Plant Engineering Evolves to Meet Environmental Needs

Incremental gains today will lead to substantial improvements for future flowsheets

By Steve Fiscor, Editor-in-Chief

The mining industry has set some ambitious goals regarding sustainability. The trucks that transport ore from the pit to the primary crusher are responsible for a considerable amount of the carbon emissions at a mining operation. Crushing and comminution also consume large quantities of energy too. To attain their goals, mining companies are reviewing the entire production chain from pit to port.

While the mining companies have their goals, their customers also have a similar set of needs. Some of their customers have already said they will pay a premium for a low-carbon product. Others are demanding purity levels that are difficult to achieve. If a mining company can’t supply the product, the customer will likely go elsewhere.

To assist mining companies in meeting these goals, equipment suppliers and services providers are aligning themselves with their goals. They have invested in research and development (R&D) and brought new equipment online. They have also acquired companies and formed partnerships with others to improve plant performance. 

Today, mining companies are making incremental changes at the plant and those improvements are compounding annually. What will tomorrow’s flowsheet look like? The changes that the industry will see in the next eight years will be both evolutionary and revolutionary.

The Campaign for Continuous Improvement

In fall 2019, FLSmidth launched MissionZero to offer the mining industry solutions that support a move toward zero water waste, zero emissions and zero energy waste. Dedicated to the development of digital and innovative solutions tied to sustainable productivity, the company said it planned to offer the required technological solutions to move toward zero-emissions mining processes by 2030, with a specific focus on water management.

The company has already developed solutions such as dry-stack tailings that enable mine sites to recover up to 95% of their process water and multiple digital solutions that provide greater processing efficiency. FLSmidth has also identified opportunities to significantly improve productivity and environmental impact across the entire flowsheet, including crushing, flotation, thickener upgrades and filtration, as well as the maximizing potential of pumps and cyclones.

“Our long-term drive toward MissionZero is vitally important, however, the current day-to-day challenges remain, which is to be as profitable as possible and produce as much as possible,” said Marnus Fick, head of the North American region for FLSmidth. “It’s the incremental gains day-to-day that we are helping our customers with right now as they scrutinize their environmental footprint. Meanwhile, FLSmidth’s R&D department is working toward finding the silver bullets and working in that white space to commercialize that technology.”

A prime example of this would be the large installed base of Wemco flotation systems, Fick explained. “The recently announced Wemco II essentially allows for a drop-in replacement of the old mechanisms, and that will move the plant’s recovery curve up three to five times,” Fick said. “It’s the same type of equipment with the same footprint, no major disruption to the plant’s operation, and suddenly the recovery curve increases.”

FLSmidth is doing this across all of its product lines. “We want to provide incremental gains that will achieve savings in power and costs, and improve sustainability,” Fick said. “We’re working diligently on the simple things like pump cycles. If we optimize the efficiency of the plant’s pumps, we can typically save them 10% to 15% in energy consumption.”

Digitalization is a big topic and FLSmidth recently signed a global partnership with AVEVA to deliver digitally enabled solutions and services to the mining industry. AVEVA’s PI System will serve as the central digital platform across FLSmidth’s operations. Most large mining companies around the world use the PI System to support data-driven decisions and can now leverage their existing investments to gain new advanced insights from FLSmidth. A select group of mining companies have already agreed to form part of a pilot project around equipment availability and optimization, with customer value expected to be proven in a short time frame.

“Data just for the sake of data does not make sense,” Fick said. “But, having the ability to capture data and interrogate it intelligently, we can provide mining companies with a comparative analysis of how we see our machines performing at similar operations.”

FLSmidth is also working with mines to perform asset optimization and condition monitoring. “We are focusing on the areas where we can get the most gains and that’s the milling circuit,” Fick said. “With the acquisition of KnowledgeScape, FLSmidth has introduced LoadIQ, which optimizes the rotation speed to eliminate material loss, improve wear and lower energy consumption.”

Similarly, the SMART Pump platform measures pump performance. This is something most mines are already doing, Fick explained, and we are latching on to their signals and interrogating their data.

Projecting to 2030

FLSmidth’s Salt Lake City campus includes the company’s Mineral Testing and Research Center. “Our lab provides mineralogical and metallurgical services, testing ores from mines all over the world,” said Pete Flanagan, key account manager and senior vice president for FLSmidth. “Using that information, we can help with equipment selection, flowsheet design and plant troubleshooting. The lab also operates independently with more than 40 years of collective experience.

The Mineral Testing and Research Center is the largest commercial mineralogy lab in the world. It has five scanning electron microscopes, multiple XRDs, near infrared, XRF analysis, etc. And we have two of the best process mineralogists working for us, explained Wayne Douglas, global head of mining R&D, who oversees the facility.

“The lab not only gives us the ability to characterize the mineralogy of a deposit, it also allows us to work with mining companies to help them really understand what they have,” Douglas said. “We can show them how the ore will crush, comminute, convey, grind, float, etc. The what is nice to have, but the additional real power we have is understanding of why.”

The “why” can often be attributed to the gangue minerals, Douglas explained. “It causes abrasion,” Douglas said. “It will increase acid consumption on a copper heap if the gangue is carbonate. We want to look at the concentrate because that’s what’s valuable, and similarly what floated, what didn’t float and what size fraction was it. Knowing this, we can start to paint a picture of the flowsheet and the ideal design for the process. Knowing the why gives us a tremendous advantage. 

“This a commercial lab and we run it independently,” Douglas said. “We compete with the other commercial labs and give the mining companies what they need. We hope they go with FLSmidth, but they can work with anyone.”

Douglas discussed the advantages of working in parallel with mining companies. “Often we’re seeing repeated problems or challenges, because a lot of these orebodies are getting more refractory and certain things are popping up that didn’t use to,” Douglas said. “The FLSmidth R&D team is in the same building and they’re under the same management as the professionals designing the equipment and processes. We discuss problems internally and we may not have an ideal solution, but we can design a process that can address that issue.”

“When FLSmidth launched its Mission-Zero campaign, we began to review everything in our flowsheet and evaluated the elements within our control,” Douglas said. “We developed a flowsheet that illustrates holistically the 2030 goal (see flowsheet on p. 38). For every area, we are looking at three things: improving an existing process, developing an evolutionary process and pioneering a revolutionary process.”

Load IQ is a classic example of improving an existing process. “With Load IQ, we can get an 8% bump in throughput with 11% power savings at the same time,” Douglas said. The Wemco II Flotation is a prime example of an evolutionary development.

“We’re not going to change the world overnight but, if we can gain about 1.5% per year in efficiency, that would be considered a pretty good pace of innovation,” Douglas said.

Looking at 2030, Douglas said they took a blank canvas approach. “We’re going to do all three approaches in parallel, but really we would like to offer the mining companies something revolutionary,” Douglas said. “Everything on the flowsheet is at least at the pilot scale, if not full scale. For the last two years, we’ve taken ideas from concept to small lab units, but everything is advanced to the point where they should be commercialized in the next couple of years. By 2030, it would be really great to see them installed in new plants.”

Readers should note the flowsheet has a few blank (gray) cubes. “We have some partnerships with different funds that are privy to these early-stage innovations, so we keep placeholders there because we are hoping one of these is bound to pan out. From a commercial standpoint, when it gets out of the university lab doing just more than a couple of kilos, we want to be the first to know. We can quickly understand the whole impact to the flowsheet.

Comminution is more than 50% of the energy for this entire flowsheet. “We have a couple of ways to really attack most of the energy,” Douglas said. “We saw the cement industry transition from wet milling to roll crushing and then to vertical roller-mill technology. Mines are still wet milling and we’ve seen more roll crushing or HPGRs, and we see the OK Mill as the next step in that evolutionary process.”

The traditional line of thought is that the liberation curve dictates the grinding size. Ores are ground to a certain point so that metal is free enough to liberate through conventional flotation.

“With coarse particle flotation, we could grind ores a lot coarser if we had a gentler and more effective mechanism or way of having those bubbles come to the particle, even with gangue still attached,” Douglas said. “And if it’s gentle enough, we think that the bubble is just hanging on to the non-gangue part should be able to lift that up carefully. Perhaps we could do more with the froth phase.” 

For every 50 microns, how much energy would the industry save? “With an existing SAG mill, if we can create a 100-micron shift, it would increase throughput by 20%-30% in some cases. That amounts to a lot more copper for the exact same energy if we’re successful with coarse particle flotation.”

The REFLUX Flotation Cell (RFC) was also launched recently and coarseAIR is right on its heels “We’re very excited about the implications of coarseAIR,” Douglas said. “The upstream milling benefit is huge, but there’s a downstream benefit too. With coarse particle flotation, there will be a regrind step on that concentrate and that’s where the RFC comes into play. We have beaten the conventional-grade recovery curve on all the ore bodies we’ve tested with that, and that’s why we’re so excited about RFC. We’re seeing higher grades and recovery.”

From a footprint standpoint, both the coarseAIR and an RFC, the size is much smaller. “We’re using a lot less steel compared to what a conventional row would look like,” Douglas said. “For a new plant, that’s a lot less concrete and building space for the equipment.

“Numbers are dangerous to throw around because the devil is in the details and all the assumptions. In an ideal world, if everything would work for this technology and we could see a 100-micron shift in the grind size and still get a recovery with coarseAIR, the energy we could save is not insignificant. Each process has a value prop of its own, but the way everything interacts is where the value lies.

“A large portion of this will hinge on having the dialogue with mining companies and saying, you can implement portions of this,” Fick said. “Let’s grab the gains we can because this is a journey, it’s not just a race.

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Developments With Dry Magnetic Separation

Eriez noted that it is seeing renewed interest in dry magnetic separation from both traditional and non-traditional areas. “We are going through some interesting phases in the mining industry these days,” said Jose Marin, mining and minerals processing director for Eriez. “Iron ore is a big market for magnetic separation and it’s also a cyclic market. For the last two years, the demand for steel has been through the roof, so we’ve been fortunate to be able to participate in some projects related to iron ore.”

Traditionally, iron ore miners use a conventional wet magnetic separation process. Some of the projects today, however, are considering deposits in arid regions. These projects will require dry iron ore concentration and Eriez has completed some work recently in this area. “We’re currently working with a mining company that is trying to develop a deposit in Nevada that will require a dry process and, so far, we have had some very promising results,” Marin said. “Normally, we are able to concentrate iron ore up to about 63%-64% total iron, which would be very difficult to achieve with a dry process. We have made some modifications to our equipment and we were able to attain similar numbers, which is very exciting.”

The process uses conventional magnetic-drum separators during the first few stages of separation. The coarse material, the pre-concentrate, goes to a rougher. There will be a size reduction between those two stages. After the rougher stage, the concentrated ore goes to a cleaner and a finisher. “That’s where we made the modification by adding a dry magnetic separator,” Marin said. “We were able to bring the total iron in the final concentrate up to about 64%, which is unheard of.”

If iron ore miners could get the iron level to 60%-62% in the concentrate, they felt that was a really good number, Marin explained. “With this process modification, adding the dry magnetic separator, we were able to improve the final product,” Marin said. “Another minor modification was to vacuum the air from the area where the dry magnetic separator is fed. Normally, a dust cloud forms in that area. Vacuuming all the light material out makes a big difference with the final result.” 

Another area of mining that has gained a lot of attention recently is lithium and it is also benefitting dry magnetic separation. The raw materials that are used to make lithium-ion batteries, whether its lithium carbonate or lithium hydroxide, must be ultra clean. “By ultra clean, we’re talking about metal concentrations of 50 parts per billion or less,” Marin said. “That is really almost nothing. Few laboratories have those standards or even the ability to analyze battery-grade lithium for levels that low. A single particle of metal can throw the results off.”

Neither lithium carbonate nor lithium hydroxide contains a naturally occurring iron component. The iron impurities are generated from processing machinery wear and piping system abrasion.

All battery-grade lithium producers use magnetic separators throughout processing and, by installing a dry high-intensity magnetic separator at the end of the process, they can achieve that desired level of purity, Marin explained. “Many of them are using the Eriez dry vibrating magnetic filter, which for simplicity’s sake is an electromagnet in a vibrating canister,” Marin said.

A magnetic field is induced into a matrix that generates an extremely high gradient. As the material filters through the matrix while it’s vibrating, metallic particles are retained magnetically while the non-magnetic product filters through. Occasionally, the magnet is de-energized and the reject device at the bottom discharges the magnetic impurities. “This product is very popular with lithium producers, and a lot of the projects, which are being developed, are considering our dry vibrating magnetic filters near the end of the processing line so that right before it gets packaged, there is a high-intensity magnetic separation,” Marin said.

Battery-grade lithium is chemically precipitated and then it passes through the milling and classifying process and then magnetic separation. At the final product stage, the drive vibrating magnetic filter provides for the final classification to achieve the highest levels of purity.