12 replies to this topic

Hellow all,

This is my first enginnering assignment to suggest modification in tray design. Conventionally we are using Bubble cap trays. As we know they are costly than sieve or valve trays but the they possese good turndown, which is important for us.
I am not getting from where to start. Whether i should reduce downcomer area, or reduce tray spacing, or increase slot area.
Can anybody advice me which way to go and why?
How can i take help from Hysis or Chemcad or i need to look for other softwares.

[Padmakar Katre]

Dear,
You can use the tray sizing utility in Hysys for the perticular tower. You have to modes in Hysys one is to design and other is rating. You can select the Bubble cap trays and check for the results. In design mode you have options to vary the Tray Spacing and the Wier height.

[abhi_agrawa]

Mj4u,
I am not sure how much you know about tray hydraulics, so my suggestions will be a bit general.

First of all do you have the design point for the bubble cap trays? ie. do you have the design loads, the jet flood the tray was designed for, the maximum allowed downcomer backup allowed? and do you understand the meaning and importance of these terms? If your design point is quite close to the maximum allowed values for these parameter, then we may have a bit of problem. I'll explain this with a small example, let us say you you reduce the downcomer area, now if the new downcomer area is too small then froth that is fed to the downcomer may not separate. This will result in what is called downcomer flooding.

Next, how critical is the turndown for you? Is is absolutely necessary to be met? If not then you can probably look at floating valve trays (the V-1 series by Koch-Glitsch).

Have you thought about changing the pressure of the column? This will change the vapor-liquid traffic and affect the hydraulics.

abhishek

[Zauberberg]

It looks like you didn't tell us what is the basis for tray modification requirements: without knowing this information, no one of us is able to give you any advice or guidance in this subject. This should be the minimum input data from your side: whether the column is lacking of hydraulic capacity, separation efficiency, or tower operating conditions and/or feed type have been changed. Before you start any work in tower internals revamp, I'd suggest you to get the answers on these questions. Otherwise, you will be wasting your time for nothing.

What kind of tower is it, and what is the application? Have you performed any analysis of actual column operation? What are the targets of internals modification?

Good luck,

[indy]

on this subject go to

http://www.kolmetz.c...gpaperfinal.pdf

maybe it can be useful

Best regards

Luis Marques

[djack77494]

My two cents worth - Though I use general purpose process simulators all the time, and they are wonderful tools for process engineers, I don't trust them at all when it comes to tray (or packing) sizing. I greatly prefer to use the vendor's own software for their equipment. Of course, if a licensor is involved, they should be even better aware of the best approach to use.
Doug

Dear djack77494,

I have Hysys and Chemcad with me but in our case are the technology providers ao i dont have any licensors software available with me.
Previously i was involved in process development and not in enginnering assignment as this. So as a newcomer i wish you gyys will help out me in this.

[Zauberberg]

If you know why these bubble-cap trays need to be replaced, then you'll probably don't need any licensor software.
As I have said in my previous post, knowing the reason for tray revamp will save you a lot of time and efforts.

Best regards,

Thanks Zauberberg

Thank you Abhi,

As you rightly said i am not expert in this area. can you just tell me from where i can get more information about the trays mentioned above.

[Snowflutter]

you can use FRI,it can calculate the tray very well.

[abhi_agrawa]

Well you can contact any of the tray vendors. Koch-Glitsch and Sulzer are quite popular ones.

abhishek

[djack77494]

Well you can contact any of the tray vendors. Koch-Glitsch and Sulzer are quite popular ones.

Both should readily and at no cost supply you with their own tray sizing software, assuming you are a likely (or at least potential) tray customer.