Frictional diffusion, briefly FricDiff, is a novel and promising separation technology, based on the difference in diffusion rate of two components when diffusing in opposite direction to a third component-the so-called counter gas [M. Geboers, P. Kerkhof, P. Lipman, F. Peters, FricDiff: a novel separation concept, Sep. Purif. Technol. (Corrected proof, available online on 20 January 2007), in press]. The potential of FricDiff can be found in energy consuming separations like azeotropic distillation. This paper presents a model which has been used to simulate the effect of design parameters and operating conditions on the performance of a single tube FricDiff module. The model will be used as a design-tool for the construction of a test unit which has to demonstrate the technical viability of FricDiff technology under industrial conditions. Modeling and simulation studies were executed with an objective to determine the sensitivity of design parameters and operating conditions such as sweep ratio, feed flow rate and tube characteristics on two performance criteria, namely enrichment factor and recovery. It was found that a third performance parameter, productivity, is needed to be able to fully assess the performance of a FricDiff module at given operating conditions. In one stage an enrichment factor of 2 can be obtained at a reasonable recovery of 40% with productivity up to 4 kg m(-2) h(-1). The ratio of the flow rates of the counter gas and the feed (sweep-ratio) has a dominant effect on the performance. The simulation results support the claim that FricDiff technology has a potential for breaking azeotropic mixtures. (C) 2007 Elsevier B.V. All rights reserved.