A LABORATORY STUDY ON THE NO, NO2, SO2, CO AND CO2 EMISSIONS FROM THECOMBUSTION OF PULVERIZED COAL, MUNICIPAL WASTE PLASTICS AND TIRES

This is a laboratory study on the combustion emissions from pulverized solid fuels: NOx (NO and NO2), SO2, CO and CO2, Coal, waste tire crum b and waste plastics, such as poly(styrene), poly(ethylene), poly(meth yl methacrylate), poly(propylene) and poly(vinyl chloride) (PVC), were burned in an electrically heated drop-tube furnace at high particle h eating rates (10(4)-10(5) K s(-1)) and elevated gas temperatures (1300 -1600 K). The fuel to air bulk equivalence ratio, phi, was varied in t he range of 0.4-1.8. Air or a nitrogen-free mixture of O-2-CO2-Ar were used as oxidizing gases. Results showed that fuels which contain nitr ogen generated the highest NOx emissions. Combustion of coal generated four times more NOx than combustion of tire crumb, in proportion to t heir nitrogen content, and ten times more NOx than that of the nitroge n-free plastics. The specific NOx emissions decreased dramatically (3- 6 times) with increasing bulk equivalence ratio for all fuels. However , the NO2/NO ratio increased with the equivalence ratio in the fuel-ri ch region. Increasing the gas temperature, in the range 1300-1600 K, r esulted in 10-25% more NOx, depending on the fuel. Atmospheric nitroge n contributed 20% of the total NOx emissions for coal, 308 for tires a nd 100% for the plastics. SO2 emissions of the particular coal and tir e crumb tested were comparable. While absolute SO2 emissions of coal a nd tire increased with the equivalence ratio, specific emissions exhib ited a mild downward trend. SO2 emissions were higher in the absence o f atmospheric nitrogen, especially at fuel-rich conditions. Mild emiss ions of CO were encountered in the fuel-lean regions, but they increas ed exponentially in the fuel-rich region accounting for as much as 10% of the carbon at phi = 2. Overall, the CO2 emissions were proportiona l to the carbon content of the fuels. (C) 1998 Elsevier Science Ltd.