Product quality of extraction towers
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This post was last edited by sson on 2010-7-26 at 15:55. Regarding the operation of the extraction tower in the low-temperature benzene hydrogenation process, we have been in operation for over a year now, and the level of non-aromatic compounds containing benzene remains high. Meanwhile, the level of methylcyclohexane in the pure aromatic compounds is also quite high. The design manufacturer suggested keeping the temperature at the top of the extraction tower at a higher level, but our management believes that this would increase the amount of non-aromatic compounds containing benzene. Personally, I think the design manufacturer is right; however, our current operating conditions already involve a higher temperature than that specified in the design, yet the results are not satisfactory. I would appreciate some advice from those with experience in this field.
Reply to 1# Panda1024: I’ll be more careful next time; thanks for the advice
What is the amount of methylcyclohexane in your pure benzene? Is it at the highest level, or is it higher when NA contains benzene? Are you using sulfolane or NFM?
It is primarily related to the temperature and flow rate of the feed BT, the solvent ratio, as well as the top pressure and bottom temperature of the tower. It is crucial to maintain an appropriate temperature in the absorption zone of the packing section; even minor fluctuations can cause benzene to be vaporized. Additionally, during the initial phase, the temperature of NFM should be kept relatively high, around 102–125 degrees, and it should then be gradually reduced to around 115–120 degrees once normal operation is achieved. It is also very important that the content of non-aromatic compounds in BT, as well as the amount of stabilizers present, remain stable. By using BT from large storage tanks, the content of non-aromatic compounds can be kept quite stable at around 15–20%. If production is continuous, then isn’t the benzene content in non-aromatics basically difficult to keep stable? In addition to the BT tank in the reservoir area, we need to consider whether an intermediate BT tank should be installed in the device to mix and stabilize the composition of the BT raw material.
When the temperature rises, the amount of non-aromatic compounds increases; their solubility rises as well, and some of these non-aromatic compounds dissolve. This leads to an increase in the reflux of non-aromatic compounds, with non-aromatic compounds being used to displace other non-aromatic compounds； Then look at the feed position again; raising it allows more non-aromatics to be extracted from the top of the tower.
The content of non-aromatic hydrocarbons in your BT compound is 15%-20% – isn’t that quite high? Is it less controllable at the back? What level can you achieve for the non-aromatic compounds in your V508?
How are your products doing at the moment?