Membrane Gas Separation

 
 ® 
  
/PEG blend membranes is 
similar when compared with pristine polymer at 8 bar (around 17), but by increasing the 
pressure it dropped ( 
∼
10), which is most evident in blends with higher PEG content 
(Pebax  
 ® 
  /PEG with 50 wt.% of PEG). As expected and according to the sorption effects 
of CO 
2
and CH 
4
, the high fl ux ( 
>
0.33 m 
3
/m 
2
h bar) of CO 
2
in this mixture is accompanied 
with a fl ux increase of CH 
4
, which leads to lower selectivity in mixed gas.
These membranes, evaluated at different temperatures, presented promising results 
[93] . They also presented good stability and a CO 
2
fl ux higher than 0.5 m 
3
/m 
2
h bar was 
obtained at 55 ° C, which is approximately the fl ue gas temperature. This membrane was 
tested and used for simulation and optimization of multi - stage membrane systems used 
8
10
12
14
16
18
20
0,1
0,2
0,3
0,4
0,5
Total fugacity [bar] 
0,1
0,2
0,3
0,4
Fl
ux of CO
2
[m
3
/ (
m
2
h ba
r)] 
0,1
0,2
0,3
0,4
0,5
CO
2
/ H
2
mixture
CO
2
/ N
2
mixture
CO
2
/ CH
4
mixture
Figure 12.15 Flux of CO 
2
in mixed gas as a function of total fugacity. ( -
䊏
- 0% PEG, 
 -
䊊
- 10% PEG, -
䉱
- 20% PEG, -
䉮
- 30% PEG, -
䉬
- 40% PEG and -
夽
- 50% PEG [Reprinted 
with permission 93 ]

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248
Membrane Gas Separation
6
8
10
12
14
16
18
20
20
30
S
ingle gas
Mixed gas
Total fugacity 
[
bar
]
60
75
90
105
S
ingle gas
Mixed gas
9
12
15
18
21
α
(CO
2
/ H
2
)
α
(CO
2
/ N
2
)
α
(CO
2
/ CH
4
)
Mixed gas
S
ingle gas
Figure 12.16 CO 
2
 /gas selectivity in single gas and different mixed gas as a function of 
fugacity. ( -
䊏
- 0% PEG, -
䊊
- 10% PEG, -
䉱
- 20% PEG, -
䉮
- 30% PEG, -
䉬
- 40% PEG and 
 -
夽
- 50% PEG . Reprinted with permission from Advanced Functional Materials, Tailor - made 
polymeric membranes based on segmented block copolymers for CO 
2 
 separation, by A. 
Car, C. Stropnik, W. Yave, K. - V. Peinemann, 23, 2815 – 2823, Copyright (2008) Wiley - VCH
in a coal - fi red power plant [94] . Based on ideal feed gas of 14% CO 
2
and 86% N 
2
, a 
two - stage cascade membrane system presented the best results. For the developed mem-
brane (Pebax 
® 
/PEG) a CO 
2
- capture cost of 57 Euro/tonne of separated CO 
2
was calculated 
which is clearly higher than absorption process (30 – 50 Euro/tonne). However, an improve-
ment of fl ux from 0.5 to 1.4 m 
3
(STP)/m 
2
h bar can reduce the cost to 40 Euro/tonne, which 
demonstrates that membrane technology can compete with absorption process, although 
a membrane with higher fl ux is required.