Overview of Coal Ash Deposition in Boilers

The management of coal ash in utility boilers continues to be one of the most important fuel property considerations in the design and operation of commercial boilers. The behavior of mineral matter in coal can significantly influence furnace sizing, heat transfer surface placement, and convection pass tube spacing. Ironically, many of the more reactive, low rank U. S. coals must have larger furnaces than the less reactive higher rank coals. This is strictly a requirement based on the mineral matter behavior; Figure 1 illustrates this point. Given the same mineral matter behavior the more reactive, lower rank coals would require less residence time and therefore smaller furnace volumes than the less reactive, higher rank coals.