Ash chemistry and mineralogy of an Indonesian coal during combustion: Part II — Pilot scale observations

This paper reports on combustion experiments carried out in a pilot scale furnace as a follow-up to research previously carried out using a drop-tube furnace to investigate the combustion behaviour of an Indonesian coal, in particular the effects of additives on ash chemistry, mineralogy and ash deposit formation. Combustion experiments were carried out in a pilot scale furnace to test the effectiveness of bauxite addition in reducing ash build-up. Samples collected from deposits on the slagging panels and fouling probe tubes, electrostatic precipitator fly ash, the furnace ash and tunnel ash were fully characterized using various analytical techniques.Experimental results substantiated earlier drop-tube observations suggesting that the use of raw coal with an addition of 3 wt.% bauxite would appear to offer the best performance with respect to slagging and fouling propensity in comparison to use of the raw coal alone. Observations on the reduction in glass content resulting from the addition of bauxite during PSF test runs support the earlier findings of the drop-tube tests. The reduction in glass content found in the slagging panel and fouling probe samples is comparable to that found in ash formation experiments conducted at 1400 °C despite the observed differences in mineralogy. Although deposits are still likely to form as indicated by the PSF runs they appear to be more friable and hence amenable to removal by conventional methods such as frequent soot blowing. These findings demonstrate how the results of laboratory experiments can be combined with those of pilot scale trials to provide data for full-scale trials on the effects of additives in the remediation of ash problems associated with the firing low-rank coals.