DRYING AND CONVERSION ANALYSIS OF BIOMASS BY A DEM-CFD COUPLING APPROACH

Biomass materials as a type of renewable energy sources have attracted many attention nowadays to decrease fossil fuel usage due to ecological and economical benefits. The main objective of this PhD thesis is studying the drying and conversion of biomass materials with employing a hybrid four-way DEM-CFD coupling approach in which considers the solid particulates as discrete elements coupled via heat, mass and momentum transfer to the surrounding gas as continuous phase. Where a comprehensive three-dimensional numerical model is developed and applied to investigate the complex phenomena taking place during biomass drying and conversion in a reactor. That is referred to take into account the physical and chemical processes as heat-up, drying, pyrolysis, gasification and combustion including the essential heterogeneous and homogeneous reactions which is considered as an interactive solid-gas multiphase system. In the proposed model, the motion and thermodynamic state of the particles are involved with employing the relevant governing equations. Where the conductive and radiative heat transfer between particles as well as convective heat transfer between particles and gas phase are taken into account. In addition, some interfaces are extended for coupling the solid particles and the gas phase to consider the interactions in between. At first, the importance of biomass resources is discussed and then the mathematical modeling employed in the PhD thesis is explained thoroughly. To apply the model, four different cases are assessed where two chapters discuss the drying behavior of biomass particles in two different situations. Afterwards, the motion of solid particles in a bubbling fluidized bed is examined. Finally, the conversion of wood materials in a bubbling fluidized bed is determined.