Zeolite monoliths for air separation part 2: Oxygen enrichment, pressure drop and pressurization

Experiments have been carried out on two individual idealized steps in a pr essure swing cycle in order to compare the performance of a novel absorbent monolith with that of a packed bed of commercial pellets containing the sa me weight of adsorbent. The application is the production of oxygen-enriche d air using 5A zeolite. For feed pressures up to 3.8 bar, maximum oxygen co mpositions in the constant pressure production step up to 100% and 52% were achieved for the monolith with the previous step being carried out (1) by purging the column with pure oxygen at 1 bar, and (2) by evacuating the col umn, respectively. For virtually all experimental conditions studied, the s eparative performance of the monolith was found to be somewhat inferior to that of the bed of pellets, this being due largely to the former's poorer f ilm mass transfer coefficient together with the virtual independence of thi s coefficient on velocity. To its advantage, however, the pressure drop thr ough the monolith was found to be 3-5 times lower than that through the equ ivalent packed bed and consequently the time to pressurize the monolith was found to be 3-5 times faster than for the bed of pellets. This experimenta l feasibility study has demonstrated that the novel zeolite monolith config uration shows good potential for the production of oxygen-enriched air of l ow-to-medium purity, in a low energy, short cycle time, pressure swing proc ess. The challenges associated with both improving and modelling the perfor mance of the monolith are described.