Designing the Siilinjärvi thickened tailings storage facility

Abstract

This case study presents some of the key aspects of the design of the thickened tailings storage facility that recently commenced operation at Yara’s Siilinjarvi apatite mine in Finland. The mine is located near the Arctic Circle, and therefore operates in a cold climate. The tailings are also quite coarse (with a D90 of 700 microns), which creates challenges in the operation of a thickened tailings storage facility. This paper describes a series of pilot plant trials from 2007 to 2010 and demonstration plant beaching trials that took place in 2013 and 2014, not only in terms of the collection of data, but also with respect to the many engineering challenges that were overcome in the thickening and transport of the tailings slurry under these difficult conditions. The beaching trials provided good validating data for the design of the tailings storage facility. The beaching results are presented, along with some discussion of their comparison with the predicted beach slopes used in the tailings storage facility design. The paper further discusses and presents images of the thickeners, pumps, pipelines and tailings storage area.