JP2005125319A - Method and apparatus for power generation by organic waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an economical and extremely low environmental-load technology which produces electric energy from organic waste by using biological reactions and chemical reactions. <P>SOLUTION: The method and the apparatus for power generation by the organic waste are characterized in that, in the power generation method by the organic waste comprising a process for producing gaseous fuel from the organic waste by the biological reactions, a gas purification process for purifying gas obtained from the gaseous fuel production process, and a power generation process for supplying the purified gas and generating power, whole or a part of waste liquid containing a residue discharged from the process for producing the gaseous fuel by the biological reactions is fed to a hydrothermal electrolysis process for supplying a direct current, at a temperature not less than 100°C and below the critical temperature of the waste liquid, under the pressure making the waste liquid maintain its liquid phase, and hydrogen gas recovered in the hydrothermal electrolysis process is used after being mixed with gas obtained from the gaseous fuel production process, or both gases are used independently. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for generating power from organic waste by utilizing biological reactions and chemical reactions.

In recent years, energy produced from biomass has attracted attention as carbon neutral energy that is not included in CO ₂ emissions. Biomass includes waste biomass, such as garbage and sewage sludge, in addition to woody biomass such as thinned wood and construction waste, and crop residues. It needs to be treated and disposed of from the surface.

  Methane fermentation has long been applied as a method for reducing and stabilizing organic waste such as food waste, livestock waste, and sewage sludge, but in recent years it has been positioned as a method for recovering energy from unused biomass resources. It has become. The form of energy to be recovered includes methane gas itself as a fuel, heat, electric energy, and the like, but electric energy is the best in terms of versatility. As a power generation device, a device that generates power using a heat engine such as a gas engine or a gas turbine has been used, but in recent years, as a high-efficiency power generation device that can be applied to relatively small-scale facilities. Fuel cells are attracting attention.

However, in the methane fermentation of organic waste, although the major component of the generated gas is methane (60% to 70%) and _CO 2 (30 to 40%), hydrogen sulfide as a minor component in other, ammonia, methyl mercaptan , Hydrogen chloride, SOx, NOx, CO, siloxane and the like. In gas engines, gas turbines, etc., acidic gases such as hydrogen sulfide cause corrosion in the equipment, and siloxanes block gas flow and cause deposits. Various gas purification apparatuses have been developed (see Patent Document 1).

  On the other hand, in a polymer electrolyte fuel cell or a phosphoric acid fuel cell that is currently in practical use, since the fuel substance is hydrogen, a gas reforming process that converts methane to hydrogen is essential, and sulfurization is also required. The restriction of acidic gases such as hydrogen is very strict (300 to 5000 times) compared to gas engines and gas turbines, and the ammonia, CO, and siloxane concentrations are also limited, so even more sophisticated gas purification processes. Is necessary (see Patent Document 2, etc.).

JP 2002-275482 A Japanese Patent Laid-Open No. 2001-804046

  As described above, in a device that produces a gaseous fuel such as methane from organic waste using a biological reaction and generates electricity using this, it is necessary to remove harmful components from the power generation device. A gas purification apparatus is required, and particularly when a fuel cell is used, a gas reforming process for converting methane into hydrogen and a high-level gas purification process are required.

  The present invention has been made in view of such conventional problems, and provides an economical and extremely low environmental impact technology for producing electrical energy from organic waste using biological and chemical reactions. It is an object to do.

  In order to solve the above-mentioned problems, the present inventors set the total amount or a part of the waste liquid containing the residue after producing the gaseous fuel from the organic waste by using a biological reaction at a critical temperature of 100 ° C. or higher. Alcohol by microbial action (eg ethanol fermentation, lactic acid fermentation, hydrogen fermentation, methane fermentation) from organic matter after hydrothermal electrolysis that supplies direct current under pressure that maintains the liquid phase of the waste liquid at a temperature below By returning to the valuable production process that produces valuables such as fuel and gaseous fuel, the production of valuable resources can be increased and the organic matter concentration and nitrogen concentration in the waste liquid can be greatly reduced. The present inventors have found that gas can be recovered and have completed the present invention.

That is, the present invention has solved the above problems by the following means.
(1) A process for producing gaseous fuel from organic waste by a biological reaction, a gas purification process for purifying gas obtained from the process for producing gaseous fuel, and a power generation process for generating electricity by supplying the purified gas In the power generation method using the organic waste having the above, the total amount or a part of the waste liquid containing the residue discharged from the step of producing the gaseous fuel by the biological reaction at a temperature of 100 ° C. or higher and lower than the critical temperature of the waste liquid. Is supplied to a hydrothermal electrolysis process for supplying a direct current under a pressure that maintains a liquid phase, and hydrogen gas recovered in the hydrothermal electrolysis process is obtained by using a gas obtained from a process for producing gaseous fuel. A power generation method using organic waste, characterized by using both of them individually or individually.

(2) The power generation method using the organic waste according to (1), wherein the power generation step of generating power by supplying purified gas includes a fuel cell.
(3) The power generation method using organic waste according to (1) or (2) above, wherein the gas purification step includes a step of reforming methane to hydrogen gas.
(4) A power generation step of generating power by supplying purified gas is a step of generating power using a heat engine, and a power generation step of generating power by supplying hydrogen gas recovered in the hydrothermal electrolysis step, The power generation method using organic waste according to any one of (1) to (3), wherein the power generation is performed using a fuel cell.

(5) An apparatus for producing gaseous fuel from organic waste by a biological reaction, a gas purification apparatus for purifying gas obtained from the process for producing gaseous fuel, and a residue discharged from the process for producing gaseous fuel. A hydrothermal electrolysis apparatus that supplies a direct current under a pressure at which the waste liquid maintains a liquid phase at a temperature that is 100 ° C. or higher and lower than the critical temperature of the waste liquid, in which all or a part of the waste liquid is supplied. A power generation apparatus using organic waste, comprising: a power generation apparatus that generates electricity by supplying purified gas and hydrogen gas recovered in the hydrothermal electrolysis apparatus.

In the present invention, it is possible to provide a method for generating electricity from organic waste that significantly reduces the residue discharged from the process of producing valuable materials and has an extremely low environmental load. In particular, the process of producing gaseous fuels such as hydrogen and methane from solid or high-concentration organic wastes using biological reactions discharges waste liquids that contain a large amount of residues, thus reducing residues or environmental impact. More effective. Moreover, since a power generation system suitable for the scale can be selected, it can greatly contribute to the reduction of CO ₂ emissions. Furthermore, since hydrogen gas is obtained by hydrothermally electrolyzing the waste liquid, it is possible to increase the amount of power generation using the hydrogen gas.

  In the present invention, the gaseous fuel produced by the biological reaction from the organic waste is preferably a gas containing methane and / or hydrogen, but when methane is the main component, the methane concentration is 60% or more. It is preferable that the methane concentration be 70% or more.

  Preferable embodiments for producing a gaseous fuel containing methane and / or hydrogen from an organic waste using a biological method include an acid fermentation method, a hydrogen fermentation method, a methane fermentation method, and the like. These are all fermentative methods called anaerobic treatment methods, such as methane and / or a valuable material in an anaerobic atmosphere at a temperature of 30 to 70 ° C., a pH of 5 to 8.5, and a redox potential of −100 to −600 mV. Or produce gaseous fuel containing hydrogen. In these anaerobic fermentation systems, microbial cells (excess sludge) and ammonia nitrogen are also produced, and solids that are hardly decomposable remain as undegraded residues.

  Here, the hydrogen fermentation method is a biological reaction process in which hydrogen is generated in an anaerobic fermentation process such as acid fermentation, ethanol fermentation, and lactic acid fermentation after the solid matter of organic waste is hydrolyzed. In the hydrogen fermentation step, the reaction is preferably performed at a reaction temperature of 30 to 70 ° C., pH 4.5 to 7, more preferably pH 5 to 6, and a hydraulic residence time (HRT) of 1 to 5 days. In particular, depending on the type of organic waste, the solubilization step tends to be rate-determining, so it is preferable to carry out the reaction at a high temperature of 45 to 70 ° C. for 2 to 5 days. In processes such as acid fermentation, lactic acid fermentation, ethanol fermentation, hydrogen fermentation, in addition to hydrogen, carbon dioxide, hydrogen sulfide, organic acids such as formic acid, acetic acid, propionic acid, lactic acid, butyric acid, valeric acid, caproic acid, ethanol, Alcohols such as propanol, 2,3-butanediol, acetone and butanol are mainly produced.

In methane fermentation, biogas such as methane, carbon dioxide, hydrogen sulfide and ammonia is mainly produced. In methane fermentation, 0.35 m ³ (standard state) of methane is produced per 1 kg of decomposed organic matter. The methane fermentation method is performed in a fermentation temperature of 30 to 70 ° C, preferably in a mesophilic methane fermentation region of 35 to 40 ° C or in a high temperature methane fermentation region of 50 to 65 ° C. This is because the optimum growth temperature of many mesophilic or thermophilic methanogenic bacteria and other anaerobic bacteria is within these ranges. The pH conditions are preferably pH 6-9, more preferably pH 7-8, and HRT is preferably operated under the operating conditions of 5-30 days, more preferably 10-25 days.

  In the methane fermentation process of organic waste treatment according to the present invention, any of the floating treatment type, fixed bed type, fluidized bed type, and UASB (upward flow type anaerobic sludge blanket) type can be applied as a reaction treatment type. It is. In this selection, it is necessary to pay particular attention to the SS (Suspended Solids) concentration and the fat and oil concentration. Specifically, when the SS concentration is 2,000 mg / L or more, it is preferable to apply floating bed type methane fermentation. In addition, when the oil and fat concentration is 1,000 mg / L or more, it is preferable to apply floating bed type methane fermentation. In the methane fermenter, neutral fats and higher fatty acids have higher dispersibility at higher temperatures, so when applying waste materials that contain a large amount of fats and oils, select a high-temperature methane fermentation method of 50 to 65 ° C. It is preferable to do.

  In the present invention, the gas purification step for purifying the gas obtained from the step of producing the gaseous fuel can be any type of device as long as it is a device for purifying the gas supplied to the power generation device, When supplying to a power generation device that generates power using a heat engine such as a gas engine or a gas turbine, it is preferable to use a device suitable for the power generation device. In general, a desulfurization apparatus for removing hydrogen sulfide in the gas is used. As the desulfurization apparatus, a dry desulfurization apparatus using a pellet or powder desulfurization agent mainly composed of iron hydroxide or magnesium, a microbial desulfurization apparatus that performs wet desulfurization using a microbial reaction, or the like is used. By the desulfurization apparatus, the hydrogen sulfide concentration in the gaseous fuel is desulfurized to 10 mg / L or less, preferably 1 mg / L or less, more preferably 0.1 mg / L or less.

  In the present invention, in the hydrothermal electrolysis method that passes through all or part of the waste liquid containing residues discharged from the process of producing gaseous fuel by microorganisms from organic waste, hydrothermal reaction and electrolysis are performed simultaneously. By doing so, reducing substances such as organic substances and ammonia can be effectively oxidatively decomposed. However, when a hydrothermal electrolysis reaction is performed with very little or no oxidant added, When organic sludge is a target, it can be expressed as, for example, Equation (1).

C ₅ H ₇ NO ₂ + 8H ₂ O → 11.5H ₂ + 5CO ₂ + 0.5N ₂ (1)
If ammonia is the target, as shown in equation (2),
2NH ₃ → N ₂ + 3H ₂ (2)
Thus, hydrogen gas is generated. That is, when the hydrothermal reaction and electrolysis are simultaneously performed in a reducing atmosphere, unlike the normal temperature and normal pressure, the reaction in which oxygen and hydrogen are generated simultaneously does not occur, and hydrogen can be generated safely from ammonia.

  In the hydrothermal electrolysis reaction, the removal rate varies depending on the concentration of organic matter or ammonia, the reaction temperature, pressure, pH of the reaction solution, the presence or absence of the addition of an oxidant, and the like in the present invention, a process for producing valuable materials using microorganisms. The removal rate in the hydrothermal electrolysis reaction process of organic matter or ammonia contained in the waste liquid including residues discharged from the wastewater is determined by the ratio of the waste liquid transferred to the hydrothermal electrolysis reaction process and the conditions of the hydrothermal electrolysis reaction. Can be adjusted by.

The basic reaction of hydrothermal electrolysis will be described. When the aqueous solution is electrolyzed at room temperature and normal pressure, hypohalous acid is generated when halogen such as oxygen or chlorine ions is contained in the anode. Even if ammonia or an organic substance is contained, in this case, the efficiency of the oxidation reaction is poor and the reaction hardly proceeds or becomes very slow, so that basically a large amount of oxygen is generated at the anode. In this case, a large amount of hydrogen is generated at the cathode.
When the same electrolysis reaction is performed under hydrothermal conditions, oxygen and hypohalous acid are not generated (or consumed immediately after generation), and the organic substance and ammonia are oxidatively decomposed into CO ₂ , N ₂ and water. Again, hydrogen is generated at the cathode.

  When an oxidant such as oxygen is positively inserted from the outside into a reaction field in which an aqueous solution containing ammonia and organic substances is hydrothermally electrolyzed, hydrogen is not generated at the cathode, and oxygen is converted into active oxygen. This active oxygen oxidizes ammonia and organic matter. Similarly, at the anode, a reaction for oxidizing these ammonia and organic substances proceeds, so that all contaminants in the aqueous solution are mineralized to carbon dioxide and nitrogen gas. However, since hydrogen gas is not generated in this case, the hydrothermal electrolysis reaction in which oxygen is positively added is merely a purification reaction and not a valuable material recovery reaction.

  Furthermore, when a NaCl aqueous solution that does not contain oxidizable substances such as ammonia and organic substances is hydrothermally electrolyzed, hydrogen, oxygen, and hypochlorous acid are not generated. Under this condition, the phenomenon of “electrolysis of water without hydrogen and oxygen” occurs. More precisely, there is a possibility that oxygen and hydrogen are generated at the anode and the cathode, but some neutralization such that the oxidant generated at the anode is reduced at the cathode or the hydrogen generated at the cathode is reduced at the anode. The reaction takes place (the mechanism is still unknown), and as a result, no explosive hydrogen and oxygen gas mixture accumulates in the reactor. Hydrothermal electrolysis is a safe process because such a neutralization reaction proceeds or hydrogen and oxygen are not generated simultaneously.

In hydrothermal electrolysis, the diaphragm is basically not used. One of the reasons is that there is no film that can withstand this hydrothermal condition (in terms of heat resistance, corrosion resistance, and pressure resistance). For a fluororesin type diaphragm such as Nafion (DuPont, registered trademark), 150 and 160 ° C. are usable limits. Ceramic solid electrolytes used in solid electrolyte fuel cells, for example, ceramic solid electrolytes such as yttrium-stabilized zirconia, have problems such as cracking when the temperature shock or pressure balance is broken or corrosion in a hydrothermal atmosphere. In fact, the diaphragm cannot be used. Another reason is that no diaphragm is required because explosive gas is not generated without a diaphragm as described above. When ammonia and organic substances are hydrothermally electrolyzed without adding an oxidant, hydrogen is generated at the cathode, but only CO ₂ and N ₂ are generated at the anode, and oxygen is not generated, which is safe. It is also an advantage of hydrothermal electrolysis that the reaction proceeds without using a diaphragm.
Note that the liquid that has undergone reduction at the cathode and the liquid that has undergone oxidation at the anode are mixed and the reverse reaction does not occur at the counter electrode. In hydrothermal electrolysis, the hydrothermal reaction atmosphere is basically oxidative, so when organic matter and ammonia are treated, the overall reaction is an oxidative decomposition reaction.

The temperature conditions for hydrothermal electrolysis are preferably high-temperature and high-pressure liquid water of 100 ° C. or higher, preferably 150 ° C. or higher, more preferably 200 ° C. or higher, and a critical temperature of less than 374 ° C. As the pressure condition, the saturated vapor pressure or higher of the reaction temperature is preferable, preferably saturated vapor pressure to saturated vapor pressure + 10 MPa, more preferably saturated vapor pressure to saturated vapor pressure + 3 MPa. The voltage under electrolysis conditions is 1.0 V to 500 V, preferably 1.5 V to 100 V, more preferably 2 V to 50 V. The current density conditions of the electrolysis 0.1 mA / cm ² or more 2000 mA / cm ² or less, preferably 1 mA / cm ² or more 1000 mA / cm ² or less, still more preferably is 10 mA / cm ² or more 1000 mA / cm ² or less.

The hydrothermal electrolysis reaction is greatly influenced by the amount of electricity applied to the aqueous solution to be treated. The quantity of electricity is the product of current and energization time, and its unit is C (1 coulomb = 1 As) or Ah. When 10 A is energized for 1 hour in a 1 L aqueous solution, the amount of electricity applied to the solution becomes 10 Ah / L. The decomposition rate of organic matter or ammonia contained in the solution varies depending on the initial COD concentration (chemical oxygen consumption) of the solution. In the present invention, basically, no oxidizing agent is added or only a small amount of oxidizing agent is added. In this case, it can be calculated from the Faraday rule that 3.3 Ah is necessary to completely decompose 1 gram of COD. For example, when an amount of electricity of 3.3 Ah is applied to 1 L of residual waste liquid having a COD of 1 g / L, organic substances and ammonia contained in the solution can be completely mineralized to CO ₂ and nitrogen. When the residual waste liquid has a COD concentration of 10 g / L, if 33 Ah / L is given, it can be completely mineralized. Thus, in hydrothermal electrolysis, the organic matter decomposition rate can be controlled by the amount of electricity.

  The present invention does not limit how many times the theoretical amount of electricity is given to the waste liquid. In the case where only a part of the residual waste liquid in the valuable material production process is hydrothermally electrolyzed, it may be completely decomposed by giving 10 times or less of this theoretical electricity amount. In addition, since it will be a waste of electric power if it gives extra, Preferably it is 4 times or less of theoretical amount. More preferably, it is 2 times or less. In the case where the entire amount of the residue from the biological value production process is sent to the hydrothermal electrolysis process, a theoretical electric quantity or less may be given. As will be described later, when surplus sludge from the activated sludge process that is in the post-hydrothermal electrolysis process is returned to the hydrothermal electrolysis process, the COD amount is the sum of the residue flowing from the valuable production process and the returned sludge. The theoretical amount of electricity can be calculated from In the present invention, there is no need to completely decompose the residual COD discharged from the process of producing valuable materials. What is necessary is just to be able to reduce the organic matter and ammonia load in the post-process biological water treatment or phosphorus recovery process and to improve efficiency.

In hydrothermal electrolysis, reactions such as formula (10) and formula (11) in which the oxidant is reduced proceed preferentially over the reaction that generates hydrogen. Accordingly, in hydrothermal electrolysis, the generation of hydrogen is suppressed, and the possibility that oxygen gas and hydrogen gas coexist in the reactor at the same time is reduced, and the risk of explosion is reduced. In addition, since an oxidizing agent such as hypohalous acid is decomposed at the cathode, a secondary treatment for detoxifying the oxidizing agent in the treated water becomes unnecessary. For example, in electrolysis at room temperature, hypohalite ions are generated at a high concentration. On the other hand, generation of hypohalite ions was hardly detected in the electrolysis at high temperature.
Regardless of the reaction mechanism, reducing substances such as organic substances and ammonia are oxidatively decomposed and the generation of hydrogen gas or oxygen gas can be suppressed by the present invention.

  In the present invention, the gas mainly composed of methane obtained from the step of producing the gaseous fuel is a gas reforming in which acidic gas such as hydrogen sulfide is removed in the gas purification step and further reformed into a gas mainly composed of hydrogen. After the process, it can be supplied to the fuel cell together with the hydrogen gas generated in the hydrothermal electrolysis process. As a gas reforming method, any reforming method used for producing a gas to be supplied to a polymer electrolyte fuel cell or a phosphoric acid fuel cell from a fuel gas such as natural gas may be used. However, a method including a step of removing CO in the gas after reforming (see, for example, JP-A-2001-23677) is preferable. Hydrogen gas generated in the hydrothermal electrolysis process not only has a very low concentration of acidic gases such as hydrogen sulfide and ammonia, but also has a very low CO concentration, so it must be supplied directly to the fuel cell without going through a gas purification process. Can do.

  In the present invention, a gas mainly composed of methane obtained from a process of producing gaseous fuel is removed from an acidic gas such as hydrogen sulfide in a gas purification process, and then a heat engine such as a gas engine or a gas turbine is used. The hydrogen gas generated in the hydrothermal electrolysis process can be directly supplied to the fuel cell without going through the gas purification process. In gas engines, gas turbines, and the like, the allowable concentration of acidic gas such as hydrogen sulfide is higher than that of a fuel cell, and thus a device such as a scrubber and / or a dry desulfurizer can be used for gas purification.

  In general, since a power generation apparatus that generates power using a heat engine such as a gas engine or a gas turbine is expensive to maintain, a facility for processing a large volume of organic waste is required. However, it is not preferable to collect organic waste having a high water content such as garbage in a wide area because it consumes a lot of transportation energy. For this reason, facilities that produce gaseous fuel using organic waste such as garbage are often relatively small and medium-sized, but especially in small-scale facilities, power generation is performed using heat engines. As the power generation device, a micro gas turbine is preferably used.

  On the other hand, since the fuel cell has been downsized in recent years and can sufficiently cope with a small-scale facility, in the present invention, in the case of a small-scale facility, (1) methane obtained from the process of producing gaseous fuel is mainly used. The gas to be used is combined with the hydrogen gas generated in the hydrothermal electrolysis process after the gas reforming process in which acidic gas such as hydrogen sulfide is removed in the gas purification process and further reformed into a gas mainly composed of hydrogen. Then, after removing the gas mainly composed of methane obtained from the method of supplying to the fuel cell or (2) the process of producing the gaseous fuel, the gas gas purification process removes acidic gas such as hydrogen sulfide, In addition to supplying hydrogen gas generated in the hydrothermal electrolysis process directly to the fuel cell without going through the gas purification process, (3) a gas mainly composed of methane obtained from the process of producing gaseous fuel The After being removed by a simple gas purification process, the hydrogen gas generated in the hydrothermal electrolysis process is supplied directly to the fuel cell without going through the gas purification process. A method of generating electricity can also be employed.

The apparatus of the above step (1) is shown in FIG. 1, and the apparatuses of steps (2) and (3) are shown as a block diagram in FIG.
In FIG. 1, an organic waste (hereinafter also referred to as “raw material”) 5 is supplied to a gaseous fuel production reaction tank 1, and in this case, methane 13 is generated by an anaerobic reaction. The generated methane 13 is purified by removing, for example, hydrogen sulfide in the gas purifier 14, and then enters the gas reformer 15 to be a gas mainly composed of hydrogen 16. Part of the residue waste liquid 6 exiting from the gaseous fuel production reaction tank 1 enters the hydrothermal electrolysis reaction tank 3, where hydrothermal electrolysis reaction is performed, and the generated hydrogen 11 is stored in the hydrogen storage tank 12, and is described above. It is combined with hydrogen from the gas reformer 15 and supplied to the fuel cell 17 to generate electric power.

The hydrothermal electrolysis reaction treatment liquid 7 exiting from the hydrothermal electrolysis reaction tank 3 is combined with the remainder of the residual waste liquid 6 and sent to the aeration tank 2 where it is subjected to an aerobic treatment. The treatment liquid is a solid-liquid separation tank 4. The sludge is settled and separated and discharged into the water area as discharge water 8. Most of the settled sludge in the solid-liquid separation tank 4 is returned to the aeration tank 2 as return sludge 9 and the excess is sent to the hydrothermal electrolysis reaction tank 3 for processing. Or it takes out as the excess sludge 10 and processes by a conventional method.
FIG. 1 shows a case where hydrogen obtained by reforming methane 13 generated from the gaseous fuel production reaction tank 1 and hydrogen discharged from the hydrothermal electrolysis reaction tank 3 are used together. FIG. 2 shows an example in which methane 13 is used for a micro gas turbine 18 or a boiler 19, and hydrogen 11 discharged from the hydrothermal electrolysis reactor 3 is used for a fuel cell 17. Is shown.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description.

Example 1
Manufacture of valuable materials by continuous fermentation type high temperature methane fermentation (55 ° C) for mixed raw materials of human waste, food waste, septic tank sludge, surplus sludge (VS 10%, COD _Cr 140,000mg / L concentration adjusted with process water) . A fully mixed high-temperature methane fermenter was used as a valuable material production apparatus (cylindrical type, made of polyvinyl chloride, total volume 30 L, effective volume 25 L, jacket hot water circulation type, 55 ° C., stirring speed 30 / min). The raw water input was 1.2 to 1.5 L / day, and HRT was 17 to 20 days. Water quality and biogas were analyzed by the following method.

(Analysis method)
・ TS (Total Solids, total evaporation residue); 105 ℃ evaporation residue weight (JIS K 0102)
・ VS (Volatile Solids, loss on ignition); 600 ° C loss on ignition (JIS K 0102)
・ COD _Cr (chemical oxygen consumption); potassium dichromate method (JIS K 0102)
・ Methane gas / carbon dioxide gas chromatograph (GL Science GC-322, detector TCD, TCD current value 120mA, separation column Active Carbon 30/60, column temperature 95 ℃, carrier gas helium)
・ Hydrogen gas: Gas chromatograph (GL Science GC-322, detector TCD, TCD current value 50mA, separation column Unibeads C 60/80, column temperature 140 ℃, carrier gas argon)
・ Hydrogen sulfide and ammonia; Detector tube method

This anaerobic microbial treatment valuables production processes using was _{CH 4 62 vol%, CO 2} 38 vol% of the raw fuel gas having a composition (biogas) the raw material 1 kg (wet weight) per 110~140L recovery . Furthermore, although H ₂ S 400~700 mg / L as another gas component contained was purified in the following always 1 mg / L in the desulfurization apparatus by Dry desulfurization agent (pelletized iron hydroxide). As a result of passing this gas through a wet alkali adsorption tower and an activated carbon adsorption tower, CO, NH ₃ , Cl ₂ and HCl gas components are not detected and can be concentrated to a CH ₄ concentration of 92%, after being stored in a methane gas tank 1m ³ , Supplied to the fuel cell generator. This fuel gas was generated by a 1.2 kW fuel cell with S / CH ₄ (Steam / CH ₄ ratio) condition = 3.0, reformer outlet temperature 700 ° C., and transformer outlet temperature 200 ° C. The reformer outlet CO ₂ concentration was 13%, the reformer outlet CO concentration was 10%, and the reformer methane conversion rate was 85%. The CO concentration at the outlet of the transformer was 0.5% or less, and the CO conversion rate of the transformer was 100%.

Furthermore, this methane fermentation residue liquid (COD _Cr 46,4000mg / L) is treated with a continuous hydrothermal electrolysis reactor at a flow rate of 10L / h to recover hydrogen gas, and then the hydrothermal electrolysis reaction treatment liquid Was purified by aerobic treatment. Titanium autoclave (reactor volume 300ml, HC276, maximum operating temperature 320 ° C, maximum operating pressure 13MPa) is used for hydrothermal electrolysis of fermentation residue, hydrothermal electrolysis reaction is operated at 250 ° C and 7MPa, and sludge Electric quantity of 20Ah was given to 1L. The gas flow rate generated in the steady operation was 112 L / h, and the composition was 73.3 vol% hydrogen, 24.0 vol% carbon dioxide, and 2.7 vol% N ₂ gas. O ₂ , CO, and H ₂ S were not detected, and good fuel gas used for fuel cells and the like was obtained. This was concentrated to about 90% H ₂ concentration by washing with water, stored in a hydrogen gas tank, and then used as fuel gas for the fuel cell to generate electricity. In the fuel cell power generation in this case, the chemical cost and the power cost in the gas purification process and the gas reforming process can be reduced by 35 to 45% compared to the case of using the biogas recovered by methane fermentation.

  The present invention greatly reduces the amount of residue discharged from the process of producing valuable materials, has a large environmental impact reduction effect, and is a thermal power generation effective for pollution prevention and environmental conservation in an area where environmental pollution is a particular problem. It is useful as an alternative technology.

It is a process block diagram of the electric power generation method using together the gas obtained from the gaseous fuel production process and the gas collect | recovered by the hydrothermal electrolysis process combined with the waste liquid process by a standard activated sludge method. It is a process block diagram of the electric power generation method which utilizes separately the gas obtained from a gaseous fuel production process, and the gas collect | recovered at the hydrothermal electrolysis process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas fuel production reaction tank 2 Aeration tank 3 Hydrothermal electrolysis reaction tank 4 Solid-liquid separation tank 5 Raw material 6 Residue waste liquid 7 Hydrothermal electrolysis reaction processing liquid 8 Discharge water 9 Return sludge 10 Surplus sludge 11 Hydrogen gas 12 Hydrogen storage tank 13 methane-based gas 14 gas refining device 15 gas reformer 16 hydrogen-based gas 17 fuel cell 18 micro gas turbine 19 boiler

Claims (5)

  Organic having a process for producing gaseous fuel from organic waste by biological reaction, a gas purification process for purifying gas obtained from the process for producing gaseous fuel, and a power generation process for supplying the purified gas to generate electricity In the power generation method using a volatile waste, the waste liquid is in a liquid phase at a temperature of 100 ° C. or higher and lower than the critical temperature of the waste liquid, including all or part of the waste liquid including residues discharged from the step of producing gaseous fuel by biological reaction. The hydrogen gas supplied to the hydrothermal electrolysis process for supplying a direct current under a pressure to maintain the hydrogen gas recovered in the hydrothermal electrolysis process, together with the gas obtained from the process for producing gaseous fuel, Alternatively, a power generation method using organic waste, characterized in that each gas is used alone.   The power generation method using organic waste according to claim 1, wherein the power generation step of generating power by supplying purified gas includes a fuel cell.   The power generation method using organic waste according to claim 1 or 2, wherein the gas purification step includes a step of reforming methane to hydrogen gas.   The power generation step of generating power by supplying purified gas is a step of generating power by using a heat engine, and the power generation step of generating power by supplying hydrogen gas recovered in the hydrothermal electrolysis step includes the steps of: The power generation method using organic waste according to any one of claims 1 to 3, wherein the power generation method uses power generation by utilization.   A device for producing gaseous fuel from organic waste by biological reaction, a gas purification device for purifying gas obtained from the step of producing gaseous fuel, and a waste liquid containing residues discharged from the step of producing gaseous fuel. A hydrothermal electrolysis apparatus that supplies a direct current under a pressure at which the waste liquid maintains a liquid phase at a temperature of 100 ° C. or higher and lower than the critical temperature of the waste liquid, in which the whole amount or a part is supplied, and the purified gas And a power generation apparatus that generates power by supplying hydrogen gas recovered in the hydrothermal electrolysis apparatus.

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