New developments in acoustic chemometric prediction of particle size distribution??the problem is the solution?

Abstract

We present a new prototype acoustic chemometric approach for prediction of powder particle size distributions, intended for in-line implementation. The standard basic solutions demand that calibration be carried out on representative, ‘non-segregated’ reference powder samples. However, as practical powder flow with no segregation is extremely difficult to achieve with the precision needed for calibration, there will always be a significant uncertainty in the reference values relative to what is actually measured. The problem is flow segregation. In order to solve this problem, we have designed a completely new acoustic chemometric approach, which by way of contrast forces the flowing powder mass to segregate as much as possible by various mechanical means. The new approach measures the acoustic signals from an integrated series of segregated, part-sample characteristics. The calibration X-data matrix now becomes a three-way matrix, which demands a three-way calibration solution to ‘unscramble’ the latent information in the maximally segregated powder sample. Thus the problem is now the solution. Our earlier forays into this matter, which were based on two-way calibrations, have all been limited by a severe ‘particle size ratio’ bracket outside which destructive self-damping has effectively negated practical, useful accuracy and precision. The new approach allows a much greater range of contrasting particle sizes. Our first-generation results achieved by using three-way PLS-R as well as the standard two-way calibrations show that it is more precise than all earlier attempts and can be used for many-component mixtures without extensive further modifications. We also look at the feasibility of quantifying for prediction of in-line particle size distributions in an industrial environment. Copyright © 2000 John Wiley & Sons, Ltd.