Temperature drop between Furnace and Drums

[Claudio CarmonaParticipant]

Hi everyone, greetings from Argentina!

I’m doing a kind of survey to know what the typical values of temperature drop in transference line from heater to drums are. Can you share your experience with us?
Thanks!

Regards,
Claudio

[Evan HydeKeymaster]

Temperature drop is a function of…
+ velocity, distance, diameter, etc
+ reactivity (parafinic vs naphthenic vs asphaltenes/ccr etc)
+ Coil outlet temp, COT
+ Measurement location (not all COT and drum inlet Ti’s are in the same place)

That being said…. typically we expect 15-25degF drop in the transfer line.

What are you seeing?

[Claudio CarmonaParticipant]

Evan,

Thanks for replying.

Let me share some process data:
– Piping diameter: 8″. Distance: about 50 m
– COT= 491°C
– Temp. measurement next to furnace and drum inlet

That being said, we are seeing between 27 and 35 °F. Line is completely isolated and this temperature drop has been constant in the last 5 years. But I wanted to understand a little bit more the nature of this drop and to make like a benchmark with other refineries.

[Evan HydeKeymaster]

Seems a bit high dT but not completely out of line.

What is the velocity in the line?
Have you seen any increase in pressure drop in the transfer line for coking?
When was the last time you cleaned the transfer line? Last TAR was when?
Is the insulation in good condition?

[Francisco FernandezMember]

Hi Claudio and Evan! I’m new to this forum, so I’m still trying to find my way around the site, but sharing experiences with friends around the world is a great way to start!

In our 6-drum DCU in Venezuela we typically have a 13°C (23°F) DT between the heater outlet and the drum inlet.

To me the reason of the drop is simply due to the endothermic nature of the coking process. Temperature decreases as reactions start to take place. Of course, having poor insulation or high pressure drop can increase the DT, but if you consider that those items are ok, I’d say that the difference between in coker and another is related to the characteristics of the feed (it would be interesting to try to quantify or to correlate that effect).

Kind regards

Francisco

[Evan HydeKeymaster]

Fransisco, thanks for adding to the conversation.

I wanted to add that some refiners have been seeing increases of 3-5degC on drum inlet temperatures by going to a high tech insulation from Aerogel. Yes, most of the dT is from endothermic reactions but insulation matter too.

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