MICROMIXING AND FAST CHEMICAL-REACTIONS IN STATIC MIXERS

Turbulent reactive mixing in static mixers has not been widely studied. Knowledge of the turbulent energy dissipation rate is needed to make predictions about the course of chemical reactions in mixing elements. It was determined by applying the engulfment model of micromixing to the measured product distributions of fast competitive-consecutive diazo couplings between 1-naphthol and diazotized sulphanilic acid. Three static mixers, differing mainly in the width of their channels (hydraulic diameters from 0.0021 to 0.0053 m), were studied. Dissipation rates in the range 700-1000 W kg-1 were obtained when the superficial liquid velocity was 2 m s-1 and the viscosity was 7.9 mPa s. The channel width influenced these values as well as the turbulent part (29%-67%) of the total energy dissipation. The performance of the static mixers was compared with that of the empty tube. Turbulence decay downstream from a mixer, the spacing between the feed pipe and the first element and the change from semi-batch to in-line operation were also investigated.