Chemical Engineering Science 62 (2007) 4717 – 4728 www.elsevier.com/locate/ces Modelling and validation of granulation with heterogeneous binder dispersion and chemical reaction Andreas Braumann a , Mike J. Goodson a , Markus Kraft a , ∗ , Paul R. Mort b a Department of Chemical Engineering, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK b Procter and Gamble Co., ITC, 5299 Spring Grove Avenue, Cincinnati, OH 45217, USA Received 29 May 2006; received in revised form 4 April 2007; accepted 21 May 2007 Available online 29 May 2007 Abstract In this paper a multidimensional model for binder granulation is presented. The particles undergo different transformations such as coalescence, compaction, and breakage. Further chemical reaction in the granules is taken into account in order to incorporate binder solidification which is observed to be a significant transformation in many industrial applications. The equations of the model framework are solved numerically with a direct simulation Monte Carlo (DSMC) algorithm. In addition to the comparison between experiment and simulation, the model framework also enables the study of critical parameters in binder granulation such as reaction rate (solidification of binder) and size of the added binder droplets, which demonstrates its promising potential.  2007 Elsevier Ltd. All rights reserved. Keywords: Granulation; Agglomeration; Product design; Particle formation; Dispersion; Reactive binder 1. Introduction and background Granulation is a common industrial process which transforms fine powders into coarser grains that are user-friendly for hand- ling, storage, post-processing, re-dispersion, and other pro- cessing or usage needs. Benefits include improved flowability and compaction behaviour for subsequent industrial processes (pharmaceutical tabletting, ceramic dry forming, minerals processing), storage stability, handling, and re-dispersion re- quired by end-use applications (foods, detergents, agricultural chemicals, etc.). Besides the improvement to powder handling, granulation is also used to create ordered micro-mixtures of different components (Mort and Riman, 1994), to prevent segregation and to control dissolution (Iveson et al., 2001; Wauters, 2001). Granulation is often accomplished using a liquid binder to create a composite structure of fine particles connected by a binder phase. In the granular product, the binder is usually converted into a stable solid phase, for example by drying, cooling, or reaction of the binder with the particulate substrate. ∗ Corresponding author. Tel.: +44 1223 762784; fax: +44 1223 334796. E-mail address: mk306@cam.ac.uk (M. Kraft). 0009-2509/$ - see front matter  2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ces.2007.05.028 The conversion of the binder from a liquid to a solid state can be done as a post-process (e.g., a separate drying step) or it can be an integral part of the granulation process. In the latter case, the rate of the binder transformation from liquid to solid is critical to the granulation process. Binder granulation is typically achieved by adding a liquid binder to small solid particles in a mixer-granulator, fluidised bed, or other appropriate unit operation. The binder can be atomised as individual droplets contacting the particle bed (Hapgood, 2000) or as a liquid stream that is dispersed by contact transfer in a mechanically induced shear field. Al- ternatively, a binder can be added as a solid particulate, and then brought to a liquid or soft-solid state during the granula- tion process, as in hot melt (Schæfer and Mathiesen, 1996). Flow and shear fields within the process induce collisions between particles and further the dispersion and transfer of the binder (Simmons et al., 2006). The stress associated with these collisions and the dissipation of energy by viscous binder layers and/or plastic deformation of the granular structures is fundamental to the mechanics of the granulation process. While the particles are bound due to capillary pressure, sur- face tension, and viscous forces related to the binder phase (Iveson and Litster, 1998), the critical properties of the binder This is the computational modelling group's latest version of the publication. For the published version please refer to doi: 10.1016/j.ces.2007.05.028