Page 189 - Pressure Swing Adsorption

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164 PRESSURE SWING ADSORPTION
CHAPTER
21. S.-S. Suh and P. C. Wanka1, "A New Pressure Swmg Adsorptmn Process for High
Enrichment and Recovery," Chem. Eng. Sci. 44, 567-74 0989). 5
22. S. Sircar, "Air Fracuonatmn bv Adsorption," Separ, Sci. and Tech. 24(14 & 15), 2379-96
(1988).
23. K. P. Kolliopoulos, M.S.Ch.E. Thesis, Ohio State Umvers1ty, Columbus, OH, 1987.
24. J. E, 'Mitchell, and L H. Shendalman, "A Study of Heatless Adsorpuon in the Model Dynamic Modeling of a
Svstem CO in H. ll," A/Ch£ S_vmp. Ser. 69, 2S (1973).
25. G. Flores Fernandez and C. N. Kenney, "Modelling the Pressure Swmg Air Separation l PSA System
Process," Chem. Ettg. Sci, 38, 827-34 (1983).
i
26. M. J. Matz and K. S. Knaebel, "'Temperature Front Sensing ,for "Feed Step· Conirol m I
Pressure Swing Adsorption," Ind. Eng. Chem. Res. 26(8), 1638 (1987).
27. R. R. Hill and K. S. Knaebel, "Effects of Combined Steps m Pressure Swmg Adsorption I
Cvcies: An Expen!Tlental and Theoretical Study," Adsorptwn: Fundam.- and Applic., Proc.
China-Jap.-USA Syn'lp. on Adv, Ads. Separ. Sci. and Tech., Zheiiang Univ. Press (1988),
28. J. J. Collins. '"Air Separntion by Adsorption," U.S. Patent No. 4,026,680 0977).
I
29. D. R. Garg and C. M. Yon, Chem. E11g. Prog. 82(2), 54-60 (1986).
30. G. W. Miller, K, S. Knaebel, and K. G. lkels, "Equilibria of Nitrogen, Oxygen, Argon, and
Air m Molecular Sieve SA," A/Ch£ J. 33, 194-201 (1987).
31. I. Rousar and P. Ditl, "Opt1m1zauon of Pressure Swing Adsorption Equipment: Part I.,"
Chem. Eng. Commun. 70, 67-91 (1988).
32. R. Kumar, "Adsorption Column BJowdown: Adiabatic Equilibrium Model for Bulk Binary The simplest approach to the modeling of a PSA separation process involves
Gas Mixtures," Ind. Em:. Chem. Research 28, 1677-83 {1989).
the use of equilibrium theory, which has been discussed m the previous
33. z. P. LU," J. M. Loureiro, M. D. LeVan, and A. E. Rodrigues, "lutraparticle Convection chapter. The advantage of this approach 1s that tt allows analytic solution of
Effect on Pressunzation and Slowdown of Adsorbers," A/ChE J. 38, 857-67 0992). the governing matenai balance eQuations by the method of characteristics.
34. z. p_ Lu, J. M. Loureiro, M. D. uVan, and A. E. Rodrigues, "lntraparticle The closed-form eauilibnum theory soiutions provide orelimmary design
Diffusion/ConvectlOn Models for Pressurization and Blowdown of Adsorption Beds with guidance and useful insight mto the system behav10r. The auantitat1ve value
Langmuir Isotherm," Separ. Sci. Tech. 21, 1857-74 (1992). of this approach is, however, restncted to idealized systems in which the
35. z. P. Lu, J. M. Loureiro, A. E. Rodrigues, and M. D. LeVan, "Pressurization and adsorption selectivity is based on differences in eauilibnum and there are no
Blowdown of Adsorption Beds," Chem. Eng. Sci. 48, 1699 (1993). significant dispersive effects such as axial mixing or fintte res1stance to mass
J6. A. E. Rodrigues, J, M. Loureiro, nnd M. D. Le Van. Gas Sep. and Purification, S, I 15 ( 1991 ). transfer. Under these conditions a oerfectly oure raffinate product is ob-
tamed. Eotiilibrium theory does not allow easy extension to the more realistic
37. H. Cheng and F. B. Hill, A/Ch£ 1. 31, 95 (1985).
s1tuat1on where dispersive effects are significant and product purity is limited.
38. D. M, Scott, Chem, Er,g. Sci. 46, 2977 (1991).
Moreover, in real PSA systems (eauilibrmrn controlled) there are two prob-
39. J. Han, M. r. Baltrum, and W. J. Thomas, Gas Sep. and Pur~ficatwn, 4, 97 (1990). lems with this approach. In bulk separations the velocity vanes through the
40. N, Sundaram and P. C. Wankat, Chem. Eng. Sci. 43, 123 (1988). bed, and, although an analytic solution for the concentration front may still
be obtamect, except in the case of a linear isotherm, fhe solution 1s m the
41. S. J, Doong and R. T. Yang, A/Cl1E Symp. Ser. 84(284), 145 (1989).
form of a cumbersome mtegral which generally requires numencai evalua-
42. R. L. Pigford, Private communicauon, July 23, 1986.
tion. i A more serious difficulty arises in tracking the concentration waves for
adsorption and desorptJOn in oart1ally ioaded beds since, depending on the
initial profile and the form of the cauilihnum relationship, one may observe
the fonnatmn of combined wave fronts (e.g., parttai shoCk plus simple waves).
Under these conditions the simple model 1s no longer adequate and it 1s
necessary to track both waves and the transition point s1mu1taneous1v.'
Durmg pressure changes the charactenst,c lines are curved and the task of

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