Lime slaking systems may operate in the background, but their reliability is critical to mining and mineral processing operations in bulk handling.
While lime slaking plants rarely sit at the centre of production, their reliability is critical in keeping entire operations running.
The slurry of lime and water, commonly referred to as ‘milk of lime’, is used across a range of applications like pH adjustment, water softening, flotation and impurity removal.
Perth-based bulk materials handling equipment and systems supplier Bulk Handling Technologies (BHT) was recently commissioned to supply a large lime slaking system for a rare earths facility in Western Australia.
According to BHT Engineering Manager Paul Ingleson, the company’s approach to lime slaking has been shaped by decades of operational experience and a strong focus on maintainability.
“Sites need to ensure milk of lime is available at all times,” Ingleson said. “That means having a lime slaking facility that can produce it reliably whenever it’s needed. Lime slaking plants aren’t production assets as such, they’re supporting reagent plants, but if they fail, the entire process can come to a stop.”
Milk of lime is used across virtually every extraction process, from gold and nickel to alumina and rare earths. While its purpose varies between sites, the requirement for reliability does not. Ingleson said lime slaking systems need to operate consistently in the background with minimal operator intervention, regardless of application.
“Whether it’s neutralising acids, assisting with flotation or separation, or meeting environmental requirements, the lime plant has to be reliable,” he said.
Designing for maintainability
To meet these requirements, BHT has incorporated a range of design features aimed at improving safety and reducing unplanned downtime. Central to this is the company’s tyre-driven slaking ball mill, where quicklime and water meet.
“That’s the heart of the lime slaking plant,” Ingleson said.
“It’s where the quicklime particles are ground, mixed with water and the exothermic slaking reaction occurs, generating steam and producing milk of lime.”
Drawing on more than 25 years of involvement in lime slaking plants, including refurbishments, troubleshooting, and audits across a wide range of installations, BHT identified common operational pain points and designed them out of its system. These include areas prone to blockages, hang-ups or excessive wear, and components that are difficult to inspect or maintain.
“We took the lessons we learned from auditing and maintaining other plants, not just our own, and focused on addressing those pain points,” Ingleson said.
Key improvements include a re-engineered pre-wetting vortex feed bowl and mill inlet pipe, designed to reduce blockages and improve access for inspection, cleaning, and replacement. On the discharge side of the mill, BHT has incorporated options such as agitators to prevent hang-ups, improved access doors and a refined hopper design to ensure smooth slurry flow to the pump suction.
Historically, many areas have been difficult or unsafe to access, requiring scaffolding or work at height. BHT’s designs incorporate features such as additional access stairs and platforms and even integrated overhead hoists and beam trolleys to support components during removal, significantly improving safety and ease of maintenance.
“If people can’t get to an area easily, they won’t inspect or maintain it,” Ingleson said. “So, accessibility is critical. If you make it easier and safer to maintain, the plant will be more reliable over time.”
Managing operational risks
An unreliable lime slaking plant can create operational and environmental risks. Ingleson said inadequate storage capacity is a common issue.
“If sites don’t allow for the fact that deliveries can be disrupted, whether due to weather or logistics, they can run out of lime, he said. “If you can’t produce milk of lime, you may have to shut your process down entirely.”
Another key consideration is steam management. The exothermic slaking reaction produces significant amounts of steam which must be carefully controlled.
“What sites need to be wary of is making sure that steam is drawn away from the dry part of the plant,” Ingleson said. “That means having the right extraction design and ensuring the dry handling equipment can cope with higher humidity levels.”
Beyond storage and steam, overall plant layout plays a critical role. Proper access platforms, inspection points and maintenance provisions are essential to ensure components can be inspected, disconnected and serviced efficiently.
Growth driven by experience
BHT’s growing presence in the lime slaking space has been driven less by market shifts and more by internal capability. Ingleson said the company recognised early on that it had deep expertise in this area and a genuine opportunity to offer something different.
“It’s an area we knew we had a lot to offer,” he said.
“Our engineering personnel have extensive experience in the design and manufacture of lime slaking systems, and we are currently assembling a further three systems for customers in Australia and overseas.”
Increased activity across gold mining, major plant upgrades and the rapid growth of rare earths projects have also contributed to rising demand. Each new installation has allowed BHT to further standardise and expand its range of components.
“The key is doing these efficiently,” Ingleson said. “We’re now focused on modularising larger sections of the plant so we can reduce lead times, lower costs and customise layouts without reinventing the engineering each time.
Looking ahead
Feedback from clients to date has been positive, particularly around commissioning and early operation. However, Ingleson said the real measure of success is long-term performance.
“Lime slaking systems need to remain reliable and achieve high availability throughout the life of the plant. We like to stay connected to our customers over the long term to help them achieve maximum returns on their investment,” he said. “In addition, we are always looking for opportunities to collaborate with our customers whenever opportunities arise to implement improvements.”
For BHT, the goal is clear: to establish itself as a long-term, competitive supplier of lime slaking systems.
“We want the market to know we’ve arrived,” Ingleson said. “We’re a viable option, and we’re not just doing what others have done before. We’ve brought improvements and ideas that make these plants safer, more reliable, and easier to maintain.”
