Online measurement of bauxite grade has been achieved.
Release time:
2026-01-07
Challenge:
Online measurement of bauxite grade (including Al₂O₃, SiO₂, Fe₂O₃, etc.) is highly valuable in both mining operations and the alumina (Bayer process) industry. However, it is also widely recognized within the industry as one of the most challenging online analyses to achieve accurate results and maintain long-term stability.
First, the “inherent challenges” posed by bauxite itself.
The mineral assemblage is highly complex and exhibits significant variability. It can include gibbsite, boehmite, and diaspore—along with kaolinite, hematite, goethite, and other minerals—all within the same mining area or even during the same shift. The mineral composition can vary dramatically from one location to another.
Traditional online instruments typically measure “elements” or “characteristic signals,” whereas the Bayer process focuses on soluble alumina and active silica—these two are not in a one-to-one correspondence.
The grade indicators for production control are not single variables; the actual control targets include: the A/S ratio (Al₂O₃ / Reactive SiO₂), available alumina (Available Al₂O₃), reactive silica (Reactive SiO₂), and iron, among others.
The laboratory methods themselves also vary (different mines, different laboratories).
Moisture and particle size exert a strong interference; changes in moisture content alone can lead to “spurious grade fluctuations.”
Second, the “technical challenges” of mainstream online technologies.
The advantage of PGNAA (Prompt Gamma Neutron Activation) is its strong penetrating power, yet it is insensitive to moisture and particle size.
Direct measurement of elements (Al, Si, Fe) does not equate to reactivity indicators.
High safety and post-maintenance costs, large scale, and requires radiation licensing.
So although the market has existed for a long time, it has failed to address the actual needs of customers.
The advantage of XRF (online X-ray fluorescence) is its high elemental resolution and mature technology; however, it has shallow penetration, is strongly affected by surface moisture and particle size, and is extremely sensitive to belt unevenness. While highly accurate in the laboratory, it’s difficult to maintain stable performance when used online.
LIBS (Laser-Induced Breakdown Spectroscopy)
The drawbacks include element measurement, small measurement points, safety hazards, and significant influence from moisture. Due to issues with industrial online stability, this approach has not yet achieved success in alumina applications and currently remains largely at the “advanced pilot” stage.
Solution:
Near-infrared (NIR) online ore measurement technology offers the advantage of distinguishing between different types of aluminum minerals (gibbsite vs. boehmite).
Active silicon holds promise, and high-frequency surface measurements can address representative issues.
Industry Applications
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