The effects of devolatilization temperature (750-900 degreesC), coal size (2-12 mm) and coal properties (carbon content, Hardgrove index (HGI), pore volume) of anthracite coals on the primary fragmentation and particle size reduction during devolatilization have been determined in a thermobalance reactor. The fragmentation index increases with increasing devolatilization temperature and particle size. The fragmentation index is also influenced by coal properties, such as carbon content, HGI, pore Volume, etc. Thus, the reduction ratio of particle size before and after devolatilization increases with increasing devolatilization temperature and particle size. (C) 2002 Elsevier Science Ltd. All rights reserved.