Page 292 - Chiral Separation Techniques

10.4 Example of process design 271

Equation 13 is used to calculate the SMB flow rates. To ensure a throughput of 10
–1
tons/year of the racemic mixture we need a feed flow rate of 1250 L h . The γ value
must fulfill 1 ^ γ ^ 1.22 with our recommended value of 1.02.
The reduced flow rates given by Equation (12) are thus:

m = 3.213 m = 2.142 m = 3.088 m =2.059
I II III IV
leading to the following internal flow rates for the TMB:
–
Q= 1321 l h –1
Q = 4244 l h –1 Q = 2829 l h –1 Q = 4079 l h –1 Q = 2719 l h –1
I II III IV
The inlet-outlet flow rates are then given by:

Q = 1415 l h –1 Q = 1250 l h –1 Q = 1360 l h –1
ext Feed Raf
Calculation of the SMB flowrates: The flow rate in each zone of a TMB is
related to the flow rate of a SMB by Equation (20):

Q SMB = Q TMB + ε ⋅ Q.
I I 1− ε
Consequently, one obtains for the SMB:
Q = 5125 l h –1 Q = 3710 l h –1 Q = 4960 l h –1 Q = 3600 l h –1
I II III IV
the mean value of the flow rates in the different zone is thus approximately Q mean =
–1
4350 l h .
Calculation of the SMB system: The SMB system requires between 200 and 400
theoretical plates for an enantioselectivity of 1.5. The working system pressure is
10 bar. With the equations for the HETP and the pressure-drop, we have two equa-
tions for two unknowns.

HETP = L = L = 0 0003 0. u ⋅ 7
+
.
N 300
∆ P = 10 u ⋅
L L = 1097
To solve the total column length for the SMB system, one eliminates the fluid
velocity:

L = 0 0003 0 7⋅. + . 10
⋅
300 L 1097
L − 0 09⋅ −. L 1 91 0
=
2
.