Conditions used in catalytic cracking and hydrocracking processes
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I would like to ask fellow enthusiasts: under what circumstances is catalytic cracking used in refining units? Under what circumstances is hydrocracking used? Or use them all at the same time? Thank you!
This post was last edited by lijianhuai on 2012-2-23 10:13. Due to differences in raw material composition, some foreign companies have imposed certain restrictions on the raw materials used for catalytic cracking, particularly heavy oil catalytic cracking. Criteria for feedstock properties proposed by Kellogg Company: Residue percentage on a weight basis, Heavy metals (Ni+V) in ppm. Measures taken: <5, <10 – Use a passivator and carry out conventional regeneration; 5–10, 10–30 – Use a passivator and employ a regenerator for heat extraction to achieve complete regeneration; 10–20, 30–150 – Hydrogen treatment is required; >20, >150 – Processing in a coking unit is necessary. Criteria for feedstock properties proposed by UOP Company: Residue percentage on a weight basis, Heavy metals (Ni+V) in ppm, Relative density d420. Measures taken: <5, <10, <0.9340 – Regeneration in the first stage of fractional oil catalytic cracking; 4–10, 10–18, 0.9340–1 – Two-stage regeneration using heavy oil catalytic cracking technology; >10, 100–300, >0.9650 – Pre-deposition of heavy metals is required. In principle, any feedstock with a boiling range between 380 and 550 can be used as a catalyst feedstock. As for hydrocracking, it primarily deals with reduced-pressure heavy gas oil; in terms of products such as light diesel and heavy diesel, the volume yield of the liquid products obtained through hydrocracking can exceed 100%, while the quality yield is greater than 90%. The jet fuel produced has a low freezing point, a high cetane number for diesel, a low pour point, and it causes less environmental pollution, among other advantages
Due to the increasingly stringent environmental requirements for automobile fuels, refineries are making more use of hydrogenation units; even when catalytic cracking units are installed, the feedstock comes from these hydrogenation units.
There are also many hydrocracking units in the country now, but they account for a relatively small proportion.