Appendices to Group II Research Note, ICI Central Instrument Research Lab.

S F Bush
Also as Mond Division Report, J D Birchall, 9th March 1970.

Summary

The fundamentals of crysallisation are briefly reviewed. Industrial crystallisation operations are usually characterised (a) by the presence of impurities in the solutions, liquors etc. from which crystals grow; (b) the use of large vessels etc. in which the conditions are non-uniform and largely unknown and (c) unsteady conditions of operation due to changes in parts of the plant before and after the crystallisation unit, stoppages due to scale formation, failures etc. Impurity effects can be of paramount importance, but often these can be characterised by laboratory experiments so that the effect on product quality of changes in plant conditions can be understood qualitatively.

The most profitable research would be in refining laboratory characterisation techniques, in the development of instruments for the on-line monitoring of important crystallisation variables, in particular supersaturation and in eliminating factors that cause fluctuation in operating conditions, particularly scale formation.

Research in the general field of crystallisation has a number of functions. The solution of specific plant problems as they arise is difficult unless there exists background knowledge of the theory and of techniques and experience of past problems. Such knowledge and experience is especially valuable when new processes fail to perform as planned. If crysallisation is properly regarded as phase transformation in its broadest sense, then research in the field is vital because of much common theory in aspects as apparently remote as the crystalisation of salt, the strength of metals, the formation of bone, the properties of plastics, rain-making, ceramics, strong materials etc.