Patent Application
20170098853
The subject matter of this document pertains to fuel cells. More particularly, and without limitation, the subject matter of this document pertains to manifolds for fuel cells.
Fuel cells generate electricity based on an electrochemical reaction. There are various types of fuel cells that have been proposed or are in use. One type of fuel cell is known as a phosphoric acid fuel cell (PAFC). One of the problems associated with PAFCs are potential ground faults resulting from an electrical short caused by acid bridging from the fuel cell stack to the manifold. Such ground faults may result in an entire power plant shutdown, for example. While PAFCs typically include seals to prevent acid migration that may result in acid bridging, for example, such seals are not always entirely effective. If it were possible to prevent such acid bridging or to reduce the likelihood of a shutdown resulting from acid bridging, that would improve the reliability of PAFCs.
An illustrative example fuel cell manifold includes a manifold structure having at least one surface situated where the surface may be exposed to phosphoric acid. The surface has a coating that reduces a possibility of an electrical short between the manifold and the fuel cell stack adjacent the manifold if that surface is exposed to phosphoric acid during fuel cell operation.
In an example embodiment of a fuel cell manifold having one or more features of the manifold of the previous paragraph, the coating comprises phosphate.
In an example embodiment of a fuel cell manifold having one or more features of the manifold of either of the previous paragraphs, the coating comprises a pre-cursor that yields a phosphate layer if the pre-cursor is contacted by phosphoric acid.
In an example embodiment of a fuel cell manifold having one or more features of the manifold of any of the previous paragraphs, the pre-cursor comprises iron oxide.
In an example embodiment of a fuel cell manifold having one or more features of the manifold of any of the previous paragraphs, the coating comprises a dielectric insulator.
An illustrative example fuel cell assembly includes a cell stack configured to generate electricity based on an electrochemical reaction. A manifold adjacent the cell stack includes at least one surface situated where the surface may be exposed to phosphoric acid. The surface has a coating that reduces the possibility of an electrical short between the manifold and the cell stack if that surface is exposed to phosphoric acid during fuel cell operation.
In an example embodiment having one or more features of the fuel cell assembly of the previous paragraph, the coating comprises phosphate.
In an example embodiment having one or more features of the fuel cell assembly of either of the previous paragraphs, the coating comprises a pre-cursor that yields a phosphate layer if the pre-cursor is contacted by phosphoric acid.
In an example embodiment having one or more features of the fuel cell assembly of any of the previous paragraphs, the pre-cursor comprises iron oxide.
In an example embodiment having one or more features of the fuel cell assembly of any of the previous paragraphs, the coating comprises a dielectric insulator.
An illustrative example method of operating a fuel cell assembly, which includes a cell stack and a manifold adjacent to the cell stack, includes providing a coating on at least one surface of the manifold. The surface is situated where the surface may be exposed to phosphoric acid. The coating reduces the possibility of an electrical short between the manifold and the cell stack if that surface is exposed to phosphoric acid during fuel cell operation.
In an example embodiment having one or more features of the method of the previous paragraph, the coating comprises phosphate.
In an example embodiment having one or more features of the method of either of the previous paragraphs, the coating comprises a pre-cursor that yields a phosphate layer if the pre-cursor is contacted by phosphoric acid.
In an example embodiment having one or more features of the method of any of the previous paragraphs, the pre-cursor comprises iron oxide.
In an example embodiment having one or more features of the method of any of the previous paragraphs, the coating comprises a dielectric insulator.
Various features and advantages of an example embodiment will become apparent to those skilled in the art from the following detailed description. The drawing that accompanies the detailed description can be briefly described as follows.
The fuel cell assembly 20 includes a manifold 24 that is configured to deliver reactant to the CSA 22, to carry away excess reactant or exhaust from the CSA 22, or both. The manifold 24 includes a manifold structure that may be configured in a known manner to achieve appropriate fluid flow to or from the CSA 22.
As schematically shown in
The coating 28 on the surface 26 reduces or eliminates the possibility of an electrical short occurring because of acid bridging from the CSA 22 to the manifold 24. The coating in one embodiment comprises a phosphate. One example process of establishing a phosphate coating 28 includes exposing the surface 26 of the manifold 24 to a phosphoric acid solution that includes zinc or manganese with varying additional amounts of nitrates, chlorates and copper. A variety of known processes for coating metal parts using such a solution are known. One embodiment includes such a known process of establishing the coating 28. According to one embodiment, the coating occurs because of a reaction in a metal phosphate solution as follows
2Fe(s)+Fe3+(aq)+3H3PO4−(aq)3FePO4(s)+3H2(g)
In another example, the coating 28 comprises a pre-cursor layer of the type that contact with phosphoric acid results in a self-healing phosphate layer on the surface 26. One example pre-cursor includes iron oxide, which is useful with a carbon steel manifold 24, for example.
The coating 28 comprises a dielectric insulator and is compatible with phosphoric acid such that the coating 28 eliminates or reduces instances of ground-fault otherwise caused by acid bridging between the CSA 22 and the manifold 24.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2014/031273 | 3/20/2014 | WO | 00 |
