Following the positive results on reducing NOx emission obtained by testing the combustion of coal dust by combustion theory in steps, it could be detached the final solution for retrofitting of the existing industrial burners. The boiler of 525 t/h construction MAN has 6 slots burners tangential mounted to the firebox. Each burner is connected with a mill-fan in a direct injection system. For drying the coal, the grinding system includes one pre-drying tower for each mill-burner ensemble, the drying being carried out based on flue gas recirculation at the end of the firebox. The burner retrofit solution is based on previous research results, materialized in the construction of an experimental model burner of 400 kW, which was tested at coal combustion from Oltenia basin on a pilot boiler from UPB. The pilot burner had two slots coal and two air intakes, secondary and tertiary respectively, thus simulating an industrial burner module-fig.1 Fig.1.The burner of coal dust from boilers 525 t / h SE Isalnita 64 Constructive, the retrofitting starts from the burner modular design concept – fig.1, this having 4 modules of four slacking slots, two vertical and two horizontal, and secondary intermediate air blown through pipes forming a cross framing the four slacking slots-fig.2 Fig.2.The burner module subjected to retrofitting The implementation concept of stepwise combustion for burner module, includes a sequential routing of jets penetration in the furnace space, for the maintenance with secondary air to be realized towards the firebox core, the deficit of air in the first sequence of combustion limiting the emission of oxides of nitrogen. This will be achieved by shifting the length of the inlet channel for routing the coal dust and the intermediate secondary air. As a result, a burner module will have channels of different lengths , arranged between them so that the air – gasodynamic control be more beneficial to low NOx combustion. The modular construction performed will be repeated four times at the height of the firebox. Retrofitting will achieve:-maintaining the output speeds for both primary air and coal dust and secondary air;-framing the new burner construction in embrasure boiler ;-the compatibility of slacking circuits and secondary air with networks around the burner ; Modification constructive solution of the burner keeps the following aerodynamic characteristics for nominal regime: