Feed crackability

The K factor is a very useful indication of feed crackability. The K factor relates to the hydrogen content of the feed. It is normally calculated using feed distillation and gravity data, and measures aromaticity relative to paraffinicity. Higher K values indicate increased paraffinicity and more crackability. A K value above 12.0 indicates a paraffinic feed a K value below 11.0, aromatic. 

Similar to aniline point, refractive index (RI) shows how refractive or aromatic a sample is. The higher the RI, the more the aromatics and the less crackable the sample. A feed having an RI of 1.5105 is more difficult to crack than a feed with an RI of 1.4990. The RI can be measured in a lab (ASTM D-1218) or predicted using correlations such as the one published by TOTAL. 

The properties of the feedstocks used for the GSR study are given in Table 1. A low- and mid-sulfur feed was used, besides the different sulfur levels the feeds also showed different crackabilities which was expected from the different K factors. 

Table 4-134 Index numbers from thermogravimetry of original samples (feed) and heavy oils. Coke residues and crackable part. 

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