Abstract An algorithm using the discrete element method (DEM) for simulating the particulate behaviour of flow and heat transfer is developed and described, the reasonable hypothesis and the ingenious design of which have been presented in detail. The organizational structure of the developed algorithm contains an efficient method for determining particle collisions, the status analysis for each particle and the particulate-kinematics analysis during the time step. The reasonability and correctness of the developed DEM algorithm are validated by laboratory experiments: the discharge process of glass beads from a silo; and heating of metal alloy particles in a calciner. Afterwards, a group of validated mechanics parameter values for coal and sand have been tested and verified in the article, preparing for the simulation of the pyrolysis process in a downer or screw reactor in subsequent research projects.