This book contains papers presented at the Engineering Foundation Conference on mineral matter in fuels held on November 2-7, 1997 in Kona, Hawaii.The conference is one of a continuing series that was initiated by the CEGB March-wood Engineering Laboratories in 1963. The conference was to be eventually organised by the Engineering Foundation as the need for multi-disciplinary work related to controlling ash effects in combustors became apparent. The conference covers both the science and the applications. The papers also present case histories, particularly for current fuel technologies, developments in advanced technologies for power generation and mathematical modelling of these processes.