In order to dig into the potential of flue gas waste heat utilization in tail duct of boilers

further enhance the unit efficiency and reduce the net coal consumption rate

a deep waste heat utilization system of power plant boiler that based on a series design of segmented air preheater was proposed

on the basis of energy cascade utilization principle.This design can improve the deficiency of the conventional waste heat utilization system based on low temperature economizer.The system is divided into three air preheaters arranged in series

and the smoke water heat exchanger is set between two adjacent air preheaters.Combined with a typical 1 000 MW coal-fied unit

thermal efficiency of the novel heat utilization system and conventional system were compared via thermal performance analysis

exergy analysis and technical economic analysis.The results show that

this unit could save standard coal about 1.94g/(kW·h)if adopting new type of waste heat utilization system

which is about 1.7times of that adopting the conventional heat utilization system

at the same time

the economic effect is about 1.4times of the latter.Both the energy saving effect and economic effect of the new waste heat utilization system are very significant.