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

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.

Preconditions for successful implementation of the Finnish standard for sustainable mining

“…The current novel discussion in relation to mine operations' water management in ore beneficiation processes is towards closed water systems to minimise the need for freshwater intake (Kinnunen et el., 2021;Tarkkio, 2017). For a closed water circuit, a mine-specific open issue is how the closed water system affects the recovery of minerals and quality of end-product (Le et al, 2020). The use of chemicals in flotation processes can lead to the requirement for separate water systems for each process step besides an efficient water treatment (Tarkkio, 2017).…”

The Impact of Pulp Temperature on the Water Chemistry and Flotation Performance

“…The effects of the major contaminating ions, such as calcium, magnesium, sulfate, thiosulfate, and residual organics are investigated using different experimental methods. However, the temperature of the process water is also considered a significant parameter affecting dissolution and surface characteristics of minerals, water chemistry and hence the flotation performance [11][12][13][14][15][16][17][18][19]. Seasonal variations and the grinding/regrinding processes can significantly change the water temperature in a process plant.…”

“…This effect has been observed particularly for fluorspar [22], for the rate of pyrite flotation [13] and for mixtures of sphalerite and chalcopyrite [23]. However, elevated pulp temperatures (>40 °C) may adversely affect the flotation performance through desorption of the collector molecules from mineral surfaces, decomposition of the collector molecules, increasing dissolution of minerals, and precipitation of sulfoxy complex species in the pulp [18,19,24]. The pulp temperature may also affect the flotation performance through the changes in hydrodynamics (pulp viscosity, gas solubility, bubble size and velocity, froth stability and bubble-particle interactions [25][26][27][28].…”

The Impact of Residual Dispersant on the Flocculation and Sedimentation of Synthetic Tailings in Seawater

“…The recovery and recirculation of good quality water from thickeners is key and is today mandatory for the sustainability of the industry [ 1 , 2 ]. The challenge is to recirculate as much water as possible, today between 70 and 80 percent, sufficiently clear and through a quick process [ 3 , 4 ]. Several conditions must be controlled, and the chemistry must be correctly chosen.…”