Optimizing Anaerobic Digester Agitation throu...

Optimizing Anaerobic Digester Agitation through CFD Analysis

Author Name : Siddharth, V. K. Pandey, Paveen Kumar Maurya

DOI: https://doi.org/10.56025/IJARESM.2025.1304250967

ABSTRACT Anaerobic digestion, a widely adopted process for energy conservation and wastewater sludge stabilization, relies on solids retention time (SRT) to determine digester volume and biogas production. The design of the digester’s geometry and agitation system is crucial for meeting the required SRT. Early studies on digester agitation were limited in providing detailed insights, often relying on tracers or biogas production as indicators. However, computational fluid dynamics (CFD) now allows for detailed simulations of sludge movement within digesters. This research simulates full-scale anaerobic digesters (approximately 2000 m³) with recirculation pumps to evaluate the impact of factors like the diameter-to-height ratio, floor slope, pump number, and recirculation flow rate on performance. The study aims to define the velocity field, assess mixing efficiency, and conduct an energy and economic analysis. Results show that a diameter-to-height ratio over one negatively affects agitation, while a sloped floor improves mixing, with tank slenderness being more influential. Proper design parameters for the stirring system, especially the recirculation flow rate, are critical for achieving optimal mixing and avoiding dead zones. In suboptimal designs, increasing the number of pumps may enhance agitation, but full mixing may still be unattainable due to the initial design flaws.