An improved model of pol extraction for mills and diffusers

Extraction models for mills and diffusers were developed to determine the brix (total dissolved solids) extraction of the process. Pol extraction was calculated from the brix extraction based on arbitrary constants or empirical relationships. The Australian sugar industry introduced a term “purity ratio” in the early 1980s and has since been using the term in extraction models to predict the pol extraction of the milling process. Here, an improved model of pol extraction is presented which replaces the purity ratio concept. The new model can be used in two different approaches, based on which brix extraction model (imbibition coefficient or crushing factor-mixing efficiency) is used. When using imbibition coefficient, an analogous term “purity coefficient” is used to determine the pol extraction of the milling unit. When using the crushing factor-mixing efficiency model for the bagasse mills, the model equations have been extended to determine the pol in delivery bagasse. The model is presented and, using factory experimental data, the results of purity coefficient of individual milling units are given. The same data is used to compare, for the bagasse mills, the measured pol and predicted pol in delivery bagasse of individual milling units.