A numerical study on the pyrolysis of large coal particles: Heat transfer and volatile evolution

Abstract

A pyrolysis model coupled with heat transfer and volatile evolution has been presented to characterize the internal heat transfer and pyrolysis behavior of a large coal particle. The applicability of kinetic model (DAEM) was first verified, then the ability of the large particle pyrolysis model to estimate the particle temperature variation was validated. In order to investigate the effects of pyrolysis temperature and particle size on pyrolysis characteristics of large particles, temperature and volatile yield profiles inside the particle were numerically studied. Results showed that the influence of pyrolysis temperature and particle size were quite significant. For the low pyrolysis temperature (600 °C) and small particle size (6 mm), the maximum temperature difference inside the particle was less than 100 °C, an assumption of homogeneous pyrolysis may be roughly adopted. While for the high pyrolysis temperature (1000 °C) and large particle size (22 mm), more than 200 °C temperature difference was found in the particle, notable gradients could be observed in the transient profiles of volatile yield. The effects of pyrolysis temperature and particle size on the residual density inside the coal particle have also been investigated numerically using the pyrolysis model.