What to do if the benzene content in the stable gasoline produced during reprocessing is above the specified limit?
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Currently, the unit is engaged in pre-hydrogenation and reforming; phenol extraction is not in operation – only reforming is active. At present, the benzene content in the stabilized gasoline is 7%. In the distillation tower, C5 fractions are separated out, along with some C6 fractions, which are then added to the stabilized gasoline for distribution. As a result, the benzene content has dropped to 4%. I’m wondering if there are experts who can reduce the benzene content while maintaining a high octane rating
Raising the initial boiling point of the reforming feed to above 85 degrees helps to remove the benzene-containing compounds from the feedstock, such as methylcyclopentane and cyclohexane; this greatly reduces the benzene content in the resulting oil. Of course, it is not easy to completely eliminate these benzene-containing compounds, and both the cracking reactions that occur during reforming and the dealkylation reactions generate some amount of benzene. It is therefore unrealistic to achieve a situation in which there is no benzene present in the resulting oil.
Yes, by raising the initial boiling point of the feed and removing the components that can be converted into benzene, the benzene content naturally decreases!
The poster said, “Currently, C5 is being extracted from the fractionation tower, along with some C6, which is then mixed into stabilized gasoline for distribution.” It seems that C6 has already been separated out earlier? If even this doesn’t work, then there’s no solution at all
We plan to lower the initial boiling point to 90°C. We also don’t want to use extraction. Hey, what’s the hydrogen concentration there? What are the approximate levels of methane, ethane, and propane in the hydrogen? Here, the amount of methane is increasing
It’s useless; we’ve already raised the initial boiling point to 90 degrees, but the large molecules break apart, and benzene is still produced. The higher the initial boiling point, the higher the hydrogen purity, and the methane content in your recycled hydrogen will decrease.
Adjusting the reaction conditions to reduce the cracking reaction may result in a certain decrease in conversion rate!
Additionally, by losing the mass of C5 at the top of the depentanizer and lifting the draw point higher, it is also possible to reduce it a bit further