Investigation of waste to energy techniques with computational fluid dynamics study of gasification

Abstract

Fossil fuels have been sitting at the bottom of the energy pyramid due to the destructive effect they have on the environment. Arising from the ashes, renewable energy is gaining global attention with a plan of replacing fossil fuels in the future. Waste, and in particularly municipal solid waste, marked itself as an effective energy source. In this context, three waste-to-energy (WtE) processes are meticulously discussed: incineration, gasification, and pyrolysis. With attention being drawn towards gasification, a computational study of the bubbling fluidized bed was conducted via ANSYS Fluent, a commercial computational fluid dynamics (CFD) software. The multiphase gas-solid flow was simulated using the Eulerian model based on the kinetic theory of granular flow. Qualitative patterns were extracted. The main drag model used was the Syamlal-O’Brien and was compared with the Gidaspow drag model, showing little to no differences. Other parameters were also varied, including the gas inlet velocity whose change proved that small velocities prohibit the flow from initiating bubble formation due to their unmatured character. Density alternations showed that fluidizations at higher densities is more stable.