A concurrent flotation column for fly ash cleaning and materials separation: Its design and separation system development.

摘要

In order to widely reuse fly ash, which was previously landfilled, the unburned carbons must be removed to below 1% in cleaned fly ash. This research is aimed at developing a highly efficiency and effective flotation process and equipment for fly ash cleaning and materials' separation.;The froth flotation process is an approximate first-order reaction. Hence, a concurrent flotation column, which can closely simulate a plug flow reactor, has a high potential to resolve the problems, such as high energy consumption and low separation efficiency, existing in commercial flotation machines. Based on the above considerations, a concurrent flotation column has been developed by combining a static mixer and froth separator.;Experimental results have shown that the carbon removal under a concurrent flotation column with one static mixer is 22% below that of the Denver Cell. Mechanism analysis showed that froth rupture might occur along a static mixer. The froth formation and breakage in a static mixer are a reversible process. Therefore, a perfect carbon removal could not be achieved using only one static mixer.;Using dual static mixers, the carbon removal was elevated slightly higher than that of the Denver Cell. The concurrent flotation column shows an obviously higher throughput. Moreover, the energy consumption of a concurrent flotation column is only 20% of the Denver Cell.;The size of air bubbles produced from a static mixer is significantly correlated to the surface tension, air flowrate and channel number of packings. Bubble size increases with surface tension, but decreases with the increase of air flowrate and channel number.;In conclusion, the concurrent flotation column has proved to be a highly effective and efficient flotation device. Its extremely low energy cost and high unit throughput would significantly reduce the operation cost of fly ash cleaning, and potentially extend its applications in other industries.