Analysis of moisture, ash, carbon, and volatile content in coal by NIRS

Significance of the topic

Near-infrared spectroscopy (NIRS) enables rapid, cost-effective evaluation of coal quality by simultaneously measuring moisture, ash, fixed carbon, and volatile matter in seconds, offering a practical alternative to traditional furnace-based methods.

Objectives and Overview of the Study

This application note demonstrates the use of the Metrohm NIRS DS2500 Solid Analyzer for fast, simultaneous determination of four key coal quality parameters in under one minute without any sample preparation.

Methodology

• Thirty pulverized coal samples (0.2 mm particle size) were measured.
• Samples placed in a rotating large sample cup to average out particle size distribution effects.
• Vis-NIR spectra acquired over 400–2500 nm.
• Calibration and validation used reference data from ASTM D3172, D3173, D3174, and D3175.
• Data acquisition and chemometric modeling performed with Vision Air Complete software.

Used Instrumentation

• Metrohm NIRS DS2500 Solid Analyzer (Art. No. 2.922.0010)
• DS2500 large sample cup (Art. No. 6.7402.050)
• Vision Air 2.0 Complete software (Art. No. 6.6072.208)

Main Results and Discussion

The calibration models achieved high correlation between predicted and reference values:

• Ash content: R² = 0.973, SECV = 0.73 %
• Volatile matter: R² = 0.944, SECV = 0.38 %
• Fixed carbon: R² = 0.937, SECV = 0.52 %
• Moisture content: R² = 0.896, SECV = 0.28 %

All four parameters can be determined in less than one minute without using nitrogen gas, meeting routine quality control precision requirements.

Benefits and Practical Applications

• Rapid multi-parameter analysis in a single run.
• No sample preparation or consumables required.
• Elimination of combustion furnaces and gas usage.
• Reduced analysis time from hours to seconds.
• Suitable for lab and production-line quality control environments.

Future Trends and Potential Applications

• Integration with automated sampling for real-time process monitoring.
• Extension to other solid fuels and industrial materials.
• Advanced chemometric approaches for complex mixtures.
• Portable NIRS systems for field deployment.
• Cloud-based analytics and remote monitoring platforms.

Conclusion

The Metrohm NIRS DS2500 Solid Analyzer offers a reliable, fast, and economical alternative to standard combustion methods for coal quality assessment, streamlining workflows and cutting operational costs.

Reference

• ASTM D3172: Proximate Analysis of Coal and Coke
• ASTM D3173: Moisture in Coal and Coke by Drying
• ASTM D3174: Ash in Coal and Coke
• ASTM D3175: Volatile Matter in Coal and Coke