1. Introduction - Firenze University Press

K
~
K 1
eK 1a p K 1a
iK
mK
N m
c T
, (3)
The mass flow rate flowing through the expander is lower than the oxygen mass flow rate separated
in the membrane by the mass flow rate flowing through the compressor. This mass flow rate
depends on the oxygen mass flow rate separated from the air in the membrane ( m O2 ) and the air
flow rate ( m 1a ). The relationship between these quantities is as follows:
m m
m
, (4)
4a
1a
O2
The expander effective power depends on the retentate mass flow rate ( a m 4 ), the retentate
temperature ( T 4a ), the average specific heat ( ~c p ), the compressor pressure ratio (
K
K ),the
reduction factor of compressor pressure ratio ( ), the heat capacity ratio contained in the factor
1
( T ), the expander isentropic efficiency ( iT ) and the expander mechanical efficiency
T
( mT ). The equation showing the relationship between these quantities is as follows:
~ T
N m
c T 1 ( )
,(5)
eT
4a
p 4a K iT mT
T
Figure 3 shows computed gross electric power as a function of oxygen recovery rate. The curve in
this figure is determined for K =20 and t 3a =750 o C. The gross electrical power depends on the
expander gross power ( N eT ), the compressor gross power ( N eK ) and the generator efficiency ( g ).
The relationship between these quantities is as follows:
elTG
N eT eK g
N N , (6)
Electrical power of gas turbine, MW
80
60
40
20
0
-20
40 45 50 55 60 65 70 75 80 85 90 95 100
Oxygen recovery rate, %
Fig. 3. Electrical power achieved or required for power the turbine set in ASU model as a function
of oxygen recovery rate for K =20 and t 3a =750 o C
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