STABILITY AT THE HEART OF MINERAL PROCESSING OPTIMISATION

By Minopex

Through her experience in minerals processing, Leanie Naude, Process Superintendent at Minopex believes that stabilisation and optimisation of any process is essential to operational success. To achieve stabilisation and optimised operations of any Concentrator, Naude has found that controlling flotation cell levels is vital. As such, stabilisation is a key focus of the Minopex Operations teams.

What is Flotation?

Explaining flotation simplistically, Naude describes it as the method used to separate and concentrate valuable minerals from waste. “Depending on whether your valuable mineral needs to be in your concentrate or tails, the surfaces of the valuable minerals are repelled by or attracted to water. This effectively separates the valuable minerals from the gangue using air bubbles.”  

 

The Flotation Process

In Naude’s view, The Journal of The South African Institute of Mining and Metallurgy summarises the challenge best: “Automatic control of industrial flotation cells and circuits presents a set of significant challenges due to the number of variables, the sensitivity of flotation cells to variation in these variables and the complexity of predicting flotation performance and/or developing a strategy for optimisation. These variables in flotation are all interrelated, and disturbances can have negative impact on grades and recoveries. The result is an unstable plant with limited scope for optimisation.”

In the bullet points that follow, she provides a high-level overview of the steps employed to recover valuable minerals to the concentrate:

  • Ores are crushed to reduce the size and then
  • Mixed with water and milled to ensure valuable minerals are liberated from the gangue
  • Minerals in the slurry gets treated with collectors and then pumped into the flotation cell, equipped with a rotor and stator mechanism
  • Air is added into the cell
  • Valuable minerals are rendered hydrophobic, attaches to the air bubbles and then rise to the surface in the bubbles
  • A froth is formed at the surface
  • Concentrate becomes available to extract from the cell; and the measurement of the amount of concentrated recovered is referred to as the mass pull

Mass Pull Optimisation

A key element in flotation is optimising the mass pull quantity. “There are many factors that influence the amount and quality of concentrate that comes from each cell. Each of these variables, i.e. air, reagents, flow, particle size, etc. is interrelated, which makes this a complex process,” she adds.

On the site Naude is based on, a mass pull optimisation project was being run. The Minopex team faced the challenge of instability, where the instability in one circuit caused a ripple effect to the next circuit. Although a third-party mass pull optimiser control package had been implemented, the results were not optimal.

Minopex Builds its Own Mass Pull Optimiser

With full understanding of the mass pull challenges, the Minopex Engineering Department designed and built its own, custom mass pull optimiser. “Having identified air addition as the easiest variable to influence, the Engineers effectively modified the level of air added to the cells. This successfully created a stable mass pull from the cells,” confirms Naude.

The Benefits of the Minopex Mass Pull Optimiser

  • Stable level in cells, resulting in improved drainage
  • Consistent recovery improvement year-on-year, culminating in record recoveries
  • Penalty element reduction in the concentrate since the installation of the Minopex mass pull optimiser

“The Minopex team takes great pride in the professional services we offer, driving stability optimisation and improvement in mines we operate across the world,” concludes Naude.

For more information, please contact Renira Reddy at renira.reddy@minopex.com.