The context of this study is the modelling of reactive extrusion process based on an alginate extraction protocol. Residence Time Distribution (RTD) is one important part to predict the kinetics of reactive compounds. A simple model is proposed to predict RTD in fully intermeshing co-rotating twin-screw extruders without reaction. This model, which can be easily extended to reactive case in a future work, is based on the extension of an axial dispersion model, including control parameters (screw speed and flow rate) and geometrical parameters (screw profile and die design). Simulations were performed for various operating and geometrical conditions so as to illustrate possibilities offered by the proposed model. Validation was conducted for two different extrusion applications, seaweed extrusion and polymer extrusion. This highlighted the model ability to predict RID for various kinds of materials after adjusting only one parameter thanks to a unique experimental RID curve. (C) 2010 Elsevier Ltd. All rights reserved.