JP4008051B2 - Power generation method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a power generation method excellent in power generation efficiency per unit fuel.
[0002]
[Prior art]
In recent years, a fuel cell having an extremely high power generation efficiency of 60% has been developed as an urban power source that is low in noise and vibration and has no fear of air pollution. The fuel cell separately performs the oxidation reaction of the fuel and the reduction reaction of oxygen, and electrons and ions move through the external circuit and the electrolyte, respectively, so that the energy that becomes heat can be taken out as electrical energy if they react directly. If a reformer is provided in order to supply a hydrogen-rich gas used as fuel for the fuel cell, it is possible to perform power generation by the fuel cell with high efficiency as a whole.
[0003]
On the other hand, a combined membrane separation technique has been proposed as a method for producing hydrogen using a reformer. For example, US Pat. No. 5,229,102 describes a reformer that selectively permeates generated hydrogen by supplying hydrocarbons to a tubular porous ceramic membrane filled with a catalyst. Has been. In this method, by removing the produced hydrogen from the system, the equilibrium of the reforming reaction is inclined to the hydrogen producing system. As a result, a high temperature of 750 to 880 ° C. was required in the conventional reformer, but 300 It describes that it can be modified at a relatively low temperature of ˜700 ° C. Further, it is described that since the reforming can be performed at a relatively low temperature, a temperature about the exhaust gas of a gas turbine or a gas engine can be used as a reforming heat source.
[0004]
[Problems to be solved by the invention]
In this way, each technology has been developed individually for the production of high-purity hydrogen by a fuel cell, the production of high-purity hydrogen by a reformer, or the use of thermal energy generated by an engine, or the technology relating to the combination of these has been tried in pieces. Efforts are being made to increase power generation efficiency per unit fuel. However, simply combining these causes the following problems. That is, fuel cells are classified into phosphoric acid type, polymer type, alkali type, molten carbonate type, etc., depending on the electrolyte, and among them, the polymer type operates at 100 ° or less and is said to have good operability. ing. However, since the catalyst such as platinum of the electrode is poisoned by CO, the CO concentration in the hydrogen-containing gas supplied to the fuel cell needs to be 10 ppm or less. Therefore, it is necessary to further refine the crude hydrogen produced by the steam reforming method of hydrocarbons or alcohols with a CO converter or a hydrogen purifier so that the CO content is 10 ppm or less. However, the process is complicated, requires a large amount of high-temperature heat energy, and has many problems in terms of cost.
[0005]
In addition, although the fuel cell has good overall thermal efficiency, the fuel cell alone has to provide a new heat source for heating the reformer, resulting in an increase in equipment costs and a decrease in energy efficiency. Further, in addition to the case of using a gas turbine or a steam turbine, surplus thermal energy is discharged from the engine itself at the time of driving, and effective utilization of such thermal energy is also desired. Therefore, there is a demand for the development of a power generation method that takes advantage of the prior art, solves the problems, and further improves the power generation efficiency.
[0006]
[Means for Solving the Problems]
In view of the current state of the art, the present inventors have comprehensively studied to increase the power generation efficiency per unit fuel as a whole, and as a result, the existing power equipment and power generation equipment are comprehensively determined by a predetermined method. It was conceived that, by combining, extremely high power generation efficiency higher than hitherto known was achieved, and the present invention could be completed.
[0007]
That is, the present invention (1) takes out power generation or power by driving the engine, and installs a reformer having a hydrogen separation / permeation membrane in close contact with a part of the engine so that the operating heat generated by driving the engine is reduced by the reforming. A high-purity hydrogen is produced by steam reforming methanol with a reformer having a hydrogen separation and permeable membrane, and used as a heating source for the apparatus, and the resulting high-purity hydrogen is supplied to a fuel cell to generate electricity. power generation method, (2) power generation method according to (1), characterized in that said hydrogen separation permeable membrane is one having a thin film was formed structure of the palladium-containing alloy on the surface of the inorganic porous material to, ( 3) The power generation method as described in any one of (1) to (2 ) above, wherein the fuel cell is a polymer fuel cell .
[0008]
The reformer employed in the present invention has a hydrogen separation and permeable membrane (membrane). Accordingly, there is no particular limitation as long as high-purity hydrogen, for example, high-purity hydrogen having a CO concentration of 10 ppm or less can be supplied and reforming can be performed in a temperature range of 200 to 500 ° C. Since the reforming reaction occurring in the reformer is an endothermic reaction, it is necessary to heat the reformer, and the temperature required when methanol is used as the main raw material is about 200 to 500 ° C. This heating temperature is a temperature that can be sufficiently reformed even with a normal methanol reformer that does not use a membrane, but the reforming can be performed at a lower temperature by using a reformer having a membrane. This is because the generated hydrogen is taken out of the system by the action of the membrane, so that the chemical equilibrium is transferred to the hydrogen generation system as described above.
[0009]
A reformer equipped with such a membrane is usually called a membrane reactor, and various economical shapes are devised in consideration of thermal efficiency. As the membrane, a membrane that selectively permeates hydrogen and has heat resistance is used. For example, a palladium-containing alloy film having a film thickness of 100 μm or more, or a palladium-containing alloy thin film having a film thickness of 50 μm or less coated on an inorganic porous material, for example, a metal or ceramic porous material or a metal nonwoven fabric is used. The inorganic porous body is preferably a metal porous body from the viewpoints of workability such as sealing, impact resistance, hydrogen permeability and the like. The palladium-containing alloy is preferably palladium alone or containing 10% by weight or more of palladium, in addition to palladium, Group 10 elements such as Pt, Group 9 elements such as Rh and Ir, Group 8 elements such as Ru, Cu, Ag, Those having Group 11 elements such as Au are preferred. In addition, an alloy film containing vanadium (V), for example, a film in which palladium is coated on a Ni—Co—V alloy is used.
[0010]
As a reforming catalyst for steam reforming methanol, a catalyst containing a group 8-10 metal (Fe, Co, Ni, Ru, Pd, Pt, etc.) is preferable, a catalyst supporting Ni, Ru, Rh or containing NiO. A catalyst is particularly preferred.
[0011]
There are no particular limitations on the specific reformer used in the present invention, and known ones can be used. For example, JP-A-2-311301 discloses a separation membrane having a hydrogen separation function in a reaction tube filled with a catalyst, an outer cylinder provided outside the reaction tube, and a reforming raw material in the reaction tube filled with the catalyst. Describes technology for supplying hydrogen to generate hydrogen, allowing an inert gas (sweep gas) to flow inside the separation membrane, allowing hydrogen that has permeated through the separation membrane to be taken out of the system with the sweep gas, and supplied to the fuel cell Has been. That is, the reforming part is a concentric triple pipe, the intermediate layer is filled with a catalyst to produce hydrogen, and the hydrogen separated in the central part of the pipe through the separation membrane is accompanied by the sweep gas and discharged. The remaining off-gas from which hydrogen is separated from the reformer contains CO ₂ , unreacted methanol, hydrogen, CO, steam, by-product methane, and the like, which are reused as part of engine fuel. Can also help improve power generation efficiency. The preferred reforming apparatus is as described above, but in addition to this, a ceramic membrane as described in the aforementioned US patent specification can also be used.
[0012]
Examples of the fuel cell used in the present invention include the phosphoric acid type, the polymer type, the alkali type, and the molten carbonate type. Among these, the polymer type fuel cell is particularly preferable.
[0013]
In the present invention, power can be generated or power can be extracted by driving the engine. The engine that can be used in the present invention is a mechanical device that continuously converts energy generated by fuel combustion into mechanical energy, and an internal combustion engine such as a gasoline engine, a diesel engine, or a roasted ball engine can be used. . In the present invention, a reformer is provided in close contact with the engine, and heat energy generated from the engine itself generated by driving the engine is used as a heating source of the reformer. Further, off-gas generated from a reformer installed in close contact with the engine can be used as a part of engine driving fuel, and the generated heat can be used without waste. In addition, some or all of the energy driven by the engine can be extracted and used as power instead of power generation.
[0014]
[Reference example]
1184048814906_0
These are the schematic explanatory drawings of an example of the electric power generating apparatus which concerns on a reference example , show only main equipment, and abbreviate | omitted the attached equipment.
1184048814906_1
The engine driving fuel 1 is fed directly into the engine 2. Further, the remaining off-gas separated from the reformer 4 by the line 5 is supplied to the engine 2 as part of the fuel. The off gas includes CO ₂ , unreacted methanol, hydrogen, CO, steam, methane produced as a by-product, and the like. The exhaust gas after taking out the electric power or power obtained by driving the engine 2 is guided to the exhaust heat recovery device 6 through the line 3, and this exhaust gas is at normal pressure and the temperature is in the range of 400 to 500 ° C. In the exhaust heat recovery device 6, the reformer 4, the methanol heater 11 and the boiler 20 are installed and heated by the exhaust gas from the line 3. In the reformer 4, hydrogen generated by the reforming reaction of methanol is supplied to the fuel cell 8 through the line 7 as high-purity hydrogen by the action of the membrane and used for power generation. To the reformer 4, methanol vapor from the methanol heater 11 and steam from the boiler 20 are supplied as reforming raw materials via lines 10 and 12, respectively. The reforming reaction occurring in the reformer 4 is mainly the reaction of the following chemical formula 1
It is. Further, the fuel cell 8 needs a capacity capable of consuming the generated hydrogen, but a part of the hydrogen can be used for other purposes. In addition,
1184048814906_2
Medium 13 indicates a chimney.
[0015]
1184048814906_3
In the fuel cell 8, heat energy at a normal pressure of 400 to 500 ° C. of the exhaust gas generated by driving the engine is used for heating the exhaust heat recovery device 6. This thermal energy is used for producing hydrogen as a raw material for the fuel cell 8 in the reformer 4 or for heating the methanol heater 11 for heating methanol to be supplied to the reformer 4. When the power generation efficiency of the engine 2 and the fuel cell 8 is comprehensively observed, the power generation efficiency for the used engine fuel and methanol can be at least about 50%.
[0016]
【Example】
Hereinafter, although an example is given and the present invention is explained, the present invention is not limited to this .
Example 1 In this example is an embodiment of the present invention the power generation device, showing the schematic illustration in FIG. Components common to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. That is, in addition to the use of exhaust gas thermal energy of the engine shown in FIG. 1, reformers 18 and 19 are installed adjacent to the engine 2, and hydrogen generated by these reformers 18 and 19 also passes through the line 17. It is sent to the fuel cell 8. Since the reformers 18 and 19 are adjacent to the engine 2, the heat generated by driving the engine can be directly used. For this reason, the reformers 18 and 19 can maintain a higher temperature than the reformer 4. Accordingly, natural gas, methane, etc. can be used in addition to methanol as the fuel supplied to the reformers 18 and 19 via the line 14. Further, the off-gas generated from the reformers 18 and 19 is reused as part of the engine driving fuel via the line 15 or the line 16. The off-gas generated from the reformer 4 is also used as part of the engine driving fuel via the line 5. In FIG. 1, supply lines to the reformers 18 and 19 of the steam 12 are omitted.
[0017]
【The invention's effect】
As described in detail above, in the present invention, since a high reforming conversion ratio by using a modified apparatus using a membrane are possible reforming methanol, effective use of the heat energy due to engine drive it can. By supplying the high-purity hydrogen obtained from the reformer to the fuel cell with good power generation efficiency, extremely high power generation efficiency with respect to the unit fuel can be achieved comprehensively.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram showing an embodiment of a power generation method of a reference example .
FIG. 2 is a schematic explanatory view showing one embodiment of the power generation method of the present invention.

Claims (3)

Taking out power generation or power by driving the engine , installing a reformer having a hydrogen separation and permeable membrane in close contact with a part of the engine, using the operating heat generated by driving the engine as a heating source of the reformer, A power generation method characterized in that methanol is steam reformed to produce high purity hydrogen, and the resulting high purity hydrogen is supplied to a fuel cell to generate electricity. The power generation method according to claim 1, wherein the hydrogen separation and permeable membrane has a structure in which a thin film of a palladium-containing alloy is formed on the surface of an inorganic porous body. 3. The power generation method according to claim 1, wherein the fuel cell is a polymer fuel cell.

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