ABSTRACT
Introduction In this chapter, we move to the situation where the reactors are no longer ideal and begin our description by showing how the ideal PFR and MFR can be represented in terms of each other. As a result, we expect to develop an understanding of how simple combinations of these ideal reactors can be used to describe the behavior of complex reaction/reactor geometries. Then we logically move on to the subject of nonidealities in chemical reactors and go into the considerations of channeling and bypassing in MFRs and axial and radial dispersion in PFRs. While discussing these, we explain the RTD theory and axial dispersion theory. The RTD theory is a very frequently employed method of treating nonidealities in chemical reactors. Thus, we focus a little more on this theory in the next section and give its merits and demerits. In the same section, we also discuss the concept of mixing and give four commonly used mixing models from the literature. We dedicate the next section
to modern theories of mixing that include the turbulent theory, the socalled zone model, the IEM model, the engulfment-deformation models, and the joint PDF model. We conclude the treatment by giving a comparative analysis of the timescales of different processes and their relevance to mixing.
