Effect of additives on pyrite oxidation.
Minneapolis, MN: U.S. Department of the Interior, Bureau of Mines, RI 9353, 1991 Jan; :1-13
Exothermic oxidation reactions of sulfide minerals can produce self- heating situations in underground mines. If the self-heating is unchecked and the resulting heat is not sufficiently dissipated, the results can be spontaneous combustion fires. This U.S. Bureau of Mines report describes laboratory tests conducted to measure the reactivity of pyrite following treatment with additives to counter its self-heating tendencies. Thermal gravimetric analysis and isothermal oxidation procedures were used to obtain information on pyrite ignition and the behavior of pyrite during low-temperature oxidation to ferrous sulfate. The determination of treatment effectiveness was evaluated by adding 5 wt pct of the compound to the pyrite before milling. The resulting samples were then heated in moistened air; after 24 h, the amount of pyrite oxidation was determined. Results of these tests indicated that several phosphate compounds reduced the oxidation of pyrite to sulfate to about 50 pct or less compared with the oxidation of untreated sample at 200 deg C. Cupric sulfate reduced oxidation to about 20 pct untreated sample at 200 deg c. Sodium, calcium, and potassium chloride reduced pyrite oxidation to levels of approximately 15 pct or less of the untreated sample. Using only 1 pct of sodium or calcium chloride was effective in slowing pyrite oxidation to less than 20 pct of the untreated sample.
Additives; Chemical-reactions; Laboratory-tests; Chlorides; Phosphates; Copper-sulfates; Pyrite; Oxidation; Spontaneous-combustion
IH; Report of Investigations
NTIS Accession No.
Minneapolis, MN: U.S. Department of the Interior, Bureau of Mines, RI 9353