When considering the efficiency of a mining operation businesses often only look at the process plant aspects such as grade, recovery or yield data. While these are critical (and usually easy to measure) it means comparing the short-term performance to a design benchmark. To consider the efficiency of a process plant the position in the ore processing stream should also be considered.
Ore is a natural aggregation of one or more minerals that can be mined, processed, and sold at a profit. Therefore the operation should be viewed holistically, not just focused towards the process plant operation.
An operation uses many resources to process the ore and the efficiency of the utilisation of each of these resources is critical. The ore is the most critical resource so it gets the bulk of the efforts.
The original consideration of ore treatment is the development of ore body modelling so that it can be determined how many lodes and in what form is the ore. This allows development of the flowsheet and the engineering to treat the ore, as sampled by subsequent drill programmes.
This engineering will investigate the most efficient equipment to get the required tonnage of mined material to the required size and then processed by the most efficient means to get the most value from the ore. Various ore sample composites would be tested to ensure the optimal plant design and performance, but further work will be needed to treat special ores as they arrive at the primary crusher.
A plant will be designed to treat a range of ores, as found by the exploration efforts, but may need some fine tuning to treat special ores. Transition ores are notorious for specific treatment regimes.
The continued sampling and testwork programmes maintain plant efficiency by ensuring a continued and well-managed geo-metallurgical effort assesses future ore zones and determines any specific actions needed to treat these ores. Such actions may be a different chemical or air flow regime in a flotation operation, a variation to media specific gravity in a dense media plant or a variation in crusher setting or screen apertures in a crushing and screening operation.
If recovery is the driving factor in an operation, like in gold mining for example, the tailings samples should be retested in the laboratory on a regular basis by retreatment through the plant flowsheet to assess if the losses to tails can be reduced economically. Size assays of the tails is especially useful in determining the losses profile that can direct fine tuning of the plant for a more efficient operation.
Sometimes a grade is a contract requirement so making a superior grade may not be efficient if product yield is sacrificed. The revenue return is a major efficiency driver in these cases and should be monitored well.
In ore treatment, knowledge of the ore passing through the plant at the time under consideration is critical and testwork should be continuous, not just performed for design or to retrospectively check on a problem.
Two major operational costs are reagents and maintaining the plant, both critical for long term efficiency. These are the responsibility of the operations team but should be backed up by professional audits and independent surveys of the operation to maintain the plant at peak efficiency. This can lead to more efficient (or maybe just cheaper) chemicals as well as optimising plant operations, minimising process delays or reducing maintenance costs.
Good communication between the plant and mine may also reduce tonnage losses due to oversize rocks in the primary crusher feed. This will have a large effect on efficiency.
Another major driver to efficiency is the labour force. This needs to be well managed, maintaining high morale but minimised in numbers. To assist in the labour efficiency the operation needs to be well designed to maximise safety, usually minimising human touches, so that problems are solved quickly with minimal physical efforts. A well automated plant provides this in all aspects of the operation, from autonomous mining equipment, plant alarms and operations, to driverless trains.
A major factor in plant efficiency is the use of energy. It is a major cost driver, typically around a third of the total cost, and is becoming more critical as an environmental consideration. The plant design will use processes such as high-pressure grinding rolls, autogenous or semi-autogenous grinding or vertimilling, to minimise energy consumption.
Renewable energy in mining operations is becoming more common in recent years thanks to cost effective energy storage – a key enabler for renewable energy technology. A great example is the rapidly maturing solar energy project being embarked upon by Alinta Energy, which is set to provide up to 60MW of generation capacity through a solar farm to be installed in the Pilbara region of Western Australia - something that Engenium are currently assisting Alinta Energy with.
Logistics and Transport
Transporting bulk commodities can be a major efficiency driver. Looking at transport alternatives such as slurry pipelines, road trains and rail transport has major efficiency considerations. Each one has its own matrix of capital and operating costs, and client ownership or leasing considerations. Careful analysis of such items is critical and should be performed before financing is finalised.
Efficiency improvements, such as those discussed above or those specific to your operation, need to be rigorously assessed to determine the technical and commercial advantages of implementation as well as the change management required to perform them.
Engenium’s team of Process and Discipline Engineers, Project Managers and support staff welcome the opportunity to discuss how we can increase the efficiency of your operation, irrespective of your project or operational status.
Principal Process Engineer, Perth WA
Engenium Pty Ltd