Novel approaches to ultrasonic particle sizing in suspensions with uncertain properties, and to the design of ultrasonic spectrometers

Abstract

Ultrasonic spectrometry is now recognised as an effective approach to monitoring chemical processes online, an important application being measurement of the particle size distribution (PSD) in suspensions. The ultrasonic method is based on adaptively fitting a model of wave propagation to measured attenuation. This requires seven physical properties for each of the dispersed and continuous phases, some of which may be unknown and difficult to measure. The sensitivity of the model to these physical parameters is established, with a view to using approximate values for them. This leads to novel approach to PSD estimation; it is based on a combination of "guessing" some parameters and fitting more than two when running the model adaptively. The current wave propagation model uses as its viscosity input the value for water; it breaks down at high solids concentration. Various viscosity models have been applied in the wave propagation model to better simulate local viscosity in the vicinity of suspended particles. The current particle sizing algorithm is relatively slow. Improvements in the algorithm speed have been achieved by the use of a two step fitting procedure which permits rapid adaption of the model and thereby much faster PSD estimation. Conventional ultrasonic spectrometers generate high excitation pulses of 50- 200 V. A novel ultrasonic spectrometer for highly attenuating media has been designed which operates at low transmitted voltage and over a wide frequency bandwidth whilst preserving workable signal to noise ratios (SNRs). The new spectrometer is based on pseudo random binary sequences (PRBSs).EThOS - Electronic Theses Online ServiceGBUnited Kingdo