Application of fly ash in the agglomeration of reactive mine tailings

摘要

Agglomeration is one of the most effective methods of dealing with reactive mine tailings in the prevention of acid mine drainage. The agglomeration process, accomplished with the use of a conventional binder such as Portland cement, immobilizes the reactive components of the mine tailings and results in the formation of strong pellets which remain impervious to weathering and leaching. The objective of this study was to evaluate the fly ash as a binder, either by itself or in combination with cement, in the mitigation of acid mine drainage caused by the reactive tailings. Two different acid mine tailings samples differing in their reactivities were chosen. These tailings were obtained from Noranda, Quebec, Canada and Cyprus Thompson Creek, Clayton, Idaho. The fly ash was obtained from Mineral Specialities Inc., Billings, Montana. Agglomeration tests were performed with fly ash and Portland cement. The crushing strength and the teachability of the cured agglomerates were evaluated. Preliminary results indicate that the use of fly ash significantly reduces the requirement of cement without any decrease in strength and immobilization effect. In fact, it was shown that the fly ash improved crushing strength of the agglomerates. This increase was substantial in the case of reactive tailings (Noranda). The leaching (simulated TCLP) tests performed on the Noranda Tailings agglomerates prepared using fly ash/cement resulted in the much lower level of extractable ions concentration and well below the regulatory level than from the agglomerates prepared using either fly ash or cement alone.