Centrifugal washing optimisation by real-time colour measurement

Removal of colour is the main purpose of the refining process in sugar factories and refineries. However, colour measurements from the laboratory are not available until the sugar has reached the silo, so control of the process is based on historical values and statistical process control instead of current product status. Automatic real-time colour measurement with the in-line ColourQ 800 colorimeter by Neltec Denmark has been tested on wet sugar from second-strike centrifugals and compared with laboratory measurements, The test has focused on the accuracy of the methods and on the influence of real-time measurements on process control. A special investigation was made to reduce the loss of sugar due to superfluous washing in the centrifugals. The instrument showed a high level of accuracy. Furthermore, loss of sugar due to unnecessary melting of good sugar in the centrifugals was reduced by at least 250 tonnes per year, leading to a very favourable payback on the investment.