Design and implementation of a very short retention time filtrate clarifier

Abstract

Filtrate, which accounts for almost 15 to 20% of the mixed juice produced in a raw sugar factory, is usually recirculated, which is detrimental to the process. This can lead to: increased sugar inversion and reduction in both sugar quality and clarifier performance. Previous attempts on filtrate clarification have shown limitations for its implementation due to the long residence times of the clarifiers, complex operations and low quality of clarified filtrate. A filtrate clarification pilot plant using a very short residence time clarifier (10 minutes) was designed and tested during the 2012 Louisiana sugarcane harvesting season. Louisiana Low Turbulence technology (LLT) that has been successfully used for mixed juice clarification was utilized. The results show that when clarified filtrate and the clear juice of the main factory clarifiers were mixed in a proportion of 1:5, no significant difference was found between the clarified juice and this mixture. Additionally, the suspended solids removal achieved in the filtrate clarifier was as high as 95% and the color of the clarified filtrate was lower than the clear juice color. Finally, these results suggest that the unit operated satisfactorily and a full scale implementation of this technology can avoid the undesirable recirculation of filtrate by using a simple process, with high throughput and small footprint.