TURBULENT MICROMIXING IN CHEMICAL REACTORS - A REVIEW

The idea of micromixing, its definition and measures are outlined. The concepts of mixing environments and mixing earliness are presented. T he paper concentrates on the effects of turbulent mixing of incompress ible fluids in single-phase systems on the course of chemical reaction s. The processes of turbulent micromixing are discussed in detail: the fluid mechanical interpretation of turbulent micromixing (effect of f luid element deformation on the acceleration of molecular diffusion, e ngulfing of environment, inertial-convective disintegration of large e ddies and local intermittency) is presented. It is concluded that stre tching of material elements and vortices, accompanied by molecular dif fusion results in the growth of the mixing zones. The growth of the zo ne mixed on the molecular scale is a characteristic feature of micromi xing and should be included in micromixing modelling. The characterist ic time constants for the consecutive stages of mixing are presented a nd compared with the characteristic time for chemical reaction - the n umerical criteria are outlined. The two approaches, i.e. eulerian and lagrangian, are described; it is shown that each requires different me thods of description and generates specific problems (closure problem, problem of environment). The applications of the micromixing theory t o the most important fields of industrial practice, such as complex re actions, precipitations and polymerizations, are outlined.