(288d) Design of Bypass-Simulated Moving Bed Process for Reduced Purity Requirements

Simulated moving bed separations are typically studied for cases where high target product purities are required. However, there are situations where reduced purities could be desired: e.g., hybrid separations and products where lower purities are tolerated. In such situations, the bypass SMB- a process configuration where the SMB over-purifies a portion of the feed which is then mixed with the feed to obtain the target purity can be considered. In fact, the manufacture of high-fructose corn syrup uses this approach.

In this presentation the design of BP-SMB is considered. For systems that follow linear isotherms, based on the equilibrium theory of chromatography, explicit expressions to compare the productivity of the BP-SMB with respect to the classical SMB and the desorbent requirements are derived. Numerical simulations are used to confirm these results. For systems following non-linear isotherms, numerical simulations are used to study the potential advantage of the technique. It is shown that the BP-SMB is preferred for systems where the selectivity is high, column efficiencies are high. The manufacture of HFCS is considered and it is shown that in this separation, while there are no productivity gains to be obtained using the BP-SMB, there are operational advantages that improve the robustness of the process.