Characterisation and issues with the use of a conductivity meter to monitor the level of liquid in a cane diffuser bed

Abstract

The extraction of sucrose in a cane diffuser depends mainly on the percolation rate, and its optimisation requires the monitoring and control of the liquid holdup with the cane bed. However, most conventional methods that measure liquid levels are not suitable for this application. Operators control the observed liquid level through diffusers’ sight glasses, adjusting the spray position according to visual inspections. The method is inefficient, and a more accurate and reliable measurement process should be implemented towards maximising the sucrose extraction. This article proposes a novel methodology that uses conductance measurements as indicators of the liquid level in cane beds. Conductance, observed liquid level and flow rate variations were analysed under several conditions, such as steady and unsteady states. The effects of the main variables on the observed liquid level and their mathematical relationship were assessed for the validation of the measurements, and experimental tests were conducted on a BMA cane diffuser at Maidstone factory in South Africa. The results are reproducible and show conductance can qualitatively characterise a flooded cane bed.