Gross Calorific Value in Metallurgical Coke

Importance of the Topic

Metallurgical coke is a key high-carbon fuel in blast furnace ironmaking. Its gross calorific value determines the heat available for reduction reactions and slag melting, directly affecting process efficiency, fuel consumption and cost management in the steel industry.

Objectives and Study Overview

This application note demonstrates a robust procedure for determining the gross calorific value of metallurgical coke using the LECO AC600 calorimeter in compliance with ASTM D5865. The goals are to outline sample preparation, calibration, measurement steps, and correction procedures to ensure accurate, repeatable results for both routine quality control and process optimization.

Methodology and Instrumentation

The methodology follows the TruSpeed™ mode for rapid, automated calorimetric analysis. Key steps include:

• Sample Preparation: Obtain a representative, dry coke sample (~0.75 g) and pelletize benzoic acid calibration standards (~1.0 g).
• Calibration: Condition the system with benzoic acid pellets, perform at least five replicate runs, and establish calibration factors with nitrogen correction.
• Combustion Analysis: Load the sample with a cotton thread fuse into a nickel crucible, pressurize the vessel with oxygen, initiate combustion, and record heat release.
• Corrections: Apply nitrogen correction via titration of wash waters and enter values into the AC600 software. For coke, perform additional sulfur and moisture corrections.

Instrumentation

The following equipment and accessories are used:

• LECO AC600 Calorimeter with TruSpeed™ mode
• Nickel crucibles (LECO 774-204)
• Heated particulate filters (502-450-100)
• Cotton thread fuses (502-461)
• Benzoic acid pellets (LECO 774-208-150) or NIST reference powder
• Oxygen supply, titration reagents (sodium carbonate, indicator)

Main Results and Discussion

Calibration with benzoic acid yielded a mean gross heat of 11,375 BTU/lb (±4 BTU/lb). Metallurgical coke samples returned an average gross calorific value of 12,599 BTU/lb (±13 BTU/lb) after nitrogen, sulfur and moisture corrections. The low standard deviations confirm method precision. These values align with proficiency testing benchmarks, demonstrating the AC600’s reliability for routine QC.

Benefits and Practical Applications

The described procedure offers:

• High throughput: ~5 minutes per analysis.
• Automated corrections: integrated software reduces manual calculation errors.
• Regulatory compliance: meets ASTM D5865 requirements.
• Enhanced process control: accurate calorific data support optimized coke blending and furnace performance.

Future Trends and Possibilities

Emerging trends include integrating real-time data analytics for dynamic furnace control, coupling calorimetry with gas analysis for enhanced emission profiling, and miniaturized, field-deployable calorimeters for on-site monitoring. Advances in sample automation and AI-driven correction algorithms may further improve throughput and accuracy.

Conclusion

The LECO AC600 method provides a rapid, precise and standardized approach for gross calorific value determination in metallurgical coke. Its ease of use, rigorous calibration protocol and robust correction procedures ensure consistent results that support efficient blast furnace operation and quality assurance in steel manufacturing.

Reference

ASTM D5865 Standard Test Method for Gross Calorific Value of Coal and Coke by the Bomb Calorimeter.