Hydrodesorption tower
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This post was last edited by jbcyf on 2012-1-15 at 10:10. Recently, the unit has been operating at low load, accepting vacuum distillate oil and a small amount of coker gasoline; the distillation column is not operating stably. The dry point of the naphtha is above the specified range, while the flash point of the diesel is below it. Operating under these conditions is very difficult. Could experts help analyze this situation?
Generally, when a hydrocracking unit operates at low load, the degree of reaction tends to be too high. Try reducing this degree of reaction. Also, check whether there are significant changes in the feed ratio; adjusting it might help!
Coker gasoline has a low initial boiling point; if the top temperature is not properly controlled, this can lead to a decrease in the flash point of diesel. Given the small scale of processing, it is essential to pay close attention to changes in the temperatures along various streams, as this can disrupt the equilibrium within the tower
No matter how the raw materials change, only timely adjustments to the distillation system can ensure compliance with standards. ““The dry point of naphtha rises above the set value while the flash point of diesel falls below it” is because the backflow rate is low, preventing sufficient contact between the gas and liquid phases inside the tower and resulting in insufficient separation accuracy.
Does a high dry point of naphtha indicate that the tower top temperature is controlled too high?
①A low flash point of diesel indicates a low temperature at the bottom of the tower or a low amount of stripping steam; ② it is also possible that the processing volume is too low, resulting in liquid leakage across the distillation column trays and a reduced separation efficiency
The proportion of coker gasoline is too high; try using less of it. When the load is reduced, the proportion of coke gas also needs to be decreased accordingly