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Jun 2021

Monitoring of multiphase pharmaceutical processes using electrical resistance tomography

GlaxoSmithKline (GSK) & Imperial College London have joined forces to investigate the use of non-intrusive electrical tomography measurements to interrogate mixing processes in batch vessels. With ITS being at the heart of the technology and experiment, we are reviewing the original work for the benefit of existing and prospective customers.

The goal of this investigation was to ‘evaluate the applicability of ERT to the chemical development of active pharmaceutical ingredients (APIs) in stirred tanks’. They ultimately aimed to describe the application of the technology to solid –liquid and liquid –liquid systems in stirred tanks and how the subsequent data could be used to assess the legitimacy of related computational fluid dynamics (CFD) models and correlations.

For the purpose of the experiment, a linear ERT sensor with an array of 16 measurement electrodes was used. The probe was made of glass which was embedded with silver enamel electrodes to further enhance chemical compatibility. Furthermore, the sensor was connected ITS’ very own P2+ instrument which was hooked up to a computer system in order to provide real-time, accurate data, representing the electrical conductivity distribution on a vertical plane through the reactor.

In the solid-liquid tests, it was concluded that ERT can indeed be used to monitor the crystallisation of paracetamol, therefore indicating that its use could be applied to further crystallisation process’ that GSK wish to conduct. In the subsequent experiment, it was demonstrated that the use of ERT was able to monitor phase dispersion and separation for liquid – liquid processes.

In summary, both experiments were deemed to be a success and provided a strong insight into the application of the technology to multiphase systems using an ERT sensor within pharmaceutical process’. The focus of the suspension of sand particles, as well as the crystallisation within paracetamol showed strong correlation when compared with visual observation and alternative on-line measurement techniques as well as CFD modelling. This further provides evidence that the ERT system developed by ITS can provide integral and reliable real-time data within multiphase flow processing aligned to the pharmaceutical industry.

Effect of impeller speed on suspension of paracetamol


Reference: Ricard, F., Brechtelsbauer, C., Xu, X. Y. & Lawrence, C. J. Monitoring of Multiphase Pharmaceutical Processes Using Electrical Resistance Tomography. Chem. Eng. Res. Des. 83, 794–805 (2005).

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