Unit of Environmental Engineering, University of Innsbruck, Innsbruck, Austria.
Department of Environmental, Process, and Energy Engineering, Management Center Innsbruck, Innsbruck, Austria.
Bioprocess Biosyst Eng. 2021 Dec;44(12):2455-2468. doi: 10.1007/s00449-021-02617-4. Epub 2021 Jul 21.
Sludge recirculation mixing in anaerobic digesters is essential for the stable operation of the digestion process. While often neglected, the configuration of the sludge inlet has a substantial influence on the efficiency of the mixing process. The fluid is either injected directly into the enclosed fluid domain or splashes onto the free surface of the slurry flow. In this paper, the aim was to investigate the effect of the inlet configuration by means of computational fluid dynamics-using ANSYS Fluent. Single-phase and multi-phase models are applied for a submerged and splashing inlet, respectively. To reduce the high computational demand, we also develop surrogate single-phase models for the splashing inlet. The digester mixing is analyzed by comparing velocity contours, velocity profiles, mixing time and dead volume. The non-Newtonian characteristics of the sludge is considered, and a [Formula: see text] model is employed for obtaining turbulence closure. Our method is validated by means of a previous study on the same geometry. Applying a submerged inlet configuration, the resulting dead volume in the tank is estimated around 80 times lower than for the case of a splashing inlet. Additionally, by emulating the multi-phase model for splashing inlet configurations with a single-phase one, the simulation clock time reduced to 15%.
在厌氧消化池中，污泥再循环混合对于消化过程的稳定运行至关重要。尽管常常被忽视，但污泥进口的配置对混合过程的效率有很大影响。流体要么直接注入封闭的流域，要么溅射到泥浆流的自由表面上。在本文中，我们旨在通过使用 ANSYS Fluent 的计算流体动力学来研究进口配置的影响。单相和多相模型分别用于浸没式和飞溅式进口。为了降低高计算需求，我们还为飞溅式进口开发了替代单相模型。通过比较速度轮廓、速度分布、混合时间和死区体积来分析消化器的混合情况。考虑了污泥的非牛顿特性，并采用[公式：见正文]模型获得了湍流封闭。我们的方法通过对同一几何形状的先前研究进行验证。采用浸没式进口配置，估计罐中的死区体积比飞溅式进口低约 80 倍。此外，通过使用单相模型模拟飞溅式进口配置的多相模型，可以将仿真时钟时间缩短到 15%。
