3.5 MACC experiment.
Experimental setup of MACC is shown in Figure 3. The concentration of thiourea aqueous solution was 23.5 wt% (saturated at 39 °C). Crystallizer size ranged from 100 mL to 10 L (for the terminal comparison with conventional cooling crystallization, 10 L crystallizer was utilized). The thiourea aqueous solution was circulated into the membrane module through the shell side at a certain flow rate (range 200 to 400 mL min -1) by a fluid pump. The saturated thiourea solution was pumped into the membrane module when it decreased to the nucleation temperature. After the stable circulation reached, coolant was circulated through the tube side of the membrane module by a fluid pump. When sufficient number of crystal nucleus were appeared in the membrane module and recycled with the solution to the crystallizer, shut off the coolant and the solution transferred into a membrane module. Go on the cooling procedure in the crystallizer via following the cooling curve until the required yield reached. The high-speed microscopic camera was introduced as the online image monitoring unit to observe the nucleus particle motion on the membrane surface; PVM (Mettler Toledo Ltd, V19) was used for detecting crystal growth images and size distribution in the crystallizer. Then, the crystals product was filtrate and dried for further analysis.