Results match in mix tests
15 Jan 2000
Scaling-up reactors is a perennial problem in process design. Reactions are carried out in small reactors while processes are being developed, but the same reaction carried out at industrial scale can perform differently.
A set of reactions causing particular problems, under investigation by a consortium of companies including Neste and EniChem, are competitive reaction systems. Here, a fast reaction procedes simultaneously with a slow one. When the reactants are well mixed, the fast reaction predominates. But in large tanks, mixing can vary widely, and the selectivity of the reaction can plummet.
Neste is currently developing a computational fluid dynamics model to help design stirred tank reactors. The team, led by Jukka Kosinken, is using AEA Technology's CFX package to model kinetics, thermodynamics and flows within the reactor and comparing the results with real reactors.
First results on the validation have been encouraging. Using a model which simulated the resistance effects of the bundles of tubes which heat the reaction mixture, the team calculated a `mixing timescale' for the reactor. This, they have now confirmed, coincides precisely with the results of an experiment using acid as a tracer material in the tank.
