Assessment on combustion chemistry of coal volatiles for various pyrolysis temperatures.

Carrying out in-depth research on the formation characteristics and mechanisms of organic products in coal combustion will help to provide theoretical guidance for the emission reduction of coal-fired pollutants. Since the combustion of coal volatiles plays a vital role in the whole process of coal combustion, this work took coal pyrolysis gases as fuels and focused on the organic pollutants such as alkanes, olefins and aromatics in the combustion of coal pyrolysis gases. To explore the effects of three pyrolysis temperatures of 600 °C, 750 °C and 900 °C on the formation characteristics and mechanisms of hydrocarbon products during coal pyrolysis gases combustion, the online detection was carried out by gas chromatography (GC) and gas chromatography-mass spectrometer (GC-MS) on the counterflow diffusion flame platform, combined with chemical reaction kinetics simulations. The results showed that rising pyrolysis temperature had an inhibitory effect on the formation of light hydrocarbons and aromatic hydrocarbons, such as acetylene (C 2 H 2), propyne (PC 3 H 4), 1,3-butadiene (C 4 H 6 -13), vinylacetylene (C 4 H 4), diacetylene (C 4 H 2), benzene (C 6 H 6), toluene (C 6 H 5 CH 3) and naphthalene (C 10 H 8), during the combustion of pyrolysis gases. Among three mechanisms used in this study, Creck mechanism was more accurate and applicable than KM2 mechanism and AramcoMech 3.0 mechanism. As the pyrolysis temperature rose, the rate of the reactions which dominated the formation of C 2 H 2 , propargyl (C 3 H 3), C 6 H 6 and C 10 H 8 decreased continuously, because the decrease of CH 3 concentration and the increase of H concentration inhibited the forward progress of these reactions. In addition, with rising pyrolysis temperature, less C 3 H 3 was converted to butadiene (C 4 H 6), C 6 H 6 and Fulvene, and more inclined to its upstream reactants, allene (AC 3 H 4) and PC 3 H 4. The tendency of phenyl (C 6 H 5) to form C 6 H 6 was strengthened. Meanwhile, less C 10 H 8 was generated from C 4 H 4 and C 6 H 5 , but the dominant role of this reaction was still enhanced. •Effects of pyrolysis temperature on coal volatiles flame chemistry was revealed. • Light and aromatic hydrocarbons in coal pyrolysis gas flames were analyzed. • Kinetic analysis was performed to explore pollutants formation mechanisms. • Results can serve for future coal volatiles combustion mechanisms optimization. [ABSTRACT FROM AUTHOR]