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Keywords:

  • Flow visualization;
  • Separation columns;
  • Structured packings;
  • Tomographic techniques

Abstract

Design and optimization of separation units, e.g., distillation and absorption columns with flow distribution packings, require detailed knowledge about the internal flow conditions and their impact on the process behavior. This in turn calls for suitable measuring techniques, which can give a detailed insight into such devices, especially for studies on a laboratory and pilot scale. Traditional instrumentation, such as compartment-type liquid collectors installed below packings, or distributed temperature, pressure and conductivity probes, often falls too short if detailed knowledge on flow conditions is required. This concerns especially local liquid holdup, liquid maldistribution, liquid films thickness, wetting of the packing surface, or bubble size and droplet distribution at trays. Advanced imaging techniques, such as tomography, have found only marginal attention in investigations of separation columns with structured and modern dumped flow distribution packings, mostly due to limited spatial and temporal resolution but also due to prevailing technological problems encountered in such applications. In this study, the potentials and limits of some of the most recently emerged tomographic imaging modalities for multiphase flows have been investigated and reviewed, i.e., ultra-fast X-ray tomography, high-resolution gamma-ray tomography, wire-mesh sensor techniques, and X-ray microtomography with respect to a possible application in separation columns with flow distribution packings.