ISO 18894:2018

INTERNATIONAL ISO
STANDARD 18894
Second edition
2018-02
Coke — Determination of coke
reactivity index (CRI) and coke
strength after reaction (CSR)
Coke — Détermination de l'indice de réactivité du coke (CRI) et de la
résistance post-réactionelle du coke (CSR)
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 3
6 Apparatus . 3
7 Preparation of test sample . 4
8 Procedure. 5
8.1 Number of tests . 5
8.2 Assembly of the reaction vessel . 5
8.3 Determination of CRI . 5
8.4 Determination of CSR . 6
9 Expression of results . 6
9.1 Coke reactivity index (CRI) . 6
9.2 Coke strength after reaction (CSR) . 6
10 Precision . 7
10.1 Quality control . 7
10.2 Repeatability limit . 8
10.2.1 General. 8
10.2.2 Coke reactivity index . 8
10.2.3 Coke strength after reaction . 8
10.3 Reproducibility limit . 9
11 Test report . 9
Annex A (normative) Reactivity test apparatus “type A”, single wall .11
Annex B (normative) Reactivity test apparatus “type B”, double wall .13
Annex C (normative) Coke-strength-after-reaction tumbler .15
Annex D (informative) Determination of abrasion value .17
Annex E (informative) Results of the Interlaboratory Study (precision data) .18
Foreword
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electrotechnical standardization.
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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
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URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee
SC 3, Coke.
This second edition cancels and replaces the first edition (ISO 18894:2006), which has been technically
revised.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 18894:2018(E)
Coke — Determination of coke reactivity index (CRI) and
coke strength after reaction (CSR)
1 Scope
This document specifies the equipment and techniques used for determining lump-coke (nominal top
size >20 mm) reactivity in carbon dioxide gas at elevated temperatures and its strength after reaction
in carbon dioxide gas by tumbling in a cylindrical chamber.
Main application is the testing of coke to be used in iron making blast furnaces (CRI~ < 33, CSR~ > 55).
This standard can also be applied to other coke types (e.g. foundry coke), but limited precision is to be
expected. Application to coke for non-iron making blast furnaces is beyond the scope of this document.
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 579, Coke — Determination of total moisture
ISO 3310 (all parts), Test sieves — Technical requirements and testing
ISO 1213-2, Solid mineral fuels — Vocabulary — Part 2: Terms relating to sampling, testing and analysis
ISO 13909-5, Hard coal and coke — Mechanical sampling — Part 5: Coke — Sampling from moving streams
ISO 13909-6, Hard coal and coke — Mechanical sampling — Part 6: Coke — Preparation of test samples
ISO 18283, Hard coal and coke — Manual sampling
IEC 60584-1, Thermocouples — Part 1: EMF specifications and tolerances
IEC 60584-3, Thermocouples — Part 3: Extension and compensating cables — Tolerances and
identification system
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1213-2 and the following 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/
3.1
abrasion value
lack of resistance to abrasion of the coke after reaction with carbon dioxide in the CRI test, measured as
the percentage of a sample passing through a 0,5 mm sieve after tumbling under conditions specified in
this document
Note 1 to entry: See Annex D.
3.2
coke reactivity index
CRI
percentage weight loss of coke after reaction with carbon dioxide to form carbon monoxide under
conditions specified in this document
3.3
coke strength after reaction
CSR
strength of coke after reaction with carbon dioxide in the CRI test, measured as the percentage retained
on either a 10,0 mm or a 9,5 mm sieve after tumbling under conditions specified in this document
4 Principle
A test portion of the dried coke sample having a size range from 19,0 mm to 22,4 mm is heated in a
reaction vessel to 1 100 °C in a nitrogen atmosphere. For the test, the atmosphere is changed to carbon
dioxide for exactly 2 h. After the test, the reaction vessel is allowed to cool down to about 50 °C in a
nitrogen atmosphere. The comparison of the sample weight before and after the reaction determines
the coke reactivity index (CRI).
The reacted coke is treated in a specially designed tumbler for 600 revolutions for 30 min. The coke
strength after reaction (CSR) value is determined by sieving and weighing the amount of coke passing
through either a 10,0 mm or a 9,5 mm sieve.
An example of the arrangement of the test unit is shown in Figure 1.
NOTE During the development of this document, it was found that 10,0 mm and 9,5 mm sieves are both
commonly used for these types of test. When reacted coke is tumbled, abrasion usually takes place. Particles of
about 20 mm lose some edges, but they do not break into pieces. Therefore, it makes almost no difference if the
sieving after tumbling is made with a 10,0 mm or a 9,5 mm sieve, as the size of the coke pieces is either about
20 mm or 0 mm to 5 mm, but not in the range of 10 mm. This has been verified by experiments over a long period
of time. It has been shown that the difference in CSR using both sieve sizes is within the precision range of this
document.
2 © ISO 2018 – All rights reserved

Key
1 device for temperature recording 6 electrically heated furnace
2 thermocouple 7 gas-flow meters
3 single or double wall retort with perforated plate as sample holder 8 control valves
4 test portion 9 tumbler
5 layer of ceramic balls
a
Gas outlet to stack.
b
Gas inlet.
Figure 1 — Example of test unit arrangement
5 Reagents
5.1 Nitrogen, having a purity of >99,9 % by volume, dry and having a maximum oxygen and carbon
dioxide (CO + O ) concentration of 100 mg/kg.
2 2
5.2 Carbon dioxide, having a purity of >99,5 % by volume, dry and having an oxygen concentration
<100 mg/kg.
6 Apparatus
6.1 Electric furnace (see Annexes A and B), capable of housing the reaction-vessel assembly
containing the test portion and providing a uniform temperature of (1 100 ± 3) °C in the centre of the
test portion. The uniform temperature zone shall be at least three times longer than the sample height.
It is preferable that the furnace have independently controlled heating in three zones to achieve
uniformity of heating in the reaction vessel.
6.2 Reaction vessel (see Annexes A and B), constructed from heat-resistant steel or nickel alloy to
the dimensions required to fit inside the electric furnace selected for use.
The coke to be tested is placed on a perforated plate in the reaction vessel. Below this perforated plate,
a gas preheater, such as a bed of ceramic Al O balls on a second perforated plate, diffuses the nitrogen
2 3
and carbon dioxide introduced into the vessel up through the coke bed during the course of the test.
Both perforated plates are fixed between two sets of lugs in the reaction vessel. The gas enters through
inlets at the bottom and exits through outlets positioned at the top of the reaction vessel.
The reaction vessel is positioned such that the coke sample contained in the vessel is in the centre of the
uniform temperature zone of the furnace.
6.3 Flowmeters, variable area flowmeter or, preferably, mass flowmeters, used to monitor the
nitrogen and carbon dioxide flow during the test, having an accuracy of gas flow rates of ±5 % for both
nitrogen and carbon dioxide.
NOTE Fluctuations in the gas flow can cause variability in the test results.
Gas pressures through the flowmeters shall be maintained at the manufacturer’s calibration
specification.
6.4 Thermocouple, in accordance with IEC 60584-1 and IEC 60584-3, used for measuring and
controlling the sample temperature, which shall be designed according to the test conditions [e.g.
platinum–rhodium/platinum (90 % Rh and 10 % Pt, percentage by mass)], enclosed in a heat-resistant
steel or nickel alloy or ceramic protection tube. The protection tube shall be made of gas-tight casing
to prevent faulty measurement caused by a poisoning of the thermocouple by gaseous products. The
protection tube is fastened to the centre of the lid to ensure the positioning of the thermocouple tip in
the centre of the coke bed.
6.5 Sieves, square hole in accordance with ISO 3310, with actual openings of 9,5 mm or 10,0 mm,
19,0 mm and 22,4 mm. A 0,5 mm sieve is also required if the abrasion test (see Annex D) is carried out.
6.6 Balance, capable of weighing to the nearest 0,1 g.
6.7 Tumbler (see Annex C), with a revolution counter and a time-relay device.
7 Preparation of test sample
The coke shall be sampled in accordance with ISO 18283 or ISO 13909-5.
Crush approximately 50 kg of the gross sample with a representative size distribution in a jaw crusher
or rolling crusher. The opening of the crusher shall be set such that the gross sample yields between
10 % and 30 % of the fraction 19,0 mm to 22,4 mm.
NOTE 1 The specification for the crusher in the initial step is to avoid “over-crushing” samples. The first
crushing step is without any sieving, so the opening of the crusher is set by experience. “Over-careful” crushing
would reduce the size too little; therefore division of sample could easily be non-representative. “Heavy” crushing
might lead to too much fines.
Divide the crushed sample to obtain a mass of approximately 25 kg in accordance with ISO 13909-6.
The mass of sample required for the test depends on the following.
a) The minimum mass required for the test is governed by the minimum mass of the 19,0 mm to
22,4 mm fraction, i.e. 1 000 g.
b) A sample of large coke shall be of sufficient size to ensure that it is representative. Therefore,
smaller sample amounts (e.g. from pilot oven programs) may be used only when representativeness
is guaranteed. This shall be indicated in the test report.
Sieve the crushed sample using a 22,4 mm sieve placed on top of a 19,0 mm sieve. Recycle the >22,4 mm
fraction to the crusher until the oversize is less than 3 % of the crushed sample. Discard the <19,0 mm
and >22,4 mm fractions.
Dry the 19,0 mm to 22,4 mm fraction in accordance with ISO 579 to less than 1 % moisture. Sieve the
crushed and dried sample again using 22,4 mm and 19,0 mm sieves to remove adhering breeze. Divide
the crushed and sieved sample to obtain a test sample of approximately 1 000 g.
4 © ISO 2018 – All rights reserved

Alternatively, the sample (fraction 19,0 mm to 22,4 mm) may be divided to approximately 1 000 g before
drying and sieving.
Divide the test sample to get test portions of approximately 200 g each. For each test, prepare a test
portion of 200 g ± 2 g and weigh accurately to the nearest 0,1 g. The final mass adjustment can be made
by exchanging a single piece of coke for one slightly lighter or heavier as appropriate.
Record the number of pieces in each test portion.
NOTE 2 This can be helpful for comparing the test runs.
If necessary, use a magnet to remove any magnetic material from the test portions.
8 Procedure
8.1 Number of tests
A minimum of two tests shall be carried out.
8.2 Assembly of the reaction vessel
Carefully place the weighed test portion (coke pieces) on top of the perforated plate inside the reaction
vessel (see Annex A for single-wall and Annex B for double-wall equipment).
Placing may be aided by the insertion of a temporary guide tube vertically into the centre of the reaction
vessel and placing the test portion evenly around this temporary guide tube.
Ensure that the thermocouple sits vertically in the centre of the coke bed with its tip in the centre (at
half the height of the test portion above the perfo
...