【作者】 崔奇志；

【导师】 许松林；

【作者基本信息】 天津大学 ， 制药工程， 2009， 硕士

【摘要】 毛细管精馏是上个世纪70年代开始应用的一种新型的分离技术,它主要用于分离二元共沸的液体混合物。毛细管精馏的原理完全不同于传统精馏的传质机理,它依靠气-液界面的表面张力使蒸汽在毛细管中发生毛细管凝结,通过凝结液与管道壁面之间的界面作用力,改变组分的活度,从而改变二组分的相对挥发度,突破共沸点。目前,由于技术保密原因,国内外关于毛细管精馏工艺技术基础理论方面的文献报道很少,因此对毛细管精馏中毛细管道内两相流特性的研究,将有助于揭示毛细管精馏的传质机理,掌握这项技术的工艺条件。利用计算流体力学软件FLUENT6.2对毛细管内的凝结液滴进行气-液两相流模拟。在2D物理模型下,发现当We数小于20后,表面张力和壁面粘性力对液滴的形态基本无影响,管长对流动的影响也很小,与直管道相比,管道倾角和弯道使液滴的破裂程度更大,并增加了液滴的流出时间,通过与文献实验对比,验证了模拟结果的有效性。在3D模型中,比较了不同管道截面下,液滴的变形和破裂情况,发现方形管道截面下,固-液两相界面作用程度大于圆形管道截面,多孔不锈钢板的气液平衡数据证明了这一结论的合理性。在方形管道模型下,对液滴前后压差进行了量纲分析和回归计算,利用回归公式计算出的不同表面张力的物质在毛细管道中形成液滴的压差,可以与文献实验数据较好的吻合。在蒸汽量较大的条件下,管道中的液滴常会凝聚成小段的液柱,通过模拟液柱在上升过程中又破裂成小液滴的过程,并利用液滴粒径分布方程,建立了液柱和液滴运动的联系。更多还原

【Abstract】 Capillary distillation is a new-type separation process dating back to the1970s,which is mainly used for the separation of the binary azeotropic liquid mixtures. Theprinciple of capillary distillation is totally different from conventional distillationprocess. It relies on the surface tension of the gas-liquid interface to make vaporcondensedinthecapillary,andthenutilizestheinterfacialforcebetweenthetubewallandthecondensedliquidtoalterthecomponentactivity,therebychangingtherelativevolatility to break azeotropic point of the two components. Nowadays, due to thetechnical privacy protection, there are few literatures that can be found at home andabroadregardingthefundamentaltheoryofcapillarydistillation,soaninsightintothecharacteristics of two-phase flow in capillary would be helpful for the application ofthetechnologyinChina.FLUENT6.2, a commercial computational fluid dynamics (CFD) package, wereadopted for the numerical simulation of gas-liquid two-phase flow in the capillary.Under2Dmodel,itcouldbeseenthatboththesurfaceintentionandthewalladhesionhad almost no effect on the shape of droplet, and the capillary length also did littleeffect on the flow. Besides, compared to vertical-straight pipe, the inclined or bendpipe could dramatically increase the breakup degree of droplet, and prolong theoutflow time. The simulation results were found to be in good agreement with theliteraturedata.As for 3D model, a series of capillaries which had different shape of crosssection were used to simulate the deformation and breakup of a droplet. The squarecapillarywas found to have greater interfacial interaction than the circular one, whichwas proved by the vapor-liquid equilibrium data of the sintered porous stainless steelplate. Under square model, using dimensional analysis and regression calculationdealt with pressure drop over the droplet,and the computed values of the pressuredropofmaterialsthathaddifferentsurfaceintentionfitwellwiththeliteraturedata.Inthe high vapor rate condition, the droplet can assemble to liquid column. To simulatethe process of the liquid column breaking up into small droplets when the liquidcolumn moved upward in capillary and the correlation between liquid column anddropletmotionwasdevelopedthroughdrop-size-distributionequation.更多还原