NOVELTY - A carbon monoxide removal system comprises preferential oxidation reactors disposed in series which remove carbon monoxide contained in reformate gas via a catalyst. The preferential oxidation reactors comprise first preferential oxidation reactor and second preferential reactor arranged further downstream than the first preferential oxidation reactor.    USE - Removing carbon monoxide from reformate gas used in fuel cell power plant.    ADVANTAGE - The system maximizes the carbon monoxide removal performance of the preferential reactors while preventing excessive catalyst temperature rise.    DETAILED DESCRIPTION - A carbon monoxide removal system comprises preferential oxidation reactors disposed in series which remove carbon monoxide contained in reformate gas via a catalyst, where the preferential oxidation reactors comprise:    (i) a first preferential oxidation reactor and a second preferential reactor arranged further downstream than the first preferential oxidation reactor;    (ii) an air supply mechanism that supplies air containing oxygen as an oxidizing agent to the first and second preferential oxidation reactors;    (iii) first temperature sensor that detects the temperature of the first preferential reactor;    (iv) second temperature that detects the temperature of the second preferential reactor; and    (v) a controller for controlling the air supply mechanism so that the air supply flow rate to the first preferential oxidation reactor and the air supply flow rate to the second preferential oxidation reactor vary based on the temperature of the first and second preferential oxidation reactors.    An INDEPENDENT CLAIM is also included for a control method of a carbon monoxide removal system comprising:    (a) supplying air to the first and second preferential oxidation reactors;    (b) detecting the temperature of the first and second preferential reactors; and    (c) varying the air supply flow rate to the second preferential oxidation reactor and the air supply flow rate to the second preferential oxidation reactor based on the temperature of the first and second reactors.    DESCRIPTION OF DRAWING(S) - The figure is a schematic diagram of a fuel cell power plant.    Anode (4A)    Cathode (4B)    Air pumps (6A, 6B)    Valves (7, 8)