CFD Modeling of Two-Stage Parallel Plate Sedimentation Centrifuge for Microalgae Dewatering

Abstract

As one of the most fast growing species on earth, microalgae provides great potential to satisfy the ever increasing demand in food, energy and material in a sustainable way. The focus for this thesis work is on one of the most important bottle neck of microalgae harvest process: microalgae dewatering, by CFD modeling of the flow and sedimentation separation in Evodos SPT centrifuge. Various microalgae dewatering technologies have been reviewed and evaluated. Compare to traditional conical disk centrifuge Evodos SPT centrifuge provides 10% to 20% energy consumption, removing up to 95% extracellular water and other benefits i.e. mechanical simplicity and process flexibility etc. In the model, the fluid dynamic behaviors of multiphase flow has been considered. In this research a complete 3D CFD model of the Evodos centrifuge consisting of five sub components have been built. The particle behavior for the centrifugation separation is based on DPM (Discrete Phase Model) in Fluent. The result of the 3D CFD model gives a clear overview of the pathline, flow pattern and pressure profile inside the centrifuge as well as separation efficiency on particle sizes. The model has been validated through visual result from algae separation test runs, theoretical equations and starch test run measurements. A test and sample taking with starch solution has also been carried out on Evodos site in Breda. This thesis work laid a good foundation for future studies in the CFD modeling of Evodos SPT centrifuge and similar machines. The future focus should be on optimizing the geometry of the parallel plates, impeller chamber for separation efficiency; understanding the effects and impacts of operation conditions and further develop the multiphase model.