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International Journal of Energy for a Clean Environment

ISSN Print: 2150-3621
ISSN Online: 2150-363X

International Journal of Energy for a Clean Environment

Formerly Known as Clean Air: International Journal on Energy for a Clean Environment

DOI: 10.1615/InterJEnerCleanEnv.v5.i3.20
20 pages

A GENERAL AND NEW KINETIC MODEL OF COAL DEVOLATILIZATION

G. Migliavacca
CMIC Politecnico di Milano; and Stazione Sperimentale per i Combustibili, San Donato Milanese, Italy
T. Faravelli
CMIC Politecnico di Milano, Italy
S. Pierucci
CMIC Politecnico di Milano, Italy
E. Ranzi
CMIC Politecnico di Milano, Italy
Loretta Bonfanti
ENEL Produzione-Ricerca, Pisa, Italy
E. Parodi
Stazione Sperimentale per i Combustibili, San Donato Milanese, Italy

ABSTRACT

The aim of this paper is to present and discuss a new and detailed kinetic model able to describe the devolatilization of several different reference coals under pyrolysis conditions. The major reason of the interest in a better understanding of coal pyrolysis and combustion lies in the increasing concern of the environmental impact of combustion processes. The formation of light gases and liquid tars is the first step in this coal pyrolysis process. Several coals of industrial interest, having different rank, from lignite to anthracite, are analyzed in order to find simple relations among proximate analysis and the initial structure and morphology of the coals. The initial coal structure is defined as a macromolecular lattice, with aromatic units and aliphatic chains. The chemical reactions and successive transformations of the coal, to form liquid and gaseous products, are described by a complete network of decomposition and reticulation (cross-linking) reactions. The importance of bond-breaking and cross-linking during coal pyrolysis is deduced on the basis of recent studies on the detailed kinetic modeling of the degradation of plastics, such as polyethylene, polypropylene, and polystyrene. These classes of reactions and related kinetic parameters allow to describe the full evolution of coal towards light gases and heavier compounds with variable molecular weights.
Several comparisons between experimental data taken from the literature and model predictions make it possible to assess the reliability and the possibilities of the proposed approach.