Study of coal combustion aerosols using size fractionating sampling and nuclear analytical techniques

The chemical composition of aerosols emitted during coal combustion was studied as a function of particle size down to sizes down of 0.01 μm. The aerosol collections were carried out in a circulating fluidized bed coal boiler, upstream of the electrostatic precipitator. The sampling device consisted of a cyclone and Berner low-pressure impactor, placed in a series. The samples were analyzed by instrumental neutron activation analysis for up to about 40 elements. The elemental concentrations in the particulate matter for each impaction stage were plotted as a function of stage number (particle size). For the elements Na, Al, K, Ca, Sc, Ti, V, Ga, La and Sm, the concentration variation was limited to a factor of 2 to 4 and the concentrations of these elements were lower for the initial and final impactor stages than for the intermediate particle sizes. The concentration variations were also limited to a factor of 2-4 for the elements Mn, Fe, As, Sb and Th, but all these elements showed increasing concentrations with decreasing particle size. Still other elements, such as Ni, Cr, Co, Zn, W, Mo and the halogens were highly enriched (up to 20-100 fold) in the fine particles when compared to the coarse particles. (author). 14 refs, 6 figs, 2 tabs