BURNING CHARACTERISTICS AND GASEOUS SOLID EMISSIONS OF BLENDS OF PULVERIZED COAL WITH WASTE TIRE-DERIVED FUEL/

This work examined the combustion behavior (flame characteristics and temperatures) and the emissions (SO2, NO, NO2, CO, CO2, polynuclear ar omatic hydrocarbons (PAH), soot and ash) from blends of a pulverized b ituminous coal and ground waste automobile tires. The following fuel f eed compositions were examined: 100% coal, 75-25% and 50-50% coal and tire blends, as well as 100% tire. Coal and tire particles were in the size ranges of 63-75 and 180-212 fun, respectively. Combustion of cyl indrical streams of particles took place under steady flow conditions, in an electrically-heated drop-tube furnace in air, at a gas temperat ure of 1150 degrees C and a particle heating rate of approximate to 10 (5) degrees C/s. The bulk equivalence ratio, phi, in the furnace was v aried in the range of 0.5 to 2, by varying the particle mass loading. Combustion observations on burning clouds of particles were conducted with simultaneous pyrometry and cinematography. Interparticle flame in teractions were visually observed mostly in the near-stoichiometric an d fuel-rich regions. Volatile flame interactions were apparent at a lo wer phi for tire crumb particles than for coal particles and became pr ogressively more intense with increasing phi, until, at sufficiently h igh phi s large group flames formed for tire particles. As particle fl ame interactions increased, average maximum temperatures in the flame decreased. Coal particles resisted the formation of group flames, even at high phi s. Such observations correlated with the trends observed for the PAH emissions of the two fuels, those of tire crumb being much higher than those of coal and commencing at a lower phi. A certain de gree of stratification in the combustion of blends of particles of the two fuels was observed. This kept the PAH emissions at levels much lo wer than those expected based on the weighted average emissions of the two fuels. NOx emissions from tires were much lower than those of coa l, while those of the blends were close to the weighted average emissi ons. Combustion of fuel blends in the two aforementioned particle size cuts, generated the lowest NOx emissions when the small coal particle s were combined with either the small or the large tire particles. SO2 emissions from the blends were found to be close to the weighted aver age emissions of the two fuels. Blending coal with tire reduced the CO 2 emissions of coal but increased the CO emissions. CO emissions were significant only in the fuel-rich region. Tire ash was of similar size and shape as the parent tire particles themselves. To the contrary, t he ash of coal was polydisperse, including large cenospheres and tiny particle fragments. Particulate emissions (soot and ash), measured in the range of 0.4 to 8 mu m, increased with phi. Generally, tire produc ed more mass of submicron particulates than coal. Particulate emission s of blends of the two fuels were close to those expected based on wei ghted average of the two fuels.