INVESTIGATION OF MIXING IN JET REACTORS USING FAST, COMPETITIVE CONSECUTIVE REACTIONS

Although several aspects of turbulent free jets have already been stud ied, multi-step mixing-controlled reactions in liquid jets were not wi dely investigated. A network of five well-characterized chemical react ions having a mixing-sensitive product distribution was considered her e. A model of turbulent mixing and reaction was first built up. It con siders the near-field as well as the fully developed flow regions and includes radial and axial variations in the jet velocity and time-aver aged concentrations, axial variation and intermittency in the turbulen t energy dissipation rate, expansion of the jet with entrainment and i ntermittency of its boundary, micromixing controlled by engulfment and inertial-convective decay of segregation (mesomixing). The radial dis tribution of the energy dissipation rate as well as its axial variatio n in the near-field region could not be adequately specified from the literature. Two parameters, determined from experiments, were employed to describe this axial profile. The resulting model then predicted we ll the influences of jet velocity, reagent volume and stoichiometric r atios, reagent concentrations and feed rate on the product distributio n. A viscous silicone oil was dispersed in the jet and the measured ma ximum stable drop size was compared with predictions based on the maxi mum energy dissipation rates. Measured drops were somewhat smaller and indicated local maxima in the dissipation rate up to 40,000 W/kg. The simple and robust jet reactor is suitable for competitive reactions n eeding dissipation rates of order 10(2)-10(4) W/kg to attain high sele ctivities.