Separation of Carbon Dioxide and Methane Using Well-Mixed Gas Permeation

stage cut

0.4

feed composition

0.4

A mixture of carbon dioxide and methane are to be separated by a cellulose acetate membrane at 35 °C.

The permeability of carbon dioxide and methane are

15.0×

-10

10

and

0.48×

-10

10

3

cm

(STP)cm/

2

cm

scmHg

, respectively. Thus, the selectivity,

α

CO2-CH4

=31.25

.

The high (retentate side) and low (permeate side) pressures are 20.0 and 1.1 atm, respectively.

The Demonstration plots (1) the RT curve, which relates

CO

2

mole fractions on both sides of the membrane, and (2) the operating line, whose slope depends on the stage cut,

θ

.

Assuming that both retentate and permeate sides are well mixed, the graphical solution of this gas permeation problem is given by the intersection point shown in cyan in the figure. You can set the value of the feed composition (i.e. mole fraction of

CO

2

) as well as the stage cut.