Towards further improvement in clarifier performance: evaluating juice and mud residence times

As designs of short-residence-time clarifiers continue to be improved, it is appropriate to evaluate their performance and seek opportunities for further improvement. Lithium chloride tracer tests were carried out on the SRI New Generation (NG) design 11 m diameter clarifier at Kalamia Mill. The residence time (RT) distributions and the mean RTs for the clarified juice and mud phases were determined. One of the challenges in these measurements is to make adjustments to the mean RTs determined from the Li tracer tests to allow for variations in the clarifier mud level and the clarifier feed rate to provide mean RTs for operation at standard conditions. As expected, mud level has a large effect on the mean RT of both the juice and mud. The importance of operating at close to the bottom window was highlighted in order to achieve effective separation of mud particles in the feed zone into the clarifier and to avoid excessively long residence times for mud which could increase sucrose inversion losses. A similar tracer test evaluation and analysis is planned for an installation of the High Performance New Generation (HPNG) clarifier design that includes an improved mud separation system at the entry of feed to the clarifier.