JP3976575B2 - Fuel cell power generation system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell power generation system that generates power using a fuel cell, and more particularly to a temperature raising means for a fuel cell at the time of startup.
[0002]
[Prior art]
As shown in FIG. 2, the fuel cell power generation system generally reforms a hydrocarbon-based raw fuel into a hydrogen-based reformed gas by the fuel reformer 1, and uses the reformed gas as fuel for the anode (fuel). In addition, the air is supplied to the cathode (air electrode) as an oxidant gas, and electricity is generated by an electrochemical reaction via an electrolyte such as a solid polymer film.
[0003]
The fuel cell 2 has an appropriate operating temperature (for example, about 80 ° C. in the case of a polymer electrolyte fuel cell), and is required to be raised to the operating temperature as soon as possible at the time of startup. For this reason, conventionally, the first switching valve 3 is closed and the second switching valve 4 is opened to introduce the reformed gas into the PG burner 5 for combustion, and the combustion exhaust gas is used to pass through the heat exchanger 6. The water is warmed, and the warm water is supplied to the fuel cell 2 to raise the temperature.
[0004]
[Problems to be solved by the invention]
According to the fuel cell temperature raising means, there is a problem that it takes a considerably long time for the fuel cell 2 to reach an appropriate operating temperature. In order to solve this problem, a circulation path for returning the hot water discharged from the fuel cell 2 to the heat exchanger 6 is formed, and the temperature rise efficiency in the heat exchanger 6 is increased to bring the fuel cell 2 to the operating temperature at an early stage. Attempts were made to raise the temperature. However, when hot water is circulated and used, dissolved oxygen in the hot water becomes bubbles, which deteriorates the performance of the pump provided in the circulation path and causes a problem that hinders water supply control.
[0005]
The present invention is made to solve such a conventional problem, and provides a fuel cell power generation system capable of eliminating bubbles generated in hot water when the temperature of the fuel cell is raised by circulating hot water. With the goal.
[0006]
[Means for Solving the Problems]
The means of the present invention for solving this object, as described in claim 1, combusts the reformed gas reformed by the fuel reformer at the time of start-up with a PG burner, and uses the combustion exhaust gas to install the heat exchanger. In the fuel cell power generation system configured to circulate warm water heated through the fuel cell and raise the temperature of the fuel cell, a circulation path is formed that leads from the heat exchanger to the fuel cell and returns from the fuel cell to the heat exchanger, The gist of the fuel cell power generation system is characterized in that an air vent valve is provided upstream of the heat exchanger in the circulation path and downstream of the pump provided in the circulation path .
According to a second aspect of the present invention, a branch path is provided on the downstream side of the fuel cell in the circulation path via a switching valve, and this branch path is connected to a hot water storage tank.
[0007]
In the present invention, since the fuel cell provided with the air vent valve on the downstream side of the pump provided and the circulation path upstream of the heat exchanger definitive the circulation path of the hot water to raise the temperature to eliminate the air bubbles generated in hot water As a result, the performance and water supply control of the pump provided in the circulation path can be satisfactorily maintained. In addition, a branch passage is provided downstream of the fuel cell in the circulation path via a switching valve, and this branch path is connected to the hot water storage tank. When the fuel cell is heated to the operating temperature, the switching valve of the circulation path is switched. Hot water can flow into the branch and feed into the hot water storage tank.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of a fuel cell power generation system according to the present invention will be described with reference to the accompanying drawings. Here, the same members as those in the past are denoted by the same reference numerals.
In FIG. 1, reference numeral 1 denotes a fuel reformer, which is not shown, but is composed of a reformer, a CO converter and a CO remover, and reforms raw fuel such as city gas into reformed gas mainly composed of hydrogen. To do. That is, the raw fuel after desulfurization is steam reformed with a reformer, then most of the CO in the reformed gas is converted to CO ₂ with a CO converter, and further selectively oxidized with a CO remover to reduce the CO concentration. Reduce.
[0009]
A reformer burner 1a is provided in association with the reformer, and at the time of start-up, raw fuel is supplied to the reformer burner 1a and burned to raise the temperature of the reformer catalyst. During operation of the fuel cell 2, unreacted reformed gas discharged from the anode is supplied to the reformer burner 1a and burned. Air necessary for combustion is supplied to the reformer burner 1a by a fan (not shown).
[0010]
Since the reformed gas reformed by the fuel reformer 1 is not yet stable at the time of start-up, the first switching valve 3 is closed and not supplied to the fuel cell 2 as described above. Open and supply to the PG burner 5 to burn. Using the combustion exhaust gas in the PG burner 5, warm water is produced by the heat exchanger 6, and the warm water is supplied to the fuel cell 2 to raise the temperature of the fuel cell 2 to the operating temperature.
[0011]
In order to efficiently raise the temperature of the fuel cell 2, a circulation path 7 that leads from the heat exchanger 6 to the fuel cell 2 and returns from the fuel cell 2 to the heat exchanger 6 is formed. In this circulation path 7, an air vent valve 8 is provided on the upstream side of the heat exchanger 6, a water supply path 10 is connected via a third switching valve 9, and a fourth switching valve on the downstream side of the fuel cell 2. A branch path 12 is provided via 11, and this branch path 12 is connected to a hot water storage tank 13. Further, a pump 14 is provided at a key point of the circulation path 7.
[0012]
The hot water heated by the heat exchanger 6 raises the temperature of the fuel cell 2 in a short time while circulating through the circulation path 7. Circulating warm water gradually becomes high temperature, and there is a phenomenon that dissolved oxygen contained in the warm water is mixed in as bubbles, but the circulation path 7 is provided with the air vent valve 8 as described above. Bubbles are discharged from the hot water. As a result, the pump 14 that feeds the hot water into the heat exchanger 6 is not hindered by the bubbles, and the pump performance is not deteriorated or the water supply control is not hindered.
[0013]
When the temperature of the fuel cell 2 rises to the operating temperature, the fourth switching valve 11 is switched to guide the hot water to the branch path 12 side and flow into the hot water storage tank 13. When the reformed gas in the fuel reformer 1 is stabilized, the second switching valve 4 is closed and the reformed gas supply to the PG burner 5 is stopped, and at the same time, the first switching valve 3 is opened to the anode of the fuel cell 2. The reformed gas supply starts. Then, the reaction air is supplied to the cathode of the fuel cell 2 and the fuel cell 2 enters the operation stage.
[0014]
【The invention's effect】
As described above, according to the present invention, in a fuel cell power generation system, hot water is produced through a heat exchanger using combustion exhaust gas combusted by a PG burner at start-up, and the fuel cell is heated to a predetermined temperature with this hot water. In this case, a circulation path that leads from the heat exchanger to the fuel cell and returns from the fuel cell to the heat exchanger is formed, upstream of the heat exchanger in the circulation path and downstream of the pump provided in the circulation path. Since the air vent valve is provided on the side, dissolved oxygen bubbles generated in the warm water can be eliminated. As a result, the performance and water supply control of the pump provided in the circulation path can be satisfactorily maintained, and the temperature of the fuel cell can be efficiently increased by the circulating hot water. As a result, the effect of shortening the battery temperature increase time can be obtained. . In addition, a branch path is provided downstream of the fuel cell in the circulation path via a switching valve, and this branch path is connected to the hot water storage tank. Can be increased.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a main part of a fuel cell power generation system according to the present invention. FIG. 2 is an explanatory view showing a main part of a conventional fuel cell power generation system.
DESCRIPTION OF SYMBOLS 1 ... Fuel reformer 2 ... Fuel cell 3 ... 1st switching valve 4 ... 2nd switching valve 5 ... PG burner 6 ... Heat exchanger 7 ... Circulation path 8 ... Air vent valve 9 ... 3rd switching valve 10 ... Water supply path 11 ... Fourth switching valve 12 ... Branch 13 ... Hot water storage tank 14 ... Pump

Claims (2)

Fuel cell power generation configured to burn the reformed gas reformed by the fuel reformer at the time of startup with a PG burner and circulate warm water heated by the combustion exhaust gas through the heat exchanger to raise the temperature of the fuel cell In the system, a circulation path leading from the heat exchanger to the fuel cell and returning from the fuel cell to the heat exchanger is formed, upstream of the heat exchanger in the circulation path and downstream of the pump provided in the circulation path. fuel cell power generation system characterized in that a vent valve.   2. The fuel cell power generation system according to claim 1, wherein a branch path is provided downstream of the fuel cell in the circulation path via a switching valve, and the branch path is connected to a hot water storage tank.

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