Independent thesis Advanced level (professional degree), 20 credits / 30 HE credits
Chemical reactors are a part of modern industry and the catalytic tubular ﬁxed bed reactor examined in this work is an important reactor for chemicals production.
In this work two diﬀerent types of models for the reactor are studied; a pseudohomogeneous model and a heterogeneous model. The goal is to ﬁnd diﬀerences in behaviour between these two types of reactor models and explain these.
In a real reactor there exists two phases, a solid catalyst and a ﬂuid reactant. Both these phases are in the pseudohomogeneous model treated as a single phase, a pseudoﬂuid. In the heterogeneous model the two phases are treated separately.
When comparing these types of models a few structural diﬀerences exist, void fraction, heat exchange between two phases, and heat dispersion in the phases, and all of these will aﬀect the behaviour of the models diﬀerently.
The models are studied using bifurcation analysis and linear analysis. Bifurcation theory is used to ﬁnd and track diﬀerent solutions depending on a certain parameter and to get a good overall picture of a system’s solutions and their type, steady state or sustained oscillation.
Linear analysis is used to study linearization around a speciﬁc solution and to determine stability and frequency dependency.
It is found that the concept of void fraction in the reactor model aﬀects the behaviour only as a time scaling, while the concept of interfacial heat exchange aﬀects the stability. The distribution of heat dispersion between phases has a signiﬁcant impact on the reaction behaviour. Feedback is determined as the main cause for instabilities and oscillative solutions.
2005. , 43 p.