COMPUTATIONAL STUDIES TO INVESTIGATE THE FUEL FEEDING POINT IN FLUIDIZED BED REACTOR

As the world is concerned with the dependence of the transportation fuel on fossil fuels and its impact on greenhouse gas emissions, all regions in the world are driven to deploy bio-oil as the alternative transportation fuel. Pyrolysis, a process in which the organic materials undergo thermal degradation in the absence of oxygen, has shown great potential to be competitive with the conventional petroleum production in terms of economy and quality. With the advancement of computational fluid dynamics (CFD), it allows detailed analysis and optimization of a pyrolysis process to be carried out easily and thus indirectly minimizes all the expensive and time-consuming experiment. As different biomass species show varied physical and chemical properties, feeding point of the biomass in the fluidized bed reactor (FBR) requires careful consideration. This is because the feeding point will affect the conversion efficiency of the biomass, the heat transfer of the biomass particles and also the residence time in the reactor. In this paper, the influence of the fuel feeding point on the products’ yield is investigated in a pyrolysis FBR using ANSYS Fluent 14.0 simulation. The biomass feeding point will be focused on 3 different zones – the freeboard, the splash zone and the dense bed. The reactor’s dimension, boundary conditions and initial conditions are similar as described in the selected benchmark paper by Xue et al. (2012). Simulation result is compared with the result reported in the benchmark paper for validation. With the validated model, the effect of feeding point was studied and it is observed that for pure cellulose feedstock the optimum feeding point is at the dense bed zone and for red oak the optimum feeding point is at the splash zone. Overall, this study provides a fundamental understanding of the influence of the fuel feeding point on the products yield and reactor temperature distribution during the pyrolysis process in a FBR.