Traditional cylindrical adsorbers in pressure swing adsorption processes are replaced by flat-box-type adsorbers, which are stacked together, to make the heat released from adsorption bed be transferred to desorption bed to enhance adsorption in adsorption bed and desorption in desorption bed, respectively. The simulation is performed for the bulk separation of air (21% oxygen ; 79% nitrogen) in Skarstrom cycle and 5A zeolite is utilized as adsorbent. The simulation results of flat-box adsorbers and traditional cylindrical adsorbers are compared. The oxygen concentration of products of the flat-box adsorbers is higher than that of the traditional cylindrical adsorbers when the heat transfer coefficient between neighboring flat-box adsorbers is high. The effects of operating variables such as step time, adsorption pressure, the ratio of bed width to bed height, the heat transfer coefficient between neighboring adsorbers are investigated on the performance of PSA.