气升式内环流反应器中反应结晶过程的实验研究

发布时间：2018-03-05 21:12

本文选题：反应结晶　切入点：环流结晶器　出处：《中国科学院大学(中国科学院过程工程研究所)》2017年硕士论文　论文类型：学位论文

【摘要】：气升式内环流反应器混合性能好、传热传质效率高,被广泛应用在生物技术、废水处理等领域。相对于搅拌结晶器,其内部剪切力小、剪切场均匀且无机械传动部件,因此在结晶领域受到越来越多的关注。然而,对于环流反应器中的反应结晶过程,尚未有人对其进行过研究。本文以氢氧化镍沉淀反应为模型反应,对环流反应器中的反应结晶过程进行了研究。首先采用正交实验,在气升式内环流结晶器中制得了类球形的氢氧化镍颗粒,并与搅拌结晶器进行对比实验。通过对两类结晶器中所得颗粒进行XRD、SEM、粒径大小、振实密度、显微镜图像等分析,完善了氢氧化镍颗粒的生长机制,即:溶液中析出的晶粒在流体中运动时,随机碰撞团聚在一起,形成氢氧化镍颗粒,这个聚并过程决定了颗粒的粒径大小;新生成的颗粒中,晶粒间空隙较大,在适当的反应条件下,组成颗粒的晶粒可以继续生长,填补晶粒间的空隙,使得颗粒密度上升。在此基础上,依次探索了初始氨水添加量VN、pH、加料方式、导流筒长度Hd和气体流量qg等操作条件对氢氧化镍颗粒内晶粒生长的影响规律,主要结果如下:(1)Ni(OH)2颗粒内的晶粒大小D随VN、pH及Hd的增加,均呈现先逐渐增大,而后逐渐降低的规律,当VN=300 mL、pH=11.4和Hd=250 mm时,所制备氢氧化镍颗粒内的晶粒最大、产品质量最佳。(2)环流结晶器顶部气液分离区的微观混合最佳,当加料位置选在此处时,所制备氢氧化镍颗粒内的晶粒最大。(3)qg对环流结晶器内所制备氢氧化镍颗粒内的晶粒大小影响显著。随着qg的增加,晶粒大小也逐渐变大。
[Abstract]:The air-lift inner loop reactor has good mixing performance and high heat and mass transfer efficiency. It is widely used in biotechnology, wastewater treatment and other fields. Compared with the stirring mould, the internal shear force is small, the shear field is uniform and there are no mechanical transmission parts. Therefore, more and more attention has been paid in the field of crystallization. However, the reaction crystallization process in the loop reactor has not been studied. In this paper, the nickel hydroxide precipitation reaction is used as a model reaction. The reaction crystallization process in a loop reactor was studied. Firstly, spherical nickel hydroxide particles were prepared in an air-lift inner loop mold by orthogonal experiment. The growth mechanism of nickel hydroxide particles was improved by the analysis of XRDX SEM, particle size, vibrational density, microscope image and so on. That is, when the precipitated grains in the solution move in the fluid, they are randomly collided and agglomerated together to form nickel hydroxide particles, which determines the size of the particles. Under the appropriate reaction conditions, the grains can continue to grow, fill the gap between the grains, and increase the density of the particles. On this basis, the initial amount of ammonia water added VN ~ (2 +) pH and the feeding method are explored in turn. The effect of operating conditions such as tube length and gas flow rate QG on the grain growth in nickel hydroxide particles is studied. The main results are as follows: the grain size D increases with the increase of VNN pH and H d, and the main results are as follows: (1) the grain size D increases at first with the increase of VNN pH and H d. However, when the pH value of VN=300 MLX was 11.4 and Hd=250 mm, the grain size of nickel hydroxide particles was the largest and the product quality was the best. The micromixing of gas-liquid separation zone at the top of the circulator was the best, and when the feeding position was selected here, The maximum grain size in nickel hydroxide particles. QG has a significant effect on the grain size of nickel hydroxide particles prepared in the loop crystallizer. With the increase of QG, the grain size of nickel hydroxide particles increases gradually.
【学位授予单位】：中国科学院大学(中国科学院过程工程研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ138.13

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