Analysis of thickening performance of unclassified tailings in rakeless deep cone thickener

Abstract

Typical tailings discharge at low solids concentrations can cause serious environmental pollution and disasters, including tailings dam failures and the collapse of underground voids. High-density cemented backfill, which consists of unclassified mine tailings, binders, additive agents, and water, are increasingly being considered as simple and effective means for reducing the hazards of conventional slurry deposition and recovering water for recycling. Gravity thickening has been widely used in the minerals industry to increase solids concentrations of tailings. The prediction of gravity thickener performance by characterizing relevant material properties is of great importance, and batch settling and pressure filtration have proven to be the most useful methods for characterizing the dewaterability of tailings for gravity thickener performance predictions. In this research, batch settling and pressure filtration experiments were conducted to obtain dewatering data with respect to gel point, compressive yield stress, and hindered settling function by curve fitting. A predictive algorithm of steady-state thickening, proposed by Usher, was introduced and a rakeless deep cone thickener model was constructed to analyze the effect of flocculant dosage, underflow concentration, and mud height on solid flux and solid throughput. The results indicate that flocculant dosage has a greater impact on the settling zone than on the compaction zone, optimum thickening performance is obtained at a dosage of 20 g·t-1, and as underflow concentration increases, solid flux decreases. Solid flux was determined to be related to the concentration, and not influenced by mud height in the settling zone, whereas, in the compaction zone, solid flux is a function of concentration and mud height. In the range of the model's parameters, solid throughput is a function of concentration and mud height at heights less than 3.5 m, and the change law of solid throughput is similar to that of solid flux.

Keywords

• rakeless deep cone thickener
• flocculant dosage
• mud height
• underflow concentration
• solid flux
• solid throughput