| 摘要 |
The mixture is enriched in one minority component and the other minority components are eliminated by selective permeation across a specific membrane; purification by adsorption at ambient temperature on a solid adsorbent and concentration of the first minority component by successive adsorption(s) and elution(s) until the desired (substantially enriched) concentration is obtained The initial mixture contains a majority component and two or more minority components. The process involves: selective permeation of the initial gaseous mixture across a membrane which is specific to the gas to be treated, to obtain a mixture enriched in the first minority component and impoverished or slightly enriched in the other minority component(s); purification of the enriched mixture by adsorption at ambient temperature on a solid absorbent, then elution to obtain a gaseous mixture comprising the majority component and the first minority component and from which the other components have been eliminated; concentration of the first minority component by successive adsorption(s) and elution(s) on a solid adsorbent until a final mixture is obtained containing the majority and first minority component, substantially enriched in the first minority component relative to the initial gas and with the desired concentration of first minority component. The majority component is nitrogen, hydrogen, oxygen, gaseous hydrocarbon or carbon dioxide, e.g. air. The first minority component is a rare gas: helium, neon, argon, krypton, xenon or radon, in particular one of their isotopes or a mixture of two isotopes such as 131Xe, 135Xe, 131mXe or 133mXe. After the first permeation stage, the gas flow rate and/or the pressure upstream of the membrane is controlled. The solid adsorbent is chosen specifically to have a high affinity for the first minority constituent. The conditions for elution (temperature, pressure, duration) are carefully selected to allow separation of the first minority component from the other minority components. The purification stage comprises at least two adsorption devices, so one is in the adsorption phase while the other is in desorption. The elution gas used is the purified majority component from the adsorption phase without intermediate storage. The concentration is obtained by multiplying the adsorption - desorption stages and reducing the mass of adsorbent and volume of elution gas in each stage. A different adsorbent with an affinity for the primary component is used in the concentration stage. The gaseous mixture is air and the primary component is Xenon. The selective permeation uses a small flow of nitrogen. The solid adsorbent in the purification stage is active carbon. Elution is carried out at 250 degree C for 20 minutes or more under pressure using a small flow of pure nitrogen. The adsorbent in the concentration stage is Carboxene (R). Installation for carrying out the above process
|
