Optimization and experimental study of variable frequency intermittent stirring strategy for anaerobic digestion based on CFD

Abstract

The stirring strategy has a significant effect on the efficiency of anaerobic digestion (AD). In this study, the suspension velocity of multi-layer blade particles was characterized based on CFD simulation, and a variable frequency intermittent stirring strategy was proposed to study the stirring effect and mixing energy consumption. Firstly, the fermentation cycle was divided into three parts, and three stirring speeds and mixing times were set for each part to carry out an orthogonal combination test. Taking methane production and mixing energy consumption as optimization indexes, a net energy output equation was established to optimize the new stirring strategy. The results showed that the new variable frequency intermittent stirring strategy could effectively improve digestion efficiency. This provides a theoretical basis for setting a stirring strategy in a biogas project.