Coal flash pyrolysis: secondary cracking of tar vapours in the range 870–2000 K
✍ Scribed by Kenneth R. Doolan; John C. Mackie; Ralph J. Tyler
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- English
- Weight
- 818 KB
- Volume
- 66
- Category
- Article
- ISSN
- 0016-2361
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✦ Synopsis
Tar free from influences of the original coal or char was cracked in two reaction systems, one using tar vapour in tubular quartz reactors at 9OG1400 K and reactor residence times of = 0.2 and = 1 s, the other using tar aerosol in a shock tube at I1 O&2000 K and residence time = 1 ms. In the latter system the aerosol evaporated rapidly after passage of the shock front and the tar behaved kinetically as a vapour. Yields of light hydrocarbons including C,H, and CO from tar cracking were determined as a function of temperature. Maximum yields of individual species agreed well between the two reactors but the temperatures ofmaximum yield depended on residence time. Hydrocarbon yields on a dafcoal basis were very similar to those obtained previously by direct flash pyrolysis of the same coal at 870-1270 K. Kinetic analyses of the formation of C,H,, C,H, and C,H, gave activation energies of 220-260kJ mol-', similar to those for formation of the same hydrocarbons from n-hexadecane. The precursors of the alkenes could be polymethylene groups in the tar. CH,, C,H, and CO all had low activation energies offormation, reflecting the many different functional groups capable of eliminating these molecules.