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Alternative TitleExperimental Investigation on the Precipitation Process of Nickel Hydroxide Crystallites
Thesis Advisor程景才 ; 杨超
Degree Grantor中国科学院研究生院
Degree Discipline化学工艺
Keyword氢氧化镍 沉淀 搅拌槽 粒径 粒径分布
Abstract氢氧化镍作为重要的电极正极材料,其电化学性能主要受颗粒大小、粒径分布和晶体形貌的影响,因此采用在线测量技术来监控氢氧化镍结晶过程是非常关键的。氢氧化镍反应结晶是一个快速反应,因此只有通过实时在线测量技术才能比较真实准确地反映出氢氧化镍这一复杂络合沉淀反应的结晶过程,从而为建立氢氧化镍结晶动力学模型和工业生产具备高电化学性能的氢氧化镍晶体和性能调控提供指导和调控作用。 本文在直径T = 240 mm 的平底有机玻璃搅拌槽内,采用氨水络合沉淀的方法制备氢氧化镍,通过在线测量技术,以单进料的方式(fedbatch)研究不同转速、不同桨型(标准Rushton桨与下压式六叶斜叶桨)、反应温度、浓度、加料位置、桨径等条件下的颗粒粒径、PSD以及形貌的变化,综合考察了不同操作条件对氢氧化镍结晶过程的影响。主要取得了以下研究结果: (1)与其他因素相比,转速的影响相对较大。转速N = 500 rpm,晶体平均粒径约13 μm;而N = 300 rpm时,粒径约25 μm;在较高的反应物浓度下生成粒径较大的晶体;温度对晶体粒径的影响较复杂。当反应物浓度为CNiSO4 = 0.1 mol/L时,颗粒的粒径随温度的增加而减小;当反应物浓度为CNiSO4 = 0.5 mol/L时,温度越高,颗粒的粒径越大。 (2)在相同的操作条件下,采用45°下推式斜叶桨(PBTD)比采用标准Rushton桨所生成的晶体大一些;进料位置对粒径和PSD的影响相对较小;在较低的转速下(N = 300 rpm),进料位置位于桨区(B点)所生成的颗粒粒径要略大于进料位置位于液面下方(A点)所生成的颗粒。 (3)随转速的增加,粒度分布(PSD)向粒度较小方向移动,且峰值逐渐增大;在高浓度下,PSD出现双峰分布,并随温度的升高整体PSD向粒径较大的区域偏移。而在较低浓度下PSD随温度增加的变化不明显;pH值在整个沉淀初期保持相对稳定,然后逐渐升高,到反应最后阶段又趋于稳定。整个实验过程中,pH的变化范围为8.21 ~ 11.98。 关键词: 氢氧化镍,沉淀,搅拌槽,粒径,粒径分布
Other AbstractUsing online measurement technique to investigate the crystallizing precipitation process is of nickel hydroxide is of particular importance. As the main active material for positive electrode in rechargeable batteries, the electrical performance of nickel hydroxide is greatly influenced by mean particle size, particle size distribution (PSD) and morphology. The precipitation reaction of Ni(OH)2 is very fast, therefore, with the help of online measurement technology, we can precisely investigate the precipitation process of nickel hydroxide in a complicated complexation-precipitation system. Then, it is possible to establish the crystallization kinetics model of nickel hydroxide, which will play an essential role in guiding and controlling the industrial production of nickel hydroxide with high electrical performance. In this thesis, the effect of operating conditions on the precipitation of nickel hydroxide has been studied using online measurements in a single batch-fed stirred reaction system with an airtight cover, whose diameter is 240 mm. The influences of impeller speed, operating temperature, initial concentration, feed position, impeller type and impeller diameter have been investigated. The effect of various operating conditions on mean particles size, PSD and morphology has been considered. The main conclusions are as follows: (1) Compare to other operating conditions, impeller speed has the most significant effect. When N = 500 rpm, the average particles size d43 is about 13 μm; when N = 300 rpm, the average d43 is about 25 μm. A higher initial reaction concentration produces larger particles. The effect of temperature on d43 is complex. Under lower initial concentrations, CNiSO4 = 0.1 mol/L, the particle size decreases with temperature, however, when CNiSO4 = 0.5 mol/L, the higher the temperature, the lager the particle size is. (2) For the impeller type, a 45° PBTD produces comparatively larger crystal sizes than a Rushton impeller does. Feed location has a relatively weaker effect on d43 and PSD when compared with other operating parameters. Under a lower impeller speed (N = 300 rpm), slightly larger crystals are obtained if the reactant is fed close to the impeller (feeding location B) than that with feed under the free surface (feeding location A). (3) The PSD slides to a smaller size range with the increase of stirrer speed. The peak values also increase with the impeller speed. Under higher initical concentrations, there is a bimodal distribution in PSDs. Generally, under lower initical concentrations, temperature doesn’t have significant influence on PSDs. The pH value varying with time shows that the pH rises consistently with time, from 8.44 to 11.93. At different time periods, the rise rates are different. Key words: Nickel hydroxide, Precipitation, Stirred tank, Mean particle size, Particle size distribution
Document Type学位论文
Recommended Citation
GB/T 7714
鄂巍巍. 氢氧化镍结晶沉淀过程的实验研究[D]. 中国科学院研究生院,2014.
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