Dissociation in a Tubular Reactor
Model ID: 221
Tubular reactors are often used in continuous large-scale production, for example in the petroleum industry. One key design and optimization parameter is the conversion, or the amount of reactant that reacts to form the desired product. In order to achieve high conversion, process engineers optimize the reactor design: its length, width and heating system. An accurate reactor model is a very useful tool, both at the design stage and in tuning an existing reactor.
This example deals with a gas-phase dissociation process, species A reacts to form B. First, the conversion and reaction distribution is modeled as an isothermal tubular reactor under steady-state conditions. Secondly, the temperature dependence of the reaction kinetics are included and the changes in reaction distribution and conversion are studied.
This model illustrates several attractive features in the Chemical Reaction Engineering Module:
- The use of the Transport of Concentrated Species to account for multicomponent diffusion.
- How to couple the variable density to a Laminar Flow interface.
- Implementation of temperature- and composition?dependent reaction kinetics.
- The use of a mapped mesh, which is structured, to discretize a long and thin geometry, typical for tubular reactors
- The setup of heat balances and how to couple these to both the mass balances and the velocity field
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REACTIVE FLOWS: A simple tubular reactor is modeled where an irreversible dimerization reaction of a species (i.e., A -> 2B) takes place. As the reactant is consumed, the concentration in the gas phase increases, which leads to an expansion of the gas mixture, and an acceleration in the flow field. |
