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Abstract

The process of column crystallisation was initially developed for the
small scale production of ultra-pure organic compounds. The original
units were small bench scale systems producing only a few grams of
purified product. The work presented in the thesis is the scale up
of a Schildknecht column to give a unit capable of producing several
kilograms of purified product, continuously. A 100 millimetre
diameter column crystalliser was designed and construeted, the layout
being based upon results from the 50 millimetre diameter column. The
equipment assembled is capable of processing a range of aqueous and
organic, binary, eutectic mixtures. The column is able to operate
batchwise or continuously.

Systems investigated on the 100 millimetre column include~desalination
and ethanol concentration. Waste effluent recovery and heavy water
regeneration were evaluated on the 50 millimetre column. Cperation
of the columns is optimised for the above systems, the parameters
investigated being, speed of rotation of the transport conveyor,
crystal production rate, product removal rate and reflux ratio. In
order to elucidate the dominant factors in the purification process,
an extractive washing model is utilised to calculate values of the
diffusion and mass transfer groups. The important factors controlling
the separation efficiency of the columns are the axial diffusion of
impurity and the mass transfer between the adhering and free liquids
around the crystal phase. The variation in these two parameters for
each column is discussed. An attempt at simplifying the mathematical
model is presented. The aim is to develop an equation capable of
predicting key parameters rapidly, that is, product purity and column
length. Also the effects of speed of rotation of the helical transfer
unit on mean crystal size is reported.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QD Chemistry
Departments:	School of Science & Technology School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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