Three Dimensional Flow Visualization in a Mimic Anaerobic Digester to Obtain the Impact of Temperature on Biogas Production by Star CCM+

Abstract Production of biogas from organic solid wastes by anaerobic digestion method is not a new idea. But still we are facing a lot of obstacles to optimize the digestion technique. In such situation, computational fluid dynamics (CFD) can be very useful to understand the approaches by which we can enhance the digestion process for maximum biogas production. As we know that, the increment of the reactor temperature can enhance biogas production, so we have aimed to obtain the optimum temperature range for maximum biogas production by means of CFD simulation. In this paper, we have develop a three dimensional CFD model to predict the impact of temperature on biogas production by understanding the vector filed pattern of velocity of the sludge particles. We have carried out the simulation process with commercial software Star CCM+. Large enough cell count and domain size was taken into account to achieve an acceptable simulation. Additionally, appropriate initial and boundary conditions were imposed before starting the simulation process. We have utilized standard k-? turbulent model for the computational process. Fluid flow characteristics were presented by means of vector filed contour of velocity of the sludge particles and the vector field variation of velocity were determined with the increment of the reactor temperature. Here, we have presented five vector field contours at 298K, 308K, 318K, 328K and 333K. The temperature range was set within mesophilic and thermophilic condition (298K to 333K). Besides, we have also determined the scalar field distribution of both turbulent kinetic energy and turbulent dissipation rate through our simulation. Although we have found very low turbulent flow in the digester, but such turbulent flow was very momentous to obtain a consistent growth of velocity with temperature which can be very helpful to understand the favourable temperature condition to accelerate biogas production before implant real anaerobic digester. Keywords: Anaerobic digestion, computational fluid dynamics (CFD), turbulence models, vector field pattern, residuals