Abstract: Abstract:The theory and the technology route of the variable energy level system for deep utilization of boiler flue gas waste heat were introduced. The features of the energysaving effect calculation of the system were described. The technical and economical performance of exhaust gas temperature deep reducing technology was analyzed. In the system, the hightemperature flue gas is used to heat the condensate water of the turbine, and the lowtemperature flue gas is used to heat the forced air of the boiler. By the method, more squeezedout power can be obtained, and the coldend protection of the air preheater can realized all year around. Comparing the system with conventional lowpressure economizer, the net coal consumption rate is reduced by 0.5～0.6g/(kW•h), the coldend comprehensive temperature of the air preheater is increased by 30～40℃, the steam consumption for boiler forced air heating in winter is reduced to zero. The system is applicable to the boilers with relative lower exhaust gas temperature to recover the waste heat deeply.

Key words: Keywords:flue gas waste heat, variable energy levelmode utilization, exhaust gas temperature, energy conservation