采用烟气旁路的燃煤机组脱硝系统变负荷过程的经济性分析

Setting up an economizer flue gas bypass system is an effective approach to increase the inlet flue gas temperature of the denitration system in a coal-fired power plant and maintain high De-NO_x efficiency under all working conditions. In order to analyze the economy of the denitration system in a coal-fired power plant during frequent load cycling processes,the dynamic models of a 660 MW ultrasupercritical coal-fired power plant and the SCR system are developed. Then,the cost of urea,the environmental cost of NO_x emission and the cost of coal are obtained and compared under different flue gas bypass baffle opening during the loading up processes from 50%THA to 100%THA. The results show that the change value of coal cost is the largest,and the total cost has a certain increase when the economizer flue gas bypass baffle is opened during the load cycling processes. When the flue gas bypass baffle opening is 5% and 10%,the cost of coal increases by ¥ 600 and ¥ 1 200 respectively during the loading up processes from 50% to 75%THA. Meanwhile,the cost of urea decreased by ¥ 442.48 and ¥ 554.89 respectively,while the environmental cost of NO_x emission changed less,only ¥ 62.22 and ¥ 63.19. Moreover,the cost of coal increased by ¥ 1 800 and ¥ 2 300 respectively during the loading up processes from 75% to 100%THA,and the amounts of change in urea cost and NO_x emission environmental cost were little. Therefore,it is not recommended for coal-fired power plant to open the flue gas baffle during the loading up processes from 75% to 100%THA.