Reaching steady state under cyclic operations with dispersion: The case of the reverse flow adsorber

The reverse flow adsorber (RFA) can be used as a catalytic reactor for homogeneous catalysis to avoid the issues of catalyst separation. The RFA combines the reverse flow circulation and the separation of the dissolved solute from the liquid homogeneous mixture. In this work, the RFA is modeled and simulated in order to evaluate its separation performances and its behavior. The studied adsorber is a single adsorption/desorption packed bed, and the reversal of flows is applied to keep the solute inside the bed as longer as possible while minimizing its outlet concentration (leaching). The chosen one dimensional model accounts for the axial dispersion and the non-equilibrium effects (mass transfer resistances, etc). The numerical method of lines (MOL) is used to solve the partial differential algebraic model equations (PDAEs). Two cases are studied; the first one is the dynamic of the homogeneous solute concentration starting from a pre-loaded column and without solute addition. The second case considers operations with continuous solute side stream addition. In the first case, leaching persists until the initially pre-loaded adsorption column with solute is completely emptied thus demonstrating unsteady-state operations in contrast with previous works. To compensate leaching, solute makeup is added at the center of the column. This leads, after priming a number of cycles, to a stationary periodic state operation. (C) 2016 Elsevier B.V. All rights reserved.