Simulation investigation on the design and operation strategy of a 660 MW coal-fired power plant coupled with a steam ejector to ensure NOx reduction ability

Abstract

A 660MW supercritical coal-fired power plant with feedwater heater coupled with a steam ejector is applied to address nitrogen oxide (NOx) removal problem under low load conditions. The present study conducts simulation on design and operation strategy for this coupled system. Results show that the system can effectively improve NOx removal efficiency, and improvement is significant under low unit loads. When unit load is 40% THA condition, NOx removal efficiency of the coupled system reaches 70.77%, whereas selective catalytic reduction (SCR) system should be cut off under benchmark condition. A new system is then proposed to deal with the operation problem under extremely low and high loads. This improvement method is effective under extremely low loads, and NOx removal efficiency remains efficient when the unit approximates 20% THA condition. When unit load rate is higher than 75% THA condition, the plant thermal efficiency could be improved by adjusting primary pressure of steam ejector. This study may serve as reference for the design of power plants to ensure efficient NOx removal ability under low loads.