Study On The Effect Of Lignite Coal Drying On Boiler Operation Economy

Lignite has low price and worldwide abundant minable reserves. In the growingenergy issues, more and more scientific research institutions and coal-fired powerstations pay attention to lignite. However, lignite coal with high moisture and low heatvalue will result in the reduction in efficiency of the boiler thermal which directly forutility boiler combustion. Due to that, lignite is not widely used. In order to improvethe coal utilization efficiency and reduce the high moisture content, removal water inthe lignite efficiently with existing technology and equipment is an effective way ofreducing costs and enhancing the market competitiveness.In this paper, we combine with predrying system in the power generation system,draw the drying system and boiler combustion system diagram, established lignitepredrying by flue gas in power generation system thermal economy analysis model.Analysis shows that the thermal efficiency of power generation system mainly comesfrom the dry lignite combustion, and the boiler thermal efficiency is improved.The temperature of the flue gas emission is lower, the greater degree of lignitedrying, the thermal efficiency of drying system is higher; the power generation wouldbe higher.On the thermodynamic calculation of boiler combustion with different moisturelignite, the boiler thermal efficiency, the characteristics of boiler flue gas and theheat-transfer characteristics of heating surface would be analyzed. Furthermore,detailed analysis of the causes of change and its impact on power plant thermalefficiency are discussed. The results indicated that less moisture in lignite, smallamount of air needed and flue gas production in the boiler are lead to the reduction ofthe flow rate of gas through the heating surface. The date shows that the boilerthermal efficiency is improved after lignite predrying; the highest can be increased by1.47%, save raw coal amount5.11%.Finally, on the basis of the boiler thermodynamic calculations results, andcombine with different specific lignite drying scheme, calculate the economy changesof drying system addition to the combustion of lignite power systems. Then analysisthe feasibility of burning lignite boiler increased lignite predrying system.