Effects of coal quality on utility furnace performance

Abstract

Use of lower than design grade coals can cause problems in furnaces and boilers due to increased ash deposits. A single-zone model has been developed to relate coal quality to thermal performance of pulverized, coal-fired power-generating boilers. The model, based on algebraic mass and energy balances and necessary auxiliary equations, estimates some of the required chemical and physical coal/ash properties. Three wall ash deposit parameters, thermal conductivity, emittance and thickness, have been determined by a sensitivity analysis to be critical to furnace performance and have been obtained by experimental procedures described herein. Data for ash properties are reported for Utah, Illinois and Western Kentucky bituminous coals. With these measured properties, the model has been used to predict effects of coal quality on furnace performance and to interpret changes in ash property data from a small scale combustor to a large scale utility boiler.