JPH06163066A - Heat recovering device for high temperature type fuel cell - Google Patents

Abstract

PURPOSE:To efficiently remove a heat and efficiently recover the removed heat by providing a heat recovering vessel having a heat recovering chamber formed in the inner part and a high temperature type fuel cell arranged in the heat recovering chamber, and passing a heat recovering medium into the heat recovering chamber. CONSTITUTION:A heat recovering vessel 12 is formed of a wall member 13 and a heat insulating material 14 arranged on the inside, and a heat recovering chamber 15 is formed in the inner part. In the chamber 15, a high temperature type fuel cell 11 is arranged. The heat recovering chamber 15 has a heat recovering medium feed pipe 16 and a heat recovering medium discharge pipe 17, so that a heat recovering medium can flow in the heat recovering chamber 15. The heat generated by the generation of the cell 11 is radiated from a housing 7, and efficiently recovered by the heat recovering medium flowing in the vessel 12.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a molten carbonate type (MCF
The present invention relates to a heat recovery device for high temperature fuel cells such as C) and solid oxide type (SOFC).

[0002]

2. Description of the Related Art A fuel cell is a device that directly converts chemical energy of a fuel gas such as hydrogen, carbon monoxide, or hydrocarbon and an oxidant gas such as air into an electrical energy by an electrochemical reaction. Depending on the type of electrolyte used
It is classified into alkaline type, phosphoric acid type, molten carbonate type, and solid electrolyte type. Of these, the molten carbonate type and the solid electrolyte type have high operating temperatures of about 650 ° C. and about 1000 ° C., respectively, and are said to be high-temperature fuel cells. They do not require an expensive catalyst such as platinum and exhaust heat is exhausted from a gas turbine or steam By leading to the turbine, high energy utilization efficiency can be obtained. In particular, the solid electrolyte type is different from the phosphoric acid type and molten carbonate type, in which the electrolyte is liquid under normal or operating conditions, and the battery structure is simplified without corrosion of surrounding materials by the electrolyte, decomposition of the electrolyte itself, evaporation, etc. Also, the operating temperature is about 1000 ℃
Since it is high, methane or natural gas as a fuel can be used as it is without being reformed in addition to hydrogen.

A solid electrolyte type high temperature fuel cell will be described below as an example. The solid electrolyte type is roughly classified into a cylindrical type, a monolithic type (or honeycomb type) and a flat plate type according to the difference in the manufacturing method and the structure. Among them, the flat plate type is noted from the viewpoint of high output density, low cost and compactness. Has been done.

FIG. 5 shows a conventional example of a flat plate type solid oxide fuel cell. An anode and a cathode made of a porous electrode material are formed on both sides of the electrolyte plate 1, and both sides of the electrolyte plate 1 are formed. A separator 2 that also serves as a gas passage and an electrical joint is provided, and an upper terminal plate 3 and a lower terminal plate 4 are provided on the uppermost and lowermost electrolyte plates 1. An oxidant gas passage 5 and a fuel gas passage 6 are formed on both surfaces of the separator 2 so as to be orthogonal to each other, and the fuel gas passage 6 and the oxidant gas passage 6 are formed on one surface of the upper terminal plate 3 and the lower terminal plate 4, respectively. A passage 5 is formed, and the electrolyte plate 1, the fuel gas passage 6 sandwiching the electrolyte plate 1 and the oxidant gas passage 5 form a unit cell of the fuel cell.

A large number of such unit cells are stacked to form a battery stack 10, a fuel gas is supplied to each fuel gas passage 6 of the battery stack 10, and an air is supplied to each oxidant gas passage 5. In order to do so, the battery stack 10 is mounted in a cylindrical housing 7, and the contact points between the four corners of the battery stack 10 and the housing 7 are gas-sealed with a sealant. As a result, the four side surfaces of the battery stack 10 and the housing 7
Four gas passages are formed between them, and the fuel gas supply pipe 8a, the fuel gas return pipe 8b, the oxidant gas supply pipe 9a, and the oxidant gas return pipe 9b are provided in the lower portion of the housing 7.
Are connected.

When fuel gas is supplied to each fuel gas passage 6 and air is supplied to each oxidant gas passage 5, the upper and lower terminal plates 3 and 4 are connected to an external circuit (not shown).
Oxygen is ionized and flows through the electrolyte plate 1 in an attempt to react with the fuel gas. At this time, oxygen is taken into the electron on the cathode side to become oxygen ion, and on the anode side, the oxygen ion reacts with the fuel gas to release the electron. So
In the external circuit, a current flows from the lower terminal plate 4 to the upper terminal plate 3 with the cathode serving as a positive electrode and the anode serving as a negative electrode. The chemical formula for this is as follows.

[0007] The ^{_{cathode: 1 / 2O 2 + 2e -}} → O hydrogen ^2- fuel gas, the ^{_{anode: H 2 + O 2- → H}} 2 O + 2e - overall electrode _{reaction: 1 / 2O 2 + H 2} → H 2 O Carbon monoxide in the fuel gas is anode: CO + O ^2- → CO ₂ + 2e ^- Overall electrode reaction: CO + 1 / 2O ₂ → CO ₂

[0008]

In the above high temperature fuel cell, the thermal energy generated by the chemical reaction, the electric resistance of the electrode or the electrolyte, and the contact resistance between the electrode and the current collector are caused by the electromotive force of the fuel cell. And the heat is generated in the fuel cell. Therefore, if the heat generated in the fuel cell is not removed and the operating temperature of the fuel cell is not maintained, various inconveniences such as local overheating of the device and variations in temperature distribution that hinder stable operation occur. Efficient removal of heat by cooling is an important issue, and efficient recovery of the removed heat is an important issue to enhance energy utilization efficiency.

However, in the conventional method described with reference to FIG. 5, since the cooling of the fuel cell is radiated from the outer peripheral portion of the housing 7, this heat cannot be efficiently recovered, and The fuel gas and the oxidant gas are heated while passing through both surfaces of the electrode-attached electrolyte plate, and a non-uniform temperature distribution of heat generated by power generation is generated on the electrolyte surface from the inlet to the outlet. In addition, since the heat generated in the central portion is accumulated, the temperature difference between the peripheral portion and the inner portion of the fuel cell becomes large, which causes a problem in stable operation.

In order to solve this problem, a method of cooling by flowing an increased amount of the oxidant gas into the oxidant gas passage has been studied, but in this method, the amount of the oxidant gas passing through the cell increases and the pressure is increased. There is a problem that the loss becomes large and good battery performance cannot be obtained. Further, a method of separately providing a cooling gas passage in the stack of the fuel cell has been proposed, but it has a problem that the structure becomes complicated and the cost increases.

The present invention solves the above problems and problems, and provides a heat recovery device capable of efficiently removing heat in a high temperature fuel cell and efficiently recovering the removed heat. The purpose is to do.

[0012]

To this end, the heat recovery device for a high temperature fuel cell according to the present invention includes a heat recovery container 12 in which a heat recovery chamber 15 is formed via a heat insulating material 14, and a heat recovery chamber 15. The heat recovery medium is provided inside the heat recovery chamber 15, and the heat recovery medium is circulated in the heat recovery chamber 15. It should be noted that the numbers added to the above-mentioned configurations are for comparison with the drawings in order to facilitate the understanding of the present invention, and the configurations of the present invention are not limited thereby.

[0013]

In the present invention, the heat generated by the power generation of the high temperature fuel cell is radiated from the housing and is recovered by the heat recovery medium flowing in the heat recovery container.
On the fuel cell side, the heat is efficiently removed by cooling,
Moreover, the removed heat can be efficiently recovered.

In an example of a flat plate type solid oxide fuel cell, when hydrogen is used as a fuel, a 10 kW cell (30 cm square 60 cm)
Operation at 40% efficiency (fuel utilization: 70%, voltage:
0.7V / stage, current: 240A), fuel and air 1
If it is sent to the cell at 000 ° C, the amount of hydrogen consumed in the cell is 240 (A / stage) × 7 (SCCM / A) × 60 (stage) = 100,800 (SCC
M) = 6,048 (Sl / hr). Since H ₂ + 1 / 2O ₂ + → H ₂ O + 249.5 (KJ / mol) at 1000 ° C., the calorific value of the cell is 6,048 (Sl / hr) /22.4 (Sl / mol) × 249.5 (KJ / mo).
l) -10 (kW) x 3,600 (sec) = 31,365 (KJ / hr) = 7,4
It becomes 96 (Kcal / hr). For example, if air is sent as a heat recovery medium, the enthalpy change of air from room temperature to 500 ° C. is 1
Since it is 5.21 (KJ / mol), the amount of air that can be heated from room temperature to 500 ° C is 31,365 (KJ / hr) /15.21 (KJ / mol) = 2,062 (mol / h)
r) = 46,192 (sl / hr). Even if about 1/3 of the calorific value is released from the heat recovery container to the outside air, about 30 (m ³ / hr) of air can be heated from room temperature to about 500 ° C. The air thus heated may be directly used or may be recovered by another means such as a heat exchanger.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In the following example, an example of the flat plate type solid oxide fuel cell described in FIG. 5 will be described, but the present invention is not limited to this, and a cylindrical or monolithic solid oxide fuel cell, and further, In short, it is applied to all fuel cells having a high operating temperature, such as molten carbonate fuel cells.

FIG. 1 is a sectional view showing an embodiment of a heat recovery apparatus for a high temperature fuel cell according to the present invention. Heat recovery container 12
Is composed of a wall member 13 and a heat insulating material 14 arranged inside thereof, and a heat recovery chamber 15 is formed inside. Inside the heat recovery chamber 15, the high temperature fuel cell 11 described with reference to FIG. 5 is arranged and connected to the housing 7 of the fuel gas supply pipe 8a, the fuel gas return pipe 8b, the oxidant gas supply pipe 9a,
An oxidant gas return pipe 9b is provided outside the heat recovery container 12. A heat recovery medium supply pipe 16 and a heat recovery medium discharge pipe 17 are provided in the heat recovery chamber 15 so that the heat recovery medium can be circulated in the heat recovery chamber 15. In addition,
Although one fuel cell 11 is arranged in the heat recovery chamber 15 in this embodiment, a plurality of fuel cells may be arranged.

In the present invention, the heat generated by the power generation of the high temperature fuel cell 11 is radiated from the housing 7,
Since the heat recovery medium flowing through the heat recovery container 12 efficiently recovers the heat, the heat is efficiently removed by cooling on the fuel cell 11 side, and the removed heat is efficiently transferred to the heat recovery medium. Can be collected.

As the heat recovery medium, hydrogen, hydrocarbon,
A process gas that uses an anode gas for power generation such as water vapor and a cathode gas for power generation such as air, oxygen, and an inert gas to preheat these gases or to supply to other power generation systems such as gas turbines and steam turbines. Or a heating gas supplied to the outside of the power generation system is used.

2, 3 and 4 show another embodiment of the present invention. The same components as those in the embodiment of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In the embodiment of FIG. 2, a partition wall 18 is provided in the heat recovery chamber 15 to form an annular passage 19, and the heat recovery medium is allowed to flow in the annular passage 19. Further, in the embodiment of FIG. 3, the heat recovery chamber 15
A coil-shaped pipe 20 is provided inside, and a heat recovery medium is allowed to flow in the pipe 20.

The embodiment of FIG. 4 shows a modification of the fuel cell 11. The two housings 7, 7 are arranged at intervals, and the battery stack 10 is separately mounted in each of the housings 7. A fuel gas supply pipe 8a, a fuel gas return pipe 8b, an oxidant gas supply pipe 9a, and an oxidant gas return pipe 9b are connected to the lower portion of the lower housing 7 in the figure, and the upper and lower housings 7 are connected to each other. By connecting the connection pipes 22, it is possible to supply and discharge the fuel gas and the oxidant gas to the upper and lower cell stacks 10. Then, a conductive member 23 for electrically connecting the upper and lower battery stacks 10 is provided. Although the battery stacks 10 are mounted in the two housings 7 spaced apart in the drawing, the number of the battery stacks 10 is not limited to two, and may be three or more.

In this embodiment, the battery stack 10 is divided and mounted in the plurality of housings 7 arranged at intervals, so that the heat generated by the power generation is applied to the housing 7.
The heat is not only radiated from the outer peripheral portion of the housing but also radiated from the gap between the adjacent housings 7, and the heat is collected.
It is recovered by the heat recovery medium flowing through. Therefore, the temperature distribution in each unit cell and the temperature distribution of the stacking method can be minimized and the current distribution can be made smaller as compared with the above-mentioned embodiment. In addition, deterioration due to partial heating and breakage of the seal can be eliminated.

[0023]

As is apparent from the above description, according to the present invention, it is possible to efficiently remove the heat in the high temperature fuel cell and to efficiently recover the removed heat.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a heat recovery device for a high temperature fuel cell according to the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the heat recovery device of the high temperature fuel cell of the present invention.

FIG. 3 is a cross-sectional view showing another embodiment of the heat recovery device of the high temperature fuel cell of the present invention.

FIG. 4 is a perspective view showing a modified example of the fuel cell according to the present invention.

FIG. 5 is a perspective view showing a conventional example of a high temperature fuel cell.

[Explanation of symbols]

7 ... Housing, 8a ... Fuel gas supply pipe, 8b ... Fuel gas return pipe 9a ... Oxidizing gas supply pipe, 9b ... Oxidizing gas return pipe, 1
DESCRIPTION OF SYMBOLS 1 ... High temperature fuel cell 12 ... Heat recovery container, 13 ... Wall member, 14 ... Insulating material, 15
... Heat recovery chamber 16 ... Heat recovery medium supply pipe, 17 ... Heat recovery medium discharge pipe

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Seto Nishitsurugaoka 1-3-1, Oi-cho, Iruma-gun, Saitama Tonen Corporation Research Institute (72) Toshihiko Yoshida Nishitsurugaoka, Oi-cho, Saitama-ken 3-3-1 Tonen Co., Ltd. Research Institute

Claims (1)

[Claims] 1. A heat recovery container having a heat recovery chamber formed therein via a heat insulating material, and a high temperature fuel cell disposed in the heat recovery chamber, wherein the heat recovery medium is in the heat recovery chamber. A heat recovery device for a high temperature fuel cell, characterized in that