Nature of Homogeneous and Catalytic Reactors

Multi-scale Nature of Homogeneous and Catalytic Reactors 

The issue of multiple time scales is also present in the case of homogeneous tank reactors. As in Fig. 2, a tank reactor consists of several circulating flow loops which exchange material with each other and within which micromixing occurs at the continuum scale. Therefore, there are three physical length scales present in a tank reactor. The size of the reactor is the macroscale. The meso length scale could be anywhere from the size of a circulation loop to the size of an eddy (or cell). The continuum scale is the microscale. The time scales 

Channel Diameter 0,5- 2 mm Washcoat Thickness 10-50 im Support Thickness 100 - 180 p.m 

In all of the above cases, a strong non-linear coupling exists between reaction and transport at micro- and mesoscales, and the reactor performance at the macroscale. As a result, the physics at small scales influences the reactor and hence the process performance significantly. As stated in the introduction, such small-scale effects could be quantified by numerically solving the full CDR equation from the macro down to the microscale. However, the solution of the CDR equation from the reactor (macro) scale down to the local diffusional (micro) scale using CFD is prohibitive in terms of numerical effort, and impractical for the purpose of reactor control and optimization. Our focus here is how to obtain accurate low-dimensional models of these multi-scale systems in terms of average (and measurable) variables. 

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B. Multi-scale Nature of Homogeneous and Catalytic Reactors... 

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