JPS5853164A - Fuel cell device - Google Patents

Abstract

PURPOSE:To provide a fuel cell device which enables the differential pressure between a fuel and an oxidant to be regulated within the minimum value, and enables the pressure of the oxidant to be higher than that of the fuel at any part of the surface of an electrode constantly even when the flow rate of the fuel or the oxidant, the load or the fuel cell is changed. CONSTITUTION:The pressures of a fuel and an oxidant inside a pressure case 2 are adjusted to become the minimum at the point (P). The pressure of the oxidant is made higher than that of the fuel at any other point in the case 2. In order to achieve the above mentioned condition, a differential pressure gauge 3' on the fuel side is installed at the inlet of the fuel, and a differential pressure gauge 4 on the oxidant side is installed at the outlet of the oxidant as usual so as to detect the differential pressures independently. After that, the detection signals are compared with set values through computing elements 5 and 6, and gas-exhaust valves 7 and 8 are controlled with the operation signals so that a pressure distribution as indicated in the figure is realized. By the means mentioned above, evek when the flow rate or the load changes, or when the pressure loss changes according to the alteration of the fuel cell, the diffeential pressure at the point (P) is constantly zero, and the differential pressures at the other points change only slightly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fuel cell system that improves the supply of fuel and oxidant to the fuel electrode and oxidizer electrode of rich +7y acid electrolyte fuel cells and molten carbonate fuel cells. O A conventional differential pressure control method will be explained using Fig. 1. O The fuel cell main body l is placed in a pressure vessel 2 and pressurized with inert gas. Then, fuel and oxidizer are supplied to this fuel cell. In this case, if the differential pressure between the fuel and oxidizer exceeds the pressure of the electrolyte, a phenomenon called crossover occurs in which the fuel and oxidizer do not undergo an electrochemical reaction, but instead undergo a consequential flame hook reaction. This happens, and this not only causes a decrease in battery performance.

Extreme loss-overs also run the risk of causing a stir. Therefore, in FIG. 1, the pressure inside the pressure vessel 2 is used as a reference, the pressure at the fuel side and the outlet of the oxidizer is detected by a differential pressure gauge 3.4, and this signal is compared with the set value via the calculators 5 and 6. The differential pressure is controlled by adjusting the gas discharge valves 7 and 8 based on the operation signal.◇The differential pressure is set to be extremely low compared to the standard pressure (inert gas pressure) on both the fuel side and the oxidizer side. Prevents leakage of fuel or oxidizer. Furthermore, if the set differential pressures on the fuel side and the oxidizer side are the same, a pressure gradient will be created due to pressure loss as shown in FIG. That is, in both cases, the pressure increases from the outlet side to the inlet side. Therefore, with the two-dot chain line as the border, the oxidizer side is higher in the human part, and the fuel side is higher in the B part. Therefore, in the human part, crossover is likely to occur at the fuel electrode, and in the BO part, crossover is likely to occur at the oxidizer electrode. In general, in fuel cells, crossover at the fuel electrode does not have much of an effect on output performance, but crossover at the oxidizer electrode has a large effect. Therefore, as shown in Figure 3, the pressure difference on the oxidizer side is set higher than that on the fuel side by the amount of pressure loss on the fuel side, so that the pressure on the oxidizer side is always higher than that on the fuel side over the entire electrode surface. are doing. The problem here is that the pressure loss on the fuel side varies depending on the supply gas flow rate and load, and also varies depending on the fuel cell, so it is almost impossible to follow the set value each time. Therefore, although it is set to a certain estimated value, it cannot be said that this value is the optimal value. Therefore, there is a need for differential pressure control in which the oxidant side is always higher than the fuel side and the difference can be minimized at any point even if the flow rate, load, or fuel cell changes.

This invention was made to solve the above-mentioned drawbacks, and even if the fuel and oxidant gas supply flow rate and the load fuel cell change, the oxidizer side is always higher than the fuel side at any part of the electrode surface. The present invention provides nine fuel cell devices that make it possible to minimize the difference.

Next, one embodiment of the present invention will be described with reference to the drawings.

In Figure 3, the pressure on the fuel side and oxidizer side is minimum (=0
) is point P. In all other cases, the oxidizer side is higher than the fuel side. Therefore, it is most desirable to control the differential pressure as shown in Fig. 3. This can be accomplished by assigning the same numbers to the pressure control points on the fuel side as in FIG. 1, and by making the fuel side differential pressure gauge 3' the inlet of the fuel side, as shown in FIG. That is, the pressure on the line segment OP and the line segment Pq in Fig. 3 should be the same. Therefore, the pressure on the fuel side will decrease from the pressure on the line segment OF by the pressure loss, and the pressure on the oxidizer side will decrease from the pressure on the line segment OF. The pressure increases by the amount of pressure loss from the pressure on line segment P4, and eventually a pressure distribution as shown in FIG. 3 is obtained. By doing this, even if the flow rate, load, or fuel cell changes and the pressure loss changes accordingly, the differential pressure at point P will always remain zero, and the differential pressure at the tray and other parts will only change slightly.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a fuel cell device using the conventional method on the differential pressure side, and FIG. 2 is a pressure distribution diagram using the conventional method. FIG. 3 is a pressure distribution diagram according to the present invention, and FIG. 4 is a diagram showing an embodiment according to the present invention. l...Fuel cell, 2...Pressure vessel. 3.3", 4... Differential pressure needle, 5, 6... Arithmetic unit, 7
．． 8...Gas exhaust valve 0 Representative Patent attorney Kensuke Chika (and 1 other person)

Claims (1)

[Claims] H at high pressure! In a fuel cell device that generates electrical output by electrochemically reacting 02 and 02, inert gas is sealed in the container housing the fuel cell, and the pressure at the H2 side inlet and 03 side outlet of the fuel cell is adjusted based on this pressure. Fuel cell device 0 characterized by having a differential pressure control system for adjusting pressure