Coordinated Optimization Control of Flue Gas Temperature for Improving Reaction Efficiency of Catalyst

Different control programs of flue gas temperature and selective catalytic reduction(SCR) economizer were designed and studied to reduce ammonia slip rate and relieve air preheater fouling problem. A 300MW unit was selected for the study. The boiler thermal calculation results indicate that through the joint arrangements between the high temperature flue gas bypass and SCR economizer, the SCR inlet flue gas temperature could be regulated to nearly 340 ℃ under the lowest flue gas temperature condition with maximum 20% bypass flue gas ratio and 40% the original economizer area of SCR economizer. While, under the highest flue gas temperature condition, the SCR inlet flue gas temperature would not be regulated, and the exhaust gas temperature could be decreased 6.1 ℃. In this way, the highly efficient operation of catalyst at 340 ℃ or more of SCR inlet flue gas temperature and variation of exhaust gas temperature in much smaller and more optimal range are almost completely achieved under all operating conditions. If the annual average load was 75%, the average exhaust gas temperature would approximately be dropped 5.2 ℃ and the standard coal consumption decreased was nearly 1 g/(kW?h).