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