Many novel reactor concepts based on the integration of membranes in fluidized beds have been proposed. For the detailed numerical investigation of such systems, a method is required describing the motion of the particles while accounting for (i) the gas motion and (ii) the encounters between particles and confining walls/membranes. In this paper a novel hybrid computational method is presented, combining the Discrete Particle Model (DPM) and the Immersed Boundary Method (IBM). The first part focuses on the implementation and validation of these models. The IBM component of the model has been verified by comparing the computed drag coefficients for Simple Cubic (SC) arrays of cylinders with data of Sangani and Acrivos (1982) at creeping flow conditions. For higher Reynolds numbers the code has been compared to Ferziger and Peric (2002) for a single off-center cylinder, after which simulations with addition and extraction of gas through the membrane surface have been conducted. In the second part of this work we will focus on actual fluidized bed membrane systems, and will report results of simulations for several membrane geometries as well as permeation ratios. (c) 2012 Elsevier Ltd. All rights reserved.