Year of Publication

2012

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Engineering

Department

Mining Engineering

First Advisor

Dr. Frank E. Huggins

Second Advisor

Dr. Rick Q. Honaker

Abstract

To assess strategies aimed at minimizing the release of trace elements and the impact of disposal of coal waste materials on the environment, two long-term leaching experiments of up to five months duration were performed using waste materials from two plants cleaning high and low sulfur bituminous coal. The tests evaluated the mobility of major trace elements under different disposal scenarios: (i) a static leaching test designed to simulate the quiescent conditions encountered by coal waste material stored under water in a stable impoundment, and (ii) a dynamic test to simulate waste materials exposed to the atmosphere, either in variable wet/dry storage conditions, or in unusual circumstances like those resulting from breaching of an impoundment containment wall. The results indicate that different refuse streams have different leaching characteristics due to difference in their mineralogy and the mobility of most elements is enhanced under highly alkaline or acidic conditions with a few being mobilized under both conditions, suggesting that the minimization of element mobility requires the pH value of the medium to be maintained around neutral. In addition, most of heavy metals were associated with the illite and pyrite minerals. Two strategies of treating coal refuse were evaluated: fly ash mixed with coarse refuse and co-disposal of coarse and fine refuse. Both methods were found to neutralize the pH conditions and thus reduce mobility of the trace elements in static leaching tests whereas the opposite was found from dynamic experiments. The results indicate that such controlled storage under water could retard acid generation and the mobility of trace elements.

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