Experimental and numerical investigation of combustion system improvement on 600MW bituminous coal boiler for burning lignite coal

Abstract

Abstract A 600MW supercritical direct-current (DC) utility boiler co-firing bituminous coal with lignite, has the problems from over-large desuperheating water yield in the reheater and over-high NO x emission concentration. In this paper, the causes of the problems are analyzed through, the initial tests of pulverization system and combustion system, the adjustment of combustion, etc. The results show that the combustion in furnace lagged behind to some extent after co-firing the bituminous coal with the lignite and the center of the flame was elevated, which shortened the relative distance between the flame of the main burners and over fire air(OFA), enlarged the absorbed heat amount of the reheater and reduced the residence time of flame in the reduction zone prominently. The much less residence time would increase NO x emission. Based on the calculations of the actual operation conditions of the burners, a series of improvement measures were proposed. After performing numerical simulation and cold test verification for the improvement measures, the corresponding transformations of the power plant were carried out. The desuperheating water yield in the reheater decrease, obviously, and over-high NO x emission is controlled effectively.