Cascade Impactor Sampling to measure Polycyclic Aromatic Hydrocarbons from Biomass Combustion Processes

The increased use of biomass as a fuel in thermochemical conversion processes over the coming years, makes the research of a clean and efficient process necessary. The experiments were carried out in a pilot atmospheric fluidised bed combustion plant of 1 MW[th], where the parameters had been optimised to obtain a clean biomass combustion process. All types of combustion produce organic compounds, especially polycyclic aromatic hydrocarbons (PAHs). The distribution of PAHs was isolated from the eight size particle fractions collected in the fly ash emitted from the biomass combustion process. The particle size distribution was carried out with a multistage cascade impactor system (Andersen Mark III) with a diameter cut ranging from 0·01 to 4·00 nm. It was observed that most of the heavy PAHs are adsorbed on particles having an aerodynamic diameter of less than 2 μm and an unimodal distribution was deduced from the results of the scanning mobility particle size. Polycyclic aromatic hydrocarbons pollutants were studied on a gas chromatograph coupled to a mass spectrometer operating in an ion monitoring mode. High concentrations of heavy PAHs were measured in a small particle size distribution. A high combustion efficiency reduced the PAH emissions. Under stable combustion conditions, the particle emission in the size range 0·1–1 μm was increased and mass concentration was reduced considerably. This was due to a reduction in the number of coarse particles.