METHOD AND DEVICE FOR CONTROLLING BOILER EXHAUST GAS FLOW RATE OF AIR PREHEATER IN EXHAUST RE-BURNING TYPE COMBINED CYCLE POWER PLANT

摘要

PROBLEM TO BE SOLVED: To restrict an overshoot and an undershoot of an outlet gas temperature of an air preheater with respect to an outlet gas temperature set value of an air preheater after a combined cycle operation is started, thereby to improve controllability, prevent the outlet gas temperature of the air preheater from exceeding largely the outlet gas temperature of the air preheater, and eliminate a harmful influence on the air preheater. SOLUTION: A deviation 26 of a temperature of an air preheater outlet gas is obtained from a set value 25 of the temperature of the air preheater outlet gas and a temperature 23 thereof, an opening command 28 of an air preheater inlet gas damper 22 is obtained to eliminate the deviation 26 of the temperature of the air preheater outlet gas, upper and lower limit values 31 and 33 of the opening of the air preheater inlet gas damper 22 is obtained based on a gas turbine load 30, the opening command 28 is restricted so that it is held within a range of the upper and lower limit values 31 and 33 of the opening, and outputted to the air preheater inlet gas damper 22 as a restricted opening degree command 28'.