Plug flow reactor, adiabatic operation heat transfer

For adiabatic operations, HTN = 0 (no heat-transfer area), and for plug-flow reactors Eq. 5.2.55 reduces to... 

Parametric Sensitivity. One last feature of packed-bed reactors that is perhaps worth mentioning is the so-called "parametric sensitivity" problem. For exothermic gas-solid reactions occurring in non-adiabatic packed-bed reactors, the temperature profile in some cases exhibits extreme sensitivity to the operational conditions. For example, a relatively small increase in the feed temperature, reactant concentration in the feed, or the coolant temperature can cause the hot-spot temperature to increase enormously (cf. 54). This sensitivity is a type of instability, which is important to understand for reactor design and operation. The problem was first studied by Bilous and Amundson (55). Various authors (cf. 57) have attempted to provide estimates of the heat of reaction and heat transfer parameters defining the parametrically sensitive region for the plug-flow pseudohomogeneous model, critical values of these parameters can now be obtained for any reaction order rather easily (58). 

All simulators provide one-dimensional, plug-flow models that neglect axial dispersion Thus, there are no radial gradients of temperature, composition, or pressure and mass diffusion and heat conduction do not occur in the axial direction. Operation of the reactor can bt adiabatic, isothermal, or nonadiabatic, nonisothermal. For the latter, heat transfer to or fron the reacting mixture occurs along the length of the reactor. 

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