ISO 11258:2015

INTERNATIONAL ISO
STANDARD 11258
Third edition
2015-08-15
Iron ores for shaft direct-reduction
feedstocks — Determination of the
reducibility index, final degree of
reduction and degree of metallization
Minerais de fer pour charges utilisées dans les procédés par réduction
directe — Détermination de l’indice de réductibilité, du degré final de
réduction et du degré de métallisation
Reference number
ISO 11258:2015(E)
©
ISO 2015

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ISO 11258:2015(E)

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© ISO 2015, Published in Switzerland
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ISO 11258:2015(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Sampling, sample preparation, and preparation of test portions . 2
5.1 Sampling and sample preparation . 2
5.2 Preparation of test portions . 2
6 Apparatus . 2
6.1 General . 2
7 Test conditions . 3
7.1 General . 3
7.2 Reducing gas . 3
7.2.1 Composition . 3
7.2.2 Purity . 3
7.2.3 Flow rate . 3
7.3 Heating and cooling gas . 3
7.4 Temperature of the test portion . 4
8 Procedure. 4
8.1 Number of determinations for the test . 4
8.2 Chemical analysis . 4
8.3 Reduction . 4
8.4 Chemical analysis after reduction . 4
9 Expression of results . 5
9.1 Calculation of the final degree of reduction (R ) . 5
90
9.2 Calculation of the reducibility indices dR/dt(R=40) and dR/dt(R=90) . 5
9.2.1 Reduction curve . 5
9.2.2 Reducibility index for 40 % reduction . 5
9.2.3 Reducibility index for 90 % reduction . 6
9.3 Calculation of the degree of metallization (M) . 6
9.3.1 Determination of the degree of metallization from chemical analysis (M). 6
9.3.2 Determination of the degree of metallization from R (MR) . 6
90
9.4 Repeatability for R and acceptance of test results . 7
90
10 Test report . 7
11 Verification . 7
Annex A (normative) Flowsheet of the procedure for the acceptance of test results .11
Annex B (informative) Derivation of formula for reducibility .12
Annex C (informative) Derivation of formula for degree of metallization from R .14
90
Bibliography .16
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ISO 11258:2015(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 meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 102, Iron ore and direct reduced iron,
Subcommittee SC 3, Physical testing.
This third edition cancels and replaces the second edition (ISO 11258:2007), of which it constitutes a
minor revision to contemplate the outcomes of the studies on mass definition, as well as minor editorial
improvements.
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ISO 11258:2015(E)

Introduction
This International Standard concerns one of a number of physical test methods that have been
developed to measure various physical parameters and to evaluate the behaviour of iron ores, including
reducibility, disintegration, crushing strength, apparent density, etc. This method was developed to
provide a uniform procedure, validated by collaborative testing, to facilitate comparisons of tests made
in different laboratories.
The results of this test have to be considered in conjunction with other tests used to evaluate the quality
of iron ores as feedstocks for direct reduction processes.
This International Standard can be used to provide test results as part of a production quality control
system, as a basis of a contract, or as part of a research project.
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INTERNATIONAL STANDARD ISO 11258:2015(E)
Iron ores for shaft direct-reduction feedstocks —
Determination of the reducibility index, final degree of
reduction and degree of metallization
CAUTION — This International Standard can involve hazardous operations and equipment. This
International Standard does not purport to address all of the safety issues associated with its use.
It is the responsibility of the user of this International Standard to establish appropriate safety
and health practices and determine the applicability of regulatory limitations prior to its use.
1 Scope
This International Standard specifies a method to provide a relative measure for evaluating the extent
to and ease to which oxygen can be removed from iron ores, when reduced under conditions resembling
those prevailing in shaft direct-reduction processes. It specifies the determination of the reducibility,
final degree of reduction, and degree of metallization.
This International Standard is applicable to lump ores and hot-bonded pellets.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 2597-1, Iron ores — Determination of total iron content — Part 1: Titrimetric method after tin(II)
chloride reduction
ISO 2597-2, Iron ores — Determination of total iron content — Part 2: Titrimetric methods after
titanium(III) chloride reduction
ISO 3082, Iron ores — Sampling and sample preparation procedures
ISO 5416, Direct reduced iron — Determination of metallic iron — Bromine-methanol titrimetric method
ISO 9035, Iron ores — Determination of acid-soluble iron(II) content — Titrimetric method
ISO 11323, Iron ore and direct reduced iron — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11323 apply.
4 Principle
The test portion is isothermally reduced in a fixed bed, at 800 °C, using a reducing gas consisting of H
2,
CO, CO , and N , and is weighed continuously or at specified time intervals until 90 min of reduction
2 2
is reached. The rate of reduction is calculated at the oxygen/iron ratio of 0,9 and the final degree of
reduction is calculated from the oxygen mass loss after 90 min (R ). The degree of metallization is
90
calculated either by a formula based on R or by chemical analysis of the reduced product.
90
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ISO 11258:2015(E)

5 Sampling, sample preparation, and preparation of test portions
5.1 Sampling and sample preparation
Sampling of a lot and preparation of a test sample shall be in accordance with ISO 3082.
The size range for pellets shall be 50 % - 16,0 mm + 12,5 mm and 50 % - 12,5 mm + 10,0 mm.
The size range for lump ores shall be 50 % - 20,0 mm + 16,0 mm and 50 % - 16,0 mm + 10,0 mm.
A test sample of at least 2,5 kg, on dry basis, of the sized material shall be obtained.
Oven-dry the test sample to constant mass at 105 °C ± 5 °C and cool it to room temperature before
preparation of the test portions.
NOTE Constant mass is achieved when the difference in mass between two subsequent measurements
becomes less than 0,05 % of the initial mass of the test sample.
5.2 Preparation of test portions
Collect each test portion by taking ore particles at random.
NOTE Manual methods of division recommended in ISO 3082, such as riffling, can be applied to obtain the
test portions.
At least five test portions, each of approximately 500 g (± the mass of 1 particle) shall be prepared from
the test sample: four test portions for testing and one for chemical analysis.
Weigh the test portions to the nearest 1 g and register the mass of each test portion on its recipient label.
6 Apparatus
6.1 General
The test apparatus shall comprise the following:
a) ordinary laboratory equipment, such as an oven, hand tools, and safety equipment;
b) reduction-tube assembly;
c) furnace, equipped with a balance for permitting the mass loss of the test portion to be read at any
time during the test;
d) system to supply the gases and regulate the flow rates;
e) weighing device.
Figure 1 shows an example of the test apparatus.
6.2 Reduction tube, made of non-scaling, heat-resistant metal to withstand temperatures higher than
800 °C and resistant to deformation.
The internal diameter shall be 75 mm ± 1 mm. A removable perforated plate, made of non-scaling, heat-
resistant metal to withstand temperatures high
...