Sedimentation(Settling) in Sugar Processing Industry

Sedimentation is the process where solid substances such as sand, stones, organic materials etcetera are carried to the bottom of the liquid in question (water, sugar juice, milk and so on) where they accumulate and lead to the formation of the solid layer. There are three important methods of sedimentation. They include; centrifugal sedimentation, electrostatic precipitation, and gravity sedimentation or settling out. This article discusses a type of the gravity sedimentation, which is the separation of materials by the use of the earth gravity. It separates dust, emulsions, and suspension. It is often employed in the partial separation of homogeneous systems. Gravity sedimentation involves placing a feed that composed of substances (dust, suspension or emulsion) to be separated in a vessel or a tank, and the separated materials are given appropriate time to settle at the bottom. The industrial settlers are grouped into three classes, that is, settlers for; suspension, emulsion, and dust.

This post focuses on suspension or slurry settlers. Suspension settlers can either be continuous or intermittent in their functions. Continuous suspension settler is the mostly used in industries, For instance, a continuous flow-rake settler type. If you have been in sugar processing industry, the flow –rake type is referred to as the clarifier in the juice treatment section. The feed slurry (sugar juice) enters at the center valve of the vessel (clarifier), and the clarified sugar juice leaves at another valve as shown in the diagram. The solid substances accumulate at the tank bottom. The rake usually revolves at 0.02 to 0.05 per minute, thereby relaxes the solid materials (sediment) and pushes them towards the discharge valve located in the center of the vessel bottom. 

Continuous flow-rake settler Type