Moisture, Volatile Matter, Ash, and Fixed Carbon Determination in Coal

Significance of the topic

Proximate analysis of coal—determining moisture, volatile matter, ash content, and fixed carbon—is fundamental for coal quality assessment, combustion efficiency, and compliance with environmental regulations. Reliable results guide fuel selection, process control and reporting in mining, power generation, and industrial applications.

Objectives and Study Overview

This application note outlines a standardized procedure using the LECO TGA701 thermogravimetric analyzer to quantify the four key coal parameters on a dry basis. The aim is to demonstrate the method’s accuracy, precision, and operational workflow for routine laboratory testing.

Methodology and Instrumentation

• Sample preparation follows ASTM D2013 or ASTM Practice D346; typical sample mass is ~1 g.
• Thermogravimetric program comprises three sequential steps:
  • Moisture: heat from 25 °C to 107 °C at 6 °C/min, hold 15 min under nitrogen.
  • Volatile matter: heat from 107 °C to 950 °C at 43 °C/min, hold 7 min under nitrogen.
  • Ash: heat from 600 °C to 750 °C at 3 °C/min under oxygen.
• Calibration for volatile matter uses at least three coal reference materials covering the expected range; moisture and ash calibrations are typically stable without additional standards.
• Key balance settings: 0.80–1.20 g weight range, 0.0005 g mass resolution, stable temperature control up to 1200 °C.

Instrumentation Used

The analysis employs a LECO TGA701 thermogravimetric analyzer equipped with ceramic crucibles and covers, nitrogen and oxygen gas supply, and an automated balance for real-time mass measurements.

Main Results and Discussion

Typical dry-basis results on LECO reference coals demonstrate: average moisture ~0.92 % (RSD <0.8 %), volatile matter ranging from 17.1 % to 41.3 % (RSD <0.6 %), ash content 5.8–11.0 % (RSD <0.4 %), and fixed carbon balance of 52.7–72.0 % (RSD <0.4 %). These low relative standard deviations confirm method repeatability and instrument stability across widely varying coal ranks.

Benefits and Practical Applications

• Comprehensive proximate analysis in a single automated run saves time and reduces handling errors.
• High precision supports quality assurance in coal blending and calorific value estimation.
• Accurate ash and volatile matter data inform boiler tuning, emission control, and ash disposal management.

Future Trends and Potential Applications

Advances may include integration with real-time process monitoring, expanded capabilities for biomass and waste co-processing, and coupling with advanced data analytics for predictive modelling of feedstock performance.

Conclusion

The TGA701 method reliably quantifies moisture, volatile matter, ash, and fixed carbon in coal samples, delivering precise, reproducible results that streamline laboratory workflows and support critical decision-making in energy and materials industries.

Reference

• ASTM D2013 – Standard Practice for Preparation of Coal Samples for Analysis.
• ASTM D346 – Practice for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis.
• ASTM D7582 – Standard Test Method for Proximate Analysis of the Analysis Sample of Coal and Coke by Thermogravimetric Analysis.