Analysis of Bayer aluminate liquors using online thermometric titration

Significance of the Topic

The Bayer process is the primary method for converting bauxite into alumina, requiring precise monitoring of aluminate liquor composition to optimize yield, maintain process stability, and reduce operational costs.

Objectives and Study Overview

This note presents an online thermometric titration approach for continuous measurement of total hydroxide (caustic), carbonate (soda), and alumina in Bayer aluminate liquors, demonstrating integration with Metrohm Process Analytics systems.

Methodology and Instrumentation

Liquor samples are diluted and complexed with sodium potassium tartrate to release hydroxide ions for the first HCl titration (total caustic). Carbonate is quantified by acid titration in the same run. For alumina determination, potassium fluoride is added to break the tartrate complex, releasing additional hydroxide for a second titration. Endpoints are detected by monitoring solution temperature changes.
Instrumentation used:

• 2060 TI Process Analyzer – modular online analyzer for thermometric titration
• 2035 Process Analyzer – dedicated thermometric titration platform with robust sensor

Main Results and Discussion

Thermometric titration enables:

• Accurate endpoint detection via enthalpy changes
• Rapid analyses without sensor calibration
• Robust performance in high-temperature and aggressive matrices
• Measurement ranges: 17–150 g/L Na₂O (caustic), 1–155 g/L Na₂O (soda), 17–170 g/L Al₂O₃ (alumina)

Benefits and Practical Applications

This automated method supports 24/7 process control by providing real-time data for early upset detection, improved reproducibility, optimized chemical dosing, and reduced maintenance compared to potentiometric titration.

Future Trends and Applications

Emerging opportunities include integration with advanced process control systems, AI-driven predictive maintenance, remote monitoring via digital platforms, and extension to other industrial streams such as water treatment and synthetic zeolite production.

Conclusion

Online thermometric titration with Metrohm analyzers offers a fast, sensitive, and maintenance-free solution for continuous monitoring of Bayer aluminate liquors, enhancing aluminum refinery productivity and efficiency.

Reference

Metrohm Process Analytics. Application Note AN-PAN-1034, Analysis of Bayer aluminate liquors using online thermometric titration.