ISO 5071-1:2021

Overview

ISO 5071-1:2021 specifies a standardized laboratory method - the two-furnace method - for determining the volatile matter in analysis samples of brown coals and lignites. The test measures the mass loss (corrected for moisture) after controlled heating out of contact with air. The procedure is empirical and designed for reproducible results across coal testing and quality-control laboratories.

Key Topics and Requirements

• Principle: Heat the sample at 400 °C for 7 minutes, then immediately transfer to 900 °C for 7 minutes; calculate volatile matter from the mass loss of oven-dried or moisture-corrected analysis sample.
• Sample preparation: Use a general analysis test sample prepared to a nominal top size of 212 µm; bring to laboratory moisture equilibrium and mix thoroughly.
• Sample charge: Transfer 1.00 g to 1.01 g of sample into preconditioned crucibles.
• Apparatus:
  • Two electric furnaces with uniform temperature zones (400 °C ±10 °C and 900 °C ±5 °C) and rapid recovery after insertion.
  • Oven controllable at 105–110 °C with dry, oxygen-free nitrogen flow changing atmosphere ~15 times/hour.
  • Fused silica crucibles and lids (10–14 g) with horizontal clearance ≤ 0.5 mm; balance with 0.1 mg resolution.
  • Unsheathed thermocouple (wire ≤ 1 mm) to check furnace temperature.
• Reagents: Dry desiccants (e.g., silica gel, activated alumina) and dry nitrogen (max O2 30 µl/l).
• Procedure variants: Methods for both oven-dried and air-dried coal samples are described, with preconditioning and predetermination steps.
• Calculation and reporting: Results are expressed as volatile matter mass fraction, corrected for moisture when applicable. Clause on precision (repeatability and reproducibility) and required test report elements are included.
• Notes: Initial 400 °C heating minimizes sample ejection. Mineral matter in the sample can also lose mass under test conditions and affect results.

Applications and Who Uses It

ISO 5071-1:2021 is used by:

• Coal testing and analytical laboratories performing volatile matter determination.
• Mining and fuel-quality control teams monitoring brown coal and lignite properties.
• Power plants, combustion engineers, and fuel suppliers needing consistent coal analysis for combustion performance and contractual specifications.
• Research institutions studying coal behavior, devolatilization, and thermal properties.

Benefits include harmonized testing, better comparability of volatile-matter data, and support for fuel specification, combustion modelling, and quality assurance.

Related Standards

• ISO 5068-2 - moisture determination in analysis samples (referenced for moisture correction)
• ISO 13909-4, ISO 18283 - sampling and test sample preparation
• ISO 1170 - calculation of analyses to different bases
• ISO 1213-2 - vocabulary for sampling, testing and analysis

Keywords: ISO 5071-1:2021, volatile matter determination, brown coals, lignites, two-furnace method, coal analysis, laboratory procedure, fuel quality.