The conversion of CO2 from the flue gas stream of marine engines on-board cargo ships via the catalytic cycloaddition to styrene oxide (SO) using fixed-bed reactors (FBRs) packed with silica-supported pyrrolidino­pyridinium iodide (SSPI) catalyst was studied. The hydrodynamics and performance of these FBRs exposed to tilting and rolling/heaving motions were explored via a Eulerian 3D unsteady state model with the aim of understanding their behavior under changes in sea state. In the case of permanent inclination of selected (large-diameter) FBRs, the secondary flow of liquid in circumferential and radial directions generated by gravity-driven migration of liquid is less important compared to the flow in axial direction and causes axial symmetry breaking only in the wall regions of the reactor. The performance of CO2 cycloaddition process increases slowly with inclination of FBR. CO2 conversion oscillations under externally induced sinusoidal heave motion (SHM) (with amplitude up to 0.2g and period up to 20 s) or sinusoidal angular motion (SAM) (with amplitude up to 15 deg and period up to 40 s) are maintained around the conversion of vertical reactor (SHM) or are slightly offset upward compared to the conversion of vertical reactor (SAM). The results show a little impact of forced SAM and SHM on the hydrodynamics of large-diameter FBRs. The reactor proposed for the conversion of CO2 into a value-added chemical (styrene carbonate) on-board a middle size cargo ship is much smaller than the offshore units suggested in the open literature for the capture of carbon via an absorption process.

The urgency of reducing flue gas pollution in maritime transport makes it necessary to take a holistic view of its sustainability and environmental impacts. Among the approaches to reducing ship exhaust emissions, marinized gas scrubbers, given their ability to be retrofitted to existing ships, are a central element in the tradeoff against the use of expensive low-sulfur fuels. However, compounding this issue, the priority of reducing greenhouse gas (GHG) emissions in the coming decades poses new challenges to emissions compliance. The use of exhaust gas cleaning systems to remove SO X , NO X , and particulate matter (PM) emissions will be enhanced in the short to medium term by GHG reductions. In this study, the different types of scrubbers for seaborne operation and the potential risks associated with their secondary emissions will be critically reviewed. In addition, NO X reduction systems and recent efforts to reduce CO 2 through onboard carbon capture systems or alternative fuel combustion will also be covered.

Mining practices, chiefly froth flotation, are being critically reassessed to replace their use of biohazardous chemical reagents in favor of biofriendly alternatives as a path toward green processes. In this regard, this study aimed at evaluating the interactions of peptides, as potential floatation collectors, with quartz using phage display and molecular dynamics (MD) simulations. Quartz-selective peptide sequences were initially identified by phage display at pH = 9 and further modeled by a robust simulation scheme combining classical MD, replica exchange MD, and steered MD calculations. Our residue-specific analyses of the peptides revealed that positively charged arginine and lysine residues were favorably attracted by the quartz surface at basic pH. The negatively charged residues at pH 9 (i.e., aspartic acid and glutamic acid) further showed affinity toward the quartz surface through electrostatic interactions with the positively charged surface-bound Na+ ions. The best-binding heptapeptide combinations, however, contained both positively and negatively charged residues in their composition. The flexibility of peptide chains was also shown to directly affect the adsorption behavior of the peptide. While attractive intrapeptide interactions were dominated by a weak peptide–quartz binding, the repulsive self-interactions in the peptides improved the binding propensity to the quartz surface. Our results showed that MD simulations are fully capable of revealing mechanistic details of peptide adsorption to inorganic surfaces and are an invaluable tool to accelerate the rational design of peptide sequences for mineral processing applications.

Hydrodynamics and mass transfer characteristics are analyzed in a bubble column subjected to simulated ship motions using a hexapod robot with six-degree-of-freedom motions. Wire-mesh sensors have been used for collecting local gas holdup and flow patterns under nonreactive conditions. Additionally, the electrical conductivity of the liquid phase during CO 2 uptake was extracted to determine hydroxide ion consumption rates as an indicator of mass transfer. The two-phase flow patterns in the bubble column operating under offshore conditions deviate significantly from the stationary ones due to the buoyancy-driven lateral migration of bubbles. The consumption rates of hydroxide ions during the chemical absorption of CO 2 revealed that the amplitude of oscillations imposed on the bubble column is the dominant factor for the mass transfer in moving columns. Contrarily, the effect of the oscillation frequency is negligible, which is attributed to bubble coalescence and bubble flow maldistribution in the bubble column subjected to rotational oscillations. Bubble-free zones are formed in the liquid phase because of the buoyancy effects in the column tilted from the vertical axis, while the frequency of the oscillations does not add any additional effects to the bubble kinematics. The latter is attributed to the low shear rates maintained over the range of frequencies simulating marine swells.

Marinized bubbling fluidized beds hold promise for reducing CO 2 , NO X , and SO X in ship exhaust gases, but their use at sea is hampered by a limited understanding of the influence of sea waves on hydrodynamics, heat transfer, and efficiency. To address this gap, this study used direct visualization techniques to investigate the solids mixing and hydrodynamics of bubbling fluidized beds under different gas distribution patterns in pseudo-2D vertical, inclined, and rolling beds. Digital Image Analysis (DIA) was used to determine the Lacey mixing index and the local void fraction, while Particle Image Velocimetry (PIV) was used to capture the particle velocity fields. Additionally, the effects of tilt angles and oscillation parameters of the nonvertical beds were compared with the conventional straight bubbling fluidized bed unit. The uniform inlet distribution of the fluidizing agent was compared with a variety of convex feed distributions at the bed entrance to correct for the negative effects of static/dynamic deviations from bed verticality necessary for optimal operation of bubbling fluidized bed reactors in marine environments.