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Influence of reducing conditions on the softening-melting characteristics of taconite pellets.

Authors
Haas-LA; Aldinger-JA; Zahl-RK
Source
Minneapolis, MN: U.S. Department of the Interior, Bureau of Mines, RI 9357, 1991 Jan; :1-21
Link
NIOSHTIC No.
10009111
Abstract
The U.S. Bureau of Mines is investigating ways of enhancing the high- temperature softening-melting (htsm) properties of domestic taconite pellets. These properties, which are important for determining the performance of pellets in blast furnaces, include pellet bed contraction, pressure drop, S-value (area under the pressure- temperature curve), and softening and metal-slag drainout temperatures. Experiments showed that HTSM properties were related to the physiochemical properties (fired strengths and reducibilities) of pellets containing different levels of limestone and dolomite flux. Flux additions resulted in slightly lower green and fired pellet strengths, but improved metallurgical properties, such as reducibility. The influence of reduction conditions on HTSM properties was evaluated by varying the pellet metallization starting temperature and the carbon monoxide content of the CO-N2 gas mixture. HTSM property change was more sensitive to flux addition levels when metallization was initiated at 1,100 deg C with 20 pct CO in the gas stream. The S-value and the metal-slag drainout temperature were found to be the best criteria for characterizing htsm properties. The optimum flux addition level was about 8 pct (4 pct dolomite, 4 pct limestone) or a basicity of about 1. At higher flux levels, a higher metal-slag drainout temperature was obtained.
Keywords
Thermophysical-properties; Limestone; Dolomite-Mineral; Fluxes; Carbon-monoxide; Iron-ores; Blast-furnaces; Metallurgy; Chemical-reactions; Taconite; Softening-points; Melting; Pellets
Publication Date
19910101
Document Type
IH; Report of Investigations
Fiscal Year
1991
NTIS Accession No.
PB91-225086
NTIS Price
A03
Identifying No.
RI-9357
NIOSH Division
TCRC
Source Name
Minneapolis, MN: U.S. Department of the Interior, Bureau of Mines, RI 9357
State
MN
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