5 replies to this topic

Hi guys,

I am simulating a sour water stripper in HYSYS. I have the sour water stream being fed to the stripper on tray 36. Reflux is drawn off at tray 37 and is returned at tray 44 after passing through a condenser. The overhead gas product goes to a seperate drum. I have a standard reboiler with the stripper bottoms being taken away to another unit. My problem is the setup in HYSYS. I cannot find a suitable operation that will allow me to specify which tray my feed enters the stripper and also does not have a condenser. The standard distillation column allow for variable tray feed but you have to have a condenser on the tops with that and I do not want one. How can I get around this problem?

Regards,

Tom

[shreyas]

Hi,

I am not used to HYSYS, but I have a thought of putting Condenser duty = 0.
See whether this option works or not.

Thats what I can say.

Regards.

Hi guys,

I am simulating a sour water stripper in HYSYS. I have the sour water stream being fed to the stripper on tray 36. Reflux is drawn off at tray 37 and is returned at tray 44 after passing through a condenser. The overhead gas product goes to a seperate drum. I have a standard reboiler with the stripper bottoms being taken away to another unit. My problem is the setup in HYSYS. I cannot find a suitable operation that will allow me to specify which tray my feed enters the stripper and also does not have a condenser. The standard distillation column allow for variable tray feed but you have to have a condenser on the tops with that and I do not want one. How can I get around this problem?

Regards,

Tom

[Zauberberg]

Schismatic,

Just use "reboiled absorber" template (this will eliminate overhead condenser) and specify pumparound stream within column configuration procedure. Your "reflux" is not a reflux actually, it is a pumparound (circulating reflux) stream. It should not be more complicated than that.

Regards,

[abhi_agrawa]

Tom,
Your query lacks several basic information without which no one can truly help you like, what if the total number of trays? Your tray numbering criteria top to bottom or bottom to top.
My guess is that you have a total of 44 trays, with the tray numbering from top to bottom. With this assumption I can recommend that you use a reboiled absorber with a pumparound from tray 37 to tray 44. Remember that the default tray numbering in HYSYS is from top to bottom (ie. top tray is tray #1). Also make sure that you take into account the tray efficiencies for entering the proper number of theoritical trays to be entered into the simulator.

hope this helps,
abhishek

thanks for your replies guys, the reboiled absorber seems to fit the bill. yes it is a pumparound, it was just referred to as a reflux in the manual i was reading about the process. one hysys problem i've encountered however.......i cannot seem to change the number of trays on the reboiled absorber operation. be default it has 10 trays, but when i try to add 34 trays above this, it gives the error message: "Topological changes cannot be made whilst the solver is in hold mode." Has anybody ever encountered this before? What is 'hold mode'?

[Srikrishna Chaitanya]

thanks for your replies guys, the reboiled absorber seems to fit the bill. yes it is a pumparound, it was just referred to as a reflux in the manual i was reading about the process. one hysys problem i've encountered however.......i cannot seem to change the number of trays on the reboiled absorber operation. be default it has 10 trays, but when i try to add 34 trays above this, it gives the error message: "Topological changes cannot be made whilst the solver is in hold mode." Has anybody ever encountered this before? What is 'hold mode'?

Hi
schismatic

I think HYSYS may not accept changes while the solver is in hold mode, just click on the solver active icon on HYSYS tool bar that’s green in color and present almost in centre ( top) in the hysys simulation environment window ,and then you can change the number of trays . In HYSYS Flow sheet palette there is a unit operation called custom column with that we can build our columns but I am not sure whether that is for distillation or absorption, try it , hope this will help

Regards

Satish