Separation of air

Gas-phase adsorption is widely employed for the large-scale purification or bulk separation of air, natural gas, chemicals, and petrochemicals (Table 1). In these uses it is often a preferred alternative to the older unit operations of distillation and absorption. 

No internal piping and no conventional filter valve are needed with single-cell dmm filters where the entire dmm also operates under vacuum. The cake discharge is effected by air blowback from an internal stationary shoe mounted inside the dmm at the point of discharge. There are very close tolerances between the inside surface of the dmm and the shoe in order to minimize the leakage. The inside of the dmm acts as a receiver for the separation of air and filtrate conventional multicompartment dmm filters require a separate external receiver. This type of filter permits operation of the filter with thin cakes so that high dmm speeds, up to 26 rpm, can be used and high capacities can be achieved. Sizes up to 14 m are available. 

Figure 2-4 shows a low temperature (-300°F) applieation of a turboexpander in the separation of air in a simplified eyele. The air is eooled in a heat exehanger down to near its liquefaetion point, and then some further heat is removed by the turboexpander while a portion of the stream is eondensed. By visualizing a heat envelope around the proeess it ean be seen that virtually all the energy deerease... 

The noble gases make up about 1% of the earth s atmosphere in which their major component is At. Smaller concentrations are occluded in igneous rocks, but the atmosphere is the principal commercial source of Ne, Ar, Kr and Xe, which are obtained as by-products of the liquefaction and separation of air (p. 604). Some Ar is also obtained from synthetic ammonia plants in which it accumulates after entering as impurity in the N2 and H2 feeds. World production of... 

After performing the mild and effective extraction process the carotenoids must be separated in order to make structural assignments. Robust and reproducible separations of air and UV-sensitive... 

If, on the other hand, he means only the separation of air from water by boiling, as illustrated in the latter of the above sentences, then it may be conjectured that lie only observes the conversion of water into vapor (air) in. boiling. In no case is there any justification for Iloefer s conclusion. Paracelsus and Basilius Valentinus may therefore both be eliminated as early observers of the formation of the gas now known as hydrogen. 

Purification of Air Prior to Liquefaction. Separation of air by cryogenic fractionation processes requires removal of water vapor and carbon dioxide to avoid heat exchanger freeze-up. Many plants today are using a 13X (Na-X) molecular sieve adsorbent to remove both water vapor and carbon dioxide from air in one adsorption step. Since there is no necessity for size selective adsorption, 13X molecular sieves are generally preferred over type A molecular sieves. The 13X molecular sieves have not only higher adsorptive capacities but also faster rates of C02 adsorption than type A molecular sieves. The rate of C02 adsorption in a commercial 13X molecular sieve seems to be controlled by macropore diffusion 37). The optimum operating temperature for C02 removal by 13X molecular sieve is reported as 160-190°K 38). 

N. M. Wiederhorn, N. F. Surprenant, and A. J. Leffler, "Research on New Methods of Separation of Air into 0 and Ng Components," C-63825, First-Quarterly Progress Report, September 1961, Arthur D. Little, Inc. 

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