Heap leach depths have increased from 15 m of ore depth to 150 m since the turn of the century. Higher closure and reclamation costs, as well as a need to decrease the impact on agricultural land, has forced mine managers to increase ore depths to work around limited surface areas and make mining operations more efficient.

However, this change has made the recovery of metals more difficult for mines that rely on drip lines to spread leaching solution.

Heap piles are comprised of numerous segregate layers of coarse and fine-textured material, and leaching solutions must be able to percolate through all the layers. Leaching solutions flow more readily in the more conductive layers, potentially leaving areas within the heap unleached. This condition becomes more prevalent as the trend of larger and deeper leach piles increases, resulting in channelling within the piles.

The issue with drip systems is they depend on source point application of the solution, which promotes channelling. Because there is minimal lateral movement of the solution applied over the ore material, close spacing of the drippers and laterals is necessary to achieve the desired application rate. This increases the potential for clogged orifices and lines – owing to the small flow passages required – and results in uneven ore/solution contact and inadequate saturation of the entire leach pad.

For Senninger, designer and manufacturer of high-quality irrigation solutions for agricultural and industrial applications, these changes presented an opportunity and a challenge to develop new irrigation technology capable of fully saturating a leach pad from top to bottom without clogging.

SENNINGER SOLUTIONS

After analysing the issues, Senninger sought to create an irrigation system capable of distributing the leach solution in a uniform pattern and at an adequate application rate over an entire heap pile, as determined by a metallurgist. Senninger also knew the wetted pattern must be able to infiltrate the pile at the same point where it falls.

Senninger enhanced the material of its low- pressure Wobbler sprinklers so they could evenly apply solution over large surface areas, enhancing solution/ore contact while reducing the potential for channelling or clogging. These low-pressure sprinklers distribute the leaching solution in consistently-sized droplets resistant to evaporation and wind-drift.

KEY BENEFITS OF WOBBLER SPRINKLERS

• Operate at low pressures between 0.69 bar to 2.07 bar to save energy costs

• Uniformity of distribution (+90%) over full 360o area.

• Half to one-third lower cost than drip systems

• Versatility of being moved and used repeatedly • Visual confirmation of uniformity not afforded by drip systems

• Adapt to pad rinsing for reclamation

• Operate without the need for expensive filtration • Directly install over existing drip systems to complete the leach cycle or provide a final rinse

WOBBLER SPRINKLERS VS. DRIP IRRIGATION

At +90% of uniformity, Wobbler technology provides the most effective method for total solution contact. Uniformity of solution distribution reduces the risk of channelling and maximises metals recovery.

Wobblers can utilise the same low pressures as drip emitters and be installed on existing drip systems, but with a wider spacing of 6 m x 7 m between sprinklers and lateral lines. Drip irrigation systems would require 0.6 m spacing between drip lines and emitters to achieve the same application rate. This significantly reduces material and labour costs with wobbler applicators.

OTHER CONSIDERATIONS

Senninger’s mining products are constructed using engineering-grade thermoplastic resins, which are specially formulated and selected for resistance to corrosion, abrasion, ultraviolet degradation and the rugged conditions specific to solution mining. Other Senninger sprinklers available for mining are the Super Spray, which provides a full 360° spray

pattern and is extremely useful for evaporation of excess water in gold and silver mining installations. Senninger’s impact sprinkler lines include the 30 Series, 40 Series and 50 Series for low application rates with a large diameter of coverage. The part- circle impact sprinklers are designed for dust control and provide the most flexible option to leach side slopes and dust control when coupled to a portable pipe system. The 80 Series impact sprinklers are ideal to water over a large diameter with maximum

efficiency at high flow rates.

Senninger’s pressure regulators control excessive

and varying inlet pressures to a constant outlet pressure to help maintain the overall efficiency of an irrigation system.