2016 Volume 95 Issue 1 Pages 144-151
In coal fired power plants using low rank coal containing significant amounts of moisture, improvement of the thermal efficiency has been desired. This paper presents estimation results of thermal efficiency for an existing 316 MWe power plant with and without steam tube dryers (STDs). An original estimation methodology has built for estimation of the efficiency. Coal feed rates were predicted by coal properties and turbine heat rates, and process simulation based on heat balance was applied to estimate net thermal efficiency of the power plant with the STDs. When total moisture of low rank coal was dried from 35.0% to 11.4% by the STDs, the absolute values of boiler efficiency and net thermal efficiency were increased by up to 4.2% and 1.8%, respectively. A decrease in power consumption of mills and fans was contributed to an increase in net thermal efficiency. It found that application of the STDs for low rank coal fired power stations have the advantage of reduction of fuel cost and CO2 mitigation.
