ABSTRACT

Although column flotation cells have been extensively studied in the literature, the hydrodynamic impact of orifice properties has not been adequately addressed yet. This paper initially investigates the effect of sparger orifice diameter on hydrodynamic behavior of coal particles in a pilot-scale column flotation. The metallurgical responses (i.e., ash, yield and recovery contents) were evaluated for four different sparger orifice sizes including 1, 3, 5, and 7 mm under constant operating conditions by experimental measurements associated with computational fluid dynamics (CFD) simulations. A numerical model of a two-phase air-water flow in the column (3 m × 0.5 m) was chosen and the turbulence patterns inside the collection zone and at the pulp-froth interface were simulated by employing the Volume-Of-Fluid (VOF) model. The experimental results indicated that desiring concentrated product i.e., ash content of 8.8% and yield of 57.2% could be obtained using the 3 mm orifice size. Simulation results revealed that as the sparger orifice size decreased to 1 mm, the reduced carrying capacity of the bubbly regime led to the poor flotation performance. In contrast, the turbulence condition intensified as the sparger orifice size was increased to 7 mm. Another negative consequence of the 7 mm orifice was attributed to the exceeded entrainment of high ash fines due to a bubble swarm mechanism. The 7 mm sparger orifice diameter showed a concentrate of 17.1% ash and 12.5% yield. Finally, according to the obtained results in this work and literature studies, several necessary highlights were suggested for future works in this scope.

摘要

尽管在文献中对柱式浮选池进行了广泛的研究，但孔口特性的流体动力学影响尚未得到充分解决。本文初步研究了鼓泡器孔口直径对中试规模柱浮选中煤颗粒流体动力学行为的影响。在恒定操作条件下，通过与计算流体动力学 (CFD) 模拟相关的实验测量，对四种不同的喷头孔尺寸（包括 1、3、5 和 7 毫米）的冶金响应（即，灰分、产量和回收率）进行了评估。选择了柱中两相空气-水流的数值模型 (3 m × 0.5 m)，并通过使用体积流体 (Volume-Of-Fluid ( VOF) 模型。实验结果表明，使用3 mm 的孔口尺寸可以得到所需的浓缩产品，即灰分含量为8.8%，产率为57.2%。模拟结果表明，随着分布器孔口尺寸减小到 1 mm，气泡区的承载能力降低，导致浮选性能变差。相比之下，随着分布器孔口尺寸增加到 7 毫米，湍流条件加剧。7 毫米孔口的另一个负面后果是由于气泡群机制导致的高灰分夹带量过多。7 毫米的喷头孔直径显示出 17.1% 的灰分和 12.5% 的产率。最后，根据本工作和文献研究中获得的结果，为该范围内的未来工作提出了几个必要的亮点。