Abstract: Reduction of nitrogen oxide emissions from thermal incinerators is accomplished in installations for calcining solid carbonaceous materials such as petroleum coke and anthracite coal. A hot effluent gas stream containing hydrocarbon vapors and entrained carbonaceous solid particles is removed from the calciner, and means are provided to effect preliminary combustion of the hydrocarbon vapors but not the carbonaceous solid particles in the gas stream using substantially the stoichiometric amount of combustion air. The resultant gas that is substantially free of hydrocarbons and oxygen is introduced into the thermal incinerator, and combustion of the carbonaceous solid particles is effected with additional combustion air.