ECT imaging and CFD simulation of different cyclic modulation strategies for the catalytic abatement of hazardous liquid pollutants in trickle-bed reactors

Aiming to accomplish stringent regulations for the secure disposal of hazardous compounds, trickle beds have been envisaged from a process intensification point of view to adhere to environmental guidelines. In this work, several experimental and computational runs were performed under reacting flow conditions and cyclic (flow rate) modulations for the mineralization of liquid pollutants through electrical capacitance tomography (ECT) and computational fluid dynamics (CFD) techniques, respectively. First, we have investigated the hydrodynamics of propagating liquid pulsations generated via ON–OFF liquid, ON–OFF gas, and gas/liquid alternating cyclic operations. Here, the liquid pulsation intensity generated in ON–OFF gas mode indicated a negligible dependence with respect to cycle frequency apart from being qualitatively analogous with respect to ON–OFF liquid mode. Second, the effect of oxidation temperature and the gas and liquid flow rates unveiled the gas/liquid alternating mode as being able to generate sizable liquid payloads interrupted by gas and liquid streams. Correspondingly, we found higher detoxification rates due to the periodic pulsations sustained down to the reactor outlet by conferring improved catalyst wetting efficiencies. Finally, two-dimensional mappings of different cross-sections allowed inferring by means of ECT and CFD how the liquid payloads were morphologically in disposition to preserve or dissipate their original structure.

► Various cyclic-based modes in TBR were investigated for liquid pollutant removal.
► ON–OFF liquid, ON–OFF gas, and gas/liquid alternating promoted TOC conversion.
► ECT flow patterns underlined the liquid pulsation intensity and cycle frequency.
► CFD mappings of interstitial flow replicated accordingly the ECT measurements.