Nitration of polynuclear aromatic hydrocarbons in coal combustors and exhaust streams: Final report, September 1, 1991--September 30, 1994

The objectives of this three-year project were to (1) identify the conditions which promote the nitration of PAH during primary combustion, reburning, hot gas cleanup, and particulate removal; and (2) investigate the potential relationship between NOx abatement and PAH nitration. Meeting the objectives of this program involved two broad tasks: (1) Preparing the polynuclear aromatic hydrocarbons (PAH) under closely monitored pulverized fuel (p. f.) firing conditions; and, (2) analyzing the PAH samples to monitor extents of nitration, ring number distribution, etc. A novel coal flow reactor burning actual coal products that operates over the domains of heating rates, temperatures, fuel-equivalence ratios, and residence times in utility boilers was used to generate the coal tar samples. The distribution of products obtained from primary, secondary, and oxidative pyrolysis of two coal types, Pittsburgh No. 8 and Dietz, were analyzed, with emphasis on the nitrogen-containing species generated. The coal tax samples collected from the coal flow reactor were fractionated based on their size and polarity using gravity flow column chromatography. After examining how the sample fractionation depended on the coal type and pyrolysis conditions, the relatively nonpolar fraction was further analyzed via high performance liquid chromatography, to characterize the ring number distribution of the polycyclic aromatic compounds (PAC) present. Finally, gas chromatographic techniques were utilized to measure the amount of nitrogen-containing PAC present, and to investigate how much of these nitrogen-containing species consist of nitro-PAH