PNNL

Abstract

The interfacial area, also known as the effective mass transfer area, is a key factor for determining the mass transfer for carbon dioxide (CO2) capture via the chemical absorption process in a packed column, and thus the overall capture efficiency of the packed column. Most of the widely used empirical and semi-empirical models for interfacial area were derived indirectly through absorption mass transfer with simplifications based on fast chemical kinetics. This report presents the comprehensive unique multiscale approach to develop a surrogate model for effective mass transfer area in structured packed columns that accounts local hydrodynamics as well as variation in physical properties, and changes in solid surface characteristics. The effective contact angle on the packing surface, which describes the packing surface and solvent interaction, was measured using the modified Wilhelmy plate method accounting the physical properties of solvent, CO2 loading, and temperatures. Next, a comprehensive CFD simulation campaign based on the design of experiments (DOE) were performed to derive a surrogate model of the effective mass transfer area that takes into consideration the physical properties of solvent, contact angle, local hydrodynamics, etc. The developed algebraic surrogate model was integrated into the ASPEN PLUS process modelling via a FORTRAN subroutine in form of .dll file. This .dll file integrated into process modelling takes into account the effective mass transfer area in order to capture CO2 absorption in each stage of the column. The present multiscale approach has advantage of two-way coupling i.e. interchanging information both direction: 1, ASPEN PLUS to surrogate model (temperature, physical properties, CO2 loading, etc., at each stage) and 2. Surrogate model in form of .dll files computes the effective mass transfer area for determining CO2 absorption. This unique and promising capability can aid process modeling to accelerating the carbon capture technology at column scale, particularly supporting large scale pilot experiments.