Determination of Ash Fusibility

The test method for determining the fusibility of coal ash (ASTM D-1857) covers the observation of the temperatures at which triangular pyramids (cones) prepared from coal and coke ash attain and pass through certain defined stages of fusing and flow when heated at a specified rate in controlled, mildly reducing, and where desired, oxidizing atmospheres. 

In the test method (ASTM D-1857 ISO 540), coal passing a number 60 (250 pm) sieve (analysis sample prepared in accordance with method ASTM D-2013) is heated gradually to a temperature of 800 to 900°C (1472 to 1652°F) 

FIGURE 7.5 Critical temperature points. (From ASTM, 2004.) 

In electrically heated furnaces, a mixture of 60% v/v carbon monoxide and 40% v/v 5% v/v carbon dioxide produces a reducing atmosphere in the furnace. A regulated stream of air produces an oxidizing atmosphere. 

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