Regarding diesel fractions
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What is the boiling range of diesel? I remember when I was designing atmospheric distillation columns at school, the top of the column contained gasoline, while the first fraction column held aviation fuel. The second and third fraction columns contained light diesel and heavy diesel respectively. The bottom of the column contained heavy oil fractions – those fractions with temperatures above 350°C. If I’m remembering correctly, here’s the problem: since the heavy oil fractions at the bottom of the column have temperatures above 350°C, how is it that the feed to the diesel hydrogenation unit, as specified in our process sheets, should consist of 95% of fractions with temperatures not exceeding 365°C? If these are fractions from the second or third fraction columns, how can there be fractions with temperatures above 350°C?
Your components need to go through diesel hydrogenation for further processing; after hydrogenation, the composition levels will be lower. Additionally, blending takes place after hydrogenation as well
What is the relationship between the bottom stream from the atmospheric and vacuum distillation unit and the feed stream for your diesel hydrogenation unit? Since it is a diesel hydrogenation unit, it is sufficient to keep the feed stream at ≤365 degrees; subsequent hydrogenation saturation is then carried out, with a small amount of cracking agent present in the catalyst, thereby breaking down the heavier components into lighter ones
It doesn’t really matter that much. What’s specified on the process card is that 95% of the feedstock for straight-run diesel should not exceed 365 degrees Celsius. What I want to ask is: are there any components in straight-run diesel with temperatures above 365 degrees Celsius? Since anything above 350 degrees Celsius counts as heavy oil from the bottom of the tower, right? If not, then why is there a specification of over 365°C on the process card?
During the distillation of oils, it’s not possible to distinguish things very clearly; they are all hydrocarbon compounds with excellent mutual solubility. The final boiling point of our product is also around 365 degrees