Distribution of the activation energies for the thermal decomposition of organic and pyritic sulphur in coal

Abstract

The activation energies for the thermal cracking of the organic sulphur of several coals ranking from lignite to subbituminous have been calculated. Likewise, the activation energies for the thermal decomposition of the pyrite associated with different density fractions obtained from a subbituminous coal by sink-float analysis have been determined. The model of multiple, parallel, independent (MPI) first order reaction has been assumed for the thermal cracking. The kinetic equations associated with a Gaussian distribution of the activation energies (DAE) have been used for calculating the average activation energy, E 0, and the standard distribution, σ. The results obtained show small differences between the parameters calculated for the cracking of the organic sulphur contained in the different coals tested. Decomposition of pyritic sulphur needs a higher activation energy than the organic sulphur. The decomposition of the pyrite associated with coal fractions with different density shows that a correlationship can be stablished between the pyrite content, E 0 and σ. The higher content in pyrite, the lower E 0 and the higher σ. It is probably due to a larger variety of pyritic sulphur forms, as the pyritic content increases, which leads to a more dispersive distribution of activation energies.