Tag Archives: Fresnillo

Robbins accelerates Fresnillo development with MDM rectangular tunnel boring machine

At Fresnillo, a silver mine in Mexico, Robbins and the mine operator are making good headway on accessing a deep underground orebody using a rectangular tunnel boring machine.

Known as the MDM5000 (standing for Mine Development Machine), the TBM has dimensions of 5 m x 4.5 m and is capable of excavating a flat tunnel invert for immediate use by rubber-tyred vehicles, Robbins says.

The successful operation is the result of extensive discussions between tunnel boring machine (TBM) and mining equipment manufacturer, Robbins, who designed and supplied the machine, with TOPO Machinery and Fresnillo plc.

Fidel Morin, Projects Superintendent for Fresnillo Mine, said: “We decided to work with Robbins for their experience. A lot of people have tried to provide these kinds of machines, but nobody has done it. Robbins used their experience and their skills to provide us with a rectangular profile machine.”

With more than 1,700 m of advance thus far at rates up to 52 m in one week and 191 m in one month, the MDM is significantly faster than drill and blast excavation, Robbins claims. The MDM is excavating in andesites and shales with quartz intrusions that have defeated earlier attempts to excavate these tunnels with heavy roadheaders, according to the company.

A crew member operates the MDM5000 in Fresnillo, Mexico from an  air-conditioned control cabin using touch screen technology

“We’re making history,” Morin said. “Fresnillo is always looking for new technology, and we believe that the usage of the MDM5000 is going to be something extremely successful, not only for our company but also for the mining industry.”

While the MDM5000 has proven itself in underground mining, Robbins sees it as just one component of a new approach. A multi-faceted solution for underground mine development would see the use of Robbins shaft boring machines for ventilation and mine access, as well as TBMs and conveyors to directly mine the orebody and transport material. The unique TBMs would be lighter, more mobile and able to bore inclines, according to the company.

“It’s all about reaching first ore quicker, and then economically mining the orebody while reducing tailings,” Robbins President, Lok Home, said of the strategy. “Mechanised tunnelling machines have the potential to revolutionise the underground mining industry.”

Robbins’ new solutions for underground mining are the latest in a legacy of innovations the company has developed over the years.

“Introduced equipment ranges from raise drills to non-circular mobile miners to continuous conveyors and customised TBMs at projects including the Grosvenor Mine in Australia, the Stillwater Mine in Montana, USA, and others,” the company said.

As for the MDM5000, the machine has undergone major component enhancements during the course of its successful bore at Fresnillo mine. It was first transported to the -695 m level of the mine and underwent final assembly and launch in a cavern, where sections of the MDM were moved by crawlers and pieces were lifted by hoist. The machine is now boring a 270° spiral to end above the original tunnel. It will then be backed up to the original tunnel and continue driving straight ahead.

MDM tunnelling has advance rates roughly twice those of a drill and blast heading, and results in smooth tunnel walls, less overbreak and minimised ground support, according to Robbins (credit: Fresnillo plc)

Fresnillo previously said it was using the Robbins TBM to develop the new San Alberto orebody at the underground mine, with plans to carry out 11 km of development in total for that project.

Developed for use in underground mining in rock up to 200 MPa UCS, the MDM5000 is particularly useful for long access tunnels and development drifts, Robbins says. Using disc cutter technology proven on traditional, circular TBMs, the MDM5000 excavates with a reciprocating cutterhead and swinging cutterhead motion to create a rectangular cross section tunnel.

“The MDM offers a number of advantages for mines over other methods including drill and blast,” Robbins says. “MDM tunnelling has advance rates roughly twice those of a drill and blast heading, and results in smooth tunnel walls, less overbreak and minimised ground support. The increased advance rates are partly due to the machine’s continuous progress, unlike drill and blast operations where crews must exit the tunnel during blasting for safety. In addition, simultaneous ground support installation further increases overall advance rates compared with drill and blast operations that must install ground support sequentially.”

Orla Mining on course for first gold in 2021 at Camino Rojo Oxide project

The publication of the updated feasibility study on Orla Mining’s Camino Rojo Oxide Gold asset in Zacatecas, Mexico, has come with a 54% increase in contained gold reserves and a 3.5-year extension to the mine life of the in-construction project.

The new reserve estimate at Camino Rojo includes a proven and probable total of 67.4 Mt at 0.73 g/t Au and 14.5 g/t Ag, for total mineral reserves of 1.59 Moz of gold and 31.5 Moz of silver.

The updated study outlined open-pit mining of 67.4 Mt of oxide and transitional ore at a rate of 18,000 t/d. Ore from the pit will be crushed to 80% passing 28 mm, conveyor stacked onto a heap leach pad and leached using a low concentration sodium cyanide solution. Pregnant solution from the heap leach will be processed in a Merrill-Crowe recovery plant where gold and silver will be precipitated and doré will be produced. The site’s proximity to infrastructure, low stripping ratio, compact footprint and flat pad location all contribute to the project’s simplicity and low estimated all-in-sustaining costs of $543/oz of gold, the company said.

An after-tax net present value (5% discount) of $452 million was calculated by the study team led by Kappes Cassiday and Associates and supported by Independent Mining Consultants, Resource Geosciences Inc, John Ward Groundwater Consultant, Barranca Group, Piteau Associates Engineering and HydroGeoLogica Inc.

The main notable physical changes from the 2019 feasibility study are an increase in the size of the open pit, heap leach pad, and mine waste dump because of a layback agreement with the adjacent Fresnillo mine, all of which were anticipated in the initial design. While all material to be mined on the Fresnillo concession has been classified as waste in the latest study, Orla sees opportunities to further expand the reserve and resource base following further work on material in this area.

Jason Simpson, President and Chief Executive Officer of Orla, said: “The updated feasibility study for the Camino Rojo Oxide project demonstrates an increase in recovered gold, mine life, and cash flows.

“An already excellent project has been improved due to the hard work of the entire Orla team and I thank them for their efforts. We are pleased to announce this important enhancement and we will continue to optimise this asset as we move through construction and into production.”

Detailed engineering of the project described in the 2019 feasibility study is over 90% complete and procurement is 85% complete, with the start of earthworks announced on November 26, 2020. Since that time, 230 ha have been cleared for construction activities with over 20,000 cu.m of topsoil being removed and stockpiled. Equipment deliveries to site commenced in December, with a total of $78 million of the total project capital committed through purchase orders and contracts.

Orla says the mining contract is being finalised and expected to be in place early in the March quarter, with first gold production planned for late 2021.

MAG Silver and Fresnillo make processing leap at Juanicipio

Fresnillo and MAG Silver Corp’s Juanicipio silver-gold-lead-zinc project, in Mexico, has reached a major milestone, with development material from the project being processed at the Fresnillo beneficiation plant during the September quarter.

The joint venture, owned 56% by Fresnillo and 44% by MAG, saw 42,476 t processed during the quarter, with total production of 394,000 oz of silver, 610 oz of gold, 138 t of lead and 174 t of zinc, Fresnillo reported.

This first development material was processed through the nearby Fresnillo processing plant (100% owned by Fresnillo) with the lead (silver-rich) and zinc concentrates treated at market terms under offtake agreements with Met-Mex Peñoles, SA De CV in Torreón, Mexico, MAG said. The revenue from this production, net of processing and treatment costs, will be used by the joint venture to offset cash requirements of the initial project capital, according to MAG.

“This first production from Juanicipio is a major milestone for the company,” George Paspalas, MAG Silver’s President and CEO, said. “The successful processing of development material not only provides cash flow to offset capex, but further de-risks the project as it heads toward commercial production. We are looking forward to the first production stope coming online in Q4 (December quarter) 2020, and our potential to continue to produce cash whilst we complete the process plant construction.”

Fresnillo expects to process an average of 16,000 t/mth of mineralised material from the joint venture through its processing facility to mid-2021, at which time the Juanicipio beneficiation plant is scheduled for commissioning.

Development continues on site and the final preparation of the first production stope was concluded during the September quarter. Also during the quarter, progress was achieved on the construction of the Juanicipio processing plant.

Cat’s DGB dual-fuel technology cuts costs, emissions at La Herradura gold mine

Caterpillar has been showing one of Mexico’s biggest gold mining operations that its Dynamic Gas Blending™ (DGB) technology can provide savings on fuel costs and emissions while maintaining the same performance, payload and productivity of its diesel haul trucks.

The mining OEM and its Mexico-based dealer, Matco Cat, have been working with Fresnillo’s Penmont division to convert its entire fleet of large mining trucks at the La Herradura open-pit mine, in Sonora.

Caterpillar’s dual-fuel DGB technology, which has accumulated 10 million hours in the oil and gas industry since 2013, works by blending lower cost liquefied natural gas (LNG) with diesel fuel, according to Cat.

The resultant improvements in fuel, emissions and maintenance can add up to millions of dollars each year in cost savings, Cat said.

La Herradura, since 2016, has acted as a great case study for the technology given it has more than 250 Cat trucks and the operation hauls at least 25 Mt of volume per quarter (based on Fresnillo’s most recent Q4 production results).

In addition, the company has been looking for ways to “produce (gold) in a sustainable manner”, Fresnillo’s Abel Villa said in a recent Cat customer story.

According to Steve Igoe, Commercial Manager for Caterpillar’s Gas Engine Business, the benefits of DGB technology include, primarily, a lower cost per tonne, realised through a lower fuel cost. “DGB truck operation with LNG has proven very beneficial to La Herradura, and this is why they have decided to convert their entire fleet,” he said.

“Typically, LNG is 30% lower than the price of diesel. And, on a typical fleet at a mine, that adds up to millions of dollars a year,” he said. “And the trucks maintain the ability to operate 100% on diesel.”

Cat estimates a fleet of 100 trucks spends approximately $60-70 million/y on diesel fuel. With 65% displacement to LNG using DGB, that fleet could save $13 million/y on fuel alone.

DGB can also bring about a 30% cut in emissions compared with diesel-only operation – another important saving for mining companies looking at sustainability.

Trials during 2016 and 2017 of the technology at a gold mine in Turkey and a phosphate mine in the US have proven these claims.

For instance, the Turkey gold mine has retrofitted DGB technology on Cat 150-ton (136-t) 785C haul trucks and, since installation, has reached an average 70% average fuel displacement in addition to an operating cost reduction of $30/h.

Fresnillo’s Villa said La Herradura had gone further than this in terms of displacement.

“Initially when we started the project, the substitution rate was 70:30. We evaluated the results and changed the substitution to 85:15,” he said. This is close to the peak substitution rate Cat typically recommends.

Villa continued: “We have an average reduction of 70% in diesel consumption. We also considerably reduced the amount of emissions. When we compare both diesel and gas, the operation is the same.”

Cat said it observed a less than 1% difference in speed, payload and gear shifting, plus a 30% reduction in fuel cost, during one customer’s 5,000-h DGB trial.

La Herradura has also seen no unexpected maintenance issues during the trials, according to Fresnillo’s Enrique Leal. This is in keeping with Cat’s focus on reliability and productivity, with the company saying it has tallied zero hours of unplanned downtime.

So far, La Herradura has retrofitted 31 of its 785C haul trucks and a significant number of 240-ton (218-t) 793D trucks with the DGB technology.

Fresnillo’s Villa said the operation also plans to partner with a third party to build an LNG plant near the mine to ensure a sustainable supply.