Mine power options.
Ensuring a reliable power supply is essential to any exploration and mining project, with requirements varying enormously depending on the stage the project has reached. In remote areas of the world, local utility grids--if they exist at all--may not have the capacity to support a new power-hungry mine, and establishing a standalone generating station may be the only option. Innovation has long been the watchword in this respect, with mini-hydro and low-temperature geothermal schemes having been used to supply mines, as well as more conventional diesel-, natural gas-and oil-fueled generating capacity.
These systems are, of course, reliant on fuel transport, so today cost-conscious mine operators are increasingly investigating renewable energy as a potential replacement for a proportion of their conventionally generated power. The availability obviously depends on whether the wind blows or the sun shines, but in suitable locations, this is fast becoming a viable option, with a number of companies now offering the technology needed to regulate and manage power being produced from different sources at different times of the day.
This article looks at some of the options available for power supplies in places where grids are inadequate for mining and mineral processing needs. Gensets for this market are rated in megawatts rather than the kilowatts provided by the ubiquitous machines that can be towed behind a fitter's pickup; often rented, these have their place in the mining world too, but have their limitations in terms of permanent power supply.
Cat Races to Plug a Power Gap
Having been building engines and electric power systems for nearly 90 years, Caterpillar can provide a complete line of diesel gensets, containerized power modules, heat recovery solutions and rental units, for both continuous or temporary needs. In addition, its gensets can be customized with a wide range of attachments, components and performance options tailored to fit specific applications, Cat told E&MJ.
The company also supplies microgrid systems for use in remote operations. Using an optimized combination of power sources--both renewable and from traditional fuels--its Hybrid Microgrid solutions can be customized to improve power reliability, reduce fuel consumption, lower emissions, and ultimately decrease the total cost of ownership, according to Cat.
At the end of last year, Australia-based Perseus Mining faced a power problem at its Edikan gold mine in Ghana. With power shortages across the country, the government initially cut supplies to industrial users, including mines, by 25%, then in January increased this load shedding to 33%. Not surprisingly, Edikan's production capability was under threat.
Within six weeks of Perseus placing an order with the local Caterpillar dealer, Mantrac, four Cat 3516 2,000-kVA prime power units were on site, with Mantrac supplying not only the gensets, but also undertaking the civils design, installation and commissioning. Also included in the $3.3 million contract were 11-kV switchgear and step-up transformers, with the new power plant capable of replacing 5.8 MW lost from the national grid supply.
The sales development manager for Mantrac's parent company, Unatrac, Damien Valente, told E&MJ that the company's ability to respond so quickly was a key factor in winning the contract. "These were off-the-shelf units, since Mantrac keeps large stocks in all the countries where it is the Caterpillar dealer, as well as having backup equipment in Antwerp, Belgium," he said.
A 16-cylinder diesel engine, the 3516 has a long track record of stability and reliability, Valente added. "It can also be run on up to 70% natural gas, with a dynamic gas blending kit available from new or as a retrofit option. In terms of synchronizing the output from these gensets with the power from the national grid, each unit has its own synch panel attached, so the genset can adjust itself as required."
Another benefit of the 3516 unit is its small footprint, Valente said, claiming that this can be 25% smaller than competitive gensets. And as far as maintenance requirements go, the important thing to remember is that service on the gensets is best done when other major power-use equipment (such as a SAG mill) is offline and demand is lower, he explained.
More QEC Gensets From Atlas Copco
In May, Atlas Copco launched four new containerized generator models that have been designed for prime power and critical standby applications in mining and other industries. The company's range now consists of the 50/60-Hz switchable QEC 800, 1000 and 1250 units for the global market, while the QEC 950 and 1200 are 60 Hz, Tier 2-certified for the U.S. and Canada. All QEC models come in a standard container, with integral forklift slots and lifting eyes for maneuvering on site.
The units include a Cummins engine and a Leroy Somer alternator, and Atlas Copco noted that users can tailor their gensets to individual key requirements such as power output and noise suppression. An optional Qc4003 controller can put two or more QEC models into parallel where loads exceed the output capability of a single genset. This type of power-management system can also be used to provide continuous power when one of the units needs to be offline for scheduled maintenance or repair.
Atlas Copco added that the QEC range comes with 500-hour service intervals. A slide-in/slide-out concept means that the engine and alternator can be removed easily, and there are large access panels. Additional maintenance features include heavy-duty dual-stage fuel and air filtration, a dedicated door for easy cleaning of the engine coolers, and directly accessible power cable connections.
Worldwide Cable Specialist
With its headquarters in France, Nexans is one of the world's largest suppliers of electrical cables for infrastructure projects, aerospace and heavy industry, including mining. Spun out of the Alcatel group in 2001, Nexans has since acquired a number of other cable manufacturers, including Arkansas-based AmerCable.
With its Powermine range of cables, Nexans offers cabling for all aspects of mining operations, both surface and underground. The company said that these cables--which it introduced in 2011--are fully compliant with all the relevant national standards, and that it can provide turnkey solutions for the complete outfitting of a mine or processing plant.
The company's mining-sector marketing vice-president, Jean Fehlbaum, told E&MJ that Nexans has a major share in countries such as the U.S., Chile, Australia and Germany, as well as in China, Indonesia, South Africa, Peru and Colombia.
For underground applications, the range includes coal-cutter cables that offer fire resistance, durability and tensile strength; loader and drill trailing cables; and shaft and haulage cables that are designed for easy installation and good fire resistance. Surface cables are designed to withstand mechanical forces and to provide non-stop power and reliable control for conveyors, excavators, electric shovels, draglines and dredges.
For both types of mining, composite cables comprising optical fibers and copper conductors can be integrated for remote control, surveillance and monitoring--often using an active switch system to provide Power over Ethernet (POE) for vital equipment. Nexans has also developed submersible cables to handle groundwater drainage and fluorescent/reflective cables that increase their visibility.
As well as supplying cables, the company offers a comprehensive repair and emergency service for trailing cables, including fault location, repairs to the insulation and inner and outer sheaths, cable splicing, and repairs to optical fibers. Nexans can also provide training for end users, with the aim of improving safety, speeding up installation and prolonging cable life, and provides on-site cable inspection services through its MineCableSafe program. Benefits include less downtime, greater productivity and lower per-ton cable costs, the company said.
Gas Turbines for Fast-track Power
With its headquarters in Florida, APR Energy--which traces its corporate roots back to Alstom Power Rentals--claims to be among the world leaders in providing fast-track power solutions. In October 2013, when the company launched a strategic alliance with GE, it noted that mobile turbine usage for fast-track power has grown rapidly as customers look toward larger-scale, semipermanent solutions that integrate into their existing plants or operations and offer greater reliability, fuel flexibility and lower emissions.
Within a few months, APR had announced the award of its largest industrial contract, using mobile turbine technology to power a mining operation in the South Pacific region. Scheduled to come on stream in mid-2014 and run until late this year, the mobile gas turbine plant produces a guaranteed 60 MW. The company noted at the time that the use of mobile turbines--fueled by diesel but with the flexibility to switch seamlessly to natural gas if needed--was the customer's preferred solution, meeting strict emissions requirements and able to fit within challenging space constraints at the mine site.
The use of gas turbines for power generation has traditionally been more of a focus for utilities than for mining users, although another of APR's recent contracts covered both spectra. The Western Australia utility, Horizon Power, awarded the company a contract to provide four dual-fuel, 25-MW GE TM2500 mobile gas-turbine units to provide bridging power to the Pilbara region while a long-term power-supply source was being built. APR noted at the time that this fast-track, power-dense station required only one-third of the space needed by a reciprocating-engine power station for the same power output.
The Pilbara project brought with it some challenges, however, not least of which were the high temperatures (up to 48[degrees]C in summer) and the prevalence of cyclones and tropical storms. The facility was fitted with tie-downs designed to withstand wind speeds of up to 300 km/h.
In another mining-specific project, in 2010 APR supplied, installed and commissioned a diesel-fueled 10-MW turnkey power plant to Vale, providing additional capacity during the commissioning phase of the Moatize coal project in Mozambique and supplementing supplies from the local grid. Customization included the implementation of a volumetric fuel measurement system and the design of a 2-km overhead line from the plant to a nearby substation. APR reported that it configured the plant to operate in base load parallel with the grid, with the capability of instantaneously switching to island mode in the event of grid failure.
Turnkey Solutions to Power Needs
Aggreko told E&MJ that it is a major provider of temporary power and temperature-control services to the global mining industry. With more than 50 years of experience, it offers fully flexible power packages for every stage of a mine's life, from project planning to eventual ramp-down.
The company pointed out that while reaching remote locations and dealing with harsh environments is a challenge, it can overcome this through the mobility of its fleet, which can be transported within days rather than months. Aggreko's 20-ft (6.1-m) stackable containerized units are designed to be easily transported by sea, air or land. And whereas extreme temperatures can significantly reduce the efficiency of a diesel engine, its G3+ engine has been built to deliver full power even at high ambient temperatures.
Aggreko provided E&MJ with details of a number of mine projects with which it has been associated. For example, at Banro Corp.'s Twangiza gold project in the remote eastern part of the DRC, Aggreko generators have provided power through all stages of mine development. The company supplied an initial 500-kVA generator for camp power, then an additional 1,250-kVA unit for welding and construction work. This was again increased sequentially to reach the 8 MW of generating capacity the mine needs for full operation.
In Chile, meanwhile, Codelco needed a power supply during construction of its Gaby project in the high Atacama desert. Aggreko initially supplied the site by small generators located appropriately, then followed this with a 5-MW power package consisting of generators, a transformer, bulk fuel tanks and a control room.
At the opposite end of the temperature spectrum, Aggreko also provided a turnkey power plant to help overcome temporary power shortfalls at a coal-mine development in northern Alberta. This consisted of 6 MW of cold-weather generators, together with a crane for installing them, with the equipment remaining on site until the client--which had production commitments--was able to secure its utility grid connection.
Power Management From Eaton
With mines under increasing pressure to curtail rising energy costs and offset the costs associated with utility-dedicated distribution, Eaton offers a wide range of electrical solutions to optimize mine-site generation assets and support reliable power distribution for generation and co-generation applications.
Through the Intelligent Switchgear Organization (ISO), a joint venture with Caterpillar, Eaton offers an extensive array of both emergency transfer and load-management generator paralleling switchgear. When generators operate in parallel with a utility, closed transition functionality, soft loading and unloading, and peak shaving capabilities are often required. This design approach eliminates the need for automatic transfer switches and enhances voltage, Eaton said.
A lineup of paralleling switchgear is often used to control several diesel gensets in either low- or medium-voltage configurations. Eaton utility-grade metering delivers onboard diagnostics, protection and advanced energy management.
Larger bus-connected generation used to supplement or replace utility services is typically driven by gas turbines, often rated at 40-100 MW. Unique fault and switching applications in these applications require the careful selection of circuit-breaker technology to avoid field failures and associated downtime and safety issues. Eaton's VCP-WG circuit breakers meet IEEE's strict service requirements for generator circuit applications, including high continuous and fault duty currents, unique voltage conditions, out-of-phase switching, and very fast rate of rise of recovery voltage.
Parallel generators at this scale also present some added challenges with system grounding or earthing. Eaton offers a hybrid resistance grounding system, while its InsulGard partial discharge relay delivers an added level of protection.
As utilities across the world become less regulated and additional alternative energy technologies become financially viable, major mine sites are increasingly taking control of their energy assets. This includes not only the generation of megawatts but also voltage control, reactive power compensation and power quality/system reliability, as well as increasing interest in renewable energy sources. Eaton's solutions bring all of these assets together with a single controller, the company told E&MJ.
Diesel Engines to Drive Gensets
A major provider of engines for power generation, delivering to genset OEMs all over the world, Volvo Penta offers a range of 85-700-kVA engines that it said are optimized power nodes with excellent power density for their size. The company focuses on developing its engines for gensets used in both prime power and standby applications, and has tested them extensively in the most extreme environments.
Volvo Penta claims that high reliability, durability and low operating costs are key benefits of its engines. The range covers 5-16-liter diesel engines, with output levels ranging from 75 kW to 640 kW. Most engines are dual speed--1,500 rpm (50 Hz) and 1,800 rpm (60 Hz)--making it easy for OEMs to adapt generator sets to different market demands. Engines meet all stages of emissions regulations, up to the current Tier 4f.
For example, since the beginning of this year, Volvo Penta customers in North America have had access to two 16-liter, Tier 4f-compliant genset engines that provide 508 kW and 570 kW on prime power. A major advantage of these engines is their use of SCR emissions-reduction technology without the need for a diesel particulate filter or diesel oxidation catalyst, the company stated.
Power for Mining Communities
With its expertise in both gas- and steam-turbine technology, Siemens is in a position to offer large-capacity power plants that can fulfill the needs of mines and their surrounding communities. Two examples that the company highlights are the generating stations at La Caridad in northern Mexico, and at Mount Isa in Queensland, Australia.
In Mexico, Siemens supplied two turnkey combined-cycle power plants to provide power for Grupo Mexico's La Caridad and Buenavista del Cobre mines, together with the local community and other industries. The company undertook engineering, procurement and construction of the two 250-MW plants, in which the heat generated by a gas turbine is used to power a steam turbine, adding to the output. Siemens estimated that the technology will save Grupo Mexico around 40% on its power-generation costs.
Siemens made extensive use of factory prefabricated modules for these plants, with about 60% of the components used being prefabricated before site installation. This approach helped save both time and costs, as well as improving construction quality, the company stated.
At Mount Isa, meanwhile, Siemens designed and provided construction advisory services for the 2 x 121-MW Diamantina power plant, which also uses combined-cycle technology. Each power island includes two Siemens SGT-800 gas turbines and an SST-400 stream turbine, as well as two heat-recovery steam generators. "The new Diamantina power plant is a great example of our eco-friendly power-generation solutions for off-grid operation, matching the variable power demands of the adjacent copper mine," said Erling Bruun, head of industrial power plant solutions at Siemens' Power and Gas Division.
Big Multifuel Plants
The Finnish company, Wartsila, focuses on the marine propulsion and energy markets, with considerable experience in designing and supplying power plants for remote locations. As an example, the company recently signed a three-year service agreement with Newcrest Mining for its power station at the Lihir gold mine in Papua New Guinea. The agreement covers major engine services and spares for the mine's three power plants, consisting of 22 Wartsila engines with a combined output of 172 MW. Wartsi la provided the first diesel power station to Lihir in 1996, with subsequent additions.
Wartsala also supplied the equipment for a 53-MW gas engine-based expansion to McArthur River's power plant in Australia's Northern Territory, commissioned in late 2013. The company delivered six 34SG engines running on natural gas, plus related engineering services.
However, these projects are dwarfed by the power plant Wartslla installed for Barrick Gold and a local utility at Pueblo Viejo in the Dominican Republic in 2013, which consists of two identical 215-MW units. Each of the Quisqueya plants features Wartsila's Flexicycle combined-cycle technology and has 12 50DF dual-fuel gensets that can run on natural gas or liquid fuels. Designed for flexible baseload, the plant has a net efficiency of 48%, which is high for tropical conditions.
The 50DF can run on natural gas or any liquid fuel, including heavy fuel oil, and switch back and forth between them while delivering power to the grid. Full power can be achieved with a wide range of gas qualities, the company describing it as being a robust, reliable genset, proven in the most challenging environments.
Power From Coal-mine Methane
Part of Caterpillar's Electric Power Division since 2011, the German manufacturer of natural gas and alternative-fuel engines, MWM, has developed gas engines and power generators specifically for coal-mine methane. The company noted that using this gas as an alternative fuel can help improve mine safety, reduce C[O.sub2] emissions, cut electrical energy costs and generate income. With a methane content of 30%-95%, coal-bed methane, coal-mine methane and abandoned mine methane are all suitable for gas-engine fuel.
MWM's product portfolio comprises gas engines and gensets in the output range from 400 kW to 4.3 MW, offering the potential for building power plants with capacities of 100 MW or more.
Between 2008 and 2010, MWM delivered seven containerized TCG 2020 V20 gensets to Shanxi Coking Coal for use at its Xishan mine. The units run on coal-mine gas, with a total capacity of 12 MW. In Poland, meanwhile, jastrzebie has been operating a trigeneration plant at Its Pniowek mine with three mine gas-fueled engines since 1999. MWM noted that this project is unique In that the mine gas is used to cover the operation's own power needs and for underground air conditioning.
Protection in Harsh Environments
Schweitzer Engineering Laboratories (SEU told E&MJ that its solutions make electrical power systems safer, more reliable, and more economical with its mining-sector customers, including companies such as Alcoa, Ma'aden, Grupo Mexico, Freeport McMoRan Copper & Gold, PotashCorp and Worsley Alumina.
Designed to meet the specific needs of the mining industry, SEL protection, control and metering solutions cover requirements for power management and protection, feeder protection, arc-flash detection, automation and integration, generator and motor protection, fault indication and sensing, and power-quality metering and monitoring. For example, SEL relays are designed to trip a circuit breaker when a fault is detected or when too much electricity could damage the system or create an unsafe environment. The company also supplies substation control enclosures, custom panels and secure data communications equipment.
Last year, SEL reported an order for relays and communications products to protect and control K+S Potash Canada's new Legacy potash mine in Saskatchewan. It noted that this takes the use of Its equipment in Canada's potash industry one step further by introducing IEC 61850 communication for complete electrical distribution system control, monitoring and integration.
SEL added that its relays and fault indicators are already installed in nine of the province's 10 major potash mines, providing protection in some of the harshest mining applications. In one installation, mobile underground substations (sleds) carry a breaker, a transformer and both primary and secondary SEL-751A feeder protection relays, in addition, there are two types of sleds: miner sleds power the mining equipment, and drive sleds power pumps, fans, lighting, and everything else in the mine.
Designed for Low Maintenance
Cummins PowerGen exhibited some of its diesel-powered genset capabilities at this year's Indaba meeting in Cape Town. The company's range of pre-integrated generator sets covers outputs from 8 kVA to 3,300 kVA, which, it said, can meet all of a mining projects' energy needs, including continuous, prime, peaking, standby or cogeneration--or as a complete turnkey power plant.
Speaking at the time, Cummins Africa's Power Solutions Director Kenny Gaynor explained that mining operations can lower their fuel costs and minimize their impact on the environment with the company's new HHP QSK95 series gensets. The company's most powerful diesel gensets to date, these supply up to 3.5 MW at 60 Hz and 3.75 MVA at 50 Hz. "They are engineered with the highest kilowatt per square foot ratio in their class, resulting in a smaller footprint that achieves a 20% improvement in power density," Gaynor stated.
Fewer maintenance requirements, longer service intervals and 25,000 hours to major overhaul make these gensets "ideal for prime power applications," he added, noting that their smaller footprint means that the QSK95 series requires less space to install and, in multiple-genset applications, fewer generators are required to achieve the necessary power output.
In 2014, Cummins supplied a 28-MW peak-load generating station for CuDeco's new Rocklands copper project in Queensland, Australia. The station includes a 750-[m.sup.2] generator building housing 16 C2250 D5 6.6-kV gensets controlled by a DMC 200/16 digital master control.
Cummins South Pacific supplied the station as a turnkey project, including a switch room and switchgear, an acoustic building and remote radiators. Environmental factors played a significant part in the station design, with 24 bag filters and 24 screen filters per engine, while 20 km of termite-resistant cables were used for underground runs.
In 2011, meanwhile, Cummins won a $15 million contract to provide 30 gensets for prime power at Sherritt International's Ambatovy nickel project in Madagascar. The C1250 D2R gensets provide 30 MW of power from two plants, synchronizing with the local grid and existing Cummins generators and turbines for load management.
As Eaton pointed out to E&MJ, many of the world's mines are moving toward multiple energy sources. To augment utility service, mine owners are deploying new energy sources including continuous and stand-by diesel generators and bus-connected natural-gas turbine generators, as
well as solar photovoltaics and wind turbines with energy storage.
In May, Santiago, Chile, became the venue for the fourth Renewables and Mining summit and exhibition. Energy and Mines, the organizer, noted that with energy accounting for 20%-40% of operating costs in Chile's mining industry, reducing electricity expenditure has become a major operational and strategic goal, in which renewables are set to play a significant role.
Climatic conditions in Chile's high-altitude mines offer good potential for solar generation, with Collahuasi's 25-MW plant--capable of supplying 13% of the mine's needs--officially opening last September. Other mines have also been working with solar technology: Antofagasta's El Tesoro commissioned 10 MW of solar process water-heating capacity in 2013, while iron-ore producer CAP began producing power from its 100-MW array near Copiapo a year ago.
And it's not only the sun that is providing mine power. In 2012, Rio Tinto commissioned the four wind turbines that last year provided 11% of Diavik's power needs and, more importantly, reduced its diesel transport demand along the seasonal ice road by the equivalent of 100 tanker truck loads. Similarly, Glencore constructed the first of possibly six wind turbines at its Raglan nickel mine in northern Quebec last year, and also has plans for energy storage by producing hydrogen that can then be used as a replacement fuel on site.
Renewable power sources are unquestionably set to become big business over the next few years, with more and more mines seeking reliable alternatives to conventional generation. In the meantime, suppliers will be honing the technologies needed to manage hybrid power systems, which will be the topic of a future E&MJ review.
A Nuclear Option?
Given that mine developments are increasingly taking place in off-grid locations, selecting the most appropriate power source can be critical, not only in terms of reliability but also with regard to ensuring regular supplies of fuel. Having easy access to natural gas networks may not be an option, while hauling diesel is both costly and--in the case of the far north, at least--season-dependent.
Two presentations at the 2015 Nunavut Mining Symposium, held in Iqaluit in April, looked at the potential for using small-scale nuclear reactors as a cost-effective and more reliable alternative to conventional diesel-powered generation. From Dunedin Energy Systems, Peter Lang compared the advantages of the diesel-based option--a mature technology that is reliable, scalable, portable and has a low capital cost--with its disadvantages--high and unpredictable fuel costs, expensive and difficult logistics, and the potential for environmental hazards. In addition, he said, each liter of diesel burnt generates 2.7 kg of C[O.sub.2], while exhaust soot is thought to be a significant factor in regional climate warming.
Lang went on to describe the floating nuclear cogeneration plant concept currently being built for the Russian energy company, OKBM. Designed to provide power and heat to remote Arctic communities, the Akademik Lomonosov carries two nuclear reactors capable of producing up to 77 MW of electricity or 300 MW of heat. For comparison, he pointed out, Agnico Eagle's Meadowbank gold mine in Nunavut has 26 MW of generating capacity.
Lang compared the performance of a 16-MWe OKBM ABV-6M reactor, capable of producing 126,000 MWh/y of power, with a diesel station of comparable output--which would require 31.5 million liters of fuel a year and would emit 85,000 metric tons of greenhouse gases. There is also the potential for diesel-fueled generators to be subject to any carbon taxes that governments may decide to impose, whereas nuclear would be exempt.
"Clean, safe and portable energy is absolutely key to mine profitability, and the current diesel model is not sustainable for the scale of development we want to see," Lang stated.
by Simon Walker, European Editor
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|Title Annotation:||POWER SYSTEMS|
|Publication:||E&MJ - Engineering & Mining Journal|
|Date:||Jul 1, 2015|
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