Africa hosts substantial reserves of metals and minerals, with gold, diamonds, iron ore and copper being particularly notable. Two of the world’s top ten gold- and copper-producing countries are situated in Africa, with their production predominantly centred on the copper belt.
The Copper Belt, a natural region in Central Africa that spans the border of northern Zambia and southern DRC, is renowned for its mining activities. The Kansanshi copper-gold deposit is situated in the area, and boasts a rich history dating back over 1500 years to indigenous people who extracted copper from its abundant veins. Situated near Solwezi, the Kansanshi copper-gold deposit is a vibrant area with active open-pit sites.
Kansanshi represents a vein-style deposit where valuable copper and gold mineralisation is present in three distinct ore types: primary sulphide, mixed supergene, and oxide. Mining operations are conducted in two open pits known as Main and Northwest, utilising conventional open-pit mining techniques.
The process for treating ore offers flexibility to accommodate variations in ore composition. This flexibility includes options for oxide leaching, sulphide flotation, and a circuit for transitional ore. Oxide ore undergoes a
multi-step treatment process, including crushing, milling, flotation, leaching and solvent extraction. This process leads to the generation of a flotation concentrate rich in sulphides and gold, alongside the production of cathode copper through electrowinning.
Kansanshi faced measurement challenges in the gland water tanks, slurry and raw materials in the stockpiles and crusher bins. The instrumentation supervisor, Japhet Ng’andu Mutambo explains, “Accurate measurement plays a critical role in mining operations. It ensures precise reagent dosing and level monitoring, enabling us to achieve a high quality and superior end product. Equally vital is safeguarding our mining equipment from any potential damage, which is a priority we strive to uphold.”
Although the mine had sensors and measuring instrumentation installed, the readings received were not accurate, and required a manual and visual inspection to verify the levels in these tanks, hoppers, piles and bins. The inventory management system used for the crusher bins and the stockpiles also left much to be desired. The gland water tanks had non-contact level ultrasonic sensors installed, which presented various problems for the mine, and resulted in considerable inaccuracies and increased maintenance costs. The challenge experienced with the slurry hoppers was the amount of foam created because of the reagents added to the refining process, but VEGA was able to offer a suitable solution to resolve these challenges.
Preventing mixed signals
Effective stockpile management depends on accurate, timely readings of the volume and content of piles and crusher bins. Until fairly recently, operators at Kansanshi Mine could not have both criteria met, and had to visually and manually assess these stockpiles. It was a tedious and labour-intensive job. To use all assets effectively, including its human resources, the producers are taking advantage of new technology available from VEGA.
“The merits of employing VEGA instrumentation are multifaceted. VEGA offers cost-effectiveness, reliability and accuracy. What tipped the scale for us was the customisation option that VEGA provides, tailoring instruments to match our precise requirements. For instance, it reduces labour intensity as there’s no need to allocate personnel specifically for cleaning the instrument before obtaining reliable measurement results,” notes Mutambo.
The first challenge the mine faced was the measurement of crushed material in the stockpiles and crusher bins. This in itself is a difficult task due to the dust created during the materials handling process. What also needed to be taken into account was the irregular surface of the crushed ore and rock. VEGA had the solution to this, its VEGAPULS 6X radar sensor. These sensors are best suited to non-contact level measurement of bulk solids, and they can be installed at the top of the stockpile or from a distance up to 120 metres to provide continuous and reliable level readings.
“The environment where these sensors and instrumentation are deployed can be described as challenging. While certain areas like the gland water tanks remain relatively clean, the crushing bins contend with dust and particles, and the hoppers are inundated with slurry. This combination of conditions poses a notable challenge for any measurement instrumentation,” Mutambo explains.
Slurry hoppers provide a holding area for the slurry mixtures before they can be directed to other stages of the refining process. This temporary stage helps to maintain a continuous flow of material throughout the system towards further treatment units. Proper control of the slurry level in the hopper ensures a consistent and controlled flow into these downstream systems. Monitoring the slurry level within the hopper is essential to prevent overflow or emptying.
“We opted to transition from our previous supplier primarily because the sensors they installed proved to be unreliable. Since implementing the VEGA sensors, we have had more confidence in the readings of the installed instrumentation. We initiated the upgrade process in 2019, focusing on numerous flotation cell hoppers, as a direct response to the issues we faced with the instrumentation from our previous supplier,” adds Mutambo.
Since slurry is an abrasive substance, the ceramic measuring cell on the VEGABAR 82 pressure transmitter proved to be invaluable, as this pressure transmitter can withstand contact with abrasive materials. The VEGABAR 86 is a hydrostatic pressure transmitter and can double up as an electronic differential pressure sensor. It is not affected by the foam in the hopper, making it an excellent choice and ensuring accurate readings time and time again. The submersible VEGABAR 86 is suitable for level measurement in wells, basins and open vessels such as the floatation cells at Kansanshi Mine. The sensor’s front-flush abrasion-resistant ceramic diaphragm allows it to operate in harsh conditions where there are chemically aggressive liquids, alongside dust and grime build-up.
Gland water tanks are a crucial component of equipment used to prevent the ingress of contaminants like dust and water into mechanical systems, such as pumps and agitators. These systems typically have rotating shafts that require proper sealing to prevent
leaks and maintain efficient operation. “We encountered challenges with the measuring solutions provided by a previous supplier. The equipment they supplied lacked accuracy in predicting levels within the gland water tanks,” Mutambo notes.
Monitoring the water level is of the utmost importance as levels need to be maintained for the equipment to function optimally without breakdowns. This installation was complemented with the VEGABAR 38 universal pressure transmitter. This solution has ceramic measuring cells guaranteeing durability, especially in a closed, moist environment.
Reliability
The installation of the sensors and commissioning of the instrumentation was done independently by the employees at Kansanshi Mine. They were impressed not only by the sensors but also by the service and support they received from VEGA. “We undertook the setup of the sensors and instruments independently. While VEGA in South Africa provided us with guidance and support, we took charge of the installation process ourselves. This proved to be a valuable exercise and a positive experience,” Mutambo adds. VEGA technicians provided support every step of the way, assisting in eliminating measurement disturbances.
Conclusion
Not only does VEGA supply reliable, high-quality sensors and measurement instrumentation, but the staff at Kansanshi appreciated the VEGA technicians’ experience and technical competence. In the end, however, VEGA’s attention to detail and persistence in searching for perfect solutions made a lasting impression.
“The merits of employing VEGA instrumentation are multifaceted. It offers cost-effectiveness, reliability and peace of mind. What tipped the scale for us was the customisation option that VEGA provides, tailoring instruments to match our precise requirements. For instance, it reduces labour intensity as there is no need to allocate personnel specifically for cleaning the instrument before obtaining reliable measurement results,“ Mutambo concludes.
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