of a pump, a pipe, a membrane, and a control prat without an evaporator or a condenser.

In the case of a polymer membrane, there is a method in which a gas molecule passes through a minute gap existing between the side chain of a polymer and a side wall of the polymer due to a difference in speed of movement within the membrane after absorption or dissolution. Hydrogen and helium are permeated by the gap between polymer side chains as in the latter case, and water vapor and CO ₂ are absorbed or dissolved and transmitted through the inside of the membrane.

Initial gas separation membrane process, but started to separate hydrogen _{(H 2 / CO, H 2} / CH 4) and recovered. At present, it is expanding to various fields such as generation of nitrogen, production of oxygen enriched air, recovery of hydrogen and volatile organic vapor, and separation of carbon dioxide.

The use of carbon dioxide and its reuse are studied in biological processes and mineralization methods. Biological processes include the capture and use of carbon dioxide using bacteria, the production of various energy and bio-based chemicals using microalgae, and artificial photosynthesis, but this approach generally requires a large range of paper Is a big obstacle. The carbon dioxide mineralization method is based on a chemical reaction using a substance such as rocks made of silicate and magnesium and has a merit that it goes through a simple process. However, it solves the economical problem of adding a process for extracting high purity carbon dioxide Should be.

The calcium carbonate manufacturing method includes a carbonation process, a Solvay process, and a lime-soda process. Of these, the carbonation process is a process in which calcium carbonate is produced by synthesizing lime or calcium hydroxide with carbon dioxide The advantage of using carbon dioxide, which is a greenhouse gas, is that calcium carbonate can be produced in a wide variety of industrial fields.

However, most of the technologies for separating and solidifying methane from the biogas currently include very high pressures as disclosed in Korean Patent No. 10-0908782 (fueling apparatus for biogas for a microturbine) The gas separation membrane technology that operates in the above-described operation also operates at a high pressure of 5 bar or more. Therefore, an expensive gas compression device is required, which consumes a relatively high initial investment cost and a relatively high energy. And the refining by-product, carbon dioxide, is releasing to the atmosphere rather than recycling.

Patent Registration No. 10-0908782

SUMMARY OF THE INVENTION It is an object of the present invention, which has been made in view of the above, to provide a method of separating methane from a biogas (landfill gas, anaerobic digestion gas, etc.) with high purity even at a relatively low pressure of 2 Bar or less and separating carbon dioxide into calcium carbonate And to provide a method and system for the whole biogas resource conversion.

A first separation step of separating methane from biogas including methane and carbon dioxide using a separation membrane; And a second separating step of separating methane from the methane-carbon dioxide mixed gas containing methane not separated in the first separating step by using the carbon dioxide fixing reaction, thereby fixing the carbon dioxide, .

Further, the present invention may further comprise a pretreatment step for removing substances other than methane and carbon dioxide in the biogas, or a first pressurization step for increasing the efficiency of the separation membrane apparatus by pressurizing the biogas before the first separation step; And a second pressurization step of pressurizing the methane-carbon dioxide gas mixture to increase the yield of the carbon dioxide fixation reaction before the second separation step.

The present invention separates methane from biogas including methane and carbon dioxide using a separation membrane of a material selected from the group consisting of polysulfone, polyimide, and polyisophosphorus. The ratio of methane-carbon dioxide gas flow rate to biogas flow rate To control the flow rate of separated methane; And the carbon dioxide fixing reaction to remove methane from the methane-carbon dioxide mixed gas containing methane, which has not been separated in the first separation step, by fixing the carbon dioxide, and terminating the reaction when the pH of the product reaches 7 And a reaction device.

The present invention also provides a first pressurizing device for increasing the efficiency of the membrane separation device by pressurizing the biogas to 2 bar or less in a previous stage of the separation membrane device; And a second pressurizing device for increasing the yield of the carbon dioxide fixing reaction by pressurizing the methane-carbon dioxide gas mixture to 2 bar or less in the previous step of the reaction device.

The method and system for recycling biogas in accordance with the present invention can separate methane of high purity of 97% or more from biogas generated in a biogas generating facility to increase separation efficiency, It can be used as an automobile fuel.

In addition, carbon dioxide can be fixed and separated in the form of calcium carbonate without releasing carbon dioxide into the atmosphere, thereby reducing greenhouse gas emissions and facilitating particle size and shape control by controlling the parameters of the synthesis reaction. Thus, fine chemicals such as paper, It can be used as a high value-added raw material for the food industry and medicine as well as the industry.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a process diagram of a biogas whole-volume recycling system according to a preferred embodiment of the present invention.

Before describing the present invention in detail, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is defined solely by the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise stated.

Throughout this specification and claims, the word "comprise", "comprises", "comprising" means including a stated article, step or group of articles, and steps, , Step, or group of objects, or a group of steps.

On the contrary, the various embodiments of the present invention can be combined with any other embodiments as long as there is no clear counterpoint. Any feature that is specifically or advantageously indicated as being advantageous may be combined with any other feature or feature that is indicated as being preferred or advantageous. Hereinafter, embodiments of the present invention and effects thereof will be described with reference to the accompanying drawings.

The biogas recycling method, which is an embodiment of the present invention, will be described in more detail as follows.

A first separation step of separating methane from the biogas including methane and carbon dioxide using a separation membrane, a second separation step of separating methane from the methane-carbon dioxide mixture gas including the methane-containing methane in the first separation step by using the carbon dioxide fixing reaction, And a second separation step of re-separating the biogas.

Biogas includes 50 to 90% of methane (CH ₄ ), 10 to 20% of methane (CH ₄ ) and the like, including organic fuels such as livestock manure, food waste and sewage sludge, It consists of 50% of carbon dioxide (CO ₂ ) and other pollutants such as less than 1% water, hydrogen sulfide (H ₂ S), and siloxane.

The first separation step separates the methane and carbon dioxide contained in the biogas generated in the biogas generating facility by using a separation membrane. The separation membrane may be a material selected from the group consisting of polysulfone, polyimide, and polyisophthalon But is not limited thereto.

Also, the first separation step may be controlled by controlling the flow rate of methane separated by adjusting the ratio of the methane-carbon dioxide flow rate to the biogas flow rate.

When the biogas is subjected to the first separation step, methane of high purity of 97% or more can be primarily obtained. Methane not removed through the first separation step is present in the methane-carbon dioxide mixture gas together with the carbon dioxide in the biogas, and can be re-separated by the second separation step to be described later.

The second separation step is a step of separating methane from the methane-carbon dioxide mixed gas containing methane which has not been separated in the first separation step by using the carbon dioxide fixing reaction. The carbon dioxide fixing reaction is a step of separating the methane- A reaction in which calcium oxide (CaO) and water (H ₂ O) are reacted or calcium hydroxide (Ca (OH) ₂ ) is reacted to remove carbon dioxide in the form of calcium carbonate (CaCO ₃ ) may be used. The carbon dioxide fixing reaction can fix the carbon dioxide in the form of calcium carbonate by the reaction of the following [Reaction Scheme 1].

[Reaction Scheme 1]

And the second separation step can be controlled in such a manner that the reaction is terminated when the pH of the product is 7.

In the second separation step, carbon dioxide in the methane-carbon dioxide gas mixture is fixed with calcium carbonate as the precipitating substance, and the methane that can not be separated in the first separation step and does not participate in the carbon dioxide fixing reaction in the second separation step is secondarily separated .

The methane obtained through the first separation step and the second separation step can be utilized as a city gas supply and an automobile fuel and can be separated into calcium carbonate form without discharging carbon dioxide into the atmosphere to reduce greenhouse gas emissions, , Plastics, rubber, paints, etc., as well as high-value raw materials such as foods and pharmaceuticals.

As another embodiment of the present invention, the biogas recycling method may further include a pretreatment step of removing substances other than methane and carbon dioxide in the biogas.

The biogas that has not undergone the preprocessing step contains 50 to 90% of methane (CH ₄ ), 10 to 50% of carbon dioxide (CO ₂ ) and other less than 1% of water, hydrogen sulfide (H ₂ S), siloxane It is possible to increase the purity of the separated methane and carbon dioxide (in the form of calcium carbonate) by removing contaminants through the pretreatment step, and sulfur (S) It is possible to improve the durability of the apparatus.

As another embodiment of the present invention, the biogas full-volume recycling method may further include a first pressurization step for increasing the efficiency of the separation membrane apparatus by pressurizing the biogas before the first separation step. A driving force may be applied to the biogas supplied to the separation membrane through the first pressurization step to increase the separation efficiency in the separation membrane.

It is preferable to use a centrifugal high pressure blower as the pressurizing device used in the first pressurizing step, but not limited thereto, all the pressurizing devices commonly used in the technical field of the present invention can be used.

As another embodiment of the present invention, the biogas recycling method may further include a second pressurization step for pressurizing the methane-carbon dioxide gas mixture before the second separation step to increase the yield of the carbon dioxide fixation reaction. Through the second pressurization step, the separation membrane of the first separation step is provided with a suction pressure to increase the separation efficiency. In addition, the methane-carbon dioxide gas mixture is injected under pressure to increase the rate of dissolution of carbon dioxide to increase the yield of the carbon dioxide fixing reaction .

As the pressurizing device used in the second pressurizing step, it is preferable to use a device for applying pressure by increasing or decreasing the volume by reciprocating the piston in the reciprocating cylinder in the reciprocating cylinder. However, the present invention is not limited thereto, May be used.

The pressure in the first pressurization step or the second pressurization step can be pressurized to 2 bar or less. Separation of methane from the biogas using a separation membrane is usually required to have a pressure of 5 bar or more. By separating the methane through the first separation step and the second separation step, which are one embodiment of the present invention, % Or more of methane can be separated, so that the operation efficiency can be improved.

 It is possible to obtain high purity methane of 97% or more even by using relatively low pressure by the biogas recycling method. It can be used as city gas supply and automobile fuel, and the produced calcium carbonate can be used as paper, plastic, rubber, paint It can be used as a high value-added raw material for food and medicine as well as fine chemical industry.

As another aspect of the present invention, a biogas whole volume resource conversion system will be described in more detail with reference to the accompanying drawings.

As shown in the flow chart of the biogas recycling system shown in FIG. 1, methane is separated from biogas including methane and carbon dioxide, and the ratio of the methane-carbon dioxide gas mixture flow rate to the biogas flow rate is controlled, And a second separation step of separating the methane from the methane-carbon dioxide gas mixture containing methane by the carbon dioxide fixing reaction, thereby separating the methane from the methane- Is 7, the reaction is controlled in such a manner that the reaction is terminated.

The separation membrane device 30 may be any separation membrane device commonly used in the art to which the present invention pertains. Preferably, a multi-stage separation membrane apparatus can be used, but the present invention is not limited thereto. In the multistage membrane module, the membrane area of the first membrane module and the second membrane module is 2: 1, the biogas is supplied to the first membrane module through the first membrane membrane inlet header, and the methane gas concentrated in the first membrane membrane is 1 However, it can be recovered as a fuel and recovered by a single-stage separation membrane gas pipe connected to the header of the separation membrane exclusion section. The gas permeated through the separation membrane of the biogas supplied to the first separation membrane module is discharged to the first separation membrane permeation header, compressed by the second separation compressor, and supplied to the second separation membrane module through the second separation membrane inlet header. Concentrated methane in the two-stage membrane module was transferred to the two-stage membrane exclusion gas piping connected to the two-stage membrane exclusion header, and the two-stage membrane exclusion gas piping was connected to the one- Can be maximized. The high purity methane concentrated in the first stage separation membrane module and the second stage separation membrane module is pressurized and stored in the methane storage tank (60).

The separation membrane may be selected from the group consisting of polysulfone, polyimide, and polyisapharm, but is not limited thereto.

Also, the separation membrane device 30 may be controlled by controlling the flow rate of methane separated by adjusting the ratio of the methane-carbon dioxide flow rate to the biogas flow rate.

When the biogas passes through the separation membrane device 30, methane having a purity of 97% or more can be primarily obtained. The methane that can not be removed through the separator 30 is present in the methane-carbon dioxide mixed gas together with the carbon dioxide in the biogas, and can be separated again by the reactor 50 to be described later.

The reaction apparatus 50 is a device for re-separating methane from carbon dioxide-containing methane-carbon dioxide mixed gas containing methane that has not been separated in the separation membrane apparatus 30 by using a carbon dioxide fixation reaction. A reaction occurs in which calcium oxide (CaO) and water (H ₂ O) are added to a carbon dioxide gas mixture or calcium carbonate (Ca (OH) ₂ ) is added to remove carbon dioxide in the form of calcium carbonate (CaCO ₃ ).

Also, the reaction apparatus 50 can be controlled in such a manner that the reaction is terminated when the pH of the product is 7.

The carbon dioxide in the methane-carbon dioxide mixed gas is fixed by the calcium carbonate, which is a precipitating substance, and the methane which can not be separated in the separation membrane device and does not participate in the carbon dioxide fixing reaction in the reaction device 50 is secondarily Can be separated.

 The methane obtained through the separation membrane device 30 and the reaction device 50 can be used as a city gas supply and an automobile fuel and can be separated into calcium carbonate without discharging carbon dioxide into the atmosphere to reduce greenhouse gas emissions , Paper, plastics, rubber, and paints, as well as food and pharmaceuticals.

The total amount of biogas recycling system of the present invention includes a first pressurizing device 20 for increasing the efficiency of the separator device by pressurizing the biogas to 2 bar or less in the previous stage of the separator device 30 and a methane- And a second pressurizing device 40 for pressurizing the gas to 2 bar or less to increase the yield of the carbon dioxide fixing reaction.

A driving force may be applied to the biogas supplied to the separation membrane device through the first biasing device 20 to increase the separation efficiency in the separation membrane device.

As the first pressurizing device 20, it is preferable to use a centrifugal high-pressure blower, but not limited thereto, all the pressurizing devices commonly used in the technical field of the present invention can be used.

In addition to increasing the separation efficiency by providing suction pressure to the membrane separation device through the second pressure device 40, the methane-carbon dioxide gas mixture is pressurized and injected into the lower part of the reaction device to increase the dissolution rate of carbon dioxide, The yield can be increased.

As the pressurizing device used in the second pressurizing device 40, it is preferable to use a device for applying pressure by reciprocation of the piston by reciprocation of the piston by increasing or decreasing the volume of the piston. However, the present invention is not limited thereto, Any pressure device commonly used in the field may be used.

 The first pressurizing device (20) and the second pressurizing device (40) have discharge pressures of up to 2 bar. Separation of methane from the biogas using a membrane separation apparatus typically requires a pressure of 5 bar or more. By re-separating the methane through the separation membrane apparatus 30 and the reaction apparatus 50, which are one embodiment of the present invention, Methane of high purity of 97% or more can be separated, so that the operation efficiency can be improved.

 It is possible to obtain methane with high purity of 97% or more even if relatively low pressure is used by the whole biogas recycling system. It can be used as city gas supply and automobile fuel, and the produced calcium carbonate can be used as paper, plastic, It can be used as a high value-added raw material for food and medicine as well as fine chemical industry.

As an embodiment of the present invention, the biogas full volume recycling system may further include a pretreatment apparatus 10 for removing substances other than methane and carbon dioxide in the biogas.

The preprocessing apparatus 10 may be any preprocessing apparatus commonly used in the technical field of the present invention. Preferably a gas filter for removing impurities and moisture contained in the biogas introduced into the interior by two elements having a filtration degree of 3 micron by inertia and impact action, A dryer that condenses the moisture contained in the biogas and discharges it, an adsorption tower that removes water contained in the biogas by using an adsorbent material, and a filtration layer with many fine holes to form a biogas, , The serpentine flowing biogas may be, but is not limited to, a pretreatment device comprising an after filter that removes moisture and particulate matter from the inside of the element rather than from the surface of the element.

The biogas not having passed through the pretreatment apparatus 10 contains 50 to 90% of methane (CH ₄ ), 10 to 50% of carbon dioxide (CO ₂ ) and other less than 1% of water, hydrogen sulfide (H ₂ S), siloxane ). By removing contaminants through the pretreatment device 10, the purity of methane and carbon dioxide (in the form of calcium carbonate) separated thereafter can be increased, and the sulfur (S) component Can cause corrosion and odor of the device. Therefore, the durability of the device constituting the biogas whole-volume recycling system of the present invention can be improved by removing it.

Test Example - Evaluation of Separation Efficiency

The biogas recycling method including the first pressurization step and the second pressurization step according to the present invention was applied to the landfill site to perform the separation efficiency evaluation at the first separation step. The amount of CH ₄ and CO _{2 in} the landfill gas was about 56 ~ 57% and 43 ~ 44% after the removal of trace pollutants through the pretreatment step.

 As shown in Table 1 below, the components of methane and carbon dioxide separated in the first separation step were measured, and the suction pressure acting on the separation membrane device was measured by the second pressurization step. The stage-cut was calculated by dividing the flow rate of the separated methane-carbon dioxide mixture gas by the flow rate of the biogas supplied. The passing portion means a portion where a large amount of methane separated through the first separating step is obtained and the transmitting portion means a portion where the methane-carbon dioxide mixed gas separated through the first separating step is obtained.

Table 2 shows the separation efficiency of the biogas all-encompassing method including the first pressurization step and the second pressurization step according to the present invention as a performance test in which only the supply pressure of the first pressurization step is separated.

division stage-cut Permeate
pressure
(bar) Pass portion Transmission portion CH ₄ concentration
(%) CO ₂ concentration
(%) flux
(LPM) CH ₄ concentration
(%) CO ₂ concentration
(%) flux
(LPM) One 0.306 -0.27 74.9 25.1 10 21.6 78.4 4.4 2 0.350 -0.28 76.8 23.2 8 22.7 77.3 4.3 3 0.417 -0.29 79.6 20.4 6 23.7 76.3 4.3 4 0.512 -0.33 84.1 15.9 4 25.3 74.7 4.2 5 0.655 -0.35 92.2 7.8 2 31.6 68.4 3.8 6 0.688 -0.38 97 3.0 One 37.0 63.0 2.2

division stage-cut Pass portion Transmission portion CH ₄ concentration
(%) CO ₂ concentration
(%) flux
(LPM) CH ₄ concentration
(%) CO ₂ concentration
(%) flux
(LPM) One 0.160 69.8 30.2 10 27.0 73.0 2.5 2 0.190 71.5 28.5 8 27.3 72.7 2.5 3 0.238 73.6 26.4 6 28.0 72.0 2.4 4 0.317 77.3 22.7 4 30.3 69.7 2.3 5 0.513 84.7 15.3 2 35.0 65.0 1.9 6 0.714 90.1 9.9 One 38.0 62.0 1.8

As shown in Table 1, as the stage-cut increases, the higher the suction pressure, the higher the concentration of methane in the pass. However, it can be seen that the concentration of methane in the permeate portion also increases. This shows that the separation efficiency can be improved by re-separating the methane through the second separation step according to the present invention, when compared with Table 2.

The separation efficiency according to the stage-cut is shown in FIG. 2 in comparison with the biogas total recycling method including only the first pressurization step and the biogas recycling method including the first pressurization step and the second pressurization step.

Features, effects, devices, and the like according to the above-described embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Further, the steps, features, effects, devices, and the like illustrated in the embodiments may be combined or modified for other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

10: Pretreatment device
20: First pressurizing device
30: Membrane device
40: Second pressurizing device
50: Reactor
60: methane storage tank

Claims (10)

A first separation step of separating methane from biogas including methane and carbon dioxide using a separation membrane; And
And a second separation step of separating the methane from the methane-carbon dioxide mixed gas containing methane not separated in the first separation step by fixing the carbon dioxide using the carbon dioxide fixing reaction. The method according to claim 1,
Wherein the separation membrane in the first separation step is made of a material selected from the group consisting of polysulfone, polyimide, and polyisophthalon. The method according to claim 1,
Wherein the first separation step is controlled by controlling the flow rate of methane separated by adjusting the ratio of the flow rate of the methane-carbon dioxide gas mixture to the flow rate of the biogas. The method according to claim 1,
Carbon dioxide fixation reaction of the second separation stage is the methane-reacting calcium (CaO) and water (H ₂ O) oxidation to carbon dioxide gas mixture, or calcium hydroxide, calcium carbonate, the carbon dioxide by the reaction of _{(Ca (OH) 2) (} CaCO 3 ). ≪ / RTI > The method according to claim 1,
Wherein the second separation step is controlled in such a manner that the reaction is terminated when the pH of the product is 7. [ The method according to claim 1,
Further comprising a pretreatment step of removing substances other than methane and carbon dioxide in the biogas. The method according to claim 1,
A first pressurization step of pressurizing the biogas before the first separation step to increase the efficiency of the separation membrane apparatus; And
Further comprising a second pressurization step for pressurizing the methane-carbon dioxide gas mixture to increase the yield of the carbon dioxide fixation reaction prior to the second separation step. 8. The method of claim 7,
Wherein the pressurization pressure of the first pressurization step or the second pressurization step is 2 bar or less. The separation of methane from biogas including methane and carbon dioxide is carried out by using a membrane of material selected from the group consisting of polysulfone, polyimide and polyisophthalon, and the ratio of the methane-carbon dioxide gas mixture flow rate to the biogas flow rate is adjusted A separation membrane device controlled in such a manner as to control the flow rate of separated methane; And
The carbon dioxide is fixed from the methane-carbon dioxide mixed gas containing methane, which has not been separated in the first separation step, by using the carbon dioxide fixation reaction, and the reaction is terminated when the pH of the product reaches 7 Wherein the biogas is recovered from the biogas. 10. The method of claim 9,
A first pressurizing device that pressurizes the biogas to 2 bar or less in the previous stage of the separator device to increase the efficiency of the separator device; And
And a second pressurizing device for pressurizing the methane-carbon dioxide mixed gas to 2 bar or less in the previous step of the reaction device to increase the yield of the carbon dioxide fixing reaction.

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