Abubeker, Yimam (PhD)Seada, Mohammed2020-12-092023-11-102020-12-092023-11-102017-11http://etd.aau.edu.et/handle/12345678/23911With the gradual depletion of coal and petroleum resources, biomass is being perceived as a self-sustainable source of energy production. It is cheap and readily available as well. Gasification is one of the potential sources for production of clean and eco-friendly fuel. ASPEN PLUS simulator is a strong tool for investigating the behavior of a process and it can be readily used to access various aspects like feasibility of an operation, effect of operating parameters on the performance of a gasifier. In this paper, steady state simulation model of air gasification has been developed in Aspen plus for fixed bed biomass gasifier using rice husk, coffee husk and saw dust as a fuel and the analysis of fuel samples was done through ultimate and proximate properties of the biomass. 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 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 Air to fuel ratio, gasification temperature, gasification pressure, and, steam to biomass ratio have been varied over wide range and the effect of these parameters on syngas composition and lower heating value has been investigated. The sensitivity analysis results indicated that increase in air to fuel ratio decreases the heating value of the producer gas. Temperature increases the production of CO and H2 and enhances the heating value of the producer gas. Higher pressure reduces H2 rich syngas hence decreases the lower heating value of the producer gases. Steam as a gasifying agent 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 simulation results, maximum lower heating value of syngas was found at the gasification temperature of 800ºC, steam flow rate of 0.3 kg/hr, and pressure of 1bar was obtained at air flow rate of 0.5 kg/hr for 1.5 kg/hr of each feed stocks.en-USBiomass gasificationSensitivity analysisAspen PlusThesis