Page 114 - Process simulation and control using Aspen

104 PROCESS SIMULATION AND CONTROL USING ASPF.N

SUMMARY AND CONCLUSIONS |

This chapter presents the simulation of several reactor models. Here, we have considered
a variety of chemical reactions in the Aspen Plus simulator. Probably the most useful
kinetic models. Power law and Langmuir-Hinshelwood-Hougen-Watson (LHHW). have
been used in the solved examples. A number of problems are given in the exercise for
extensive practice.

PROBLEMS |

2 .1 Ethyl acetate is produced in an esterification reaction between acetic acid and
ethyl alcohol.
acetic acid + ethyl alcohol <-> ethyl acetate + water
The feed mixture, consisting of 52.5 mole% acetic acid, 45 mole% ethyl alcohol
and 2.5 mole% water, enters the RCSTR model with a flow rate of 400 kmol/hr at
750C and 1.1 atm. The reactor operates at 70oC and 1 atm. Both the reactions
are first-order with respect to each of the reactants (i.e., overall second-order). For
these liquid-phase reactions, the kinetic data for the Arrhenius law are given below:
Forward reaction: k = 2.0 x 108 m3/kmol - s
E= 6 0 x 107 J/kmol
.
Reverse reaction: k = 5.0 x 107 m3/kmol . s
E= 6 0 x 107 J/kmol
.
[C,l basis = Molarity

Perform the Aspen Plus simulation using the NRTL thermodynamic model and
reactor volume of 0.15 m 3
.
2 .2 Repeat the above problem replacing RCSTR model by RStoic model with 80%
conversion of ethyl alcohol.
2 .3 Simulate the reactor (Problem 2.1) for the case of an RGibbs model.
2 .4 An input stream, consisting of 90 raole% di-tert-huty\ peroxide, 5 mole% ethane
and 5 mole% acetone, is introduced in a CSTR at 10 atm and 1250C and a flow
rate of 0.2 kmol/hr. The following elementary irreversible vapour-phase reaction
is performed isothermally with no pressure drop.
(CH3)3COOC(CH3)3 C2H6 + 2CH3COCH3

Fake kinetic data for the Arrhenius formula are given as:
k = 1.67 x 104 kmol/m3 s (N/m2)
£ = 85 x 103 kJ/kmol
LCJ basis = Partial pressure
The reactor operates at 50oC and its volume is 6 m3. Using the SYSOP0
thermodynamic method, simulate the CSTR model and compute the component
mole fractions in the product stream.