Effect of the chlorine/sulphur ratio on organic emissions from the combustion of mixed fuels. Final Report

摘要

It can be concluded that the energy recovery of mixed plastics, when representing 15-70 % of thermal input, through co-combustion with coal, can be performed efficiently and safely, with all emissions except HCl being lower than for coal alone. Combustion of 100 % mixed plastics was incomplete and led to elevated carbon monoxide, hydrocarbon (CH(sub tox) and C(sub 6)-C(sub 12) aromatics), and PCDD/PCDF emissions. The PS/PVC fraction performed equally to the polyolefins-rich plastic mixture. All the co-combustion tests gave total PCDD/PCDF emissions (as Nordic equivalents) equal to coal alone, and well below 0.1 ng/Nm(sup 3) in the flue gas. Limestone injection improved combustion efficiency, reduced carbon monoxide levels, and bound sulphur and some chlorine to the bottom slag and fly ash. It also caused somewhat elevated PCDD/PCDF emissions, 0.07 ng/Nm(sup 3) compared to 0.02 ng/Nm(sup 3) in tests with coal and plastic/coal mixtures. This could be explained by either deactivation of the catalyst (by sulphur) and/or increased activity of the catalyst in the fly ash (calcium, tin, chlorine). Formation of PCDD/PCDF in the ESP could not be detected. No significant variations in the copper content of the fly ash could be seen.