Double-Gaussian Distributed Activation Energy Model for Coal Devolatilization

Understanding and modeling of coal pyrolysis assume particular importance, since it is the first step of combustion and gasification processes. The complex reactions occurring during pyrolysis lead to difficulties in the process modeling. The aim of this work is to find a global kinetic model that well represents the pyrolysis of two different coals with opposite rank, a sub-bituminous and an anthracite coal, in order to carry out the kinetic parameters of the process. The Distributed Activation Energy Model (DAEM) was used to fit experimental data obtained with a thermogravimetric analysis. The model assumes that a series of first order parallel reactions occurs sharing the same pre-exponental factor, k(0), and having a continuous distribution of the activation energy. One of the limits of the standard Gaussian DAEM is that with this model is not possible to distinguish the primary from the secondary pyrolysis. A two Gaussians DAEM was developed considering that two classes of reactions take place having the same k(0) and different distribution of activation energy. Since in the model k0 is highly correlated with the mean activation energies, it was fixed at characteristic values taken from literature.