ISO 4698:2007

INTERNATIONAL ISO
STANDARD 4698
Second edition
2007-10-15

Iron ore pellets for blast furnace
feedstocks — Determination of the
free-swelling index
Boulettes de minerais de fer pour l'alimentation de hauts fourneaux —
Détermination de l'indice de gonflement libre




Reference number
ISO 4698:2007(E)
©
ISO 2007

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ISO 4698:2007(E)
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ISO 4698:2007(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
6 Apparatus . 2
7 Test conditions . 3
8 Procedure . 4
9 Expression of results . 4
10 Test report . 5
11 Verification . 5
Annex A (normative) Flowsheet of the procedure for the acceptance of test results . 8
Annex B (normative) Methods for determination of the volume of the test portion . 9

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ISO 4698:2007(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 4698 was prepared by Technical Committee ISO/TC 102, Iron ore and direct reduced iron, Subcommittee
SC 3, Physical testing.
This second edition cancels and replaces the first edition (ISO 4698:1994), which has been revised to
homogenise with other physical test standards.
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ISO 4698:2007(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 should be considered in conjunction with other tests used to evaluate the quality of iron
ores as feedstocks for blast furnace processes.
This International Standard may 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 4698:2007(E)

Iron ore pellets for blast furnace feedstocks — Determination of
the free-swelling index
CAUTION — This International Standard may involve hazardous materials, operations and equipment.
This 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 increase in
volume of iron ore pellets, when reduced in an unconstrained bed under conditions resembling those
prevailing in the reduction zone of a blast furnace. It specifies the determination of the free-swelling index.
This International Standard is applicable to hot-bonded pellets.
2 Normative references
The following referenced documents are indispensable for the application 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 3082:2000 , Iron ores — Sampling and sample preparation procedures
ISO 11323:2002, 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 volume of pellets in the test portion is measured at room temperature, using a volumetric apparatus. The
test portion is isothermally reduced under unconstrained conditions in a fixed bed at 900 °C, using a reducing
gas consisting of CO and N , for 60 min. The volume of the reduced pellets is measured at room temperature.
2
The swelling index is calculated as the difference between the volume of the pellets after and before reduction,
expressed as a percentage.

1) Under revision to incorporate ISO 10836, Iron ores — Method of sampling and sample preparation for physical testing.
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ISO 4698:2007(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 − 12,5 mm + 10,0 mm.
A test sample of at least 1 kg, on a dry basis, of whole-sized pellets 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
At least 4 test portions, each one made up of 18 whole pellets, shall be obtained from the test sample by
random selection.
6 Apparatus
6.1 General
The test apparatus shall comprise:
a) ordinary laboratory equipment, such as an oven, hand tools, a time-control device and safety equipment;
b) a reduction-tube assembly;
c) a furnace;
d) a test portion holder;
e) a system to supply the gases and regulate the flow rates;
f) volumetric apparatus.
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
900 °C and resistant to deformation. The internal diameter shall be 75 mm ± 1 mm.
6.3 Test portion holder, a wire basket made of non-scaling, heat-resistant metal to withstand temperatures
higher than 900 °C. It shall comprise three levels, each made to receive six pellets, for a total of 18 pellets.
Alternatively, the test portion holder may be made by welding a tube to the centre of three perforated plates,
mutually parallel and equally spaced. The tube shall be top-opened and bottom-closed to allow the
thermocouple insertion up to the middle of the test portion. The set shall be made of non-scaling, heat-
resistant metal to withstand temperatures higher than 900 °C. The perforated plate shall be 4 mm thick, with
its diameter 1 mm less than the tube internal diameter, the holes in the plate shall be 2 mm to 3 mm in
diameter, at a pitch centre distance of 4 mm to 5 mm.
Figure 2 shows an example of a reduction tube with the test portion holder.
6.4 Furnace, having a heating capacity and temperature control able to maintain the entire test portion, as
well as the gas entering the bed, at 900 °C ± 10 °C.
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ISO 4698:2007(E)
6.5 Gas-supply system, capable of supplying the gases and regulating gas flow rates.
6.6 Volumetric apparatus, capable of measuring the volume of the test portion to an accuracy of 0,2 mL.
Annex B shows examples of volumetric apparatus.
7 Test conditions
7.1 General
Volumes and flow rates of gases are measured at a reference temperature of 0 °C and at a reference
atmospheric pressure of 101,325 kPa (1,013 25 bar).
7.2 Reducing gas
7.2.1 Composition
The reducing gas shall consist of:
CO 30,0 % ± 0,5 % (volume fraction)
N 70,0 % ± 0,5 % (volume fraction)
2
7.2.2 Purity
Impurities in the reducing gas shall not exceed:
H 0,2 % (volume fraction)
2
CO 0,2 % (volume fraction)
2
O 0,1 % (volume fraction)
2
H O 0,2 % (volume fraction)
2
7.2.3 Flow rate
The flow rate of the reducing gas, during the entire reducing period, shall be maintained at 15 L/min ± 1 L/min.
7.3 Heating and cooling gas
Nitrogen (N ) shall be used as the heating and cooling gas. Impurities shall not exceed 0,1 % (volume
2
fraction).
The flow rate of N shall be maintained at 10 L/min until the test portion reaches 900 °C, and at 15 L/min
2
during the temperature-equilibration period. During cooling, it shall be maintained at 5 L/min.
7.4 Temperature of the test portion
The temperature of the entire test portion shall be maintained at 900 °C ± 10 °C during the entire reducing
period and, as such, the reducing gas shall be preheated before entering the test portion.
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ISO 4698:2007(E)
8 Procedure
8.1 Number of determinations for the test
Carry out the test as many times as required by the procedure in Annex A.
8.2 Reduction
Determine the volume of the test portion (V ) to an accuracy of 0,2 mL, in accordance with one of the methods
0
specified in Annex B.
Place 6 pellets on each of the 3 levels of the test portion holder (6.3) and place it in the reduction tube (6.2).
Close the top of the reduction tube. Connect the thermocouple, ensuring that its tip is in the centre of the test
portion. Close the top of the reduction tube and insert it in the furnace.
Connect the gas-supply system (6.5).
Pass a flow of N through the test portion at a rate of at least 5 L/min and commence heating. When the
2
temperature of the test portion approaches 900 °C, increase the flow to 15 L/min ± 1 L/min. After reaching
900 °C ± 10 °C, maintain the test portion under these conditions for 15 min.
DANGER — Carbon monoxide and the reducing gas, which contains carbon monoxide, are toxic and
therefore hazardous. Testing shall be carried out in a well ventilated area or under a ventilation hood.
Precautions should be taken for the safety of the operator, according to the safety codes of each
country.
Introduce the reducing gas at a flow rate of 15 L/min ± 1 L/min to replace the N . After 60 min of reduction,
2
turn off the power.
NOTE Some pellets show a higher degree of swelling within a shorter reduction time than 60 min. Therefore, a
shorter reduction time may be used as an alternative when appropriate, e.g. 40 min.
Replace the reducing gas with N at a flow rate of 5 L/min. Remove the reduction tube from the furnace (6.4)
2
while maintaining the flow of N until the test portion reaches room temperature (below 50 °C).
2
8.3 Volume determination
Remove the test portion from the reduction tube and immediately determine and register the total volume of
the test portion (V ), applying the same method used for the determination of V .
1 0
9 Expression of results
9.1 Calculation of the free-swelling index (V )
FS
The free-swelling index, V , expressed as a percentage, is calculated from the following equation:
FS
VV−
10
V=×100
FS
V
0
where
V is the volume, in millilitres, of the test portion before reduction;
0
V is the volume, in millilitres, of the test portion after reduction.
1
Record the result to one decimal place.
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ISO 4698:2007(E)
9.2 Repeatability and acceptance of test results
Follow the procedure in Annex A by using the repeatability value, r = 3,0 (%, absolute). The results shall be
reported to one decimal place.
10 Test report
The test report shall include the following information:
a) a reference to this International Standard, i.e. ISO 4698:2007;
b) all details necessary for the identification of the sample;
c) the name and address of the test laboratory;
d) the date of the test;
e) the date of the test report;
f) the signature of the person responsible for the test;
g) details of any operation and any test conditions not specified in this International Standard or regar
...