ISO/TR 9686:2017

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

General Information

• Status: Published
• Publication Date: 16-May-2017
• ICS: 73.060.10 - Iron ores
• Technical Committee: ISO/TC 102/SC 2 - Chemical analysis
• Drafting Committee: ISO/TC 102/SC 2 - Chemical analysis
• Current Stage: 6060 - International Standard published
• Start Date: 17-May-2017
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 9686:2006 - Direct reduced iron - Determination of carbon and/or sulfur - High-frequency combustion method with infrared measurement
• Effective Date: 09-Jul-2016

Overview - ISO/TR 9686:2017 (Direct reduced iron, HF combustion + IR)

ISO/TR 9686:2017 specifies a laboratory method for the determination of carbon and/or sulfur mass fractions in direct reduced iron (DRI) using high-frequency (HF) combustion followed by infrared (IR) measurement of CO2 and SO2. The method applies to carbon levels from 0.05 % to 2.5 % and sulfur levels from 0.001 % to 0.05 %. It describes sample preparation, reagents, crucible preparation, calibration, blank tests and instrument operation for commercial HF combustion/IR analyzers.

Key topics and technical requirements

• Principle: Combustion of a weighed test portion in oxygen in a refractory crucible within an HF furnace; CO2 and SO2 measured by IR absorption.
• Scope limits: Carbon 0.05–2.5 % (mass fraction); sulfur 0.001–0.05 % (mass fraction).
• Sample: Laboratory sample milled to −160 µm and predried at 105 °C ± 2 °C (per ISO 10835 / ISO 7764). Typical test portion: 0.400 g.
• Reagents & materials: Oxygen (≥ 99.5 %), magnesium perchlorate, ascarite (for C), tungsten accelerator (low C/S content), tin capsules, barium carbonate for carbon calibration and potassium sulfate standard solutions for sulfur calibration.
• Crucibles: Ceramic combustion crucibles must be pre‑ignited (≥ 1 350 °C for general use; 1 100 °C if only sulfur is determined) and precisely dimensioned for the instrument.
• Calibration & blanks: Multi-point calibration using prepared standards (BaCO3 for carbon; K2SO4 solutions for sulfur). At least three blank burns are recommended to establish zero adjustment.
• Instrumentation & operation: Uses commercial HF combustion/infrared sulfur analysers; follow manufacturer instructions for oxygen flow (typically ~2.0 L/min during combustion), filter maintenance and stabilization.
• Safety: Addresses combustion hazards, oxygen handling and high-frequency radiation screening.

Applications and users

ISO/TR 9686:2017 is intended for:

• Steelmakers, iron producers and DRI manufacturing labs monitoring carbon and sulfur content for process control and product specification.
• Quality control and metallurgical laboratories performing routine compositional analysis of direct reduced iron.
• Equipment manufacturers and analytical service providers implementing or validating HF combustion + IR analyzers for DRI.

Practical benefits include fast, direct measurement of C and S in DRI, clear calibration procedures, and guidance on sample preparation and instrument setup.

Related standards and annex material

• Related ISO references cited for sampling and glassware: ISO 10835, ISO 7764, ISO 7550, ISO 1042.
• Annexes provide crucible loading sequences, calibration flowsheets, features of commercial analyzers, repeatability/tolerance derivations and international precision data.
• Note: ISO/TR 9686:2017 replaces ISO 9686:2006 and is published as a Technical Report (not a referee method).

Keywords: ISO/TR 9686:2017, direct reduced iron, HF combustion, infrared measurement, carbon determination, sulfur determination, DRI analysis, barium carbonate calibration, potassium sulfate standard.

Standards Content (Sample)

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 2017
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
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www.iso.org
ii © ISO 2017 – All rights reserved

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
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
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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
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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
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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

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.
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

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
...