How digitalized gearless drive technology results in energy savings and improved performance ?

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The challenges facing the global mining industry are well-documented. Overarching market volatility and the sustained long-term decrease in commodity prices combines with geopolitical risks, regulatory and environmental concerns. Then there are industry-specific factors - depleted resources and ore variability. Mining operators must reduce costs while increasing operational efficiency through automation. 

The World Economic Forum has identified trends shaping the future of the mining and metals industry.

Transition to a low carbon economy, access to resources in frontier areas where extraction was not previously economically viable, and the role of big data were top. 

Technologies for extraction and processing, including gearless mill drives (GMDs) and gearless conveyor drives (GCDs), help operators save energy and achieve greater throughput at large mills with higher grinding capacities. When big data is also applied, this lowers costs using preventive and predictive maintenance. 

How do GMDs contribute to sustainable operations?

1. When used to power semi-autogenous (SAG), ball and autogenous (AG) mills, GMDs provide improved throughput, reliability and availability at processing plants

    Traditional ring-geared mill drives have a ring-shaped gear that encircles the mill and drives it through one or two pinions followed by conventional motors. GMDs mount rotor poles directly to the mill body and surround it with the stator ring, incorporating the mill itself into the motor.  

    The necessary torque is transmitted between the GMD motor and the mill via the magnetic field in the tiny air gap between the stator and rotor. This type of motor system requires no gearing or direct contact transmission, meaning GMDs improve efficiency by reducing frictional losses, while fewer mechanical components equals less maintenance downtime due to wear and tear.   

    Less electricity means that every kilowatt hour saved goes straight to the bottom line and increases the payback period of investments in savings programs and energy-efficient capital equipment. 

2. GMDs are now the accepted technology in remote environments, where the need for higher-power drives to achieve greater throughput must be balanced with optimum availability.   

    Resource depletion and declining ore grades are forcing operators to enter frontier mining locations, where they may have to run multiple, large-capacity mines with higher grinding capacities in parallel. 

    Most new mines have high quality surface ore to begin with, however after years of operations the ore grade often deteriorates. This means mills grind larger quantities to extract the same amount of ore. The best mining companies plan for this situation. 

    GMDs have become the accepted technology for this challenge in these remote environments, where the need for higher-power drives to achieve greater throughput must be balanced with optimum availability. Eliminating complex mechanical components that may fail, resulting in production downtime, means energy savings of up to 3% – a substantial economy when some modern mines may have as many as six 15–25MW drives running in tandem. 

3. GMDs can reduce the overall operational footprint and CO2 emissions, and increase efficiency by grinding large capacities 

    Running many smaller mills simultaneously was standard in the past, but in addition to energy losses mechanical components required regular maintenance. The need for larger footprint spaces and spare parts inventories proved impractical and costly. 

    Operators are now opting for one or two very large lines, with big SAG mills and ball mills, enabling them to reduce their overall operational footprint and CO2 emissions while increasing efficiency by grinding large capacities.  

    ABB recently took an order for 12 GMDs in Russia, the largest single order in the history of GMDs in mining, where companies are eschewing the traditional model of multiple, small-capacity mills in favor of fewer mills with larger grinding capacities. 

Marcelo Perrucci, Global Product Line Manager - Grinding 

“Installing GMDs potentially means using less on-site mechanical equipment, and thus a reduced footprint in terms of mechanical space. It is a more efficient technology in terms of energy savings and higher overall system efficiency. Savings of as much as 3% are possible compared with conventional solutions – and that means lower carbon emissions and cost savings.” 

Gearless mill drive (GMD) in Sierra Gorda, Chile.

How can we show the savings created by GCDs? 

1. The use of GCDs in the world’s largest conveyor system

    In Chile, ABB is partnering with TAKRAF Tenova Chile to supply gearless conveyor drives (GCDs) for the extension of a copper mine, which incorporates the world's largest conveyor system (13km) connecting the subterranean operation directly to the concentrator.

    Located at an altitude of 2,850m, the mine has a design capacity of 11,000t per hour (tph). Eleven 5MW gearless drives with synchronous motors running at low speeds (50-60rpm) drive three conveyors; two with four motors each and one with three. Two 20MW conveyors transport the ore from the open pit operation to the surface, overcoming an elevation change of around 1,300m, while the second conveyor feeds into a slightly smaller, 15MW, overland conveyor.

    Each conveyer is around 3km long, which means at this length it overcomes around 600m of altitude. To transport 11,000tph of ore requires a high drive power and the strongest available belt.

    Once the mine reaches full production, the change from open pit with truck/shovel operations to underground operations with the TAKRAF system using ABB gearless conveyor drives will eradicate the need for 120 large-haul trucks, each consuming roughly 3,100 litres of diesel per day. This equates to around 130 million litres of gasoline consumption saved, and carbon emissions savings of around 66%, or 240,000 tonnes a year.

Conveyor flight underground. Source: TAKRAF.

2. Noise emissions reduction using gearless conveyor drives

    In Europe, ABB is working with a mine in the Czech Republic to replace shaft mounted geared drives on an existing conveyor system with ABB Gearless Conveyor Drives powered by synchronous permanent magnet motors.

    In addition to preventing frequent motor bearing failing due to vibration issues, ABB’s silent GCD technology also helps the operator to meet stringent EU noise emission limits. Noise emissions in the EU must be lower than 85dB(A) (A-weighted decibels). When a gearbox, with a lot of parts turning at 1,000rpm or higher, is active it can be very loud and these conveyers are close to villages.

    By using GCDs at around 50rpm, it was possible to reduce the noise emissions of the drive unit to less than 75dBA. In this way, the end user can install the gearless drive without the need for additional noise reduction measures such as installing noise encapsulation (housing around the whole geared drive unit) or noise protection walls along the conveyor.

Increased savings are built in

Using the ABB Ability™ cloud platform, mining operators can gather and collate real-time data from sensors in the systems, enabling them to carry out preventive and predictive maintenance from remote locations using machine learning, artificial intelligence (AI) and other techniques.

To be truly digital and gain understanding, mining operators need information. ABB began adding instrumentation to GMDs and GCDs many years ago. Fast forward 10 years, and sensors are embedded in the system to communicate exactly how machines are behaving. There is also a model of each machine; a digital twin. With this information and using big data from previous operational records, it is possible to predict how the machine is going to behave in the future.

Customers can now use a secure web platform remotely from anywhere in the world to see, for example, the status of the air gap, the centricity of the mill, and the pole alignment - and ABB can proactively alert them on potential issues.

To complete the picture, customers have access to Visual Remote Support, a new augmented reality platform designed to improve response times, extend asset lifecycles, improve production performance and ensure operational excellence.

Using augmented reality to overlay computer-generated information, data, images, video or other content onto the real-world environment through Microsoft HoloLens mixed reality devices, the

solution enables a field service technician to share his or her view of a situation using the device’s camera, and communicate directly with an expert via on-screen annotations, chat, and document sharing.

Developed for use in multiple industry sectors, including metals and mining, Visual Remote Support not only improves asset and production availability by ensuring that maintenance actions are completed faster, but also reduces training costs, and improves safety for ABB and customers. The move is increasingly towards mixed reality, and ABB has been working to implement it into operations.

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