Biomass Gasifier

Drying : Biomass fuels consist of moisture ranging from 5 to 35%. At the temperature above 100 o C, the water is removed and converted into steam. In the drying, fuels do not experience any kind of decomposition. 
Pyrolysis : Pyrolysis is the thermal decomposition of biomass fuels in the absence of oxygen. Pyrolysis involves release of three kinds of products such as solid, liquid and gases. The ratio of products is influenced by the chemical composition of biomass fuels and the operating conditions. The heating value of gas produced during the pyrolysis process is low (3.5 - 8.9 MJ/m 3 ). It is noted that no matter how gasifier is built, there will always be a low temperature zone, where pyrolysis takes place, generating condensable hydrocarbon. 
Oxidation : Introduced air in the oxidation zone contains, besides oxygen and water vapors, inert gases such as nitrogen and argon. These inert gases are considered to be non-reactive with fuel constituents. The oxidation takes place at the temperature of 700-2000oc. Heterogeneous reaction takes place between oxygen in the air and solid carbonized fuel, producing carbon monoxide. Plus and minus sign indicate the release and supply of heat energy during the process respectively 
C + O 2 = CO 2 + 406 [ MJ/kmol] In reaction 12.01 kg of carbon is completely combusted with 22.39 m3 of oxygen supplied by air blast to yield 22.26 m 3 of carbon dioxide and 393.8 MJ of heat. 
Hydrogen in fuel reacts with oxygen in the air blast, producing steam . H 2 + ½ O 2 = H 2 O + 242 [ MJ/kmol] Reduction In reduction zone, a number of high temperature chemical reactions take place in the absence of oxygen. The principal reactions that takes place in reduction are mentioned below. 
Boudouard reaction - CO 2 + C = 2CO - 172.6 [MJ/kmol] 
Water-gas reaction - C + H2 O = CO + H 2 - 131.4 [MJ/kmol]
Water shift reaction - CO 2 + H 2 = CO + H 2 O + 41.2 [MJ/kmol]
Methane production reaction - C + 2H 2 = CH 4 + 75 [MJ/kmol] 
From above thermo-chemical reaction it may be understood that heat generated in pyrolysis is absorbed in reduction process. Hence, the temperature of gas which is very high in the beginning goes down as it passes through various stages. If complete gasification takes place, all the carbon is burned or reduced to carbon monoxide, a combustible gas and some other mineral matter is vaporized. The remains are ash and some char (unburned carbon). 

Advantage Gasification

It saves upto 73% of fuel cost when compared to conventional fuel options Low initial investment and cost of power production Applied over a range of output ratings (5KWe to 2Mwe) with flexuble process control

Range of Applications
Power Generation:

Round the clock Power Generation Pumping and Irrigation Village electrification Captive power(industries) Grid -fed power from energy plant installed on wastelands

Thermal Applications

Hot Air Generators Dryers Boilers Thermic Fluid Heaters Ovens Furnaces & Kilns

Gasification for Energy Supply 
Rural areas in the developing countries India are characterized by disperse population and a lack of infrastructure. Energy is the basic mean in improving the living standard and productivity. Energy is required in household for lighting and running electrical apparatus such as TV and Radio. Energy is also demanded in agriculture for operating irrigation pumps and other machinery such as thresher.