A novel flue gas treatment system was proposed in this paper. The system integrates the low pressure economizer (LPE) with the desulphurized flue gas heater (DFGH) for both waste heat recovery of the exhaust gas and the desulphurized flue gas heating. A model for the system was established based on the equivalent enthalpy drop theory. The thermal economic comparisons among 5 feasible connection schemes for the flue gas treatment system of a 300 MW unit were executed. The parametric analyses were also performed to evaluate the effects of the outlet flue gas temperature and the condensate temperature of the DFGH. Results indicate that the optimized flue gas treatment system can improve the thermal economy and heat the desulphurized flue gas. Better thermal economy is achieved when the LPE is connected with the high energy level feed water heater, and the low pressure extraction steam is extracted for heating desulphurized flue gas. The thermal economy decreases with the increase of the outlet flue gas temperature of the DFGH while it increases slightly with the decrease of the condensate temperature of the DFGH.

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