SIST EN ISO 22940:2021

SLOVENSKI STANDARD
oSIST prEN ISO 22940:2020
01-november-2020
Trdna alternativna goriva - Določevanje elementne sestave z rentgensko
fluorescenco (ISO/DIS 22940:2020)
Solid recovered fuels - Determination of elemental composition by X-ray fluorescence
(ISO/DIS 22940:2020)
Feste Sekundärbrennstoffe - Bestimmung der Elementzusammensetzung durch
Röntgenfluoreszenz (ISO/DIS 22940:2020)
Combustibles solides de recuperation - Détermination de la composition élémentaire par
fluorescence de rayons X (ISO/DIS 22940:2020)
Ta slovenski standard je istoveten z: prEN ISO 22940
ICS:
75.160.10 Trda goriva Solid fuels
oSIST prEN ISO 22940:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 22940:2020

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oSIST prEN ISO 22940:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 22940
ISO/TC 300 Secretariat: SFS
Voting begins on: Voting terminates on:
2020-09-10 2020-12-03
Solid recovered fuels — Determination of elemental
composition by X-ray fluorescence
Combustibles solides de recuperation — Détermination de la composition élémentaire par fluorescence de
rayons X
ICS: 75.160.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
This document is circulated as received from the committee secretariat.
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 22940:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2020

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oSIST prEN ISO 22940:2020
ISO/DIS 22940:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
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oSIST prEN ISO 22940:2020
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Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Safety remarks . 3
5 Symbols and abbreviated terms . 3
5.1 Symbols . 3
5.2 Abbreviated terms . 4
6 Principle . 4
7 Apparatus . 4
8 Interferences and sources of error . 5
9 Sample preparation . 5
9.1 Preparation principles . 5
9.2 Drying of general analysis sample material . 5
9.3 Preparation of pressed pellet . 6
10 Procedure. 6
10.1 Analytical measurement conditions . 6
10.1.1 Wavelength dispersive instruments . 6
10.1.2 Energy dispersive instruments . 7
10.1.3 Intensities and background corrections . 7
10.2 Calibration . 8
10.2.1 General. 8
10.2.2 General calibration procedure . 8
10.2.3 Calibration procedure using the pressed pellet method (recommended method) 9
10.3 Procedures for correcting matrix effect . 9
10.3.1 Internal standard correction using Compton (incoherent) scattering method . 9
10.3.2 Fundamental parameter approach .10
10.3.3 Fundamental or theoretical influence coefficient method .10
10.3.4 Empirical alpha correction . .11
10.4 Analysis of the samples .11
11 Quality control .12
11.1 Drift correction procedure .12
11.2 Reference materials and quality control samples .12
12 Calculation of the result .12
13 Performance characteristics .12
14 Test report .13
Annex A (informative) Publicly available solid recovered fuel reference materials .14
Annex B (informative) Validation .15
Bibliography .35
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oSIST prEN ISO 22940:2020
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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.
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 documents 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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 300, Solid Recovered Fuels.
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.
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Introduction
X-ray fluorescence spectrometry can be used as a fast method for a qualitative overview of ash forming
elements and impurities. When calibration is based on reference materials or on matrix-matched
homogeneous solid recovered fuel samples with known content, X-ray fluorescence spectrometry can
be used for a quantitative analysis of the total content of the specified elements within different solid
recovered fuels.
The quality of the results obtained depends very closely on the type of instrument used, e.g. bench
top or high performance, energy dispersive or wavelength dispersive instruments. When selecting a
specific instrument, several factors have to be considered, such as the matrices to be analysed, elements
to be determined, detection limits required and the measuring time.
Due to the wide range of matrix compositions and the lack of suitable reference materials in the case
of solid recovered fuels from various origin, it is generally difficult to set up a calibration with matrix-
matched reference materials. Therefore, it is important to use several homogenized solid recovered
fuel samples with properties that sufficiently match the matrices of interest and whose content has
been derived by independent measurement techniques, e.g. total digestion of solid recovered fuels and
characterization of major and minor elements by measurement of digestion solutions with ICP-MS or
ICP-OES or by other techniques like elemental analysis using combustion technology on sulfur or by
combustion and ion chromatographic determination for chlorine.
Therefore, this document describes two different procedures:
1) Quantitative analytical procedure for major elements of solid recovered fuels. The calibration is
based on different reference materials and solid recovered fuel samples with known content.
The elements described as major elements of solid recovered fuels are in fact major elements of the
fuel ashes more than of the fuels. The determination of these elements may be helpful to predict the
melting behaviour and slagging of the ashes. Moreover, contamination of fuel with sand or soil is
indicated by high values of several elements.
2) Total element characterization at a semi-quantitative level for major and minor elements of solid
recovered fuels. The calibration is based on matrix-independent calibration curves, previously set
up by the manufacturer.
In general, the sensitivity of X-ray fluorescence is not sufficient for a determination of the content of
minor elements (trace metals) in solid recovered fuels. However, determination of minor elements
after calibration with solid recovered fuel samples with known content or at a semi-quantitative
level based on matrix-independent calibration curves could be used to collect data for higher
sample numbers taking into account lower achievable precision. Therefore, it may be used to reveal
excessive contents of minor elements in solid recovered fuels.
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oSIST prEN ISO 22940:2020

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oSIST prEN ISO 22940:2020
DRAFT INTERNATIONAL STANDARD ISO/DIS 22940:2020(E)
Solid recovered fuels — Determination of elemental
composition by X-ray fluorescence
1 Scope
This document specifies the procedure for a determination of major and minor element concentrations
in solid recovered fuel material by energy dispersive X-ray fluorescence (EDXRF) spectrometry or
wavelength dispersive X-ray fluorescence (WDXRF) spectrometry using a calibration with solid
recovered fuel reference materials or solid recovered fuel samples with known content. A semi-
quantitative determination may be carried out using matrix independent standards.
X-ray fluorescence spectrometry may be used as a fast method for a qualitative overview of elements
and impurities and after suitable calibration it is very useful for determining major elements or even
minor elements (except Hg) in order to quickly identify increased concentrations of minor elements in
solid recovered fuels (e.g. during SRF-production).
This document is applicable for the following elements: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co,
Ni, Cu, Zn, As, Br, Mo, Cd, Sb, Sn, Tl and Pb. Concentrations from approximately 0,000 1 % and above can
be determined depending on the element, the calibration materials used and the instrument used.
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.
1)
ISO 21637:—, Solid recovered Fuels — Terminology, definitions and descriptions
2)
ISO 21646:—, Solid recovered fuels — Sample preparation
3)
ISO 21660-3:—, Solid recovered fuels — Determination of moisture content using the oven dry method —
Part 3: Moisture in general analysis sample
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 21637:— and the
following apply.
3.1
absorption edge
abrupt change in mass absorption coefficient at a specific wavelength or energy
3.2
absorption of X-rays
loss of intensity of X-rays through absorption by an isotropic and homogenous material as described by
the Beer-Lambert law
1) Under preparation. (Stage at the time of publication ISO/FDIS 21637.)
2) Under preparation. (Stage at the time of publication ISO/CD 21646)
3) Under preparation. (Stage at the time of publication ISO/DIS 21660-3.)
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3.3
analytical line
specific characteristic X-ray spectral line of the atom or ion of the analyte used for determination of the
analyte content
3.4
continuous radiation
electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when
deflected by another charged particle, such as an atomic nucleus
3.5
compton-line
spectral line due to incoherent scattering (Compton-effect), occurring when the incident X-ray photon
strikes an atom without promoting fluorescence
Note 1 to entry: Energy is lost in the collision and therefore, the resulting scattered X-ray photon is of lower
energy than the incident X-ray photon.
3.6
drift correction monitors
physically stable samples used to correct for instrumental drift
3.7
emitted sample X-rays
radiation emitted by sample consisting of X-ray fluorescence radiation (3.14) and scattered primary
X-rays (3.12)
3.8
mass absorption coefficient
constant describing the fractional decrease in the intensity of a beam of X-radiation as it passes through
an absorbing medium
2
Note 1 to entry: It is expressed in cm /g.
Note 2 to entry: The mass absorption coefficient is a function of the wavelength of the absorbed radiation and the
atomic number of the absorbing element.
3.9
polarised excitation X-ray spectrometer
energy dispersive X-ray spectrometer where the excitation is performed by polarised radiation and the
emitted X-ray fluorescence radiation (3.14) is detected along the direction of polarisation
3.10
powder sample
analyte sample submitted as a powder for direct measurement in the sample cup
3.11
pressed pellet
analyte sample prepared by pressing milled material into a disk
3.12
primary X-rays
X-rays by which the sample is radiated
3.13
quality control sample
stable sample with known contents, e.g. (certified) reference material (CRM) or homogenized solid
recovered fuel samples from known origin which contents have been derived by independent analysis
used to monitor instrument and calibration performance
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3.14
X-ray fluorescence radiation
emission of characteristic X-rays from a sample that has been bombarded by high-energy X-rays or
gamma rays
4 Safety remarks
The X-ray fluorescence spectrometer shall comply with international and national regulations relevant
to radiation protection.
The person responsible for managing or supervising the operation of X-ray equipment shall provide
evidence of his knowledge of radiation protection according to national regulations.
5 Symbols and abbreviated terms
5.1 Symbols
Al Aluminium
As Arsenic
Br Bromine
Ca Calcium
Cd Cadmium
Cl Chlorine
Co Cobalt
Cr Chromium
Cu Copper
Fe Iron
K Potassium
Mg Magnesium
Mn Manganese
Mo Molybdenum
Na Sodium
Ni Nickel
P Phosphorus
Pb Lead
S Sulphur
Sb Antimony
Si Silicon
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Sn Tin
Ti Titanium
Tl Thallium
V Vanadium
Zn Zinc
5.2 Abbreviated terms
EDXRF Energy dispersive X-ray fluorescence
MCA Multi-Channel Analyser
WDXRF Wavelength dispersive X-ray fluorescence
6 Principle
After a suitable preparation, the sample is introduced into a XRF-spectrometer and excited by primary
X-rays. The intensities of the secondary fluorescent energy lines specific for each element are measured
and the elemental composition of the sample is determined by reference to previously established
calibration graphs or equations and applying corrections for inter-element effects. The calibration
equations and inter-element corrections are established using pure reagents and/or series of internal or
reference materials provided that they meet all the requirements of the relevant preparation technique.
7 Apparatus
7.1 X-ray fluorescence spectrometer shall be able to analyse the elements according to the scope of
this document. The following types of X-ray fluorescence spectrometers are applicable:
− energy dispersive X-ray fluorescence (EDXRF) spectrometer that achieves the dispersion of the
emitted X-ray fluorescence radiation by an energy dispersive detector;
− wavelength dispersive X-ray fluorescence (WDXRF) spectrometer that achieves the dispersion of
the emitted X-ray fluorescence radiation by diffraction by a crystal or a synthetic multilayer.
The spectrometer consists of the following components:
− primary X-ray source, an X-ray tube with a high voltage generator;
− sample holder;
− detector unit including electronic equipment;
− source modifiers to modify the shape or intensity of the source spectrum or the beam shape (like
source filters, secondary targets, polarizing targets, collimators, focusing optics, etc.).
The detector unit is different for WDXRF and for EDXRF spectrometers. WDXRF spectrometers take
advantage of the dispersion of the emitted radiation by diffraction by a crystal or a synthetic multilayer.
The detector does not need to be capable of energy discrimination. EDXRF spectrometers use an energy
dispersive detector. Pulses of current from the detector, which are a measure of the energy of the incoming
X-rays, are segregated into channels according to energy using a Multi-Channel Analyser (MCA).
NOTE 1 The use of a high-energy X-ray tube increases the potential for losses of volatile analytes from samples
by heating in the spectrometer during analysis.
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NOTE 2 The new generation of EDXRF spectrometers takes advantage of the polarizing target theory resulting
in a significant decrease of the background scattering, and therefore lower limits of detection can be achieved
(comparable to WDXRF).
7.2 Pellet press, capable of providing a pressure of at least 30 kN. The pellet press may be a cold press
or a hot mould press, operating at temperatures not exceeding 180 °C.
8 Interferences and sources of error
Interferences in X-ray fluorescence spectrometry are due to spectral line overlaps, matrix effects,
spectral artefacts and particle size or mineralogical effects.
Spectral line overlaps occur when an analytical line cannot be resolved from the line of a different
element. Corrections for these interferences are made using the algorithms provided with the
instrument software.
Matrix effects occur when the X-ray fluorescence radiation from the analyte element is absorbed
or enhanced by other elements in the sample before it reaches the detector. In the case of complex
matrices, these effects generally have to be corrected. The correction procedure depends on the X-ray
fluorescence spectrometry system (EDXRF or WDXRF) and the apparatus type itself.
Spectral artefacts, e.g. escape peaks, sum peaks, pulse pile up lines, dead time, Bremsstrahlung
correction, are accounted for by the provided instrument software. Spectral artefacts differ for energy
dispersive and wavelength dispersive XRF spectrometry.
9 Sample preparation
9.1 Preparation principles
The sample preparation is very critical for XRF analysis of solid recovered fuels. The quality of sample
preparation strongly influences the accuracy of the results. The following different options exist:
− For quantitative analysis of solid recovered fuel samples, the preparation of pressed pellets from
prepared general analysis sample material is recommended.
− For semi-quantitative analysis of solid recovered fuels, the general analysis material may be used
directly (in powder form) and concerning samples of solid recovered fuel pellets, the original
pellets may be used directly without any sample preparation. It may be used to provide fast basic
information about the approximate composition of a sample. Similar results may be obtained using
portable XRF instruments for field analysis.
For a given calibration, the same preparation method shall be used throughout, for both samples and
standards.
For precise quantitative measurements, homogeneous and representative test portions are necessary.
The nominal top size of the material shall be 0,5 mm or less, according to ISO 21646:—.
9.2 Drying of general analysis sample material
Dry a sufficient amount of general analysis sample material according to ISO 21660-3:— immediately
before pressing pellets for XRF-analysis.
NOTE Concerning some XRF-instruments, the applied vacuum will dry the general analysis sample material
during the determination giving the same results as if the sample was previously dried.
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9.3 Preparation of pressed pellet
A pellet is prepared in the pellet press (7.2). Before pressing, the sample shall be mixed and homogenized.
Use the same weight for any single set of standards and samples and add binder (e.g. wax or liquid
organic binder), if necessary.
For the preparation, follow the manufacturer’s instructions.
NOTE 1 Different binders can be used. In case of organic liquid binders (~ 0,6 % weight of sample) the pressed
pellet will be placed in an oven at between 70-100 °C for a minimum of 10 minutes to evaporate the organic
solvent or for the formation of long chain polymers formed by heating (e.g. PVP-methylcellulose binders).
NOTE 2 In case of wax binder the ratio of the sample weight to wax is around 10:1.
10 Procedure
10.1 Analytical measurement conditions
10.1.1 Wavelength dispersive instruments
The analytical lines to be used and suggested operating conditions are given in Table 1. The settings
strongly depend on the spectrometer configuration, e.g. the type of X-ray tube (Rh, Cr), tube power,
available crystals, type of collimators. Instrument manufacturer’s recommendations should be followed
in all cases.
10.1.1.1 Intensities and background corrections
For the determination of trace elements, the measured intensities have to be background corrected.
The measured background positions should be free of spectral line interferences. The net peak intensity,
I , expressed as the number of counts per second of the element of interest (i), is calculated as the
difference between the measured peak intensity of the element and the background intensity, as given
in Formula (1):
II=−I (1)
pb
where
I is the count rate of the element i, expressed as the number of counts per second;
p
I is the background count rate of the element i with no analyte present, expressed as the number
b
of counts per second.
10.1.1.2 Counting time
The minimum counting time is the time necessary to achieve an uncertainty (2σ ), which is less than
%
the desired precision of the measurement. Choose a reference material or quality control sample with a
concentration level in the middle of the working range and measure the count rate. The counting time
for each element can be calculated according to Formula (2):
2
T =− ()100//21σ xI I (2)
()
% pb
where
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