HYSYS Topping unit distillation crude 2

[paulinaote]

Hello everyone:
I simulate topping unit where in current operating conditions. After reconstituting the oil improve the simulate data. But I do not matches the pour point of diesel.
The pour point (API 1974) is -8 ° C and should be 0 ° C.
Urgent need that this simulation is as real as possible because I have design a simple vacuum flasher to recover the diesel that is lost as reduced crude.
Attached is my simulation.
Hopefully someone can help me, my mind is somewhat blocked.
The product specifications are as follows:

Naphta:
API:65,2

Kerosene:
API: 46,8
Flash Point °C: 42
Freeze Point °C: -50,2

Diesel:
API: 38,2
Flash Point °C: 79.

 

[paulinaote]

My HYSYS version its 7.3

 

[poli60]

You won't obtain accurate cold properties from hysys (or other simulators).... it's simply a fact of the life!
The only way to have good data passes from the lab.
Some lab data can be managed for interpolation and "narrow" extrapolation by means of a good CAM (Crude Assay Management) software.
Good luck

 

[georgeverghese]

The built in prediction routines for these properties often doesnt predict correctly, but that is because of the way the crude fractions are characterized - you've probably got a large number of pseudo components with unknown physical properties.

If you know properties for each fraction, and if you know blending formulas, you could try to set up your own calculator routines in the simulator to estimate these.

 

[EmmanuelTop]

Apart from the comments above - which are correct - you can do something else in case this is just an academic exercise. Try to pull more Diesel from the column and the pour point will increase because of decreased internal reflux.

Dejan IVANOVIC
Process Engineer, MSChE

 

[paulinaote]

The problem is to know if the simulation I did is "real".
At the top and bottom temperature are out of range (a little..)
Calculate the freeze point of kerosene and adjusted to reality (-48°C from -50°C). But, not if my simulated diesel resembles the real diesel.
Shipping excel with a comparison D86 real v.s D86 from Hysys.
I have no experience simulating crude distillation it is part of my thesis
any suggestions are welcome.
If someone could check my simulation really appreciate it
Thank you very much

 

[EmmanuelTop]

Look at the Diesel D86 distillation - it spans from 169 to 439 degC. This can never be the case in reality. On the other hand, it seems like there is a lot of Diesel in the Reduced Crude. This can be due to several things:

1) Insufficient/incomplete characterization of crude oil - plug more data from Crude Assay in the Oil Manager;
2) Software deficiencies (as mentioned above) - can be somewhat combated against if you can fulfill the item No.1;
3) Insufficient separation between Diesel and Reduced Crude - try adding more trays between the Diesel draw-off tray and the flash zone, increase heater temperature, add more stripping steam.

When posting simulation models please save them as XML files so they can be opened in earlier versions of Aspen.





Dejan IVANOVIC
Process Engineer, MSChE

 

[paulinaote]

That is precisely the objective of my thesis. Recover diesel from reduced crude, but no room to install a drawoff tray in the tower because between diesel and reduced crude there a mellapack. So I recover diesel from recuded crude with a "Torre de repaso" (operating 100mmHg) (simple vacuum flasher...i think).

But before we can design the "Torre de repaso" i need an a good simulation of actual situation the topping.

 

[paulinaote]

If I could guide me in the current simulation really would appreciate. I'm a little lost.

 

[paulinaote]

I send mi simulation in XML format
Regards

 

[EmmanuelTop]

You are drawing off Diesel one tray above the flash zone! Of course it will have FBP at 439 degC or higher.

Are you simulating an actual, existing column, or this is a project/student work? I find it hard to believe that there is a CDU column anywhere in the world with such draw-off arrangements.

Dejan IVANOVIC
Process Engineer, MSChE

 

[paulinaote]

I simulate a real topping column.
Believe it or not it works well here lol.
Do you need data to help me?

 

[paulinaote]

I'll add another theoretical plate above de flash zone according to your advice...hopefully converges me

 

[EmmanuelTop]

Can you share a simple information on the number of actual trays and the corresponding tray number for product draw-off's?
Your model shows 11 trays only which is FAR too less for any CDU column.

Dejan IVANOVIC
Process Engineer, MSChE

 

[paulinaote]

Real Trays: 24
Reflux Return: 1
Kero Draw: 7
Diesel Draw: low the Packing Bed, 17 tray.
Zona Flash: Mellapack, (18-19-20)
Crude Feed: up tray 21 (20)
Stripping Reduced Crude: 21-22-23-24

(page 1)

 

[EmmanuelTop]

You see? You have completely omitted this fact in your model. There are packing layers in the Diesel P/A section and in the wash zone. You need to install them in your model - either as packing or substituted with trays. It looks like you have Flexipac in the flash zone and I don't know what is installed in the P/A zone.

Wash zone seems to be equivalent to 4 theoretical trays and assume the P/A packing equal to 3 theoretical trays. Then rerun the model.

Dejan IVANOVIC
Process Engineer, MSChE

 

[paulinaote]

Thank you very much for your support, needed advice from someone with experience. I realized my mistake.'ll add the dishes in the areas mentioned.
Many thank you very much.....hopefully converges me

 

[paulinaote]

P/A zone its nutter rings

 

[EmmanuelTop]

OK. It doesn't say which size they are but you can safely assume 3 theoretical trays for the Nutter ring section. Use 100% efficiency for all trays in the column. You can tune the efficiency later.

Another thing is the way you mixed the column feed - it doesn't look good. You have generated the feed by re-mixing of all the products (which is in principle OK) but then you added almost 50% of the flow, coming as another Crude oil stream. Why is that so?

Dejan IVANOVIC
Process Engineer, MSChE

 

[paulinaote]

Because, feedin to the plant is a mix of many crude in different percentage.
Only I have the characterization of two raw(I could not get more because they must ask at an external laboratory).
These crudes are:
CRUDO X
CRUDO Y

CRUDO X, its 35% of feed and CRUDO Y its 1% of feed. Of these crude i have a TBP, API and viscosity.
What I did was reconstitute the remaining 64% of feed.
The yield od the products its:
Naphta: 20%
Kero: 15%
Diesel: 20%
Reduced Crude: 45%
Then the flows are approximate:
CRUDO X: 849 m3/d
CRUDO Y: 24
NAPHTA: 310.6
KERO: 232.95
DIESEL:310.6
REDUCED CRUDE: 698.85

I request ASTM D86 of the oil fed to the plant (mixture of many things) and add it to food with flow 0 m3/d.

What would you??
Regards