Tag Archives: CIL

Gekko brings real-time grade measurement to the gold sector

Environmental, Mineral processing, Mining services, Precious metals, , , , , ,

Gekko has launched “Mark 3” of its online gold analyser, OLGA, the flagship product for the company’s real-time data instrumentation division, which operates alongside other key products such as the Carbon Scout to assist in measuring the recovery of gold real-time in gold processing plants, Nigel Grigg, General Manager – Global Sales & Solutions, Gekko Systems, says.

“We are really excited about these new design elements which will improve value and returns for our clients as well as improve ease of operation,” he said. “Now gold grades can be measured in real time compared with the traditional assay-based process which can often result in two-day delays. Operating management will be able to respond immediately if there is a gold excursion or if the data provides other insights into plant trends. This is a breakthrough technology which is now even more affordable and will deliver higher yields in processing plants.”

The OLGA has at its heart the world-first proprietary “Golden Eye” lens technology developed and designed in Australia’s government-funded CSIRO research laboratories.

This component measures gold grade in slurries and solutions combined including low grade slurry streams down to as low 0.1 parts per million. Other elements are also measured including copper, silver, platinum and nickel. The multiplexing feature will allow for up to four streams within a processing plant to be assessed for gold grades, according to Gekko.

The OLGA is the only real-time online measurement system purpose built for gold, Gekko claims. The unit is typically installed to measure the cyclone overflow stream in CIL leach circuits, around the electrowinning circuit and on flotation feed, tails and concentrate. With the multiplexing function, the OLGA can switch measurement of grade from stream to stream.

“The technology represents a significant step forward in the potential to automate gold leaching circuits,” Grigg says.

Another key feature of OLGA is the dedicated sample feed line, facilitating continuous sampling of large volumes with no potential for cross-contamination. The system also offers additional sample points for ad-hoc samples, providing flexibility and adaptability to changing operational needs. Furthermore, the ad-hoc samples can be analysed as batch samples, minimising sampling errors and substituting the need for other sampling systems.

The OLGA Mk3 has undergone rigorous testing and refinement to ensure its robustness, reliability and accuracy in various operational conditions, while offering low maintenance requirements, Gekko says.

Gekko says OLGA’s development was supported by collaboration partners who assisted and provided critical feedback to improve an earlier OLGA technology design. That collaboration included the management and technical teams at Gold Fields, CSIRO, Orway IQ, Curtin University, METS Ignited and Gekko Systems.

Core to the assessment was an OLGA installation at Gruyere Gold Mine (a JV between Gold Fields and Gold Road Resources) where the OLGA achieved excellent results indicating a strong correlation between the automated OLGA and manual assay data and giving the Gekko team the confidence to further develop the OLGA, Gekko concluded.

Wood tradeoff study puts HPGR, POx processing ahead at De Grey’s Mallina gold project

Comminution of minerals, Environmental, Mineral processing, Mineral project development, Mining equipment, Mining services, Precious metals, Sustainable mining, , , , , , ,

Prefeasibility process engineer Wood Australia has completed a comprehensive nine-month trade-off study into the preferred process flowsheet design for De Grey Mining’s Mallina gold project, selecting a process flowsheet that incorporates high pressure grinding roll (HPGR) and pressure oxidation (POx) technology.

The project, which includes the Hemi Deposit, is in the Pilbara region of Western Australia.

In late 2019, De Grey made a large scale, high value, near surface gold discovery at Hemi – an intrusion-hosted form of gold mineralisation new to the Pilbara region that, the company says, shows a scale of mineralisation not previously encountered in the Mallina Basin. The company currently has 6.9 Moz of measured and indicated resources declared at the project, with plans to turn this into an open-pit mining operation down the line.

The findings have come out ahead of the full PFS, which is due for announcement in the September quarter of this year.

The trade-off study has confirmed that Hemi mineralisation has excellent recovery and is amenable to HPGR and POx processing technologies, the company said. The process route chosen has demonstrated advantages relative to other processing technologies including:

  • Proven and accepted technology for the scale of operation and style of mineralisation;
  • Lower capital and operating costs;
  • Higher gold recovery between 93% and 95% depending on average feed grades;
  • Circa-20% lower energy consumption;
  • Circa-25% lower reagent (lime) consumption;
  • Circa-25% lower CO2 emissions;
  • No heat addition required to sustain – or cooling to control – the POx process; and
  • Robust and proven equipment.

The flowsheet selections have the benefit of lower carbon emissions through lower energy requirements and lower greenhouse gas emissions as a result of improved neutralisation and consequent lower lime consumption, De Grey added.
“Further studies are in progress as part of the PFS on the carbon intensity and greenhouse gas emissions for the Mallina Gold Project development,” it said.

The currently envisaged flowsheet at Hemi sees ore crushed and ground in the comminution circuit before being fed to the flotation circuit. Any gravity recoverable gold will be recovered prior to flotation with the use of, for example, a Knelson or Falcon concentrator. Test work has shown gravity recoverable gold is present in the Hemi and regional mineralisation, and the extent of gravity-recoverable gold will continue to be assessed through test work.

The flotation circuit will process gold bearing sulphides in Hemi ore producing a “low mass pull” gold-rich sulphide concentrate. The POx circuit is designed to receive the gold-rich sulphide concentrate from the flotation circuit. The POx circuit will have a throughput of 8% (800,000 t/y) of the throughput of the comminution circuit.

The POx circuit will convert the sulphide concentrate to a gold bearing residue amenable to standard carbon in leach (CIL) processing. The underflow from flotation is also amenable to standard CIL processing. Both streams will enter the CIL circuit followed by electrowinning to produce gold bars on site. This has numerous benefits for the POx circuit including lower capital and operating costs compared with projects that require whole of ore treatment through POx.

Tailings from the CIL circuit will be pumped to a tailing storage facility.

Hemi mineralisation has two significant and attractive mineralogical characteristics that lead to the overall expected metallurgical recovery of between 93% and 95% at expected mined grades, namely:

  • The majority of gold at Hemi can be floated into a low mass pull concentrate that recovers very high levels of sulphides and gold ahead of oxidation; and
  • The flotation tail contains gold that can be successfully recovered using standard CIL processing.

The crushing circuit will include a primary gyratory crusher, a secondary cone crusher and. The secondary cone crusher will operate in closed circuit with a sizing screen while the HPGR will operate in closed circuit with wet sizing screens to produce a nominal less than 7 mm mill feed. The grinding circuit will consist of two ball mills with conventional pinion drives each with their own classification circuit.

The oxidation circuit throughput for Hemi is proposed to be 800,000 t/y, or 8% of the proposed comminution circuit throughput of 10 Mt/y. The oxidation circuit will treat the gold-bearing sulphide concentrate generated by the flotation circuit. The POx circuit will consist of flotation concentrate thickening and storage, POx utilising autoclave technology and neutralisation in association with the flotation tail prior to co-leaching in a CIL circuit.

The oxidation circuit will be designed to have sufficient storage capacity prior to the autoclave to allow for maintenance shutdowns without the need for a mill shutdown. This decouples the comminution and oxidation circuits ensuring that each circuit does not impact on the availability of the other.

Gekko Systems releases Mark 6 Carbon Scout sampling system for CIL, CIP plants

Mineral processing, Mining equipment, Mining services, Precious metals, , , , , , ,

The team at Gekko Systems has announced the release of its next-gen Mark 6 Carbon Scout solution.

The Carbon Scout is a self-contained, ground-level sampling system that measures the pH, dissolved oxygen, slurry density and gold concentration in carbon-in-leach (CIL) and carbon-in-pulp (CIP) circuits. An important new feature is the optional X-ray Fluorescence sensor to measure gold on carbon for real-time gold circuit inventory.

The self-contained device collects slurry samples from CIL/CIP tanks to determine the concentration of the activated carbon in the pulp for each tank, to an accuracy of ±0.5 grams of carbon per litre of pulp, Gekko claims. The concentration levels are then used to automate carbon movement to optimise the carbon distribution.

Gekko said: “The Carbon Scout benefits sites by providing real-time data which allows operators to significantly reduce soluble gold loss from the circuit by providing advanced measurements ahead of any unwanted excursions. The Carbon Scout also allows for automation of the carbon movement, minimising exposure to hydrogen cyanide gas and reducing the need for manual handling of samples.”

Constructed from stainless steel, the ground-level system enhances operator efficiency by removing the need to undertake time consuming manual sampling and provides a single point sampling station to improve accuracy and increase safety, according to the company. The automation of carbon movement, meanwhile, increases the efficiency of the process, ensures carbon inventory set points are achieved and reduces the need for operator, metallurgist and other processing staff input.

Some of the sites to have installed the Carbon Scout solution include Gruyere in Western Australia (pictured above on the left with the Gekko OLGA on the right) and Ity in Cote d’Ivoire.

The solution was commercially released in 2017.

Outotec addresses carbon losses in CIP, CIL gold circuits

Automation, Metallurgy, Mineral processing, Mining equipment, Mining services, Precious metals, , , , , ,

Outotec has released a fully automated in-situ measurement system that, it says, can minimise gold solution losses in carbon-in-pulp (CIP) and carbon-in-leach (CIL) circuits.

Outotec CarbonSense is a system that is directly immersed in the slurry, eliminating the need for sample transfer and ensuring optimal carbon management, according to the company. It is designed to operate continuously in the agitated area of the reactor to ensure a highly representative analysis. It also features a reference probe to ensure reliable measurement even in changing process conditions.

As part of the solution, a single connection cabinet can support up to eight measurement assemblies, along with fibre-optic and copper media connections to the plant network, according to Outotec. “The system supports virtually any network topology, including star and ring configurations,” it said. “Maintenance is simplified with all power supplies and fuses located in one place.”

The portable calibration unit uses authentic slurry and carbon to ensure the best possible results and reliable measurement performance, Outotec said. No recalibration is needed when slurry properties change since the measurement is based on the difference between the measurement probe and the reference probe.

Continuous and reliable carbon concentration measurements minimise gold losses by enabling accurate control over carbon transfer between reactors, according to Outotec, with the Outotec ACT Carbon Management application designed to take full advantage of the measurement data.

The system is delivered as a ready-to-install package including measurement assemblies, connection cabinets and analysis software and licences.

The key benefits of Outotec CarbonSense, according to the company, are:

  • Enables continuous, representative, and reliable carbon measurement;
  • Supports development of efficient strategies for advanced CIP/CIL control;
  • Fully automatic operation;
  • Simple to install, operate, and maintain with no moving parts or sample transfer; and
  • Increases safety by helping to avoid blockages and other sampling issues.

Africa first for Gekko’s Carbon Scout technology

Environmental, Mine operation news, Mining consumables, Precious metals, , , , , , , ,

Gekko Systems says Endeavour Mining’s Ity gold operation, in Cote d’Ivoire, has become the first mine in Africa to install a Gekko Carbon Scout.

The self-contained Carbon Scout device collects slurry samples from carbon-in-pulp (CIP) and carbon-in-leach (CIL) tanks to determine the distribution of the activated carbon in the pulp for each tank, to an accuracy of ± 0.5 grams of carbon per litre of pulp, according to Gekko.

Gekko, following a collaboration agreement signed with Curtin University for the development and commercialisation of a cutting-edge carbon management technology, went commercial with the technology in 2017. At that point, the company said the product promised to quickly become critical for gold process plant optimisation and for minimising soluble gold losses on tails.

By advancing the accuracy, regularity and consistency of sampling, the self-contained, ground-level unit will improve measurements in CIL and CIP circuits, Gekko said, adding that the Carbon Scout will also greatly improve the safety of operations by reducing operator exposure to cyanide and other hazards.

As recently as November, Endeavour announced it had completed a planned CIL plant expansion at Ity, upping capacity from 4 Mt/y to 5 Mt/y. This followed the commissioning of the 4 Mt/y plant in April 2019.

Leagold planning Los Filos gold mine expansion following latest study

Mine operation news, Mineral project development, Mining services, Precious metals, , , , , , , ,

A feasibility study on the expansion of Leagold Mining’s Los Filos mine, in Mexico, has shown potential for the development of the Bermejal underground mine, enlarging the Los Filos open pit, re-phasing the Bermejal open pit into two distinct open pits (Bermejal and Guadalupe), and construction of a carbon-in-leach (CIL) processing facility.

The study shows total gold production of 3.3 Moz over a 10-year mine life (2019 to 2028) at an average all-in sustaining cost of $795/oz at Los Filos. Post expansion (2021 onwards), average annual production would step up to 350,000 oz at an AISC of $759/oz, compared with 195,362 oz last year, which came from the existing heap leach facilities.

The capital cost came out at $180 million to develop the Bermejal underground and construct a new 4,000 t/d CIL plant with related infrastructure, with an NPV (5% discount) of $565 million generated using an average gold price of $1,250/oz.

Leagold CEO, Neil Woodyer, said: “When we acquired Los Filos in April 2017 from Goldcorp, we identified its potential to be developed into a long-life, low-cost operation with significant scale. During the 20 months since the acquisition, we have carried out extensive exploration programmes for both open pit and underground deposits, developed a 1,330-m ramp to access the orebody at Bermejal underground, completed the Bermejal underground mine design, completed comprehensive metallurgical testwork on all of the mineral deposits to support the CIL plant design, and learned a lot from current operations.

“The study identifies a new operating strategy, which includes three large open pits, two high-grade underground mines, the addition of a CIL plant to process the higher-grade ore, and the continued heap leaching of the lower-grade open-pit ore. The Los Filos expansion will also benefit from existing operations and excellent infrastructure. Approximately 51% of the gold production in the life of mine plan is from the CIL plant and 49% is from the existing heap leach facility.”

Woodyer added the company was now putting the study findings into its “overall corporate business model for planning and corporate financing purposes”, but he said it was “obviously a project we should undertake”.

Bermejal Underground

Bermejal underground mine design and cost estimation was completed by SRK Consulting. A total of 11 km of horizontal and vertical development was planned during the initial development period and a further 45 km over the life of mine. The mine life extends for nine years producing 6.4 Mt at 6.57 g/t for contained gold of 1.348 Moz.

Mining costs of $99/t were based on contractor mining, with the mining method being underhand drift and fill with cemented rock fill (CRF) used as backfill. Bermejal underground will have a dedicated CRF production plant. The production rate averages 2,000 t/d and peaks at 2,150 t/d. Bermejal underground contributes 31% of the contained gold in the life of mine plan.

Los Filos Underground

The Los Filos underground mine is currently operating at over 1,800 t/d and, in the life of mine plan, averages 1,700 t/d with mining costs of $73/t based on owner and contract mining. Reduced operating costs, improved mining efficiencies and additional drilling have enabled the update of the Los Filos underground mine plan to extend to 2021. The reserves are 1.9 Mt at 5.50 g/t for a total of 338,000 oz.

Open-pit mining

Los Filos uses conventional open-pit mining methods with an owner-operated fleet supplemented with rental of additional equipment during peak production periods. The average open-pit mining costs are $1.41/t mined.

Los Filos Open Pit

The expanded Los Filos open pit has a proven and probable reserve of 42.7 Mt at 0.57 g/t containing 776,000 oz. The mine life was extended seven years to 2027. The Los Filos open pit has an overall strip ratio of 4:1

Bermejal and Guadalupe Open Pits

The Bermejal and Guadalupe open pits have been split into two open pits and rescheduled to mine the higher-grade Guadalupe ore earlier in the schedule, which significantly improves the economics, according to Leagold. Guadalupe has a proven and probable mineral reserve of 26.3 Mt at 1.55 g/t Au for 1.313 Moz. A pushback in 2020 will open this up as a separate open pit that has a 10-year life, Leagold says. The Guadalupe pit has an overall strip ratio of 8:1.

The Bermejal open pit extends for at least five years to 2025 based on the current reserves. Proven and probable mineral reserves are 34 Mt at 0.54 g/t Au for 588,000 oz. The overall strip ratio of the Bermejal open pit is 2.7:1.

CIL and heap leach processing

The CIL plant is expected to achieve higher recoveries (an average of 89.7%) and better financial returns than heap leach processing for the underground ore and the higher-grade portion of the open-pit ores.

“The plant also provides the ability to process some ore types that were previously not included in reserves as they were not amenable to heap leach processing; this includes material with an elevated sulphur content which exhibits lower gold recoveries at the crush sizes typically used in crushing for heap leach processing,” Leagold says.

The plant is predicted to process a total of 12.4 Mt at an average grade of ore feed of 4.63 g/t Au with an average recovery of 89.7% to produce 1.658 Moz gold.

The expansion feasibility study contemplates the existing heap leach facility continuing to operate throughout the full life of mine plan. A total of 95.6 Mt of ore with an average grade of 0.79 g/t Au will be placed on the leach pads and have an average recovery of 61.9% to produce approximately 1.5 Moz of gold.

Secondary recovery is expected to contribute an additional 111,000 oz from surface re-leaching and re-handling of previously leached ore, Leagold says.

Contributions to the gold production in the life of mine plan are 51% from the CIL plant, 46% from the heap leach and 3% from secondary recovery.

Para and Clark Construction partner up at Gold Road in Arizona

Mine operation news, Mineral project development, Mining services, Precious metals, , , , , , ,

Para Resources has entered into a final services agreement with Clark Construction Group, whereby Clark will provide contract mining services at the company-owned Gold Road mine in Arizona, US.

The contract transitions from the original “time and materials” pact announced in November with an open book target pricing contract. This new contract establishes the basis on which mining and extraction will occur at the Gold Road mine, Para said.

Clark has already been present on the project with equipment and crews and Atkinson is currently driving an exhaust drift in preparations of installing an exhaust fan to upgrade the ventilation system, upgrading the main decline to accommodate larger trucks rehabilitating the secondary escape routes and remediating the previously announced ground control issues.

In addition, maintenance, testing, repair, and general clean-up of the mill has been completed, Para said. The mill is now in functional condition with the exception of additional ball mill liners and first fills which are expected later in January.

Mineralised rock production is on schedule and expected to commence in late January with the re-commissioning of the plant. First gold pour is anticipated in February 2019.

Geoff Hampson, Para’s CEO, said: “We are very pleased to have now transitioned our relationship with Clark Construction Group to a Target Price contract which will ensure continuity of costs and production. We have implemented several key bonus programmes to ensure that Para’s and Clarks’ interests and incentives are in sync.

“Clark is one of the most experienced and respected building and civil construction firms in the US and they bring extensive experience and knowledge to our operations and capacity. The partnership between Clark and our highly skilled and tested Para team will ensure a smooth and successful production ramp up.”

In August 2017, Para, through its 88%-owned subsidiary Gold Road Mining, acquired the 500 t/d carbon-in-leach/carbon-in-pulp Gold Road mine and mill, including patented claims and a mill and processing facility, located in the historic Oatman Mining District of north-western Arizona.

In other news, Para said the mill at the company’s El Limon mine in Colombia continues to perform as anticipated, with the ramp up of feed continuing.

“Para is now assisting several of the larger formalised artisanal miners with equipment, technology and management. The new winch and the new tailing disposal site at El Limon are expected to be completed by the end of Q1 (March quarter) 2019,” it said.

“The current ramp up at El Limon is anticipated to move the operation into positive cash flow in the coming months and commercial production is expected to be declared by the end of the March quarter.”