Regarding the compressor outlet flow rate of the hydrogenation unit
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Everyone, I have a question: What determines the pressure or outlet flow rate at the outlet of the circulator in a hydrogenation unit? Is it based on the system pressure or the hydrogen-to-oil ratio?
As a further clarification, does the hydrogen-to-oil ratio of the unit take the cold hydrogen in each bed into account?
The outlet flow rate of the circulator in the hydrogenation unit is controlled based on the hydrogen-to-oil ratio; this ratio refers to that at the reactor inlet, and does not include cold hydrogen. The system pressure is controlled by the amount of new hydrogen supplied.
Then, in theory, wouldn’t that cold hydrogen participate in the reaction? Also, if the purity of hydrogen is not sufficient, which parameter indicates that?
Cold hydrogen is generally not taken into account in the calculation of the hydrogen-to-oil ratio, but it still participates in the reaction; after all, its amount is not very large. When the amount of cold hydrogen is significant, the reactor inlet temperature must be considered. As for hydrogen purity, it can be determined by sampling and analyzing the recycled hydrogen (after desulfurization); generally, this analysis is carried out regularly, at least once per shift.
Hydrogen purity is determined by analyzing the hydrogen in the recycled hydrogen; sampling is generally carried out at the top of the liquid separation tank at the inlet of the recycled hydrogen compressor, with samples taken every 8 hours.