Advanced characterization with multimodal measurement techniques for process intensification in gas–liquid tubular reactors

In this work we investigate turbulent gas–liquid mixing and separation in a vertical pipeline equipped with Kenics Static Elements for process intensification applications in continuous operations. The investigation is based on Electrical Resistance Tomography, digital image analysis and pressure drop measurements to provide a comprehensive characterization of the two-phase system. The gas volume fraction distribution is calculated from the voltage difference measurement using two different reconstruction algorithms: the Sensitivity Conjugate Gradient and the Linear Back Projection. The Sensitivity Conjugate Gradient algorithm provides better resolution near the pipe wall and a clear detection of the asymmetric patterns typical of the helical elements. The bubble size distributions obtained from digital image analysis allow to assess the effectiveness of the static elements in providing mixing and separation, depending on their orientation. The spatial distributions of the gas phase measured by the optical and the tomographic techniques are adopted to obtain the average gas hold-up leading to similar results. Overall, the experimental data analysis demonstrates that optimal performance can be determined by balancing energy consumption and gas dispersion. The findings provide valuable insights for the design of in-line reactors where both efficient mixing and controlled separation are required.