Page 262 - Adsorption Technology & Design, Elsevier (1998)

Selected adsorption processes 237

ethanol-rich product will contain some of the desorbent liquid: when
this is the case ethanol and desorbent have to be separated by a
subsequent distillation.
(4) During the last and fourth step of the cycle the column is rinsed with
water in a countercurrent direction. Initially the effluent is liquid
adsorbent which can be recycled to another column in which Step 3 is
occurring. Subsequently, the effluent is a mixture of water and
desorbent liquid which is separated by distillation so that the
desorbent can be recirculated.

Four adsorption columns, with appropriate valves for switching liquid
streams between columns, are required to operate this concentration swing
cycle so as to obtain a continuous flow of enriched ethanol. The process
operates at ambient temperatures and can be designed to produce 98%
pure ethanol with a very high recovery of ethanol (as high as 99%) from
the feed mixture. It is claimed that the separation of ethanol-water
mixtures by concentration swing adsorption has the potential for significant
reduction of energy requirements when compared with separation by
distillation.

REFERENCES

Asher, W.J., Campbell, W.R., Epperley, W.R. and Robertson, J.L.
(1969) Hydrocarbon Processing, 48(1), 134
Ausikaitis, J. P. (1978) in Encyclopaedia of Chemical Technology, Vol. 8,
p. 126, Wiley
Barker, P. E., England, K. and Vlachogiannis, G. (1983) Trans. IChemE
Res. Dev., 61, 241
Barrer, R. M. and Strachan, E. (1955) Proc. Roy. Soc., A231, 52
Bellows, R.J., Pirkle, C.J. and Wu, T.D. (1986) Paper l18e, AIChE
Meeting, Miami
Berg, C. (1946) Trans. IChemE, 42, 665
Berlin, N. H. (1966) US Patent 3,280,536, assigned to Exxon Research &
Eng.
Bernard, J.R., Gourlia, J.P. and Guttierrez, M. J. (1981) Chem. Eng.
88 (May), 92
Broughton, D. B. and Gembicki, S. A. (1984) AIChE Symp. Series, 80 (No
233), 62
Broughton, D. B., Neuzil, R. W., Pharis, J. M. and Brearley, C. S. (1970)
Chem. Eng. Prog., 66, (No 9), 70