ISO/DIS 728

Coke – Size analysis by sieving

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DRAFT INTERNATIONAL STANDARD
ISO/DIS 728
ISO/TC 27/SC 3 Secretariat: SABS
Voting begins on: Voting terminates on:
2020-08-13 2020-11-05
Coke – Size analysis by sieving
ICS: 75.160.10
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ISO/DIS 728:2020(E)
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ISO/DIS 728:2020(E)
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ISO/DIS 728:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Apparatus ..................................................................................................................................................................................................................... 1

6 Sampling and preparation of sizing sample ............................................................................................................................ 2

7 Procedures .................................................................................................................................................................................................................. 3

7.1 Sizing sample of particle size greater than 22,4 mm but less than 125 mm ..................................... 3

7.2 Division of coke minus 22,4 mm .............................................................................................................................................. 6

7.3 Sizing sample of maximum particle size between 4,0 mm and 22,4 mm — manual

method ........................................................................................................................................................................................................... 6

7.4 Sizing sample of particle size less than 4,0 mm — manual method ......................................................... 7

7.5 Sizing sample of particle size between 4,0 mm and 22,4 mm and minus 4 mm —

mechanical method ............................................................................................................................................................................. 8

8 Expression of results for all sizes ........................................................................................................................................................ 8

9 Precision of the method .............................................................................................................................................................................10

9.1 Repeatability ..........................................................................................................................................................................................10

9.2 Reproducibility ....................................................................................................................................................................................10

10 Test report ................................................................................................................................................................................................................11

Annex A (informative) Guide to sizing coke products above 125 mm ............................................................................12

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ISO/DIS 728:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

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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

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iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 27, Coal and coke, Subcommittee SC 3, Coke.

This fourth edition cancels and replaces the third editions (ISO 728:1995 and ISO 2325:1986), which

has been technically revised.
The main changes compared to the previous edition are as follows:

a) The coke size analysis of the minus 20 mm fractions has been moved to this document;

b) Mechanical sieving was added to the scope;
c) Hand placing of coke was increased from 40 mm down to 22,4 mm;
d) ISO 728 now incorporates ISO 2325;

e) The coke mean size calculation was modified, moved from an annex to the main document and a

worked example added.
Annex A of this International Standard is for information only.
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DRAFT INTERNATIONAL STANDARD ISO/DIS 728:2020(E)
Coke – Size analysis by sieving
1 Scope

This International Standard specifies procedures for the size analysis of coke by manual and/or

mechanical sieving, using square or round holed sieves of aperture sizes between 125 mm and 0,5 mm.

Some guidance on handling the sampling and sizing of coke products greater than 125 mm is given in

Annex A.
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. The latest edition of the referenced document (including

any amendments) applies.
ISO 579, Coke — Determination of total moisture

ISO 1213-2, Solid mineral fuels — Vocabulary — Part 2: Terms relating to sampling, testing and analysis

ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth

ISO 3310-2, Test sieves — Technical requirements and testing — Part 2: Test sieves of perforated metal plate

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
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 1213-2 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/
4 Principle

A sample of coke with less than 5 % moisture is subjected to a process of size analysis by a specified

manual and or mechanical sieving, and the results are expressed in terms of the cumulative percentage

by mass of the coke remaining on sieves of different sized openings.
5 Apparatus

a) Test sieves, complying with ISO 3310-1 and ISO 3310-2. The set of sieves used shall have

exclusively round holes or exclusively square holes. It is important to check the sieves from time

to time, using the methods specified in ISO 1310, to ensure that the hole dimensions are within

the specified tolerances. Worn or damaged sieves can give rise to serious errors in size analysis

and shall be discarded. The test sieves should be selected according to the requirements of the test

and the characteristics of the sample. If possible, the series of sieves should be selected so that the

mass of coke in any size fraction does not exceed 25 % of the total mass of sample being sieved.

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ISO/DIS 728:2020(E)

For ungraded cokes, an example of a series of test sieves of nominal hole sizes 125 mm; 100 mm;

75 mm; 63 mm; 50 mm; 45 mm; 35,5 mm; 31,5 mm; 25; 22,4 mm; 16 mm; 10 mm; 8 mm; 5,6 mm;

4,0 mm and 2,8 mm may be suitable. For samples containing pieces with a particle size greater

than 125 mm, single-hole gauges may be used instead of test sieves;

b) Weighing scale or weighing machine, capable of measuring the mass of each size fraction to the

nearest 0,1 %;
c) Receivers or bins, for collecting material passing through the sieves;

d) Trays, smooth, of non-corrodible material, of at least 400 mm × 400 mm, depending on the mass of

sample and number of analysis required;
e) Lids, to fit the test sieves;
f) Flat brush, for cleaning the sieves and for brushing dust from the trays;

g) Hardwood block, about 150 mm long with a 10 mm × 10 mm cross-section, for tapping the sieves;

h) Shovel or scoop;
i) Vibratory sieve shaker for mechanical sieving. (see example Figure 2).
6 Sampling and preparation of sizing sample

The sieving shall be carried out on samples having less than 5,0 % moisture as per the following

procedures:

a) For unknown cokes two gross samples shall be sampled in accordance with ISO 13909-5 or

ISO 18283. Each gross sample shall be prepared in accordance with ISO 13909-6 or ISO 18283

and meet the minimum masses as quoted in Table 1 below. Prepare one of these samples for total

moisture determination in accordance with ISO 579. If the total moisture is higher than 5,0 % (as

sampled), dry the other sample sufficiently to reduce the total moisture content to lower than

5,0 % (as sampled). After the initial drying if the total moisture is still above 5,0 % further drying

will be necessary until the sample moisture is less than 5,0 %. The final dried sample less than

5,0 % moisture is used for the test;

b) For known cokes with less than 5,0 % moisture from the same plant or same supplier no further

pretreatment is required. If the moisture is above the 5,0 % level the drying time to reach less than

5,0 % (as sampled) may be determined by taking the average drying time over 10 lots. Alternatively,

drying most coke samples for 12 h or more at 100 to 200 °C should render the sample suitable for

sizing only. If only size analysis is required it is permissible to take one gross sample for sizing and

use the determined period or the longer 12 h drying time at 100-200 °C to prepare the gross sample

for sizing. Table 2 is used to determine the minimum mass needed at different levels of precision.

Table 1 — Minimum mass of sample for total moisture
Nominal top size Minimum mass
mm kg
> 125 2 000
125 1 000
90 500
63 250
45 125
31,5 60
22,4 30
16,0 15
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ISO/DIS 728:2020(E)
Table 1 (continued)
Nominal top size Minimum mass
mm kg
11,2 8
10,0 6
8,0 4
5,6 2
4 1
Reference: ISO 13909-6
Table 2 — Minimum mass of sample for size analysis
Nominal top Minimum mass for a Minimum mass for a
size of coal or precision of 1 % precision of 2 %
coke
kg kg
125 4 000 1 000
90 1 500 400
75 950 250
63 500 125
50 280 70
45 200 50
38 130 30
31,5 65 15
22,4 25 6
16,0 8 2
11,2 3 0,70
10,0 2 0,50
8,0 1 0,25
5,6 0,50 0,25
4,0 0,25 0,25
2,8 0,25 0,25
Reference: ISO 18283
7 Procedures
7.1 Sizing sample of particle size greater than 22,4 mm but less than 125 mm

a) Weigh the coke sample to be sized to the nearest 0,1 % of the mass of the sample;

b) Position the 22,4 mm aperture size sieve over an empty receiver or bin made from plastic to

minimize breakage;

c) Place the coke on the sieve and move the coke by hand. Hand place each piece of coke in turn and if

in any position and without forcing, it passes through the sieve opening, it is designated as passing

22,4 mm. See Figure 1. Alternatively, a mechanical sieve shaker (Figure 2) can be used to assist this

process on a stop start basis;

d) Re-sieve the oversize by hand placing from the 22,4 mm aperture size sieve, on the larger aperture

size sieves in the set, starting with the largest aperture size and working down to the smallest. (e.g.

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ISO/DIS 728:2020(E)

start from the 125 mm sieve and hand place through subsequent smaller sieves down to 22,4 mm).

Alternatively, a mechanical sieve shaker (Figure 2) can be used to assist this process on a stop

start basis also. Collect each size fraction in a weighed (tared) empty bin (Figure 1) and reweigh to

obtain the mass of each individual fraction;

e) Sieve the undersize from the 22,4 mm aperture size sieve as described in 7.3 or 7.4 or 7.5;

f) The 22,4 mm size has historically been used to size coke by hand placing above this size. However,

it is permissible to use a similar screen in the 19 to 25 mm range for this function.

NOTE 1 Hand placing” refers to the operation defined in ISO 1213-2.
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ISO/DIS 728:2020(E)

Figure 1 — Example of Standard sieves and tared bins for “Hand Placing” coke sizing

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