Ash formation mechanisms during of combustion in reducing conditions

Citation
Ar. Mclennan et al., Ash formation mechanisms during of combustion in reducing conditions, ENERG FUEL, 14(1), 2000, pp. 150-159
Citations number
21
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Environmental Engineering & Energy
Journal title
ENERGY & FUELS
ISSN journal
0887-0624 → ACNP
Volume
14
Issue
1
Year of publication
2000
Pages
150 - 159
Database
ISI
SICI code
0887-0624(200001/02)14:1<150:AFMDOC>2.0.ZU;2-6
Abstract
A range of pulverized coals were combusted in a laboratory drop-tube furnac e at temperatures of 1573, 1723, and 1873 K under oxidizing and reducing co nditions to determine the effect of combustion stoichiometry on ash formati on mechanisms. As iron mineral transformations were expected to be most aff ected by combustion stoichiometry, two of the test coals chosen were of hig h pyrite (FeS2) content and two of high siderite (FeCO3) content. It was fo und that the ash formation mechanisms of excluded quartz, koalinite, and ca lcite were not affected by oxidizing or reducing combustion conditions. Exc luded pyrite was found to decompose to pyrrhotite, which oxidized to produc e an FeO-FeS melt phase which was stable under reducing conditions. Under o xidizing conditions oxidation continued, producing magnetite and hematite. Excluded siderite was found to decompose to wustite, which was stable under reducing conditions, but oxidized to produce magnetite under oxidizing con ditions. Included pyrite and siderite were determined to behave as for excl uded pyrite and siderite if there was no contact with alumino-silicates. In cluded pyrite that contacted alumino-silicate minerals was observed to form two-phase FeS/Fe-glass ash particles, with incorporation of iron into the glass proceeding as the FeS phase was oxidized. Included siderite that cont acted alumino-silicate minerals was determined to directly form iron alumin o-silicate glass ash particles. Iron alumino-silicate glass ash was determi ned to form with iron in the Fe2+ state, much of which subsequently transfo rmed to the Fe3+ state in oxidizing conditions, but remained primarily as i n the Fe2+ state under reducing conditions.