Absorber design 2

[GreenHawk]

I'm currently working on designing an absorber in Aspen Plus. For the required absorption, Aspen is telling me that I need 4 stages. Can someone guide me how to convert the 4 stages to the height of a packed bed or of a trayed column? Are there any good correlations for this purpose?

On a side note, is it wise to size an absorber in Aspen Plus or do I have to use some other method? I will appreciate if any one can provide me guidance on this matter too.

Thanks,

 

[dcasto]

I use the simulator to get all the conditions for the column and and approximate size and then use the manufacturers data to get the exact sizing.

 

[siretb]

1) Aspen has a module RATEFRAC that can do what you want. It works with actual ^packing heigths.
2) Any vendor will do a preliminary design for you
3) as a rough estimate, with proper wetting and 2 inches nominal size of packing, you may expect about 2 stages per meter of packing. This will be only a rough estimate and is system dependant, wetting rate dependant, and many factors will make that change. Nonetheless .....
For correlations many orrelations are available (Onda's for packing, HTRI's for trays, ..... I would not go for trays unless you have a very specic reason. For a preliminary design, without making any calculations, and without knowing your system, assuming the sytem is "normal (that means what?)" I would pre size on the following basis
U gas velocity 2 m/s this gives diameter and croos section
L irrigation rate 15 to 100 m3/m2/s m2 of cross section
H packed heigth 2 meters + 25% safety
packing type CMR 2" or equivalent

I do not think you should rely on ASPEN for that. It is a good tool, but specific software is more accurate, I think. If you use ASPEN, be sure to use the rate based models (RATEFRAC or equiovalent)