Department of Civil Engineering, University of Salerno, via Giovanni Paolo II, 132, 84084 Fisciano, Italy E-mail:
MEA S.R.L., Foro Buonaparte, 70, 20121, Milano, Italy.
Water Sci Technol. 2020 Apr;81(7):1406-1419. doi: 10.2166/wst.2020.248.
The anaerobic digestion (AD) process is influenced by a variety of operation parameters, such as sludge rheology, mixing, temperature, solid retention time (SRT), hydraulic retention time (HRT) and solids concentration. The optimum in the mixing lies somewhere between no-mixing and continuous mixing, as the lack or excessive mixing can lead to poor AD performance instead. A three-dimensional computational fluid dynamics steady/unsteady model, incorporating the rheological properties of the sludge, was developed and applied to quantify mixing in a full-scale anaerobic digester. Mechanical and gas mixing solutions were taken into account, keeping constant the daily energy consumption. Results, consisting of velocity magnitude and patterns, dead zone formation and turbulence levels were discussed. Compared to the mechanical mixing, gas mixing had lower percentage of dead zones (about 5% against 50%), larger maximum velocity (about 3 m/s against 1 m/s) as well as larger turbulent kinetic energy levels (0.24 m/s against 0.001 m/s).
厌氧消化（AD）过程受到多种操作参数的影响，例如污泥流变性、混合、温度、固体停留时间（SRT）、水力停留时间（HRT）和固体浓度。混合的最佳状态介于无混合和连续混合之间，因为缺乏或过度混合会导致 AD 性能不佳。开发了一个包含污泥流变性的三维计算流体动力学稳态/非稳态模型，并将其应用于量化全规模厌氧消化器中的混合。考虑了机械混合和气体混合解决方案，同时保持每日能耗不变。讨论了速度大小和模式、死区形成和湍流水平的结果。与机械混合相比，气体混合的死区比例更低（约 5%对 50%），最大速度更大（约 3 m/s 对 1 m/s），以及湍流动能水平更高（0.24 m/s 对 0.001 m/s）。
