Abstract Flotation is a density separation process which is influenced by physico-chemical interaction between a particle and a bubble. In biotechnology, it finds application in the solid-liquid separation of biomass. The process mechanism depends on the formation of stable microorganism-bubble-complexes by collision and adsorption. The difference in density of these complexes and the surrounding liquid medium causes them to rise to the liquid surface, where a foam develops. This microorganism enriched foam can then be removed. An economical comparison of the separation technologies centrifugation, cross-flow-filtration and flotation showed, that flotation is a financially and energetically interesting alternative process step for the harvest of microorganisms. In this work separation results with a model microorganism S. cerevisiae are presented. Experiments were conducted batch-wise in a 6L-laboratory dissolved air flotation setup, where bubble generation classically results from expanding air from supersaturated medium. Goal was the optimization of the flotation rate and the energy efficiency of the flotation process by adaptation of operational parameters, such as gas- and recycle flow rate and saturation pressure. Flotation models show proportional dependency between the flotation rate and the bubble size and bubble surface area flow rate. Therefore, the effect of operational parameters, such as saturation pressure, recycle and gas flow rate, on the bubble size and surface area flow rate was analyzed. The positive effect of an increasing bubble surface area was possible with increasing gas flow rate, recycle flow rate and saturation pressure. Decreasing bubble sizes were measured for increasing recycle flow rate and saturation pressure, meanwhile the contrary was the case with an increasing gas flow rate. Evaluation of the flotation rate and flotation energy efficiency showed, increasing the recycle flow rate and the saturation pressure both improved the flotation rate, but had low effect on the energy efficiency. Increasing the gas flow rate improved both flotation rate and energy efficiency. It is the most interesting operational parameter for enhancing the process efficacy.

中文翻译：

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浮选作为生物技术中替代分离工艺的潜力，重点关注成本和能源效率

摘要 浮选是受颗粒与气泡之间物理化学作用影响的密度分离过程。在生物技术中，它在生物质的固液分离中得到应用。该过程机制取决于通过碰撞和吸附形成稳定的微生物-气泡-复合物。这些复合物和周围液体介质的密度差异导致它们上升到液体表面，在那里形成泡沫。然后可以去除这种富含微生物的泡沫。离心、错流过滤和浮选分离技术的经济比较表明，浮选是一种在经济和能源上有趣的微生物收获替代工艺步骤。在这项工作中，展示了模型微生物酿酒酵母的分离结果。实验是在 6L 实验室溶气气浮装置中分批进行的，其中气泡的产生通常是由过饱和介质中的空气膨胀引起的。目标是通过调整操作参数（例如气体和循环流量以及饱和压力）来优化浮选速率和浮选过程的能源效率。浮选模型显示浮选率与气泡大小和气泡表面积流速之间的比例相关性。因此，分析了操作参数，如饱和压力、循环和气体流速，对气泡尺寸和表面积流速的影响。随着气体流速、循环流速和饱和压力的增加，增加气泡表面积的积极影响是可能的。随着循环流速和饱和压力的增加，测量气泡尺寸的减小，而气体流速的增加则相反。浮选率和浮选能效评价表明，提高循环流量和饱和压力均能提高浮选率，但对能效影响不大。增加气体流速可以提高浮选率和能源效率。它是提高过程效率的最有趣的操作参数。但对能源效率影响不大。增加气体流速可以提高浮选率和能源效率。它是提高过程效率的最有趣的操作参数。但对能源效率影响不大。增加气体流速可以提高浮选率和能源效率。它是提高过程效率的最有趣的操作参数。