ISO 8858-2:2004

INTERNATIONAL ISO
STANDARD 8858-2
First edition
2004-08-15
Hard coal — Froth flotation testing —
Part 2:
Sequential evaluation
Houille — Essais de flottation —
Partie 2: Évaluation séquentielle

Reference number
©
ISO 2004
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ii © ISO 2004 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Principle. 2
5 Sample. 2
6 Apparatus. 2
7 Flotation conditions. 2
7.1 Collector dosage. 2
7.2 Frother dosage. 3
7.3 Solids content. 3
7.4 Air flow rate . 3
7.5 Test temperature. 3
8 Procedure. 3
8.1 Initial procedure. 3
8.2 Initial separation. 3
8.3 Subsequent separations. 3
8.4 Analysis of concentrate and tailings . 4
9 Calculation of results. 4
10 Test report. 5
Annex A (informative) Worked example of calculation of results . 6
Annex B (informative) Presentation of results . 11

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 ISO
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International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 8858-2 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee SC 1, Coal
preparation: Terminology and performance.
ISO 8858 consists of the following parts, under the general title Hard coal — Froth flotation testing:
 Part 1: Laboratory procedure
 Part 2: Sequential evaluation
 Part 3: Release evaluation
iv © ISO 2004 – All rights reserved

Introduction
The froth flotation of coal has a 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 8858-1:1990 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 part of ISO 8858 describes a procedure for the more complete
determination of the flotation characteristics of a coal, using the apparatus and basic procedures described in
ISO 8858-1. The purpose of this extended procedure is to provide information similar to that provided by the
sink/float curve, which is the basis for density separations. The data obtained are expressed as a yield/ash
curve. The information can be used to define the limitations on the cleaning of fine coal by froth flotation.
The procedures specified in this part of ISO 8858 are of practical significance in the development and
evaluation of coal-preparation-plant flotation circuits, although engineering design aspects, such as flotation
kinetics and the selection of size and type of cell, are not addressed.
The flotation response curve (yield/ash) indicates the maximum possible yield at any specified ash content.
The general shape of the curve indicates the sensitivity of flotation performance to the nature of the coal and
to operating conditions.
The procedure may be modified to test and compare the performance of different frother and collector types,
the assessment of liberation by grinding, and the comparison of alternative feed size ranges. However, results
of such tests should clearly indicate any use of non-standard procedures.

INTERNATIONAL STANDARD ISO 8858-2:2004(E)

Hard coal — Froth flotation testing —
Part 2:
Sequential evaluation
1 Scope
This part of ISO 8858 sets out a laboratory sequential procedure for the froth flotation testing of fine coal, e.g.
coal having a particle size of less than 0,5 mm. The procedure provides a means of evaluating for a coal the
flotation characteristics (expressed as a yield/ash relationship) that may be expected from the froth flotation
process.
Pulp samples that cannot be dewatered without the use of heat or chemical additives are not covered by this
part of ISO 8858; nor does it cover procedures for the investigation of flotation kinetics.
The test is not intended to provide plant design data.
This part of ISO 8858 should be read in conjunction with ISO 8858-1.
2 Normative references
The following referenced documents are indispensable for the application 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 589:2003, Hard coal — Determination of total moisture
ISO 1171:1997, Solid mineral fuels — Determination of ash
ISO 1213-1:1993, Solid mineral fuels — Vocabulary — Part 1: Terms relating to coal preparation
ISO 1953:1994, Hard coal — Size analysis by sieving
ISO 7936:1992, Hard coal — Determination and presentation of float and sink characteristics — General
directions for apparatus and procedures
ISO 8858-1:1990, Hard coal — Froth flotation testing — Part 1: Laboratory procedure
ISO 13909-4: 2001, Hard coal and coke — Mechanical sampling — Part 4: Coal — Preparation of test
samples
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1213-1 and the following apply.
3.1
higher rank coal
coal having a gross specific energy of 21,00 MJ/kg or greater on an ash-free, moist (afm) basis and
27,00 MJ/kg or greater on a dry, ash-free (daf) basis
4 Principle
A sequence of laboratory flotation tests is carried out on a single coal sample, using a procedure based on
that described in ISO 8858-1. Variations on that procedure are made to generate a number of products, by
refloating concentrates and tailings a number of times. The masses and ash percentages of the various
products are used to construct a yield/ash curve showing the flotation response.
5 Sample
The history and method of preparation of samples can affect the flotation characteristics of the coal
considerably. The history of the sample should be recorded, and care should be taken to ensure that samples
for comparison purposes are prepared in a similar manner and, where applicable, in accordance with the
sample preparation procedures specified in ISO 13909-4.
A size analysis of the sample shall be carried out in accordance with ISO 1953.
6 Apparatus
The apparatus shall be as specified in ISO 8858-1.
7 Flotation conditions
7.1 Collector dosage
To establish well-defined flotation response curves, it is necessary to extend the range of conditions specified
in ISO 8858-1. Different coals will require different conditions to display the attainable range of yields and
corresponding product ash levels. To obtain a preliminary guide to the appropriate flotation conditions for this
extended test, it is recommended that a sample of the coal be first tested according to the procedure specified
in ISO 8858-1.
NOTE It is suggested that the collector increments referred to in 8.3 be selected on the basis of the result of the
ISO 8858-1 test in Table 1.
Table 1
ISO 8858-1 yield
ISO 8858-1 suggested collector dosage
(fraction of dosage used in ISO 8858-1)
%
< 40
As in ISO 8858-1 = 1 ml/kg
W 40 < 60
25 % = 0,25 ml/kg
10 % = 0,10 ml/kg
W 60 u80
2,5 % = 0,025 ml/kg
> 80
The final result is largely independent of the selected increment size. Experienced operators may prefer to use
other dosage rates.
2 © ISO 2004 – All rights reserved

7.2 Frother dosage
Frother addition at each stage may be made at approximately half the dosage specified in ISO 8858-1, i.e. at
0,05 ml of 4-methyl-2-pentanol (formerly called methyl isobutyl carbinol MIBC) (50 ml of 0,1 % aqueous
solution) per kilogram of dry solids in the initial sample.
NOTE Frother dosages are not critical beyond the initial separation. Operator judgment may be used to maintain an
adequate froth.
7.3 Solids content
The solids content for the first flotation stage shall be as specified in ISO 8858-1. For all subsequent stages,
the mass of solids shall be that which results from the previous flotation stage.
7.4 Air flow rate
The air flow rate shall be as specified in ISO 8858-1.
7.5 Test temperature
The test temperature shall be as specified in ISO 8858-1 and shall be reported with the test results.
8 Procedure
8.1 Initial procedure
The moisture content, size analysis and other parameters specified in ISO 8858-1 shall be determined.
8.2 Initial separation
The initial separation shall be carried out generally following the principles given in ISO 8858-1 with the
exceptions that
a) no collector shall be used,
b) no conditioning time is required, and
c) no frother shall be used.
Both concentrate and tailings shall be retained as pulps for subsequent reflotation.
NOTE Experience has shown that omission of frother and collector permits selective recovery of low-ash rapid
floating particles and bet
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