Kinetic models for the pyrolysis and combustion of two types of sewage sludge

Following a similar methodology, for the combustion of each sludge, two series of three runs at different oxygen concentrations (10 and 20%) and heating rates were carried out. For the sludge with oxidative pyrolysis behaviour, the scheme of three parallel reactions (as in pyrolysis) was appropriate for correlating the data, using the same values of activation energy, reaction order and maximum amount of volatiles evolved, and optimizing only the value of the pre-exponential factor, that is correlated with oxygen pressure. On the other hand, for the other sludge, with the first stage coinciding with pyrolysis and the second stage concerning the char combustion, the kinetic parameters of the second stage are obtained, with an apparent activation energy of 144.1 kJ/mol.