MUD THICKENING IN SRI CLARIFIERS

摘要

The throughput capacity of a clarifier is based on its ability to perform the two-fold functions of clarifying the juice, and thickening and removing the settled mud at a rate to match the factory throughput. The high throughput rates and low residence times that are achievable with the new generation clarifier, have focussed attention on the need to improve the settling and thickening characteristics of the mud, and its handling and transport properties in the mud thickening zone. As juice rates increase, the residence time of the mud must reduce to maintain satisfactory mud levels in the mud zone. This places more emphasis on the ability of the mud scraper designs to thicken the mud to an acceptable consistency and to transport the mud towards the centre mud cone in a significantly reduced time. The investigations into the factors affecting mud thickening have been conducted using pilot tests and two factory clarifiers of similar size. One of the clarifiers was a standard design and the other was a modified design incorporating the new generation technology. There appears to be a maximum mud density that can be achieved in the clarifier and this is achieved within 30 minutes. The final density is not dependent on either the depth of mud or the addition rate of fiocculant. The results obtained with a settling tube were similar to those obtained directly from the clarifiers. Tests with the settling tube indicated that final mud densities will be lower if the rakes extend the full depth of the mud layer and into the juice. The largest increase in mud density was achieved when a maximum number of rakes was used provided all rakes remained below the level of the mud-juice interface. The speed of the rakes did not affect the final mud density.