Coal blend performance during pulverised-fuel combustion: estimation of relative reactivities by a bomb-calorimeter test

Abstract

Blending coals as fuel for pulverised-fuel-fired power stations provides a way of minimising costs and increasing fuel flexibility. The use of blends can, however, introduce operating difficulties, such as poor ignition, carbon losses in ash, flame instability and emissions to atmosphere. A simple laboratory method is presented for assessing the changes in the reactivity of coal blends with blend composition. It is based on a commercial bomb calorimeter, with small modifications to hardware and procedures. The test is applicable to any size fraction. Two sets of coal samples and their blends, previously tested in a single-burner pilot plant and in a commercial power station, respectively, have been studied using the new bomb-calorimeter procedure. The combustion performance of the individual coals was not always consistent with performance at the larger scale. However, the technique was able to distinguish between the combustion reactivities, of different blends and reproduce the trends observed in the pilot-scale burner and the full-sized power plant. This laboratory-scale experiment provides a simple means of assessing the relative combustion reactivity of coal blends, using equipment that is simple and generally available. (C) 2001 Elsevier Science Ltd. All rights reserved.