Simulation model

The simulation model is based on Turton’s1 design except that it also incorporates a feed effluent heat exchanger, as suggested by Luyben2. The control scheme is based on Luyben’s control design except that we manipulate the reflux of the benzene column to control the top stage temperature instead of manipulating the feed-to-reflux ratio. Similar to Turton’s work, the simulation model also uses SRK thermodynamics with VLE.

We use the same rate expressions for the surface kinetics reported by Turton.

Reaction 1

where

r1 is the rate of reaction 1 in mol/(g catalyst)-sec

k1 is the reaction constant for reaction 1

cp is the concentration of propylene in mol/L

cb is the concentration of benzene in mol/L

T is the temperature in Kelvin

Reaction 2

where

r2 is the rate of reaction 2 in mol/(g catalyst)-sec

k2 is the reaction constant for reaction 2

cp is the concentration of propylene in mol/L

cc is the concentration of cumene in mol/L

T is the temperature in Kelvin

Catalyst

Both reaction rates are specific to the catalyst reference conditions:

• Catalyst mass density (rcat)= 1600 kg/m3

• Catalyst void fraction (e) = 0.5

To derive the reaction rates for the individual reactants, we must multiply the preceding rate expressions by the catalyst mass, which relates to the reactor volume, V, the catalyst void fraction, e, and catalyst density, rcat, as follows:

where

Gi1 is the production or consumption rate in kmol/s for component i in reaction 1

Gi2 is the production or consumption rate in kmol/s for component i in reaction 2

V is the reactor volume in m3

e is the catalyst void fraction

rcat is the density of the catalyst in kg/m3

r1 is the rate of reaction 1 in kmol/(kg catalyst)-sec

r2 is the rate of reaction 2 in kmol/(kg catalyst)-sec

Additional features

The simulation also includes the following specific elements of AVEVA Process Simulation.

• AVEVA Process Simulation’s Column model.

• AVEVA Process Simulation’s model writing environment, which we use to formulate the following:

  • The kinetics of the chemical reactions.

  • The plug flow reactor modeled as an array of reactor elements.

• AVEVA Process Simulation’s Stream model, which reports component molar rates that are important in the context of reaction models.

• AVEVA Process Simulation’s Recycle model, which allows you to break recycles for open loop calculations to initialize recycles in a sequential modular manner. We insert Recycle models into the following:

  • The benzene recycle.

  • The thermosiphon circulations for both columns.

• AVEVA Process Simulation’s Heat Exchanger (HXTR) model.