Producer/pyrolysis gas from thermochemical conversion of biomass contains undesired condensable hydrocarbons termed as tar. Intended conversion of tar to syngas using catalytic and non-catalytic techniques generates undesirable coke. This thesis investigates the conversion of tar model benzene in Al₂O₃ packed bed reactor using non-catalytic techniques of partial combustion and thermal cracking. Simulated producer gas (SPG) and different fuel gas mixtures (FGMs) are used in partial combustion technique. SPG and FGMs are similar gas mixtures, however, FGMs contain either similar components as SPG contains or one component less than of SPG components, and contain relatively low lower heating value (LHV) than of SPG. Steam, CO₂ or both are used as benzene reforming media in thermal cracking technique. Different experimental conditions and Al₂O₃ packed bed configurations are used to understand their influences on benzene conversion. Used experimental conditions comprise of different reactor temperatures, SPG/FGM compositions, gas flow rates, concentrations of benzene and reforming media. Whereas, used packed bed configurations are different combinations of packed bed positions (top, center and bottom of reactor), bed particles sizes (large, medium and small) and bed heights (large, medium and small). A CFD model is developed to simulate the benzene conversions from SPG/FGMs partial combustion.

Benzene conversions from SPG partial combustion and thermal cracking in a reactor with Al₂O₃ packed bed (position: top of reactor, particles size: medium, height: large) show no coke generation. Whereas, comparative benzene conversions from both SPG partial combustion and thermal cracking without the Al₂O₃ packed bed show significant generation of coke precursors and coke respectively. Investigating benzene conversions from thermal cracking using other configurations of packed bed in reactor shows coke generation with packed beds of all considered heights and particles sizes at center and bottom of reactor. That may be because of homogeneous thermal reforming/polymerization of benzene occurring in empty space above the packed beds partially leading to coke formation. Coke generation is also experienced with packed beds of considered particle sizes with small and medium heights at top of reactor. Moreover, benzene conversions with no coke generation than ones with coke generation at similar experimental conditions are relatively low. Investigating benzene conversions from thermal cracking at different experimental conditions in a particular configured packed bed reactor shows increasing benzene conversions and coke generation (if occurring) at increasing reactor temperatures. Whereas, benzene conversions from SPG/FGM partial combustion at different reactor temperatures are nearly similar. Varying the H₂ and CH₄ contents of SPG and FGM influenced the benzene conversion significantly. Benzene conversion from thermal cracking in presence of CO₂ reforming medium than in presence of steam or both steam and CO₂ reforming media was relatively higher. Characterization of coke generated during benzene conversions from thermal cracking at different reactor temperatures indicates its increasing condensed structure at increasing reactor temperature. The generated coke is predicted accurately by developed kinetic model. The developed CFD model simulates the benzene conversions and concentrations of outlet gas components form SPG/FGMs partial combustion well. Computed benzene concentration profiles show gradual reductions in benzene concentrations across the reactor except the minute sharp reductions by the points of FGMs/SPG partial combustion