from Fluidized Bed

When coal undergoes combustion, important physical EXPERIMENTAL and chemical changes (contraction—swelling, devolatiliz-ation, decarboxylation, changes in fluidity and plasticity) occur and some of the resulting compounds are released into the atmosphere. In addition, cyclization reactions caused by the thermal process may occur, and, as a conse-quence, further aromatic clusters may develop. Both the inherent aromatic hydrocarbons and those formed during the process are significant atmospheric pollutants (Smith, 1984). Depending on their molecular mass, polycylic aro-A high-rank coal and a low-rank coal from different mining areas in Spain (Table 1) were burned in a laboratory-scale fluidized bed combustor (up to 200 g/h) at 750, 850, and 950°C, with a 40 % excess of O 2 and sand as fluidizer. The gas flow was twice the minimum fluidization velocity (Mastral et al., 1995). Combustion efficiencies are listed i