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Novel product separations
Separation Applications in
downstream processing
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Pervaporation,
Membrane distillation,
Vapor permeation and Gas permeation,
Membrane distillation,
Vapor permeation and Gas permeation
Contents
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Pervaporation
Pervaporation is a membrane process, in
which a liquid mixture is brought in contact
with a membrane at the upstream side and the
permeate is removed as a vapor at thepermeate side. The driving force for the
process is established by reducing the relative
pressure at the downstream side by either the
use of an inert carrier gas or an appliedvacuum. The vapor is usually obtained as a
liquid in a condenser.
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vapor
non condensables
feed retentate
membrane module
vacuum pump
condensed permeate
condenser
feed retentate
membrane module
condensed permeate
condenser
blower
carrier gas recycle
vacuum
pervaporation
carrier gas
pervaporation
Fig. 1: Schematic representation
of pervaporation processes
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Types of industrial applications of
pervaporation
The dehydration of water-organic liquid
azeotropes and
The extraction of volatile trace organics
contained in aqueous mixtures.
In every case, pervaporation is combined
with distillation and is mainly used to
pass over the azeotropic composition.
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applications for pervaporation …
Dehydration of organic solvents
Removal of dilute organics from
aqueous streams
Continuous extraction of products and
inhibitory by-products in biological and
food processes
Separation of organic mixtures
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Membrane distillation (MD)-1
Membrane distillation is a distillation process,
in which two aqueous solutions with different
temperatures are separated by a microporous
hydrophobic membrane. In this process the pores of the microporous
membrane, which are not wetted by the liquid
mixtures at the feed side or the permeate side,
act as the vapor phase.
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Module of membrane distillation.
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Membrane distillation (MD)-2
The vapor pressure difference, resulting
usually from the temperature difference
across the membrane, causes vapor
molecules to be transported from thewarm feed side to the cold permeate
side.
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industrial applications of
membrane dist i l lat ion
Due to very low entrainment of droplets
through the microporous membrane, the
production of utrapure low conductivity water
seems to be an interesting application. Also, the production of potable water from salt
containing water in arid regions (e.g. Australia)
by membrane distillation using solar energy
has been commercialized.
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characteristics of a membrane
distillation process
The characteristics of a membrane
distillation process can be reduced to
one important point: the permeant is
t ranspo rted as a vapo r through the
pores o f a porous membrane, which
is at least at one side in d irect contact
w i th the l iqu id [Franken (1988)].
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Vapor and Gas Permeation
compounds that are condensable
at standard conditions
so-called permanent gases
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Vapor permeation (VP)
Vapor permeation denotes the transport of
matter through a membrane from a vapor
feed mixture to a vapor permeate. It is
related closely to gas permeation differing onlyin that a vapor mixture contains compounds
that are condensable at standard conditions (1
bar and 0°C), whereas a gas mixture contains
only so-called permanent gases [Cen andLichtenthaler (1995)].
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Comparison of VP (vapor permeation) and PV
(pervaporation):
VP
+ no phase change
+ no heat of vaporization necessary
+ no severe concentration polarization problem
+ suitable for several hybrid processes (e.g.purification of top stream of rectification columns)
PerVap
- strong dependence of separation characteristics
on the feed pressure - sensitivity to friction losses in the feed stream
- possibility of condensation
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Gas permeation (GP)
A gas separation membrane process comprises the transport of gases through amembrane. A gas separation membranepreferentially removes one or morecomponents of a gas mixture that is passedacross a membrane surface.
Usually, the feed gas mixture is pressurized toincrease the partial pressure differencebetween feed side and permeate side and,therefore, to increase mass transfer.
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gas separation membranes :
Asymmetric polymer membranes
consisting of a highly permeable,
permselective and dense polymer film
fixed to a porous support.
Membrane polymers should have both
high solubility and high diffusivity of
gases as well as easy membraneformation properties.
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Classes of gases that are separated
by membranes:
(significance of the development of gas
separation membranes varies with the type
of mixed gas)
1 The property and the molecular size of thecomponent gases in the gas mixture are
similar. Typical examples of the separation of
such mixed gases are O2/N2 separation and
alkane/alkene separation (same number ofcarbon atoms).
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Classes of gases….
2 One component (e.g. SO2, CO2, NH3 or Cl2)in the gas mixture has a much largersolubility coefficient than other components.
A typical case is CO2/CH4 or CO2/COseparation.
3 One component in the gas mixture - such asH2 or He - has a small molecular diameterand low molecular weight. A typical exampleis the separation of H2/CO, H2/N2, or theseparation of He from natural gas.
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Application of gas permeation
processes
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Literature-1
Baker, R.W.: Recovering organic vapors from air. USPat. 4,553,983 (1985).
Beaumelle, D.; Marin, M.; Gibert, H.: Pervaporationwith Organophilic Membranes: State of the Art. Trans.
IChemE Part C, 71 (1993), 77-89. Belafi-Bakó, K.; Harasek, M.; Friedl, A.: Product
removal in ethanol and ABE fermentations. Hung. J.Ind. Chem., 23 (1995), 309-319.
Bengtsson, E.; Trägårdh, G.; Hallström, B.: Recoveryand Concentration of Apple Juice Aroma Compoundsby Pervaporation. J. Food Eng., 10 (1989), 65-71.
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Literature-1a
Bennett, M.: Pervaporation Using ModifiedPolysiloxanes: Removal of Priority OrganicContaminants from Aqueous Streams. PhD thesis,University of Bath, United Kingdom (1996).
Blume, I.; Baker, R.W. (Membrane Technology &Research, Inc.): Process for recovering organiccomponents from liquid streams. US Pat. 5,030,356(1991).
Brüschke, H.E.A.: Multilayered membrane and its use
in separating liquid mixtures by the pervaporationmethod. DE Pat. 3 220 570 (1983).
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Literature-2
Brüschke, H.E.A.; Schneider, W.; Tusel, G.F.:Verfahren zur Reduktion des Alkoholgehaltes vonalkoholischen Getränken. EP 0 332 738 (1988).
Cen, Y.; Lichtenthaler, R.N.: Vapor permeation. In:
Membrane Separations Technology – Principles and Applications. Membrane Science and TechnologySeries, 2 (1995), 85-112.
Franken, T.: Membrane distillation: a new approachusing composite membranes. PhD thesis, University of
Twente, The Netherlands (1988).
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Literature-3
Friedl, A.; Windsperger, A.M.; Minkov, S.:Inertgasstrippen als Produktabtrennung beider Aceton-Butanolgärung und derEthanolgärung. Zuckerind., 114 (1989), 216-221.
Friedl, A.; Harasek, M.; Schmidt, A.:Concentration of hydrochloric acid and sulfuricacid by pervaporation and membranedistillation. Proceedings of Euromembrane´95, Bath (UK), 18-20 Sept. 1995, Volume II,198-203.
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Literature-4
Geng, Q.; Park, C.-H.: Pervaporative ButanolFermentation by Clostridium acetobutylicum B18.Biotechnol. Bioeng., 43 (1994), 978-986.
Groot, W.J.; den Reyer, M.C.H.; Baart de la Faille, T.;
van der Lans, R.G.J.M.; Luyben, K.Ch.A.M.:Integration of pervaporation and continuous butanolfermentation with immobilized cells. I: Experimentalresults. Chem. Eng. J., 46 (1991), B1-B10.
Gudernatsch, W.; Chmiel, H.: Verfahren zur selektiven
An- oder Abreicherung flüchtiger Bestandteile einesFluidgemisches. DE Pat. 39 40 520 (1989).
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Literature-5
Gudernatsch, W.; Kimmerle, K.: New Capillary
Modules for Pervaporation. Proc. 5th Int. Conf.
on Pervap. Proc. in Chem. Ind., Heidelberg
(Germany), 1991, R.Bakish (Ed.), BakishMaterials Corporation, Englewood (NJ, USA),
259-271.
Gupta, B.D.; Mukherhee, A.K.: Separation of
Liquid Mixtures by Pervaporation. Poly.-Plast.Technol. Eng., 29(4), 299-337 (1990).
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Literature-6
Harasek, M.: Pervaporation and Membrane Distillation for the
Removal of Organic Compounds from Aqueous Mixtures. PhD
thesis, Vienna University of Technology (1997).
Henis, J.M.S.; Tripodi, M.K.: Multicomponent membranes for
separation of gases. US Pat. 4,230,463 (1978).
Karlsson, H.O.E.; Trägårdh, G.: Pervaporation of dilute organic-
water mixtures. A literature review on modelling studies andapplications to aroma compound recovery. J. Membr. Sci., 76
(1993), 121-146.
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Literature-7
Karlsson, H.O.E.; Trägårdh, G.: Aroma
compound recovery with pervaporation -
the effect of high ethanol concentration.
J. Membr. Sci., 91 (1994), 189-198.
Kober, P.A.: Pervaporation, perstillation
and percrystallisation. J. Am. Chem.
Soc., 39 (1917), 944-948.
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Literature-8
Meckl, K.; Lichtenthaler, R.N.: HybridProcesses Including Pervaporation for theRemoval of Organic Compounds from Processand Waste Waters. Proc. 6th Int. Conf. on
Pervap. Proc. in Chem. Ind., Ottawa (Canada),1992, R.Bakish (Ed.), Bakish MaterialsCorporation, Englewood (NJ, USA), 476-483.
Néel, J.: Pervaporation. In: MembraneSeparation Technology, Membrane Scienceand Technology Series, 2, edited byR.D.Noble and S.A.Stern, Elsevier,
Amsterdam (1995), 143-211.
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Literature-9
Noezar, L.; Nguyen, Q.T.; Clément, R.; Néel,J.: High Performance Polymer BlendMembranes for Alcohol - Ether Separation.Proc. 7th Int. Conf. on Pervap. Proc. in Chem.
Ind., Reno (NV/USA), 1995, R.Bakish (Ed.),Bakish Materials Corporation, Englewood (NJ,USA), 45-51.
Pinnau, I.; Koros, W.J.: Relationship betweenSubstructure Resistance and Gas SeparationProperties of Defect-Free Integrally Skinned
Asymmetric Membranes. Ind. Eng. Chem.Res., 30 (1991), 1837-1840.
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Literature-10
Rautenbach, R.; Klatt, S.; Vier, J.: State of the Art ofPervaporation, 10 Years of Industrial PV. Proc. 6th Int.Conf. on Pervap. Proc. in Chem. Ind., Ottawa(Canada), 1992, R.Bakish (Ed.), Bakish MaterialsCorporation, Englewood (NJ, USA), 2-15.
Schofield, R.W.; McCray, B.; Ray, R.J.; Newbold,D.D.: Opportunities for Pervaporation in the WaterTreatment Industry. Proc. 5th Int. Conf. on Pervap.Proc. in Chem. Ind., Heidelberg (Germany), 1991,R.Bakish (Ed.), Bakish Materials Corporation,
Englewood (NJ, USA), 409-420. Scott, K.: Handbook of Industrial Membranes. Elsevier
Advanced Technology (1995), ISBN 1-85617-233-3.
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Literature-11
Pinnau, I.; Wind, J.; Peinemann, K.-V.:Ultrathin Multicomponent Poly(ether sulfone)Membranes for Gas Separation Made byDry/Wet Phase Inversion. Ind. Eng. Chem.
Res., 29 (1990), 2028-2032. Qureshi, N.; Maddox, I.S.; Friedl, A.:
Application of Continuous Substrate Feedingto the ABE Fermentation: Relief of ProductInhibition Using Extraction, Perstraction,Stripping and Pervaporation. Biotechnol.Prog., 8 (1992), 382-390.
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Literature-12
Strathmann, H.; Bell, C.-M.; Gudernatsch, W.;Kimmerle, K.: Die Entwicklung vonLösungsmittel-selektiven Membranen und ihre
Anwendung für die Gastrennung und
Pervaporation. Chem.-Ing.-Tech., 60 (1988),590-603.
Strathmann, H.; Bell, C.-M.; Kerres, J.: GasSeparation and Pervaporation: Membrane andModule Development. Desalination, 77 (1990),259-278.
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Literature-13
Streicher, C.; Kremer, P.; Tomas, V.; Hubner, A.; Ellinghorst, G.:
Development of new pervaporation membranes, systems and
processes to separate alcohols/ethers/hydrocarbons mixtures.
Proc. 7th Int. Conf. on Pervap. Proc. in Chem. Ind., Reno
(NV/USA), 1995, R.Bakish (Ed.), Bakish Materials Corporation,Englewood (NJ, USA), 297-309.
Udriot, H.; Araque, A.; von Stockar, U.: Azeotropic mixtures may
be broken by membrane distillation. Chem. Eng. J., 54 (1994),
87-93. Ward, R.R.; Chang, R.C.; Danos, J.C.; Carden, J.A.: Processes
for coating bundles of hollow fiber membranes. US Pat.
4,214,020 (1980).