Utilisation of on-line colour instruments to optimise the operation of centrifugals

The development of instruments to measure on-line sugar colour has provided operators with real-time data to control sugar colour, sugar purity and detect process errors. The optimisation of centrifugal parameters to maximise sugar yield and quality, while minimising molasses loss, has traditionally relied on the skill and diligence of operational staff. Feedback from the factory laboratory to the fugal operator as to the product quality is generally provided after a delay of several hours. If there has been a deviation from the target range, then adjustments of the centrifugal or other process parameters will be necessary. The time delay from product sampling to reporting and subsequent process correction can result in significant lost opportunity in terms of product quality, recovery and process efficiency. The on-line sugar-colour instruments provide the tools for operators to improve the efficiency and stability of the centrifugal process. The devices are robust and can measure the colour of wet and dry sugar in conveying systems, as well as the sugar being produced inside both batch and continuous centrifugals. The application of the instruments measuring the colour of sugar inside the centrifugal has provided operators with previously unavailable information to optimise the centrifugal parameters. In the case of the batch centrifugal an additional sensor to indicate the purging rate throughout each cycle along with the monitoring of colour allows the optimisation of centrifugal work in terms of more efficient spray water addition and optimising the spinning time at high speed. For the continuous centrifugal, the water and steam rate and its distribution between the feed system and screen can also be optimised by measuring the colour of sugar as it travels across the fugal screen. This presentation reviews some experiences of sugar factories utilising these instruments to improve sugar quality and recovery, as well as provide significant capital, energy and labour savings.