Overview - ISO 20905:2024 (Coal preparation - dust/moisture relationship for coal)
ISO 20905:2024 specifies a laboratory procedure to quantify the relationship between coal moisture and dust generation for higher-rank coals. The standard formalizes the Rio Tinto Dust Tumbler Test to produce a dust/moisture curve and to determine a dust extinction moisture (DEM) - the total moisture at which a defined dust number (10 in the worked example) is reached. The method measures airborne particles ≤150 µm collected during a controlled tumbling test and reports a dust number (mass yield × 100 000).
Key topics and technical requirements
- Scope and purpose: Establishes a repeatable laboratory test for coal dustiness and DEM to compare coals and assess dust-control measures.
- Controlled environment: Test laboratory at 63 % ± 2 % relative humidity and 20 °C ± 2 °C.
- Apparatus: Dust-test drum (30 cm diameter × 30 cm effective length), 29 r/min drum speed, airflow ~175 L/min, and double-filter bags for −150 µm dust collection.
- Sample requirements: Approximately 1.2 kg per dust test; about eight subsamples (~10 kg total) across a range of moisture values to develop the dust/moisture curve. Initial particle fraction >6.3 mm is removed and not reintroduced.
- Moisture adjustment and reagents: Procedures for increasing or reducing total moisture (spray addition, low-temperature drying, or 40 °C oven when needed) and for adding aqueous reagents with controlled dosing. Use of a syringe per ISO 7886-1 for final additions is specified.
- Safety and quality controls: Personal protective equipment (dust mask, safety glasses, gloves); ensure exhausts remain clear; environmental and equipment checks; calculation, reporting, and precision clauses.
- Definitions: Dust = particles ≤150 µm entrained in an airstream; DEM = moisture at dust number 10 on the curve.
Applications - practical value and users
ISO 20905 is used to:
- Predict operational dust problems and set moisture targets for handling and transport.
- Evaluate effectiveness and dosing of dust-suppression reagents.
- Optimize water use in mines and coal-handling facilities by identifying minimal moisture needed to control dust (supporting water conservation).
Primary users include coal preparation laboratories, mine operators, process engineers, reagent manufacturers, environmental & occupational health teams, and testing service providers.
Related standards
- ISO 589 - Hard coal - Determination of total moisture (referenced for moisture measurement).
- ISO 7886-1 - Sterile hypodermic syringes for single use (syringe use for reagent dosing).
- ISO 1953 - Particle size distribution (referenced for sample characterization).
Keywords: ISO 20905, dust/moisture relationship, coal dust testing, dust extinction moisture (DEM), Rio Tinto Dust Tumbler Test, coal preparation, dust suppression, laboratory procedure.