Dissolution Test Protocol for Estimating Water Quality Changes in Minerals Processing Plants Operating With Closed Water Circulation

Thi Le,Nóra Schreithofer,Olli Dahl

doi:10.3390/min10080653

Abstract

To save freshwater resources and comply with environmental regulations, minerals processing operations are transitioning to partially or fully closed water circulation. However, the accumulation of electrolytes and the addition of reagents lead to changes in water composition and may compromise flotation performance and plant maintenance. As a consequence, costly modifications are often required to cope with these challenges. Therefore, knowledge about water quality variation owing to closed water circulation and its potential effect on the flotation performance is crucial. The experimental methodology presented in this paper targeted three main objectives: (1) predicting the tendency of the accumulation of elements and compounds into the process water during comminution, flotation, and storage in tailings facilities; (2) establishing a relationship between laboratory results and plant historical water quality data; and (3) predicting the potential effect of recycling water on flotation performance. The results obtained with Boliden Kevitsa ore showed a good correlation between the water matrix of the actual process water on-site and that obtained in the ore dissolution tests done in the laboratory. The final water composition came close to the process water in terms of major elements and some of the minor elements. Additionally, the work presented in this paper demonstrated that a dissolution loop allowed us to predict the potential impact of the recycling water on the ore flotability. This methodology could serve as an aid for predicting water quality matrix variation and designing closed water circulation systems at existing and new plants.

Highlights

Due to water scarcity in many regions in the world and environmental regulations enforced by the governments, mining operations need to lower their freshwater intake used for metallurgical processes and the volume of wastewater discharged in the surrounding environment
The dissolution loop’s laboratory protocol described in this paper is an important tool that allows the prediction of the water quality variation over time due to the dissolution of the ore when the plant is operated in closed water circulation
The results showed that the final water composition came close to the in-situ plant water quality in terms of major elements and some of the minor elements in the studied system

Summary

Introduction

Due to water scarcity in many regions in the world and environmental regulations enforced by the governments, mining operations need to lower their freshwater intake used for metallurgical processes and the volume of wastewater discharged in the surrounding environment. For this reason, closed water circulation solutions are progressively adopted to reduce water consumption and environmental footprints of the mining industry. The effect of water recycling on flotation performance is not included in the plant design and process selection This action contributes to the gap between laboratory results and true plant performance [7]

Methods

Results

Conclusion