A modified rotating cone reactor (MRCR) was developed for the pyrolysis of coal with solid heat carrier. The experiments were performed to study the effects of cone rotational frequency, mass ratio of coal-to-sand, coal particle size and pyrolysis temperature on the pyrolysis of coal with solid heat carrier in the reactor. A real-time observation system was used to record the granular flow and mixing process in the rotating cone. The results show that the existence of bed behavior as one passive and one active layer is definitive for the granular flow in MRCR without stirrers. The rotating vessel with a stirrer is helpful to enhance the granular fluidity and mixing rate. The fine particles of coal and solid heat carrier in MRCR would be well mixed by a flat-bladed stirrer within 3-5 s. The particle discharge rate from the reactor tends to increase with the increasing of the cone rotational frequency, coal particle size or mass ratio of coal-to-heat carrier. Under the pyrolysis conditions, the weight loss of coal particles, sensitive to coal particle size, also depends on the pyrolysis temperature, the cone rotational frequency or the mass ratio of coal-to-heat carrier. (c) 2007 Elsevier B.V. All rights reserved.