Operating expenses (Opex) is one of the biggest profit or loss indicators on any mine and controlling these expenses is always a difficult task due to many factors. One such factor is power.
Constantly increasing tariffs, outages and breakdowns due to power surges, not to mention the constant change in the ore bodies’ mineralogy, all add to these costs.
“Looking at a mine’s operating costs, power consumption within the comminution circuit can contribute up to 50% of a mine’s electricity usage,” states Jonathan Smith, sales and marketing manager for comminution specialist Loesche SA.
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Smith adds that the mining industry has been trying to streamline and make the comminution section of the mine more economical. However, this has always been difficult as the technology used is not power-friendly. The circuit also has a large footprint with many associated pieces of equipment which also require power.
Taking run of mine ore and processing it to the correct size for the recovery circuit has a direct cost and this can be described as the kilowatt hours required in electricity to obtain the required fineness. “Added to this pressure is the growing volume of complex ores which have heterogeneous mineralisation which in turn requires a fine grind to extract the available mineral. This results in further power requirements,” states Smith.
As the world looks to go green, the mining sector has one of the hardest tasks ahead of it as a mine consumes large amounts of electricity, water and chemicals. For a mine to comply with future environmental targets, drastic steps need to be taken to reduce these factors.
The vertical roller mill (VRM) from Loesche is a solution for mines today which has a direct and positive effect on all spheres of the environmental pressures experienced. Apart from water and chemical usage savings, the major saving is related to power and the effect on a mine’s financial bottom line.
Some of the savings realised is attributed to the feed particle size reducing the footprint. Depending on the size of the VRM, the feed size can be up to 140 mm lumps which allows for the tertiary and even the secondary crushers and related equipment to be removed from the circuit.
As the VRM uses a dry circuit, the use of water and the need for pumps etc. up to the recovery circuit can be removed as well. The VRM allows for the comminution and recovery circuits to be de-coupled by using a surge silo which allows for each part of the plant to stay operational whilst basic maintenance is being done.
Power saving comes in the form of energy required to reduce the ore to the required recovery particle size. “Apart from the reduction of equipment prior to the mill, the VRM uses a particle-on-particle crushing milling principle. This means that all the power used is put into this phase and not into moving around grinding media. This can equate to between 38% and 45% less power being used by the mill alone compared to other mills,” adds Smith.
Due to the dry process the VRM also removes the particles via an air gas stream and classifies the material immediately. Particles of the correct size are transported to the bag house with the oversize moving back onto the table for additional grinding via the gravity designed grit cone. In doing so, the mill does not retain the ore for longer than necessary and produces a better feed for the recovery circuit. This ensures that the power required is utilised correctly and not wasted.
Digitisation creates power efficiency
In addition, Loesche offers the Digital Ready 4.0 real-time artificial intelligence operating system which constantly monitors the milling process and makes small adjustments to ensure the mill is producing the best throughput all the time, even as the ore characteristics and wear liners change. “As such, the system will ensure the best control over the electricity used and will identify any underlying maintenance issues,” states Smith.
Digital Ready 4.0 has four segments which talk to each other. The operating system software is monitored by the expert software adjusting the mill constantly through small insignificant changes. The surveillance software monitors the mill’s health and the asset management system ensures that the spare parts holding is up to date and ensures that parts are ordered on time. The digitalisation side allows for offsite monitoring of the mill as well as the control if needed.
Looking at all industries worldwide, the four main categories operations look at are power usage, efficient productivity, perfect replacement and reliability which when added together ensures good lifetime and availability of the equipment.
“The quality of the Loesche mill, combined with the digitisation software gives the end user peace of mind knowing the comminution circuit is operating optimally, thereby ensuring that the profitability of the operation is being kept at its highest level at all times,” Smith concludes.