Enhancing continuous reactive crystallization of lithium carbonate in multistage mixed suspension mixed product removal crystallizers with pulsed ultrasound.

In this work, pulsed ultrasound was used to facilitate steady-state reactive crystallization and increase the final yield and productivity of lithium carbonate in continuously operated single and multistage mixed suspension mixed product removal (MSMPR) crystallizers. Experimental analyses of the stirred tank MSMPR cascade were performed to investigate the effects of ultrasound field, residence time and temperature which contributed to the steady-state yield, crystal size distribution and crystal morphology. The results show that pulsed ultrasound can not only significantly enhance the reaction rate, but also help to improve the particle size distribution and the crystal habit. Subsequently, a population balance model was developed and applied to estimate the final yield of the continuous process of the lithium bicarbonate thermal decomposition reaction coupling lithium carbonate crystallization. The consistency of the final yield between the experiments and the simulations proved the reliability of the established model. Through the experimental and simulation analyses, it is demonstrated that the use of pulsed ultrasound, higher final stage temperature, MSMPR cascade design and appropriate residence time help to achieve higher yield and productivity. Furtherly, based on the conclusion drawn, pulsed ultrasound enhanced three-stage MSMPR cascaded lithium carbonate continuous crystallization processes were designed, and the maximum productivity of 44.0 g/h was obtained experimentally.