Ultrasound spectroscopy and electrical resistance tomography for online characterisation of concentrated emulsions in crossflow membrane emulsifications

This work presents a multiple sensor system by combining ultrasound spectroscopy and electrical resistance tomography for online characterisation of concentrated crossflow membrane emulsifications. The sensing system essentially integrates an ultrasound sensor and a tomography sensor to provide real time measurement of size distribution and concentration of droplets for emulsion processing alongside the capability of visualising the mixing quality between droplet particles and the continuous phase.

The process of crossflow membrane emulsification due to its highly controlled droplet size distribution was selected in this investigation as a convenient first test case. The intention was to move onto processes which are faster and with a more variable droplet size where control is required. The multiple sensor system was slightly stretched from online as it was developed to be more independent in order to have the functionality of plug-in.

Results have shown that the sensing system is well capable of capturing the real time key information in terms of the processing stage determined by the concentration of the droplets, size distribution and mixing quality which are often used to describe the quality of the emulsion products. Therefore, from the aspects of online monitoring and control of emulsion processes and product quality, this system has provided a useful means to realise such challenges.

The main limitations of this system are thought to be that, with ultrasound spectroscopy eight physical properties of the dispersed and continuous phases are needed for the inversion of the ultrasound spectra to particle size distribution; and, with the electrical resistance tomography, the quantification for mixing quality needed to be improved.