Gross Heat in Fuel Oils and Biomass

Importance of the Topic

The determination of gross calorific value is central to evaluating the energy potential of liquid fuels and biomass. Accurate energy measurements guide process optimization in power generation, inform fuel quality specifications in industrial settings, and support sustainability assessments when using renewable feedstocks.

Objectives and Study Overview

This application note describes a streamlined workflow for measuring the gross heat of combustion of fuel oils and various biomass samples on the LECO AC600 calorimeter. The aim is to demonstrate fast, reproducible analysis for:

• Liquid hydrocarbons (diesel, kerosene, jet fuel, gasoline)
• Bio-oils and mineral-oil-spiked biomass
• Wood chip biomass

Methodology and Instrumentation

A dedicated TruSpeed method, compliant with ASTM D5865-13, was applied. Key steps included:

1. Instrument setup and conditioning with LECO benzoic acid pellets (NIST 39j).
2. Calibration using five replicate analyses of 1 g benzoic acid pellets.
3. Sample preparation tailored by matrix:
   
   • Volatile fuels: cellophane-sealed crucibles to prevent loss.
   • Bio-oils: direct weighing into crucible.
   • Biomass: spiking with LECO 502-815 mineral oil to ensure complete combustion.
4. Combustion in oxygen-pressurized vessel with cotton fuse ignition.
5. Thermochemical corrections for sulfur, nitrogen, and moisture.

Used Instrumentation

• LECO AC600 Bomb Calorimeter
• LECO 774-208 Benzoic Acid Calibration Pellets
• LECO 774-204 Crucibles, syringes, needles, and disposable eyedroppers
• LECO 502-815 Mineral Oil Spiking Agent
• Pressure-sensitive cellophane tape

Main Results and Discussion

Reproducibility was demonstrated across matrices:

• Mineral oil standard: 19 809 ± 7 Btu/lb
• Bio-oil: 7 416 ± 31 Btu/lb
• No. 2 diesel: 19 530 ± 10 Btu/lb
• Wood chip #1: 6 734 ± 26 Btu/lb
• Wood chip #2: 8 087 ± 28 Btu/lb

The data highlight the method’s precision and its adaptability to diverse sample types. Use of a spiking agent ensured complete combustion of porous biomass, while tape sealing limited volatile loss in light fuels.

Benefits and Practical Applications

• Rapid throughput: ~5 minutes per analysis.
• Compliance with standardized ASTM methods.
• High reproducibility for QA/QC in fuel production, biofuel research, and energy auditing.
• Flexibility to handle volatile and solid samples in a single platform.

Future Trends and Potential Applications

As the bioenergy sector expands, integrated calorimetric methods will evolve to:

• Accommodate emerging feedstocks such as algae-based oils or composite wastes.
• Implement automated spiking protocols for solid samples.
• Integrate real-time data analytics and predictive maintenance for calorimeter systems.

Conclusion

The LECO AC600 and TruSpeed protocol deliver accurate gross heat values for a broad range of liquid and solid fuels. The approach balances speed, precision, and compliance, making it a valuable tool for industrial laboratories, research institutions, and regulatory compliance.

Reference

• LECO Corporation. "Gross Heat in Fuel Oils and Biomass," Application Note, Form No. 203-821-390, April 2017.