Industrial gases adsorption separation

A more complex but more versatile separation method is chromatography, a technique widely used in teaching, research, and industrial laboratories to separate all kinds of mixtures. This method takes advantage of differences in solubility and/or extent of adsorption on a solid surface. In gas-liquid chromatography, a mixture of volatile liquids and gases is introduced into one end of a heated glass tube. As little as one microliter (10-6 L) of sample may be used. The tube is packed with an inert solid whose surface is coated with a viscous... 

While inert and displacement purge regeneration is widely used in liquid phase separations, there are few industrially relevant inert purge systems employed in gas phase separations. It is sufficient to note that an inert purge regeneration can be done and it will generally be most effective at relatively high adsorption temperatures. 

Adsorption separation—an important unit operation in the separation of industrial gases—is achieved by adsorbing one or more component(s) onto the active sites of a solid adsorbent. For cyclic processes, the solid is regenerated by shifting the equilibrium toward the gas phase by increasing the adsorbent temperature or by decreasing the partial pressure of the adsorbate in the gas. Some of the more important commercial combinations... 

Modification of silica gel with volatile or gaseous compounds is performed in the vapour phase. Industrial-scale reactors and laboratory scale gas adsorption apparatus have been used. In the industrial field, fluidized bed and fluid mill reactors are of main importance. In fluidized bed reactors,82 the particles undergo constant agitation due to a turbulent gas stream. Therefore, temperatures are uniform and easy to control. Reagents are introduced in the system as gases. Mass transport in the gas phase is much faster than in solution. Furthermore, gaseous phase separations require fewer procedural steps than solution phase procedures, and may also be more cost-effective, due to independence from the use and disposal of non-aqueous solvents. All these advantages make the fluidized bed reactors preferential for controlled-process industrial modifications. 

The treatment of streams (gas or liquids) containing VOCs by zeolite-based materials belongs to adsorption/separation and/or catalytic oxidation. Regarding adsorption/separation alone, it concerns mainly industrial streams with relatively high VOCs concentrations. The VOCs taken up by zeolite are recovered and recycled. At low VOCs concentrations in complicated matrix, adsorption is often coupled with incineration or catalytic oxidation. 

MUller U etal (1990) In Gas Separation Technology, Elsevier, Amsterdam, p 255 Otowa T (1991) In Adsorptive Separation (M Suzuki, ed), Institute of Industrial Science, Tokyo, p 273... 

Physical sorbents for carbon dioxide separation and removal were extensively studied by industrial gas companies. Zeolite 13X, activated alumina, and their improved versions are typically used for removing carbon dioxide and moisture from air in either a TSA or a PSA process. The sorption temperatures for these applications are usually close to ambient temperature. There are a few studies on adsorption of carbon dioxide at high temperatures. The carbon dioxide adsorption isotherms on two commercial sorbents hydrotalcite-like compounds, EXM911 and activated alumina made by LaRoche Industries, are displayed in Fig. 8.F23,i24] shown in Fig. 8, LaRoche activated alumina has a higher carbon dioxide capacity than the EXM911 at 300° C. However, the adsorption capacities on both sorbents are too low for any practical applications in carbon dioxide sorption at high temperature. Conventional physical sorbents are basically not effective for carbon dioxide capture at flue gas temperature (> 400°C). There is a need to develop effective sorbents that can adsorb carbon dioxide at flue gas temperature to significantly reduce the gas volume to be treated for carbon sequestration. 

Its surface tension, furthermore, makes possible a totally unexpected technology membranes for separating gases. However, work of this kind with doped polyaniline by American scientists has not yet been taken up by industrial laboratories. We suspect that the results are not due, as claimed by the researchers, to more targeted creation of pores, but to the change in gas adsorption as a result of the modified surface tension of the doped plastic. 

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