Load Cycling of a 242 MW Coal Fired Steam Turbine Plant Designed for Base Load Operations

The TS Power Plant (TSPP) is a 242 MW gross coal fired power plant designed to operate base loaded. The plant is new and began commercial operations in June 2008. Due to high volumes of snow fall in the northwest the availability of low cost hydropower in 2009 reduced power demand from TSPP and other coal based generating stations. Moreover in 2009 natural gas prices fell to the lowest point in years making energy from newer more efficient combined cycle power plants very favorable. This paper examines the performance of TSPP under varying load output conditions with regard to key plant equipment such as the boiler, steam turbine generator and air quality systems for the flue gas. The plant was being operated from minimum load without firing oil (80 NMW) to sometimes full load conditions (218 NMW). Load changes were experienced on an hour to hour basis for several months. Load changes varied from 40 NMW increasing to 60 NMW decreasing during the 20 minute load change window during the hour. The boiler has three coal pulverizers. The boiler can achieve full load operations with two pulverizers, however all three pulverizers are ran at times for reliability. At loads less than 140 NMW the plant can operate one pulverizer but operations at loads lower than 80 NMW requires oil burners for flame stabilization. Transition points from one pulverizer to two pulverizer operations also cause challenges during load changes. However examining plant operating data over the load ranges has shown that TSPP has performed very well despite the varying load schedule. The plant heat rate is a good indicator as to how well the plant has performed. The heat rate has varied from under 10,000 Btu/kwhr at low loads (< 100 MW net) to around 9,400 Btu/kWhr at higher loads (> 175 MWnet). A summary of plant boiler and turbine data under various loads is also presented in this paper as well as balance of plant equipment.