The simulated counter-current process (Simulated Moving Bed - SMB) was developed in the early 60th by the Universal Oil Products Company. It was mainly applied to industrial-scale separations, like the xylene separation or the fructose-glucose separation.
There is a strong analogy between the SMB and the TMB process. Under the use of a suitable system of adsorbent and eluent, a feed stream is separated into two withdrawal streams containing the pure components of a binary or pseudo-binary mixture.In the SMB process a large column is divided into a finite number of small sections. A withdrawal tube is situated between two of such sections.These tubes are connected in a cyclic mode with the inlets and outlets via a special designed rotary valve (Knauer). An observer sitting on an in- or outlet remarks anapparent moving of solid counter-current the fluid flow at each switching although the solid is fixed in the column. Therefore, the process is called a simulated counter-current one. The SMB is equal to TMB for an infinite numberof columns.