The direct blowing pulverizing system with double-inlet and double-outlet ball mill equipped on a supercritical 600MW unit boiler can not measure the coal quantity into the furnace correctly.Therefore

the water/coal ratio control of the unit was seriously affected.Such problems as large fluctuation of superheating ratio of separator inlet steam and main steam occurred during the unit load varying

so the automatic generation control(AGC)can not be put into service.Thus

optimization of control logic for calculation of coal amount in pulverizer under different conditions was performed.The results showed that

for dynamic working condition

the main steam temperature deviation was within ±5 ℃;the reheat steam temperature deviation was within±10℃;that of the temperature at middle point of the separator was within ±6 ℃;the main steam pressure difference was within ±0.6 MPa;the load deviation was within ±3 MW.While for the stable working condition

the main steam pressure deviation was within±0.3MPa and the load deviation was within±3MW.The normal start of the AGC function was ensured.