Production loss due to tank downtime
Many mineral processing procedures rely on keeping solids in suspension in tanks.
Under gravity, solids will naturally form sediment at the bottom of mixing tanks. Stirrers and mixers are then used to resuspend the solids in solution.
Suspension mixing is usually achieved using massive impellers (rotors used to increase the pressure and flow of a fluid) attached to long shafts, at times 20 metres or more in length, resulting in the mixing equipment being heavy, unwieldy and costly.
The mixing is not entirely efficient using this approach and the equipment can be costly to fix when unexpected stoppages or system failures take place.
Problems with tanks often arise from mechanical failure of an agitator, such as the breakage of blades, shaft and gearbox, wear of impeller blades, bogging of the agitator due to sediment and scale build-up in the tank.
Delays due to maintenance and repair can go on for weeks, causing significant losses in production.
Swirl Flow: harnessing the power of a tornado in a tank
We developed Swirl Flow technology with our partners at Queensland Alumina.Swirl Flow enhances the agitation process by mixing liquids and suspended solids to create a tornado-like vortex in a tank.
The solution uses a motor, gearbox and a specially-designed radial impeller with a short shaft near the top of the tank. It is simple and inexpensive to retrofit to existing tanks.
The system improves agitator reliability, resulting in reduced maintenance and shutdowns. Due to higher and more uniform wall veolcities, the scale formation rate is also reduced.
Swirl Flow can increase tank on-line time to lower maintenance and equipment replacement costs.
Swirl Flow has been designed for slurry tanks:
- as a short-shaft system to reduce the mechanical failure risks common in conventional agitator systems
- as a low-weight, lower cost replacement or new agitator system for gold carbon-in-pulp (CIP) leach and process tanks.
- where downstream pumps are starved of feed due to sedimentation blockage of the pump inlet pipe
- to address build-up of inventory, scale or sediment that reduces tank on-line time, or results in a premature stoppage of the tanks.
The capital cost of Swirl Flow is around 50 per cent less than traditional technologies and likewise the maintenance costs are also much lower, in part due to the lower wear rates than for the impellers used in traditional systems.
Conversion to Swirl Flow is not only a major capital cost saving, but also provides long-term operating advantages such as a significant reduction in the tank scaling rate. This allows the tank to stay in operation for much longer periods, increasing production and reducing costs.
Taking the industry by storm
Swirl Flow can be applied throughout the minerals industry for a wide variety of mixing. We have done work for both the gold and zinc industries.
Swirl Flow has been successfully used for more than 15 years by Queensland Alumina at their Gladstone refinery. Currently, 21 large tanks are operating with the technology. Swirl Flow reduced bogging and increased on-line time by three to four months over a 12-month period.
Another company, LKAB Iron Ore in Sweden retrofitted their iron ore slurry surge tanks with Swirl Flow leading to improved mixing of additives, achieving about a 50 per cent increase in surge capacity.
Energy Resources of Australia retrofitted a leach tank with Swirl Flow at their Ranger Uranium Mine operation. Removal of baffles improved tank structural integrity by reducing rubber linking damage risks and tank lining costs.
Swirl Flow is effective for all applications where the prime need is to ensure no solids settle to the bottom of the tank. It can also address the need to avoid particle attrition (for example, when resins are used to absorb valuable metals), to provide effective oxygen transfer or to minimise scale formation.
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