ORGANIC EMISSIONS FROM COCOMBUSTION OF MIXED PLASTICS WITH COAL IN A BUBBLING FLUIDIZED-BED BOILER

Mixed plastics can be burned safely with coal in modem fluidized bed b oilers when flue gas carbon monoxide and dust emissions are kept low. The level of total emissions per thermal unit using plastics is smalle r than when using coal. The proportion of mixed plastics incorporated into the plastics/coal fuel blends used in the tests did not affect th e emission levels of polychlorinated dibenzodioxines and dibenzofurans (PCDD/Fs). The addition of limestone to the fluidized bed resulted in slightly increased PCDD/F levels, but these nevertheless remained sig nificantly below 0.1 ng/Nm3 TE NORDIC. It is probable that the sulphur contained in the primary fuel poisoned the catalysts responsible for the formation of PCDD/F in all the plastics/coal blends. Limestone aff ected the formation of PCDD/F by binding sulphur in the gas phase or b y increasing the calcium, tin, and chlorine levels of the fly ash. Onl y a small variation was observed in the copper concentrations of the f ly ashes generated.