Acoustic chemometrics for on-line monitoring and end-point determination of fluidised bed drying

Abstract

An emerging process analytical technology (PAT) technique, acoustic chemometrics, was applied for monitoring of heated fluidised bed drying process. The feasibility of quantitative on-line monitoring of the drying progress and end-point determination of silica gel dried in a heated fluidised bed was investigated. Silica gel was used owing to its high water adsorption property and stability to heat. Acoustic signals were acquired using four accelerometers mounted at different locations on the wall of the fluidised bed. The accelerometer located close to the base was the best based results from this study. Prediction models validated with independent acoustic data (test set validation) were developed using partial least square regression, PLS-R. Some data pre-preprocessing techniques were applied to improve the developed prediction model. The final prediction results were satisfactory for monitoring of the drying progress and end point determination. The prediction results based on the independent data indicated a slope=0.97, correlation coefficient, R2=0.99 and the root mean square error of prediction was 1.71 water %, within the range 0–35.69 water % of sampled reference. It was concluded that the results from this feasibility study show that acoustic chemometrics is a viable on-line technique for monitoring the drying progress and for determining the end-point during drying of particulate matter. This on-line monitoring technique for the drying process developed in this study can be applied in many relevant industries in order to improve the overall economics of material drying by optimising fluidised bed drying technology using this decisive end-point determination approach.