Nitrogen from air

A low calorific value gas, which includes nitrogen from air, could be produced for boiler or turbine use in electric power production, or an intermediate calorific value gas containing no nitrogen for an industrial fuel gas, or synthesis gas for chemical and methane production could be provided. This approach which has been studied in Russia, Europe, Japan, and the United States, is stiU noncommercial in part because it is not economically competitive. 

Gas separation Hollow-fibre for high-volume applications with low-flux, low-selectivity membranes in which concentration polarisation is easily controlled (nitrogen from air) Spiral-wound when fluxes are higher, feed gases more contaminated, and concentration polarisation a problem (natural gas separations, vapour permeation). 

Rate Nitrogen from air by PSA using carbon molecular sieve Nitrogen and methane using titanosilicate ETS-4... 

DWN [Druckwechsel nitrogen] A proprietary PSA system for separating nitrogen from air. Developed and offered by Linde. See also DWO. 

KURASEP [Kuraray Separation] A process for separating nitrogen from air by a variant of the PSA process, using carbon molecular sieve as the adsorbent. Developed by Kuraray Chemical Company. 

Linde Also called Hampson-Linde. A process for separating oxygen and nitrogen from air by liquifation followed by fractional distillation. Developed by K. P. G. von Linde in Germany and W. Hampson in England at the start of the 20th century. 

MOLPSA-nitrogen [Molecular sieve pressure swing adsorption] A version of the PSA process for separating nitrogen from air, developed by Kobe Steel. Most PSA processes for nitrogen use molecular sieve carbon as the adsorbent, but this one uses zeolite X. Water and carbon dioxide are first removed in a two-bed PSA system, and then the nitrogen is concentrated and purified in a three-bed system. 

This determines the size of molecules that can be admitted and the rate at which different molecules diffuse towards the surface. Molecular sieves, with their precise pore sizes, are uniquely capable of separating on the basis of molecular size. In addition, it is sometimes possible to exploit the different rates of diffusion of molecules to bring about their separation. A particularly important example referred to earlier, concerns the production of oxygen and nitrogen from air. 

Soda niter or sodium nitrate (NaNO ) is the most abundant of the nitrate minerals. It is used for fertilizer, explosives, and preservatives. The natural deposits are located in northern Chile, which was the original source for many years. More recently, nitrogen fixation, which extracts nitrogen from air, has been used for producing sodium nitrate. This synthetic process has greatly increased the availability of this useful sodium salt by ehminating the need for the natural source. It is used to preserve and cure meats and is used in photography, in pharmaceuticals, and as a color fixative in fabrics. 

All commercial processes involve either separation of nitrogen from air by cryogenic distillation or combustion of air with natural gas to remove oxygen. In the former process, air is liquefied and the liquid air is subjected to fractional distillation to separate its components. 

Recent developments in desulfurizing the effluents from sulfur plants have concentrated on the plant tail gas before incineration. This avoids the further dilution of the effluent stream with nitrogen from air used as the oxidant and many of the sulfur values are still in a reduced or at least unoxidized state. 

Another method of using PSA to obtain nitrogen from air has recently been revealed by Toray Industries, Inc (30) The standard PSA process has been modified to produce an Impure (33 percent oxygen) less-adsorbed gas and a relatively pure (up to 99 9 percent) purge stream of nitrogen A diagram is shown... 

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