Comparison of two dynamic models for FCC units

Modelling of FCC units has been an interesting activity because of the complexity of the system and the economic incentives associated. Models have been classified depending on either the used kinetic scheme or the proposed reactor configuration. The main problems to assess are the elimination of coke when catalyst is regenerated and the delicate interaction between reactor and regenerator due to the global energy balance. In this work two models, each one using a different kinetic scheme, a different formulation for the catalyst activity and a different conception of the regenerator are compared when simulating the same FCC unit. Steady-state predictions and dynamic phenomena such as stability and multiplicity are simulated. In order to emphasise the ability for predicting the dynamic phenomena, the obtained results are compared in terms of accuracy and computing resolution time. It is pointed out that even though the complexity of a model could be a limiting factor for control purposes, in the case of dynamic studies this factor is not a constraint and it is possible to use more complex models. It is also emphasised that the most useful model will be the one which fulfils the requirements of the researcher, the situation to be modelled and the results that could be necessary.