The simulated moving bed (SMB) technology is important in various fields, from sugar to enantiomer separation, and operating conditions must be carefully selected and regulated, based on an appropriate process model. Basically, two modelling approaches exist, i.e., true moving bed (TMB) and SNIB models. Both approaches show advantages and drawbacks. In this work, an attempt is made to develop a model which retains the simplicity of the original TNIB model and its modest computational load, while capturing the essential features of the cyclic steady state reproduced by the SNIB model. (c) 2006 Elsevier Ltd. All rights reserved.