Method and equipment for the co-production of high-concentration methane-containing biogas and carbonated concrete.

Abstract

The objective is to provide a co-production method and equipment that can simultaneously purify biogas containing high concentrations of methane gas and manufacture carbonated concrete. [Solution] A method and apparatus for the co-production of high-concentration methane-containing biogas and carbonated concrete, which involves contacting biogas with a concrete composition to fix carbon dioxide in the biogas to the concrete composition, thereby producing hardened carbonated concrete and purifying biogas containing methane.

Description

[Technical Field]

[0001] This invention relates to a method and equipment for the co-production of high-concentration methane-containing biogas and carbonated concrete. [Background technology]

[0002] From the perspective of wastewater treatment and the effective utilization of its resources, research is being conducted on technologies to effectively utilize biogas, mainly composed of methane (CH4), produced through methane fermentation using livestock waste from farms and pigpens, food waste from households, restaurants, hotels, and other establishments, food scraps from food processing plants, and agricultural residues as raw materials.

[0003] Biogas produced by methane fermentation consists mostly of methane and carbon dioxide. While the ratio varies depending on the type of raw materials and fermentation conditions, one example is approximately 60% methane and 40% carbon dioxide by volume. Increasing the methane concentration improves power generation efficiency and increases the amount of electricity produced; therefore, biogas purification is desirable. Furthermore, since biogas purification involves removing carbon dioxide, it reduces the amount of carbon dioxide released into the atmosphere. However, purifying biogas presents the problem of increased costs.

[0004] For example, Patent Document 1 below describes a method for treating methane fermentation gas, which involves contacting the methane fermentation gas with a calcium silicate-containing material to reduce the carbon dioxide concentration of the methane fermentation gas. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-127785 [Overview of the project] [Problems that the invention aims to solve]

[0006] The method for treating methane fermentation gas described in Patent Document 1 involves fixing CO2 in the methane fermentation gas using a calcium silicate-containing material, thereby reducing the carbon dioxide concentration in the methane fermentation gas, and using the calcium silicate-containing material with fixed CO2 as a raw material for cement clinker. Therefore, the use of carbon dioxide from biogas to harden concrete had not been considered.

[0007] This invention has been made in view of these circumstances, and aims to provide a co-production method and equipment that can simultaneously purify biogas containing high concentrations of methane gas and produce carbonated concrete. [Means for solving the problem]

[0008] The inventors of the present invention conducted intensive research to solve the above problems and found that the problems can be solved by contacting biogas with a concrete composition to remove CO2 gas from the biogas and produce a high-concentration methane-containing biogas, and by using the CO2 gas in the biogas to perform carbonation and produce carbonated concrete. This led to the present invention. In other words, the present invention is as follows. [1] A method for the co-production of high-concentration methane-containing biogas and carbonated concrete, comprising contacting biogas with a concrete composition to fix carbon dioxide in the biogas to the concrete composition, thereby producing hardened carbonated concrete and purifying methane-containing biogas. [2] The method for co-producing high-concentration methane-containing biogas and carbonated concrete according to [1], wherein the carbonated concrete is precast concrete. [3] A method for co-producing high-concentration methane-containing biogas and carbonated concrete according to [1] or [2], wherein the biogas and the concrete composition are brought into contact in an airtight state. [4] A method for co-producing high-concentration methane-containing biogas and carbonated concrete according to any one of [1] to [3], wherein the contact time between the biogas and the concrete composition is (1 / 10000) times or more and (1 / 10) times or less compared to the curing time of the concrete composition. [5] A co-production facility for high-concentration methane-containing biogas and carbonated concrete, comprising: a gas purification carbonate curing tank having a concrete composition inside, for contacting the concrete composition with biogas to produce carbonated concrete and purify the biogas; a gas supply means for supplying the biogas to the gas purification carbonate curing tank; a gas discharge means for discharging the biogas purified in the gas purification carbonate curing tank; and a transport means for transporting the carbonated concrete produced in the gas purification carbonate curing tank. [6] A co-production facility for high-concentration methane-containing biogas and carbonated concrete as described in [5], comprising a plurality of gas-purified carbonation curing tanks, wherein the gas supply means flows the biogas to the gas-purified carbonation curing tanks so that the progress of carbonation curing of the concrete compositions in the gas-purified carbonation curing tanks progresses from concrete compositions with a high degree of carbonation curing to concrete compositions with a low degree of carbonation curing. [7] The facility for the co-production of high-concentration methane-containing biogas and carbonated concrete as described in [5] or [6], further comprising a biogas generator for inputting biomass raw materials and causing methane fermentation to generate biogas. [8] A co-production facility for high-concentration methane-containing biogas and carbonated concrete according to any one of [5] to [7], wherein the carbonated concrete is precast concrete. [9] The gas purification and carbonation curing tank comprises an airtight member for preventing gas leakage from within the gas purification and carbonation curing tank, and is a co-production facility for high-concentration methane-containing biogas and carbonated concrete according to any one of [5] to [8].

[10] A co-production facility for high-concentration methane-containing biogas and carbonated concrete according to any one of [5] to [9], wherein the space time of the biogas in the gas purification and carbonation curing tank is (1 / 10000) times or more and (1 / 10) times or less than the curing time of the concrete composition. [Advantages of the Invention]

[0009] According to the present invention, it is possible to provide a co-production method and co-production equipment capable of simultaneously purifying biogas containing high-concentration methane gas and producing carbonated concrete. [Brief Description of the Drawings]

[0010] [Figure 1] It is a schematic diagram showing the co-production equipment of the first embodiment of the present invention. [Figure 2] It is a schematic diagram showing the carbonation curing tank of the co-production equipment of the second embodiment of the present invention. [Figure 3] It is a graph showing the results of the examples. [Figure 4] It is a graph showing the results of the examples. [Figure 5] It is a graph showing the results of the examples. [Figure 6] It is a graph showing the results of the examples. [Modes for Carrying Out the Invention]

[0011] Hereinafter, the co-production method and co-production equipment of high-concentration methane-containing biogas and carbonated concrete according to the present invention will be described in detail, but the present invention is not limited to the embodiments.

[0012] [Co-production Method of High-Concentration Methane-Containing Biogas and Carbonated Concrete] The co-production method of high-concentration methane-containing biogas and carbonated concrete according to the present invention (hereinafter simply referred to as "co-production method") involves bringing biogas into contact with a concrete composition to immobilize carbon dioxide in the biogas in the concrete composition, thereby producing carbonated concrete that has hardened and purifying biogas containing methane. First, the materials used in the co-production method of the present invention will be described.

[0013] [Biogas] The biogas used in the co-production method of the present invention can be, for example, biogas produced by methane fermentation of biomass raw materials such as sewage sludge, human waste sludge, septic tank sludge, food residue, treated sludge from factory wastewater generated from food factories, livestock manure, food waste, and / or plants. When biogas produced using these biomass raw materials is not subjected to concentration and / or purification treatment, it contains approximately 50-70% by volume of methane (CH4) and approximately 30-45% by volume of carbon dioxide (CO2).

[0014] (Concrete composition) The concrete composition used in the co-production method of the present invention is not particularly limited, and any general concrete composition can be used. For example, a cement composition containing cement and an admixture can be used. In this specification, "concrete" refers collectively to cement paste, cement mortar, and concrete.

[0015] ≪Cement≫ Examples of cements included in concrete compositions include various types of Portland cement such as ordinary, rapid-hardening, ultra-rapid-hardening, low-heat, and moderate-heat cements; various blended cements obtained by mixing these Portland cements with blast furnace slag, fly ash, or silica; filler cements obtained by mixing these Portland cements with limestone powder or finely powdered blast furnace slag; and environmentally friendly cements (eco-cements) manufactured using municipal solid waste incineration ash or sewage sludge incineration ash as raw materials. These cements can be used individually or in combination of two or more types.

[0016] Furthermore, it is preferable that the cement contains γ-2CaO·SiO2(γ-C2S) as a mineral component. The inclusion of γ-C2S can increase the amount of CO2 absorbed, thereby enabling efficient carbonation. The concentration of γ-C2S in the cement is preferably 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 30% by mass or less. Note that γ-C2S is not limited to being included in the cement, but may also be added to the concrete composition as an admixture as described later.

[0017] The cement content in the concrete composition used in the co-production method of the present invention is 200 kg / m³ from the viewpoint of maintaining a certain level of strength in the carbonated concrete. 3 More than 1000kg / m 3 Preferably containing the following amount: 220 kg / m³ 3 More than 800kg / m 3 It is more preferable to include the following:

[0018] ≪Water≫ The concrete composition used in the co-production method of the present invention is mixed with water, for example, in a pan-type concrete mixer. The amount of water typically used for mixing is preferably 20 to 150 parts by mass, more preferably 30 to 100 parts by mass, even more preferably 35 to 80 parts by mass, and still more preferably 40 to 60 parts by mass, per 100 parts by mass of the binder (total of cement and admixture), from the viewpoint of the workability of the concrete composition and increasing the porosity of the concrete composition to facilitate contact with CO2.

[0019] Aggregates The concrete composition used in the co-production method of the present invention may contain aggregates from the viewpoints of economy, increasing the porosity of the concrete composition to facilitate contact with CO2, and improving workability. Examples of aggregates include river sand, mountain sand, crushed stone, slag aggregate, and recycled aggregate. These aggregates can be used individually or in combination of two or more types.

[0020] The maximum particle size of the aggregate is preferably 50 mm or less, and more preferably 4 to 40 mm.

[0021] In the cement composition used in the co-production method of the present invention, the amount of aggregate used is preferably 80 to 1000 parts by mass per 100 parts by mass of total cement. If the amount of aggregate is 100 parts by mass or more, the porosity of the cement concrete can be increased, making it easier to come into contact with CO2 and improving workability. If the amount of aggregate is 1000 parts by mass or less, the strength of the carbonated concrete can be increased to a certain level or higher. From this viewpoint, the amount of aggregate used is more preferably 100 to 850 parts by mass, and even more preferably 200 to 650 parts by mass.

[0022] ≪Admixture≫ The concrete composition used in the co-production method of the present invention preferably contains admixtures. Admixtures are materials used in relatively large quantities among admixtures, and their own volume is included in the mixed volume of the concrete, etc. Admixtures are materials other than cement, water, and aggregate, and are added as needed before pouring to give concrete special properties. Examples of admixtures include blast furnace slag powder, fly ash, silica fume, rapid hardening agents, expansive agents, etc. By including admixtures in the concrete composition, CO2 emissions from raw materials can be reduced and the durability of carbonated concrete can be improved. In addition, by appropriately using rapid hardening agents, etc., demolding can be performed earlier, thereby increasing the production efficiency of carbonated concrete.

[0023] The admixture content in the concrete composition is not particularly limited, but from the viewpoint of maintaining the strength of the carbonated concrete above a certain level, it is preferably 3 to 1000 parts by mass, and more preferably 5 to 300 parts by mass, per 100 parts by mass of the total of cement and admixture.

[0024] Next, the method for co-producing high-concentration methane-containing biogas and carbonated concrete according to the present invention will be described. The co-production method of the present invention involves contacting biogas with a concrete composition and fixing the carbon dioxide in the biogas to the concrete composition, thereby producing hardened carbonated concrete and purifying methane-containing biogas. This process fixes carbon dioxide from the biogas into the concrete composition, allowing for the separation of carbon dioxide from the biogas and the purification of methane to a high concentration. Furthermore, by fixing carbon dioxide into the concrete composition, carbonated concrete can be produced. Specifically, it can be manufactured by the following method (process). The co-production method of the present invention includes at least the following step (D): a step (A) of mixing a concrete composition containing cement, aggregate, and admixture with water to produce fresh concrete; a step (B) of filling a formwork with the fresh concrete; a step (C) of curing the fresh concrete filled in the formwork and then removing the formwork to produce precast concrete; and a step (D) of carbonation curing by contacting the precast concrete with biogas.

[0025] (Process (A)) In process (A), fresh concrete is prepared by mixing a concrete composition containing cement, aggregate, and admixture with water. The mix design of the fresh concrete is preferably determined considering the molding and water curing methods, so that the fresh concrete satisfies the required quality after hardening.

[0026] (Process (B)) In step (B), fresh concrete is filled into formwork or molded into a desired shape using 3D printing or spraying. When formwork is used, it is preferable that it has a robust structure, can obtain the required shape and dimensions of the concrete, and is easy to assemble and remove. Wooden formwork may be used if the number of forms is small, but steel formwork is preferred. In step (B), after filling the formwork with fresh concrete, mechanical compaction may be performed. Examples of mechanical compaction include vibration compaction, vibration and pressure compaction, vacuum compaction, and compaction using a combination of these.

[0027] (Process (C)) In process (C), if the formwork is filled, the fresh concrete filled in the formwork is water-cured, and then the formwork is removed to produce precast concrete. The method and duration of water-curing of the fresh concrete filled in the formwork are preferably determined to obtain the required quality. It is preferable to water-cur the fresh concrete filled in the formwork thoroughly, taking care not to expose it to harmful effects such as low temperature, drying, rapid temperature changes, loads, and impacts. The method of water-curing is not particularly limited, but steam curing is preferable from the viewpoint of improving initial strength development and increasing productivity. Steam curing generally involves sending steam generated by a boiler through pipes to a steam curing room, and heating and humidifying the fresh concrete in the formwork under atmospheric pressure to accelerate strength development. The steam curing conditions are not particularly limited, but it is preferable to ensure a predetermined pre-setting time, set the heating rate to 1 to 20°C / hr, apply steam, set the maximum temperature to be in the range of 20 to 60°C, and hold the maximum temperature for 1 to 24 hours. When each condition is within the above range, the initial strength development by steam curing is improved, increasing productivity and resulting in a hardened body with the desired characteristics. After maintaining the maximum temperature reached, it is preferable to gradually lower the temperature in the curing room to prevent cracking in the hydrated hardened body. It is preferable to set the cooling time so that the precast concrete can be removed after the temperature difference with the outside air has become small. Furthermore, wet curing may be performed after steam curing to further improve the quality of the carbonated concrete. Demolding is preferably performed after the strength of the precast concrete has reached a strength that does not hinder handling. The hydrated hardened precast concrete removed from the formwork must be handled in a way that does not impair its shape and dimensions.

[0028] (Process (D)) Process (D) involves producing carbonated concrete by bringing precast concrete into contact with biogas for carbonation curing. Carbonation curing involves sending biogas into a carbonation curing room and heating and humidifying the precast concrete in a biogas atmosphere to carbonize it. The carbonation of precast concrete proceeds as the biogas diffuses into the voids within the precast concrete, carbonating the cement hydrate. Carbonation curing is preferably carried out in biogas (carbon dioxide concentration of approximately 40% by volume) at a temperature of 20-80°C and a humidity of 30-100% RH, over a period of 1 hour to 2 weeks, depending on the size of the precast concrete. In process (D), the CO2 in the biogas is fixed to the precast concrete, reducing the amount of CO2 in the biogas. Therefore, the methane concentration in the biogas can be relatively increased, making it possible to purify a high-concentration methane-containing gas.

[0029] It is preferable to carry out the contact between biogas and precast concrete in an airtight state within a carbonation curing chamber. It is preferable to carry out the carbonation curing in the carbonation curing chamber under normal pressure or under a pressurized state of 10 MPa or less. By carrying out the process in an airtight state, it is possible to bring the biogas and precast concrete into contact without biogas leaking from the curing tank, thereby facilitating the production of carbonated concrete. Furthermore, since biogas leakage is prevented, the yield of high-concentration methane-containing biogas can also be increased. Furthermore, an airtight state means that the amount of biogas leaking from the carbonation curing tank, which brings the biogas into contact with the concrete composition, is within 5% of the biogas supply amount. This can be determined from the gas volume at the inlet and outlet of the carbonation curing tank, and the concentration of methane gas. In addition, since the flammability range of methane is 5.0% to 15%, if the amount of biogas leaking from the carbonation curing tank is within 5%, the methane concentration in the atmosphere can be kept below the above-mentioned methane flammability range, allowing for safe work.

[0030] Furthermore, the contact time between biogas and precast concrete is preferably (1 / 10000) times or more and (1 / 10) times or less than the curing time of the precast concrete. When the concrete composition consists only of CaO and is cured by carbonation, the difference in volume between solid and gas per unit amount of substance is greatest. Comparing the volume per mole, CaO is (56 g / mol) / (3.34 g / cm³). 3 ) = 17cm 3 The volume is / mol. 40 vol% CO2 is 22.4 L / mol / 0.4 = 56 L / mol. Therefore, CaO and 40 vol% CO2 differ in volume by approximately 3300 times. In other words, when CaO is considered as 1, carbonation curing can be completed by contacting it with 3300 times the volume of biogas. Therefore, carbonation can be efficiently carried out by setting the biogas contact time to (1 / 3300) relative to the curing time. On the other hand, if 10 vol% of the concrete composition is cement, and 10 vol% of that is γ-C2S, then 1 vol% of the concrete composition is γ-C2S, and of the γ-C2S formula weight of 172, 112 is CaO. If the density of the concrete composition is 2.4, the above ratio becomes 3300 × 0.01 × 112 / 172 × 2.4 / 3.34 = 15. In other words, if 10% by volume of the concrete composition is cement, and 10% by volume of that is γ-C2S, then carbonation curing can be completed by contacting it with approximately 15 times the volume of biogas. Therefore, carbonation can be efficiently performed by setting the biogas contact time to (1 / 15) of the curing time. Since the curing time for carbonation curing varies depending on the CO2 concentration and the composition of the concrete composition, it is preferable that the contact time between biogas and precast concrete be between (1 / 10000) times and (1 / 10) times the curing time of the precast concrete. By setting the contact time within the above range, CO2 in the biogas can be efficiently brought into contact with the precast concrete, and the separation of CO2 from the biogas can be effectively achieved. The contact time between biogas and precast concrete is (volume of the carbonation curing tank [m³] 3 ] / Volumetric flow rate of biogas under standard conditions [m³ 3It can be defined by the spatial time obtained using [ / min]. The contact time between biogas and precast concrete can be adjusted by controlling the volumetric flow rate of biogas supplied to the carbonation curing tank and the valves on the discharge side.

[0031] The above describes a method in which precast concrete is produced by steam curing, etc., and then subjected to carbonation curing, but it is not limited to this. For example, step (C) may be omitted, and after filling the formwork with fresh concrete in step (B), carbonation curing in step (D) may be performed on the fresh concrete. Similarly, if the concrete is formed by 3D printing, carbonation curing in step (D) can be performed immediately.

[0032] According to the present invention's method for the co-production of high-concentration methane-containing biogas and carbonated concrete, by fixing the carbon dioxide in the biogas into the concrete composition, it is possible to purify biogas containing a high concentration of methane gas and produce carbonated concrete simultaneously. Furthermore, conventional methods involve costs associated with purifying biogas, and obtaining carbon dioxide for the production of carbonated concrete also incurs costs. The co-production method of the present invention reduces the costs of purifying biogas and obtaining carbon dioxide by using carbon dioxide from biogas. Additionally, increasing the methane concentration improves power generation efficiency, increasing the amount of electricity generated while simultaneously reducing carbon dioxide emissions.

[0033] [Facility for the co-production of high-concentration methane-containing biogas and carbonated concrete] Next, the co-production equipment for high-concentration methane-containing biogas and carbonated concrete of the present invention (hereinafter simply referred to as the "co-production equipment") will be described. The co-production equipment of the present invention comprises a gas purification and carbonation curing tank having a concrete composition inside, for contacting the concrete composition with biogas to produce carbonated concrete and purify the biogas, a gas supply means for supplying the biogas to the gas purification and carbonation curing tank, a gas discharge means for discharging the biogas purified in the gas purification and carbonation curing tank, and a conveying means for conveying the carbonated concrete produced in the gas purification and carbonation curing tank.

[0034] (First Embodiment) Figure 1 is a schematic diagram showing a co-production facility according to a first embodiment of the present invention. The co-production facility 10 of the first embodiment includes a gas purification carbonation curing tank 12 for manufacturing carbonated concrete and purifying biogas. Precast concrete 14 is provided as the concrete composition inside the gas purification carbonation curing tank 12, and carbonation curing is carried out by biogas supplied into the gas purification carbonation curing tank 12. Furthermore, the biogas supplied to the gas purification and carbonation curing tank 12 has its CO2 content reduced as it is used for the carbonation curing of the concrete. This reduces the CO2 concentration in the biogas, relatively increasing the methane concentration, thus allowing for the production of high-concentration methane-containing biogas.

[0035] The gas purification and carbonation curing tank 12 is equipped with a gas supply means 16 for supplying biogas to the gas purification and carbonation curing tank 12. The gas supply means 16 may include a supply pipe, a valve (not shown), a pump (not shown), etc. The gas purification and carbonation curing tank 12 is also equipped with a gas outlet 18 for discharging the purified biogas (high-concentration methane-containing biogas). The gas outlet 18 may include a discharge pipe, a valve (not shown), a pump (not shown), etc.

[0036] Contact between biogas and precast concrete 14 within the gas purification and carbonation curing tank 12 can be achieved by circulating biogas within the gas purification and carbonation curing tank 12.

[0037] In order to efficiently perform carbonation curing in the gas purification carbonation curing tank 12 and increase the yield of high-concentration methane-containing biogas, it is preferable to perform the process in an airtight state. The airtight state of the gas purification carbonation curing tank 12 means that the amount of biogas leaking from the gas purification carbonation curing tank 12 is within 5% of the supply amount. By having an airtight member that prevents the leakage of gas in the gas purification carbonation curing tank 12, an airtight state can be achieved. Examples of the airtight member include a seal member made of an elastic body provided at the connection part of the gas purification carbonation curing tank 12, such as a gasket (packing), an O-ring, an adhesive, a filler for preventing the leakage of biogas from the gas purification carbonation curing tank, and the like.

[0038] Also, it is preferable that the space time of biogas in the gas purification carbonation curing tank 12 is within the range of (1 / 10000) times or more and (1 / 10) times or less the curing time of the precast concrete 14. By setting the space time of biogas within the above range, CO2 in the biogas can be efficiently brought into contact with the precast concrete 14, and the separation of CO2 in the biogas can be effectively performed. The space time of biogas can be obtained by (the volume of the carbonation curing tank [m 3 / the volumetric flow rate of biogas in the standard state [m 3 / min]).

[0039] Moreover, the co-production facility 10 of this embodiment preferably includes a biogas generator 20. The biogas generator 20 is a device that inputs biomass raw materials and performs methane fermentation to generate biogas. The biogas generator 20 is configured to input biomass raw materials such as, for example, sewage sludge, night soil sludge, septic tank sludge, food residues, treated sludge from industrial wastewater generated from food factories, livestock manure, food waste, and / or grass and trees, and perform methane fermentation on these biomass raw materials to generate biogas.

[0040] The biogas supplied to the gas purification and carbonation curing tank 12 can be supplied by the gas supply means 16 using biogas generated by the biogas generator 20. Alternatively, as shown in Figure 1, the biogas may be supplied by connecting the biogas generator 20 and the gas supply means 16, and directly supplying the biogas generated by the biogas generator 20 to the gas purification, carbonation, and curing tank 12. Alternatively, the biogas produced by the biogas generator 20 may be filled into a container such as a cylinder, and the cylinder may be connected to the gas supply means 16 to supply the biogas to the gas purification, carbonation, and curing tank 12.

[0041] The carbonated concrete produced by carbonation curing in the gas-purified carbonation curing tank 12 is transported outside the gas-purified carbonation curing tank 12 by the transport means 24. The transport means 24 can be a manually operated means such as a forklift or trolley, or an automatically operated means such as a belt conveyor.

[0042] The biogas that has passed through the gas purification and carbonation curing tank 12 is discharged through the gas outlet 18 and discharged through the discharge pipe to fill the biogas storage tank 22. Within the gas purification and carbonation curing tank 12, the CO2 in the biogas is used for the carbonation curing of precast concrete, thus fixing the CO2 in the biogas and increasing the methane concentration, resulting in high-concentration methane-containing biogas. The high-concentration methane-containing biogas purified in the gas purification and carbonation curing tank 12 is then filled into the biogas storage tank 22 and can be used as a raw material for heat and electrical energy.

[0043] In addition, a conventional steam curing section (not shown) may be provided separately from the gas-purified carbonation curing tank 12. Precast concrete 14 can be precast concrete that has been steam-cured in this curing section. Furthermore, the concrete composition provided in the gas-purified carbonation curing tank 12 is not limited to precast concrete. Fresh concrete of the concrete composition may be prepared, and this fresh concrete may be filled into a formwork and placed in the gas-purified carbonation curing tank 12 for carbonation curing.

[0044] (Second Embodiment) Figure 2 is a schematic diagram showing a gas purification carbonation curing tank of a co-production facility according to a second embodiment of the present invention. The co-production facility of the second embodiment is equipped with a plurality of gas purification carbonation curing tanks, and biogas is supplied to the gas purification carbonation curing tanks by a gas supply means so that the concrete composition in the gas purification carbonation curing tank progresses from concrete composition with a high degree of carbonation curing to concrete composition with a low degree of carbonation curing.

[0045] The co-production equipment 110 of the second embodiment includes a first gas purification carbonation curing tank 112a, a second gas purification carbonation curing tank 112b, a third gas purification carbonation curing tank 112c, and a fourth gas purification carbonation curing tank 112d for manufacturing carbonated concrete and purifying biogas (hereinafter collectively referred to as "gas purification carbonation curing tanks 112a, 112b, 112c, and 112d"). It also includes biogas supply ports 114a, 114b, 114c, and 114d for supplying biogas to each of the gas purification carbonation curing tanks 112a, 112b, 112c, and 112d, and biogas discharge ports 116a, 116b, 116c, and 116d for discharging biogas. Furthermore, a gas flow section 118 for circulating biogas is provided between the first gas purification carbonation curing tank 112a and the second gas purification carbonation curing tank 112b, between the second gas purification carbonation curing tank 112b and the third gas purification carbonation curing tank 112c, between the third gas purification carbonation curing tank 112c and the fourth gas purification carbonation curing tank 112d, and between the fourth gas purification carbonation curing tank 112d and the first gas purification carbonation curing tank 112a. The gas flow section 118 is partially shared with the biogas supply ports 114a, 114b, 114c, 114d and the biogas outlet ports 116a, 116b, 116c, 116d, and is provided by branching using a valve 126.

[0046] Furthermore, each of the biogas supply ports 114a, 114b, 114c, and 114d is connected to the gas supply means 16 shown in Figure 1, and each of the biogas outlets 116a, 116b, 116c, and 116d is connected to the gas outlet 18. In addition, each of the biogas supply ports 114a, 114b, 114c, and 114d, and each of the biogas outlets 116a, 116b, 116c, and 116d are provided with a valve 126 that allows the carbonation curing tank to be changed to supply CO2-containing gas and the carbonation curing tank to discharge the gas. This makes it possible to change the position of the gas purification carbonation curing tank that supplies biogas and the position of the gas purification carbonation curing tank that discharges biogas, thereby changing the biogas distribution route. In Figure 2(a), biogas is supplied from biogas supply port 114a and biogas is discharged from biogas outlet 116d.

[0047] Furthermore, each of the gas purification carbonation curing tanks 112a, 112b, 112c, and 112d is equipped with precast concrete (hereinafter also simply referred to as "concrete") 122a, 122b, 122c, and 122d with different degrees of carbonation curing. Within each gas purification carbonation curing tank 112a, 112b, 112c, and 112d, the precast concrete is arranged so that it progresses from the precast concrete 122a with a high degree of carbonation curing to the precast concrete 122d with a low degree of carbonation curing, along the biogas flow path. For example, in Figure 2(a), biogas is supplied from the biogas supply port 114a of the first gas purification carbonation curing tank 112a, and biogas is discharged from the biogas discharge port 116d of the fourth gas purification carbonation curing tank 112d. At this time, the valve 126 is controlled so that biogas flows through the gas flow section 118 from the first gas purification carbonation curing tank 112a to the second gas purification carbonation curing tank 112b, from the second gas purification carbonation curing tank 112b to the third gas purification carbonation curing tank 112c, and from the third gas purification carbonation curing tank 112c to the fourth gas purification carbonation curing tank 112d. As a result, the biogas flow path becomes a flow path from the first gas purification carbonation curing tank 112a to the fourth gas purification carbonation curing tank 112d. In the precast concrete, the first gas-purified carbonation curing tank 112a contains the concrete 122a with the highest degree of carbonation curing, followed by the second gas-purified carbonation curing tank 112b containing concrete 122b with a moderately high degree of carbonation curing, the third gas-purified carbonation curing tank 112c containing concrete 122b with a moderately low degree of carbonation curing, and the fourth gas-purified carbonation curing tank 112d containing concrete 122d with a low degree of carbonation curing.

[0048] By arranging the precast concretes 122a, 122b, 122c, and 122d in this manner, the concrete 122a, which has a high degree of carbonation curing, can be reacted with biogas with a high CO2 concentration. This allows for further carbonation curing of precast concrete whose reaction has slowed down as carbonation curing progresses. Furthermore, the gas supplied from the first gas-purified carbonation curing tank 112a to the second gas-purified carbonation curing tank 112b through the gas flow section 118 does not consume much CO2 in the first gas-purified carbonation curing tank 112a because carbonation does not progress easily within that tank. As a result, biogas with a relatively high CO2 concentration is supplied. Therefore, it is possible to cure the concrete 122b in the second gas-purified carbonation curing tank 112b, which has already undergone a certain degree of carbonation curing. Furthermore, the gas supplied from the second gas-purified carbonation curing tank 112b to the third gas-purified carbonation curing tank 112c via the gas flow section 118 is biogas with a relatively low CO2 concentration because carbonation curing is being carried out in the second gas-purified carbonation curing tank 112b, thus consuming CO2 gas. However, the concrete 122c provided in the third gas-purified carbonation curing tank 112c is concrete with a relatively low degree of carbonation curing progress, and is more easily carbonized than the concrete 122a and 122b provided in the first gas-purified carbonation curing tank 112a and the second gas-purified carbonation curing tank 112b, respectively. Therefore, carbonation curing can be carried out even with biogas with a low CO2 concentration. Similarly, with respect to the fourth gas-purified carbonation curing tank 112d, the gas supplied from the third gas-purified carbonation curing tank 112c through the gas flow section 118 to the fourth gas-purified carbonation curing tank 112d is biogas with a low CO2 concentration, as CO2 gas is consumed in the third gas-purified carbonation curing tank 112c. However, the precast concrete 122d provided in the fourth gas-purified carbonation curing tank 112d is concrete with a low degree of carbonation curing progress, and is more easily carbonized than the precast concrete provided in the first gas-purified carbonation curing tank 112a, the second gas-purified carbonation curing tank 112b, and the third gas-purified carbonation curing tank 112c, so carbonation curing can be advanced even with biogas with a low CO2 concentration.

[0049] In this way, by supplying biogas along the biogas distribution path from concrete 122a with a high degree of carbonation curing to concrete 122d with a low degree of carbonation curing, high-CO2-concentration biogas is brought into contact with concrete 122a with a high degree of carbonation curing, thereby promoting carbonation curing even for concrete that is difficult to cure. Furthermore, while low-CO2-concentration biogas comes into contact with concrete 122d with a low degree of carbonation curing after passing through the gas purification carbonation curing tank, carbonation curing can still be promoted even when exposed to low-CO2-concentration biogas because the carbonation curing process is slow. Therefore, the CO2 gas in the biogas can be used effectively, improving reaction efficiency. In addition, since the CO2 concentration of the emitted biogas can be reduced, the methane concentration can be increased, and high-concentration methane-containing biogas can be produced.

[0050] Once the carbonation curing in the first gas-purified carbonation curing tank 112a is complete, the carbonated concrete 122a is removed from the first gas-purified carbonation curing tank 112a, as shown in Figure 2(b). After removing the carbonated concrete 122a from the first gas-purified carbonation curing tank 112a, precast concrete 122e that has not yet undergone carbonation curing is placed in the first gas-purified carbonation curing tank 112a. By placing the precast concrete in this manner, the precast concrete in the gas-purified carbonation curing tanks is arranged so that the degree of carbonation curing progresses in the following order: second gas-purified carbonation curing tank 112b, third gas-purified carbonation curing tank 112c, fourth gas-purified carbonation curing tank 112d, and first gas-purified carbonation curing tank 112a.

[0051] Then, the biogas supply is changed from the distribution path in Figure 2(a) to the biogas supply side, with the valve 126 of the biogas supply port 114b provided in the second gas purification carbonation curing tank 112b being switched to the biogas supply side, and the valve 126 of the biogas discharge port 116a provided in the first gas purification carbonation curing tank 112a being switched to the discharge side, so that gas containing CO2 does not flow through the gas distribution section 118 between the first gas purification carbonation curing tank 112a and the second gas purification carbonation curing tank 112b. Then, the valve 126 is controlled so that gas passes through the gas distribution section 118 between the fourth gas purification carbonation curing tank 112d and the first gas purification carbonation curing tank 112a. As a result, the biogas distribution route becomes the second gas purification carbonation curing tank 112b, the third gas purification carbonation curing tank 112c, the fourth gas purification carbonation curing tank 112d, and the first gas purification carbonation curing tank 112a, so that the carbonation curing progresses from the precast concrete 122b, which is at a higher stage, to the precast concrete 122e, which is at a lower stage.

[0052] Subsequently, after removing the carbonated concrete that has completed its carbonation curing, and installing precast concrete that has not yet undergone carbonation curing, the biogas flow path is changed so that the precast concrete with a high degree of carbonation curing progresses first, and the concrete with a low degree of carbonation curing progresses second. This allows the CO2 gas in the biogas to be efficiently used for carbonation curing, and enables the production of high-concentration methane-containing biogas with a high methane concentration. [Examples]

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Example 1] Assuming biogas production, a methane-carbon dioxide mixed gas was prepared to have a carbon dioxide concentration of 40% by volume and a methane concentration of 60% by volume. The concrete composition was prepared by mixing 100 parts by mass of cement with 300 parts by mass of sand and 50 parts by mass of water. (Materials used) Cement: Research-grade ordinary Portland cement (manufactured by the Cement Association) Sand: ISO Cement Standard Sand (manufactured by the Cement Association) Water: Tap water The prepared concrete composition was poured into a 4 x 4 x 16 cm formwork, cured in the formwork for 24 hours at a temperature of 20 degrees Celsius and a humidity of 80%, and then removed to produce a test sample simulating precast concrete. Concrete compositions were cured by carbonation using a prepared methane-carbon dioxide gas mixture. Carbonation curing was performed at a temperature of 50 degrees Celsius using a single curing tank. The methane-carbon dioxide gas mixture was supplied at a flow rate of 200 cm³ under standard conditions. 3 / min, volume of gas purification carbonation curing tank: 100 cm³ 3 The space time for the methane-carbon dioxide mixed gas was 0.5 min. The carbonation curing time was set to 180 min, and the conditions were set so that the space time for the mixed gas in the carbonation curing tank was 1 / 360 of the curing time of the concrete composition. The CH4 and CO2 concentrations of biogas discharged from the gas-purified carbonation curing tank, as well as the compressive strength of the produced carbonated concrete, were measured. Compressive strength was measured in accordance with the method specified in JIS R 5201;2015 "Physical Testing Methods for Cement". Compressive strength was measured 7 or 8 days after the completion of carbonation curing.

[0054] Table 1 shows the CH4 concentration (CH4 gas concentration at the curing tank outlet), CO2 concentration (CO2 gas concentration at the curing tank outlet), and compressive strength discharged from the gas purification carbonation curing tank after 1 minute, 10 minutes, and 180 minutes of curing time.

[0055] Figure 3 is a graph showing the changes in the concentrations of CO2 gas, CH4 gas, and water vapor at the curing tank outlet with respect to curing time. As shown in Figure 3, the outlet gas from the curing tank at 50°C contains a high concentration of water vapor, but as the temperature returns to room temperature, the water vapor pressure decreases and the water is removed, so the composition of the dry gas becomes important.

[0056] Figure 4 is a graph showing the change in the curing tank outlet gas composition, excluding water vapor, with respect to curing time. As shown in Figure 4, the curing tank outlet gas composition, excluding water vapor, showed that the CO2 gas concentration at the curing tank outlet was 4 vol% at 1 minute, 31 vol% at 10 minutes, and 39 vol% at 180 minutes, while the CH4 gas concentration at the curing tank outlet was 96 vol% at 1 minute, 69 vol% at 10 minutes, and 61 vol% at 180 minutes. It can be seen that the reactivity of the concrete composition is high in the initial stages of curing, allowing for effective absorption of CO2 and concentration of CH4. On the other hand, it can also be seen that the reactivity of the concrete composition decreases with curing time, and the degree of CO2 absorption and CH4 concentration also decreases. Furthermore, the compressive strength of the concrete composition before carbonation was 22 N / mm². 2 However, as shown in Table 1, the compressive strength of carbonated concrete after carbonation is 43 N / mm². 2 The strength increased.

[0057] Figure 5 is a graph showing the change in the cumulative concentration of CO2 and CH4, excluding water vapor, from the total amount of gas recovered at the curing tank outlet, and Figure 6 is a graph showing the change in the mass [g] of CO2 fixed in 1 kg of concrete composition with respect to the carbonation curing time. When the carbonation curing time was 180 min, the space time of the mixed gas in the carbonation curing tank was 1 / 360 of the curing time of the concrete composition, the mass of CO2 fixed in 1 kg of concrete composition was 26.4 g, and the cumulative concentration of CH4 was 61 volume%. When curing was stopped at 10 min, the space time of the mixed gas in the carbonation curing tank was 1 / 20 of the curing time of the concrete composition, at which point the mass of CO2 fixed in 1 kg of concrete composition was 6.2 g, and the cumulative concentration of CH4 was 69 volume%. It is preferable to set the space time of the mixed gas in the carbonation curing tank to be between 1 / 10000 and 1 / 10 of the curing time of the concrete composition. However, shortening the curing time increases the cumulative concentration of CH4 but decreases the amount of CO2 fixed to the concrete composition, while lengthening the curing time increases the amount of CO2 fixed to the concrete composition but decreases the cumulative concentration of CH4. In other words, shortening the space time of the mixed gas in the carbonation curing tank increases the amount of CO2 fixed to the concrete composition but decreases the cumulative concentration of CH4, while lengthening the space time increases the cumulative concentration of CH4 but decreases the amount of CO2 fixed to the concrete composition. Therefore, it is preferable to select the optimal curing time and space time considering the amount of CO2 fixed and compressive strength of the concrete composition and the cumulative concentration of CH4. Furthermore, as shown in Figure 2, by connecting multiple curing tanks and maintaining a state where concrete compositions requiring longer curing times are placed on the upstream side and concrete compositions requiring shorter curing times are placed on the downstream side, it is possible to effectively absorb CO2 and continuously concentrate CH4, and since the curing time of the concrete compositions can also be extended, the amount of CO2 fixed can also be increased.

[0058] [Reference example 1] To confirm the effect of methane, carbonation curing was performed in the same manner as in Example 1, except that the gas mixture used for carbonation curing was adjusted to a concentration of 40% by volume of carbon dioxide and 60% by volume of nitrogen. The results are shown in Table 1. There was no significant difference between the CO2 gas concentration at the curing tank outlet and the compressive strength corresponding to the carbonation curing time, confirming that there was no difference due to methane and nitrogen.

[0059] [Reference example 2] To confirm the effect of high carbon dioxide concentrations, carbonation curing was performed in the same manner as in Example 1, except that the gas mixture was adjusted to have a carbon dioxide concentration of 20 vol% and a nitrogen concentration of 80 vol%. The results are shown in Table 1. Carbonated concrete cured with a CO2 gas concentration of 40 vol% showed higher compressive strength after 180 minutes of carbonation curing. This indicates that biogas is suitable as a gas to be used for carbonation curing due to its high CO2 gas concentration.

[0060] [Table 1] [Industrial applicability]

[0061] The high-concentration methane-containing biogas obtained by this invention can be used in the energy sector to generate electricity or as fuel. Furthermore, carbonated concrete can be suitably used in the civil engineering and construction fields, among others. [Explanation of Symbols]

[0062] 10, 110 Co-production facility for high-concentration methane-containing biogas and carbonated concrete 12 Gas purification carbonation curing tank 14 Precast concrete 16 Gas supply means 18 Gas outlet 20 Biogas generator 22 Biogas storage tanks 24 Conveying means 112a First gas purification carbonation curing tank 112b Second gas purification carbonation curing tank 112c Third gas purification carbonation curing tank 112d Fourth gas purification carbonation curing tank 114a, 114b, 114c, 114d Biogas supply port 116a, 116b, 116c, 116d Biogas outlets 118 Gas Distribution Department 122a, 122b, 122c, 122d, 122e Precast concrete (carbonated concrete) 126 valves

Claims

1. This process involves contacting a concrete composition with biogas to fix the carbon dioxide in the biogas into the concrete composition, thereby producing hardened carbonated concrete and purifying biogas containing methane. A method for the co-production of high-concentration methane-containing biogas and carbonated concrete.

2. The method for co-producing high-concentration methane-containing biogas and carbonated concrete according to claim 1, wherein the carbonated concrete is precast concrete.

3. The method for co-producing high-concentration methane-containing biogas and carbonated concrete according to claim 1 or 2, wherein the contact between the biogas and the concrete composition is carried out in an airtight state.

4. The method for co-producing high-concentration methane-containing biogas and carbonated concrete according to claim 1 or 2, wherein the contact time between the biogas and the concrete composition is (1 / 10000) times or more and (1 / 10) times or less compared to the curing time of the concrete composition.

5. A gas purification and carbonation curing tank having a concrete composition inside, for contacting the concrete composition with biogas to produce carbonated concrete and purify the biogas, A gas supply means for supplying the biogas to the gas purification carbonation curing tank, A gas discharge means for discharging the biogas purified in the gas purification carbonation curing tank, The system includes a conveying means for conveying the carbonated concrete produced in the gas-purified carbonated curing tank. A facility for the co-production of high-concentration methane-containing biogas and carbonated concrete.

6. The aforementioned gas purification carbonation curing tanks are provided in multiple locations. The co-production apparatus for high-concentration methane-containing biogas and carbonated concrete according to claim 5, wherein the gas supply means circulates the biogas to the gas-purified carbonated curing tank so that the degree of carbonation curing of the concrete composition in the gas-purified carbonated curing tank progresses from a concrete composition with a high degree of carbonation curing to a concrete composition with a low degree of carbonation curing.

7. Furthermore, the co-production facility for high-concentration methane-containing biogas and carbonated concrete according to claim 5 or 6, further comprising a biogas generator for inputting biomass raw materials and performing methane fermentation to generate biogas.

8. The co-production facility for high-concentration methane-containing biogas and carbonated concrete according to claim 5 or 6, wherein the carbonated concrete is precast concrete.

9. The gas purification and carbonation curing tank has an airtight member to prevent gas leakage from within the gas purification and carbonation curing tank, as described in claim 5 or 6, for the co-production equipment of high-concentration methane-containing biogas and carbonated concrete.

10. The co-production apparatus for high-concentration methane-containing biogas and carbonated concrete according to claim 5 or 6, wherein the space time of the biogas in the gas purification and carbonation curing tank is (1 / 10000) times or more and (1 / 10) times or less than the curing time of the concrete composition.

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