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Editor: Laura White [email protected] www.outotec.com
IssuE 30June 2012OutOtEc sEap (sOutH East asIa pacIFIc) enEWsLEttEr
Author: Ben Murphy
cOntEntsLess float bank for your buck - tankcell e500 / 1
case study: Koniambo nickel / 4
Quick tip - Gas dispersion in your flotation cell / 7
Quick tip - thickener tank design options / 7
case study: QaL / 8
Quick tip - Designing mill foundations / 11 It is well recognised that many
mineral projects are under increasing pressure to stay economically viable. Challenges include declining ore grades, higher throughputs and metallurgically difficult orebodies. Additionally, the industry’s growing requirement for energy reduction, optimised water usage and decreased emissions all require high performance and proven solutions. So, it is not surprising that the
mining industry trend in recent years has been for larger flotation cells to benefit from economies of scale.
The world’s first 300m3 flotation cell was installed in 2007 at OceanaGold’s Macraes mine in New Zealand, with three installed there as roughers. The 300m3 TankCells at Macraes improved gold bearing sulphide recovery by 3%, reduced operational cost and provided greater mechanical
Breaking the 500m3 floatcell Barrier - how to make sure your operation has the Best in class
less Float Bank for your Buck - Tankcell® e500
Output sEap June 2012 / 2
relative cost relative footprint approx installed
kW power
6 x 500m3 1.0 1.0 2,400
10 x 300m3 1.1 1.3 3,150
30 x 100m3 1.6 2.9 4,500
to ensure you are working with a supplier who has sufficient ‘runs on the board’ and understands the challenges of large cell design. These ‘runs on the board’ should not just be from cleaner duties or ‘easier’ ores but truly represent the myriad of challenging duties and orebodies. Reliable scale-up methods are also critical and it is important to ensure your large cell supplier has carried out sufficient R&D in large cell design and operation. Here are some important features for large float cells.
1. forced air technologyForced air technology, as opposed to induced self-aspirated float cells, is a major contributor to the successful operation of larger float cell units. The flexibility to decouple the air addition and the mixing means there is less chance of sanding the flotation cell. In addition the ability to adjust the rate of flotation by controlling the volume of air entering the cell is a major advantage, especially when there are fewer larger cells.
Outotec’s FloatForce® mechanism has separate areas for pumping and air dispersion in the rotor design, ensuring efficient pumping even with the highest air feed rates and delivering maximum performance with low power draw, an increasingly
Table 1
Tankcell e500 in action
being equal. With a diameter of 10m, six 500m3 TankCells will utilise approximately 77% of the space required by the ten 300m3 TankCells. Apart from the lower footprint, energy saving is also an important factor in the selection of large cells, with the cost of electricity proving to be the most significant lifetime cost in any flotation operation. The six 500m3 TankCells only have 75-85% the installed power of the 10 x 300m3 cells. This can have a major impact on operational profitability – especially with a carbon tax looming! On top of this, factors such as having fewer wear parts all add up to substantial savings over the life of a project.
important features for large float cells
As the installation of large cells can represent massive risk if poorly designed or installed, it is vital
and metallurgical stability. Over 200 TankCell 300 flotation cells have been sold since then, a testament to the success and industry acceptance of this design.
With the 300m3 Tank Cell well established and proven – what’s next? What are the advantages of a cell which is now 1.5 times larger – the TankCell e500? The economies of scale for a cell of over 500m3 of flotation capacity are substantial. Additional developments in industry flotation technology such as Outotec’s FloatForce® mechanism, the direct drive gearbox design and tools such as CFD modelling have contributed to the development of cells in the 500m3 category.
500m3 of float volume By the numBers
Let’s consider a project where 3,000m3 of flotation volume is required for the desired residence time. This volume can be satisfied with 30 x 100m3 cells, 10 x 300m3 or a single line of 6 x 500m3 TankCells. Table 1 illustrates the relative costs of such scenarios on an ‘average’ rougher/scavenger duty, all things
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Some suppliers, for example, will use a standard gearbox with oversized power transmission components, resulting in decreased efficiency. The TankCell e500 uses gearboxes with dedicated 400-500kW motors, offering far more competitive operational costs.
3. cfD and process validationComputational Fluid Dynamics (CFD) also played a major role in the development of large flotation cells such as the TankCell e500. It is an effective means for evaluation of the hydrodynamics of new designs. The key, however, to making this CFD work successful is validation of the results both on a laboratory and industrial scale. Extensive testing was carried out on the first TankCell 300 prior to shipping, with subsequent on-site testwork of two years at Macraes and at other installations to ensure that the outcome of the CFD work was as expected. The learning from this and similar work over the years have been captured and integrated into the 500m3 TankCell design. An example of this effective design and scale-up methodology is reflected in the level of sites coming online with the proven larger TankCell designs. 30 x TankCell 300 cells at Kennecott on a copper rougher duty (offering approximately 3MW total saving versus any other cell in the 300m3 category), 34 x TankCell 300 at Sierra Gorda, to name a few.
conclusion
In conclusion, the economies of scale in a 500m3 unit speak for themselves. Its is important to realise that the
real key in the successful operation of 500m3 cells is using a supplier with experience in proven large cell design and scale-up. Outotec’s new 500m3 TankCell has been designed so that large operations benefit from the economies of scale of operating a few large machines rather than a forest of small machines. Leveraging Outotec’s experience of scale-up and development of the 300m3 TankCell, customers can be confident that the new 500m3 TankCell will lower an operation’s lifetime cost while maintaining the highest metallurgical performance.
important consideration for site operators. The FloatForce® stator design has been optimised via CFD, with extensive site testing for critical flow area and maximum lifespan.
Sanding of large flotation cells is of particular concern to the operator. It is vital to ensure the mechanism size and speed is selected in such a way that the mixing power and efficiency in relation to tank volume remains in proportion across all tank sizes. The proven mixing regime of Outotec’s patented FloatForce® mechanism, coupled with its location in the tank, means that operators have little to worry about on the sanding front, TankCells have the ability to start under sanded conditions that may occur due to unforeseen events such as power outages.
2. Direct gearbox drivesHistorically, the drive arrangement for mechanical flotation cells has consisted of a rotor and shaft driven by a single stage v-belt drive. Using a similar drive arrangement for a 500m3 cell would require a very large pulley, high belt tension and a special motor, which would not prove cost effective.
As a result of this, Outotec has developed and employed a series of gearbox drives for its large TankCell products. This drive strategy is particularly advantageous for the e500 as mixing is driven by a standard 4 pole motor without the need for any belt/pully arrangements or external motor cooling systems. The result is a smaller drive footprint, simplified maintenance and greater reliability as the gearbox has been developed specifically for flotation purposes.
FloatForce® in situ within TankCell e500
about the author...Ben Murphy is currently Technology Leader – Flotation for Outotec in the South East Asia Pacific region. Ben’s 13 year career has seen him gain operational mineral processing experience on four continents, working predominately in base metal flotation concentrators where he has held a variety of technical and managerial roles. He holds a Bachelor of Engineering in Mineral Processing from the University of Queensland.
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case sTudy: konIaMBo nIckel
customiseD faBric filter technology
The Koniambo project is an open cut nickel mine and metallurgical plant located in the North Province of New Caledonia, an archipelago in the South Pacific, 1500km east of Australia.
This world-class industrial complex is a joint-venture partnership between Xstrata Nickel, one of the world’s largest global diversified mining businesses and Société Minière du Sud Pacifique (SMSP), a local mining company in the region.
The Koniambo complex will be among the world’s lowest cost producers of nickel with initial annual production of 60,000 tonnes of nickel in ferronickel per annum and substantial further high-return, expansion potential.
BackgrounD
Based on its reputation in the industry, Outotec was involved in
concept development for the fabric filters’ bankable feasibility studies from the project’s early stages in 2004. Outotec was subsequently contracted in 2008 to supply three custom designed fabric filter plants (baghouses) to the Koniambo site in New Caledonia.
The two main fabric filter plants were to collect fine nickel laden ore in the gas from the Hammer Mill Flash Dryers (HMFDs), with the third used to clean gases picked up from various hoods around the nickel plant.
unique technology
Outotec had previously worked with Koniambo’s engineering and
fabric filter PaMs
Organisation: Koniambo Nickel SAS – a joint venture between Société Minière du Sud Pacifique (SMSP) and Xstrata Nickel
Site: Koniambo, Koné, Northern Province, New Caledonia
Year: Commissioning 2012
Application: Nickel Ore Refining
Challenges: Large gas volumes, high dust �loads, collection of hot, fine ore particles with low emissions
Positive isolation of individual �filter compartments
Remote site with limited, high cost �resources for site installation
Solution: Outotec High Volume Low �Pressure (HVLP), Pulse Jet Fabric Filters supplied for Hammer Mill Flash Dryer - Lines 1 & 2 and secondary de-dusting
Pre-fabrication for transport in �large single pre-assembled modules (PAMs)
Key Benefits: Low emissions, less than �20mg/Nm3
Safe, low maintenance operation �
Reliable technology �
Complies with sustainable �development principles – maximum ore collection efficiency with minimum energy consumption
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procurement contractors in supplying High Volume Low Pressure (HVLP) pulse jet filter technology, so partnership was easily established. Additionally, Outotec’s long track record using HVLP technology in process industry and utility applications is well known. The HVLP technology is unique when compared to conventional technology, as its design uses low pressure pulses and a rotating cleaning system. This design results in high reliability, long bag life and low maintenance.
extensive moDelling
Extensive flow modelling was conducted to ascertain the optimum flow distribution using both physical modelling and Computer Fluid Dynamics (CFD). Once the overall design was finalised, a 1:10 scale model was built, with further testing carried out on gas distribution screens and baffles to ascertain optimum gas flow distribution. Additional CFD modelling was also used to confirm findings from the physical modelling. Testing of the scale model was verified by the
University of NSW – Research Testing Facilities.
The solution and testwork were challenging as changes were necessary to the conventional baghouse layout to incorporate positive isolation guillotine dampers into each compartment. However the resulting Outotec design was engineered to overcome these challenging criteria, without altering the fabric filter plant’s footprint or compromising gas distribution.
pam feasiBility stuDy
Delivery of the PAMs presented a new and interesting challenge with the initial concept based on splitting the baghouse components into a number of large modules for shipment and erection at site. However, further discussions were held regarding even larger modules, leading to Outotec assessing the potential for each baghouse to be delivered as one large single module.
This large scale modular construction would require careful planning, delivery coordination and detailed
route assessment, utilising Outotec’s previous experience in the delivery of PAMs to remote sites, including calciners to Gove in Northern Australia.
After considering issues such as the distance, the assembly configuration, local labour and infrastructure, the outcome of the study indicated that a full PAM delivery was feasible and the preferred method for the project. Outotec’s original contract scope was subsequently altered to include full PAM delivery of the fabric filters.
Delivering the pams
The baghouses were constructed on temporary foundations overseas, with all steelwork, insulation, cladding, access and stairways installed. Mechanical equipment and piping were fitted and pre-commissioned where possible. This equipment included pulse cleaning systems, complete with pressure vessels, cell ventilation hatches and pulse air piping.
With construction complete, each pre-assembled baghouse was loaded
Assembly of the fabric filter PAMs Moving the PAM via self-propelled modular transporter
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onto the ship using a number of Self-Propelled Modular Transporters (SPMTs). The SPMTs have a grid of several dozen computer controlled wheels, all individually controllable and steerable. Each wheel can swivel independently from the others, allowing the SPMTs to turn, move sideways, or even spin in place.
The SPMTs lifted the baghouses via transport beams attached low on the support structures. Once loaded onto the ship, the beams were welded to the deck, with shipping completed over a 4-6 week period. Upon arrival in New Caledonia, SPMTs were once again used to transport the fabric filter plants and lower them into position on the foundations at the nickel plant site.
The two HMFD baghouses weighed 1,158 tonne each, including transport steel, with the secondary filter plant PAM weighing 489 tonne including transport steel, giving a total of 2,805 tonne. The transport steel comprised of temporary beams and bracing added to the baghouse structures to accommodate the additional loads during shipment to site. The transport
beams were sized to support the full dead load of the baghouses and the transport bracing was required to resist forces produced by the pitch and roll accelerations of the ship while at sea. The transport steel was removed once the PAMs were positioned on their foundations.
challenges
The location of a large nickel processing plant on a remote Pacific island presented difficulties in resourcing qualified expertise in construction. The decision to build the majority of the plant overseas was initiated by this factor.
With regards to the fabric filter plant, once its construction was complete, transportation to site was the next challenge, demanding additional engineering input, multi-lingual co-ordination and planning. For example, Outotec produced various engineering documents and drawings in three separate languages. Final installation of the plant at New Caledonia required internationally sourced supervisors and tradesmen to be flown in.
unique process = unique technology
The nickel refining process at Koniambo is unique, with the ore milling and drying completed in one process (the Hammer Mill Flash Dryer) and the baghouse integrated into the main process flow sheet. Outotec’s baghouse technology is therefore not solely considered as pollution control equipment but also as solids separation devices, critical in ensuring reliable delivery of feed solids to all downstream equipment.
Each baghouse must be operational in order for its process plant to work, so high availability and reliability are essential. Both baghouses handle flash dryer off-gas when the dryer is operating and calciner off-gas when the flash dryer is not operating.
High dust load and fine particle sizing, combined with a high collection efficiency and low emission requirement, demanded careful selection of the bag filter material along with careful design
delivery of the PaMs to koniambo
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of the gas flow path to each filter compartment. In addition, excellent quality control in both bag manufacturing and installation procedures were required for low emissions to be achievable.
The final design incorporates positive isolating guillotine dampers for safe personnel access. However, as previously mentioned, this design was achieved without compromising filter performance whilst still fitting within the original footprint constraints.
the result
Outotec delivered the fabric filter technology on time and, thanks to highly detailed planning, engineering and close co-operation with all parties, the baghouses were installed without any difficulties. With particulate emissions of less than 20 mg/Nm3, the baghouses will minimise any harm to the local environment as well as maximise the ore feed to the process, with a minimum energy consumption.
This project reinforced Outotec’s continued development in executing these types of large scale installations using very large PAMs.
Commissioning of the baghouses and associated infrastructure is due to take place in 2012.
If you would like more information click here
Quick tipthickener tank design optionsreviewing and questioning the way we ‘normally’ do things can result in simple, clever and more cost-effective options. reviewing thickener tank design, for example, can bring substantial rewards. so what are your options?
Piece small fabrication �Piece large fabrication �Fully pre-assembled �Bolt together �
When analysing the above options you not only have to look at a thickener’s capital cost, but also take installation time, risk and final quality or workmanship into consideration...
Meet Outotec at Booth 17, Hotel realm, canberraseptember 9th-13th, 2012
australia coal Preparation society
Quick tipgas dispersion in your flotation cellthe gas phase of any flotation cell is critical for optimum cell performance. understanding and varying these four key parameters can improve recovery. at one site, for example, up to 30% was achieved at the same grade:
Gas hold-up �Bubble size and bubble size distribution �Superficial gas velocity �Bubble surface area flux �
Once you have the right tools and expertise to benchmark the gas dispersion in your current flotation cells, it becomes far easier to get the most out of your operation...
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case sTudy: Queensland aluMIna lTd
Queensland Alumina Limited (QAL) commenced operation in March 1967 with an annual production rate of 600,000 tonnes of alumina. Today QAL is one of the world’s largest alumina refineries, producing 3.95 mtpa of the world’s best smelter grade alumina. With an average workforce of 1,050 employees, QAL is the region’s largest employer and
annually contributes approximately $400 million directly to the local economy.
processing
The QAL refinery at Gladstone can produce up to 800m3/h of red mud slurry, derived from digesting the aluminium containing ore, bauxite, with sodium hydroxide. After washing, the red mud residue is pumped to the Residue Disposal Area (RDA) on Boyne Island to be stored pending neutralisation of any remaining caustic soda.
To avoid expansion of their existing dam facilities, yet address high slurry volume and increasing environmental and availability demands,QAL implemented a complete refurbishment of the original disposal area as part of their plan to increase the available dam capacity for a further fifty years of operation.
qal seawater neutralisation facility
Organisation:Queensland Alumina Ltd (QAL)
Site:QAL Seawater Neutralisation Facility, QLD, Australia
Year:2008
Application:Seawater neutralisation of bauxite residue (red mud)
Challenge:Lump sum turnkey installation of seawater neutralisation plant
Solution:Vane Feedwell™ technology; strong partnership approach to optimise customers design concept
Key benefits:Red mud neutralised and �concentrated for semi-dry-stacking
Small footprint clarifier �
Consistently clear water overflow �meeting specific chemistry
Zero harm to the environment �
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separation plant, with the process itself designed by QAL. This scope included civils and all remote site facilities (ie office and maintenance space). Being remote from the main refinery, the entire infrastructure, had to be delivered to the RDA site and also designed to be as self-managing as possible, requiring minimum operator activity and controlled from the refinery.
With regards to the clarifying process, the customer initially considered two clarifiers, however, Outotec’s testwork and design modelling indicated that a single clarifier would meet requirements. Further design input from Outotec included the use of gravity systems for all slurry forwarding.
challenges
The neutralisation step produces a low specific gravity precipitate (hydrotalcite), which can cause adverse solids compaction and reduce the bulk density of the neutralised, thickened mud. To effectively thicken this mixture
and produce a clear overflow, the clarifier required a feedwell capable of maximising the entire volume. The feedwell also had to ensure minimum breakage during the mixing of flocculant and mud/aggregate particles.
Outotec had just recently patented its Vane Feedwell™ design, which was the first major feedwell innovation since the 1990s. This design has seven global patents and incorporates unique innovations to maximise performance.
vane feeDwell™
To accommodate the high energy of the incoming feed whilst maintaining adequate mixing of dilution liquor and flocculant, the new concept of axially sloped vanes, coupled with a radially sloped feedwell, was proposed. This design also provided a low energy zone and low shear necessary for aggregate growth.
CFD modelling indicated an increased hold-up of the high density
Seawater
seawater
Neutralised mudCLARIFIER
NEUTRALISATIONREACTOR
Red mud Flocculent
Magnesium deficient
Neutralisation with seawater, combined with semi-dry stacking was elected as the safest method to allow long term storage of the red mud residue. However, as the process can use up to 5000m3/h of seawater, a dedicated seawater neutralisation plant was required to provide continuous supply.
The neutralisation process utilises the magnesium content in the seawater to react with the caustic content in the red mud to form insoluble salts, thus reducing liquor phase alkalinity and soluble aluminium. The neutralised red mud and liquor are then separated into a slurry that is sufficiently concentrated to allow semi-dry stacking of the solids and a clean water stream, sufficiently low in suspended solids, dissolved aluminium and at the correct pH for discharge to the environment.
the scope
Outotec’s scope was the delivery of a lump sum turnkey (LSTK) seawater neutralisation and
Seawater neutralisation process
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to uniformly discharge under low shear conditions.
CFD modelling of the flow pattern demonstrated a far improved retention of solids concentration with the modified feedwell. A new Outotec Vane Feedwell™ was thus retrofitted to the clarifier and had the immediate desired impact with consistently improved underflow density and overflow clarity.
footprint
Industry demands for lower capital and maintenance costs have resulted in the trend towards smaller footprint clarifiers capable of handlinglarge slurry flowrates. The VaneFeedwell™ clarifier at the seawater neutralisation facility is a single unit with a relatively small footprint. The red mud from Queensland Alumina, however, is produced via three parallel banks of counter current washers.
adsorption, reducing coarse/ fines segregation, ensuring all particles are aggregated together by the flocculant. The lower zone promotes gentle mixing for continued aggregate growth, with the option for secondary flocculant dosing. This zone also enables aggregates
feed while removing energy from the feed stream and effectively splitting the feedwell into upper and lower zones. The upper zone into which feed, dilution water and flocculant are added provides enhanced mixing and energy dissipation. This promotes maximised flocculant
How the Vane Feedwell™ works
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sustainaBility & environment
QAL’s long term residue disposal plan involves achieving and maintaining a sustainable operation with zero harm to the environment and the semi-dry stacking process used at the facility was chosen for this reason.
The alkaline liquor phase of the red mud, (originally at a level of pH 14), is neutralised and lowered to pH 9 and is therefore harmless and safe for release into the surrounding estuary. Water quality is monitored routinely, not only by QAL, but also by the Port Curtis Integrated Monitoring Program (PCIMP) group, who carry out independent testing of the surrounding estuarine waters.
If you would like more information click here
results
Outotec interpreted the customer flowsheet to deliver a robust design to meet the customer’s stringent performance and availability requirements and also capable of complete remote control from the refinery itself.
Outotec’s focus on cost minimisation was achieved by using gravity forwarding systems where possible and via a high availability single clarifier which, through efficient flocculant techniques, negated the need for an additional unit, so reducing the footprint. With Vane Feedwell™ technology, this single clarifier is capable of separating 5800m3/h of neutralised red mud
whilst also achieving a consistent and desirable underflow density of 340g/l.
The LSTK project has successfully demonstrated that large scale seawater neutralisation of red mud, with an environmentally acceptable discharge, is achievable. The new plant has enabled QAL to continue utilising their existing containment areas and improve the vegetation and environmental conditions in the area.
Meet Outotec at stand 21 & 23, Grand chancellor Hotel,
Hobart, tasmaniaOctober 29-31st, 2012
11th AusIMM Mill OperatOrs’ COnferenCe 2012
Quick tipDesigning mill foundationssome factors the engineer should consider include:
Mill supplier data �Loadings and directions of loadings are easy to misinterpret.local conditions �small inaccuracies in strata data can dramatically compromise mill performance.outside influences �Vibrations from other equipment, and adjacent mills in particular, can accumulate to detrimental effect.
