Tag Archives: diamonds

Weir Cavex hydrocyclones prove their worth at South Africa diamond mine

Comminution of minerals, Environmental, Mine operation news, Mineral processing, Mining equipment, Mining services, Precious metals, , , , , ,

Weir Minerals’ Cavex® hydrocyclones have been put to the test at a diamond mine in South Africa’s Northern Cape Province, proving the technology can be applied in dense medium separation (DMS) plants treating diamondiferous material, according to the company.

In her presentation to the Southern African Institute of Mining and Metallurgy (SAIMM) diamond conference in Johannesburg in 2018, Weir Minerals Africa’s Senior Process Engineer, Boitumelo Zimba, said the hydrocyclones improved plant efficiency and produced 40% more tonnage than the mine’s target.

“As the Cavex hydrocyclone is tried and tested in hard-rock mining and coal classification, the Cavex 360° laminar spiral inlet profile was used as a basis for the development of a dense medium cyclone,” Zimba said. “Individual casting patterns were developed and produced in order to fabricate the Cavex dense medium hard chrome cyclone with the exact laminar spiral feed chamber that exists when moulded out of rubber.”

The customer required a solution that could offer at least six months wear-life, and a probable error of separation (Ep) of no greater than 0.08 at a cut density of 3.1 t/m³. Tracer tests were used to monitor the efficiency of the separation achieved by the Cavex hydrocyclones to ensure all of these requirements were met.

“Ep values achieved were 0.042 for the 4 mm tracer tests and 0.035 for the 8 mm tracer tests, which were below the set maximum target of 0.08 from the mine,” Zimba said. “This highlighted the benefits and improved efficiencies of the Cavex laminar spiral feed inlet.”

The lower the Ep – or probable error of separation – the more efficient the separation; it is defined as half the difference between the density at which 75% is recovered to sinks, and that at which 25% is recovered to sinks, Weir said.

“The customer’s tracer tests on the Cavex hydrocyclones showed that cut points of 3.08 t/m³ were achieved for both the 4 mm and 8 mm tracers,” Zimba said. “This was within the performance levels of 3.1 t/m³ that the customer had specified.”

Initially, the hydrocyclones were commissioned to treat only fines at the diamond plant – the minus 8+1 mm material. Later however, the mine decided to run a combined DMS, after which the full DMS size range of minus 20+1 mm was treated through all the fines DMS hydrocyclones.

“The unique design of the laminar spiral inlet geometry delivers sharper separation and maximises capacity while delivering a longer wear-life than conventional involute or tangential feed inlet designs,” Weir says. “By providing a natural flow path into the hydrocyclone body the design allows the feed stream to blend smoothly with the rotating slurry inside the chamber, reducing turbulence and improving separation efficiency.”

Zimba explained: “Combining our cone and spigot components in the hard metal range is an important contribution to the reduction in turbulence. Another vital factor is the Cavex inlet design with 360° scroll; this design was proven through extensive computational fluid dynamics analysis as well as our multiple installations to date.”

Weir Minerals also conducts ongoing research and development on methods to minimise turbulence on assembled casted components. The Cavex hydrocyclones are designed with a variety of inlet sizes to accommodate a wide top size at specified medium-to-ore ratios. The inlet sizes range from 0.2 to 0.33 as a function of the hydrocyclone diameter.

“The Cavex CVX hydrocyclone also has a wide range of vortex finder sizes to maintain separation efficiency at different operating yields and spigot sizes. The vortex finder sizes range from 0.4 to 0.5 as a function of cyclone diameter, and are designed to maintain a strong air-core at different spigot sizes,” Weir says.

To prolong life and efficiency, the hydrocyclones can also be manufactured with different materials.

“Cavex CVXA hydrocyclones are hard-wearing and are cast in 27% chromium iron for maximum abrasion resistance; components are designed for ease of maintenance, with all surfaces joined with a layer of epoxy cement,” the company says.

Weir Minerals Africa operates two foundries in South Africa – one at its Isando facility and the other at its Heavy Bay Foundry in Port Elizabeth. “This allows the organisation to cast items in-house leveraging its local foundry personnel’s knowledge, experience and expertise, ensuring that the highest standards are maintained,” Weir says.

“This approach ensures optimal life of the hydrocyclone in operation, and reduced maintenance costs by replacing worn parts in situ. It also eliminates the risk of any adverse effects on performance arising from mixing old and new hydrocyclone components. Further, safety on site is enhanced by minimising the maintenance work necessary on the installed hydrocyclones.”

Zimba said future work will include the investigation of various alloys to combat high wear rates on some of the hydrocyclone components, in particular the vortex finder and the cone sections. “This will allow longer operation and plant stability,” she said.

De Beers Canada aiming for 100% renewable energy solution at Chidliak

Environmental, Gem stone mining, Mineral project development, Mining policy, Power supply for mines, Sustainable mining, , , , , , ,

De Beers Canada, having successfully “winterised” the conventional power solution at its mines in northern Canada, is now looking at a 100% renewable electricity solution for its recently-acquired Chidliak diamond project, CEO Kim Truter told attendees at the Energy and Mines World Congress in Toronto this week.

While the Chidliak project is located on Baffin Island, which runs 100% on diesel power, Truter said due to the extreme remoteness of the proposed operation, “the energy solution for Chidliak has to be different”. The company acquired the mine earlier this year after taking over Peregrine Diamonds.

The hidden cost that comes with diesel power generation is the required supply chain infrastructure, ie roads, according to Truter. If Chidliak was a non-road supplied site, it would drive the need for renewable power, he said.

Another consideration is the size of Chidliak’s orebodies. As these are small, there is a need for a smaller overall footprint and the movability of plant as the bodies become mined out, he said.

So far, 51 kimberlites have been tested for the presence of diamonds at Chidliak, with 41 of these showing positive results. Two kimberlites, CH-6 and CH-7, were prioritised for advanced exploration and were tested for grade and diamond value.

The CH-6 kimberlite pipe is estimated to contain about 18 Mct of inferred resources in about 7.5 Mt of kimberlite, an estimated grade of 2.41 ct/t to a depth of 525 m below surface. The CH-7 pipe is estimated to contain about 4.2 Mct of inferred resources in about 5 Mt of kimberlite; an average grade of 0.85 ct/t to a depth of 240 m.

At the conference, Truter said renewable supplementation of diesel baseload was growing in the industrial sector, but a micro-grid to regulate and accurately feed power through to a 100% renewable power system “does not appear to exist”.

Yet, the Princess Elisabeth Base in Antarctica is occupied 365 days per year and is powered by 100% renewable sources, he said.

“The next step is an Arctic mine with continuous (renewable) operations,” he told delegates, adding that the Chidliak development can achieve maximum potential if a 100% renewable energy solution is realised.

In order to achieve this, he laid out several solutions.

First, the company needed to look to shrink its footprint at Chidliak – size, people, power, thermal and environmental – then partner with best-in-class companies to tap into available natural energy sources; whether that be solar, wind or geothermal sources. Following this, De Beers Canada needed to confront the challenge of multiple-day power fluctuations with energy storage solutions and, finally, find an appropriate business model for the power solution.

In addition to retaining the company’s social licence to operate, Truter said the eco-credibility that came with using renewable energy was an additional motivator for De Beers Canada, bringing intangible value to its product.

De Beers Group has a global commitment by 2020 to reduce its energy requirements by 8% and cut its carbon emissions by 9%.

Kimberley Ekapa Mining chooses Epiroc MMI solution to go down digitalisation route

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Kimberley Ekapa Mining has agreed to use Epiroc’s Mobilaris Mining Intelligence (MMI) solution as it looks to embrace mine digitalisation and create a decision support system to boost safety and increase productivity.

With the use of MMI, Kimberley Ekapa Mining will be able to track assets in real-time; to integrate and visualise machine data, machine location and the shift plan together to close the loop between the plan and the reality, according to Epiroc.

Howard Marsden, General Manager of Kimberley Ekapa Mining, said: “MMI will help us start to modernise our old diamond mine and be the tipping point in terms of production optimisation.”

Marsden added MMI would allow the company to tag and keep better track of its mining personnel and equipment and provide access to real-time data, shedding some light into the “normally dark world of the underground mine”.

“We expect this is to be productivity game changer,” he concluded.

Thanks to its open architecture, MMI can be integrated easily with other systems in the mine, Epiroc says. Kimberly Ekapa Mining will rely on MMI to compile information from other systems and make all information searchable and easily accessible to decision-makers in real time.

Ulla Korsman-Kopra, Global Business Manager, Automation and Information Management Systems at Epiroc’s Underground Rock Excavation division, said: “The MMI is the world’s leading multi-role 3D location based decision support system, which enhances safety, productivity and efficiency in the mining operations.”

Users can access the web-based MMI interface from different devices to visualise the locations and movements of workers, vehicles and other equipment in real-time, Epiroc says.

Korsman-Kopra said: “When a problematic situation arises, and for example lives are at stake, MMI can be critical. You need to act quickly and make informed decisions to save time and ultimately save lives.”

Epiroc will supply Kimberley Ekapa Mining with an MMI hardware and software package that includes personnel training and support. The system installation will be operational by year’s end.

The Kimberley Ekapa Mining diamond operation in South Africa produced 755,645 ct in the year to end-June 2018. The Kimberley mines were at the heart of South Africa’s early diamond rush in Kimberley in the late 1800s, where the world’s first hard rock diamond deposits were discovered.