| This is an experimental investigation on the combustion and emissions of solid carbonaceous fuels. The fuels considered were coal, coal/carbon-water fuels (CWF) and waste automobile tire-derived-fuel. Combustion studies on single fuel particles or streams of particles were conducted in lab scale furnaces: two similar electrically heated drop-tube laminar-flow furnaces, a horizontal muffle furnace and a thermo-gravimetric analyzer (TGA). A three-color near-infrared optical pyrometer and a high-speed camera were used to monitor combustion behavior. Emissions of sulfur dioxide (SO{dollar}sb2),{dollar} nitrogen oxides (NO{dollar}sb{lcub}x{rcub}),{dollar} carbon monoxide (CO), carbon dioxide (CO{dollar}sb2),{dollar} polycyclic aromatic hydrocarbons (PAHs) and particulates (soot, ash, etc.) were measured at the exit of the furnace(s). The main parameters varied were the gas temperature and the fuel to air equivalence ratio.; Results showed that heating of single bituminous CWF droplets evaporated the water and resulted in agglomerates, which upon devolatilization were observed to melt and swell. Addition of the organic salt of calcium magnesium acetate (CMA) suppressed the melting and swelling. In the furnace gas temperature range (1300-1600 K) considered, coal (75-212 {dollar}mu{dollar}m) and CWF agglomerates (150-900 {dollar}mu{dollar}m) burned with distinct volatile and char combustion phases. The char combustion phase of most particle sizes took place under oxygen diffusion control. The combustion behavior of the CWF agglomerates from either plain coal, pulverized (30-45{dollar}mu{dollar}m) or micronized (0.5-7.5{dollar}mu{dollar}m), or coal impregnated with CMA, was similar. On the other hand, pulverized coal particles (75-90{dollar}mu{dollar}m) impregnated with CMA burned hotter than untreated coal particles. Tire particles did not exhibit swelling or melting upon devolatilization. Tire particles experienced an intense primary volatile combustion phase followed by a phase of secondary volatile combustion and char combustion. Char burnout times were considerably shorter for tire particles than coal particles of similar size.; Emissions of SO{dollar}sb2{dollar} and CO{dollar}sb2{dollar} from combustion of the coal and tire particles considered herein were comparable. NO{dollar}sb{lcub}x{rcub}{dollar} emissions from burning tire particles were much lower than those from burning coal particles, reflecting the lower initial fuel nitrogen content. Generally, the CO and, especially, the PAH emissions from tire-derived fuel were much higher than those from coal. Results showed that both CO and PAH emissions increased with the bulk equivalence ratio, in the furnace, at a fixed gas temperature. However, at fixed bulk equivalence ratios the CO emissions of both fuels increased with increasing furnace gas temperature, while the PAH emissions decreased drastically. PAH emissions from continuos combustion of streams of pulverized tires in the drop tube furnace were much lower than batch combustion in the horizontal muffle furnace. For coal the above modes of combustion had little influence on these emissions. Emissions of particulates closely followed the trend of PAH emissions. Total particulate emissions from batch combustion of coal were significantly less than those from TDF. Combustion of coal and tire particles mixed with CMA particles drastically reduced SO{dollar}sb2{dollar} emissions, while it did not appreciably reduce NO{dollar}sb{lcub}x{rcub}.{dollar} Combustion of the two fuels mixed with CMA or CaCO{dollar}sb3{dollar} generated enhanced amounts of PAHs, while combustion with CaO had no effect on the PAH emissions. |
