THE FATE OF TRACE-ELEMENTS AND BULK MINERALS IN PULVERIZED COAL COMBUSTION IN A POWER-STATION

The behaviour of 15 trace elements (As, Ba, Cr, Cu, Mn, Mo, Nb, Ni, Pb , Rb, Sr, V, Y, Zn and Zr) and 10 major and minor elements (Al, Ca, Fe , K, Mg, Na, P, S, Si and Ti) in coal during combustion in a power sta tion has been studied. Synchronized sampling of pulverized coal, botto m ash and fly ash was undertaken over a limited time period. Fly ash m orphology was studied by SEM and the mineral composition was studied b y EDX and XRD. Major, minor and trace elements were determined by XRF and AAS. Differences between the composition of the ashes of pulverize d coal, bottom ashes and fly ashes have been observed. As, Cu, Mo, Pb and Zn were concentrated in the fly ash. The relationship between the composition of the fly ashes and their particle size was studied. Enri chment factors were calculated for each element in different size frac tions. As the particle sizes of fly ash decrease, the concentrations o f As, Cu, Mo, Pb and Zn increase. From the different composition of bo ttom ashes and fly ashes (and relying on the results of the characteri zation of the feed coal carried out in previous work), it can be assum ed that pyrite and carbonates make a greater contribution to the furna ce bottom ashes. Quartz carries through into the fly ash. This mineral is almost absent in the finest fractions, reflecting the absence of s mall quartz particles in the feed coal.