Field and laboratory leaching studies of retorted Kentucky oil shale. Final report.

摘要

The purpose of this report is to present the results of a field study on the environmental and reclamation characteristics of retorted eastern oil shale and associated materials. Retorted, raw and raw and retorted mixtures of eastern oil shale from a pilot test using the Dravo Traveling Grate Retort were placed in field lysimeters and sampled weekly or biweekly over a period of 1300 days. Retorting the oil shale induced significant changes in the clay minerals, with the decrystallization of kaolinite and illite being the major effects. The leachates generated in the field lysimeters were highly acidic, with pH's varying from approximately 2.5 to 3.5. The leachates had high concentrations of dissolved elements with sulfate, Mg and Fe present at tens of thousands or thousands of ppM. Acid generation and elemental concentrations in the leachates were highest in the first year. Even after 1300 days, the leachates remained very acidic with pH's in the 2.9 to 3.4 range and sulfate concentrations of 3,000 to 5,000 ppM. Iron, Mg and sulfate were present in the highest concentrations in the leachates from the unretorted oil shale. The clay minerals of the retorted shale were found relatively reactive in comparison to the raw shale as indicated by much higher Al and K concentrations in their leachates compared to that of the raw shale. In general, the chemistry of the leachates was determined by the kinetics of solution reactions and materials transport. Calcium concentration however appeared to be controlled by mineral equilibria with respect to gypsum. Laboratory-based leaching experiments produced leachates with elemental concentrations much lower than the field study. Leachates from column experiments, that closely simulated field conditions, were found to have chemical compositions comparable to that from the field and also produced similar elemental release patterns. 38 refs., 22 figs., 12 tabs.