ISO 8858-3:2025
(Main)Coal — Froth flotation testing — Part 3: Release evaluation
Coal — Froth flotation testing — Part 3: Release evaluation
This document describes a laboratory method for release evaluation of the froth flotation characteristics of hard coal, of particle size less than 0,5 mm. It is applicable to coal in powder form or in the form of a slurry.
Charbon — Essais de flottation — Partie 3: Évaluation des émission
General Information
Relations
Standards Content (Sample)
International
Standard
ISO 8858-3
Second edition
Coal — Froth flotation testing —
2025-11
Part 3:
Release evaluation
Charbon — Essais de flottation —
Partie 3: Évaluation des émission
Reference number
ISO 8858-3:2025(en)
© ISO 2025
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ii
ISO 8858-3:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus . 2
7 Sampling and preparation of test sample . 4
8 Flotation test conditions . 5
8.1 Test temperature .5
8.2 Impeller operating speed .5
8.3 Air flow rate .5
8.4 Pulp level .5
9 Procedure . 5
9.1 Test portion .5
9.2 Preparation .5
9.3 Flotation test .5
10 Presentation of results . 6
11 Test report . 7
iii
ISO 8858-3:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
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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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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 8858-3:2004), which has been technically
revised.
The main changes are as follows:
— the title has been updated;
— ISO 13909-2, ISO 13909-4 and ISO 20904 were included as normative references.
A list of all parts in the ISO 8858 series can be found on the ISO website.
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
ISO 8858-3:2025(en)
Introduction
The froth flotation of coal has widespread application for the recovery of fine coal particles and their
separation from unwanted mineral matter. The response of coal to the froth flotation process is measured
initially by a laboratory scale test. ISO 8858-1 provides a means of evaluating the general flotation
characteristics of a coal under a set of specified conditions and will not necessarily indicate the full potential
of that coal. It is accepted that variation of the many parameters in the froth flotation process can be used to
effect the beneficiation of the product. This document describes methods of applying certain test conditions
to reveal the relative response of coals to the flotation process.
To facilitate the determination of how a particular coal will respond to froth flotation, a method of
controlling the recovery of froth is used. This is done by inhibiting the process to a degree, determining the
rate at which coal reacts and by progressively sampling the froth. This method provides a basis to vary test
parameters to explore any special flotation characteristics.
This document is applicable to a wide range of coals and provides a method of comparison of flotation
behaviour and will facilitate the exchange of information relating to specific performance. It is expected that
the use of this method will provide a tool for comparison of flotation characteristics.
From the results of the standard test, it is possible to draw evaluation curves similar to those obtained from
the float and sinking of coal.
Because of the high reproducibility of results, the test represents a reliable means of comparing the flotation
response of different samples.
v
International Standard ISO 8858-3:2025(en)
Coal — Froth flotation testing —
Part 3:
Release evaluation
1 Scope
This document describes a laboratory method for release evaluation of the froth flotation characteristics of
hard coal, of particle size less than 0,5 mm. It is applicable to coal in powder form or in the form of a slurry.
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 1213-1, Coal and coke — Vocabulary — Part 1: Terms relating to coal preparation
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 8858-1:2019, Hard coal — Froth flotation testing — Part 1: Laboratory procedure
ISO 13909-2, Coal and coke — Mechanical sampling — Part 2: Sampling of coal from moving streams
ISO 13909-4, Coal and coke — Mechanical sampling — Part 4: Preparation of test samples of coal
ISO 18283, Coal and coke — Manual sampling
ISO 20904, Hard coal — Sampling of slurries
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1213-1 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/
4 Principle
A test portion of coal is mixed with water to form a suspension in the flotation cell, or a test portion of slurry
is added to the cell and diluted. A collector and frother are added, the suspension is conditioned and air is
then introduced to the cell while agitation is maintained by means of an impeller.
To study differing flotation characteristics, the flotation operation is inhibited in two ways, relating to
reagent dosage rate in the first stage of the test and to air flow rate in the second stage.
A number of froth increments are obtained which give spaced points for comparison.
ISO 8858-3:2025(en)
5 Reagents
Use only reagents of recognized analytical grade and the following.
5.1 Water, conforming to grade 3 of ISO 3696.
5.2 Collector, undiluted n-dodecane.
5.3 Frother.
Prepare a solution of 0,1 % volume fraction 4-methylpentan-2-ol (formerly called methyl isobutyl carbinol
or MIBC) by diluting 1 ml of MIBC to 1 litre using water (see 5.1). All dosages of MIBC stated refer to this
solution.
6 Apparatus
6.1 Flotation machine
As described in 6.1 of ISO 8858-1:2019, consisting of a mechanical impeller-type flotation machine designed
for laboratory-scale flotation testing, comprising the following.
a) A flotation cell, of capacity approximately 3,5 l, made from an inert material, such as stainless steel,
glass or polymethyl methacrylate.
b) An impeller assembly, capable of being driven so that the periphery of the impeller moves at a speed
of approximately 5,7 m/s. The impeller shall be positioned centrally with a clearance of no more than
5 mm from the base of the cell.
c) A means of supplying air to the impeller.
A typical flotation machine is shown in Figures 1 and 2.
6.2 Air flowmeter, with a needle valve to control the air flow rate to the flotation cell.
6.3 Constant level, for maintaining the pulp at a constant level during the test.
NOTE The level can be maintained by the manual addition of water.
6.4 Two scrapers, for removing the froth from the entire surface of the pulp, including the area behind
the standpipe.
6.5 Calibrated micro syringe or micro-pipette.
6.6 Containers, capable of holding individual samples of froth and tailings.
ISO 8858-3:2025(en)
6.7 Timing device, accurate to ±1 s and capable of being zeroed and started as required.
Key
1 drive mechanism
2 cell
3 metal base
4 levelling screws
Figure 1 — Typical flotation machine
ISO 8858-3:2025(en)
Key
1 cell
2 hood diffuser
3 impeller
4 impeller shaft
Figure 2 — Detail of flotation cell and impeller
7 Sampling and preparation of test sample
Take a gross sample which is at least five times the mass required for a single flotation test (see 9.1).
W
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