Distribution of PAH generated in fluidized bed combustion and pyrolysis experiments

Abstract

This chapter discusses the distribution of Polycyclic aromatic hydrocarbons (PAH) generated in fluidized-bed combustion and pyrolysis experiments. PAH is quantified following the extraction of samples recovered from fluidized-bed combustion (FBC) tests on Spanish lignite (Aragon) at various combustion temperatures and air/fuel ratios in a pilot plant scale FBC unit. A selection of the results are detailed and discussed with respect to the sampling, extraction, and analysis procedures. FBC conditions markedly affect the amount of PAHs produced and emitted into the atmosphere. Maximum PAH concentrations occur at low temperatures, when combustion is less efficient, and at high air excesses. In the PAH recovery from the materials of the different sampling points, supercritical fluid extraction (SFE) provides a more reliable method for high molecular weight compounds than Soxhlet extraction. Observations are made under fluidized-bed pyrolysis conditions, where condensation reactions predominate at higher temperatures.