dc.description.abstract |
In this paper, steady state simulation model of air gasification has been developed in Aspen plus for
fixed bed biomass gasifier using rice husk. Aspen plus is selected as a simulation tool due to its
higher capability of handling solid feed using physical models. The fixed bed gasifier used here is an
updraft type one with drying, pyrolysis, gasification, and combustion stages. The hydrodynamic
process of the reactor was investigated using Ansys Fluent. The gasifier has been modeled based on
thermodynamic equilibrium model by Gibbs free energy minimization in four stages. In the first stage
moisture content of biomass feed is reduce through drying. In the second stage biomass is
decomposed into its elements by specifying yield distribution. In the third and fourth stages
gasification and combustion reactions has been modeled using Gibbs free energy minimization
approach. Simulation result include; sensitivity analysis of Equivalence ratio(ER), gasification
temperature, gasification pressure, biomass moisture content, steam injection have been varied over
wide range and the effect of these parameters on syngas composition and heating value(LHV) has
been investigated. The sensitivity analysis results indicated that temperature increases the
production of CO and H2. Increase in Equivalence ratio decreases the heating value of the producer
gas. Steam injection favors hydrogen production which results in increase of hydrogen content in the
syngas, while increase of the steam to biomass ratio had negative effects on lower heating value of
syngas. Based on the results, maximum lower heating value of syngas was found at the gasification temperature of 4000C, pressure of 1bar, Equivalence ratio of 0.1, steam to fuel ratio of 0.1 and 5%
moisture content of biomass. |
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