PURPOSE: For efficient NOx removal from waste gas from cement firing furnace, the waste gas is contacted to dispersed mixture of powder grains of prepared cement production material, hydrocarbon gas fuel and ammonia source at a specified temperature.

CONSTITUTION: Waste gas from cement firing furnace is contacted to dispersed mixrure of powder grains of prepared material for portland cement production, hydrocarbon gas fuel such as methane, ethane, etc., and ammonia source at 600 to 1300°C. The process actuates mixed dispersion to cause active CH radical formation from hydrocarbon gas fuel, structural transformation of prepared material, and NH radical formation from ammonia. These occurrence contribute to effective NOx removal from the waste gas without being affected by the presence of dust, moisture and sulfur oxides.