Effects of pyrolysis conditions and ion-exchangeable cations on the thermal decomposition of a Victorian low-rank coal
- Monash Univ., Clayton, Victoria (Australia)
A Loy Yang brown coal sample was acid-washed and ion-exchanged with Na and Ca to prepare the H-form, Na-form and Ca-form coal samples. These coal samples were pyrolyzed in a wire-mesh reactor where the extraparticle secondary reactions of the evolved volatiles were minimized. The ion-exchanged coal samples were found to give very different tar yields from those of the raw coal samples. The tar yields from the pyrolysis of the raw and H-form coal samples were observed to be very sensitive to changes in heating rate and the tar yields at 600 C were found to increase much more than the corresponding increases in the total volatile yields as the heating rate was increased from 1 to 1,000 K/s. In contrast, the tar yields from the Ca-form and Na-form coal samples showed little heating rate sensitivity. The heating rate sensitivity of pyrolysis yields is believed to be at least partly related to the presence of carboxyl/carboxylate groups and other bulky substitution groups in the coal as well as the rapid pressure buildup within the particles. Re-exchanging Na in the Na-form coal sample and Ca in the Ca-form coal sample with H confirmed the effects of Na and Ca, but also suggested that the irreversible structural changes taking place during ion-exchange should also be considered to evaluate the effects of ion-exchangeable cations during pyrolysis. The major roles of ion-exchangeable cations during pyrolysis are thought to be associated with the transformation of the alkali and alkaline earth metallic species. Some Ca was volatilized during pyrolysis, even at temperatures as low as 600 C.
- OSTI ID:
- 349216
- Report Number(s):
- CONF-980985-; ISBN 1-890977-15-2; TRN: IM9924%%216
- Resource Relation:
- Conference: 15. annual international Pittsburgh coal conference, Pittsburgh, PA (United States), 14-18 Sep 1998; Other Information: PBD: 1998; Related Information: Is Part Of Fifteenth annual international Pittsburgh coal conference: Proceedings; PB: [1500] p.
- Country of Publication:
- United States
- Language:
- English
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