Effect of increasing Pressure on distillation

Question

Effect of increasing Pressure on distillation

Falcon03 (Chemical)

(OP)

27 Dec 02 00:18

Hello everybody,

These days we are trying to increase our Crude unit throughput by 7% in order to determine the unit constrain(s). So far we have achieved 3% increase and some listed some constrain (such as control valve hydraulic problems). On other hand, in some cases we have been not been able to maintain our product spec. such as Kerosine flash point and/or our Naphtha 90 % cut point.

I’m wondering if there is a big impact by increasing the top pressure of the Atmospheric tower, in order to maintain the products spec? thanks

jproj (Chemical) · Answer 1 · 2002-12-27 09:13:57

You say this is an atmospheric tank. Have you considered the shell / head stresses that increased pressure would create?

jproj

spekuljak (Chemical) · Answer 2 · 2002-12-27 09:45:39

Increasing the top pressure of a topping, you will obtain a naphta with greater Reid vapor pressure, side product (Kero, G.O.) with lower Ignition and Flash point, and the bottom stream will have lower I.P. Obviously, this will be corrected with more live steam inyection, and more head venting.

Falcon03 (Chemical) · Answer 3 · 2002-12-28 00:15:40

Thank you spekuljak:

What you mentioned is correct, we also did some moves in the mid and bottom pump around to correct for product spec.

FYI, we have increased our top pressure from 1.8 barg to 2.48 barg but we couldn’t maintain our Napth cut point. If we increase the reflux the Kero flash will go off spec. So I'm not sure that increasing the pressure is the write action to do especially if you increase your unit throughput?

owg (Chemical) · Answer 4 · 2002-12-28 08:54:19

jproj - I believe that the term Atmospheric Tower in the oil industry is used to distinguish the tower from the vacuum tower. A typical Atmospheric tower would have a design pressure of around 50 psig. The term atospheric tank would however mean a tank that could contain only a few ounces per sqare inch of pressure.

spekuljak (Chemical) · Answer 5 · 2002-12-31 06:44:39

More, if you increase the operating pressure, you need more energy supply to feed stream to maintain the product streams specs. The simulation is a valuable tool for such a case, because of allow to visualize the influence of the different variables in the process.
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Effect of increasing Pressure on distillation