Whether working with copper, platinum group metals, gold or phosphates, VEGA says the efficiency of the flotation stage of minerals processing determines the amount of valuable material that actually makes it out of the slurry and into a plant’s revenue stream.

“Flotation is a fragile balance. Slight shifts in density, level or foam stability can send efficiency plummeting,” the company adds.

VEGA’s VEGABAR 86 is a smart, durable and low-maintenance density-compensated level measurement option for plants dealing with tough slurry conditions and constantly shifting process variables.

Flotation cells rely on a stable froth layer to effectively separate valuable particles from waste. While VEGA says the chemistry is theoretically simple – aerated slurry forms bubbles, valuable particles cling to the bubble surfaces and the froth layer transports them to the top for removal – in reality, maintaining that froth layer at the right thickness “is anything but simple”.

If the froth is too thin, it will lack the buoyant structure needed to carry hydrophobic particles upward.

A froth that is too thick signals excessive reaction time, often meaning that less of the medium is being processed, resulting in a drop in throughput and an increase in energy and reagent costs.

Complicating this further is constantly changing slurry density, says VEGA, adding that feed variations, solids loading, air entrainment and chemical dosing all shift the density profile inside the tank. Without compensation, VEGA says a level sensor might misread the process, giving operators a false sense of stability while efficiency deteriorates.

A density-compensated level measurement solves this by simultaneously measuring both level and density, the company says.

The VEGABAR 86 uses electronic differential pressure to calculate accurate level values even when solids content changes. This stabilises the control loop and lets operators keep the froth “exactly where it needs to be”, says VEGA.

Demanding Conditions

Flotation cells operate in demanding conditions where they are constantly exposed to sudden changes in density and varying solids content, while turbulent surfaces caused by aeration create additional instability. Over time, VEGA says continuous buildup and abrasion from suspended solids can significantly impact equipment integrity.

The sticky nature of froth layers further complicates the process, as do pressures typically ranging between 80 mbar and 200 mbar and process temperatures from 25 ºC to 35 ºC.

VEGA says many traditional instruments struggle to withstand these challenges, with mechanical components wearing out, impulse lines becoming clogged, capillaries losing their accuracy and the frequent necessity to clean serving to severely hamper productivity.

VEGA says in these applications, its VEGABAR 86 stands out owing to its purpose-built design for challenging environments that are characterised by sticky, abrasive and slurry-heavy processes.

Making it suitable is its proprietary CERTEC ceramic measuring cell, which ensures long-term stability and performance, even in settings where abrasion is a constant threat. This ceramic sensor resists wear far more effectively than traditional metallic diaphragms, particularly when exposed to slurries with high solids content, says VEGA.

As a result, the VEGABAR 86 experiences less measurement drift and is far less prone to failure.

No Mechanical Components

An important advantage of the VEGABAR 86 is its design, which eliminates the need for mechanical components such as capillaries or impulse lines. This means operators do not have to contend with blockages, signal delays or the regular maintenance routines involving hot water and compressed air that other instruments require.

Additionally, because the VEGABAR 86 can simultaneously measure density and level, operators can respond swiftly to changing process conditions, such as sudden collapses in the froth layer or fluctuations in solids loading, ensuring more consistent control and improved process stability.

Further, plants that have implemented density-compensated level measurement in their flotation cells, see more stable, leading to increased recovery rates, enabling operators to spend less time manually adjusting levels.

Moreover, the wear-free ceramic cell and absence of mechanical parts translate into lower maintenance requirements, fewer unplanned stoppages and a longer lifespan for the instrument.