Etude de la combustion de gaz de synthèse issus d'un processus de ...

Chapter 2
Biomass
Gas
Drying
Pyrolysis
Reduction
Oxidation
Grate
Oxidant
Figure 2.3 – Updraft gasifier
Ashs
tel-00623090, version 1 - 13 Sep 2011
The advantages of updraft gasification are:
- simple, low cost process;
- able to handle biomass with a high moisture and high inorganic content;
- proven technology.
The primary disadvantage of updraft gasification is:
- syngas contains 10-20% tar by weight, requiring extensive syngas cleanup before
engine, turbine or synthesis applications.
Downdraft
Downdraft gasification also known as co-current-flow gasification is simple, reliable and
proven for certain fuels. The downdraft gasifier has the same mechanical configuration
as the updraft gasifier except that the oxidant and product gases flow down the reactor,
in the same direction as the biomass. A major difference is that this process can
combust up to 99 % of the tars formed (Reed and Das, 1988). Low moisture biomass
(