Integral Isothermal Reactor Models

Summary

In Chapter 3 we considered chemical reactors with ideal macro flow patterns, where the reactor behaviour was independent of scale. In Chapters 4, 5 and 6 an overview was given of various physical phenomena on the intermediate scale, some of which interact with chemical reactions. Several of these phenomena are scale dependent. To arrive at integral reactor models, we have to consider macro-flow effects, i.e. the effects of transport phenomena on the scale of the reactor dimensions. These are as a rule strongly scale dependent.

In most batch reactors macro flow effects are of little consequence, though there are a few important exceptions. In semi-batch reactors the macro-flow effects may be particularly relevant in view of the selectivity of the process.

For describing macro-flow effects in continuous reactors the concepts of residence time distribution, backmixing and axial dispersion or axial mixing are used.

Mass balances including volume element models and macro-flow effects have to be integrated to arrive at integral reactor models.

For reactors with two process streams, mass balances have to be made for each stream, and these have to be integrated. The results are different for countercurrent, cocurrent or mixed flows.