研究不同单球颗粒在立方搅拌槽内的层流运动

发布时间：2018-06-20 19:27

本文选题：搅拌槽 + 固-液悬浮　；参考：《北京化工大学》2015年硕士论文

【摘要】：搅拌操作在化工、食品、石油、造纸、冶金和水处理诸多行业中被广泛应用,其中固体颗粒在液相中的悬浮操作是搅拌操作中非常常见的类型。固液悬浮操作是将颗粒分散到液相中,借助搅拌器的作用,形成固液混合物或悬浮液,搅拌的作用使悬浮液剧烈湍动,增强了传质,有利于化学反应的进行。本实验是在尺寸为0.22m×0.22m×0.22m的方形槽和直径为0.11m的圆盘组成的搅拌体系中,以甘油,硅油,玻璃珠,塑料珠和氮化硅小球为实验物料,研究了在固-液两相搅拌槽内固体颗粒在不同温度,圆盘不同离底高度C,不同颗粒密度及尺寸dp,液体不同粘度等条件下固体颗粒离底临界悬浮状态下的的搅拌桨转速Njs,以及固体颗粒悬浮过程中Z方向上的速度变化规律。实验结果表明：C/L增大,临界悬浮转速会相应增大,同样,颗粒密度越大,液体粘度越小,离底临界悬浮转速越大。而固体颗粒的上升速度也与上述条件有关,我们分别试验了不同密度的玻璃珠(ρ=2450 kg·m-3),塑料颗粒(ρ=1400 kg·m-3)及氮化硅颗粒(ρ=3260 kg·m-3)在硅油中离底临界悬浮转速下的上升速度,结果表明z方向的上升速度经历了一个先增大后减小的过程,大约在搅拌桨离底高度的中间速度达到最大。而同一材质的小球随着粒径的增大,最大上升速度随之减小。
[Abstract]:Stirring operations are widely used in chemical, food, petroleum, papermaking, metallurgical and water treatment industries, among which the suspension of solid particles in liquid phase is a very common type in stirring operations. Solid-liquid suspension operation is to disperse particles into liquid phase and form solid-liquid mixtures or suspensions with the aid of agitators. The effect of stirring makes the suspensions turbulent, enhances mass transfer, and is conducive to the development of chemical reactions. In this experiment, glycerin, silicone oil, glass beads, plastic beads and silicon nitride pellets were used as experimental materials in a mixing system consisting of a square slot of 0.22m 脳 0.22m in size and a disc of 0.11m in diameter. The solid particles in a solid-liquid two-phase stirred tank at different temperatures were studied. The rotating speed Njs of the impeller in the critical suspension state of solid particles under the condition of different bottom height C, different particle density and size DP, liquid viscosity and so on, and the variation of velocity in Z direction in the course of solid particle suspension. The experimental results show that the critical suspension speed increases with the increase of C / L, and the higher the particle density, the smaller the viscosity of the liquid and the higher the critical suspension speed from the bottom. The rising rate of solid particles is also related to the above conditions. The rise rates of glass beads with different density (蟻 ~ (2 450) kg m ~ (-3), plastic particles (蟻 ~ (1 400) kg m ~ (-3) and silicon nitride particles (蟻 ~ (3 260 kg m ~ (-3) in the bottom suspension of silicon oil were tested. The results show that the rising velocity in the z direction goes through a process of first increasing and then decreasing, and the velocity reaches the maximum at the middle of the bottom height of the impeller. However, with the increase of particle size, the maximum rising speed of the ball of the same material decreases.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ027.2

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