The Department of Energy is sponsoring a multiphase program to investigate the filtration potential of the moving bed granular filter (GBF) for application in pressurized high temperature energy conversion systems. Phase I, which has been completed, included the development of a mathematical model, a cold flow parametric test series in a 0.746 Nm/sup 3//s GBF, and investigations of potential dust plugging problems at the inlet screen. During the experimental program, collection efficiencies of 99% and filter outlet loadings less than 0.0074 g/m/sup 3/ were demonstrated. The objectives of Phase II are to investigate the effects of elevated temperature and coal combustion particulate on GBF filtration performance; to update the analytical model developed in Phase I to reflect the high temperature effects; to optimize filter internal configuration; to perform parametric and long duration tests to characterize the effects of filter design improvements on filtration efficiencies; and to conduct an economic analysis of full scale filters for 1600 F service and a scaleup of the filter and combustion additive suppressant effect identified in the analytical and hot flow tasks. Earlier hot flow testing confirmed that the original GBF design incorporating inlet and outlet screens exhibited a tendency for extensive and irreversible ash plugging. An alternative screenless design, with demonstrated high filtration efficiency, has been confirmed during both cold flow and hot flow tests as a more viable approach for continued development and tests. This report describes the continuation of work for development and design improvement of the GBF system during this reporting period.