In heap leach mining, leach solution (or lixiviant) is distributed onto the top of a heap of ore. The goal is to evenly distribute the solution so that the target minerals are dissolved by the solution. After the solution picks up the target minerals it is referred to as a “pregnant solution”, and is then collected for further chemical processing.
A critical factor in the overall mineral extraction rates and irrigation system operation is the method in which the lixiviant is distributed to the heap. Leach mining operations generally choose between using sprinkler irrigation or drip irrigation systems. The biggest issue with sprinkler systems is that toxic chemicals can be spread beyond the mining site due to wind, whereas a drip irrigation systems ensures that all lixiviant is applied directly to the heap.
Based on our experience, we at DRTS see that majority of operations choose drip irrigation and believe that drip irrigation is the future of leach mining. However, not all drip irrigation systems are created equal, there are a number of factors that affect the efficiency of a drip irrigation system, ranging from proper hydraulic design to incorporating the necessary redundancies, proper system monitoring, maintenance procedures and the use of specialized mining grade drippers.
Leach Mining System Design Variables
Although serving different purposes, a drip irrigation system used at a leach mining site has many similarities with irrigation systems used in agriculture. All drip irrigation system components must be selected to suit the operational requirements, while taking into account certain safety factors. However this safety factor must not exceed a certain threshold, otherwise the cost of the system will be unnecessarily increased.
Every mining operation is unique so drip irrigation systems must be designed specifically for each individual mine. Since there are no off the shelf universal systems, the following variables must be taken into account when designing a mining system:
- Required lixiviant solution application rate
- Site elevation changes & overall topography
- Available solution pressure & temperature
- Line head-loss (pressure loss) due to the distance for solution to travel from the pump station, peripheral accessories (filters, valves, flowmeters) and the dripline
- Maintaining desired pressure at the drippers nominal 1-1.2 bar, and a solution velocity of 2-2.5m/s. Any velocity greater than that and the flow friction threshold will be reached, resulting in head-loss and inefficient pump operation
Leach Mining System Layout
Leach pad stacking usually takes a lengthy period to construct, a common practice is to sub-divide the total surface into smaller more manageable sized cells. A typical leach operation will not wait until the entire leach pad is constructed and thus will begin leaching partially stacked individual cells, while additional cells are being stacked. This type of progression leaching has led to the establishment of best practices regarding the layout of drip irrigation systems for use at leach mining sites:
- Place piping in a way that gives access to maintenance crews, being able to drive up with heavy machinery to install or remove the irrigation system components.
- Routing of the drip irrigation system piping as to limit the number of unnecessary bends for simplicity and reduction of head-loss.
- Incorporate into design temporary dead-end service valves that can be opened at a later time, providing the capability to remove, add, and block off sections as required. This also ensures the necessary modularity of the drip irrigation system, to expand as new cells of a leach pad come online.
Drip irrigation systems for use in heap leach mining must be designed according to the size, topography and specific parameters of each operation. It is also important to incorporate redundancies, modularity and easy maintenance access to the system from the start. These two factors play a critical role that are taken into account when designing a drip irrigation system in order to achieve target extraction rates.
DRTS @ MiningWorld Russia
DRTS will be exhibiting at the MiningWolrd Russia trade show from April 23 – 25. MiningWorld Russia is one of Russia’s leading mining industry trade shows. The show features the latest technology, machinery & equipment for mining & processing of minerals. Visit DRTS and learn more about our Minoro dripper and how we can help design your next leach mining project. Click here to schedule a meeting at the show.
Visit our booth: Hall 1-3 | Stand C377
Learn More with DRTS
To find out more about leach mining drip irrigation systems, products and project design, contact DRTS to request a free expert consultation with a field expert and receive a custom quote tailored to your needs and budget. Or feel free to learn more about our mining products and services on our leach mining page.
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