Fluidized Bed Combustion (FBC) of Fossil and Nonfossil Fuels. A Comparative Study

Abstract

A comparative study on FBC of coal and waste tire was performed from an environmental point of view. A sub-bituminous coal and a nonspecific waste tire blend were used, respectively, as fossil and nonfossil fuels in a fluidized bed combustion (FBC) experimental laboratory installation. The same FBC conditions were carried out keeping constant the air total flow (860 L/h), the percentage of excess oxygen (20%), and varying the combustion temperature (650, 750, 850, and 950 °C). The main objective was to establish the influence of the fuel used in PAH formation and emission. Regarding the PAH formation and emission in FBC, this is the first time that emissions from coal and waste tire combustion are compared. The PAH were collected in different traps and extracted with dimethylformamide (DMF). PAH analysis and quantification were determined by fluorescence spectroscopy in the synchronous mode (FS). Data on polycyclic aromatic hydrocarbons (PAH) are reported and the results obtained show the following: (1) Independently of the combustion temperature, a drastic increase in PAH emissions is obtained when tire is used instead of coal at the same conditions. In this case, the PAH formation and emission seem to be promoted. (2) The pyrolytic process and the interaction between radicals in the mechanisms implied in PAH formation are highly important. (3) The combustion temperature influence is more remarkable in tire combustion than in coal combustion. In the first one, the lowest PAH emissions are obtained at low combustion temperatures (750 °C) while for coal, the highest PAH emissions appear in the range of 750−850 °C.