Polyester DuPont three-reactor process: reasons for the high solid content of esterified EG
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Seeking help: Our company uses the DuPont three-reactor process to produce PET (PTA + EG = PET). The esterification reactor consists of a heat exchanger, a vapor separator, a separation column, and a thermo-syphon loop. The heat transfer medium used is Dowtherm (biphenyl + phenyl ether). Recently, the solid content of EG in the esterification process has suddenly increased, rising from around 8% to 18% or even higher. This has affected the preparation of the slurry, and the acid value and brightness have also become unstable. Does anyone with similar experience have any ideas on what might be causing this? Thank you so much~!
Are you referring to the solid content in the process tower? Is the load on your plant very high?
Reply to 2# rockey: The load can be said to be relatively high; it was previously at 930 T/D, but now it has dropped to 870 T/D. The thing is, there were no issues before, and even with reduced production, the problem of high solid content remains unresolved. It’s not yet clear whether there is damage to a certain part of the equipment itself or if there is an issue with the manufacturing process... It’s confusing……
With an increase in entrainment in the gas phase, the resulting issues are not surprising; measures should be taken to remove these entrained substances. This phenomenon tends to occur frequently when the gas-phase system is unstable during operation.
Let’s ask the people at Contess first; it seems that the problem you’re facing isn’t an isolated incident
Reply to 5# rockey: Chemtex suggested raising the level of the esterification tank; as a result…………raising it made the situation worse, as the solid content increased even further!
There is excessive foam entrainment, which is usually due to poor esterification. You can try the following: 1. Improve the esterification conditions； 2. Check whether the slurry molar ratio is stable ； 3. Is the reflux EG flow correct? Also, has the PTA been changed? The particle size is too small. For reference. Once it’s resolved, I hope we can share the results
For this reason, a reward of 1000 yuan can be offered. Based on my many years of experience, it is likely that the uneven heating of the heat exchanger is to blame. It is recommended to check the temperature of all SXB units on the heat exchanger; if the temperatures are low, it will affect the mixing process inside the vapor separator, and during periods of intense mixing, large amounts of esters may be carried away. Another possibility is that there is damage to the cover surrounding the esterification process, but this is less likely! If you get the money, don’t forget to treat me to a meal! If there is a better way, please share the results :lol
Reply to 6# killallstars: A higher liquid level leads to more entrainment
The esterification level needs to be lowered to ensure thorough separation of vapor and liquid.