Pinched Wave Design of a Four-Zone Simulated Moving Bed for Linear Adsorption Systems with Significant Mass-Transfer Effects

Speedy standing wave design and simulated moving bed splitting strategies for the separation of ternary mixtures with linear isotherms

Simulated Moving Bed (SMB) has advantages over batch chromatography in terms of productivity and solvent efficiency. However, SMB applications in large scale production are still limited because of the many design parameters that must be specified and the multiple splitting strategies that can be implemented. To overcome these barriers, this study extends the Speedy Standing Wave Design (SSWD) method of Weeden and Wang for binary linear systems to ternary linear adsorption systems. The dimensionless operating parameters, sorbent productivity, and solvent efficiency can be quickly calculated without process simulations. SSWD also gives an overview of the productivity and solvent efficiency as a function of two key dimensionless groups. This overview can be used for optimization of separation costs and for comparison of splitting strategies. The SSWD method was verified using rate model simulations for the separation of three amino acids. The simulated yields agree with the SSWD target yields within 1% for all components. The example was also used to illustrate the key design rules for ternary separations. High productivity and solvent efficiency can be achieved with a large difference in the retention factors of the heavy key and light key, which are the components that define the split of the feed between extract and raffinate products. For ternary ideal systems, solvent efficiency is inversely proportional to the largest difference in retention factors. For this reason, minimizing the overall range of retention factors can significantly improve the solvent efficiency and product concentration without sacrificing productivity. If more than one SMB is needed, the easiest split should be done first for higher productivity, solvent efficiency, and product concentration. In the example case study, both the productivity and solvent efficiency were about an order of magnitude higher when the easiest split was done in the first ring. The SSWD method can be used to design a wide array of multi-component separations with high yield, productivity, and solvent efficiency.