Statistical modelling of the clarification station

In Colombia the crushing season lasts all year round, through the dry seaso n and the rainy season, As a result, the mixed juice can throw up a wide va riation in solids content over the course of the campaign, rendering consis tency and control in the evaporation station more difficult. This leads to high lime and flocculant consumption, resulting in different levels of clar ification and colour. From January-August 1997 the clarification process was studied at Colombia' s "La Cabana" mill. Average rainfall figures for the first three quarters o f 1997 on the estates serving the mill were 136, 178 and 54 mm/month. In the first instance the process variables of each stage were used. It was found by multiple regression analysis that there exists a quadratic relati onship between the turbidity of clarified juice and the insoluble solids co ntent of the diluted juice, its colour, pH after liming, and flocculant dos age. Next, a study was carried out on the sedimentation rate in relation to the insoluble solids content of the diluted juice, the liming pH, floccula nt dosage and all the variables which according to Stoke's law could affect it. It was concluded that a linear dependency exists between insoluble sol ids content and flocculant dosage and sedimentation rate, while the relatio nship between liming pH and rate of sedimentation is quadratic. The relationships obtained for clarified juice turbidity and rare of sedime ntation according to the variables selected provide a useful prediction too l.