A small four-stage gas turbine was directly fired with woodchips using a novel downdraft, gravel-bed combustor for a total 250 hours of tests. The average turbine blockage due to deposits was 0.19 percent per hour. The composition of deposits was studied using plasma emission spectroscopy and x-ray diffraction. The main constituents of the deposits were CaO, MgO, and K2SO4. The deposits contained 5 to 15 percent potassium and 0.5 to 3 percent sulfur.
