3 replies to this topic

[cruam]

Dear All

I want to know whate is the typical fraction flooding in packed/tray amine absorber and regenarator columns. I mean for initial estimation and design, we should work on howmany percent of flooding?
I'm trying to simulate amine plant by Promax in which column diameter or fraction flooding should be determined. I think fraction flooding is more better specification for column than diameter?

Thanks all

cruam

Edited by cruam, 12 April 2010 - 02:08 AM.

[Propacket]

cruam,
Packed and trayed towers are designed for maximum fraction flooding of 0.85. However this is not the sole parameter for tower sizing. There are also some other paramters which will affect the tower sizing.e.g.
1-Foaming Factor
2-Tray Pressure Drop
3-Max weir Load
4-Downcomer BackUp etc.
These parameters must be taken into account when sizing the towers. You may calculate tower size based on 85% flooding but you also have to keep the above parameters within limits.

[Chellani]

There are three types of flooding (or flooding parameters) which should be considered while sizing column diameter & trays i.e. jet flooding, downcomer choke flooding and downcomer back-up limit. The limit for new design could be; jet flooding – 82%, dowcomer choke flooding – 82% and downcomer back-up limit (including weir height) – 55%. For debottlencking purpose you can push them to 85%, 85% and 60% respectively. I’ve heard of columns operating without any problem with 90% jet flooding.
Apart from these parameters few other parameters which should be considered for amine systems are
- Temperature approach between lean amine and fed gas
- Rich amine acid gas loading
- System / foam factor
Most of the parameters account for foaming caused by this typical system. I guess system / foam factor is sort of margin used in designing these systems. You’ll find this as input in tray hydraulics tools e.g. KG tower. Typical factor used for amine systems is 0.65. Not sure about the foaming in regenerator columns, never got chance to work on them.

Hope this would be useful

[K.K.]

Dear Cruam

For sizing a distillation column, the typical jet flooding limits are maximum 85%, minimum 20-30%. While simulating in Promax you can specify maximum limit up to 85%. But this is the maximum recommended for column operation. If you are designing a new distillation column, it is advisable to size for about 60% flooding. The reason is that the column is the main equipment in the unit. Most units undergo expansions, modifications, revamps after a few years of operation. So distillation columns "must" be designed with a good margin so they can be retained for expansions/revamps.

For column sizing, I would suggest you not take a simulation software estimate. If you need to specify something just for simulating the column, you can put anything, but for selecting the column diameter, you shall use dedicated column sizing software, such as KG-Tower and Sultray. In fact, if you have time, it is most recommended that you send a query to a tray vendor (Koch Glitch, Sulzer, or other) and have a rating run by them. Tray vendor can give you the best diameter selection. Alternatively, they give you free software and you can do it at your own.

It is important to mention here that when you use tray rating software, it will ask a foaming factor which is typically 0.8 for general service. For amine Absorber and regenerator, 0.6-0.7 is used. This is very important and affects the diameter selection. Other things, as mentioned by Chellani and P.Engr, shall also be considered.

Sufyan Khan K.K.