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I. Operating Characteristics and Technical Challenges of Alumina Production
Alumina production utilizes the Bayer process, a long and complex industrial cycle where different
stages place significantly different demands on level measurement instruments. The primary measurement scenarios can be categorized into four main areas:
1.1 Digestion Process
Operating Characteristics: High temperatures (up to 260°C), high pressure, and strong alkalinity (NaOH concentration of 180–220 g/L). The medium is a mixed slurry of sodium aluminate solution and ore.
Measurement Challenges:
Extreme requirements for instrument structure and sealing due to high temperature and pressure.
Antenna materials must be highly corrosion-resistant to withstand strong alkali.
Solid particles in the slurry may cause scaling on the antenna surface
1.2 Settling and Separation Process
Operating Characteristics: Large-diameter settling tanks (up to 20m) with moderate height. A stable foam layer (5–15 cm thick) is present on the surface, and the tank is equipped with a rotating rake for agitation.
Measurement Challenges:
The foam layer scatters and attenuates radar signals, which is the primary cause of signal loss.
The slow rotation of the rake can be misidentified by the radar as level changes.
Complex internal structures (overflow weirs, central feeding pipes) generate false echoes.
