Modeling CO₂ Adsorption in a Thin Discrete Packing

Local dynamics of CO2 adsorption in a discrete packing contained in a thin tube was assessed by 3D modeling. Thin tube packed bed adsorbers are currently used over tube structures in thermochemical energy storage systems and atmospheric revitalization of confined spaces. Driven by the interplay between key factors such as the exothermicity and the fluid flow, the advective transport was found less effective than the diffusive one on the breakthrough trends of CO2 which displayed significant concentration gradients at both inter- and intraparticle scales. The lack of angular symmetry inside the particles by the reduction in resistance to mass transfer in the area of solid particles exposed to high velocities led to greater convective transports from the bulk of the gaseous phase to the pores. The result of the modeling agreed with the experimental data obtained at the exit of the adsorber, helping reduction in reliance on the empirical dispersion models used in the one-dimensional modeling

Modeling CO₂ Adsorption in a Thin Discrete Packing

Local dynamics of CO2 adsorption in a discrete packing contained in a thin tube was assessed by 3D modeling. Thin tube packed bed adsorbers are currently used over tube structures in thermochemical energy storage systems and atmospheric revitalization of confined spaces. Driven by the interplay between key factors such as the exothermicity and the fluid flow, the advective transport was found less effective than the diffusive one on the breakthrough trends of CO2 which displayed significant concentration gradients at both inter- and intraparticle scales. The lack of angular symmetry inside the particles by the reduction in resistance to mass transfer in the area of solid particles exposed to high velocities led to greater convective transports from the bulk of the gaseous phase to the pores. The result of the modeling agreed with the experimental data obtained at the exit of the adsorber, helping reduction in reliance on the empirical dispersion models used in the one-dimensional modeling

Modeling CO₂ Adsorption in a Thin Discrete Packing

Local dynamics of CO2 adsorption in a discrete packing contained in a thin tube was assessed by 3D modeling. Thin tube packed bed adsorbers are currently used over tube structures in thermochemical energy storage systems and atmospheric revitalization of confined spaces. Driven by the interplay between key factors such as the exothermicity and the fluid flow, the advective transport was found less effective than the diffusive one on the breakthrough trends of CO2 which displayed significant concentration gradients at both inter- and intraparticle scales. The lack of angular symmetry inside the particles by the reduction in resistance to mass transfer in the area of solid particles exposed to high velocities led to greater convective transports from the bulk of the gaseous phase to the pores. The result of the modeling agreed with the experimental data obtained at the exit of the adsorber, helping reduction in reliance on the empirical dispersion models used in the one-dimensional modeling

Extraction of Lead Ions and Partitioning Behavior in Aqueous Biphasic Systems Based on Polyethylene Glycol and Different Salts

Lead ions are environmental pollutants often present in very low concentrations, which makes them difficult to detect and, thus, present problems for environmental monitoring. In this study, we examined the performance of aqueous biphasic systems based on polyethylene glycol (PEG, molecular mass of 4000 g mol–1) with ammonium sulfate (NH4)2SO4, magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), and trisodium citrate (Na3C6H5O7) for the separation of lead(II) ions from aqueous solutions. We investigated the effects of salt types and the ratio of PEG4000 to salt on the extraction efficiency of lead(II) removal at constant temperatures of 303 K and 0.1 MPa. Additionally, we determined the cloud points (solubility equilibrium curve) and tie-lines for four ternary systems comprising PEG4000, water, and salt (either (NH4)2SO4, MgSO4, Na2SO4, or Na3C6H5O7) under the same conditions. A maximum lead(II) extraction efficiency of 74.4% was achieved using the PEG4000/(NH4)2SO4 system with a mass fraction ratio of PEG4000 to (NH4)2SO4 of 0.2:0.12. This outcome highlights the significant potential of utilizing aqueous biphasic systems based on PEG4000 to separate lead(II) from aqueous solutions efficiently

Gas Flow Visualization in Low Aspect Ratio Packed Beds by Three-Dimensional Modeling and Near-Infrared Tomography

Nonuniform local flow inside randomly porous media of gas–solid packed beds of low aspect ratios ranging from 1.5 to 5 was investigated by three-dimensional modeling and near-infrared tomography. These beds are known to demonstrate heterogeneous mixing and uneven distributions of mass and heat. The effects of the confining wall on flow dynamics were found nonlinear, particularly for aspect ratios lower than 3. High velocities were mainly observed in regions near the wall of aspect ratio value of 1.5 and those of values higher than 3, owing to high local porosities in these zones. Mass dispersion characterized both by experimental near-infrared imaging and by particle tracking showed discrepancies with literature models, particularly for aspect ratios lower than 3. Uncertainties were more significant with the radial dispersion due to bed size limits. Beyond this value, the wall affected more the axial dispersion, confirming the nonlinear impact of the wall on global hydrodynamics