The optimisation of a spiral concentrator plant’s performance can be undertaken in the two phases: in the initial design of the plant flowsheet, and subsequently in fine tuning the operation of the processing plant for the ore being processed.
Getting the desired grade and recovery in mineral processing generally, and spiral separation specifically, can rarely be predicted from first principles as the conditions under which every plant operates are unique. However, in every situation there are key considerations in the design and operation of an effective and efficient spiral separation plant. This is the point that Dale Henderson, Business Development Manager at Mineral Technologies, makes in an interview with African Mining Brief. Mineral Technologies is a globally recognised company in the development of operations using spiral separation.
Understanding spiral characteristics
At the outset, it is important to understand the exact spiral characteristics that are required in design and operation. This knowledge is vital in the process of plant performance optimisation.
Henderson advises mining companies to carefully consider the available spiral options. “There is a range of spirals available on the market globally. They can loosely be grouped into two broad groups – those that have been developed through extensive research and development, testing, operational experience and advanced manufacturing technology (advanced technology spirals), and those that have been designed and developed more simply (simple spirals),” he clarifies.
Elaborating further, Henderson says, of the advanced technology spirals, there are a wide range of makes and models that can be used to maximise separation efficiency when treating various feed types, including high concentrations of heavy mineral (HM), low concentrations of HM, high feed capacity (tph), fine feeds (less than 100 microns) and low density feeds ( i.e. coal).
And while these advanced technology spirals have been engineered to perform well in these various duties, it is essential that they are also well engineered into the process plant to ensure that the required separation is achieved.
Key considerations in design and operation
In particular, Henderson points out, there are two key considerations in the design and operation of an effective and efficient spiral separation plant: spiral selection and operating conditions.
- Spiral Selection
It is important to select the correct spiral for a given duty and incorporate these into an appropriate flowsheet. The use of an incorrectly selected spiral will provide poor separation performance (i.e. a highly efficient fine mineral spiral will not be effective at treating a coarse feed).
Moreover, it is critical that the spiral circuit flowsheet be developed carefully to take into account the changing spiral duties at various points in the processing flowsheet (ie: a spiral capable of effectively treating low HM feeds is often required in the primary treatment stage followed by spirals capable of effectively treating high HM material in heavy concentrate cleaning duties).
- Operating Conditions
Typically, spirals will accept a wide range of feed conditions. However, to maximise performance they must be fed with slurry with an appropriate size distribution, solids feed rate (tph) and slurry density (% solids).
It is also important that the ore body and mining method are considered for their impact on the variability of the feed to the spirals. Substantial variation in the HM concentration of the spiral feed will reduce overall separation efficiency.
Spiral performance optimisation
Henderson explains that the optimisation of a spiral concentrator plant’s performance can be undertaken in two phases: in the initial design of the plant flowsheet, and subsequently in fine tuning the operation of the processing plant for the ore being processed. He shares how Mining Technologies help mining companies implement the optimisation process:
“In the initial design phase, we typically start with a characterisation study to better understand the unique properties of the ore to be treated. The results of this work will then guide the next stage of test work to develop the flowsheet needed to achieve the required performance parameters (grade, recovery, throughput).
“Through this test work, on industrial scale equipment where possible, the plant flowsheet will be locked-in and equipment selections made based on this test work. This flowsheet must then be effectively embodied in the final plant design and then proven through the commissioning and ramp-up of the facilities.”
For existing operations, Henderson adds, process optimisation will usual include on-site technical and operational training and metallurgical surveys, which may include quantitative mineralogy of product and tails streams. He explains that, once the site surveys are completed, Mineral Technologies will use its propriety modelling software to analyse the site data and overlay this with metallurgical performance curves for each separation stage.
Essentially, this becomes a metallurgical “digital twin” of the operating plant. The results from such modelling can be used to explore changes in mass balances, alternate flowsheets or the opportunity for capacity upgrades. In consultation with the client, Mineral Technologies would then undertake any site changes/modifications necessary to yield a continuous process improvement.
4IR reshapes optimisation of spiral separation
Mineral Technologies is continuously seeking ways to optimise the performance of spiral separation plants. The company views various innovations that are emerging with the fourth industrial revolution as avenues that it can utilise to improve the output of these plants.
Henderson observes that the fourth industrial revolution is providing a range of opportunities for spiral separation plants, which the company is exploring. “In the development of new spiral models, 3D printing is used to enable new prototypes to be developed and tested quickly and we may see full scale spirals being manufactured using 3D printing in the near future.
Smart sensor technology may be incorporated into spiral separators with the on-line measurement of slurry streams providing data for the adjustment of spiral splitters, feed conditions and concentrate grade and recovery. Control logic, possibly incorporating artificial intelligence, will continue to drive improvements in plant performance.”
How a global iron producer’s ore treatment problem was solved
When needed, Mineral Technologies can further increase separation efficiency through customisation of spiral geometry to yield additional overall project benefits. One specific application for a globally significant iron ore producer investigated an upgrade to their existing concentrator to treat new ore type from a different location.
To tackle this problem, Mineral Technologies undertook a development program focused on the specific grain size and iron grade in that operation and combined this with the client’s need to increase capacity within the existing building envelope. The result of an 18 month development program was a new generation iron ore spiral that achieved a higher unit capacity whilst exceeding the metallurgical requirements. To date, the HC33 model developed has now been in successful operation for more than ten years. Following on from this development the newer generation HC34 is currently undergoing field trials in Canada.
Written by Jimmy Swira