Direct reduced iron — Determination of carbon and/or sulfur — High-frequency combustion method with infrared measurement

ISO/TR 9686:2017 specifies a method for the determination of the mass fraction of carbon and/or sulfur in direct reduced iron by infrared measurement after high-frequency combustion. This method is applicable to mass fractions of carbon between 0,05 % and 2,5 %, and/or mass fractions of sulfur between 0,001 % and 0,05 % in direct reduced iron.

Minerais de fer préréduits — Dosage du carbone et/ou du soufre — Méthode par combustion haute fréquence et mesurage par infrarouge

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Status
Published
Publication Date
16-May-2017
Current Stage
6060 - International Standard published
Start Date
17-May-2017
Completion Date
17-May-2017
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TECHNICAL ISO/TR
REPORT 9686
First edition
2017-05
Direct reduced iron — Determination
of carbon and/or sulfur — High-
frequency combustion method with
infrared measurement
Minerais de fer préréduits — Dosage du carbone et/ou du soufre —
Méthode par combustion haute fréquence et mesurage par infrarouge
Reference number
ISO/TR 9686:2017(E)
ISO 2017
---------------------- Page: 1 ----------------------
ISO/TR 9686:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

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ii © ISO 2017 – All rights reserved
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ISO/TR 9686:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Reagents ........................................................................................................................................................................................................................ 1

6 Apparatus ..................................................................................................................................................................................................................... 2

7 Sampling and samples .................................................................................................................................................................................... 3

7.1 Laboratory sample ............................................................................................................................................................................... 3

7.2 Preparation of predried test samples .................................................................................................................................. 3

8 Procedure..................................................................................................................................................................................................................... 3

8.1 General operating instructions ................................................................................................................................................. 3

8.2 Test portion ................................................................................................................................................................................................ 3

8.3 Blank test ..................................................................................................................................................................................................... 3

8.4 Calibration .................................................................................................................................................................................................. 4

8.4.1 Crucible preparation .................................................................................................................................................... 4

8.4.2 Combustion .......................................................................................................................................................................... 5

8.5 Determination ......................................................................................................................................................................................... 5

9 Expression of results ........................................................................................................................................................................................ 5

9.1 Calculation of mass fraction of carbon or sulfur ........................................................................................................ 5

9.2 General treatment of results ....................................................................................................................................................... 5

9.2.1 Repeatability and permissible tolerance .................................................................................................... 5

9.2.2 Determination of analytical result .................................................................................................................... 6

9.2.3 Between-laboratories precision ......................................................................................................................... 6

9.2.4 Check for trueness .......................................................................................................................................................... 7

9.2.5 Calculation of final result .......................................................................................................................................... 8

10 Test report ................................................................................................................................................................................................................... 8

Annex A (informative) Crucible loading sequence ................................................................................................................................. 9

Annex B (informative) Flowsheet of the procedure for the acceptance of analytical values

for test samples ...................................................................................................................................................................................................10

Annex C (informative) Features of commercial HF combustion/infrared sulfur analysers .....................11

Annex D (informative) Derivation of repeatability and permissible tolerance formulae .........................12

Annex E (informative) Precision data obtained by international analytical trials ...........................................13

Bibliography .............................................................................................................................................................................................................................15

© ISO 2017 – All rights reserved iii
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ISO/TR 9686:2017(E)
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: w w w . i s o .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 102, Iron ore and direct reduced iron,

Subcommittee SC 2, Chemical analysis.

This first edition Technical Report cancels and replaces the second edition International Standard

(ISO 9686:2006), which has been technically revised and has been converted to a Technical Report

because it is not suitable for determination of carbon or sulfur as a referee method.

iv © ISO 2017 – All rights reserved
---------------------- Page: 4 ----------------------
TECHNICAL REPORT ISO/TR 9686:2017(E)
Direct reduced iron — Determination of carbon and/or
sulfur — High-frequency combustion method with infrared
measurement

WARNING — This document may 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 health and safety practices.

1 Scope

This document specifies a method for the determination of the mass fraction of carbon and/or sulfur in

direct reduced iron by infrared measurement after high-frequency combustion.

This method is applicable to mass fractions of carbon between 0,05 % and 2,5 %, and/or mass fractions

of sulfur between 0,001 % and 0,05 % in direct reduced iron.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Principle

The test portion is combusted in a refractory crucible in a flow of oxygen in the presence of an

accelerator, the crucible being inserted in the combustion tube of a high-frequency (HF) furnace.

The carbon present is converted into carbon dioxide and the sulfur into sulfur dioxide. Each gas is

measured by infrared absorption, with calibration using barium carbonate and potassium sulfate.

5 Reagents

During analysis, use only reagents of recognized analytical grade and only distilled water or water of

equivalent purity.
5.1 Oxygen, minimum purity 99,5 % (mass fraction).

The pressure in the furnace should be controlled by a pressure regulator designed especially for the

purpose and complying with the manufacturer’s specification.
5.2 Magnesium perchlorate, grain size 0,7 mm to 1,2 mm.
© ISO 2017 – All rights reserved 1
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ISO/TR 9686:2017(E)

5.3 Accelerator, tungsten (granular form) with known low mass fractions of carbon (<0,002 %) and

sulfur (<0,000 5 %).

5.4 Pure iron, or iron of known low mass fractions of carbon and sulfur, as in 5.3.

5.5 Tin capsules, of capacity 0,3 ml, diameter 5 mm, length 17 mm.
5.6 Barium carbonate (BaCO ), fine powder.
Dry at 105 °C for 3 h and cool in a desiccator.
5.7 Sulfur standard solutions.
Dry potassium sulfate (K SO ) at 105 °C for 1 h and cool in a desiccator.
2 4

Weigh, to the nearest 0,000 2 g, the amounts of potassium sulfate specified in Table 1.

Transfer to five 100 ml one-mark volumetric flasks, dissolve with 50 ml of water, dilute to volume and mix.

5.8 Ascarite, used only for carbon determination.
Table 1 — Sulfur standard solutions
Sulfur standard solution Mass of K SO Sulfur concentration
2 4
g mg/ml
SS 1 0,217 4 0,4
SS 2 0,434 8 0,8
SS 3 0,652 2 1,2
SS 4 0,869 6 1,6
SS 5 2,174 0 4,0
6 Apparatus

Ordinary laboratory apparatus, including micropipettes and one-mark volumetric flasks complying

with the specifications of ISO 7550 and ISO 1042, respectively, and the following.

6.1 Commercial carbon/sulfur apparatus

The apparatus required for HF combustion of the samples and the subsequent infrared absorption

measurement of evolved carbon dioxide and/or sulfur dioxide may be obtained commercially from a

number of manufacturers. Common features of such systems are discussed in Annex C.

The manufacturer’s instruction for the operation of their equipment should be followed.

6.2 Ceramic combustion crucibles, required for containing the sample and any additions that may

be necessary for the subsequent combustion.

The crucibles should be of precise dimensions for the system, and should adapt to the supporting

pedestal post, so that the sample in the crucible will be positioned at the correct height within the

induction coil when it is in the raised position.

These crucibles should be pre-ignited in an oxygen flow, in a furnace, for not less than 2 h at 1 350 °C (or at

1 100 °C if only sulfur is to be determined), and then stored in a desiccator or closed container before use.

For pre-ignition, a resistance furnace may be used.
2 © ISO 2017 – All rights reserved
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ISO/TR 9686:2017(E)
6.3 Micropipette, of capacity 50 µl.
7 Sampling and samples
7.1 Laboratory sample

For analysis, use a laboratory sample of minus 160 µm particle size, which has been taken and prepared

in accordance with ISO 10835.
7.2 Preparation of predried test samples

Thoroughly mix the laboratory sample using non-magnetic materials. Taking multiple increments with

a non-magnetic spatula, extract a test sample in such a manner that it is representative of the whole

contents of the container.

Dry the test sample at 105 °C ± 2 °C as specified in ISO 7764. (This is the predried test sample.)

8 Procedure

WARNING — The risks related to combustion analysis are mainly hand burns when pre-igniting

the ceramic crucibles, and in the subsequent combustion. Normal precautions for handling

oxygen cylinders should be taken. Oxygen from the combustion process should be removed

effectively from the apparatus and room, since a too high concentration of oxygen in a confined

space may present a fire hazard. HF screening should be effective to avoid radiation hazards.

8.1 General operating instructions

Purify the oxygen supply using tubes packed with ascarite (5.8) and magnesium perchlorate (5.2) and

maintain a quiescent flow rate of about 0,5 l/min whilst on standby.

Maintain a glass-wool filter between the furnace chamber and the analyser and change as necessary. The

furnace chamber, pedestal post and filter trap should be cleaned frequently to remove oxide build-up.

The oxygen flow rate may vary from one instrument to another, but is usually about 2,0 l/min during

the combustion period, according to the nature of the material
...

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