NOVELTY - A fuel cell is connected after the gas generator (1). Its anode chamber (9a) is supplied with hydrogen-rich gas from the generator. The cathode chamber (9b) is supplied with oxygen-containing gas. The cooling unit of the CO shift reactor (4) receives air flow leaving the cathode. The cooling unit of the gas purification unit (5a) is supplied with the gas flow leaving the anode.    USE - A gas generator producing hydrogen-rich gas by steam reforming, suitable for supply to fuel cells.    ADVANTAGE - Liquid fuels other than methanol, for which the infrastructure is not yet adequate, can be employed. The gas generator has high energy efficiency and the start up method proposed is rapid. Efficiency is improved by greater thermal integration, which makes maximum use of waste heat. Preheating gases from the fuel before entry into the catalytic burner, promotes high combustion temperature and high conversion of residual hydrocarbons, without having to raise the efficiency of the fuel cell. This is significant in a system with partial fuel oxidation. A cooling circuit for the CO shift reactor and the gas purification unit is obviated, making the system more compact and efficient.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for the method of starting up the equipment. When starting, the reformer reactor (2) is supplied with liquid fuel from the liquid fuel tank (10) and an oxygen-containing gas. Simultaneously the bypass line is opened. On completion of start-up, water is supplied to the reformer (2) and the bypass line (16) is closed. Preferred features: The gas generator has in addition a catalytic burner (6) for heating. It is supplied with gas leaving the anode and cathode, downstream of the cooling units. Heat exchangers (3, 8) transfer thermal energy from reformate gas leaving the reformer reactor (2), and/or from the catalytic burner, to an educt supplied to the reformer. An evaporator (8) is directly or indirectly heated by the catalytic burner, is supplied with a mixture containing liquid water and an oxygen-containing medium. A line supplies from the liquid fuel tank (10) to an evaporator (23) at least partially vaporizing it, before entry into the reformer. Further lines (18a, 18b, 19) supply oxygen-containing medium into the gas purification unit (5a, 5b) and/or the CO shift reactor (4). The bypass line (16) and valve (17) supply reformate gas to the catalytic burner, bypassing the fuel cell. During start up, oxygen-containing gas is additionally supplied to the CO shift reactor. Excess oxygen is supplied to the gas purification unit (5a, 5b) during start-up, beyond that required for selective oxidation of carbon monoxide.    DESCRIPTION OF DRAWING(S) - A block schematic flow diagram of the system is presented.    gas generator (1)    reformer reactor (2)    heat exchanger (3)    CO shift reactor (4)    gas purification unit (5a, 5b)    catalytic burner (6)    anode chamber (9a)    evaporator (8)    cathode chamber (9b)    liquid fuel tank (10)    bypass line (16)    bypass valve (17)    lines supplying oxygen-containing medium (18a, 18b, 19)    evaporator (23)