Application of in-line polymer addition for tailings disposal in Australia- learning and challenges

摘要

Polymer flocculants are normally used for tailings thickening before its disposal at the tailings storage facility (TSF). In recent years, a technique consisting of adding high molecular weight polymers near the tailings discharge points in order to accelerate the rate of dewatering of deposited tailings is being considered in the conceptual design phase and trialled in Australia. The intended result of implementing this technique is to achieve one or more of the following: improved water recovery; a steeper beach slope; and/or a more trafficable surface on the TSF, compared to the conventional tailings disposal method.The authors have conducted several testing programmes for the polymer selection for in-line polymer addition applications. Three main parameters of the polymer selection criteria were investigated through a number of local projects. Selection parameters such as settling rate, water recovery percentage and rheology of the treated tailings were analysed using different polymers from different polymer suppliers. A number of findings from studies undertaken on magnetite tailings, hematite tailings and mineral sand residue are discussed in this paper.It is demonstrated in this paper that there may be significant differences in cost between polymers that achieve similar flocculation performances. Our project results indicated that the selection of the polymer is site-specific and operation-specific. With different projects, the selection process varies in accordance with the different outcomes that are targeted. An improved understanding of the importance of each polymer selection criterion would lead to a more efficient polymer selection process.Future challenges are also discussed in this paper, including the investigation of the degree of mixing of the polymer with tailings at the point of deposition, and the rate of reduction in yield stress as the tailings flow across the tailings beach.