DEVOLATILIZATION AND PYROLYSIS OF REFUSE DERIVED FUELS - CHARACTERIZATION AND KINETIC MODELING BY A THERMOGRAVIMETRIC AND CALORIMETRIC APPROACH

A characterization of pyrolysis behaviour of different refuse derived fuels (RDFs) under heating rates typical of conventional pyrolysis pro cesses is presented. The results of thermogravimetric analysis (TGA) a nd differential scanning calorimetry (d.s.c.) on different RDFs, and o n some materials which have been considered 'key components' towards t hermal degradation characteristics of RDFs, are reported. The RDF weig ht loss curve presents two distinct weight loss steps attributable, re spectively, to cellulosic materials and plastic degradation. Samples f rom different plants and different municipal solid waste (MSW) feedsto cks show the same qualitative behaviour. In interpretation of the expe rimental results, the assumption has been made that the pyrolysis rate of thermal degradation of RDF can be considered as the sum of the rat es of the main RDF components: paper (cellulose), wood-like materials (cellulose, lignin and hemicellulose), plastics mainly polyethylene (P E); and that each component contributed to the formation of this sum t o an extent proportional to its contribution to the composition of the RDF. On the basis of these data and by means of a simple mathematical approach a method is proposed which provides a simple tool for RDF ch aracterization and, in particular, evaluation of plastic content. A ki netic model has been developed, based on the assumption that the RDF d egradation rate is the weighed sum of the rates of primary reacting sp ecies: cellulose, lignin, hemicellulose, PE. Simplified kinetic pathwa ys were used for the description of the degradation processes of RDF c omponents. The model allows quantitative prediction of RDF weight loss and char yield at least at the heating rates used in present work.