Preliminary evaluation of modifications to the FCB continuous evaporating crystallizers at Eston and Sezela

Five Fives Cail Babcock (FCB) continuous evaporating crystallizers have been installed in South Africa. A first crystallizer of 64 m3, with plate calandria type, for C-sugar was installed in 1976 in the Maidstone sugar factory of the Tongaat-Hulett group. In the Illovo Group, a first CCTR (Cuite Continue with Tubes with Round body) evaporating crystallizer of 104 m3 for C-sugar was installed in 1980 in the Gledhow sugar factory, and in 1981 two CCTR crystallizers of 90 m3 each for B- and C-sugar were installed in the Illovo sugar factory (sugar factory transferred to Eston in 1995) and one CCTR crystallizer of 90 m3 for C-sugar in the Sezela sugar factory. These crystallizers were originally designed for the beet sugar industry, where viscosity is much less than in the cane sugar industry. The initial performance of the crystallizers, in terms of throughput and exhaustion, was poor on low grade massecuites due to poor circulation.

In 1995, the Eston crystallizer was installed in series with a Tongaat Hulett Sugar (THS) vertical tube type continuous evaporating crystallizer and the performance was evaluated. It was found that the capacity of the THS type crystallizer with an equivalent heating surface was twice that of the FCB crystallizer. Modifications were carried out on the FCB crystallizer to double its capacity and improved its performance. The Sezela crystallizer was modified in a similar manner and then evaluated against the Australian Sugar Research Institute continuous evaporating crystallizer, on lower grade massecuites. This paper discusses the modifications and improved results achieved at both the Eston and Sezela sugar factories.