NOVELTY - An apparatus comprises a reactor (1) including an inlet to receive hydrocarbon, and an outlet to discharge a mixture containing hydrogen gas, carbon dioxide and carbon monoxide; a carbon monoxide remover (3) configured to receive the mixture and remove or convert at least part of the carbon monoxide of the mixture; and a heater (10) configured to heat the carbon monoxide remover, where the heater is configured to receive the mixture from the reactor and use the mixture to generate heat. The heater comprises an oxidation catalyst to facilitate an oxidation reaction to generate heat.    USE - As an apparatus such as a self-contained fuel cell system, a fuel cell reformer module, an electronic or electrical device comprising a fuel cell, and a transportation vehicle comprising a fuel cell (claimed).    ADVANTAGE - The reformed gas produced when the reformer is initially driven is used as the fuel for the heat source unit of preheating the water gas shift reaction unit. Thus, the temperature of the water gas shift reaction unit can quickly increase without consuming separate fuel or energy, thereby shortening the starting time of the reformer the fuel cell. Further, a large quantity of carbon monoxide contained in the reformed gas produced at the beginning of driving the reformer can be effectively removed, and the fuel efficiency is improved. The reformed gas is instead used as a fuel for the heat source unit supplying heat to the water gas shift reaction unit. Thus, the fuel efficiency of the reformer can be enhanced, and the water gas shift reaction unit can be quickly preheated.    DETAILED DESCRIPTION - An apparatus comprises a reactor (1) including an inlet configured to receive hydrocarbon, and an outlet configured to discharge a mixture comprising hydrogen gas, carbon dioxide and carbon monoxide; a carbon monoxide remover (3) configured to receive the mixture and remove or convert at least part of the carbon monoxide of the mixture; and a heater (10) configured to heat the carbon monoxide remover, where the heater is configured to receive the mixture from the reactor and use the mixture to generate heat. The heater comprises an oxidation catalyst to facilitate an oxidation reaction to generate heat. The apparatus further comprises at least one valve (31a) connecting the outlet of the reactor to the carbon monoxide remover and the heater and configured to selectively direct the mixture between the carbon monoxide remover and the heater; a timer (52) configured to measure time; a temperature sensor configured to measure temperature of the mixture at the outlet, temperature of the reactor or temperature of the carbon monoxide remover; concentration sensor; and a controller (50) configured to control operation of the valve, using the time measured by the timer, temperature measured by sensor and concentration measured by sensor. INDEPENDENT CLAIMS are included for the following:    (1) method of warming up a carbon monoxide remover for use with a fuel cell, involving providing a mixture comprising hydrogen gas and carbon monoxide; oxidizing at least part of the mixture, to generate heat; and applying the heat to warm up a carbon monoxide remover; and    (2) method of operating an apparatus involving receiving the mixture from the reactor and use the mixture to generate heat; and applying the heat to warm up the carbon monoxide remover.    DESCRIPTION OF DRAWING(S) - The figure shows a block diagram of a reformer for a fuel cell.    reactor (1)    carbon monoxide remover (3)    heater (10)    valves (31a, 31b)    controller (50)    timer. (52)