ISO 728:2021

INTERNATIONAL ISO
STANDARD 728
Fourth edition
2021-06
Coke — Size analysis by sieving
Cok — Analyse granulométrique par tamisage
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

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
8 Expression of results for all sizes . 7
9 Determination of mean coke size from results in Table 2 . 7
9.1 Calculation of mean coke size . 7
9.2 Calculation of coke mean size from data in Table 3 . 8
10 Precision of the method . 9
10.1 Repeatability . 9
10.2 Reproducibility . 9
11 Test report . 9
Annex A (informative) Guide to sizing coke products above 125 mm .10
Foreword
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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 of ISO 728 cancels and replaces ISO 728:1995 and ISO 2325:1986, which have been
technically revised.
The main changes compared to the previous edition are as follows:
— the coke size analysis of the minus 20 mm fractions has been moved to this document;
— low impact mechanical sieving was added to the scope;
— hand placing of coke was introduced from 125 mm down to 22,4 mm to be consistent with coal
sizing ISO 1953;
— ISO 728 now incorporates ISO 2325;
— the coke mean size calculation was modified, moved from an annex to the main document and a
worked example added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved

INTERNATIONAL STANDARD ISO 728:2021(E)
Coke — Size analysis by sieving
1 Scope
This document specifies procedures for the size analysis of coke by manual and/or low impact
mechanical sieving, using square or round holed sieves of aperture sizes between 125 mm and 0,5 mm.
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
5.1 Test sieves, in accordance 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 3310-1 and ISO 3310-2, 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. For ungraded cokes, an example of a series of test sieves of nominal hole sizes in Table 1
are outlined. Other sieves of various nominal hole sizes can also be chosen. For samples containing
pieces with a particle size greater than 125 mm, single-hole gauges may be used instead of test sieves.
5.2 Balance or scale, capable of measuring the mass of each size fraction to the nearest 0,1 %.
5.3 Receivers or bins, for collecting material passing through the sieve.
5.4 Trays, smooth, of non-corrodible material, of at least 400 mm × 400 mm, depending on the mass of
sample and number of analysis required.
5.5 Lids, to fit the test sieves.
5.6 Flat brush, for cleaning the sieves and for brushing dust from the trays.
5.7 Hardwood block, about 150 mm long with a 10 mm × 10 mm cross-section, for tapping the sieve.
5.8 Shovel or scoop.
5.9 Vibratory sieve shaker for mechanical sieving, (see example Figure 2). Small low impact
vibratory sieve shakers may be used, providing that their action does not break the coke and that the
results are known to be not biased with respect to the results obtained by hand shaking.
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. 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
pre-treatment 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 °C 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 °C to 200 °C to prepare the gross
sample for sizing.
2 © ISO 2021 – All rights reserved

Table 1 — Minimum mass of coke samples for general analysis, determination of total moisture
content and sizing
Nominal top size of
Minimum mass
coke
kg
mm
Plus 125 2 000
125 1 000
100 650
90 500
75 320
63 250
50 200
45 125
31,5 60
22,4 30
16,0 15
11,2 8
10,0 6
8,0 4
5,6 2
4 1
See ISO 18283
7 Procedures
7.1 Sizing sample of particle size greater than 22,4 mm but less than 125 mm
The sieves outlined in the procedure described in this subclause (7.1) are used as an example in how
to size a test sample for all the sieves in Table 1. Other sieve sizes may be used between 125 mm and
22,4 mm.
a) Determine the mass of the coke sample to be sized to the nearest 0,1 % of the mass of the sample.
b) Arrange a set or nest of 450 mm sieves (125 mm, 100 mm, 90 mm and 75 mm) (maximum 4 sieves
are recommended at one time) in order of sieve aperture size with the smallest at the bottom over
an empty tared receiver or bin made from plastic to minimize breakage or place on a sieve shaker
similar to Figure 1.
c) Place a portion of the coke test sample at a time on the top sieve small enough that not more than
75 % of the sieve area is covered and shake manually to allow most of the undersize to pass. Hand
place the remaining particles of coke in turn. If it passes through the sieve opening in any position
and without forcing it, it is designated as passing 125 mm. Alternatively, a low impact mechanical
sieve shaker (see Figure 1) can be used to assist this process on a stop start basis. Hand place each
particle with the sieve shaker in the “off” position. Collect the plus 125 mm size fraction in a tared
empty bin and record its mass in kg. Repeat this process through 100 mm, 90 mm and 75 mm
screens, and record the mass of these size fractions.
d) Repeat the process in c) for size fractions 63 mm, 50 mm, 45 mm and 31,5 mm, and record the mass
of these size fractions.
e) Repeat the process in c) for 22,4 mm and redetermine the mass of that size fraction and the minus
22,4 mm fraction.
NOTE 1 The minus 22,4 mm fraction from 7.1 e) is sized as per 7.3 or 7.5.
The 22,4 mm sieve in this document has been used to indicate that in the size fractions above this
size each particle shall be hand placed. However, it is permissible to use a similar screen in the
19 mm to 25 mm range for this function.
NOTE 2 "Hand placing" refers to the operation defined in ISO 1213-2.
Figure 1 — Example of a large low impact vibratory mechanical sieve shaker
4 © ISO 2021 – All rights reserved

7.2 Division of coke minus 22,4 mm
Divide the sample (minus 22,4 mm fraction from 7.1 e) to the required minimum mass in Table 1 by
means of a suitable mechanical sample divider or riffle avoiding size degradation and loss of dust.
Alternatively, for division, use either the flattened heap method or the strip mixing method described
in ISO 13909-6 and ISO 18283. Determine the mass of all the coke not included as part of the test sample
and retain it until all analyses and calculations are complete.
7.3 Sizing sample of maximum particle size between 22,4 and 4 mm — Manual method
a) Determine the mass (of the divided minus 22,4 mm fraction from 7.2) of the sample to the nearest
0,1 %.
b) Position the largest aperture size sieve in the set over an empty receiver or bin. Move the sieve
horizont
...