A quantitative model for scrap tire pyrolysis in a batch scale reactor developed comprises the following basic phenomena : conduction inside tire particles; conduction, conduction, and radiation between the feedstock particles or between rite fluids and the particles; tire pyrolysis reaction; exothermicity and endothermicity caused by tire decomposition and volatilization; and the variation of the composition and tile thermal properties of tire particles, This model was used to predict tile transient temperature and density distributions in the bed of particles, the volatile product evolution rate the mass change, the energy consumption during the pyrolysis process, and the pressure history in a tire pyrolysis reactor with a load of I kg. The model predictions agree well with independent experimental data.