Soot formation during coal pyrolysis

Journal ArticleSoot can be found in almost all combustion and pyrolysis systems. In a coal system, the impact of soot on coal combustion can be identified in two ways. First, soot particles suspended in the combustion flame significantly enhance radiative heat transfer near the burner due to their large surface area, small size and spectrally continuous radiation characteristics [1]. Second, part of the nitrogen released from coal during devolatilization will be reincorporated into soot, which complicates nitrogen transformations and NOx production. The study of the chemical structure of soot is also important for many environmental and health reasons. Soot, formed by condensation of polyaromatic hydrocarbons (PAH), poses a health hazard, since many PAH produced in pyrolysis or combustion processes are carcinogenic and mutagenic materials [2]. Soot has also been found in the unburned carbon in flyash [3]

Investigation of the structural conformation of biphenyl by solid state 13C NMR and quantum chemical NMR shift calculations

abstractThe principal values of the 13C chemical-shift tensor (CST) for biphenyl have been determined with the FIREMAT experiment. The internal dihedral angle between the benzene rings in biphenyl is estimated to fall between 10 and 20° on the basis of quantum mechanical calculations of the CST principal values. A composite model of motion in the system, with contributions both from internal jumping between enantiomeric structures and from overall molecular librations, yields the smallest variance between predicted and measured values for an internal twist angle of 15° between the rings and a mean libration angle of ±12° from the most favored molecular orientation. The composite model is clearly preferred to a motionless model (with >98% probability) and is also preferred over either of the isolated contributing dynamics, i.e., only libration or only internal jumping