High exhaust temperature and large heat loss of flue gas are common problems occurred in utility boilers. Therefore

on the basis of energy cascade utilization principle

a complete system model including boiler

steam turbine and generator was established using the commercial software EBSILON

by taking a supercritical 600 MW unit as the example. On this basis

the thermodynamic characteristics of the normal low pressure economizer system and air preheater bypass flue gas waste heat utilization system were numerically simulated. The results show that

the air preheater bypass flue gas waste heat utilization system can increase the utilization level of flue gas waste heat

realize the cascade utilization of energy

of which the energy saving effect is about 2 times of that of the conventional low pressure economizer system. The air preheater bypass flue gas waste heat utilization system is more suitable for the units with larger hot primary air drying capacity.