Principle,Development And Application Of Flotation Column Producing High Bubble Surface Area Flux In Lab Scale

Mineral industry is currently facing challenges associated with ecnomics, energy, enviroment and resource (exhaustion of rich and easily-processing reserves) issues, so it is becoming more and more essential to exploit new methods and develop new equipment to process progressively lower grade and fmer-dissemination ores. Column flotation is regarded as one of most effective technological innovations to improve separation efficiency and enhance the comprehensive utilization of resource, which has been applied in the flotation of coal and various ores on an industrial scale since 1980's. This thesis summarised history of column flotation and predicted future development trends of column flotation.It was one of main objectives to characterize, understand and control the interaction of particles and bubbles. Based on theoretical analysis of bubble-particle interaction in column flotation, new concept of column producing high bubble surface area flux (HBSAF) was put forward. A laboratory flotation column (100-mm diameter by 2.3 m tall) and column flotation test system (TUB-ARR) have been designed, built, installed and used in order to extend limited knowledge of column flotation and treat progressively lower grade and finer-dissemination ore and coal. High bubble surface area flux column designed can regulate size and number of bubbles as well as other parameters conveniently according to properties of material to be processed.In this work, video microscopy, which couples a CCD camera to an objective microscopic lens, has been exploited to study velocity, size, distribution and shape of bubbles. The simple and reliable method to measure bubble size and bubble surface area flux has been found, which was in good agreement with theoretical calculation. The model of superficial bubble surface rate with gas hold-up has been established.Bubble generation techniques are know-how for column flotation. Great effort has been made to design wokable and durable aerators to overcome problems such as excessive bubble diameters, resistant to wear and areator plugging. Very high superficial bubble surface rate can be achieved by adapting multi-spargers, which are made from porous tube with very fine pore size (10-30 micrometer) and high density of holes (6-7x105holes/m2). It is certain that the column designed can produce very fine bubbles (ca 0.75 mm) at high superficial gas velocity (4x10-2m/s). One of effective solutions to produce very fine bubble, which is essential to particle-bubble collision and subsequent collection of hydrophobic particles, has been innovated. Experimental results showed that multi-sparger can also reduce bubble coalescence and distances of some floes of bubble-particle, therefore, reduce the possibility of detachment and are suitable for the flotation of both coarse and fine particles.Effects of column structure parameters and operation parameters on the flotation performance have beeninvestigated. Besides positions of bubble generators and pore size of sparger, some other parameters such as gas holdup, gas rate, gas pressure, static pressure of fluid and surface tension of pulp are very important to the formation of bubble. Because this column flotation test system is easy to control the number and size of bubbles, operation parameters and structure parameters and pulp level and maintain a proper thickness of the froth layer, satisfactory processing results have been achieved for flotation of low rank coal and fine-dissemination copper sulfide.Compared with mechanical agitation flotation cell, the new column flotation test system improved the separation efficiency of both low rank fat coal and ,low rank gas coal greatly. Carbon recovery of concentrate increased 1-2 percentage and ash content of concentrate decreased 1.1 percentage, ash discharge increasing by 5 percentage. On the condition of run of mine coal ash content 25-30 %, two stages of column flotation (one rough and one clean circuit) obtained clean coal with ash content only 3.66% (combustible recovery 85-90%) and reject with ash conte...