ISO 20905:2004

Overview

ISO 20905:2004 - Coal preparation - Determination of dust/moisture relationship for coal - describes a laboratory procedure for measuring coal dustiness and the relationship between dust generation and total moisture for higher‑rank coals. The method uses the Rio Tinto Dust Tumbler Test to produce a dust/moisture curve and to determine the dust extinction moisture (DEM), a practical metric for comparing coals and assessing dust‑suppression measures.

Key topics and technical requirements

• Scope: Laboratory dust testing of higher‑rank coals to evaluate dust/moisture behavior and derive DEM.
• Dust definition: Particles ≤ 150 µm entrained in an airstream.
• Controlled environment: Laboratory humidity 63 ± 2% and temperature 20 ± 2 °C.
• Apparatus:
  • Rotating drum dust tester (30 cm diameter × 30 cm length), 29 r/min drum speed and ~175 L/min airflow.
  • Double filter bags (single use), thermohydrograph, tachometer, balance readable to 0.01 g, mixer, ovens.
• Sample requirements:
  • Remove >6.3 mm fraction (do not crush); prepare ~1.2 kg subsamples.
  • Typical program: eight subsamples across a moisture range (≈10 kg total) to build a dust/moisture curve.
• Moisture adjustment:
  • Measure initial moisture per ISO 589; add water or remove moisture by low‑temperature drying to target levels (≈1% intervals).
  • Reagent dosing (aqueous solutions) is applied using controlled mixing and syringe dosing (ISO 7886‑1 referenced).
• Test procedure:
  • 1 000 g sample tumbled for 10 minutes with fan on; fan runs an additional 13 s to collect airborne dust.
  • Dust collected on pre‑weighed filter bag; dust number = mass yield × 100 000.
• Outputs:
  • Dust/moisture curve, slope (sensitivity of dustiness to moisture), and DEM (moisture at which dust number = 10).

Applications and users

ISO 20905:2004 is practical for:

• Coal preparation laboratories and QA/QC teams validating product handling risks.
• Mine operators and material‑handling engineers determining minimum water addition for dust suppression.
• Occupational health & safety and environmental compliance groups assessing airborne particulate risk.
• Manufacturers and evaluators of dust‑suppression reagents (to validate reagent performance and optimal dosing).
• Researchers comparing coal types using the DEM and dust/moisture curves.

Benefits include improved dust control strategies, water‑use optimization in mines, and standardized, reproducible dustiness data for operational decision‑making.

Related standards

• ISO 589 - Hard coal: Determination of total moisture
• ISO 1953 - Hard coal: Size analysis by sieving
• ISO 7886‑1 - Sterile hypodermic syringes (used for dosing technique guidance)

Keywords: ISO 20905:2004, coal dust testing, dust/moisture relationship, dust extinction moisture (DEM), Rio Tinto Dust Tumbler Test, coal handling, dust suppression, laboratory procedure.