Caking free-swelling index

FREE-SWELLING INDEX. The ASTM Standard method D 720 is used for obtaining information regarding the free-swelling property of a coal. Since it is a measure of the behavior of rapidly heated coal, it may be used as an indication of the caking characteristics of coal... 

If further measures are considered (e.g., integration of a stirrer), the gasifier can cope with caking coal, e.g., having a free swelling index of less than 6 [197]. 

Some chemical and textural data of oxidized coals are given in Table 2. The caking properties of samples decrease as a result of air oxidation, so a drastic reduction in free swelling index (FSI) occurs, from 8 in fresh coal to 1 and 0 in oxidized samples. Likewise, an important decrease in carbon content, and a parallel increase in volatile matter and oxygen content, mainly in this latter element, is observed. 

Free-swelling tests are commonly used to measure a coal s caking characteristics. A sample of coal is packed in a cmcible or tube, without compaction, and heated at a fixed rate to about 800°C. Infusible coals distill without changing appearance or state of agglomeration. The fusible coals soften, fuse, and usually sweU. The profile of the resultant coke is compared to a series of reference profiles so that a swelling index can be assigned. The profiles represent indexes between 0 and 9. The best cokes come from coals having indexes between 4 and 9. 

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