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.