JP2670607B2 - Fuel cell power plant using methanol as fuel - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a phosphoric acid fuel cell power plant using methanol as a fuel. [Prior Art] Conventionally, a phosphoric acid fuel cell having a fuel electrode and an air electrode, and having a phosphoric acid electrolyte present between both electrodes is known. In this case, it is also known to use methanol as the fuel. This phosphoric acid fuel cell usually has a temperature of 170 ° C to 220 ° C.
Since it is operated at, methanol as fuel is introduced in the form of a mixture with steam into a cracker whose temperature is kept constant with a heat carrier oil, decomposed by the catalyst in this slacker, and produced in this cracker. A method of supplying a gas containing hydrogen to the fuel electrode is adopted. FIG. 2 shows a flow sheet of a conventionally proposed phosphorus-type fuel cell power plant using methanol as a fuel. However, such a conventional phosphoric acid fuel cell power plant requires, as described above, a heat medium heating furnace for heating the heat medium oil, a heat medium oil circulation system, and the use of a methanol cracker. Therefore, there is a problem that the entire plant becomes large and complicated. [Purpose] It is an object of the present invention to provide a phosphoric acid fuel cell power plant that does not require the use of the heat medium heating furnace and the methanol cracker as described above. [Structure] According to the present invention, a phosphoric acid fuel cell body having a fuel electrode and an air electrode, a phosphoric acid electrolyte interposed between both electrodes, and a methanol cracking catalyst present in the fuel electrode,
A cooler unit for cooling the battery body, an air blower for supplying air to the air electrode of the battery body, a heat exchanger for vaporizing methanol, a steam generating furnace, a steam drum, and a fuel gas cooler. A pipe for supplying condensed water of the steam drum to the steam generating furnace, a pipe for returning the steam generated in the steam generating furnace to the steam drum, and a steam of the steam drum. To the heat exchanger for vaporizing methanol, a pipe for mixing steam of a steam drum with the methanol vapor vaporized in the heat exchanger, and a mixture of methanol vapor and steam to the fuel electrode For supplying the condensed water of the steam drum to the cooler section, and supplying the exhaust gas from the fuel electrode as fuel gas to the steam generating furnace A pipe, a pipe for supplying the combustion gas obtained in the steam generating furnace to the cooler, and a pipe for supplying the cooling combustion gas containing the condensed water obtained in the cooler to the gas-liquid separator, There is provided a phosphoric acid fuel cell power generation plant using methanol as a fuel, comprising a pipe for supplying the condensed water obtained by the gas-liquid separator to the steam drum. In the phosphoric acid fuel cell used in the present invention, a cracking catalyst for methanol is present in the fuel electrode, and methanol reacts with steam in the fuel electrode.
The reaction in this case is represented by the following formula. CH ₃ OH + H ₂ OCO ₂ ＋ 3H ₂ (I) This reaction is an endothermic reaction, and hydrogen is more likely to be generated at higher temperatures. However, in a phosphoric acid fuel cell, its operating temperature is 17
Since the temperature is 0 to 220 ° C, it is necessary to allow the reaction to proceed at the fuel electrode. In the case of methanol decomposition reaction,
Although a temperature near 0 ° C. was required, according to the research conducted by the present inventors, when steam and methanol are introduced into the fuel electrode and steam and methanol are introduced into the fuel electrode, surprisingly, It has been found that the above reaction sufficiently proceeds even at a low temperature of about 220 ° C. When methanol is reacted with steam at the fuel electrode, the produced hydrogen immediately dissolves in the phosphoric acid electrolyte, moves to the air electrode, and is consumed by reaction. Therefore, it is considered that such hydrogen transfer from the fuel electrode to the air electrode serves as a reaction driving force to promote the decomposition reaction of methanol at the fuel electrode, so that the reaction proceeds sufficiently smoothly even at the low temperature. To be As the methanol steam cracking catalyst used in the present invention, a conventionally known methanol synthesis catalyst can be used. The catalyst only needs to be present in the fuel electrode, and for example, it can be packed and arranged in a granular shape in the passage (groove) of the fuel electrode through which methanol flows. In the present invention, in the presence of such a methanol cracking catalyst, methanol is steam cracked at about 200 ° C. in the fuel electrode to generate hydrogen. Next, FIG. 1 shows a flow sheet of the embodiment of the phosphoric acid fuel cell power plant according to the present invention. In FIG. 1, a part of the condensed water separated by the steam drum 4 is circulated to a cooler part of the fuel cell through a line 24, and the remaining part is circulated through a line 14 to the steam generating reactor 2
After being sent to, heated here and converted to steam,
It is sent to the steam drum 4 again through the line 20. In this way, steam of constant temperature is generated from the steam drum 4, and this steam is introduced into the methanol vapor line 16 through the line 15. On the other hand, methanol passes through the line 11 and the heat exchanger 3 to become methanol vapor, is mixed with the steam from the line 15 in the line 16, and is then introduced into the fuel electrode of the fuel cell body 1. Since the fuel electrode is filled with the cracking catalyst for methanol as described above, the methanol is cracked according to the reaction formula (I) to generate hydrogen, which is consumed as fuel in the fuel cell. . Exhaust gas from the fuel electrode is sent to the steam generator 2 through the line 17 and burned as fuel. Part of the methanol is sent to the steam generator through the line 10 and is burned as fuel. The air from the blower 8 is supplied to the air electrode of the fuel cell after passing through the line 25 and the heat exchanger 7, and the oxygen contained therein is used for the reaction with hydrogen. The exhaust gas from the air pole passes through the line 26, passes through the heat exchanger 7 and the cooler 6, and then is introduced into the gas-liquid separator 5, where it is discharged to the atmosphere. Part of the air from the blower 8 passes through the line 13 and is used as combustion air for the steam generator 2. Combustion gas from the steam generating furnace is introduced into the gas-liquid separator 5 through the line 19 and the cooler 6, and is discharged to the atmosphere from here. Condensed water produced by heat exchange with methanol in the heat exchanger 3 is introduced into the gas-liquid separator 5 through the line 18 and the cooler 6. The condensed water separated by the gas-liquid separator 5 is sent to the steam drum 4 through the line 21. The electricity obtained by the fuel cell is converted into AC power by the inverter. Next, the main operating conditions in the phosphoric acid fuel cell configured as described above will be outlined below. (1) Steam temperature generated in the steam drum (line 1
5): 180 ° C. (2) Methanol temperature (line 11): normal temperature. (3) Temperature and pressure of methanol / steam mixture (line 16) Temperature: 170 ° C, pressure: slightly pressurized (4) Exhaust gas temperature from fuel electrode (line 17): 200 ° C (5) Air introduction to air electrode Temperature (line 27): 160 ° C (6) Exhaust gas temperature from air electrode (line 26): 200 ° C (7) Methanol conversion rate at the fuel electrode: 99 mol% (8) Hydrogen per mol of methanol at the fuel electrode generation rate: 4 mol% (9) exhaust gas composition from the fuel electrode (mol%) (line _{17) H 2: 36%,} CO: 0.5%, CO 2: 46%, H 2 O: 17%, CH 3 OH : 0.5% [Effect] In the phosphoric acid type combustion battery power generation plant of the present invention, as described above, the methanol / steam mixture was directly introduced into the fuel electrode, and the methanol was cracked there. As shown in, the use of the methanol cracker and heat transfer oil heating furnace required in the conventional method is eliminated. Therefore, a heat medium oil circulation system is not required, and the entire system is simplified. Furthermore, since the steam for fuel cell start-up heating can be provided from the steam generating furnace in the present invention, the start-up furnace required in the conventional method is also unnecessary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a flow sheet of a phosphoric acid fuel cell power plant of the present invention, and FIG. 2 shows a flow sheet of a conventional phosphoric acid fuel cell power plant. 1 ... Fuel cell main body, 2 ... Steam generating furnace, 3 ... Heat exchanger, 4 ... Steam drum, 5 ... Gas-liquid separator.

Claims (1)

(57) [Claims] A phosphoric acid fuel cell main body having a fuel electrode and an air electrode, a phosphoric acid electrolyte interposed between both electrodes, and a methanol cracking catalyst present in the fuel electrode; and a cooler section for cooling the cell main body. An air blower for supplying air to the air electrode of the battery body, a heat exchanger for vaporizing methanol, a steam generating furnace, a steam drum, a combustion gas cooler, and a gas-liquid separator, and Piping for supplying condensed water of the steam drum to the steam generating furnace,
Piping for returning steam generated in the steam generation furnace to the steam drum, piping for supplying steam of the steam drum to the heat exchanger for vaporizing methanol, and steam drum for vaporizing methanol vapor in the heat exchanger A pipe for mixing the steam, a pipe for supplying a mixture of methanol vapor and steam to the fuel electrode, a pipe for supplying condensed water of the steam drum to the cooler part, and an exhaust gas from the fuel electrode. A pipe for supplying the steam generating furnace as a fuel gas, a pipe for supplying the combustion gas obtained in the steam generating furnace to the cooler, and a cooling combustion gas containing condensed water obtained in the cooler Piping to supply to the liquid separator,
A phosphoric acid fuel cell power plant using methanol as a fuel, comprising a pipe for supplying condensed water obtained by the gas-liquid separator to the steam drum.