Flooding limit in countercurrent gas–liquid structured packed beds—Prediction from a linear stability analysis of an Eulerian two-fluid model

Modeling and Simulations of NOx and SO2 Seawater Scrubbing in Packed-Bed Columns for Marine Applications

Seawater scrubbing of nitrogen oxides and sulfur oxide from marine emissions was simulated in packed-bed columns exposed to static inclination and heaving/oscillating motions. Fourth generation random packings (Raschig super-Rings) while providing much smaller pressure drop than traditional Pall-Rings ensure comparable absorption efficiency for the pollutants. Complete removal of SO2 was predicted over the tested pressure range with absorption efficiency indifferent to scrubber inclination or heaving/oscillating motions. In contrast, NOx and CO2 absorptions are negatively impacted for inclined seawater scrubbers. Removal efficiency is not lowered significantly owing to larger scrubber pressure and because diffusion of N2O4 into the liquid phase is associated with a rapid pseudo first-order reaction. The asymmetrical oscillating motion of the scrubber degrades the removal performance which exhibits wavy patterns close to the steady-state solution of the average inclination angle. NO and CO2 absorption performance waves are moving toward a steady-state solution of vertical scrubber when the asymmetry of the two inclined positions of the scrubber downgrades. Symmetric oscillation and heaving motion led to performance disturbance waves around a steady-state solution of the vertical scrubber which are determined by the parameters of angular/heaving motion.

Hydrodynamics and Reaction Performances of Multiphase Reactors for Marine Applications – A Review

Hydrodynamics and (catalytic & non-catalytic) reaction [high-pressure hydrodesulfurization; Fischer-Tropsch synthesis; CO2-monoethanolamine (MEA) absorption; simultaneous CO2 and H2S absorption in MEA; CO2 thermal desorption, enzymatic CO2 hydration] performances of trickle-bed and packed-bed column reactors subjected to static inclination, rolling (symmetrical/asymmetrical externally-generated reactor oscillations) and heaving motions were analyzed via detailed dynamic 3-D models which couple the macroscopic volume-averaged momentum, mass, energy and species balance equations in the liquid/gas phases with diffusion/chemical reaction inside the catalyst particles, enzyme washcoat or liquid film near the gas-liquid interface. Axial symmetry breakdown once the packed bed systems become inclined inflicts noticeable reductions of the reactor (or scrubber) performances. Only the performance of Fischer-Tropsch synthesis in the presence of water-gas shift reaction increases slightly with the increase of trickle-bed reactor inclination because of facile uptake of reactants in the key reactions from the gas phase while a fraction of valuable CO can be forwarded in water gas-shift reaction. For most of the reactions examined, the reactor performance is negatively impacted in asymmetric oscillating multiphase reactors with Fischer-Tropsch synthesis as an exception owing to the presence of water-gas shift reaction the performance of which is slightly improved. This performance deterioration/enhancement is maximal for the reactor moving between vertical and an inclined position when the time-dependent performance waves develop around the steady-state solution of the mid-inclination angle. The oscillatory reactor performance moves towards the steady-state solution of the vertical state when the asymmetry between the two inclined positions dwindles. Symmetric oscillating and heaving trickle-bed and packed-bed column reactors generate an oscillatory performance around the steady-state solution of vertical state which is affected by the amplitude and period of the angular and heaving motions of the vessel.