Tomography and Separation Technology

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Head of Group: Prof. Dr.-Ing. Wolfgang Arlt

Group Members:

CT Scanner

The research group focusses on X-ray computed tomography (CT) for investigations in process equipment for separation processes. The tomographic setup works similar to a medical CT scanner and allows non-invasive measurements of column internals. These measurements provide a better understanding of the phenomena inside separation equipment and can be used for the improvement of column internals such as structured and random packings.

The institute´s tomographic setup was specifically designed for process technology applications. It allows non-intrusive measurements of vertical objects such as columns, which are widely used in separation processes. The tomographic setup is mounted on a high precision gantry system which allows three dimensional CT scans of the objects. At this time the tomographic setup enables the worldwide fastest (1 frame per second) and highest resolution (80 µm) tomographic images of columns up to a diameter of 100 mm.

Distillation / absorption (gas-liquid)

Gas-liquid flows occur in separation processes like distillation and gas absorption. For these processes columns packed with structured or random packing materials play an important role. It was believed, that the liquid forms continuous, thin films on the packing surfaces. Tomographic measurements proved this assumption wrong. The current research objective is the optimization of structured packing materials to generate a higher wetted surface area per volume. This surface area has direct impact on the mass-transfer and therefore the efficiency in separation processes.

Three-phase distillation (gas-liquid-liquid)

DThe fluid dynamic behavior of two poorly miscible liquids and a gas phase in packed columns occurs in three-phase distillation. It is very complex, poorly understood and rarely described in literature. The frequently occurring negative influence of the additional liquid phase on the mass transfer between gas and liquid phase is only described empirically. Therefore the objective of this work is to determine the fluid dynamics in a three-phase system in order to build models for predictions of such systems.

Extraction (liquid-liquid)

Beside gas-liquid flows, liquid-liquid flows play an important role in separation technology. One poorly miscible phase is dispersed in a continuous phase inducing a flow regime called bubble flow. These flow regimes typically occur in liquid-liquid extraction processes. The tomographic setup enables determination of hydrodynamic parameters such as disperse phase hold-up, drop size distributions and phase interfaces between the two liquid phases. These parameters can be measured non-intrusively and locally inside packed sections. The research objective in this field is the understanding of coalescence phenomena induced by internals of extraction columns.

Chromatography (liquid-solid)

Injection of a X-ray attenuating tracer enables dynamic measurements of residence time distributions (RTD) in chromatographic columns. The RTDs can be obtained spatially resolved from the measured tomographic images. Beside RTDs it is possible to quantify porosity distributions of the packed bed and calculate HETP values for a separation problem. These parameters are included in a simulation model for the selection of stationary phases based on specific separation problems.