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) production chain; however, it is also widely recognized as one of the most challenging analytical tasks to achieve accurate, long-term stability.
First, the “inherent challenges” posed by bauxite itself.
The mineral assemblage is highly complex and exhibits substantial variability, ranging from gibbsite through boehmite to diaspor. Even within the same mining area—or even during the same shift—the mineral composition can vary markedly.
Conventional online instruments typically measure “elements” or “characteristic signals,” whereas the Bayer process focuses on soluble aluminum oxide and active silica, which do not have 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 aluminum oxide (Available Al₂O₃), reactive silica (Reactive SiO₂), and iron, among others.
Laboratory methods themselves also vary (between different mines and different laboratories).
Moisture and particle size exert strong interference; variations in moisture content alone can give rise to “apparent grade fluctuations.”
Secondly, the “technical challenges” of mainstream online technologies.
The advantage of PGNAA (Prompt Gamma Neutron Activation Analysis) is its strong penetration capability, coupled with insensitivity to moisture and particle size.
Direct measurement of elements (Al, Si, Fe) does not equate to reactive indicators.
High safety and post‑maintenance costs, large scale, and requiring radiation licensing.
Therefore, although a market has long existed, it has failed to address actual customer needs.
The advantages of XRF (online X-ray fluorescence) are 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 non-uniformity. While highly accurate in the laboratory, it is difficult to maintain stable performance in online applications.
LIBS (Laser-Induced Breakdown Spectroscopy)
The drawbacks include elemental measurement, small measurement spots, and potential safety hazards, as well as significant interference from moisture. Due to challenges in industrial‑on‑line stability, this approach has not yet achieved success in alumina production and remains largely at the “advanced pilot” stage.
Solution:
Near-infrared (NIR) online ore analysis technology offers the advantage of distinguishing between aluminum mineral types (gibbsite vs. boehmite).
It holds promise for active silicon and addresses representativeness issues through high-frequency surface measurements.
Solution
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