4I-3 Ultrasonic Monitoring of Heterogeneous Chemical Reactions

This paper describes a novel approach to analyse the complex interactions between chemical particles and the vessel wall of a reactor vessel using Finite Element (FE) modeling. A 4-layer model has been developed comprising a liquid load medium and a glass-oil-glass combination corresponding to the jacketed reactor. The model has been experimentally validated with excellent correlation achieved. The excitation function was derived from Hertz's theory and used as the model stimulus corresponding to particles striking the inner glass wall. The FE simulations predict: an increase in energy with an increase in either particle size or concentration; a lowering of principal frequency components with increasing particle size; and a low pass filtering effect introduced by the reactor vessel itself. The most significant outcome is that the frequency range of interest is below 150 kHz with the principal components between 10-60 kHz. This has been confirmed experimentally using ultrasonic transducers, in both resonant and non-resonant modes of operation. Consequently, both stacked composite and 1-3 connectivity composite transducers have been designed to match the desired spectral range. This work has resulted in successful discrimination of both particle size and concentration, with a detection limit of 0.1 g/dm
³