|Date: Friday, October 15, 2021
Location: 2866 East Hall (4:00 PM to 5:00 PM)
Title: Approximate multi-step reaction rates in spherical and cylindrical particles
Abstract: In this talk we will discuss challenges in modeling multi-step reactions in porous catalyst particles. Single-step effectiveness factors based on Thiele modulus, while useful, cannot accurately capture the cascading reactions common in high temperature vapor-phase chemical reactors like FCC units. Multi-step effectiveness factors were derived analytically from steady-state solutions to the governing reaction-diffusion equations in spherical and cylindrical coordinates by diagonalization. The resulting method consists of a coordinate transform of the boundary conditions, evaluation of single-stage effectiveness coefficients, and a coordinate transform back to concentration. Performance and optimization of this process will be discussed. Comparisons are made against particle-resolved direct numerical simulations (DNS) in the single-stage and multi-stage cases. Additional estimates for more general geometries will be proposed. Efficient computation of effectiveness factors depends on carefully balancing pre-processing with online computation; rationale for the division made and alternatives will be presented. The resulting open-source library is designed to be integrated into reactor scale models (e.g., discrete element models, two-fluid models) to accurately predict chemistry with dramatically less computational cost than DNS.
Speaker: Jack Wakefield
Institution: University of Michigan