ISO 647:2017

Overview

ISO 647:2017 - Brown coals and lignites: Determination of the yields of tar, water, gas and coke residue by low temperature distillation - specifies a laboratory method to quantify tar yield, total water (moisture + decomposition water), gas and coke residue from brown coal and lignite. The test uses a low‑temperature distillation sequence to 520 °C (80 min total heating) with product condensation and gravimetric determination. Results are reported on the as‑analysed and dry bases and are used as a basis for classification and quality assessment for low temperature carbonization.

Key topics and technical requirements

• Scope: Determination of yields of tar, water, gas and coke residue from brown coals and lignites by distillation to 520 °C.
• Principle: Heat a ~50 g sample in an aluminium retort; condense tar and water in a water‑cooled receiver; weigh coke residue; determine water by entrainment with toluene or xylene; calculate tar by difference and gas by subtraction.
• Apparatus and reagents: Aluminium retort (≈170 ml ±10 ml), brass outlet tube, 750 ml round‑bottom receiver, cooling bath (10–15 °C), calibrated thermocouple or mercury thermometer (to 550 °C), toluene/xylene for entrainment, graphite paste for sealing.
• Heating schedule: Controlled temperature ramp to 520 °C over 80 minutes (specified intermediate points, hold 520 °C at end).
• Sample preparation: Crush to pass 1 mm sieve (≥90 %), moisture between 10–20 % recommended; determine moisture separately per ISO 5068-2.
• Results and reporting: Report means of duplicate determinations to 0.1 %; tar may also be expressed on a dry ash‑free basis; include any deviations and test conditions in the test report.
• Precision: Repeatability and reproducibility (dry basis) limits are specified:
  • Tar: r = 0.5 % abs, R = 0.7 % abs
  • Decomposition water: r = 0.4 % abs, R = 0.8 % abs
  • Coke residue: r = 0.7 % abs, R = 1.0 % abs

Applications

• Classification of brown coal and lignite for low temperature carbonization and tar production.
• Quality control and product specification in coal processing laboratories.
• Research into coal devolatilization and char (coke) formation.
• Regulatory and commercial testing where tar and gas yields are contractually relevant.

Who uses this standard

• Coal testing laboratories and quality control teams
• Coal producers and processors involved in low temperature carbonization
• Utilities, chemical manufacturers and research institutions studying coal pyrolysis
• Accreditation bodies and conformity assessment labs performing standardized fuel analyses

Related standards

• ISO 5068-2 - Determination of moisture content (indirect gravimetric method) - referenced for moisture correction.
• ISO 1170 - Calculation of analyses to different bases (used for converting to dry/dry ash‑free bases).

Keywords: ISO 647:2017, brown coals, lignites, low temperature distillation, tar yield, coke residue, decomposition water, gas yield, retort, receiver, toluene entrainment, coal analysis.