JP4822263B2 - Methane fermentation equipment for solid organic waste - Google Patents

Description

  The present invention relates to a methane fermentation apparatus for solid organic waste, and more particularly to an apparatus for methane fermentation treatment of solid organic waste having a low water content at an undiluted or low dilution rate. The present invention is a biogas produced by fermentation of solid organic waste such as food waste, food residue, livestock waste, dewatered sludge, etc. by fermentation with methane fermentation microorganisms (hereinafter referred to as anaerobic microorganisms). Can be effectively used in a waste recycling type methane fermentation facility that collects as an energy source.

  Organic wastes with low water content (eg, water content of about 65-80%) such as food waste, food residues, livestock waste, and dewatered sludge have been mostly landfilled and incinerated in the past. Recycling processing is required from the viewpoint of building a society. Although it is possible to collect and recycle compost, feed, etc. from organic waste, since the scope of utilization of the recycled material is limited, as a recycling technology with a wider range of utilization, organic Methane fermentation treatment that recovers biogas (including about 70% methane gas, about 30% carbon dioxide gas, a small amount of hydrogen sulfide, etc.) that can be used as an energy source by microbial decomposition of radioactive waste has attracted attention and has been put into practical use Is underway.

  Conventionally, wet methane fermentation and dry methane fermentation are known as methods for methane fermentation of organic waste. In the wet methane fermentation method, for example, as disclosed in Patent Documents 1 and 2, organic waste is separated from mixed foreign matters and finely pulverized to form a slurry with a TS concentration (organic solid concentration) of about 5 to 15%. This is a method in which a methane fermentation tank (hereinafter referred to as an anaerobic fermentation tank) is charged, and an organic slurry is brought into contact with anaerobic microorganisms in the fermentation tank for methane fermentation. Solid organic waste with a low water content can also be treated by wet methane fermentation by pulverizing and diluting with water.

  However, in the wet methane fermentation method, it is necessary to add at least 1 to 2 times dilution water to the finely pulverized organic waste to lower the TS concentration, so the capacity of the fermenter increases with dilution, The amount of liquid residue (hereinafter sometimes referred to as a fermented liquid) generated after the treatment also increases. Since undegraded organic matter remains in the fermented liquid, a secondary treatment (such as wastewater treatment) may be required to further purify the residual organic matter before release into the environment. Increasing the volume leads to an increase in the size of secondary processing facilities and an increase in secondary processing costs. Especially in rural areas that are not fully equipped with sewerage, etc., advanced secondary treatment is required to release them into public water areas, so the amount of residue required for secondary treatment is as small as possible from the viewpoint of cost reduction. It is hoped to do.

  In contrast, the dry methane fermentation method is a method in which organic waste is brought into contact with anaerobic microorganisms at a TS concentration of about 20 to 40% for methane fermentation, as disclosed in Patent Documents 3 to 5, for example. In the dry methane fermentation method, solid organic waste with a low water content can be methane-fermented without dilution or at a low dilution rate. Therefore, compared to the wet methane fermentation method, the total amount to be treated is reduced by the amount of diluted water. Therefore, it is expected that the secondary treatment cost can be kept low because the amount of residue generated after the treatment is reduced.

  For example, in the dry methane fermentation method disclosed in Patent Document 3, organic waste having a low water content is pulverized into particles or sludges having a particle size of less than 2 cm, and has a larger particle size than the waste in order to provide air permeability and fluidity. It is mixed with granular air-permeable auxiliary materials (wood chips, twigs / leaves, dried chicken manure pellets, etc.) and adjusted to a TS concentration of about 25 to 35%, and then put into an anaerobic fermenter. The mixture of materials is subjected to methane fermentation by contacting with anaerobic microorganisms while stirring so as to extrude in a piston flow manner. Further, in the dry methane fermentation method of Patent Document 4, instead of the auxiliary material, a part of the dewatered sludge of the sludge residue generated after the fermentation process is mixed with the organic waste, and the organic waste is mixed by mixing with the dehydrated sludge. After adjusting the TS concentration, it is put into a fermenter and subjected to methane fermentation.

Japanese Patent No. 270887 Japanese Patent No. 3064272 JP 11-309493 A JP 2004-017024 A Japanese Patent Laid-Open No. 2003-053309

  However, in the dry methane fermentation methods of Patent Documents 3 and 4, an easily degradable organic solid (hereinafter referred to as an easily decomposable solid) having a relatively fast decomposition rate by anaerobic microorganisms and a relatively slow hardly decomposed organic Since methane fermentation treatment is carried out in the same way by mixing solids (hereinafter referred to as hardly decomposable solids), there is a problem that the hardly decomposable solids flow out of the anaerobic fermenter with insufficient decomposition. . In general, it is difficult to perform methane fermentation treatment of a hardly-decomposable organic substance and an easily-degradable organic substance having different degradation rates by anaerobic microorganisms at the same time. However, in the methods of Patent Documents 3 and 4, the TS concentration in the fermenter is adjusted. Since it is necessary to mix hardly decomposable solids (sub-materials, dehydrated sludge, etc.), a large amount of undecomposed hardly decomposable solids remain in the residue flowing out from the fermenter.

  For this reason, the dry methane fermentation method described above requires processes and facilities for secondary separation and recovery of the hard-to-decompose solids in the residue flowing out of the anaerobic fermenter, reducing the secondary treatment costs. Difficult to do. For example, in the fermentation method of Patent Document 3, the sludge residue flowing out from the fermenter is sieved to separate and recover the undecomposed auxiliary material, and the undecomposed auxiliary material is returned to the fermenter for recycling. However, the separation and recovery costs increase, and it is difficult to recover all the hardly decomposable solids that are decomposed by the methane fermentation process with a sieve alone. Necessary. Moreover, in the fermentation method of patent document 4, although sludge residue is dehydrated and a part is returned to a fermenter, since a lot of hard-to-decompose solids are also contained in the remaining dewatered sludge, Secondary treatment for the remaining dewatered sludge is required.

  Moreover, since the dry methane fermentation method of patent documents 3 and 4 will flow out a hard-to-decompose solid matter in an anaerobic fermentation tank, without fully methane-fermenting, the methane fermentation rate (recovery rate of biogas) of a fermenter ) Is difficult to increase and may result in an inefficient processing system. Furthermore, the conventional dry methane fermentation method stirs organic waste in a low water content state with low fluidity, and it is difficult to stir so that the organic waste and anaerobic microorganisms are in uniform contact. However, it is difficult to obtain efficient methane fermentation. In order to put the organic waste to methane fermentation undiluted or at low dilution, the amount of undecomposed organic matter contained in the residue is small, and the methane fermentation is equivalent to the conventional wet methane fermentation method. It is necessary to develop technology that can obtain the rate.

  Therefore, an object of the present invention is to provide a methane fermentation apparatus capable of efficiently performing methane fermentation treatment of solid organic waste without dilution.

Referring to the embodiment of FIG. 1, a solid organic waste methane fermentation apparatus according to the present invention includes an anaerobic fermentation tank 2 for storing a fermentation liquor L, a perforated partition wall 3 for vertically dividing the interior of the fermentation tank 2, and a fermentation tank. The solid organic waste A intake 5 provided above the partition wall 3 and the fermentation liquor L in the fermenter 2 are drawn from the bottom below the partition wall 3 and above the partition wall 3 through the outside of the fermenter 2. Is provided with a reflux passage 10 with a pump 11 for anaerobically circulating back to the top, and solubilizes the organic waste A above the partition wall 3 and moves it below the partition wall 3 for methane fermentation. .

Preferably, an overflow channel 15 is provided at the bottom of the fermenter 2 to allow the fermented liquor L to rise to a height h corresponding to the liquid level outside the vessel. Moreover, as shown in FIG. 4, the stirring means 30 can be provided above the partition wall 3 in the fermenter 2 or on the partition wall 3. Desirably, as shown in FIG. 5, on the return path 10, the fermentation liquid anaerobic stay temporarily tank 40 to flow out L a from the other end mixture was allowed to flow from one end to the required residence time is provided, in a fermenter 2 by migrating organic waste a solubilized in the temporary retention tank 40 Ru by methane fermentation. In this case, as shown in the figure, the temporary residence tank 40 and the fermentation tank 2 are provided at the same height, and the fermentation liquid L is placed outside the tank at the bottom of the temporary residence tank 40 in place of the bottom of the fermentation tank 2. It is possible to provide an overflow channel 15 that rises to the height h corresponding to the surface and overflows.

More preferably, as shown in FIGS. 1 and 5, a fixed bed 20 of anaerobic microorganisms through which the fermentation liquor L can permeate is provided below the partition wall 3 in the fermentation tank 2 and / or in the temporary residence tank 40. As shown in FIGS. 3 and 5, the biogas G produced by fermentation is extracted from the gas phase portions 4 and 43 into the gas phase portions 4 and 43 at the top of the fermenter 2 and / or the temporary residence tank 40. It is desirable to provide a circulating gas passage 36 that is sent to the ammonia collector 37 and returns the output gas of the collector 37 to the gas phase sections 4 and 43. Furthermore, a recovery port 18 for recovering the biogas G produced by fermentation can be provided in the gas phase portions 4 and 43 at the top of the fermentation tank 2 and / or the temporary residence tank 40.

In the solid organic waste methane fermentation apparatus according to the present invention, the inside of the anaerobic fermenter 2 storing the fermentation liquor L is divided up and down by a perforated partition wall 3, and the solid organic waste A is taken up above the partition wall. The solid organic waste A is removed by anaerobically circulating the fermented liquor L in the fermenter 2 from the bottom part below the partition wall through the outside of the partition tank 2 and returning to the top part above the partition wall by the reflux path 10 with 11. Since it is solubilized above the partition wall 3 and moved below the partition wall 3 for methane fermentation, the following remarkable effects are exhibited.

(B) The solid organic waste A introduced above the perforated partition wall 3 is gradually solubilized and extracted below the perforated partition wall 3, and the solubilized organic matter is circulated with the fermentation liquor L while anaerobic microorganisms are circulated. Therefore, the methane fermentation rate can be improved as compared with the conventional dry methane fermentation method in which stirring is performed in a low fluidity state.
(B) In the solid organic waste A, easily decomposable solids are solubilized relatively early, whereas hardly decomposable solids are solubilized over the perforated partition walls 3 over time. Therefore, even when the hardly decomposable organic substance and the easily decomposable organic substance are mixed, each can be efficiently methane-fermented.
(C) By providing the temporary residence tank 40 on the reflux path 10, the solubilized organic matter can be efficiently methane-fermented not only in the fermenter 2 but also on the reflux path 10, and the entire apparatus Methane fermentation rate can be increased.
(D) By providing a fixed bed 20 of anaerobic microorganisms below the partition wall 3 in the fermenter 2 and in the temporary residence tank 40, the methane fermentation rate can be further improved, which is the same as the conventional wet methane fermentation method. It is possible to increase the methane fermentation rate to an extent.

(E) By providing an overflow channel for the fermented liquid communicating with the bottom of the fermenter 2, it is possible to prevent the hardly-decomposable solids from flowing out of the fermenter with insufficient decomposition, and in the fermented liquid The amount of undecomposed organic matter contained can be reduced.
(F) By storing the fermentation liquor L in the fermenter 2 up to the upper side of the partition wall, it becomes possible to agitate the solid organic waste A taken in the upper side of the partition wall, and promotes the solubilization of the solid organic waste A. Prevention of clogging of the partition walls 3 can also be expected.
(G) Since solid organic waste A having a low water content can be methane-fermented without dilution, the amount of fermented liquid produced after treatment can be greatly reduced, and economical methane fermentation by reducing secondary treatment costs Processing is possible.
(H) Even if solid foreign matter is mixed in the solid organic waste A, the foreign matter that is not solubilized remains above the partition wall and does not inhibit the methane fermentation below the partition wall. There is no need to remove foreign substances from the radioactive waste A, and economics due to a reduction in pretreatment costs can be expected.

  FIG. 1 shows an embodiment of a methane fermentation apparatus 1 of the present invention. The illustrated example of the methane fermentation apparatus 1 includes an anaerobic fermentation tank 2 that stores the fermentation liquor L in an airtight manner, a perforated partition 3 that partitions the inside of the fermentation tank 2 up and down, and an upper space P1 of the perforated partition 3 in the fermentation tank 2 And the lower space P2 through the outside of the fermenter 2 and the reflux path 10 with the pump 11, and the overflow port 16 connected to the bottom of the fermenter 2 and at the liquid level corresponding height h outside the fermenter 2. An overflow channel 15 is provided. However, the overflow channel 15 is not necessarily connected to the fermenter 2, and the overflow channel 15 may be provided on the reflux channel 10 as described later (see FIG. 5). An example of the fermented liquor L is water containing anaerobic microorganisms, but a decomposition treatment additive such as a neutralizing agent or a micronutrient may be added as necessary.

  FIG. 2 shows an example of a perforated partition wall 3 installed in the fermenter 2. For example, a porous plate having the same outer edge shape as the inner peripheral cross-sectional shape of the fermenter 2 and having small holes 3a formed on the entire surface or a part thereof is used as the perforated partition wall 3 and porous at a predetermined portion on the inner peripheral surface of the fermenter 2. The inner edge of the fermenter 2 is partitioned into an upper space P1 and a lower space P2 by fitting the outer edges of the plates in close contact. The upper space P1 of the fermenter 2 partitioned by the perforated partition wall 3 is provided with an inlet 5 for the solid organic waste A, and the solid organic waste A is introduced into the upper space P1 of the fermenter 2 from the inlet 5 To do. It is desirable that the solid organic waste A is roughly pulverized into an appropriate size before being charged. The solid organic waste A put into the upper space P1 is solid-liquid separated by the perforated partition wall 3, and the solid organic matter having a relatively large particle size is accumulated in the upper space P1 of the perforated partition wall 3, and the particle size is smaller than the small hole 3a. Small organic matter moves to the lower space P2 of the perforated partition wall 3.

  The fermentation liquor L in the fermenter 2 is drawn from the bottom of the lower space P2 of the perforated partition wall 3 and returned to the top of the upper space P1 by the reflux path 10 with the pump 11 to circulate the liquid in the fermenter 2 A gentle downward flow is formed. The fermenter 1 in the illustrated example has a structure in which the level of the fermentation liquid L in the fermenter 2 is determined by the height h of the overflow port 16 of the overflow channel 15, and the overflow port 16 is located in the upper space P1. Are provided at a height h at which the solid organic waste A is submerged. The solid organic waste A in the upper space P1 submerged in the fermentation broth L is gradually decomposed and solubilized by contact with the anaerobic microorganisms in the fermentation broth L, and becomes an organic substance having a small particle diameter. The downward flow of L shifts to the lower space P2 of the perforated partition wall 3. The organic matter transferred to the lower space P2 of the perforated partition wall 3 is further decomposed into biogas G (methane fermentation) by contact with anaerobic microorganisms while being uniformly stirred by the downward flow of the fermentation liquor L.

However, the level of the fermented liquid L in the fermenter 2 does not necessarily have to be the height h at which the solid organic waste A is submerged, and the type / grains of the solid organic waste A to be introduced into the fermenter 2 It can be appropriately selected depending on conditions such as diameter. For example, when the organic waste A is easily decomposable, as shown in FIG. 3, the overflow port 16 of the overflow channel 15 is set to the same height h as the perforated partition wall 3 and the space below the perforated partition wall 3. The fermented liquor L is filled with the fermented liquor L, and the fermented liquor L returned from the return port 10b of the reflux path 10 to the top of the upper space P1 is sprayed on the solid organic waste A so that the fermented liquor L is not flooded. The solid organic waste A can be gradually decomposed and solubilized. In this case, a dispersion discharge device 12 such as a spray is attached to the return port 10b of the reflux path 10, and the fermentation liquid L is evenly supplied to the entire solid organic waste A from the plurality of discharge ports 13 of the dispersion discharge device 12. However, it is desirable to prevent the microbial reaction in the upper space P1 from becoming uneven. In addition, the dispersion | distribution discharger 12 can also be attached to the return port 10b of the reflux path 10 of FIG.

  The hole diameter, inter-hole pitch, shape, arrangement, etc. of the small holes 3a of the perforated partition wall 3 can also be appropriately selected according to the conditions such as the type and particle diameter of the solid organic waste A to be introduced into the fermentation tank 2. . For example, if the hole diameter of the small holes 3a is selected from the range of 0.1 mm to 50 mm, the shape is selected from round holes, square holes, etc., the arrangement is selected from parallel arrangement, staggered arrangement, etc. As shown in FIG. 2A, a staggered angle θ or the like can be further selected. Moreover, the aperture ratio of the perforated partition wall 3 can be selected from a range of 10 to 60%, for example, depending on conditions such as the type and particle size of the solid organic waste A, as shown in FIG. A non-porous portion 3c can be appropriately provided on the perforated partition wall 3. For example, when the organic waste A is easily decomposable, the aperture ratio of the perforated partition wall 3 and the hole diameter of the small holes 3a are relatively large, and when the organic waste A contains hardly decomposable solids, the space above the perforated partition wall 3 In order to solubilize with P1 over time, the aperture ratio and the hole diameter of the small holes 3a can be made relatively small. If necessary, a plurality of perforated partition walls 3 may be prepared as shown in Table 1, and the perforated partition walls 3 in the fermenter 2 may be replaced according to the conditions of the solid organic waste A.

The overflow channel 15 in the illustrated example allows the fermentation liquor L at the bottom of the lower space P2 to enter from the outlet 15a and raises it to the level h corresponding to the liquid level to overflow from the overflow port 16 to the outside of the fermenter 2. Is. The organic matter that has migrated from the upper space P1 to the lower space P2 of the perforated partition wall 3 is reduced in particle size by contact with anaerobic microorganisms in the lower space P2, but the particle size becomes smaller, but the fermentation has not progressed relatively. Large organic matter easily moves on the descending flow of the fermentation liquor L, and is extracted to the extraction port 10a of the reflux path 10 and further circulates. For this reason, as shown in the figure, by providing the outlet 10a of the reflux channel 10 and the outlet 15a of the overflow channel 15 at the bottom of the lower space P2, only the organic matter having a relatively small particle size that has undergone fermentation is collected. The amount of undecomposed organic matter contained in the fermented liquid C that enters the overflow channel 15 from the outlet 15a, suppresses the unfermented organic matter from flowing out of the fermenter 2, and overflows from the overflow port 16. Can be suppressed. In the illustrated example, reference numeral 15b is a vent hole.

  Preferably, a fixed bed 20 of anaerobic microorganisms through which the fermentation liquor L can permeate is provided in the lower space P2 in the fermenter 2 to promote organic methane fermentation in the lower space P2. For example, hollow cylindrical microbial carriers 21 as shown in FIG. 6 are regularly arranged in the lower space P2 so that the center axis of each carrier 21 coincides with the downward flow direction of the fermentation liquor L to form the fixed bed 20. The hollow cylindrical microbial carrier 21 in the illustrated example is formed into a hollow cylindrical shape by holding a porous peripheral wall 22 made of carbon fiber or glass fiber on a frame body 23 made of, for example, epoxy resin. The porous peripheral wall 22 formed of carbon fiber or glass fiber woven or non-woven fabric has innumerable small voids with a diameter of several μm to several hundred μm inside, and microorganisms adhere to the voids and grow at a high concentration. Therefore, anaerobic microorganisms can be carried efficiently. However, the kind and shape of the fixed bed 20 are not limited to the illustrated examples, and an appropriate microbial carrier to which anaerobic microorganisms can adhere at a high concentration can be used.

Further, when the upper solid organic waste A in the fermenter 2 is submerged in the fermentation liquor L, as shown in FIG. 4, the stirring means 30 is provided in the upper space P1 while flowing the solid organic matter. Solubilization can be promoted. In FIG. 2A, the stirring blade 31 disposed in the upper space P1 of the fermenter 2 is used as the stirring means 30, and the stirring blade 31 is rotated by the stirring motor 32 provided in the upper portion of the fermenter 2, so that the upper space P1 Solid organic waste A is being stirred. By stirring the solid organic waste A while submerging it in the fermentation liquor L, the organic waste A can be easily stirred in a state of higher fluidity than the conventional dry methane fermentation method. Further, as shown in FIG. 2B, the stirring means 30 is perforated in the non-hole portion formed in the central portion 3b of the perforated partition wall 3 (see FIG. 2A) and in the return port 10b of the reflux passage 10. A guide tube 34 attached toward the central non-hole portion 3b of the partition wall 3 can also be used. The return flow of the fermentation liquor L is guided by the guide tube 34 to the central non-porous portion 3b of the perforated partition wall 3 and sprayed downward to cause liquid circulation of the fermentation liquor L in the upper space P1, thereby causing solid organic disposal. Stir thing A.

  The fermenter 2 in the illustrated example is adjacent to the recovery port 18 of the biogas G provided in the gas phase section 4 at the top, and the upper side surface of the perforated partition wall 3 in addition to the intake 5 of the solid organic waste A. And a discharge port 9. Since the biogas G generated by methane fermentation in the lower space P2 in the fermenter 2 passes through the perforated partition wall 3 and moves to the gas phase section 4 at the top, energy from the recovery port 18 through the gas recovery path 17 It can be collected in a conversion device (not shown). When the biogas G generated in the lower space P2 passes through the perforated partition wall 3, the gas pressure can also be expected to prevent clogging of the small holes 3a of the perforated partition wall 3. Further, the stirring means 30 of the solid organic waste A provided in the upper space P1 has an action of preventing the accumulation and deposition of the organic waste A on the perforated partition wall 3, and the small holes of the perforated partition wall 3 are provided. It is also effective in preventing clogging of 3a.

  The discharge port 9 provided in the fermenter 2 is for discharging the solid foreign matter B that may be mixed in the solid organic waste A. Since the solid foreign matter B which is not solubilized does not move to the lower space P2 but stays on the perforated partition wall 3, the solid foreign matter B accumulated on the perforated partition wall 3 is appropriately taken out from the discharge port 9 and collected. It is sufficient that the organic waste A taken into the fermenter 2 in the illustrated example is roughly pulverized in the pretreatment stage, and even if solid foreign matter B is mixed in, the organic waste A stays on the perforated partition wall 3 and remains in the lower space P2. Since methane fermentation is not inhibited, it is not always necessary to separate the solid foreign matter B in the pretreatment stage. Therefore, compared with the conventional methane fermentation method, the fermentation apparatus 1 of the present invention has an advantage that the pretreatment of the solid organic waste A can be extremely simplified.

  It is desirable that the methane fermentation apparatus 1 includes a heat retaining device 26 that retains the fermentation liquid L in the fermenter 2 at a temperature (for example, 37 ° C. or 55 ° C.) at which the anaerobic microorganisms are active. In the illustrated example, for example, a heat-retaining device 26 that is a heat exchanger is provided on the reflux path 10, and by sending a heat medium H such as high-temperature water or steam into the heat-retaining device 26, the fermentation liquid L in the fermenter 2 is anaerobic microorganisms. The active temperature is maintained. Instead of the heat retaining device 26 in the illustrated example, a jacket type heat exchanger or a heater or the like may be attached to the peripheral wall of the fermenter 2 to form the heat retaining device 26. The organic matter transferred from the upper space P1 in the lower space P2 of the fermenter 2 is brought into contact with anaerobic microorganisms at the active temperature and subjected to methane fermentation. It can be raised to the same level as the law.

  Although the fermented liquor L in the fermenter 2 decreases due to the overflow from the overflow channel 15, the fermented liquor L is supplemented by the water in the waste A, so that it is basically not necessary to replenish the fermented liquor L. . It is sufficient to add water or the like from the intake 5 only when necessary. Therefore, the solid organic waste A having a low water content can be introduced undiluted from the intake port 5 for methane fermentation, and the fermentation liquid flowing out from the overflow channel 15 as compared with the conventional wet methane fermentation method. The amount of the spent solution C can be greatly reduced. In addition, among the solid organic waste A put into the upper space P1, the readily decomposable solids are solubilized relatively early, whereas the hardly decomposable solids are solubilized in the upper space P1 over time. Therefore, even when the hardly decomposable organic substance and the easily decomposable organic substance are mixed, each can be efficiently methane-fermented.

[Experimental Example 1]
In order to confirm the efficiency of methane fermentation by the methane fermentation apparatus 1 of the present invention, a prototype was made using an anaerobic fermentation tank 2 having an effective volume of 10 liters shown in FIG. An experiment was conducted to measure the amount generated. In this experiment, garbage with a moisture content of 70% obtained by crushing a canteen residue was used as the solid organic waste A. The total chemical oxygen demand (T-CODcr) of this garbage was 400,000 mg / kg.

  The inside of the fermenter 2 is divided up and down by a perforated partition wall 3 having a small hole 3a having a hole diameter of 1 mm, and the solid organic waste A in the upper space P1 enters the fermenter 2 from the intake 5 or the overflow port 16. The fermented liquor L is filled up to the height h to be submerged, and the fermented liquor L filled in the fermenter 2 is circulated from the lower space P2 to the upper space P1 through the reflux path 10 with the pump 11, and then gently put into the fermenter 2. A downward flow was formed. In the lower space P2 of the fermenter 2, the hollow cylindrical microbial carriers 21 of FIG. 6 are regularly arranged to form a fixed bed 20, and in the upper space P1 of the fermenter 2, an agitating blade 31 is disposed. The fermented liquid L in the fermenter 2 was kept at 55 ° C., which is the active temperature of anaerobic microorganisms (thermophilic bacteria), by the above heat retaining device 26.

Solid organic waste A was continuously added at a rate of 250 g / day to the fermenter 2 in FIG. 7 , and the change over time in the amount of biogas G generated was measured while stirring with the stirring blade 31. The results of this experiment are shown in the graph of FIG. As can be seen from the graph, the amount of biogas G generated is stable for 60 days, and the efficiency of microbial reaction is reduced by non-uniform contact between organic waste and anaerobic microorganisms as in conventional dry methane fermentation. Therefore, it was confirmed that the solid organic waste A can be uniformly methane-fermented by the fermentation apparatus 1 of the present invention. In addition, when the organic matter decomposition rate was calculated from the amount of biogas G generated with respect to the supply amount of the solid organic waste A, the fermentation apparatus 1 of the present invention has a solid organic material with high efficiency almost equal to that of the conventional wet methane fermentation method. It was confirmed that the organic waste A was methane-fermented. Note that reference numeral 19 in the illustrated example is a drainage tank.

[Experiment 2]
Moreover, in order to confirm that methane fermentation can be efficiently performed even when the hardly decomposable organic substance and the easily decomposable organic substance are mixed by the methane fermentation apparatus 1 of the present invention, the anaerobic fermentation of FIG. Experiments were performed using tank 2. In this experiment, solid organic waste A in which the raw garbage of Experiment Example 1 and paper waste (office discharge shredder discharge) were mixed was used as a raw material. The solid organic waste A was adjusted so that the mixing ratio of garbage to paper waste was 19: 1 by weight ratio. The T-CODcr for garbage was 400,000 mg / kg, and the T-CODcr for paper waste was 1,086,000 mg / kg.

The above-mentioned solid organic waste A is continuously added to the fermenter 2 in FIG. 7 at a rate of 200 g / day (190 g of raw garbage + 10 g of paper waste), and the amount of biogas G generated while stirring with the stirring blade 31. Daily changes were measured. The result of this experiment is shown in the graph of FIG. From the graph, it can be seen that the paper waste was decomposed in about 10 days, and the amount of biogas G generated gradually increased with the decomposition of the paper waste. The organic matter decomposition rate calculated from the amount of biogas G generated with respect to the supply amount of solid organic waste A in the steady state after 10th is about 80%, and the hard-to-decompose organic matter and the easily-decomposable organic matter are mixed. It was confirmed that the solid organic waste A can also be efficiently methane-fermented by the fermentation apparatus 1 of the present invention. Further, when the amount of organic matter in the fermented liquid C overflowing from the overflow port 16 of the overflow channel 15 was measured, the amount of residual organic matter was almost the same as that of the conventional wet methane fermentation method, It was proved that methane fermentation of each easily decomposable organic substance was possible efficiently.

  Thus, the provision of “a methane fermentation apparatus capable of efficiently subjecting a solid organic waste to a methane fermentation treatment without dilution”, which is an object of the present invention, can be achieved.

FIG. 5 shows the present invention in which a temporary residence tank 40 is provided on the reflux path 10 for circulating the fermentation liquor L in the fermentation tank 2, allowing the fermentation liquor L to flow from one end side, stay for a required time, and then flow out from the other end side. The Example of the methane fermentation apparatus 1 of this is shown. By providing the temporary residence tank 40 on the reflux path 10, the height of the fermenter 2 can be reduced, and the solubilized organic matter is methane-fermented not only inside the fermentation tank 2 but also on the reflux path 10. Therefore, the methane fermentation rate of the entire apparatus can be further increased.

  The fermenter 2 in the illustrated example is provided with a perforated partition wall 3 at a relatively bottom portion and charged with the solid organic waste A, and is provided with a perforated lid 27 above the charged solid organic waste A. The intake pipe 7 and the intake valve 6 communicated between the perforated partition wall 3 and the perforated lid 27 from the outside. The solid organic waste A introduced between the perforated partition wall 3 and the perforated lid 27 is gradually decomposed and solubilized by the downward flow of the fermentation liquor L, and is extracted from the extraction port 10a of the reflux path 10. To the inlet 41 of the temporary storage tank 20. A perforated cradle (grating, etc.) 24 is fixed inside the temporary storage tank 20, and an appropriate microbial carrier is spread on the cradle 24 to form a fixed floor 20, which is used to prevent floating above the fixed floor 10. A perforated lid (grating) 25 is provided. The fermented liquor L that has flowed into the temporary storage tank 20 from the inlet 41 is decomposed by anaerobic microorganisms while ascending between the fixed beds 20, and then flows from the outlet 42 a on the fixed bed 20 through the outlet 42. And returned to the top of the fermenter 2 for circulation.

  In the fermenter 2 in the illustrated example, since the solid organic waste A is introduced between the perforated partition wall 3 and the perforated lid 27, the fermented liquor L is reversed by the reflux path 10 with the pump 11 (same as above). It is also possible to circulate in the direction opposite to the arrow in the figure. By switching the descending flow of the fermentation liquor L in the fermenter 2 to the ascending flow appropriately by reverse circulation of the fermented liquor L, the clogging of the perforated partition walls 3 and the small holes 3a of the perforated lid 27 is effectively prevented. it can.

  Further, in the illustrated example, the temporary residence tank 40 is provided at the same horizontal height as the fermentation tank 2, and instead of the bottom of the fermentation tank 2, the fermentation liquid L is placed at the bottom of the temporary residence tank 40 and the height h corresponding to the liquid level outside the tank. An overflow channel 15 is provided to rise to overflow. Since an upward flow of the fermentation liquor L is formed in the temporary residence tank 40, organic matter having a relatively large particle size in the fermentation liquor L is carried on the upward flow to the fixed bed 20 and the fermented small particles Only the organic substance having a diameter can be overflowed from the overflow channel 15, and the outflow of the organic substance with insufficient fermentation can be more effectively suppressed. In the illustrated example, the gas phase part 4 of the fermenter 2 and the gas phase part 43 of the temporary residence tank 40 are connected by a gas phase part communication path 44, and the recovery port 18 of the biogas G is connected to the gas phase of the temporary residence tank 40. Provided in the department.

5 and 3, the biogas G is extracted from the gas phase portion 4 to the gas phase portion 4 at the top of the fermenter 2 and sent to the ammonia collecting device 37, and the output gas of the collecting device 37 is supplied. A circulating gas flow path 36 that returns to the gas phase section 4 is provided. When organic waste A having a low water content is subjected to methane fermentation without dilution, ammonia nitrogen that inhibits methane fermentation may accumulate in the fermenter 2. For example, the decomposed biogas G in the gas phase section 4 is extracted from the intake end 36a to the gas flow path 36 by the blower 38 provided on the circulation gas flow path 36, and the ammonia in the biogas G is removed by the ammonia collector 37. The ammonia partial pressure of the gas phase part 4 is lowered by blowing the biogas G after the ammonia removal from the exhaust end 36b into the gas phase part 4 via the gas flow path 36, and dissolved or suspended in the fermentation liquid L of the fermenter 2 The turbid ammonia can be transferred to the gas phase part 4 to remove the ammonia in the fermentation liquor L. An example of the ammonia collection device 37 is a scrubber (cleaning dust collector) that collects ammonia in the biogas G using a cleaning liquid such as water or an acid solution (for example, dilute sulfuric acid solution). Such an ammonia inhibition-reducing methane fermentation method is described in detail in Japanese Patent Application No. 2005-117813 by the present inventor.

It is explanatory drawing of one Example of this invention. It is explanatory drawing of an example of the perforated partition used by this invention. It is explanatory drawing of the other Example of this invention. It is explanatory drawing of the Example of this invention which provided the stirring means. It is explanatory drawing of the Example of this invention which provided the temporary residence tank. It is explanatory drawing of an example of the microorganisms carrier used for the fixed bed of this invention. It is explanatory drawing of the experimental apparatus which confirms the effect of this invention. It is an example of the graph which shows the result of the effect confirmation experiment of this invention. It is another example of the graph which shows the result of the effect confirmation experiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Methane fermentation apparatus 2 ... Anaerobic fermenter 3 ... Perforated partition 3a ... Small hole
3b ... central (recess) 3c ... imperforate portion 4 ... gas phase 5 ... inlet 6 ... intake valve 7 ... intake pipe 9 ... outlet 10 ... return path
10a ... Pullout port 10b ... Return port
11 ... Pump 12 ... Distributed dispenser
13 ... Discharge port 15 ... Overflow channel
15a ... take-out port 15b ... vent
16 ... Overflow port 17 ... Gas recovery path
18 ... Recovery port 19 ... Drainage tank
20 ... fixed bed 21 ... microbial carrier
22… Porous peripheral wall 23… Frame
24 ... perforated cradle 25 ... perforated lid (grating)
26… Heat insulation device 27… Perforated lid
30 ... Agitating means 31 ... Agitating blade
32 ... Agitator motor 34 ... Guiding tube
36… Circulating gas flow path 36a… Intake end
36b… Exhaust end 37… Ammonia collector
38 ... Blower 40 ... Temporary residence tank
41 ... Inlet 42 ... Outlet
42a ... Outlet 43 ... Gas phase
44… Gas phase part communication passage A… Solid organic waste (low water content waste)
B ... Solid foreign matter C ... Fermented liquid L ... Fermented liquid P1 ... Upper space
P2 ... Lower space G ... Biogas H ... Heat medium

Claims (9)

An anaerobic fermenter for storing the fermented liquid, a perforated partition for partitioning the fermenter vertically, an intake of solid organic waste provided above the partition of the fermenter, and the fermented liquid in the fermenter below the partition A reflux passage with a pump for drawing out from the bottom of the tank and returning to the top of the partition via the outside of the fermenter and circulating anaerobically, solubilizing the organic waste above the partition and moving it down to the methane methane fermentation apparatus solid organic waste product obtained by fermentation. The fermentation apparatus of Claim 1 WHEREIN: The methane fermentation apparatus of the solid organic waste which uses the said fermentation liquid as anaerobic microorganisms containing water. 3. The methane fermentation apparatus for solid organic waste according to claim 1, wherein an overflow channel is provided at the bottom of the fermenter to raise the fermented liquid to a height corresponding to the liquid level outside the tank and to overflow. In any of the fermenter of claims 1 to 3, wherein the reflux path, provided anaerobic stay temporarily tank to flow out from the other end after was required residence time allowed to flow into the fermentation fluid from the one end, the fermenter A solid organic waste methane fermentation apparatus, in which organic waste solubilized in 1 is transferred to a temporary retention tank and subjected to methane fermentation. The fermentation apparatus according to any one of claims 1 to 4 , wherein the solid organic waste methane fermentation apparatus is provided with stirring means above or on the partition walls in the fermenter. The methane fermentation apparatus for solid organic waste according to any one of claims 1 to 5 , wherein a fixed bed of anaerobic microorganisms through which the fermentation liquid can permeate is provided below the partition walls in the fermentation tank. 6. The methane fermentation apparatus for solid organic waste according to claim 4 , wherein a fixed bed of anaerobic microorganisms through which the fermentation liquid can permeate is provided in the temporary retention tank. The fermentation apparatus according to any one of claims 1 to 5 , wherein a biogas produced by fermentation is extracted from the vapor phase portion to the vapor phase portion at the top of the fermenter and sent to an ammonia collection device, and the output gas of the collection device. A solid organic waste methane fermentation apparatus provided with a circulating gas flow path for returning the gas to the gas phase part. The fermentation apparatus according to claim 4 or 5 , wherein a biogas produced by fermentation is extracted from the gas phase portion to the gas phase portion at the top of the temporary residence tank and sent to an ammonia collector, and the output gas of the collector is A solid organic waste methane fermentation apparatus provided with a circulating gas flow path to return to the gas phase.

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