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

In lignite-fired power plants, the high water content of lignite (35-40%) is responsible for significant reductions in boiler efficiency due to the large amounts of heat loss experienced through water evaporation during coal combustion. Installation of a water condensation device in the outlet of the desulfurization absorption tower can recover substantial amounts of water and latent heat from the flue gas that containing saturated steam. In the present study, a pilot test platform was built into a 600MW lignite-fired power plant, and a 50,000m3/h flue gas flow was been extracted and cooled by 5°Cduring the test. Using our theoretical model for this energy efficiency innovation, the test results demonstrate that 129.5GJ/h of latent heat can be recovered and 61.6t/h condensate water can be collected from the flue gas (2,500,000m3/h) for the600MWlignite-fired power plant. The wet flue gas desulphurization system (wet FGD) consumes the supplemental water of 60-80 t/h for this power plant. Consequently, the water recovery quantity of 73 t/h demonstrate that zero net water consumption can be achieved by returning the recovered water back into wet FGD.