新型转盘萃取塔在己内酰胺生产中的应用

探讨了转盘萃取塔在己内酰胺精制中萃取效率的影响因素,影响转盘萃取塔传质性能的主要因素是级间的轴向返混和沟流。介绍了新型转盘萃取塔的设计及其在70 kt/a己内酰胺精制装置中的工业应用效果。与原装置转盘萃取塔的运行情况比较,新型转盘萃取塔内的固定环平面增加了筛孔挡板,能有效抑制转盘萃取塔内的轴向返混,提高转盘萃取塔的传质效率。     

激光测速仪在萃取装置研究中的应用

本文探讨了激光测速仪(LDV)在化工萃取研究中的应用,论证了LDV对Kühni萃取塔和转盘萃取塔(RDC)流场进行测量的可能性,并对Kühni塔和RDC切向速度场进行了测量和分析。     

带有丝网凝聚的改进型转盘塔

<正> 一种改进型转盘塔(MRDC)已装置试验。该装置是将金属丝网环简单地插入转盘萃取塔(RDC)的隔室中,金属丝网能增进分散相液滴频繁的凝聚和表面更新。流体力学的研究结果表明转盘转速只有高于一定的值数,MRDC才与RDC不同,发挥其独特的性能,如较多的滞留量、较大的平均液滴直径、较小的特征速度和较高的通量。应用返流模型处理轴向混和数据得到MRDC中的连续相和分散相的返流比仅分别为RDC中的50％和85％。与RDC相比,     

萃取塔设备研究和应用的若干新进展

溶剂萃取是一种重要的化工分离技术,在湿法冶金、原子能化工、石油化工等领域有着广泛的应用。萃取塔优点突出但设计放大困难。本文介绍了国外萃取塔数学模型和设计放大研究概况及其最新进展,并较详细地介绍了我国萃取塔设备的研究、创新和应用。鉴于脉冲筛板塔在核工业中的重要地位,着重介绍了在汪家鼎先生指导下所进行的脉冲筛板塔两相流体力学、纵向返混和传质特性等方面的系统研究工作,指出所形成的以特性速度进行塔径放大和考虑纵向混合的按基本原理进行脉冲筛板萃取塔放大设计的体系具有重要的普遍意义。所创制的"分散-聚并型"脉冲筛板塔性能优越,已在大型工业装置中得到成功的应用。也介绍了在我国广泛应用的转盘萃取塔、填料萃取塔和脉冲填料萃取塔的研究、创新和应用情况。其中在理论研究基础上创制的新型转盘萃取塔(NRDC)、内弯弧形筋片扁环填料(SMR)和挠性梅花扁环填料(PFMR)性能优良,推广应用效果显著。     

开式涡轮转盘塔用于液液固体系的性能研究

由转盘塔改型的开式涡轮转盘塔是一种新型的搅拌萃取塔,它适用于固含量较高的体系.其特点是每个转盘下方有3条叶片.选用水-煤油-石英砂体系,以丁酸为溶质,在内径52mm的塔中作流体力学和传质实验.结果表明,传质方向对液体分散相滞留率、固相滞留率和体积传质系数都有一定影响.固体颗粒的存在可降低扩散单元高度,但对传质并不总是有利.     

基于CFD的搅拌萃取塔结构优化与流场分析

为降低搅拌萃取塔内轴向返混并增大通量，在搅拌筛板萃取塔基础上改进内部结构，设计了返混相对较轻的搅拌萃取塔。通过停留时间分布模拟，结合返混模型和流场分析，研究了通道面积、环隙位置、开孔方式和澄清段高度等因素对流体流动特性的影响。结果表明，级间转动挡板可以有效抑制塔内轴向返混，且挡板直径越大，塔内通道面积越窄，抑制返混效果越好；固定环开孔和级间挡板开孔均会带来一定程度的返混，尤以搅拌桨下方的级间挡板开孔影响最为严重；设立澄清段可以降低塔内返混，且澄清段高度越高返混越小，实际应用时考虑到设备成本，澄清段高度与塔径之比以0.7左右为宜。     

用计算流体力学方法研究转盘塔内的流场

利用计算流体力学（ＣＦＤ） 方法, 以水为连续相, 对三种不同规模的转盘萃取塔（ＲＤＣ）内的单相流动的流场进行模拟。计算结果表明, 随着塔径的增加, 级内混合减弱, 级间的返混增加。对于φ２ ．４ ｍ 的工业转盘塔, 存在约５０ ％ 的径向死区以及２０ ％ 左右的轴向死区。     

超临界流体萃取筛板塔中二氧化碳/醇/水体系流体力学特性和传质性能的初步研究

在内径25mm的连续逆流超临界流体萃取筛板塔中,对超临界二氧化碳/乙醇/水和二氧化碳/异丙醇/水2种体系的流体力学特性和传质性能进行了实验研究;对实验数据进行了分析处理,得到了描述超临界流体萃取筛板塔流动特性的关联式,应用柱塞流模型对超临界流体萃取筛板塔的传质性能进行了模拟计算.     

超临界流体萃取筛板塔中二氧化碳/醇/水体系流体力学特性和传质性能的初步研究

在内径25mm的连续逆流超临界流体萃取筛板塔中,对超临界二氧化碳/乙醇/水和二氧化碳/异丙醇/水2种体系的流体力学特性和传质性能进行了实验研究;对实验数据进行了分析处理,得到了描述超临界流体萃取筛板塔流动特性的关联式,应用柱塞流模型对超临界流体萃取筛板塔的传质性能进行了模拟计算.     

萃取塔数学模型及过程强化的若干研究进展

萃取塔因生产能力大、占地面积小、密闭性好等优点,在石油、化工、生物、医药和环境工程等多领域被广泛应用。本文从以下几个方面介绍了萃取塔近些年的研究进展：综述了传统萃取塔（脉冲萃取塔、转盘塔与Kühni塔等）的水力学、轴向扩散与传质模型的发展,分析比较了表面张力、传质方向、放大效应等因素对模型的影响;介绍了计算流体动力学（CFD）在萃取塔中单液滴、单相流模拟、液-液两相流模拟、外加能量模拟、与群体平衡模型（PBM）耦合模拟中的应用进展;介绍了国内外设计开发的新型萃取塔,包括改变传统塔的内构件和引入多种外场能量等方式来强化相间传质。研究表明,将先进实验研究方法、准确经验模型和可靠理论计算相结合,将会是萃取塔研究的重要手段和方向。     

Hydrodynamics and mass transfer performance of rotating sieved disc contactors used for reversed micellar extraction of protein

The extraction of protein by continuous liquid-liquid extraction was investigated in a rotating disc contactor (RDC) and a rotating sieved disc contactor (RSDC) with and without stators. Hydrodynamics and mass transfer performance for reversed micellar extraction of lysozyme in RDC/RSDC I and RSDC II have been investigated. The dispersed phase holdup has increased with the increase of rotor speed. Pratt's equation was used for calculating the characteristic velocity. An inverse relation was observed between the characteristic velocity and rotor speed. The estimated overall mass transfer coefficient was increased by increasing the rotor speed. For an extraction column, the overall hydrodynamics and mass transfer performance can be judged by a volumetric utilization factor. At high rotor speeds, volumetric utilization factor for RSDCs is higher than that of RDC. The RSDC II has been successfully applied in reversed micellar extraction of protein.     

Finite pointset method for simulation of the liquid–liquid flow field in an extractor

Finite pointset method (FPM) is applied for the simulation of the single- and two-phase flow field in a rotating disc contactor (RDC) type extraction column. FPM is a numerical method to solve fluid dynamic equations. This is a Lagrangian and meshfree particle method, where the particles move with fluid velocity and carry all information necessary for solving fluid dynamic quantities. The simulations are validated by single- and two-phase 2D particle image velocimetry (PIV) measurements. In addition, the results are compared to simulations of the commercial CFD code Fluent. The results show that FPM can predict the one- and two-phase flow field in the RDC, whereas the predicted velocities are in good agreement with the experimental ones. FPM also bears comparison with the results of the commercial CFD code Fluent.     

Droplet population balance modelling—hydrodynamics and mass transfer

The hydrodynamic and mass transfer behavior of a rotating disc contactor extraction (RDC) column based on a bivariate population balance model is investigated using the generalized fixed-pivot technique for the discretization of droplet internal coordinate. Single-droplet and swarm-droplet studies in small lab-scale devices were used to evaluate breakage and coalescence parameters necessary for column simulations. The breakage probability of single droplets was measured and a new correlation was developed, which also takes viscosity effects into account. Coalescence probability studies resulted in chemical system dependent parameters, which were obtained by an inverse solution of a simplified balance model. In a final study, the hydrodynamic and mass transfer behavior of pilot plant RDC columns have been simulated based on the parameter set derived from the lab-scale units. The simulated mean Sauter diameter, hold-up values and concentration profiles were found to be well predicted at different operating conditions. The relative error for the simulated mean Sauter diameters is about 15%, for the hold-up about 20% and for the concentration profiles about 20%.     

New Approach in the Prediction of RDC Liquid‐Liquid Extraction Column Parameters

The liquid‐liquid extraction process is well‐known for its complexity and often entails intensive modeling and computational efforts to simulate its dynamic behavior. This paper presents a new application of the Genetic Algorithm (GA) to predict the modeling parameters of a chemical pilot plant involving a rotating disc liquid‐liquid extraction contactor (RDC). In this process, the droplet behavior of the dispersed phase has a strong influence on the mass transfer performance of the column. The mass transfer mechanism inside the drops of the dispersed phase was modeled by the Handlos‐Baron circulating drop model with consideration of the effect of forward mixing. Using the Genetic Algorithm method and the Numerical Analysis Group (NAG) software, the mass transfer and axial dispersion coefficients in the continuous phase in these columns were optimized. In order to obtain the RDC column parameters, a least‐square function of differences between the simulated and experimental concentration profiles (SSD) and 95 % confidence limit in the plug flow number of the transfer unit prediction were considered. The minus 95 % confidence limit and sum of square deviations for the GA method justified it as a successful method for optimization of the mass transfer and axial dispersion coefficients of liquid‐liquid extraction columns.     

Hydrodynamic and mass transfer parameter correlations for the rotating disc contactor

The normal, fragmented manner in which various model hydrodynamic and mass transfer parameters are measured and correlated separately, in the vain hope that accurate predictions of extraction column performance will be eventually possible, is avoided here. The ‘forward mixing’ model parameters are all determined simultaneously, in experiments with two sizes of rotating disc contactor where all required measurements, including drop size distributions and continuous phase profile compositions, are made during solute transfer between phases. Accurate predictions from the derived correlations of dispersed phase hold-up fraction, drop size distributions and extraction efficiency are the result.     

CFD simulations and particle image velocimetry measurements in an industrial scale rotating disc contactor

Fluid dynamics of the single‐phase and two‐phase flow in a segment of a rotating disc contactor (RDC) liquid–liquid extraction column with 450 mm inner diameter were studied by performing computational fluid dynamics (CFD) simulations and particle image velocimetry (PIV) measurements. The fluid dynamics were investigated to test the predictivity of CFD at industrial scale. Different turbulence models in conjunction with the Eulerian approach were applied in the single‐phase and two‐phase simulations. The turbulent flow characteristics were analyzed by PIV measurements to validate the CFD simulations. An iso‐optical system composed of CaCl₂/water–butylacetate allows for the two‐phase PIV measurements. Local turbulent energy dissipation was derived from velocity gradients in PIV data. In this connection, the influence of the PIV spatial resolution on the measured energy dissipation was also analyzed, and different fit functions were tested to scale the measured energy dissipation. Simulated velocity fields as well as the energy dissipation were compared with the experimental PIV data. The results from the simulations and experiments are in good agreement. The work shows that CFD can predict hydrodynamic characteristics even at bigger scales but is still subject to some minor restrictions. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Hydrodynamics,axial mixing and mass transfer in open turbine rotating disc contactor (OTRDC)

An experimental study of hydrodynamics, axial mixing and mass transfer has been carried out in a newly developed liquid-liquid extraction contactor, namely the open turbine rotating disc contactor (OTRDC). It has been established that the OTRDC can be operated with larger holdups of the dispersed phase, larger interfaces and, hence, more efficient mass transfer than the conventional RDC. In correlating axial mixing data, a combined model has been applied in which both the forward mixing due to drop size distribution and the backmixing of droplets are taken into account. The RTD curves of dispersed phase predicted by the model agree well with the experimental data. Comparison of experimental mass transfer data with those predicted by the proposed axial mixing model and the theoretical single drop model shows that they are in good agreement.     

A NEWLY DEVELOPED LIQUID-LIQUID EXTRACTION COLUMN——The Open Turbine Rotating Disc Contactor(OTRDC)

The experimental study on hydrodynamics,axial mixing and mass transfer has been carried out in anewly developed liquid-liquid contactor,the open turbine rotating disc contactor(OTRDC).It has been foundthat the OTRDC is possible to be operated with higher hold-up of dispersed phase,larger interface and hencehigher efficiency of mass transfer comparing with the ordinary RDC.In correlating axial mixing data,a combinedmodel has been used in which both forward mixing due to the drop size distribution and backmixingof droplets are taken into account.The RTD curves of dispersed phase predicted by the model were fit wellwith the experimental data.The comparison of the experimental mass transfer data with thosc predicted by theaxial mixing model and theoretical single drop models shown they are in good agreement.