Experimental and simulation study on the surface contact between biogas fermentation liquid and straw material based on hydraulic mixing.

Straw used for biogas fermentation raw materials is an important way to reduce the environmental pollution and utilize straw resource. Owing to waxy layer on the straw particles surface during the fermentation process, biogas production and pollutant removal rate is not high enough, restricting the further promotion. In order to achieve high-efficient fermentation and biogas production, new type biogas fermentation material liquid circulation fluidization scheme is proposed in this study. Based on hydraulic mixing, the raw straw surface loose flocculating organization is broken, the dense part is exposed, the surface waxy layer formed in the long time of fermentation is teared, so as to enhance surface contact effect between solid straw and liquid material, increase organic matter and bacteria in the slurry of biochemical reaction, then promote efficiency of anaerobic co-digestion. Through the comparison experiment of three 635.5 L anaerobic digesters, it's found that the high centralized pressure outlet scheme and the high distributed pressure outlet scheme increase the average daily gas production rate by 176% and 253%, the removal rate of total solid (TS) increase by 41% and 69%, and the removal rate of volatile solid (VS) increases by 51% and 71%, respectively, compared with the non-mixing scheme. • New type biogas fermentation circulation fluidization scheme is proposed. • Hydraulic mixing shear stress can remove straw particles surface spore structure. • Hydraulic mixing shear stress can tear surface wax layer. • Hydraulic mixing shear stress can improve anaerobic co-digestion efficiency. [ABSTRACT FROM AUTHOR]