9 replies to this topic

[mehul]

dear,
i want to simulate butadiene unit column RLP (rectifire lower part), but inside at the bottom of column has divided in to two compartment with vertical plate, from the first compartment pre degassed solvent pump through heat exchanger enter in to second compartment of column . how can i simulate this column in hysys.
regards
Mehul Patel

Edited by mehul, 14 February 2011 - 10:33 AM.

[Zauberberg]

Newer versions of Hysys provide you with an additional option to specify the reboiler type. However, you can always use a trick and modify the column/flowsheet in order to accurately represent your process.

If I understood you well, you have a thermosyphon reboiler with a baffle, i.e. liquid from the bottom tray flows into the first compartment and from there feeds the reboiler. Discharge from the reboiler flows into the other compartment, from where you are taking the liquid portion as bottom product. Is that your configuration?

[mehul]

yes, some thing like that the column have segmental baffle dividing column in to two section as part 1 and part 2 , in the first part there is a rich solvent NMP with hydrocarbon called as a predegassed solvent and it has to be pumped through E-30 A-D (process heat exchanger) for heating up and sent back to part second for flashing to degassed it , so lighter like EA,VA,1:3 butadiene will separate easily,here i attached the pfd for better clarification.

Regards.
Mehul Patel

Newer versions of Hysys provide you with an additional option to specify the reboiler type. However, you can always use a trick and modify the column/flowsheet in order to accurately represent your process.

If I understood you well, you have a thermosyphon reboiler with a baffle, i.e. liquid from the bottom tray flows into the first compartment and from there feeds the reboiler. Discharge from the reboiler flows into the other compartment, from where you are taking the liquid portion as bottom product. Is that your configuration?

[Zauberberg]

Mehul,

It is still not clear to me - which one is the column you want to simulate? Furthermore, the PFD does not show configuration of columns i.e. the locations of reboiler draw-offs and reboiler return lines, and without clear information which type of heat exchange equipment is in question.

[mehul]

sir,
here i am attach a particular column file .
regards,
Mehul Patel

Edited by mehul, 16 February 2011 - 02:17 PM.

[Zauberberg]

Now it is clear.

What you need to do, is to built your column from absorber template. Liquid from the bottom tray flows into the "Cold sump" (tower bottom compartment on the right side) along with Water/NMP and Recycled HC streams, as shown in the flowsheet.

Liquid from the Cold sump is pumped through the heat exchangers, and then returned into the "Hot sump" which is tower bottom compartment on the left side (i.e. the reboiler return).

Vapor streams from both compartments are mixed and as a single recycle stream flow back to the column. This would represent a scheme of a forced circulation reboiler with a baffle.

Key things to remember: streams Solvent #1, Solvent #2, Water/NMP, Recycle HC, and the Stream 13 (vapor recycle) need to be completely defined so that the model can be run. It is not possible to know the composition of stream #13 but you have to provide initial guess - you may use data from the Heat & Material Balance (design case). Since it is a recycle stream, once when the flowsheet converges you will obtain true composition and other process parameters of this stream.

Hysys flowsheet is uploaded below for your reference.

Attached Files

•  Baffle Reboiler.JPG   26.67KB   70 downloads

[mehul]

sir,
i will try it toconverge it, another thing i want to share with you that i have got error in my main washer column convergence it is also a absorber column ,i have take NRTL-SRK as a thermodynamic model but bip set not producing it appear 0.0 ,tell me how to get BIP set? my feed rate of mix c4 is about 9300kg/hr
and respect to that my solvent NMP rate should be 110000kg/hr.but with this parameter i have got an error , here i am attaching my work on it,please guide me on that.
regards.
Mehul Patel

Attached Files

•  main washer2.zip   207.21KB   53 downloads

[mehul]

sir,
i will try it toconverge it, another thing i want to share with you that i have got error in my main washer column convergence it is also a absorber column ,i have take NRTL-SRK as a thermodynamic model but bip set not producing it appear 0.0 ,tell me how to get BIP set? my feed rate of mix c4 is about 9300kg/hr
and respect to that my solvent NMP rate should be 110000kg/hr.but with this parameter i have got an error , here i am attaching my work on it,please guide me on that.
regards.
Mehul Patel

i have converge RLP as per your guideline but it has error with two liquid phase all the tray of column , why it has appear ,i am here attached a file . please look in to it and suggest on it.
regards
Mehul patel

Attached Files

•  my work on RLP.zip   79.59KB   45 downloads

[jmukund]

Hi,

Attachments by Mehul of Column details is not visible to me!!
What i have understood is A column with a weir in the sump. If my understanding is correct the i find no reason to simulate the weir in steady state simulation. If one still needs use weir due to diffrence in composition the you can try "weir option" available in Hysys (I use Unisim Design).

I guess it helps!

Mukund

Attached Files

•  weir option.GIF   37.69KB   20 downloads

[mehul]

Hi,

Attachments by Mehul of Column details is not visible to me!!
What i have understood is A column with a weir in the sump. If my understanding is correct the i find no reason to simulate the weir in steady state simulation. If one still needs use weir due to diffrence in composition the you can try "weir option" available in Hysys (I use Unisim Design).

I guess it helps!

Mukund

yes, as i done the simulation in hysys7 , but you mean to says that i have to choose option of weir at the column bottom during sizing.

regards.
Mehul Patel