ISO 13605:2018

INTERNATIONAL ISO
STANDARD 13605
First edition
2018-10
Solid mineral fuels — Major and
minor elements in coal ash and coke
ash — Wavelength dispersive x-ray
fluorescence spectrometric method
Combustibles minéraux solides — Éléments en minorité et en majorité
dans les cendres de houille et de coke — Méthode spectrométrique
par fluorescence aux rayons X à une longueur d'onde dispersive
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 2
5 Reagents . 2
5.1 General . 2
5.2 Flux and heavy absorber . 2
6 Apparatus . 2
7 Sample . 3
7.1 Coal and coke ash prepared in the laboratory . 3
7.2 Coal and coke ash . 4
8 Procedure. 4
8.1 Number of determinations . 4
8.2 Test portion . 4
8.3 Check test . 4
8.4 Calibration . 4
8.5 Preparation of the fused discs . 4
8.5.1 General. 4
8.5.2 Disc storage . 5
8.5.3 Fused disc quality . 5
8.6 XRF measurement . 5
8.6.1 Instrumental conditions . 5
8.6.2 Monitor measurements . . 6
9 Calculation . 7
9.1 General . 7
9.2 Correction of instrumental drift . 7
9.3 Correction for dead time losses . 7
9.4 Matrix corrections . 7
10 Reporting results . 8
11 Precision . 8
12 Test report . 9
Annex A (normative) Acceptance of analytical results for laboratory method .10
Annex B (informative) Reagents suitable for the preparation of synthetic calibration standards .12
Annex C (normative) Standard deviation of glass disc preparation .13
Annex D (informative) Calculation of phosphorus using P O .15
2 5
Bibliography .16
Foreword
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This document was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee
SC 5, Methods of analysis.
This first edition of ISO 13605 cancels and replaces ISO/TS 13605:2012, which has been technically
revised.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 13605:2018(E)
Solid mineral fuels — Major and minor elements in
coal ash and coke ash — Wavelength dispersive x-ray
fluorescence spectrometric method
WARNING — Use of this document can involve hazardous materials, operations and equipment.
This document does not purport to address all of the safety problems associated with its use.
It is the responsibility of the user of this document to establish appropriate safety and health
practices and determine the applicability of regulatory limitations prior to use.
1 Scope
This document sets out a wavelength dispersive X-ray fluorescence (XRF) procedure for the
determination of silicon, aluminium, iron, calcium, magnesium, sodium, potassium, titanium,
manganese, phosphorus and sulfur.
The method is applicable to coal ashes, coke ashes and boiler ashes having components within the
concentration ranges specified in Table 1.
Table 1 — Ranges of application of the method
Concentration range
Oxide
%
SiO 5 to 100
Al O 5 to 80
2 3
Fe O 0,1 to 25
2 3
CaO 0,05 to 25
MgO 0,05 to 25
Na O 0,05 to 5
K O 0,05 to 5
TiO 0,05 to 5
Mn O 0,005 to 5
3 4
a
P O 0,01 to 5
2 5
SO 0,05 to 10
NOTE 1  Additional analytes can be included in the method, provided that appropriate validation using reference materials
is carried out.
NOTE 2  The precision statistics can be determined using suitable reference materials.
NOTE 3  The method described in this document has been tested for the following additional analytes: BaO (0,01 % to 1 %);
SrO (0,01 % to 1 %) and ZnO (0,005 % to 1 %).
a
For information relating to phosphorus calculations, refer to Annex D.
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 1171, Solid mineral fuels — Determination of ash
ISO 1213-2, Solid mineral fuels — Vocabulary — Part 2: Terms relating to sampling, testing and analysis
ISO 13909-4, Hard coal and coke — Mechanical sampling — Part 4: Coal — Preparation of test samples
ISO 13909-6, Hard coal and coke — Mechanical sampling — Part 6: Coke — Preparation of test samples
ISO 18283, Hard coal and coke — Manual sampling
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1213-2 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle
The specimen on which X-ray fluorescence measurements are made is prepared by incorporating
the test portion of the sample, via fusion, into a borate glass disc using a casting or press-quenching
procedure. By using such a specimen, particle size effects are eliminated.
Calibration is carried out using pure chemicals and/or reference standards, and by making matrix
corrections for inter-element effects.
It is expected that laboratories using this document have experience in analysing coal ashes of certain
compositions and that they employ calibrations that cover these compositions.
5 Reagents
5.1 General
Unless otherwise specified, all reagents shall be of analytical grade and only distilled water or water of
equivalent purity shall be used.
5.2 Flux and heavy absorber
Borate fluxes of differing compositions have been found suitable for preparing glass discs from coal/coke
ash samples. These fluxes are based on mixtures of one or more of the following: lithium tetraborate,
lithium metaborate and lanthanum oxide. Flux may be purchased commercially or prepared by fusion
of a mixture of individual reagents.
NOTE The levels of contamination in the flux should be checked. Because levels of contamination may vary
from batch to batch, the same batch of flux should be used for all specimens (synthetic standards, external
standards and unknowns). When using a fresh batch of flux, reference material specimens should be prepared to
determine whether adjustments to the calibration are required.
6 Apparatus
All apparatus shall be constructed from materials that are thermally stable and chemically inert under
the conditions of the procedure.
2 © ISO 2018 – All rights reserved

6.1 Crucible, made from a non-wetting platinum alloy.
The crucible shall have sufficient capacity to hold the flux and sample required for fusion. Normally,
15 ml crucibles are adequate for discs of 32 mm in diameter, and 25 ml crucibles for discs of 40 mm in
diameter.
NOTE Either platinum/gold or platinum/gold/rhodium alloys are suitable.
Because the crucible and lid (if used) are to be used for fusion work, the normal precautions associated
with the care of hot platinum ware should be observed. It is necessary, therefore, to have suitable tongs
and a surface on which to rest the crucible. The hot crucible can be rested on a refractory surface,
which shall be kept very clean.
Although the crucible is fabricated from an alloy that is not wetted by the glass, for the greatest
precision, the crucible should be cleaned between each fusion. The use of citric acid (mass concentration
of 20 %), dilute hydrochloric acid (volume fraction of 10 % to 50 %) or dilute chlorine-free nitric acid
(volume fraction of 10 %) have proven to be suitable for crucible cleaning. The use of an ultrasonic bath
will accelerate this process. An alternative method of cleaning is to fuse several grams of flux in the
crucible, moving the melt around so as to clean the entire inner surface. The molten flux is poured from
the crucible. If a droplet adheres to the crucible, this can easily be flaked off when the crucible is cold.
6.2 Mould, made from non-wetting material. For example, platinum alloy is commonly used for casting
discs, and aluminium or graphite is suitable for press quenching.
In the casting technique, the bottom of the disc is the analytical surface. The mould should therefore
be flat and sufficiently thick that it is not easily deformed. Casting moulds should be checked regularly
for flatness and should be polished regularly, to ensure that the disc releases from the mould. Platens
for press-quenching are constructed so that the depth gradually increases from the perimeter to the
centre. The analytical surface for press-quenched discs is the surface which contacts the plunger head.
Care should be taken not to choose the platen side for intensity measurements.
6.3 Crucible tongs, platinum-tipped or stainless steel or titanium.
NOTE Stainless steel or titanium tongs are a suitable alternative to platinum-tipped tongs.
6.4 Desiccator, containing freshly regenerated, self-indicating silica gel.
6.5 Sample holders, used for specimen presentation.
6.6 X-ray fluorescence spectrometer, any conventional wavelength dispersive (sequential,
simultaneous, or combination simultaneous/sequential) vacuum path X-ray fluorescence spectrometer
may be used, provided that it conforms to precision requirements at the 0,1 % (10 counts) precision level.
7 Sample
7.1 Coal and coke ash prepared in the laboratory
The coal or coke sample shall be the analysis sample, prepared to a nominal top size of 212 µm. Sample
preparation shall be in accordance with ISO 13909-4 for coal samples or ISO 13909-6 for coke samples
or ISO 18283.
The sample shall then be ashed using the procedure specified in ISO 1171.
7.2 Coal and coke ash
Laboratory-prepared ashes for XRF analysis should be received at the laboratory, freshly prepared If
not freshly prepared coal or coke ash, reheat at 815 °C for 15 min and cool in a desiccator immediately
prior to weighing for analysis.
Boiler ash received at the laboratory should be ground to a nominal top size of 63 µm and dried at
105 °C for 1 h, then stored in a desiccator over freshly regenerated, self-indicating silica gel.
8 Procedure
8.1 Number of determinations
Discs shall be prepared and analysed as single determinations and a reference material shall be
prepared and analysed at the beginning and end of each batch of samples containing a maximum of
25 samples.
8.2 Test portion
The mass of the test portion shall be appropriate for the mould size and sample flux ratio chosen.
NOTE 1 Typically, sample-to-flux ratios are in the range 1:5 to 1:10.
NOTE 2 Typical total mass (sample plus flux) is 4 g for a 32 mm diameter and 7,5 g for a 40 mm diameter mould.
8.3 Check test
At least one reference material of similar composition to the samples being analysed shall be included
with each batch of test samples and shall be analysed in parallel with, and under the same conditions
as, the test samples. The results for the batch of samples shall be rejected if the results for the reference
material fail to meet the acceptance criteria detailed in Annex A.
8.4 Calibration
Calibration shall be effected using either reference materials, synthetic standards or mixtures of
reference materials and synthetic standards. Reference materials shall be pre-treated in accordance
with the instructions contained on
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