dAVEBE produces starch from potato, wheat and tapioca. Annually approximately 800,000 ton potato starch, used in paper and food industry is produced. Hydrocyclones are used for classification of starch and fibres and for washing out remaining soluble components from the starch slurry. The hydrocyclone batteries have between 6 and 20 stages. To choose the "optimal" (meaning economical optimum based on energy consumption (pressure drop), flow, separation efficiency, wear resistance etc., which is determined by the dimensions of the hydrocyclone) hydrocyclone dimensions and column configuration, 26 different species of hydrocyclones of 10 and 15 nun were tested. For these investigations a statistical central composite experimental design is used. The results of the experimental design are used to model the response area of the hydrocyclone performance for the complete process parameter space. From the statistical process model the economic performance in the factory is calculated. All the different hydrocyclones have. been listed based on economical performance in terms of exploitation costs per unit product (potato starch). Although the hydrocyclones ran under different process conditions, these process conditions gave optimal economical results for any particular hydrocyclone type. (C) 2004 Elsevier Ltd. All rights reserved.