Foaming and non-foaming systems have been distilled in a sieve plate column. It has been confirmed that the plate efficiency of the foaming (surface tension positive) system is higher than that of the non-foaming (surface tension negative) system under foam inducing conditions. At high vapour rates and low weir heights a liquid phase dispersed 'spray regime' is encountered. Under these conditions the surface tension positive system gives a lower plate performance than the negative system. It is thought that the difference is caused by the higher proportion of small drops present in the dispersion for the negative system. For both types of system the performance in the spray regime is found to increase with decrease in the absolute value of surface tension. This is in qualitative agreement with an analogy based on spray atomisation, and consistent with the effect of surface tension on drop size. A model is proposed for the spray regime which assumes a distribution of drop sizes projected upwards at initial velocities which are a function of drop size. The model has been used to deduce values for the drop size distribution parameters from the measured dispersion density profiles. It is found that the deduced mean drop size increases with surface tension. The dependence is similar to that predicted by the spray analogy. Values of plate performance in the spray regime estimated from the deduced drop size distribution with the help of the model are close to the measured values of plate performance.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:623016 |
| Date | January 1968 |
| Creators | Fane, Anthony Gordon |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/15791 |
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