Evaluating the suitability of two mud level sensing technologies for juice clarifiers : final report 2020/201

Abstract

Mud level measurement using sensors in juice clarifiers is a challenge for Australian sugar mills. Measurement of the mud/juice interface is typically by manual means and the operator must visually locate the position of the interface through sight glass windows and make adjustments to either mixed juice feed rates or mud filtration rates to keep the interface at a ‘safe’ operating level. High level excursions can cause carry-over of mud particles into the clarified juice (with subsequent impact on evaporation and crystallisation). If the interface is too low, then rat-holing of juice to mud can occur (impacting mud filtration and increasing filtrate recycle). Sugar mill juice clarifiers present a harsh environment for in-situ interface monitoring owing to the high temperature (100℃), varying populations of suspended floc particles, relatively fine density profiles and rotating equipment inside the vessel.

This report evaluates the performance of two different mud level measuring technologies on SRI type clarifiers: 1) an ultrasonic in-situ transducer; and 2) an externally mounted system using visual monitoring of the interface through the sight glasses. Recommendations for the viability of both these technologies and the outcomes of a cost/benefit analysis are presented.

During the 2020 crushing season both systems demonstrated their ability to identify and continuously track juice clarifier mud levels. The advantages of a visual point monitoring system (VPMS) include external installation with real-time remote visual monitoring of mud level through sight glasses, a potentially lower overall cost of installation and the ability to monitor both suspended (dispersed) solid level as well as the compacted mud level. The VPMS is also showing potential, with further software development, to provide a measure of average size of the mud flocs. The ultrasonic transducer is situated inside a clarifier vessel and offers the benefit of a simple robust installation with analogue outputs to use in a SCADA system.