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.