Large-scale gas separation

The use of membranes to separate gases commercially is a relatively new application. Both Du Pont and Union Carbide had ventures in the early 1970s for recovering H2 and He ffom industrial processes, but these projects were never fully commercialized. Recently, however, a combination of improved economics and better technology has resulted in membrane products that signal a new era in the commercial use of membranes for large-scale gas separation. 

Koros, W. J., and Mahajan, R. (2000). "Pushing the limits on possibilities for large scale gas separation Which strategies J. Membr. Sci. 175, 181-196. 

The large-scale gas-separation processes may be conveniently divided into two classes, the cryogenic separation systems and the adsorption separation processes. In this chapter we are dealing with adsorption processes only. 

Non-porous polymeric membranes are usually employed for gas separation, although porous ones can also be used. Composite polymeric membranes developed in the 1970s made the separation of gas streams commercially feasible. The first large-scale gas separation modules were developed by DuPont in early 1970s, but the first successful commercial membrane gas separation processes (PRISM) were announced by Monsanto in late 1970s. 

By contrast porous ceramic membranes had found application since the 1960s in the field of large-scale gas diffusion processes for uranium isotope separation. It was only in the 1980s that porous ceramic membranes found other non-nuclear industrial applications, mainly oriented towards microfiltration and ultrafiltration water treatment processes. 

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. 

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