Essay On Gasification

1.4.2 Gasification

The char gasification is the endothermic process where the char, solid residue from a pyrolysis process, is transformed into a gaseous mixture of CO, CO2, CH4, H2O and H2 in a reducing atmosphere usually composed of CO2 and H2O.

As mentioned above that the process is endothermic process, so for that process some source of heat is required. The main heat source is from the combustion of the volatile matter, which is released during pyrolysis process. The addition for the oxidation agent is necessary for the combustion process. As mentioned previously that the thermal degradation of biomass is carried out in the presence of oxidation agent and should rather be referred as devolatilization and not pyrolysis. The following figure

==> Burned to produce water or steam in a boiler (Thermal Use).

==> Burned for electricity production either in a gas turbine or in internal combustion engine.

As in the chemical synthesis process generally requires the use of a medium calorific value gas (MCV) (non nitrogen diluted) with the minimum contaminants for optimal conversion o chemicals by Paisley et al., 1994.

If the product gas is use for the electricity generation, the gas needs to be very clean from the char-particles, tar and ash before entering a gas turbine or a combustion engine. Still the hot outlet gas from the gas turbine can be used to produce steam for a steam turbine, as the process is being integrated to the Gasification Combined Cycle (IGCC).

Compares to that of a coal, biomass is more reactive. This can result in higher gasification efficiencies and lower gasification temperatures. However the research conducted on coal gasification is in some respect very relevant for biomass gasification, for instance the design of a biomass integrated gasifier/gas turbine (BIG/GT) as mentioned by Consonni and Larson,