Vaccum residue IBP

[dieselpet07]

Hello.everybody..

The vaccum crude distillation unit is having two similar trains of similar capacities and processing the same crudeblend with the same operating window.Now the question is how do one should structurally analyze the difference in the variations in the IBP of Vaccum residue produced from vaccum column bottom.

You can refer the graphical trend run chart of VR IBP for ready reference.

http://files.engineering.com/getfil...bf1f-29a1c7605983&file=Runchart_of_VR_IBP.ppt

with warm regards,

 

[EmmanuelTop]

How do you explain such high difference in IBP which is sometimes as high as 200C, when you say the same crude blend is processed all the time in both distillation trains?

The difference cannot originate from bad sampling, I am sure about this. What I can think of is:

1. Bad control of wash oil flow rate
2. Thermal cracking of vacuum residue in the tower boot (high temperature, long residence time, unstable feed)
3. Poor control of vacuum system which causes high losses of distillates into the residue


What kind of system is it, wet or dry tower? With our without bottoms quench? COT? Feed type?

http://antwrp.gsfc.nasa.gov/apod/astropix.html

 

[dieselpet07]

Normally,

There are total 4 packed section – LVGO ,LVGO Circulation,HVGO & slopwax packed bed section.HVGO IR on below section is being maintained around 205 m3/hr ,It is damp vacuum condition i.e. 20 mmhg top section & around 32-34 mmhg vaccum at flash zone section.Yes,In the bottom VR quench flow is there to restrict bottom temp. around 354-360 C & Vaccum heater COT usually remains around 393 C .In the feed VR cut remains usually around 27 wt % & RCO feed to VDU section around 5-7 wt % 360 minus remains present usually.No much variations in column overhead or flashzone pressure.

with warm regards,

 

[EmmanuelTop]

What is the change in 5% and 10% distillation points (is it ASTM D1160), if any? This can give you a clue - whether something is happening in the upstream ADU tower, or simply you have vey small (negligible) amounts of distillates in the residue that are lowering IBP without affecting/increasing overall residue yield.

Best regards,

http://antwrp.gsfc.nasa.gov/apod/astropix.html

 

[dieselpet07]

http://files.engineering.com/getfil...06-891d-505cec90c96b&file=SIMDIST_Results.xls

with regards,

 

[25362]

Dieselpet, Shalom.

As I see it the real enigma pops up in those cases when the IBP of the VR is lower than that of the HVGO. Your report covers from november to a week ago. Try to investigate what happened on those days on which the gap was wide and "normal" vs the other days. Include a possible "contamination" of the bottom quench stream from a leaking heat exchanger.

 

[EmmanuelTop]

HTSD analysis is not very reliable, in my opinion. And I have my reasons for saying this. Especially when you look there are no changes in VR yield while the difference in IBP is huge.

Did you employ any other method for VR distillation?

http://antwrp.gsfc.nasa.gov/apod/astropix.html