Haldor Topsoe A/s

Ernst Jorn

Jens R Rostrup-Nielsen

Tommy Hansen

The invention relates to a process for the production of electricity in a fuel cell system by steam reforming a carbonaceous fuel to form fuel cell reactant gas and recycling recovered reactants from the anode exhaust gas to the anode inlet. There is obtained an increase of the electricity production of 20-30% if prior to the recovery and recycling the anode exhaust gas is passed over a steam reforming catalyst by which lower hydrocarbons in said exhaust gas is converted to reactants for use in the fuel. The carbonaceous fuel may for instance be natural gas or methane. A fuel cell system for use in the process comprises supply means (2,10) for carbonaceous fuel; an inlet reformer unit (6) for producing reactant gas for the fuel cell (4); an outlet reforming unit (12) for converting hydrocarbon-containing anode exhaust gas to anode reactant gas; and means (18,90) for recovering the reactant gas and recycling recovered anode reactant gas.

Fuel cell system

A fuel cell power plant utilizing hydrogen and carbon oxide rich feed gas (4) and comprising a hydrogen-carbon oxide consuming fuel cell (2) with an anode compartment (2a) and a cathode compartment (2c), means for supplying feed gas (8, 10, 12) to the anode compartment (2a), compression means (41) for supplying the cathode compartment (2c) with compressed cathode oxidant gas (44), and means for recirculating fuel cell exhaust gas (46, 50, 42) to the cathode compartment (2c), which fuel cell power plant further comprises a methanation unit (9) for converting the hydrogen and carbon-oxide rich feed gas (4) into a methanated gas, a reforming catalyst bed (13) adapted to receive and reform the methanated gas to anode process gas (14) by absorbing waste heat from said fuel cell (2).

Fuel cell power plant

Hydrogen and carbon oxides are reacted to form methane by passing an inlet stream of preheated methanation synthesis gas together with a recycle stream of product gas through a catalyst bed in an adiabatic methanation reactor. The inlet temperature is between 250.degree. and 350.degree. C, the outlet temperature between 500.degree. and 700.degree. C. The recycle stream is withdrawn from the outlet stream after the latter has been cooled to a temperature between 250.degree. and 350.degree. C and being, however, at least 50.degree. C above the dew point. A preferred means for withdrawing the recycle stream is an ejector driven by the inlet stream or by added steam.

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Lyngby, Denmark

Ernst Jorn