Determination of Carbon and Nitrogen in Coal and Coke

Importance of the Topic

Ultimate analysis of coal and coke fuels by carbon and nitrogen determination supports characterization of fuel quality, energy balance, process efficiencies, and emission potential. Reliable data underpin process control in power generation, coking, gasification, and liquefaction workflows.

Study Objectives and Overview

This application note demonstrates the method for simultaneous determination of carbon and nitrogen in coal and coke samples using the LECO CN928 macro combustion instrument. The procedure follows ASTM D5373 standards, detailing sample preparation, instrument configuration, and calibration strategies.

Methodology and Instrumentation

The LECO CN928 employs high-temperature horizontal ceramic combustion in a pure oxygen environment, with ceramic boats to hold 0.2–1.0 g samples. Combustion gases are dehumidified, equilibrated in a ballast, and sampled in 3 cm3 or 10 cm3 aliquot loops. Carbon dioxide is detected by nondispersive infrared and nitrogen by thermal conductivity after reduction of NOx over copper. Helium or argon serve as carrier gases; helium provides superior sensitivity at low N levels. Key parameters include 1350 °C furnace temperature, 12 °C/min ramp rate, and multiple purge and equilibrate cycles. Calibration uses certified reference materials via full‐range linear regression for carbon and zero‐origin linear calibration for nitrogen.

Main Results and Discussion

Typical analyses of prox‐plus coal, metallurgical coke, and petroleum coke yielded carbon contents consistent with certified values (approximately 70% for coal, 88% for cokes) and nitrogen results with standard deviations below 0.1% for carbon and 0.02% for nitrogen. The 10 cm3 loop delivered optimal precision, while the 3 cm3 loop extended reagent life with minimal performance loss. Helium carrier gas outperformed argon in detection sensitivity for nitrogen.

Benefits and Practical Applications

• Rapid and accurate carbon/nitrogen quantification for QA/QC in fuel production.
• Essential data for material and energy balance calculations.
• Supports emission potential assessment and regulatory compliance.
• Enables feedstock evaluation for gasification and liquefaction processes.

Future Trends and Potential Applications

Advances in detector design, automation, and data integration are expected to further streamline ultimate analysis. Potential developments include higher throughput sample introduction systems, real-time remote monitoring, multi-element analysis coupling, and enhanced reagent conservation techniques.

Conclusion

The LECO CN928 provides a robust, standardized method for simultaneous determination of carbon and nitrogen in coal and coke, delivering accurate and precise results in accordance with ASTM D5373. Its flexible carrier gas options and aliquot loop configurations optimize both sensitivity and cost-efficiency.

References

1. ASTM D5373 Standard Test Methods for Determination of Carbon, Hydrogen, and Nitrogen in Analysis Samples of Coal and Coke
2. ASTM D2013 Standard Practice for Preparation of Coal Samples for Analysis
3. ASTM D346/D346M Standard Practice for Preparation of Coke Samples for Analysis
4. LECO 928 Series Operator’s Instruction Manual