ISO 7404-2:2009

INTERNATIONAL ISO
STANDARD 7404-2
Second edition
2009-10-01
Methods for the petrographic analysis of
coals —
Part 2:
Methods of preparing coal samples
Méthodes d'analyse pétrographique des charbons —
Partie 2: Préparation des échantillons de charbon

Reference number
©
ISO 2009
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2009
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2009 – All rights reserved

Contents
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Definitions .1
4 Principle .1
5 Reagents and materials .1
6 Apparatus.2
7 Procedure.3
Annex A (informative) Examples of procedures for the preparation of a polished particulate block
suitable for petrographic analysis from a sample of crushed coal .6

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
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
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 7404-2 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels.
This second edition cancels and replaces the first edition (ISO 7404-2:1985),which has been technically
revised.
ISO 7404 consists of the following parts, under the general title Methods for the petrographic analysis of coals:
1)
⎯ Part 1: Vocabulary
⎯ Part 2: Methods of preparing coal samples
⎯ Part 3: Method of determining maceral group composition
1)
⎯ Part 4: Methods of determining microlithotype, carbominerite and minerite composition
⎯ Part 5: Method of determining microscopically the reflectance of vitrinite

1) Parts 1 and 4 of this International Standard will be available under the original title, Methods for the petrographic
analysis of bituminous coal and anthracite, until the revisions of these documents have reached the stage at which they
are publicly available.
iv © ISO 2009 – All rights reserved

Introduction
Petrographic analyses have been recognized internationally as important in the context of the genesis, vertical
and lateral variation, continuity, metamorphism and usage of coal. The International Committee for Coal
Petrology (ICCP) has made recommendations concerning nomenclature and analytical methods and has
published an extensive handbook that is continuously updated, describing in detail the characteristics of a
wide range of coals. The text of this part of ISO 7404 agrees substantially with the text of the handbook and
incorporates many useful comments made by members of the ICCP and by member bodies of
ISO/TC 27, Solid mineral fuels.
Petrographic analyses of single-seam coals provide information about the rank, the maceral and
microlithotype compositions and the distribution of mineral matter in the coal. The reflectance of vitrinite is a
useful measure of coal rank and the distribution of the reflectance of vitrinite in a coal blend. Together with a
maceral group analysis, it can provide information about chemical and technological properties of the coal and
coal blend. Various other applications, like the characterization of bulk samples, cargoes, etc., and the precise
determination of different rank vitrinites in complex coal blends are in use.
ISO 7404 (all parts) is concerned with the methods of petrographic analysis currently employed in
characterizing coal in the context of its technological use and establishes a system for petrographic analysis.
The method is applicable for low-, medium- and high-rank coals.
The varied petrographic composition and hardness of coal and the type and amount of included mineral
matter does not permit the formulation of a precise procedure that can be applied with equal success to all
types and ranks of coal. For example, a successful preparation method for use with medium- and high-rank
coals might not be applicable among low-rank coals. Within these limits, therefore, this part of ISO 7404
allows the operator to apply individual skills and experience to the preparation of a satisfactory polished
surface. Nevertheless, recommended procedures that have been found applicable to a variety of coals, are
given in the Annex A, which is for information only.
Many processes are involved between the mining of the coal and its preparation for industrial use.
Petrographic analysis can be required at any stage on samples from the coal seam in situ, from borehole
cores, on the raw product from the colliery, on the products from the preparation plant, or on the final product.
The amount and size distribution of the coal being investigated thus varies widely and it is important to ensure
that the sample obtained for petrographic analysis is fully representative.
INTERNATIONAL STANDARD ISO 7404-2:2009(E)

Methods for the petrographic analysis of coals —
Part 2:
Methods of preparing coal samples
1 Scope
This part of ISO 7404 specifies methods for preparing a polished particulate block from a sample of crushed
coal for analysis by reflectance microscopy. These methods can also be applied to the preparation of a
polished, embedded lump of coal.
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 amendment) applies.
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
1)
ISO 7404-1, Methods for the petrographic analysis of bituminous coal and anthracite — Part 1: Vocabulary
ISO 18283, Hard coal and coke — Manual sampling
ICCP International Handbook of Coal Petrography
3 Definitions
For the purpose of this document, the definitions given in ICCP International Handbook and in ISO 7404-1
apply.
4 Principle
A representative sample of air-dried coal is crushed to a specified particle size and mixed with a suitable
binder. The mixture is formed into a particulate block, one face of which is ground and polished to give a relief-
free and scratch-free surface for analysis by reflectance microscopy.
5 Reagents and materials
5.1 Binder, used to hold the particles of crushed coal together as a particulate block, or to embed a lump of
coal.
The properties of the binder shall be such that
a) there shall be no chemical reaction with the coal or immersion oil;
b) for liquid binders such as polyester resin, the curing temperature required to make the particulate block
should not exceed 100 °C and a temperature of less than 60 °C is preferable;
c) for thermoplastic mounting materials such as polymethylmethacrylate (PMMA) powder, a temperature of
about 120 °C is required for proper annealing;
d) the surfaces of the coal particles should be easily wetted and there shall be good penetration of pores
and cracks;
e) the coal particles should be held securely during grinding and polishing;
f) there should be a marked contrast with the coal particles when immersed in oil and focused under the
microscope;
g) the hardness should be comparable with that of the coal so that a flat, relief-free and scratch-free surface
can be obtained by grinding and polishing;
h) there should be no large volume changes during curing, which can cause possible damage to the coal
particles;
i) the viscosity of liquid binder should be such that the tendency of coal grains to segregate due to density
and size is minimized.
5.2 Mould release agent, that does not affect the coal and mounting compound, nor damage the mould.
5.3 Grinding abrasives, consisting of silicon carbide papers of decreasing grain size, [53,5 µm (240 grit or
P280), 23,6 µm (400 grit or P800), 16,0 µm (600 grit or P1200)].
Metal-bonded, diamond-impregnated 15 µm grinding disks may be used as a substitute for the smaller-grain-
size silicon carbide paper.
5.4 Polishing abrasives, consisting of metal oxide powders, colloidal silica suspension, or diamond pastes
of decreasing grain size.
A polishing abrasive having a maximum particle size not exceeding 0,05 µm shall be used for the final
polishing stage.
NOTE The number of polishing stages depends on the grain size of the abrasive used at the final stage of grinding
and on the grain size of the polishing abrasives available. It is recommended that aluminium oxide powders be used
throughout and that an abrasive having a maximum particle size of 0,3 µm be used for the penultimate polishing stage.
5.5 Lap cloths, made of cotton, silk or synthetic fabric with a minimum of nap.
6 Apparatus
6.1 Test sieve, having an aperture 1,00 mm, in accordance with the requirements of ISO 3310-1, with a
suitable lid and receiver.
6.2 Grinding mill or mortar and pestle, suitable for crushing 0,3 kg to 0,45 kg of coal to pass through the
test sieve (6.1), with the minimum production of fines.
The grinding mill may be manually or electrically operated.
6.3 Press, for use when pressure is required during curing, for example when using PMMA.
2)
It shall be capable of producing a pressure of up to 21 MPa and may be a simple hand operated lever, a
torque-wrench, or a hydraulic press.

6 2
2) 1 MPa = 10 N/m = 145 psi.
2 © ISO 2009 – All rights reserved

6.4 Moulds, to hold the mixture of coal and binder during the curing process.
In simple moulding, these may be made from heavy-gauge aluminium foil, but reusable moulds may be made
from silicone rubber, flexible plastic, aluminium or steel. For pressure moulding, a cuboid or cylindrical steel
mould equipped with a removable base and cap or other means of removing the block from the mould after
curing; see Note. The interior surfaces of the metal mould should have a ground finish.
Metal moulds for use in pressure moulding shall be capable of withstanding double the pressure normally
applied in making the particulate block. The internal dimensions of the mould shall be such that the face of the
block that will be polished has a surface area of at least 500 mm .
NOTE For reflectance analysis, if the coal is deficient in vitrinite, it can be necessary to make more than one block of
minimum size.
6.5 Pelletizing machine, consisting of an automatic mounting press that can be pre-programmed for mould
size, type of binder (thermosetting, thermoplastic), heating time, cooling time, initial temperature, and curing
pressure.
These have been found to be time-saving and produce blocks of consistent quality. By employing a spacer in
a tall mould, two pellets can be made during one cy
...