Patent ID: 7419733

Claim:
A fuel cell system, comprising a reformer for reforming a hydrocarbon base fuel into hydrogen, a CO transformer for transforming carbon monoxide, a CO eliminator for removing carbon monoxide, a fuel cell for generating electricity from hydrogen, and a burner for the reformer for burning exclusively a gas containing hydrogen discharged from the fuel cell and for supplying said reformer with heat necessary for reforming reaction, said burner having a burner head receiving fuel and air from below, said burner having a wall surface on a bottom of said burner, said burner not receiving fuel and air through the wall surface on the bottom of said burner, the wall surface on the bottom of said burner being in contact with said burner head, a flame rod type flame detection means detecting the flame of the burner for the reformer, said flame rod type flame detections means including an insulator installed on the wall surface on the bottom of said burner and including a flame detection rod mounted to pass through the insulator and through the wall surface on the bottom of said burner and through an area between another wall of said burner and said burner head, wherein: said hydrogen gas discharged from the fuel cell contains residual methane from the reformer of 7 to 33% in volume, wherein: a reforming catalyst used for the reformer is a precious metal base reforming catalyst, and a means controlling a ratio of the steam supplied to the reformer and a carbon contained in the fuel (S/C) in the range of 2.5 or more to 3.5 or less and a means for controlling a temperature of the reformer from 550° C. to 640° C., and thereby said gas containing hydrogen discharged from the fuel cell contains residual methane from the reformer of 7 to 33% in volume.