First of all I would like say Mole sieves 13 X is OK for both moisture and Co2 removal.
This design can be divided into two parts.
1. Amount of molecular sieves required : that you can calculate by knowing adsorption capacity(dynamic) of the sieves for moisture and
CO2 adsorption.
The capacity mentioned in the vendor data sheet is not the one you should use. As dynamic adsorption capacity depends on the
following :
Operating pressure
Operating temperature
Regeneration temperature/flow
Type of regeneration gas(Dry or wet).
So dynamic adsorption capacity should be chosen based on above parameters and then should be used to find out the amount
required.
Take 10% margin(general) you got your amount of Sieves.
2. Next thing : Diameter and height
Calculate minimum diameter by Ergun equation.
Use around 60-70% of fluidisation velocity to arrive at diameter. Calculate height based on that.
Also calculate pressure drop across the bed using the selected diameter.
If it is within limit then you use the diameter u got else reduce dia and repeat.