An algorithm for determining the kinetics of devolatilisation of complex solid fuels from thermogravimetric experiments

An algorithm is introduced for determining the kinetics of devolatilisation of complex fuels, e.g. coal or biomass, when heated in an inert atmosphere. The algorithm uses information from thermogravimetric experiments, at several different, but constant, rates of heating, to identify and characterise the underlying distribution of reactions governing devolatilisation. The algorithm also provides an approximate way of inverting the distributed activation energy model (DAEM), commonly used to model the pyrolysis of coal. Such techniques provide the activation energy, E, and pre-exponential factor, A, for each parallel step participating in the thermal decomposition of a solid fuel. In addition, the amount of material associated with each pair of A and E can be derived. The method is tested on (i) imaginary data from simulated TGA experiments with one or more first-order reactions and (ii) real data from thermogravimetric experiments on the pyrolysis of sewage sludge. In every case the algorithm gave excellent predictions for heating rates other than those at which the pair of E and A were derived. Thus, the algorithm is a useful method of analysing and summarising measurements to provide kinetic data and facilitate predictions.