Tag Archives: IPCC

Apron feeders: the material handling workhorses

Following the publication of the International Mining October issue and, more specifically, the annual in-pit crushing and conveying feature, we have taken a closer look at one of the core elements that makes up these systems, apron feeders.

In mining, apron feeders play a major role in ensuring smooth operations and increasing uptime. They are very diverse in their application within a mineral processing circuit; however, their full capabilities are not widely known throughout the industry leading to many raised questions.

Martin Yester, Global Product Support of Bulk Products at Metso, has answered some of the more important ones.

What is an apron feeder and when should it be used?

In simple terms, an apron feeder (also known as a pan feeder) is a mechanical type of feeder used in material handing operations to transfer (feed) material to other equipment or extract material (ore/rock) from storage stockpiles, bins or hoppers at a controlled rate of speed.

These feeders can be used in a variety of applications in primary, secondary and tertiary (reclaiming) operations.

Apron feeders are the preferred feeder for several reasons. Some of these are:

  • Aprons provide better feed control to prevent material feeding in downstream equipment from choking;
  • They can absorb the shock of loading material directly onto the feeder with a shallow bed (the impact coming down on the feeder when the material is dumped is great); and
  • Apron feeders can reclaim a variety of dry or wet materials of various sizes at a uniform rate, with this flexibility applied in many applications.

What are the advantages of using a tractor chain style apron feeder?

A tractor chain style apron feeder refers to the undercarriage chain, rollers and tail wheels that are also used in bulldozers and excavators. This style of feeder dominates the market in industries where users require a feeder that can extract materials of varying characteristics. Polyurethane seals in the chain prevent abrasive materials from entering the internal pin and bushing, which reduces wear and extends equipment life in comparison with a dry chain style. Tractor chain style apron feeders also create less noise pollution for quieter operation. The links of the chain are heat treated, which results in an increased service life.

Overall, the benefits include increased reliability, fewer spare parts, less maintenance and better feed control. In return, these benefits lead to more productivity with minimal bottlenecks within any mineral processing circuit.

Can apron feeders be installed on an incline?

The common belief about apron feeders is that they must be installed horizontally. Well, contrary to popular belief they can be installed on an incline! There are many added benefits and capabilities that come from this. Less space is needed overall when installing an apron feeder on an incline – not only does the inclination limit floor space, the height of the receiving hopper can also be reduced. Inclined apron feeders are more forgiving when it comes to larger lumps of material and, overall, will increase volume in the hopper and reduce the cycle time of the haul trucks.

Keep in mind there are some factors to pay attention to when installing a pan feeder on an incline to optimise the process. A properly designed hopper, the angle of inclination, the design of the support structure and the access and stair system around the feeder are all key factors.

Apron feeder optimal speed – faster is always better, right?

The common misconception around operating any equipment is: “faster is better.” In the case of apron feeders, nothing could be further from the truth. Optimal speed comes from finding that balance where efficiency meets transportation speed. They do operate at slower speeds than belt feeders, but for a good reason.

Normally, the optimal speed of an apron feeder is 0.05-0.40 m/s. If the ores are non-abrasive, the speed can increase to above 0.30 m/s due to the likely reduced wear.

Higher speeds would hurt an operation: if your speed is too high, you run the risk of accelerated wear of components. Energy efficiency, too, decreases due to the increase in energy demand.

Another concern to keep in mind when running an apron feeder at high speeds is the increased possibility of fines being generated. There can be a grinding effect between the material and the pans. Not only would the generation of fines create more issues because of possible fugitive dust in the air, but this also creates a more hazardous work environment for employees overall. So, finding an optimal speed is more important for the productivity and operational safety of the plant.

What are the limitations on size and type of ore?

Apron feeders do have limitations when it comes to the size and type of ore. The limitations will vary, but there should never be senseless dumping of material onto the feeder. You will need to not only factor in the application you will be using the feeder for, but also where in the process this feeder will be placed.

Generally, an industry rule to follow for your apron feeder dimensions is that the width of the pans (inside skirts) should be twice the maximum lump size of the material. Other factors, like a properly designed open hopper incorporating the use of “rock turning plates”, can affect the pan size, but that’s only relevant in certain circumstances.

It is not unusual for 1,500 mm of material to be extracted if a 3,000 mm wide feeder is used. Material of minus-300 mm from crusher ore stockpiles or storage/blending bins is typically extracted with apron feeders to feed secondary crushers.

What information is required when sizing an apron feeder?

When sizing an apron feeder and respective drive system (motor), as with a lot of equipment in the mining industry, experience and knowledge of the entire process is valuable. Apron feeder sizing requires basic knowledge of plant data to be able to accurately fill in the criteria needed for a vendor’s “application data sheet” (or however the vendor receives their information).

Basic criteria that should go into this includes feed rate (peak and normal), material characteristics (such as moisture, gradation and shape), maximum lump size of the ore/rock, bulk density of the ore/rock (maximum and minimum) and feed and discharge conditions.

However, occasionally there can be added variables to the apron feeder sizing process that should be included. A primary additional variable that vendors should be asking about is the hopper configuration. Specifically, the hopper shear length opening (L2) directly above the apron feeder. When applicable, this is not only a key parameter in properly sizing the apron feeder, but also the drive system as well.

How does “bulk” density affect the sizing of an apron feeder?

As stated above, bulk density of the ore/rock is one of the basic criteria requirements that should be included for effective apron feeder sizing. Density is the weight of material in a given volume and usually bulk density is measured as tonnes/cubic meter (t/m³), or pounds/cubic foot (lbs/ft³). One specific note to remember is that bulk density is used for apron feeders and not solid density like in other mineral processing equipment.

So why is bulk density so important? Apron feeders are volumetric-type feeders, which means bulk density is used to determine the speed and power needed to extract a certain tonnage per hour of the material. The minimum bulk density is used to determine the speed, and the maximum bulk density establishes the power (torque) needed for the feeder.

To conclude, it is important the correct “bulk” density and not “solid” density is used for sizing apron feeders. If these calculations are incorrect, this could jeopardise the resulting feed rate for the downstream process.

How do you determine the hopper shear length of the apron feeder?

Identifying the hopper shear length is a key component for correctly sizing and selecting an apron feeder and drive system (motor). But, how can this be determined? The hopper shear length is the dimension from the back plate of the hopper at the skirt line to the shear bar located at the exit end of the hopper. It sounds very simple, but it is key to note that this should not be confused with the dimension at the top of the hopper where material is loaded.

The goal of finding this measurement of the hopper shear length is to establish the actual shear plane line of material and where material inside the skirts is separated (sheared) from the material inside the hopper (L2). The resistance to shear the material is typically estimated to be between 50-70% of the total force/power. This calculation of the shear length will result in either insufficient power (lost production) or excessive power (rising operating expenses (opex)).

How do I find the optimal length of my apron feeder?

Spacing of equipment is essential to any plant. As mentioned before, apron feeders can be installed on an incline to save space. Selecting the correct length of an apron feeder will not only reduce capital expenditure (capex), it will also reduce power consumption and opex.

But how is the optimal length determined? The optimum length of an apron feeder is one that can fulfil the required duty in the shortest length possible. However, in some cases for an operation, the choice of feeder might want to be a little longer to “convey” materials to reach downstream equipment and eliminate a transfer point (and unnecessary costs).

To determine the shortest and optimal feeder possible requires flexibility in the layout of positioning the apron feeder under the hopper (L2). After determining the shear length and bed depth, the overall length can then be minimised just enough to prevent what is referred to as “self-flushing” over the discharge end when the feeder is idle.

I properly selected my apron feeder, but what about my drive system?

Selecting the proper drive system for your apron feeder will depend on the operation and goals of the feeder. Apron feeders are designed to be ran at variable speeds to extract from storage and feed downstream at a controlled rate of speed for maximum efficiency. The material could vary depending on factors such as the season of the year, orebody, or blasting and blending patterns.

The two types of drives suited for variable speeds are a mechanical drive using a gear reducer, inverter duty motor and variable frequency drive (VFD), or hydraulic motor and power unit with a variable pump. Today, variable speed mechanical drives have been proven as the preferred drive system due to the advancements in technology and capex benefits.

Hydraulic drive systems do have their place but are not seen as the ideal option between the two variable drives.

This Q&A was taken from a series of Metso blogs on apron feeders. For more information, please follow these links:

https://www.metso.com/blog-hub/mining-minds/feeding-the-facts-part-1-apron-feeder-basics/

https://www.metso.com/blog-hub/mining-minds/feeding-the-facts-23-proper-sizing-and-selection-of-your-apron-feeder/

NEPEAN offers mine truck haulage alternative with relocatable conveyors

NEPEAN Conveyors’ New South Wales General Manager, Bill Munday, thinks its relocatable conveyor system will “change the game for materials handling” in 2019.

Munday said this to the Australian Mining publication during a site visit to Port Kembla.

Last year, NEPEAN Conveyors acquired Sandvik’s International Conveyor Components businesses and Sandvik’s Specialist Conveyor Systems business in Hollola, Finland.

NEPEAN’s Relocatable Conveyor system has taken over two years of research and design to develop and “promises to upend the traditional approach to conveyor design on account of its improved mobility, operational flexibility, ease of transport and speed of installation”, the company said.

Instead of building conveyor parts to meet the needs of freight shipping container dimensions, the NEPEAN Relocatable Conveyor is a half-height high cube portal frame configuration certified for standard freight shipping.

This means the conveyor is transportable anywhere in the world as a fully assembled unit, according to the company.

The frames are 12 m long, with the unit inside supporting belt widths of up to 1,800 mm on straight conveyors and 1,600 mm on curved conveyors. Roof-mounted wind guards are also available for each module in a single curve or straight two-piece configuration.

The modules can be triple stacked on a prime mover and unloaded in one bundle using standard container handling equipment, which can then place each module in line for final connection, according to the company.

This approach vastly reduces the total install cost per lineal metre by minimising both time and staff requirements during setup, NEPEAN said.

“One of the areas we really wanted to target was logistics,” Munday told Australian Mining.

“It can turn into a real logistical exercise moving all this equipment from one site to the next and doing so efficiently. The beauty of having a half-height hi cube shipping container format is that they can be multi-stacked on ships, trains or trucks,” he said.

“You can potentially get nine modules per road train at a length of 12 m per module.”

The frame’s integral legs can be set in place by removing a pin, folding them out and replacing the pin to lock the legs in position, minimising ground works.

The foot plates also have holes in for additional stakes to be inserted, which adds stability and security.

Once the modules are aligned to an installation jig on the ground – adjustable for idler spacing and roller configurations – the structure can be super elevated by up to 7° and banked around corners, according to the company.

“All the equipment is pre-designed for a fully functioning conveyor and the container module is just part of the system,” Munday said. “We have also designed a unique one-piece head end that incorporates a drive system up to approximately 4,000 kW, a loop take-up and delivery jib that can be put on a 200-t float to transport around mine sites. It is held in place by large ground anchors — there’s minimal concreting or civil works — you just dig a couple of holes and bury the ground anchor.”

In addition to significantly lowering civil works and installation costs, the NEPEAN Relocatable Conveyors mobility allows it to be adaptable to changes in mining operations and positions it as a true alternative to mine trucks when it is time to move the conveyor on site, according to the company.

First ore for FQM’s Cobre Panama copper mine

First Quantum Minerals has introduced first ore to the processing plant at its 74 Mt/y Cobre Panama open-pit copper mine in Panama.

On February 7, ore was introduced through primary crushing and onto the stockpile with initial feed rates between 4,000-5,000 t/h. Then, on February 11, ore was introduced through to the first milling circuit.

Operation on ore continues and will move into all other sections of the processing plant including producing copper concentrate, according to First Quantum. The company is now focused on an efficient phased ramp-up for Cobre Panama continuing through 2019.

At full tilt, Cobre Panama is expected to produce 350,000 t of copper from an in-pit crushing and conveying set up that includes four box cuts with semi-mobile primary crushers – two per conveyor line – feeding two in-pit conveyor lines that feed two overland conveyors after a transfer station to the secondary crushing and the main process plant. The company uses a fleet of Komatsu Mining P&H 4100XPC electric shovels; 363 t Liebherr T 284C trucks, Komatsu Mining Le Tourneau L2350 large wheel loaders (with SR drive), Liebherr R 9350 hydraulic excavators and Cat 777G 100 t trucks at the operation.

NRW Holdings signs A$10 million deal to buy RCR’s Mining and Heat Treatment businesses

NRW Holdings has entered into an agreement to acquire RCR Tomlinson’s Mining and Heat Treatment businesses for A$10 million ($7.3 million) in cash.

The agreement was signed with RCR’s administrators, which have been offloading various RCR subsidiaries since shortly after the company declared total liabilities of A$581.3 million alongside cash and equivalents of A$89.9 million in its 2018 financial year.

The purchase consideration will be funded from NRW’s existing cash reserves, with the deal expected to complete within the next two weeks, NRW said.

RCR Mining and Heat Treatment form part of the original RCR Tomlinson business established over 100 years ago.

RCR Mining includes the Mining Technologies business, which owns significant intellectual property across a range of products and processes and is recognised as a market leader by global resources clients, according to NRW.

“The Mining Technologies business is a leading national and international original equipment manufacturer and innovative materials handling designer with an extensive product range including apron and belt feeders, high capacity conveyors, slide gates, stackers, spreaders, fully track-mounted in-pit mining units (an example pictured above), sizers, scrubbers and screening plants,” NRW said.

One of RCR’s recent mining technology innovations is a 5 km relocatable conveyor, which includes a semi-mobile primary crushing station and feeds directly into Fortescue Metals’ Cloudbreak iron ore processing facility in the Pilbara of Western Australia.

Both the Mining Technologies and Heat treatment businesses have a high proportion of activity in equipment product support and maintenance (both on site and off site), NRW said, adding that the Heat Treatment business has facilities that include the largest stress relieving furnace in Australia.

Mining Technologies and Heat Treatment generated around A$110 million of revenue in the 2018 financial year and have a track record of delivering positive earnings, NRW noted, explaining the acquisition would be earnings per share accretive on a full-year basis, excluding integration and other one-off costs.

Jules Pemberton, NRW’s Managing Director and Chief Executive Officer, said the acquisition would allow NRW to provide incremental services, in line with its strategic objectives, to several core clients common to both NRW and the RCR businesses.

“In addition, the annuity style income from the maintenance activities of Mining Technologies and Heat Treatment will provide a platform to continue to build a broader service offering across an expanded resources and oil and gas client base.”

Nouveau Monde Graphite’s all-electric Matawinie mine plan stacks up

Quebec, Canada-based Nouveau Monde Graphite’s latest economic study on the West Zone deposit of the Tony Claim Block, part of its Matawinie graphite property, in Saint-Michel-Des-Saints, has shown an all-electric open-pit mine can be built that delivers ample shareholder returns and the reduced carbon footprint the company was after.

The feasibility study builds on a prefeasibility study that envisaged a 52,000 t/y graphite concentrate operation being built for C$179 million ($137 million) for a post-tax internal rate of return of 25.9%.

The latest study has upped the production ante – looking at a 100,000 t/y concentrate operation over 25.5 years – as well as the potential shareholder returns. The feasibility study estimates the mine can be built for C$276 million, can operate at a cash operating cost of C$499/t and bring in a 32.2% after-tax IRR based on a life-of-mine average sales price of $1,730/t.

These results have proven so favourable the company is already set on completing the project’s Environmental and Social Impact Assessment, in addition to starting the engineering, procurement, construction and management phase. This could see the mill constructed in 2020 and production starting in 2022.

Met-Chem, a division of DRA Americas, prepared this latest study, which has fleshed out some of the company’s plans for an all-electric open-pit mine.

“The mine will be using an all-electric, zero-emission mine fleet, consisting of electric battery-driven 36.3-t mining trucks, battery-driven front-end loaders, cable reel excavators and bulldozers, and battery-driven service vehicles,” Nouveau Monde said.

The mine will also use an electric in-pit mobile crusher and overland conveyor system to feed crushed material to the plant, according to the company.

Medatech Engineering Services Ltd and ABB Inc were responsible for developing the technology used in this fleet. The two companies, part of Nouveau Monde’s Task Force Committee for the project, assisted Met-Chem in preparing a fully-electric equipment fleet estimate. This information was then passed onto a mining contractor to establish a technical and commercial proposal for the mine operation on a contractual basis as well as on the basis of a fully-electric equipment fleet, Nouveau Monde said.

Nouveau Monde’s COO, Karl Trudeau previously told IM that Doppelmayr Canada would supply the company with ore handling solutions (RailCon® technology), while a mobile charging station, including fast-charging capability of up to 600 kW,  was to be positioned in the pit to charge the trucks and other equipment.

In addition to the eco-friendly nature of the mining fleet, the company has also looked to reduce the footprint of the mine’s infrastructure.

The processing plant and the co-disposal of tailings and waste rock will be located less than 500 m from the mine to minimise truck cycle times and lower the project’s operating costs, while progressive backfilling of waste rock and tailings will take place to “further minimise the project’s environmental footprint”, while allowing site rehabilitation during the operating life of the mine. The mine waste rock and tailings management plan, as well as the water management infrastructure, was designed by SNC-Lavalin.

The flowsheet for the 2.35 Mt/y mine consists of in-pit crushing, followed by multiple steps of grinding and flotation separation circuits. The graphite concentrate is then filtered, dried and classified to recover over 94% of the graphite and produce four products with various flake sizes, all with finished product purity above 97%.

Eric Desaulniers, President and Chief Executive Officer of Nouveau Monde, said: “We have designed a state-of-the-art mine that not only maximises efficiency but also aims to be one of the most eco-friendly mines in the world, having a very low carbon footprint relative to our peers. This is a key product differentiator, especially for our electric vehicle manufacturing customers whose environmental and social acceptability values align perfectly with our own.”

Karl Trudeau, Chief Operating Officer, Nouveau Monde Graphite; Michel Serres, VP Mining Solutions North America, ABB Canada and David Lyon, Business Development Manager, MEDATECH will be presenting ‘The NMG journey to the all-electric open-pit mine: innovation from collaboration’ at The Electric Mine conference in Toronto, Canada, on April 4-5, 2019. For more information about the event, please click here.

BHP considering IPCC, autonomous trucks at Spence copper mine

BHP says it is continuing to evaluate materials handling and fleet replenishment options at its Spence copper mine, in Chile, with one possibility being the use of an in-pit crushing and conveying ore system in tandem with autonomous trucks.

In its 2018 annual report, the company said the timing and sequencing of these options was “pertinent” to reducing health and safety risks and operating costs, with “technology-enabled solutions potentially significantly reducing risks associated with crash, collision and rollover, silica exposure, dust and greenhouse gas emissions”.

Spence is a key part of BHP’s copper portfolio in Chile and is due to produce some 185,000-200,000 t of the red metal in the company’s 2019 financial year to end-June.