Biogas reformer

Abstract

To provide a biogas reformer which efficiently removes carbon dioxide from a methane fermentation biogas.SOLUTION: A biogas reformer includes: a device main part; a biogas supply unit for supplying a biogas to the interior of the device main part; and a reaction liquid jet unit which is disposed above the biogas supply unit and jets an alkali reaction liquid downward in the device main part. A biogas generation device may further include a reaction liquid return unit which returns the alkali reaction liquid stored at a bottom part of the device main part to the reaction liquid jet unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a biogas reformer. [Background technology]

[0002] Conventionally, power plants that recover energy from methane fermentation biogas (hereinafter simply referred to as "biogas") have been known. Biogas is composed primarily of approximately 60% methane and 40% carbon dioxide, and can be produced by fermenting organic waste such as food waste. The power plants described above generate electricity using the calorific value of biogas, but the calorific value of biogas is lower than that of city gas, resulting in poor energy recovery efficiency. In light of this problem, a technique is known for removing carbon dioxide contained in biogas and increasing the methane concentration in order to increase the calorific value of biogas. For example, Patent Document 1 discloses a method for concentrating methane from biogas, which uses a separation membrane process to concentrate and recover methane from biogas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-095727 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned conventional methane concentration methods use multi-stage separation membranes to remove carbon dioxide, but separation membranes are essentially consumables, and deteriorated membranes must be replaced each time they deteriorate. Therefore, devices using conventional methane concentration methods have the problem of high operating costs. Furthermore, conventional methane concentration methods using separation membranes require a high-pressure compressor to pressurize and supply biogas to the separation membrane, and the need for such equipment also hinders efforts to reduce the cost and size of the device.

[0005] One of the objects of the present invention is to provide a biogas reforming apparatus that efficiently removes carbon dioxide from methane fermentation biogas. [Means for solving the problem]

[0006] A biogas reforming device in one embodiment of the present invention includes a device main body, a biogas supply unit that supplies biogas into the device main body, and a reaction liquid injection unit that is positioned above the biogas supply unit and that injects alkaline reaction liquid downward inside the device main body.

[0007] The biogas reforming apparatus may further include a reaction liquid returning section that returns the alkaline reaction liquid stored in the bottom of the apparatus body to the reaction liquid spraying section.

[0008] The biogas reforming apparatus may further include a gas-liquid separation unit provided above the reaction liquid injection unit. In this case, the gas-liquid separation unit may include a filter layer that separates water and biogas, and a cleaning unit that cleans the filter layer.

[0009] The gas-liquid separation unit may include a first filter layer and a second filter layer disposed above the first filter layer. In this case, the second filter layer may be made of a filter material having a lower porosity than the first filter layer. For example, the first filter layer may be a demister, and the second filter layer may be made of an adsorbent (preferably, activated carbon).

[0010] In the biogas reforming apparatus, the cleaning unit may include a cleaning pipe having a plurality of injection holes for injecting cleaning water, and a cleaning water supply pipe for supplying the cleaning water into the cleaning pipe. In this case, the cleaning pipe may be disposed between the first filter layer and the second filter layer. The cleaning pipe may be configured to be rotatable within the apparatus body around a rotation axis extending in the longitudinal direction.

[0011] The biogas reforming apparatus may further include a concentration adjusting unit that adds an adjusting liquid to the alkaline reaction liquid sprayed from the reaction liquid spraying unit, and in this case, the adjusting liquid may contain hydroxide ions at a higher concentration than the alkaline reaction liquid stored in the bottom of the apparatus body.

[0012] In the biogas reforming apparatus, the biogas supply unit may include a gas distribution pipe extending toward the inside of the apparatus body, and a purge execution unit that executes air purging of the gas distribution pipe. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing the configuration of a biogas reforming device according to a first embodiment. [Figure 2] FIG. 2 is an enlarged schematic view showing the configuration of a cleaning unit in the biogas reforming apparatus according to the first embodiment. [Figure 3] FIG. 4 is a schematic diagram showing the configuration of a biogas reforming device according to a modified example of the first embodiment. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of a biogas reforming device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be embodied in various forms without departing from the spirit of the present invention, and should not be construed as being limited to the description of the embodiments exemplified below. To clarify the explanation, the drawings may show the size, width, thickness, shape, etc. of each part schematically compared to the actual form, but these are merely examples and do not limit the interpretation of the present invention. In this specification and each drawing, elements having the same functions as those described with reference to the previous drawings may be assigned the same reference numerals, and redundant explanations may be omitted.

[0015] In this specification and drawings, "up" refers to the direction opposite to the direction of gravity, and "down" refers to the direction of gravity. Additionally, "left" and "right" refer to directions perpendicular to "up" and "down." For convenience of explanation, the "up-down direction" of the biogas reformer may be expressed as the "height direction," and the "left-right direction" may be expressed as the "width direction."

[0016] (First embodiment) [Configuration of biogas reformer 100] FIG. 1 is a schematic diagram showing the configuration of a biogas reformer 100 according to a first embodiment. The biogas reformer 100 is a device equipped with a function for reforming methane fermentation-type biogas. The primary purpose of the biogas reformer 100 is to increase the methane concentration of biogas. However, as will be described later, the biogas reformer 100 can also secondarily reduce SOx and NOx in the biogas.

[0017] The biogas reformer 100 includes an apparatus main body 10, a biogas supply unit 20, a reaction liquid injection unit 30, a reaction liquid return unit 40, a concentration adjustment unit 50, and a gas-liquid separation unit 60. However, the configuration of the biogas reformer 100 is not limited to the configuration shown in the figure, and some of the components may be omitted or other components may be added. For example, in Figure 1, the reaction liquid return unit 40, the concentration adjustment unit 50, and the gas-liquid separation unit 60 are not essential components and may be omitted.

[0018] Each component will be described using Figure 1. The device main body 10 is the part that corresponds to the housing of the biogas reformer 100, and corresponds to the reaction vessel that carries out the biogas reforming process. The biogas reforming process (processing to increase the methane concentration in the biogas) is carried out inside the device main body 10.

[0019] A gas exhaust pipe 91 is connected to the top of the device main body 10. The gas exhaust pipe 91 is a pipe that exhausts the biogas reformed by the biogas reforming device 100, i.e., biogas with an increased methane concentration. The reformed biogas is sent via the gas exhaust pipe 91 to downstream facilities (for example, a gas holder that stores methane gas).

[0020] A reactant discharge pipe 92 is connected to the lower part (bottom) of the apparatus main body 10. As will be described in detail later, when the biogas reforming apparatus 100 is operated, reactants mainly composed of calcium carbonate and sodium carbonate precipitate over time at the bottom of the apparatus main body 10. For this reason, in this embodiment, the valve 81 is opened periodically to discharge the precipitated reactants to the outside. The reactants discharged through the reactant discharge pipe 92 are sent to a downstream sludge treatment device (not shown).

[0021] The biogas supply unit 20 is a section that supplies biogas to the inside of the apparatus main body 10. The biogas supply unit 20 in this embodiment includes a gas supply port 21 and a gas distribution pipe 22. The gas supply port 21 corresponds to an introduction section (opening) for supplying biogas to the inside of the apparatus main body 10. A gas supply pipe 93 is connected to the gas supply port 21 via a valve 82. Biogas generated in an upstream facility (for example, a fermentation treatment device such as a bioreactor that generates methane gas) is supplied to the gas supply port 21 via the gas supply pipe 93.

[0022] The gas distribution pipe 22 is a pipe-shaped component that extends toward the inside of the device body 10 and is connected to the gas supply port 21. The gas distribution pipe 22 has a longitudinal direction that corresponds to the width direction of the device body 10. The gas distribution pipe 22 is provided with a plurality of discharge holes 22a for discharging biogas at predetermined intervals. The biogas introduced from the gas supply port 21 travels through the inside of the device body 10 via the gas distribution pipe 22 and is discharged into the inside of the device body 10 from the plurality of discharge holes 22a. The discharge holes 22a may be simple through-holes or may be nozzles capable of spraying gas.

[0023] In this embodiment, an example has been shown in which the biogas supply unit 20 is configured with the gas supply port 21 and the gas distribution pipe 22, but this is not limited to this example, and only the gas supply port 21 may be provided, and the gas distribution pipe 22 may be omitted. Furthermore, in this embodiment, an example has been shown in which the biogas is diffused inside the device main body 10 using the gas distribution pipe 22, but this is not limited to this example, and the biogas may be released into the device main body 10 using another configuration (for example, a gas injector arranged on the side wall of the device main body 10).

[0024] The reaction liquid spraying unit 30 is a section that sprays a solution containing a component that reacts with carbon dioxide to immobilize (solidify) the carbon dioxide (hereinafter referred to as "alkaline reaction liquid") toward the inside of the device main body 10. In this embodiment, an example is shown in which milk of lime (for example, a solution containing slaked lime) is used as the alkaline reaction liquid 15, but the present invention is not limited to this example, and other solutions such as a sodium hydroxide solution (caustic soda solution) and a sodium carbonate solution (sodium carbonate solution) can also be used.

[0025] The reaction liquid jetting unit 30 of this embodiment includes a reaction liquid supply port 31 and a reaction liquid jetting pipe 32. The reaction liquid supply port 31 corresponds to an introduction part (opening) for supplying the alkaline reaction liquid 15 into the inside of the apparatus main body 10. A reaction liquid return pipe 41 of a reaction liquid return unit 40, which will be described later, is connected to the reaction liquid supply port 31. However, the present invention is not limited to this example, and a configuration may also be adopted in which another pipe is connected to the reaction liquid supply port 31 and the reaction liquid return unit 40 is connected to the other pipe.

[0026] The reaction liquid injection pipe 32 is a pipe-shaped component extending toward the inside of the apparatus body 10, and is connected to the reaction liquid supply port 31. Like the gas distribution pipe 22, the reaction liquid injection pipe 32 has a longitudinal direction in the width direction of the apparatus body 10. The reaction liquid injection pipe 32 is provided with a plurality of injection holes 32a for injecting the alkaline reaction liquid 15 at predetermined intervals. The plurality of injection holes 32a are provided facing downward toward the apparatus body 10. The alkaline reaction liquid 15 that flows in from the reaction liquid supply port 31 passes through the reaction liquid injection pipe 32 and advances inside the apparatus body 10, and is injected into the inside of the apparatus body 10 from the plurality of injection holes 32a. The injection holes 32a are preferably nozzles that have the function of injecting the alkaline reaction liquid 15 in the form of a mist.

[0027] In this embodiment, before the biogas reforming apparatus 100 is operated, the alkaline reaction liquid 15 is stored in advance at the bottom of the apparatus main body 10, and once the apparatus is started, the alkaline reaction liquid 15 is supplied to the reaction liquid spraying unit 30 using the reaction liquid return unit 40. However, the present invention is not limited to this example, and the alkaline reaction liquid 15 may be supplied from another reaction liquid storage tank (not shown).

[0028] The reaction liquid return section 40 is a section that returns the alkaline reaction liquid 15 stored at the bottom of the device body 10 to the reaction liquid injection section 30. The reaction liquid return section 40 includes a reaction liquid return pipe 41 and a pump 42. As described above, the reaction liquid return pipe 41 is connected to the reaction liquid supply port 31, and supplies the alkaline reaction liquid 15 pumped up by the action of the pump 42 to the reaction liquid supply port 31. In this way, the alkaline reaction liquid 15 stored at the bottom of the device body 10 is returned to the reaction liquid injection section 30 through the reaction liquid return pipe 41 by the action of the pump 42, and is injected again from the reaction liquid injection pipe 32. In other words, the biogas reformer 100 of this embodiment is configured so that the alkaline reaction liquid 15 circulates between the inside of the device body 10 and the outside of the device body 10 (the reaction liquid return section 40).

[0029] The concentration adjusting unit 50 is a component for adjusting the concentration of the alkaline reaction solution 15 supplied to the device body 10. As will be described in detail later, in this embodiment, the alkaline reaction solution 15 supplied to the device body 10 has a reduced slaked lime content as the biogas reforming process progresses. In other words, the hydroxide ion concentration contained in the alkaline reaction solution 15 decreases, causing the pH value to drop. Therefore, the concentration adjusting unit 50 has a function of increasing the slaked lime content that decreases as the reforming process progresses, and adjusting the concentration so as to maintain the hydroxide ion concentration contained in the alkaline reaction solution 15 at a predetermined concentration.

[0030] The concentration adjusting unit 50 includes a tank body 51, an adjusting liquid supply pipe 52, a pump 53, a filter 54, and an adjusting liquid 55. The concentration adjusting unit 50 pumps up the adjusting liquid 55 stored inside the tank body 51 by the action of the pump 53, and supplies the adjusting liquid 55 to the reaction liquid spraying unit 30 via the adjusting liquid supply pipe 52. The adjusting liquid 55 is milk of lime that contains more slaked lime than the alkaline reaction liquid 15 supplied inside the apparatus body 10. The filter 54 is provided to filter out the slaked lime when the adjusting liquid 55 is pumped up by the adjusting liquid supply pipe 52.

[0031] In this embodiment, an example has been shown in which the adjustment liquid supply pipe 52 is connected to the reaction liquid return pipe 41 and the concentration is adjusted by mixing the adjustment liquid 55 into the alkaline reaction liquid 15 returned by the reaction liquid return unit 40, but the present invention is not limited to this example. Any other configuration may be adopted as long as it is possible to adjust the concentration by mixing the adjustment liquid 55 into the alkaline reaction liquid 15 supplied to the reaction liquid spray unit 30 at some timing.

[0032] The gas-liquid separation unit 60 is a section for removing moisture from the biogas that has been reformed. The gas-liquid separation unit 60 includes a first filter layer 61, a second filter layer 62, and a cleaning unit 63. Specifically, the gas-liquid separation unit 60 has a laminated filter structure in which the first filter layer 61 is disposed directly above the reaction liquid injection pipe 32, and the second filter layer 62 is disposed thereon.

[0033] The first filter layer 61 is a layer composed of a "filter material" generally called a demister. In this embodiment, a ball filter material is used as the demister, but this is not limited to this example, and other materials such as a composite corrugated sheet material can also be used. The ball filter material is a ball-shaped structure made of a plastic material or the like, and has the advantage of being less likely to clog due to its high porosity. Although not shown in the figures, the first filter layer 61 in this embodiment has a layered structure in which multiple ball filter materials are sandwiched between a net made of a material such as PVC. The first filter layer 61 mainly serves to separate the biogas that has been reformed inside the device main body 10 from the moisture contained in the biogas and return the separated moisture to the device main body 10.

[0034] The second filter layer 62 is a layer made of a filter material (for example, an adsorbent material such as activated carbon) having a lower porosity than the first filter layer 61. Although not shown in the drawings, the second filter layer 62 has a layer structure in which activated carbon is sandwiched between fine mesh plates with openings of about 1 mm. The second filter layer 62 mainly serves to separate NOx from the reformed biogas. Note that, although the present embodiment shows an example in which activated carbon is used as the second filter layer 62, the present invention is not limited to this example and other adsorbents can also be used.

[0035] The cleaning unit 63 is a section that has the function of cleaning the first filter layer 61 and the second filter layer 62. The cleaning unit 63 includes a cleaning pipe 63a having a plurality of injection holes for injecting cleaning water, and a cleaning water supply pipe 63b that supplies cleaning water to the inside of the cleaning pipe 63a. The cleaning water flowing through the cleaning water supply pipe 63b can be stopped or started by a valve 83 provided on the cleaning water supply pipe 63b.

[0036] In this embodiment, the cleaning pipe 63a is disposed between the first filter layer 61 and the second filter layer 62. The cleaning pipe 63a is configured to be rotatable around a rotation axis in the longitudinal direction (the width direction of the device body 10) inside the device body 10. Here, the specific structure of the cleaning unit 63 of this embodiment will be described with reference to FIG.

[0037] Fig. 2 is an enlarged schematic view showing the configuration of the cleaning unit 63 in the biogas reforming apparatus 100 according to the first embodiment. As shown in Fig. 2, the cleaning pipe 63a is attached by passing through the opening 11a in the side wall 11 of the apparatus body 10. In this case, the outer diameter of the cleaning pipe 63a is larger than the outer diameter of the cleaning water supply pipe 63b, and the cleaning water supply pipe 63b is inserted into the cleaning pipe 63a.

[0038] A flange-shaped bearing unit 63d is attached to the side wall 11 of the apparatus body 10. The bearing unit 63d is a component in which a flange 63da and a bearing 63db are integrated, and the flange 63da is fixed to the side wall 11 with fastening means (not shown) such as bolts. The bearing 63db is a ball bearing fixed to the flange 63da, and an opening is also formed in the flange 63da to match the position of the inner ring (bearing) of the bearing 63db. The cleaning pipe 63a passes through the opening in the flange 63da and is inserted into the inner ring of the bearing 63db.

[0039] Furthermore, a cartridge-type bearing unit 63e is attached to the tip of the cleaning pipe 63a. The bearing unit 63e is a component that integrates a cylindrical bearing housing with a ball bearing inside, and the cylindrical bearing housing is inserted and fixed into the cleaning pipe 63a. The cleaning water supply pipe 63b is inserted into the cleaning pipe 63a while being supported by the bearing unit 63e.

[0040] As described above, the cleaning pipe 63a is rotatably supported relative to the apparatus body 10 by the bearing unit 63d. Furthermore, the cleaning pipe 63a is connected to the cleaning water supply pipe 63b via the bearing unit 63e, and is therefore rotatable relative to the fixed cleaning water supply pipe 63b. In this embodiment, a sprocket 63f is attached to the outer surface of the cleaning pipe 63a. Although not shown, the sprocket 63f is connected to a drive mechanism such as a motor via a gear (cogwheel) or the like. Therefore, the cleaning pipe 63a can be rotated at a desired speed by transmitting the power of the drive mechanism to the sprocket 63f at a desired transmission ratio. Therefore, in the cleaning section 63, cleaning water is sprayed radially around the rotation axis as the cleaning pipe 63a rotates, so that the first filter layer 61 located below the cleaning pipe 63a and the second filter layer 62 located above the cleaning pipe 63a can be continuously cleaned using a single cleaning pipe 63.

[0041] In this embodiment, an example using sprocket 63f has been shown, but the present invention is not limited to this example and may be configured, for example, by combining a pulley and a belt.Furthermore, for example, a blade member may be provided inside cleaning pipe 63a, and the blade member may be rotated by the water pressure of cleaning water flowing in from cleaning water supply pipe 63b, thereby rotating cleaning pipe 63a.

[0042] The biogas reformer 100 having the structure described above can perform a reforming process in which carbon dioxide is removed from the biogas and the concentration of methane gas is increased by reacting the biogas supplied inside the device main body 10 with the alkaline reaction liquid 15. In controlling the biogas reformer 100, elements that require electronic control, such as valves (e.g., electromagnetic valves) and motors, can be controlled according to a predetermined sequence by a control unit (not shown).

[0043] [Operation of the biogas reformer 100] Next, the reforming process by the biogas reformer 100 will be described below. The biogas released into the inside of the device body 10 through the gas distribution pipe 22 rises inside the device body 10 as indicated by the dashed arrow. At this time, the alkaline reaction liquid 15 sprayed downward through the reaction liquid spray pipe 32 into the device body 10 turns into a mist and descends inside the device body 10. Therefore, inside the device body 10, the biogas containing carbon dioxide comes into contact with the alkaline reaction liquid 15 made of milk of lime (a solution containing calcium hydroxide), and calcium carbonate and water are produced by the following reaction: Ca(OH)2+CO2 → CaCO3+H2O

[0044] Since the calcium carbonate described above is a solid, most of it falls together with the alkaline reaction liquid 15 and is mixed into the alkaline reaction liquid 15 accumulated at the bottom of the device body 10. The mixed calcium carbonate (reactant) accumulates as a precipitate at the bottom of the device body 10. The reactant accumulated at the bottom of the device body 10 is periodically discharged via the reactant discharge pipe 92.

[0045] On the other hand, the biogas from which carbon dioxide has been removed by the above reaction rises as it is inside the device main body 10 as biogas with a high methane concentration. The rising biogas first comes into contact with the first filter layer 61 of the gas-liquid separation unit 60, where the moisture contained in the gas is separated. The moisture separated by the first filter layer 61 falls inside the device main body 10 and is returned to the alkaline reaction liquid 15 stored at the bottom of the device main body 10. The biogas from which moisture has been removed continues to rise and comes into contact with the second filter layer 62. In the second filter layer 62, the NOx components in the biogas are adsorbed and removed by the action of activated carbon. In this way, the biogas reformed by the above reaction formula passes through the gas-liquid separation unit 60, where moisture and NOx components are further removed, and the reformed biogas is sent to a downstream facility (such as a gas holder) via the gas exhaust pipe 91.

[0046] The alkaline reaction liquid 15 used in the above-described reforming process falls to the bottom of the apparatus main body 10 and is then returned to the reaction liquid injection unit 30 by the reaction liquid return unit 40 for reuse. Furthermore, as shown in the above reaction formula, the milk of lime contained in the alkaline reaction liquid 15 is consumed during the reforming process, and the slaked lime content of the alkaline reaction liquid 15 decreases over time. However, the biogas reforming apparatus 100 can replenish the lost slaked lime using the concentration adjustment unit 50, thereby appropriately maintaining the slaked lime content in the alkaline reaction liquid 15 (i.e., the concentration of hydroxide ions generated by dissolution of slaked lime). In this way, the biogas reforming apparatus 100 of this embodiment can be continuously operated while performing the biogas reforming process based on the above reaction formula.

[0047] As described above, the biogas reforming apparatus 100 of this embodiment can efficiently remove carbon dioxide from methane fermentation biogas containing methane gas and carbon dioxide, thereby producing biogas with an increased methane concentration. Such biogas with an increased methane concentration has a calorific value comparable to that of gas for 12A or 13A city gas standards, allowing for efficient energy recovery. Furthermore, this embodiment has the advantage that there is no need to prepare dedicated equipment to recover energy from biogas, and existing equipment for city gas applications (power generation equipment and gas appliances) can be used.

[0048] Furthermore, the biogas reforming apparatus 100 of this embodiment does not require a dedicated filter such as a decarbonation membrane used in membrane separation methods, or a high-pressure compressor, so there is also the advantage that the cost of the apparatus can be significantly reduced.

[0049] In addition, milk of lime also reacts with sulfur dioxide to produce calcium sulfite through the following reaction: Ca(OH)2+SO2 → CaSO3+H2O Calcium sulfite is easily removed because it becomes solid calcium sulfate through oxidation. In other words, inside the device body 10, it is possible to remove not only carbon dioxide but also the SOx components contained in biogas.

[0050] (Variation) In the biogas reformer 100 of this embodiment, the biogas released from the gas distribution pipe 22 comes into contact with the alkaline reaction liquid 15 falling from above as it rises, so that the alkaline reaction liquid 15 containing calcium carbonate falls into the gas distribution pipe 22. In this case, there is a risk that the calcium carbonate adhering to the gas distribution pipe 22 will clog the discharge hole 22a. Therefore, in this modified example, an example will be described in which the gas distribution pipe 22 is provided with a function to prevent clogging.

[0051] Figure 3 is a schematic diagram showing the configuration of a biogas reforming apparatus 100A according to the second embodiment. In Figure 3, the same components as those in the first embodiment are indicated by the same reference numerals. Therefore, the following description will focus on the components that are different from those in the first embodiment, and will omit redundant description of the components that are the same as those in the first embodiment.

[0052] The biogas reformer 100A of this modification differs from the biogas reformer 100 described above in that the gas distribution pipe 22A has a plurality of discharge holes 22Aa facing downward in the apparatus body 10. The other configurations are the same as those of the biogas reformer 100.

[0053] In the biogas reformer 100A of this modified example, the discharge holes 22Aa of the gas distribution pipe 22A face downward, so there is no risk that the alkaline reaction solution 15 containing calcium carbonate that falls from above will pass through the discharge holes 22Aa and enter the inside of the gas distribution pipe 22A. In other words, calcium carbonate does not adhere to the inside of the gas distribution pipe 22A, and the possibility of clogging of the discharge holes 22Aa of the gas distribution pipe 22A can be reduced.

[0054] In this way, in the biogas reformer 100 of the first embodiment, clogging of the discharge hole 22a can be easily avoided simply by shifting the position of the discharge hole 22a arranged in the gas distribution pipe 22 downward. However, the position of the discharge hole 22a is not limited to the downward side and may be on the lateral side. In this case, too, it is possible to prevent the alkaline reaction solution 15 pouring down from above from directly entering the gas distribution pipe 22.

[0055] The biogas reformer 100 may further include a purge unit that performs air purging on the gas distribution pipe 22. Specifically, the purge unit may include a means for sending high-pressure air into the gas distribution pipe 22 and removing solid matter (calcium carbonate, etc.) adhering to the discharge hole 22a by air pressure.

[0056] As another means, it is also possible to provide a blade member such as a squeegee that moves on the surface of the gas distribution pipe 22. In this case, by periodically moving the blade member back and forth to remove solid matter adhering to the surface of the gas distribution pipe 22, it is possible to prevent the solid matter from becoming thicker near the discharge hole 22a and prevent the discharge hole 22a from becoming clogged.

[0057] Furthermore, it is also possible to adopt a structure similar to that of the cleaning pipe 63a described above, making the gas distribution pipe 22 rotatable. That is, the gas distribution pipe 22 may be configured to release biogas from the release holes 22a while rotating. In this case, the alkaline reaction solution 15 containing calcium carbonate that falls from above is less likely to enter the inside of the gas distribution pipe 22, thereby preventing problems such as calcium carbonate from swelling inside the gas distribution pipe 22.

[0058] (Second embodiment) In this embodiment, an example will be described in which the configuration of the density adjustment unit is different from that of the first embodiment. In the description of this embodiment, the same elements as those in the first embodiment will be indicated in the drawings using the same reference numerals, and duplicated explanations will be omitted.

[0059] 4 is a schematic diagram showing the configuration of a biogas reformer 100B according to the second embodiment. The biogas reformer 100B of this embodiment corresponds to an example in which the reaction liquid return unit 40 and the concentration adjustment unit 50 in the biogas reformer 100 of the first embodiment are integrated. That is, in this embodiment, the concentration adjustment unit 50B also serves to return the alkaline reaction liquid 15 to the reaction liquid injection unit 30.

[0060] As shown in Fig. 4, the tank body 51B of the concentration adjusting section 50B is connected to the apparatus body 10 via a first reaction liquid return pipe 41Ba. The interior of the tank body 51B is separated into a first tank 50Ba and a second tank 50Bb by a partition plate 51Ba. The above-mentioned first reaction liquid return pipe 41Ba is connected to the first tank 50Ba. Therefore, the first tank 50Ba stores the alkaline reaction liquid 15 returned from the bottom of the apparatus body 10 via the first reaction liquid return pipe 41Ba.

[0061] On the other hand, the second tank 50Bb stores the adjusting solution 55 described in the first embodiment. The adjusting solution 55 is pumped out by a pump 53B and can be sent to the first tank 50Ba via an adjusting solution supply pipe 52B. In other words, by sending the adjusting solution 55 from the second tank 50Bb to the first tank 50Ba, the concentration of the alkaline reaction liquid 15 stored in the first tank 50Ba can be adjusted.

[0062] A second reaction liquid return pipe 41Bb extends downward from the first tank 50Ba, and the second reaction liquid return pipe 41Bb is connected to the reaction liquid injection unit 30 via a pump 53. That is, the alkaline reaction liquid 15 stored in the first tank 50Ba is adjusted by the concentration adjustment unit 50B to become a solution containing slaked lime at a desired content, and then is returned to the reaction liquid injection unit 30 via the second reaction liquid return pipe 41Bb.

[0063] As described above, in this embodiment, the concentration adjustment unit 50B has both the function of adjusting the concentration of the alkaline reaction liquid 15 and the function of returning the alkaline reaction liquid 15 to the reaction liquid injection unit 30, thereby providing the same benefits as in the first embodiment and enabling the biogas reforming apparatus 100B to be made smaller.

[0064] The above-described embodiments (including modifications) of the present invention can be combined as appropriate as long as they are not mutually inconsistent. A person skilled in the art may add or delete components or modify designs, or add or omit processes or modify conditions based on the above-described embodiments, and these additions or deletions or modifications are included in the scope of the present invention as long as they include the gist of the present invention.

[0065] Furthermore, even if there are other effects and advantages different from those brought about by the above-described embodiments, if they are clear from the description in this specification or can be easily predicted by a person skilled in the art, they are naturally understood to be brought about by the present invention. [Explanation of symbols]

[0066] 10... device body, 11... side wall, 11a... opening, 15... alkaline reaction liquid, 20... biogas supply unit, 21... gas supply port, 22, 22A... gas distribution pipe, 22a, 22Aa... discharge hole, 30... reaction liquid injection unit, 31... reaction liquid supply port, 32... reaction liquid injection pipe, 32a... injection hole, 40... reaction liquid return unit, 41... reaction liquid return pipe, 41Ba... first reaction liquid return pipe, 41Bb... second reaction liquid return pipe, 42... pump, 50, 50B... concentration adjustment unit, 50Ba... first tank, 50Bb... second tank, 51, 51B... tank body, 5 1Ba...partition plate, 52, 52B...adjusted liquid supply pipe, 53, 53B...pump, 54...filter, 55...adjusted liquid, 60...gas-liquid separation section, 61...first filter layer, 62...second filter layer, 63...cleaning section, 63a...cleaning pipe, 63b...cleaning water supply pipe, 63d, 63e...bearing unit, 63da...flange, 63db...bearing, 63f...sprocket, 81 to 83...valve, 91...gas exhaust pipe, 92...reactant discharge pipe, 93...gas supply pipe, 100, 100A, 100B...biogas reformer

Claims

1. A device body, a biogas supply unit that supplies biogas to the inside of the device body; a reaction liquid injection unit that is disposed above the biogas supply unit and that injects an alkaline reaction liquid downward inside the device body; A biogas reforming device comprising:

2. The biogas reforming apparatus according to claim 1, further comprising a reaction liquid return unit that returns the alkaline reaction liquid stored in the bottom of the apparatus body to the reaction liquid spray unit.

3. The biogas reforming apparatus according to claim 1 , further comprising a gas-liquid separator provided above the reaction liquid injection section.

4. The biogas reforming apparatus according to claim 3 , wherein the gas-liquid separation unit includes a filter layer that separates water and biogas, and a cleaning unit that cleans the filter layer.

5. the filter layer includes a first filter layer and a second filter layer disposed above the first filter layer, The biogas reformer according to claim 4 , wherein the second filter layer is made of a filter material having a lower porosity than the first filter layer.

6. the first filter layer is a demister; 6. The biogas reformer of claim 5, wherein the second filter layer is an adsorbent.

7. the cleaning unit includes a cleaning pipe having a plurality of injection holes for injecting cleaning water, and a cleaning water supply pipe for supplying the cleaning water into the cleaning pipe; The biogas reformer according to claim 5 , wherein the cleaning pipe is disposed between the first filter layer and the second filter layer.

8. The biogas reforming apparatus according to claim 7, wherein the cleaning pipe is configured to be rotatable inside the apparatus body with its longitudinal direction as a rotation axis.

9. a concentration adjusting unit that adds an adjusting solution to the alkaline reaction solution sprayed from the reaction solution spraying unit; The biogas reforming apparatus according to claim 1 , wherein the adjusting liquid contains hydroxide ions at a concentration higher than that of the alkaline reaction liquid stored in the bottom of the apparatus body.

10. The biogas reforming apparatus according to claim 1, wherein the biogas supply unit includes a gas distribution pipe extending toward the inside of the apparatus body, and a purge execution unit that executes air purging of the gas distribution pipe.

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