Tag Archives: ventilation on demand

Howden, Agnico Eagle Fosterville to complete Oz mining first with Ventsim CONTROL VoD installation

Howden says it has secured a contract for the upgrade of an existent licence of its Ventsim™ CONTROL ventilation system at the Agnico Eagle-owned Fosterville Gold Mine in Victoria, Australia.

The initial installation of Ventsim CONTROL Level 3 (scheduling and flow control) has already greatly improved the operability and flexibility of the ventilation system, as well as providing efficiency to pay for itself in just six months, Howden claims. Now, in a first for the Australian mining sector, the mine tracking system will be integrated to Ventsim CONTROL Level 4. This will provide real-time feedback on the vehicle locations in Ventsim CONTROL to adjust the ventilation automatically based on demand.

Camille Levy, President of the Asia Pacific Region at Howden, said: “This next stage contract for Fosterville mine is significant for Australian mining and the Howden Ventsim team as it represents the first Ventsim CONTROL Level 4 system that has been commissioned remotely as well as a first in APAC. The success of the operation and the level of power it saves serve as a test case for further installations of Ventsim CONTROL globally. The fact that the system paid for itself within six months is impressive.

“As the system allows the mine to optimise its ventilation based on fully remote vehicle and personnel monitoring, it directly contributes to Australia’s 2030 emissions reduction targets – something of which the Howden team is very proud.”

Level 4 – Ventilation on Demand (VoD) is the process of adjusting mine air flow in real time based on vehicle and personnel position. Ventsim CONTROL provides an ‘on demand’ solution for mine ventilation. Software connected to hardware devices remotely monitors, controls and automates airflow. The technology provides safer ventilation that is more productive and cost effective, according to the company. The Ventsim CONTROL solution also offers a 3D modelling capability within the software, which helps users to better predict and control air flows based on what is evidenced in the simulation.

Howden recently announced its target to be carbon net zero by 2035 through the purchase of renewable energy and carbon-free energy; efficiency gains from energy conservation measures; and by renewable energy projects at its manufacturing facilities. The largest impact the business will have on global sustainability will be through its partnership with customers to supply equipment that will make a major impact on their carbon emissions and sustainability, it says.

In 2020, Fosterville produced a record 640,467 oz of gold at an average grade of 33.9 g/t Au and average recoveries of 98.9%.

Howden tapping into South African deep mining experience

Mines are getting deeper with every year that passes – 30 m deeper, if industry reports are correct.

With increased depth, comes increased ventilation and cooling needs, a fact Howden knows well from its experience of working with the deepest mines in South Africa.

Originally founded in 1854 by James Howden in Scotland as a marine engineering firm, Howden made an entry into South Africa in the 1950s seeking to cater to the demands of the mining and power industries. By the 1960s, it was helping equip the country’s deep gold mines with all the ventilation and cooling products they needed to extract ore safely and productively from kilometres below surface.

“Initially mines used only ventilation as a method of cooling, but, as mining depth increased, mechanical refrigeration was required to counteract the increasing heat loads in mines,” Theuns Wasserman: Team Leader – Howden SA’s Mine Cooling and Compressor Division, told IM.

This saw many deep gold mines in South Africa install Freon™ centrifugal chillers above and below ground to provide the necessary cooling for personnel and machines underground.

While an improvement on the status quo, the heat rejection system for underground machines proved problematic, with the machines’ cooling capacity limited by the temperature and amount of reject air available, according to Wasserman. At the same time, the water quality of the mines resulted in high fouling on the piping shell and tube heat exchangers employed on these early centrifugal chillers.

This resulted in the machines being limited to cooled water temperatures of 6-8°C, he said.

To rectify this, mines started to pump chilled air from surface to underground. While this boosted cooling capacity, the required infrastructure took up space in the shaft and the process was both energy- and opex-intensive.

Battling these issues, mines looked to maximise the amount of cooled air that was sent underground via chilled water plants.

This led Howden to introduce ammonia-based screw chillers into South African mines, which were initially employed in series after the existing surface centrifugal chillers. This enabled a step change in the amount of cooling that could be transported to these deep underground gold mines, bringing the average water temperature sent from surface down from 6-8°C, to 1°C. Mines were able to use the same shaft pipe infrastructure, which many of them had in place, while drastically increasing the amount of cooling sent to deep levels.

Some 20 years after their introduction, Howden, as a leading market player in the space, developed the WRV 510 – a large block screw compressor with a 510 mm rotor. This was, at the time, one of the largest screw compressors on the market, which suited the module sizes of the chillers required for refrigerating these deep South African mines.

“That changed the game as mines could install a single refrigeration machine with 10-12 MW of capacity, instead of a fleet of chillers,” Wasserman said. “At the same time, ammonia, as a ‘green’ refrigerant, perfectly suited the screw compressor and plate heat exchanger combination.”

The considerations around the use of ammonia were formalised into mining-specific ammonia codes and safety standards that Howden was instrumental in devising. These have since been updated and incorporated into South African legislation.

Such success is evidenced by more than 350 MW of ammonia-based refrigeration capacity installed in the South African mining sector, believed to be the most of any country in the world.

But Howden’s South Africa-based innovations did not end there, with the company, in 1985, adding ice production plants on surface to its expanding mine cooling remit.

With surface and underground refrigeration options maximised or deemed too expensive, mines needed a new cooling solution to further expand mining into even deeper levels.

The first surface ice plant (example below) was installed by Howden in 1985 at the ERPM (East Rand Proprietary Mines) mine, east of Johannesburg, which had a final total cooling capacity of some 40 MW with an ice production capacity of 4,320 t/h.

The basis of operation saw ice produced on surface and sent down the mine shaft to an underground ice dam, with water from the ice dam then circulated to underground cooling stations or used as service water for drilling. The ice melt was then pumped back to surface.

The primary benefit of this ice system was the pumping cost reduction, being some 75-80% less than the opex associated with a system where chilled water is sent from surface. This is down to the inherent “cooling energy stored in the phase change of the water”, Wasserman said, explaining that 1 kg/s of ice has the same cooling capacity as 4.5-5 kg/s of chilled water.

With a “superior positional efficiency”, an underground water dam can be maintained at 2-5°C to enhance the thermal performance of underground air cooling stations – again, maximising the cooling capacity.

Another benefit of ice production plants that has specific relevance in South Africa – a country renowned for grid instability – is the ability for the system to be used as a method of thermal storage where ice is produced and accumulated in the underground ice dam and used during peak periods.

This latter advantage led to the development of an Eskom-backed industry collaboration project involving Howden looking at using an ice plant to reduce peak power demand, with test cases situated at Mponeng, the world’s deepest underground mine, and Moab Khotsong.

“We froze up a dam of water during the night (off-peak) and that water and ice melt was used during peak time as a mine cooling source,” Wasserman explained. “The baseload refrigeration plant was switched off during peak periods, taking the pressure off the grid.”

It led to the development of a full turnkey ice plant at Mponeng where Howden carried out works including the civils, electrical and mechanical equipment for a 12 MW, 120 t/h ice plant.

The latest addition to the primary cooling strategy for Mponeng mine that already included soft ice, chilled water from surface, surface bulk air coolers (BACs) and underground refrigeration systems, the ice plant was equipped with duplex stainless steel plate ice makers to deal with the high concentrations of dissolved salts and chlorides present in the mine water at the operation.

It is this wealth of experience in South Africa and a focus on solutions rather than solely products that continues to be translated on a global scale, as MG Mynhardt, Howden’s current Manager of Compressors in South Africa and soon-to-be Head of Global Mine Cooling, said.

With more mines going deeper and space within the shaft at a premium, it is easy to see such a solution having applications in other parts of the world, as Wasserman hinted at.

Mynhardt said: “Howden has been ‘exporting’ its South African deep mine cooling expertise for decades. Back in the 1990s, for instance, we provided a mine cooling solution for an underground gold mine in Nevada.

“One interesting technology utilised by some South African mines is thermal ice storage that is used for load shifting – where thermal energy is stored in large ice dams. The ice is produced during peak periods and utilised in peak periods,” he said. “Conventionally, refrigeration plants are sized for maximum ambient temperature, which might be experienced for three hours a day in the summer months. Yet, if you have a facility to store your cooling energy, you could reduce this capacity.”

The parallels with battery energy storage for replacing excess spinning reserves are obvious here.

“If you have an electricity tariff plan where you have a quite high peak power tariff that you want to shift to a cheaper off-peak tariff, these ice plant solutions could make for a strong business case,” he said. “The upfront capital for the plant could be offset against the lower operating costs.”

At the same time as these, BACs used at mines in South Africa for decades are gaining prominence across the globe.

The newest generation BACs have higher thermal efficiency than their predecessors, lower limits on the shaft air temperature and a reduced footprint when compared with traditional BAC construction types. They are also embedded with the cooling on demand (CoD) module within Howden’s Ventsim CONTROL platform where the temperature of the shaft collar air can be automatically modified to meet the demand below surface.

Howden supplied three of these new-generation BACs in the past year to customers in Brazil and Burkina Faso.

The company can also manufacture customised solutions to deal with challenging operating environments; a recent example being the “unique BAC” operating with ammonia chillers installed at the Carrapateena mine in South Australia for OZ Minerals.

“Without any water available, in Australia, Howden installed dry condensers with Howden ammonia-based compressors along with a closed-loop dry bulk air cooler,” Wasserman said of this installation. “These coolers were engineered for ultimate efficiency considering it was a ‘dry’ plant as opposed to an open-headed spray cooler installed in applications where water resources are available.”

And the company is currently trialling an “uptime” condition monitoring solution at the 8 MW surface BAC plant (pictured below) it designed and engineered for Fortuna Silver’s Yaramoko mine (previously Roxgold) in Burkina Faso.

This system, monitored from Howden’s Johannesburg facility, allows the company to advise of potential efficiency gains and maintenance issues to ensure the plant is run as optimally as possible. The BAC installation at Ero Copper’s Caraiba mining complex in Brazil has also been designed to use such functionality.

This isn’t to say Howden is only focused on projects outside of South Africa – far from it.

Its Total Mine Ventilation Solution (TMVS) platform is continuing to build sustainable, value-adding relationships, which saw the company carry out two ventilation on demand (VoD) feasibility studies in the country in 2021.

Just over the border in Zimbabwe, it is working on a project that could see VoD-enablement of an automated door at an underground mine, to allow it to open at different increments and supply the required quantity of cooled air based on specific vehicle demand.

Such technology developments – using existing available mine infrastructure and readily available data feeds – will become part and parcel of the Howden offering in the future.

Howden’s South Africa experience – learning how to engineer cooling solutions to deal with the poor water quality at its deep gold mines, how to make solutions as energy efficient as possible to circumvent grid issues and how to cater to some of the strictest air quality, temperature and occupational hygiene regulations across the globe – will continue to pay off for mines all over the world.

Yamana Gold retains electrification path for Wasamac in new study

Yamana Gold has reiterated a plan to minimise the amount of carbon emissions generated with the development and operation of the Wasamac gold project in Quebec, Canada, in its first study since acquiring the asset from Monarch Gold.

Monarch, prior to being taken over by Yamana Gold, had laid out plans for an underground mine at Wasamac producing 6,000 t/d, on average, with an expected mine life of 11 years. It expected to use a Rail-Veyor® electrically powered, remote-controlled underground haulage system in addition to an almost entirely electric fleet of production and development equipment.

The December 2018 feasibility study by BBA indicated the Wasamac deposit hosted a measured and indicated mineral resource of 29.86 Mt at an average grade of 2.7 g/t Au, for a total of 2.6 Moz of gold, and proven and probable mineral reserves of 21.46 Mt at an average grade of 2.56 g/t Au, for a total of 1.8 Moz of gold. The study forecast average annual production of 142,000 oz of gold for 11 years at a cash cost of $550/oz.

With drilling, due diligence and further studies, Yamana Gold, in studies forming the new feasibility level studies, has come up with baseline technical and financial aspects of the Wasamac project that, it says, underpin the decision to advance the project to production.

This has resulted in a few changes to the Wasamac plan.

For starters, the company plans to use the extract the now 1.91 Moz of reserves quicker than Monarch’s strategy, with a rapid production ramp-up in the first year followed by sustained gold production of approximately 200,000 oz/y for at least the next four years.

Including the ramp-up phase, average annual production for the first five years of operation is expected to be 184,000 oz, the company said, with life of mine production of 169,000 oz/y. Mill throughput has been increased to 7,000 t/d, on average, but the plant and associated infrastructure were being sized for 7,500 t/d. Production could start up in the December quarter of 2026, the initial capital expense was expected to be $416 million and all-in sustaining costs over the life of mine had been calculated at $828/oz.

The use of a conveyor is still within this plan, but a company spokesperson told IM that Yamana was now considering a conventional belt conveyor rather than the Rail-Veyor system.

Yamana explained: “The optimised materials handling system uses ore passes and haul trucks to transport ore from the production levels to a central underground primary crusher. The haul trucks will be automated to allow haulage to continue between shifts. From the underground crusher, ore will be transported to the crushed-ore stockpile on the surface using a 3-km-long conventional conveyor system in two segments.”

Yamana added: “Using a conveyor rather than diesel trucks to transport ore to surface reduces CO2 emissions by 2,233 t/y, equivalent to taking 500 cars off the road. Over the life of mine, the company expects to reduce CO2 emissions by more than 20,000 t.”

The aim to use electric vehicles wherever possible remains in place.

“The Wasamac underground mine is designed to create a safe working environment and reduce consumption of non-renewable energy through the use of electric and high-efficiency equipment,” the company said. “Yamana has selected electric and battery-electric mobile equipment provided that the equipment is available at the required specifications.

“Battery-electric underground haul trucks are not yet available at the required capacity with autonomous operation, so diesel trucks have been selected in combination with the underground conveyor. However, Yamana continues to collaborate with equipment suppliers with the expectation that the desired battery-electric equipment will be available before Wasamac is in operation.”

In tandem with this, the company plans to use a ventilation on demand solution and high-efficiency fans to reduce its power requirements. This will likely rely on an underground LTE network.

“Heating of the underground mine and surface facilities is designed with the assumption of propane burners, but an opportunity exists to extend the natural gas line to the project site,” it added. “Yamana has initiated discussions with the natural gas supplier and will study this opportunity further as the project advances.”

The site for the processing plant and offices is confined to a small footprint strategically located in a naturally concealed area, and the processing plant has been designed with a low profile to minimise the visual impact as well as minimise noise and dust, according to Yamana.

The primary crusher, previously planned to be located on surface, has been moved underground, with the crushed material transported to surface from the underground mining area using conventional conveyors and stored on surface in a covered stockpile to control dust.

Several design improvements to the previous Wasamac plans have also been made to reduce consumption of fresh water to minimise the effect on watersheds, according to Yamana. Underground mine water will be used in the processing plant, minimising the draw of fresh water and reducing the required size of the mill basin pond.

The Wasamac tailings storage strategy is designed to minimise environmental footprint and mitigate risk, it added.

“Around 39% of tailings will be deposited underground as paste fill and 61% of tailings will be pumped as a slurry to the filter plant located approximately 6 km northwest of the processing plant and then hauled to the nearby dry-stack tailings storage facility,” Yamana said.

Strategic phasing of the tailings storage facility design allows for the same footprint as previously planned, even with the increase in mineral reserves, the company clarified. Also, the progressive reclamation plan for this facility minimises the possibility of dust generation and expedites the return of the landscape to its natural state.

Howden causes a fanfare with launch of Jetsteam AX

Howden is looking to re-enter the Australian secondary ventilation market with a bang, coming out with a new product that offers the energy efficiency, durability and smarts to help ‘future proof’ underground mines.

Its Jetstream AX secondary fans were launched across the globe this month, with service centres on the east and west coast of Australia having already received units.

Phil Durham, Global Mining Applications Engineer, said the Jetstream AX secondary fan is the missing piece to complete the full Howden ventilation puzzle.

“Howden, in the past, was heavily involved in the secondary market in Australia, but some years after exiting this space, the new Jetstream AX is filling the gap in our lineup, helping complete our total mine ventilation solution approach,” he told IM. “Howden has the Ventsim™ DESIGN software, the Ventsim CONTROL ventilation on demand software, plus all the required equipment including a comprehensive primary fan offering, mine cooling options and mine heating options.

“A global secondary fan was needed to complete the set, meaning we can now be considered a one-stop shop for miners wanting to go down the full Howden route for ventilation.”

While the Jetsteam AX will be available in all markets – bar USA where Howden already has a secondary fan offering – Howden sees it being particularly relevant for the Australian market where evolving diesel particulate emission regulations are making effective ventilation operations a must.

“These regulations will definitely affect how those mines manage, monitor and control their ventilation network,” Durham said. “The smart move would be to use their secondary fans more efficiently in terms of how and where they are locating them, which ones are operating and tightening up on where the working areas, vehicles and personnel are.

“In this respect, the Australia region is a key one in terms of the secondary fan product rollout.”

Just some of the attributes the region’s miners could benefit from, according to Howden, include:

  • The highest fan output at low power consumption, providing high efficiencies across a broad operating range;
  • A range of fans from 762-1,600 mm in diameter, with flow rates from 6.5-108 cu.m/sec;
  • Single-stage or twin-stage configuration;
  • A flexible modular design providing commonality of parts;
  • Adjustable pitch aerofoil blades to maximise operational envelope and provide reliable high-efficiency aerodynamic performance across a wide range;
  • An anti-stall chamber for continued safe operation during transient high-pressure events, offering a “risk-free process” in parallel fan arrangements; and
  • Downstream guide vanes with full inner fairing tube and tail cone in each fan to ensure maximum static pressure regain.

Durham expanded on some of these.

“That main inner fairing tube serves a couple of purposes, with one of the main ones being a reduction in shock losses,” he said. “That same design helps from a maintenance perspective, too, providing protection for the motor. In other ventilation fan designs, the motors are exposed to the dusty mine air. The inner tube provides a good level of protection, without being a totally sealed environment. Some air gets through for motor cooling purposes, but it is much less than your typical exposed fan.”

The option of a dual-speed fan could also be important for gaining sales in Australia given there are limited variable speed drive options in this market than others, according to Durham.

“In Australia, specifically, variable speed control is not a very common option due to the required 1,000 V supply,” he said. “Currently there are no proven reliable variable speed drives at such voltages.”

This dual-speed fan offering provides the mines with high and low speed settings – with high typically employed to, for example, clear blasting gases and low employed when a vehicle leaves the airway, and the ventilation demand reduces.

To get the best out of dual-speed fans, mines will most likely require remote access to easily switch from one setting to the next, according to Durham.

Miners that understand the benefits of using dual-speed fans – reducing energy consumption and costs – will also, most likely, be potential customers for Howden’s ventilation on demand and smart ventilation solutions, namely Ventsim CONTROL.

“We are definitely seeing an increase with the number of mines looking to adopt these new technologies and smarter ventilation control methods,” Durham said. “As they are moving towards digitalisation and automation of mining methods, ventilation is also coming into that equation. This is especially so when you consider that the energy cost coming from ventilation and cooling can be around 50% of the mine’s total expense.”

The use of effective secondary fans is part of that exercise, according to Durham, who said efficiencies of over 85% are possible with these units when used optimally.

“Although the primary fans are generally a much higher kilowatt rating, these mines usually have quite a number of secondary fans in operation,” he said. “Being able to use them in a smarter way on a day-to-day basis means they will be able to make some large savings there.”

Barrick continues to adopt new technologies at Kibali gold mine

Barrick Gold says its 45%-owned Kibali gold mine in the Democratic Republic of the Congo is continuing its technological advances with the introduction of truck and drill training simulators and the integration of systems for personnel safety tracking and ventilation on demand.

The mine, which is owned 45% by AngloGold Ashanti and 10% by SOKIMO, surpassed its 2019 guidance of 750,000 oz in 2019, delivering 814,027 oz in another record year, Barrick said this week.

Barrick President and Chief Executive, Mark Bristow, told a media briefing that Kibali’s continuing stellar performance was a demonstration of how a modern, Tier One gold mine could be developed and operated successfully in what is one of the world’s most remote and infrastructurally under-endowed regions.

He also noted that, in line with Barrick’s policy of employing, training and advancing locals, the mine was managed by a majority Congolese team, supported by a corps of majority Congolese supervisors and personnel.

Kibali is already one of the world’s most highly automated underground gold mines, with the operation’s backbone being Sandvik’s Automine Multi Fleet system, supervised on surface by a single operator. In a world first, it allows a fleet of up to five LHDs to be operated autonomously, 750 m below the surface, within the same 6 m x 6 m production drive while using designated passing bays to maintain traffic flow, the company says. A similar system is used in the production levels to feed the ore passes, according to Barrick.

The company said it had now introduced truck and drill training simulators and integrated systems for personnel safety tracking and ventilation demand control, adding that the simulators will also be used to train operators from Barrick’s Tanzanian mines.

Bristow also said that the company was maintaining a strong focus on energy efficiency at the mine through the development of its grid stabiliser project, scheduled for commissioning in the June quarter of 2020.

He said: “This uses new battery technology to offset the need for running diesel generators as a spinning reserve and ensures we maximise the use of renewable hydro power. The installation of three new elution diesel heaters will also help improve efficiencies and control power costs. It’s worth noting that our clean energy strategy not only achieves cost and efficiency benefits but also once again reduces Kibali’s environmental footprint.”

Bristow said despite the pace of production and the size and complexity of the mine, Kibali was maintaining its solid safety and environmental records, certified by ISO 45001 and ISO 14001 accreditations.