Study On The Mixing And Mass Transfer Of Collection Zone In A Packed Flotation Column

Packed flotation column is a new kind of flotation device with lots ofadvantages, such as: easy operation, lower energy consumption and withoutstirring device. It is widely used in many engineering field, especially for itsgood separating effect of the fine paticles in recent years in the field ofmineral flotation and sewage treatment.This article aims to provide a quantitative basis as well as theoreticaltools for the design, scaleup and operating conditions for packed flotationcolumn. In this study, packed flotation column is Φ104×1500mm, partlyfilled with350Y-type structured packings. My research is basic on thestudies in our group with the conclusions of phosphate flotation process. Inthis article, the mixing condition, gas holdup and mass transfer character-istics of collection zone in a packed flotation column were discussed in thedomain of experimental phenomenon and theoretical mechanism.The particle size of the tracer response method was used for theexperiments about mixing conditions of the collection zone. In order tomeasure the gas holdup and liquid volumetric mass transfer coefficient, thelevel rises method and dynamic ventilation method were applied. Differentcharacteristics was considered according to method of each experiment, theinfluence parameters, such as: superficial gas velocity，the ratio of collectionzone height to diameter and the superficial liquid flow rate and the amountof froth agent were studied in those three experiments.(1) For the residence time distribution experiments: with the increase ofsuperficial gas velocity，the average particle residence time in collectionzone increase, dimensionless variance increases, the particles flow approachto the stirring mixing; with the ratio of height to diameter increase，theaverage particle residence time increases，the dimensionless variance toreduce，the flow of solid particles is closer to plug flow. The wash flow rate has little effect on particle residence time. The following relationship waseestablished by the experimental correlation:(2) For the experiment of gas holdup: with the increase of the intakeair，the gas holdup growth is slowing; the size of the gas holdup decreaseswith the amount of froth agent is now inceased at the amount of froth agentbetween200ml/h to300ml/h; gas holdup decrease with the increase of theratio of height to diameter in collection zone, but when the the ratio reachesto7.1, the gas holdup decrease closer to flat. Simulation training and resultscan predict the experimental data very well. And it’s found that the artificialneural network built in this experiment has a good preidictive simulationcapability，the relative error is less than±5%.(3) For the mass transfer experiments: with the increases of superficialgas velocity Jg, the liquid volumetric mass transfer coefficient kLa increases.But the ratio of height to diameter has little impact on the liquid volumetricmass transfer corfficient kLa. This article also associates the mass transferdiffusion with the flotation kinetics and found that the correlation coefficientcan be concluded by the following expression:...