Roga Index

Coal type Free-swelling index Dilatation (%) Roga index Gray-King type  

It must be noted that old coal samples, which might have experienced weathering or oxidation, exhibit a low free-swelling. The reverse effect is observed if the fines fraction ( 0.149 mm) of the sample is too high [10,11]. 

The Roga index (Rl) assesses the caking power of a coal sample under controlled conditions (ISO 335 [52]). The procedure consists of mixing 1 g of coal sample with 5 g of standard anthracite and pressing it to a small cylinder. The sample is placed in a crucible and heated to 850 °C for 7 min. The produced coke 

The higher the remaining mass of coarse particles, the higher the coke strength and with it RI [53]. 

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Eor the free swelling index which is also known as the cmcible swelling number (ASTM D720), a coal sample is rapidly heated to 820°C in a covered cmcible. Then the profile of the resulting char is compared to a series of standard numbered profiles (18). Eor the Roga index weighed amounts of coal and standard anthracite are mixed and carbonized, and the product coke is tested in a Roga dmm for its resistance to abrasion (89). 

Free-Swelling Index (Crucible Swelling Number) Roga Index Dilatometer Gray- King... 

The classes of coal are subdivided into groups according to their coking properties, as reflected in the behavior of coals when heated rapidly. A broad correlation exists between the crucible swelling number and the Roga index (ISO methods), and either of these may be used to determine the group number of a coal. 

The agglomerating for agglutinating) tendency of coal may also be determined by the Roga test (ISO 335), and the Roga index (calculated from the abrasion properties when a mixture of a specific coal and anthracite is heated) is used as an indicator of the agglomerating tendencies of coals (Table 7.4). 

Coal Type Swelling Index Dilation (%) Roga Index... 

The only small-scale methods that have stood the test of time and have been accepted as standard plasticity tests are the crucible swelling number, Gray-King coke type, dilatation characteristics, Gieseler plasticity, and, in some countries, the Rogas index. All of these are essentially empirical in nature and many are subjective, at least to some degree. 

The Roga index provides information on the caking properties of the coal. The index itself is derived from the strength or cohesion of the coke produced in the crucible, as evaluated by a subsequent tnmbler test. 

Table 5 Comparison between free-swelling index, Gray-King coke type, and Roga index...

Some of the most common methods to evaluate the suitability of a coal or coal blend for coke production are the free-swelling index test, Gray-King assay, Roga assay, various dilatometer tests, and Gieseler plastometer test. In addition, research using larger amount of coal sample is also performed by means of a pilot coke oven. 

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