Abstract: In the process of oil water separation by deoiling hydrocyclone, the separation effect of emulsion oil droplets and dispersed phase oil droplets whose particle sizes are less than 20 μm is not ideal. A fluid particle model was established to reflect the coalescence law of oil droplets, and collision coalescence process of oil droplet particles was simulated by using the standard k-ε turbulence model and the CLSVOF multiphase flow model coupled with the surface tension model. The results showed that the probability of positive collision and coalescence of non-uniform size oil droplets was greater than that of uniform size oil droplets under the condition of approaching velocity of 0.50 m/s. The probability of positive collision coalescence of oil droplets with uniform size increased nonlinearly with the approaching velocity, and when the approaching velocity increased from 0.16 m/s to 0.80 m/s, the probability of forward collision coalescence increased by 17%. When the approach velocity of oil droplets with uniform particle size was 0.50 m/s, there was a negative correlation between the probability of collision coalescence and the angle of collision, and the effective collision angle for collision coalescence was 0°- 45°. The research results can improve the ability of the deoiling hydrocyclone for oil water elaborately separation.

Key words: collision coalescence, fluid particle model, numerical simulation, deoiling hydrocyclone, coalescence probability