Why be energy efficient?
Valuable minerals are extracted from rock via the process of comminution (crushing and grinding). This process can be further refined using various means of separation, such as froth flotation, optical sensors and centrifugal devices.
The comminution phase can consume more than 50% of the total energy used in a mining operation.
According to the Coalition for Energy Efficient Comminution (CEEC), comminution accounts for 3% of the entire world’s energy consumption.
Additional energy is needed to mine and process ore grades of declining quality.
As well as being less profitable or cost-effective, this situation increases the embodied energy of primary metal production and the associated greenhouse gas emissions.
These consequences are especially significant for the most production-intensive metals, like copper, gold and nickel.
Ways to save
Improve grinding technologies
A range of comminution systems are available for working with various materials and under differing conditions. The choice of equipment and design of circuits has a significant influence on energy use.
Historically, semi-autogenous grinding (SAG) equipment has been preferred for its ability to handle all ore types.
However, modern improvements in high-pressure grinding rolls and stirred grinding mills mean these technologies can now be more widely used instead. Both are more energy-efficient than SAG technology.
Improve froth flotation efficiency
Froth flotation in a tank (called a cell) is a method of mineral separation in fluid which relies on the difference between the chemical composition of minerals compared to gangue.
High-grade mineral particles attach to bubbles, which rise to the surface and form a froth which can then be recovered. The froth produces a concentrate of the targeted mineral.
Precise airflow measurement improves the efficiency of froth flotation.
Smart blasting and rock movement monitoring
Conventional blasting explodes the entire region of a mine to yield manageable rock size for haulage and crushing. Smart blast design technologies, using remote imaging and sensing, help determine optimal blasting boundaries and track the dispersal of quality ore. These procedures can prevent unnecessary wastage of primary material by up to 15%.
Pre-concentration ore sorting
Pre-concentration is the rejection of gangue (barren material) from coarse ore feed.
- Automated ore sorting with optical sensors puts ore into categories based on size, hue, quality and even atomic density. This technology is a highly efficient method of separating valuable minerals from gangue.
- Gravity separation can be achieved when there’s a distinct density difference between the ore and gangue at fairly coarse sizes.