Here are some abstracts on the topic of agglomerating fine materials destined for the heap leach pad or for backfill underground. Go to the links to get information on purchasing the complete paper.


For many years the mining industry has used backfill as a means of partially disposing of their tailings. This accomplished method reduces surface disposal of tailings, while providing sound underground support. In recent years, the aim has been to further increase the use of tailings, specifically fine tailings within underground paste fills. Currently, a few Canadian mines are practicing the use of paste fill, with its application becoming increasingly more popular, ideally, from a waste disposal perspective, a total tailings paste fill, made entirely of tailings and binders would be preferred. However, backfill strength criteria often limit the use of total tailings paste fills, which is a reason why paste fills are often supplemented with strength enhancing sand, gravel, or rock chips. Amaratunga and Annor (1989) first presented the concept of the Cold-Bond Tailings Agglomeration (CBTA) process. The Laurentian University Tailings Agglomeration Research Laboratory has since engaged in research into the application of the CBTA process, with reactive and non-reactive tailings, in the development of high strength backfill, with the aim of maximum utilization of fine tailings. This paper presents the concept, and results of agglomerating fine tailings into pellets, thereby creating a coarse aggregate for use in paste fills. Because imported aggregates are eliminated in this process, a total tailings paste fill is developed which fully utilizes its potentials as a means of disposing of tailings. In addition to the waste disposal advantage, results have shown that agglomerated tailings pellets, within a total tailings paste fill, significantly enhances strength and elastic modulus over a non-aggregate, total tailings paste fill. By utilizing this approach of creating aggregates though tailings agglomeration, and using them within a total tailings paste fill, surface disposal of tailings is minimized while providing a strong underground backfill. The paper also discusses the cost and operational benefit of this process.

From World Science:

A large problem in the mining industry from a waste disposal and environmental perspective is the effective disposal of mill tailings. The use of tailings in underground backfill has been the most common means of reducing the quantity of tailings for surface disposal in tailings ponds. While the coarse fraction of the tailings are used, only a small percentage of the fine tailings are incorporated into underground "paste fills", with aggregates often needed to enhance the strength. This paper evaluates the potential of utilizing agglomerated fine mill tailings as an aggregate resource in the production of a total tailings paste backfill, thereby allowing a greater percentage of fine tailings to be disposed of underground. It was shown that agglomerated tailings can be effectively utilized as an aggregate resource in producing a high strength total tailings paste backfill. In developing this paste backfill it was found that high strength and low binder costs can be achieved by using Type C fly ash and Portland cement as binders. By utilizing this approach to paste fill design, operational benefits such as the elimination of the need for outside aggregate resources and high strength are realized. This approach as well has environmental benefits such as reduced tailings impoundment on the surface and the associated reduction in acid mine drainage potential.

From SpringerLink:

In the mining industry today there is some caution about using fine tailings as a backfill material. Traditionally, hydraulic backfill has only used the coarse fraction of tailings, excluding the fines by a classification process. With the development of paste fill, the percentage of fine tailings being sent underground has increased, but still remains low due to the high percentages of sand and gravel which usually make up these fills. Sand and gravel have been added to paste fills to aid pumpability and to increase fill strength and stiffness. This leaves the remainder of fine tailings destined for surface disposal. The main focus of this paper is to evaluate what effect the addition of fine gold mill tailings in the form of agglomerated tailings pellets has on the strength and stiffness characteristics of a total tailings paste fill. The purpose is to create a high modulus fill which is made up entirely of fine tailings. A constant slump design of 20 cm (8 in) was used for each mix. Various binder dosages, curing periods and combinations of pellet to tailings ratio were studied. Raw fill slump and density, and cured fill compressive strength and modulus of elasticity were also examined. Results from the above study indicate that agglomerated tailings paste fill (ATPF) has superior strength and stiffness characteristics. Compressive strengths were enhanced while the modulus of elasticity values was tripled when compared to total tailings paste fills of the same binder content and consistency. ATPF minimizes the surface disposal of tailings and maximizes the utilization of fine tailings underground as a useful backfill material.

From Taylor and Francis:

The agglomeration of ore has as its main objective to form a uniform and highly permeable heap for leaching. Poor agglomeration itself is the result of the incorrect dosage of agglomeration moisture. This article is based on the experience of Minera Cerro Verde in the development and application of a quantitative method to control moisture during agglomeration. As the amount of fine particles/clays varies, the quantity of moisture has to be altered in real time. The measurement of agglomerate electrical conductivity is used for this. Moisture is adjusted to reproduce a value of conductivity established previously and is the guiding parameter.

From Ingentaconnect:

This article reviews agglomeration practices for precious metal and copper heap leaching. Both industries prefer drum to conveyor agglomeration, particularly for clayey ore or ore having a high fines content. Precious metal heap leaching operations opt for cement in a dosage from 2.5 to 10kg cement/t of ore (5–20lb/ton) added to a cyanide solution. Copper ores are agglomerated with water and up to 40kg sulfuric acid/t of ore (80lb/ton) without binder. The agglomerate physical characteristics, with the exception of their strength, can be measured precisely and automatically. The impact of agglomeration on the in situ physical characteristics of the heap, other than the observable ponding and slumping, is not understood well. The most substantial benefits of agglomeration include up to 90% metal recovery from poorly permeable ores, shorter leach cycles, extra metal recovery from already-leached tailings, and better environmental heap closure.