The work concerns an important in our times problem related to different areas as ecology, economy and proper use of energy resources: reduction of NOx by rebuming process. The main goal of the work was to develop the technology of NOx reduction during zone combustion of coal and mine gas with process optimal conditions determination in power boilers in aspect of environmental protection. In the work was presented: investigation of numeric model of zone combustion of coal and mine gas; aplied combustion research of the boiler OCG-64 produce on RAFAKO.