Capacity Range : 600-12000
kWth output (Equivalent to 50-1000 litres/hour oil substitution)
: Biomass or coal with ash content upto 30
Gas Calorific Value : 1100-1300
Kcal/Nm3 (4.6-5.4 MJ/Nm3)
Fuel flexibility is the main feature of
Updraft Multifuel Gasifeirs. These gasifiers can operate on either coal or
biomass and fuel switching does not require any changes in the reactor.
Updraft gasifiers tolerate higher ash content, higher moisture content and
greater size variation in fuel as compared to downdraft gasifiers.
updraft gasifiers, gas is drawn out of the gasifier from the top of the fuel
bed while the gasification reactions take place near the bottom. As the
producer gas passes through the fuel bed, it picks-up volatile matter (tars)
and moisture from the fuel. Therefore, the gas from the updraft gasifier
contains condensable volatiles. The design and operation of the gasifiers is
such that the gas comes out at 200-400 C temperature. At this temperature,
most of the volatile hydrocarbons are in vapor form, which add to the energy
content of the gas. It is most appropriate to utilize updraft gasifiers in
close-coupled-hot gas mode for direct heating applications. However, if the
application warrants, the scrubbing of gas to remove the volatiles/tars is
also carried out.
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.