JP2006110540A - Efficient biogas recovery system using microorganism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent biogas recovery system for recovering biogas efficiently from biomass. <P>SOLUTION: There is provided a biogas recovery system comprising: an anaerobic fermentation tank for anaerobic fermenting biomass; a biogas recovery unit to which the anaerobic fermentation tank is connected and in which biogas produced is recovered; a biodrying unit for drying a residue of the anaerobic fermented biomass using a microorganism; and an incineration unit for incinerating the dried residue obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a system for efficiently recovering biogas from biomass.

  Biomass, which is a biological organic resource, includes organic waste, resource crops, or waste thereof. Among these biomass, organic waste such as food waste, livestock manure, food residues and seafood residues, or resource crops or their wastes are generally relatively low in water compared to sewage sludge. It is often dried easily and incinerated (Patent Document 1). On the other hand, from the viewpoint of effective use of resources and environmental preservation, various studies have been made for effective use of biomass, not just incineration. For example, studies have been made to recover biogas such as methane gas and hydrogen gas from biomass using microorganisms as energy (see Patent Document 2 or Patent Document 3). Among these biogases, hydrogen is used for applications such as fuel cells, and methane is used for applications such as gas engines and power generation. However, most of the fermentation residue produced by recovering biogas from biomass is incinerated in the same manner as in the past, except that it is partially composted. This fermentation residue, especially the organic waste containing a large amount of water such as sewage sludge, food industry wastewater, and paper industry wastewater, is subjected to anaerobic fermentation, and the fermentation residue from which biogas is recovered has a very high water content. Before incineration, it is necessary to dry to a moisture level that can withstand combustion. If the biogas, which is the recovered energy, is used to dry the fermentation residue, or if the recovered biogas is used to assist the combustion of the dried fermentation residue (supplement), the recovered biogas will not be recovered. It is not used for the purpose, and as a result, the recovery efficiency of biogas decreases.

Therefore, a biogas recovery system that recovers biogas from biomass by anaerobic fermentation and dries and incinerate the fermentation residue without using the recovered biogas for auxiliary combustion is desired. In particular, in the case of biomass having a high water content, the demand is high.
Japanese Patent Laid-Open No. 2002-174412 JP 2001-149983 A JP 2003-135089 A

  The present invention recovers biogas from biomass by anaerobic fermentation and uses biogas or external auxiliary fuel as a fuel for drying and / or incineration of the anaerobic fermentation residue or as an auxiliary fuel for combustion of the fermentation residue. It is an object of the present invention to provide a system that does not need to be used, increases the biogas recovery rate as a whole, and does not use auxiliary fuel.

  The present invention relates to an anaerobic fermenter for anaerobically fermenting biomass; a biogas recovery device connected to the anaerobic fermenter to recover biogas produced; a biodrying device for reducing and drying the anaerobic fermentation residue by microorganisms; and And a biogas recovery system including an incinerator for incinerating the obtained dry residue.

  The present invention also provides a methane fermentation tank for methane fermentation of biomass; a methane fermentation gas recovery apparatus for recovering methane fermentation gas generated by being connected to the methane fermentation tank; and biodrying for reducing and drying the residue of the methane fermentation by microorganisms. There is provided a biogas recovery system including an apparatus; and an incinerator for incinerating the obtained dry residue.

  In a preferred embodiment, it further comprises a solid-liquid separation device for solid-liquid separation of the methane fermentation residue and recovering the dehydrated residue, and the dehydrated residue is dried in a biodrying device.

  Furthermore, the present invention provides a hydrogen fermentation tank for hydrogen fermentation of biomass; a hydrogen fermentation gas recovery apparatus for recovering the hydrogen fermentation gas generated by being connected to the hydrogen fermentation tank; A biogas recovery system comprising: a solid-liquid separation apparatus for recovering the wastewater; a biodrying apparatus for reducing and drying the dehydrated residue with microorganisms; and an incinerator for incinerating the obtained dry residue.

  Another aspect of the present invention is a hydrogen fermenter for hydrogen fermentation of biomass; a hydrogen fermentation gas recovery device for recovering a hydrogen fermentation gas generated by being connected to the hydrogen fermenter; a methane for accepting a residue of the hydrogen fermentation and for methane fermentation A fermenter; a methane fermentation gas recovery device connected to the methane fermenter and recovering the generated methane fermentation gas; a solid-liquid separator for recovering the dehydrated residue by solid-liquid separation of the residue of the methane fermentation; There is provided a biogas recovery system including a biodrying device for reducing and drying the residue by microorganisms; and an incinerator for incinerating the obtained dry residue.

Since the biogas recovery system of the present invention includes a biodrying apparatus, the anaerobic fermentation residue having a high water content after anaerobic fermentation can be reduced by microorganisms and dried to an appropriate level for combustion. Therefore, it is not necessary to use biogas recovered by anaerobic fermentation as combustion energy for anaerobic fermentation residues or as auxiliary fuel for fermentation residue combustion. Therefore, biogas can be recovered efficiently. Furthermore, since the external fuel used for incineration or auxiliary combustion of the anaerobic fermentation residue becomes unnecessary, the running cost can be reduced. In addition, anaerobic fermentation reduces the amount of organic matter in the fermentation residue, and further reduces the amount of organic matter due to the action of microorganisms in the biodrying device. The amount of CO _{2 to} be reduced is reduced.

  The biogas recovery system of the present invention will be described with reference to the accompanying drawings. In the present specification, the biomass means an organic resource derived from a living organism. Preferably, organic substances such as organic waste, resource crops or waste thereof are used. Examples of organic waste include organic waste water, organic waste, manure, sludge, etc. in the food industry, paper industry, livestock industry, etc. Not limited to these. Examples of resource crops include corn and sugar cane, and waste generated in these treatment steps is also used in the present invention.

(System 1)
FIG. 1 is a system diagram showing an embodiment (system 1) of the biogas recovery system of the present invention. The biogas recovery system of the present invention is widely used for anaerobic fermentation (hydrogen fermentation, methane fermentation, butane fermentation, etc.). FIG. 1A shows a system suitable for biomass with relatively little water (for example, raw garbage, livestock manure, manure, food residue, seafood residue, and resource crops). FIG. 1A shows an anaerobic fermentation tank 20 for anaerobically fermenting biomass 1, a biogas recovery device 22 for recovering biogas 21 generated in the anaerobic fermentation tank 20, and anaerobic fermentation residue 23 after biogas fermentation with microorganisms. It is configured to include a bio-drying device 11 that is reduced in weight and dried, and an incinerator 13 that incinerates the obtained dry residue 12.

  The system shown in FIG. 1B is a system suitable for biomass having a high water content (for example, sewage sludge, food industry wastewater, paper industry wastewater, etc.). FIG. 1B shows a case where the solid-liquid separation device 8 is provided between the anaerobic fermentation tank 20 and the drying device 11 in the system of FIG. The anaerobic fermentation residue 23 having a high water content is separated into the dehydrated residue 9 and the separated water 10 by the solid-liquid separator 8. The dehydrated residue 9 is transferred to the bio-drying device 11, and the bio-dried dry residue 12 is incinerated by the incinerator 13.

  Although not shown in FIGS. 1 (A) and (B), a pretreatment tank 30 for pretreating biomass 1 may be provided, and the pretreated biomass 31 may be introduced into the anaerobic fermentation tank 20. Good. The preprocessing will be described later.

  In the system 1 shown in FIGS. 1 (A) and (B), the biomass 1 is pretreated as necessary and sent to the anaerobic fermenter 20. In the anaerobic fermenter 20, anaerobic fermentation (for example, methane fermentation, hydrogen fermentation, butane fermentation, etc.) is performed, and biogas 21 is generated and recovered by the biogas recovery device 22. In the case of methane fermentation, the biogas 22 is methane fermentation gas mainly composed of methane and carbon dioxide. In the case of hydrogen fermentation, the biogas 22 is a hydrogen fermentation gas mainly composed of hydrogen and carbon dioxide.

  In the case of FIG. 1A, the anaerobic fermentation residue 23 is transferred to the drying device 11 and bio-dried. In the case of FIG. 1B, the solid-liquid separator 8 separates the dehydrated residue 9 and the separated water 10. The dehydrated residue 9 is transferred to the biodrying device 11 and biodried.

  The solid-liquid separator 8 is not particularly limited as long as it is a dehydrator generally used for separating sludge and has sufficient solid-liquid separation ability. Examples of such a solid-liquid separator include a centrifugal dehydrator, a screw press dehydrator, and a rotary press dehydrator. The anaerobic fermentation residue 23 is solid-liquid separated by the solid-liquid separator 8 and separated into a dehydrated residue (solid content) 9 and separated water 10. In general, the water content in the dehydration residue (solid content) 9 by the solid-liquid separator 8 is preferably 85% by mass or less, and more preferably 80% by mass or less.

  A part of the separated water 10 may be returned to the treatment system or may be discarded.

  The anaerobic fermentation residue 23 in FIG. 1 (A) and the dehydrated residue 9 in FIG. 1 (B) are bio-dried by the bio-drying device 11. Hereinafter, the anaerobic fermentation residue 23 and the dehydration residue 9 are collectively referred to as a fermentation residue. The feature of the present invention is that the amount of fermentation residue is reduced by biodrying of the fermentation residue by the biodrying apparatus 11, that is, fermentation by microorganisms, preferably aerobic fermentation. There is also an advantage that the heat of fermentation by fermentation during biodrying can be used for biodrying.

  The biodrying apparatus 11 includes various means for aerobically fermenting the fermentation residue. For example, the biodrying apparatus 11 includes an aeration unit for sending air and an agitation unit for agitating the fermentation residue. By mixing the fermentation residue put into the bio-drying device 11 and a microorganism (fermentation microorganism) capable of fermenting the fermentation residue, aerobic fermentation is performed by aeration and stirring, and the fermentation residue is consumed. Then it ferments and generates heat. The heat of fermentation is used to dry further fermentation residues. That is, the organic matter in the fermentation residue is consumed during the fermentation, and the water is evaporated to dry the fermentation residue. In addition, although fermenting microorganisms may use what adhered to biomass 1 as it is, it is fermentation efficiency that what used fermentation residue aerobically fermented once (namely, dry residue 12) as an inoculum. That is, the drying efficiency is good. Excess fermentation heat is used for preheating and predrying the fermentation residue. In particular, the water content of the dehydrated residue 9 produced by anaerobic fermentation such as sewage sludge as shown in FIG. 1 (B) is generally 75 to 85%. Therefore, excess heat of fermentation may be used for preliminary drying of the fermentation residue. With such a biodrying device 11, the moisture concentration of the fermentation residue is set to about 30 to 40%, and the dry residue 12 is obtained. At the same time, during the bio-drying, the organic matter is used for metabolism such as the growth of microorganisms, so that the organic matter in the fermentation residue is consumed and the amount of the dry residue 12 is greatly reduced. In addition, when malodor occurs during anaerobic fermentation, a deodorizing device may be provided to prevent malodor.

  As the bio-drying device 11, a rotary drum type aeration drying device or the like is used. This apparatus can continuously dry the fermentation residue, and the resulting dried residue 12 is introduced into the incinerator 13 as it is after being dried and incinerated.

  There is no restriction | limiting in particular in the incinerator 13, For example, a circulation flow type combustion apparatus etc. are used. Efficient mixing and agitation of heat, air, and fuel in the furnace, and a device capable of incineration at a uniform temperature of 1000 ° C. or less provides clean exhaust gas characteristics such as low NOx, low sulfur, and dioxin reduction. From the viewpoint, it is preferably used.

  In the system 1 configured in this manner, energy is recovered from biomass by anaerobic fermentation, and energy that has been conventionally used for drying of fermentation residues or auxiliary combustion for incineration by biodrying in the biodrying apparatus 11 is: It is used for fuel cells, gas engines, etc., which are the original applications. Therefore, the energy recovery rate is improved. The amount of organic matter is reduced by anaerobic fermentation, the anaerobic fermentation residue is modified, and the moisture content of the dehydrated residue 9 is reduced. Thus, the organic matter content is reduced by anaerobic fermentation, and the amount of organic matter is greatly reduced during biodrying. Therefore, the biodryer 11 and the incinerator 13 can be downsized.

(System 2)
FIG. 2 is a system diagram showing an embodiment (system 2) of the biogas recovery system of the present invention, and is a diagram when anaerobic fermentation is methane fermentation.

  In this system 2, FIG. 2 (A) shows a methane fermentation tank 5 (anaerobic fermentation tank) for methane fermentation of biomass 1, a methane gas recovery device 16 for recovering methane fermentation gas 6 (biogas), and a methane fermentation residue 7 (anaerobic). A biodrying device 11 for biodrying the fermentative fermentation residue) and an incineration device 13 for incinerating the resulting dry residue 12. The system of FIG. 2A is a system suitable for methane fermentation from biomass (for example, raw garbage, livestock manure, manure, food residue, seafood residue, resource crop, etc.) with relatively little water.

  The system of FIG. 2 (B) is a system suitable for biomass with high water content (for example, sewage sludge, food industry wastewater, paper industry wastewater, etc.). Therefore, in FIG. 2 (A), the solid-liquid separation apparatus 8 for carrying out solid-liquid separation of the methane fermentation residue 7 is provided.

  In addition, the system 2 of FIG. 2 may also be provided with a system that performs pretreatment of the biomass 1, as in the system 1.

  In this system 2, the biomass 1 is pretreated as necessary, transferred to the methane fermentation tank 5, and anaerobically methane-fermented. Methane-fermenting bacteria are accumulated by acclimatizing activated sludge and digested sludge under anaerobic conditions. Methane fermentation is generally performed at 25 to 65 ° C, preferably 30 to 40 ° C, and in the case of thermophilic bacteria, 50 to 60 ° C. Methane fermentation is generally carried out on the alkaline side at pH 5-10, preferably 7-9. The amount of methane gas generated (decomposition rate of organic matter) is generally higher in high temperature fermentation than in medium temperature fermentation.

  The methane fermentation gas 6 produced by methane fermentation is usually a mixed gas of methane gas and carbon dioxide. The methane fermentation gas 6 may be stored in the methane fermentation gas recovery device 16 as it is or after carbon dioxide removal.

  The produced | generated methane fermentation gas 6 is collect | recovered suitably (removal of carbon dioxide etc.) after being collect | recovered by the methane fermentation gas collection | recovery apparatus 22, and it can use for gas power generation as methane gas. Alternatively, methane gas can be further reformed to hydrogen and used separately as hydrogen.

  The methane fermentation residue 7 is introduced into the drying device 11 as it is as in the system 1 (see FIG. 2A) or is once recovered as a solid (dehydrated residue 9) by the solid-liquid separation device 8 (see FIG. 2). 2 (see (B)), introduced into the bio-drying device 11, subjected to aerobic fermentation treatment (bio-drying) with microorganisms, reduced in weight and made into a dry residue 12, and then incinerated by the incinerator 13. About the system after this biodrying, the description in the said system 1 is applied.

  The system 2 configured as described above recovers methane as energy from biomass by methane fermentation. In this system, methane is not used for supporting combustion for drying or incineration of the fermentation residue 7 (Fig. 2 (A) or dehydrated residue 9 (Fig. 2 (B)). As a result, the energy recovery rate is improved, and the organic matter content is reduced by methane fermentation, and the amount of organic matter is greatly reduced by the metabolism of microorganisms during biodrying, so that the biodryer 11 and the incinerator 13 Can also be miniaturized.

(System 3)
FIG. 3 is a system diagram showing one embodiment (system 3) of the biogas recovery system of the present invention, and is a diagram when anaerobic fermentation is hydrogen fermentation. This system 3 includes a pretreatment tank 30 for pretreating biomass 1, a hydrogen fermenter 2 (anaerobic fermenter) for fermenting pretreated biomass 31 with hydrogen, and a hydrogen gas recovery device for collecting hydrogen fermentation gas 3 (biogas). 15. Solid-liquid separation device 8 for solid-liquid separation of the hydrogen fermentation residue 4, a dehydration residue (solid content) 9 obtained, a bio-drying device 11 for bio-drying the dehydration residue 9, and an incinerator 13 for incinerating the resulting dry residue 12 It has.

  There is no restriction | limiting in particular in the pre-processing method of biomass 1, For example, physicochemical processes, such as heat processing, an ultrasonic treatment, a crushing process, an acid process, an alkali process, are mentioned. These processes are performed alone or in combination. By these pretreatments, the biomass 1 is changed to a form that is easily fermented.

  When the biomass 1 contains a hardly decomposable substance such as organic sludge, it is preferable to perform an alkali treatment in order to solubilize these hardly decomposable substances. By performing the alkali pretreatment, the pretreated biomass 31 is easily used by the hydrogen fermentation microorganisms, and the hydrogen generation efficiency is improved. Furthermore, since pH falls during a hydrogen fermentation process, it is preferable to introduce | transduce the biomass 31 after alkaline pretreatment into the hydrogen fermenter 2. FIG. That is, the pretreated biomass 31 subjected to the alkali treatment is put into the hydrogen fermenter 2 in place of an alkali agent such as sodium hydroxide or potassium hydroxide.

  There is no restriction | limiting in particular in alkali treatment, For example, the pH of biomass 1 is adjusted to 10 or more, Preferably pH 10-12 using alkaline agents, such as sodium hydroxide and potassium hydroxide. The alkali treatment is usually performed by stirring for 0.5 to 24 hours, preferably 2 to 12 hours. When the alkali pretreatment is continuously performed, the treatment is performed so that the residence time is 0.5 to 24 hours, preferably 2 to 12 hours. By such treatment, the activity of hydrogen-consuming bacteria contained in the biomass 1 or microorganisms (for example, lactic acid bacteria, methanogens, etc.) that adversely affect hydrogen fermentation can be reduced, or these microorganisms can be killed. it can.

  The alkali pretreatment may be performed under heating. Although there is no restriction | limiting in particular in heating temperature, It carries out at 30 to 90 degreeC or 35 to 80 degreeC. Furthermore, ultrasonic treatment, crushing treatment, and the like may be combined to increase the efficiency of alkali treatment. There are no particular limitations on the conditions of the ultrasonic treatment, and the frequency and the treatment time may be appropriately determined in consideration of the treatment temperature and the treatment amount.

  When the biomass 1 is suitable for acid treatment, it may be used as the post-pretreatment biomass 31 as it is after acid treatment. However, when it is advantageous to adjust to alkaline in the next hydrogen fermentation step, the pH of the biomass after acid treatment may be further adjusted to the alkali side to obtain the biomass 31 after alkaline pretreatment. Also in this case, the pH can be adjusted to preferably 10 or more, more preferably pH 10-12.

  In addition, it cannot be overemphasized that the description of the said pre-processing is applied also in the methane fermentation of the system 2. FIG.

  The biomass 1 or the pretreated biomass 31 is introduced into the hydrogen fermenter 2 and subjected to hydrogen fermentation. The inside of the hydrogen fermenter 2 is maintained in an anaerobic atmosphere. In this hydrogen fermenter 2, hydrogen fermentation gas 3 mainly composed of hydrogen and carbon dioxide is generated by subjecting biomass 1 to hydrogen fermentation.

  The microorganism used for the hydrogen fermentation is an anaerobic non-photosynthetic microorganism group or a pure bacterium, and may be of any origin as long as it is a microorganism group or a pure bacterium having hydrogen-producing ability. Preferably, a microorganism group having hydrogen-producing ability is used, for example, sewage sludge, sludge after methane fermentation of garbage, or a culture thereof. Hydrogen fermentation is generally performed at 20 to 60 ° C, preferably 30 to 37 ° C.

  Hydrogen fermentation is performed under acidic conditions or alkaline conditions. When carried out under acidic conditions, the pH is preferably 4 to 7.5, and more preferably pH 5.5 to 7. Since an organic acid is generated during hydrogen fermentation and the pH of the hydrogen fermentation liquor is lowered, the pretreated biomass 14 subjected to alkali pretreatment may be added to the hydrogen fermenter 2 for pH adjustment. When performed under alkaline conditions, the pH is preferably 10-12.

  The produced hydrogen fermentation gas 3 is recovered by the hydrogen fermentation gas recovery device 15 and then appropriately purified (removal of carbon dioxide or the like), and can be used as a fuel for a fuel cell or supplied to a hydrogen gas station.

  The hydrogen fermentation residue 4 is recovered as a solid content (dehydrated residue 9) by the solid-liquid separation device 8, introduced into the biodrying device 11, subjected to an aerobic fermentation process with microorganisms, reduced in weight, and dried residue 12. After that, it is incinerated by the incinerator 13. About the system after this biodrying, the description in the said system 1 is applied.

  The system 3 configured as described above recovers hydrogen as energy from biomass by hydrogen fermentation. Furthermore, since the organic matter content is reduced by hydrogen fermentation, and the amount of organic matter is greatly reduced by the metabolism of microorganisms during biodrying, the biodrying device 11 and the incineration device 13 can be downsized.

(System 4)
FIG. 4 is a system diagram showing the most preferable mode (system 4) in the biogas recovery system of the present invention. The system 4 includes a pretreatment tank 30 that pretreats biomass 1, a hydrogen fermentation tank 2, and a methane fermentation tank 5. A hydrogen fermentation gas recovery device 15 that recovers the generated hydrogen fermentation gas 3 is connected to the hydrogen fermentation tank 2. The methane fermentation tank 5 is connected to a methane fermentation gas recovery device 16 that recovers the generated methane fermentation gas 6. Furthermore, a solid-liquid separation device 8 for solid-liquid separation of the methane fermentation residue 7, a bio-drying device 11 for bio-drying the resulting dehydrated residue (solid content) 9, and an incinerator 13 for incinerating the resulting dry residue 12 ing.

  The system 4 is configured to pre-process the biomass 1 as necessary, introduce it into the hydrogen fermentation tank 2 to perform anaerobic fermentation, and recover the generated hydrogen fermentation gas 3 to the hydrogen fermentation gas recovery device 15. . The hydrogen fermentation residue 4 contains an organic acid generated in the hydrogen fermentation tank 2, an organic matter that has not been decomposed, and the like, and transfers this to the methane fermentation tank 5. Methane fermentation gas 6 mainly composed of methane and carbon dioxide produced by methane fermentation is recovered by a methane fermentation gas recovery device 16. For hydrogen fermentation and methane fermentation, the description of the systems 2 and 3 is applied.

  The methane fermentation residue 7 is solid-liquid separated using a solid-liquid separation device 8, and the dehydration residue 9 is introduced into a biodrying device 11 (for example, a rotary drum type aeration drying device) in the same manner as in the systems 1 to 3 and is caused by microorganisms. Aerobic fermentation treatment is performed to reduce the weight and dry. The obtained dry residue 12 is introduced into the incinerator 13 and incinerated.

  Therefore, it is not necessary to use the hydrogen and methane recovered by the hydrogen fermentation gas recovery device 15 and the methane fermentation gas recovery device 16 for auxiliary combustion for drying or incineration of the dehydrated residue 9. Hydrogen and methane are appropriately purified (removal of carbon dioxide, etc.) and used for fuel cells, gas engines, and the like.

  In the system 4, the amount of energy recovered from biomass increases by performing hydrogen fermentation and methane fermentation. Furthermore, the methane fermentation residue 7 has a reduced organic matter content and is easily separated into solid and liquid as compared with the case where each fermentation is performed individually. Therefore, the solid content and water content of the dehydrated residue 9 are reduced. Furthermore, hydrogen content and methane fermentation reduce the organic matter content, and during biodrying the organic matter content is greatly reduced due to microbial metabolism. Therefore, the drying device 11 and the incinerator 12 can be reduced in size, the amount of external fuel used for incineration can be reduced or unnecessary, and the running cost can be reduced.

  Hereinafter, the present invention will be described in more detail with reference to examples.

  Sewage sludge was subjected to hydrogen fermentation and methane fermentation. After the sludge was heated to 80 ° C. and pretreated, hydrogen fermentation was performed at a temperature of 35 ° C. and a hydraulic residence time (HRT) of 1 day, and the hydrogen fermentation residue was subjected to methane fermentation. Methane fermentation was carried out at a high temperature (temperature of 55 ° C.) and a hydraulic residence time (HRT) of 10 days. The methane fermentation residue was dehydrated with a screw press, and the solid content and moisture content of the dehydrated residue were measured. The dehydrated residue was put into a rotary drum type aeration drying apparatus (drying apparatus 11) and bio-dried. For comparison, drying was performed using external fuel. A comparative study was conducted on the dry residue when the dehydrated residue was treated at 100 t / day by these methods. The results are shown in Table 1.

As shown in the results of Table 1, when biodrying and fuel drying (drying using external fuel) are performed so as to have the same water content (40%), when the biodrying apparatus used in the present invention is used The weight of the dry residue was 28 t, but it was 42 t when the fuel was dried. This indicates that 1/3 of the combustible content was reduced during biodrying. And the amount of water evaporation was also larger in bio-drying. When the amount of water evaporation in bio-drying is converted into energy, it is about 8.2 million kJ, but since this energy is produced by microorganisms, the external energy consumption is zero. On the other hand, when dried using fuel, the energy used to evaporate the water was about 7.5 million kJ. When this was converted into methane, it was 209 m ³ N. Therefore, the biogas recovery system of the present invention was able to recover energy without consuming 209 m ³ N methane necessary for drying until auxiliary combustion or self-combustion.

  Thus, the biogas recovery system of the present invention is an excellent biomass processing system, and is an environment-friendly system in which the generation of carbon dioxide due to the recovery of energy and the reduction of the incineration amount of organic matter is suppressed.

  In the biogas recovery system of the present invention, since the fermentation residue after biogas recovery can be bio-dried, the amount of organic matter can be greatly reduced and the fermentation residue can be dried. It is not necessary to use the biogas that has been used, and external energy is greatly reduced or unnecessary. That is, it is an energy recovery system from biomass that efficiently recovers biogas while suppressing energy consumption, and is also a biomass processing system. Therefore, it can be widely used as an energy recovery system and processing system from biomass.

It is a systematic diagram showing one embodiment of the energy recovery system of the present invention. It is an energy recovery system of this invention, Comprising: It is a systematic diagram which shows the aspect in the case of performing methane fermentation. It is an energy recovery system of this invention, Comprising: It is a systematic diagram which shows the aspect in the case of performing hydrogen fermentation. It is an energy recovery system of this invention, Comprising: It is a systematic diagram which shows the aspect in the case of performing hydrogen fermentation and methane fermentation.

Explanation of symbols

1 Biomass 2 Hydrogen Fermenter 3 Hydrogen Fermentation Gas 4 Hydrogen Fermentation Residue 5 Methane Fermenter 6 Methane Gas 7 Methane Fermentation Residue 8 Solid-Liquid Separator 9 Dehydrated Residue 10 Separated Water 11 Bio Dryer 12 Dry Residue 13 Incinerator 15 Hydrogen Gas Recovery Device 16 Methane gas recovery device 20 Anaerobic fermenter 21 Biogas 22 Biogas recovery device 23 Anaerobic fermentation residue 30 Pretreatment tank 31 Pretreated biomass

Claims (5)

  Anaerobic fermenter for anaerobically fermenting biomass; a biogas recovery device connected to the anaerobic fermenter to recover biogas produced; a biodrying device for reducing and drying the anaerobic fermentation residue by microorganisms; and obtained A biogas recovery system comprising: an incinerator for incinerating dry residues;   A methane fermentation tank for methane fermentation of biomass; a methane fermentation gas recovery apparatus for recovering the generated methane fermentation gas connected to the methane fermentation tank; a biodrying apparatus for reducing and drying the residue of the methane fermentation by microorganisms; A biogas recovery system comprising: an incinerator that incinerates the dried residue.   The biogas recovery system according to claim 2, further comprising a solid-liquid separator for solid-liquid separation of the methane fermentation residue and recovering the dehydrated residue, and drying the dehydrated residue with the biodryer.   Hydrogen fermentation tank for hydrogen fermentation of biomass; Hydrogen fermentation gas recovery device connected to the hydrogen fermentation tank and recovering hydrogen fermentation gas produced; Solid for liquid-liquid separation of the hydrogen fermentation residue and recovery of dehydration residue A biogas recovery system comprising: a liquid separation device; a biodrying device for reducing and drying the dehydrated residue by microorganisms; and an incinerator for incinerating the obtained dry residue.   Hydrogen fermentation tank for hydrogen fermentation of biomass; Hydrogen fermentation gas recovery apparatus for recovering hydrogen fermentation gas generated by connecting to the hydrogen fermentation tank; Methane fermentation tank for receiving methane fermentation from the residue of hydrogen fermentation; A methane fermentation gas recovery device that connects and recovers the produced methane fermentation gas; a solid-liquid separation device for solid-liquid separation of the residue of the methane fermentation, and recovery of the dehydrated residue; A biogas recovery system comprising: a biodrying device; and an incinerator for incinerating the obtained dry residue.

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