Study on Crystallization Kinetics of Macallisterite using an MSMPR Crystallizer

21.8802 g of boric acid (H3BO3), 5.2539 g of sodium hydroxide (NaOH), and 115.0812 g of magnesium chloride hexahydrate (MgCl2·6H2O) were dissolved in 210 mL of deionized water to prepare the supersaturated stock solution. A small volume stock solution was then transferred to a 200 mL MSMPR crystallizer, and 0.30 g seed crystals were added to induce the crystallization. The crystallization temperature was maintained at 10 ℃, 15 ℃, 20 ℃ or 25 ℃ with a stirring rate of 300 rpm, 400 rpm, 500 rpm, 600 rpm or 700 rpm. During the crystallization process, the supersaturated stock solution was maintained at 40 °C and continuously fed into the crystallizer at a flow rate of 1.11 mL·min-1, 0.667 mL·min-1, 0.476 mL·min-1, or 0.333 mL·min-1 using a peristaltic pump. When the suspension in the crystallizer reached to 200 mL, the slurry was discharged from the outlet. The corresponding residence time factor of 3 hours, 5 hours, 7 hours or 10 hours on the crystal particle size distribution were studied. Furthermore, crystal particle size distribution analysis was conducted on the samples in the crystallizer at 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times and 11 times residence time to ensure that the crystallizer reached steady state. Once the system reached a steady state, the slurry of 10 mL was sampled, filtered, washed and dried at 45 ℃ until achieving a constant weight. The suspension density and crystal particle size distribution were measured.