Pumps are often overlooked when it comes to energy efficiency programs but their performance can be easily tweaked to better suit operating conditions and new designs are constantly evolving. (Photo: Weir Minerals)

Better energy efficiency can save costs, increase production and lower the carbon footprint

By Carly Leonida, European Editor

In 2021, Weir Minerals commissioned a definitive report into mine energy usage across five commodities — copper, gold, iron ore, nickel and lithium. The study found that diesel used in mobile equipment accounts for 46% of final energy use at the “average” mine site, electricity used in comminution (the reduction in size of mineral particles) accounts for a whopping 25%, while electricity used in mining (primarily ventilation) accounts for 15% and “other electricity,”14%.

Using the current production rates of these five commodities as well as average energy intensities, the author — Marc Allen, technical director at engeco — found that their production consumes approximately 0.5% of total final energy globally, equal to 1.68 exajoules per year (EJ/y). The mining industry, as a whole, consumes 3.5% of global final energy, or 12 EJ/y.

While these numbers sound enormous, what this study shows is that mining, as an activity, is not the biggest consumer of energy globally. According to the International Energy Agency, transport and residential usages are higher.

However, the sector is a significant industrial user; one on which the weight of the green energy transition now rests. Ore grades are declining and, if mining companies are to produce the critical metals required to overhaul global energy production and transfer over the next 30 years while meeting their environmental, social and economic goals, then energy efficiency is clearly an area that warrants attention and investment.

Aside from the obvious (although not always synonymous) reductions in greenhouse gas (GHG) emissions, which can be associated with better energy efficiency, there are significant operational savings to be made. Very few mining operations are untouched by rising energy costs in one form or another. Regardless of the percentage of its energy a mine sources from diesel, the grid or an on-site source of power, renewable or otherwise, the fact remains that power costs money.

Building and running mining operations in line with the highest environmental, social and governance (ESG) standards, as expected today, is not cheap. Any savings that operations can make on their power consumption through operational optimization measures can directly lower their cost per ton. Or the more likely scenario as metals demand soars, it can allow production increases in operations that were previously power constrained.

While it’s easier to design energy efficiency into greenfield projects using state-of-the-art equipment and digital technologies, there are various changes that can be made, both at the equipment and process level, in existing operations to improve energy usage. Some of these will be more significant than others in terms of capital, time and resource requirements, but the return on investment (ROI) can be surprisingly swift and can help to lower a mine’s long-term risk exposure.

The cumulative impacts of small energy improvement projects can also be impressive. As explained in the Weir report, “As comminution circuits have been shown to be the largest single consumer of final energy for hard-rock mining operations… small improvements in comminution technologies can lead to large savings in both energy consumption and GHG emissions. For example, a 5% incremental improvement in energy efficiency across comminution [globally] could result in GHG emissions reductions of more than 30 million metric tons of CO2-e2.”

As E&MJ has recently covered future power options for haul trucks in detail (see May 2022, Powering Trucks for the Long Haul) and also new applications and efficiencies in flotation (April 2022, Floating New Ideas), this article will focus on everything in between, highlighting a few areas from pit to plant that may be of interest for future-savvy operational improvements.

The first step in driving efficiency and better managing electricity usage is accurately measuring energy consumption, so that operations can benchmark their usage. (Photo: Eaton)

Driving Electrical Efficiency

Mine energy efficiency begins (and ends) with the site’s overarching power infrastructure and management. Marc Elliott, global segment director for mining, minerals and metals at Eaton, outlined some of the challenges and opportunities.

“The structure of energy systems powering mining operations is changing fast, creating opportunities to rethink how power is managed and optimized,” he said. “For miners, there are new ways to leverage proven technologies to drive efficiencies that reduce energy costs and bolster energy independence from the local utility grid.

“With electricity costs already accounting for 20% to 30% of operating costs and rising, driving new efficiencies in how electricity is used and managed will have a massive payoff for mining operations — especially as vehicles are electrified and implementations of electrified mines are realized.”

For decades, mines have used diesel generators to ensure reliable energy supplies and island certain operations. While this strategy helps to reduce dependency on the local utility, there are fuel costs and emissions to consider. Today, there’s an opportunity to use self-generated power to drive new efficiencies, especially as renewables move beyond an “alternative” energy source and into the mainstream.

Elliott explained that there are four key strategies to drive efficiency and improve bottom lines, while also reducing scope 1 and 2 emissions.

1. Make electrical power monitoring foundational. The first step in driving efficiency and better managing electricity usage is accurately measuring energy consumption so that operations can benchmark their usage, detect anomalies and take steps toward reductions.   

“As infrastructure becomes more electrified, with electric vehicles on the roads and on-site, monitoring electric usage in real-time and over time will be even more important, and the potential to drive efficiencies (and reduce costs) will be greater,” explained Elliott. “Electrical power monitoring provides accurate insights on system performance across multiple devices within mining operations, making it easier to manage electricity usage and costs, and know when to run diesel generators, use utility power or rely on other on-site energy sources.”

2. Identify and address grounding and power quality issues. At remote sites, it’s common to have poor power quality issues that create conditions for faults and electrical power inefficiencies. Electrical conditions such as “sags and swells,” ground faults, transients and power factor are typical and often result in electrical equipment using excessive power to operate properly or trip offline, causing downtime. Focused power system engineering studies evaluate these issues and provide recommendations essential to solving the problems at hand that are critical to driving energy efficiency and supporting electrification. 

3. Enhance operations through digitalization. “Digital solutions, like Eaton’s microgrid controller and Brightlayer Industrial suite that are customized for industrial operations, can improve power efficiency and productivity and inform decisions with data and insights,” Elliott said. “Our microgrid controller can help mines automatically shift power sources to whichever is most economical and make decisions such as when to charge or discharge battery storage systems, allowing the site to operate its energy sources most efficiently. Additionally, monitoring the broader production ecosystem helps identify and correct anomalies, so you can plug energy leaks — from air, water, gas or electrical lines — and reduce consumption.”  

4. Balance energy with new tools. Cogeneration is not new and diesel generators have been a staple of mining for decades. What is new is the ability to integrate on-site renewables such as solar combined with the intelligence of a microgrid controller to balance energy needs. This can help add clean energy into the mix, while lowering utility bills and increasing resiliency of the electrical power infrastructure. Further, by optimizing energy systems to maximize on-site energy sources, mines can ensure the power is always on and that the most cost-efficient source is used.

“Fundamentally, the best energy is the energy you don’t use, so efficiency is key,” Elliott said. “Using field-tested solutions, new energy ecosystems create opportunities to meet growing energy needs more locally, efficiently and sustainably.”

Rubber: Transferring Energy Savings

Although not always visible, rubber products touch and therefore can influence the performance of many different types of equipment in a mine. In material handling, off-the-road (OTR) tires are essential drivers of performance for haul trucks and other vehicles, while conveyor belts provide an economic solution for long-haul transport of ore and waste.

David Reynolds, vice president and general manager at Cabot Engineered Elastomer Composites, explained: “Rubber’s flexibility, resilience and resistance to abrasion combined with its ability to effectively absorb and dissipate energy generated through impacts make it one of the best materials mining companies have in the fight against rising operating costs. However, it is a material that is often overlooked for optimization in the quest for high-performance and environmental excellence.”

Rubber is a naturally resilient material that easily dissipates or releases energy absorbed through impact and deformation. Rubber is typically strengthened through the addition of reinforcing agents, including solid particles like carbon black, which increase its toughness. If these agents aren’t properly incorporated into rubber, the rubber loses its ability to efficiently absorb energy, adversely affecting energy consumption in critical applications.

Cabot Corp. has created products, including its Engineered Elastomer Composites (E2C) solutions and ENDURE series of carbon blacks, which deliver high durability in a range of mining applications while preserving the inherent resilience and energy efficiency of rubber.

“Effective design of rubber compounds and products can deliver significant energy efficiency improvements in material handling,” Reynolds said. “For example, Cabot produces E2C solutions that are formulated specifically for OTR truck tires. These solutions have unique combinations of elastomers and specialty reinforcing agents mixed using an optimized dispersion process. This provides strength while enabling the elastomer to retain its inherent resilience and energy efficiency. In haul truck tires, these composites can deliver both greater tire durability and improved fuel efficiency, helping mines to achieve carbon reduction and sustainability targets, while maximizing production.”

Cabot’s E2C solutions can reduce the rolling resistance of haul truck tires and overland conveyor belts. (Image: Cabot Corporation)

Cabot’s E2C solutions can reduce the rolling resistance of haul truck tires, increasing fuel efficiency (miles per gallon). By increasing the life of tires as much as 30%, E2C reduces the quantity of new tires that must be transported to distant mine sites, further reducing total fuel consumption. And, by increasing the load carrying capacity (TKPH) of tires, E2C solutions can reduce the number of trips required to transport ore, reducing the total amount of energy needed to power haul trucks.

For long overland conveyors, the rolling resistance of the bottom cover determines the belt’s energy efficiency. As the belt passes over idlers, it has the potential to generate heat, wasting energy and reducing efficiency. The energy that is lost in this manner can constitute up to 60% of energy loss in the entire conveyor system. Cabot has created specialty carbon black products like its ENDURE E series that deliver high durability with reduced heat build-up for applications such as long-haul conveyor belts. As some overland conveyors are 15 km or more in length, choosing the right bottom cover can potentially save mines up to 10% of the capital cost of the project, which equates to around US$10-15 million.

Optimizing Comminution

According to the above report from Weir Minerals, comminution in mining consumes up to 1% of total final energy consumption globally — equivalent to the power consumed by 221 million typical U.K. homes. This makes comminution circuits, both new and existing, a priority area for optimization, as small improvements can lead to large energy savings.

Grant Ballantyne, global director for technical solutions at Ausenco, and Malcolm Powell, emeritus professor, University of Queensland, joined E&MJ to discuss potential operational improvements.

“There are three main things that we can do to improve energy efficiency in existing milling circuits,” Ballantyne explained. “We can reduce the mass, reduce the intensity or reduce the production of fines. In terms of reducing the mass, progressive recovery strategies such as preconcentration and early rejection of waste can reduce the amount, and increase the grade of material fed to the comminution plant.

“To reduce the intensity, we can recover the metals at a coarser grind size using coarse particle flotation (CPF) or another alternative separation technique. Reducing the fines can be achieved via improved external classification using screens and cyclones, as well as improved internal classification within the comminution unit, which some people refer to as the ‘selection function.’ Reducing the mass, intensity and fines can reduce energy consumption in milling by 50%.”

Ausenco has performed a number of studies recently on preconcentration, specifically bulk ore sorting, as well as coarse particle recovery (CPR). The company designed and commissioned the world’s first commercial CPR plant in base metals at Newcrest’s Cadia mine in Australia, and Ballantyne said these techniques/technologies are now routinely included in the firm’s studies.

Powell weighed in: “It’s also possible to use improved predictive control to stabilize the load on comminution equipment, the most critical generally being the filling of semi-autogenous grinding (SAG) mills, as this dictates downstream stability of product size distribution and throughput,” he said. “The predictive control should be based on mechanistic/phenomenological models as opposed to black-box fitting of responses (the standard basis of ‘model-based’ control).”

Improving measurement of the work balance across the circuit to distribute breakage more evenly across the crushing and grinding stages can also help prevent one section becoming overloaded while another is underutilized — a common issue in SAG-ball-crusher (SABC) circuits.

Powell explained: “The work balance is based on keeping each stage of comminution in the best envelope of operation e.g., avoiding feeding oversized material to ball mills, and recycling crusher top-size to suit the desired crushed product size. This, in turn, is set at the ideal recycle feed-size range of -10 mm, which is finer than applied on most sites.”

Weir Minerals’ Enduron high-pressure grinding roll can offer a 40% energy efficiency increase compared to traditional grinding circuits. (Photo: Weir Minerals)

He added that the efficiency of cyclone classification is often overlooked, and these units are routinely operated outside of their natural range i.e., at high density to coarsen up the final product size. This leads to high recycling of final product sized material and sliming of the flotation/leach product.

“This wastes a considerable amount of grinding energy, with case studies showing improved throughput for the same energy input of 15%-20% in poor operations,” he said. “Reducing the hidden embodied energy cost of steel grinding media and maximizing the use of the rocks in the feed as grinding media rather than crushing it all to below media size is another strategy worthy of attention.”

The benefits of these types of improvement programs can be significant, but instigating them can be dependent upon the operator’s mindset and business structures. Powell said inadequate education in the principles of comminution equipment, classification systems and control mean that process operating staff often fall back on tried and tested methods rather than innovating.

“I see education as the key,” he said. “This can be applied through technical courses at a range of levels, not just academic, that provide industry-certified levels of skill.”

Ballantyne agreed but was sympathetic to mining companies’ attitudes toward risk. “There’s so much risk in mining in general, primarily related to the orebody,” he said. “It’s understandable that these companies can be reticent to take on additional risk associated with technology.

“As engineers, when we address energy efficiency in mining, we need to keep in mind the capital cost challenge and the possibility of subtraction rather than addition. Do we really need two cyclone feed pumps or could we manage with a single duty pump by concentrating on preventative maintenance? There’s no point designing an energy-efficient circuit that is so costly that it never gets built or results in a low economic return.”

Designing Energy-Efficient Circuits

How can we design circuits to be more energy efficient from the get-go? E&MJ asked.

“The general answer is to move away from tumbling mills,” Powell said. “There is a limit to their efficiency that is well below that which is practically achievable. Designing new circuits requires a more sophisticated level of design, using tools such as discrete element modelling and computational fluid dynamics to model material handling, monitor product size distribution between stages, and dynamically balance the load across equipment as the ore type varies to create flexible circuits. Dynamic process simulation for design and understanding the circuit response as the feed varies and how control will be implemented is essential to these improvements.”

Superior design starts with thorough ore characterization. It’s hard to assess and quantify the potential impact of new circuit designs without first understanding the nature of the ore. 

“We also need to look, not just at the energy consumed by the comminution device, but also the embodied energy of the grinding media, or the ancillary equipment like pumps and conveyors,” Ballantyne said. “I conducted a study recently, which examined the media consumption rates in grinding mills and found that, in six weeks, the mill consumes the equivalent weight in steel grinding media to the entire milling circuit structure. When we talk about energy efficiency in comminution today, we need to consider the metal in that media that had to be mined, processed and smelted before it’s consumed. When we take that into account, autogenous grinding (AG) and pebble mills tend to improve their energy efficiency relative to SAG and ball mills, because they don’t use grinding media.”

Boliden’s Aitik and Kevitsa mines are a good example of where AG and pebble mills have been applied to create a low OPEX circuit. But there are also design tweaks that can be made to both SAG and ball mill design, such as increasing the SAG shell length to reduce the media load at the required power draw or reducing the ball mill charge level and running at lower speed that can also improve the energy efficiency.

“When designing new circuits now, as part of the technoeconomic analysis, we tend to incorporate inbuilt carbon pricing,” Ballantyne said. “As well as other typically qualitative measures such as tailings, water and dust. It’s important that we look at the social and environmental outcomes as well as the financial ones.”

Innovative Comminution Technologies

In terms of technologies with the potential to deliver step changes in energy consumption, vertical roller mills (a technology taken from the cement industry) and dry fine crushing in general are extremely promising, and several mines are conducting trials/simulations to quantify the potential benefits. Dry classification and high-pressure grinding rolls (HPGRs) designed for hard-rock applications are other options, but Ballantyne cautioned that circuit design is key to their success.

“With some of these technologies, comminution energy consumption can be reduced by half,” he said. “But we need to manage the heating requirements of high moisture ores, as well as the fan energy for the air classification. At Ausenco, we’ve been working on strategies to maintain the efficiency of dry fine crushing while reducing the classification energy. We’ve also been working on microwave projects through Impact Canada’s Crush It! challenge, and we recently sponsored a Ph.D. student who’s done some great work around combining microwave pre-weakening with particle sorting as well.

“Outside of grinding and milling technologies, I’ve found that bulk ore sorting combined with CPF can have a greater impact on energy consumption in grinding than optimizing the grinding technology itself. And that’s where reducing the mass, intensity, and fines that I talked about earlier are key.”

Powell added: “The issue with many of the innovations presented today is that they’re not based on sound science of rock fracturing and often miss the point of where the major energy savings are. The use of historic energy measures can be quite misleading in assessing the value of new technology, as the measures are locked into comparison of traditional technologies. For example, the P80 value is ubiquitously used, and it gives no credit to producing less fines for a given top-size (where fines are particles below the required size for recovery).

“Any novel energy-efficient technology should be assessed in terms of the total process, not as an individual piece of equipment, using energy-per-unit final product produced as the measure, rather than kWh/t (energy needed to break rock) or energy to a given product size. Additionally, as Grant said earlier, the positive influence on water consumption, tailings reduction and environmental impact must be an integral part of any process assessment.”

Perfecting Pump Performance

Pumps are another area of low-hanging fruit when it comes to optimizing energy consumption in mineral processing. These are often overlooked in favor of bigger energy consumers such as SAG and ball mills or ultra-fine grinding equipment but, once operational, those pieces of equipment are much harder and more costly to make incremental changes to.

“Pumps are ancillary pieces of equipment, so mines tend to install them and forget about them. Unless, for whatever reason, they become a bottleneck,” said Ben Murphy, industry director and global key account manager for gold, FLSmidth. “Two or three years after installation, the operating conditions will have changed. For instance, the mine might have increased the flow rate, or the solids percentage might have changed, and that means that the pump won’t be operating at the efficiency point it was designed for.

“We see it all the time, particularly with cyclone feed pumps. We do an audit, and collect the data — we have a software package called Site Connect that is specifically designed for this — and we can plot where the pump is running on the efficiency curve, then adjust the operating parameters so that it’s working at the optimum efficiency point. We can also change the pump design where necessary, things like switching out the casing. These are all wet-end changes that can be done quickly. There’s no need to replace the pump completely.”

Pumps are taken offline regularly for wear parts maintenance, so it makes sense to check their operating efficiency at the same time.

“We see a lot of benefit and savings, not only in materials and reduced downtime, but also in tweaking the design to get the pumps operating at the best efficiency point for the conditions and the duty,” Murphy explained. “Typically, when we go about this exercise, we’ll see a 5%-10% energy savings on the pump. When you start looking at the number of pumps that are installed on mine sites and the number of mines around the world, and you multiply that savings out… it’s clear that there are massive potential savings to be gained.”

At a midsized (approximately 10,000 t/d) gold mine in South Africa, the FLSmidth team changed the design of a cyclone-feed pump to improve the casing life from four to 12 weeks. On its own, that was a significant operational saving, but the changes also resulted in a 21% power saving, which equated to around 1,000 MWh per year.

“It’s not an earth-shattering improvement, but it was a low-risk project that offered a big ROI,” Murphy said. “For remote sites that are paying 20 cents a kilowatt hour or more for their power, a saving of 21% can have a decent impact on the operating cost per ton, and it costs very little. And, unless the mine is running 100% on renewable energy, then there’s going to be a CO2 reduction as well.”

Don’t Forget Hydrocyclones

Cyclones are also worth consideration when it comes to energy efficiency. Cyclones separate material based on particle size and control how much material recirculates to the mill. Performance optimization is more complicated here than for pumps and usually requires a longer-term exercise. However, the premise is the same — there are a lot of units on site (usually installed in packs) and ensuring the optimum setup can deliver decent energy savings.

“Making sure that cyclones have the optimum setup on the inside in terms of the vortex finder and the apex is important in getting the most efficient classification for the desired product,” Murphy said.

“There are a number of big mining companies that are playing around with this now. It does require a complete circuit survey and the energy benefits of these changes aren’t always immediately obvious, because the big circuits tend to be maxed out on energy and any gains go toward increasing the throughput. But cyclones are another easy and low-risk variable that can be optimized. And, of course, there can be energy savings in downstream processes too thanks to better classification.”

There are various control technologies available for cyclones. For instance, FLSmidth KREBS’s SmartCyclone package. This is an automated software solution for monitoring and controlling closed-circuit grinding processes, which can detect a common overload condition called “roping,” whereby cyclones lose their efficiency and coarse particles start reporting to the top and fines to the bottom.

Adding a digital control system that can minimize unnecessary process variations or keep it within certain tolerances will create a net energy saving over time.

“Ultimately, it’s about making more metal with less resources,” Murphy said. “If a mine is compromising production to make certain pieces of equipment or processes within a flowsheet more energy efficient, then that’s not going to be sustainable from a business perspective. When approaching optimization programs, it’s important to look at the bigger picture and consider the knock-on impacts of changes across the value chain.”

Applying Digital Insights

While there are gains to be made in energy efficiency at the equipment level, to achieve step-change efficiencies requires optimization from a process or overall value chain perspective. And digitization is the tool that enables this.

“At the equipment or individual process level, digital technologies can enhance the availability of asset information by collecting data from sensors, analyzing it and making recommendations toward the best operational point,” said Bernardo Marinho, business development and sales manager at Siemens AG Digital Solutions for Minerals. “But I believe that to achieve a quantum leap in productivity and decrease energy usage, we need to look at the interdependencies between the steps in the value chain.

“To do that, we need an overview of material flow. Having that transparency allows mines to identify potential bottlenecks and areas of higher energy consumption and align their processes in a more dynamic way. For instance, if we look at discontinuous mining operations, there are various processes like drilling, blasting, loading and haulage in the pit. There is some level of automation in each of these steps, but the way in which we align those processes today is quite rudimentary. It’s still done by humans using lots of different point solutions.

“If we pull the data from those solutions into a single management platform, then it’s much easier to track that material from one process to the next and manage them in an integrated way. If an event or disruption occurs, say a machine breaks down, then there is the possibility to adjust the production plan to mitigate the negative effects.”

The overall effect is a more streamlined operation with minimal idle time for mobile equipment, less switching on and off of equipment, and a reduction in unnecessary energy consumption.

Advanced modelling tools such as digital twins can be useful in achieving this level of integration. Siemens is currently expanding its SIMINE Digital Twin for mining processes. While this has been available for grinding mills for some time with asset health analytics systems, the solution has been extended to incorporate the transportation and crushing portions of the value chain as well.

“We’re really focused on optimizing transportation right now,” Marinho explained. “We’re using digital twins to simulate the behavior of conveyor components under certain conditions, and this allows us to identify potential issues up front and adjust the operating parameters before they become reality. For instance, with belt conveyors, we analyze the mechanical impacts of different material loading scenarios, and we can assess different strategies for starting and stopping the equipment to optimize the energy loading.

“We combine the results of the simulation with feedback from the actual equipment to establish the operational fingerprint. For example, we can determine the optimal parameters like torque and speed for motors that drive a conveyor belt. With this information, we can define over an extended period of operation, the impacts that a higher torque or speed would have on the integrity of the equipment and the overall consumption of energy.”

Integrated Efficiencies

Digital twins can be used to monitor and optimize existing equipment and can also be applied in the design and engineering phase of a project to simulate material flow using different handling techniques and find the best possible solution given the various constraints; they allow engineers to apply that “subtract” rather than “addition” mentality that Ballantyne discussed earlier with confidence.

The benefits of this integrated operate and management approach are clearly visible at smaller operations, but for larger, more complex operations, they are invaluable. For instance, Siemens has been working with a large iron-ore mining company in Brazil. The company uses Siemens’ software to operate its complete operations from pit to product shipment across 40 sites.

“We have standardized reporting and tracking across multiple plants and sites, and this allows the customer to create integrated plans and have real-time production information,” Marinho said. “The associated benefits in energy consumption are quite significant, resulting from a reduction in production downtime and improved utilization of the assets.

“For me, the major difference today compared to in the past, is the ability to look at mining operations holistically and to optimize them, not just from an energy efficiency perspective, but also with regards to productivity and resources. Digital technologies provide us with the tools to bring information from different processes into a common platform look at the interdependencies and identify any hidden challenges or opportunities.”

Weir Minerals: From HPGR to Paste

Energy-efficient equipment will play a vital role in the transition to a low-carbon economy, but it must be backed by a clear vision of what sustainability means, why it’s important and how it will be implemented.

Stephen Marshall, head of engineering operations at Weir Minerals, said: “Weir Minerals’ Enduron HPGR technology can save up to 40% in power consumption when compared to traditional grinding circuits, allowing mine operators to produce more for less. Additionally, each installation is estimated to save 12,000 metric tons of CO2 annually, or the equivalent of removing 3,500 cars from the road. And the Enduron HPGR has downstream benefits as well.” 

At Iron Bridge, a magnetite project in Australia, Weir Minerals helped to design a dry comminution flowsheet that involved a multistage HPGR circuit, including air classification, which allows for interstage rejection of around 20% of the waste material. 

“At Iron Bridge, more efficient comminution is directly tied to improved tailings management. This highlights why it’s important to consider these challenges holistically, rather than focusing on a piece of equipment or a single aspect of the process in isolation. This can lead, in some instances, to a distorted picture of what constitutes the best environmental outcomes,” Marshall said.  

“It’s common to see this in tailings. For instance, there is a widespread misperception in the industry that drier equals more environmentally friendly, but this is only a partial picture.” 

“Sustainable tailings management means finding the right balance between tailings storage facility (TSF) stability, water conservation, energy consumption and CO2 emissions. It’s generally true that drier tailings are more stable. However, dewatering tailings is energy intensive and that increases relative to the level of dewatering required. In applications where the long-term dryness of the tailings cannot be guaranteed due to climatic or operational conditions, ‘over’ dewatering tailings causes unnecessary CO2 emissions related to the processing, transporting and compacting of the ‘dry’ cakes. Paste, on the other hand, can be pumped over long distances directly to the TSF.”

As paste exhibits a higher viscosity and yield stress, leading to higher pipeline friction, it normally requires the use of positive displacement pumps for transportation. 

“The GEHO (T)ZPM and DH series pumps provide miners with effective, sustainable tailings management and pumping solutions,” Marshall said. “Sustainable tailings management is essentially an exercise in identifying and realising the optimum solution for each specific project.

“We work with our customers to find the right balance between dry and sustainable tailings. On many projects, we’re finding this often has us opting for a high-density paste system. These systems offer a reliable and durable solution that’s more energy efficient than filtered tailings solutions.”