A coke removal system removes coke deposits from the walls of a high temperature passage in which hydrocarbon fuel is present. The system includes a carbon-steam gasification catalyst and a water source. The carbon-steam gasification catalyst is applied to the walls of the high temperature passage. The water reacts with the coke deposits on the walls of the high temperature passage to remove the coke deposits from the walls of the high temperature passage by carbon-steam gasification in the presence of the carbon-steam gasification catalyst.