A numerical simulation of the Mechanofusion (MF) device, which is used for powder surface modification (dry particle coating, mixing, etc.), is carried out using the discrete element modeling (DEM) technique. An existing, widely used, cohensionless contact model (Walton-Braun) is used for two-dimensional simulation studies, in which the particles are assumed to be frictional, elastic-plastic spheres. The Mechanofusion device consists of a rotating cylindrical chamber in which a fixed, eccentrically located, rounded inner-piece and a fixed scraper blade are placed. Two simplified geometric models of the Mechanofusion chamber, one with and the other without the scraper, are studied. Qualitative visualization of the particulate patterns and quantitative diagnostic analysis in the terms of average kinetic energy, rotational energy and collisional granular pressure within two systems demonstrate the effect of the scraper on the particles. The force on the fixed rounded inner-piece, which forms a compression region with chamber wall by its cylindrical surface end, as a function of the rotational speed of the chamber and particle loading is calculated. The numerical simulation results are verified by comparing them with available experimental results. Simulations are also performed to compute useful quantities such as impact forces and collision velocities experienced by the particles due to the interactions with other particles as well as with the vessel walls, and the frequency of collisions within various regions of the device. These quantities are useful for developing a full-scale system simulation that captures the phenomena at multiple length scales. (C) 2004 Elsevier B.V. All rights reserved.