ISO 540:2008 pdf download – Hard coal and coke — Determination of ash fusibility.
6.4 Support for the test piece, of such a material that the support does not either become distorted or react with or absorb the ash during the determination. Supports of sintered alumina or fine-textured mullite are generally satisfactory, but difficulties can arise with individual ashes, in which case a non-absorbent interface such as platinum foil can be used between the original support and the test piece. 6.5 Flowmeters, two, for measuring the components of the reducing gases (see 7.1); it is not necessary to measure the flow rate when using an oxidizing gas. If the flowmeter contains a liquid, this liquid shall be a non-volatile oil. 6.6 Agate mortar and pestle. 6.7 Test sieve, of aperture 0,075 mm (or less) and diameter of approximately either 100 mm or 200 mm, complete with lid and receiver. 6.8 Optical instrument, which enables the profile of the test piece to be observed throughout the determination. The relative dimensions of the profile can be conveniently assessed by using a graticule. Additional use of photographic equipment such as a camera or video equipment is optional but recommended. 7 Test conditions 7.1 Test atmosphere The reducing atmosphere is obtained by introducing into the furnace one of the following mixtures of gases at a minimum linear rate of flow past the test piece of 400 mm/min, calculated at ambient room temperature; the rate is not critical, provided that it is sufficient to prevent any leakage of air into the furnace: a) 55 volume % to 65 volume % carbon monoxide with 35 volume % to 45 volume % carbon dioxide; or b) 45 volume % to 55 volume % hydrogen with 45 volume % to 55 volume % carbon dioxide.
NOTE 1 If a mixture of CO/CO 2 is used to produce the reducing atmosphere, ensure that the contents are totally mixed in accordance with manufacturer’s instructions and that the temperature of the cylinder is maintained above the critical temperature at which CO 2 can liquefy and separate. NOTE 2 Ashes rich in iron oxide can react with any oxygen present in the furnace, resulting in poor repeatability and reproducibility of characteristic temperatures. An oxidizing atmosphere is obtained with air or carbon dioxide; the rate of flow is not critical. WARNING — When using the reducing atmospheres given above, the gases emerging from the furnace contain a proportion of carbon monoxide. It is essential, therefore, to ensure that these gases are vented to the outside atmosphere, preferably by means of a hood or an efficient fan system. If hydrogen is used in the reducing atmosphere, great care shall be taken to prevent an explosion occurring, by purging the furnace with carbon dioxide both prior to the introduction of the hydrogen and after the hydrogen supply is shut off.