ISO 18806:2019

INTERNATIONAL ISO
STANDARD 18806
First edition
2019-09
Solid mineral fuels — Determination
of chlorine content
Combustibles minéraux solides — Dosage de la teneur en chlore
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 Method A — High temperature combustion . 1
4.2 Method B — High pressure vessel combustion . 1
5 Reagents . 2
5.1 Method A . 2
5.2 Method B . 2
6 Apparatus . 2
6.1 Method A . 2
6.2 Method B . 4
7 Test sample . 4
8 Procedure. 4
8.1 Blank value determination . 4
8.2 Method A — High temperature combustion . 4
8.2.1 General. 4
8.2.2 Preparation . 5
8.2.3 Combustion procedure . 5
8.3 Method B — High pressure vessel combustion . 5
8.3.1 Preparation . 5
8.3.2 Combustion procedure . 5
9 Determination of dissolved chloride . 6
10 Calculation and expression of results . 6
11 Precision . 7
11.1 Precision data origin . 7
11.2 Repeatability limit, r . 7
11.3 Reproducibility limit, R . 7
11.4 Quality control . 7
12 Test report . 7
Annex A (normative) Quality control . 9
Annex B (informative) Results of the interlaboratory study (precision data) .10
Bibliography .13
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 cancels and replaces ISO/TS 18806:2014, which has been technically revised.
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iv © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 18806:2019(E)
Solid mineral fuels — Determination of chlorine content
1 Scope
This document specifies two methods (high temperature combustion and high pressure vessel
combustion) for the determination of chlorine in solid mineral fuels. It is applicable to solid mineral fuels.
The chlorine in the absorption solution can be determined using different finishes, such as coulometric
or potentiometric titration, spectrophotometry or ion chromatography.
The method is applicable to determine the chlorine content higher than 0,005 % mass fraction.
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 687, Solid mineral fuels — Coke — Determination of moisture in the general analysis test sample
ISO 1170, Coal and coke — Calculation of analyses to different bases
ISO 1213-2, Solid mineral fuels — Vocabulary — Part 2: Terms relating to sampling, testing and analysis
ISO 5068-2, Brown coals and lignites — Determination of moisture content — Part 2: Indirect gravimetric
method for moisture in the analysis sample
ISO 11722, Solid mineral fuels — Hard coal — Determination of moisture in the general analysis test
sample by drying in nitrogen
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
4.1 Method A — High temperature combustion
The sample is combusted in an oxygen atmosphere at high temperature. The gaseous combustion
products collected in a trap filled with water include dissolved chloride compounds.
4.2 Method B — High pressure vessel combustion
The sample is combusted in an oxygen atmosphere in a high pressure vessel containing an absorption
solution. The combustion products collected in an absorption solution include dissolved chloride
compounds.
5 Reagents
5.1 Method A
5.1.1 Oxygen, pure, with an assay of at least 99,5 % volume fraction.
5.1.2 Combustion aid (optional), e.g. spectroscopic carbon, iron phosphate (FePO ), tungsten or quartz.
5.1.3 Deionised water, with a specific conductivity not higher than 0,2 mS/m at 25 °C.
5.2 Method B
5.2.1 Oxygen, pure, with an assay of at least 99,5 % volume fraction.
5.2.2 Combustion aid (optional), paraffin, benzoic acid, polyethylene combustion bags, acetobutyrate
capsules or other suitable materials.
5.2.3 Fuse, ignition wire (e.g. platinum) and cotton fuse (optional).
NOTE Check for a possible contribution of the cotton fuse to the chlorine content.
5.2.4 Absorption solution, either eluent used for ion chromatographic determination or alkaline
solution (e.g. 0,2 mol/l KOH or 0,1 mol/l NaOH) or deionised water (5.1.3).
6 Apparatus
6.1 Method A
An example for the equipment for high-temperature combustion is given below. This equipment is
suitable for manual determinations and is well established.
Automated systems with autosamplers can also be used if their main features comply with the manual
apparatus specified below, i.e. mainly temperature of the oven, the use of fused silica glass tubes, and
the absorption unit.
6.1.1 Fused silica combustion tube, absorber and headpiece (see Figure 1).
6.1.2 Porcelain combustion boat, with handle, e.g. 70 mm long, 10 mm wide, and 7 mm deep.
6.1.3 Silica pusher, with iron inlay (see Figure 2).
6.1.4 Magnet.
6.1.5 Electrical tube furnace, about 300 mm long, capable of being heated to preferably 1 300 °C and
maintained at the combustion temperature of (1 250 ± 25) °C.
6.1.6 Flow meter.
6.1.7 Oxygen inlet, consisting of a pierced silicon stopper with a glass tube.
2 © ISO 2019 – All rights reserved

Dimensions in millimetres
Key
1 headpiece 5 VS 13 spherical joint (see ISO 641)
2 sintered glass disc (pore size of 90 µm to 150 µm) 6 oxygen inlet
3 V45/50 conical ground joint (see ISO 383) 7 absorber
4 combustion tube 8 sintered glass disc (pore size of 90 µm to 150 µm)
Figure 1 — Example of an apparatus for Method A
Dimensions in millimetres
Key
1 silica pusher
2 iron inlay
Figure 2 — Example of a silica pusher
6.2 Method B
6.2.1 Digestion unit.
6.2.1.1 Digestion vessel, capable of withstanding safely the pressures developed during combustion
and with an inner surface that is resistant to corrosion by acidic gases formed or emitted during
combustion.
6.2.1.2 Pressure regulator, to control the filling of the vessel with oxygen and discharging afterwards.
6.2.1.3 Pressure gauge, with relief valve operating at 3,5 MPa.
6.2.1.4 Ignition circuit.
6.2.2 Crucible, of silica, nickel-chromium, platinum or similar non-reactive material that is resistant to
corrosion by acidic gases formed or emitted during combustion.
6.2.3 Alternate digestion equipment.
The apparatus employed for determination of calorific value in accordance with ISO 1928 can be used
simultaneously for chlorine determination provided it meets the specifications of 6.2.1. Attention is
drawn to the fact that deionised water should be used as absorption solution.
7 Test sample
The sample used for the determ
...