Capacity Range : 120-2400
kWth output (Equivalent to 10-200 liters /hour oil substitution)
: Wood chips, biomass briquettes of agro residues,loose Biomass like
Rice Husk,Soyabean Husk,Musturd Husk with ash content upto 15%
Gas Calorific Value : 1000-1200
Kcal/Nm3 (4.2-5.0 MJ/Nm3)
Downdraft gasifiers are fuel specific.
Downdraft wood gasifiers can operate on wood like biomass materials and
biomass briquettes with a minimum bulk density of 250 kg/m3 and ash content
of less than 5%. In downdraft gasifiers, gas is drawn from the bottom of the
reactor while the hottest reaction zone is in the middle.
volatile matter in the fuel gets cracked within the reactor and therefore
the output gas is almost tar-free. However, the gas, as it comes out of the
reactor, contains small amounts of ash and soot. The gas comes out of the
gasifier at 250-450 C. This gas can also be used either in hot condition
(after preliminary cleaning) or in cold-clean condition (after appropriate
gas clean-up arrangement). The gas from the downdraft gasifiers can be
cleaned to very high purity such that it can be used in IC engines or for
direct heating applications where purity of gas is critical requirement.
The selection of Updraft or
Downdraft Gasifier would mainly depend upon the available fuel and the
requirements of the application. Downdraft wood Gasifier requires wood
chips, biomass briquettes or wood like agro-residues (such as stems,
stalks). If fuel flexibility is required and need for fuel switching (say
from biomass to coal or from one biomass to another) is anticipated, the
updraft gasifier would be suitable.
For gasification of coal,
updraft gasifier is suitable. Downdraft gasifier cannot accept coal. For
direct heating applications, such as firing in kiln, furnaces, boilers, etc,
updraft gasifier would make a better choice. However, if the contaminants in
fuel gas are likely to affect the end-product quality, the choice of
downdraft gasifier makes better sense. There are situations where effect on
end product quality is critical, but fuel flexibility is also an important
consideration. In such situations, updraft gasifier with gas scrubbing
arrangement may be selected.
For running IC engines, normally
downdraft gasifiers are selected. However, for large installations where
flexibility may be additional requirement, updraft gasifiers with extensive
gas clean-up system could be an option. In addition to the above general
criteria, there would be site specific requirements, which need to be
analyzed in detail while making the final selection.