JP3935197B2 - Method and apparatus for removing carbon dioxide using biomass - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for removing carbon dioxide using biomass, and more particularly, to a method and apparatus for removing carbon dioxide in the atmosphere or water as solid carbon through biomass.
[0002]
[Prior art]
Carbon dioxide (CO) that causes global warming₂) And other greenhouse gases have been increasing in atmospheric concentration with increasing fossil fuel consumption since the Industrial Revolution. If the current economic growth continues without limiting emissions, CO in the atmosphere₂Concentrations are currently around 360 ppm, but are expected to be 450 ppm in 2030 and 700 ppm in 2100. CO in the atmosphere₂When the concentration reaches 700 ppm, the average global temperature rises by about 2 ° C (1-3.5 ° C), abnormal weather occurs, ecosystem disruption and food production changes, land decline due to sea level rise (land land decline) And so on. For this reason, atmospheric CO₂For the purpose of reducing the concentration, CO₂CO emissions in the atmosphere along with emission control₂Removal is required.
[0003]
Traditionally, CO₂As elemental technologies related to the removal of water, membrane separation from the air using polymer membranes and ceramic membranes, adsorption / recovery methods such as PSA (Pressure Swing Adsorption), methods of storing in the deep sea and underground, and absorption in organic solvents There have been proposed physical and chemical methods such as a method and a method of reducing and fixing to methanol, solid carbon or the like with a catalyst.
[0004]
Figure 6 shows natural gas (methane, CH_Four) CO with reducing agent₂1 schematically shows a reduction and fixation system for solid carbon. In the figure, in the first stage reactor 26, CH_FourCatalyst (Ni / SiO₂The catalyst) decomposes into solid carbon and hydrogen (endothermic reaction), and the hydrogen and CO₂In a two-stage reactor 27_FourConverted into water and water vapor (exothermic reaction), this CH_FourCH is replenished from the outside after being separated from water in the condenser 28_FourAt the same time, it is returned to the first-stage reactor 26 and reused as a reducing agent. After all, the net reaction in FIG._Four+ CO₂→ 2C + 2H₂O (Equation (3) below).
[0005]
In addition, as shown in FIG. 7, JP-A-2000-271472 discloses CH generated by anaerobic treatment of organic waste._FourCO using₂A fixing device is proposed. Conventional physical and chemical CO₂The removal method is mainly high concentration CO in the source.₂In the atmosphere, but CO in the atmosphere₂Concentration is extremely dilute, about 360ppm, and dilute CO₂It is necessary to use the photosynthetic action of living organisms in order to efficiently remove water. The apparatus in FIG. 7A has been proposed from such a viewpoint.
[0006]
The device shown in FIG.₂And biogas generated in the organic waste disposal unit 31 (CH_FourAnd CO₂Are mixed in a gas mixing / condenser 32, and a reaction is performed in the reaction tank 34 using a catalyst to produce the following equations (1) and (2) to produce solid carbon and water. The net reaction in this case is expressed by the following equation (3) as in the case of FIG. CO in equation (2)₂Although the conversion rate of carbon to solid carbon is not high, as shown in FIG.₂In the gas mixing / condenser 32 by circulating the gas into the reaction tank 34.₂All into solid carbon and water. The device is used for CH in biogas._FourAnd CO₂And CO in the atmosphere₂As solid carbon and CO₂CO2 in the atmosphere by suppressing emissions to the outside₂The aim is to improve the removal rate.
[0007]
[Chemical 1]
CH_Four→ C + 2H₂   …………………………………………………… (1)
CO₂+ 2H₂→ C + 2H₂O ………………………………………… (2)
CH_Four+ CO₂→ 2C + 2H₂O …………………………………………… (3)
[0008]
[Problems to be solved by the invention]
However, the CO mentioned above₂All of these fixed removal systems are CO₂There is a problem that energy must be supplied from the outside for removal. The net reaction (Equation (3)) in FIGS. 6 and 7 is an exothermic reaction with a small reaction heat. For example, in the system of FIG. 6, the heat recovery from the two-stage reactor 27 and the one-stage reaction of the recovered heat Heat loss during transfer to condenser 26, CH separated from water by condenser 28_FourIn consideration of the heat necessary for reheating, it is presumed that heat supply from the outside is indispensable. Further, in the system of FIG. 7, it is necessary to supply heat necessary for heating the organic waste treatment unit 31, the reaction tank 34, the catalyst regenerator 36, and the like, and driving power of the system.
[0009]
In the system of FIG. 7, in order to reduce the energy supply from the outside, unreacted hydrogen in the reaction tank 34 is recovered by the hydrogen separator 38, and a part of the recovered hydrogen is converted into thermal energy by the hydrogen combustor 40. It has been proposed to supply the organic waste treatment unit 31, the reaction tank 34, and the catalyst regenerator 36 to use surplus hydrogen for power generation (see FIG. 1A). However, the hydrogen produced by equation (1) is CO₂Since the amount of hydrogen that can be recovered decreases if the amount of hydrogen consumed by equation (2) is large, there is a limit to energy supply and power generation that depend on surplus hydrogen. Increasing the amount of hydrogen recovered by the hydrogen separator 38 increases energy self-sufficiency, but the hydrogen concentration in the reaction vessel 34 decreases, so CO₂There is a risk of lowering the removal efficiency. That is, in the system shown in FIG.
[0010]
CO in the atmosphere₂Consumption of new fossil fuels to remove CO2 should be avoided as much as possible, and CO without external energy supply₂It is desired to develop a system that can efficiently remove water.
Accordingly, an object of the present invention is to provide a biomass-based carbon dioxide removal method and apparatus that can efficiently and spontaneously remove carbon dioxide in the atmosphere.
[0011]
[Means for Solving the Problems]
The present inventor₂Is a fixed organism that can be used as an energy resource (hereinafter referred to as “biomass”) to produce biogas by methane fermentation treatment, and CH in this biogas_FourAs a result of studying a method for reforming hydrogen into hydrogen, CH in biogas_FourOnly CO₂According to the method of reforming to hydrogen without production, atmospheric CO₂The prospect of solving the difficult problem of achieving energy removal by energy self-sufficiency was obtained.
[0012]
Plants that inhabit the earth are converted to atmospheric CO by photosynthesis.₂Is fixed as an organic substance in the body, and CO₂Carbon based on is stored as organic matter. The carbon fixed in the living organisms is regenerated by combustion, etc.₂Even if it is diffused into the atmosphere, CO on a global scale₂It will not cause a loss of balance. For this reason, even if biomass is burned,₂It is drawing attention as an alternative energy source that does not break the balance of the environment.
[0013]
Conventional CH_FourIn the reforming reaction of hydrogen into hydrogen, CH_FourSteam is added to generate hydrogen and carbon monoxide (CO) (steam reforming reaction, equation (4)), and steam is added to CO to generate hydrogen and CO.₂(Shift reaction, formula (5)). The net reaction is as shown in equation (6) (hereinafter, this reaction is referred to as steam reforming). In this reaction, H₂O is also H₂The amount of hydrogen generation is large because it is a source, but at the same time CO₂Occurs. This CO₂As mentioned above, global CO₂Although it does not break the balance of CO in the atmosphere₂For the purpose of removal, CO in the system₂Occurrence is undesirable. In steam reforming, it is difficult to avoid carbon monoxide (CO) by-product from equation (4).₂When mixed with gas and enters the fuel cell, the electrode catalyst is poisoned and must be removed in advance by a selective catalytic oxidation method or the like.
[0014]
[Chemical 2]
CH_Four+ H₂O → 2CO + 3H₂      …………………………………………(Four)
CO + H₂O → CO₂+ H₂    ………………………………………………(Five)
CH_Four+ 2H₂O → CO₂+ 4H₂   …………………………………………… (6)
[0015]
CH_FourThere is the above formula (1) as a reaction for directly decomposing C into solid carbon and hydrogen. According to equation (1), CO and CO as in the steam reforming method.₂Since hydrogen is not discharged, hydrogen after decomposition can be directly used as a fuel for a fuel cell or the like. CO fixed in biomass₂Can be extracted as solid carbon rather than being diffused again into the atmosphere. CO fixed in biomass₂Can be extracted as solid carbon, resulting in atmospheric CO₂The concentration can be reduced.
[0016]
  Referring to the embodiment of FIG. 1, the biomass-utilizing carbon dioxide removal method of the present invention pulverizes biomass B in which atmospheric carbon dioxide is fixed into an organic slurry S, and maintains the organic slurry S at an activation temperature. Methane fermentation with a group of methanogensCarbon dioxide was removed from the resulting biogas G and concentrated.Hydrogen and solid carbon are brought into contact with catalyst 14 while heating methane gas to the decomposition temperatureDirectlyDisassembleAnd a part of the hydrogen provides heating energy to the decomposition temperature, and another part of the hydrogen is used as a fuel cell. 17 Converted into electric power and high temperature water and its fuel cell 17 The high temperature water from the water covers the holding energy of the active temperature and the fuel cell 17 The energy of grinding biomass BBy paying,It is formed by removing carbon dioxide in the atmosphere as solid carbon with sufficient energy.
[0017]
  Preferably, the main component of the catalyst 14 is nickel, iron, or cobalt, and the methane gas is heated to 200 to 900 ° C. and brought into contact with the catalyst 14.
[0018]
  In addition, referring to the embodiment of FIG. 1, the biomass-utilizing carbon dioxide removal apparatus of the present invention includes pulverizing means 2 and 3 for pulverizing biomass B in which atmospheric carbon dioxide is fixed into an organic slurry S, and methane generation. Bioreactor 6, bioreactor 6 having a fermentation chamber 20 for holding the fungus group at a high concentration, and a heat retaining means 7 for maintaining the slurry S taken into the fermentation chamber 20 at the activation temperature of the methanogen groupConcentration device that removes carbon dioxide from biogas G produced in the process and concentrates methane gas 12 The concentratedMethane gas into hydrogen and solid carbonDirectlyA methane decomposition means 13 having a reaction chamber 16 in which a catalyst 14 for decomposition exists and a heating means 15 for heating methane gas to a decomposition temperature in a part of the hydrogen, and another part of the hydrogen is converted into electric power and high-temperature water. The fuel cell 17 is provided, the heat retaining means 7 is kept warm by the high-temperature water from the fuel cell 17, and the pulverizing means 2 and 3 are driven by the electric power from the fuel cell 17 so that carbon dioxide in the atmosphere is converted into solid carbon by itself. It is removed.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
In the embodiment of FIG. 1, carbon dioxide (CO₂) Plants are grown as biomass B in the immobilization facility 1, and the cultivated biomass B is pulverized by means of pulverizing means 2 and 3 for methane gas (CH_Four) Grind into high-concentration organic slurry with a large amount of generation. As biomass B, CO₂Highly efficient land-based sugar cane and corn, soybeans and sesame with a high oil content, seaweeds with high growth rate and other seaweeds can be used, but the biomass B used in the present invention is not limited to plants. . According to the present invention, on the condition that it can be pulverized into the organic slurry S, many animals and plants or parts thereof (vegetables, fruits, vegetable oils, seafood, meats, etc.) living on the earth or their Processed products, residues (garbage etc.), animal excrement etc.₂It can be used as biomass B for removal.
[0020]
CO₂The typical organic substances in biomass B converted to sucrose are polysaccharides, fats, proteins, etc., but when these organic substances are pulverized into a slurry and methane-fermented by methanogenic bacteria, they are gradually decomposed over time. It turns into a simple substance. First, in the first stage, a polysaccharide is changed to a monosaccharide and a protein is changed to an amino acid by a hydrolyzing bacterium in the methanogen group. Subsequently, these compounds are decomposed into lower fatty acids such as acetic acid, butyric acid and propionic acid, and a small amount of alcohol, aldehyde and the like by acid producing bacteria in the group of methanogenic bacteria. Finally, the methanogens in the methanogen group_FourAnd CO₂It becomes a gaseous product having as a main component. This gaseous product is called biogas, CH_Four60-70%, CO₂30 to 40%.
[0021]
CO in the atmosphere₂In order to remove the gas efficiently, it is necessary to efficiently recover as much biogas G as possible from the biomass B. In order to increase the recovery amount of the biogas G, it is effective to pulverize the biomass B into a small particle size slurry, and preferably pulverize to a particle size of 1 mm or less. In the embodiment of FIG. 1, the non-slurable portion in the biomass B is separated by the pulverizer 2 with the foreign matter separating function, and the slurryable portion is crushed to a predetermined size, and the slurryable portion is averaged by the fine pulverizer 3. Finely pulverize to about several hundred microns. In the present invention, since the pulverizers 2 and 3 are driven by energy conversion of a part of hydrogen from the methane decomposition means 13 described later, it is not necessary to supply drive energy for foreign matter separation and pulverization from the outside.
[0022]
The crushed slurry S is diluted with an amount of water such as an equal amount of water that improves fluidity, and temporarily stored in the slurry tank 4 or the like. Setting the organic substance concentration to a high concentration without diluting the slurry S not only reduces the dilution water cost, but also reduces the volume of the bioreactor 6 to reduce the reactor heating energy, thus improving the energy self-sufficiency of the system. It is effective in. For example, the organic substance concentration (CODcr value, chemical oxygen demand amount) of the slurry S after dilution is set to 150 to 200,000 mg / L (L represents liter, the same applies hereinafter). The stored organic slurry S is gradually fed into the bioreactor 6 by the slurry pump 5.
[0023]
Since methane fermentation in the bioreactor 6 is performed in an anaerobic state, supply of oxygen is unnecessary and energy consumption is small. However, in order to efficiently perform methane fermentation in the bioreactor 6, (1) the organic slurry S is maintained at about pH 6.5 to 8.0, and (2) the slurry S is maintained at the activation temperature of the methanogen group. (3) Maintaining a high concentration of methanogenic bacteria in the fermentation chamber 20 of the bioreactor 6, (4) No blockage due to a large amount of solid content (SS) contained in the slurry S This condition is necessary.
[0024]
The methanogenic bacteria group includes mesophilic bacteria that are active in the medium temperature range (35 to 40 ° C.) and thermophilic bacteria that are active in the high temperature range (52 to 58 ° C.). Preferably, the required biogas is recovered in a short time using a high-temperature bacterium having a higher decomposition rate than that of a mesophilic bacterium. In the present invention, it is assumed that the heat retaining means 7 provided in the bioreactor 6 holds the slurry S at the activation temperature of the methane producing bacteria group by energy conversion of a part of hydrogen from the methane decomposition means 13 described later. An example of the heat retaining means 7 is a heat exchanger between the high-temperature water heated by hydrogen combustion and the slurry S in the fermentation chamber 20, as shown in the embodiment of FIG. Also, the slurry circulation pump 9 shown in FIG. 2 can be driven by, for example, a part of electric power from a fuel cell 17 described later.
[0025]
Methods for increasing the concentration of methanogenic bacteria in the fermentation chamber 20 include the UASB method for granulating microorganisms (Upflow Anaerobic Sludge Blanket), and the fixed bed method for filling the fermentation chamber 20 with a carrier to which microorganisms have adhered. is there. In the fermentation chamber 20 of the bioreactor 6 shown in FIG. 2, a hollow cylinder 22 having an inner diameter of 50 to 70 mm and a porous peripheral wall 23 made of glass fiber or carbon fiber nonwoven fabric as shown in FIG. The supported microbial carrier 21 is regularly packed vertically. By attaching methanogenic bacteria to the carrier 21, the microbial concentration in the fermentation chamber 20 can be increased. Further, since the hollow cylindrical carrier 21 is regularly packed vertically, the biogas G can pass through the cylindrical carrier 21, thereby preventing the carrier 21 from being blocked by SS or the like.
[0026]
CH in biogas G generated in bioreactor 6_FourIs the carbon that constitutes the organic matter in biomass B, that is, CO in the atmosphere.₂Of carbon. In the present invention, CH in the biogas G_FourAre taken out as solid carbon by the methane decomposition means 13 (see formula (1)). Traditionally, CH_FourAre known, for example, a catalyst mainly composed of nickel, cobalt, iron, etc., and such a catalyst 14 is used as a reaction chamber 16 of the methane decomposition means 13 of the present invention. Available to exist.
[0027]
In FIGS. 1 and 4, the reaction system is illustrated as a solid having a state, size, shape and the like that can be used in a gas-solid system, the reactor as a fixed bed reactor, and the catalyst 14 in a fixed bed reactor. The reaction system, reactor, and catalyst are not limited to gas-solid systems, fixed bed reactors, and fixed bed catalysts, respectively. The reaction system may be, for example, a gas-liquid-solid system. The reactor may be, for example, a fluidized bed reactor or a moving bed reactor. The state of the catalyst may be liquid or gas, and the size and shape of the catalyst may be fine powder, fine particles, powder, small diameter particles, or the like.
[0028]
1 and 4 exemplify a method in which a catalyst is placed in the reaction chamber in advance as a method for causing the catalyst to be present in the reaction chamber. However, the catalyst or catalyst precursor is CH as a reactant._FourMethod of introducing into the reaction chamber together with gas, CH as the reactant in advance_FourA method of introducing gas and introducing a catalyst or a catalyst precursor to the gas can also be employed.
[0029]
Further, the catalyst is usually composed of a main catalyst component, a promoter component, and a support, and is formally called a supported catalyst, but the catalyst used in the present invention is not limited to a supported catalyst. For example, the catalyst precursor itself_FourActivated by heating in a gas atmosphere, used as it is as a catalyst, or heated in the form of a fluid such as a solution, sol, slurry, etc. catalyst precursor_FourIt can be activated by being blown into a gas and used as it is as a catalyst.
[0030]
Since the reaction of formula (1) is an endothermic reaction, CH_FourNeeds to be heated by the heating means 15 to a temperature at which the decomposition reaction occurs. CH_FourThe energy required for heating the gas can be covered by a part of the hydrogen generated by the methane decomposition means 13. For example, a part of the hydrogen produced by the methane decomposition means 13 is introduced to the heating means 15 and burned, so that CH_FourIs heated to the decomposition temperature.
[0031]
In the methane decomposition means 13 of FIG. 4, the main component of the catalyst 14 is nickel, cobalt, iron or the like. In the illustrated example, the shape of the catalyst 14 is a spherical shape (see FIGS. 1A and 1B) or a quadrangular pyramid shape (see FIG. 1D). However, the shape of the catalyst 14 is not limited to the illustrated example. Various shapes such as a cylindrical shape, a honeycomb shape, a granular shape, a spiral shape, a pellet shape, and a ring shape can be employed. The quadrangular pyramid-shaped catalyst in FIG. 4D is employed when carbon is produced and used as it is as a heat-resistant electromagnetic wave absorber.
[0032]
In the embodiment of FIG._FourIs heated to 200-900 ° C. and brought into contact with the catalyst 14. When the temperature is lower than 200 ° C., the conversion rate (hydrogen generation amount) in the decomposition reaction is lowered. When the temperature exceeds 900 ° C., the catalyst life is shortened, and although the conversion rate does not decrease, the final hydrogen generation amount is consequently reduced. The inventor_FourIt was experimentally confirmed that by heating the catalyst to the decomposition temperature and bringing it into contact with the catalyst 14, it was possible to generate approximately the same amount of hydrogen as the theoretical calculation value based on the equation (1).
[0033]
By contacting with catalyst 14 after heating to decomposition temperature, CH_FourIs decomposed to solid carbon and hydrogen, and the solid carbon accumulates on the catalyst 14. The crystal structure and shape of the accumulated carbon can vary depending on the type of the catalyst 14, but in the case of the nickel catalyst 14, the structure of the accumulated carbon can be a hollow graphite filament structure useful as a functional material. When a powder or particulate catalyst is used for a long time reaction, the catalyst is subdivided and buried in the solid carbon as the solid carbon is generated and grown, so that the catalyst and the solid carbon can be separated by a normal method. It becomes difficult. In this case, since the catalyst is widely dispersed in a large amount of solid carbon, the catalyst content in the solid carbon is extremely low. Depending on the application, it can be effectively used as it is as a functional carbon material. On the other hand, when it is desired to recover the catalyst, the catalytic metal component is removed from the solid carbon by an appropriate method and used for catalyst regeneration. In the present invention, the energy required for taking out the catalyst metal component and regenerating the catalyst 14 can be covered by a part of the hydrogen generated by the methane decomposition means 13.
[0034]
The gas discharged from the reaction chamber 16 of the methane decomposition means 13 is unreacted CH by an appropriate method such as adsorption and membrane separation._FourAnd hydrogen. Unreacted CH_FourIs returned to the methane decomposition means 13. Hydrogen is also CO2 when burned.₂In addition to being a clean energy source that does not release the heat, it has three times as much heat energy as petroleum, and can be converted into electric energy by a fuel cell. In the present invention, a large amount of biogas G is efficiently recovered from the biomass B in the pulverizing means 2, 3 and the bioreactor 6, and the CH in the biogas G in the methane decomposition means 13._FourBy generating almost the same amount of hydrogen as the theoretical calculation value from the above, it is possible to take out from the methane decomposition means 13 an amount of hydrogen that can cover all the energy required in the pulverization, fermentation, decomposition, and other systems. Moreover, atmospheric CO fixed in biomass B₂Is taken out as solid carbon and not returned to the atmosphere.₂The concentration can be reduced.
[0035]
In this way, the provision of “a biomass-based carbon dioxide removal method and apparatus that can efficiently and spontaneously remove carbon dioxide in the atmosphere”, which is an object of the present invention, can be achieved.
[0036]
【Example】
The organic slurry S obtained by pulverizing the biomass B is biogas G and fermentation broth E in which 80 to 90% of the organic matter is decomposed by the methanogen in the bioreactor 6. When organic slurry S with a CODcr value of about 210 g / L is decomposed by high-temperature methane fermentation bioreactor 6, 200 Nm per ton of slurry^ThreeSome degree of biogas is generated. On the other hand, since the fermented liquid E remaining in the bioreactor 6 also contains a small amount (10 to 20%) of organic matter, the fermented liquid E is sent to the final treatment facility 8 in the embodiment of FIG. It is discharged into sewers and rivers as treated water. In the final treatment facility 8, activated sludge treatment using aerobic microorganisms is usually performed. However, the fermentation broth E remaining in the bioreactor 6 can be used as liquid fertilizer as it is.
[0037]
In the embodiment of FIG. 1, a desulfurization / denitrification purification apparatus 10 and a methane concentration apparatus 12 are provided between the bioreactor 6 and the methane decomposition means 13. Biogas G is mainly CH_FourAnd CO₂However, impurities such as hydrogen sulfide and ammonia are also contained in the range of tens to hundreds of ppm. These impurity substances are removed by the desulfurization and denitrification purification apparatus 10 in order to deteriorate the catalyst 14 of the methane decomposition means 13 and shorten the life. In the desulfurization / denitrification purification apparatus 10 in the illustrated example, the biogas G is purified by removing hydrogen sulfide using, for example, iron oxide pellets and removing ammonia using activated carbon or the like. The methane concentrator 12 uses the biogas G after purification to CO₂Remove CH_FourIs concentrated to, for example, 98% or more. In the methane concentrator 12 shown in the figure, CO₂CH in biogas G by adsorbing and removing_FourConcentrate.
[0038]
CO removed from biogas G in methane concentrator 12₂Can be returned to the atmosphere, for example. CO in biogas G₂Is the atmospheric CO originally fixed in biomass B₂Even if it is returned to the atmosphere, CO on a global scale₂It does not break the balance. Also, CO contained in biogas G by 30-40%₂Even if it is returned to the atmosphere, CH contained 60 to 70% in biogas_FourIs extracted as solid carbon, CO fixed in biomass B₂(Carbon equivalent) can be removed more than half, so CO in the atmosphere₂It will not be an obstacle to removal. CO removed from biogas G₂Is CH_FourIt can also be used by reacting with solid carbon obtained from the above and converting it to CO, which is a chemical raw material.
[0039]
Further, in the embodiment of FIG. 1, a fuel cell 17 is provided, and a part of hydrogen taken out from the methane decomposition means 13 is converted into high-temperature water and electric power. The power generation efficiency of the fuel cell 17 is about 40 to 50%, but high-temperature water (or steam) is discharged from the fuel cell 17, so if this high-temperature heat is effectively used, the total energy efficiency of about 80% is achieved. (Kenki Hirose “Fuel Cell Story” Japanese Standards Association, July 5, 1992, 1st edition, p56). The high-temperature water that is the exhaust heat of the fuel cell 17 is effectively used for the heat retaining means 7 of the bioreactor 6. Further, the pulverization means 2 and 3 shown in FIG. 1, the slurry circulation pump 9 (FIG. 2) of the bioreactor 6, the final treatment facility 8, the desulfurization and denitrification purification apparatus 10, and the methane concentrator are obtained by using a part of the electric power from the fuel cell 17. Covers the power required to drive 12 mag.
[0040]
In the embodiment of FIG. 1, the heating means 15 is heated by a part of the hydrogen generated by the methane decomposition means 13, and the other part of the hydrogen is converted into electric power and hot water by the fuel cell 17. The heat retaining means 7 can be kept warm by at least a part of the high-temperature water from the fuel cell 17, and the grinding means 2, 3, etc. can be driven by at least a part of the electric power from the fuel cell 17.₂The energy is removed as solid carbon by itself.
[0041]
One of the grounds for determining that the present invention is energy self-sufficient will be described with reference to FIG. FIG. 8 is a graph showing the relationship between the power generation amount of the system using the above-described methane steam reforming reactor instead of the methane decomposition means 13 in FIG. 1 and the system power consumption (clean energy (November 2000)). , P34-38, Yoshitaka Togo “Metacres and Fuel Cell”). The graph α in the figure shows the amount of power generation corresponding to the amount of biomass (garbage in FIG. 8), and the graph β shows the change in power consumption required for driving the system. According to the graph, the amount of power generated when processing 5 tons of biomass per day is approximately 3 x 10^ThreekWh / day, about 1 × 10 power consumption required to drive the system^ThreeIt exceeds kWh / day. Moreover, it can be seen that the difference between the power generation amount and the system power consumption increases as the biomass throughput increases.
[0042]
CH_FourWhen the methane steam reforming reaction apparatus as shown in FIG. 8 is used for hydrogen production from methane, and when the methane decomposition means 13 is used as in the present invention, the equations (6) and (1) As is clear from the comparison, the amount of hydrogen generated when the methane decomposition means 13 is used is half that when the methane steam reforming reaction apparatus is used. Considering this point, looking at FIG. 8, the amount of power generated when processing 5 tons of biomass per day using the methane decomposition means 13 is about 1.5 × 10^ThreekWh / day can be expected.
[0043]
On the other hand, when the power consumption required for driving the system is compared, the change in the enthalpy of the reaction when using the methane decomposition means 13 and when using the methane steam reforming reaction apparatus shows that the reaction temperature is 500 ° C. and 800 ° C. per mole of hydrogen. It becomes almost the same at ° C. Furthermore, the reaction temperature range also includes a region where 200 to 900 ° C. overlaps with methane decomposition and 600 to 850 ° C. overlaps with methane steam reforming. The reaction pressure is atmospheric pressure and 20-30 atm respectively, and methane decomposition is slightly more advantageous (cited data of methane steam reforming data: Mikimoto Sato, Petrotech, vol.24, 543 (2001)). From the above comparison, the system power consumption when the methane decomposition means 13 is used as in the present invention is the power consumption when the methane steam reforming reaction apparatus is used as shown in FIG.^ThreekWh / day). That is, when using the methane decomposition means 13, 5.0 × 10²kWh / day (= 1.5 × 10^Three−1.0 × 10^Three) About surplus power, and this surplus power increases as the amount of biomass increases. That is, it can be said that the present invention is energy self-sufficient.
[0044]
Figure 5 shows CO in the atmosphere.₂A specific example of a material balance and an energy balance in the case where 5 tons of biomass B to which is fixed is processed per day is shown. Five tons of biomass B are removed by a pulverizer 2 with a foreign matter separating function before fermentation, and pulverized by a fine pulverizer 3 to obtain an organic slurry S. Further, in order to improve the fluidity of the slurry S, 5 tons of dilution water is added to dilute it twice. The CODcr value at this time is about 210 g / L, and the BOD value (biological oxygen demand) is about 160 g / L. When this slurry S is methane-fermented with high-temperature bacteria in the bioreactor 6 while maintaining the active temperature of the high-temperature bacteria at 55 ° C., about 85% of CODcr is decomposed and biogas G is 1,000 Nm per day.^Threeappear. CH in this biogas G_FourThe average concentration of is 65% and CH_FourThe amount is 650Nm per day^ThreeIt becomes. Impurities in the biogas G are removed by the desulfurization and denitrification purifier 10 and further CH by the methane concentrator 12_FourTo 98% or more.
[0045]
Concentrated CH_FourIs supplied to the methane decomposition means 13. The reaction chamber 16 of the methane decomposition means 13 has a catalyst 14 and is maintained at a decomposition temperature of 500 ° C. 650 Nm for methane decomposition means 13^Three/ Day CH_FourSupply 348 kg of carbon and 116 kg of hydrogen per day. The amount of heat of the extracted hydrogen is 3,357 × 10^Threekcal / day, and part of the hydrogen is used as fuel for the heating means 15 of the methane decomposition means 13. 650Nm^Three/ Day CH_Four622 × 10 to decompose at 500 ℃^ThreeSince kcal / day (equivalent to 21kg-hydrogen / day) is required, the remaining heat of hydrogen is 2,735 × 10^Threekcal / day (corresponding to 95 kg-hydrogen / day). When the remainder of the hydrogen is used as the fuel of the phosphoric acid fuel cell 17, the power generation efficiency of the fuel cell 17 when hydrogen is used as the fuel is about 45%, and thus the power that can be generated is 1,431 kwh / day.
[0046]
Since the power consumption required for driving the entire system of FIG. 5 is about 1,000 to 1,200 kwh / day, the power from the fuel cell 17 can sufficiently cover the power consumption of the entire system. Even when the decomposition temperature is increased to 800 ° C, the heat of reaction is 688 × 10^ThreeSince it is kcal / day (equivalent to 24kg-hydrogen / day), the amount of power generation is 1,397kwh / day, which exceeds the system power consumption. Also, assuming that about 45% of the reaction heat of hydrogen can be recovered, 1,231 x 10 from the fuel cell 17^ThreeSince kcal / day waste heat is generated, it is collected as hot water or steam. The amount of heat required to heat biomass and diluted water from 20 ° C to 55 ° C is 350 x 10^Threekcal / day, and the amount of heat released from the bioreactor 6 is 150 × 10^ThreeSince it is about kcal / day, the amount of heat to keep the bioreactor 6 at 55 ° C is 500 × 10^Threekcal / day is sufficient, and it can be sufficiently covered by hot water from the fuel cell 17.
[0047]
From the flowchart of FIG. 5, according to the present invention, atmospheric CO₂By processing 5 tons / day of biomass B with the fixed amount, 348 kg of CO₂(Carbon conversion) can be removed as solid carbon. CO₂All of the energy required for the removal of hydrogen can be covered by the energy conversion of the hydrogen recovered in the system.₂Can be removed. Furthermore, surplus power of about 231kwh / day (= 1,431–1,200) and 731 × 10^Three kcal / day (= 1,231 × 10^Three−500 × 10^ThreeCO2 in the atmosphere can be produced with excess high-temperature water₂It can also be expected to obtain economic efficiency as a power generation facility while removing the wastewater.
[0048]
【The invention's effect】
  As described above, the method and apparatus for removing carbon dioxide using biomass according to the present invention pulverizes biomass in which atmospheric carbon dioxide is fixed into an organic slurry, and maintains it at an active temperature to perform methane fermentation by a group of methanogenic bacteria. Let it fermentRemoved carbon dioxide from the resulting biogas and concentratedHydrogen and solid carbon are brought into contact with the catalyst while heating the methane gas to the decomposition temperature.DirectlyDisassembleAnd a part of the hydrogen provides heating energy to the decomposition temperature.,The other part of the hydrogen is converted into electric power and high-temperature water by the fuel cell, and the holding energy of the active temperature is covered by the high-temperature water from the fuel cell, and the pulverization energy of the biomass is supplied by the electric power from the fuel cell.Since it covers, it has the following remarkable effects.
[0049]
(A) Since the system can be driven using hydrogen generated in the system as fuel, it is not necessary to replenish energy from the outside, and carbon dioxide in the atmosphere can be removed as solid carbon by itself.
(B) Since carbon dioxide in the atmosphere is removed through biomass, extremely dilute carbon dioxide in the atmosphere can be efficiently removed.
(C) If biomass such as garbage that can be easily obtained is used, a carbon dioxide removal facility in the atmosphere can be constructed regardless of the location.
(D) Since anaerobic treatment with low energy consumption is used, it is expected that surplus energy is supplied to the outside as heat and electricity while minimizing the energy consumption in the system.
(E) By using a highly active high-temperature methanogen or the like, a device such as a bioreactor becomes compact and economically advantageous.
(F) By using a catalyst mainly composed of nickel, cobalt, iron, etc., solid carbon having a structure / shape useful as a functional material can be taken out, and a battery electrode material, an electromagnetic wave absorber loss material For example, solid carbon can be effectively used.
[Brief description of the drawings]
FIG. 1 is a schematic flow diagram of one embodiment of the present invention.
FIG. 2 is an explanatory diagram of a bioreactor according to the present invention.
FIG. 3 is an explanatory diagram of an example of a microbial carrier used in the present invention.
FIG. 4 is an explanatory diagram of an example of methane decomposition means.
FIG. 5 is a diagram showing an example of a material balance and an energy balance in the present invention.
FIG. 6 is an explanatory diagram of an example of a conventional method for removing carbon dioxide in the atmosphere.
FIG. 7 is an explanatory diagram of another example of a conventional method for removing carbon dioxide in the atmosphere.
FIG. 8 is an explanatory diagram of a relationship between a power generation amount of a fuel cell incorporating a conventional methane steam reforming reaction apparatus and system power consumption.
[Explanation of symbols]
1 ... Carbon dioxide fixation facility
2 ... Crusher with foreign matter separating function (grinding means)
3 ... Fine grinding machine (grinding means)
4 ... Slurry tank
5 ... Slurry pump 6 ... Bioreactor
7 ... Thermal insulation means 8 ... Final treatment facility
9 ... Slurry circulation pump 10 ... Desulfurization denitrification purification equipment
12… Methane concentrator 13… Methane decomposition means
14 ... Catalyst 15 ... Heating means
16 ... Reaction chamber 17 ... Fuel cell
20 ... Fermentation chamber 21 ... Microorganism carrier
22 ... Hollow cylinder 23 ... Porous peripheral wall
24 ... Frame 26 ... Primary reactor
27 ... Secondary reactor 28 ... Condenser
31… Organic waste treatment part 32… Gas mixing / condenser
33 ... Pump 34 ... Reaction tank
35 ... Catalyst / carbon separator 36 ... Catalyst regenerator
37 ... Pump 38 ... Hydrogen separator
39 ... Pump 40 ... Hydrogen combustor
E ... Fermentation liquid G ... Biogas
S ... Organic slurry

Claims (8)

Biomass carbon dioxide in the atmosphere is fixed to ground to organic slurry, removing carbon dioxide from the organic slurry is methane fermentation by holding the activation temperature methanogens group the biogas generated Ri by the said fermentation The concentrated methane gas is heated to the decomposition temperature and brought into contact with the catalyst to be directly decomposed into hydrogen and solid carbon, and a part of the hydrogen provides heating energy to the decomposition temperature, and the other part of the hydrogen is fueled. Carbon dioxide in the atmosphere is converted into electric power and high-temperature water by the battery, and the energy for holding the active temperature is covered with the high-temperature water from the fuel cell and the biomass is crushed with the electric power from the fuel cell. Biomass-based carbon dioxide removal method by removing energy as self-sufficient solid carbon. In the method of removing the claim 1, sugarcane the biomass, corn, soybean, sesame, seaweed, or algae, of the biomass biomass obtained by grinding the organic matter concentration 15-200000 mg / liter or more organic material slurry dioxide Carbon removal method. The removal method according to claim 1 or 2 , wherein the main component of the catalyst is nickel, iron, or cobalt, and the methane gas is heated to 200 to 900 ° C and brought into contact with the catalyst to remove the biomass. The method for removing carbon dioxide using biomass according to any one of claims 1 to 3 , wherein the organic slurry is held at 52 to 58 ° C and methane-fermented by a methanogen group. A pulverizing means for pulverizing biomass in which atmospheric carbon dioxide is fixed into an organic slurry, a fermentation chamber for maintaining a high concentration of the methanogen group, and maintaining the slurry incorporated in the fermentation chamber at the activation temperature of the methanogen group A reaction including a bioreactor having a heat retaining means, a methane concentrator for concentrating methane gas by removing carbon dioxide from the biogas generated in the bioreactor , and a catalyst for directly decomposing the concentrated methane gas into hydrogen and solid carbon A methane decomposition means having a chamber and a heating means for heating the methane gas to a decomposition temperature in a part of the hydrogen, and a fuel cell for converting another part of the hydrogen into electric power and high-temperature water, from the fuel cell The heat retaining means is kept warm by high-temperature water, and the pulverizing means is driven by the electric power from the fuel cell, thereby Containing carbon dioxide removal apparatus biomass formed by removing an energy self-sufficient in the solid carbon. 6. The removal apparatus according to claim 5 , wherein the main component of the catalyst is nickel, iron, or cobalt, and methane gas is heated to 200 to 900 ° C. by the heating means. The removal apparatus according to claim 5 or 6 , wherein a desulfurization / denitrification purification apparatus is provided between the bioreactor and the methane concentrator . In any of the removal apparatus of claims 5 7, the biomass sugarcane, corn, soybean, sesame, seaweed, or algae, biomass organic matter concentration 15-200000 mg / liter or more organic material slurry by the milling means Carbon dioxide removal device using biomass that is pulverized.

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