Abstract
The pyrolysis of four pairs of raw and acid-washed coals under N2 atmosphere was carried out in a drop tube reactor at 1250 °C. The results show that both organic structures and metal elements have an important influence on the formation of soot. The total area of aromatic and aliphatic hydrogen absorption bands is positively correlated with soot yield. Aromatic compounds have a greater contribution to soot and tar formation. The absorption band area of oxygen structures in coal FTIR spectra is negatively correlated with the soot conversion rate of tar. During pyrolysis, metal substances in coal can catalyze the dehydrogenation and deoxygenation of tar, reduce the content and stability of the aliphatic compound, and catalyze aromatic ring rupturing. More importantly, gasified metals can inhibit the polymerization reaction of aromatic compounds.
Highlights
When in a high-temperature environment, coal will first undergo pyrolysis
The results showed that the formation of soot could not be observed in the combustion process of anthracite with a low volatile content, while lignite with a high volatile content has no initial soot particles generated in the vicinity of coal particles due to its low content of macromolecular heavy hydrocarbons in the volatile matter
The effect of coal chemical structure on the formation of soot was analyzed by studying the yield and chemical structure of soot and tar generated by coal pyrolysis
Summary
When in a high-temperature environment, coal will first undergo pyrolysis. Soot is produced in the boundary layer of coal particles during pyrolysis [1]. Wornat et al [13] studied the production and composition changes of soot and PAC (polycyclic aromatic compounds, which are the main component of coal tar) using a drop tube reactor at different temperatures (1130~1480 K) and residence time. In contrast to the experimental result observed by Wornat [13] and Nenniger [14], the yield of coal-derived soot produced in the flue-gas environment is lower than the inert atmosphere, this may due to the reaction of tar molecules and even soot with oxygen-containing components (H2 O, OH, O etc.) in a flue-gas environment Both organic and inorganic structures of coal affect the pyrolysis products. The yields and particle size distributions (PSDs) of the solid secondary pyrolysis products (soot and tar) and its Fourier transform infrared spectroscopy (FTIR) spectra are analyzed to explore the relationship between coal chemical structure (FTIR parameters and inherent metal content) and its soot generation characteristics
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