(383v) Modeling Complex Gas Mixture Breakthrough Curves Using IAST and an Advanced Finite Volume Scheme_Poster

A MATLAB toolbox is presented for predicting gas mixture breakthrough curves with IAST. This toolbox incorporates two isothermal adsorption bed models: the constant pressure and velocity model for dilute adsorbate feed scenarios, and the pressure and velocity drop model for concentrated adsorbate feed cases involving effective adsorption or fine adsorbent particle sizes. The weighted essentially non-oscillatory (WENO) finite volume scheme is employed to solve the governing equations of the models, offering second-order accuracy in space. It ensures the capture of sharp fronts caused by effective adsorption.

Gas mixture isotherm grids are established, with node uptakes computed using the Modified FastIAS algorithm. Spline interpolation techniques are then applied to determine gas mixture uptake throughout the breakthrough simulation process. This approach circumvents repetitive IAST calculations during simulation, consequently reducing computational expenses. In addition to incorporating popular isotherm models within the package, the toolbox also explores the direct utilization of single gas isotherm datapoints for breakthrough simulation through numerical quadrature IAST.

The analysis includes an in-depth examination of the error in mixture gas uptake calculation and breakthrough simulation stemming from numerical quadrature IAST calculation and spline interpolation. Regarding numerical quadrature IAST calculation, extrapolation is observed to occur more frequently for weakly adsorbed components. The constant slope extrapolation strategy demonstrates successful application in predicting gas uptake beyond the range of isotherm data points. The non-smoothness of gas mixture isotherms, arising from numerical quadrature IAST calculation using isotherm data points, contributes to noise in the breakthrough curve. This noise is mitigated by spline interpolation, which helps to smooth out the gas mixture isotherm. Spline interpolation of the gas mixture isotherm grids, when employed with appropriate step sizes, has been demonstrated to offer good accuracy in gas mixture uptake calculation, leading to reliable breakthrough curve simulations. However, large interpolation sizes can distort the isotherm and result in significant oscillations in the breakthrough curves.