Coming soon to a factory near you - the new Tongaat Hulett continuous evaporating crystallizer

A new design continuous evaporating crystallizer (pan) has been developed by Tongaat Hulett, and has been installed at their Xinavane factory in Mozambique. The crystallizer is unlike any previous continuous crystallizer design in that it is of a circular (round) construction with two internal floating calandrias stacked one above the other in a common vapor space. Although the calandrias share this common vapor space, each can be boiled independently of the other. This allows for 'on the run' cleaning of the pan, thus alleviating an inherent problem of high grade (A massecuite) continuous crystallization which requires regular shut down and boiling-out to remove encrustation above the heating surface and/or in the tubes. The design of the evaporating crystallizer is such that it is possible to convert an existing batch pan into a continuous vessel or to install a continuous crystallizer on the footprint of an existing batch evaporating crystallizer. This paper describes the design of the crystallizer and lists its advantages and reasons for the development of the design.