An assessment of different biomass feedstocks in a downdraft gasifier for engine application

Abstract A performance analysis of downdraft biomass gasifier has been done using an equilibrium model for the pyro-oxidation zone and kinetic model for the reduction zone. The motivation of the analysis is to find out the suitable operating parameters when different biomass feedstocks are used in the gasifier as fuel. The study has been carried out with three woody biomass (rubber wood, eucalyptus wood and bamboo wood), two agricultural wastes (wheat straw and rice straw) and coconut shell. The fuel feed rate, equivalence ratio and feed particle size are adjusted to target the critical char bed length, constant gas production rate and pressure drop with every biomass, such that the gasifier with its accessories can be optimally used. However, it is found that the heating value of the producer gas and the bio-energy generation rate in the gasification process would change with the variation in the gasifier fuel. This will result in a change in rating of the engine coupled with the gasifier for producing power. Finally, an economic analysis based on fuel price is made for the corresponding operating conditions of all the fuels. It is found that wheat straw gives the maximum bio-energy generation rate and the minimum specific fuel cost (Rs./MJ of energy) among the fuels compared.