Simulation of the gas temperature deviation in large-scale tangential coal fired utility boilers

Abstract For tangential coal fired boilers, the gas temperature deviation at the exit of the furnace will occur when boiler capacity becomes large. In this paper, the flow, heat transfer and combustion process in a boiler of 300 MWe unit at Shiheng Power Plant, Shandong, China and a boiler of 600 MWe unit at Shidongkou Power Plant, Shanghai are simulated. The causes and decrease ways of the gas temperature deviation are investigated. It is found that the gas temperature deviation results from the after twirl and the platen superheater. Decreasing the diameter of tangential circle formed by secondary air flow can result in the decrease of temperature deviation to a certain extent. Although the after twirl can be decreased by opposing the tangential direction of some secondary air flows, the flow field in the furnace might be disturbed, and the temperature deviation might be increased, if the momentum and the angle of the opposite secondary air flow are not appropriate.