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Process optimisation in minerals processing [opinion]

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With the Australian mining industry facing an increasingly tough market environment, the sector is demanding that companies improve productivity and continually add value to their operations, according to mining services consultancy pitt&sherry. 

For innovative companies, process optimisation and operational excellence in mineral processing have become essential to securing a profitable future and differentiation from their competitors.

Process optimisation and operational excellence have never been more important for mining companies.

As outlined in Deloitte’s Tracking the Trends 2014, mine operating costs continue to escalate and productivity in the industry has dropped by up to 30 per cent since 2003, making application of innovative methods that optimise operations imperative.

The success stories of process optimisation and operational excellence in mineral processing are driven by innovative leaders who challenge the status quo.

Leading process engineers identify opportunities within the current operation that would not have been solved by traditional thought processes by challenging long standing practices

These leaders go about systematically identifying opportunities and then devising, implementing and interpreting diagnostic testing programs to exploit the highest economic return from investment under the prevailing conditions. This is generally an inherent, rather than learned, skill of an inquisitive engineer.

Advances in process optimisation and operational excellence can have focused or widespread effects on mineral processing activities.

The targeted outcomes will generally concentrate on increasing productivity, improving safety and management of environmental risks, lowering operating costs and human factors.

Productivity

According to the Bureau of Resources and Energy Economics (BREE), productivity in Australia’s mining industry declined throughout the 2000s due to factors such as rising costs, changing resource quality and volatile commodity prices.

These conditions have put innovation at the forefront of process optimisation for mining companies aiming to lift productivity through higher recoveries and/or grades, increased throughput or improved asset management.

As a mine progresses through its life cycle and the plant feed changes, the plant operation process should be continually reviewed and adjusted to maintain optimum performance. This is where new or novel ideas are required to deliver productivity gains and efficiency improvements through new technologies.

Process control (automation) of the operation is a key area to attain operational excellence and maintain the plant at peak performance. An innovative idea, implemented at an Australian mine following consultation with pitt&sherry, involved the complete automation and optimisation of the crushing, milling and flotation circuit, inclusive of an in-house automatic gap adjustment on the secondary crusher to maximise the equipment efficiency.

The float circuit was also fully automated with In Stream analysers, level and air automatic control to maintain the target concentrate grade. 

The effect of these changes resulted in lower operational risk, increased productivity, a 30 per cent reduction in power and labour costs ($/t), as well as stable concentrate grades for downstream processing at higher overall recoveries.

Operating costs

Rising operating costs have increasingly become a burden for mining companies over the past decade. To help combat this there are several approaches an operation can pursue which have proven to reduce costs, explains Holder.

A prominent approach is to lower energy usage, which Deloitte says can represent around 40 per cent of a mine’s operating costs.

pitt&sherry has successfully lowered the energy usage at mining operations by exploring different methods, including equipment automation and improving asset utilisation, as well as optimisation (balancing) of energy input through the crushing/grinding and milling circuits to achieve the best outcome with the installed equipment.

Other cost reduction initiatives that have proven successful have included grind size manipulation based on a geo-metallurgy review, use of carbonaceous tailings for acid neutralisation, re-use of reject SAG mill balls, and justified equipment replacements and upgrades through interrogation of asset data.

Often the biggest challenge in reducing costs comes from operations which do not question their current operational performance because ‘it has always been that way.

Safety and environmental risks

Managing safety and environmental risks in the Australian mining industry remains a priority for mining companies. It is also another area where new or novel ideas of operational excellence deliver key benefits.

In mineral processing, cyanide is widely used for leaching and pyrite depression, but is also emotive due to it being toxic for humans and animals.

Holder initiated (with Orica) a federally recognised leading practice in cyanide management for the Cyanide Mini Sparge System during an operational excellence project at an Australian gold mine.

The outcome reduced the risk associated with cyanide mixing on-site to less than one per cent of the original risk score.

Human factors

The potential for mine personnel to have a significant influence on process optimisation of an operation should not be underestimated, according to Holder.

Empowering an operation’s employees through consultation and participation to identify issues and then resolve them to avoid repeats has the ability to have a profound effect when optimising mineral processing activities.

This will generally involve employee training and nationally recognised education programs and motivating employees, which leads to flow on effects such as improved site culture and a tangible reduction in incidents, improved site ownership and operational efficiency.

Lasting legacy

By targeting and then realising outcomes in these areas, mineral processing companies have the opportunity to establish industry leading performance through a combination of sound strategy and operational excellence, while creating value for shareholders and providing business leverage.

However, achieving this with widespread results will require several specialty services before the desired outcome is delivered, he continues.

These services include facility and flowsheet inspections, understanding of the geo-metallurgy, a review of each level of the operation, interviews with site personnel, identification of system and process constraints, determining the most effective modifications, automation opportunities, reviewing manpower requirements, compiling a detailed improvement plan and implementing agreed actions, as well as providing training and mentoring.

The mining industry is well known for its volatility, but by adopting these measures resources companies have the opportunity to make effective changes or improvements that will be sustainable and maintain market competitiveness through differentiation.

*Richard Holder is the principal process engineer at pitt&sherry

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