Abstract: A process for purifying a gas stream containing at least one impurity chosen from the group formed by propane, nitrogen protoxide and ethylene, in which process: (a) the gas stream to be purified is brought into contact with at least one adsorbent including at least one X zeolite containing barium cations; (b) at least one impurity is adsorbed on the adsorbent. Preferably, the adsorbent includes particles of X zeolite exchanged to at least 70%, preferably at least 89%, with barium cations, it being possible for the adsorbent to furthermore include a bed of activated alumina particles which is located upstream of the bed of barium-exchanged X zeolite.

Abstract: A process, particularly of the TSA type, for separating impurities of the nitrogen protoxide (N2O) and possibly carbon dioxide (CO2) or ethylene (C2H4) type which are contained in a gas stream, such as air. The impurities of nitrogen protoxide type are removed on a faujasite zeolite having a Si/Al ratio of 1 to 1.5 and containing from 0 to 35% of K+ cations, between 1 and 99% of Na+ cations and between 1 and 99% of Ca2+ cations, preferably at least 50% of Ca2+ cations. The separation is preferably carried out at a temperature of approximately −40° C. to +80° C., preferably at room temperature. Advantageously, the process is employed for prepurifying atmospheric air before cryogenic distillation of the air thus prepurified.

Abstract: Process for separating at least carbon dioxide (CO2) contained in a gas stream, preferably air, in which at least carbon dioxide is adsorbed on a zeolite-X having a Si/Al ratio of approximately 1 to 1.5 and containing at most 35% of K+ cations, between 1 and 99% of Na+ cations and at most 99% of Ca2+ cations. This process is carried out at a temperature ranging from −40° C. to +80° C. Optionally, impurities chosen from water vapour and hydrocarbons, particularly ethylene, are also removed. The air thus purified is then capable of being cryogenically distilled.

Abstract: Process and apparatus for the purification of a gaseous flow containing at least one impurity which can be carbon dioxide, water vapor and/or hydrocarbon. The impurity is adsorbed on a bed of adsorbent containing at least one adsorbent material, it being possible to use stacked adsorbent beds. Atop the uppermost bed is a layer of particulate ballast having a density greater than that of the adsorbent. The bed of ballast exerts a mechanical pressure on the subjacent adsorbent and prevents fluidization of the upper portion of the subjacent adsorbent. As a result, the rate of gas flow through the adsorbent can be increased.

Abstract: Process for purifying an air flow containing carbon dioxide (CO.sub.2) and water vapour, in which at least some of the CO.sub.2 and water vapour impurities are removed by adsorbing the impurities on at least one calcined alumina containing at most 10% by weight of at least one alkali or alkaline-earth metal oxide, the adsorption being carried out at a temperature of between -10.degree. C. and 80.degree. C.

Abstract: A miniature open circuit refrigerator of the Joule-Thompson type, functions as a demand cryostat by virtue of a pressure-operated refrigerant supply control. The refrigerant fluid under high pressure is introduced at a first relatively rapid flow rate into the cryostat through a calibrated opening that is fully open during the initial or start-up period of the device, for rapid cool down. This calibrated opening is thereafter at least partially closed by a valve which is urged open by a spring and which is urged closed, against the action of the spring, by a bellows containing a gas at high pressure and which is exposed on its outer side to at least a portion of the pressure of the refrigerant fluid. Upon the fall in pressure of the stored refrigerant fluid, toward the end of the start-up, the bellows expands so as at least partially to close the valve, thereby to decrease the flow of refrigerant during the final portion of the cool-down period and during the steady state or on-stream operation of the device.