A gasifier is disclosed combining a fixed bed gasification section where coarse
fuel is gasified and an entrained flow gasification section where fine fuel is
gasified. The fixed bed section includes upper and lower sections. Coarse fuel
is devolatilized in the upper fixed bed section and subjected to elevated temperatures
sufficient to crack and destroy tars and oils in the effluent gases. The entrained
flow gasification section is disposed in a lower plenum adjacent the lower fixed
bed section. A plurality of injection ports are configured to introduce oxygen,
steam, or air into different sections of the gasifier to control temperature and
operating conditions. Activated carbon may be formed in the upper fixed bed section
and in the entrained flow section. The activated carbon may be used as a sorbent
to remove pollutants from the effluent gases. The gasifier may be used with various
coarse and fine fuel feedstocks.