Tailings Central Thickened Discharge: Challenges Faced and Lessons Learned From Design to Operation

摘要

With the mining industry transitioning through a well-publicized downturn as a result of lower commodity prices and unstable macro-economic conditions around the world, mine owners have sharpened their focus on increasing operational productivity and minimizing unnecessary capital expenditure. The management of tailings, already perceived by many as simply a cost to the mine, is one of the key areas targeted for savings. With constraints on water availability and costs associated with water, particularly in arid environments, thickened tailings disposal becomes an attractive scenario. A central thickened discharge (CTD) tailings storage facility (TSF) was designed and commissioned at a phosphate mining operation in the Kingdom of Saudi Arabia. The design stage included comprehensive rheological and geotechnical characterization of the tailings. The facility design was optimized for cost savings to store a specific thickened tailings product with a predicted beach slope profile and minimal supernatant pond, which influenced the perimeter embankment type and sizing. However, subsequent operational issues with variations in thickener performance and tailings properties, combined with a disconnection from the design stage to the construction and commissioning of the TSF, led to an inconsistently segregating tailings product with a significantly increased volume of water sent to the facility and beach slopes that were flatter than designed.This paper discusses the lessons learned from this project and the potential challenges and risks when there are large unforeseen variations in thickener performance and limited operator experience, which can lead to significantly more water to manage and reduced storage capacity compared to that designed. The paper also proposes key areas to focus on to mitigate against and lessen the impact of significant variations in the thickening process and tailings product sent to the TSF.