ppt on gas and liquid permeation

1. GAS PERMEATION AND LIQUID PERMEATION
Step 1
Step 2
Step 3
ASHWINI KUMAR
RISHABH RAJ

2. PERMEATION
Permeation is the penetration of a permeate (such as
liquid,gas or vapour) through a solid.
 It is directly related to the concentration gradient of the
permeate, a material's intrinsic permeability, and the
materials' Mass diffusivity.
 Permeation is modeled by equations such as Fick's laws
of diffusion, and can be measured using tools such as a
minipermeameter.
 Permeation works through diffusion; the permeant will
move from high concentration to low concentration
across the interface.

3. THEORY
 Gas permeation is the term used to describe a membrane
separation process using a non-porous semi-permeable
membrane. In this, a gaseous feed stream is fractionated
into per-meate and non-permeate streams. Transport
occurs by a solution-diffusion mechanism and
membrane selectivity is based upon the relative
permeation rates of the components through the
membrane. Each gaseous component transporting
through the membrane has a characteristic permeation
rate that is a function of the ability to dissolve and
diffuse

4.  Separation mechanism:
different velocity of gas permeation (sorption, diffusion,
sieving effect, desorption)
 Driving force: partial pressure gradient.
 Working pressure: up to 100 bar.
 Non-porous polymeric membranes:
PDMS(polydimethylsulphoxan),PS(polysulphone),PES.
 Ceramic Membranes (small pores for Knudsen).
 Metallic membranes (Pd and Ag alloys).

6. process
 In the process as shown in fig. The feed gas at high
pressure P1 contains some low molecular weight species
(molecular weight <50) to be separated from small
amounts of high molecular weight species.
 The other side of the membrane is maintained at much
lower pressure P2 often near ambient pressure the
membrane used is micro pores perm selectivity for
certain low molecular weight species in the feed
gas(species A)
 If the membrane is dense these species are absorbed at
the surface and then transported though the membrane
by one or mechanism.

7.  Thus perm selectivity depends on both membrane
adsorption and membrane transport rate.
 In this process perfect separation is generally not
achievable, If the difference of molecular weight of
substance is near by.

8. Calculation:
 The gas permeability was calculated according to the
following equation.
 where l is the film thickness (m), Q is the permeate
volumetric flow rate (mol/s), p2 is the feed absolute
pressure, p1 is the downstream absolute pressure (Pa)
and A is the membrane area available for transport (m2).
Permeability is reported in units of (mol. m /(m2.s.Pa)).

9. Application:
 Separation of hydrogen from methane,
 Removal of carbon di oxide,
 Removal of organic solvent from air,
 Nitrogen enrichment from air.

10. Advantages:
 Low capital investment,
 Ease of installation,
 Ease of operation,
 High pressure flexibility,
 Low weight and space requirement,
 Low environmental impact.

11. Gas
permeation
Residuals gases
to fuel-gas
Hydrogen
Recycle of n-C4
Unitat de
isomerització
n-Butane
Isobutane
Recycle
H2 (96%)
Hydrogen recovery in a butane isomeration plant. A typical PRISM®
Separator
(Airproducts)

12. LIQUID PERMEATION
 DEFINITION-When a volatile liquid mixture is
imposed on the feed side of a nonporous membrane and
the other side of the membrane has a liquid phase ,the
process is called liquid permeation.
 The molecular structure of the permeating gas or liquid
is an important factor in permeation.Liquid permeation
depends upon the molecular size of the liquid,that is to
say,molecules such as pentane permeate more rapidly
than larger molecules such as decane.

13.  The polarity of the liquid also plays an important role in
permeation.For example,non polar liquids such as
toluene permeate more rapidly than polar aniline in
membranes such as polyethylene.