Has diesel had its day in mining machines?

Louise Smyth

Diesel has been the fuel of choice for many mining applications for decades, but increasing environmental awareness and cost – both initial and life-cycle – have encouraged suppliers and OEMs to examine alternatives.

Engine manufacturer Yanmar is currently gearing up to produce two new liquefied petroleum gas engines, a 2.2 litre 45kW unit to be launched in 2020 and a 3.3 litre 63kW unit for 2021. Both were shown for the first time at bauma.

Yanmar’s Carlo Giudici says: “LPG is a good choice of fuel for mining applications because it is so clean, in particular with respect to particulate matter. This makes it good for enclosed areas.”

The brief for the design team was to concentrate its efforts on achieving the ideal stoichiometric combustion ratio. Giudici continues, “We examined the available mixer intake methods and decided we weren’t satisfied, so we designed a new system from scratch. It has improved economy by a tenth and allowed us to use a higher compression ratio to improve performance. In fact, both engines will outperform their equivalent diesel models even though they are EPA Tier 2, CARB Tier 4 and EU Stage V-compliant.”

Once the models are established in the marketplace the next step is to offer a bi-fuel option, so they can also run on petrol if that’s the customer preference or if no gas is available.

Caterpillar has also been diversifying its product offering to include a retrofit alternative gas option for the 785C Mining Truck. Launched in 2018, the dynamic gas blending (DGB) technology allows engines to run on both diesel and liquefied natural gas (LNG). Diesel fuel savings are reported to be as high as 40% (there is a pilot injection of diesel of 15-40% of the charge) with no loss of performance.  

From a drivetrain perspective, Cat is launching two new mining trucks, the 798 AC, with a 372 tonne payload and the 796 AC with a 326 tonne payload. Both feature electric drives coupled to conventional diesel engines. The latter is touted as a replacement for the 795 AC in regions where engine emissions are highly regulated.

The AC drive is a high voltage system (2,600V) and drivetrain software adjustments can tune the whole thing to a particular mine’s needs. The engine is the C175-16 in 2,610kW (3,500 hp) or 2,312kW (3,100 hp) tune, and all the associated components (engine, traction alternator, motors, inverter, grid and final drives) have been designed to be removed independently to ease maintenance.

Going underground

The company’s Underground Mining Group is currently testing a R1300G proof-of-concept battery electric LHD in a mine in Canada.

Before the electrics were installed, a full performance examination was undertaken, to set a benchmark. Then the old diesel engine was removed and the frame adapted to house the battery boxes and electric motors. The conventional drive shafts and axles were retained, and no efficient electro-hydraulics are present, allowing the battery to be worked to its fullest extent.

Mark Sprouls from Cat North America explains, “The programme is still progressing, so it’s premature to say much about it just yet. What we can say is that it’s providing much needed data that will be put to good use in prototype design in other machines.”

Sandvik sells three electric LHDs with payloads ranging from 3.5 to 14 tons, and is rapidly expanding this side of the business. Minna Pirkkanen, process excellence manager, Load and Haul, Sandvik Mining and Rock Technology, says: “As ore bodies close to the surface become depleted, mines are going deeper. The combustion of diesel fuel and oxygen produces a lot of heat that must be removed using ventilation and refrigeration systems – which poses challenges and increases costs. Today, customers are planning mines for the next decade and are asking about how to prepare for electrification as one solution for going deeper.”

“New solutions for more sustainable mining are required all the time, and these include the need to improve health, safety and environmental issues, such as reducing diesel emissions and noise. Additionally, there is a growing demand for loader and truck automation and connectivity. Customers are asking for increased safety, productivity and lower operating cost through use of automation.”

The company has just made a big purchase. Pirkkanen explains, “Our ambition is to lead the market for battery electric vehicle (BEV) solutions. Sandvik has just acquired Artisan Vehicle Systems, a manufacturer of battery-powered underground mining equipment based in, California, USA. Artisan’s core technology is battery packs, electric motors, power electronics, software and control systems. Last year we opened an advanced Battery Electrification Innovation and Development Centre in Finland. The recent acquisition of Artisan will strengthen our capability to develop BEV solutions for underground mining needs.”

Research is important at Sandvik. The product development process starts with input from customers, who drive the scoping of new products and upgrades. “Customers become part of the process,” confirms Pirkkanen. “To meet the needs that arise from the mining industry electrification requirements, we are further developing battery electric solutions for hard rock mining operations. To support the development of these solutions for mining houses’ needs, we host customer workshops and forums as an effective and successful means of collaboration; a concept with outstanding results in our development projects.”

One example of a participant is Goldcorp, which presented its Borden Lake project in the recent Canadian customer forum, at the world’s first all-electric underground mine in northern Ontario.

In range

Whether for consumer or industry, no conversation about electric vehicles can be complete without discussing range. Pirkkanen feels it’s important to consider the whole vehicle here: “The operating range of traditional electric loaders, equipped with a trailing cable is limited by the cable length. When loaders or trucks are equipped with Lithium ion batteries, it allows more flexibility. However, underground loaders and trucks are probably the most difficult products to replace the diesel engine as a power source, as considerable energy content and power is needed. Lithium ion batteries typically have 1% the energy content of diesel fuel per kilogramme. This means that you need to increase the efficiency of the driveline and hydraulics to maximise the operating range.

“Some customers are also considering traveling down a decline with a fully loaded truck or loader to take advantage of driveline regeneration where the electric motors use the kinetic energy from slowing the vehicle to charge the batteries. The vehicle then trams up the decline empty. This type of cycle minimises net energy consumption by extending the operating range of the battery.”

JCB’s electric first

Officially launched at February’s Executive Hire Show, the 19C-1E is JCB’s first electric excavator. Equipped with three lithium ion cells with a 312Ah (15kWh) storage capacity, a standard load-sensing hydraulic system and battery management system aim to wring the most work out of it between charges, which take from five to eight hours.

Alan Tolley, JCB Group Director of Engines, observes, “Electric machines do require a recharge period, so this has to be factored into the work pattern. However this is not usually a problem for the mini excavator category, but could be for other machine types that are used more in a continuous process mode.”

Looking forward, Tolley still feels diesel will remain crucial for the industry: “Electric will have a part to play but clean diesel technology will continue to power the vast majority of machines. When you compare electric to diesel, the latest Stage V JCB diesel engines have almost eradicated harmful emissions, with NOx down 97% and soot particulates down by 98% compared to 20 years ago. We have also reduced CO2 emissions by almost half by improving machine and engine efficiency. So with diesel, we are firmly on the road to zero.”

Volvo has electric ambitions too, with a brace of launches planned for 2020: a compact wheel loader and excavator. Alongside Telia and Ericsson, the company is also embarking on a research project in Eskilstuna, Sweden to establish the viability of using 5G to control autonomous vehicles. As well as a conventional wheel loader, further testing of the HX2 concept electric load carrier will take place. This follows on from the successful 10 week Electric Site project last year alongside Skanska at the Vikan Kross quarry, near Gothenburg, where 8 HX2s followed a GPS path transporting material from a primary mobile crusher up to a secondary static crusher.

The aim of the project was to break down each stage of mining transport and electrify it. Overall there was a 98% reduction in carbon emissions with a 70% reduction in energy cost.
So although diesel isn’t done yet, it’s clear that there are alternatives out there and with ongoing improvements in battery management and solid state technology potentially on the horizon increasing interest in electric mining vehicles seems inevitable.

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