Bilinear driving force approximation in the modeling of a simulated moving bed using bidisperse adsorbents

The linear driving force (LDF) approximation has been extensively used to represent the intraparticle diffusion in adsorptive processes regardless of its real nature. This work introduces a bilinear driving force (bi-LDF) approximation to account for intraparticle diffusion and to obtain concentration profiles in the macropores and microparticles of the adsorbent. The bi-LDF approximation is applied to the simulation of glucose/fructose breakthrough curves in a fixed bed and to their separation in a simulated moving bed (SMB). Equivalence with the simple LDF model is well-established for both fixed-bed operation and the SMB mode. The flow rate constraints that define a region of separation (both product purities higher than 99.5%) for a SMB configuration are shown to be greatly affected by relatively small deviations in the macro- and microparticle time constants, which illustrate the relevance of the proposed approximation.