The distributions of gas velocity and NO_x mass concentration at the economizer outlet vary greatly with the unit load and coal mill combination in opposite wall fired furnace. Consequently

the adaptability of the selective catalytic reduction(SCR) denitration device is poor

and the blockage of ammonium hydrogen sulfate in the air preheater is aggravated. Conventional ammonia injection grid(AIG) optimization can not achieve good adaptability to full load operation. To solve this problem

a comprehensive balance adjustment test method was proposed by taking into account 5 operation combinations of 6 coal mills at different unit loads. Moreover

the AIG optimization was studied on a 600 MW unit using this comprehensive balance adjustment test method. The test results showed that

under the 5 conventional running mill combinations

the relative standard deviation CV values of the NO_x mass concentration distribution at the outlet cross section of the SCR flue gas denitration device reached 31%

31%

27%

26% and 32%

respectively. The historical data of DCS showed that

after 14 months operation

the differential pressure of the air preheater at full load has basically not increased.