Following a rigorous two-year validation process in both pilot and industrial field trials, Metso’s new MHC Series range of hydrocyclones is now available to the mining industry. At a time when the industry is grappling with depleting ore grades and rising energy costs, the range has a special design focus on improved process performance and maintainability to help balance cost and performance of a grinding circuit. By Munesu Shoko.
Despite rebounding commodity prices, the mining sector is still facing plenty challenges, ranging from depleting ore grades to increased operational expenses. No large-scale investments are being made into the mining sector, and developments are mainly in operational optimisation through processing improvements such as adjustment to equipment, reduced losses and increased product quality.
For these reasons, selecting equipment that improves overall plant performance through improved grinding circuit performance and optimised recovery of valuable minerals is a key objective for any mine owner. Bearing in mind the impact that classification equipment technology has on both capital and operating expenses, as well as overall plant performance, it should, therefore, be a priority for mining management to prioritise the selection of equipment that provides acceptable availability and maintenance costs.
Based on extensive market research and industry feedback, Metso identified these parameters as the basis for the development of its MHC Series hydrocylone range, focusing on both improved process performance and maintainability. Initially introduced at MineExpo in 2016, the line has seven different hydrocyclone sizes available, ranging from 100 to 800 mm in diameter, and will cover a range of classification requirements from 300 microns down to 20 microns in wet processing applications.
According to Charles Ntsele, Metso’s GM of Capital Equipment Sales, Africa and Middle East, the hydrocylone range closes the last gap in Metso’s product portfolio, allowing the OEM to offer a full solution
to its customers’ grinding circuit needs. He tells Capital Equipment News that hydrocyclones are not new to
Metso. The OEM previously had a range of cyclones which it sold off at some stage as it was considered not to be core business at the time.
“That was really influenced by the strategy at the time,” explains Ntsele. “The decision to offer cyclones again was informed by our new approach to offer a total solution to our customers. We want to be able to guarantee the whole process within a grinding circuit.” Reiterating the significance of cyclones, Ntsele says they are the heart of the milling circuit, as their operation is responsible for both the quality and much of the overall cost of processing.
Big range; big benefits
Metso’s MHC Series is available in seven different sizes, ranging from the MHC100, with a 100 mm diameter, to the larger MHC800 with its 800 mm diameter.
“That enables us to cover classification requirements from 300 microns down to sub-20 microns,” says Ntsele.
The range comes with several innovative features aimed at improving process performance and maintainability. With costs in mind, the internal geometry of the Metso MHC Series hydrocylone has been optimised to promote smooth flow from the inlet through the entire hydrocyclone, minimising turbulence and increasing throughput. “We have optimised the inlet to the cyclone, which is a key design area in terms of turbulence that is associated with the material flow, which eventually affects what happens in the cyclone,” says Ntsele. He says that the low turbulence has the added benefit of reducing wear rates in the inlet head.
A unique design improvement is the single component conical section that eliminates the need for multiple housing and liner parts. “The conical section of the cyclone comes in one piece and it’s made of polyurethane. Typically the conical section comes in two parts and it’s usually made of steel with a rubber insert. Our design approach speaks to ease of maintenance, and polyurethane is a low wear material than steel, translating into reduced cost of operation and increased uptime,” says
Ntsele, adding that the conical section’s angle has been kept constant throughout the length of the cyclone. “It’s sloping but the angle that influences the performance of the cyclone has been kept straight, which is an industry-first.”
Metso’s improved manifold design ensures accurate feed distribution, including overflow and underflow collection from multiple hydrocyclones operating in parallel. Meanwhile, high grade polyurethane and ceramic wear component options offer a balance between wear performance and cost depending on the project specifics.
“The spigot of the cyclone itself is also made of polyurethane with ceramic inserts. From the trials we have run, we have seen a very significant improvement in the life of that part of the cyclone,” says Ntsele. He adds that the ceramic inserts of the apex make a huge difference because that’s the smallest part of the cyclone, diameterwise, and is exposed to high pressure vibration. It is one of the parts that wears fast because of the force from the vibration and using ceramic insets slows down the wear rate.
The Metso MHC cluster design ismstandardised, but application specific engineering is available when required.
Linear and radial distributors ensure even split and consistent pressure between the hydrocyclones. Pneumaticallycontrolled isolation knife gate valves (or optional manually controlled valves) seamlessly transition between operating hydrocyclones and stand-by hydrocyclones for maintenance.
Also, pressure monitoring ports for optional local pressure gauge and pressure transmitter are provided on the feed distributor. Range of wear resistant linings are available and rubber lining is incorporated into the feed distributor, as well as the overflow and underflow launders. In the manifold design, special attention was paid to ensure safe access for monitoring, sampling and maintaining the hydrocyclones and manifold components.
Ntsele says this is a great feature to include in the design of the plant, especially in greenfields projects.
Proven prowess
After going through a stringent validation process, Ntsele says the cyclone range is now available for local mining customers.
“For starters, we are looking for a site where we can exchange the whole existing cluster of cyclones and install Metso cyclones. Using the historical data of the existing cluster, it will be easy to make a comparison,” he says. To make sure the designed features meet the targeted results in practical production, the range has undergone an extensive validation process covering various hydrocyclone sizes and applications in both pilot and field trials. “Essentially, Metso conducts an extensive modelling process to understand where we can differentiate our product and add value to our customers through the design,” says Ntsele.
The first step was to validate the design in a laboratory environment. The laboratory testing was performed in the Metso York Laboratory in Pennsylvania, United States.
The targets for the initial testing were to evaluate efficiency, sharpness, fines bypass and cut size for a homogenous ore type (limestone).
The results from the laboratory test indicated very encouraging performance from the MHC internal geometry. At a reasonable operating pressure of 124 kPa, the cut size on a 250 mm hydrocyclone is below 30 microns. When operating in this condition, the cyclone efficiency is almost 90%. Efficiency
is defined as the mass percentage of product size in the hydrocyclone feed that reported to the overflow (product size defined at the 80% passing point of the overflow).
For the field trial, a Metso MHC650 (650 mm diameter) was installed in the grinding circuit at a copper concentrator in Arizona, where it has been running for over two years. The goal of testing a production unit in a large-scale copper mine was primarily for wear component prototyping and continued process data collection.
Various grades of rubber and polyurethane have been tested within the different hydrocyclone components. Ceramic inserts into polyurethane was first introduced as an apex insert, and secondly at the bottom of the conical section. The ceramic components are still in operation and are the focus of current wear component development and prototyping.
To date, the field trial has been in operation for over 12 000 hours. The data generated from the trial is being applied to Metso’s empirical hydrocyclone model used for sizing and simulation purposes.
It has confirmed the MHC Series achieves the performance for industry leading hydrocyclone technology. The field trial also confirmed that the MHC performance is predictable and responds as expected due to changes in operating conditions.
“The range is now ready for commercialisation. The first unit – an MHC250 – has been installed in Canada during the first quarter of this year in a gold processing application,” concludes Ntsele. b
