Solid oxide fuel cell system

Patent metadata

Field	Value
Publication number	US-10115985-B2
Application number	US-201314385626-A
Country	US
Kind code	B2
Filing date	Mar 25, 2013
Priority date	Mar 23, 2012
Publication date	Oct 30, 2018
Grant date	Oct 30, 2018

Abstract

To provide a solid oxide fuel cell system capable of avoiding the reduction of air electrodes. The present invention is a solid oxide fuel cell system including: a fuel cell module, a fuel supply apparatus, a water supply apparatus, an oxidant gas supply apparatus, a reformer, and a control section for controlling the extraction of power, whereby the controller having a shutdown stop circuit for executing a shutdown stop when the fuel cell stack is above the predetermined temperature, and after a shutdown stop, during a period when pressure on the fuel electrode side is sufficiently higher than pressure on the air electrode side, and no reverse flow of oxidant gas to the fuel electrode side is occurring, a temperature drop operation is executed whereby high temperature oxidant gas remaining on the oxidant gas electrode side is discharged.

First claim

What is claimed is:

1. A solid oxide fuel cell system for generating electrical power by reacting fuel with oxidant gas, comprising:
a fuel cell module that includes a stack of fuel cells each comprising a pair of fuel electrode and air electrode formed, respectively, on inner and outer sides of the cell;
a fuel supply apparatus configured to supply fuel to the fuel cell module;
a water supply apparatus configured to supply water to the fuel cell module for steam reforming of the fuel;
an oxidant gas supply apparatus configured to supply oxidant gas to the outer side of each fuel cell;
a power extraction apparatus configured to extract the electrical power from the fuel cell module at a desired level;
a reformer disposed inside the fuel cell module and configured to perform steam reforming on fuel supplied from the fuel supply apparatus using the water supplied from the water supply apparatus and to supply the reformed fuel to the inner side of each fuel cell; and
a controller programmed to control the fuel supply apparatus, the water supply apparatus, the oxidant gas supply apparatus, and the power extraction apparatus, wherein the controller includes a shutdown circuit,
wherein the shutdown circuit is programmed to execute a shutoff operation in which the fuel supply apparatus, the water supply apparatus and the power extraction apparatus are all shut off to stop supply of the fuel from the fuel supply apparatus and the water from the water supply apparatus and stop extraction of the electrical power from the fuel cell module, and
wherein the shutdown circuit is further programmed to continue operating the oxidant gas supply apparatus, after executing the shutoff operation to shut off the fuel supply apparatus, the water supply apparatus and the power extraction apparatus, to execute a temperature drop operation in which the oxidant gas supply apparatus, after execution of the shutoff operation, continues supplying the oxidant gas that purges oxidant gas remaining on the outer side of each fuel cell from before execution of the shutoff operation to outside the fuel cell module.

2. The solid oxide fuel cell system of claim 1 , wherein the shutdown circuit is programmed to keep the water supply apparatus inoperative during the temperature drop operation.

3. The solid oxide fuel cell system of claim 2 , wherein the shutdown circuit is programmed to initiate execution of the temperature drop operation without any interruption after executing the shutoff operation.

4. The solid oxide fuel cell system of claim 3 , wherein each fuel cell is in a tubular shape having one end thereof at which the inner side of the fuel cell formed with the fuel electrode is open and from which the reformed fuel is discharged outside of the fuel cell after flowing through the inner side of the fuel cell, and each fuel cell comprises an acceleration section attached to said one end and shaped to increase a flow rate of the reformed fuel flowing out of said one end the fuel cell.

5. The solid oxide fuel cell system of claim 4 , wherein the acceleration section comprises a flow path formed therethrough, through which the reformed fuel flows, the flow path having a cross section narrower than a cross section of the inner side of the fuel cell.

6. The solid oxide fuel cell system of claim 5 , wherein the flow path has the cross section shaped narrower than the cross section of the inner side of the fuel cell so that subsequent to the shutoff operation, the pressure on the inner side of each fuel cell drops at a rate lower than a rate at which the pressure on the outer side of each fuel cell drops.

7. The solid oxide fuel cell system of claim 3 , further comprising a voltage detection sensor that detects the output voltage of the fuel cell module, and the controller comprising a temperature drop operation halt circuit, wherein the temperature drop operation halt circuit halts the temperature drop operation in cases where the voltage detected by the voltage detection sensor satisfies predetermined stopping conditions during the temperature drop operation in which power is not being extracted from the fuel cell module after the shutdown stop.

8. The solid oxide fuel cell system of claim 7 , wherein the shutdown stopping circuit is constituted so that the temperature drop operation is executed over a predetermined temperature drop operation execution period after the shutdown stop, and the temperature drop operation halt circuit stops the temperature drop operation when a detected voltage satisfies stopping conditions during the temperature drop operation execution period.

9. The solid oxide fuel cell system of claim 8 , wherein the shutdown stop circuit does not execute the temperature drop operation when the fuel cell stack temperature at the time of the shutdown stop is below a predetermined temperature.

10. The solid oxide fuel cell system of claim 3 , further comprising a temperature detection sensor that detects the temperature of the fuel cell stack, wherein after the shutdown stop, the shutdown stop circuit executes a temperature drop operation in response to the temperature detected by the temperature detection sensor.

11. The solid oxide fuel cell system of claim 10 , wherein after a shutdown stop, the shutdown stop circuit reduces the total amount of oxidant gas supplied during the temperature drop operation more when the temperature detected by the temperature detection sensor is low than when it is high, or the shutdown stop circuit does not execute the temperature drop operation when the temperature detected by the temperature detection sensor is below a predetermined temperature.

12. The solid oxide fuel cell system of claim 11 , wherein the controller comprises a pre-shutdown operation circuit, and in cases where the fuel cell stack temperature is higher than a predetermined shutdown stop temperature, the pre-shutdown operation circuit executes a pre-shutdown operation to increase the amount of oxidant gas supplied by the oxidant gas supply apparatus before the shutdown stop so that the temperature of the fuel cell stack is reduced, and then a temperature drop operation is executed after a shutdown stop.

13. The solid oxide fuel cell system of claim 12 , wherein the pre-shutdown operation circuit continues the pre-shutdown operation until temperature of the fuel cell stack drops to the shutdown stop temperature, after which the shutdown stop is executed.

Assignees

• Toto Ltd

Inventors

• Matsuo Takuya
• Otsuka Toshiharu
• Tsuchiya Katsuhisa
• Akagi Yousuke
• Shimazu Megumi
• Kobayashi Chihiro
• Shiono Mitsunobu
• Omoshiki Koji

Classifications

• H01M8/04753

  of fuel cell reactants · CPC title

• H01M8/04228 Primary

  during shut-down · CPC title

• H01M8/0625

  in a modular combined reactor/fuel cell structure · CPC title

• H01M8/2428

  Grouping by arranging unit cells on a surface of any form, e.g. planar or tubular · CPC title

• H01M8/1246

  the electrolyte consisting of oxides · CPC title