JP5061328B2 - Methane separation method, methane separation device, and methane utilization system - Google Patents

Description

  The present invention relates to natural gas produced by the origin of anaerobic fermentation of organisms mainly produced from methane, underground fermentation that is produced by natural and anaerobic fermentation of industrial and household waste. A methane separation method for separating methane from gas or biogas such as artificial fermentation gas discharged from an anaerobic fermentation process generated artificially, a methane separation apparatus using the same, and the methane can be supplied to the energy market It relates to methane utilization system.

  Natural gas produced by anaerobic fermentation of living organisms produced from the ground, gas produced by natural anaerobic fermentation by underground storage of industrial and household waste, or artificially generated anaerobic fermentation process In a gas composed mainly of methane, such as a gas exhausted from CO2 or COG gas generated during coke production, it may contain a large amount of carbon dioxide and moisture that do not become a heat energy source. In order to use these gases as high-quality thermal energy sources and fuels, it is necessary to remove carbon dioxide and moisture, which cannot be contained in the mixed gas, to increase the purity of methane.

  As a method for increasing the purity of specific gas components from these mixed gases, a cryogenic separation method in which the mixed gas is separated by distillation under low temperature conditions, a chemical absorption method, a dry membrane separation method using a gas separation membrane, a PSA method (pressure swing) Adsorption method), membrane / absorption hybrid method and the like are known. In the cryogenic separation method, heat enters and leaves the separation process, and it is economically undesirable to obtain a highly pure methane because the apparatus becomes complicated and large.

  In addition, the conventional chemical absorption method includes an absorption tower that absorbs the gas to be separated in the absorption liquid and a regeneration tower that dissipates the separated component gas from the absorption liquid, and the absorption liquid circulates continuously between the absorption tower and the regeneration tower. In order to separate the gas to be separated, there is a problem that the initial cost and the operating cost of the gas separation become high due to the absorption tower for efficiently bringing the absorbing liquid into contact with the target gas and the large heating energy for the diffusion. In addition, there is a carbon dioxide absorption method using high-pressure water using the action of dissolving carbon dioxide in water, but there is a problem that a large amount of water is required to purify biogas.

  On the other hand, the dry membrane separation method and the PSA method do not involve heat input and output, can be separated with low energy, can be operated at room temperature, and have a simple structure and downsizing of the equipment. There is. In the former dry membrane separation method, since the difference in permeation rate in the membrane is used, in order to obtain high-purity methane, it is necessary to increase the number of membrane modules, and there is a problem that the cost is increased. As shown in Patent Documents 1 and 2, the latter PSA method uses activated carbon, natural or synthetic zeolite, silica gel and activated alumina, MSC (molecular sieve carbon), etc. as an adsorbent that easily adsorbs carbon dioxide. It is used that the amount of adsorption varies depending on the pressure and temperature.

  However, in the PSA method, in order to obtain high-purity methane, the operating pressure range must be in a wide range of -90 KPaG to 0.7 MPaG, which has a problem that the power cost becomes high. In order to obtain high methane, it is necessary to sacrifice the recovery rate. Along with this, a lot of exhaust gas containing methane is generated, and in order to safely process flammable methane, combustion facilities etc. are required for separation. This is a factor that increases costs. Even if methane can be safely released into the atmosphere, releasing methane with a high global warming potential into the atmosphere is a major obstacle to the growing interest in global environmental problems.

Therefore, recently, a membrane / absorption hybrid method aimed at a synergistic effect in a form in which a membrane separation method and a chemical absorption method are simultaneously mixed has been attracting attention and studied (see Patent Document 3 and Non-Patent Document 1). In this method, a gas containing carbon dioxide (CO ₂ ) and an absorbing solution are supplied to one of the membranes, the carbon dioxide is absorbed in the absorbing solution, passed through the membrane, and the other is decompressed from the absorbing solution that has passed through the membrane. Carbon dioxide is released.

  For this reason, since only unnecessary carbon dioxide is selectively separated into the absorbent, it can be separated from the combustible component, the recovery rate of methane as the fuel component can be improved, and the combustible component is contained in the exhaust gas. Since there is no need to provide a combustion facility for exhaust gas treatment, there is an advantage that exhaust gas can be treated at an extremely low cost. Moreover, according to this method, the reaction that carbon dioxide absorbs is an exothermic reaction, and it is an endothermic reaction that dissipates carbon dioxide. Carbon dioxide can be separated very efficiently while balancing the heat balance in the process of release. Furthermore, continuous separation of methane can be performed by circulating the absorbent and reusing it. Therefore, by applying the membrane / absorption hybrid method to biogas, it is possible to separate methane having high purity from biogas at a lower operating cost than the conventional absorption method, dry membrane method, and PSA method.

JP 2001-293340 A JP 2003-204853 A JP-A-2005-270814 Masaaki Teramoto, Nobuaki Ohnishi, Nao Takeuchi, Satoru Kitada, Hideto Matsuyama, Norifumi Matsumiya, Hiroshi Mano: “Separation and enrichment of carbon dioxide by capillary membrance module with permeation of carrier solution”; Separation and Purification 227

  In the case where the conventional membrane / absorption hybrid method is applied to biogas, for example, the membrane module is supplied with a gas to be separated including carbon dioxide and a separation gas such as methane together with an absorption liquid. There is a problem in that the efficiency of methane separation is reduced due to the gas-liquid mixed state of methane that does not dissolve in the absorbent and the absorbent. In addition, since biogas contains high-concentration carbon dioxide, carbon dioxide absorbed in the absorption liquid that has permeated through the permeable membrane of the membrane module is not sufficiently diffused and the absorption liquid is not sufficiently regenerated. There was also a problem that it returned to the liquid circulation system and the efficiency of methane separation and purification decreased.

  Accordingly, an object of the present invention is to provide a methane separation method capable of separating and purifying methane from biogas containing methane as a main component and containing high concentration of carbon dioxide with high efficiency, a methane separation apparatus using the same, and existing petroleum It is to provide a methane utilization system that can supply methane to the energy market as well as fossil fuels.

The present invention has been made to solve the above problems, and in the methane separation method and methane separation apparatus according to the present invention, methane is separated from biogas containing methane and carbon dioxide as components by the following steps. It is characterized by. That is, in the first embodiment of the present invention, a step of producing a mixed liquid in a gas-liquid mixed phase state by using a mixer with an absorption liquid that absorbs carbon dioxide and the biogas, and the mixed liquid is a first gas-liquid separator. A step of gas-liquid separation into methane and a CO ₂ absorbent that has absorbed carbon dioxide, a step of recovering methane separated in the first gas-liquid separator, and a plurality of hollow fiber permeable membranes The CO ₂ absorbing liquid is supplied to the inside of the permeable membrane from the supply port of the membrane module incorporated in the inside so as to permeate the permeable membrane, and the pressure outside the permeable membrane is made lower than the inside of the permeable membrane. A methane separation method comprising at least a step of dissipating carbon dioxide absorbed in the CO ₂ absorbent to the outside of the permeable membrane to separate the carbon dioxide and recovering the absorbent after the carbon dioxide separation; and Using the separation method And a methane separation apparatus. In this embodiment, it is preferable that the excess CO ₂ absorbent flow rate led out to the outlet of the membrane module is close to zero as much as possible.

In the second embodiment of the present invention, excess CO ₂ absorbing liquid led to the outlet of the membrane module is introduced into the second gas-liquid separator, and gas-liquid separation into a small amount of methane and excess CO ₂ absorbing liquid is performed. A methane separation method comprising a step of recovering methane separated in the second gas-liquid separator, a step of recovering the excess CO ₂ absorbent, and a methane separation apparatus using the separation method. . Most of the methane is separated by the first gas-liquid separator of the first form, but when a small amount of methane remains in the CO ₂ absorbent, excess CO ₂ discharged from the outlet of the membrane module. The absorption liquid is introduced into the second gas-liquid separator, and the methane is separated and recovered by the second gas-liquid separator, and the excess CO ₂ absorption liquid is recovered.

  A third aspect of the present invention is a methane separation method and a methane separation apparatus, wherein a packing density of a permeable membrane in the membrane module is 30% or less. In this embodiment, the filling density is preferably 20% or less. In the present invention, the packing density of the permeable membrane in the membrane module refers to the area occupancy ratio of the permeable membrane in the cross section of the membrane module, for example, the hollow fiber-like porous membrane, and the hollow area of the hollow fiber permeable membrane is also included in the occupied area. It is.

  According to a fourth aspect of the present invention, the permeable membranes in the membrane module are arranged in small bundles, and each of the small bundles is arranged in a non-congested space so that the overall packing density is 30% or less. A certain methane separation method and methane separation apparatus.

  According to a fifth aspect of the present invention, the mixer includes at least an ejector provided in a flow passage communicating with the inlet of the first gas-liquid separator, and the flow of the absorbing liquid is allowed to flow into the flow passage. A methane separation method and a methane separation device that generate a negative pressure by forming, suck the biogas into the absorption liquid to generate the mixed liquid, and efficiently absorb carbon dioxide in the absorption liquid. The ejector can strongly and finely disperse the biogas in the absorption liquid, and can efficiently absorb carbon dioxide in the absorption liquid.

According to a sixth aspect of the present invention, there is provided a methane separation method and a methane separation in which the mixer supplies the mixed liquid generated by the ejector to a packed bubble column to further promote absorption of carbon dioxide into the mixed liquid. Device. CO ₂ absorption can be further enhanced by connecting packed bubble columns in series.

  A seventh aspect of the present invention is the methane separation method and the methane separation apparatus, wherein the absorption liquid is an aqueous solution of diethanolamine, and the concentration thereof is 0.1 to 6 mol / L. In this embodiment, the aqueous concentration of diethanolamine is preferably 2 to 4 mol / L.

According to an eighth aspect of the present invention, there is provided a methane separation method and a methane separation apparatus, wherein the membrane module has a permeation flow rate of the CO ₂ absorbent that permeates the permeable membrane of 5 to 50 L / m ² · min per membrane area. is there. In this embodiment, preferably, the permeation flow rate of the CO ₂ absorbent is 20 to 40 L / m ² · min per membrane area.

  According to a ninth aspect of the present invention, there is provided a methane separation method and a methane separation apparatus in which the permeable membrane is made of polyethylene, and the tenth aspect of the present invention is a methane separation method and an methane separation method in which a membrane outer surface of the permeable membrane is subjected to hydrophilic treatment.

  According to an eleventh aspect of the present invention, natural gas produced from anaerobic fermentation of organisms produced from the ground containing methane as a main component, industrial and household waste, using the methane separation method according to the present invention. By removing the carbon dioxide using the underground fermentation gas produced by natural anaerobic fermentation by the underground reserve, or the artificial fermentation gas discharged from the artificially generated anaerobic fermentation process as the biogas This is a methane utilization system in which methane is purified and stored, and the stored methane can be supplied as fuel. The twelfth aspect includes a power generation facility that generates power using the stored methane as fuel, and a storage control means that adjusts the amount of purified methane stored according to the season, operation period, or time zone, and is generated by the power generation facility. It is a methane utilization system that can supply the generated power to the outside. Furthermore, the 13th form is a methane utilization system provided with the carbon dioxide supply facility which enabled the hybrid supply of the carbon dioxide isolate | separated simultaneously in the said methane refinement | purification.

According to the first aspect of the present invention, the gas-liquid mixed phase mixture produced in the mixer is introduced into the first gas-liquid separator, and the separated methane is recovered, and then the CO ₂ is placed inside the membrane module. Separation and purification of methane from biogas containing high concentration of carbon dioxide is highly efficient because the separation of carbon dioxide is promoted by supplying the absorption liquid and making the pressure outside the permeable membrane lower than the inside. be able to. Therefore, the present invention makes it possible to reduce the power load and membrane module cost by the membrane / absorption hybrid method compared to existing devices such as PSA method, dry membrane separation method, chemical absorption method, etc. Gas separation and concentration can be performed. Since most of the methane contained in the biogas can be recovered with only the first gas-liquid separator, the device configuration of the methane separation device can be simplified and the price can be reduced. Further, if the flow rate of excess CO ₂ absorbent overflowing from the membrane module outlet is reduced to the minimum necessary, the power load can be reduced. As the mixer, various mixers capable of dispersing fine bubbles in the absorption liquid can be used. Specifically, an ejector, a mixer, an aeration device, and a gas-liquid contact tower filled with a filler are used. A single mixer such as a gas-liquid co-current packed bubble column or a combination mixer in which two or more of them are combined can be used.

According to the second aspect of the present invention, excess CO ₂ absorption liquid led out from the outlet of the membrane module is introduced into the second gas-liquid separator to re-separate and collect residual trace methane. Therefore, further improvement in methane separation can be realized.

The third and fourth aspects of the present invention contribute to the improvement of methane separation performance. According to the verification by the present inventors, it was found that the membrane module is overcrowded during the absorption liquid regeneration stage when carbon dioxide or the like is released. That is, the density of carbon dioxide in the membrane module is affected by the packing density of the permeable membrane. The packing density of the hollow fiber-shaped permeable membrane in the commercially available membrane module is 30 to 70%, and the gap between the adjacent permeable membranes is too close, so when the liquid flow rate increases, the space between the membranes is covered with the liquid membrane, and the pressure decreases toward the center side. As a result, the carbon dioxide emission efficiency due to the above becomes worse, and as a result, a large membrane area is required, resulting in a high cost.
On the other hand, according to the third embodiment of the present invention, since the packing density of the permeable membrane is a sparse density of 30% or less (preferably 20% or less), the diffusibility of carbon dioxide is improved and methane is separated with high efficiency. can do. Further, according to the fourth embodiment of the present invention, the permeable membranes in the membrane module are arranged in small bundles, and each small bundle is arranged keeping a non-congested space so that the packing density as a whole is 30. % Or less, the packing density of the permeable membrane can be reduced, the carbon dioxide emission can be increased, and methane can be separated with high efficiency.

  According to the fifth aspect of the present invention, since at least an ejector is used as the mixer, a strong negative pressure is generated by rapid squeezing of the absorbing liquid to generate a strong negative pressure. Biogas is driven by this negative pressure. In this case, the gas can be automatically sucked into the absorption liquid, and fine bubbles are instantaneously formed inside the absorption liquid, and a gas-liquid mixed phase mixed liquid is efficiently generated. As a result, the gas-liquid contact surface area is increased, and a large amount of carbon dioxide in the biogas can be absorbed into the absorbent with a shorter contact time and a smaller amount of absorbent compared to the conventional case. Therefore, an optimal gas-liquid mixed phase mixed liquid can be generated and gas-liquid separated, and high-concentration carbon dioxide contained in biogas can be absorbed with the minimum necessary absorption liquid. It is not necessary to distribute the absorption liquid excessively through the permeable membrane, and methane separation can be performed with high efficiency. When the mixer is composed of only an ejector, simplification of the apparatus configuration, reduction in price and reduction in power cost can be realized. Of course, more efficient mixing and absorption can be realized by adding other mixing means to the ejector.

  According to the sixth aspect of the present invention, on the downstream side of the ejector, since a gas-liquid co-current packed bubble column that is a gas-liquid contact column packed with a filler is connected in series, a two-stage configuration is provided. Since the gas-liquid two-phase flow can be efficiently formed by the ejector, and the gas-liquid two-phase flow can be further promoted by the packed bubble column, carbon dioxide is almost completely absorbed into the absorption liquid, ensuring gas separation from methane. Thus, methane can be separated and recovered almost completely with only the first gas-liquid separator.

  According to the seventh aspect of the present invention, the absorption liquid is an aqueous solution of diethanolamine, and its concentration is 0.1 to 6 mol / L (preferably 2 to 4 mol / L). Methane can be separated and purified from biogas with high efficiency.

The 8th form of this invention contributes to the improvement of methane concentration. According to the verification by the present inventors, it has been found that unless the permeation flow rate of the CO ₂ absorbing liquid that permeates the permeable membrane is not less than a predetermined value, the carbon dioxide emission efficiency is not improved, so that the methane concentration does not increase. That is, according to this embodiment, in the membrane module, the permeate flow rate of the CO ₂ absorbing liquid that permeates the permeable membrane is 5 to 50 L / m ² · min per membrane area (preferably the permeate flow rate of the CO ₂ absorbent is the membrane area. 20 to 40 L / m ² · min), the dispersibility of carbon dioxide is improved, so that the concentration of purified methane can be improved.

  According to the ninth aspect of the present invention, since the permeable membrane is made of polyethylene, high-efficiency processing of methane separation and purification is possible. That is, by using a hydrophobic PE (polyethylene) membrane as a permeable membrane, separation selectivity, permeation rate and long-term stability are improved as compared with conventional permeable membranes. For example, diethanolamine as an absorbing solution It is possible to remarkably improve the resistance to water, the substantial permeation amount of the necessary absorbent and the economic efficiency. In addition, since the PE membrane is hydrophobic, if the membrane module is not filled with the absorption liquid when the apparatus is stopped, the absorption liquid on the outer surface of the permeable membrane is not wet when the apparatus is started up, and the separation efficiency may decrease. However, according to the tenth aspect of the present invention, only the outer surface of the hydrophobic permeable membrane is subjected to chemical hydrophilic treatment, or physical treatment is performed to increase the affinity with the absorbing solution. It is possible to eliminate a decrease in separation efficiency when the apparatus is activated.

  According to the methane utilization system of the eleventh aspect of the present invention, methane is purified and stored based on the high-efficiency methane separation method of the present invention, and the stored methane can be supplied as fuel. A methane utilization system capable of supplying methane separated in concentration can be realized. In addition, according to the twelfth embodiment, it is possible to realize a methane utilization system in which the amount of purified methane stored can be efficiently adjusted so that the power generated by the power generation facility can be stably supplied to the outside. Furthermore, according to the thirteenth embodiment, it is possible to realize a methane utilization system that can supply carbon dioxide generated as a by-product during the separation and purification of methane.

  Hereinafter, embodiments of a methane separation method and a methane separation apparatus using the same according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a methane separation apparatus which is an embodiment of a one-stage gas-liquid separation method using a membrane / absorption hybrid method. This methane separation device supplies a biogas containing methane and carbon dioxide as components, mixes an absorbent that absorbs carbon dioxide and generates a mixed liquid in a gas-liquid mixed phase, and a mixed liquid. The first gas-liquid separator 7 which is introduced and gas-liquid separates into methane and a CO ₂ absorbent that has absorbed carbon dioxide, and a plurality of hollow fiber-like permeable membranes 11 incorporated in the container, and is transmitted from the supply port 28. A CO ₂ absorbing solution is supplied to the inside of the membrane to permeate the permeable membrane 11, and the pressure outside the permeable membrane 11 is made lower than the inside of the permeable membrane, thereby allowing the carbon dioxide absorbed in the CO ₂ absorbing solution to pass through. It has a membrane module 10 that diffuses to the outside of the membrane 11 and separates carbon dioxide.

  In this methane separation apparatus, carbon dioxide is recovered to the carbon dioxide recovery unit 27 by the exhaust path 21, the opening / closing valve 22 and the exhaust pump 23. The absorption liquid from which carbon dioxide has been released is discharged from the membrane module 10 and is collected and stored in the absorption liquid storage tank 19 through the collection path 24. Further, the absorption liquid discharged from the membrane module discharge port 29 is collected and stored in the absorption liquid storage tank 19 through the discharge path 13, the opening / closing valve 13 a and the recovery path 18. The membrane module 10 and the absorption liquid storage tank 19 constitute first separation means for recovering the absorption liquid after separating carbon dioxide in the present invention.

  The biogas is supplied to the mixer 5 through the supply path 3. Moreover, the absorption liquid collect | recovered by the absorption liquid storage tank 19 is cyclically supplied to the mixer 5 through the supply paths 20 and 31 by the introduction pump 30, and the absorption liquid circulation system is comprised as a whole.

  FIG. 2 shows a schematic configuration of the mixer 5. In (2A), the mixer 5 is configured by connecting the ejector 5a and the packed bubble column 5b in series. The biogas supplied from the biogas supply path 3 and the absorption liquid supplied from the supply path 31 are mixed by the ejector 5a, and a gas-liquid mixed phase mixed liquid in which the biogas is mixed with the absorption liquid in countless fine bubbles is sent out. It is sent out from the path 6a to the packed bubble column 5b. Gas-liquid mixed phase stirring is further performed in the packed bubble column 5b. After the two-stage operation, the carbon dioxide in the biogas is dissolved in the absorbing liquid, and the carbon dioxide is separated from the gaseous methane. It is sent out from the flow path 6. In particular, in the device configuration in which the above-described packed bubble column is disposed on the downstream side of the gas mixing and confluence portion of the ejector 5a, carbon dioxide in the biogas can be absorbed by the absorbing solution at a higher rate, Methane can be separated efficiently. In (2B), the mixer 5 is comprised only from the ejector 5a. It has been clarified in the present invention that carbon dioxide is sufficiently dissolved in the absorbing liquid even in the gas-liquid mixed phase action by the ejector 5a, and the efficiency of methane separation can be achieved. In this case, the liquid mixture is sent from the delivery path 6 a to the flow path 6.

(2C) and (2D) in FIG. 2 are cross-sectional views of two types of ejectors 5a. In the present invention, it goes without saying that an ejector 5a having another structure may be used. Below, the detail of the gas-liquid multiphase effect | action by the ejector 5a is demonstrated. A rapidly narrowed nozzle 32 is formed inside the ejector 5a. The absorption liquid is supplied from the supply path 31 to the ejector 5 a by the introduction pump 30, and the absorption liquid is injected at a high speed from the nozzle 32, and a negative pressure is generated in the biogas supply path 3 by the formation of the high-speed flow. As the flow velocity of the high-speed flow increases, the negative pressure action increases, and the biogas supplied at a supply pressure slightly higher than atmospheric pressure is sucked into the absorption liquid and instantly becomes a fine bubble state. Can be done. The surface area of gas-liquid contact with the absorbing liquid increases dramatically due to the infinite number of microbubbles, carbon dioxide in the microbubbles dissolves rapidly in the absorbing liquid, and the carbon dioxide is gas-separated from the gaseous methane. Methane fine bubbles are formed, and a gas-liquid two-phase flow of an absorbing solution in which methane fine bubbles and carbon dioxide are dissolved is sent out from the delivery path 6a. In FIG. 2, one absorbent liquid supply path 31 is shown, but a plurality of absorbent liquid supply paths 31 may be provided.
Further, the mixer 5 is not limited to the ejector-type gas mixing and merging portion of FIG. 2, but may be another fluid merging mechanism having equivalent performance. When the ejector method shown in FIG. 2 is adopted as the mixer 5, a negative pressure is automatically generated in the biogas supply path 3 hydrodynamically. Since the biogas is sucked into the absorption liquid by the action of the negative pressure, a biogas blower (not shown) usually installed in the biogas supply path is not necessary, and the apparatus power can be further reduced.

The mixed liquid generated in the mixer 5 is introduced into the first gas-liquid separator 7 through the flow path 6. The first gas-liquid separator 7, and methane, storing and liquid separation in the CO ₂ absorbing solution which has absorbed carbon dioxide. The separated methane is exhausted by an exhaust pump (not shown) through the recovery path 8 and recovered by the methane recovery unit 26. The CO ₂ absorption liquid stored in the first gas-liquid separator 7 passes through the supply path 9 by its own weight action due to the height difference between the first gas-liquid separator 7 and the membrane module 10 or by a supply pump drive (not shown). It is transferred to the membrane module 10. The transfer amount of the absorbing liquid can be adjusted by an opening / closing valve 12 provided in the supply path 9.

The CO ₂ absorbent from the first gas-liquid separator 7 is introduced inside the permeable membrane and permeates through the permeable membrane 11. The inside of the membrane module 10 is exhausted by the low pressure exhaust pump 23 through the exhaust passage 21 and the opening / closing valve 22, and the pressure outside the permeable membrane 11 is made lower than the inside of the permeable membrane, thereby reducing the CO ₂ absorbent. The carbon dioxide absorbed in the gas is diffused to the outside of the permeable membrane 11 to separate the carbon dioxide. The separated carbon dioxide is collected in the carbon dioxide recovery unit 27 through the exhaust passage 21, and the absorption liquid from which the carbon dioxide has been separated is collected in the absorption liquid storage tank 19 through the recovery path 24, and is again mixed from the absorption liquid storage tank 19 into the mixer. 5 is recycled and used. Excess CO ₂ absorption liquid led to the discharge port 29 of the membrane module 10 is recovered in the absorption liquid storage tank 19 through the discharge path 13, the opening / closing valve 13 a and the recovery path 18. The carbon dioxide diffused in the absorption liquid storage tank 19 is recovered by the carbon dioxide recovery unit 27 through the recovery path 25. The on-off valve 13a is provided to keep the permeable membrane 11 in a liquid-sealed state, and a method of reducing the pipe diameter, for example, a limiting orifice may be used.

As described above, in the present embodiment, after collecting the methane separated in the first gas-liquid separator 7, the CO ₂ absorbent is supplied to the membrane module 10 to separate carbon dioxide, and further from the membrane module 10. The derived excess CO ₂ absorption liquid is recovered in the absorption liquid storage tank 19 to dissipate carbon dioxide and separate from the absorption liquid, so that methane and carbon dioxide are efficiently separated in the circulation process of the absorption liquid, Methane can be separated and purified with high efficiency from biogas containing a high concentration of carbon dioxide. Therefore, it is possible to reduce the power load and the membrane module cost, and it is possible to realize a methane separation system that can perform biogas separation / concentration at a low separation cost.

  In this embodiment, an aqueous solution of diethanolamine (DEA) having excellent carbon dioxide absorbability is used as the absorbing solution. The DEA concentration can be 0.1 to 6 mol / L (preferably 2 to 4 mol / L). At this DEA concentration, carbon dioxide can be absorbed and released, and methane can be separated and purified from biogas with high efficiency.

According to the verification by the present inventors, unless the permeation flow rate of the CO ₂ absorbing liquid that permeates the permeable membrane is not less than a predetermined value, the emission efficiency of carbon dioxide per biogas treatment flow rate is not improved, so the methane concentration does not increase. , since it was found that without the use of excess membrane module (area) when the liquid permeation flow rate per membrane area is small not higher methane concentration, the flux of CO ₂ absorbing liquid that passes through the permeable membrane 11 By using the membrane module 10 that can be 5 to 50 L / m ² · min per membrane area (preferably, the permeate flow rate of the CO ₂ absorbent is ^{20 to} 40 L / m ² · min per membrane area), Improves the concentration of purified methane by improving the carbon dispersibility.

In addition, when the CO ₂ absorption liquid flow rate decreases and the liquid film becomes thin at the top of the membrane module, so-called out of liquid state, in the case of gas-liquid mixed introduction (simultaneous introduction of methane and absorption liquid), methane yield decreases due to gas permeation Careful consideration is necessary as it may lead to the inability to supply product gas. In the case of gas-liquid separation (only the absorption liquid is introduced into the membrane module), when the membrane is not used effectively, for example, in a system where the absorption liquid side of the membrane is connected to the product gas line, Care must be taken because the methane yield may be reduced by backflow.

  Further, according to the verification by the present inventors, it has been found that the membrane module is overcrowded when the carbon dioxide or the like is released during the regeneration of the absorbing solution. That is, the density of carbon dioxide in the membrane module is affected by the packing density of the permeable membrane. In a commercially available membrane module, the packing density of the permeable membrane is 30 to 70%, and the distance between adjacent permeable membranes is too close, so that when the liquid flow rate is increased, the space between the membranes is covered with the liquid membrane, As a result, the efficiency of carbon emission deteriorates, and as a result, a large area of the film is required, resulting in high cost. Therefore, in the present embodiment, the membrane module 10 having a sparse density with a permeable membrane packing density of 30% or less (preferably 20% or less) is used to improve the carbon dioxide emission and to efficiently separate methane. Realized. Further, the hollow fiber membranes in the membrane module are divided and arranged in small bundles, and each small bundle is preferably arranged so as to maintain a non-adhering space, and the overall packing density is 30% or less, and carbon dioxide is emitted. Methane can be separated with high efficiency.

FIG. 3 is a comparison diagram of concentrated methane concentrations obtained by performing methane separation from an absorbing solution in which carbon dioxide has been absorbed by three types of methods according to the present invention. This comparative test was carried out by the methane separation apparatus of the single stage separation system shown in FIG. The vertical axis represents the concentrated CH ₄ concentration (%) of the separated methane. The horizontal axis represents the required membrane area (m ² / (Nl / min)) and represents the permeable membrane surface area per unit biogas flow to be treated. More specifically, the required membrane area = the surface area of the permeable membrane installed in the membrane module [m ² ] / biogas treatment flow rate [Nl / min], and the smaller the required membrane area value, It means that carbon dioxide absorption performance is good, that is, methane separation performance is good.
The three types of absorption means the absorption method of biogas into the absorbent by the mixer, the method using only the packed bubble column (● two-dot chain line, ○ one-dot chain line), the series method of ejector and packed bubble column ( ◇ A solid line) and a method using only an ejector (□ dashed line). The solid line, the broken line, and the alternate long and short dash line are the results obtained with a DEA flow rate = 1.5 (L / min), and the double-dotted line is a result obtained with a DEA flow rate = 2.5 (L / min). This indicates that the area of the membrane module required to obtain a product with the same methane concentration differs depending on the method of absorbing carbon dioxide in the mixer.

  As is clear from Fig. 3, the series system of ejector and packed bubble column (◇ solid line) has the best carbon dioxide absorption performance of the absorbing liquid, so the downstream gas-liquid separator has high purity and high yield of methane. It can be seen that it can be recovered. However, this method reduces the merit because the device becomes larger and the device price becomes higher. In addition, although the packed bubble column alone (● two-dot chain line) and the ejector alone (□ dashed line) appear to have almost the same carbon dioxide absorption performance, it can be judged that the ejector is superior in the following points. In the packed bubble column simplex system, it can be seen that the required methane concentration cannot be obtained unless the supply amount of the absorbing liquid is 1.5 times or more that of the ejector simplex system. That is, the two-dot chain line (●) for the packed bubble column alone is the result obtained with a DEA flow rate = 2.5 (L / min), while the broken line (□) for the ejector alone shows a DEA flow rate = 1.5 (L / Min). Therefore, it was found that the ejector single unit method has better carbon dioxide absorption performance than the packed bubble column single unit method, and methane separation can be performed efficiently. Since the gas-liquid phase mixing of the ejector alone can be naturally realized by the hydrodynamic effect, it can be judged that the effect is higher in that the power cost can be reduced. Therefore, the ejector unit system does not require a large packed bubble column, and can provide an excellent methane separation device in terms of cost reduction. In addition, high purity methane could not be obtained with a packed bubble column alone (circle one-dot chain line) with a DEA flow rate = 1.5 (L / min). This graph also shows the outline of the device (area of the permeable membrane required for the membrane module) if the specifications of the methane separation device (for example, the flow rate of biogas to be processed, the concentration of impurities contained, the flow rate of methane to be recovered, the concentration, etc.) ).

FIG. 4 shows an embodiment using the methane separator. (4A), (4B), (4C), and (4D) are details of the execution condition data of Examples 1, 2, 3, and 4. First, in (4A) and (4B), the required membrane area was 0.09 m ² / (NL / min-biogas) and the membrane material was PE (polyethylene). Shows the change in the separated methane concentration and methane yield. The membrane permeate flow rates were 40.6 [L / m ² · min] and 28.4 [L / m ² · min], respectively, and the methane yield was almost 100%. They were 98.4% and 98.2%. (4C), (4D) shows the case where the required membrane area is 0.1 m ² / (NL / min-biogas) and the membrane material is PES (polyethersulfone) and the membrane permeate flow rate is changed. , Shows the change in methane concentration and methane yield. As the flow rate of the membrane permeate increases, the concentration of methane increases. In order to dissipate carbon dioxide absorbed by the absorbing solution with high efficiency, it is suggested that it is effective to increase the permeate flow rate per membrane area and increase the absorbing solution regeneration efficiency by the decompression operation.
In the examples of (4C) and (4D), the methane recovery rate is 99.7 to 99.9% under any conditions, but the methane concentration is in the range of 93.0% to 98.2%. Depending on conditions, the concentration may not be high. On the other hand, in the examples of (4A) and (4B), the methane recovery rate is 99.5 to 99.8% under any condition, and the methane concentration changes in the range of 98.2% to 98.4%. And it shows that the methane separation apparatus which concerns on this embodiment comprises the highly efficient recovery performance of high concentration methane.

FIG. 5 shows the results obtained under the conditions of FIG. 4 in relation to the flow rate of the membrane permeate, the methane yield, and the methane concentration. FIG. 5 shows that when the membrane permeate flow rate is 5 [L / m ² · min] or more, both the methane yield and the methane concentration satisfy the performance.

  Polyethylene is preferable as the material of the permeable membrane 11, and since the outer surface of the membrane is subjected to a hydrophilic treatment, a highly efficient treatment of methane separation and purification is possible. As for the membrane material, polysulfone (PS: membrane density adjustment not supported by the manufacturer), polyethersulfone (PES), polyethylene (PE) and other membrane materials were tested, and good results were obtained with PES and PE. PES swells with time due to the contact of the absorbing solution with diethanolamine (DEA), and a decrease in permeate flow rate is observed, leading to a decrease in biogas separation performance. Is preferred. That is, by using a hydrophobic polyethylene membrane as a permeable membrane, separation selectivity, permeation rate and long-term stability are improved as compared to conventional permeable membranes, for example, resistance to diethanolamine as an absorbing solution, The substantial permeation amount and the economical efficiency of the necessary absorbent can be remarkably improved. However, since the polyethylene membrane is hydrophobic, if the membrane module is not filled with the absorbing solution when the device is stopped, the absorbing solution on the outer surface of the permeable membrane will not be wet when the device is started up, and the separation efficiency may decrease. However, in the present invention, only the outer surface of the permeable membrane is subjected to a chemically hydrophilic surface treatment, or a treatment such as fine unevenness that increases the affinity with the absorbing solution by a physical treatment is performed, so that the separation efficiency at the start-up of the apparatus. It was possible to prevent the decrease in the temperature.

FIG. 6 is a table comparing with a conventional methane purification system apparatus in terms of gas separation performance, purification cost, and the like by the methane separation apparatus according to the present embodiment. In this table, the methane purification methods are compared under the condition that the composition of the raw material biogas is methane (60 vol%), carbon dioxide (40 vol%), and the raw material gas flow rate is 100 m ³ / hr.

FIG. 7 is a graph showing the relationship between the membrane permeate flow rate, the methane separation cost (compared to the conventional art), and the absorption liquid pump power (kW). Although the absorption liquid pump power (kW) is increased by increasing the membrane permeate flow rate, according to the membrane / absorption hybrid methane separation method of the present invention, the membrane permeate flow rate is 15 to 60 [L] compared to the conventional separation method. / M ² · min], the separation cost is reduced. In terms of performance, methane can be separated with high efficiency when the membrane permeate flow rate is 5 [L / m ² · min] or more from FIG. [L / m ² · min]. Further, from FIG. 7 to 20 to 40 [L / m ² · min], a more remarkable reduction in separation cost is shown.

  From FIG. 6 and FIG. 7, in the separation of biogas containing carbon dioxide at high concentration, the membrane / absorption hybrid methane separation method of the present invention and the methane separation apparatus using the same are low-cost and highly efficient from methane. It can be said that it can be separated and purified.

Next, an embodiment of a methane utilization system according to the present invention will be described.
FIG. 8 shows a schematic configuration of a methane utilization system 100 incorporating the methane separation apparatus according to the present invention. This utilization system includes generators 52, 61 and 63 that generate electricity using methane as fuel, and the power generated by the generator can be supplied to the user for sale. Methane is separated and purified from the biogas supplied from the biogas fermenter 51 by using a membrane / absorption hybrid device 50 that is the same methane separation device as in the above embodiment. The electric power generated by the generator 52 is also used to drive each component of the system. The purified methane obtained from the membrane / absorption hybrid device 50 is supplied to the generators 61 and 63 through the supply pump 66 through the calorie adjuster 67 and the supply path 64. Purified methane is supplied to the liquefier 56 via the supply path 65, and the liquefied methane is stored in the liquefied methane storage tank 57. Liquefied methane can be supplied externally through the external supply path 59. Also, liquefied methane can be supplied to the generators 61 and 63. Each supply path is provided with a flow rate regulator 54, 55, 58, 60, 62. The membrane / absorption hybrid device 50 is provided with a hot water supply mechanism (not shown) for temperature adjustment, and the hot water supply by the hot water supply mechanism is performed by a hot water storage tank 53 that is controlled by a generator 52 with heater heating. .
In the methane utilization system having the above-described configuration, the methane separated and refined by the methane separation apparatus according to the present invention is used as fuel to generate electric power from the generators 52, 61 and 63, and the generated electric power is transmitted to the relay 81, 82 and the power line 80 are supplied to the user.

  As an operation example in the methane utilization system 100, the storage level adjustment of the liquefied methane storage tank 57 is controlled by the flow rate control of the flow rate regulators 54, 55, 58, 60, 62, and the power selling price (for example, 8:00 to 20: noon). 00 9 yen / kW, night 20: 00 to the next 8:00 4 yen / kW) can be taken into account to optimize the operating rates of the generators 52, 61, 63. Furthermore, a specific operation example is shown below.

(1) Example of generator operating rate control based on fluctuations in power sales price The generator 52 is always in operation, and during the daytime 8:00 to 20:00, the generators 60 and 62 are operated to reduce the storage speed as much as possible. At night from 20: 00 to the next 8:00, the generators 60 and 62 are stopped and the stored amount is operated at maximum.
(2) Example of absorption control of seasonal variation of biogas generation amount The amount of biogas generation varies depending on the average temperature. For example, since the summer generation amount is large and the winter generation amount is small, the summer storage amount may be controlled to be large, and control may be performed so that the summer storage amount can be used in winter.
(3) Biogas calorie fluctuation absorption control example The methane concentration is measured using the gas concentration meter 68 provided on the methane discharge side, and the gas calorie is calculated. According to the calculation result, the LPG gas from the LPG (liquefied petroleum gas) tank 69 is supplied to the calorie adjuster 67 and added to the purified methane, and the addition amount is controlled to stabilize the fuel quality. it can.

  As described above, it is possible to construct a methane utilization system in which methane is purified and stored based on the high-efficiency methane separation method of the present invention, and the stored methane can be supplied as fuel. Thus, it is possible to realize a power supply system using methane fuel that can be adjusted efficiently in the time zone of the date and time so that the power generated by the power generation facility can be stably supplied to the outside.

  The methane utilization system 100 is provided with a carbon dioxide utilization system 101 that utilizes carbon dioxide produced as a by-product during the separation and purification of methane. In FIG. 8, the recovered carbon dioxide obtained from the membrane / absorption hybrid device 50 is supplied to the liquefier 72 through the supply path 70 through the recovery path 83, and carbon dioxide is liquefied. The liquefied carbon dioxide is stored in the liquefied carbon dioxide storage tank 73. The liquefied carbon dioxide can be supplied from the liquefied carbon dioxide storage tank 73 to the user's house cultivation facilities 77 and 79. The liquefied carbon dioxide can be supplied externally through the external supply path 75. Each supply path is provided with a flow rate regulator 71, 74, 76, 78. While controlling the remaining amount of the liquefied carbon dioxide storage tank 73 by adjusting control of the flow regulators 71, 74, 76, 78, carbon dioxide is liquefied to house-grown plants in the daytime when photosynthesis is active. By supplying directly from the storage tank 73 and the membrane / absorption hybrid apparatus 50 and stopping the supply to house cultivation at night and storing it in the liquefied carbon dioxide storage tank 73, stable supply of carbon dioxide becomes possible.

  With the above carbon dioxide supply system, effective utilization of carbon dioxide as a by-product can be achieved. It is also possible to construct a composite gas supply system that can supply industrial gases to different supply destinations via a carbon dioxide supply facility.

  FIG. 9 shows a schematic configuration of a methane separation apparatus which is an embodiment of a two-stage gas-liquid separation method using a membrane / absorption hybrid method. This methane separator differs from the methane separator shown in FIG. 1 in that a second gas-liquid separator 14 is added. The discharge path 13 is connected to the second gas-liquid separator 14, and methane contained in a trace amount in the excess CO 2 absorbing liquid is separated and recovered by the methane recovery section 26 via the recovery path 15. The excess CO2 absorption liquid from which the trace amount of methane has been separated is recovered in the absorption liquid storage tank 19 through the recovery path 18. In addition, the components shown in FIG. 1 are denoted by the same reference numerals, and the operations and effects of the components indicated by the same reference numerals are the same as those in FIG. To do.

In the present embodiment, after collecting the methane separated in the first gas-liquid separator 7, the CO ₂ absorbent is supplied to the membrane module 10 to separate carbon dioxide, and the excess CO derived from the membrane module 10 is further separated. ₂ is introduced into the second gas-liquid separator 14 to recover the separated methane, and the excess CO ₂ absorption liquid is recovered in the absorption liquid storage tank 19 to dissipate carbon dioxide and separate from the absorption liquid. It is possible to efficiently separate methane and carbon dioxide during the circulation of the absorption liquid, and to separate and purify methane from biogas containing high concentration of carbon dioxide with high efficiency. Therefore, it is possible to reduce the power load and the membrane module cost, and it is possible to realize a methane separation system that can perform biogas separation / concentration at a low separation cost.

  The present invention is not limited to the above-described embodiment, and various modifications, design changes and the like within the scope not departing from the technical idea of the present invention are included in the technical scope. Absent.

  According to the present invention, in the membrane-absorption hybrid method, methane purification processing of biogas containing methane as a main component and containing high concentration of carbon dioxide can be performed with high efficiency and low separation cost, and purified methane with high purity can be used as an energy source. A methane utilization facility and a methane utilization system that can be supplied as

1 is a schematic configuration diagram of a first-stage gas-liquid separation type methane separation apparatus according to the present invention. 2 is a schematic configuration diagram of a mixer 5. FIG. It is a comparison figure of the concentrated methane concentration obtained by implementing methane separation from the absorption liquid which absorbed carbon dioxide by three kinds of methods. It is each implementation condition data table of the Example which changed the permeable membrane material. It is a graph which shows the result of having investigated the relationship between the flow rate of membrane permeate in Examples 1 to ₄ , the yield of methane (CH ₄ ), and the separation concentration. It is a performance comparison table of the methane separation device concerning this embodiment, and a conventional device. It is a graph which shows the relationship between the membrane permeate flow volume in the methane separation apparatus which concerns on this embodiment, methane separation cost, and absorption liquid pump power. It is a schematic block diagram of the biogas utilization system which is another embodiment. 1 is a schematic configuration diagram of a two-stage gas-liquid separation type methane separation apparatus according to the present invention.

Explanation of symbols

3, 9, 20, 31, 64, 65: supply path, 5: mixer
5a: ejector, 5b: packed bubble column, 6a: delivery path 6: flow path, 13: discharge path, 7: first gas-liquid separator,
8, 15, 18, 24, 25, 83: recovery path, 10: membrane module,
11: permeable membrane, 12, 13a, 22: open / close valve, 14: second gas-liquid separator,
19: Absorption liquid storage tank, 21: Exhaust passage, 23: Exhaust pump,
26: Methane recovery unit, 27: Carbon dioxide recovery unit, 28: Supply port,
29: discharge port, 30: introduction pump, 32: nozzle,
50: membrane / absorption hybrid device, 51: biogas fermenter,
52, 61, 63: Generator, 53: Hot water tank,
54, 55, 58, 60, 62, 71, 74, 76, 78: flow rate regulator,
56, 72: liquefier, 57: liquefied methane storage tank,
59, 75: External supply path, 66, 70: Supply pump,
67: Calorie adjuster, 68: Gas concentration meter, 69: LPG tank,
73: Liquefied carbon dioxide storage tank, 77, 79: Facility for house cultivation,
80: Power line, 81, 82: Repeater

Claims (20)

A methane separation method for separating methane from a biogas containing methane and carbon dioxide as components, the step of producing a gas-liquid mixed phase mixed liquid by using a mixer with an absorption liquid that absorbs carbon dioxide and the biogas; , Introducing the mixed liquid into the first gas-liquid separator, separating the methane and the carbon dioxide-absorbed CO ₂ absorption liquid, and recovering the methane separated in the first gas-liquid separator; A step of supplying a CO ₂ absorbing solution to the inside of the permeable membrane from a supply port of a membrane module in which a plurality of hollow fiber-like permeable membranes are incorporated in a container to permeate the permeable membrane, and a pressure outside the permeable membrane. By making the pressure lower than the inside of the permeable membrane, carbon dioxide absorbed in the CO ₂ absorbing liquid is diffused to the outside of the permeable membrane to separate carbon dioxide, and the absorbing liquid after carbon dioxide separation is recovered. You Methane separation method characterized by comprising the step of at least. By introducing an excess of the CO ₂ absorbing solution derived in the outlet of the membrane module to a second gas-liquid separator, the steps of gas-liquid separation into methane and excess CO ₂ absorbing solution of trace, the second gas The methane separation method according to claim 1, further comprising a step of recovering methane separated in a liquid separator and a step of recovering the excess CO ₂ absorbent. The methane separation method according to claim 1 or 2, wherein a packing density of the permeable membrane in the membrane module is 30% or less. 4. The methane separation according to claim 3, wherein the permeable membranes in the membrane module are divided and arranged in small bundles, and each of the small bundles is arranged so as not to be densely packed, and the packing density as a whole is 30% or less. Method. The mixer includes at least an ejector provided in a flow passage communicating with the inlet of the first gas-liquid separator, and generates a negative pressure by forming a flow of the absorbing liquid in the flow passage. The methane separation method according to claim 1, wherein the biogas is sucked into the absorption liquid to generate the mixed liquid, and the carbon dioxide is efficiently absorbed by the absorption liquid. The methane separation method according to claim 5, wherein the mixed liquid generated by the ejector is supplied to a packed bubble column to further promote absorption of carbon dioxide into the mixed liquid. The method for separating methane according to any one of claims 1 to 6, wherein the absorbing solution is an aqueous solution of di-ethanolamine and has a concentration of 0.1 to 6 mol / L. The methane separation method according to any one of claims 1 to 7, wherein the membrane module has a permeation flow rate of the CO ₂ absorbing liquid that permeates the permeable membrane of 5 to 50 L / m ² · min per membrane area. The methane separation method according to claim 1, wherein the permeable membrane is made of polyethylene. The methane separation method according to claim 1, wherein a hydrophilic treatment is applied to an outer surface of the permeable membrane. A methane separator that separates methane from a biogas containing methane and carbon dioxide as components, and a mixer that mixes an absorption liquid that absorbs carbon dioxide and the biogas to produce a gas-liquid mixed phase mixed liquid A first gas-liquid separator that introduces the mixed liquid and gas-liquid separates into methane and a CO ₂ absorbing liquid that has absorbed carbon dioxide, and a plurality of hollow fiber-like permeable membranes incorporated in the container, and supplying the CO ₂ absorbing solution inside the permeable membrane from the mouth is transmitted through the transmissive film, the pressure outside the permeable membrane by the low pressure from the inside of the permeable membrane, the CO ₂ absorbing solution It has a membrane module that separates carbon dioxide by dissipating absorbed carbon dioxide to the outside of the permeable membrane, and has at least first separation means for recovering the absorption liquid after carbon dioxide separation by the membrane module Methane separation apparatus, characterized in that. A second gas-liquid separator that introduces an excess of the CO ₂ absorbing liquid led out to the outlet of the membrane module and separates it into a small amount of methane and excess CO ₂ absorbing liquid, and the excess CO ₂ absorbing The methane separation apparatus according to claim 11, further comprising: a second separation unit that collects liquid, wherein methane separated by the first gas-liquid separator and the second gas-liquid separator is collected. The methane separation device according to claim 11 or 12, wherein a packing density of the permeable membrane in the membrane module is 30% or less. The mixer has at least an ejector provided in a flow passage communicating with an inlet of the first gas-liquid separator, means for introducing the absorption liquid, and means for introducing the biogas, A negative pressure is generated by forming a flow of the absorption liquid in a path, the biogas is sucked into the absorption liquid to generate the mixed liquid, and the absorption liquid efficiently absorbs carbon dioxide. Item 13. The methane separator according to Item 11 or 12. The methane separation device according to any one of claims 11 to 14, wherein the absorption liquid is an aqueous solution of diethanolamine, and the concentration thereof is 0.1 to 6 mol / L. The methane separation device according to any one of claims 11 to 15, wherein the membrane module has a permeation flow rate of the CO ₂ absorbing liquid that permeates the permeable membrane of 5 to 50 L / m ² · min per membrane area. The methane separation apparatus according to claim 11, wherein the permeable membrane is made of polyethylene. Natural gas produced from the anaerobic fermentation of organisms produced mainly from methane using the methane separation method according to any one of claims 1 to 10, underground storage of industrial and household waste Refining methane by removing carbon dioxide using the above-mentioned biogas as an underground fermentation gas that is produced by anaerobic fermentation naturally or by an artificially generated anaerobic fermentation process. The methane utilization system is characterized in that the stored methane can be supplied as fuel. Power generation equipment that generates electricity using the stored methane as fuel and storage control means that adjusts the amount of purified methane stored according to the season, operation period, or time zone, and can supply the power generated by the power generation equipment to the outside The methane utilization system according to claim 18. The methane utilization system of Claim 18 or 19 provided with the carbon dioxide supply facility which enabled the hybrid supply of the carbon dioxide isolate | separated simultaneously in the said methane utilization system in the said methane utilization system.

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