Settler coking
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Two-stage regenerated MIP technique. At the beginning of the year, severe coking occurred in the settler, causing blockages that forced the slurry leg to stop operating for maintenance. Do any of you experts have any good suggestions for reducing coking in sedimentators? Thank you first! ! ! :)
Everyone in the world is researching it; it’s quite difficult! Haha! Let’s look for some reasons in terms of raw material composition, reaction temperature, oil-gas ratio, nozzle, catalyst, oil-gas partial pressure, and oil-gas residence time!
MIP units rarely suffer from coking, as this setup creates a space for contact between the catalyst and the oil components~~~ Coking mainly occurs at the beginning of operation, when the catalyst circulation is unstable, resulting in a much higher likelihood of low catalyst-to-oil ratios. Under such conditions, the feedstock comes into contact with the catalyst, and insufficient heat leads to the formation of unvaporized oil; this unvaporized oil is the root cause of coking in the settler. Once a coking nucleus forms, it continues to grow indefinitely. Therefore, it is essential to strictly control the conditions related to oil injection, such as the temperature of the regenerated catalyst and the temperature of the settler. The key is to maintain stability in the catalyst circulation process~~~ Some units use gasoline or wax oil to start up in order to prevent coking in the settler, and only switch to heavy oil once the temperature of the settler rises~~~
Reply to 1# zyf6619zyf: Increase the anti-coking steam at the top of the settler, so that a gas cushion can be formed in the dilute phase, thereby effectively preventing coking at the top of the settler.
Do you use medium pressure or low pressure for preventing scorching by steam? If it’s low pressure, switching to medium pressure will yield better results!
Coking can also occur when the processing volume is too low.
Steam used for anti-scorching is steam with a high superheat, such as 1.0 MPa and 400 degrees
I’ve learned it, thank you so much! ! !
Coking occurs in the settler, and the causes of coking vary depending on the specific location; it cannot be generalized – a detailed analysis is required. Most cases of coking are caused by unvaporized oil fumes, so attention must be paid to the method of starting up the system, in order to avoid unstable catalyst circulation rates at the beginning of operation, which can lead to a low catalyst-to-oil ratio. This situation is particularly dangerous, as once coking nuclei form, they continue to grow throughout the subsequent reaction process. It is advisable to increase the thickness of the settler’s lining and raise the temperature of its walls. The design approach for anti-coking steam should also be revised – the temperature of this steam should be increased, and the way in which it creates a vapor cushion should be changed (so that a vapor shield is formed along the wall surfaces). Considering product quality, it is recommended to switch to the MIP process; increasing the catalyst exposure time and the mixing time between catalyst and oil helps facilitate heat exchange, which is beneficial in reducing coking~~~
What is the structure of the riser terminal separator?
Changing the centrifuge to a direct connection can effectively resolve the coking issue