TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The rate of supply of the fuel is zero during at least one of the successive time intervals. The oxygen content of the substance leaving the reformer is measured and when a threshold value of the oxygen content exceeded, the reformer shifts to the continuous mode of operation. The oxygen content is measured by means of a lambda probe or a fuel cell. In a reformer with two fuel supplies, one of the fuel supplies operates during the recovery at a supply rate that corresponds to that in continuous mode of operation. The reformer exhibits an oxidation zone and a reforming zone, heat can be supplied to the reforming zone, a mixture of fuel and oxidizing agent is supplied to the oxidation zone using a first fuel supply, where the fuel mixture is supplied at least after a partial oxidation of the fuel or at least partly to the reforming zone, additionally fuel is supplied to the reforming zone using a second fuel supply, and the second fuel supply operates during the successive time intervals at a reduced rate of supply. The heat from the exothermic oxidation in the oxidation zone is supplied to the reforming zone. The reforming zone exhibits a supply of oxidizing agent, by means of which additionally oxidizing agent is supplied. The additional fuel is supplied to an injection and a mixture-forming zone, and the additional fuel from the injection and mixture-formation zone is flow into the reforming zone. The additional fuel is at least partly evaporated by the heat energy of the gas mixture leaving the oxidation zone. The gas mixture produced in the oxidation zone is supplied to the reforming zone by partially bypassing the injection and the mixture-formation zone. The recovery takes place during each non-operation phase of the reformer. The reformer is operated in the start-up phase with an air/fuel-ratio of greater than or equal to 1. The critical threshold temperature is defined such that the reformer or the components of the reformer exhibits a temperature of 450-650degreesC. The critical threshold temperature of a stack of fuel cells arranged downstream to the reformer or components of the stack of fuel cells exhibit 450-550degreesC. The recovery takes place following the start-up phase of the reformer such that the reformer is operated at several successive time intervals with an air/fuel-ratio that is greater than the operation mode of the reformer. The recovery takes place during each start-up phase of the reformer. EXAMPLE - No suitable example given.