Coke -- Determination of coke reactivity index (CRI) and coke strength after reaction (CSR)

ISO 18894:2018 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~ 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.

Coke -- Détermination de l'indice de réactivité du coke (CRI) et de la résistance post-réactionelle du coke (CSR)

General Information

Status
Published
Publication Date
13-Feb-2018
Technical Committee
Drafting Committee
Current Stage
6060 - International Standard published
Start Date
10-Jan-2018
Completion Date
14-Feb-2018
Ref Project

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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 18894:2018(E)
ISO 2018
---------------------- Page: 1 ----------------------
ISO 18894:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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Published in Switzerland
ii © ISO 2018 – All rights reserved
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ISO 18894:2018(E)
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

© ISO 2018 – All rights reserved iii
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ISO 18894:2018(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: 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
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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.
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ISO 18894:2018(E)
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.
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ISO 18894:2018(E)
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
Gas outlet to stack.
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.

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ISO 18894:2018(E)

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
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ISO 18894:2018(E)

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
...

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