Let’s discuss how to prevent polymerization and coking in the styrene distillation reboiler
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For some time now, the distillation reboilers in the styrene unit of this plant have been experiencing polymerization and coking issues, which has led to frequent replacements. I wonder how things are in other styrene units – do you have any good suggestions?
Add an effective polymerization inhibitor. I wonder what kind of polymerization inhibitor is used for your distillation process?
It would be better to specify which particular reboiler in the distillation unit is prone to polymerization and coking, as this would facilitate analysis. Generally, it is caused by an excessive amount of tar forming at the bottom of the tower; in other words, styrene undergoes a thermally induced polymerization reaction without the need for any initiator, and this reaction depends only on temperature and residence time.
In my workshop, this issue has occurred several times mainly due to an insufficient amount of the polymerization inhibitor; over time, styrene in the tar undergoes self-polymerization, resulting in a significant increase in viscosity.
The main cause should be investigated in terms of the polymerization inhibitor, and furthermore, it should be considered whether the degree of forced reflux at the outlet of the bottom pump is too low
Stabilizers are divided into two types: true polymerization inhibitors and radical stabilizers； Commonly added DNBP-based substances are radical stabilizers that can only prolong the time during which polymerization occurs, whereas only true chain inhibitors can eliminate radicals and halt the chain reaction. To enhance the anti-polymerization effect while considering cost-effectiveness, it is recommended to combine true anti-polymerizers with stabilizers when adding them.
During operation, it is necessary to keep the liquid level in the tower bottom from dropping too low； The heat load of the reboiler should not be too high. Of course, coking is inevitable; adding a polymerization inhibitor is the key
I’ve learned it..... Thank you to all of LS.