This paper describes the design and operation of an entrained flow reactor to assess the slagging propensity of a coal-ash. Temperatures and residence times have been chosen to closely simulate those experienced by pulverised fuel (pf) particles in a full-size utility boiler. Ash deposits have been collected on ceramic coupons at 1500°C and 1200°C and on an air-cooled metal probe at 830°C.

Ten UK coals and one US coal were selected to give a wide range of coal-ash compositions, a range similar to that found at many power stations. Deposits ranged from dense, highly fused material collected at 1500°C, to lightly sintered ash-particles collected at 830°C. A visual inspection of the deposits allowed a provisional ranking of the slagging propensity to be made. A computer-controlled scanning electron microscope (CCSEM) technique has been developed to provide a quantitative characterisation of each microstructure, thus providing the basis for a more rigorous assessment of the slagging propensity.

The technique described provides the basis for a reliable assessment of coal-ash slagging propensity to be made from a few kgs of coal. It removes many of the uncertainties associated with conventional indices and the previous subjectively based laboratory techniques.