过硫酸铵连续结晶器流场模拟
发布时间：2018-11-09 20:14
【摘要】：工业上制取过硫酸铵的过程属于固体物质以晶体的状态从溶液、蒸汽或熔融物质中析出的结晶过程。目前,由于缺乏系统的理论研究,国内生产过硫酸铵的工艺只能采用间歇结晶的方式,存在着生产效率低下、产品质量不高等问题,而过硫酸铵连续结晶器就可以解决这些问题。对过硫酸铵结晶热力学、动力学、流场和温度场的研究对于开发过硫酸铵连续结晶器有着非常重要的意义。首先,对过硫酸铵结晶过程进行了热力学研究,得到了过硫酸铵在水中的溶解度和超溶解度,确定了介稳区宽度,确定了过硫酸铵在工业生产中较好的热力学条件是以每小时降40℃的降温速率降温,结晶温度范围控制在20-45℃。随后,对过硫酸铵结晶过程进行了动力学研究,得到了在不同的降温速率下的过硫酸铵的悬浮密度、相对过饱和度,从而根据经验公式得到了33℃的过硫酸铵溶液在以1小时降40度的降温速率下的成核速率0B和晶体生长速率G,确定了过硫酸铵的结晶过程不需要单独添加晶种,从而优化了过硫酸铵的生产过程。在此基础上,采用Fluent软件对过硫酸铵结晶器流场和温度场进行了模拟,分别得到了框式搅拌桨的搅拌转速在60r/min、100r/min、200r/min时单相流场速度的大小、方向和剪切率大小,加入平均粒度为800?m的晶体后的连续相和固体相流场的变化情况,计算出了100r/min时的框式搅拌桨的扭矩和单位体积的输入功率。通过模拟结果对比得到了粒子相的加入对连续相的速度大小和方向影响不是很大,粒子相的体积分率分布比较均匀,剪切率相对单相流场时有所减小,选择结晶器的搅拌速率在100r/min时流场的流动效果和粒子相的体积分率分布效果更好,这样使得晶体粒度得到了有效的控制。通过温度场的计算得到了在三种不同的盘管内冷却盐水流速下,结晶器内部和换热盘管从入口到出口的温度变化情况,再根据热力学的研究结论,0.6m/s的冷却盐水流速下的温度场分布符合适宜的降温区间,确定了0.6m/s的冷却盐水流速是一个合适的选择,可以使结晶过程充分换热,从而提高了效率。通过以上理论、实验及模拟研究,得到了影响过硫酸铵结晶性能的重要参数,为工业过硫酸铵的生产提供了一定的参考和理论依据。
[Abstract]:The industrial production of ammonium persulfate is a crystallization process in which solid matter is precipitated in crystal form from solution, steam or molten substance. At present, due to the lack of systematic theoretical research, the domestic production process of ammonium persulfate can only be produced by batch crystallization, which has some problems such as low production efficiency and low product quality. And ammonium persulfate continuous crystallizer can solve these problems. The study of crystallization thermodynamics, kinetics, flow field and temperature field of ammonium persulfate is of great significance for the development of continuous crystallizer for ammonium persulfate. Firstly, the crystallization process of ammonium persulfate was studied by thermodynamics. The solubility and supersolubility of ammonium persulfate in water were obtained, and the width of the metastable zone was determined. The better thermodynamic conditions of ammonium persulfate in industrial production were determined as follows: the cooling rate was reduced by 40 鈩，
本文编号：2321443
[Abstract]:The industrial production of ammonium persulfate is a crystallization process in which solid matter is precipitated in crystal form from solution, steam or molten substance. At present, due to the lack of systematic theoretical research, the domestic production process of ammonium persulfate can only be produced by batch crystallization, which has some problems such as low production efficiency and low product quality. And ammonium persulfate continuous crystallizer can solve these problems. The study of crystallization thermodynamics, kinetics, flow field and temperature field of ammonium persulfate is of great significance for the development of continuous crystallizer for ammonium persulfate. Firstly, the crystallization process of ammonium persulfate was studied by thermodynamics. The solubility and supersolubility of ammonium persulfate in water were obtained, and the width of the metastable zone was determined. The better thermodynamic conditions of ammonium persulfate in industrial production were determined as follows: the cooling rate was reduced by 40 鈩，
本文编号：2321443
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