Evaluation of liquid hold-up in a rotating packed bed for high gravity fluid separation using process-synchronized gamma-ray computed tomography

A Rotating Packed Bed (RPB) is a compact and flexible fluid separation equipment, which utilizes a centrifugal forces to achieve enhanced mass and energy transfer between a liquid and a vapour phase, brought in contact within a porous rotating packing. In order to perform a reliable design and scale-up of RPBs, detailed knowledge about the hydrodynamics and flow mechanisms within the equipment is strongly required. However, due to the non-transparent solid casing, such insight cannot be generated by common analytics. In the present study, liquid hold-up and gas-liquid phase distribution are determined in a porous metal foam packing of 450 mm diameter installed in a pilot-scale RPB using a high-energetic gamma-ray computed tomography (CT). The CT system consists of an isotopic source Cs 137 and an in-house developed radiation detector comprising 320 scintillation detector elements operated in photon counting mode in order to detect each single gamma photon. In particular, the liquid hold-up distribution and the lateral spreading behaviour is visualized and analysed relative to the motion of the rotating packing applying conventional CT scanning and a time-averaged angular-resolved CT scanning procedure, respectively.