Xore customer case Boliden, Aitik mine
In the northern parts of Sweden, near Gallivare, lies the Boliden Aitik mine. It was first established in 1968, and has since then grown to be Sweden’s largest copper mine, milling over 40 Mtonnes of ore in 2019. From the ore some 90.000 tonnes of copper was extracted along with byproducts of silver and gold. Aitik's productivity is higher than almost any other copper mine in the world (see facts and figures below). The Boliden Aitik concentrator plant uses a Boxray 24 onstream analyzer.
The extremely low head grade of copper (0.2 %) sets very high requirements for the analyzer. First of all the detection limits need to be well below the average grade to cover the full range of process variations. And on top of that, the tailings is more than ten times lower than the head grade.
Another challenge is that the analyzer has to give consistent measurements even when percent solids in the slurry is low. A weak x-ray signal from a highly diluted sample can be hard to extract information from, but the Boxray 24 does it very well. With a high production pace all this has to be fulfilled at an equally high pace from the online analyzer. For proper process control, whether it is manual or automatic, the analyser must be able to track events at a really high pace. In fact, data points must be collected at double the speed compared to the rate of change in the process.
Boliden Aitik control room
Great challenge for the Xore on-stream analyzer at Boliden
Boliden Aitik concentrator plant has a high copper recovery of some 85-90 %. With a low head grade and high recovery there is very little copper left in the tailings, about 0.02 – 0.05 %. This is a challenge to measure for an on-stream analyzer but the Boxray analyzer’s energy dispersive detector enables very low detection limits and reliable measurements even at these super-low grades.
The final product is a copper concentrate typically consisting of 25 % copper, 250 g/t silver and 8 g/t gold. There is an extreme difference in magnitude between the concentrate and head grade, and tailings:
Concentrate - Head Grade: 100-150 times larger
Head Grade - tailings: 20 times larger
This introduces a risk of contamination from the concentrate to the other samples. The Boxray 24 eliminates this risk by having separate sample loops and measurement cells for each sample stream. The Boxray Compact uses two measurement cells so high grade samples are kept in one cell and low grade samples in the other cell. These features are unique to the Boxray on-stream analyzers.
Boxray 24 in duty
The flotation circuit is monitored with a single Boxray 24 on-stream analyzer. Process control is based on a large array of sample streams and accurate process data from the online analyzer being updated frequently. For most samples an analysis time of 25 seconds is used. The control room in Boliden Aitik relies on a single analyzer to provide them with process data. Other mines of this size, using competing systems, often have to use multiple analyzers in order to achieve acceptable performance and an acceptable level of availability.
The Boxray 24 has on its own high enough capacity to do the job sufficiently fast and accurate. With a service program consisting of preventive maintenance on a regular basis the availability is maximized.
“To run an operation of this scale and dignity with a single Xore on-stream analyzer at Boliden Aitik says a whole lot about the analyzers performance and reliability“ says Mikael Normark, CEO of Xore.
