Analysis of the pyrolysis and combustion of different sewage sludges by TG

The pyrolysis and combustion of seven samples of sewage sludge were studied by TG dynamic runs carried out at 15 degreesC min(-1). Two different behaviors were observed. For some samples, considering the variations of weight loss versus temperature or time, the combustion thermograms are similar to those of pyrolysis but with a displacement of the corresponding curves of combustion to temperature intervals less than those of the pyrolysis runs. For the other samples, the pyrolysis thermograms coincide with the combustion thermograms, except in the last part of the combustion thermogram where a final decomposition appears as a consequence of the combustion of the char previously formed. The different behavior can be associated to aerobic stabilization of the samples. Some runs were also done with acid-washed samples to test the influence of the metal content. (C) 2001 Elsevier Science B.V. All rights reserved.