Lighter Crude Feed in Crude Distilling Unit 1

[janmikel]

What do I need to consider if I have to change the design of an existing Crude Distilling Unit that was designed for a 33 API feed to accomodate a 40-45 API feed?

The existing crude distilling unit does not have a pre-flash drum. Will a preflash drum placed after the pre-heat exchanger network and before the furnace help? If so, how do I design the preflash drum?

Do I need to change the overhead condensing system?

 

[ggordonstewart]

You will need to simulate the process with a program such as Hysys. With lighter Crude, you will have more vapour/liquid traffic at the top of your tower and less at the bottom. All equipment sizes must be checked to ensure that your intended operating conditions can be handled with the existing sizes. Hysys shows a suggested flowsheet in their Refining Tutorial that contains a pre-flash. If you follow the tutorial and modify the suggested flowsheet to reflect your existing process, you should find the answers to your question. G. Gordon Stewart, P.Eng.
Gas & Oil Process Engineering Consultant

http://www.ggordonstewart.com/

ggstewar@telusplanet.net

 

[whylie]

Hi janmikel,

Yes,you put the Flash drum after the last heat exchanger,and you assume the bubble point of all components,with boiling points lower than the final exchanger temperature.

A good procedure for the design will be by using Hysis,otherwise the rigirous methods..

wayil@hotmail.com

 

[Sandeep1970]

yes, you should try using the industry simulation tools, Hysis or PRO- II. Some times the results derived by PRO-II are more realistic. This is little cumbersome to use, but technically it is good tool. It has good corelations. If you are not familiar with these tools you can contact back for further details and tips.

 

[chemeng12345]

First you should consider caustic
injection at the crude after the
desalter. This will reduce the
amount of chlorides at the boot
of the overhead drum. You can
use both NH3 and filming amines
and target for a pH at the water
that your chemical vendor will
suggest. The tip of the story is
to use carefully the ammonia because
high ammonia concentrations can raise
the sublimation point of NH4CL above
the water dew point causing salt precipitation
prior to water condensation that will lead
to severe underdeposit corrosion.
Depending on your overhead system you may use
continious water recirculation prior to the
fin fan coolers.

 

[Hossem]

first you must have the TBP curve of your new crude, this may be done in lab with a representative sample.
These data help you to get an idea of crude composition (cut-points) and products caracteristics (density, viscosity...)
The preflash drum placed after the pre-heat exchanger network and before the furnace will diminuate the operation pressure of the furnace and helps to get the accomodate flow in tubes.
since you have a lighter feed will change gasoline rate in the overhead,you can help with an air-cooler
using the industry simulation tools (like Hysis or PRO- II...) you can try and get the appropriate solution
good luck

 

[Kaemeel]

As everyone has indicated you must first have an accurate simulation. This will take a large chunk of time, but will payoff numerous times over. Your preflash drum (or tower if you choose to fractionate) won't necasserily be at the end of your preheat train. To determine where in the preheat train you want it you must first simulate your crude column with the new crude slate and determine where it is bottelnecked. At this point (temperature) is where the preflash drum should be placed in your preheat train. Best of luck!

 

[fsm77]

Hello all,
I am new of using of hysys and I am trying to simulate the ammonia plant in hysys, but it seems that I got lost can anybody tell me from where to start and if any books or papers can help me in that

 

[TD2K]

It's best fsm77 to start a new thread for something like this. I suggest talking to Hysys, they typically have models already set up that you could use as a starting point and they provide a troubleshooting service for users.