Modelling and simulation of intensified absorber for post-combustion CO₂ capture using different mass transfer correlations

This paper studied mass transfer in rotating packed bed (RPB) which has the potential to significantly reduce capital and operating costs in post-combustion CO₂capture. To model intensified absorber, mass transfer correlations were implemented in visual FORTRAN and then were dynamically linked with Aspen Plus® rate-based model. Therefore, this represents a newly developed model for intensified absorber using RPB. Two sets of mass transfer correlations were studied and compared through model validations. The second set of correlations performed better at the MEA concentrations tested as compared with the first set of correlations. For insights into the design and operation of intensified absorber, process analysis was carried out, which indicates: (a) With fixed RPB equipment size and fixed Lean MEA flow rate, CO₂ capture level decreases with increase in flue gas flow rate; (b) Higher lean MEA inlet temperature leads to higher CO₂ capture level. (c) At higher flue gas temperature (from 30 °C to 80 °C), the CO₂ capture level of the intensified absorber can be maintained. Compared with conventional absorber using packed columns, the insights obtained from this study are (1) Intensified absorber using rotating packed bed (RPB) improves mass transfer significantly. (2) Cooling duty cost can be saved since higher lean MEA temperature and/or higher flue gas temperature shows little or no effect on the performance of the RPB

Commentary on Family Planning Association of Northern Ireland v The Minister for Health, Social Services and Public Safety

This is the author accepted manuscript. The final version is available from Hart Publishin

Process analysis of intensified absorber for post-combustion CO₂ capture through modelling and simulation

Process intensification (PI) has the potential to significantly reduce capital and operating costs in postcombustion CO₂ capture using monoethanolamine (MEA) solvent for power plants. The intensified absorber using rotating packed bed (RPB) was modelled based on Aspen Plus® rate-based model, but some build-in correlations in Aspen Plus® rate-based model were replaced with new correlations suitable for RPB. These correlations reflect centrifugal acceleration which is present in RPB. The new correlations were implemented in visual FORTRAN as sub-routines and were dynamically linked to Aspen Plus® rate based model. The model for intensified absorber was validated using experimental data and showed good agreement. Process analysis carried out indicates: (a) CO₂ capture level increases with rotating speed. (b) Higher lean MEA inlet temperature leads to higher CO₂ capture level. (c) Increase in lean MEA concentration results in increase in CO₂ capture level. (d) Temperature bulge is not present in intensified absorber. Compared with conventional absorber using packed columns, the insights obtained from this study are (1) intensified absorber using RPB improves mass transfer significantly. (2) Higher flue gas temperature or lean MEA temperature will not be detrimental to the reactive separation as such cooling duty for flue gas can be saved. (3) Inter-cooling cost will not be incurred since there is no temperature bulge. A detail comparison between conventional absorber and intensified absorber using RPB was carried out and absorber volume reduction factor of 12 times was found. These insights can be useful for design and operation of intensified absorber for CO₂ capture

Tsallis Statistics: Averages and a Physical Interpretation of the Lagrange Multiplier β\beta

Tsallis has proposed a generalisation of the standard entropy, which has since been applied to a variety of physical systems. In the canonical ensemble approach that is mostly used, average energy is given by an unnromalised, or normalised, $q$-expectation value. A Lagrange multiplier $\beta$ enforces the energy constraint whose physical interpretation, however, is lacking. Here, we use a microcanonical ensemble approach and find that consistency requires that only normalised $q$-expectation values are to be used. We then present a physical interpretation of $\beta$, relating it to a physical temperature. We derive this interpretation by a different method also.Comment: Latex file. 11 pages. Sections 2 and 3 modified and shortened; an implicit assumption in Sec 4 is made explicit; a note and a reference added; other minor changes. To appear in Physics Letters

An Approximate Variational Method for Improved Thermodynamics of Molecular Fluids

For a certain class of thermodynamic perturbation theories, a generalization of the Gibbs-Bogoliubov inequality holds through second order of perturbation theory and for a subset of terms the inequality is true to infinite order. Using this approximate variational principle, a perturbation theory is chosen for which the Helmholtz free energy of the reference system is minimized under the constraint that the first order term is identically zero. We apply these ideas to the determination of effective spherical potentials that accurately reproduce the thermodynamics of nonspherical molecular potentials. For a diatomic-Lennard-Jones (DLJ) potential with l ∕σ = 0.793, the resulting spherical reference potential is identical to the median average over angles for the repulsive part of the potential, but differs in the attractive well. The variational effective spherical potential leads to more accurate thermodynamics than the median, however, particularly in the triple point region