CFD simulation of the laboratory-scale anaerobic digester to study the impacts of impeller geometric and operational parameters on its performance

This research numerically surveys the effects of several main parameters of an agitated anaerobic digester on mixing rate and power input. The numerical simulation is handled applying the finite volume method (FVM), and it is validated with the available experimental data. The results indicate that doubling the blade length enhances the mixing rate by 39.9% and makes the power input enhance 13.5 times; increasing the number of blades (from 4 to 6) improves the mixing rate by 12.5% and makes the power input grow 1.4 times, and decreasing the blade tilt angle from 45° to 30° causes the mixing rate to drop by 14% and decreases the power input 1.8 times. Furthermore, the observations show that the mixing rate and power input are adversely influenced by the wastewater concentration. At last, the most effective impeller design, among 144 cases investigated, is found out and suggested.