Conversion of CO₂from the Energy Systems On-Board Ships via Catalytic Cycloaddition to Styrene Oxide: Modeling and Numerical Simulation

Abstract

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.

Modeling the Reduction of Ship Exhaust Emissions through CO2 Capture/Chemical Conversion and SO2 Seawater Scrubbing

“…Thus, only a marginal liquid fraction is subjected to channeling and, accordingly, the downward liquid flow is predominantly located in the extended central part of the packed bed. It is important to note that the loss of axial symmetry of liquid flow, associated with greater liquid accumulation and higher axial liquid velocity in the bottommost cross-sectional area of the packed-bed column, extends over a larger cross section of the packed bed as the column diameter decreases. ,, In these circumstances, the extent of the secondary liquid flow progressively increases, and the gas–liquid flow becomes dominated by the liquid flow in the lowermost cross-sectional areas of the packed bed.…”

“…This is reflected in the time-dependent low-amplitude waves for two-phase pressure drop (not shown) and cross-sectional averaged liquid holdup (Figure ) that surround the steady-state solutions of the vertical packed-bed column. Forced secondary liquid flow develops and generates greater liquid holdup in the lowermost cross-sectional areas of the column as the column diameter decreases, and therefore the fluid dynamics are significantly affected by the rolling motion, which generates time-dependent high-amplitude waves. ,, …”

“…Forced secondary liquid flow develops and generates greater liquid holdup in the lowermost cross-sectional areas of the column as the column diameter decreases, and therefore the fluid dynamics are significantly affected by the rolling motion, which generates time-dependent high-amplitude waves. 14,24,26 The limited effect of forced sinusoidal angular motion (period up to 40 s and large amplitude of 15°) on the twophase flow fluid dynamics is reflected in the time-dependent S4 and S5). low-amplitude waves of the outlet SO 2 and CO 2 concentrations in the gas phase maintained around the steady-state solution of vertical packed-bed columns (Figure 10).…”

“…The sustainable CO 2 management using innovative and energy-efficient technologies for an integrated CO 2 capture and conversion can play an important role in solving the problem of controlling marine emissions. 14 Integrating CO 2 capture and conversion opens up opportunities to save energy by bypassing the energy-intensive steps of regeneration, compression, and transport of conventional CO 2 capture/ sequestration systems and can generate revenue to help recover the capture costs. In this context, this study is proposed as an exploration of opportunities by presenting an analysis of an integrated intensified process to capture CO 2 and SO 2 from marine emissions and convert the captured CO 2 into methanol, thus reducing the CO 2 emissions to the atmosphere and initiating a process that is close to carbon neutrality.…”

“…Also, the coupled process combining plasma CO 2 reduction and methanol synthesis can be an interesting option for CO 2 conversion . The conversion of CO 2 to cyclic carbonates via catalytic CO 2 cycloaddition to epoxides is a promising reaction in terms of sustainability to transform CO 2 into valuable products. − Enzyme-based CO 2 fixation is one of the most important metabolic reactions for converting inorganic carbon from the atmosphere into organic chemicals and is a more promising process compared to chemical catalysis . However, these reactions remain challenging for CO 2 conversion due to unfavorable thermodynamics and limitations associated with fixation of CO 2 at low atmospheric concentrations.…”