ABSTRACT

Coal Mending may be used to supply coal with the characteristics required for the U.K. industrial market. Although the performance of any coal or coal blend for use on industrial boiler plant depends on a number of factors, this paper is only concerned with the fouling aspects. Fouling indices, eg Rf (base/acid × %Na2O on ash), are used as a guide in calculating coal blend compositions, but the fouling behaviour of a blend may not always be as expected. A procedure has been developed, at the Coal Research Establishment of the British Coal Corporation, for assessing the fouling propensities of coal blends by operation of a small chain grate stoker fired horizontal shell boiler. Deposition is measured by insertion of a mass accumulation probe. Tests have been carried out on individual coals and coal blends of 'smalls' and 'singles' grade coals. The probe data were in good agreement with operational experience in industrial boilers and showed a reasonable relationship with Rf. In this paper, the test procedure and results are described.