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, prompted mine managers to increase ore depths as a way to make mining operations more efficient and work around limited surface areas.
While this change has made some mines more efficient, it has also made the recovery of metals more difficult for mines that traditionally relied on drip lines for mineral recovery.
Application rates for leach solutions are designed to increase the efficiency of metals recovery and limit chemical consumption. Critical aspects that need to be considered during heap leach design are the depth of ore, the presence of water/solution and the local terrain conditions.
Heap piles are comprised of numerous segregate layers of coarse and fine-textured material, and leaching solutions must be able to percolate through all of these layers. Leaching solutions flow more readily in the more conductive layers, potentially leaving areas within the heap unleached.
As the trend of larger and deeper leach piles increases, this condition becomes more prevalent resulting in channeling within the piles.
Unfortunately, drip lines are prone to channeling and clogging, which results in uneven ore/solution contact and inadequate saturation of the entire leach pad. For designer and manufacturer of high-quality irrigation solutions for agricultural, horticultural, and industrial applications Senninger, these changes presented an opportunity and a challenge to develop new irrigation technology capable of uniformly saturating a leach pad from
top to bottom without clogging.
Senninger Solutions
After analysing the issues, Senninger’s objective was to create an irrigation system capable of distributing water in a uniform pattern and at an adequate application rate, as determined by a metallurgist, over an entire heap pile. The wetted pattern must also be able to infiltrate the pile at the same point where it falls.
Senninger’s low-pressure Wobblers evenly apply solution over large surface areas, enhancing solution/ore contact, while reducing the potential for channeling or clogging. These low-pressure sprinklers distribute water in consistently sized
droplets resistant to evaporation and wind-drift.
Key Benefits
- Operate at low pressures between 1 bar to 1.38 bar to save energy costs
- Wet the entire surface with a 90% and more uniformity of distribution in a full 360° pattern
- Offer a half to one-third lower cost than drip systems
- Offer the versatility of being moved and used repeatedly
- Provide visual confirmation of uniformity not afforded by surface drip application
- 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
Wobblers vs Drip
Leaching processes using drip methods depend on source point application of the solution, which promotes channeling. 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.
Low-pressure spray nozzles like Wobblers evenly apply solution over large surface areas, much like a gentle rain, improving solution/ore contact, while decreasing the potential for channeling or clogging.
Wobblers sprinklers can be spaced 6 m × 7 m between sprinklers and lateral lines, while 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’s 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 sprinklers line includes the 30, 40, 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.