纤维膜萃取分离器内二相传质特性及工业应用

在一套直径70 mm,高2 630 mm的有机玻璃纤维液膜萃取分离器冷态实验装置上,以苯甲酸水溶液-煤油为传质体系,考察了纤维丝填充密度1.89%—5.08%,水-油或油-水体积流量比3—6的操作区间内,纤维膜分离器内二相传质性能。结果表明,对于不同的进料顺序,不同二相流量比,纤维丝最佳填充密度均在3%—3.5%。"先油后水"所对应的最佳纤维丝填充密度略低于"先水后油"的情况。根据冷态实验的结果以及最大雷诺数设计准则,设计了一套0.01 Mt/a的汽油脱硫醇工业侧线装置,并进行了实验。结果表明,与传统设备比较,采用纤维膜萃取分离器的脱硫醇效果更佳。     

纤维膜萃取分离器内两相流动、传质特性的研究——进料顺序的影响

纤维膜萃取分离器是一种新型高效传质设备。今以苯甲酸水溶液-煤油为传质体系,在一套70mm×2630mm的有机玻璃纤维液膜萃取分离器冷态实验装置上,在纤维丝填充密度1.89%～5.08%、水-油或油-水体积流量比分别为3～6的操作区间内,考察了不同油、水进料顺序对纤维膜分离器内两相流动、传质性能的影响。结果表明,若水先引入,油后引入,体积传质系数随水-油体积流量比W/O的增大而减小;而在先油后水的情况下,体积传质系数随水-油体积流量比W/O的增大呈先增大后减小的趋势,并在水-油流量比W/O为5附近取得最大值;在两种进料方式下,体积传质系数均随纤维丝填充密度的递增而先增后减,并在填充密度为3.0%～3.5%之间取得最大值。根据实验数据,分别给出了对应两种进料顺序的传质系数计算关联式,计算值与实验值吻合较好。     

纤维膜萃取分离器内两相流动、传质特性的研究——液体黏度的影响

纤维膜萃取分离器是一种新型高效传质设备。今以苯甲酸水溶液-煤油为传质体系,在一直径70mm,高2630mm的有机玻璃纤维液膜萃取分离器冷态实验装置上,考察了纤维丝填充密度1.89%～5.08%,运动黏性系数0.942～1.138mm2·s-1,水油体积流量比3～6的操作区间内,考察了原料液黏度对纤维膜分离器内两相流动、传质性能的影响。结果表明,在几种填充密度和水油比条件下,随着黏度的增加,流体停留时间延长,两相接触、混合得更均匀;传质系数呈现先增大后减小的趋势;最佳传质工况(即体积传质系数达到最大值)与原料液黏度和纤维丝填充密度密切相关。根据实验结果,给出了用于计算流体在萃取分离器内停留时间以及两相混合均匀性指数的关联式。     

中空纤维膜萃取苯酚的传质及流动特性

以体积分数为30％的磷酸三丁酯＋煤油－水为实验体系，研究了中、高装填密度的中空纤维膜萃取处理苯酚衡溶液的传质效果和传质特性以及膜器壳程流动状况。实验结果表明，中空纤维膜萃取可以高效去除水中的苯酚，萃取率最高可达到99．9％。比较了总传质系数的实验值与多个传质系数关联式的预测值之间的偏差，发现从中、高装填密度膜器得到的传质关联式偏差较小，而从低装填密度膜器得到的传质关联式偏差较大。通过测量膜器壳程流动的停留时间分布曲线，证实了偏差是由于中、高装填密度的膜器壳程流动的复杂性造成的。     

螺旋状中空纤维膜萃取传质特性

在对中空纤维膜萃取以及螺旋管技术进行充分调研的基础上 ,选择水 -苯酚 - 30 %TBP煤油为实验体系 ,溶质由水相萃取到有机相 ,在不同结构的单束螺旋状中空纤维膜器中研究了螺旋管纤维膜管内外流速以及螺旋管结构等因素对传质系数的影响 .实验结果表明 ,螺旋管中空纤维膜可以有效地提高中空纤维膜的传质特性 .随着管内流速的增加 ,传质系数将有很大提高 ,而管外流速对于传质系数的影响则较小 .至于螺旋结构的影响为 :随着螺旋内径的减小或者是螺旋螺距的减小 ,总传质系数相应地有很大提高 .最后得到了在本实验条件下计算总传质系数K的关联式     

填充密度对中空纤维膜接触器精馏过程壳程传质的影响

探讨了填充密度对新型聚丙烯中空纤维膜接触器精馏过程中壳程传质的影响。中空纤维膜接触器在填充密度为4.7%、9.5%、19%时均可在远离常规填料液泛线以上的气速范围操作。低填充密度下,壳程的Sherwood数理论值大于实验值,但填充密度较高时,实验值大于理论值。高Reynolds数有利于壳程传质,低填充密度时的Sherwood数高于高填充密度时。随着F因子逐步增大,壳程气相传质阻力随之变小,且膜接触器的填充密度越高,气相传质阻力越大。3种不同填充密度膜接触器的气相总传质系数随着接触器填充密度的增大而迅速减小,由391.84×10^-5 m·s^-1降低为83.28×10^-5 m·s^-1。     

聚丙烯中空纤维膜萃取过程传质特性研究

在自制的中空纤维膜器中研究了膜萃取过程的传质特性.研究表明,自制的带折流板的膜器可以提供较高的传质效率.增大水相流速可以提高传质速率,而改变有机相流速对传质没有影响.通过对实验数据的回归分析得出了折流膜器的壳间传质关联式.该研究对折流膜萃取器的开发和设计具有参考价值.     

中空纤维管随机分布时透析器内的管外传质

利用Matlab软件计算了中空纤维透析器外壳内壁面(简称壁面)影响下,中空纤维随机分布、管外流场充分发展、纤维表面定质量流量时的管外流场分布,进而求得了不同填充密度下透析器的管外传质系数. 结果表明,中空纤维的排布方式对传质系数有很大的影响;在所研究的中空纤维填充密度范围内(10%～50%),随着填充密度的增大,透析器的管外传质系数先变大,后变小;其随机性整体上逐渐减小.     

膜分散萃取净化湿法磷酸

采用膜分散方法研究了湿法磷酸的萃取特性,以水/磷酸/TBP+煤油为实验体系,以不同名义孔径的不锈钢纤维烧结膜为分散介质,在自制的萃取器中研究了流量、膜孔径、煤油含量、相比、磷酸浓度、萃取室体积和停留时间对单级萃取效率的影响,找出适宜操作条件。实验结果表明,流量增加,单级萃取效率呈现先增加后降低的趋势;减小膜孔名义直径,...     

中空纤维膜基萃取脱除油品中硫醇的研究

以高亲水性的纤维素中空纤维膜组件为膜接触器,NaOH溶液为萃取剂,乙硫醇/正辛烷体系为模拟油品,进行了硫醇硫的脱除实验.考察了萃取剂种类、萃取剂浓度、油/碱体积比、萃取相流量及油相流量对硫醇脱除率和总传质系数的影响,并采用数学模型对实验结果进行了初步分析.其中,采用3%(wt)的NaOH作为萃取剂时,油相主体传质为控制步骤.结果表明,该膜接触器可长时间稳定工作,得到油品中硫醇硫含量低于10 μg·g-1;萃取液中含油量小于3 mg·L-1.     

错流旋转填料床传质特性影响因素的实验研究

采用CO2-NaOH体系,在中试规模的实验装置上进行传质实验,考察了气速、液体喷淋密度、超重力因子、气液接触时间对错流旋转填料床的总体积传质系数KLa及有效传质比表面积ae的影响. 结果表明,KLa和ae均随气速、液体喷淋密度和超重力因子增加而增大,KLa随气液接触时间增加先缓慢增大后急剧下降,ae则随气液接触时间增加而缓慢下降. 最佳操作条件为：气速1.69 m/s,液体喷淋密度32 m3/(m2×h),超重力因子104,气液接触时间0.1 s. 错流旋转填料床在处理大气量气体时传质效果增强,是同类文献错报道的1.52~2.32倍. 对各操作参数下所得实验数据进行回归,得关联式KLa=1.8221(atDL/dp)ReL0.6371GrL0.0548ScL0.0623和ae/at=2980.9ReL0.2349FrL-0.045WeL0.5023f-0.5.     

Compact multiplexing of monodisperse electrosprays

Widespread application of the cone-jet electrospray has been hampered by the low flow rate at which the spray is dispersed, despite the unique ability of this device to disperse quasi-monodispersed particles over a phenomenal size range. Compact multiplexing, that is, with a high number of sources per unit area, is indispensable for dramatically increasing the throughput and reducing the cost per electrospray source. We demonstrate the successful operation of multiplexed electrospray systems with an unprecedented packing density of up to 11,547 sources/cm². The devices were fabricated and operated by implementing three criteria: (a) the extractor electrode configuration should be used to localize the electric field; (b) the viscous pressure drop acting on the liquid should dominate with respect to the electrostatic pulling force by the electric field; and (c) the electric field “driving” the droplets between the extractor electrode and the collector should be sufficiently intense to avoid reversal of the droplet motion near the extractor (satellite trapping). All devices showed excellent droplet size uniformity across the entire spray region, which indicates effective decoupling of the electrospray sources even for closely packed nozzles. The experimental results show that these design criteria provide effective and reliable guidelines for the successful design and operation of multiplexed devices from first principles, that is, based only on knowledge of the suitability of a liquid for electrospray dispersion and of the critical liquid properties such as surface tension, viscosity and electric conductivity. As a result, the design of these devices for a given application is achievable without costly trial-and-error microfabrication trials. This development opens the door for applications requiring flows from multiplexing 10⁶–10⁷ individual electrospray sources from industry-standard 12-in silicon wafers.     

A stochastic model for the simulation of the natural flow in random packed columns

A stochastic model has been developed to simulate the “natural flow” and the spatial evolution of flow patterns in the downstream direction in randomly packed beds. The natural flow is defined as the tendency of liquids flowing down a packed bed to redistribute radially in a natural fashion. A column of 0.5 m diameter with 25 mm Pall rings is selected to test the model. The simulation results of flow distributions are in good agreement with available experimental data from the literature. Unlike the existing models, our approach can simulate liquid flow distributions for different realizations of random packings.     

Experimental study of mass transfer on structured packings of direct-contact crossflow heat exchangers

Some experimental results of studying mass transfer during the evaporation of a liquid film from the surface of flat-plate and corrugated perforated packing into an air flow have been presented. An empirical equation for calculating the average coefficient of mass transfer with allowance for the effect produced by temperatures of heat-transfer agents, their physical properties, and flow rates, as well as the geometrical dimensions of a packed bed, on the mass-transfer process has been given.     

Effects of baffles on separation of aqueous ethanol solution with hollow fibers

The effects of baffles on the operation and mass-transfer characteristics in novel hollow fiber membrane contactor used in distillation were investigated. Hollow fiber membranes, coated with a 7 μm polydimethyl-siloxane, were operated as structural packing in the separation of ethanol-water solutions. The parallel flow mode was chosen for separation due to the stronger driving force of the concentration difference, in which liquid flows through the lumens of the fibers and vapor flows countercurrent-wise outside the fibers. Two baffles were installed on the shell side of the membrane contactors to enhance separation, which had a round shape with a semi-lunar hole. The results show that both baffled and unbaffled membrane contactors gave better, more productive separations than traditional packing in distillation, such as the excellent Sulzer Gauze BX structured packing. The baffled membrane contactors performed better than unbaffled ones, especially at high vapor velocities. The minimal HTU of membrane contactor with baffles could reach as low as 4.5 cm, and almost all the contactors could work well above the limit where flooding normally occurs in conventional cases. Theoretical analysis predicted that baffles helped membrane module to obtain a higher masstransfer coefficient and a smaller mass-transfer resistance. Finally, theoretical mass-transfer coefficient and experimental value were compared as well as the contribution of each individual mass-transfer coefficients among liquid, gas and membrane.     

Mass and momentum transfer at a wall in the presence of turbulence promoters

This paper deals with the influence of cylindrical turbulence promoters on mass and energy transfers at the wall of a narrow channel with a flowing liquid. The experimental distributions of the mass-transfer coefficient and shear stresses along the wall appear to be similar. The results show that an elementary “mesh step” is reproduced periodically when the promoters are very near the wall. For this case, a model assuming symmetrical boundary layers between two neighbouring promoters, allows a quantitative correlation of the local mass-transfer coefficient and the local velocity-gradient at the wall.     

新型气液逆流接触洗涤器流动-传质模型

通过冷模实验对一种新型气液逆流式洗涤器流动传质特性进行了考察。实验结果表明,在不同的操作条件下,洗涤器内气液两相流动会呈现出不同的流型。其中,洗涤器在泡沫流状态下的高效传质段体积和解吸率的数值均较大。将实验结果与理论分析相结合,依据其气液接触表面更新极快、形成高度湍动泡沫流的特点,提出了一种基于该洗涤器结构和操作特性、可以预测洗涤器传质效果的“两段式”流动-传质模型。模型将洗涤器内气液作用区分为两个区段：旋转射流段和高效传质段。利用该模型分析了解吸率与液气比L/G和旋流比ω的变化关系;结果表明,在不同操作条件下,该模型的计算结果与实验数据吻合较好,可供工程设计参考。     

撞击流-旋转填料床萃取器传质性能研究

以磷酸三丁酯(煤油)-苯酚-水为试验体系，研究了IS—RPB萃取器的传质性能。在研究主要操作参数对萃取级效率影响的基础上，确定了最适宜的操作条件，得到了97％以上萃取级效率。试验结果表明，撞击流-旋转填料床萃取器是一种新型快速高效的萃取设备。     

加压下规整填料塔内气液两相流返混的实验研究:气相返混系数

规整填料因具有生产能力大、分离效率高、压降低、操作弹性大、持液量低等诸多优点 ,目前已被广泛应用于精馏、吸收及萃取等多种化工单元操作中 .通常只在常压或减压条件下操作 ,而在高压或大液相负荷下 ,因流体物性的变化及流动状态的改变 ,使塔内产生严重的返混 ,塔效率显著降低 .因此 ,研究加压下规整填料塔内流体的流动状态具有重要意义 .对于加压下填料塔内气相返混的研究 ,中国台湾的ＴａｎＣｈｕｎｇ -Ｓｕｎｇ[1] 在低实验气速 (0 .0 0 2～ 0 .1ｃｍ·ｓ- 1)下做过初步的研究 ,其实验填料为散堆填料 .Ｋｕｒｔｚ[2 ] 在这方面的研究…