title: CFD simulation of mixing for high-solids anaerobic digestion.
abstract: A computational fluid dynamics (CFD) model that simulates mechanical mixing for high-solids anaerobic digestion was developed. Numerical simulations of mixing manure slurry which exhibits non-Newtonian pseudo-plastic fluid behavior were performed for six designs: (i) one helical ribbon impeller; (ii) one anchor impeller; (iii) one curtain-type impeller; (iv) three counterflow (CF-2) impellers; (v) two modified high solidity (MHS 3/39°) impellers; and (vi) two pitched blade turbine impellers. The CFD model was validated against measurements for mixing a Herschel-Bulkley fluid by ribbon and anchor impellers. Based on mixing time with respect to mixing energy level, three impeller types (ribbon, CF-2, and MHS 3/39°) stand out when agitating highly viscous fluids, of these mixing with two MHS 3/39° impellers requires the lowest power input to homogenize the manure slurry. A comparison of digestion material demonstrates that the mixing energy varies with manure type and total solids concentration to obtain a given mixing time. Moreover, an in-depth discussion about the CFD strategy, the influences of flow regime and impeller type on mixing characteristics, and the intrinsic relation between mixing and flow field is included.
authors.affiliation: Philadelphia Mixing Solutions Ltd., Palmyra, Pennsylvania 17078, USA. bwu@philamixers.com
authors.forename: Binxin
authors.initials: B
authors.lastname: Wu
mesh_terms: D000693:Anaerobiosis; D003198:Computer Simulation; D005285:Fermentation; D008372:Manure / Q000382:microbiology*; D012037:Refuse Disposal / Q000379:methods*; D013997:Time Factors
chemical_list: D008372:Manure