Quantitative imaging of gas adsorption equilibrium and dynamics by X-ray computed tomography
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Quantitative imaging of gas adsorption equilibrium and dynamics by X‑ray computed tomography Ronny Pini1 · Lisa Joss2 · Sayed Alireza Hosseinzadeh Hejazi3 Received: 1 June 2020 / Revised: 3 September 2020 / Accepted: 10 September 2020 © The Author(s) 2020
Abstract We present the development and application of X-ray Computed Tomography (CT) for the determination of the adsorption properties of microporous adsorbents and the study of breakthrough experiments in a laboratory fixed-bed adsorption column. Using the model system CO2 ∕helium on activated carbon, equilibrium and dynamic adsorption/desorption measurements by X-ray CT are described, and the results are successfully compared to those obtained from conventional methods, including the application of a one-dimensional dynamic column breakthrough model. The study demonstrates the practical feasibility of applying X-ray CT to measure internal and transient concentration profiles in adsorbent systems on the length-scales from a single adsorbent pellet to a packed column. Keywords Breakthrough experiments · Adsorption imaging · Multi-scale tomography Abbreviations A Column cross sectional area [m2 ] b Parameter in dual-site Langmuir isotherm [m3 mol−1 ] b0 Parameter in dual-site Langmuir isotherm [m3 mol−1 ] c Gas phase concentration [mol m−3 ] Cp,a Specific heat capacity of the adsorbed phase [J mol−1 K−1 ] Cp,g Specific heat capacity of the gas phase [J mol−1 K−1 ] Cp,s Specific heat capacity of the adsorbent [J kg−1 K−1 ] Cp,w Specific heat capacity of the column wall [J kg−1 K−1 ] CT CT number [HU] DL Axial dispersion [m2 s−1 ] Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10450-020-00268-7) contains supplementary material, which is available to authorized users. * Ronny Pini [email protected] 1
Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK
2
School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, UK
3
Department of Chemical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Islamic Republic of Iran
Dm Molecular diffusivity [m2 s−1 ] f Flow rate [m3 min−1 ] H ex Hounsfield units of the excess amount adsorbed per voxel volume [HU] hin Inside heat transfer coefficient [J m−2 K−1 s−1 ] hout Outside heat transfer coefficient [J m−2 K−1 s−1 ] J Minimization objective function ki Mass transfer coefficient [s−1 ] Kw Thermal conductivity of column wall [J m−1 K−1 s−1 ] Kz Effective gas thermal conductivity [J m−1 K−1 s−1 ] L Column length [m] mex Excess amount adsorbed per voxel volume [kg m−3 ] Mm Molecular mass [kg mol−1 ] N Number of time steps p Pressure [Pa] p∗ Reference pressure [Pa] p1 CT number calibration coefficient [HU m3 kg−1 ] p2 CT number calibration coefficient [HU m3 kg−1 ] q Solid phase concentration [mol kg−1 ] qs Saturation concentration in the solid phase [mol kg−1 ] q∗ Equilibrium solid phase concentration [mol kg−1 ] R Universal gas constant [
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