Issue Date: March 21, 2011
Searching For Gold
The U.S. government announced in June 2010 that it had discovered untapped mineral deposits in Afghanistan worth more than $1 trillion. The team of Pentagon researchers and geologists found deposits of valuable metals such as gold, copper, cobalt, and lithium.
The team discovered the minerals with aerial and field surveys using near-infrared (near-IR) reflectance spectroscopy instruments from the Boulder, Colo.-based scientific instrumentation firm ASD. According to Brian Curtiss, ASD’s chief technology officer, the same technology is being adapted for use by mining companies to improve production and lower costs.
Seeking to enter the commercial mining market, ASD has developed a near-IR detector that can be mounted over a conveyor belt moving crushed ore at up to 9 feet per second. The detector can measure mineral and moisture content, allowing mineral processors to quickly determine how to best extract the valuable stuff locked inside the ore. Curtiss says mining customers such as BHP Billiton and Rio Tinto, which already use ASD’s portable and lab-based near-IR instruments to analyze ores, wanted a conveyor-mounted instrument.
“Instead of pulling samples, taking them to the lab, then making decisions based on stale data, the analysis is performed instantly,” Curtiss says. “Measuring ore using real-time spectroscopic technology on nonuniform raw material moving fast over a conveyor belt represents a significant productivity advancement for the mining industry.”
With ASD’s conveyor-mounted near-IR analyzer, mining companies can, for instance, reduce the amount of sulfuric acid needed to extract copper from ore. Although the instrument costs roughly $200,000, operators can earn that money back by using only as much of the $200-per-ton acid as is needed for optimal yield, Curtiss notes.
“Ore grades today are a fraction of what they were in the 1970s and 1980s,” he observes. “And because the easy deposits are gone, we need more technology to get minerals out of the ground.” In addition, deposits are “more variable over a given area,” he says. Using the conveyor-mounted analyzer allows ore processors to adjust processing conditions to the quality of the ore on the fly.
Applying near-IR spectroscopy in mining is new to Terry McMahon, an industrial instrument consultant and principal of PAI Partners. He’s more familiar with near-IR as a technique that is used to monitor surface compositions in industrial settings, such as the quality of pharmaceutical tablets or the thickness and moisture content of paper.
X-ray fluorescence (XRF) is the industry standard for analyzing the mineral content of ore, especially in slurries of crushed rock and water, McMahon notes. Suppliers of such slurry analysis systems include Outotec, a Finnish provider of mining technology and equipment, and the instrument giant Thermo Fisher Scientific.
Scott Ferguson, sales manager for Thermo’s mining industry division, points out that XRF is a low-penetration measurement technique requiring close proximity to the sample. XRF systems that Thermo supplies to mining customers place a sample probe in the slurry stream to “provide real-time data for process control and optimization.”
To monitor crushed rock alone the way ASD does with its near-IR instrument, Thermo provides a through-belt measurement system called prompt gamma neutron activation analysis (PGNAA). The technique depends on readings from a γ-ray spectrometer to determine mineral content, Ferguson says. PGNAA, however, is limited to analyzing ore for light elements such as sulfur, silicon, and magnesium.
Curtiss claims that ASD’s conveyor-belt-mounted instruments are the first of their kind in the mining industry for heavy-metal analysis. Near-IR sensors from other companies monitor flat materials, but “our systems work where the distance to the sample varies,” he says.
A privately held company with 45 employees, ASD started out in 1990 developing portable near-IR instruments for government and academic customers. Curtiss cofounded the firm with Alexander F. H. Goetz, who is now its chairman. They both came from the University of Colorado’s Center for the Study of Earth from Space, now part of the university’s Cooperative Institute for Research in Environmental Sciences.
ASD’s early instruments supported remote sensing from satellite or airborne platforms, Curtiss says. Most of those instruments were used by governments and academic institutions to collect forestry, mining, and agricultural data.
“Our comfort zone is in looking at Earth’s surface,” Curtiss notes. With its foray into ore analysis, “we are taking our expertise to the natural resources industry.”
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