The bed height depends on the adsorption capacities of the various components. The bed must be able to contain the water inside i.e. no breakthrough of water, but not long enough to trap all of the other gas components. You should also remember that higher the flow rate, you will also have a high pressure drop and that is also taken into consideration while determining bed height.

Thanks a lot for your input Shreenath Krishnamurthy sir. I would also like to know about the mathematical co-relations that associated with the theories you had suggested. Bed height, L = f(P, T, Vo,......) and I am still struggling to find the function f. It does not have to be an accurate one with error coefficients integrated with it. Even an empirical co-relation would be of great help.

No there are not empirical correlations related to it as Adsorption is an unsteady state process. The breakthrough time is a combination of heat and mass transfer effects. Simple correlations can give an idea of mean residence time for a given feed concentration. Higher the flowrate, the longer is the length needed or you flow the gas for shorter duration. The best is to solve a detailed process model to get a more accurate packed bed height.