To explore the optimum operation mode for the operation optimization of the low-temperature economizer combined heater system under different loads

operation optimization test is carried out in a 300 MW unit. The results show that ambient air temperature is basically unchanged and the temperature of the boiler exhaust shows a linearly increasing trend with the increased air temperature of the air heater. With the temperature rise of the air heater

the heat exchange proportion of the air heater increases approximately linearly at medium and high loads

and at low load the ratio increases at first and then tends to be gentle. Based on the outage state of the low-low temperature economizer combined heater system

within the experimental range

the reduction of the heat rate of steam turbine is linear with the recuperated heat

the increase of the thermal efficiency of the boiler is positively correlated with the increase of air temperature of the air heater outlet

the decrease of coal consumption of power supply is positively correlated with the increase of air temperature of the air heater outlet and the proportion of the absorbed heat at the air heater side. In actual operation

when the air temperature of the air heater outlet is controlled at 70 ℃

the economy of the overall unit is best. The results of this study provide some technical references for improving the economy of thermal power units.