ISO 20905:2024

Coal preparation - Determination of dust/moisture relationship for coal

This document sets out a laboratory procedure for the dust testing of higher rank coals. The procedure defines a means of evaluating the dust/moisture relationship characteristic of a coal and a dust extinction moisture (DEM). NOTE In this document, an experimental dust number of 10 has been used in the example given in Annex A.

Préparation du charbon — Détermination de la relation particules/humidité du charbon

General Information

• Status: Published
• Publication Date: 08-Oct-2024
• ICS: 73.040 - Coals
• Technical Committee: ISO/TC 27/SC 1 - Coal preparation: Terminology and performance
• Drafting Committee: ISO/TC 27/SC 1 - Coal preparation: Terminology and performance
• Current Stage: 6060 - International Standard published
• Start Date: 09-Oct-2024
• Due Date: 11-Apr-2025
• Completion Date: 09-Oct-2024

Relations

• Revises: ISO 20905:2004 - Coal preparation - Determination of dust/moisture relationship for coal
• Effective Date: 14-Oct-2023

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.

Standards Content (Sample)

International
Standard
ISO 20905
Second edition
Coal preparation — Determination of
2024-10
dust/moisture relationship for coal
Préparation du charbon — Détermination de la relation
particules/humidité du charbon
Reference number
© ISO 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Safety . 1
5 Apparatus and equipment . 2
6 Reagent . 2
7 Sample — Initial . 2
8 Sample preparation — Initial. 3
8.1 Initial total moisture .3
8.2 Moisture adjustment .4
9 Sample preparation — Reagent . 4
10 Dust determination . 5
10.1 Environment and equipment checks .5
10.2 Dust testing .5
11 Calculation . 6
12 Report . 6
13 Precision . 6
Annex A (informative) Worked example . 7
Annex B (informative) Worksheet example . 10
Bibliography .12

iii
Foreword
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The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 27, Coal and Coke, Subcommittee SC 1, Coal
preparation: Terminology and performance.
This second edition cancels and replaces the first edition (ISO 20905:2004), of which it constitutes a minor
revision. The changes compared to the previous edition are as follows:
— the title of ISO/TC 27 was changed from "Solid mineral fuels" to "Coal";
— some terminology was changed to align with ISO rules, for example the terms "percentage", "weight" and
"weighing".
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
The development of the dust/moisture curve provides an indication of the likely response of different
coal types to drying or water addition during mining and handling processes. The dust/moisture curve
provides a good basis for comparing the response of different coal types. Understanding the dust/moisture
characteristics of a coal allows minimized water addition to the product for dust suppression. This in turn
assists in water conservation at mines and other handling facilities, as well as minimizing the total moisture
of the product.
This document describes a reliable measurement of dustiness of coal and extends to cover the relationship
between dust and total moisture utilizing the Rio Tinto Dust Tumbler Test. This test provides a quantitative
measure of the dustiness of a coal that can be used to predict operational dust problems and is also suitable
for the assessment of dust suppression chemicals.
The Rio Tinto Dust Tumbler Test was developed using rotating equipment in a controlled temperature and
humidity environment and uses a stream of air to remove particles which become airborne during the
tumbling process. It is a batch test in which dust particles (−150 µm particles) are collected in a filter bag
of known mass and their mass is determined. From this mass, a dust number, calculated as the mass yield
of dust multiplied by 100 000, is determined for the test total moisture. Only 1 kg of sample is required for
each dust test, but eight sample lots are required to develop the dust/moisture curve for a particular coal,
i.e. approximately 10 kg is required for each coal type.
This dust test can be repeated with subsamples at different coal total moisture levels to develop a dust/
moisture curve. The slope of the curve provides information on how sensitive the dustiness is to changes in
total moisture and a dust number of 10 has been used to provide a comparison between coals.
The test has been successfully used for several years on many coals and other bulk materials. The results
have been correlated with the operating practice. The method has been applied to the evaluation of dust-
control products and the determination of dust-elimination total moisture requirements for coal-handling
systems.
v
International Standard ISO 20905:2024(en)
Coal preparation — Determination of dust/moisture
relationship for coal
1 Scope
This document sets out a laboratory procedure for the dust testing of higher rank coals. The procedure
defines a means of evaluating the dust/moisture relationship characteristic of a coal and a dust extinction
moisture (DEM).
NOTE In this document, an experimental dust number of 10 has been used in the example given in Annex A.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 589, Hard coal — Determination of total moisture
ISO 7886-1, Sterile hypodermic syringes for single use — Part 1: Syringes for manual use
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
dust
particles of size 150 µm or less entrained in an air stream
3.2
dust extinction moisture
DEM
total moisture at which a dust number of 10 is attained on the dust/moisture curve
Note 1 to entry: DEM is a useful point for comparing different coals and the effectiveness of reagents.
4 Safety
The following safety precautions shall be observed:
— To prevent nitrogen build-up within the laboratory, the exhaust tube of the minimum-free-space oven
shall remain clear of obstruction.
— Safety glasses shall be worn at all times.
— The exhaust tube of the minimum-head-space oven shall remain free of obstruction to prevent nitrogen
build-up within the laboratory.

— A dust mask shall be worn when handling coal.
— Cloth or leather gloves shall be worn when using ovens.
— The hazards associated with a reagent shall be determined prior to use. Instructions on all relevant
material safety data sheets shall be followed.
5 Apparatus and equipment
The following apparatus and equipment is required.
5.1 Humidity- and temperature-controlled laboratory, with relative humidity of 63 % ± 2 % and
temperature of 20 °C ± 2 °C.
5.2 Dust-test apparatus, with a rotating drum of 30 cm diameter and 30 cm effective length, as shown in
Figure 1. The required drum speed is 29 r/min,
...