With the release of the HPGR Pro, thyssenkrupp is taking crushing and grinding circuits to new levels of operational efficiency: higher throughput, improved product quality, and reliability with much lower production costs. MechChem Africa talks to Gerhard Van Wyk, the process manager for thyssenkrupp Industrial Solutions in South Africa.
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“For decades, our high-pressure grinding roll (HPGR) has been the machine of choice for efficient, high-pressure grinding and processing of ores. But our new thyssenkrupp HPGR Pro takes grinding to the next level,” begins Van Wyk. “Through a multitude of innovations and features, minerals processing plants now have access to better-than-ever throughput, product quality and machine reliability, which can significantly improve production efficiencies and reduce operating costs – and all of these things are as necessary now as they have ever been,”
he tells MechChem Africa.
Glbally, van Wyk says that HPGRs started to be introduced in the cement and diamond industries in the mid to late 1980s. In hard rock applications, their use has steadily grown, especially since 2006 with the commissioning of the first thyssenkrupp HPGR at a large copper mine in Peru, which was soon followed in 2007 when a leading South African platinum producer began to investigate replacing problematic SAG mills at its Limpopo mine in South Africa.
This mine was struggling to get its semi-autogenous grinding (SAG) mill to do conventional fine crushing of the very competent Platreef ore. The low efficiency of this tertiary crushing stage was causing bottlenecks on the feed line into the ball-mill.
This drove the mine to investigate a more efficient comminution technology for its new North concentrator plant. After extensive work, an HPGR-based circuit was selected and commissioned in 2007. Originally designed for 20 000 t/day, the later addition of variable speed drives enabled a production increase of 20 to 33% above nameplate capacity.
“We have been installing solutions such as these for over 40 years and, worldwide, we now have over 150 HPGR installations for hard rock applications and more than 300 in the cement industry. Over the years, we have made steady improvements, but the new HPGR Pro combines the best modern innovations to create a more efficient and economical solution than ever,” he explains, adding the complete HPGR Pro package typically offers 20% more throughput, 15% energy savings, and rolls that last up to 30% longer.
Turning attention to the specific innovations included in the new thyssenkrupp HPGR Pro, Van Wyk says that several individual design improvements have been incorporated, which all deliver operational performance enhancements.
Rotating side plates
The throughput improvement is largely as a result of the shift from using conventional static cheek plates to rotating side plates to keep the feed material running in a uniform line in the gap between the rolls. “Rotating side-plates on fixed grinding rolls improve material feed by up to 20% in terms of throughput. What’s more, the machine’s specific energy consumption is reduced by around 15%,” Van Wyk tells MechChem Africa.
Explaining why, he says the more dynamic and sealed rotating side plates enable better grinding at the roll edges. “They enable crushing across the full length of the roll, which not only crushes more material, but the pressure is better distributed across the grinding rolls. The side plates rotate with the roll, unlike the static cheek plates that reduce the speed of the material close to the edge, which reduces the pressure and increases wear.
“Traditional HPGRs produce higher pressures in the centre, tapering off towards the roll edges. Rotating plates reduce peak central pressure while raising the effective crushing area, hence the rolls can process more feed using less energy,” he explains.
“And rotating plates can be retrofitted to any of our legacy HPGRs,” Van Wyk adds. “As with all of our HPGR Pro innovations, they have been designed as potential add-ons to installed units. By just adding rotating plates, existing thyssenkrupp HPGRs can either be set up to produce more downstream material of the same cut size or to run at the same feed rate with a finer cut size,” he notes.
In terms of wear life, the uniform pressure profile in the milling gap results in better grinding and more even roll wear. This prolongs the service life of the rolls by up to 30%. “The rotating plate design with lower peak pressure reduces the ‘bathtub effect’ on the rolls, which enables them to be replaced less frequently. So the HPGR Pro can run for longer with less downtime,” he explains
Controlled mechanical skew limitation for greater safety
While many believe that roller skew should be completely prevented, Van Wyk argues that a certain amount of skew is beneficial, because it ensures uniform grinding. “A small and limited amount of skewing enables the HPGR to compensate for different nip-in conditions on either side of the rolls, due to feed segregation, for example,” he explains.
“The new and uniquely controlled mechanical skew limitation built into the HPGR Pro allows skew but prevents excessive skew, making sure that damage cannot occur while enabling enough skew to promote grinding uniformity,” he says. The skew limiting device also prevents excessive forces going through the bearings, which can easily occur when skewing is suppressed.
Oil lubrication for increased availability
With the HPGR Pro, the roll bearings are now being lubricated with oil instead of grease. This enables better control of temperatures, since the oil can be circulated through the bearings and back through an oil cooling and filtration system. High temperatures during higher machine usage periods can therefore be avoided and the oil circulation system supports easier cleaning. Optimised bearing seals, oil quality monitoring and continual filtering also reduce contamination and allow the oil to be used for longer, reducing costs and environmental impacts.
Laser-based stud damage detection
“The availability of the HPGR Pro is increased even further through our unique stud detection system. While the machine is operating, the surface of the rolls is automatically monitored and measured by a laser, constantly informing the operator about the state of the studs and the rolls,” Van Wyk continues.
The stud detection system is used to predict the best possible time for roller replacement. “And there is no longer a need to routinely stop the machine for precautionary inspections, which saves valuable time and money.”
Analytics and machine learning
Continual optimisation via data analysis has been incorporated into the thyssenkrupp HPGR Pro by adding modern sensor technology and an Advanced Machine Protection System. “Based on our specialist expertise, we are able to use data collected to automatically ensure that any installed HPGR Pro runs at its optimum operating point. This prevents overloading and vibrations, and ensures production is optimised.
“What’s more, our global specialists collect and process the machine data to enable us to continuously improve a particular HPGR Pro’s operation and to optimise throughput, energy consumption or machine availability in line with specific targets. This transparency enables fast diagnosis and root cause analysis,” says Van Wyk.
In summary, he notes that the new thyssenkrupp HPGR Pro is:
- More efficient than ever: It offers best possible grinding outcomes with up to 20% more throughput thanks to optimised material feed and reduced wear and tear.
- More reliable than ever: It delivers higher machine availability through increased transparency on roller status, predictive maintenance of machine components such as bearings, combined with fast, professional service at any location worldwide.
- More high-end than ever: State-of-the-art sensor technology and data analysis gives greater transparency and ongoing optimisation, resulting in an even better performance and higher productivity through continual roller monitoring while the machine is in operation.
Concluding, he reminds us that all of the new HPGR Pro features can be retrofitted to thyssenkrupp legacy units, and customers may pick and choose which combination of upgrades best suits their needs.
“Customers and HPGR operators can rely on our full support in equipping existing machines with the latest technical features from the HPGR Pro, making machines that are fit for the future. Through our local network of service centres and specialists, thyssenkrupp is able to offer rapid support, wherever and whenever it is needed,” Van Wyk assures.
