2 replies to this topic

[vibhor]

Hello,

I am just a beginner in hysys..and m facing some problems in cdu/vdu simulations like....

I am facing some problem while going with Absorber as a crude distillation column, as over head vapors first exchange the latent heat with cold crude as a first pre heat exchanger, but in absorber column it requires 2 feed stream, as i have one as feed stream but the top stage feed stream is reflux, so while defining reflux what parameters should i use...my main problem is in defining the composition, in case if i m using the option define from other stream its composition is very different and uptil now i have only crude stream as the only defined stream, so please guide in that case.....how to go with the absorber column....

Next problem......how to calculate how much pump around flow is require and in which tray it should come back..with how much delta t.....as we can put the flow conditions for other products from the crude characterization data...but not for pump around...and what is the criteria for choosing the quantity for steam...means how much steam we should put for stripping....so this are some general doubts.......as in tutorials no where it is mention how they have calculated the parameters like pump around flow, quantity of stripping steam, product draw off temperature with tray location and many more general calculations.....so it is not clear exactly how one should get this data......

Please reply....


Thank you...


Vibhor...

[Zauberberg]

It appears to be a grassroots plant simulation, since you are missing basic data?

To define the top stream use "Recycle" operation with pre-defined composition and parameters (p, T). Then simply connect the portion of liquid from the overhead receiver to the Recycle module. That should work - if you setup the tower correctly.

As far as pumparounds and product draw-off locations are concerned, that is a tricky thing to do - a lot of trial and error attempts is required. First, you need to know what products you will draw from the tower, what are their specs, etc etc. Perhaps you could look into the sample simulation from Hysys files and try to see where you are.

Good luck,

[Padmakar Katre]

Dear,
Use refluxed absorber template in Hysys and then using internal stream export option you export the column ovhd stream i.e. from Main TS tray 1 vapor outside and exchange heat with the exchanger(crude-column ovhd vap HE). Hope this solves your problem. (This is a normal practice which I do prefer whenever I model the column ovhd system.)