Future Directions for Adsorption Technology and Uses

In the sections diet follow we will point onl the likely areas of growth for ndsorplion in existing aad new applications. We will also suggest some technological innovations thet could stimulate this growth. 

Inen-puige cycles, given the recently demonstrated success in drying of azeotropes,1 would seem to be poised for use in several new separations. Prime candidates include those systems now separated by azeotropic and extractive distillation, many of which contain water as one constituent. The use of inert-purge cycles for isomer and other close-boiler sepurations sheuld also grow for those systems whose components can be easily separated from the purge gas, 

Displncement-puige cycles will not fiad meny new uses, primarily because of the inherent complexity of these cycles. 

Fixed-bed, temperature-swing processes rarely turn onl to be economical for bulk separations. Moving-bed and fluidized-bed processes based on thermal regeneration may prove to be much more economical because of lower heal requirements per unit of feed. The key to the success of these processes lies in the development of highly attrition-resistant adsorbent particles such as Kureha s bead activated carbon.2 

Applications for liquid purifications by adsorption should grew faster than the industries they serve. 

Distillation and related vapor-liquid processes are by far the most widely used molecular separation processes in the petroleum, natural gas, petrochemical, and chemical industries, as mentioned earlier. It is highly unlikely that adsorption will ever rival distillation in frequency of use, but adsorption will continue to m e inroads into its domain. Adsorption s serious competition for the separations for which it is now used would seem to come chiefly from membrane-based processes, and especially fixed-membrane processes. For example, Monsanto s Prism hollow-fiber-based process has been commercialized in a number of hydrogen-upgrading applications, and a growing number of other applications are being pursued. 

As hmg as displaceinent liquids are used in liquid bulk-separation processes—be they simulated moving beds, chromatographs, or other configurations—these processes will not be able to compete successfully with distillation for very many of the sqiarations now made by distillation. The problem is one of process complexity, which reflects itself in high invesimem, and energy usage in recovery of the displacement 

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