Information Technology Reference
In-Depth Information
1. Ethylbenzene is converted to styrene by the catalytic dehydrogenation reaction
C
8
H
10
(
g
)
→
C
8
H
8
(
g
)
+
H
2
(
g
)
The presence of steam in the reactor is known to suppress side reactions.
2. Fresh ethylbenzene, stream 1, and a recycle, stream 15, containing primarily
liquid ethylbenzene, combine at A, producing stream 3, which is heated to 500
◦
C
at B, producing stream 4.
3. A recycle, stream 11, which is primarily water, is combined with stream 14, a
freshwater makeup, at E, producing stream 13 at 50
◦
C.
4. Stream 13 is heated to 700
◦
C, producing stream 5, which is combined with
stream 4 at C, producing stream 6 at 560
◦
C.
5. Stream 6 feeds the reactor, F. Stream 7 exits the reactor at a temperature and
pressure of 560
◦
C and 14.7 psi, respectively. The reaction conversion is 35%.
6. Stream 7 is cooled to 50
◦
C at G, producing stream 9, which is primarily H
2
,
and goes to another part of the plant. Stream 8 is cooled further to 25
◦
CatH,
to separate the water, stream 11, and organics, stream 10.
7. Ethylbenzene and styrene in stream 10 are separated at J, producing the prod-
uct stream 12, containing primarily styrene, and a stream containing primarily
ethylbenzene, which is condensed at K, producing stream 15.
The process model is to be based on the following:
Stream 1: 100 lbmol/hr of pure ethylbenzene at 25
◦
C and 14.7 psi
Stream 14: 40 lbmol/hr of pure water at 25
◦
C and 14.7 psi
The entire process operates at approximately 1 atmosphere.
12.3 A MODEL WITH BASIC BLOCKS
The first model of this process was developed using split blocks for the separations.
The process description above was used to estimate the split values and a simple
conversion based block was used to describe the reaction. The model results are given
at Chapter Twelve Examples/Example Twelve-1. Analysis of the results seem to agree
with the process description.
12.4 PROPERTIES
There are three separations that require rigorous modeling in the development of
a process flow diagram. All the necessary pure component data are available in
the Aspen Plus data bank. Vapor-liquid, equilibrium and liquid-liquid equilibrium
data are required to model the flash, the decantation, and the distillation elements
of the process. The Uniquac binary parameters stored in Aspen Plus will be used
as a source for the equilibrium data. Property analysis runs designed to present
vapor-liquid equilibria for the three possible systems exclusive of hydrogen are
shown at Examples/ExampleTwelve1-a. Figure 12.2 shows the binary parameter data
