Abstract:
Fast depletion of petroleum and its related products is leading to shortage of fossil fuels and their high prices in the market. So the adoption of new and renewable energy sources is being encouraged. Biomass is a form of renewable energy and is preferable to fossil energy on account of its excellent storage properties, availability and competing cost with all other forms of renewable energies like, wind, solar, tidal, ocean thermal etc. The attractiveness of biomass as a fuel for power generation stemss from its many similarities to fossil fuel.
Biomass such as bagasse, rice husk, wood and cotton stalk are now available as agricultural wastes. Therefore it is necessary to study the gasification characteristics of such biomass in a downdraft thermal gasification reactor. Present study reports experimental investigation carried out with three biomass materials namely, wood, briquettes (press mud) and blend (mixture of wood and rice husk)
A downdraft gasifier of capacity 5 kg/hr has been designed and operated. A blower supplied air and its rate was measured by a venturimeter. The temperatures at strategic point were measured by k-type thermocouples. Gas flow was measured by another venturimeter. The gas was scrubbed using a jet scrubber and the clean and cool gas was snap-sampled under steady state operating conditions of the gasifier for various air flow rates. The gas samples were analyzed by using a gas chromatograph. Heating values of the gas were calculated using heating values of the individual components of the gas.
Experimental results indicated that optimum gasification rate is achieved at a certain value of airflow rate. Reactor temperature also depends on airflow rate. With increasing airflow rate beyond a certain value the heating value decreases.
Operational experience indicated that high ash low bulk density and small sized biomass materials are not suitable as a feedstock for a venturi type downdedil gasifier.
