Large slow coking units for Mangyshlak residues

Conclusions

• 1. The 21–10/600 unit operates steadily on the straight-run Mangyshlak crude residues in the two-stream system. Its operating cycle is not less than 30 days, and it produces about 13% coke on the feed. In order to raise coke yield to 16–17% and higher, the unit should be converted for operation on heavier feed (30–35% Mangyshlak crude tar).

• 2. The high-temperature heating of the paraffinic (Mangyshlak type) residues of secondary origin results in their separation into two phases in the pipe-furnace coils, and the latter are rapidly choked with coke (in 1–5 days).

• 3. In choosing the feed for coking in nonheated chambers, attention should be paid not only to the quality and yield of coke but also to the stability of the feed against separation into two phases in the coils, and this depends largely on the group composition and extent of homogeneity of its components.

• 4. In the case of different residues, the coke yield does not depend to the same extent on the coking power of the feed.

Residues with high content of asphalt-resin substances yield coke whose coking power is 1.5 times higher than that of the feed, while in the case of a feed with high content of oil hydrocarbons this value is much higher (up to 2 and more).