Page 244 - Pressure Swing Adsorption

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CHAPTER
6

PSA Processes

In orevwus chapters we have described the orinc1oles underlying the opera~
tion of a PSA orocess and shown how the process may be represented in
terms of simplified mathematical models. However, aoart from the discussion
in Chapter 3 concernmg the factors govemmg the ch01ce of cvcle. the more
practical aspects of PSA process design have been 1gnorecl ancl few details of
comparative oerformance have been given. An account of several representa-
tive PSA processes that have been developed to the mdustnal scale 1s
presented in this chapter together with comments on some of the more
practical design aspects and the thennodynamic efficiency. Detailed informa-
tion on practical design and system performance 1s not widely available m the
ooen literature and the comments presented here therefore represent only a
partiai account. Further mforrnat1on can be obtained from the extensive
patent literature, although the details are often confuSmg.

6.1 Air Drying

The "heattess ctner" was the earliest practical PSA process, and the factors
governing the design and performance were studied in detail by Skarstrom. i
The process, which IS widely used for small.scale applications such as the
clrymg of instrument a1r operates on the simple two-bed Skarstrom cycle (see
Section 3.2). Essentially bone-clry product air (1 ppm H 0) can be readily
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achievecl with either alumma or zeolite (4A or 5A) as the desiccant, but
beaded alumma IS the ·usual choice.