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首页> 外文期刊>Journal Of The South African Institute Of Mining & Metallurgy >Investigation of flow regime transition in a column flotation cell using CFD
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Investigation of flow regime transition in a column flotation cell using CFD

机译：CFD柱浮选细胞流动制度转换的研究

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Flotation columns are normally operated at optimal superficial gas velocities to maintain bubbly flow conditions. However, with increasing superficial gas velocity, loss of bubbly flow may occur with adverse effects on column performance. It is therefore important to identify the maximum superficial gas velocity above which loss of bubbly flow occurs. The maximum superficial gas velocity is usually obtained from a gas holdup versus superficial gas velocity plot in which the linear portion of the graph represents bubbly flow while deviation from the linear relationship indicates a change from the bubbly flow to the churn-turbulent regime. However, this method is difficult to use when the transition from bubbly flow to churn-turbulent flow is gradual, as happens in the presence of frothers. We present two alternative methods in which the flow regime in the column is distinguished by means of radial gas holdup profiles and gas holdup versus time graphs obtained from CFD simulations. Bubbly flow was characterized by saddle-shaped profiles with three distinct peaks, or saddle-shaped profiles with two near-wall peaks and a central minimum, or flat profiles with intermediate features between saddle and parabolic gas holdup profiles. The transition regime was gradual and characterized by flat to parabolic gas holdup profiles that become steeper with increasing superficial gas velocity. The churn-turbulent flow was distinguished by steep parabolic radial gas holdup profiles. Gas holdup versus time graphs were also used to define flow regimes with a constant gas holdup indicating bubbly flow, while wide gas holdup variations indicate churn-turbulent flow.
机译：浮选柱通常在最佳的浅表气体速度下操作以保持起泡的流动条件。然而，随着浅表的浅表气体速度的增加，可能对柱性能的不利影响可能发生泡沫流失。因此，重要的是识别最大浅表气体速度，上述最大浅表气体速度发生损失。最大浅表气体速度通常由气体保持与浅表气体速度图获得，其中图的线性部分表示起泡流动，同时与线性关系的偏差表示从气泡流向湍流状态的变化。然而，当从起泡流到流失湍流的过渡时，这种方法难以使用，因为在奶嘴的存在下发生。我们提出了两种替代方法，其中柱中的流动制度通过径向气体储存轮廓和来自CFD模拟获得的气体堆叠与时间图来区分。使用具有三个不同峰的鞍形曲线或具有两个近壁峰和中央最小峰的鞍形曲线或具有中间特征的鞍形曲线，或者在鞍座和抛物线气体储气型材之间具有中间特征的鞍形曲线，或鞍形轮廓的特征在于鞍形曲线。过渡方案逐渐逐渐，其特征在于抛物线气体储能曲线，其变得较为陡峭的浅表气体速度。通过陡峭的抛物线径向气体储能型材区分搅拌湍流。气体保持与时间图相对于时间图来定义具有指示气泡流量的恒定气体堆积的流动状态，而宽气体持有变化则表示流失湍流。

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