Liquid-liquid dispersions in intensified impinging-jets cells

The formation of dispersions of two immiscible liquids in a confined impinging-jets cell was studied experimentally. The jets of the liquids formed at two opposing channels and collided in a main channel, which was perpendicular to the previous two. Jet channels with diameters either 0.25 or 0.5 mm and main channels with diameters either 2 or 3 mm were used. The jet velocities varied from 0.17 to 6.2 m/s and the dispersed to continuous phase ratios varied from 0.05 to 0.28. Deionised water and kerosene (Exxsol D80: ρ = 795 kg/m3 and μ = 1.73 mPa s) were used as test fluids. Drop sizes were measured with high-speed imaging. It was found that the total velocity of the two jets was the main parameter that affected both the average drop size and the interfacial area, whilst the dispersed to continuous phase flow rate ratio was less significant. Both phases could become continuous depending on the phase flowrate ratio; drops were, however, larger in the organic continuous dispersions. The interfacial area produced with the impinging-jets cell was almost 3 times larger than in capillary contactors at similar conditions (umix = 0.024-0.19 m/s). The size of the main channel affected the drop size and smaller drops formed in the large channel compared to the small one. With increasing energy dissipation rate, ε, in the impingement zone, the Sauter mean diameter decreased following a relation of the form ∼ε−b. Apart from the lower velocities, the drop sizes did not change significantly at distances equal to 15 channel diameters downstream the impingement area.