A key factor in the direct use of coal in gas turbines is the behavior of ash. Advanced coal cleaning processes will reduce ash levels of the order of 0.2 to 1%, which are substantially higher than for crude or residual oils. Perhaps, even of greater concern are the alkali metals, which have been directly implicated in corrosion and deposition enhancement for petroleum fuels. The objective of the program described in this report was to experimentally examine the transformation of ash, and in particular, alkali metals during combustion and deposition in gas turbine environments, and to examine the effect of these transformations on deposition rates and deposit character. It is likely that the coal cleaning method will have a major effect on the composition of the CWM ash. Thus CWM fuels prepared by physical cleaning and by chemical leaching were investigated. Ash transformation experiments yielded key information regarding the corrosive and erosive behavior of CWM fuels. Ash particles, which were in the submicron range, also are not expected to be erosive because of their small size. Thus it can be concluded that erosion for these CWM fuels that contain coal particles a few microns in diameter will be minimal as long as good fuel atomization is achieved. In summary, it has been shown that alkali behavior for coal fuels is unlike that for petroleum fuels. The presence of aluminosilicates in coal ash inhibits the formation of corrosive alkali sulfates. This also affects deposition rates by eliminating the presence of deposition ''glues.''Coal ash deposits, however, are hard and adherent, and are cleaned with difficulty. Because of the small size of the ash particles and the buoyancy of any carbonaceous cenospheres, erosion is not expected to be a significant issue with micronized CWM fuels. 41 refs., 29 figs., 6 tabs.