Burning Characteristics and Gaseous/Solid Emissions of Blends of Pulverized Coal with WasteTire-Derived Fuel

Abstract

This work examined the combustion behavior (flame characteristics and temperatures) and the emissions (SO₂, NO, NO₂, CO, CO₂, polynuclear aromatic hydrocarbons (PAH), soot and ash) from blends of a pulverized bituminous coal and ground waste automobile tires. The following fuel feed 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 μm, respectively. Combustion of cylindrical streams of particles look place under steady flow conditions, in an electrically-heated drop-tube furnace in air, at a gas temperature of 1150°C and a particle heating rate of ≈105°C/s, The bulk equivalence ratio, φ, in the furnace was varied 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 interactions were visually observed mostly in the near-stoichiometric and fuel-rich regions. Volatile flame interactions were apparent at a lower φ for tire crumb particles than for coal particles and became progressively more intense with increasing φ until, at sufficiently high φs large group flames formed for tire particles. As particle flame interactions increased, average maximum temperatures in the flame decreased. Coal particles resisted the formation of group flames, even at high φs. 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 φ. A certain degree of stratification in the combustion of blends of particles of the two fuels was observed. This kept the PAH emissions at levels much lower than those expected based on the weighted average emissions of the two fuels. NO_x emissions from tires were much lower than those of coal, while those of the blends were close to the weighted average emissions. Combustion or fuel blends in the two aforementioned particle size cuts, generated the lowest NO_x emissions when the small coal particles were combined with either the small or the large tire particles. SO₂ emissions from the blends were found to be close to the weighted average emissions of the two fuels. Blending coal with tire reduced the CO₂ emissions of coal but increasedtheCO emissions. CO emissions were significant only in the fuelrich region. Tire ash was of similar size and shape as the parent tire particles themselves. To the contrary, the 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 Sum, increased with φ. Generally, tire produced more mass of submicron particulates than coal. Particulate emissions of blends of the two fuels were close to those expected based on weighted average of the two.fuels,

Keywords:

• Flame characteristics
• emissions bulk equivalence ratio

Additional information

Notes on contributors

YIANNISA. LEVENDIS

Corresponding author.