Circulating fluidized bed(CFB) boilers are characterized by high thermal inertia and strong heat storage capacity

enabling banked fire and near-zero output peak shaving. However

there is limited experimental research on banked fire and peak regulation in large-scale CFB units

with a lack of studies on key parameter variations and control strategies during this process. In this study

a banked fire and peak regulation test was conducted on a supercritical 350 MW CFB boiler to investigate the evolution of critical parameters during shutdown and propose optimization strategies for boiler feedwater flow rate and integrated turbine valve position control. These optimizations aim to maximize the peak shaving duration while ensuring operational safety. Experimental results demonstrate that the optimized supercritical CFB unit achieved 85 minutes of shutdown peak regulation with a load of 5～8 MW. Throughout the test

the boiler maintained dry operation

while the main and reheat steam temperatures decreased from 566.0 ℃ and 553.0 ℃ to 482.0 ℃ and 472.0 ℃

with average cooling rates of 0.99 ℃/min and 0.95 ℃/min

respectively. The average bed temperature declined from 875.8 ℃ to 730.9 ℃ at a rate of 1.70 ℃/min. During the test

the maximum exhaust temperature of the high-pressure cylinder reached 380.0 ℃

with the steam temperature at the regulating stage exceeding that of the cylinder inner wall. The wall temperature deviation at the outlet of the boiler water-cooled walls and mid-partition walls gradually decreased

peaking at 97.5 ℃. These findings confirm the feasibility of hour-level shutdown peak regulation in supercritical CFB units and provide a reference for engineering applications of similar units.