Functionally, the three-stage gasifier was designed to remove
tar generated during gasification in stages. First, the feed material is
devolatilized in the auger reactor, liberating a high amount of tar. In
this step, a small portion of the tar generated in the reactor can be
destructed by oxidative thermal decomposition in air supplied
from the feeding system. Second, the vapors containing the tar and
solid leaving the auger reactor enter the fluidized bed gasifier,
where the tar coming from the auger reactor and tar newly
generated in the fluidized bed gasifier can be further cracked.
Finally, the tar escaping the fluidized bed gasifier enters the fixed
bed reactor usually filled with activated carbon, where the tar is
adsorbed on the activated carbon and subsequently cracked by heat
with the assistance of metals of activated carbon