The coalescence of drops in liquid‐liquid fluidized beds

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Abstract
The coalescence rates of equisized drops of organic liquids fluidized by water under conditions of mutual saturation were studied. A drop‐size separation technique permitted the direct count of the coalesced drops. Six organic liquids (benzene, cyclohexane, n‐butylacetate, methyl isobutyl ketone, diisobutyl carbinol, and tetrahydrobenzaldehyde) were used, and the coalescence was in all cases total, that is, without formation of small satellite drops.A new hydrodynamic model is presented to calculate the parameters governing the drainage of liquid between two deformable drops in head‐on collision. A parameter from this model permits correlation of the coalescence rates with only two arbitrary constants, provided the ratio of dispersed to continuous liquid viscosities lies between 0.5 and 2. High viscosity ratios or the presence of trace quantities of surfactant greatly depress the coalescence rate, while continued reuse of the dispersed liquid leads to a statistically significant reduction. The presence of a fog of very small droplets increases the coalescence rate.