JP4605992B2 - Fuel cell power generation process and fuel cell system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell power generation process, and in particular, a fuel cell power generation process capable of efficiently generating electric power using components generated in the course of methane fermentation treatment and pyrolysis treatment of organic waste and the like, and fuel The present invention relates to a battery system.
[0002]
[Prior art]
The methane fermentation method is widely used for the treatment of organic waste such as livestock waste and garbage. In the methane fermentation treatment, biogas mainly composed of methane produced by metabolism of anaerobic microorganisms can be collected and used as recycled energy. In addition to methane fermentation, a process of pyrolyzing organic waste under anaerobic conditions is also performed, and even in this method, a pyrolysis gas containing a large amount of methane can be obtained.
[0003]
Biogas by methane fermentation and pyrolysis gas by pyrolysis (in the present invention, these may be collectively referred to as “methane-containing gas”) can be used as an energy source in various ways such as fuel cells, micro gas turbines, gas engines, etc. Methods are envisaged, and among these fuel cells are attracting attention as clean power generation facilities. Since the methane-containing gas contains about 60% by weight of methane containing a large amount of hydrogen atoms as the main component, efficient power generation is possible by extracting hydrogen from this methane. (For example, see Patent Documents 1 to 3).
[0004]
[Patent Document 1]
JP-A-11-149933
[Patent Document 2]
JP 2000-167523 A
[Patent Document 3]
JP 2002-45832 A
[0005]
[Problems to be solved by the invention]
However, the problem of the fuel cell power generation process is that the process efficiency is not so good in reality, and the energy efficiency is less than the direct use of methane gas (for example, cogeneration by a micro gas turbine). Also, cost reduction is an important issue for practical application.
[0006]
Another problem when using methane-containing gas in fuel cells is that methane-containing gas, such as biogas, inevitably contains about several thousand ppm of hydrogen sulfide. Then, there is a problem that it acts as a catalyst poison for a platinum-based catalyst used as an electrode of the fuel cell, and the performance of the fuel cell is lowered. Therefore, in order to use the methane-containing gas for a fuel cell, a desulfurization facility must be provided in the middle.
[0007]
An object of the present invention is to provide a fuel cell power generation process capable of efficiently converting methane-containing gas obtained by subjecting organic waste to methane fermentation treatment or thermal decomposition treatment into electric energy.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention of the fuel cell power generation process according to claim 1 is based on methane, which is obtained by fermentation and / or pyrolysis of organic waste under anaerobic conditions, and contains ammonia and / or Alternatively, a methane-containing gas generation step for recovering a gas containing hydrogen sulfide, a decomposition step for decomposing the ammonia and / or hydrogen sulfide to generate hydrogen, and a power generation step for generating power with a fuel cell using the hydrogen as fuel. , Including.
[0009]
In this fuel cell power generation process, ammonia and / or hydrogen sulfide in methane-containing gas obtained by anaerobically fermenting or thermally decomposing organic waste is decomposed to produce hydrogen, which is used as a fuel cell. Therefore, it is possible to make maximum use of the hydrogen source contained in the methane-containing gas.
[0010]
Further, since hydrogen sulfide serving as the catalyst poison is removed in the decomposition step and only hydrogen is supplied to the fuel cell, there is no possibility of reducing the power generation efficiency. That is, since the decomposition process itself for hydrogen generation has a desulfurization action, there is an advantage that the conventional desulfurization process is not essential in the fuel cell power generation process.
[0011]
Note that methane, which is the main component in the methane-containing gas, can be used in a fuel cell after reforming, and can also be used as a fuel for a gas turbine, a gas engine, or the like.
[0012]
An invention of a fuel cell power generation process according to a second aspect includes the reforming step of decomposing the methane to generate hydrogen in the first aspect, wherein the power generation step includes the reforming step and the decomposition step. It is characterized by using hydrogen as a fuel.
[0013]
According to this feature, by supplying hydrogen obtained by reforming methane to the fuel cell, it is possible to add hydrogen from methane to hydrogen from ammonia and / or hydrogen from hydrogen sulfide. Thus, the power generation amount of the fuel cell can be increased.
[0014]
The invention of the fuel cell power generation process according to claim 3 includes an ammonia recovery step in which alkali is added to the fermentation liquor produced by the fermentation to extract ammonia in claim 1 or claim 2, wherein the ammonia recovery step The obtained ammonia is treated in the decomposition step, and the obtained hydrogen is used in the power generation step.
[0015]
A large amount of ammonia is contained in the fermented liquid (fermentation residue) after fermenting organic waste under anaerobic conditions. By introducing this into a fuel cell as a hydrogen source, It becomes possible to greatly increase the amount of power generation.
[0016]
According to a fourth aspect of the present invention, there is provided the fuel cell power generation process according to any one of the first to third aspects, wherein the fuel cell is a phosphate fuel cell or a solid polymer membrane fuel cell. It is characterized by. Phosphate type fuel cells or polymer electrolyte membrane fuel cells react at a relatively low temperature of 200 ° C. or lower, so that the catalyst is likely to be poisoned by hydrogen sulfide. However, hydrogen sulfide and ammonia are decomposed in advance. Thus, according to the process of the present invention supplied as hydrogen, there is almost no worry of poisoning.
[0017]
The invention of the methane fermentation liquid fuel cell power generation process according to claim 5 includes a methane fermentation process in which organic waste is fermented under anaerobic conditions, and ammonia is added to the fermentation liquid obtained in the methane fermentation process to add ammonia. It includes an ammonia recovery step to be taken out, an ammonia decomposition step in which the ammonia is decomposed to generate hydrogen, and a power generation step in which power is generated by a fuel cell using the hydrogen as a fuel. According to this methane fermentation liquid fuel cell power generation process, a large amount of ammonia is contained in the fermentation liquid (fermentation residue) after methane fermentation of organic waste under anaerobic conditions. By introducing the fuel cell as a source and generating power, the amount of power generation can be greatly increased.
[0018]
The fuel cell system invention according to claim 6 is a methane fermentation that ferments organic waste under anaerobic conditions and collects biogas containing ammonia and / or hydrogen sulfide as a main component of the produced methane. An apparatus, a reformer that decomposes the methane to generate hydrogen, a cracker that decomposes the ammonia and / or hydrogen sulfide to generate hydrogen, and hydrogen generated by the reformer and the cracker And a power generation device that generates power using a fuel cell as fuel.
[0019]
According to this feature, since the decomposition device for decomposing ammonia and / or hydrogen sulfide and generating hydrogen is provided, it is possible to supply the fuel cell, which is a power generation device, including the hydrogen decomposed and generated by this decomposition device. Become. Therefore, it is possible to obtain a larger amount of power generation than that of a conventional fuel cell system, and it is possible to avoid poisoning of the catalyst, which is a factor that hinders the electrode reaction of the fuel cell.
[0020]
The invention of the fuel cell system according to claim 7 thermally decomposes organic waste under anaerobic conditions, and collects pyrolysis gas containing the generated methane as a main component and containing ammonia and / or hydrogen sulfide. A thermal decomposition apparatus, a reformer that decomposes the pyrolysis gas to generate hydrogen, a decomposition apparatus that decomposes the ammonia and / or hydrogen sulfide to generate hydrogen, and the reformer and the decomposition apparatus. And a power generation device that generates power with a fuel cell using the generated hydrogen as a fuel. According to this feature, since the decomposition device for decomposing ammonia and / or hydrogen sulfide and generating hydrogen is provided, it is possible to supply the fuel cell, which is a power generation device, including the hydrogen decomposed and generated by this decomposition device. Become. Therefore, it is possible to obtain a larger amount of power generation than that of a conventional fuel cell system, and it is possible to avoid poisoning of the catalyst, which is a factor that hinders the electrode reaction of the fuel cell.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
The fuel cell power generation process of the present invention is a methane-containing process that recovers a gas containing ammonia and / or hydrogen sulfide, which is obtained by fermentation and / or pyrolysis of organic waste under anaerobic conditions. It is carried out by performing a gas generation step, a decomposition step of decomposing ammonia and / or hydrogen sulfide to generate hydrogen, and a power generation step of generating power with a fuel cell using hydrogen as a fuel. Preferably, a reforming step of further decomposing methane to generate hydrogen is performed, and hydrogen obtained in the reforming step and the cracking step can be used as fuel in the power generation step.
[0022]
In the present invention, organic waste includes, for example, livestock waste, green waste, and wastewater treatment sludge. Examples of livestock waste include livestock manure, carcass and / or processed products thereof. More specifically, livestock carcasses such as cattle, sheep, goats and chickens, and bones separated therefrom. In addition to meat, fat, internal organs, blood, brain, eyeballs, skin, hoofs, horns, etc., crushed material of bones, meat, etc. of livestock carcasses represented by meat and bone meal, meat meal, bone meal, blood meal In addition, a dried product obtained by drying blood or the like is also included. In addition to household garbage, green-rich waste includes agricultural and industrial waste, food processing waste, etc. as industrial waste.
[0023]
In the present invention, depending on the state of the organic waste as a raw material, a crushing / sorting step can be performed as a pretreatment as necessary. The crushing / sorting step can be performed by, for example, fractionating crushing as shown below, or crushing the entire amount.
In the case of fractional crushing, a crushing / separating machine is used to collect a portion of the organic waste that can be easily crushed as a slurry together with the liquid. On the other hand, parts that are difficult to crush are collected separately as a lump. The water content of the slurry is 70 to 90% by weight, and the water content of the lump is about 40 to 60% by weight. The crushing / separating machine crushes organic solids by a shearing force and a pulling force, and a two-axis type or a three-axis type cutter can be used. When animal carcasses such as cattle are used as raw materials, it is preferable to crush the triaxial type from the viewpoint of crushing fineness and uniformity.
[0024]
The mixed plastics and sheets to be sorted and removed can be removed by mesh sorting, wind sorting (wind sorting), or the like.
[0025]
In the case of pulverizing the entire amount, for example, the entire object is crushed using a crusher such as a disposer. The moisture content is, for example, 60 to 70% by weight, but takes a wide range in the case of processed products.
[0026]
<Methane-containing gas production process>
In the fuel cell power generation process of the present invention, the methane-containing gas generation step for recovering the methane-containing gas is performed, for example, by methane fermentation, thermal decomposition, or the like.
[0027]
Methane fermentation:
Methane fermentation can be applied to any of a so-called medium temperature type, a high temperature type, a slurry (wet) type, and a dry (dry) type.
[0028]
In order to maintain the activity by the absolute anaerobic methane fermentation bacteria, the fermenter is composed of a tank in which air is completely shut off in the latter stage even in the case of a fermentation process using a two-tank system. The shape and operating conditions of the fermenter vary depending on the solid matter concentration (usually in the range of 7% to 40% by weight) and the fermentation temperature (usually 37 ° C for medium temperature fermentation and 55 ° C for high temperature fermentation). In particular, in the present invention, in the case of a raw material having a high water content (up to a solid concentration of 10% by weight) mixed with washing wastewater, a wet type complete mixing type fermenter, a raw material having a low water content (solid In the case of a product concentration of 30 to 40% by weight, it is preferable to use a so-called dry type plug flow type (extrusion type) fermenter.
[0029]
In addition to the recovery means for recovering the biogas to be produced, it is preferable that the fermenter is provided with a heating means for keeping warm if necessary. In addition, the biogas recovery means may be provided with a desulfurization apparatus as required. Those having a known configuration can be used.
[0030]
In the case of a raw material with a high water content (solids concentration up to about 10% by weight), a complete mixing type fermenter is used. For medium-temperature methane-fermenting bacteria (optimum temperature of 37 ° C.) for about a day, the residence time can be about 15 to 20 days, which is shorter than the required number of days for normal methane fermentation. In the present invention, unlike ordinary anaerobic digestion treatment, methane fermentation is performed for the purpose of recovering methane. Therefore, it is not necessary to complete the decomposition treatment by methane fermentation. In general methane fermentation, the residence time is about 15 days for high temperature fermentation and about 20 to 30 days for medium temperature fermentation.
[0031]
In the case of a raw material having a low water content (solids concentration of 30 to 40% by weight), the solid content concentration of the object to be treated is adjusted to 30 to 40% by weight to adjust the hardness to such an extent that an extrusion type fermenter can be used. About residence time, it can set similarly to the case of high moisture content. If necessary, some organic components can be introduced to adjust the carbon / nitrogen ratio.
[0032]
The main purpose of the methane fermentation process is to recover biogas as an energy source. A solid-liquid separation step of the fermentation broth can be provided as necessary after methane fermentation. In order to suppress energy consumption in the subsequent carbonization step, it is preferable to perform solid-liquid separation to reduce the initial moisture content.
[0033]
For the solid-liquid separation, an apparatus capable of increasing the slurry concentration, such as a decanter, a coagulation sedimentation tank, a centrifugal dehydrator, a screw press, and a membrane separator, can be used, and is selected according to the properties of the fermentation broth. In addition to the above, a solid-liquid separation method by an evaporation method is also possible. In this case, biogas produced by methane fermentation can be used as an energy source for evaporation.
[0034]
Thermal decomposition:
Thermal decomposition heats and carbonizes organic waste, the fermented material after the methane fermentation, etc. up to a predetermined temperature under the condition of blocking air. Examples of the apparatus used for the thermal decomposition process include a drying / carbonizing apparatus capable of blocking outside air such as a rotary kiln type, a screw conveyor type, a gravity drop type, and a batch fixed bed type. When drying and carbonizing at a relatively low temperature (450 to 500 ° C.), any method can be used, but when drying and carbonizing at a high temperature of 800 ° C. or higher, a rotary kiln method, a screw conveyor method, etc. It is important to select a heat-resistant material in a drying / carbonizing apparatus with large elements. In the carbonization treatment at 800 ° C. to 850 ° C., the recovery rate of the combustible gas from the organic waste can be improved.
[0035]
In the thermal decomposition process, a large amount of methane-containing gas is generated as the organic substance is thermally decomposed. The pyrolysis gas is recovered and supplied to the fuel cell, and can be used as a heat source in the pyrolysis process.
[0036]
<Disassembly process>
Methane-containing gas produced by methane fermentation and pyrolysis varies depending on the type of organic waste, but usually contains about 60% by weight of methane and about 40% by weight of carbon dioxide, and is about several thousand ppm as a contaminant component. Of hydrogen sulfide and ammonia of about several hundred ppm. In the decomposition step, for example, by passing a methane-containing gas, hydrogen sulfide separated from the metal catalyst layer, ammonia, or the like through a metal catalyst layer, ammonia is decomposed into hydrogen and nitrogen, and hydrogen sulfide is decomposed into hydrogen and sulfur. As described above, in the present invention, since hydrogen is also taken out from ammonia and hydrogen sulfide contained as impurities in the methane-containing gas, the power generation efficiency of the fuel cell is excellent, and poisoning due to hydrogen sulfide is also generated. Avoid as much as possible. If it is desired to avoid poisoning of the fuel cell as much as possible, it is possible to provide a desulfurization step prior to the reforming step to reliably remove hydrogen sulfide.
[0037]
In the decomposition step, it is preferable to use a reactor having a packed tower structure containing a catalyst packing. As the catalyst to be used, an iron compound catalyst is preferable for ammonia, and a noble metal catalyst is preferable for hydrogen sulfide. In particular, both ammonia and hydrogen sulfide in the methane-containing gas can be decomposed by using a noble metal-based catalyst such as a platinum-based catalyst and passing the gas at 600 to 700 ° C. Sulfur generated by the decomposition of hydrogen sulfide in the decomposition step can be captured and removed from the methane-containing gas by providing a sulfur removal filter in the subsequent stage. In addition, when the decomposition target contained in the methane-containing gas is only ammonia (for example, when desulfurization of the methane-containing gas is performed separately), it is only necessary to perform decomposition of ammonia in the decomposition step. Decomposition can be performed by using only an iron catalyst and passing a gas at a temperature of about 300 ° C. In the case of separately treating hydrogen sulfide and ammonia extracted from the methane-containing gas, the same catalyst as described above can be used.
[0038]
<Power generation process>
In the power generation process, power is generated by a fuel cell using hydrogen as a fuel. As is well known, a fuel cell has a basic structure in which an electrolyte is sandwiched between a hydrogen electrode and an oxygen electrode. At the hydrogen electrode, hydrogen reacts to release electrons and generate hydrogen ions. This hydrogen passes through the electrolyte and moves to the oxygen electrode, where it reacts with oxygen to produce water. In the course of this reaction, electrons flow from the hydrogen electrode to the oxygen electrode to generate electricity. As described above, in the present invention, ammonia and / or hydrogen derived from hydrogen sulfide can be used as a raw material of the fuel cell.
[0039]
Examples of the fuel cell that can be used in the fuel cell power generation process of the present invention include a phosphate type, a solid polymer membrane type, a molten salt type, and a solid electrolyte type. Phosphate type and solid polymer type fuel cells are susceptible to poisoning by hydrogen sulfide because the reaction is carried out at a relatively low temperature of 200 ° C. or less. The problem of catalyst poisoning can be almost avoided because the portion is removed.
[0040]
In the case of a molten salt type or solid electrolyte type fuel cell, the reaction temperature is higher than 500 ° C., and the reaction proceeds sufficiently even without a catalyst, so that the problem of catalyst poisoning hardly occurs. In the case of a molten salt type or solid electrolyte type fuel cell, for example, methane-containing gas can be supplied to the fuel cell as it is without desulfurization or reforming.
[0041]
<Absorption separation process>
In the fuel cell power generation process of the present invention, as a preferred embodiment, prior to the decomposition step, an absorption / separation step in which the impurities contained in the methane-containing gas are absorbed by the solution can be performed. In this absorption / separation step, high-concentration methane gas is recovered on the one hand by collecting and separating contaminant components and carbon dioxide contained in the gas, and on the other hand, hydrogen sulfide and ammonia gas are recovered and supplied to the fuel cell.
[0042]
Absorption separation can be performed using a normal gas absorption tower. For example, a packed tower system or a plate tower system is preferable. In the absorption separation process, a gas absorption tower is used to separate the hydrogen sulfide, ammonia, and carbon dioxide in the methane-containing gas by absorbing them into the absorption liquid, and a high-concentration methane gas is recovered. Hydrogen sulfide and ammonia dissolved in the absorbing liquid are separated from the absorbing liquid by recovery (stripping) and recovered. The absorbing solution used in this process is preferably an aqueous salt buffer solution, and particularly preferably an aqueous salt solution obtained by neutralizing a part of aminopolycarboxylic acid with an alkali metal (such as sodium). Using such an absorption liquid makes it easy to adjust the pH, so that absorption and dissipation can be performed efficiently, and by setting the pH in a certain area, absorption and dissipation can be repeated only by temperature operation. Become.
[0043]
<Reforming process>
In the fuel cell power generation process of the present invention, as a preferred embodiment, it is possible to perform a reforming step for generating hydrogen from methane contained in the largest amount in the methane-containing gas, and supply the resulting hydrogen to the fuel cell.
[0044]
The reforming step is performed for the purpose of extracting hydrogen from methane in the methane-containing gas obtained in the methane-containing gas production step (methane fermentation or thermal decomposition). In the reforming step, for example, a converter using a noble metal catalyst such as a platinum catalyst is used. For example, a steam reforming system, a partial oxidation system, or an autothermal system converter can be used as a converter widely used in phosphate fuel cells, solid polymer membrane fuel cells, and the like. A methane-containing gas is introduced into the converter, and the methane in the methane-containing gas is reformed to generate hydrogen and carbon monoxide (or carbon dioxide).
[0045]
<Ammonia recovery process>
Usually, a methane fermentation broth using a material containing nitrogen such as protein as a raw material often contains a large amount of ammonia having a concentration of several percent or more. In the fuel cell power generation process of the present invention, as a preferred embodiment, it is possible to include an ammonia recovery step (ammonia stripping) in which ammonia is generated by adding an alkaline substance to the fermentation broth obtained in the methane fermentation step. . Ammonia obtained in this ammonia recovery step can be treated in a decomposition step together with a methane-containing gas to generate ammonia-derived hydrogen, which can be used in a fuel cell. This makes it possible to greatly improve the efficiency of supplying hydrogen to the fuel cell.
[0046]
As the alkaline substance to be introduced into the fermentation broth, for example, alkali metal or alkaline earth metal hydroxides (for example, slaked lime, caustic soda, etc.) can be used.
[0047]
Ammonia stripping from the fermentation broth can be performed by towers such as a spray system, a shelf system, and a packed bed system, a membrane separator, and the like.
[0048]
<Methane fermentation liquid fuel cell power generation process>
The methane fermentation liquid fuel cell power generation process according to the present invention includes a methane fermentation process for fermenting organic waste under anaerobic conditions, and an ammonia recovery process for adding ammonia to the fermentation liquid obtained in the methane fermentation process to extract ammonia. An ammonia decomposition step of decomposing the ammonia to generate hydrogen, and a power generation step of generating power with a fuel cell using the hydrogen as a fuel. The methane fermentation, the ammonia recovery step, and the power generation step include the fuel cell It can be carried out in the same manner as the power generation process. The ammonia decomposition step can be performed in the same manner as the decomposition step in the fuel cell power generation process.
[0049]
This methane fermentation liquid fuel cell power generation process can be easily incorporated into a power generation device using a biogas fuel cell, and can be used in parallel with existing biogas power generation facilities such as micro gas turbines and gas engines using biogas. It is also possible to install this process, and by incorporating this process, the hydrogen resource contained as ammonia in the methane fermentation liquid can be utilized to the maximum extent possible.
[0050]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a fuel cell system 101 according to an embodiment of the present invention. The fuel cell system 101 includes a fermentation tank 10 as a methane fermentation apparatus, an absorption tower 20, a converter 30 as a reforming apparatus, a power generation apparatus 40, and a decomposition tower 50 as a decomposition apparatus. The configuration and function of each device are as described above.
[0051]
As shown in FIG. 1, organic waste is put into a fermenter 10 and methane fermentation is performed for a predetermined period under anaerobic conditions. Biogas produced by methane fermentation is sent to the absorption tower 20 by a collecting means (not shown). In the absorption tower 20, contaminant components such as hydrogen sulfide and ammonia and carbon dioxide contained in the biogas are absorbed by the absorption liquid and separated from the methane gas. By this operation, the methane gas is purified to a high concentration and is sent to the converter 30 as it is (path 61). When desulfurization is performed, a desulfurization device (not shown) can be provided on the inlet side of the absorption tower 20, for example.
[0052]
Among the contaminated components absorbed by the absorption liquid in the absorption tower 20, ammonia and hydrogen sulfide containing hydrogen atoms in the molecule are dissipated from the absorption liquid by stripping and sent to the decomposition tower 50.
[0053]
The cracking tower 50 of this embodiment includes a platinum-based catalyst layer that also serves as an ammonia cracking catalyst and a hydrogen sulfide cracking catalyst. Ammonia vaporized by stripping is converted into nitrogen and hydrogen, hydrogen sulfide is converted into sulfur and hydrogen, respectively. Decompose. Hydrogen generated by the decomposition is sent to the converter 30 through a path 62 different from the methane gas.
[0054]
In the cracking tower 50, it is also possible to equip the ammonia cracking catalyst and the hydrogen sulfide cracking catalyst separately. In that case, a hydrogen sulfide decomposition catalyst (eg, platinum-based catalyst) is placed upstream of the gas flow direction. First, hydrogen sulfide in the stripping gas is decomposed into hydrogen and sulfur, and the sulfur is filtered out. After that, it is preferable to perform ammonia decomposition with an ammonia decomposition catalyst (eg, iron catalyst). This is because by disposing the hydrogen sulfide decomposition catalyst on the upstream side and removing hydrogen sulfide and sulfur, it is possible to prevent a decrease in the catalytic activity of the downstream iron catalyst.
[0055]
Moreover, in this embodiment, as shown in FIG. 1, the path | route 63 which sends out the ammonia which generate | occur | produced by alkali addition (stripping) to a fermented liquid directly from the fermenter 10 to the decomposition tower 50 is provided, and the said The hydrogen is decomposed together with the ammonia from the absorption tower 50, and the generated hydrogen is sent to the converter 30.
[0056]
In the converter 30, the methane gas that has passed through the absorption tower 20 is reformed and decomposed to hydrogen and carbon monoxide (or carbon dioxide) is generated. Further, hydrogen and nitrogen (sulfur is removed by filtering) generated by the decomposition of ammonia and hydrogen sulfide in the decomposition tower 50 are also sent to the converter 30 and merged with methane gas.
[0057]
When high-concentration purified methane gas from which impurities and carbon dioxide have been removed by the absorption tower 20 is used for applications other than fuel cells, it can be stored directly from the absorption tower 20 without passing through the converter 30, or by a gas turbine. It can be burned.
[0058]
In the power generation device 40 including the phosphate type or solid polymer membrane type fuel cell, the reaction is performed by the hydrogen supplied from the converter 30, and the generated electric power and heat are recovered. The amount of heat generated can be used effectively for purposes such as keeping the fermenter 10 warm.
[0059]
The fuel cell system 101 having the above configuration includes means for extracting hydrogen from ammonia and hydrogen sulfide generated by methane fermentation, so that it is possible to increase the amount of power generated by the fuel cell and to provide sulfur that is a catalyst poison. Since hydrogen can be removed, efficient power generation can be performed.
[0060]
Hereinafter, in the description of FIGS. 2 to 4, the same components as those in FIG.
[0061]
FIG. 2 is a block diagram showing a schematic configuration of a fuel cell system 102 according to another embodiment of the present invention. As a difference from FIG. 1, a pyrolysis tower 11 is provided instead of the fermenter 10. In the present embodiment (FIG. 2), except that the methane-containing gas is generated from the organic waste by thermal decomposition in the thermal decomposition tower 11 and that the fermentation liquor does not come out and the ammonia is not reused, FIG. It is the same.
[0062]
FIG. 3 shows a schematic configuration of still another fuel cell system 103 of the present invention. The fuel cell system 103 is configured to omit the absorption tower 20 in FIGS. 1 and 2 and send biogas (pyrolysis gas) directly from the fermentation tank 10 (or the pyrolysis tower 11) to the cracking tower 50. Yes. In the present embodiment, methane is also introduced into the decomposition tower 50 along with carbon dioxide, ammonia, and hydrogen sulfide. As a result, the entire fuel cell system 103 can be configured more simply than in FIG. 1 (FIG. 2).
[0063]
In addition, the system is particularly suitable when the fuel cell of the power generation apparatus 40 is reacted at a high temperature and a molten salt type or a solid electrolyte type that does not use a catalyst is used. In the future, there is a possibility that the biogas (pyrolysis gas) can be directly supplied to the power generation facility 40 by omitting the decomposition tower 50 and the converter 30 in FIG. 3 by improving the molten salt type or solid electrolyte type fuel cell. .
[0064]
The configurations of the fermenter 10 (pyrolysis tower 11), the decomposition tower 50, the converter 30, and the power generation apparatus 40 in the present embodiment are the same as those in FIG. 1 (FIG. 2). Also in FIG. 3, a desulfurization facility can be provided as necessary as in FIG.
[0065]
FIG. 4 is a diagram showing an outline of the fuel cell power generation system 104 used in the methane fermentation liquid fuel cell process according to an embodiment of the present invention. In this process, when biogas produced by methane fermentation is already used as fuel for fuel cells and other existing equipment (eg, micro gas turbines, gas engines, boilers, etc.) Therefore, this process is suitable for the purpose of effectively using the hydrogen resources in the methane fermentation broth in the fuel cell. In this process, methane fermentation, ammonia recovery (stripping), ammonia decomposition, and power generation are performed in this order. The fermenter 10, the converter 30, the power generation device 40, and the decomposition tower 50 in FIG. 4 are the same as the respective devices in FIG. In this case, the decomposition tower 50 only needs to decompose ammonia, and does not require decomposition of hydrogen sulfide. Therefore, an iron compound-based catalyst layer can be used instead of the platinum-based catalyst layer.
[0066]
【Example】
EXAMPLES Next, although an Example and a test example demonstrate this invention further in detail, this invention is not restrict | limited by these.
[0067]
Example 1
Methane fermentation gas from general garbage and livestock manure mixture is introduced into a cracking device and passed through a platinum catalyst layer heated to about 800 ° C. to decompose hydrogen sulfide, and the sulfur in the cracked product is removed by filtration. Ammonia was decomposed through the catalyst layer. Next, the desulfurization layer and a fuel converter as a reformer were passed. This reformed gas was supplied to a solid polymer membrane fuel cell body. The methane fermentation gas contained about 2000 ppm of hydrogen sulfide and about 300 ppm (measured with a detector tube) of ammonia gas, but decomposed by passing through the platinum catalyst layer and the iron catalyst layer, and the hydrogen sulfide concentration was 250 ppm. The ammonia concentration was reduced to about 20 ppm. By passing these catalyst layers, the increase in the output of the fuel cell was about 2%.
[0068]
Example 2
Slaked lime slurry was added to the methane fermentation broth to make it alkaline to pH 9.5, and then ammonia was stripped from the liquor by aeration. The ammonia gas was passed through the iron catalyst layer in the same manner as in Example 1, and then supplied to the fuel cell main body together with the methane fermentation gas. As a result, an output of about 10 W could be constantly obtained.
[0069]
Example 3
While blocking the outside air, gas obtained by thermally decomposing organic waste containing animal meat bones at about 500 ° C. was passed through a platinum catalyst layer heated to about 800 ° C. as a decomposition apparatus in the same manner as in Example 1 to pass hydrogen sulfide. After decomposing and removing the sulfur of the decomposition product by filtration, ammonia was decomposed through the iron catalyst layer, and then passed through a desulfurization layer and a fuel converter as a reformer. The ammonia concentration in the pyrolysis gas was about 100 ppm or less (measured by a detector tube). When this reformed gas was supplied to the solid polymer membrane fuel cell main body, the increase in the output of the fuel cell was about 1% or less, but it was significantly higher than when the platinum catalyst layer and the iron catalyst layer were not passed. It was a big result. As a result, an output of about 5 W was stably obtained.
[0070]
【The invention's effect】
In the fuel cell power generation process of the present invention, ammonia and / or hydrogen sulfide in a methane-containing gas obtained by anaerobically fermenting or thermally decomposing organic waste is decomposed to produce hydrogen, which is used as fuel. Since the power generation is performed by the fuel cell, the hydrogen source contained in the methane-containing gas can be utilized to the maximum extent possible. Further, since hydrogen sulfide serving as the catalyst poison is removed in the decomposition step and only hydrogen is supplied to the fuel cell, there is no possibility of reducing the power generation efficiency.
[0071]
According to the methane fermentation fuel cell power generation process of the present invention, a large amount of ammonia is contained in the fermentation liquid (fermentation residue) after methane fermentation of organic waste under anaerobic conditions. By introducing it into a fuel cell as a hydrogen source and generating power, the amount of power generation can be greatly increased.
[0072]
According to the fuel cell system of the present invention, since the decomposition device for decomposing ammonia and / or hydrogen sulfide and generating hydrogen is provided, the hydrogen that is decomposed and generated by the decomposition device is supplied to the fuel cell that is a power generation device. It becomes possible. Therefore, it is possible to obtain a larger amount of power generation than that of a conventional fuel cell system, and it is possible to avoid poisoning of the catalyst, which is a factor that hinders the electrode reaction of the fuel cell.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a fuel cell system according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a schematic configuration of a fuel cell system according to another embodiment of the present invention.
FIG. 3 is a block diagram showing a schematic configuration of a fuel cell system according to still another embodiment of the present invention.
FIG. 4 is a block diagram showing a schematic configuration of an apparatus used in the methane fermentation liquid fuel cell process of the present invention.
[Explanation of symbols]
10 Fermenter
11 Pyrolysis tower
20 Absorption tower
30 Converter
40 Power generator
50 Decomposition tower

Claims (6)

Originating 酵Ma other under anaerobic conditions of organic waste is obtained by thermal decomposition as a main component methane, methane-containing gas generating step of generating a gas containing ammonia and / or hydrogen sulfide,
An absorption separation step in which ammonia and / or hydrogen sulfide contained in the methane-containing gas is absorbed into an absorption liquid and separated from methane;
A decomposition step of decomposing the ammonia and / or hydrogen sulfide separated from methane in the absorption separation step to generate hydrogen;
A reforming step of decomposing methane separated from the ammonia and / or hydrogen sulfide to generate hydrogen in the absorption separation step ;
A power generation step of generating power by a fuel cell using hydrogen obtained in the reforming step and the decomposition step as a fuel ,
A fuel cell power generation process, wherein the absorbing solution is an aqueous solution of a salt having a pH buffering property. The fuel cell power generation process according to claim 1 , further comprising an ammonia recovery step of adding ammonia to the fermentation liquor produced by the fermentation to extract ammonia.
A fuel cell power generation process, wherein the ammonia obtained in the ammonia recovery step is also treated in the decomposition step, and the resulting hydrogen is used in the power generation step. In the fuel cell power generation process according to claim 1 or 2,
A fuel cell power generation process, wherein the gas having undergone the decomposition step is sent to the reforming step. In the fuel cell power generation process according to any one of claims 1 to 3,
A fuel cell power generation process, wherein the fuel cell is a phosphate fuel cell or a solid polymer membrane fuel cell. A methane fermentation apparatus that ferments organic waste under anaerobic conditions and generates biogas containing ammonia and / or hydrogen sulfide, the main component of which is methane.
An absorption separation device that absorbs ammonia and / or hydrogen sulfide contained in the methane-containing gas into an absorption liquid and separates it from methane;
In the absorption separation device, a reformer that decomposes methane separated from the ammonia and / or hydrogen sulfide to generate hydrogen ;
A decomposing apparatus for decomposing the ammonia and / or hydrogen sulfide separated from methane by the absorption separating apparatus to generate hydrogen;
A fuel cell system including a power generation device that generates power with a fuel cell using hydrogen produced by the reformer and the cracking device as fuel ,
The fuel cell system, wherein the absorbing solution is an aqueous solution of a salt having a pH buffering property. The organic waste as well as thermal decomposition under anaerobic conditions, the main component generated methane, and the pyrolyzer to produce pyrolysis gas containing ammonia and / or hydrogen sulfide,
An absorption separation device that absorbs ammonia and / or hydrogen sulfide contained in the methane-containing gas into an absorption liquid and separates it from methane;
In the absorption separation device, a reformer that decomposes methane separated from the ammonia and / or hydrogen sulfide to generate hydrogen ;
A decomposing apparatus for decomposing the ammonia and / or hydrogen sulfide separated from methane by the absorption separating apparatus to generate hydrogen;
A fuel cell system including a power generation device that generates power with a fuel cell using hydrogen produced by the reformer and the cracking device as fuel ,
The fuel cell system, wherein the absorbing solution is an aqueous solution of a salt having a pH buffering property.

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