Insights into nucleation and growth kinetics in seeded vacuum membrane distillation crystallization

A seeded vacuum membrane distillation crystallization (VMDC) process for treating magnesium sulfate solution was proposed. The permeate flux was investigated with respect to feed inlet temperature, vacuum pressure and feed velocity in order to determine operating conditions of VMDC. For the VMDC, the inlet and outlet temperatures of membrane distillation were maintained at 84 degrees C and 68 degrees C respectively, and the vacuum was 0.04-0.07 MPa. The nucleation and growth kinetics with the presence of seed in VMDC were investigated by comparison with the evaporation crystallization. Crystal nucleation and growth rates in evaporation crystallization and VMDC were both calculated using the population balance equation. It was found that the crystal growth rate in VMDC was slightly less than that in evaporation crystallization. Compared with evaporation crystallization, the secondary nucleation rate in VMDC was reduced due to the decrease of collision frequency between crystals.

Automated summary

A seeded vacuum membrane distillation crystallization (VMDC) process was proposed for treating magnesium sulfate solution. The permeate flux and crystal nucleation and growth kinetics were investigated, showing that the crystal growth rate in VMDC was slightly lower and the secondary nucleation rate was reduced compared to evaporation crystallization.