Lignite Fuel and Power-Plant Availability

This initial study of lignite-fueled power plants encompasses the characteristics of lignite coal, plant reliability problems associated with the handling and burning of Northern Great Plains (NGP) lignite, information on present NGP lignite-fueled plants, a study of boiler and turbine arrangement for achieving low plant unavailability, and a preliminary cost comparison of alternate boiler and turbine arrangements for lignite coal. The conclusions are listed below. 1. Little is known about lignite units. A boiler design up to 500 MW can be specified to attain objectives of low unavailability and high capacity. Consideration should be given to 2 boilers and 1 turbine for outputs greater than 500 MW. 2. Lignite is a difficult fuel to burn but is an abundant, long-term, and cost-effective energy source. 3. Conventional fossil-fuel plant design is inadequate for achieving low unavailability and high capacity factors in a Northern Great Plains lignite fueled plant unless a very conservative design is specified. 4. A lignite plant whose boiler size is identical to a conventional sub-bituminous coal-burning boiler will deliver a low output. 5. As compared to the standard sized fossil-fuel plants, the larger and more expensive lignite plants can provide lower long-term energy costs due to the abundance and ease of mining (strip mining) lignite. Cost reductions will be realized for mine-site power stations which will eliminate coal transportation costs. 6. As more operating experience is accumulated, lignite plant design criteria will improve as will plant unavailability and capacity factors. 7.