An experimental study of separation of binary and ternary gas mixtures by parametric pumping

An experimental study of gas parametric pumping is presented which examines the purification of helium using silica gel to remove the impurity carbon dioxide. Low gas flow rates are used to allow adequate time for equilibrium to be approached, assuming intraparticle diffusion is the controlling mass transfer step. By varying the cycle time, at long cycle times, the effect of penetration length (a function of dynamic capacity) is indicated. Also, at low cycle time, the effects during pressure changes become more significant. Using low flow rate improves separation effectiveness if evaluated at equal dynamic capacity. When using low flow rate and low cycle time, the gas added during repressuring and removed during blowdown should be used in calculating the purge to feed ratio. If this is not used then the purge concentration calculation method will not be accurate. When operating under conditions where the repressurizing gas makes up a large percentage of the gas fed, a poor separation efficiency resulted, due to inadequate regeneration of the purging column. The system helium, carbon dioxide, and propylene was evaluated at higher flow rate. Adsorbtion breakthrough curves from adding carbon dioxide and propylene simultaneously to silica gel showed the system to be non-ideal. The carbon dioxide adsorbed to a peak level and then desorbed as additional propylene adsorbed. Using this system, even though more propylene can adsorb than carbon dioxide, the separation of carbon dioxide was more effective than propylene. This apparent departure from theory may be due to insufficient time for the more strongly adsorbed propylene to purge from the column