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[David Paul]

I am using 3A molecular sieves for dehydration of ethanol. By my calculations I have obtained the face area of Bed=2.62 square meters. Using a superficial velocity of 0.5m/s. The bed height obtained by dividing the volume of adsorbent by area of adsorbent comes out as 0.292 meter. From here now how do I calculate length and diameter of the adsorber vessel?

[djack77494]

David,
You haven't given us all the details of your preliminary design calculations, but it sounds as if you've done something wrong. For the design a new pressure vessel, I like to "land" with a ratio of length to diameter (L/D) of roughly 3 to 5, unless circumstances suggest otherwise. For an absorber, extra sorbent volume or "wasted" volume are not a problem, except for cost. Remember that you need some vessel height above the bed to promote well distributed fluid flow onto the bed. To discourage maldistribution, you do not want your beds to be too high, and may want to add collectors and (re)distributors to prevent this undesirable phenomenum. Add to this physical and constructability constraints, and I think it unlikely that your vessel would have an L/D below 2 to 2.5.