The article presents the results of a comprehensive research on the impact of O-2/CO2/H2O atmosphere and coal milling quality on pulverized coal combustion process. In particular the content of combustibles in fly ash and heat transfer parameters were investigated. Experiments were conducted in two research stands: in a laboratory rig for single particle combustion investigations and in a semi-industrial 0.5 MW combustion chamber for pulverized fuel burner studies. It was shown that because of faster coal conversion in the oxy-fuel atmosphere it is possible to use lower quality coal grinding, which will save energy required for milling. Experimental results confirmed also the beneficial effect of the coarse coal milling that resulted in a decrease of necessary flue gas recirculation rate, which also means lowering the energy demand of flue gas fans. The impact of oxycombustion optimization on net efficiency of electric energy production was presented on the basis of 220 MW unit with OP-650 steam boiler. (C) 2015 Elsevier Ltd. All rights reserved.