Tag Archives: diamonds

Venetia Mine reflects on significant safety milestone on way to underground transition

At the end of December 2023, De Beers’ Venetia Mine near Musina, in South Africa, celebrated reaching 10.2 million fatality-free shifts, a significant achievement as it transitions from open pit to underground operations, it said.

The challenging journey to date has included reskilling the company’s open pit employees for underground operations, while coordinating the many contractors working to implement the ambitious Venetia Underground Project (VUP). Gavin Anderson, Senior Manager for Safety and Sustainable Development at Venetia, says the vision of ‘Pioneering a Brilliant Future for Venetia Mine’ needed a bold and innovative approach to safety.

This challenging task was underpinned by a very comprehensive risk management program – but there was a difference: instead of focusing on safety risk, the decision was made to take everyone on a personal journey towards safely creating one Venetia Mine.

“We developed our own holistic approach to operational risk management,” Anderson says. “Rather than focusing purely on safety or on occupational health and hygiene, we have worked on giving employees a psychologically safe workplace in which to operate.”

He explains that ‘psychological safety’ is a concept that moves away from a focus on management, and towards a new appreciation of leadership. Where leaders demonstrate care for their employees, he argues, then companies can drive safe production.

“Traditionally, a manager would pursue safety compliance through checking that certain standards and procedures were in place,” Anderson says. “A psychologically safe workplace, however, is where employees feel free to speak up when they believe a procedure or risk assessment is not adding the necessary value to their safety efforts.”

From this foundation, employees can engage directly with leadership and there can be collaborative efforts to design and apply safety improvements. Anderson notes that, once the right environment is created, more effective safety interventions and tools can be applied. One such initiative at Venetia is the Safety Sentry, in which each team elects a sentry to capture and communicate the safety observations of his colleagues during that shift.

Using a tablet to record images, conversations or videos underground, the Safety Sentry is able to highlight areas where improvements can be made at the workface. Leveraging digital communication technology, this data is uploaded to a manager who can view, assess and take forward the observations or suggestions – both with the team and senior management.

Another important avenue for Venetia’s safety approach is to remind employees of their families’ love for and reliance on them. A recent campaign asked employees’ family members to send video clips urging them to come home safely from work to enjoy the Christmas season – with these personal messages being played on screens in the workplace.

“Focusing on the human component has given Venetia Mine the edge in terms of shifting safety practices,” Anderson concluded.

De Beers taking major technology steppingstone at Venetia Underground

Making the transition from an open pit mine that has been operating successfully for 30 years to an underground operation that could become one of the most mechanised and automated in the world is not something that happens overnight.

De Beers Group embarked on the $2.3 billion underground expansion of its Venetia asset in Limpopo Province in 2012, in a move that represented the biggest single investment in South Africa’s diamond mining industry in decades.

Underground production began at the mine back in June this year, at a point when construction completion was estimated at 70%.

The introduction of autonomous mining systems performing multiple mining processes to deliver up to 6 Mt/y of kimberlite ore – for circa-4 Mct/y of diamonds – is now beginning, with a ramp-up process occurring over the next four years, according to Moses Madondo, Managing Director of De Beers Group Managed Operations.

“The technologies we are implementing – some of which are under development themselves – will be gradually phased in,” he told IM. “Where appropriate, we will take advantage of ‘proven’ technologies first to ease the change management process, before advancing to less mature technologies thereafter.

“The process should see us start operating areas of the mine in autonomous capacity by 2027.”

De Beers has engaged Sandvik Mining and Rock Solutions for its automated production machines, with the OEM delivering a 34-strong fleet made up of LHDs, ADTs, twin-boom drill rigs, roof bolters, cable bolters and production long hole drills. A further 12 units will be delivered in the future. These iSeries machines include 17- and 21-t payload LH517i and LH621i LHDs, 51-t payload TH551i ADTs, DD422i face drills, DS412i roof bolters, DS422i cable bolters and DL422i production drills.

Employee in the cab of one of the fleet of Sandvik machines

The underground mine will use sublevel caving to extract material from its K01 and K02 orebodies. Initially the ore will be hauled to surface using a combination of underground and surface haul trucks. As the operation matures, the hauling systems will transition to an automated truck loop in combination with vertical shafts for steady-state production.

Sandvik is also providing its AutoMine® system for the remote operation of loaders and trucks and its OptiMine® system for machine health monitoring, task management and location tracking.

Automation will be applied through a phased approach, beginning with manual operation and close monitoring of performance through data analytics. Automation will then gradually be introduced with the necessary training and experience in the operation and support of these technologies.

Madondo explained: “Our current fleet is made up of manually operated machines, which are optimised with automated task management. This process still requires an on-board operator, although many functions are automated.

“The next step would be autonomous machines, operated and overseen from surface, with our training centres already set up to deliver that.”

A pilot project to prepare the production team for the use of remote loading at the drawpoints and autonomous tramming to the tip is in the process of being established, with trials set for later this year and into 2024.

With sublevel cave mining, there is a risk of mud rushes and water ingress at drawpoints and remote loading will allow material to be loaded without putting operators at risk.

This pilot project will have a single loader operating under AutoMine Lite in a dedicated area on 46 Level that is isolated from other areas of the mine, with the machine controlled locally from a mobile tele-remote station just outside the autonomous operating area (ie not from surface).

An integrated operations centre on surface has been constructed and is in the final stages of commissioning.

Moses Madondo, Managing Director of De Beers Group Managed Operations

This is but a fraction of the emerging technology the company plans to employ at the mine, as Madondo highlighted.

“Of course, we will be integrating more technologies into the mix – digital mobility, data analytics, a cave management system, collision prevention, personnel alert systems, equipment location and tracking, production management through digital platforms, centralised blasting systems and digital twins,” he said. “All of these projects have people working on them to deliver our project objectives.”

For Madondo, the business case for employing such high levels of mechanisation and automation has only strengthened in the 11 years since the first shovel was placed in the ground for the underground project.

“This is a challenge with deep underground mining projects – they take a long time to develop and, in that period, technology and economics change,” he said. “It is, however, clear that mechanised mining allows you to take on these advanced technologies as the years go by.

“The investments are not just for technology’s sake. The business case must be built on our ability to improve safety and keep our people away from harm; as well as to make us more efficient and beat inflation, ensuring the margins we promised investors are realised.”

On the former, the company has partnered with Booyco Electronics on rolling out the South Africa-based company’s Level 9 – as defined by the Mining Industry Occupational Safety and Health (MOSH) organisation of South Africa – Booyco Electronics CWS850 collision prevention system at the mine.

“All of our Sandvik equipment is Level 9-enabled and we’re busy on this rollout,” Madondo said. “We’re already employing Level 7 (a system that warns pedestrians of their proximity to trackless mobile machinery) for this equipment. It’s now just a matter of getting to that new advanced level efficiently and safely.”

The company is also employing the Mobilaris Mining Intelligence platform for personnel location and situational awareness to help locate individuals in case of an emergency and notify them of incidents should they occur.

On the productivity side, the company is employing a cave management system to prevent overdrawing, Madondo says, linking the sub level caving mine plan with on-board LHD diagnostics and bucket weighing for efficiency and safety.

Process controller overseeing processing operations within the Venetia Mine

On top of OptiMine and AutoMine from Sandvik, the company is looking to integrate Howden’s Ventsim™ CONTROL system for monitoring, control and optimisation of underground mine ventilation in a ventilation on demand (VoD) application.

“We will gradually introduce VoD and Ventsim CONTROL as it allows us to 1) optimise the use of air and ventilation; and 2) retain the right condition and hygiene levels in the areas of the active mine,” Madondo said.

In an automated mining scenario, Ventsim CONTROL could potentially start ventilating an area of the mine in line with the expected arrival of the autonomous equipment, optimising the process and environment, and, as a result, reducing energy use.

Reaching the pinnacle

Also part of that discussion is decarbonisation – an area the company has already made significant progress on with its move underground.

“Transitioning from surface to underground has reset the energy balance,” Madondo said. “This has seen the site become far less reliant on energy from fossil fuel sources, with the big trucks and loaders from the pit replaced with smaller underground equipment and more electrical infrastructure.

“We predict by that, by 2030, 85% of all energy consumed will be electrical and only 6% will be diesel. That is a significant shift from the open-pit operation where nearly 85% of all energy consumed was from diesel.”

The company’s broader electrification work is currently in the review stage, but Madondo did provide some insight into the focus areas.

“We are looking at battery LHDs and trucks; we will consider trolley assist hauling loops and tethered electrical loading in some of the areas too,” he said. “It is all part of a progressive shift that will be integrated with the sourcing of renewable power for the mine.”

De Beers itself has set targets to become carbon neutral across its operations by 2030, Venetia Underground included.

The first electrification project the company is likely to embark on is a battery-electric retrofit of one of its light duty vehicles, Madondo said, explaining that this technology is relatively mature and comes with less infrastructure requirements due to the ability to charge the machines on surface.

“Our wider electrification plans are being influenced by the maturity of the technology; it may be more beneficial to wait until the adoption rate and learnings increase before we commit,” he added.

Even with the planned integration of such advanced technology at Venetia Underground, Madondo says De Beers still has some way to go to achieve the FutureSmart Mining innovation-led approach to sustainable mining that its parent company, Anglo American, advocates for.

“The pinnacle of De Beers mining expertise will probably be realised when we get to rollout our Diamond FutureSmart Mining, which ultimately is a mine design that we can use to develop future mines that make mining safer, more efficient, more sustainable and with a smaller environmental footprint,” he said.

“Of course, Venetia is certainly a steppingstone to that, but we will hopefully apply the learnings from Venetia for Jwaneng Underground (in Botswana) in the not-too-distant future. That could represent a different, more technologically advanced proposition where all processes are setup to benefit from the latest innovations.”

He concluded: “This will ensure we help create a healthy environment, that we catalyse thriving communities, and that we build trust as a corporate leader. We are shaping a future that creates shared value for all our stakeholders.”

WEC Projects to help trap sediment at Lucara Diamond’s Karowe mine

Following its successful expansion of the sewage treatment plant at the Lucara Diamond’s Karowe mine in Botswana, WEC Projects has secured further orders from the client, it says.

This time, it has been engaged for the design and construction of a sedimentation trap, tanker filling station and associated infrastructure, including storm water drains and fencing.

Karowe, where a 1174.76 ct, high-quality white gem diamond, the third largest found in Botswana, was recently recovered, is near the village of Letlhakane in the arid eastern Kalahari Basin where temperatures average 35°C. As a result, water is scarce, so much so that the Government of Botswana has imposed severe water restrictions on companies operating in the region.

WEC Projects originally designed and built artificial wetlands which the mine uses to treat its effluent, removing contaminants such as BOD, ammonia, suspended solids and heavy metals, to a standard for reuse as process water.

The new sedimentation trap will be used in the water recycling process of the mine’s drilling operations. The effluent is pumped from the underground drilling areas to a concrete trap and clarification unit where it is dosed with alum and a polymer to enhance the settling of the solids. The effluent overflows from the trap to the plant’s oil skimmer to remove floating oil. The system treats an average of 34 cu.m/d of effluent but can be expanded up to 150 cu.m/d, if required, according to WEC Projects.

The polished water is drawn from the tanker station and disinfected by dosing chlorine. Although the water is not suitable for human consumption, it is reused in applications such as dust suppression.

WEC Projects Contracts Manager, Ruan Kellerman, said: “This project is a fairly standard one for WEC Projects, except for the wetlands section which was certainly the largest of its kind we have undertaken. Our clients, many of whom are located in some of the driest and hottest areas of Africa where water is scarce, rely on us to come up with agile solutions for water reuse. We can provide solutions capable of treating water to process water reuse standards all the way up to potable standards.”

TOMRA Mining to demonstrate Final Recovery diamond sorter at Electra Mining 2022

TOMRA Mining will showcase its sensor-based sorting solutions at the Electra Mining 2022 exhibition, in Johannesburg, South Africa, in September, showcasing, for the first time, live demonstrations of its COM XRT 300 /FR Final Recovery sorter for diamond operations.

Representatives from its Sales and Field Service teams will also present TOMRA’s offering of advanced digital products and services, such as the TOMRA Insight cloud-based platform and its latest generation TOMRA ACT PC-based system, as well as its portfolio of sorting solutions for the diamonds, metals and industrial minerals industry at the show, which runs from September 5-9.

Corné de Jager, Diamond Segment Manager TOMRA Mining, said: “The Electra Mining Show is the perfect platform for us to showcase TOMRA’s advanced mining solutions. This important exhibition attracts a wide audience – from operators and metallurgists – interested in smart solutions that are simple to operate and maintain, to decision makers who need to be up to date with the latest value-adding technologies. At the event we will have the opportunity to meet them face-to-face and discuss their requirements, giving them a taste or TOMRA’s collaborative approach, product expertise and after-sales support.”

TOMRA will demonstrate the Final Recovery sorter with fine kimberlitic or alluvial ore together with diamond powdered tracers in a Final Recovery and Sort House application. Visitors will be able to experience first-hand the sorter’s capability to produce an ultra-high diamond-by-weight concentrate with an exceptionally low yield by using TOMRA’s proprietary ultra-high-resolution sensor, advanced new image processing and high-precision ejector valve system, the company says. The sorter offers 100% diamond detection within the specified size fraction and > 99% guaranteed diamond recovery with appropriate feed material preparation.

“We are very excited to demonstrate the TOMRA COM XRT 300 /FR sorter,” de Jager says. “It completes our unique partnered diamond recovery ecosystem, which covers the entire process. We are now able to offer our customers a full XRT solution to sort +2-100 mm particles: +4-100 mm particles with our bulk concentration sorters, and +2-32 mm particles with the COM XRT 300 /FR in its Final Recovery, Sort House or small-capacity exploration applications. The sorter offers higher efficiency, better grade, simplified security requirements with fewer sorting stages and a smaller footprint. It reduces complexity and operational costs, and unlocks the potential for previously deemed non-profitable projects and marginal deposits to be economically viable. ”

The COM XRT 300 /FR sorter can also add value to existing kimberlitic and alluvial operations that use conventional bulk-concentration methods like rotary pans, dense medium separation or X-ray luminescence, if installed in a Final Recovery and/or Sort House function after these existing processes. With a contained capital expense, operations can benefit from a quick, simple and significant revenue gain, TOMRA says.

The TOMRA team at the exhibition will explain the full benefits of its complete partnered diamond recovery ecosystem consisting of XRT technology covering the entire process – from Bulk Concentration to Final Recovery and Sort House applications – as well as its advanced digital products and services. These include the newly refreshed TOMRA ACT PC-based system interface and TOMRA Insight cloud-based subscription solution.

TOMRA Mining has 190 sorter installations operating around the world, of which more than 60 are in Africa. It offers installation opportunities in Africa in the metals industry, for example in applications such as lithium, chromite, platinum, manganese and gold.

WEC Projects devises sewage treatment plant plan for Mothae diamond mine

WEC Projects, a South Africa-based EPC contractor specialising in water and wastewater treatment solutions, says it will soon complete the installation of a new WEC Model B packaged sewage  treatment plant at the Mothae diamond mine in Lesotho.

The mine is 70% owned by Lucapa Diamond Company and 30% by the Government of Lesotho.

Rudolf de Koning, Sales Representative at WEC Projects, says: “The mine lacked a sustainable sewage solution. Producing 60 cu.m of domestic raw sewage per day, Mothae utilised honeysuckers – sewage trucks – to dispose of the sewage at the nearest disposal facility, almost 130 km away. This was obviously a very costly method of sewage disposal. WEC proposed the installation of its Model B conventional activated sludge treatment plant with a daily capacity of 80 cu.m, which allows for future upgrading and expansions of the mine operations.”

The R3.2 million ($194,817) installation is a combined activated sludge and clarification treatment plant. Its modular design simplifies the logistics involved in transporting to the site and simplifies assembly as well as ensures a smaller overall footprint, according to WEC Projects. The Mothae installation also integrates a Wastemaster that includes screening, de-gritting and oil removal to cope with fats and oils present in the sewage which could adversely affect the aerobic process in the plant’s reactor. The Wastemaster removes the oils, fats and non-biodegradable material upstream from the treatment process. The plant will treat the mine’s grey and black water piped to the current septic system.

“Besides the high fat and oil levels, another factor which could affect the treatment plant’s effectiveness was the high altitude of the site which results in low, fluctuating temperatures,” de Koning explains. “The biological population growth occurs optimally at around 19°C and above. In order to ensure the proper ambient temperature is maintained, the plant will be assembled within a larger enclosed facility.”

In addition to making the mine more environmentally compatible through the effective treatment of its domestic sewage, the plant also reduces the costs of transporting waste to the nearest disposal facility, it says. Another consideration is that water availability reduces considerably in the area during the winter. The new plant can help the mine reduce its water consumption.

Thato Tsephe, Project Foreman at Mothae, says: “We worked closely with WEC Projects on-site to develop a sustainable solution. WEC Projects had previously installed a sewage treatment plant at the neighbouring Letseng Mine and it was that facility that encouraged us to approach them. What is critical for us, what is critical for us is to complete the civil works and installation and commissioning of the plant during the winter season with the harsh climate posing many challenges.”

Concor to construct new pollution control dam at Venetia Underground Project

Leading South Africa-based, black-owned contractor Concor is engaging on a 17-month project to construct a new pollution control dam at De Beers’ Venetia diamond mine, South Africa’s largest diamond producer.

The well-advanced Venetia Underground Project (VUP) will extend the mine’s life span to at least 2045, and the new dam – Pollution Control Dam 3 (PCD3) – is the main containment facility in its Storm Water Management Project (SWMP). The SWMP is a key part of the mine expansion, ensuring compliance with the Government Notice R704 on the protection of water resources, preventing the possibility of flooding and ensuring the safety of people working in the new underground mine.

Concor Operations Executive, Christo Schoeman, explains that PCD3 will cover some 27 ha to the west of the mine and will be constructed to a maximum height of 13 m. This will equip the facility to hold over 1 million cu.m of water. The water will emanate from upstream catchments including runoff from the adjacent coarse residue deposit and fine residue deposit, as well as potential overflow from the other upstream water containment facility. It will also contain water that has been pumped out the of mine’s open-cast pits and the VUP underground workings.

“Zero harm to our employees and the environment whilst executing our projects remains our principle objective,” Schoeman says. “In order to prioritise these endeavours and ensure that construction work does not impinge on the mining operation itself, among the first tasks required will be to secure the works by installing a new security fence, and upgrading the existing access road to our temporary site facilities which will ensure optimised access to our site and help streamline our workflow.”

As part of the bulk earthworks operations, the topsoil over the dam area will be stockpiled during the excavation operations, to be used later for slope protection and to ensure the regrowth of flora once construction is completed.

“In line with environmental requirements and legislation, the excavated structure will be lined with am HDPE geomembrane to prevent any seepage into the groundwater system,” he says. “A specialised service provider will supply and install the lining.”

Concor’s scope of work includes the construction of a pump station and dam spillways, as well as the installation of a 2.5 km return water pipeline to the mine’s processing plant. This will allow significant volumes of water to be efficiently recycled and re-used in processing, it says.

Schoeman highlights that the project contains a strong local procurement, employment and skills development component. He notes that Concor has always been committed to local enterprise and skills development initiatives in the areas where it undertakes projects.

“We are working closely with our client to source general workers and suppliers locally, who we will, where necessary, upskill with training, supervision and mentoring,” he says. “Certain aspects of the project can be subcontracted to these local enterprises, following the systematic process of identification and engagement.”

Concor supervises the work of subcontractors closely as part of its enterprise development commitments, he notes. Combined with dedicated mentoring, this ensures not only a quality outcome in each deliverable, but also higher levels of sustainability amongst subcontractors once the project is complete.

African Star appoints new mining contractor at Oena diamond mine

Southstone Minerals Ltd’s 43% owned subsidiary, African Star Minerals, has entered into a contract mining and diamond recovery agreement with Oryx Mining for the Oena diamond mine, in South Africa.

Oryx, at its own cost and expense, will provide and maintain all the plant and equipment as required to perform the mining services, Southstone says.

The diamonds produced by Oryx will be sold via a designated tender facility in South Africa and 80% of the gross income of net diamond sales, less commission, will be paid to Oryx for the duration of the 36-month agreement, the company explained. For any individual stones recovered with a gross selling price, less commission, of greater that ZAR10 million ($664,529) Oryx will be paid 70% of the gross income.

Oryx specialises in the processing of alluvial diamond deposits in South Africa and the operation is currently targeting to operate 24 h/d, six days a week with total headfeed capacity of 200 t/h. Equipment and road building is ongoing, and it is expected production will commence in May 2022.

The contract award follows the conclusion of mining by another contractor, Bluedust 7 Propriety Ltd.

Oena consists of an 8,800-ha mining right located along the Orange River in a well-established alluvial diamond-mining province that produces high quality and large sized diamonds.

TOMRA continues to build ore sorting Insight across mining space

Some 18 months after launching TOMRA Insight to mining customers, the cloud-based data platform is making inroads across the North American mining sector, Harold Cline and Jordan Rutledge told IM on the side lines of the MINEXCHANGE 2022 SME Annual Conference & Expo in Salt Lake City recently.

TOMRA rolled out the subscription-based service to mining back in late 2020, with one of the early adopters being the Black chrome mine in South Africa, one of two mining projects that form the basis of the Sail Group’s plans for long-term sustainable chrome production.

TOMRA Insight, the company says, enables sorting machine users to improve operational efficiencies through a service that turns these machines into connected devices for the generation of valuable process data.

Cline and Rutledge, both TOMRA Sorting Area Sales Managers for North America, said numerous customers were now taking advantage of TOMRA Insight across the region, with many more interested in leveraging the continuous data streams coming off a web-based portal stored securely in the cloud.

TOMRA’s Harold Cline & Jordan Rutledge

“This is seeing mine managers able to tap into how operations are performing today, while tracking that against performance over the last day, week, month, quarter, etc,” Cline told IM. “With the help of our support network, these operations are able to achieve more consistent performance.”

With more customers signing up to TOMRA Insight and more data being generated, the pair were confident future iterations of the platform would be able to offer machine-learning algorithms that helped, for example, predict failures or highlight potential areas for operational improvements.

At the show, the pair were also highlighting the ongoing demand for TOMRA’s Final Recovery sorter, the COM XRT 300/FR, which, since launch, has been successfully deployed at the Letšeng diamond mine in Lesotho, owned by Gem Diamonds. The solution has gone on to be rolled out at other operations.

The introduction of the COM XRT 300/FR, TOMRA became the first company in the industry able to supply a full diamond recovery solution using XRT technology from 2-100 mm, with the unit delivering concentration factors of up to one million with limited stages and guaranteeing more than 99% diamond recovery, according to the company.

Outside of diamonds and sorter analytics, Cline was keen to talk up demand from the gold sector for the company’s sorters.

One of the key differentiators of its offering to the yellow metal space is the ability to scan the material with a multi-channel laser sensor. In an ore sorting setup that involves both XRT and LASER sensor-based machines, the TOMRA solution can remove particles containing sulphide minerals using XRT and subsequently leverage laser sensors to remove particles containing quartz and calcite.

TOMRA says its segregated option can potentially improve recoveries in quartz-associated gold applications thanks to a laser chute-based machine that analyses rocks from both sides. Other belt-based laser machines can only analyse a maximum of 40% of the rock’s surface, according to TOMRA.

“In the gold scenario, we are using XRT to sense and sort with sulphide minerals as a proxy,” Cline said. “At the same time, our laser scanner allows further separation capabilities through identification of minerals such as quartz and calcite.”

Vista Gold, which is developing the Mt Todd project in Australia, anticipates that this combined solution could eliminate approximately 10% of the run-of-mine feed to the grinding circuit, allowing the company to decrease the grind size and thereby increase recovery of the contained gold.

The COM XRT 300/FR offers a full diamond recovery solution

Cline added: “In North America, we have three projects in the gold space we’re working on at the moment that appreciate our unit’s ability to analyse the whole of the particle through our chute mechanism, as opposed to conveyor-based systems that can only analyse one angle of the particle.”

While TOMRA offers multiple sensors on its units through its modular platform, Rutledge said the company continues to have discussions on combining its solutions with other bulk sorting suppliers to further improve the process, naming prompt gamma neutron activation analysis (PGNAA) technology as one specific area of interest.

“We very often refer clients on to other companies when our solution may not match their brief,” she said. “At the same time, we have done some flowsheet work to include our solution with others currently on the market and believe it is only a matter of time before a combination of the two comes into a flowsheet.”

Weba Chute Systems solves choking problem at Botswana diamond mine

Weba Chute Systems has come to the rescue of a large Botswana diamond producer suffering from continuous chute maintenance with a customised solution that came with a 12-month guarantee.

This primary crusher discharge chute had been a headache for the company, with the crunch coming when, after considerable capital expenditure, the new conventional chute needed maintenance just six weeks after installation.

Hilton Buys, Regional Manager at Weba Chute Systems, said: “This could not continue and the mine needed a long-term solution which is why we believe they came to us for a proposal. Senior experts from our company visited the site to take a careful look at the conditions the chute needed to deal with, and we took our conclusions back to our design office.”

Among the challenges were large lump sizes in the ore stream, contributing to build-up of material in the chute and regular choking, Buys said. Also, while Botswana’s dry season is long, the rain that does fall causes considerable problems to the flow dynamics. The kimberlite on the mine – depending on which part of the pit it comes from – can become very sticky in wet weather, according to the company.

“We therefore had to pay particular attention to flow angles, and the design had to effectively accommodate both wet and dry conditions,” Buys said. The concept design – which included quick-release lips on dead boxes – was approved by the mine and the final design, manufacture and successful installation was conducted.

Adding to the complexity was that the feed end of the primary crusher was some 8 m below ground level, while the crusher itself stood about 10 m tall. The chute had to be positioned below the rock box, which stores the material from the crusher discharge, channelling the stream into the Weba chute at a transfer height of 9 m to the conveyor belt.

“The conventional chute also created excessive dust through uncontrolled rock velocity over this considerable transfer height,” Buys said. “By contrast, our chute’s controlled flow meant that the mine did not even have to apply its dust suppression system.”

After installation, Weba Chute Systems gave the customer a 12-month guarantee on this chute, as it does with all its new chutes. This guarantee, which comes with regular inspection reports, assures the customer that the performance will meet their expectations.

“These inspections allow us to monitor wear, so we can advise the customer on what action is required so that they can schedule maintenance and avoid unexpected downtime,” Buys said.

Installed in 2017, the chute is still operating with little maintenance, having been delivered at a highly competitive price compared to the one it replaced.

“Designing a long-lasting chute is not just about creating a box with some reinforcing where you think there will be wear,” Buys said. “It is an endeavour that must be scientific, based on in-depth analysis of material and flow conditions.”

Buys highlighted the importance of asking a range of technical questions about the specific application so the design answers those needs. The latest software and modelling tools are then applied by the Weba Chute Systems team to guide the most effective design.

WEC Projects looks to nature for Lucara Karowe sewage treatment plant

WEC Projects has secured a R3 million ($187,460) contract to supply a new sewage treatment plant for the expansion of Lucara Diamond’s Karowe diamond mine in Botswana.

The mine, near the village of Letlhakane in the eastern Kalahari Basin region of Botswana, is planning to cease open-pit activities by 2026 after which it will continue mining underground, extending its operational life to around 2040. More than 1,000 m above sea level, the mine operates in a region where temperatures average 35°C and water is scarce; so much so that the Government of Botswana has legislated mandatory water saving requirements for industry.

WEC Projects installed the original treatment plant in 2012 and will integrate the new system into the existing facility, increasing throughput from 100 cu.m/d to 150 cu.m/d to meet the requirements of an increase in the number of staff at the mine. While the treatment plant itself is a fairly standard installation, the mine requested a variation to the original project scope – a man-made natural reed bed wetland system that will provide a “polishing” phase to the treatment process, using natural organisms and filtration processes to further clean the wastewater, WEC Projects said.

Wayne Taljaard, Managing Director of WEC Projects, said: “This is a particularly unique feature for a mine as usually such reed bed wetlands are built for much larger installations such as municipal sewage treatment. The government’s mandate for water conservation has forced companies in Botswana to apply creative thinking to overcome the challenge of operating in an arid country.”

The main sewage treatment facility will consist of a WEC Projects Model A treatment plant, an extended aeration system using conventional activated sludge to process the sewage. The wastewater passes through a mechanical screen which removes solids and is then treated by a biological reactor which integrates anoxic, aerobic and clarification zones.

After treatment, the water will enter the reed bed wetland area where it will percolate through the reed bed allowing microorganisms to breakdown contaminants such as sulphur, heavy metals and chlorine. The water produced by this process, while not for human consumption, will be reused by the mine for applications such as irrigation and dust suppression, according to the company.

To create the wetland, a shallow dam will be built, its bottom to be filled with gravel and reeds planted. The water from the treatment plant will feed into the wetland area where nature will be left to take its course.

Taljaard added: “The reed bed solution offers a number of advantages for the mine as the effluent will be relatively odourless and is flexible enough to cope with fluctuations in input. It also requires little maintenance once it is up and running and will ensure that the mine remains within the constructs of the law.”