A novel fluidized bed drying and density segregation process for upgrading low-rank coals

Lignite and sub-bituminous coals are attractive due to their low cost, low emissions, and high reactivity. However, these coals contain large amounts of moisture, which reduces calorific value and lowers plant efficiency. A novel fluidized bed drying process was developed that uses low-grade waste heat to reduce fuel moisture content of low-rank high-moisture coals and concurrently lowers sulfur and mercury content of dried coal through density segregation. This paper discusses quality improvement of low-rank coals by low-temperature thermal drying, describes changes in microstructure of coal particles and describes the reduction in sulfur and mercury via density segregation during thermal drying of lignite in a specially designed fluidized bed.