(272d) Importance of Using Adiabatic Columns for PSA/VSA Pilot Testing and Guidelines for Their Design

Small scale benches are often used in order to validate the modeling tools of PSA or VPSA processes. These processes are often subjected to important temperature variations during cycles linked mostly to the exothermicity of the adsorption phenomenon (and reversely the endothermicity of the desorption). It is known that such behavior can have a huge impact on process performances, up to 50% in recovery loss in an adiabatic configuration (where the temperature swing between adsorption and desorption phases is maximized) compared to an isothermal operation. Hence, it is crucial to take into account the level of adiabaticity of lab. scale benches to have a proper validation of adsorption models and allow a safe scale-up to industrial applications. The heat transfer between the adsorbent bed and the walls of the adsorbers can be modeled; nevertheless, this approach needs multiple parameters to be properly defined and leads to detrimental computation time when thousands of cycles must be simulated to reach a cycling steady-state.

The most convenient approach is to design the adsorption columns so that they are as adiabatical as possible.

The main characteristics of the adsorbeurs, such as column diameter, wall thickness, adsorbent bed-wall heat transfer coefficient, materials, have been taken into account to determine the “adiabatic factor” of the system. The criteria for designing a pilot scale adiabatic column will be given.

Finally, the performances obtained in a O2 VSA pilot plant using two columns built with two different materials (PVDF and Inox) will be shown.