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You hear it time and time again: our froth pumps succeed in tough applications where no one else’s can. We take a look at why Weir Minerals leads the industry in managing mineral froths.
The challenge of pumping mineral froths has evolved due to changes in the flotation process and technologies to align with the demand of lower grade recoveries of high value commodities.
Slurries consisting of finely ground particles, water, air and a variety of flocculants designed to maximise mineral recovery range from brittle, with large bubbles of entrained air that break easily, to tenacious or persistent froths, where smaller bubbles can survive for hours in the liquid (commonly referred as a gas binding in the pumped medium).
These characteristics can change frequently, complicating pumping systems with insufficient ability to remove air from the slurry, impeding the performance of traditional centrifugal pump designs.
Today, Weir Minerals offer “state of the art” pump design developments which can accommodate froth bearing slurries with much higher Froth Volume Factors (FVF), (which describes the volume of air in the froth), thanks to the combination of efficient horizontal froth pump designs and the Weir Minerals’ patented Continual Air Removal System (CARS) design.
In this article, we explore our journey from using vertical slurry pumps (Warman® AF) to the pioneering work done by our engineers to adapt the traditional Warman® horizontal pump to froth pumping applications, (culminating in the Warman® AHF, LF and MF pumps) and the recent release of Weir Minerals’ Continual Air Removal System (CARS).
For more technical information on using a Warman® centrifugal slurry froth pump, please download our full white paper and Technical Bulletin #28: Froth Pumping.
Prior to the introduction of horizontal froth pumps, the Warman® AF vertical pumps were a common sight in flotation circuits around the world.
However, as flotation technology has evolved the requirement to meet larger plant throughputs and process demands have increased, it became impractical for the traditional vertical froth tank design to increase in size to meet tonnage and flow performance demands.
Our journey with horizontal froth pumps began in the 80’s, when Warman design engineers began experimenting with the Warman® AH pump to manage mineral froths in hard rock processing sites in Queensland, Australia.
This development evolved into the Warman® AHF and later the MF and LF range of Warman® froth pumps with a view to accommodate mineral froths more efficiently through the large suction and open scoop impeller features.
Requiring a lower upfront investment and much more efficient to operate, Warman® centrifugal froth pumps quickly replaced vertical pumps as the preferred choice of froth pump operators across the globe. They’ve been found to be more resilient to bearing and shaft failures than vertical pumps, reducing their maintenance overhead and further reducing the total cost of ownership.
While the Warman® range of centrifugal froth pumps proved even more adept at handling mineral froths as their vertical counterparts, the gradual increase in tenacious, high Froth Volume Factors (FVF) froths over the last few decades have posed a significant challenge, as entrained gases in the pumped media was becoming problematic with traditional centrifugal pump configurations.
To manage tenacious froths, which are often implicated by the introduction into the process stream of significant quantities of flocculants and other chemicals designed to increase mineral yield, Weir Minerals engineers took inspiration from the methodologies of gas separation and venting used in the paper stock pump industry.
They used a semi-open impeller with venting holes that allowed gas to move into a collection chamber behind the impeller, where it was evacuated from the pump with the help of a vacuum pump. This proved unsuitable for slurry pumps because it required tight clearances, which contributed to blockages and excessive wear.
Designed with the use of Computational Fluid Dynamics (CFD) analysis, the Continuous Air Removal System (CARS) utilises a flow inducer behind the main impeller to vent gas from the pump’s gas collection chamber. The inducer vanes apply a swirl effect to the feed, forcing the heavier slurry to the outer edge of the pump while the gas gathers in the middle, where it’s transferred to the collection chamber by holes in the impeller.
Since its introduction in 2014, the vented CARS design has been successfully deployed for managing copper, gold, zinc, bitumen, talc, molybdenum and potash froths in sites around the world.
The key advantage of our vented CARS configuration over traditional froth pump designs is the ability to handle elevated FVF’s in highly tenacious applications and with improved overall operating efficiencies.
CARS is recommended for pumps in applications with certain Froth Volume Factors, as indicated in the chart above. For more information, please download our white paper: Froth Pumping using Warman® centrifugal slurry froth pumps and our Technical Bulletin #28: Froth Pumping.
Today, we offer three types of froth pump – the classic Warman® AHF, as well as the MF and LF. These models offer a range of hydraulics parameters to meet specific duties and materials to accommodate typical froth applications.
All Warman® froth pumps have the optional benefit of the interchangeability for the CARS (Continuous Air Removal System) and when used in conjunction with recommended specific sump designs, use a large, oversized inlet and the unique Warman froth impeller design to handle froth slurries with ease.
The Warman® froth pump offers discharge sizes ranging from 50-550mm making them suitable for a variety of applications. Larger models can support flow rates up to 4,550 m 3/hr in throughput and design heads normally associated with typical froth installations.
All Warman® froth pumps offer expeller sealing and low flow gland sealing as standard configuration to minimise water usage and operating costs. Mechanical sealing is available in limited applications. Pumps equipped with CARS vents can only use a gland-style shaft seal, due to the venting pipe in the collection chamber.
Our range of Warman® froth pumps combine the time-tested Warman® centrifugal pump design with CARS, to meet the challenges posed by the most tenacious froths.
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