Outotec has introduced the 2nd Generation Paste Thickener to, it says, maximise underflow density regardless of challenging mineralogy and tailings feed-rate variation.

The thickener enables consistent and efficient dewatering performance – even with changing process conditions, according to the company.

“Through consistent performance and high underflow density, the 2nd Generation Outotec Paste Thickener maximises beaching angle in the tailings storage facility to provide safer operations and maximised lifespan,” Outotec said.

The new paste thickener provides ease of operation and reliability for applications requiring a high degree of dewatering, such as minerals tailings, mine backfill, and pre-leach and counter current decantation circuits, according to the company. “The technology is customised to address each operation’s unique drivers, which can include environmental concerns, water recovery, regulatory requirements, tailings management, or limitations on available land space,” the company said.

Outotec has a history of developing paste thickeners, as well as the design and delivery of large-scale paste thickening projects. “This has given us a deep understanding of the key aspects of high-density thickeners, including effective flocculation, dewatering, raking, prevention of rotating mud beds, process control, and the discharge of thickened solids,” it said.

“One such case was the deployment of Outotec paste thickener technology – including a full-scale paste tailings plant and Outotec ACT Thickener Optimizer system – at Yara’s Siilinjärvi apatite mine in Finland (pictured),” Simon Courtenay, Product Manager for the Outotec 2nd Generation Paste Thickener, said. “The plant generates around 10 Mt of tailings a year and, thanks to the Outotec ACT Thickener Optimizer, the paste thickeners can consistently run with a high and stable underflow solids content of 66-68%, regardless of challenging mineralogy and tailings feed-rate variation. This results in average beach slope angles of 3.5° (6.1%) in the tailings disposal area, helping to extend its lifespan. The system has also enabled a 10-20% reduction in flocculant costs.”

The new 2nd Generation Paste Thickener builds on this proven performance with a range of innovative new features, according to the company. For example, vertical load monitoring with the Smart Rake Lift system means the Outotec Paste Thickener is one of the only systems in the world that can detect early formation of rotating beds, enabling counteractions to be taken early, Outotec said.

The system also monitors and actively adjusts the individual hydraulic cylinders to maintain alignment of the rake mechanism. Incorporating vertical load sensing with plant process data in the Outotec ACT Thickener Optimizer control system means the solids inventory within the tank can be maintained to ensure a consistent underflow density, stable process, and improved overall thickener performance, according to the company.

In addition to mechanical improvements, process control has been further developed to stabilise and optimise the performance of the paste thickener, Outotec said.

The company said: “Outotec’s ACT Thickener Optimizer utilises a multivariable controller to manage process changes and the associated delays in the response time of the thickener that can be challenging for traditional control systems. It can also be configured to manage the effects of variable feed types to ensure optimum performance despite changing inputs to the process. Short installation and configuration time of the system is coupled with on-going services to ensure a practical yet flexible long term control solution.

“Our application-specific design of the thickener begins with the use of methods such as discrete element modelling to understand solid particle movement within the thickener, computational fluid dynamics for feed system design and finite element analysis for structural steel design. Our paste thickening solutions are also designed with ease of maintenance in mind, with a skid-mounted hydraulic power unit for centralised connection of hydraulic hosing from the rake lift cylinders and drive unit.”

Other key design features include:

• Low profile rakes with tie-cable load sharing that minimise rake drive torque requirements;
• Rake blades supported by thixoposts to move the rake arm away from the highest density thickened solids;
• High sidewall and steep tank floor slope for more efficient dewatering of flocculated solids and compaction of the bed, as well as better transport of the solids inward toward the tank discharge point;
• High installed drive torque to move the rake blades through beds of thickened solids with high yield stress and viscosity, and;
• Feed systems with break tanks when required for different thickener feed situations, including our patented Vane Feedwell, and break tanks inside the thickener perimeter to save on site layout space.

“Beyond technology and equipment, Outotec provides complete solutions for thickening needs,” the company said. “Proven design features and process guarantees, combined with lifecycle service support, help ensure operational reliability. We can also support customers with ongoing operation and maintenance services after plant commissioning.”