Abstract
An efficient metal recovery in heap leach operations relies on uniform distribution of leaching reagent solution over the heap leach pad surface. However, the current practices for heap leach pad (HLP) surface moisture monitoring often rely on manual inspection, which is labor-intensive, time-consuming, discontinuous, and intermittent. In order to complement the manual monitoring process and reduce the frequency of exposing technical manpower to the hazardous leaching reagent (e.g., dilute cyanide solution in gold leaching), this manuscript describes a case study of implementing an HLP surface moisture monitoring method based on drone-based aerial images and convolutional neural networks (CNNs). Field data collection was conducted on a gold HLP at the El Gallo mine, Mexico. A commercially available hexa-copter drone was equipped with one visible-light (RGB) camera and one thermal infrared sensor to acquire RGB and thermal images from the HLP surface. The collected data had high spatial and temporal resolutions. The high-quality aerial images were used to generate surface moisture maps of the HLP based on two CNN approaches. The generated maps provide direct visualization of the different moisture zones across the HLP surface, and such information can be used to detect potential operational issues related to distribution of reagent solution and to facilitate timely decision making in heap leach operations.
Highlights
We present a case study of a unmannedaerial aerialvehicle vehicle (UAV) equipped with a dual gimbal system which allowed mounting a visible-light camera and a thermal infrared sensor on the drone to acquire aerial images
There are several advantages of using UAV platforms equipped with imaging sensors to acquire data over heap leach pad (HLP)
The collected aerial data were processed through digital photogrammetry and convolutional neural networks, and the generated results provided direct visualization of the different moisture contents across the HLP surface
Summary
Heap leaching (HL) is a hydrometallurgical technology that has been widely adopted by the mining industry in recent years due to its easy implementation and high economic feasibility for metal and mineral extraction from low-grade ore deposits [1]. In an HL operation, metal-bearing ore is piled on an impermeable pad (i.e., an engineered liner), and a water-based lixiviant (or leaching reagent) is irrigated on top of the heap surface [2]. The leach solution, driven by gravity, flows through the rock pile and contact with the ore, such that the metal or mineral of interest is extracted from the rock and dissolved into the solution [3]. The solution exits the base of the heap through slotted pipes and a gravel drainage layer located above the liner [2].
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