Aspen+plus案例教程-苯加氢生产环己烷.pdf

Aspen Plus Tutorial 1: Hydrogenation of Benzene
Hydrogenation of benzene is used to produce cyclohexane in the process showed below.
This example is typical of a model developed for preliminary process flowsheet evaluation.§ Fresh benzene and make-up hydrogen are mixed with recycle hydrogen and recycle cyclohexane from the process and fed to a fixed-bed catalytic reactor. In the reactor, the reaction is
C6H6 + 3H2 C6H12
The heat released from this highly exothermic reaction is removed by boiling water outside tubes containing the catalyst pellets. The reactor effluent is cooled and separated into liquid and vapor phases. The liquid phase is fed to a distillation column to remove the dissolved light ends and to stabilize the liquid product. Part of the liquid from the separator is recycled to the reactor to aid in temperature control.
Once a flowsheet simulation model of the process is developed, it can be used to investigate the effect of the cyclohexane recycle rate on the heat load from the reactor. We can also study the effect of the purge rate on the buildup of inert components in the system.
For now, you just need to put the flowsheet together. Use the Redlich-Kwong-Soave (RK-SOAVE) property method in the simulation. The input data are listed as follows:
§ The description here is taken verbatim from an old Aspen Manual. When you write a report, you need to make a decision if the description should include explicitly the unit and stream labels. Roughly, we do not if we are just making a general conception description. Otherwise, we do if we are writing a technical description of the process and how it is designed.
Feed Streams
Composition (Mole Percent) Fresh Benzene Make-up Hydrogen
97.5
Hydrogen -
0.5
Nitrogen -
2.0
Methane -
-
Benzene 100.0
Flow rate (lb-mol/h) 100 300 (estimate*)
Temperature (°F) 100 120
Pressure (psia) 15 335
*
The flow of make-up hydrogen should be set to obtain a mole ratio of
hydrogen to benzene equal to 3.3 in the feed to the reactor
Feed Pump
Centrifugal pump
Outlet pressure (psia) 335
Feed Preheater
Outlet temperature (°F) 300
Pressure drop (psi) 5
Reactor
Stoichiometry: as stated in the process description
Conversion 99.8 percent conversion of benzene in feed
Outlet temperature (°F) 400
Pressure drop (psi) 15
Product Cooler
Outlet temperature (°F) 120
Pressure drop (psi) 5
Separator
Heat loss negligible
Pressure drop negligible
Purge
Purge rate 8 percent of vapor from separator
Recycle Compressor
Positive displacement
Outlet pressure (psia) 335
Cyclohexane Recycle
Recycle flow 30 percent of liquid from separator
Recycle Pump
Centrifuge pump
Outlet pressure (psia) 335
Stabilizer (Column)
No. of theoretical stages 13 (plus additional condenser and reboiler)
Feed location 8 (counting from top, condenser = 1)
throughout Pressure 200
psia Reflux ratio 1.2
Cyclohexane recovery 99.99 percent in bottoms
Partial condenser
Distillate is vapor product。