Chapter 35
Iron Sulfide Oxidation Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on August 26, 2015 | http://pubs.acs.org Publication Date: December 20, 1993 | doi: 10.1021/bk-1994-0550.ch035
Impact on Chemistry of Leachates from Natural and Pyrolyzed Organic-Rich Shales Thomas L. Robl Center for Applied Energy Research, University of Kentucky, 3572 Iron Works Pike, Lexington, KY 40511
Retorted and raw Devonian oil shales were placed in large field lysimeters and allowed to weather for a period of 1300 days. The shales were composed of iron sulfides and silicates (quartz, illite, chlorite and kaolinite). Retorting induced the dehydroxylation and decrystallization of kaolinite and illite and converted part of the pyrite to pyrrhotite. The leachates generated in the field lysimeters were highly acidic (pH 2.5 to 3.5) with high concentrations ofSO 2-,Mg and Fe (1,000 to 10,000 ppm); Al, Zn, Na, Ca, Κ (100 to 1,000 ppm); Ni and Mn (10 to 100 ppm). The concentrations of most of the elements in the raw-shale leachates were a function of the rate of acid generation. The matrix of the retorted shale was more reactive than the raw shale. Elemental release was transport controlled, with the exception of Ca, which appeared to be near equilibrium with respect to gypsum. 4
Organic-rich Devonian black shale occurs throughout much of the mid-western United States. In addition to serving as a major source of oil and gas, certain stratigraphie intervals are sufficiently high in kerogen to be considered oil shales (1). A significant research effort was initiated in the early 1980's to study the economic feasibility of developing this resource, with environmental research as a component. A focus of concern was the acid-generating and elemental-release characteristics of retorted and raw shale. An opportunity to examine the weathering characteristics of these shales occurred in 1983 when a pilot-plant study of Devonian oil shale was undertaken by a consortium, led by the Southern Pacific Petroleum Company, in response to a solicitation by the Synthetic Fuels Corporation. The pilot plant was the Dravo traveling-grate facility located in Cleveland, Ohio. This plant consists of a circular grate retort 8.2 m in area, capable of retorting up to 250 tonnes/day of raw shale (2-4). The test utilized 1,000 tonnes of 25 mm χ 6 mm sized shale, two-thirds of 2
0097-6156/94/0550-0574$06.00/0 © 1994 American Chemical Society In Environmental Geochemistry of Sulfide Oxidation; Alpers, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.
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Iron Sulfide Oxidation
which was mined from the Cleveland Member of the Ohio shale and one-third from the overlying Sunbury Shale. The shale was mined in Montgomery County, Kentucky. The spent shale along with the
