Inside Mining May 2015

www.miningne.ws

af r ic an u pdates on th e

g ro un d a n d un d e rg ro un d

in the

spotlight Anglo American (Coal) GM Bonke Ntimane on Floating Wetlands

TANZANIA

Land of opportunity

DRA

PHOLA COAL

innovative plant design

SISHEN

Watering the problem

MAINTENANCE Preventative vs predictive

GEOSYNTHETHICS Solving the underlying problem

REAGENTS

Increased grade yields

ISSN 1999-8872 • R50.00 (incl. VAT) • Vol. 8 • No. 05 • May 2015

contents Endorsed by

Af r ic a n u pdates on th e

May 2015

g rou nd a nd u nderg rou nd

on the cover

www.miningne.ws

a fr i c a n up dates on t he

IN THE

SpOTlIGHT Bonke Ntimane, General Manager, Anglo American (Coal)

Floating Wetlands

ground a nd underground

DRA

PHOLA COAL

innovative plant design

TANZANIA

Land of opportunity

SISHEN

Watering the problem

MAINTENANCE

Preventative v predictive

GEOSYNTHETHICS

Solving the underlying problem

REAGENTS

Increased grade yields

ISSN 1999-8872 • R50.00 (incl. VAT) • Vol. 8 • No. 05 • May 2015

8

P4

DRA's design of the Phola coal preparation plant, a classic twostage processing plant producing a prime export product and middlings for the nearby Kendal power station in Mpumalanga, fully met its specification requirements.

EDITOR'S COMMENT

3 Africa's black gold COVER STORY

4 Innovative coal processing plant design Africa round-up

7 Africa round-up in the spotlight

8 Floating wetlands ECONOMICS, FINANCE & RISK

10 One environmental system for mines 14

12 Risk management and insurance efficacy commodities

13 Phosphate: A key to life 14 Tanzania’s black gold pipes, pumps & valves

20 Mine water disposal 22 Mine dewatering and safety 23 Water for Malawian villages 24 In the pink is not always good 27 Geosynthetics in mining 29 Lessons from Mexico 27

30 Capacity and capability mineral processing

33 Small, perhaps insignificant, but important 35 Optimising your crusher 37 Work smarter, not harder 39 Solving two problems with one solution TECHNOLOGY

40

40 No challenge too tough In sid e M in in g 0 5 | 2015

1

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Publisher Elizabeth Shorten Editor Tony Stone Editorial assistant Mpinane Senkhane Head of design Beren Bauermeister Designer Ramon Chinian Chief sub-editor Tristan Snijders Sub-editor Morgan Carter Contributors Mark Cresswell, Bonke Ntimane, Angela Graham & Danie Vermeulen Client services & production manager Antois-Leigh Botma Production coordinator Jacqueline Modise Marketing & digital manager Esther Le Roux Marketing specialist Philip Rosenberg Financial manager Andrew Lobban Administration Tonya Hebenton Distribution manager Nomsa Masina Distribution coordinator Asha Pursotham Printers United Litho Johannesburg Tel: +27 (0)11 402 0571 ___________________________________ Advertising Sales

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Africa’s black gold

A

s much as the greenies complain about the current carbon footprint of coal, the reality is that South Africa has an abundance of this natural resource. In fact, we have between 119 and 200 years’ supply, depending on which source of information one uses. Tanzania, too, has an abundance of coal, with new commercially exploitable reserves being discovered quite regularly. What we have to do is use the latest technology when building power stations. This will reduce coal’s carbon footprint by as much as 40% – an immediate gain.

No doubt, with human innovation, we can improve on this.

The critical thing, if the supply chain is efficiently maintained, as well as the power stations, is that the reliability of coal, as an energy resource, is unquestioned.

On the other hand, wind power may be cleaner but it is not that reliable, because wind does not blow every day. Nor does it blow at a constant We just have to be speed. Moreover, those huge propellers kill birds. innovative – something Many birds! To get biofuels, from plant material, be this land- or water-based, up to a level that will we are more than maintain a regular supply of quantity, as an energy capable of resource, will take a few years. Added to this equation is climate change, and its impact. South Africa, already a water-strapped country, is experiencing a drought in the usually high-rainfall eastern areas of the county.

Solar power is also clean, but the size of the solar farms required to produce the quantities of energy needed are impractical, especially for a mine with a mineral processing plant. In areas where high temperatures are experienced, the adhesive on the panels peels off, as experienced in the Middle East. This introduces a high maintenance cost. Nuclear energy may be cheaper to produce but the dangers, as in Fukushima in Japan, are huge. So, yes, every alternative has its good and bad points. But coal is a known quantity, and it is reliable.

Recent technological developments, such as UCG (underground coal gasification), introduce alternate uses for coal as an energy source. Perhaps, though, the very problem of coal, its carbon footprint, can be turned from a negative to a positive. Carbon capture is a very real technology, not just to have it stored underground but to use it as an energy resource. Groundbreaking research and development is being carried out by Professors Dianne Hilderbrandt and David Glaser, of the University of South Africa, in turning carbon-based solid waste into energy resources using a Fischer-Tropsch synthesiser process.

If this groundbreaking work can be done using solid waste, captured carbon can be equally exploited. We just have to be innovative – something we are more than capable of. This is certainly the case when looking at what is happening in the realm of pipes, pumps and valves, and in mineral processing, especially in the field of chemistry where reagents and processes have been optimised to maximise the yield from low-grade ores. Clearly, if we can put a robot on Mars, we can do anything we set our minds to. Coal is Africa’s black gold!

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cover story

Process Design

Phola coal

preparation plant DRA's design of the Phola coal preparation plant, a classic two-stage plant producing a prime 27.5 mj/kg export product and a 21.5–23 mj/kg middlings for the nearby Kendal power station, fully met its specification requirements.

BY Mark Cresswell

T

he design brief for the Phola coal preparation plant near Ogies, Mpumalanga, was for a classic two-stage Witbank plant producing a prime 27.5 MJ/kg export product and a 21.5–23 MJ/kg middlings for the nearby Kendal power station.

The plant concept doubled in size when Anglocoal formed a 50:50 JV with BECSA for a plant that would also treat coal from their new Zondagsfontein underground coal mine, approximately 15 km to the south.

The advantages of a combined plant lay mainly in the access the Klipspruit plant gave to the Richards Bay coal terminal railway line and lower operating costs, as a combined plant allowed a larger unit module size whilst still keeping the flexibility of a multi-modular design. This has resulted in the design, construction and commissioning of one of the largest and most modern coal preparation plants built in the area for 30 years.

The key to reducing the plant footprint and significantly lowering the capital costs lay in two relatively simple concepts – first, the maximum equipment size allowed was extended to include proven

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sizes from overseas (principally Australia, where many reference sites were visited) and, second, to simplify the process such that all the coal was washed and no intermediate product was allowed to be withdrawn or added. The key concept of separating the coarse and small coal fractions in order to optimise the yield was retained, as this allowed the module size to increase in overall throughput.

The maximum equipment size settled upon was 4.2 m width banana screens and 1 150 mm dense material (DM) cyclones for the coarse coal and secondary highdensity separation. These sizes were well proven in Australia by early 2005. This allowed the plant to be enormously simplified into a two-module plant of 1 180 t/h capacity per module.

It was interesting to note that the footprint of the final 16 Mtpa, plant design was smaller than the previous 8 Mtpa plant, which consisted of five major processing sections. Smaller 710 mm diameter cyclones are used for the small coal primary separation to ensure that the separation efficiency is maintained.

The final flowsheet is given in Figure 1 and overall mass balance in Figure 2:

Innovative plant design concepts Primary sinks static panels

A key point in the final plant design was the internal arrangement to combine the primary sinks from both coarse and small coal sections, and deliver them to the high-gravity section mixing box. This is achieved by the use of static drain panels (the old DSM method was to use double sieve bends) rather than vibrating screens, as the advantage lies in not only the saving in equipment and vibrating load on the structure, but in the fact that on crash stops (which are all too frequent in the Highveld summer lightning storms) the coal will sit in on the static screen rather than be discharged into the mixing box feed launder and potentially block it.

Having agreed on the concept, the design problem is what angle to set them at and how much drainage capacity to allow for, as provision needs to be made for the coal to sit on the screen whilst the medium drains and then gently drop off into the collecting launder. Note was taken of ABOVE & OPPOSITE INSET Stockpiling coal RIGHT Phola's processing plant

cover story

the method adopted at the Mafube plant where a similar design concept was used

by DRA, but with an adjustable screen height and linked to the raw coal feed control system. At Phola, where the tonnage is at least 25% greater, having an adjustable screen would have been an unwieldy option, so, instead, a generous 50% extra area was allowed using a 30 degree slope for the coal to settle on. The main design challenge here was not so much the concept or equipment sizing, but the layout due the huge volume of material going through the module.

Elevated cyclone feed pumps When laying out a pump-fed DM cyclone plant, there is generally scope to elevate the DM cyclone and feed pumps, as the height of the plant is dictated by the gravity flow of material from the DM cyclone floats to the drain panel, drain and rinse screen, dewatering centrifuge and product conveyor.

Given the size of the Phola plant, there was an opportunity to save approximately 15 m in pumping head by elevating the pumps and mixing

box above the ground floor. There is also the considerable advantage of being able to drain the mixing box directly into the CM sump on a crash stop, allowing for a quick start-up.

Protection panels above the CM sumps This is an Australian concept that involves gathering all the return flows into the sumps that could contain coal into a box and then allowing the combined flow to drop into the CM sump through a static drain panel. The idea being to firstly stop any large coal entering the medium, then for this coal to be shovelled over the side of the sump in a controlled manner onto the floor for pick-up.

Normally, return lines are routed directly back into the sump but, if this concept is followed, it has a considerable impact on the layout, not necessarily adding height but complexity in gathering all the drain lines into a single discharge box immediately before the CM sump. These air agitation valves, originally designed for the South African gold industry leaching

tanks, are situated in the centre of the bottom of the sump, with the air being fed to them through the sump or preferably under the sump if the layout allows. They are self-sealing by a double-lock cone system and, because they introduce agitation air into the middle of the sump rather than at the sides, they appear to be far more effective and have eliminated start-up problems due to settled magnetite.

Filtration of slimes It was integral in the design concept to filter the slimes in order to reduce the freshwater requirements and then add the filter cake to the middlings or discards.

Given the maximum design tonnage involved, the different qualities of the raw coal slimes from the two different mines and the requirement to produce as-dryas-possible filter cake when it can be added to the middlings, the duty was split equally between two filter types – the TH filter, with its single cloth per plate, and the continuous cloth Lasta filter, which also incorporates a membrane squeeze in its operation.

Both these filters are relatively new models in the South African coal industry with the Lasta being far more automated and complex in both design and operation. The

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cover story

FIGURE 1 Final design concept block diagram

FIGURE 2 Overall average mass balance

filters are laid out at right angles to the product belts and, by using reversible conveyors, the filter cake can be fed to either the discard or middlings belt.

There are six filter cake conveyors and nine filters and, given the variability in the time they can take to complete the filtration cycle, a dynamic simulation modeling exercise was carried out to calculate the maximum filter cake that could be added to the products and the optimum speed the filter cake and product conveyors should run at.

Plant mass balance A detailed coal/water/magnetite mass balance was calculated for the wet plant using an Excel spreadsheet. Besides being used for pump and pipe sizing, it was used to calculate the maximum flow conditions for the many variables that the plant could experience, e.g. average flowrate, min/max

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medium densities, maximum yield for the maximum coarse, smalls, fines and slimes sections, the 'no coal' condition and the gravity spirals bypass condition.

This had been calculated for the coal solids, but these simulations gave the maximum volumes and allowed the pump and pipe sizes to be finalised. The mass balance was split into the five main sections of the plant – coarse low gravity, smalls low gravity, high gravity, fine coal and slimes.

The balance for each section was calculated and finally the overall balance for coal, water and magnetite in both t/h and m3/h.

Process equipment selection As stated earlier, the original design brief was not to use any equipment or size of equipment not fully proved in South Africa, therefore the type of equipment selected tended to be conservative in terms of manufacturer.

• Screen capacities: The most notable area in which the design boundaries were pushed were the screen capacities, through the use of modern banana screens. These screens, with their multiple-angle decks, allow previous capacity standards in terms of t/h coal/m2 screen area to be greatly exceeded due to the velocities achieved on the screens and the thin bed layers. Particular care was taken in the design of the feed boxes ahead of the screens, in order to spread the feed slurry as evenly as possible across them.

In this area in particular, the designs from previous plants built by DRA, such as Mafube, were carefully scrutinised and further developed.

• Filter presses: The most conservative equipment selection was in the filter presses, where 50% extra design capacity was allowed since there is no slimes dam. Filter cake surface moistures averaging around 20% are being obtained from the units, but can vary according to the amount of clay in the coal, as much as 16%–25%.

• Linings and pipe materials: All boxes, lower sections of pump sumps and pump suctions that are in contact with coal were ceramic-lined with thicknesses varying from 12.5 mm up to 50 mm for spigot boxes. All pipes handling magnetite media were basalt-lined, while other slurry pipes used HDPE. Nearly all screen and drainage panels are of HDPE construction with some use being made of the 'polywedge wire' panels, which offer larger open area and similar ease of replacement to that of HDPE panels.

• Plant control: The plant is fully automated with a Profibus Scada system, allowing the control room operators to run the full plant from the raw coal crushing plants, through the stockpiles, process plant, product stockpiles and rail load-out.

Conclusions With the commissioning of the DRA designed Phola plant, all is well and on its way to becoming one of the largest throughput capacity plants in the Witbank coalfield. It has been designed using the latest concepts in an integrated plant layout and, whilst breaking new boundaries in terms of throughput capacity, has borrowed heavily from lessons learnt during previous plant designs.

www.draglobal.com

africa round-up

Mining news

from around the continent in association with Burundi Funding secured for Gakara project Rainbow Rare Earths has announced that it has secured funding from Pala Investments for the

Martin-Eales, Rainbow Rare Earths MD

development of its high-grade Gakara rare earth project in Burundi. The financing agreement is for an amount of $12 million. This agreement, subject to the completion of certain milestones, will fund the project through to full production. The first stage of funding is a two-tranche convertible loan for a total of $6 million. The first tranche is allocated for studies, to detail the mining method and sequence, investigate the optimal processing methods, and prepare for trial mining. The second tranche will provide the capital to commence trial mining, which will be used to optimise the mining method and increase efficiencies.

On success of the trial mining phase, Pala can opt to convert the loan and invest a further $6 million on an equity basis. These funds will be used to expand mine infrastructure on-site and allow larger-scale mining to commence, with

a targeted production run rate of 5 000 tonnes of >50% TREO concentrate per annum.

Martin Eales, managing director at Rainbow Rare Earths, comments: “We are very pleased to have secured this investment from Pala, who will provide both financial and technical advice and will be a valued partner going forward. Their detailed due diligence and subsequent participation provides significant third-party endorsement of the potential and quality of our project’’

Kenya Encouraging new bill

passed before the fiscal year ends on June 30.” Kenya is overhauling its mining code to increase the share of revenue from an industry that represents only about 1% of gross domestic product, partly because poor regulation has deterred investment. Under this new law, the government will impose royalty rates ranging from 1% of the gross sales value of industrial minerals such as gypsum and limestone, to 10% for coal, titanium ores, niobium and rare earth elements, and 12% for diamonds.

Zambia

400 workers redundant. The Zambian government said that this was done without any prior information, as is required under Zambian law.

Chief government spokesperson Chishimba Kambwili told reporters: “All mining companies are aware of the standing order, which obliges them to consult the government through the Ministry of Labour before any decision to sack any worker becomes effective.” According to Kansanshi, 343 workers were going to lose their jobs at the mine, mainly from contracting companies building a smelter that had been completed in December 2014. Located about 10 km north of the town of Solwezi and 180 km northwest of the Copperbelt town of Chingola, the Kansanshi mine has undergone several expansions since it began operating in 2005. The mine had an initial production capacity of 110 000 tonnes of copper and is now capable of producing 340 000 tonnes, as well as more than 120 000 ounces of gold a year.

A survey released by HR consultancy has revealed that Kenya could experience a jobs boom from the mining and

Zambian government cracks the whip

Cabinet Secretary for Mining Najib Balala

First Quantum Minerals chairman and CEO Philip Pascal

The Zambian government has issued a warning to First Quantum Minerals-owned copper mine Kansanshi due to its decision to lay off workers without a consultation period.

The mine, 80% owned by First Quantum (the remaining 20% owned by a subsidiary of ZCC), had previously announced plans to make

construction sectors in the next quarter. The Kenyan government is anticipating enacting a mining law later this year to provide policy stability in the country. At the moment, Kenya is ranked by an industry institute as one of the world’s least attractive places to invest. Cabinet Secretary for Mining Najib Balala said, “The Mining Bill, currently before the nation’s senate, is expected to be In sid e M in in g 0 5 | 2015

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in the spotlight

Floating

wetlands T

project

hese floating wetlands are proving to not only remove pollutants from water, but also create a rich habitat for a diverse range of fauna and flora. This project is a first in the South African mining industry and, if proved viable in the long term, could represent a cheaper and more sustainable alternative to traditional mine water treatment methods around the world.

Extracting and processing minerals and metals provide the backbone of South Africa’s economy, but, unavoidably, these activities also disturb the land, consume

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An innovative part of Anglo American’s work in the environmental arena is the use of floating wetlands to address contaminated water sources resulting from mining operations.

This is a proof of concept project. By Bonke Ntimane*

resources and generate waste and pollutants. Constantly aware of the need to mitigate these environmental impacts, we follow the Anglo American Environment Way, a group-wide standard that sets out a consistent approach to responsible environmental management. This standard supports its vision to minimise harm through the design, operation and eventual closing of operations in an environmentally responsible manner.

The floating wetlands project is an exciting new approach supporting Anglo's commitment to water sustainability. While many mines are harnessing

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in the spotlight

conventional water treatment methods, the concept of floating wetlands to remove pollutants from water should attract attention as a solution that has no secondary impacts on the environment. Polluted water is treated at source through naturally occurring biochemical processes that remove the pollutants and restore pH balance. Effectively, the wetland acts as a biofilter that captures and biologically degrades process pollutants.

The concept originated from a Department of Water Affairs’ Water Wise initiative and was applied as part of the Hartbeespoort Dam's integrated biological remediation programme to address the severe tainting of the waterscape by pollution over the years. Floating wetlands were also trialled by the University of Pretoria with the aim of removing high sulfate concentrations in water.

Recognising the potential for water treatment in the mining industry and the manner in which the outcome aligns with our water strategy and policy, Anglo American has initiated a trial using native wetland plants as a form of passive remediation to remove pollutants from water bodies on rehabilitated mine land.

This is a South African coal mining industry first. An Anglo American Coal South Africa mine outside Kriel in Mpumalanga is conducting the trial, in partnership with independent wetlands expert Paul Fairall, who has 40 years of experience in the conservation and rehabilitation of biologically diverse eco-systems. Fairall is a past winner of a Mondi National Wetland Award and heads up the floating wetland project at Hartbeespoort Dam. The project utilises 2 m x 2 m

grids made of alien Spanish reed, laced together to form rafts on which indigenous aquatic vegetation has been planted. The objective is to create a biomass that starts a ‘food web’ on which an abundance of microbes can live. This process breaks down harmful sulphates into removable sulfides, before frogs, snakes, birds and small mammals can come to any harm. The root systems provide a habitat for zooplankton, macro-invertebrates, fish and other aquatic organisms, while surface growth attracts insects, birds and reptiles.

If the initial trial is a success, the mine is likely to deploy floating wetlands on large stretches of rehabilitated mine land. Water quality and bio-diversity baselines have been established and a three-hectare floating wetland has been earmarked for construction on a large water body situated in the rehabilitation area. The findings of this trial could be of major significance, as wetlands are the most threatened of all South African eco-systems, totalling 48% of threatened bio-diversity.

Wetlands make up just 2.4% of the country’s landmass and half of them are critically endangered. A little known fact is that more carbon is sequestrated in peat and wetlands than in all of the world’s rain forests. The floating project has already yielded significant benefits and it is expected to continue to do so as the trial advances to implementation. Particularly attractive is the fact that these wetlands have the potential to negate the costly operation of a water treatment facility that requires funding well beyond mine closure. With this view to the longer term, as a global leader in water purification technology, our coal business in South Africa strives to harness our water

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treatment and reclamation technology to minimise any future risk of mine water.

Our approach is to embed sustainable development in everything that we do. The fact is, if we are to maintain our licence to operate, we cannot degrade water quality or compromise the rights of other users.

We, therefore, seek to minimise our environmental impacts and to take advantage of opportunities like this, which we believe will deliver long-term benefits to our stakeholders.

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A black-headed heron

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A pristine wetland

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Tree frog

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Brown house snake

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Brown snake eagle

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A diagram of how a wetland works The author *Bonke Ntimane, general manager, Anglo American (Coal)

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Economics, finance & risk

One environmental

system for mines Tracking the progress in the transition of the mining operations environmental management regulations is important. With expert opinion to boot, it’s an advantage. By Angela Graham

L

AST YEAR was filled with public statements, legislative amendments and proposed legislation published for comment; signalling and accelerating the progress of the transition of the of mining operations environmental management regulations from the Mineral and Petroleum Resources Development Act (MPRDA) to the National Environmental Management Act (NEMA).

Sandra Gore, director in the environmental practice at Cliffe Dekker Hofmeyr, explains that the Department of Mineral Resources (DMR), the Department of Water Affairs and Sanitation (DWS), and the Department of Environmental Affairs (DEA) released a statement in December 2014 confirming that the government would commence the roll-out of the much-anticipated One Environmental System in the same month. “This system will result in far greater integration of environmental regulation needed for mining,” she says.

“It was confirmed that, under the system, the Minister of Mineral Resources (currently Ngoako Ramathlodi) will be responsible for issuing environmental authorisations (EAs) and waste management licences (WMLs); and the Minister of Water and Environmental Affairs (currently Edina Molewa) will be the appeal authority for EAs and WMLs issued by the Minister of Mineral Resources. The ministers have agreed to fixed time frames for processing and issuing EAs, WMLs, water-use licences (WULs) and other environmental consents within their respective competencies. They have also committed to synchronising the processes, to ensure all environmental consents are issued within

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a 300-day period. In addition, the Minister of Mineral Resources will be authorised to appoint environmental mineral resource inspectors, who will have the same power as environmental management inspectors under NEMA, to enforce environmental legislation at mines,” explains Gore.

2014 Environmental Impact Assessment Regulations Gore says that the 2014 EIA Regulations took effect on 8 December 2014 and repealed and replaced the Environmental Impact Assessment Regulations published on 1 August 2010 (2010 EIA Regulations).

“These regulations include a number of provisions to provide for the transition of the environmental regulation of mining from the MPRDA to NEMA and the introduction of the One Environmental System. These provisions note the inclusion of mineral activities under the 2014 Listing Notices, requiring mineral right holders to obtain EAs for, inter alia, the commencement and decommissioning of these activities.

There are, however, still pending draft regulations under NEMA pertaining to financial provision for the environmental impacts of mining, whose provision is also referred to in the requirements for applications for EAs in NEMA and a gap remains. They also detail that, pending applications under the MPRDA and its regulations (MPRDA Regulations), when the 2014 EIA Regulations come into force fully, they will, despite the repeal of the MPRDA Regulations, be dealt with as if the MPRDA Regulations have not been repealed. “The MPRDA Regulations have not been repealed (and are not likely to be, as

they deal with several issues beyond environmental regulation). However, the legislature’s intention appears to be that pending applications for EMP approval must be processed under the MPRDA applications that include amendments to an EMP. “The provisions also contain shorter prescriptive time frames for the EA application process, to ensure EAs are issued within the timeframes in the One Environmental System. Also noted are the requirements

Economics, finance & risk

to ensure issuing of EAs and other environmental consents required for activities are coordinated, as well as substantive requirements for audits of compliance with EAs and EMPs,” notes Gore. She says that separate regulations were published on 8 December 2014 under NEMA, regulating appeal and exemption procedures. The new Exemption Regulations prescribe more onerous and time-consuming procedural requirements for applications for exemptions from the provisions of the 2014 EIA Regulations.

Financial Provision requirements Tracy-Lee Erasmus, senior associate in the environmental practice, explains that under the One Environmental System, the requirements for financial provision for the environmental impacts of mining operations is to be regulated by NEMA and no longer the MPRDA. Draft Financial Provision and Closure Regulations were published for public comment in October 2014. She notes that these are more detailed and onerous than the current regulations. “Failure to comply with these regulations would result in a fine of R10

Haul trucks in a busy pit mine

million under NEMA,” Erasmus says.

“Despite their title, the Draft Financial Provision and Closure Regulations propose provisions wider than just financial provision and deal with care and maintenance of mining operations and ‘deemed

“For mining and prospecting rights, the methods of acceptable payment have been limited. The wording of the trust deed and financial guarantee are prescribed in the Draft Financial Provision and Closure Regulations. Environmental risk assessments and annual rehabilitation plans would be required, with prescribed contents, and must Environmental impacts be audited annually. Rehabilof mining operations are itation and cost closure liability would need to be reviewed to be regulated by NEMA, annually, after reviewing specand no longer the MPRDA ified reports by a specialist team (which must include a mining engineer, a surveyor, closure of mines’, which are not currently and an environmental assessment practiregulated under the MPRDA. A mine can tioner) and being audited by an independent auditor. Only one extension is allowed be deemed to be under closure by the Defor submission of the review and audit partment of Mineral Resources in specified (and far-reaching) circumstances. for a prescribed period. “Specified time periods are also included for an increase “Under the proposed regulations, minerof the financial provision. If the holder al rights holders will have to apply to the is unable to cover any shortfall, the minMinister of Mineral Resources to be placed ister can agree to enter a payment agreeunder care and maintenance, which may ment (that must be less than five years),” not exceed a specified period,” she notes.

Erasmus says.

Erasmus says that the Draft Financial ProShe notes that under the proposed tranvision and Closure Regulations have more sitional provisions, existing financial prodetailed provisions regarding financial provision must be regarded as having been visions, rehabilitation and the required reapproved. In addition, a holder that operports than those previously in the MPRDA. ates under an approved financial provision must review and align it with the Draft Financial Provision and Closure Regulations. Lastly, a holder must, within 15 months after the coming into effect of the draft regulations, assess and adjust the financial provisions in accordance with the procedures contained in these regulations and submit a revised sum to the minister for approval.

If the holder fails to comply with this requirement, the existing financial provision will lapse 45 days after the expiry of the 15-month period. “It is unclear when these regulations will be enacted into law,” Erasmus concludes.

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Economics, finance & risk

Risk management and insurance efficacy For most companies, insurance protects their biggest investment and is their largest source of contingent capital. It protects them from events that might otherwise threaten output, jobs and even the future existence of the company.

T

he best way to mitigate risk is to insure against it. To some, this may be a grudging concession, but to others a non-negotiable necessity, especially when looking at business sustainability and continuity.

On the plus side, knowing that you are effectively insured makes investors feel more secure. And, your insurance company may charge you less on premiums if they believe you have taken steps to minimise the number and po-

tential size of claims. This is a distinct and possible reward for good risk management. The Institute of Risk Management defines risk as “the probability of an event and its impact where the consequences can range from positive to negative.” In the end it’s all about protecting your balance sheet and reducing volatility in the profit and loss account caused by unforeseen losses. Additionally, the purchase of insurance is often required by regulators, clients and customers in relation, for example, to professional indemnity exposures.

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Finally, insurance can facilitate business activities by providing the financial security needed to cover exposures such as those associated with mergers and acquisitions, joint ventures or expansion. Risk management involves the identification, measurement and economic control of the risks that threaten the assets and earnings of a business. A risk is defined as the peril or hazard that is covered by the insurance policy. You need to decide whether you have adequate controls in place to manage the risks that your business faces, some of which can be quite significant. You will also need to consider whether or not you could cost-effectively do more to control risks, including the evaluation of your health and safety standards and the assessment of measures in place to protect your property against theft and fire, or even an act of God. Before looking in detail at the different types of insurance, it is worth considering the vital role of risk management. A good starting point is the risk process.

Adopting a risk management approach will protect your business, add value to the business and support the achievement of your objectives by: • providing a framework that enables future activity to take place in a consistent and controlled manner • improving decision-making, planning and prioritisation by comprehensive and structured understanding of the threats to your business activities • contributing to the more efficient allocation and use of capital and resources • reducing volatility in the non-essential areas of the business • protecting and enhancing assets and company image • developing and supporting people and knowledge base

• optimising operational efficiency within your business.

Adopting the risk management approach will help you concentrate on reducing the likelihood and consequences of a loss, as well as evaluate what you can do to minimise the extent of damage and the cost of disruption.

Business continuity planning of this type is a key part of the risk management process, and you should carefully consider how you would continue your business processes after a serious loss that causes disruption to normal operations. Adequate training of staff and periodic practice of the business continuity procedures are essential. Keep in mind that insurance requires a governance framework that sets out the roles and responsibilities of the various parties, both internal and external. In particular, the board must be satisfied that the arrangements provide the required level of coverage and the policy terms and conditions are reliable, adequate and represent appropriate use of funds.

Insurance buyers need to consider cover design, insurer selection, wording reviews, scenario testing, and claims protocols. They need to be aware of the importance of warranties and conditions precedent, together with the potential impact of basis clauses.

Significant planning and professional expertise are necessary. The professional support of insurance brokers can be an important part of achieving the required level of efficacy of insurance contracts.

Buyers may need to validate that the insurance structure is compliant with regulatory requirements around the world. If a master policy is purchased in South Africa or the UK, it is essential that the cover complies with regulations in all countries where it applies. This will be especially challenging when a captive insurance company is involved. Without risk management and insurance cover, you could lose your shirt, and a little bit more.

COMMODITY: PHOSPHATE

A key to life “Zero harm” and “putting nature first” are the slogans of a mining company that plans to strip-mine phosphate in an environmentally sensitive and significant area.

Time will tell whether these slogans hold true.

E

landsfontein Exploration and Mining is a South African company currently exploring and developing the Elandsfontein phosphate deposit on the west coast of South Africa. The project is supported, technically and financially, by its major shareholder, Phosfanatio International, a European business with investments in the phosphate industry. The team involved has decades of relevant mining experience, both locally and abroad.

Phosphate rock is a naturally occurring compound of the element phosphorus, found in rocks, soils, and organic material.

Phosphorus is a key element in all known forms of life, both flora and fauna. Phosphate rock is a non-renewable resource that has taken millions of years to be formed through geological cycles and events. The dominant application of phosphorus is in fertilisers. Due to the essential nature of phosphorus to living organisms, the low solubility of natural phosphorus-containing compounds, and the slow natural cycle

of phosphorus, the agricultural industry relies on fertilisers that contain phosphate. A recent article commented: “Without plentiful phosphate supplies, the wheels will come off modern agriculture.”

The most important characteristic of phosphorus is that there are no substitutes for it. According to the Global Phosphorus Research Initiative (GPRI), phosphate reserves will last 75 to 200 years. Therefore, exploring and developing new phosphorus

resources, is of vital importance. According to phosphate marketing company CRU, the long-term industry forecast shows that the growth in phosphate rock demand will require that new mining capacity be established before 2022. The Elandsfontein deposit is a sedimentary phosphate deposit on the west coast of South Africa with a significant resource of phosphorus. It is the second largest phosphate deposit in South Africa, after the Phalaborwa deposit. Samancor, who operated a phosphate mine near Langebaan, identified and drilled the Elandsfontein deposit in 1985, but chose not to develop the project.

The phosphate mineralisation is contained in the Varswater Formation, with the phosphate occurring in two forms, namely phosphatised shell fragments and phosphorite pellets. The remainder of the deposit consists of silica sand and calcium oxide. The sandy nature of the Elandsfontein deposit means that the phosphate can be upgraded without the large crushing and milling requirements, often associated with rock processing. Elandsfontein has recently appointed a South African engineering and design company to confirm the processing route required to produce a saleable phosphate concentrate above 32% P2O5.

Besides confirming the phosphate grade across the resource, the assay results show the ore is free from the heavy metals and radioactive elements often associated with sedimentary phosphates. And, being so well positioned, near Saldanha, one of South Africa’s major bulk handling ports, the Elandsfontein deposit is in a very favourable position to earn foreign revenue.

In sid e M in in g 0 5 | 2015 13

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commodity: coal

Tanzania’s black gold After decades of poor economic performance, the cluster of countries that make up the East African Community are recording solid economic growth. Among these countries is Tanzania, which is set to launch off its bed of coal. By Tony Stone

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commodity: coal

I

n the last three years, Tanzania has discovered yet more coal deposits and has since revised its estimated coal reserves to five billion tonnes.

The net effect of this, and the discovery of other minerals, is that a new era of economic development and growth is about to be begin. In September last year, Tanzania announced that it would start construction of the $3 billion Mchuchuma coal and iron ore mines and the Mchuchuma power station, a 600 MW coal-fired power plant this year. Located 900 km south-west of Dar es Salaam, the new power station will go a long way to easing the frequent electricity blackouts that plague East Africa’s second biggest economy, due to supply shortfalls.

why invest in tanzania?

Tanzania is the fourth largest gold producer in Africa after South Africa, Ghana and Mali. Gold production currently stands at roughly 40 tonnes a year, copper at 2 980 tonnes, silver at 10 tonnes, and diamond at 112 670 carats. In total, the mining sector contributes 2.8% to GDP each year but this could rise considerably in future years, with Business Monitor International (BMI) forecasting average annual growth in the sector of 7.7% between 2011 and 2015. BMI also predicts a doubling in value of the sector between 2010 and 2015, from $0.64 billion to $1.28 billion.

Minerals that have been identified in Tanzania include gold, iron ore, nickel, copper, cobalt, silver, diamond, tanzanite,

With this, the obvious constraints on economic growth will be greatly reduced.

While the Mchuchuma coal mine will complement Tanzania’s other two coal mines, used mainly for power generation, these will, together, form part of the country’s broader energy strategy. In addition, the recent big natural gas find off its southern coast will also be exploited. Collectively, this will open up a number of other mining opportunities.

The $3 billion deal with Chinese company Sichuan Hongda, signed in 2011, will see $1.3 billion spent on developing the Mchuchuma coal mine, which has coal reserves of 526 million tonnes, and the power station.

The iron ore mine will cost $1.7 billion.

Mchuchuma has reserves of 1.2 billion tonnes of iron ore. Enabling legislation was passed in 2010 whereby the Tanzaruby, garnet, limestone, soda ash, gypsum, nian government, through the Nationsalt, phosphate, coal, uranium, gravel, al Development Corporation (NDC), sand, and dimension stones. Legislation governing the industry today is the 1997 would be allowed to own a stake in Mineral Policy, the 1998 Mineral Act, and strategic mining projects. the 2010 Mineral Act, which can be found As such, the government plans to on the website for the Parliament of raise its stake in the Mchuchuma venTanzania (http://mem.go.tz/mineral-sector). ture to 49%, from the 20% originalThe country is politically stable, and ly envisaged. Abel Ngapemba, spokespeaceful with strong government support man for the NDC, indicated that the for mining investment. It has a globally projects will be completed in 2018/19. competitive tax and regulatory regime for With one thing leading to another, mining investors, and an accelerated and Ngapemba added that the NDC had resimplified process of handling investment proposals. The country has technically ceived bids for a separate project aimed trained people in various disciplines at building the country’s first soda ash associated with mining and there is an extraction plant, which would be capaabundant supply of labour that is peaceful, ble of producing around one million free of confrontations, ethnic strife, and tonnes a year. However, conservationlabour disputes. Tanzania has a wellists have said the project could harm established mining services industry. flamingo populations in Tanzania’s In sid e M in in g 0 5 | 2015 15

commodity: coal

Realising possibilities...

Kapiri Mposhi to Dar es Salaam Tanzania and Zambia, appreciating that wellmaintained transport infrastructure is critical to sustainable economic development, are investing an additional $80 million to bail out a jointly owned loss-making company railway firm, Tanzania-Zambia Railway Authority (Tazara), suffering from decades of underinvestment. The 1 860 km railway is a key route for copper exports from Zambia and neighbouring Democratic Republic of Congo to Tanzania’s main port of Dar es Salaam, and serves as an export conduit for Tanzania’s south-western coalfields. The railway firm has been hit by frequent work stoppages due to on-off strikes by workers over $9.2 million in unpaid salaries.

The Chinese-built railway has suffered from falling cargo traffic as well as years of inadequate investment by the two shareholders.

...from mine to market.

Resource Evaluation

Mine Planning

Mining & Mine Development

Materials Handling

Environment & Approvals

Transport to Market

Non-Process Infrastructure

Lake Natron and have demanded an independent environmental study. Ngapemba said an environmental assessment would be done before the project was implemented.

Even so, a number of other coal mines are in various stages of development. Collectively, Tanzania is targeting to produce at least 5.5 million tonnes of coal annually by 2020, some of which it hopes to supply to key markets like Kenya and Somalia.

From its 423 million tonne resource base in Mbalawala mine, in the Ngaka coal fields in southern Tanzania, Tancoal is mining and supplying coal to domestic and regional industrial markets that deal in steel, cement, lyme, gypsum, and chemicals. Kibo Mining has the Rukwa thermal coal deposit and the Pinewood coal fields.

Tancoal’s rich coal vein Mineral Processing

Tailings & Waste Management

Smelting & Refining

WorleyParsons adds value through our full scope of services from pit to port including studies, mine planning, impact assessments, permitting and approvals, project management, construction management and global procurement.

43

countries

166

offices

37,500

people

Ngaka coal mine, which is a Tancoal flagship project, is located in the vast coalfields of south-western Tanzania, 40 km east of Lake Nyasa, 650 km west of the deep water port of Mtwara, and 1 100 km south-west of the main trading port of Dar es Salaam.

The Ngaka coal fields comprise the Mbalawala sub basin, the Ngaka central basin and the Mbuyura/Mkapa sub basin. Work in the Mbalawala basin is the most advanced. Intra Energy Corporation (IEC) carried out substantial exploration throughout 2011 and 2012, with 188 cored holes (exploration, stratigraphic and pre-development) drilled. Hole depths averaged 94 m.

The initial drilling of the Mbalawala coal concession confirmed the presence of multiple seams of high-quality thermal coal averaging 4.9 m in thickness. The Mbuyura-Mkapa coal

www.worleyparsons.com

16 In sid e M in in g 0 5 | 2 0 1 5

commodity: coal

project concession has the potential to yield several hundred million tonnes of high-quality thermal coal.

Exploration, with a view to development, is taking place at the coal fields located near Songea. The IEC engaged JB Mining, an independent geological and mining services company, to complete a review of all geological data Black gold and resource evaluation.

JB Mining reported a downgrade of resources for the Mbalawala Block from 251 million tonnes JORC resource to 216 million tonnes (previously reported by Ravensgate Minerals Industry Consultants in 2010). Though, with Mbuyura/Mkapa, an overall increase in JORC resources of 69%, to 423 million tonnes, is reported. JB Mining’s evaluation covered a larger geological database, and the consultants applied different JORC criteria and categorised resources on an individual seam basis compared to Ravensgate’s total deposit basis. See Table 1.

This means the Ngaka coal mine reserves can serve the country for more than 100 years, producing electricity for commercial needs within and outside the country.

Tancoal’s CEO, Tarn Brereton, says there is more than enough coal to generate power and export to neighbouring countries.

Besides thermal coal, Ngaka also supplies the cement industry. Tancoal intends on increasing its output to support industrial development in Tanzania, with some supply into Kenya, Uganda, and Malawi. With economic development driving demand, Tancoal invested in the expansion of its Kitai stockpile area and increased its production to 360 000 tonnes per year from 200 000 tonnes per year.

During 2013/14, the industrial market in East Africa was about 400 000–450 000 tonnes per year, but with industrial and construction growth it is expected to reach one million tonnes per year by the end of 2015.

Along with Tancoal’s Ngaka, Mbalawala, Mbuyura, Mkapa and Songea coal fields, Tanzania is

developing the Ngaka power station to complement the Mchuchuma power station, and associated power transmission infrastructure, to increase the country’s electricity supply by 40%.

The Ngaka power station will be a 600 MW coal-fired power station in the Mbinga district in south-west Tanzania, close to the borders with Malawi and Mozambique. Once completed, the power station will supply more than 15% of Tanzania’s operating electricity supply. In a 2013 investor presentation, Intra Energy said 200 MW of the power station was in design and planned for operation in 2017.

The company also said it was in discussion with Tanzania for an additional 120 MW power station in the north of the country.

Under the terms of a joint venture agreement, the IEC, through is subsidiary Intra Energy Tanzania Limited (IETL), owns 70% of Tancoal, and Tanzania’s National Development Corporation (NDC) owns 30%. This is in accordance with an Act of

table 1 Tancoal’s JORC resource

Criteria

Ravensgate (July 2010)

JB Mining (October 2012)

Mbalawala block

Mbalawala block Mbuyura/Mkapa

Measured

139

39

16

Indicated

66

63

49

Inferred

46

114

142

Total

251

216

207

table 2 Raw coal analysis (air-dried basis)

Mkomolo Sample

Inherent moisture (%)

Ash (%)

Volatile matter (%)

Sulfur (%)

GCV (MJ/kg)

5528 Mkomolo from Nov 2014 – sample width: 1.09

8.00

35.00

24.30

3.87

17.53

5529 Mkomolo – sample width: 2.31

8.30

39.70

23.00

2.69

14.56

table 3 Basis float and sink coal analysis (air-dried), ‘washed coal’

Sample

Mass (g)

Yield (%)

Relative density

Inherent moisture (%)

Ash (%)

Volatile matter (%)

Sulfur (%)

GCV (MJ/kg)

5528 Mkomolo – sample width: 1.09

8 995.7

65.80

1.7

7.21

15.52

32.66

2.84

25.33

5529 Mkomolo – sample width: 2.31

6 346.2

52.30

F1.70

4.50

18.00

32.70

2.42

24.07

In sid e M in in g 0 5 | 2015 17

commodity: coal

table 4 Raw coal analysis (air-dried basis) Sample

Inherent Ash moisture (%) (%)

Volatile matter (%)

5523

6.80

39.00

22.80

2.36

15.40

5.80

50.50

20.00

7.05

11.95

5521

8.30

37.80

23.60

7.54

15.22

5520

7.70

39.60

22.80

6.84

15.00

Average

7.15

41.73

22.30

5.95

14.39

Sample

Mass

Yield

R.D.

Inherent Ash moisture (%) (%)

Volatile Sulfur (%) GCV matter (%) (MJ/kg)

5523

8 027.4

54.78

F1.70

4.80

27.78

29.02

1.70

21.18

5522

5 049.3

35.89

F1.70

4.09

24.17

29.93

3.07

22.68

5521

7 826.9

58.37

F1.70

5.79

18.90

33.39

4.15

23.32

5520

7 602.9

54.29

F1.70

7.31

18.65

31.95

3.79

23.43

Average

7 126.6

50.83

F1.70

5.62

22.27

31.16

3.17

22.63

the Tanzanian Parliament passed in 1962, which mandates the identification and development of economically viable projects in partnership with the private sector.

From its simple, low-cost ‘truck and shovel’ operation in 2011, when it started, to selling up to 250 000 tonnes per annum of unwashed coal to Tanzania’s domestic customers, where it is now, to its targeted commercial market 500 000 tonnes per year by the end of 2015, Tancoal is doing very well.

The Rukwa Coalfields The three coal deposits of Mkomolo, Namwele and Muze all lie within the Rukwa Coalfields. All three projects are controlled

by Edenville Energy (EDL) and sit in a cluster; Namwele and Mkomolo are adjacent, and Muze lies just 12 km to the east.

EDL has a 90% interest in these deposits through primary mining licences (PML) and the remaining 10% is held by a local partner on the project. EDL also controls the prospecting licences surrounding the PML, which have been obtained from the Tanzanian Ministry of Mines and Energy.

All three projects are located close to existing infrastructure.

Mkomolo and Namwele lie 25 km, by road,

GCV (MJ/kg)

5522

table 5 Basis float and sink coal analysis (air-dried)

TOP Multiple coal seams at Mkomolo

Sulfur (%)

to the north-east of the major regional centre of Sumbawanga. Sumbawanga has a population of 30 000, has banks, hotels, diesel, supermarket and regional government infrastructure. Muze is located close to the small village with which it shares its name, but does not have any of these services available.

Mkomolo Previously, sample 5528 from Mkomolo (reported December 16, 2014) was taken across a visually distinctive, near-surface coal seam. A second sample (5529) was taken across the same coal horizon but also included an upper layer of weathered coal and carbonaceous mudstone previously excluded from testing.

This second test was designed to determine the effect of bulk extraction of the entire coal horizon, as opposed to extraction of a visually defined coal seam.

The results, which include the weathered coal and carbonaceous mudstone, are very positive; the combined sample returned an energy value of 14.56 MJ/kg across a 2.31 m horizon, which includes the 1.1 m of 17.53 MJ/kg coal previously reported for sample 5528. These sample results illustrate that coal measures that include weathered material could contain

sufficient energy value to add tonnage, without significant reduction in calorific value, to the near surface coal seams with the potential to improve project economics. See Table 2 and Table 3.

Namwele

Four test pits were excavated at Namwele to expose the near-surface coal seam, better defining the coal that could be extracted in the initial stage of mining operations. For near-surface coal seams, test pitting is the most common, efficient and effective way of gathering data, not only quicker and less costly than a drill programme, but also allowing a specific coal seam to be exposed, examined and sampled more thoroughly.

The excavation and sampling work was carried out by Edenville personnel with full quality control processes and procedures in place.

This near-surface coal seam has an average thickness of 2.0 m and was sampled to a maximum depth from surface of 4.0 m, with an average depth from surface of 2.56 m. The four test pits were distributed along a total strike length of approximately 870 m through the Namwele deposit.

See Table 4. The results indicate high-quality, near-surface coal is available in the Namwele area.

The utilisation of selective mining techniques to extract this coal may bring improvements in the quality of available feedstock for a thermal power station, and also provides the basis for the detailed investigation into the potential to sell higher-quality coal directly into the local and regional markets.

table 6 Basis float and sink coal analysis (air-dried), ‘washed coal’ Sample

Mass (g)

Yield (%)

Relative density

Inherent moisture (%)

Ash (%)

Volatile matter (%)

Sulfur (%) GVC (MJ/KG)

5530 Muze – sample width: 1.66

7 576.0

55.90

F1.70

5.10

23.20

32.40

5.87

18 Ins i de Mi n i n g 0 5 | 2 0 1 5

22.13

commodity: coal

a government-backed development zone and an area of significant energy-related activity. EDL’s projects have the potential for low-cost set-up to generate near-term positive cash flow.

The combination of shallow outcropping coals and an established local/regional industrial demand to facilitate cement, paper and textile production gives flexibility regarding size of initial operations and end user. The Rukwa Coalfields are strategically located near south-western Tanzania’s scheduled new power transmission corridor, linking the north and south of the country. All three projects lie within 10 km east of the proposed route for the corridor and are some 300 km from the next nearest source of coal at Kwira. Should the corridor be built, the clustered nature of Edenville’s three projects could potentially allow flexibility in production to satisfy both industrial and power production requirements.

Wrapping up

Muze A single sample was taken at Muze, through a coal seam with a thickness of 1.66 m, exposed in a stream cutting at surface. The Muze coal sample gave a raw energy value of 15.26 MJ/kg, 50% higher than previous estimates for the deposit as a whole. A simple wash process, to a relative density of 1.7, increased the energy value to 22.13 MJ/kg, with a yield of 55%.

Mirroring the situation at Mkomolo and Namwele, the results from Muze indicate the uppermost seam is of a quality sufficient to supply coal to a coal-fired power plant, with improved project economics due to increased energy value. The sulfur content in this sample was high, at approximately 7% raw value. However, this was known to be a

high-sulfur pocket and the sample location was selected due to its ease of access and existing outcrop. The average sulfur level from drilling work in the 2013 Resource Report indicated average levels of sulfur below 3% and this is considered to be more representative of the Muze deposit as a whole.

Rufus Short, CEO of Edenville Energy, commented, “This latest set of results concludes the current test work programme.

We are very pleased with the results from the test pit samples at our Rukwa deposit and consider the values in all pits to both confirm commercial grade coal near to surface and to indicate significant upside potential for the deposit as a whole.”

See Table 6.

The Rukwa region is currently dependent on electricity imported across the border from Zambia. The Rukwa Coalfields have strong political support and are located in the Mtwara Development Corridor. This is

Tanzania’s interconnected electricity grid has an installed capacity of 841 MW, of which 33.2% is fossil fuels based. With the development of its coal fields and planned thermal coal power stations, more than doubling its current megawatt capacity, Tanzania seems set on the road to economic development through industrialisation and technology adoption, all of which will be made possible through electricity. This is especially important given that Tanzania is ranked 164 out of 186 countries in terms of GDP per capita. A new future awaits, made possible by Tanzania’s black gold – coal.

BELOW Mine haul truck at Rukwa BOTTOM Rukwa's conveyor system

In sid e M in in g 0 5 | 2015 19

pipes, pumps & valves

USEFUL ALTERNATIVE

Mine water disposal Mines in Mpumalanga province produce vast quantities of mine water.

The question is what to do with it? Dr Danie Vermeulen of the University of the Free State provides an alternative solution.

I

n looking at operation and monitoring guidelines, and the development of a screening tool for irrigating coal mine water in the Mpumalanga province, it was predicted, almost a decade ago, that vast volumes of impacted mine water would be produced by mining activities in the Mpumalanga coalfields of South Africa. Irrigation is a

Major water pollutants • Disease­-causing agents (e.g. bacteria, viruses, protozoa and parasitic worms) that can enter sewage systems and untreated waste.

• Oxygen­-demanding wastes that can be decomposed by oxygen­requiring bacteria. When large populations of decomposing bacteria are converting these wastes it can deplete oxygen levels in the water. This causes other organisms in the water, such as fish, to die.

• Water­-soluble inorganic pollutants such as acids, salts and toxic metals.

Large quantities of these compounds will make water unfit to drink and will cause the death of aquatic life.

Another class of water pollutants are nutrients; they are water­soluble nitrates and phosphates that cause excessive growth of algae and other water plants, which deplete the water’s oxygen supply. This kills fish and, when found in drinking water, can kill young children.

• Organic compounds such as oil, plastics and pesticides, which are harmful to humans and all plants and animals in the water. A very

20 Ins i de Mi n i n g 0 5 | 2 0 1 5

dangerous category is suspended sediment, because it causes depletion in the water’s light absorption and the particles spread dangerous compounds such as pesticides through the water.

• Finally, water­-soluble radioactive compounds that can cause cancer, birth

Figure 1 Upper Group 2 chromitite layers as seen on the western wall of the shaft (b) footwall norite defects and genetic damage. Thus, they are, perhaps, the most dangerous water pollutants.

pipes, pumps & valves

and the associated operational and moninovel approach to the disposal and utilisoils. These sites range from sandy soils toring guidelines that should be followed. sation of mine water, under the correct to very clayey soils. The results indicate These have been based on the findings conditions (preferably treated in some that many of the soils have considerable from their study, the fundamental conway prior to disposal). The significance attenuation capacities and that, over the siderations of mine-water irrigation, the of their findings lies in the versatility of period of irrigation, a large proportion of regulatory environment and, as far as irrigation. Communities that often have the salts are contained in the upper porpossible, the practical implementation of very few other resources can utilise mine tions of the unsaturated zones below each mine-water irrigation as part of optimal water to generate livelihoods. irrigation pivot. The volumes and quality mine-water management.

Research over a period In an attempt to standardise of more than 10 years has The potential environmental decision-making regarding mine shown that this water can water irrigation, the criteria, be used successfully for the impact of excess mine water data, rules and fundamentals irrigation for a range of is of great concern in a waterdiscussed have been combined in crops. The potential environa user-friendly tool, called GIMI mental impact of this excess scarce country like South Africa (Groundwater Impacts from water is of great concern in Minewater Irrigation). This tool a water-scarce country like should assist in the practical implemenSouth Africa. There is, however, continuof water leaching through to the aquifers tation of mine water irrigation as part of ing concern from the local regulators rehave been quantified at each site. From optimal mine water management. garding the long-term impact that largethese data, mixing ratios were calculated scale mine water irrigation may have on in order to determine the effect of the irgroundwater quality and quantity. rigation water on the underlying aquifers.

For more information: Detailed research has been undertaken One of the outcomes from this study VermeulenD.SCI@ufs.ac.za over the past number of years on both was to define the conditions under which and/or download the paper from: undisturbed soils and in coal-mining mine-water irrigation can be implemented, www.ajol.info/index.php/wsa/article/view/76796 In sid e M in in g 0 5 | 2015 21

Environmental Technology Forum Africa

IFAT Environmental Technology Forum Africa September 15-18, 2015 Johannesburg Expo Centre, South Africa Water, Sewage, Refuse and Recycling Solutions for the Mining and Construction Industry

www.ifatforum-africa.com Be part of Africa’s premier Environmental Technology Forum

FREE ENTRANCE FOR ONLINE REGISTRATIONS:

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pipes, pumps & valves

Mine dewatering to ensure safety A new R250 million water treatment plant at the Matla coal mine, operated by Exxaro Resources in Mpumalanga, is set to reduce the safety risk posed by large quantities of water that have filled mined-out underground cavities while simultaneously benefiting the environment and local water users. workings from the surface, leading to flooding risks – both to the safety of workers and to the surrounding environment, which could be impacted by the contaminated water should this water be released back to the surface without prior treatment.

Following engagement with the Departments of Water and Sanitation, Environmental Affairs and Mineral Resources, The Matla colliery is situated some 20 km west of Kriel Exxaro mapped out a in Mpumalanga, South Africa. This mining complex sustainable solution to comprises three mines producing 14 Mtpa of thermal coal the underground water, and has a workforce of over 2500 permanent employees which is centred on a and contractors. It is a fully mechanised underground state-of-the-art water mine, employing continuous mining and shortwall treatment plant. The methods. The thermal coal is supplied to Eskom’s Matla power station in the terms of a cost-plus agreement, treatment entails unreviewed annually, with a variable return payable by derground water being Eskom for any excess tonnage produced. The mine has a pumped to the surface coal reserve base of 297.3 Mt and a resource of 41.7 Mt. where it undergoes comprehensive treatment using innovative filtration processes he facility, which will treat to remove contaminants and purify the 10 Mℓ per day, forms part of Exxwater. The water treatment plant will treat aro’s holistic group-wide water 10 Mℓ per day and, of this, some 6.5 Mℓ will management strategy, geared to be discharged to the Olifants River while the entrench responsible and sustainable water remainder will be used in the Matla operamanagement. As part of its water managetions, or for potable water needs at the mine. ment strategy, Exxaro manages its water Expected immediate benefits are that, by stewardship through reduction, reuse and actively managing and limiting the volume recycling of water, proactively responding to of water that is underground, Matla will have water-related risks, minimising impacts and improved the safety levels of its employees ensuring operations use water efficiently and the overall underground working enviand in the best interests of the company, as ronment; it will have reduced its daily intake well as all other users and the environment. of fresh water, thus reducing its water footThe Matla underground mining operations print by requiring a lower quantity of water experience significant water ingress into the

Matla coal mine

T

22 Ins i de Mi n i n g 0 5 | 2 0 1 5

supplies; and the clean water discharged into the Olifants River will provide an additional volume of high quality water available for use by downstream farmers and other users. “Water is a strategic natural resource in South Africa and it is our duty to ensure that we reduce the impact of our mining activities on this precious resource,” said Exxaro’s CEO, Sipho Nkosi.

“We are committed to protecting and improving water quality by ensuring the water we discharge is of the same or better quality than the original consumption. The Matla water treatment plant is a prime example of this approach and is one of three water treatment plants in the Mpumalanga region which are part of our long-term water management strategy,” he concluded.

TOP LEFT The reverse osmosis system BELOW Mellis Walker, Exxaro, and Stanford Macevele, deputy director for the Department of Water and Sanitation.

pipes, pumps & valves

Water everywhere but not a drop to drink

I

n the past, many mills were powered by water. Since drive motors have become prevalent, water is spared. Because Loesche employees often travel to distant countries, we know that clean water is scarce in many parts of the world and is a luxury.

As a company operating internationally, Loesche takes its responsibilities seriously and likes to give something back to the people in these countries as part of a corporate social responsibility programme. For this reason, Loesche has been supporting the non-profit organisation Charity: Water. Why? Diseases from unsafe water and lack of basic sanitation kill more people every year than all forms of violence, including war. Children are especially vulnerable, as their bodies aren’t strong enough to fight diarrhoea, dysentery, and other illnesses. In fact, 90% of the 30 000 deaths that occur every week from unsafe water and unhygienic living conditions are in children under five years old.

The World Health Organisation reports that over 3.6% of the global disease burden can be prevented simply by improving water supply, sanitation, and hygiene. In Africa alone, people spend 40 billion hours every year walking for water. Women and children usually bear

the burden of water collection, walking miles to the nearest source, which is unprotected and likely contaminated.

Feeding the world takes up to 90% of our freshwater withdrawals.

When a water project is built in a community, members can often use the new water source to grow small gardens near their homes and secure their own food supply. Self-sufficient households are less affected by conflict, famine or inadequate government services. In most rural communities worldwide, women and young girls are responsible for walking to collect water for their families. Building a water project nearby can give women the freedom to pursue an education or earn extra income.

Water committees are often the first chance for women to step into elected leadership roles.

By 2050, the world’s population is estimated to grow by three billion and 90% of that number will be in the developing world. Unless sustainable water solutions are scaled fast, regions already stressed for water sources will be over

capacity. Loesche’s first engagement in Africa was a water well in the Chiphwafu village in the East African country of Malawi. The well, built with the support of Loesche, provides the village community year-round access to clean drinking water that is free of pathogens and pollutants.

Alongside the construction of the well, the people in the village have been taught about safe and sustainable ways to use water. Of Malawi’s 15.9 million inhabitants, around three million have no access to clean water and 92% have no access to sanitation facilities. With more than 800 million people in the world not having clean water, the challenges, for all of us, are clear. We need your help.

For more information about Charity Water: www.charitywater.org

BELOW Loesche is installing hand pumps in Malawian villages

In sid e M in in g 0 5 | 2015 23

MILLING & CLASSIFICATION IS OUR BUSINESS E V E N 1 0 0 Y E A R S O F B E I N G A N I N N O V AT O R A N D

EVERY DAY

FROM INVENTING BETTER SOLUTIONS

Are you looking for cost-effective size-reduction and classification of ores, industrial minerals and concentrates?

Contact Loesche SA to find out the advantages of the Loesche Grinding System for your beneficiation process.

Tel: +27 (0)11 482 2933 | Fax: +27 (0)11 482 2940 | Email: umeyer@loeschesa.co.za | Web: www.loesche.com

Loesche six roller Mill

MARKET LEADER DOES NOT KEEP US

pipes, pumps & valves

In the pink is not always good Water and human health are precious. In manganese mining, the former can be used to preserve the latter, but at what cost, and with what effect? Solving the problem was a challenge for open-pit mines in the southern Kalahari. By Tony Stone

1

I

n terms of world supply, South Africa accounts for approximately 75% of identified manganese resources.

These resources occur mostly in the Kalahari manganese field contained within sediments of the Hotazel Formation of Griqualand West in the Northern Cape.

Manganese is a pinkish-grey, chemically active element used in steelmaking.

As with all things, too much of something usually turns out bad. In humans, chronic manganese poisoning may result from prolonged inhalation of dust and fumes, affecting the respiratory tract and the brain. Symptoms of manganese poisoning are: hallucinations, forgetfulness, languor, sleepiness, weakness, emotional disturbances, spastic gait, recurring leg cramps, paralysis, and nerve damage. It can also cause Parkinson’s disease, lung embolism, pneumonia, and various forms of cancer.

South Africa’s health, safety and environmental legislation, standards and regulations govern the occurrence and

24 Insi de Mi ni ng 0 5 | 2 0 1 5

emission levels of manganese dust in the workplace. Among these regulations are: • SANS 1929:2005 • Mine Health and Safety Act of 1997 • OSH Act • National Environmental Management: Air Quality Act, Act No. 39 of 2004.

Running an open-pit manganese mine, along with the necessary haul roads, creates a continuous problem with regard to dust suppression. It is a constant health and environmental concern for mine management. The traditional method of dust suppression involves the use of water sprayed on roads, which has the effect of dust binding, but, with the heat, water evaporates. This requires spraying roads at least five times per day. At 85 000 ℓ per trip, this amounts to 425 000 ℓ per day or 12 750 000 ℓ per month. In a water-scarce area such as the Kalahari, this presents its own set of problems.

In addition, running a water cart large enough for the job costs a considerable amount of money. At one mine in the

Sishen area, I-CAT Environmental Solutions (I-CAT), a company specialising in dust control, was called in to solve the problem. It was agreed that a study would be undertaken to determine the efficacy of I-CAT’s products on typical mine haul roads when compared to using only water for dust suppression.

The study also set out to determine the primary and secondary costs associated with I-CAT’s products application as a dust suppressant. In order to execute the study, a section of road that was representative of an average used haulage road was chosen. This road carried all types of traffic present at the mine.

In addition to this, the treatment methods, water-only and water plus I-CAT’s RDC 20 (for temporary and secondary roads), needed to be applied to the same stretch of road (on different sections) simultaneously, in order to expose all scenarios to the same road composition, traffic and ambient conditions. The water-only method was used as the baseline, or

pipes, pumps & valves

table 1 Study results

Outcome

Measure

(Using RDC 20)

Application frequency (total number of applications for the study period)

50.0% less

Water usage (actual water usage figures over the study period)

50.2% less

Dust fall (actual figures from dust bucket tests (average per bucket in each section for the study period))

53.8% less

pDR readings (average max figures of all readings during the study,taken at each section when vehicles passed)

47.3% less

Vehicle running costs (actual cost to treat each section for the duration of the study)

50.0% less

Fuel usage (actual usage to treat each section for the duration of the study)

53.6% less

Carbon footprint (calculated using fuel usage figures)

53.6% less

Note: The study report was written by Prof Jan JL du Plessis of the University of Pretoria.

control, for the study. During the course of the study, all conditions were carefully monitored. Data was gathered on vehicle movement, dust fallout and frequency of water or product application, and analysed by an independent contractor (detailed below). Measurements with a Personal Dust pDR were taken to determine real-time dust concentrations next to the test sections.

From the study, it is clear that the use of RDC 20 results in an almost twofold improvement in every aspect that was considered, including a reduction in dust fallout, fuel usage, water usage and the associated carbon footprint. The net financial effect of RDC 20 use for the test scenarios was that a saving of 3.22 cents per m2 treated (30% lower cost) was achieved resulting in a potential daily saving of R32 200 (or R978 075 per month) when a total area of 1 million m2 is treated.

The outcome of the study was that the water plus RDC 20 method outperformed the water-only method as a dust suppressant. Besides estimated savings of nearly a million rand per month, if the results are applied to the actual area that needs dust suppression (currently estimated at 5.2 million m2), the water saving amounts to 15 683 m3 per day, or 470 516 m3 per month and 5 724 295 m3 per year. Without a doubt, this is a winning solution.

2

3 1

Loading a haul truck

2

A Sishen mine covered by red dust

3

pDR measurements at the different sections

4

A Caterpillar 785c water cart

4 In sid e M in in g 0 5 | 2015 25

• Dust Suppression • Water Purification

ENVIRONMENTAL S

O

L

U

T

I

O

N

S

• Environmental Services • Fire Solutions

+27 (0)12 349 1441 www.i-cat.co.za info@i-cat.co.za

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Engineering Growth through Infrastructure Modern infrastructure is the key to economic growth, job creation and raising living standards and the quality of life.

Kaytech has the products and professional engineering support to meet the needs of your specific infrastructural project.

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Ins i de& Drainage Mi n i n g• Separation 0 4 | 2 0 1 5• Road Maintenance & Rehabilitation • Water & Waste Containment • Erosion Control • Reinforcement 26 Filtration

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pipes, pumps & valves

Geosynthetics

in mining The use of geosynthetics in civil engineering applications is a common occurrence around the world. But, for mining, it took a major disaster to raise interest in the application of these polymerics.

O

n 4 August 2014, a major mining disaster began in the Cariboo region of central British Columbia in Canada.

A breach in the wall of Imperial Metals’ Mount Polley copper and gold mine tailings dam released years of waste into Polley Lake. By the time it ended on 8 August 2014, the spill had flooded Polley Lake, its outflow, Hazeltine Creek, and continued into nearby Quesnel Lake and Cariboo Creek. The 4 km3 tailings dam was empty.

Tests of the polluted lakes showed elevated levels of selenium, arsenic, and other metals similar to tests before the disaster.

The cause of the dam break was investigated. The final report published on 31 January 2015 stated that a “failure in the foundation embankment was the cause.”

However, Imperial Metals was known to be operating the pond beyond its capacity since as early as 2011.

Even so, merely a month after the disaster, the first ever Geosynthetics Mining Solutions Conference was held in Vancouver, Canada. In looking at the main points of discussion, we ask whether the mining industry is ready to take the application of geosynthetic technologies in mining to the next level. Obviously, the challenge for engineers is to understand the potential, choose the appropriate products and build mining structures that are cost-effective yet incorporate the use of geosynthetics.

Successful deployment of this technology will be based on knowledge, calculations and judgment. To assist, we explain what geosynthetics are, and how this technology is used. Man-made polymeric products (in sheet form), geosynthetics are used to solve engineering problems, particularly

in stabilising terrain. These include geotextiles, which are textiles consisting of synthetic fibres rather than natural ones such as cotton, wool, or silk. This makes geotextiles less susceptible to bio-degradation. Geotextiles are porous to allow liquid flow across their manufactured plane and also within their thickness, but to a widely varying degree. There are at least 100 specific application areas for geotextiles that have been developed. However, the fabric always performs at least one of four discrete functions: separation, reinforcement, filtration, and/or drainage.

Geogrids are polymers formed into a very open, grid-like configuration, i.e. they have large apertures between individual ribs in the transverse and longitudinal directions. Geogrids are either (a) stretched in one, two or three directions for improved physical properties, (b) made on weaving or knitting machinery by standard textile

manufacturing methods, or (c) made by laser or by ultrasonically bonding rods or straps together. There are many specific application areas, but geogrids function almost exclusively as reinforcement materials. Geomembranes’ relatively thin, impervious sheets of polymeric material are used primarily for linings and covers of liquid- or solid-storage facilities. This includes all types of landfills, surface impoundments, canals, and other containment facilities. Thus, the primary function is always containment as a liquid and/or vapour barrier. The range of applications, however, is great and, in addition to the environmental area, applications are rapidly growing in geotechnical, transportation, hydraulic, and private development engineering such as heap leach mining.

Geosynthetic clay liners, or GCLs are rolls of factory-fabricated, thin-layered bentonite clay sandwiched between two geotextiles or bonded to a geomembrane. Structural integrity of the subsequent composite is obtained by needle-punching, stitching or adhesive bonding. GCLs are used as a composite component beneath a geomembrane or by themselves in geo-environmental and containment applications, as well as in transportation, geotechnical, hydraulic, and many private development applications. Geocomposites consist of a combination of geotextiles, geogrids, geonets and/or geomembranes in a factory-fabricated unit. Major applications encompass separation, reinforcement, filtration, drainage, and containment.

For a more detailed explanation and advice on the uses of geosynthetics in mining, consult Kaytech Engineered Fabrics at www.kaytech.co.za.

Mount Polley tailings dam

In sid e M in in g 0 5 | 2015 27

Stocking up on the right solutions: KSB spare parts service KSB stands for outstanding technical expertise and innovative solutions. Whether our customers need to transport fluids or solids, KSB‘s range of tailored spare parts services ensures their systems always work reliably and economically. KSB Service: fast and efficient – also available for products from other manufacturers. Benefit from our ground-breaking technology, expert consulting and comprehensive customer care.

Find out how KSB can help your company on the path to success – when it comes to innovative ideas, we have plenty in stock. www.ksb.com

Our technology. Your success.

Pumps Valves Service n

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pipes, pumps & valves

A lesson from Mexico Mexico City is repeatedly threatened by large volumes of water. The 20 million residents of this metropolis are being helped in their fight against floods by 20 submersible motor pumps, pumps which can play an important role in mining.

G

enrich Altshuller, the Soviet engineer, inventor and scientist who created the theory of inventive problem solving, better known by its Russia acronym TRIZ, once said, “Always look elsewhere for a solution before you invent your own, as it is most likely that someone else has had the same problem as you and has already solved it.” And he is quite right.

El Caracol (the snail) is the name of the combined wastewater and stormwater pumping station in which the 20 giant submersible motor pumps from KSB operate.

In June 2013, the president of Mexico, Enrique Peña Nieto, opened El Caracol in Ecatepec de Morelos, Estado de México.

Since then, 20 pumps have been protecting Mexico City against flooding.

Why is Mexico City so threatened by water? The ground on which the metropolis stands has sunk considerably over the course of many years. This is mainly due to the city being built in a basin that is surrounded by high mountains. The once plentiful groundwater has been totally overused by the city’s 20 million inhabitants,

leaving the city to sink by up to 40 cm per year. The result of this is that the most important natural drainage arm, the gran canal del desagüe, is now lacking the necessary gradients, at certain points, needed to reliably divert the masses of water coming off the mountains during the rainy season between August and October. The gran canal originally had a capacity of 80 m3 per second, but by 2007 this figure had dropped to just 15 m3 per second. Since then, huge efforts have been made to raise the drainage capacity back up to 45 m3 per second.

However, this was not enough to prevent flooding in the city during periods of heavy rainfall, particularly in the east.

Something completely new was required that would also accommodate the rapid growth of this megacity.

The national water authority decided to build an underground drainage tunnel with a capacity of 150 m3 per second, the TEO (Túnel Emisor Oriente). The first 10 km of the 62 km TEO are now in operation, with the balance due to be operational in 2015. At the end of the first section, the KSB pumps raise up to 40 m3 of water per

second to a height from which it can simply flow under the force of gravity.

The 20 submersible pumps are some of the biggest of their kind that the pump manufacturer has ever produced. Each unit has a drive rating of 1 150 kW and weighs around 14 tonnes. KSB developed and produced the pumps and their motors in Germany. The pump sets were then transported by sea to Mexico, where they were installed by a German installation coordinator and a team from KSB Mexico.

Johannesburg is currently being threatened by rising mine water. East Rand Propriety Mines has maintained the water level at 1 200 m below the surface, pumping 40 million litres of water every day from below ground. This, however, cannot continue indefinitely. The government has just 20 months in which to put the infrastructure in place to deal with acid mine drainage in the Witwatersrand. What will they do?

1

A flooded Mexico City

2

The El Caracol tunnel

3

T he two El Caracol pump sumps – each contains 10 KSB submersible pumps

1

2

3 In sid e M in in g 0 5 4 | 2015 29

MINING SERVICES

Capacity and capability

I

Coralynne & Associates +27 11 422 1949

n theory, preventative maintenance is the systematic inspection, detection and correction of incipient failures, either before they occur or before they develop into major defects. The primary goal of maintenance is to avoid or mitigate the consequences of failure of equipment, so as to prevent unnecessary and unplanned

in components. In a nutshell, preventative maintenance is not efficient. Predictive maintenance is designed to help determine the condition of in-service equipment in order to predict when maintenance should be performed. This is a more cost-effective approach and promises cost savings over routine or time-based preventive maintenance, as tasks are performed only when warranted. In the current subdued economic climate of the mining industry, a sharpened pencil MARTHINUSEN AND COUTTS - LEADERS IN ELECTRIC MOTOR AND POWER GENERATION is extremely important. The REPAIR, MAINTENANCE AND SPECIALISED MANUFACTURE. main promise of predictive maintenance is to allow for convenient scheduling of corrective maintenance, and to prevent unexpected equipment failures.

The key is the right information at the right time. By knowing which equipment needs maintenance, maintenance work can be better planned (spare parts, people, etc.) and what would have been unplanned stops are Large AC / DC Motors transformed into shorter, Small AC / DC Motors and fewer, planned stops, Traction & Flameproof Motors thus increasing plant availTransformers ability. Other potential advantages include increased Power Generation equipment lifetime, increased plant safety, fewer acON SITE SERVICES cidents with negative impact on environment, and optimised spare parts handling.

This is all well and good but, without the capacity and capabilities in place, preventative or predictive maintenance would be meaningless.

CUSTOMISED ELECTRICAL Again, in reality, because of AND MECHANICAL DESIGN the costs involved, maintaining a permanent in-house capacity and capability is not always financially optimal.

Thus, establishing an optimum balance between internal and external capacities and capabilities is a far more sensible approach. However, your choice of external service provider is critical. stoppages in production. The ideal preventive maintenance programme would prevent all equipment failure before it occurs. In reality, without proactive supervision, preventative maintenance breeds laziness and the taking of short-cuts. It is easier to simply replace a component, whether it needs replacing or not. This also fails to detect early failure

Marthinusen & Coutts Your Assets. Your Needs. Your Service Partner.

A division of ACTOM (Pty) Ltd Tel: +27 (0)11 607 170 0

www.mandc.co.za

commercial@mandc.co.za

AFRICA’S LEADER In MInInG Infrastructure anD MIneraLs PrOcessInG

Dra Infrastructure has provided consulting civil engineering and structural design work for a wide range of sectors including mining, the commercial industry and government, for more than 20 years.

Our vision has been to deliver a complete service to clients anywhere in the world, building on our reputation for quality and safety and the ability to deliver on time and under budget.

With access to Dra’s international footprint, expertise and resources, we were able to expand our service offering to include infrastructure design, project management, project engineering and construction supervision, while at the same time expanding our team of professionals, allowing us to undertake larger and more complex projects.

Tel: +27 11 202 8600

draglobal.com

mineral processing

32 Ins i de Mi n i n g 0 5 | 2 0 1 5

Mineral processing

Small, perhaps insignificant, but important

T

hese days, mineral processing plants are designed for optimised performance. It’s synergy in motion. For those techno jockeys who appreciate the level of integration a complex modular system provides, it’s a symphony. In more practical terms, Eskom’s insatiable demand for coal requires coal mines to operate their DMS (dense material separation) systems efficiently so as to meet their contractual obligations. With loadshedding ever prevalent, a shortage of coal will simply switch the lights off.

Centrifugal pumps play a crucial role in a DMS system. And, within a centrifugal pump, a mechanical seal plays a crucial role.

Acting as a check valve – a type of valve that allows fluids to flow in one direction but closes automatically to prevent flow in the opposite direction (backflow) – and as a slider bearing, which is designed to provide free motion in one direction, the mechanical seal prevents liquid under pressure from leaking out of the pump, or from drawing air into the pump when under vacuum conditions.

Because of friction, the seal has an unpredictable lifespan. Therefore, preventative, planned maintenance is critical, with the seal of a centrifugal pump usually replaced a number of times during the pump’s lifetime. The liquid being pumped acts as a seal lubricant. This liquid usually infiltrates the mechanical seal between the contact faces of the primary and mating rings. While some of this liquid will find its way through to the atmosphere, it is so slight that it will only be noticed as corrosion of ‘build-up’ on the pump adapter. However, the type of pumped liquid will greatly affect seal lifespan. In a DMS system, the slurry is a combination of water, coal and magnetite, and the smaller particles tend to act as an abrasive, which is the number one enemy of a mechanical seal. These abrasive particles infiltrate with the liquid, between the seal faces, and grind away the carbon primary

ring, the normal shiny face of the primary ring, and mating ring. Where you have abrasion, you have kinetic energy and heat.

Excessive heat can damage the mechanical seal in two areas – the primary ring and the elastomer parts. The primary ring is made largely of carbon. Should the pump be operated without liquid – even for a very short period of time – the primary and mating ring faces are denied lubricant.

This causes the faces to become very hot; and the binder mixed with the carbon breaks down, turning the face of the primary ring into a dull black powder.

The O-ring (or cup) and flexible diaphragm of the seal are made of one of many types of rubber-like substances called elastomers.

The type of elastomeric material is selected to match the temperature limit and types of material being pumped. Should the temperature limit be exceeded, the diaphragm and O-ring will become hard and sometimes crack. The seal will then start to leak, with efficiencies being lost. The consequences of this problem are clear. Under normal conditions, seals wear out much faster than the other pump parts. Abrasives and excessive

Within the overall context of a mine, a mechanical seal may be a small, and perhaps insignificant, thing. Yet, when a mechanical seal fails, an entire processing plant may grind to a halt.

By tony stone

TOP A dense material separation system BELOW Centrifugal pump mechanical seals

heat greatly shorten the seal’s lifespan. For this reason, preventative, planned maintenance is critical. It puts you in control, and enables you to shut down the system when it is convenient and less disruptive to the production process. Given Eskom’s tight contractual requirements, failing to effectively manage this small, perhaps insignificant, yet critically important detail could seal your fate and cause you to lose out on a life-saving business contract.

Reference: ‘Mechanical seals in a centrifugal pump’, Harry Short, Advantage Engineering Systems

In sid e M in in g 0 5 | 2015 33

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– because the new Metso series of Mill Discharge slurry pumps encompass all the experience coupled with an understanding of today’s market needs and demands for improved sustained performance and lower cost. Specifically designed from its inception for mill circuit applications, the MDM hard metal and MDR rubber lined double adjusted slurry pumps offer sustained performance with maximum time between mill shutdowns.

Get in touch, and find out how we can help!

Metso is a leading process performance provider, with customers in the mining, oil and gas, and aggregates industries. Discover more at www.metso.com/pumps.

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Mineral processing

Optimising your

cone crusher Cone crushers are commonly used for secondary, tertiary and quaternary crushing duties. But, the question is, why use a cone crusher?

t

he design concept of the cone crusher is an effective and smart way of realising compressive crushing. A cone crusher also has a high level of aggregate production and is a reliable, mechanical means of liberating valuable minerals.

Two variations are available: standard and short head.

The chief difference between cone and gyratory or jaw crushers is the nearly parallel arrangement of the mantle and the cone at the discharge end (the choke) in the cone crusher. This is illustrated in Figure 1 with reduction ratios, in the following ranges, common for cone crushers: • 6:1–8:1 for secondary crushing • 4:1–6:1 for tertiary/quaternary crushing.

The reduction ratio determines the extent of the open-side setting (OSS), which transports the material, and the closed-side setting (CSS), which crushes the material. The size distribution of the products tends to be determined primarily by the CSS, since no particle can fall through during a single open-side period and all particles will experience at least one closed-side nip. The CSS is adjusted by screwing the bowl up or down. In a cone crusher, stone and rock are crushed with both single particle breakage (SPB) and inter particle breakage (IPB), as the material moves down through the chamber.

The relative amounts of IPB and SPB depends on factors such as the chamber design, crusher geometry, speed, CSS, and eccentric throw. The choke area, at the base of the cone where the material is discharged, determines the cone crusher’s capacity. The width of the choke area is determined by the setting of the eccentric throw (non-circular movement). By increasing the eccentric

throw and speed, greater volumes can be processed. However, the fines/product will be greater in size as the CSS is increased. This, in turn, will create flaky particles that will more easily find a way through the chamber.

Optimisation of your crusher product will depend on the extent and quality of your planning, sampling, analysis and tuning. To obtain the best results, run the crusher at different settings. Take at least one sample at each setting, bearing in mind that multiple samples are often useful. Record your findings for comparative analysis.

Remember to pay special attention to safety when taking samples! Ensure that the conveyor will not start by accident.

If you take single samples on each CSS

table 1 Resultant material characteristics of SBP and IBP Characteristic

SBP

IBP

Fines

Less

More

Shape

Flaky

Cubic

Force

Low

High

setting, the risk of getting inconsistent results might make the graph look strange. By using Microsoft Excel, you will be able to plot your results on a graph for better interpretation. Subjecting your crusher to performance management and optimising its settings, to get the best results, will increase profits.

figure 1 Crusher performance map (tonnes per hour)

figure 2 Crusher performance map (percentage)

In sid e M in in g 0 5 | 2015 35

mineral processing

36 Ins i de Mi n i n g 0 5 | 2 0 1 5

Mineral processing

Work smarter not harder A decline in ore grades simply means a loss of yield per tonne processed. Thus, to produce the equal yield, as at peak, more tonnage needs to be processed. This effectively increases costs. What is needed is good chemistry.

By tony stone

t

oday, in many mines, highyield ore bodies have been mined out, leaving only lower-yield, but still economically viable, ore bodies remaining. Even so, maximising the yield from these ore bodies requires some smart work, not harder work, which is all in the processing plant’s design and in the chemistry.

Typical ore processing In a nutshell, run-of-mine ore feeds into a primary crusher, thereafter into a secondary crusher before going into a ball or rod mill. From here it passes through a classifier, either to a conditioner or back to the mill for reprocessing. From the conditioner it moves to the rougher concentrate, with suitable material piped to the cleaner concentrate and tailings piped to the scavenger concentrate – for that last ditch attempt at recovering what little is left, if any. And, failing which, the tailings go to a thickener and on to a tailings dump. What is scavenged is sent back to the rougher concentrate, which feeds the cleaner concentrate. If necessary, it is piped from

ABOVE World-class chemical technology for the mining industry

the cleaner concentrate to the re-cleaner concentrate, and back to the cleaner concentrate before moving to the end-ofprocess thickener, filter and dryer before going on to the smelter or consumer. It is within this realm of ore processing that Senmin assists mines. As a manufacturer of high-quality reagents, which include primary and secondary collectors, depressants, flocculants and frothers for aluminium, coal, cobalt, copper, diamonds, gold, iron, molybdenum, nickel, phosphate, platinum, silver, titanium, uranium and zircon, and in applying the science of metallurgy more effectively, they maximise a mine’s mineral processing yield.

To this end, Senmin offers a full service model as part of its value added service, which may require additional equipment installation, especially with brown or greenfield projects. The purpose of this equipment is to optimise reagent make-up, dosing and application. The service includes:

• a full team of operators and a metallurgist on a 24/7 basis • total inventory management of reagents incorporating make-up • quality control and dosing of the reagents • first line maintenance • all SHE issues related to the handling of hazardous chemicals, including safety audits.

To ensure that reagents are made up and applied in a manner that both optimises usage and maximises the metallurgical performance, clearly defined key performance standards are defined and revised in consultation with the mine’s mineral processing plant personnel on a regular basis.

With Senmin doing what it does best, namely augmenting and improving process design and managing the safe handling and quality control of the reagents up to point of dosage, yields are improved. The bottom line is quite clear – increased profits.

In sid e M in in g 0 5 | 2015 37

INTRODUCING THE FINLAY DUAL POWER CRUSHING AND SCREENING RANGE

There are two crusher models in the Dual Power range: the J-1175 Dual Power and the C-1540 Dual Power, adding to the already available 694+ Dual Power. Bell is proud to introduce this market leading technology into Southern Africa which is backed by Bell Equipment’s strong reliable support.

J-1175

694+

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Dual Power crushers and screeners are electrically driven machines allowing the end user to run from the mains supply with the aim of giving significant savings on energy costs. These machines are also fitted with an on-board gen-set allowing the operator to move and use the machine where there is no electrical supply, giving them the flexibility and versatility of the current standard models.

C-1540

www.bellequipment.com

Mineral processing

Solving two problems

with one solution

Through the effective application of just one machine, in-pit screening of material now plays an important role in cutting production costs for a leading alluvial diamond miner.

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esides cutting costs, this machine, through its application, also contributes to continuous rehabilitation, a lack of which has been the downfall of many alluvial diamond miners. Schalk Steyn is a miner through and through. Having previously worked in both underground and surface mining, he founded his first business doing drilling and blasting, trenching, haul road maintenance and a host of related tasks, all in the mining environment. Then, in 1998, he decided to try his hand at diamond mining.

“We worked on many alluvial sites in the North West province and eventually ended up mining diamonds in the Central African Republic until we were relieved of all our possessions and equipment by Sudanese rebels. That was when I decided that, perhaps, things were better, and certainly safer, in South Africa and decided to focus my efforts on mining in my home country,” says Steyn.

He moved to the Northern Cape in 2002 where he mined low-grade middling gravels for, among others, the well-known TransHex Group.

Steyn explains, “This proved to be invaluable experience for us, as we learned more about local conditions and the value of what equipment could be used efficiently. This is also where we first encountered Finlay mobile screens. When I started Steyn Diamante in 2004, the first piece of equipment I bought was a Finlay 883 Screen, as I knew then that using this machine meant a lower production cost through effective screening

of the correct size of material.” Steyn Diamante has concentrated its efforts on three main sites along the eastern banks of the Orange River, between Douglas and Hopetown.

Terrace heights vary between 20 and 110 metres and, once the topsoil and overburden have been stripped off and stockpiled for later rehabilitation, the gravel thicknesses run between 0.5 m–6 m.

“Once we hit the diamond-bearing gravels, we put a Finlay Screen in the pit where it is fed by an excavator. This means that we screen out any oversized material right there, which is handled only once,” Steyn says.

The correctly sized material of 45 mm or less is loaded directly from the screen into an articulated dump truck (ADT) for hauling to the processing plant. This is done using the Finlay Screens’ extended belt conveyor at right angles that can be set at higher angles than conventional screens, thus easing loading into an ADT’s bin. Loading from this angled conveyor also creates a very tidy and full heaped load in the dump truck’s bin, which Steyn believes adds about 15% more loaded material than using an excavator as a loading tool would allow. The oversized material is moved from the screen using a front end loader and is used to form the base of rehabilitation areas.

“Our new Finlay 893 Screen outperforms any screen I know of, and handles between 500 t–600 t of run-of-mine material per hour, which gives us about 360 t of usable and correctly sized material per hour,” enthuses Steyn. Features such as a feed

hopper, big enough to be fed by a 70 t excavator, a steel apron belt feeder and honeycomb punch-plate system all add up to make this machine outperform any other screen they’ve owned or operated. In addition, fuel consumption of between 16 ℓ/h–18 ℓ/h does not break the bank.

“We’ve also been impressed by the Donaldson filtration system Finlay are using on the 893 Screen as it tells you when you should clean or replace air filters, a crucial part of preventative maintenance in our dusty environment. If you consider, though, what this machine does and at what work rate, its maintenance is minimal,” Steyn concludes. Having started small, Steyn Diamante has grown into the single biggest alluvial diamond miner on the Orange River and this is in no small way due to the company’s economical mining and rehabilitation methods.

TOP Steyn Diamante has owned 16 Finlay Screens, mostly 883 models but recently bought the bigger 893 models BELOW Schalk Steyn (left) of Steyn Diamante with Lyndon de Meillon (mine manager) and Eric van der Merwe (Bell Equipment sales representative)

In sid e M in in g 0 5 | 2015 39

technology

No challenge too tough The Athabasca oil sands, located in northern Alberta in Canada, contain the largest deposits of bitumen (heavy crude oil) in the world.

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n estimated 1.7 trillion barrels of oil, which is comparable to the world’s total proven reserves of conventional petroleum, are contained in these deposits, which consist of a mixture of crude bitumen (a semi-solid form of crude oil), silica sand, clay minerals, and water. Approximately 10% of these deposits, or about 170 billion barrels, are currently considered to be economically recoverable at today’s prices, making Canada’s total oil reserves the second largest in the world, after Saudi Arabia. This reserve has spawned numerous large-scale operations to recover and refine this oil.

When one of the largest producers in the Athabasca oil sands required a better solution for pumps that could handle mature fine tailings (MFT) and tailings dewatering, they turned to a trusted supplier for a solution. The operators were using dredges to pump the MFT; however, the cost to own and operate the dredges was prohibitive. Therefore, a more economical method to pump the MFT was needed. With a proven history in mine dewatering and other severe applications, Weir Minerals was able to come up with a viable and cost-effective solution for the problem – a solution that was rugged enough to handle the service.

A Multiflo barge unit was selected due to features such as: • heavy-duty mining construction • the unit is outfitted with a Warman 14MD heavy-duty dredge pump: - flow rate: 6 000 gpm (1 363 m3/h) - head: 100 ft (30 m) - pump: Warman 14MD - pump materials: high-chrome iron - drive: 550 hp diesel engine • automatic priming with run dry and snore capability • the pontoon was designed so that it could be ‘skidded’ around the mine site without the use of cranes • the unit could be used in other locations for dewatering • the unit could be customised to meet the specific needs of the client • economy and delivery of Multiflo unit versus a dredge unit.

Weir Minerals has been a leading supplier of pumps to the oil sands industry for many years, providing standard and engineered-to-order pumping solutions for even the toughest services.

Weir Minerals Multiflo has been manufacturing its mine dewatering pump range in Australia for over 30 years and has a large number of units in the Australian and Asian mining industries.

Fine tailings

This comprises a suspension of fine silts, clays, residual bitumen, and water derived from extraction of bitumen from oil sands using the traditional hot water extraction process. The remainder from the extraction process is pumped to tailings facilities where coarse sand settles out. The overflow is directed to a settling pond where the fine-grained portion slowly settles to yield a suspension of fine tailings. The fine tailings suspension is typically 85% water and 15% fine particles by volume.

Further dewatering of fine tailings occurs very slowly. When first discharged, the very-low-density material is referred to as thin fine tailings.

After a year or two, when the fine tailings have reached a solids content of about 30% (by mass), they are referred to as mature fine tailings. Settling occurs much more slowly after this point and the substance remains fluid-like for decades or centuries.

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2 IBC

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For more information contact us on +27 (0)11 9292600 Weir Minerals. Expertise where it counts. www.weirminerals.com Copyright © 2012, Weir Slurry Group, Inc. All rights reserved. WARMAN is a registered trademark of Weir Minerals Australia Ltd and Weir Group African IP Ltd; MULTIFLO is a registered trademarks of Weir Minerals Australia Ltd; FLOWAY is a registered trademark of Weir Floway Inc.; GEHO is a registered trademark of Weir Minerals Netherlands bv; WEIR is a registered trademark of Weir Engineering Services Ltd.

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