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为探讨结晶釜直径对SAS(超临界抗溶剂法)过程的影响规律,并确定适宜的结晶釜直径,本文采用计算流体力学(CFD)方法,选用Realizableκ-ε湍动模型对SAS喷射过程建立模型。结晶釜高度为L=190 mm,考察了直径分别为40 mm、30 mm、20 rnm和15 mm时釜内流体迹线、溶剂浓度分布、有效扩散因子分布及湍动强度分布变化规律,尤其是喷嘴出口附近溶液射流区内的流场变化状况。结果表明,随着结晶釜直径的减小,釜内漩涡区逐渐向釜顶缩小,有利于避免釜内颗粒间碰撞造成的粘结;釜内溶剂浓度逐渐减小,而有效扩散因子分布及湍动强度的绝对值逐渐增大但分布范围逐渐向釜顶缩小:喷嘴出口附近溶液射流区内的有效扩散因子与湍动强度逐渐增大,有利于提高成核速率而减小颗粒粒径。较小直径的结晶釜,还会降低流体在釜内的停留时间,减少颗粒生长时间而利于减小颗粒粒径,因此选择小直径结晶釜对SAS过程有利。本文通过CFD模拟研究,揭示了SAS结晶釜直径对SAS成粒过程的影响规律,对SAS结晶釜的优化设计具有一定的理论指导。
In order to investigate the influence of crystallizer diameter on the process of SAS (supercritical anti-solvent) process and determine the suitable crystallizer diameter, a computational fluid dynamics (CFD) method and a Realizable κ-turbulence model were used to establish the model of SAS injection . The height of the crystallizer was L = 190 mm. The changes of the fluid in the autoclave, the solvent concentration distribution, the effective diffusion factor distribution and the turbulence intensity distribution were investigated when the diameters were 40 mm, 30 mm, 20 nm and 15 mm, respectively Flow Field Change in Solution Jet Zone near Nozzle Exit. The results show that with the decrease of the crystallizer diameter, the swirl zone in the kettle gradually decreases toward the top of the kettle, which helps to avoid the sticking caused by the collision between the granules in the kettle. The concentration of the solvent in the kettle decreases gradually while the effective diffusion factor distribution and turbulence The absolute value of dynamic strength gradually increases but the distribution gradually narrows to the top of the pot: the effective diffusion factor and turbulence intensity in the solution jet area near the exit of the nozzle gradually increase, which is favorable for increasing the nucleation rate and decreasing the particle size. Smaller diameter of the crystallizer, but also reduce the residence time of the fluid in the tank, reducing the particle growth time and help reduce the particle size, so the choice of small diameter crystallization of the reactor for the SAS process. In this paper, CFD simulation study reveals the influence of SAS crystallizer diameter on SAS granulation process, and has certain theoretical guidance on the optimal design of SAS crystallizer.