Pilot study on in-depth water saving and heat recovery from tail flue gas in power plant

The high water content in lignite (35-40%) induces a great amount of heat loss for water evaporation in coal combustion and reduces the boiler efficiency significantly. Installation a water condensation device in the outlet of desulfurization absorption tower can recover a great amount of water and latent heat from the flue gas containing saturated steam. In the present study, a pilot test platform was built in a 600MW lignite-fired power plant, and 50,000m3/h flue gas has been extracted to be cooled during the test and the flue gas temperature can be reduced by 10?. The result shows that 187.7GJ/h of latent heat can be recovered and 73.9t/h condensate water can be collected from the entire flue gas (2,500,000Nm3/h) for such a 600MW power plant burning lignite. The wet flue gas desulphurization system (WFGD) consumes the supplemental water of 60-80 t/h in this unit, consequently, the water recovery quantity of 73.0t/h means that the zero water consumption in WFGD can be achieved by supplementing the recovered water back into WFGD.