Here is a brief overview of the code we use to optimize various parameters of our prototype.
The code can calculate the mass of zeolite (in kg), the volume of the column (in m3), the area of the column (in m2), the radius of the column (in m), the length of the column (in m), and the L/D ratio of the column.
Required oxygen output (in L/min), flow rate obtained from compressor, and superficial velocity, are the only independent variables in the code. Other variables are calculated by the code. The independent variables are different in order to satisfy the below requirements:
1. (Length of column)/(Diameter of column) = L/D = 310 (the smaller the better for a lower pressure drop)
2. Diameter of column/Diameter of pellet = 10 (to avoid channeling effects)
3. In addition to satisfying requirement 1, the length and diameter of column must be practically feasible and your judgement should be used here.
4. The superficial velocity should be between 0.10.3 m/s. 0.2 m/s would be a reasonable choice here.
5. Check the specifications of your compressor before deciding the flow rate. Some flow rates may be unattainable by your compressor. Confirm if the flow rates from your compressor will match the flow rate obtained from the code (assuming about 20% conversion of air to oxygen, worstcase).
Background of the code:

A rough rule of thumb for oxygen production would be 1.5 L oxygen per kg of 13X per minute.

Volume of 13X (m3) = mass of 13X (in kg) / 1130 (kg/m3).

Volume of the column (m3) = Volume of 13X / (0.65). The 0.65 term comes from random packing of the 13X pellets in the column.

Decide on the compressor (high pressure of 56 bar (absolute) should be good enough). Get the flow rate (in m3/s) at the delivery pressure.

Compute the crosssection area. Area (in m2) of the column = Volumetric flow rate(m3/s) / Superficial velocity (m/s).

Based on the volume obtained from point 2 above, compute: length of the column (L) = Volume of the column (m3) / (pi*r**2).

If requirement 4 is completely satisfied, you are good to go. If not, you would have to adjust the flow rate coming from the compressor in order to achieve the goal in requirement 4.
In the final setup, you should have some space on the top and bottom of the column to add meshes to avoid pellets leaving the column and for a good distribution of the gas.