Stability of SiC, Si/sub 3/N/sub 4/, Si/sub 2/N/sub 2/O, SIALON and chromium oxide-containing refractories in coal-gasification environments. Final report

Technical Report · Fri Feb 13 04:00:00 EST 1981

DOI:https://doi.org/10.2172/6528894· OSTI ID:6528894

Muan, A.

The main conclusions from these studies are as follows: while the solubilities of Cr/sub 2/O/sub 3/ and chromites in the silicate melts concerned are relatively small under the atmospheric conditions usually prevailing in slagging coal gasifiers, the solubilities increase drastically at extremely low oxygen pressures, under which conditions a substantial fraction of the chromium is present in the silicate liquid as Cr/sup 2 +/. The oxygen pressures at which this situation prevails, however, are somewhat lower than those usually prevailing in coal gasification atmospheres. The lowest liquidus and solidus temperatures in the systems Ca/sub 2/Al/sub 2/SiO/sub 7/-CaAl/sub 2/Si/sub 2/O/sub 8/-MgCr/sub 2/O/sub 4/ systems are not significantly below those of the Ca/sub 2/Al/sub 2/SiO/sub 7/-CaAl/sub 2/Si/sub 2/O/sub 8/ join (approx. 1387/sup 0/C) because of the relatively low solubility of Cr/sub 2/O/sub 3/ (and MgCr/sub 2/O/sub 4/) in these silicate melts, as noted above. With increasing Al/sub 2/O/sub 3//Cr/sub 2/O/sub 3/ ratios of the refractor phases however, the lowest liquidus and solidus temperatures decrease considerably, as larger amounts of Al/sub 2/O/sub 3/ or MgAl/sub 2/O/sub 4/ of the refractory phase dissolve in the silicate liquid. The mutual solubilities between Al/sub 2/O/sub 3/- and Cr/sub 2/O/sub 3/ end members in the system CaO-Al/sub 2/O/sub 3/-Cr/sub 2/O/sub 3/ are rather limited. Two new ternary compounds, E and L, have been synthesized, with compositions approximately as follows: E: 19 wt. % CaO, 38 wt. % Al/sub 2/O/sub 3/, 43 wt. % Cr/sub 2/O/sub 3/; L: 44 wt. 5 CaO, 33 wt. % Al/sub 2/O/sub 3/, 23 wt. % Cr/sub 2/O/sub 3/. A quinary compound has been found in the system CaO-MgO-Al/sub 2/O/sub 3/-Cr/sub 2/O/sub 3/-SiO/sub 2/, with composition approximately as follows: 15 wt. % CaO, 6 wt. % MgO, 40 wt. % Al/sub 2/O/sub 3/, 30 wt. % Cr/sub 2/O/sub 3/, 9 wt. % SiO/sub 2/.

• Research Organization: Pennsylvania State Univ., University Park (USA). Coll. of Earth and Mineral Sciences
• Sponsoring Organization: USDOE
• DOE Contract Number: AS05-77ET10476
• OSTI ID: 6528894
• Report Number(s): DOE/ET/10476-T1; FE-2708-13
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010404* -- Coal
Lignite
& Peat-- Gasification
36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
ALUMINIUM SILICATES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CALCIUM SILICATES
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
COAL GASIFICATION PLANTS
DIAGRAMS
INDUSTRIAL PLANTS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MAGNESIUM SILICATES
MATERIALS TESTING
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHASE DIAGRAMS
PNICTIDES
REFRACTORIES
SILICATES
SILICON CARBIDES
SILICON COMPOUNDS
SILICON NITRIDES
SILICON OXIDES
SOLUBILITY
STABILITY
TESTING
TRANSITION ELEMENT COMPOUNDS
VERY HIGH TEMPERATURE