Reaction submodels for the A7 example simulation

This example includes two reaction submodels in the simulation-specific Model Library:

• RxnConversion

• MTBEkinetics

RxnConversion

The RxnConversion submodel is a simple stoichiometric reaction submodel based on conversion rates. We use it only in the conversion reactor (R1) in the reaction section of the process plant. It includes the following reactions:

We model the equations such that the base components for each reaction are ITBE, water, and methanol, respectively.

Figure 9: MTBE conversion reaction submodel

MTBEkinetics

The MTBEkinetics submodel is a rate-based reaction submodel. We use it only in the reactive distillation column (T1) in the reaction section of the process plant. It includes only the following reaction:

We base the MTBE reaction rate expression on the rate expression described in a paper by Al-Jarallah et al.2. The reaction rate equation described by Al-Jarallah et al. takes into account the forward and the reverse reaction. We have modified the rate equation from Al- Jarallah et al. for this example to simulate the effect of catalyst loading on the reaction rate. We achieved this by removing the catalyst terms from the concentration terms. The following equations give the modified reaction rate:

where

ks is the surface reaction rate constant in (gmol/g catalyst)^1.5/hr

KA is the equilibrium adsorption constant of IBTE in g catalyst/gmol

KC is the equilibrium adsorption constant of MTBE in g catalyst/gmol

Keq is the equilibrium constant

CA is the IBTE concentration in mol/L

CB is the MEOH concentration in mol/L

CC is the MTBE concentration in mol/L

The following figure shows the kinetic equations as modeled in AVEVA Process Simulation.

Figure 10: MTBE kinetic reaction submodel