Capital Equipment News April 2018

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, diameter- wise, 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 is standardised, but application specific engineering is available when required. Linear and radial distributors ensure even split and consistent pressure between the hydrocyclones. Pneumatically- controlled isolation knife gate valves (or optional manually controlled valves) seamlessly transition between operating

The range comes with a new inlet design for increased capacity.

The improved manifold design ensures accurate feed distribution.

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

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

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