Pressure-swing adsorption more adsorbed

Adsorption Processes. More recendy, pressure swing adsorption (PSA) processes utilizing a high selectivity copper adsorbent have been utilized to effectively separate carbon monoxide from blast furnace gas and coke oven gas (97—101). 

Processes involving total-pressure reduction to remove the adsorbed species, called pressure-swing adsorption (PSA) or heatless adsorption, are mechanically complex, since they must include separate adsorption, depressurization, desorption, and repressurization steps. To accommodate a steady flow of feed and products, several beds - usually three or more in parallel -are used. A typical four-bed process flowsheet is shown in... 

N diffuses into the structural pores of clinoptilolite 10 to 10 times faster than does CH4. Thus internal surfaces are kinetically selective for adsorption. Some clino samples are more effective at N2/CH4 separation than others and this property was correlated with the zeolite surface cation population. An incompletely exchanged clino containing doubly charged cations appears to be the most selective for N2. Using a computer-controlled pressure swing adsorption apparatus, several process variables were studied in multiple cycle experiments. These included feed composition and rates, and adsorber temperature, pressure and regeneration conditions. N2 diffusive flux reverses after about 60 seconds, but CH4 adsorption continues. This causes a decay in the observed N2/CH4 separation. Therefore, optimum process conditions include rapid adsorber pressurization and short adsorption/desorp-tion/regeneration cycles. 

Pressure swing adsorption is a commercial process for separating fluids based on their different affinities for an adsorbent. A sequence of steps involves more than one vessel ("bed") packed with adsorbent. Bed No. 1 receives the feed at the high supply pressure while bed No. 2 is opened to the low exhaust pressure. When Bed No. 1 becomes saturated with desired product (the undesired product leaves the bed at the exit), the supply is switched to Bed No. 2, and Bed No. 1 is opened to the low pressure so that the desired product is recovered. In the meantime desired product collects in Bed No. 2. After Bed No. 2 is saturated, the supply is again shifted back to Bed No. 1, and so on. More than two beds can be employed, and the specific design of the system and operating conditions are based on economical operation to conserve compression energy. 

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