The mechanism and optimization of secondary droplet fragmentation in the liquid–liquid cyclone reactor for ionic liquid alkylation

A novel liquid–liquid cyclone reactor (LLCR) with integrated reaction-separation functionality was developed to optimize ionic liquid alkylation processes. The fragmentation and aggregation of droplets play a crucial role in rapid reaction and separation for the alkylation reaction. The optimal CFD-PBM coupled model was employed to investigate the hydrodynamics, droplet dispersion and secondary droplet fragmentation in the LLCR. Additionally, a targeted optimization strategy was implemented for the cone section design based on droplet fragmentation analysis. The results showed that increased pressure pulsation in the lower cone section of LLCR promotes significant secondary fragmentation of the droplets, achieving an average diameter reduction of approximately 200 μm. However, the majority of the light phases is separated before reaching the lower cone section, which diminishes the mixing enhancement attributable to secondary droplet fragmentation. The optimal 250 mm-parabolic double-cone section enhances secondary fragmentation of the droplets and delays the separation of the light phase, with a reduction of the average droplet diameter by 49.95 μm and an increase of the flow rate by 0.11 m³·h⁻¹ in the lower cone section. Furthermore, the separation efficiency of the light phase increases under various operating conditions, with a maximum light-phase yield increase of 8.41 % and an overall efficiency gain of 10.73 %.