In nanotechnology, classification in the micron and submicron range is of growing interest. Usually, hydrocyclones do not reach these low cut sizes. This study presents a special batch processing technique using a 20 mm hydrocyclone for classification in the micron range. This hydrocyclone was equipped with a special underflow box that stored the coarse particles. The overflow was recirculated to the hydrocyclone entrance. A set of experiments was conducted using this batch hydrocyclone technology. Quartz with particle size <20 mu m and a SiC/Si residue with size <10 mu m was fed to the hydrocyclone, which operated in a closed circuit for 120 min. The results showed that the hydrocyclone preferably separates the particles that are >1 mu m in the first 60 min. Later, the particles in the submicron range were increasingly discharged in the underflow. A simulation for the classification in a batch hydrocyclone with a closed circuit and underflow box is presented. (C) 2011 Published by Elsevier Ltd.