JP4631043B2 - Methane generation method and two-phase methane generator used therefor - Google Patents

Description

  The present invention uses thermal energy and electric energy to completely decompose organic matter in waste containing organic matter such as sewage sludge and livestock excreta, and to generate methane gas at a high production amount without generating sludge. The present invention relates to a two-phase methane generator used for that purpose.

  A method for producing methane-based fuel gas by methane fermentation of various organic matter-containing wastes including sewage sludge and livestock manure is widely used industrially. For variable capacity gas holder reactor with built-in gas holder with up and down movable canopy to change the temperature, gas holder fixed reactor with gas holder fixed on top of fermentation tank and anaerobic treatment at sewage treatment plant Conventional two-phase reactors including sewage digesters, acid fermenters and methane fermenters have been developed and put into practical use.

  However, methane generators that have been put to practical use in sewage treatment so far have a low biogas production rate and poor efficiency. Therefore, a two-phase methane fermentation apparatus has been proposed as an improvement. As such an apparatus, for example, an organic wastewater purification apparatus comprising an aerobic reaction tank containing a carrier on which photosynthetic bacteria are immobilized and a two-phase methane fermentation tank comprising an acid fermentation tank and a methane fermentation tank (patented) There is a reactor for two-phase methane fermentation (see Patent Document 2), which is composed of a fermenter that contains a feed solution for fermentation treatment, and a gas holder type methane fermenter that uses the upper space as a methane gas holder. .

  The former cultivates photosynthetic bacteria under aerobic conditions in an acid fermenter, and uses the heat generated at this time for heating the methane fermenter, but has the disadvantage that the recovery rate of methane is reduced, The latter has a mechanism for transporting liquid using the gas pressure in the gas storage tank, and has the advantage that the liquid can be transferred from the acid fermentation chamber to the methane fermentation chamber without power, Unless connected, the liquid cannot be transferred, and the flow length of the plug flow cannot be sufficiently secured, and the gas stirring means cannot be provided, so that methane bacteria cannot be dispersed.

JP 2000-33394 A (Claims and others) Japanese Patent Application No. 2001-514074 (Claims and others)

  The present invention overcomes the disadvantages of the methane generation method using the above-described conventional two-phase methane generator and the inability to reduce the volume of sludge, and further makes effective use of the heat generated by methane fermentation. In addition to improving the efficiency as an autonomous methane generation method that prioritizes the use of biogas, the removal rate of COD, total nitrogen content, and total phosphorus content in the digestion and desorption liquid in the methane fermentation method is increased, and the ammonia state The object of the present invention is to provide a method and an apparatus that can discharge drainage into a river by reducing the nitrogen content.

  As a result of intensive research to increase the efficiency of a methane generation method using a two-phase methane generator, the present inventors have conducted research into a small micro gas turbine engine or an external combustion engine that is an internal combustion engine as a gas utilization system. As a heat / electricity supply system, a Stirling engine or a fuel cell with improved performance is installed in the methane generator to make effective use of the heat generated during the methane generation process and give priority to biogas use. The inventors have found that the above-mentioned problems can be solved by adding a device to the structure of the apparatus so as to improve the performance as the apparatus, and have reached the present invention based on this knowledge.

That is, the present invention relates to a method for generating methane by continuously performing acid fermentation and methane fermentation on organic substance-containing wastewater, and the acid fermentation section and the methane fermentation section, and a partition wall provided with a heat exchanger inside And a heat and electric energy generation mechanism are arranged in the generator, and the heat necessary for supplying the necessary power and heating the fermentation liquid of methane in this method is provided. In a two-phase methane generator having an acid fermentation section and a methane fermentation section, the acid fermentation section and the methane fermentation section are integrated with each other through a partition wall. It is configured as a combined horizontal cylindrical tank, and is equipped with a thermoelectric supply mechanism consisting of an internal combustion engine, an external combustion engine, a fuel cell and a heat storage unit, and uses electric energy generated by the fuel cell as internal power There is provided a two-phase methane generator characterized by comprising means for heating and heat energy from the heat storage section for heating the acid fermentation section and the methane fermentation section.

  In the method of the present invention, it is necessary to use a methane generator provided with a heat and electric energy generation mechanism. By using such a methane generator, it is possible to easily keep the heat, and 80 to 90% of the generated heat energy can be used to keep the methane generator warm. Moreover, in this method, when the digestion detachment liquid process and the sludge process are added, 20 to 40% of the thermal energy generated by these processes can be used for methane fermentation.

Next, in the method of the present invention, it is preferable to biologically desulfurize hydrogen sulfide contained in the generated gas and convert carbon dioxide in the generated gas into oxygen or methane.
The generated gas obtained by the methane generation method of the present invention contains 2000 to 4000 ppm of hydrogen sulfide, which requires 100 ppm or less for an external combustion engine, 10 ppm or less for an internal combustion engine, and 0.0 ppm or less for a fuel cell. Therefore, it must be desulfurized to fit it.

However, the conventional treatment using iron oxide pellets is not practical because the reduction value is limited and the treatment cost is high.
According to the biological treatment in the method of the present invention, anaerobic desulfurization bacteria such as a red sulfur bacterium (genus Chromatium) or a green sulfur bacterium (genus Chlorobium) are caused to act using light energy and carbon dioxide as a nutrient source. Therefore, desulfurization can be performed easily and inexpensively.
In addition, when another nutrient source is used, a sulfate-reducing bacterium (Desulofilo genus) can be used as a desulfurizing bacterium.

And red sulfur bacteria and green sulfur bacteria are photosynthetic bacteria, and when this is used, the concentration of methane bacteria can be increased, which is preferable. In addition, sulfate-reducing bacteria supply methane concentration by supplying hydrogen derived from electrolysis of water under coexistence with CO ₂ / H ₂ assimilating methane bacteria such as Methanococcus and Methanospirilum. Since it can raise to 95 to 99%, it is preferable.
Thus, by combining biological desulfurization and biological methanation with the method of the present invention, the generated gas can be easily purified.

Next, the method and apparatus of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a longitudinal sectional view showing an example of an apparatus suitable for carrying out the method of the present invention, FIG. 2 is a transverse sectional view taken along line AA in FIG. 1, and FIG. 3 is taken along line BB in FIG. FIG.

  In these drawings, the acid fermentation unit 1 and the methane fermentation unit 2 are connected to each other to constitute a horizontal cylindrical tank 3 as a whole. The organic material-containing wastewater as a raw material is introduced into the acid fermentation unit 1 through the pipe 4 and subjected to acid fermentation. Then, the methane fermentation unit passes through the pipe 7 provided in the partition wall 6 using the pressure of the gas storage chamber 5. Sent to 2. In this methane fermentation unit 2, a plurality of carriers 8,... Made of plate-like rock wool or glass wool carrying methane bacteria are erected perpendicular to the streamline, thereby extending the streamline, The contact time is increased.

Moreover, in order to discharge | emit and collect | recover the particulate sludge which is an undecomposed thing, the sludge collection needle 9 is provided in the lower part of the acid fermentation part 1 and the methane fermentation part 2. FIG. And in this case, in the horizontal cylindrical tank 3, the insulator 9 is directed toward the digestion / desorption liquid chamber 10 provided near the end of the methane fermentation part 2 opposite to the joint end with the acid fermentation part 1. Inclined downward. A plurality of holes 11,... Are formed in the top portion of the top 9 in order to take in the precipitates in the acid fermentation section 1 and the methane fermentation section 2. In addition, a pipe 12 having a small hole on the lower surface is connected to the gas storage chamber 5 through a blower 13 at the lower part of the neck 9, and gas is ejected through the pipe 12 and adhered to the sludge by stirring. Desorb and disperse methane bacteria to promote methane fermentation.
The horizontal cylindrical tank in the apparatus of the present invention includes not only those having a perfect circular cross section but also those having an elliptical cross section.

  The acid fermentation part 1 and the methane fermentation part 2 are divided by a partition wall 6 having a flange connection structure including an outer flange 20 and an inner flange 21 having cross sections as shown in FIG. 3, and a support member 8 is provided inside the methane fermentation part 2. The carrier 8 attached by ′ can be exchanged as needed. The partition wall 6 is provided with a communication part 18 and a methane discharge hole 19 between the acid fermentation part 1 and the methane fermentation part 2. Further, the partition wall 6 is provided with a hot water heat exchanger 14 and a hot water tank 15 to store hot water sent from the thermoelectric supply mechanism 16, and this is stored in the heat exchanger 14 by a pump 17 disposed in the tank. This heat energy is used for heating the acid fermentation part 1 and the methane fermentation part 2. In this invention, the acid fermentation part 1 and the methane fermentation part 2 are always maintained in the range of 30-36 degreeC in this way. The operation of the pump 17 is controlled based on the temperature detected by a temperature sensor (not shown) provided in each of the fermentation units 1 and 2.

  In the apparatus of the present invention, the Stirling engine and the fuel cell of the external combustion engine are arranged in the thermoelectric supply mechanism 16, the DC power generated thereby is stored in the storage battery, and converted into 110V and 220V AC by the frequency conversion means. And preferably used as internal power. In order to stabilize power supply, it is preferable to attach a solar cell and supply DC power.

  The power generation efficiency of the Stirling engine of the external combustion engine thus obtained is about 10%, the conversion efficiency as heat energy converted to a hot water temperature of 60 ° C. is 65 to 70%, and the overall efficiency is 75 to 80%. there were. And since 10 to 30% of the thermal energy obtained as warm water is used for heat retention of the methane fermentation apparatus, the thermal energy that can be used outside is 70 to 90%. However, the ratio of the heat energy which can be utilized can be enlarged further by the improvement of the heat retention efficiency which uses a heat insulating material, the attachment of the heat exchange serpentine tube to the outer side part of a methane fermentation apparatus, etc.

In the method of the present invention, it is preferable to use electrochemical wastewater treatment together.
This electrochemical wastewater treatment is performed by irradiating a metal surface coated with a transition metal oxide such as titanium oxide with electrons of several hundred volts to generate hydroxyl radicals and oxygen radicals, thereby producing ammonia nitrogen and phosphate groups. Phosphorus is decomposed, the former is converted into a nitrogen gas body to make it harmless, and the latter is removed as a precipitate of phosphorus oxide. However, this treatment is only applied to the methane fermentation digestion desorption liquid in the method of the present invention. Is not valid. This is because the methane digestion and desorption liquid in the method of the present invention contains a lot of suspended substances (SS), which interferes with electron irradiation and significantly reduces the anode voltage.

  Therefore, in the method of the present invention, the iron electrode is immersed in the digestion and detachment liquid containing suspended particles, and a direct current of 20 to 50 V is applied to dissolve a small amount of divalent iron ions in the liquid. It is necessary to apply in advance. At this time, oxygen radicals are generated by the Fenton effect, and at the same time, suspended particles in which hydrogen ions are suspended are aggregated and precipitated. On the other hand, the phosphorus component is precipitated as iron phosphate by the divalent iron ions, and is oxidized by oxygen radicals to be aggregated and precipitated as phosphorus oxide.

The treatment liquid coagulated and precipitated in this way is transferred to a sedimentation tank and separated into a supernatant and a precipitate, and the supernatant is again treated with a low-frequency pulse wave of 50 to 120 Hz (duty ratio 80 to 100%). Is done. In this way, using a mixed anode plate made of TiO ₂ and RuO ₂ , 90% of the total organic carbon (TOC) serving as the carbon source was obtained under the conditions of a current density of 1 to 30 mA / cm ² and a voltage of 10 to 50 V. It was possible to oxidatively decompose with the above efficiency. At this time, coloring substances such as polyphenols were also decomposed and decolorized.

  In the method of the present invention, it is preferable to perform the combination of the Fenton effect and the low-frequency pulse wave by a cascade process that repeats in two stages. However, the removal rate can be further increased by performing the process in a cascade process that repeats further three stages. Can do.

FIG. 4 is a process diagram for explaining an electrochemical wastewater treatment system in which a treatment unit using a three-stage cascade system is composed of three stages of A, B, and C. In this figure, the second stage is irradiated with a low-frequency pulse wave, and the third stage is irradiated with a high-frequency pulse wave.
Here, the cascade system means a system in which the supernatant of the sedimentation tank is gravity moved to the next stage due to overflow, and subsequent sediment formation is performed.

In the method of the present invention, when the two-stage cascade process was performed under the condition of 50 to 120 Hz, the carbon source and phosphate phosphorus in the methane digestion and desorption liquid could be removed at a removal rate of 80 to 90%. The removal rate of all nitrogen components was as low as 10 to 20%. However, when electromagnetic wave irradiation of a frequency band of 10 to 100 kHz is performed, the conversion rate of ammonia nitrogen to nitrogen gas is 50 to 60% at a low frequency of voltage 500 V, current density 1 mA / cm ² and duty ratio 20%. Improved.

  On the other hand, when the device of the present invention is configured as a prefabricated structure, the transportation of the structure from the factory causes a restriction on the diameter of the device, so the methane fermentation volume is limited by the vehicle width and length regulations of the road transport method. I can not escape. In particular, if the length of the cylindrical device is designed to exceed the regulation value, it is necessary to assemble at the site. However, this site assembly is not practical because it takes time and labor costs.

  In the apparatus of the present invention, in order to avoid this, by making the tank of the housing into an oval cross-sectional shape, most of the factory assembly can be performed at the factory, and on-site work can be minimized. For example, by integrating the tank body on one side of the tank and a sludge recovery pad, the cross-section can be made 1.8 to 2.3 times the cross-sectional area of a circular cylinder with a perfect cross-section. By forming, transportation within the regulations of the Road Traffic Law becomes possible.

  In the apparatus of the present invention, a hinge for detachably attaching a carrier support material that also serves as a pressure-resistant reinforcement for the generated methane gas can be attached.

Regarding the method of the present invention, the following was further found out.
(1) A methane concentration of 95 to 99% can be obtained by absorbing and removing carbon dioxide in the generated gas by a pressure fluctuation type gas reformer (PSR system). On the other hand, when carbon dioxide is removed using a reverse osmosis membrane, the methane concentration becomes 70 to 80%, but the heat balance with the power for internal power is just balanced, and the heat balance is within the energy of the generated gas. This concentration is the limit to stop.

(2) Using a photoreactor, the method using algae such as chlorella, spirulina, or seddesmus with a metal halide lamp as a direct light source and supplying light into the reactor both convert 30-40% of carbon dioxide into oxygen. We were able to. In this case, a 3-5% digestion and desorption solution was used, and a medium diluted with the 10 to 20-fold digestion and desorption solution was supplied semi-continuously. However, since carbon dioxide is acidic, a phosphate buffer solution is used. It was necessary to control the pH by the above. Absorption and removal of ammonia nitrogen and inorganic phosphorous phosphorus in the culture solution is close to 100%, and power consumption is controlled by using sunlight during the day and artificial light sources only at night. The methane concentration could be increased with minimal power consumption. Further, chlorella, spirulina and senedesmus obtained as by-products can be used as food and feed. Although photosynthetic bacteria do not generate oxygen, they have the same effect.

(3) Combined with a solar cell with an output voltage of 28 V and a DC power of 0.5 kW, the treated water subjected to the electrochemical water treatment of the method of the present invention is supplied as electrolyzed water to the electrolyzer, and the water is electrolyzed. The generated hydrogen was dehumidified and purified by removing impure gas due to activated carbon, and then used as hydrogen for methane generation.
On the other hand, the generated oxygen was released into the atmosphere as it was. When the purified hydrogen and the high-concentration methane gas obtained by the above-described PSR method were mixed to operate a 3 kW output fuel cell, the power efficiency was 20 to 28% and the overall efficiency was 80 to 85%. In this case, an improvement in power efficiency was observed with an increase in hydrogen concentration.
Further, by supplying purified hydrogen and high-concentration methane separately to the fuel cell, the power efficiency could be improved to 25 to 35%.

  According to the present invention, since methane gas can be efficiently produced from organic substance-containing waste, it is suitable as a method for generating methane gas priority, and each component can be reduced to a content below the wastewater standard. It is also suitable for sewage treatment and wastewater treatment.

  Next, the best mode for carrying out the present invention will be described by way of examples, but the present invention is not limited thereby.

Using the two-phase methane generator having the structure shown in FIG. 1 and having a total volume of 5 m ³ , acid fermentation section 1 m ³ , methane fermentation section 3 m ³ and gas storage chamber 1 m ³ , swine manure (water content 91%) A mixture obtained by adding an equal amount of water to 144 kg was subjected to methane fermentation. After 10 hours of treatment, methane gas could be recovered with a high yield of 0.75 m ³ / kg-vs. The COD in the wastewater was 100 ppm, the total nitrogen amount was 50 ppm, the total phosphorus amount was 2 ppm, and the suspended substance concentration was 20 ppm. The energy balance in this case was positive.

When the raw garbage discharged from the school lunch center was supplied to the apparatus used in Example 1 at a rate of 200 kg daily, the methane gas yield was 0.72 m ³ / kg-vs. The COD in the wastewater was 20 ppm, the total nitrogen amount was 5 ppm, the total phosphorus amount was 0.5 ppm, and the suspended substance concentration was 2 ppm. It was also found that sludge was completely decomposed with almost no sludge.
In this example, although the energy balance was negative, it was found that the amount of raw garbage that can be input can be increased up to 400 kg / day due to the good quality of the wastewater after treatment.

The digestion and detachment liquid obtained in Example 1 was first subjected to a low frequency pulse wave (100 Hz) for 5 minutes while passing a direct current at a voltage of 300 V, a current density of 1 mA / cm ² and a duty ratio of 20%, and then a high frequency pulse wave (100 kHz). For 5 minutes. Table 1 shows the total phosphorus amount (TP), total nitrogen amount (TN), ammonia nitrogen amount (NH ₄ -N), total organic carbon amount (TOC), BOD and COD.

  As is apparent from this table, according to the method of the present invention, harmful components in water can be removed with a removal rate of approximately 90%, so that treated water can be discharged as it is.

  According to the present invention, high-concentration methane can be generated from organic matter-containing waste such as sewage sludge and livestock excreta, so that it can be used for the production of fuel gas and the discharged water is completely free of harmful substances. Since it can be discharged as it is, it is also useful as a water treatment method.

The longitudinal cross-sectional view which shows an example of an apparatus suitable for enforcing the method of this invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. The cross-sectional view along the BB line of FIG. The process figure for demonstrating the electrochemical wastewater treatment system by the cascade method of 3 steps | paragraphs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Acid fermentation part 2 Methane fermentation part 3 Horizontal cylindrical tank 4 Pipe 5 Gas storage chamber 6 Bulkhead 7 Pipe 8 Carrier 8 'Supporting member 9 Sludge collection ring 10 Digestion desorption liquid chamber 11 Hole 12 Pipe 13 Blower 14 Hot water heat Exchanger 15 Hot water storage tank 16 Thermoelectric supply mechanism 17 Pump 18 Communication part 19 Methane discharge hole 20 Outer flange 21 Inner flange

Claims (16)

  In the method of generating acid by continuously performing acid fermentation and methane fermentation on organic substance-containing wastewater, the acid fermentation unit and the methane fermentation unit are integrally configured via a partition wall provided with a heat exchanger. In addition to using a generator, a generation mechanism of heat and electric energy is arranged in the generator to supply the necessary power and heat necessary for heating the fermentation liquid of methane in this method. Methane generation method.   The method for generating methane according to claim 1, wherein a hot water storage tank is attached to the partition wall together with a heat exchanger, and hot water sent from the heat and electric energy generation mechanism is stored in the hot water storage tank.   The method for generating methane according to claim 1 or 2, wherein sludge generated by acid fermentation and methane fermentation is discharged and removed.   The method for generating methane according to any one of claims 1 to 3, wherein an internal combustion engine, an external combustion engine, or a fuel cell is used as an electric energy generation mechanism, and a part of the generated methane is used as the fuel.   The method for generating methane according to any one of claims 1 to 4, wherein a storage amount of methane gas is detected, and a supply amount of waste water containing organic substances is controlled based on the information.   6. The method for generating methane according to any one of claims 1 to 5, wherein the digestion / elimination liquid produced through acid fermentation and methane fermentation is subjected to electrochemical treatment to remove COD, total nitrogen, total phosphorus and ammonia nitrogen. .   Electrochemical treatment is performed by immersing the iron electrode in the digestion and detachment solution as a positive electrode, and generating a divalent metal iron ion by flowing a direct current, agglomerating and precipitating suspended particles, and then adding the supernatant to the supernatant. The methane generation method according to claim 6, wherein the methane generation method is performed by processing with a low frequency pulse wave of 50 to 120 Hz.   The methane generation method according to claim 7, wherein the methane generation method is performed by processing with a high frequency pulse wave of 10 to 100 kHz after processing with a low frequency pulse wave of 50 to 120 Hz.   A part of the digestion and desorption liquid produced through acid fermentation and methane fermentation is used as a culture solution, and desulfurization bacteria are allowed to act on the generated gas to perform photosynthesis, simultaneously converting carbon dioxide in the generated gas into carbohydrates and simultaneously generating gas The method for generating methane according to any one of claims 1 to 8, wherein hydrogen sulfide is removed from the catalyst.   A part of the digestion and desorption liquid produced through acid fermentation and methane fermentation is used as a culture solution, and this is subjected to biomethanation under the coexistence of sulfate-reducing bacteria and carbon dioxide-utilizing methane bacteria to purify the generated gas. The method for generating methane according to any one of claims 1 to 9. In the two-phase methane generator having an acid fermentation section and a methane fermentation section, the acid fermentation section and the methane fermentation section are configured as a horizontal cylindrical tank integrally connected via a partition wall, and the internal combustion engine or external combustion the cogeneration system consisting of a heat storage unit engine or a fuel cell is provided, and the means and acid fermentation unit heat energy from the heat storage unit and a methane fermentation unit for utilizing the electric energy generated by the fuel cells as an internal power pressurized Means for utilizing the temperature, the upper part of the acid fermentation part and the methane fermentation part is formed in the gas storage chamber, the shape of the gas storage chamber is made arcuate with respect to the lower liquid phase part, and the generated gas A two-phase methane generator characterized by reinforcing a gas storage chamber and a tank against pressure. In the two-phase methane generator having an acid fermentation section and a methane fermentation section, the acid fermentation section and the methane fermentation section are configured as a horizontal cylindrical tank integrally connected via a partition wall, and the internal combustion engine or external combustion the cogeneration system consisting of a heat storage unit engine or a fuel cell is provided, and the means and acid fermentation unit heat energy from the heat storage unit and a methane fermentation unit for utilizing the electric energy generated by the fuel cells as an internal power pressurized Provided with a means for utilizing the temperature, and provided with a sludge discharge pipe inclined from the acid fermentation section toward the methane fermentation section through the bottom of the acid fermentation section and the methane fermentation section, A two-phase methane generator, in which a perforated pipe for blowing air is inserted. In the two-phase methane generator having an acid fermentation section and a methane fermentation section, the acid fermentation section and the methane fermentation section are configured as a horizontal cylindrical tank integrally connected via a partition wall, and the internal combustion engine or external combustion the cogeneration system consisting of a heat storage unit engine or a fuel cell is provided, and the means and acid fermentation unit heat energy from the heat storage unit and a methane fermentation unit for utilizing the electric energy generated by the fuel cells as an internal power pressurized Means for utilizing the temperature, the upper part of the acid fermentation part and the methane fermentation part is formed in the gas storage chamber, the shape of the gas storage chamber is made arcuate with respect to the lower liquid phase part, and the generated gas Reinforce the gas storage chamber and tank against pressure, provide a sludge discharge pipe inclined from the acid fermentation section toward the methane fermentation section through the bottom of the acid fermentation section and the methane fermentation section, and the sludge discharge pipe, Gas stirring Biphasic methane generator, characterized in that the insertion of the perforated pipe for blowing air for. The two-phase methane generator according to any one of claims 11 to 13 , further comprising a gas sensor that measures a gas amount in the gas storage chamber and a control mechanism that adjusts a raw material supply amount in conjunction with information output from the gas sensor. The partition wall between the acid fermentation unit and the methane fermentation unit and detachable metal barrier plate, according to any one of claims 11 through 14 to which was attached a heat exchanger through which hot water and combustion exhaust gas generated at the gas utilization system The two-phase methane generator described in 1. In the two-phase methane generator having an acid fermentation section and a methane fermentation section, the acid fermentation section and the methane fermentation section are configured as a horizontal cylindrical tank integrally connected via a partition wall, and the internal combustion engine or external combustion A thermoelectric supply mechanism comprising an engine or fuel cell and a heat storage unit is provided, and means for using the electric energy generated in the fuel cell as internal power and the heat energy from the heat storage unit are heated by the acid fermentation unit and the methane fermentation unit Provided with a sludge discharge pipe inclined from the acid fermentation part to the methane fermentation part, and connected between the acid fermentation part and the methane fermentation part. A two-phase methane generator characterized in that the partition wall is a detachable metallic partition plate, and a heat exchanger for passing hot water and combustion exhaust gas generated in the gas utilization system is attached to the partition wall.

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