Understanding Slagging and Fouling During Pf Combustion
AUTHOR: Gordon Couch
DATE: August 1994
This report covers the basics of boiler design, the factors which affect it, the nature of the ash-forming materials present and their transformations in the boiler. The mechanisms of deposition and the properties of the deposits formed are discussed. A number of empirical indices which attempt to predict the slagging or fouling propensity of a coal are described. Work is reported on advanced analytical techniques for both raw coal and for the intermediates and deposits formed. These results can be applied both to improving the capabilities of existing indices, and to computer models of the complex situation inside the boiler.
Other methods of studying and predicting the behaviour of coal in a boiler include pilot-scale tests, and drop tube furnace work. The various methods of reducing boiler deposition are discussed, including optimising the soot-blowing cycle and more extensive monitoring of the boiler operating conditions to give early warning of problems. It is concluded that general predictions of the behaviour of coals in a boiler are not yet secure, although considerable progress has been made. Both designers and operators can be more confident when trouble-shooting, or making technical assessments or decisions about coal-fired boilers, as a result of the increased understanding of the behaviour of the inorganics during and after combustion.