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UDC 662.6 : 620.1 Ref. No,: ISOlR 502 - 1966 (E)
IS0
i NTERN AT I O N A L O RG A N IZ AT1 O N FO R STA N DA RD IZATlO N
IS0 RECOMMENDATION
R 502
DETERMINATION OF THE GRAY-KING COKE TYPE OF COAL
1st EDITION
Se pte m ber 1 966
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 502, Determination of the Gray-King Coke Type of Coal,
was drawn up by Technical Committee ISO/TC 27, Solid Mineral Fuels, the Secretariat of which
is held by the British Standards Institution (BSI).
Work on this question by the Technical Committee began in 1951 and led, in 1960, to the
adoption of a Draft IS0 Recommendation.
In October 1962, this Draft IS0 Recommendation (No. 552) was circulated to all the
IS0 Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial
nature, by the following Member Bodies:
Australia Italy Spain
Austria Japan Switzerland
Belgium Netherlands Turkey
Brazil New Zealand United Kingdom
Chile Poland U.S.S.R.
Czechoslovakia Portugal Yugoslavia
Denmark Republic of
Germany South Africa
India Romania
One Member Body opposed the approval of the Draft:
France
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council which decided, in September 1966, to accept it as an IS0 RECOMMENDATION.
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ISO/R 502 - 1966 (E)
IS0 Recommendation R 502 September 1966
DETERMINATION OF THE GRAY-KING COKE TYPE OF COAL
1. SCOPE
This IS0 Recommendation describes one method of assessing the caking power of coal under
standard conditions.
The purpose of the Gray-King coke test, which is one of the parameters adopted for the lnter-
national Classification of Hard Coal by Type by the United Nations Economic Commission for
Europe, is to assess the caking properties of a type of coal or a blend of coals by carbonizing under
standard conditions. Although the Gray-King test and the Roga test both assess the caking
properties of a coal they do not measure precisely the same parameters and should not be regarded
as alternative methods.
2. PRINCIPLE
The coal is heated under standard conditions to a final temperature of 600 OC. The coke residue
obtained is classified by reference to a series of standard residues (Fig. 1, page 6). If the coke
residue produced is so swollen that it fills the cross section of the retort tube, the determination is
repeated with the coal admixed with a suitable quantity of electrode carbon or equivalent material
(see Note 1, page 11). For these highly swelling coals the Gray-King coke type is defined by the
minimum amount of electrode carbon required to produce a strong hard coke residue of the same
volume as the original coal and electrode carbon mixture.
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3. APPARATUS
3.1 Furnace
Horizontal electric furnace, 5 cm internal diameter and 30 cm long, with one end closed and
the other carrying a plug of insulating material which is bored centrally with a hole 2.5 cm in
diameter. The winding of the furnace should be such that the middle 20 cm is at a uniform
temperature within f 5 degrees Celsius at both 300 and 600 OC. Alternatively the furnace may
be constructed from an electrically-heated aluminium-bronze block, with one or several bores
of 2.5 cm diameter. The furnace should be insulated and located in a cover of metal or other
suitable material, and should be equipped with a suitable thermocouple, lying above the retort
tube when the latter is in position and with the junction at the centre of the furnace. An indicator
should be provided for showing the furnace temperature with an accuracy of & 5 degrees
Celsius. A suitable means of controlling the energy input should also be provided to permit an
increase in temperature at a rate of 5 degrees Celsius per minute. A multiple tube furnace to
allow simultaneous determinations is convenient. The furnace may be of the fixed type or
mounted on rails. Suitable furnaces are shown in Figures 2 and 3, page 8.
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ISOlR 502 - 1966 (E)
B
C
D
E
F
G
Gi
FIG. I. - Gray-King coke types”
COPYRIGHT RESERVED
Member Bodies wishing to reproduce this photograph in their national standards will have to request the per-
mission of “The Controller of Her Majesty’s Stationery Office, London”, through the intermediary of the British
Standards Institution.
The British Standards Institution is ready to supply, for a small charge, the block allowing the reproduction of
this figure.
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ISOlR 502 - 1968 (E)
3.2 Retort tube (Fig. 4, page 9)
A heat-resistant glass or transparent silica tube, 20 mm internal diameter and 300 mm long,
closed at one end, with a side arm, 8 mm internal diameter and 50 mm long, sealed in at a dis-
tance of about 20 mm from the open end. The tube should be smooth and either of uniform
bore, or with a slight taper (19 mm to 21 mm) such that the open end is the larger.
3.3 Distance rod
A distance rod with a flat disk at one end to assist in the packing of the coal and to indicate
the free end of the coal sample in the retort tube.
3.4 Receiver and outlet tube
A glass vessel of adequate size suitably supported and attached to the side arm of the retort
tube, fitted with an outlet tube leading to atmosphere or to a piece of small bore silica tubing
at the end of which the gas leaving the receiver can be burned. The receiver may conveniently
be a U-tube which can be immersed in water.
4. REAGENT
4.1 Standard electrode carbon (see Note 1, page 1 I)
High temperature electrode carbon :
Moisture less than 1 per cent
Volatile matter
less than 1.5 per cent
Ash less than 5 per cent
Bulk density at 25 "C (see Annex A, page 13) 1.00 to 1.05 g/ml
Relative density at 25 OC 2.05 to 2.09 (see Note 2, page 11)
Size analysis:
Retained on 0.2 mm mesh test sieve
nil
Through 0.2 mm mesh test sieve, retained on O. 124 mm mesh test sieve
less than 26 per cent
Through 0.124 mm mesh test sieve, retained on 0.066 mm mesh test
sieve
10 to 40 per cent
Through 0.066 mm mesh test sieve 50 to 85 per cent
5. PROCEDURE
Before commencing the determination mix the air-dried sample of coal, ground to pass a sieve
of 0.2 mm aperture, thoroughly for at least one minute, preferably by mechanical means. The
sample should be ground on the same day as the determination is carried out.
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IS01 R 502 - 1966 (E)
FIG. 2. - Single tube fumace
Dimensions in millimetres
600 w beating elements
Thermal fus
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Casing of 10 rnm asbestos cement board
Soft asbestos packing
Spring clips
FIG. 3. - Multiple tube furnace
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SOIR M2 - 1986 (E)
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Dimensions in millimetres
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ISOlR 502 - 1966 (E)
5.1 Coals with a Gray-King coke type within the range A - G, (see Note 3, page 1 I)
Raise the temperature of the furnace until it is steady at 325 OC.
Weigh on a scoop 20 to 20.01 g of the coal sample and transfer it to the retort tube, held
in such a manner that the coal cannot enter the side tube. Complete the transfer with a soft
brush and allow the coal to fall to the far end of the retort tube. Hold the tube horizontally,
insert the distance rod so that the face of the disk is 15 cm from the closed end of the
retort tube and spread the coal into a layer of uniform depth by shaking and turning. With-
draw the distance rod and insert a flattened pad of asbestos wool or a notched asbestos disk
to retain the coal in position. Without disturbing the position of the coal, close the open end
of the retort tube with a heat-resisting stopper. Connect the receiver to the sidearm and insert
the retort tube in position
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