An overview of electrical tomographic measurements in pharmaceutical and related application areas

Abstract

Tomographic measurement techniques offer the opportunity to quantify the degree of homogeneity of particulate suspensions and other multiphase mixtures. Electrical resistance tomography is a relatively simple and inexpensive technique for measuring the distribution of electrical conductivity within multiphase systems. This can provide pertinent information about the physical form, the chemical composition, or the general status of manufacturing. In this contribution, we present recent applications of this technology to processes in pharmaceutical and related application areas. Examples include on-line measurement of solids distribution in stirred tanks and crystallizers, monitoring the performance of an industrial pressure filter, and flow profile and velocity measurements in a physical model of a catalytic reactor.

Techniques for visualization of cavern boundaries in opaque industrial mixing systems

“…This is a likely artifact of the reduced sensitivity of the technique near the vessel axis as the density of the electric field lines decrease 4 as well as due to limitations of the linear back projection reconstruction method used. 5 If the gradient of the normalized conductivity, i.e., dr*/ dr*, is plotted vs. r*, a minimum is observed at r* ¼ 0.4 and 0.55 for the 80 rpm and 162 rpm data, respectively (Figure 6b), which could perhaps be argued as a reasonable method of locating the cavern boundary. However, the corresponding values of r* at these values of r* are 1.8 and 2.0, respectively, which, even allowing for smoothing of the data due to resolution artifacts, leaves a large amount of conductive material outside the cavern.…”

“…ERT has been applied previously to image macromixing within large stirred vessels containing low viscosity fluids 4 and in pharma applications to obtain flow behavior and solids distribution in multiphase complex systems. 5 Labscale ERT experiments on caverns using xanthan gum have been performed recently and compared with CFD simulations. 6 In recent work, PEPI has been applied by geologists to determine dispersion in porous rock samples.…”

Measuring Flow Velocity and Uniformity in a Model Batch Digester Using Electrical Resistance Tomography

“…These limitations have been studied and quantifi ed (Dyakowski et al, 2000;Beck et al, 1997;Williams and Beck, 1995). Despite them, ERT has been successfully used to study fl ow in a wide range of applications (Dyakowski et al, 2000;Bolton and Primrose, 2005;Tapp et al, 2003;York, 2001;Xie et al, 1995) including liquor fl ow in scale-model continuous digesters by Vlaev and Bennington, (2004;.…”

Polymerization Online Monitoring

“…Recent applications of this technology to pharmaceutical processes are presented in [146]. It has been used for online measurement of solids distribution in stirred tanks and crystallizers, monitoring the performance of an industrial pressure filter, and the determination of the flow profile and velocity distribution in a catalytic reactor [146,147].…”

“…It has been used for online measurement of solids distribution in stirred tanks and crystallizers, monitoring the performance of an industrial pressure filter, and the determination of the flow profile and velocity distribution in a catalytic reactor [146,147]. The measurement of gas and solids distribution in a 30-L laboratory vessel [148] has been demonstrated as well as the cavern formation in the mixing of opaque xanthan gum solutions [149].…”