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Use of oxygen-enriched gas for the oxidation of acid and fluxed taconite pellets.

Authors
Haas-LA
Source
Minneapolis, MN: U.S. Department of the Interior, Bureau of Mines, RI 9473, 1993 Jan; :1-22
NIOSHTIC No.
10012171
Abstract
The U.S. Bureau of Mines, in cooperation with Cleveland-Cliffs, Inc. (Hibbing, Minnesota), investigated ways of enhancing the quality (compressive strength, after-tumble and reducibility) of domestic acid and fluxed magnetite pellets by modifying the oxygen content during the preheat and induration periods of the firing operation. Oxidation of magnetite was best accomplished when sufficient oxygen and time were available before the peak induration temperature was reached. The rate of magnetite oxidation increased directly with the gas oxygen content during the preheat period at 700 deg C and above. With 30 pct (or more) O2 and a preheat rate of 200 deg C/min, most of the magnetite was oxidized during the preheat period. With laboratory tube and mini-pot furnace tests, oxygen enrichment during the preheat period improved the pellet properties more in the simulated grate-kiln tests than in the simulated straight-grate tests. The longer induration period with the grate-kiln test resulted in more sintering of the residual magnetite and its reaction with the silicon compounds. When flux was present in the pellets, calcium silicates and calcium and magnesium ferrites were formed. More calcium ferrite was formed when the magnetite was oxidized early and less iron was present in the fayalitic calcium silicate slag.
Keywords
Mineral-processing; Minerals; Metal-mining; Metal-industry; Materials-testing
Publication Date
19930101
Document Type
Report of Investigations
Fiscal Year
1993
NTIS Accession No.
PB93-232536
NTIS Price
A04
Identifying No.
RI-9473
NIOSH Division
TCRC
Source Name
Minneapolis, MN: U.S. Department of the Interior, Bureau of Mines, RI 9473
State
MN
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