Biomass gasification in Circulating fluidized beds (CFB) is one of the most promisingrnconversion processes in meeting future ecologically compatible and sustainable energy demand,rnbased on a combination of flexibility, efficiency, and environmental acceptability. Widespreadrnindustrial use of CFB technology in coal and biomass combustion and gasification depends onrnimproved control of the fluidization process that demands a better understanding of fluidized bedrnhydrodynamics. However, its application to CFB systems is limited due to the highrncomputational requirements for understanding complex fluid flow behavior. The effect ofrndifferent operating parameters on the hydrodynamic behavior of a two-phase gas-solid CFBrnbiomass gasifier were studied in this thesis work systematically using computational fluidrndynamics (CFD) software FLUENT.rnBoth 2-D and 3-D computational fluid dynamics (CFD) model based on Eulerian-Eulerianrnapproach coupled with granular kinetic theory is developed to simulate the hydrodynamics andrnflow structures of the CFB under different operating conditions. A parametric analysis isrnperformed to comprehensively investigate the influences of particle properties (Bagasse, sandrnand its sizes), operating parameters (gas velocity and solid circulation rate) and gasifierrngeometries (inlet structure/position).rnThe dynamic characteristics obtained from CFD simulation have been comparerned with the some similar conditions experimental data obtained from open literatures and inrngeneral a good agreement has been observed. Eulerian-Eulerian granular multiphase flow modelrnapproach is capable of predicting the core-annulus structure in CFB. The lower region of thernCFB riser is denser than the upper-dilute region. Back-mixing behavior or accumulation ofrnparticles near the wall has been perfectly exist in the CFB. Increasing solids flux slows down thernflow development, but increasing superficial gas velocity makes the flow development faster.rnSuperficial gas velocity has a strong influence on the axial solids velocity. The volume fractionrnof big particles is lower in the upper. This hydrodynamics model provides the powerfulrntheoretical basis for next steps on CFB designs. This study proposes that the operatingrnparameters (solid circulation rate and gas velocity) and solid inlet geometry may be the criticalrnconsideration in order to reduce non-uniform distribution of gas and solid in CFB gasifier.