Nickel is crucial in the transition to net-zero and, as a result, demand is expected to increase by around 65% by the end of the decade, according to the International Energy Agency (IEA). The adoption of electric vehicles is the primary driver, with higher quantities of nickel in the cathodes of lithium-ion batteries being used to improve performance and increase their range.

‘At the start of the decade,’ according to the International Energy Forum (IEF), ‘just four percent of nickel produced globally was used in car batteries, but this could increase to as much as 40 percent by 2030 as bans on internal combustion engine vehicles approach in many markets.’

Nickel is recovered using high-pressure autoclave technology, which poses several challenges from a processing perspective. It requires pumping high pressure, high temperature and often corrosive slurry.

Weir employs its GEHO® heat barrier piston diaphragm pumps in these arduous duties and it recently manufactured and tested the largest autoclave feed pump in the world, the GEHO® TZPM2000HB. Two of these pumps have now been delivered and are currently being commissioned at an nickel mine in Indonesia.

Meeting Nickel Demand

Indonesia is now the world’s largest nickel producer, mining 37% of global supply and forecast to increase to two-fifths by 2030.

This growing demand is causing many miners to increase their production capacity, which means there is a trend towards larger, higher-capacity pumps. This evolution has unfolded over three decades, with Weir being involved in the development of pumps for autoclave feed applications from the outset. The GEHO® TZPM2000HB continues to push the boundaries of what’s possible, not just in terms of pump capacity but, crucially, the size of the pump allows the operator to run it at the low speed.

In other words, increasing capacity by running existing, smaller pumps at higher speeds in such a demanding application often leads to failure. It significantly increases wear and the risk of equipment failure, resulting in reduced availability and, ultimately, lost production.

When sizing these pumps, Weir draws on over 30 years of installation, operational and servicing data and experience in HPAL applications. Moreover, this information is also fed back to the engineering teams and informs pump design and development.

Understanding and reducing wear

The slurry enters the pump through the suction valve and flows out via the discharge valve. Both valves come into direct contact with the hot, erosive and corrosive slurry, so it’s important that they are highly wear-resistant.

In more general applications, the valves have a valve ring that can seal off to guard against coarse particles. But in autoclave feed applications, the valve and the seat have only metal-to-metal contact and, as a result, are more susceptible to coarse particle wear caused by washout (i.e., localised wear due to slurry getting between the seat and valve).

Therefore, when pumping a coarse slurry, it’s not uncommon to see premature valve failures caused by washout before the end of the valve’s normal wear life has been reached. Combatting these challenges involves both engineering and servicing aspects.

From a technology standpoint, GEHO® heat barrier pumps feature a unique valve design with special material selection that enhance valve durability in these demanding duties. From a servicing perspective, in addition to replicator valves failing prematurely, they also lack comprehensive service support.

Weir, in contrast, has a global footprint with extensive servicing and support capabilities, which includes having consumables on hand in all major nickel mining regions.

Pumping high temp slurries

GEHO® heat barrier pumps have a unique combination of separator, cooler and diaphragm section whereby hot slurry is cooled and any contact with the pump’s moving parts is eliminated.

The separator section prevents the hot slurry from directly exchanging heat with the slurry in the cooling section, thereby minimising the cooling capacity required.

In large pumps like the GEHO® TZPM2000HB, this is achieved with a free-floating separator disc that follows the piston and diaphragm movement. A water jacket cooling pipe, then cools further down the slurry and prevents hot slurry from coming into contact with the diaphragm.

The diaphragm separates the slurry from the pump’s moving parts, allowing them to be maintained at predictive intervals of 8000 hours, typically once per year.

Delivering reliability

In nickel autoclave applications, piston diaphragm pumps have to handle larger volumes and pressures, which means the dynamic loads are higher. These larger pumps introduce more flow and pressure pulsations, which present further challenges.

In order to cope with these loads, the GEHO® heat barrier pumps have a single-piece casted power end and forged steel crankshaft, both field-proven for decades, underscoring their reliability.

Furthermore, the GEHO® TZPM heat barrier pumps feature a slide-mounted frame, allowing the entire pump to slide backward a few millimetres when it expands due to thermal elongation. This design prevents pump piping from bending, eliminates undue stress, and avoids the formation of cracks, maintaining the pump’s integrity without relying on expansion seals prone to premature failure.

Suction and discharge air vessels are also installed to compensate for the flow and pressure pulsations generated by the pump, ensuring that vibrations of the pump and connected piping are minimised.

Nickel is a critical mineral in the energy transition, but meeting demand will require innovative technologies to optimise existing processes. The GEHO® heat barrier pumps is indicative of the role that mining technologies and solutions will need to play in improving operational efficiency and, ultimately, enabling the transition to a low-carbon economy.

This article was first published in Engineering & Mining Journal, July 2024