BS ISO 562:2010 pdf download

BS ISO 562:2010 pdf download.Hard coal and coke Determination of volatile matter.
A position for the crucible stand shall be chosen within the zone of uniform temperature and this position shall be used for all determinations. The temperature of 900 C shall be attained as closely as possible with a specified tolerance of ±5 C In order to compensate for Inherent errors in the temperature measurement and lack of uniformity in the temperature distribution
5.2 Thermocouple, unsheathed, of wire no thicker than I mm.
It should be long enough to reach the centre of the underside of each crucible when placed in the zone of uniform temperature on being inserted through the front or rear of the fumace The thermojunchon shall be placed midway between the base of the crucible in its stand and the floor or the furnace, If the stand holds more than one crucible, the temperature under each crucible shall be checked In the same manner.
If desred, a sheathed thermocouple may be permanentty rstalled in the furnace (see Figure 1) with its therrnojunction as close as possible to the centre of the zone of uniform temperature; in this case furnace temperature readings shal be correlated at frequent intervals with those of the unsheathed thermocouple, which is thus mserted only when necessary.
NOTE The leniperalureieleclromorsve force reIaflonsJip of a thermouncbon maintained at elevated temperatures gradually changes with bnle.
5.3 Crucible, cylindrical, with a well-fitting lid, both of fused silica.
The crucible with lid shall have a mass between log and 149 and dimensions approximating to those shown In FIgure 2. The fit of the lid on the crucible is critical to the determination and a lid shall be selected to match the crucible so that the horizontal clearance between theni Is no greater than 0,5 mm. After selechon. the crucible and the lid shall be ground together to give smooth surfaces and then be given a common distinguishing mark.
When performing niultiple determinations on highly swelling coals, it can be necessary to use taller crucibles These may be up to 45 mm in height without affecting the determined volatile mailer, provided that the specified rate of temperature recovery be maintained,
5.4 Crucible stand, on which the crucible is placed in the furnace, such that the appropriate rate of heating can be achieved.
For example, it may consist of the following:
a) for single determinations, a ning of heat-resistant steel wire as shown in Figure 3 a) with ceramic discs, 25 mm in diameter and 2 mm thick, re5ling on the inner protection of its legs; or
b) for multiple determinations, a tray of heat.reslstant steel wire as shown In Figure 3 b). of appropriate size. with ceramic plates 2 mm thick supporting the crucibles,
5.5 Balance, capable of reading to the nearest 0,1 mg.
6 Preparation of the test sample
The coal or coke used for the determination of volatile matter is the general analysis test sample (ground 10 passe sieve of 212 pm aperture).
The sample shall be well mixed and in moisture equihbrium with the laboratory atmosphere.
A test portion from the same test sample is separated for determination of moisture in parallel with the determination of volatile matter.
7 Procedure
7.1 Furnace temperature checking
Adjust the temperature of the zone in the furnace (5.1), containing either a stand with one crucible and lid [Figure 3 a)J or a stand with the requisite number of crucables and lads [Figure 3 b)J. to 900 C ±5 C as indicated by the correctly located thermocouple (5.2). Check that the temperature under each crucible, at the same height, lies within the temperature tolerance of the uniform zone.
Temperature checking should be made before starting determinations. However, in routine operation when several analyses are performed per day, a monthly temperature check is sufficient. The check of the temperature recovery critenon (5.1) should be dealt with In a simiLar way.
7.2 Volatile matter determination
Fill either a stand with one empty crucible and led (Figure 3 a)l or a stand with the requisite number of empty crucibles and lids (Figure 3 b)] and insert in the oven Maintain at 900 C ± 5 C for 7 mm. Remove the crucible(s) from the furnace and allow to cool to room temperature on a thick metal plate.
As soon as they are cool, weigh each empty crucible and lid and weigh into each crucible, to the nearest 0.1 mg, 1 g ±0,1 g of test sample. Replace the lid and tap each crucible cii a clean hard surface until the test portion forms a layer of even thickness on the bottom of the crucible. lithe sample is coke, remove the lid of the charged crucible, add 2 drops to 4 drops of cyclohexane (4.1) and replace the lid.
NOTE I The addition of cycloilexane prevents the oxidation of the coke but does not prevent adsorption of gases. e.g. nitrogen.
Place the charged crucible(s) Wi a cold stand, transfer to the furnace, dose the door and leave for 7 mm ± 5s. If multiple determinations are being made, any vacant places in the stand should be filled with empty crucibles.
Remove and allow to cool to room temperature. When cool, weigh the crucible(s) to the nearest 0,1 mg in the same manner as for the empty crucible(s).
NOTE 2 The same treabnent of the crucible before and after the determination minanizee the effect of any film of water adsorbed on its surface. taile the rapid cooling reduces absorpbon of moisture by the coal or coke residue.