“旋流”对浮选柱气含率及气泡尺寸的影响

Influence of “Swirling Flow” on Gas Hold up and Bubble Size in Flotation Column

为研究"旋流"对浮选柱气含率及气泡尺寸的影响,通过改变中矿循环量及进气量等操作参数,以空气-水两相体系为对象,利用体积法和摄像法,对径向进气、切向进气及切向倒锥加强旋流结构进气等3种结构的浮选柱内的平均气含率及气泡尺寸的分布情况进行了试验。结果表明:无论是否采用旋流结构,浮选柱内的平均气含率均随表观气速的增大而增大,随循环压力的增大而增大,随中矿循环量的减小而增加。旋流结构的存在会使浮选柱对操作条件的变化更敏感,压力等操作条件的变化会引起气含率的显著波动。与无旋结构相比,有旋结构的变工况适应性较差;"旋流"作用显著影响浮选柱内气泡尺寸的分布:一方面能增加浮选柱内微小气泡(0.1~2 mm)的数量,微小气泡占比较无旋结构平均高出约20个百分点;另一方面也会造成气泡聚并,生成大尺度的帽状气泡,聚并效应随充气量的增大而增强。大气泡的脉动、破碎会加剧静态分选区的湍流程度,不利于粗颗粒矿物的静态分选。

To study the effect of swirling flow on gas holdup and bubble size in flotation column,by changing the operat-ing parameters as circulation quantity of middling and air volume,and with air-water two-phase system as the object,experi-ments on average gas holdup and bubble size distribution of flotation column with three kinds structures of radial inlet,tangen-tial inlet and tangential cone-swirl strengthened structure inlet are carried out by the method of volume method and photography method. Results showed：average gas holdup in flotation column increased with increase of gas velocity and cycling pressure, and increased with drease of circulating volume of middling. With presence of swirling structure,pressure and other operation parameters had greater influence on gas holdup in flotation column. Compared with the ＂non-swirling flow＂,＂Swirling Flow＂has poor adaptability in variable working conditions.＂Swirling Flow＂ greatly influenced bubble size in flotation columns：＂Swirling Flow＂ increased the number of tiny bubbles （0. 1～2 mm） in flotation column,with the proportion of micro-bubbles about 20 percentage points higher than that in the non-swirling structure. Large cap-shaped bubbles would be formed at the same time,due to the bubble coalescence by ＂Swirling Flow＂. The coalescence effect is enhanced with the increase of gas charge. The fluctuation and fragmentation of large bubbles would enhance the turbulence in static separation zone,which was not beneficial to static separation of coarse mineral materials.