ENVIRONMENTAL ASSESSMENT OF FLY ASH FROM SOME THERMAL POWER STATIONS FOR RECLAMATION OF MINED OUT AREAS

Gurdeep Singh

Centre of Mining Environment, Department of Environmental Science & Engineering
Indian School of Mines University , Dhanbad - 826 004

Published in:
Proceedings of Golden Jubilee Seminar on "Present Status of Mining and Future Prospects" April 6-8, 2007 at Hyderabad.

ABSTRACT

Coal occupies an important position in energy sector in India since India has vast reserves of thermal grade coal. Combustion of coal to generate electricity produces large volumes (>120 million tonnes) of coal combustion residues (CCRs) particularly fly ash as Indian coals contain high ash. These fly ash dominated CCRs accumulates in on-site piles and ash ponds leading to serious environmental problems, particularly contamination of ground and surface waters due to leaching of trace elements. There is a widespread concern to enhance the utilization of fly ash considerably. One of the major areas of utilization of fly ash can be as back fill material for mine reclamation. This study was carried out to evaluate the long-term leaching of trace elements for assessing the high volume utilization of fly ash in mined out areas reclamation.

The leaching characteristics were evaluated through various shake (ASTM 30 Day, TCLP, SLP) and open column percolation experiments. It has been established that open percolation column experiments are the only leaching methodology to evaluate the actual leaching behaviour of trace elements from coal/ fly ashes in real world situations. Overall the leaching characteristics envisaged that fly ash generally is environmentally benign, as there does not occur significant leaching of trace elements as determined though long-term open-column leaching experiments.

Environmental assessment through open percolation column experiments carried over three (03) years established the fly ash from various thermal power stations as environmentally benign material. Field studies from actual ash ponds also validate this observation. High volume fly ash utilization in mine reclamation is gaining momentum on the basis of initial success achieved in some areas. Overall this study indicates that fly ash can be disposed and utilised in mined out areas in an environmentally acceptable manner.

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