INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

HYSYS Topping unit distillation crude

HYSYS Topping unit distillation crude

(OP)
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.

RE: HYSYS Topping unit distillation crude

(OP)
My HYSYS version its 7.3

RE: HYSYS Topping unit distillation crude

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

RE: HYSYS Topping unit distillation crude

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.

RE: HYSYS Topping unit distillation crude

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

RE: HYSYS Topping unit distillation crude

(OP)
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

RE: HYSYS Topping unit distillation crude

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

RE: HYSYS Topping unit distillation crude

(OP)
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.

RE: HYSYS Topping unit distillation crude

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

RE: HYSYS Topping unit distillation crude

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

RE: HYSYS Topping unit distillation crude

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

RE: HYSYS Topping unit distillation crude

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

RE: HYSYS Topping unit distillation crude

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

RE: HYSYS Topping unit distillation crude

(OP)
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

RE: HYSYS Topping unit distillation crude

(OP)
P/A zone its nutter rings

RE: HYSYS Topping unit distillation crude

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

RE: HYSYS Topping unit distillation crude

(OP)
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





RE: HYSYS Topping unit distillation crude

I don't know how much different these crude oils are. It could be a big deal, it may not be a big deal. What I know for sure is that using only ASTM D86 for crude oil characterization will not be very much useful. So I guess you did the best possible thing by re-blending products and introducing them as feed, instead of relying on D86 results for the total crude charge.

A useful tip: never specify properties and yields of a product at the same time. In simple words, if you want to produce e.g. 30 m3/h of Diesel, don't specify 95% D86 or Pour Point of Diesel if you have specified the flow/yield already. Property is a direct function of draw-off rate so if you are forcing software to match both criteria, it will likely fail to converge.

Dejan IVANOVIC
Process Engineer, MSChE

RE: HYSYS Topping unit distillation crude

(OP)
Thanks for the advice, I think it's exactly the mistake I make.
Then keep the characterization as is.

RE: HYSYS Topping unit distillation crude

I think you should focus on one crude source only, for a start. There seems to be a problem with phase envelope of the crude charge stream - and this could be due to million reasons. For simulation purpose try to use the crude oil for which you have the most comprehensive information (the most detailed assay) and start from there. Start with a blank flowsheet and this will eliminate all the excessive pseudo-components.

I think your column cannot converge because of inability to perform T-P flashes. You can see that from the phase envelope - it is a single straight line (like a pure component). This needs to be fixed.

Dejan IVANOVIC
Process Engineer, MSChE

RE: HYSYS Topping unit distillation crude

(OP)
OK.. will try again tested mixtures. I shall guide from phase evelope utility as you mention.
Has you a reference picture as it should be that curve?
Regards

RE: HYSYS Topping unit distillation crude

(OP)
I did the simulation again with a feed:
CRUDO X: 50% date: TBP - API - Viscosity
CRUDO Y: 50%: TBP - API - Viscosity
a total 2650 m3/d (april average).

The result is far from the actual (Cold properties product - T Condenser - T tope - T bottom - D86 HYSYS v.s Lab)
Which is the reason this BIG difference? A master phase envelope? Do not generate the bubble point line, i don´t know why.

can you advise me?
Regards

RE: HYSYS Topping unit distillation crude

Attached is an updated model (native file in 7.3 version). I spent solid 2 hours playing with it, so you owe me a beer whenever I visit your country.

- I've changed the fluid package model to SRK. It yields more accurate results sometimes. Now the crude oil phase envelope looks more realistic.
- I managed to obtain desired product properties (speaking of D86). Targeting IBP or FBP can lead to larger errors. That is why 5%, 10%, 90%, and 95% D86 are more commonly used.
- By matching properties, there aren't many degrees of freedom to play with the flows/yields. Naphtha cut point is determined by the tower top temperature, so if you want to match the cut point (lets use 90% D86), then you have to leave the simulator to calculate the flow. There is more room to play with Diesel and Kero, but ultimately the combined yield of these two products will be more or less constant if you have fixed the product properties.
- Diesel stream has a very low flash point. Is there any stripping steam at all? A good practice is to leave steam control valves on manual, not on automatic - especially if meters are not calibrated regularly.

This is certainly more closer to reality but hard to say whether it is decently away from reality, or not. I would have to see the plant and look into operating parameters myself. Also, remember that for producing a quality model not only the feed should be characterized properly, but also the instruments and meters around the column need to be zeroed and calibrated. What they are showing currently does not necessarily need to be true.

Dejan IVANOVIC
Process Engineer, MSChE

RE: HYSYS Topping unit distillation crude

(OP)
Many many thank you very much for your time. Consider a friend in Patagonia.

I worked all day in the simulation,followind your advice. Finally arrive at more realistic results (envelope phase and operating parameters).

These are the actual data:
PRODUCTION m3/d
NAFTA: 570
KERO: 450
DIESEL: 520
CRUDO REDUCIDO: 1110
FEED TO PLANT: 2650

PROPERTIES:
NAFTA KEROSENE DIESEL
63.36 °API 47 °API 38.08 °API
ASTM D86 °C Flash point 41°C Flash Point 79 °C
0% 38 Freeze Point -51 °C Pour Point -6 °C
10% 69 ASTM D86 °C ASTM D86 °C
50% 101 0% 147 0% 179.3
90% 129 10% 165 10% 225
100% 161 50% 192 50% 274
90% 230 90% 316.3
100% 256 100% 340

In EXCEL attached plant data.
I have 3 simulation with different convergence and tray distribution.
My problem is that I have result in very light products (sim 17-sim 18) and very heavy products (sim 19, especially naphtha)

I need to prioritize a realistic result for diesel and naphtha, because i need simulate a splitter of nafta and a vacuum column to recover diesel from reduced crude.

I'm stuck in the simulation of topping, please help.
By the way do you have information to simulate HYSYS a vacuum tower? Because I have no idea how to do it(....for now). I never simulate a vacuum tower.

Hopefully you can help, I owe you a beer.





RE: HYSYS Topping unit distillation crude

(OP)
PROPERTIES:
NAFTA KEROSENE DIESEL
63.36 °API 47 °API 38.08 °API
ASTM D86 °C Flash point 41°C Flash Point 79 °C
0% 38 Freeze Point -51 °C Pour Point -6 °C
10% 69 ASTM D86 °C ASTM D86 °C
50% 101 0% 147 0% 179.3
90% 129 10% 165 10% 225
100% 161 50% 192 50% 274
90% 230 90% 316.3
100% 256 100% 340

Sorry for this

RE: HYSYS Topping unit distillation crude

I would gladly help further but I do not have the time to fine tune the simulation. Also note that I don't have access to plant operating data, and for a model to be considered successful some back and forth information flow is required. One cannot develop a reliable model unless it is calibrated and verified against multiple sets of input and plant data.

If you have obtained decently accurate simulation model (in terms of product yields and properties), that's a pretty good start. I would not bother with cold properties if you managed to match the yields and distillation cuts. Hysys isn't so good in predicting cold properties, as mentioned by others in this thread.

As for the vacuum distillation simulation, remember to use Brown K10 or Esso K thermodynamic package. I think there should be a simulation template/sample on Vacuum distillation in Hysys files - you can start from there. I am attaching one paper of oil characterization, and below is the link for Aspen property packages.

Good luck.

http://sites.poli.usp.br/d/pqi2408/bestpracticesop...

Dejan IVANOVIC
Process Engineer, MSChE

RE: HYSYS Topping unit distillation crude

(OP)
Thanks, can you send me esta paper via e-mail, there a problem with the proxy.
paulinabarrientos.s@gmail.com

RE: HYSYS Topping unit distillation crude

(OP)
Hello!!....again.
I´m tunning my simulation and I originated a question. Is there a problem if the number of theoretical trays exceeds the number of actual tray??

Regards

RE: HYSYS Topping unit distillation crude

In turn, the answer is in another question: did you ever hear of a tray efficiency greater than 1?
good luck

RE: HYSYS Topping unit distillation crude

(OP)
(Y)

RE: HYSYS Topping unit distillation crude

I'm happy for you... in >30 years of work I never had this lucky opportunity winky smile

RE: HYSYS Topping unit distillation crude

(OP)
Hello Everyone:
According to their work experiences, what are the requirements of REDUCED CRUDE to be treated in a SIMPLE VACCUM FLASHER?? (heavy metals,sulfur,etc etc etc...any requirement that you know.
Thank you very much for your attention

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close