ChE 211, Process Simulation
Exam 2
Instructions:
Open note
NOT open book (this section isn’t covered in the book anyway)
NOT open computer
Where it is appropriate, write your answers on the screen-shot. Feel free to
change the units if needed, or to fill in a value that you think will show up
after your initial selection.
Given the process description:
One system for producing styrene monomer is as follows. Toluene and
methanol are mixed, brought to temperature and fed into a reactor. The
product from the reactor is cooled, then decanted to separate the organic and
aqueous products. Hydrogen bubbles out at this step.
The organic stream is fed to a distillation column. The overhead product
becomes a toluene recycle and is pumped through a heater to be brought
back to reactor conditions. The bottoms product is fed to another
distillation column and separated into an ethylbenzene stream
(overhead) and a styrene monomer stream (bottoms).
The aqueous stream is fed to a distillation column to separate a methanol
recycle stream (the overhead product) from a waste water stream (the
bottoms product). The recycle is again pumped through a heater to come
back to reactor conditions.
Feed Conditions: saturated vapor at 460 kPa.
Reactor Temperature: 540 °C
Cooler outlet temperature: 38 °C
Molecular weight of styrene monomer: 104.152
Distillation Columns: 9 theoretical trays, top tray pressure 135 kpa, feed tray
6
Reactions:
C7H8 + CH3OH  C8H8 + H2O + H2
toluene
methanol
styrene
C7H8 + CH3OH  C8H10 + H2O
toluene
methanol
ethylbenzene
1.) Sketch a Pro/II PFD for the process Label your streams and unit ops: (10 pts)
2.) Show how you would specify the toluene feed to be saturated at 460 kPa. (10
pts)
3.) Pick a reasonable Toluene feed flowrate if you want to produce 250,000 metric
tons in a 8,320 hour year. (10 pts)
4.) What specification should we use for the reactor feed heater? (10 pts)
5.) Fill in the reaction data. (10 pts) Note, just right down what the name and
definition columns would look like when you are done putting in your
reaction(s).
6.)
Based on the information given, which type of reactor would you choose and
why? (15 pts)
7.)
Since pro/II doesn’t have a decanter, I am trying to duplicate the
functionality with a flash drum. The Flash product phases are set as follows: (10
pts)
What would be an appropriate second specification?
8.)
Specifications on the recycled Toluene stream are that it has a maximum of 4
wt% ethylbenzene, and a maximum combined 5 wt% ethylbenzene and styrene
monomer. How would you input the second of these as a column specification? (15
pts)
1) Sketch a Pro/II PFD for the process Label your streams and unit ops:
(5 pts)
2) Show how you would specify the toluene feed to be saturated at 460 kPa. (5
pts)
3.)
Pick a reasonable Toluene feed flowrate if you want to produce 250,000
metric tons in a 8,320 hour year. (5 pts)
250000 metric tons Styrene| 1000 kg | 1 kg mol styrene | 1 kg-mol Toluene
8320 h
| metric ton | 104.152 kg
| 1 kg-mol styrene
= 288.5 kg-mol toluene/hr
300 kg-mol toluene/hr would be a reasonable, and easier to work with
number that would give us a bit for the side reaction producing
ethylbenzene.
I am using 300 kg-mol/hr methanol also.
4.) What specification should we use for the reactor feed heater? (10 pts)
5.)
Fill in the reaction data. (10 pts) Note, just right down what the name and
definition columns would look like when you are done putting in your reaction(s).
6.)
Based on the information given, which type of reactor would you choose and
why? (15 pts)
While a Gibbs reactor might be a good choice because we don’t have
equilibrium or conversion data give, we also have 6 chemical species and 3
effective atoms. This means we need 3 reactions, but we only have 2. Sadly
none of the reactor will work without additional information.
7.)
Since pro/II doesn’t have a decanter, I am trying to duplicate the
functionality with a flash drum. The Flash product phases are set as follows: (5 pts)
What would be an appropriate second specification?
Honestly, I’m not positive, but I think this would be appropriate.
8.)
Specifications on the recycled Toluene stream are that it has a maximum of 4
wt% ethylbenzene, and a maximum combined 5 wt% ethylbenzene and styrene
monomer. How would you input the second of these as a column specification? (15
pts)
assuming that styrene and ethlybenzene are next to each other in your
component list: