Study Of Mixing Characteristics In Microreactor And Preparation Of Nesquehonite

The direct precipitation of nesquehonite is a fast chemical reaction process. The micro-mixing and supersaturation at initial stage of the reaction directly influences the crystal nucleation, which significantly affects the quality of the target product. The traditional mixing approach utilizing direct stirring could not provide a sufficient, homogeneous and controllable mixture, leading to an aggregated and a poor quality product. Based on the excellent micro-mixing characteristics of the microreactors, this dissertation offers a serial of novel configurations for the microreactors, and then discusses their mixing efficiency. Hence, preparation of the nesquehonite whiskers are consequently conducted using microreactor with an optimal mixing performance.Main contents are as follows:1. Mixing magnesium for chloride solution and sodium carbonate solution with the the same concentration in T-type microreactor was systematically analyzed. Meanwhile, influences of reactant flow rate, reactant concentration on mean length and length distribution was experimentally investigated. Compare to the conventional synthesis method, T-type microreator could get magnesium carbonate faster. The results also showed that nesquehonite whiskers with structural integrity can be obtained in microreactor.2. Design of coaxial microreactor with three typical configurations was presented to solve the easily blocked problem and enhance the micro-mixing characteristics. Through visualization experiment, the mixing conditions of microreactors were quantitatively characterized at different flow rate. Therefore, serpentine microreactor performed excellent mixing, followed by divergent-convergent microreactor, and straight microchannel displayed the worst.3. Direct precipitation of nesquehonite was finally carried out in the coaxial serpentine microreactor abovementioned at different flow rates and reactant concentrations. The nesquehonite product showed a good dispersivity. More specifically, when the flow rate and reactants concentration was respectively in the range of 2 mL·min-1?14 mL·min-1 and was 0.1 mol·L-1?0.5 mol·L-1, nesquehonite whisker with a particle size in the range of 11.7?m-62.8?m were obtained.In summary, this work found that coaxial inlet could effectively prevent clogging microchannel and serpentine microchannel could efficiently improve mixing in microreactor.Consequently, particle size for the products could controlled using an optimized coaxial serpentine microreactor under appropriate operation conditions.