chapter 1

Plenary Presentations

Challenges in solid-liquid separation thickener

theory and applications

Fernando Concha Water Research Center for Agriculture and Mining, University of Concepción, Chile

ABSTRACT

Thickening development and innovation in the 20th Century occurred in two decades periods.

From 1900 to 1920, Dorr invented the continuous thickener and the first method of thickener design

was proposed by Coe & Clevenger. From 1920 to 1940, the operating variables of continuous

thickening were discovered by Comings at the University of Illinois. From 1940 to 1960, the first

theory of sedimentation was proposed by Kynch and several authors, Talmage and Fitch, Ysioka

and Hasset used this theory to develop new thickener design methods. From 1960 to 1980 Shannon

and Tory demonstrated that this theory applied exactly for the sedimentation for small rigid

spheres in water and Scott showed that it is not valid for flocculated suspensions. From 1970 to 1990

the phenomenological theory of thickening was developed based on the theory of mixtures. Papers

by Kos, Bascur, Thacker and Lavelle, Concha and Bascur, Concha and Barrientos, Auzeris, Buscal

and White, Landman, White and Buscal show the application of this theory to thickening and

Adorjan presented the first thickener design method based on this theory. In 1980s the

mathematical analysis and solutions of Kynch’s model for batch and continuous thickeners was

obtained by Bustos.

The new Century brought solution to the phenomenological thickening model which was applied

to thickener design, simulation and control. The method of thickener parameter determination was

improved by designing new laboratory and on-line instruments and advanced control strategies

was designed and validated in plants.

Structural thickener design produced improved feedwells and feed dilution mechanism, stronger

raking mechanism and different thickener shapes according to new ambient requirements, such as

high rate thickener and paste thickeners that increase the water recovery.

New challenges include better flocculation and advanced control strategies.

—

There is no full article associated with this abstract.

1

Lower operating costs through enterprise dynamic

performance management

Osvaldo Bascur

OSIsoft, USA

ABSTRACT

The Metals and Mining industries continue to be challenged by deflated commodity prices,

increased energy costs, decreased quantity / quality of raw materials, and expanded regulatory

requirements. In an effort to offset these headwinds, leaders in these industries are now starting to

adopt comprehensive information strategies to improve operational efficiency and business

performance. These strategies are resulting in competitive advantage and helping to move

operating locations down the commodity cost curve. Current information trends are enabling

collaboration, analysis, and action across competence centers to ensure corporate sustainability and

ongoing profitability.

The digital revolution has created a new focus for continuous process improvement and

innovations (SIX SIGMA in practice) —one that spans operations, service organization and also

customer interaction. With this expanded focus comes the need to improve processes more openly,

more iteratively and more collaboratively.

This presentation will share examples of how mineral processors have adopted new strategies such

as self-serve business intelligence, data mining, cloud computing and internal/external

collaboration. Mine to mill integration for grade recovery optimization, mine and mill asset

availability and reductions in operating costs examples will be presented.

—

There is no full article associated with this abstract.

2

Sustainability and public engagement in mining: The

role of engineers

Marcello Veiga and Christopher Tucker

Norman B. Keevil Institute of Mining Engineering, University of British Columbia, Canada

ABSTRACT

Social issues are increasingly recognized as significant inhibitors to mineral development projects.

Increasingly social risk is being recognized as a key factor determining the success of a mineral

investment. Groups opposed to a mine for social or political reasons often use environmental

impacts, real or perceived, to prevent mine development. These risk factors depend largely on

cultural perceptions of mining activities and must be understood as such in order to be

appropriately managed. A first step to addressing social issues is inclusive, transparent and

meaningful engagement of stakeholders. This process allows stakeholders to understand what the

other parties value in order to collectively establish a common currency for development and the

creation of mutual value. Expanding the scope of benefits and values a mine can bring is of

increasing importance to mining companies who typically consult outside specialists remote from

the mine site and late in the development timeline for this purpose. Training technical staff,

engineers and geologists, who make initial and ongoing contact with local interests, in a holistic

approach to mine development is crucial to successful and economic mineral development projects.

Further extending this conversation to the general public, media governments and non-

governmental organizations is a necessary step in developing a meaningful discourse on the benefit

of mining activities.

3

SOCIAL ISSUES IN MINING

The public often perceives mining operations as causing serious adverse problems to both

environmental and human health. Past examples of poor performance in handling environmental

and human rights issues linger in the social memory and haunt new mineral development

proposals. In such cases opponents to mineral development will often cite environmental issues

such as the potential legacy of pollution left by a mine, destruction of surrounding lands and forests,

water contamination and depletion, loss of access to recreational or traditional lands, noise, dust,

and excessive truck traffic.

Environmental impacts of most mining operations are localized and relatively small compared to

many other forms of human economic activity such as agriculture, forestry and urban settlement.

Nonetheless mining can negatively impact the environment especially if not well managed. More

frequently companies around the world are facing problems with local communities and

international environmental groups when implementing mining projects (Davis and Franks, 2011).

Environmental issues are often used to justify the opposition when in fact, there are larger

unresolved social and/or political problems or the initial approach of the mining company was not

well received by the communities. Typically a mining company limits the focus of their perception

and communication of community benefits to taxation revenues and job creation. The veracity of

this position is challenged in the notion of the resource curse (Auty, 1993) where it is argued that

countries endowed with great mineral or petroleum wealth do not see a corresponding increase in

the well-being of their people with the development of those resources. As with critics of aid

programs (Moyo, 2009) resource-rich countries often see their governance structures and

sovereignty challenged rather than strengthened. One rationale for the unsustainable extraction of

non-renewable resources is when this activity can support the development of sustainable and

sustaining improvements in other areas of human wealth. For example, sustainable mining,

considered by many to be an oxymoron can be used to describe the extraction of mineral resources

in a manner that contributes to long-lasting wealth or wellbeing.

Numerous levels of human organization may be considered for wealth creation. It is possible to

look at this globally, internationally or nationally. In the latter case, financial vehicles such as

Norway’s Sovereign Wealth Fund borne out of Norway’s North Sea oil extraction, can be used to

create last well-being among a people where inclusion boundaries are clear, in this case, citizenship

(Gjessing & Syse, 2007). At a provincial or state level similar vehicles exist such as the less

successful Alberta Heritage Fund designed to provide lasting benefit from the wealth created by

Tar Sands development in Canada or even the various credits issued by local taxation authorities

(Murphy 2013). At the regional, municipal and community level, where inclusion boundaries are

more porous it is more difficult to manage distribution of benefits from resource development. As

resources such as oil and gas or minerals are often more locally situated extending their benefits

locally makes sense. In this case it can make sense that the benefits rather than being financial in

nature are themselves local distributed such as infrastructure improvements or local quality of life

enhancements. The most effective level to create real improvements in human wellbeing is at the

community level where a community is defined as a local grouping of people with some

commonality in their strategies for meeting their needs. Many different types of communities

participate in non-sustainable practices in order to meet their needs and potentially all could

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improve their way of life while decreasing their dependency on imperiled resources whether those

resources are old growth forests, wild salmon, cheap oil, or high grade gold and copper deposits.

THE CHANGING ROLE OF THE ENGINEER

Engineers usually define the steps of a “Mining Project” using technical-economic parameters that

can be simplified in “8 Ds”:

1. Detection of geological anomalies

2. Discovery of the mineral deposit

3. Definition of the ore body to be mined

4. Design of the mine

5. Decision to go ahead with the project

6. Development of the mine

7. Depletion of the ore body

8. Decommissioning of the mine

This mnemonic sequence of “Ds” does not consider that quite often another “D” happens:

Deception, which is usually caused by the lack of an interdisciplinary approach or lack of

understanding of the socio-economic environment in which a mining project is implemented. In the

past, environmental and social issues were ignored or approached at the very end of a mining

project to fulfill legal exigencies. Many mining proposals have failed because mining companies did

not believe that it was their responsibility to deal with the local stakeholders in the early stages of a

project (Owen & Kemp 2012). The lack of social license to operate has been recently stressed as one

of the major hurdles for the mining companies to start a project (Moffat and Zhang, 2014). Even

when the company has their environmental permits, the public perception of the mine, associated

with hidden political interests, prevents the project realization. For example in the case of Infinito

Gold, in Costa Rica, a project that would have created a large number of jobs for the local

community in diversified activities but strong political players associated with international NGOs,

scared the local people alleging that tailing dam failures will “lead to water contamination and

landslides” (Evans, 2012). This is also the case of Marlin Mine in Guatemala where many

environmentalists believe that the population is vulnerable to cyanide spills, despite the total

destruction and regeneration of the cyanide used in the mine (Jaccard and Condon, 2013).

In 2014, in British Columbia, Canada, Taseko Mines had its New Prosperity project rejected for the

second time. First Nation leaders in the region opposed to the project alleging it would threaten the

environmental integrity of Fish Lake, a 1 km2 productive lake in the remote region of Cariboo-

Chilcotin. The project would generate around US$ 10 billion in taxes directly and indirectly had the

potential to generate 3000 new jobs. The Federal Government, through two Assessment Panels,

predicted environmental impacts for the lake (CEEAE, 2013). For the general public and

governments, the environmental argument was the main reason given for the project rejection, but

it seems secondary in the decision process as the First Nations regard the lake as sacred and the

relationship between company and First Nations degenerated upon the failure to establish a

working joint review panel (CEAA, 2013). All activities of the company to mitigate the

environmental impacts and to preserve the lake were not enough to bring the public opinion to

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their side. In this situation both parties, initially willing to do business, could not find a common

“currency” by which to create mutual value, resulting in a breakdown of the relationship.

The above examples illustrate the importance of effective early engagement with communities. As

technical people, such as geologists and engineers, are often the point of first (and ongoing) contact

it is imperative that they have an understanding of the social dimensions of their work. Frequently

social issues are delegated to social scientists hired as consultants to establish a strategy to deal with

the local communities. The plans may be well done but the execution will still be in the hands of

technical staff permanently present at the mining site. Rarely do engineers regard understanding

social factors as part of their professional capacity. They typically fail to understand the traditions,

cultures and idiosyncrasies of the local communities. This lack of understanding can lead to

roadblocks and demonstrations by local community members that effectively halt production and

ties up management leading to serious cost overruns (Davis and Franks, 2011).

Most mining engineers have perceived education on social issues related to natural resources as a

topic of secondary importance. Unfortunately, this is a common situation in the technical academic

world. Even now, when the mining industry is being monitored by media, stakeholders and non-

governmental organizations, few academics bring the socio-political context to the engineering

classrooms. The role of mining in promoting development and reducing poverty has been

challenged, since there is no clear indicator of success (Pegg, 2006). The most significant criticisms

relate to the attitudes and performance of the mining companies in the field.

Some engineers still believe that the misunderstanding between companies and communities must

be resolved with legal interventions or they simply apply the philanthropic approach of providing

immediate benefits to the locals. In first place, rural communities around the world typically have

little faith in political systems as their politicians only appear when there is an election. Rural

communities have been relatively isolated for centuries, without political clout and receiving few

benefits from central governments. This is the case with the town Paraupebas with 110,000

inhabitants in the Brazilian Amazon, near the Vale’s gigantic Carajás Project. Mining activities in

the Carajás Ore Distric are responsible for 70% of Parauapebas’ Gross Domestic Product. In 2000,

the municipal government received US $12 million from royalties of the iron-ore mining alone

which is a fraction of the taxes from all the mines in the region. Despite the high incomes of the

municipal government, about 44% of the total population lives below the poverty line, the infant

mortality is 30 deaths per 1,000 inhabitants per annum, hospitals have 1.6 beds per 1000 inhabitants

and various other indicators do not show much in the way of the benefits to the town from the

largest mining complex in the world (Costa, 2008). Clearly the wealth from the mines is not

distributed to the community. The lesson learned in many rural communities is: “the closer the

company is to the government, the farther they are from the local community.”

The main challenge of mining companies is to engage in equitable partnership with the impacted

community to create a sustainable relationship (Veiga et al, 2001). This is usually seen as a

secondary task to be left with a department of public relations. All technical staff in a mine must be

trained to participate in the community and engage the population in the decision process, even if

this is a very technical subject. It is not a matter of communication, but engagement.

PUBLIC ENGAGEMENT

Problems with local communities are not only caused by lack of planning of the companies.

Planning usually takes place in corporate headquarters remote from the mine site and in many

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cases the companies use local employees to implement their policies. In many cases, this is seen as a

communication problem, when in fact it is a lack of participation of the locals in the decision

process (Prno, 2013).

It is well established that mining companies have a legal duty to consult local communities.

However the term “consultation” does not ensure an open dialogue or a participatory process.

Social License to Operate describes a dynamic of engagement over and above legally bound

consultation that is necessary for a development to have the support of local communities.

Companies must account for their actions and the local communities and the general public require

transparency and inclusion in the decision making process. “Organizational accountability is based

on effective engagement with stakeholders” (Petersen & Bullock, 2005). The practice of hiding

mistakes from the local community is no longer accepted.

In communicating with local communities, engineers often use facts to explain their actions.

Different stakeholders come with different levels of understanding about how a mine is built and

operated. These different knowledge bases combined with different value systems produce

radically different perceptions about the process of mine development. The perceptions of the

communities, usually in rural areas with low education, cannot be resolved with a list of facts.

Technical facts may be obvious for engineers but not clear for the public. Demonstrating that you

are more knowledgeable, that you have the correct facts can even be more frustrating and

detrimental to the process of building trust and consensus. Facts are not very useful in dealing with

perceptions as they create a hierarchy in the debate and imply the superiority of the company. The

best way to deal with perceptions of the public and local communities, is to understand and attend

to the sources of perceptions (Fig. 1). This can encourage dialogue and shift attitudes about the

project.

An example of this is the most common argument presented by mining industry associations: “you

need mineral products, therefore you need mining.” While this is true and world consumption of

minerals is around 5 tonnes/person/a and in developed countries this can reach 20 to 50

tonnes/person/a and growing (Jones 1987) it is not a persuasive or compelling argument. Relying on

this line of reasoning further fails to look at deeper social and cultural resistance to mining activity.

With this tension unresolved we see play out in the media crude arguments for or against mining.

The reality is that mineral development is not only required but also desirable while also posing

risk and tradeoffs. Accepting that both perspectives are “true” allows a more sophisticated

conversation that can more effectively manage the costs and benefits of the activity.

Figure 1 Knowing the sources of perceptions is more important than facts

Perceptions Sources

Facts

- Cultural

- Religious

- Environmental

- Political

- Economic

- “Gossips”

Perceptions Sources

Facts

- Cultural

- Religious

- Environmental

- Political

- Economic

- “Gossips”

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A common public perception in developing countries is that foreign companies are extracting gold

to take back to their home countries. This perception has led to the belief that artisanal miners bring

much more benefits to the local communities than international mining companies. In fact, artisanal

miners generate more unskilled jobs but also generate much more pollution with poor management

of mercury, cyanide and tailings. Community expectations are awoken at the beginning of the

exploration phase especially with regards to job creation. During the project discovery,

development and implementation the community expectations fluctuate and can create conflicts

with the company expectations. Ian Thomson (2000, pers. comm.) developed the following graphic

to show the lack of syntony between the company and community expectations (Fig. 2). The simple

presence of drilling in the community can create high false expectations that the mining production

will start soon. The time lag of the mining industry can be as large as 10 years from exploration to

construction (Aboriginal Affairs and Northern Development Canada, 2007).

Figure 2 Different expectations about a mining project (free adaptation of Ian Thomson’s idea)

Benefits for rural communities are important as a palliative measure to release the immediate

pressures of the local population, but in many cases they are not sustainable and tend to disappear

once the mineral resources are depleted. Once the mine has closed, infrastructure that has been

built for the community is rarely maintained leaving empty hospitals and schools behind. Life skills,

culture, friendship, and self-respect are values that are more sustainable than benefits and can both

benefit the community-company relationship as well as leave a lasting legacy. Companies are not

prepared to diversify the communities they operate in, even over the long term. They usually

believe that it is the responsibility of the government to use tax revenue obtained from the mine to

accomplish these objectives.

Recently, the mining industry has realized that environmental and social issues are key to change

the public image as well as to establish a long and sincere relationship with local communities. A

mine can be a “showcase” of environment-friendly operations but if the social issues are not

addressed (and vice versa), this can create lots of problems with the public. “Improving

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environmental performance is critical to ensure that the environment is protected but it does not

necessarily ensure the social health and welfare of any associated mining community during

operation and after closure.” (Veiga et al, 2001).

There is no formula to deal with public engagement, as in communities there are different

perceptions and emotions. It is important to identify in a community values, perceptions, historical

facts and other potential sources of conflict.

SUSTAINABLE DEVELOPMENT IN MINING

The term “Sustainable Mining” has been used to call attention to the public and the mining

industry that the non-renewable resources must be efficiently extracted, processed, used and

recycled (Fitzpatrick, Fonseca & McAllister, 2011). The community and the environment in which a

mine operates must be sustained not the mine. The concepts of efficiency have usually been

attached to the concept of sustainable development in industrial operation. However, sustainable

development is an ethical concept that is attached to “economic prosperity, environmental health,

and social equity for the benefit of current and future generations” (Shields, 2005). According to

George Francis, professor of Environmental Studies at University of Waterloo, “sustainability is

ultimately an ethical commitment based on a belief that the natural world and its component life

forms, including humanity, have value in and for themselves” (Francis, G. 1999 cited in Veiga et al.,

2001). Even in the official UN document in which Sustainable Development was conceptualized,

the Brundtland Report (1987), the definition makes reference to an ethical commitment to leave

resources for the next generations: “…development that which satisfies present needs without

compromising the possibility for future generations to satisfy theirs” (UN-WCED, 1987).

According to Kazakidis et al (2013), “sustainable development issues, are often at the centre of a

dispute that can make an empowered local community or group in a first world country the

strongest stakeholder in a new mineral resource development (either as advocates or opponents).”

In fact, nowadays the environmental and social arguments mix and are hard to divorce even in

legal terms, when a judicial dispute is taking place. The example of Prosperity Mine shows this

clearly. Taseko Mines tried to implement a mine dumping tailings in a fish-rich lake. The idea to

transport the entire population of fish to an artificial lake was opposed by the First Nations and

when the company tried another more environmentally “acceptable” solution the relationship with

locals had already deteriorated.

The question is how to implement concepts of sustainable development into a mining operation. As

mining operations occur in remote areas, the main challenge of the companies is to deal with

impoverished communities that the only contact they had with mining was probably with artisanal

mining. In Tambogrande, Peru, for example, the community expelled a mining company that

wanted to develop a mine and was accused of generating pollution that would affect agriculture in

the valley. Around 87% of the population with households in the town opposed to the project

(Muradian et al., 2003). Now the town is invaded by artisanal miners dumping mercury and

sediments into the local rivers. In the Piura region 10,000 miners and more that 160 processing

plants are dispersed in 158,000 ha applying extremely primitive techniques to extract gold (Veiga,

2014). For the community, this is acceptable since artisanal mining generates more jobs for unskilled

people than a conventional mine. But sustainable benefits of a mining activity, artisanal mining

cannot provide. This is observed in thousands of shanty villages in the Brazilian Amazon created

9

during the gold rush of artisanal miners and now they have no economic alternatives (Veiga, 1997).

Artisanal mining is regarded by most rural communities as the easiest and fastest way to get out of

the extreme poverty and the immediate environmental impacts are disregarded by the desperately

poor local communities. A similar problem has the mining companies when bring only benefits to a

community. A mine represents an opportunity to add value to a community. Traditionally, mines

are said to contribute to communities through direct employment, ancillary economic activity that

supports the mine, infrastructure investment, educational programs and scholarships, and

recreational facilities. Benefits such as these are important but not sustainable either in conventional

or in artisanal mining. After the mine closure most towns remain without the benefits. Towns left

behind by mining companies become ghost towns. The mining companies have very little

participation in helping communities in their economic diversification, i.e. to find alternatives after

mining. Mining companies rarely provide useful land use (reclamation) for community use; most

reclamation objectives are for wildlife. Beyond that, companies need to think about how a new

mine can bring long term biophysical and socio-economic improvement to a region which is

consistent with holistic principles of sustainability. The legacy left by a mine to the community after

its closure is emerging as a significant consideration in its planning. In these cases, the company

must collaborate with the community to find solutions to diversify their economy and to leave

behind sustainable benefits.

An important step to establish a good and sustainable relationship with the community is to

recognize its values. Benefits are important, but values are sustainable (Table 1). When the ore is

depleted and the company closes the mine, the communities are left with hospitals without doctors,

school without teachers, and infrastructure without maintenance (Roberts & Veiga, 2000.)

The first step to introduce concepts of sustainability in a mining community may relate to local

capacity-building and local governance (Veiga et al, 2001). Local governance can achieve several

benefits including actively involving local residents in the process of making decisions, reinforcing

community self-esteem, bringing creativity for new opportunities, and reinforcing the relationship

with the mining company.

Table 1 Values and benefits a mining project can bring to the local community

Human Values Benefits

Friendship Employment

Solidarity Schools

Family Hospitals

Culture & Traditions Paved roads

Respect Clean water

Local governance is established with education and dialogue. When a community member is able

to speak freely with a mining authority or a company representative, dialogue can be established

and viewpoints understood. Co-development of projects to improve the interaction of mine with

the community and surrounding environment can help improve community relations:

reduce tailing generation

increase metallurgical recoveries (mining and processing)

recycle materials

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find uses for tailings (bricks?)

reduce energy and materials consumption

mine other things (garbage, sewage, thermal energy)

think holistically (and beyond the mining operation)

assist and participate in community projects

Some argue that it is the role of government to assist the local communities through the investment

of mining royalties. However companies working in rural areas of developing countries are aware

that the royalties are not always well administrated by local or regional governments and at the end

of mine life the populations have no sustainable benefits. “A corollary of [the resource curse] is the

neglect of the competitive diversification of the non-mining tradeables such as agriculture and

manufacturing” (Auty, 1993). As government policies are not sustainable, especially in developing

countries, companies must create mechanisms to establish projects with the local communities to

diversify their economy. This is the case for example of Sullivan Mine in Kimberley, BC. The mine

operated from 1909 to 2001 and the city of Kimberly was incorporated in 1944. In total it was

produced: 9 million tonnes of Pb, 9 million tonnes of Zn, 280 million oz Ag, $20 billion in revenue.

After a temporary closure in 1991, the community realized its dependency on mining and thanks to

the leadership of the Mayor they started a public consultation to decide about the future of the

town. After many debates the community decided to transform the town in a tourist destination.

The town is today known as the Bavaria of the Canadian Rockies and has a steady flux of tourist to

their golf courses and ski hills (Ednie, 2006).

CONCLUSION

The social, economic, cultural, and physical effects of mineral development projects need to be

understood at a much greater level by not only local stakeholders including technical staff but also

the general public. Meaningful, inclusive decision making on resource projects requires innovative

approaches to mining and exploration education as well as broader communication initiatives. Real

and lasting value from mineral development derives largely from developing human infrastructure

or social capital and values; this in turn depends on developing a sophisticated program of

engagement with the community by numerous agencies including governments and mining

companies.

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the Changing Face of Mine-Reclamation in the Americas. In: Mine Closure: Iberoamerican Experiences, p.1-23.

Villas-BOas,R.C. & Barreto, M.L. (Eds), Pub CYTED-IMACC/UNIDO, Rio de Janeiro.456pp.

Shields, D.J. (2005) USA and UN Perspectives on Indicators of Sustainability for the Mineral

Extraction Industry. In: A Review on Indicators of Sustainability for the Minerals Extraction Industries. P.19-29.

Villas Bôas RC, Shields D, Šolar S, Anciaux P, Önal G (Eds). CETEM/MCT/ CNPq/CYTED/IMPC, Rio de

Janeiro, 230pp.

UN-WCED - United Nations World Commission on Environment and Development (1987) Our

Common Future. Oxford University Press, Oxford, UK. 383pp.

Veiga, M. M. (1997) Introducing New Technologies for Abatement of Global Mercury Pollution in

Latin America. Pub. UNIDO/UBC/CETEM. Rio de Janeiro, 94pp.

Veiga M. M., (2014) Reducing mercury use and release in Andean artisanal and small-scale gold

mining. Report to U.S. Department of State, Bureau of Oceans and International Environmental and Scientific

Affairs Office of Environmental Policy, Mercury Program. Contract SLMAQM- l0-CA-312-RC..79pp

(unpublished).

Veiga M., Scoble M., McAllister M. L., (2001) Mining with Communities. Natural Resources

Forum, .25(3), 191-202.

13

A new approach to assessing energy efficiency, grindability and HPGR technology by comminution research

Douglas Fuerstenau

Dept. of Materials Science & Engineering, University of California, USA

ABSTRACT

Comminution not only is the major energy cost in mineral processing but it also can limit the grade

of ores that can economically be processed. Rittinger first postulated that the energy for

comminution is proportional to the new surface produced. Because most of the strain energy

needed to initiate and propagate cracks in particles cannot be recovered, researchers reported

woefully low comminution efficiencies. Recognizing this, Schoenert proposed that the baseline for

assessing comminution efficiency should be the mechanical energy needed to break single particles.

After extensive single-particle studies, Schoenert turned to comminuting beds of particle in piston

dies. Finding particle-bed comminution to be energy efficient, he had the brilliant conception of

making the process continuous, namely his invention of the choke-fed high-pressure roll mill

(HPGR).

Practical comminution involves masses of particles, which can lead to energy efficiencies far less

than that of single-particle breakage. A three-way classification of grinding modes in terms of the

mobility of the particle mass provides the necessary insight into the low efficiency of different

comminution machines: namely, single-particle breakage, confined particle-bed grinding (HPGR),

and loose-bed grinding (ball mill). Examples are given for determining and comparing

comminution efficiencies.

The size distribution of comminuted products become self-similar, and a single parameter, the

median size, can be used to quantify the extent of comminution. The reduction ratio, expressed in

terms of the mean size of the feed and product, varies linearly with expended energy and the slope

of such plots is a measure of the grindability of the mineral. This approach clearly gives the order of

energy efficiency as single-particle > particle-bed > loose-bed comminution.

HPGRs are more efficient at low reduction ratios but lose that advantage at higher reduction ratios.

Extensive hybrid grinding experiments carried out with our instrumented ball mill and HPGR

showed significant energy savings by first comminuting the material in the HPGR and followed by

the ball mill. At Cerro Verde an industrial-scale hybrid HPGR/ball mill system is reported to have a

13 percent energy savings over a SAG mill/ball mill system.

—

There is no full article associated with this abstract.

14

Reducing whole of enterprise running costs through

coarse particle flotation

Graeme Jameson University of Newcastle, Australia

ABSTRACT

In current flotation circuits it is customary to grind the whole of the mill feed to an initial size,

which is determined by the liberation characteristics of the ore, and the ability of the flotation

machines to float the fully liberated particles. Usually, the product of the primary mill will be

ground further in a ball mill, to improve the liberation of the values and hence the product grade,

before passing to rougher flotation cells. The final grind size is ore-dependent, and is a balance of

factors including the relation between surface liberation and grind size, the grain size of the

valuable particles within the host rock, and the feed grade. The P80 for the feed to flotation may be

as high as 300 µm for free-milling copper ores, and as low as 53 µm for finely disseminated

complex ores.

The grinding of the feed ore requires considerable input of energy. The rate of replacement of

wear components such as mill liners and media, is proportional to the energy input. The costs of

these two factors – energy and wear – are usually comparable and together they form the major

part of the running costs of a concentrator, and indeed, of the whole mining operation. The

energy required increases as the final grind size decreases.

This talk will focus on the reduction of milling costs that could be achieved, using a fluidized bed

flotation technology that can give high recoveries at coarse particle sizes. A number of different

circuit designs will be presented, using the new technology. Calculations show that reductions in

the running costs of a mine and associated concentrator of the order of ten to twenty percent

could be achieved.

—

There is no full article associated with this abstract.

15

Drivers that will change the design and plant operation

in the mining industry

Bert Huls

Goldcorp, USA

ABSTRACT

Already starting, new drivers will dictate how future mineral processing plants will be designed and

operated. These drivers include requirements in water and energy conservation because of rising costs,

larger demand for mineral and metal products as the result of a rising population, and the increasing

demand from the population in general to have influence over what type of operations will be developed

where. Mineral operating facilities will require processing of lower grades. To do this economically,

design engineers will be influenced to introduce newer concepts, or return to older processing concepts

once deemed not desirable. Our understanding of the fundamentals must be improved, and this may

come from better measurement techniques and more process piloting, and will go in hand with a

reduction of waste generated during the process, improved separation of minerals or product size.

Process engineers will also be required to not just design according to the established 3D methodology for

efficient plant installation. Already in other industries the design concept encompasses the entire range

from source to product. Not only that, the design will be affected by public influence that must be

illustrated prior to project execution. On the one hand, the added dimension in design may slow a project;

on the other hand it may result in a blessing, and in a higher responsibility for engineering.

16

New Forces at work in Mining

About 35 years ago a young Bill Imrie prepared for his Bechtel boss a paper on the future of

mineral processing plants. At that time he advocated that the future industry would employ

economies of scale through the use of larger equipment. Nobody in the audience could accept

the premise that was put forward; however, we all know that this was exactly what the industry

did.

Use of large equipment may have resulted in some energy savings with economies of scale, but

not in conservation of water.

With increasing automation and larger equipment, lost production costs from downtime have

taken on greater importance in determining a mine’s economic performance. Studies have

shown that maintenance costs comprise the single largest controllable expense in mining

operations, as much as one-half of total operating costs. Greater integration between operations

and maintenance to optimize equipment operations and minimize downtime is the key to

improving cost structures.

Today the industry may look different. This is because different additional drivers now play a

role. These drivers are:

1. Lower grades

2. Increasing energy price

3. Water scarcity

4. Gap between demand and supply of skilled labor

5. License to operate

None of these four drivers stand alone, as all four are integrated. Any improvement in

conservation has an impact on each element. Many groups across the world are thinking about

this. For example, the World Economic Forum (Kleinfeld et al, 2005) is in the process of creating

a Green Trade Alliance (GTA) to promote environmental sustainability without compromising

competitiveness. The group argues that new government regulations, targeted taxes and carbon

pricing schemes, along with factors related to the materials themselves, are reshaping demand

patterns and will lead to innovation in the use and reuse of resources. And indeed, government

regulations and taxes will result in lower profits that will force the conservative mining industry

to reach out to technology, to smarter ways to do maintenance and mine planning and

production implementation.

Mining companies will need to look at other industries to see how they have crossed that road.

“It requires a very fundamental change in thinking and a cultural change that is organized from

the top down so that things get implemented”, as mentioned by Chris Holmes, Head-

International at IDC Manufacturing (Rivard, 2014).

Another group, the Center for Social Responsibility in Mining (part of the Sustainable Minerals

Institute at the University of Queensland) (Sullivan, 2005) defines 'low footprint mining' as

17

“minimizing the physical disturbance associated with mining (including 'keyhole' mining and

underground processing), using far fewer resources (water, energy, etc.) to extract the ore, and

minimizing or eliminating waste and discharges”. The mining footprint according to their

definition includes the social impact, not only the availability and relocation of the workforce,

also the changes in local communities. This Center believes that “any negative social and

economic impacts associated with mining development, must be minimized and preferably

avoided altogether”.

The point being made here is that the traditional slow incremental approach followed by the

mining industry may have to give way to the implementation of new innovation at a more rapid

pace to maintain compatibility in light of various new legislations and rising community

awareness.

In addition, arguably a fifth driver may be the difficulty of attracting highly skilled people in the

mining industry.

Each driver will be discussed in this paper, indicating potential trends in future operation of

mines.

Lower grade ores

The copper consumption rate, 35 years ago, was about 5 Mt/y, while it now stands at about 18

Mt/y. In that time period the population has grown by a factor of about 2. The consumption rate

per person may still not be satisfied for the current developed world, let alone the increased

consumption that can be imagined with improved living conditions in developing countries. At

face value this situation may want us to believe that the drive towards more copper demand

will continue, which will require processing of lower grade ores.

Processing of lower grade ores may result in continued use of economies of scale, thus larger

equipment. Capacity has been added with limited new/breakthrough technology. This is

because a traditional major stumbling block is the conservative nature of adopting new

technology in mining. The mining industry follows an incremental approach rather than a

transformational approach to innovation.

Changes are on the horizon. Rio Tinto expresses it thus: “The next phase of the cycle requires

significant productivity improvement. It will become an opportunity for technology

implementers, and for the technology supply market (McGagh, 2013). Productivity lies at the

core of the mining industry”. The productivity increase will not merely be the result of the

introduction of new types of equipment, but also how data is generated and transferred to and

from equipment.

We will also become more critical towards minimizing the losses inherent to the standard way

of processing. It will require from us to prevent overgrinding, to prevent losses in fines on the

18

one hand, while on the other hand, a finer grind may be required to ensure sufficient liberation

of minerals in lower grade ores.

Lower Grade Ores: Minimizing waste

Minimization of waste, in the form of non-economical material, starts at the mine. There are

technical challenges to realizing unmanned mines. Improved sensors that can accurately and

reliably perceive the environment will allow advanced robotic systems of high reliability and

high integrity to be built. Dundee Precious Metals at Chelopech turned on the program “Taking

the lid off”, which allows phone and internet accessibility everywhere underground. The

objective is real-time sensing during mining to avoid waste production through for example

drilling outside of the ore.

Especially in gold mine productions, new developments are underway to improve the efficiency

of mining of narrow veins. We can imagine a mole tunnel boring machine being applied to the

extraction of gold from narrow veins where the block model has been digitized into the “brain”

of the mole to follow the veins. This will allow reduction of dilution, so that higher grade will be

processed.

Another future technology to tackle tough veins is the thermal fragmentation process as is being

developed by Rocmec mining (Candy, 2014). Rock within a narrow vein from 30 to 100 cm will

be shattered through use of extreme heat instead of explosives, which makes it a great deal more

efficient because it means the miner needs to extract roughly four times less rock when mining a

narrow vein of gold. A first a hole is drilled into vein using a long drill. Then, "Using a burner

powered by diesel fuel, the intense heat created within the vein shatters the rock containing the

precious metal contents, into small fragments. The ore bearing vein is directly extracted, greatly

reducing the dilution factor and the inefficiencies associated with traditional mining methods

which extract large amounts of waste rock."

For processing, to satisfy the future need of the world population, an increase in economies of

scale developing bigger equipment, is not likely to be the final answer. The reduction in losses

when processing lower grade ores will be necessary to avoid not only metal price escalations,

but also to reduce energy consumption and to be more water efficient.

Rio Tinto has started their PEC (Processing Excellence Center) in Brisbane to develop new

technologies having the “Mine of the Future in mind. Many of their initiatives focus on

improved mining technologies: total automation, from trucks to drilling rigs with sophisticated

automated robotic systems, combined with remote operation of unit processes from control

centers located in major cities thousands of kilometers away from the mines. Drilling rigs are

conducting experimentation with Prompt Neutron Activation down hole to characterize the ore

around the drill core, a technology that was developed by the Schlumberger water services

division which is now employed in oil and gas. This technology will greatly improve the mine

plan as geological models are based on interpretation between holes.

19

Minimizing waste at processing starts upfront. One is presorting of ore prior to the crushing

phase. There are two types of developments on this front.

On-line cross-belt sorters are being developed by various suppliers. Using the Magnetic

Resonance Technique, it may be possible to do mineral sorting for some base metals

rather than for only industrial minerals.

Use of optic sorters, capable of upgrading low-grade ores, also is indicated by Rio Tinto

as an avenue they are pursuing. Ore at Detour Lake (gold) and other Northern Ontario

properties appear amenable to Optical sorting (alliance between Outotec and Tomra

Sorting GmbH). Tomra's sensor-based sorters can reduce specific energy consumption by

15 percent, as well as reduce the amount of water used by three to four cubic meters per

tonne of ore.

Lower grade ores: A better understanding of processing

We need to improve our processing through better understanding of particle behavior and

through better measurements.

Measurement of Particle Size and Behavior

A better understanding of liberation, or better, on-line measurement of liberation, would

enhance energy efficiency. In the past, flotation was always based on sufficient liberation of

particles for maximum recovery. In more recent process design, the comminution process aims

at 40-60 % liberation as that should be sufficient. The production of stronger reagents has also

helped make this possible.

To support their JKSimFloat model, JKMRC is experimenting with X-Ray tomography to review

the physical and chemical structure of the ore with the host rock to investigate how the texture

of the ore affects how fragments will float after breakage. In a similar vein, in the past Professor

Jan Miller of the University of Utah also experimented with X-ray computed tomography (CT), a

multi scale imaging of multiphase particulate systems in 3D to measure liberation. These

technologies don’t exist on-line, but on-line liberation analysis will be available at some time in

the future and will prove a valuable tool to reduce overgrinding and minimize energy

consumption.

Besides liberation, it is also important to properly measure particle size in the flotation feed. The

two most well-known analyzers are the PSM, originally developed by Armco Autometrics, now

part of Thermo Fisher Scientific, and the PSI (Outotec). It is unfortunate that in most plants their

measurements are rarely used in process control, which is partly due to not continually

actualizing the calibration curve. A better understanding of the true particle size is required

when optimizing downstream processes, such as split flotation. Developments have started to

generate on-line not just a single particle measurement, or a percentage smaller than a certain

size, but a full size distribution. This size distribution will include sub-sieve measurements

20

(below 30 microns), which typically constitute up to 30% of the flotation feed, and in some

operation over 60 % (Century, Cannington and Mt Isa Mines, Australia).

Further improvement in understanding of particle behavior may come from applying the

technique of Positron Emission Particle Tracking or PEPT. This is a technique for studying the

flow of particulate systems such as tumbling mills in the minerals industry. Initially developed

for the medical imaging industry, positron emission tomography has been adapted for

engineering applications at the University of Birmingham.

Professor Kristian Waters is one of the pioneers in this area of Positron Emission Particle

Tracking (PEPT) and applied it to particles in froth flotation systems to observe the behavior of

individual particles in a mixed particle–liquid–gas system (Cole et al., 2010). The intent of these

studies is to directly follow the particle position in the pulp and froth to better understand the

behavior and couple this with instantaneous froth events such as bubble coalescence. This

technique is being validated by combining it with high speed digital imaging to track a particle

within a foam column with visual verification of the tracer trajectory recorded with PEPT.

Through application of this technique, the existing fundamentals in flotation may eventually be

tested by direct measurement. We visualize that adjustments to fundamentals may be required,

which will eventually lead to better and more efficient flotation equipment. Perhaps larger

equipment is still a valid approach, but energy transfer to effect efficient collision and adhesion

of particles to bubbles may be optimized through better engineering.

Mineral Phase Analysis on line

No single technology exists to measure all the mineral phases in slurry and it appears that future

capability in this area will require several complementary analytical techniques. Moreover, a

solution for one plant may not be directly transferable to another but similar plant. Better

measurements through on-line mineralization analysis would result in better design of control

strategies. In one way or the other that ability will be available in the future. To maximize

recovery in flotation it is important to better understand the deportment of minerals. Examples

are:

Pyrite variability in copper flotation. Any change in the Fe content, which is being

analyzed on line, could be the result of changes in the chalcopyrite to bornite content, or

from more pyrite. In pyrite flotation circuits the pyrite content is important, especially if

associated with gold recovery.

Gold and other precious metals content down to ppb levels on-line.

Grade-recovery relationship on-line.

Changes in copper mineralization in circuits containing chalcopyrite, covellite, chalcocite

and bornite

21

The mineral phases that present themselves to flotation. This will allow tailoring the

reagent blend to the mineral composition in the feed. The result is better recovery, or

keeping the non-paying minerals out of the concentrate. Conversely, if for example gold

is in the pyrite, you may not prefer to depress that mineral. Technology development

may be limited by not having experienced engineers involved long enough with an

operation to be able to develop such technique for a plant.

Insolubles content to avoid overpaying by shipping concentrate full of insolubles.

Producing a concentrate with high insoluble results in paying of shipment of a material –

insoluble - that has no value.

Several units attempting on-line mineral analysis have been manufactured. The Continuous on

Stream Mineral Analyser (FCT, 2011) was developed about 10 years ago by CSIRO & INEL (a

French manufacturer of XRD analyzers). It uses an innovative curved detector so it can measure

120º area simultaneously which allows for the fast collection of XRD data. It was tested out on

powders in cement plants (including the Ash Grove plant in Leamington, UT) and worked

reasonably well in those applications where the mineralogy was very consistent.

Cross Belt Neutron Analyzers using the advanced technologies (such as perhaps PGNAA or

Prompt Gamma Neutron Activation Analysis) provide elemental (chemistry) analysis. Efforts

have been made to infer mineralogy, but this is always fraught with difficulty, as common

elements such as Fe, Cu and S are present in many different mineral phases.

Both Panalytical (who purchased the company ASD) and Bruker make an on-line (over the

conveyor) NIR (Near InfraRed) instrument that can be calibrated to give quantitative

mineralogy of alteration phases (clays, micas, carbonates, etc). Blue Cube is another on-stream

analyzer device that uses a technique called Diffuse Reflective Spectroscopy. The calibration of

these units is fairly intensive and requires a large set (several hundred) of reference samples.

The calibration is a huge challenge as is the detection issue for low concentrations of copper

minerals.

Word is that some manufacturers of on-line analyzers, such as Thermo Fisher Scientific, are

investigating a new technique to provide a direct measure of three key copper phases, i.e.

chalcopyrite, chalcocite and covellite. Bornite cannot be measured directly by this technique, but

would have to be inferred. Copper slurry mineral analysis may find its application in rejecting

pebbles from a grinding mill discharge in case these do not contain an economical mineral

content. The result may be a reduction of grinding energy per tonnes and also a throughput

increase. Note that also Pyhäsalmi, a Cu-Zn-Pyrite operation in Finland, has been practicing

rejection of pebbles due to low metal content. Another application would be measurement of

flotation rougher feed to optimize a feed forward collector dosing regimen.

Similarly investigations have started around requirements to measure pyrite in mineral slurry

streams. It requires a different technique than for a copper slurry mineral analyzer.

22

As yet, on-line mineralogy analysis is not available. However, FEI has developed an on-site

mineralogy analyzer, consisting of a compact Qemscan that can be placed in any office in a

plant. This technique provides near real-time shift-by-shift mineralogical measurements of, for

example, flotation streams in the form of element deportment, recovery, ore quality and

flotation performance (Van der Wal et al., 2013). The Qemscan analyses from the analyzer are

presented in the form of 3x3 matrices indicating particle size and liberation for different

minerals. A test at Greens Creek in Alaska showed how the pulling of rougher concentrate

affected the recovery of fine liberated freibergite.

Lower grade ores: Specification of equipment use

Most new facilities are overdesigned by engineering companies. Big companies are conservative

in design, more so than smaller companies. Partly this is caused by the mining owners

themselves, who file for law suits in case of not meeting production rates. Ausenco once was an

astute engineering designer, but now has become too large, and more conservative in design.

Perhaps there will be a future for boutique designers, resulting in a more efficient design.

Already mentioned are the fewer graduates in processing from the 1970’s to early 2000 as a

result of low metal prices. With this drop in numbers, a shift in design concept can be observed.

Design now starts prior to having a flowsheet locked in, resulting in several redo’s of layout and

wrong eventual layout. Bechtel always used to insist to lock in a flowsheet, then the design

engineers take over and no changes are allowed. We can see a trend towards standardization in

design, for example, pump boxes, sumps, sampling systems, prior to even purchasing that

equipment. This has merit to avoid repeat work by engineering companies, which is a waste of

money and often leads to the introduction of errors in design. Standardization will be both for

equipment and process design:

Standardization in PI&Ds

Merrill Crowe process

Mill aspect ratios, etc.

In fact, more focus will be directed towards simulation models that will be enhanced by more

direct measurements through techniques such as the PEPT described above. Old theorems may

fall by the wayside, even the Bond model for mill design.

More direct unit processes will be leading to higher efficiency. Several examples of old

technologies that will be refitted into a new jacket are described below.

Revisit of two-stage cycloning

We know that fine particles behave like water molecules and, as with conventional flotation

cells, do not end up in the desired product stream. For cyclones, fine particles will be entrained

23

in the water that exits the cyclone underflow stream, and this bypass causes an imperfect

separation. The fines content in the underflow is almost a quarter of that for a single stage

cyclone.

Because of this imperfect separation, two cyclones in series produce significantly higher

classification efficiency than a single cyclone. The traditional way of double stage cycloning is an

intermediate pump arrangement. However, the associated operating costs are high and this

arrangement is not often used in the industry.

Figure 1 Cavex ® DE cyclone efficiency (%) as function of XXX

Previous attempts to combine two-stage classification into one unit resulted in lower efficiency

than desired. Common problems included high wear in the transfer zone, poor control over the

flow split to the secondary cyclone and the need to operate at high pressures. With the Cavex

cyclone (Weir web site, 2014), Weir has made good advances by rearranging the bottom of the

primary cyclone. It consists of a cone within a cylindrical housing where the adjustable gap

between the cone and the housing acts like a spigot.

Horizontal cycloning, at 13.5° angle, not the traditional >45°, as tested in Cuajone (Peru)

For many years researchers have modeled cyclones and the publications are too numerous to

mention. At times a distinction is made between horizontally and vertically positioned cyclones.

In the 1980’s a trend started with positioning cyclones horizontally. Most operations nowadays

have the angle of repose just off vertical to about 45°. In that period several operations tested

cyclones positioned down to an angle of 25°.

24

Little publicity was given to the test work that was conducted in Cuajone in the 1980’s. Contrary

to common belief, it matters how a cyclone is positioned when it pertains to a large cyclone.

Naturally, the major force in a cyclone is exerted by the centrifugal action. The vortex flow

increases the static pressure radially outward. This “centrifugal static head” is primarily

determined by the distribution of the tangential fluid velocities in the flow. In large units gravity

has a significant effect on the removal of solids to the apex, due to the tall liquid column.

Horizontal mounting for large units will benefit from the possible reduction in required feed

pressure. At Cuajone the 2.3m long D26B cyclones were mounted at an inclination of 13.5°,

sufficiently steep for natural drainage when shut down. The effective vertical length of the

cyclone was thus reduced to 0.54m. To obtain the same centrifugal force within the cyclone, the

feed pressure could be reduced by 2.7m water column, assuming 50% solids by weight. This is

equivalent to a drop from 62 kPa to 37kPa.

Cyclone operation became very interesting: because of the positioning of the cyclone, the

underflow density rose to 87% solids, compared to the 78% solids at which the cyclone started

roping. Rather than a forceful stream, pulp ejection from the apex was in the form of a weak

arch; however an air core was clearly noticeable. This was due to less fines reporting to the

underflow. The Tromp separation curve was nearly vertical, steeper than the separation curve

published by Weir for the DE Cyclone. As a benefit, it became impossible to get the cyclone to

rope (Huls, 1990).

Other benefits were that the circulating load was reduced from about 350 to about 100 %, which

translates into a diminished cyclone feed flow. Combined with a reduced operating pressure

(from about 50-60 kPa to about 25-30 kPa, the pump speed could be slowed down with a net

result in energy savings and reduced wear rate. At the same separation the mill throughput

could be increased by 10%.

The negative impact was that the efficient separation resulted in a reduced cyclone overflow

density from about 25-30% to 13-16% solids. Lack of knowledge in the industry about the effect

of kinetics with reduced pulp density at that time, created the fear that insufficient retention

time would be available in the existing flotation circuit resulting in much lower recoveries. We

now know that kinetics dramatically improve with lower flotation feed pulp density. The plant

may have been able to cope with it. However, as the situation was, plant management decided

to steepen the angle of the cyclones to initially 25 and later 45 degrees.

It is believed that this practice should be revisited. It presents an expectation of lower energy

consumption in particle separation, of reduced overgrinding, higher mill feed rate and higher

flotation efficiency due to improved kinetics. The test data at the time were used to generate a

modified Plitt cyclone separation model, but the model for the horizontal cyclone was criticized

at the time because the cut size became inversely related to the cyclone feed solids content.

25

We should also ask ourselves if horizontal cyclones in an operational mode as described above

could also be applicable to separate treatment of rougher/scavenger tailings and cleaner-

scavenger tailings to enhance water separation.

Hydraulically efficient sumps and pumps

Slurry pumps are primarily used in the hydro-transportation of solids and are an essential part

of all wet mineral processing applications. Wear rates are typically high, even though the pumps

are designed for pumping a mixture of solids and liquid. “Conventional pumps reduce suction

side-recirculation by adjusting the suction liner and impeller closer together,” explains Kenny

Don, pump applications engineer at FLSmidth. “However, this causes particles to become

trapped and ground between the two, which decreases the wear life and efficiency of the pump”

(Lovejoy, 2013). FLSmidth’s patented millMAX adjustable suction side-sealing system stops

suction side-recirculation within the pump while maintaining a large gap between the suction

liner and the impeller.

Weir boasts that its Warman WBH is its most advanced slurry pump because it features one of

the broadest efficiency curves in its class, offering less power usage, reduced maintenance,

longer wear life and higher performance (Lovejoy, 2013).

Computer-assisted fluid-dynamic design has already produced a tremendous improvement in

the design of thickener feed wells. This technology has already been implemented to improve

the hydraulic performance of slurry pumps, so that their hydraulic efficiencies are now closer to

clear-water pump designs. Undoubtedly, technological advance will also address the shape of

the sump itself, and through producing a more hydraulically efficient pumping system, energy

requirements per unit volume will be reduced.

Revisit of split flotation circuits

Split flotation circuits have been in use off and on for many years. Cuajone in the 1980’s

separated slimes from sands, claiming a recovery improvement of at least 2%. Holloway et al

(2008) described the Cannington split flotation where a slimes float at 80% <16 microns was

floated separately to recover fine lead and silver. Respective increases in recovery are 4 and 3.5

%. Huls (2005) reported on separation of coarse particles from rougher tailings that would have

improved overall copper recovery by about 4%. Improvements in separation efficiency have also

been demonstrated in coal flotation.

Manufacturers are finally catching on to this old technique. In recent CFD modeling, FLSmidth

(Govender et al, 2012) seem to start thinking of Hybrid Energy Flotation™. Modeling has

indicated that preferential pulp collection zones in the Wemco and Dorr-Oliver flotation

machines may vary with size class due to the local turbulent kinetic energy dissipation. This

may lead to different, or at least improved, design of their flotation cells as their models suggest

that that the attachment rate of the fine fraction increases in the high-energy zones shrouded by

26

the stator/disperser and adjacent to the impeller tip. Not so clear is FLSmidth in describing the

process for coarse particle recovery. They surmise that coarse particle recovery is favored in

regions of lower energy dissipation. The adverse susceptibility to increased fluid turbulence

induces the detachment sub-process.

Woodgrove flotation

Woodgrove has developed a Staged Flotation Reactor (SFR) by going back to the first principles

of flotation. In doing so, it is possible to better optimize each step that makes up flotation, such

as collection and separation, without the restraints that would normally be the result of trying to

find the best middle way that satisfies each principle of flotation. In the flotation unit, each of the

three zones operates in a mutually exclusive way. By making changes to the cell emphasis may

be given to mechanically agitated flotation or progressively more to a column flotation concept.

Woodgrove’s (company website) claims are worth reviewing:

Power consumption reduced by approximately 50%

Required floor space is only 50-60% of that used by conventional mechanical cells

Air consumption reduced by approximately 80%

Fewer units needed to achieve equivalent results

Building height reduced by up to 3m on large plants

Possibly this flotation technology has jump started a future trend into dramatic savings in

energy, which not only comes from lower power requirements but also from requiring a smaller

building to achieve the same results. Several companies have already ascribed to this technology

for cleaner applications (Dundee Precious Metals at Chelopech, Newgold at Afton), while a

pyrite flotation circuit in a cleaner-scavenger operation is now also operating at Chelopech, and

testing in rougher application are being conducted at Vale.

Rising energy prices and water scarcity

Chile is a good example where rising energy prices are driving a marginal mining sector to

reconsider starting or continuing operations. At the same time, Chile is moving towards

regulating the mining industry to source its water from the ocean for any new operation to be

built. For some operations, this may mean a tenfold increase in water costs, from about $0.35/m3

to about $3.50/m3, as a result of having to pump water from the ocean to the mine site, which

can be over 100 km away and then up the mountain anywhere up to 4000m.

Some equipment, such as the HPGR, was developed to conserve energy in grinding, in which it

succeeded. For hard ore it probably is the comminution tool of choice. However, we always

need to keep in mind what are the energy requirements of a complete installation, and not just

of a single piece of equipment. Most often the net energy costs/t processed became higher due to

27

associated conveyor belt infrastructure and necessary dust collection. Further development is

required on the material handling associated with the HPGR to realize the energy savings

promise of this technology.

Pursuing water reduction

In some areas there will be a revisit of dry processing. Dry processing will produce a sharper

cut, but may be more energy intensive, which is offset by a potentially higher metal recovery. In

other words, the result is a higher production of metal per unit of energy consumption.

A mental block in engineering design for dry processing has been in trying to design the entire

process. To overcome this, we need to imagine how dry products could be processed

downstream by applying a Black Box approach for the intermediate steps. Work backwards:

Must water be added to dispose of the waste properly (avoidance of dust, stabilization?), is there

a minimum water requirement? Filling the black box then becomes a secondary exercise, as it

will focus on minimum use of water while performing magnetic or gravity separation or other.

Mineral Separation Technologies recently received a patent for its DriJet 100 technology, a

process that uses X-Rays to identify the atomic weight of coal particles and air jets to separate

coal from ash without using water or chemicals. “We remove the ash right at the mine face. Our

technology means fewer coal trucks on the road and less coal waste in impoundments,” Roos

said. The company says “DriJet requires low power and has few moving parts. Operating costs,

compared to other coal preparation technologies, are low” (Anon, 2014).

Dry stacking of tailings

Nowadays the drivers for the implementation of dry stacked tailings are limited space

availability (El Sauzal, not being able to obtain a permit for tailings pond extension (Marlin),

lack of ground stability, where bog issues made building a conventional tailings dam impossible

(Éléonore). However, for high altitude locations, mining companies are now investigating dry

stack facilities for other reasons. These may be a reduced foot print, community issues, where

visual of conventional tailings deposit and fears of potential dam failure and water infiltration,

and large distance water pumping from ocean to high altitude. Pumping up to altitude for

mines in the high Andes would increase the costs for water tenfold. This is a stimulus for

tailings filtration and dry stacking. We estimate that fresh water requirements may be reduced

up to 40%.

However, for a typical 100,000 tpd operation, the number of filters required may be anywhere

between 35 and 100, depending on filtration characteristics and filter type. In addition,

depending on how the cake is dried, energy costs may actually closely approach the savings in

pumping. Optimization at large scale is necessary.

28

Figure 2 Filtration scheme for dry stacking of tailings

It starts with not being able to obtain realistic (vs. conservative) specifications from

geotechnicians or engineering firms that can reduce filter requirements. From recent quotations

and conservative approach in engineering, the sense is that redundancy requirements are over

estimated. We fail to understand where redundancy can be effectively reduced. We must think

of the system holistically. It means understanding of best equipment composition, which leads

to a reduction in capital costs. For example, installation of an improved compressor system must

be designed compared to the compressors that now accompany the installation of a filter, not a

number of filters (Huls and Moll, 2013).

We need to become smarter about how to put filters together, not only to reduce maintenance,

increase uptime, and reduce operational personnel requirements, but also from avoiding high

energy requirements for cake blow, which may be energy intensive. For a large filter plant,

when using a Base Pattern the fee structure, spare parts, and consumables should not be derived

from the conventional model, but be built from the bottom up, and thus built against the facility.

It will require a collaborative effort (Co-Creation or Co-Innovation? (Flintoff, 2014)) between the

owners, the suppliers and specific technical experts (e.g. geotechnical engineers in the case of the

above filtration-dry stack system).

Reduction of energy consumption

Ironically, several of the pursuits that may reduce water consumption, such as dry stacking of

tailings or dry processing, may result in increased energy consumption and hence costs. This

means that further innovation is required to fully take advantage of improved technologies so

that the “overall footprint of mining”, as identified by the Center for Social Responsibility in

Mining of the University of Queensland, indeed will be reduced.

According to Siemens, electric motor systems are responsible for more than 75% of the power

consumption in industry today. We all use energy efficient motors in the mining industry today.

However, the use of gearless drives would result in energy savings between 3 and 30%

(depending on the application), but is not ubiquitous for all mining equipment. Presently only

29

large grinding mills, conveyor belts, mine winders and some pumps are propelled by gearless

drives.

From designing equipment to designing systems

Energy savings will also result from mining companies buying systems rather than equipment

from electrical equipment suppliers. Equipment purchasing will focus on an integrated

operating costs approach where systems are optimized for energy efficiency, low resource use,

etc. El Morro was one of the first to sign a Framework Agreement with Siemens on electrical

supplies that encompasses not only the execution phase but life of mine supply.

System rather than equipment focus, was above seen important for the installation of large

tailings filtration and dry stack facilities. However, the future system approach will consider Pit

to Port integration: an integrated automation system throughout the complete value chain. It

will include offline simulation (and perhaps in the future on-line) tools. This is called digital

enterprise architecture [6]. This will require more sensing and thus the development of more

sensors and it furthermore provides the ability of diagnostic systems for improved condition

monitoring and optimization of maintenance intervals with the objective to increase reliability.

The role of automation

Automation and the intelligent use of information make up the engine room of tomorrow's

mine. Research and development within these two crucial disciplines are working towards

removing people from hazardous environments and creating a highly efficient and virtually

error-proof, factory-like consistency across production. A good example is driverless trucks and

shovels which may be realized as electric trucks on trolley line to further increase efficiency and

reduce diesel consumption.

Of the 12 disruptive technologies that will transform life, business, and global economy as listed

by McKinsey (2013), automation of knowledge work, the Internet of Things and advance

robotics are specifically those to affect the mining industry. Low-cost sensors and actuators for

data collection, monitoring, decision making, and process optimization, coupled with

increasingly capable robots that have enhanced senses, dexterity, and intelligence, and coupled

with intelligent software systems, will cause a shift in worker skills.

An IT technique called “structured analysis” identifies the shared informational requirements of

production and maintenance. Modeling the procedures and data flows identify the information

shortfalls and redundancies, allowing an efficient system design of maintenance controls to

resolve failures. A study by the RAND Corporation (Peterson et al, 2001) identifies areas that are

now being developed and applied to operations and maintenance:

On-board sensors and off-board diagnostics such as vibration analysis and vital-signs

monitoring predict equipment failures and optimally schedule maintenance actions.

30

New and more robust engineering and materials such as better lubricants and “hot-

swappable” components can extend operational capabilities and minimize downtime.

Electronic transmission of diagnostic data can reduce costs significantly with the

increasing use of outsourcing for maintenance.

However, new information technologies can only go so far unless they are combined with better

work practices, such as more effective record-keeping and better follow-through between

maintenance and subsequent operations.

Sensors on machinery will record the fine detail of situations to calculate positions, conditions

and directions precisely. Information will be sent, in real-time, to operators who will make rapid

decisions and transmit instructions back to the machines. However, these self-diagnosis systems

are also developed to improve maintenance. For example, the more energy efficient drive

systems that are being developed, in reality will be smart drives as part of an embedded system.

This also means that operators not necessarily have to be where the equipment is. Robotics and

self- healing machines, exoskeletons to enable one man to do the work of many are topics of

discussion. Longer term, autonomous operation (Machine to Machine) will be the new

paradigm.

Even a lot of the maintenance may be done remotely. Predictive Maintenance will be stressed

more, as people stretch for 98% availability and a slash in maintenance costs - maybe up to 2/3rds

when everything is considered. Prognostics is an engineering discipline focused on predicting

the time at which a system or a component will no longer perform its intended function. In fact

information will be made available at the machine to anyone who needs it. Sensor fusion (or

multi-sensoring) will provide us with new ways of measuring for both technical and process

health diagnostics (Flintoff, 2013). This increase in energy efficiency and remote control will lead

to reduction of the overall footprint of mining. "The Internet has changed the way we consume

information and talk with each other, but now it can do more," CEO Jeff Immelt said (GE News

Release, 2012). "By connecting intelligent machines to each other and ultimately to people, and

by combining software and big data analytics, we can push the boundaries of physical and

material sciences to change the way the world works."

Higher energy prices and lack of control on those prices, may well force mines in remote areas

to abandon connection to a standard power grid. We can expect renewable power stations

located at mine sites that are sized to generate sufficient power to energize the operation. One

aspect of energy savings is the reduction in energy losses during power generation and

elimination of such losses in power lines with power being transported over long distances.

Local renewable power stations will run on bio-diesel fuel that can be produced from an in-situ

algae farm, efficiently producing just the amount of power needed to run the operation. In areas

of nearby forestation, biomass can be produced from low-value wood and forest thinnings

(Simet, 2014).

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Design philosophy

In a recent presentation by Freeport McMoRan about the new Climax Mill project it was

mentioned that the design philosophy was to take advantage of natural grade so that gravity

could replace pumps for moving slurry through the plant and thereby reduce energy

consumption for pumping. After the Cyclone feed pumps there is just one pump to take

Rougher Concentrate Thickener U/F back up to the head of the Cleaner circuit.

Elimination of process transfer pumps by gravity has the added benefit of reducing capital costs

and ongoing maintenance over the life of the plant. This is not a new concept, as especially in

Germany many mills were built that way in the past. This may well be setting a new trend,

especially if employing CFD modeling for a more efficient gravity flow of slurry and other

slurry transport. The picture here shows an example of such design.

Figure 3 Example of design with gravity flow of slurry (Germany)

Bridging the gap between demand and supply of skilled labor

Compared to 2009 the US will have lost 128,000 skilled senior labor, or 21%, and this number

will rise to 52% (SME, 2014). The cause of this loss is illustrated by showing the number of

mining graduates over time.

32

Figure 4 Number of Graduates in Mining per Year

Several papers have been written on how to promote young people to enter the mining

industry, the most exciting suggestion I find is providing increased research funding to

universities to advance technology or business processes to drive innovation and to allow

students to work on cutting edge technology that is applicable for the mining industry (NS,

2013). This works two ways: not only will the new generation enter the mining industry with a

desire for badly needed innovation, it may also result in a more readily acceptance of new

technology once they get promoted to the highest spots in a mining company.

License to Operate

If not input, the public wants to have more knowledge of the social and environmental impact of

a mining operation over the life cycle of the mine.

From the draft board to 4D modeling

In the past, a supervisor could immediately see how a draftsman was progressing: the drafting

board with the clean drawing stood beside the board indicating his sketches. On the table

behind it were open the standard reference books, allowing the supervisor to follow the thinking

process of the draftsmen. Now with a single screen, the process can no longer be easily followed.

In the past engineers produced plastic models of plants to visualize any interference. Although

this has been replaced by 3D models, that may prevent interference in plant design, for the very

near future 3D modeling may no longer suffice.

Just because you see a 3D model on a computer screen does not mean it is made for

construction. How do you get that means and methods data into the models for the General

Contractors and Subs? It's important to be able to harness the available intellectual property in

33

each firm and capture that data in the models. This knowledge (think: productivity, unit rates,

consumption) can be stored in a database so that it is readily accessible for all projects.

For that reason, in the non-mining industry 4D modeling is becoming in vogue, where the 4th

dimension indeed is time. The 4D model may also be called the BIM (Building Information

Model), which is presenting to the client owner as value in terms of life cycle coverage of

resources, including energy and environmental resources. BIM is defined as the digital

representation of physical and functional characteristics of a facility. A BIM is a shared

knowledge resource for information about a facility forming a reliable basis for decisions during

its life-cycle, defined as existing from earliest conception to demolition (NIBS, 2014).

An example of use of the 4D model was the design of the opening ceremony of the London

Olympics in 2012, which was designed as a life cycle model.

As an advanced construction management tool, the aim of 4D BIM (Wikipedia, 2013) clearly is to

deliver technology which supports the construction delivery team and survives the dynamics

and demands of the construction industry. If construction is a series of problems to be solved,

then 4D BIM software is the tool of choice to meet that challenge-enabling users to explore

options, manage solutions and optimize results. Yet it has the ability to be used in a sequence of

events that can be shown on a time line that has been populated by a 3D model. Use of BIM goes

beyond the planning and design phase of the project, extending throughout the building life

cycle, supporting processes including cost management, construction management, project

management and facility operation. Building Information Modelling can, of course, still produce

drawings, but the process is no longer focused on lines, shapes and text boxes; it is now based

on data sets that describe objects virtually, mimicking the way they will be handled physically in

the real world.

How this would apply to the mining industry could also be expressed as follows:

In the past there was overlap between engineering, procurement and construction. Construction

typically started at 40% completion of engineering. This is changing and likely to lead towards

starting construction only after engineering is 100% complete. This is partly due to more

detailed requirements when applying permits, but also to enhanced complexity in design. It

doesn’t mean that plant startup will be correspondingly delayed. As this approach allows the

use of BIM, construction will be more efficient, less costly and resulting in reduction of

construction time. The use of BIM allows standardization of the use of models in architecture,

engineering and construction.

In addition, by allowing each group, design and construction teams and operators, to add to and

reference back to all information they acquire during their period of contribution to the BIM

model, the model can bridge potential information loss caused by hand over. BIM can be used

for communication of the proposed project phasing to all stakeholders. With 4D modeling,

stakeholders are able to better understand how the project affects them and better understand

34

projected construction schedules. However, we can visualize an extension of this model to cover

also environmental and community aspects.

This is where public input starts. Only through showing the effects of construction of a project

and the operation on their direct environment and life, will the communities be in a position to

provide constructive feedback to the design. Community needs over time can be built into the

model further enhancing visualization of project and operational effects to the stakeholders. On

the one hand, the added dimension in design may slow a project; on the other hand it may result

in a blessing, and in a higher responsibility for engineering. To a degree, Rosemont Copper

(Rosemont Copper Website) in Arizona has utilized this concept advising communities on dry

stacking of tailings. However, this is more presented in a video concept of a future impact,

rather than it was built up from an original 3D model to which a time line was applied.

CLOSING REMARK

Of course a step change in metal requirements may happen at any time. In the early 1900s the

world’s requirement for sodium nitrate (caliche), of which Chile was a major (and almost

unique) producer, led to a booming industry in Chile. This industry fell away from one day to

the next with Fritz Haber’s invention of synthesized ammonia important for fertilizers and

explosives for which he received the Nobel Prize in 1918. ….. Analogously, the world’s appetite

for copper minerals may fall away once a perfected Graphene solution of high conductance

through a monolayer of carbon atoms will replace the need for copper.

ACKNOWLEDGEMENTS

I would like to acknowledge the insight from several colleagues in the industry who have

assisted me in putting this paper together. They are Bill Imrie, Bechtel, Brian Flintoff, Metso,

Matti Tarvainen, Outotec, Tom Strombotne and Tim Sennett, Thermo Fisher Scientific, and

Stuart Saich of Promet 101. Talking to them on what changes we foresee in the future for a

milling operation was a great pleasure. I am particularly indebted to Bill who also assisted me

with the structure of the paper.

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2014. December 8.

37

A crystal ball vision of innovation in mineral processing

Jannie van Deventer

The University of Melbourne, Australia

ABSTRACT

Innovation in the minerals industry has been lagging behind comparable industries like oil and gas.

An incremental innovation culture that tolerates long lead times between invention and adoption

has been exacerbated by a research grant structure that inhibits radical idea generation.

Entrepreneurs who can make the link between ore source, technology and finance will cause a shift

in innovation culture and open up substantial opportunities in the minerals industry of the future.

By extrapolating existing trends in technology within and outside mineral processing, a crystal ball

vision of future innovation is shaped with the aim to lower energy and water demand, reduce CO2

emissions, decrease operating and capital costs, reduce environmental impact, and secure a social

licence to operate. Advances in nanotechnology, advanced materials and biotechnology will impact

mineral processing, but the initiative for technology transfer must come from mineral processors.

Laminates of graphene oxide can offer efficient filtration and separation media, while microfluidic

devices will be used for desalination, solvent extraction and analysis. Substantial progress is

expected on benign lixiviants and separation agents, such as nanoscale supramolecular hosts that

can serve as high-capacity, selective and recyclable ligands and sorbents, and solid

aminobiphosphonate-based adsorbents.

Radical ideas for the recovery of precious metals from non-assayable ores and the generation of

energy above unity will be adopted in selected minerals projects. In-situ mining in which microbes

generate lixiviants at mineral surfaces will simplify processing circuits. Specific ores will be

subjected to microwave processing and electropulse liberation to enhance recovery. Ultrafine

grinding using devices of low energy consumption will be done mainly dry, followed by dry

separation. New flotation cells will remove efficiently either coarse particles or ultra-fine particles,

with mineral surfaces being modified not just by new reagents but also by selective microbes.

Innovation in mineral processing indeed has a bright future.

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INTRODUCTION

Mr Mark Cutifani (2014) said that research and development (R&D) in mining is lagging behind the

oil and gas sector at a time when there is an urgent need for larger and better deposits of many

metals and minerals. Innovation in oil and gas has transformed the energy landscape in the US,

with fracking and horizontal drilling unlocking vast reservoirs of shale gas previously considered

uneconomic to develop. By contrast innovation in mining has been incremental and many methods

have changed little except for the size of equipment used. “Our industry is damned by the fact that

our spending on innovation and R&D is 10% of the petroleum industry. … If we don’t start to bring

innovation back and do a lot better on our cost structures and deliver returns, the major diversifieds

will be subsidiaries of General Electric or some other conglomerate that still has innovation in their

vocabulary . . . We either pick the ball up and innovate or somebody will do it for us” Cutifani

(2014). Adding to these sobering words, it is important to note that many mining companies have

destroyed shareholder value, and with capital expenditure and debt levels on the rise, there are

other industries that offer better return on investment.

Against this background, it is no surprise that innovation in mineral processing is viewed as

incremental, not exciting, and not attracting the best young minds in a world where advanced

materials, nanotechnology, biomedicine and electronics offer more excitement. Unfortunately, the

incremental innovation culture of the minerals industry is also reflected in R&D programs and

outcomes. A scan of the major journals in minerals research shows that most papers are more of the

same and usually follow an analytical approach rather than offering a new synthesis. The

incremental innovation culture is exacerbated by the competitive grant structure in most countries,

where peer assessment has the perverse effect of inhibiting radical idea generation by conditioning

researchers to not stray too far from the norm. Consequently, some of the best ideas are generated

by inventors outside the peer assessment system, and by integrating ideas from different fields.

Fortunately, there are plenty of ideas that could nucleate future innovation in mineral processing,

as outlined in this paper. Mason et al. (2011) consider the drivers for innovation in the minerals

industry of the future as maturing demand, the challenges of energy and water, the need to reduce

CO2 emissions, the need to excel at remediation, declining ore grades, the difficulty of discovering

new ore bodies, and the importance of securing a social licence to operate. This paper demonstrates

how these drivers will enhance technological innovation in areas familiar to mineral processors,

facilitate the integration of new technologies into mineral processing, and hopefully allow a more

open-minded approach to radical ideas currently rejected by conventional science. This crystal ball

vision of innovation in mineral processing is not comprehensive, but is sufficient to demonstrate

that a changed innovation culture will bring renewed prosperity.

FAMILIAR TECHNOLOGY

Substantial progress has been made in the development of new comminution methods, the

separation of particles on the basis of physicochemical properties, biomining and non-cyanide

leaching of gold. These technologies familiar to mineral processors are expected to nucleate further

innovation as outlined below.

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Fine-grinding technology

Napier-Munn (2014) asked recently: “Is progress in energy-efficient comminution doomed?” As the

most energy-intensive part of a mineral processing circuit with a multiplier effect through other

unit operations, it is contended here that comminution is only in its infancy on a path of innovation

towards energy reduction. Bearman (2013) stated that particles break due to their tensile strength

being exceeded. However, mechanical delivery in comminution is usually in the form of

compression, which may cause local compressive failure, but outside of the impact point the stress

field generated will cause the particle to fail in tension. This key point of insight has been neglected

by inventors of fine-grinding equipment and offers substantial opportunity for future innovation.

An example where fundamental insight in comminution mechanisms has been integrated with

creativity in design is the “IMP” super-fine crusher (Kelsey & Kelly, 2014) which can generate fine

and ultra-fine products from single stage reductions of coarse or fine mineral feeds. The concept is a

rotating compression chamber and an internal gyrating mandrel, with the axis of rotation of the

shell being displaced relatively to the axis of the vertically mounted mandrel. The compression

chamber is machined inside as double cone frustums at an angle equal to the displacement angle.

The combination of extraordinarily high power intensity and extreme compressive force results in

primary compressive fracture and induced secondary tensile failure. The axially displaced rotation

of the compression chamber effectively distributes the breakage forces throughout the particle bed.

Kelsey & Kelly (2014) suggest that this design, which could be applied dry or wet, will reduce the

capital and operating cost of fine-grinding and revolutionize mineral processing flow sheets. If the

scale-up of centrifugal “IMP” technology can be demonstrated, it will lead to process intensification

in comminution with the elimination of large SAG mills, the possible elimination of closed circuit

classification, and significant savings in energy and water.

High compression dry grinding used widely for cementitious materials is more energy efficient

than the conventional tumbling mills used in mineral circuits (Aydoğan & Benzer, 2010). However,

mineral processors remain less familiar with modern dry grinding technology, and unlike Loesche

(2014), few equipment manufacturers promote their technology to minerals companies, consultants

and researchers. High compression dry grinders, for example vertical rollers, offer better grinding

and size control, hence improve liberation, minimize over-grinding, hence give sharper size

distribution curves, give activation of particle surfaces, result in energy savings and lower

operating costs, and obviously reduce water consumption.

Implications of dry processing for flow sheet design

Technology for dry separation has been aimed mainly at coarse gravity separation, for example the

continuous float-sink separation of lump iron ore and copper ore using a dry sand fluidized bed

dense medium (Franks, Firdaus & Oshitani, 2013; Oshitani et al., 2013). This method of gangue

rejection will be effective for a copper ore if the grade is a strong function of density, otherwise the

tailing would have to be subjected to heap-leaching.

Macpherson, Iveson & Galvin (2011) showed that it is possible to effectively separate particles on

the basis of density, with minimal size effects, in the air-sand dense-medium Reflux Classifier with

vibration. The Reflux Classifier combines a conventional fluidized bed with a system of inclined

40

channels to achieve enhanced rates of segregation of high density particles, and enhanced

conveying of low density particles. Greenwood, Langlois & Waters (2013) showed that a laboratory

Knelson Concentrator can operate satisfactorily on a dry basis using fluidizing air. It is expected

that developments in dry fine-grinding will catalyse further innovation in dry separation with

substantial flow-on effects for circuit design.

Loesche (2014) expects that dry fine-grinding will enhance mineral liberation, and increase flotation

kinetics and recovery. Better particle size control will result in reduced slimes production, hence

less coverage of ore particles by slime, hence improved adsorption of collector in flotation, resulting

in an improved grade-recovery relationship. Similarly, improved liberation and less fines will

increase recovery in gravity or magnetic separation. Improved liberation and enhanced mechano-

chemical activation of the particle surfaces (Baláž, 2008) will enhance leaching efficiency and reduce

reagent consumption. Even part dry processing in a circuit will reduce water consumption, but the

reduction in fines will also improve dewatering. More efficient fine-grinding using “IMP”

technology for example, could promote more hydrometallurgical processing of concentrates rather

than smelting.

Froth Flotation

Froth flotation has experienced innovation in three areas, i.e. reagents, cell design and control. Such

innovation has been incremental to a large extent, and is expected to continue, with the economic

gains difficult to quantify. A review of recent developments by International Mining (2013)

indicated that the choice of reagents is so large that reagent selection requires mining companies to

engage consultants with adequate databases to select reagents for a new venture. Nevertheless, it

happens too often that the pre-construction selection of reagents for a new flotation plant must be

revised substantially post-commissioning. With advances in analytical techniques, academic

researchers today have a thorough understanding of flotation surface chemistry. Unfortunately, it

cannot be said that all this research has led to radical improvements in flotation efficiency; it is

difficult to identify a few papers or patents on flotation chemistry that have resulted in a step

change in flotation practice.

In contrast, flotation cell design has undergone radical change, and more innovation is possible,

provided that a deep understanding of the hydrodynamics and mechanisms governing flotation is

integrated with cell design in the creative mind of the inventor. In this regard, the depth of insight

and inventiveness of Prof Graeme Jameson are without equal; he understands how to convert

analysis to synthesis, while so many others remain analysts. His creativity has accelerated through

his long career, and it is just hoped that early career inventors will learn from his example. Based on

the theory that the rate of flotation of ultra-fine particles can be improved by increasing the rate of

shear in the suspension of particles and bubbles, Jameson (2010) invented the Concorde Cell, in

which the pre-aerated feed is raised to supersonic velocities before passing into a high-shear zone in

the flotation cell. By recycling the tailings, and using the mass pull as the control variable, this Cell

can produce a high-grade concentrate at high recoveries, over a wide range of particle sizes. By

understanding that a quiescent flow field is necessary to prevent coarse particles from becoming

detached from bubbles, Jameson (2010) invented a liquid-fluidized bed cell where air bubbles are

dispersed in the fluidizing water and coarse particles attach to the rising bubbles into the froth layer

on top. This technology provides major advantages beyond the ability to recover coarse particles

41

currently lost: (a) If the upper flotation limit can be extended, the top size for grinding can be

raised, with liberation being the key constraint on size; (b) This cell can handle a much higher

percent solids in the feed, leading to significant reductions in water requirements (Jameson, 2010).

Base level control of pulp levels, air flow rates and reagent dosing has advanced significantly over

the last forty years, but advanced and optimising flotation control systems have had mixed success

(Shean & Cilliers, 2011). As machine vision and intelligent systems become more robust it is

envisaged that fully automated flotation control will be possible in future.

Microwave processing and electrical pulse liberation

Microwave (MW) processing of ores may offer enhanced kinetics, enhanced recovery and more

efficient heating by using inverse thermal gradients and overcoming the low thermal conductivity

of oxides (Pickles, 2009b). Bradshaw et al. (2007) validated their thermal stress simulations

experimentally to show that MW operation at high power densities (∼109 W/m3 absorbing phase)

and short residence times (∼ 0.1 s) can process ores economically at viable MW energy inputs (∼1

kWh/t). MW treatment could potentially enhance liberation and change progeny size distribution in

confined bed breakage, with more grain boundary damage induced in coarser textured ores having

a large thermal expansion coefficient, which causes larger differential tensile stress in the zones

surrounding the absorbing grains compared with the tensile strength of the matrix (Ali & Bradshaw

(2009; 2011). When MW roasting a refractory gold concentrate, Amankwah & Pickles (2009)

observed that the heating rate and carbon removal rates were higher and the specific energy

consumption was lower than the corresponding values for conventional roasting. The addition of

coupling agents such as carbon or magnetite, or the use of a coupling crucible could enhance

microwave absorption and heating (Pickles, 2009a). MW processing of ore is relatively new and

offers considerable potential, especially when ores are ground and separated dry.

Although Swart & Mendonidis (2013) showed that treating granite rock samples with RF power

within the VHF range did not meaningfully weaken the mineral grain boundaries, hence did not

benefit mineral liberation, they suspected that improved results would be possible for sulfide

minerals that are more absorbent of electromagnetic radiation. By applying high voltage pulses at

specific energy of 1–3 kWh/t to pre-weaken mineral particles, Wang, Shi & Manlapig (2011)

obtained evidence of cracks and microcracks measured with X-ray tomography and mercury

porosimetry. They showed that ore surface texture and mineral properties affect the efficiency of

high voltage pulse breakage, so that its feasibility must be assessed on a case by case basis.

In an insightful review of mineral liberation by application of high voltage pulses, Andres (2010)

explains how polarisation at the electrodes causes rearrangement of charges in the affected ore

fragments containing constituents of different permittivity and conductivity. The electrical

imbalance at the interfaces between metalliferous and other minerals forms substantial local

charges and hence electrical fields at the boundaries of the polarized minerals. Electrical discharge

by these polarized minerals causes plasma streamers of a tree-like pattern inside the solid

fragments when solid matter is converted into plasma gas at a high temperature of 104K. The

thermal expansion of plasma produces fractures, cracks and fissures at the boundaries of the

metalliferous minerals and metallic inclusions of slags, weakening the cohesion between different

constituents inside the aggregates of ores and in smelter slags. Andres (2010) identifies the

requirement for commercialization of high voltage pulse liberation as a well funded multi-

42

disciplinary team of electrical specialists and mineral processors. It is possible that the generation of

plasma inside ore constituents by high voltage electrical pulses could cause chemical

transformations other than the physical liberation studied so far.

Biomining

A variety of microbes can efficiently leach metals from minerals and waste streams, either in situ or

in processing equipment. Although bioleaching has been applied commercially for more than 70

years, biomining is expected to be used increasingly for lower grade complex polymetallic ore

deposits (Brierley, 2008). An improved understanding of the physicochemical factors governing

reactions, along with genetic manipulation of existing strains that will increase microbial tolerance

to high concentrations of undesirable elements, will result in enhanced metal extraction from ores

as well as urban waste such as fly ash from coal and municipal waste incineration (Bharadwaj &

Ting, 2012). Johnson, Grail & Hallberg (2013) have shown that bacterial oxidation of elemental

sulfur could be coupled to the reduction of ferric iron in the goethite fraction of a limonitic nickel

ore to solubilize Co, Cr and Mn. This work demonstrates the potential for the bioprocessing of

oxidized, iron-rich ores using an approach that is energy-saving and environmentally-benign

compared with existing processes for the extraction of Ni from lateritic ores.

Until about 1999, bioleaching focused on Acidithiobacillus ferrooxidans as the main mesophilic

bacterium, but since then the focus has shifted to the moderately thermophilic microbes, archaea,

that offer more potential for biomining. The archaea are a domain of single-celled microorganisms

called prokaryotes, which means that they have no cell nucleus or any other membrane-bound

organelles in their cells. Archaea use more energy sources than eukaryotes like fungi and plants,

ranging from organic compounds to ammonia, metal ions or even hydrogen gas. Salt-tolerant

archaea use sunlight as an energy source, while other species of archaea fix carbon; however, unlike

plants and cyanobacteria, archaea cannot do both (Wikipedia, 2014).

The biological degradation of cyanide has been proposed, but has not yet been found to be cost-

competitive. Instead of the trial and error approach often followed in biomining, a scientific

understanding of the underlying mechanisms and the geochemistry of the minerals will enhance

adoption of the technology. Cyanide production by microbes is well-known, but has been found to

be too slow for practical application. In contrast, gold-targeting microbes attach directly to the

surface of gold, form biofilms and produce cyanide, which in-turn solubilizes gold without the

need for diffusional transport of cyanide. Such microbes have extensive potential for in situ

recovery of gold with obvious economical and environmental advantages over open-cut and

underground mining (Zammit et al., 2012).

Microbes usually render mineral surfaces hydrophilic and can prevent the attachment of collectors

in flotation. By utilizing a short residence time, bio-oxidation prior to flotation of some ores may

produce sufficient surface oxidation selectively on one sulfide phase so as to allow a far greater

collector selectivity, improving the grade of the concentrate or allowing the use of less selective, and

cheaper, collectors in flotation (Rowe, 2009).

43

New chemistry of metal extraction

Feng & Van Deventer (2011) reported that gold extraction in thiosulfate solutions was largely

improved by the addition of certain amino acids (L-valine, glycine, DL-α-alanine and L-histidine).

It is well-known that amino acids form relatively stable complexes with gold, which suggests that

they offer an opportunity to replace cyanide under controlled Eh-pH conditions, with the addition

of an oxidant. Florrea (2014) in Shenyang, China, markets a proprietary non-cyanide leaching

reagent that is claimed to be a direct substitute for cyanide and with the gold recoverable onto

activated carbon; these claims require further validation. Sadly, the presumption that there is no

replacement for cyanide in gold recovery has inhibited innovation in this field over decades.

An adsorption system with exciting potential but which has been under-utilized is the Spiderweb™

technology of Intellimet (2014), which uses a tightly packed bed of beads, like a resin column, but

instead of putting the binding groups inside the beads, it has the binding groups on polymer strung

between the beads, resulting in rapid recovery. The development of a solid aminobiphosphonate-

based adsorbent for the removal of heavy metals, including uranium and gold, at low

concentrations over a wide range of pH values offers substantial potential for innovation in mineral

processing (ScienceDaily, 2013). This technology developed by the group of Prof Jouko Vepsäläinen

in the School of Pharmacy at the University of Eastern Finland and acquired by Chemec Ltd in

Finland demonstrates the need to look broader afield than traditional mineral processing research

for radically new ideas.

LESS FAMILIAR TECHNOLOGY

Developments in microfluidics, nanotechnology (Roco, Mirkin & Hersam, 2011) and advanced

materials have exploded over the last decade and have major implications for electronics,

communications, biotechnology, clinical medicine and defense. In contrast, the landmark report by

Diallo et al. (2011) states: “The application of nanotechnology to mineral discovery, mining,

extraction, and processing has thus far received little attention.” This report expects that the

convergence between nanotechnology, geosciences, synthetic biology, biotechnology, and

separations science will lead to major advances in mineral processing: (a) Development of non-

acidic microbial strains that can selectively leach valuable metals from ores without extensive

dissolution of the surrounding rock; (b) Development of more efficient and environmentally benign

leaching solutions for in situ mining; (c) Development of more efficient separation systems. It is

contended here that researchers in nanotechnology and mineral processors are mutually ignorant of

each other’s challenges and opportunities. Therefore, the review below aims to make mineral

processors aware of relevant developments in these fields.

Microfluidics

By bypassing the settler stage and eliminating undesirable particle-stabilized emulsions (crud),

microfluidic solvent extraction (μSX) was proposed by Priest et al. (2011, 2012) as an improvement

over conventional mixing-settling SX. They observed that leach solutions of copper oxide and

chromite with high concentrations of sub-micron silica particles did not cause failure of the μSX

chips for extended periods, and that the extraction kinetics were not altered by the presence of

44

particles in both reaction or diffusion controlled cases. μSX offers a reduced plant footprint, closed

systems (no escape of solvents), reduced reagent inventories, higher recycle rates, and flow-

controlled operations (no moving parts or human intervention). μSX has been proposed for the

recovery of lanthanide ions in nuclear fuel processing (Nichols et al., 2011). Yin, Nikoloski & Wang

(2013) demonstrated μSX for the extraction of platinum and palladium from chloride leach

solutions for spent automotive catalysts.

The “scale out” of microfluidic reactors through parallelization is less expensive and carries less

risk than the scale-up of conventional systems (Lo, 2013). Bhardwaj, Bagdia & Sen (2011) proposed

a microfluidic device operating as a micro-hydrocyclone for the separation of micron and

submicron size solid particles from liquid, which offers potential in lab on a chip type analytical

devices. Ceramic-like microfluidic devices that allow chemical reactions at high temperature or/and

high pressure conditions (Ren et al., 2014) could be used to synthesize reagents like cyanide on site

without the need for transport, or could be used to treat process solutions. Nanofluidic devices offer

promise for desalination of water with energy consumption that approaches that of a large-scale

reverse osmosis desalination system. Kim et al. (2010) proposed a system that uses low-pressure

and electricity to drive seawater through a channel containing a nanojunction, consisting of an ion-

selective nanoporous membrane, to connect two microchannels. This causes an ion concentration

polarization that separates the seawater stream into freshwater and a concentrate stream.

Nanotechnology and advanced materials

Significant advances have been made in the development of nanoscale supramolecular hosts that

can serve as high-capacity, selective and recyclable ligands and sorbents for extracting valuable

metal ions from solutions and mixtures, including: (a) Dendrimer-based chelating agents for

valuable metal ions, such as Cu(II), Ni(II), Zn(II), Fe(III), Co(II), Pd(II), Pt(II), Ag(I), Au(I), Gd(III), or

U(VI); (b) Dendrimer-based separation systems for recovering metal ions from aqueous solutions;

(c) Nanosorbents based on self-assembled monolayers on mesoporous supports for recovering

metal ions, such as Cu(II), Ni(II), Zn(II), Fe(III), Co(II), Pd(II), Pt(II), Ag(I), Au(I), Gd(III), or U(VI)

(Diallo et al., 2011).

Graphene has received much attention as an advanced functionalized material. The simplest

method to create graphene is by peeling off a piece of scotch tape stuck to a piece of graphite,

resulting in microscopic layers of hexagonally shaped graphene. In the same way as graphene

could be obtained from graphite, single atom thick sheets of hexagonal plates of transition metal

chalcogenides (sulfides, selenides and tellurides) could yield materials with spectacular properties.

For example, single atom sheets of molybdenum disulfide could be used as a transistor (unlike

graphene) consuming several hundred thousand times less energy than a silicon transistor

(ScienceDaily, 2014).

Functionalized graphene can adsorb heavy metal ions efficiently and selectively, so it has been used

for the removal and detection of environmental pollutants due to its unique physicochemical

properties (Lü et al., 2013). Graphene oxide has also been shown to adsorb radionuclides and other

toxins efficiently (Materials Today, 2013). Therefore, graphene and its functionalized forms offer

potential as selective adsorbents in mineral extraction.

Graphene-based materials like laminates of graphene oxide can have well-defined nanopores with

low frictional resistance to water flow, making them suitable for filtration and separation. In the dry

45

state the laminates are vacuum-tight, but if immersed in water, they become molecular sieves,

blocking all solutes with hydrated radii larger than 4.5Å, while smaller ions permeate through the

membranes at rates thousands of times faster than what is expected for simple diffusion. Joshi et al.

(2014) ascribed the anomalously fast permeation to a capillary-like high pressure acting on ions

inside graphene capillaries.

HERETICAL CONCEPTS

All scientists are taught that the law of conservation of mass and energy is beyond dispute. This

framework is then used to refute claims about the so-called “free energy” technologies with output

above unity (Eversole, 2013) as being fraudulent. Likewise, those who suggest that precious metals

can be recovered from ores that do not show values in sophisticated analytical methods, are

deemed to be fraudsters or considered to lack an understanding of metallurgy. Few professionals

will risk their reputation by debating or investigating these scientific heresies. The possibility that

radical and unconventional energy technologies are suppressed systematically is rejected outright

as conspiracy theory. Moreover, heretical technology is difficult to commercialize, as patent

applications are usually rejected on the basis that they “offend against the generally accepted laws

of physics and established theories”. What is “pathological technology” today may be the

innovation of tomorrow, as discussed below.

Unconventional energy

Eversole (2013) contends that there have been at least seventy successfully working “free energy”

technologies, including those of Nikola Tesla, that could have replaced fossil fuels and nuclear

energy, yet most of them have been suppressed. Of these technologies, the work of Dr Randell Mills

of BlackLight Power Inc. on energy release from hydrogen atoms, without combustion and without

harmful radiation, has arguably the best scientific basis (Mills & Lu, 2011). Their unified theory

predicts that a hydrogen atom’s electron orbit could be tightened, forming a smaller atom called a

“hydrino.” Independent validation has shown that his heated-hydrogen-and-catalyst reaction

produces two hundred times more energy than comes from burning an equal amount of hydrogen

gas. BlackLight Power claims that one milliliter of water provides enough hydrogen to produce one

megawatt of electric power, and that capital costs will be about 2% of conventional generation. It is

not clear whether the Energy Catalyzer of Andrea Rossi, with support from physicist Sergio

Focardi, is related to the work of Dr Mills, or whether it is cold fusion as claimed. Apparently, this

device works by infusing heated hydrogen into nickel powder, transmuting it into copper and

producing heat. In January 2014 this technology was acquired by Industrial Heat LLC, a subsidiary

of Cherokee Investment Partners. Although cold fusion has been widely rejected by the scientific

community, it is worthwhile to follow developments in unconventional energy generation.

Abnormal precious metals

There are indications that high recovery of gold and platinum group metals (PGM) not detected by

neutron activation or conventional assay techniques is possible from certain ores. Such gold and

PGM are not considered to be “invisible” to detection but rather “abnormal” at atomic level. Large-

scale extraction of precious metals from “abnormal” ores has not been achieved yet, and is a

46

prerequisite for acceptance of this emerging field. Van Deventer (2013) reviewed unconventional

observations, the pseudo-science mainly available in non-peer reviewed websites, and hypotheses

for the recovery of “non-assayable” gold, including: (a) The occurrence of high levels of nano-sized

gold in clays detectable by high precision analytical instruments, which represents “invisible” gold;

(b) Accounts of ambient transmutation of elements, mainly using thermal methods; (c) Orbitally

Rearranged Monoatomic Elements (ORMEs) which are virtually undetectable by conventional

means and their conversion to normal metals; (d) The possibility of a “high spin” state of transition

metals; and (e) The formation of microclusters altering the chemical behaviour of precious metals

and the possibility of clustering with other elements. It was suggested that precious metals in ores

display a range of clustering, from “normal” detectable gold to the ORME state. The possibility that

ORMEs could be related to the postulated “hydrino” of Mills & Lu (2011) has not been suggested

before, and presents an interesting avenue to develop a theoretical framework for this field. The

high recoveries from non-assayable ores may not be the result of transmutation, but instead the

conversion of precious metals already present as micro-clusters to “normal”’ metals.

SYNTHESIS

Innovation in mineral processing has been incremental rather than radical, with lead times of 10 to

20 years between invention and industry-wide adoption. A crystal ball vision shows that

technological incubation times in the minerals industry will shorten, otherwise it will not attract

investment capital in competition with more exciting industry sectors. Inventors in biotechology,

nano-devices and advanced materials have ample opportunity in electronics and biomedicine, so

the onus is on mineral processors to transfer these technologies to the minerals industry. A shift in

innovation culture is required in the minerals industry, which presents substantial opportunity for

entrepreneurs who can make the link between ore source, technology and finance, but poses a

threat to companies unable to change.

The integration of various technologies will result in lower energy operations with substantially

reduced CO2 emissions, lower operating and capital costs, and less environmental impact. By

positioning mining as a high technology industry with benign environmental impact, communities

will be more supportive in granting a social licence to operate. Mineral processing viewed through

the crystal ball will prefer microbial in situ mining where reagents may be generated at the surfaces

of minerals, with advanced selective separation chemistry, using nano-materials or microfluidic

devices. Efficient water purification and desalination will be possible through microfluidic devices

and modified graphene materials. Precious metals will be recovered from unconventional ores

using benign reagents. Grinding will be done mostly dry and with lower energy consumption,

followed by improved dry separation, with substantially lower water demand. Microwave pre-

treatment and electropulse liberation will be applied to specific ores. Coarse particles will be

separated in high pulp density fluidized bed flotation as a means to minimize downstream

processing. Ultra-fine particles produced by low energy grinding machines will be recovered in

supersonic, high shear flotation cells. The surface properties of ore particles subjected to flotation

will be induced by more selective reagents as well as microbes. In summary, innovation rather than

access to mineral resources will determine investment returns in the mineral industry.

47

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50

Overcoming sustainability challenges of future

concentrator plants

Kalle Härkki Outotec, Finland

ABSTRACT

Sustainability principles in the minerals industry are now becoming more and more important from the

perspective of securing a license to operate and enhancing environmental, economic and social

performance. This trend is also setting new challenges for the design and operation of future concentrator

plants. It is evident that ore grades are declining and ores are becoming more complex requiring new

technology innovations and holistic approach for process optimization. There is a demand for more

energy-efficient process technologies especially in comminution that is the major energy consuming unit

operation in the process chain. Energy is not only a major source of cost but also contributes significantly

to the carbon and environmental footprint. There is also an increasing awareness that more intelligent

water management is required for reduction of fresh water consumption and mastering the impacts of

process water recycling will cause for process performance. In association with water recycling, tailings

disposal is an integral part of concentrator plant representing significant environmental and economic

issues to the operation. This presentation will discuss general trends and challenges of future minerals

processing plants and how innovative technology solutions and better integration of unit processes in

conjunction with intelligent process control would contribute to meeting the sustainability challenges.

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There is no full article associated with this abstract.

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Sustainable mining at Antofagasta Minerals

Diego Hernández and Hernán Menares

Antofagasta Minerals, Chile

ABSTRACT

Over the last few years, the copper mining industry has been facing a changing scenario with

respect to both the market and society which has resulted in taking a closer look at the way in

which mining is being done. The cycle of high metal commodity prices of the last decade left the

industry with high costs. Together with increased environmental and social requirements, a

decrease in ore body quality, scarcity of resources such as human capital, water and energy, has

resulted in an ever-increasing challenge to make a profit out of new ore bodies but also to maintain

the current operations in the longer term competitive.

The major challenge is to create value for all stakeholders, exploiting ore bodies that nowadays are

not considered economically attractive, which applies to both new ore bodies and existing

operations, but in a sustainable way. In order to achieve this objective, it is necessary to approach

the mining business differently in five main areas: (1) operational efficiency through better use of

installed equipment and skilled labor force; (2) efficient use of energy; using opportunities for

alternative energy sources and efficient design; (3) efficient use of water; diminishing losses and use

of seawater as an alternative source; (4) minimizing environmental impact by eliminating effluents

and controlling dust emission; and (5) a more closer, proactive and collaborative relationship with

the communities allowing them to be an active player in the solution to assure a sustainable

business in the long term.

This presentation will show how Antofagasta Minerals is facing these challenges with a long term

strategy that includes all of the above mentioned aspects and that is allowing the company to

exploit its mineral properties in an efficient and successful way.

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There is no full article associated with this abstract.

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