供料对离心机内部流场影响的耦合数值研究

为研究不同供料条件对离心机内部气体流场和分离性能的影响,采用将稀薄流区和连续流区进行耦合计算的方法,即采用DSMC方法求解稀薄流区,获得供料射流的流动结构;采用有限差分方法离散非线性方程组,并用牛顿迭代法求解,计算中考虑了两种供料模型,得到了不同供料条件下的连续流区的流场分布,进而求得单机分离性能.考虑了两种供料模型,计算结果表明：考虑到实际供料射流的流场分布后,与均匀供料假设相比,离心机的分离功率有所下降.并且分离功率还与供料点的轴向和径向位置有关.     

基于部分分离法的油气水三相流量测量的研究

针对油气水三相流流量测量的难题,设计了基于部分分离原理的油气水三相流分离装置;同时,考虑了经分离后得到的油水两相流的密度分布不均匀对流量测量的影响,将油水两相混合密度进行了修正,得到了基于文丘里管两端差压和体积含水率的油水两相流流量测量模型.采用转子流量计和文丘里管分别对分离后的气相、液相进行了流量测量实验.结果表明,本文提出的分离装置的设计思想和设计结构及基于差压法的油水两相流流量测量模型是合理的、可行的,能够实现对油气水三相流流量的测量.     

中空纤维气体膜分离器丝外流速分布及其对分离性能的影响

实验测定了φ103×1300 mm中空纤维气体膜分离器丝外的流速分布.结果表明,分离器中丝外气体流速分布不均匀.而且,随着气体处理量的降低,流速不均匀程度增大,器内中心处流速最大,近壁处流速最小.假定器内流动是轴对称的,导出了流速不均匀情况下,流量分布和流道分布的数学模型,并且计算了对分离性能的影响.模拟计算结果表明,对N_2/H_2膜分离器而言,器内流动不均匀性对分离结果有明显影响.     

平行流场气液两相流动瞬态模拟

对平行流场两相流瞬态过程进行了初步模拟研究,利用VOF两相流模型对平行流场内初始分布有液体然后通入一定流量气体进行吹扫的瞬态过程进行了数值计算,分析了流场竖直布置时重力对流道内液体传递造成的影响。结果表明,平行流场竖直放置时不利于液态流体的排出,液体的分布也不均匀。为提高该种流场排出液体的能力,本文对流道进出口总管进行了改进设计,采用渐缩总管的布置形式,并进行了计算,发现渐缩型总管可以改善液体在不同流道间的分布。     

基于CFD的网带式烘干机的优化设计

为了解决网带式烘干机内部气流分布不均匀,从而导致物料干燥不均匀的问题。本文使用计算流体力学CFD软件,对网带式烘干机内部的气流速度场进行模拟研究。模拟结果是风机转速为1050 r/min时烘干机内部气流分布较合理,之后再通过调节风机的转速及风机叶片数,对不同轴流风机参数下烘干机内部的气流进行模拟分析,模拟出烘干机内物料表面各处风速,与实际生产相对比,得出10叶片的轴流风机干燥效果最好。     

两级组合式除雾器的分离性能分析

为研究两级组合式除雾器的分离性能,对两级旋流式、组合式、两级折流式3种除雾器进行性能分析。通过数值模拟方法分析除雾器内部流场差异,通过搭建实验平台,利用高速摄影技术并结合除雾器流场分布分析液滴在除雾器内部运动行为,进而从压降损失、分离效率、出口液滴粒径等方面开展除雾器分离性能的实验研究。结果表明：液滴在折流板内主要靠撞击叶片累积形成液膜而被捕集,在旋流板内沿叶片边缘滑动,以接近叶片倾角角度向壁面运动形成液膜被捕集;随入口截面速度增加,3种除雾器压降均逐渐增大,差值不断增加,两级旋流式除雾器压降最高;当入口截面速度低于5.7m/s时,两级旋流式、组合式除雾器分离效率均接近100%,同时组合式除雾器出口液滴中位粒径始终低于入口液滴中位粒径,并小于其余两种形式除雾器,对小粒径液滴分离能力显著;当液相流量从6.2m³/h逐步增加至13.7m³/h,3种形式的除雾器分离效率随液相流量增加呈下降趋势,其中两级旋流式除雾器在高气速、高液相流量下适应性最强,同时3种除雾器出口液滴中位粒径总体呈现下降趋势,其中组合式除雾器出口液滴中位粒径仍居于最低水平。     

中国水泥工业烧成系统技术升级路线图之预热器现状与创新性改造

预热器出口温度偏高的现象比较常见。下料管的布置决定着物料的分散程度,物料分散度差,预热器换热不佳,是造成预热器出口温度高的主要原因。预热器出口温度与下料管温度相差大,"热风"与"冷料"换热不充分,亦是预热器换热不佳的体现。物料分散不佳,造成预热器压力损失增大。因此,当上下两级预热器压差大时,其温差小,换热不佳;反之亦然。应改造下料管的结构形状以及下料管和翻板阀的位置。解决预热器出口温度偏高的现象,还可采用创新性地减少一级预热器的两级高固气比预热器系统。     

孔流型液体分布器二级槽内的流场分析

为了研究底孔型液体分布器二级槽中的流动特性和考察挡板与液位两种因素对性能的影响,采用数值模拟方法,通过SST湍流模型和VOF多相流模型获得槽内的气液两相流场,分析了不同液位下挡板对底孔流量均匀性的影响。结果表明：低液位时槽底附近有明显的横向流动,挡板可以抑制这种横向流并将入口射流带进的湍流扰动移向液面。高液位时槽底横向流不明显,但射流点附近液面以下有大尺度涡流,挡板顶部绕流使相应区域产生速度波动并沿高度方向衰减。液位无论高低,设置挡板都使槽底横向流被阻滞,挡板对不同位置孔附近流场的改变方式不同,射流落点位置和板后回流涡形态的改变造成流经孔口上方介质中进入孔内的比例和孔内流速的改变,共同影响孔内流量的变化。挡板使底孔流量均匀性有所下降,主要原因是射流点下游底孔附近射流和涡流的不良分布,而较高的液位由于增加了对射流、横向流和挡板扰流的惯性和黏性阻滞,可以改善底孔流量均匀性。     

L型片材挤出机头流道速度分布三维有限元分析

利用大型有限元计算软件ANSYS进行以三维模型为基础的L型机头内部流动速度分析和模拟研究。通过顺次截取沿挤出方向上 4个不同区域的速度分布图和 7个截面中间层节点横向速度分布曲线 ,分析了物料在L型片材挤出机头中的流动分布情况 ,即物料在机头内部经过几次速度调整逐步达到横向速度分布基本均匀     

新型双蜗壳式旋风分离器内流场分布的试验研究

采用五孔球探针测试仪对一种新型双渐开线入口结构旋风分离器分离空间的三维速度和压力分布进行了测量。试验结果表明,该旋风分离器分离空间的切向速度呈现“驼峰”分布,最大值达到29vp,离心力场较强,上行流区的静压变化为顺压梯度,有利于降低压力损失;在流场测量的基础上,利用积分离散化的方法计算了分离空间的下行流量,指出控制短路流和分离空间下端的旋涡流动是进一步的优化方向。     

A Mathematical Analysis of Membrane Separation Parameters for Liquid/Liquid Dialysis in Single or Multiple Stages

Abstract

The effects of membrane separation parameters using liquid/liquid dialysis under idealized conditions and using hollow fiber geometry were calculated with the aid of a computer. These calculations were carried out for both single stage and multiple stages. Membrane separation parameters include the intrinsic properties of the membrane, the nature of the dialysis solvents, the flow rates of both feed and solvent streams, and the dimension of the hollow fiber. It was concluded that an efficient process using liquid/liquid dialysis requires a membrane with a high intrinsic permeability constant and a reasonable separation factor, as small an inner radius of hollow fiber as is practical, and a dialysis solvent with an acceptable activity coefficient for the key species and a flow rate suitably coupled to that of the feed.     

Analysis of Membrane Separation Parameters. II. Counter-current and Cocurrent Flow in a Single Permeation Stage

Abstract

Analytical expressions are presented for calculating the extent of separation of binary gas mixtures achievable in a permeation stage, as well as the required membrane area, when the high- and low-pressure streams in the stage flow either countercurrently or cocurrently to each other. The derivations are similar to those of Oishi et al., but are cast in a form suitable for computer calculations. The results of a parametric study on the separation of oxygen from air are presented for four different flow patterns inside the stage: (a) countercurrent flow, (b) cocurrent flow, (c) cross-flow, and (d) perfect mixing. In the first three cases it is assumed that no mixing occurs on the two sides of the stage (or membrane). The type of flow in the permeation stage can have a significant effect on the degree of separation, but has relatively little effect on the membrane area at low separation factors. Countercurrent flow is the most efficient flow pattern, whereas perfect mixing is the least efficient one, both from the viewpoints of extent of separation and membrane area requirements.     

1种上行气固分离装置的冷态实验研究

对1种基于离心和惯性协同作用机理的新型气固分离装置进行了结构考察和改进。优选出最佳分离器结构。以废催化剂为原料，对固含量、风速、挡板和原料粒度等影响其分离效率和压降的各因素进行了考察分析。结果表明，固体含量、风速、挡板以及原料粒度对分离器性能均有不同程度的影响．分离器压降与气体所占的相对空间和排气管内旋流中心偏离轴心的程度有关。固体出口处的缩1：7可以减少分离过程中的返混现象。     

水力旋流器新型出口挡板结构对分离性能的影响

针对小直径水力旋流器,设计了不同内置挡板式的溢流管和底流管,实验研究了新型出口挡板结构对水力旋流器分离性能的影响。研究结果表明：内置挡板溢流管适用于处理量较大的工况,与传统溢流管相比,分离效率略有降低,但在高流量下其压降的降低幅度可达11.11%,挡板宜采用相对较窄、较短、三块120°间隔设计方式;底流管内置挡板采用十字交叉结构可稳定内旋流,使分离效率最大可提高5.96%;新型内置挡板的溢流口与底流口相耦合,可同时实现提高分离效率和降低压降的目标。此外,在相同情况下,发现溢流管内置挡板可消除水力旋流器内部的“空气柱”,据此推断“空气柱”并非由内部空气形成,而是其内部负压中心形成的某种湍流程度较高的强制旋流涡。     

No-Mix and Ideal Separation Cascades

Abstract

Ideal countercurrent recyle cascades are characterized by two propertie: 1) The compositions of heads and tails streams forming the feed stream to individual stages are the same, and 2) the heads separation factor for each stage is constant. When these two criteria are met, the heads and tails separation factors are constant and equal to the square root of the stage separation factor. The mixing of streams with different compositions within a separation cascade obviously constitutes an inefficiency since it is precisely the reverse of this process that is desired, hence Condition 1, which is often referred to as the no-mix-criterion. Separation cascades for which both criteria are valid are termed ideal. However, the ramifications of Condition 2 are not obvious and it is possible to design no-mix cascades which do not meet the second condition. Mathematical relationships between ideal and no-mix separation cascades are derived to quantify these differences. It is shown that Condition 2 minimizes the total interstage flow required to make a given separation for any no-mix cascade design, i.e., it is an ideal cascade by definition. Finally, the required number of ideal stages necessary to perform a specific separation with no-mix cascades are evaluated and compared to those of the ideal cascade.     

Analysis of Membrane Separation Parameters

Abstract

This study is concerned with the separation of gas mixtures by selective permeation through nonporous polymeric membranes, a technique that has made considerable progress in recent years. First, several theoretical methods for calculating the separation achievable in a single permeation stage are reviewed and their advantages and limitations are discussed. The methods under consideration assume two idealized flow regimes inside the stage, which are characterized by (a) perfect mixing on both sides of the membrane and (b) cross-flow with no mixing on either side of the membrane. Computer programs for the numerical evaluation of these methods are presented. Second, the effects of several important process variables on the single-stage separation and membrane area requirements are outlined in a parametric study, with special reference to the separation of oxygen from air. The variables include (a) the ratio of pressures on the two sides of the membrane, (b) the pressure level at constant pressure ratio, (c) the fraction of feed permeated (the stage “cut”), and (d) the ideal separation factor. The practical implications of the results are also discussed.     

Simulation and analysis of multi-stage centrifugal fractional extraction process of 4-nitrobenzene glycine enantiomers☆

Based on the interfacial ligand exchange model and the law of conservation of mass, the multi-stage enantioselective liquid–liquid extraction model has been established to analyze and discuss on multi-stage centrifugal fractional extraction process of 4-nitrobenzene glycine (PGL) enantiomers. The influence of phase ratio, extractant concentra-tion, and PF6?concentration on the concentrations of enantiomers in the extract and raffinate was investigated by experiment and simulation. A good agreement between model and experiment was obtained. On this basis, the influence of many parameters such as location of stage, concentration levels, extractant excess, and number of stages on the symmetric separation performance was simulated. The optimal location of feed stage is the middle of fractional extraction equipment. The feed flow must satisfy a restricted relationship on flow ratios and the liquid throughout of centrifugal device. For desired purity specification, the required flow ratios decrease with extractant concentration and increase with PF6?concentration. When the number of stages is 18 stages at extractant excess of 1.0 or 14 stages at extractant excess of 2.0, the eeeq (equal enantiomeric excess) can reach to 99%.     

PAC-PFS絮凝-膜分离法处理含油废水

采用PAC-PFS絮凝-膜分离法处理含油废水。通过对几种不同的絮凝剂比较,选择较好的絮凝剂,研究了PAC和PFS的原料配比、投加量、絮凝时间对含油废水中的油、CODcr、SS去除率的影响,同时研究了进料流量和操作压力对膜性能的影响,得到了较为适宜的工艺条件。经处理后的含油废水中油、CODcr、SS的去除率分别达到98%、96%、96%以上,出水水质达到国家一级排放标准。     

Reactor performance with high velocity surface feed

Reagents have traditionally been fed into the impeller region of stirred tank reactors to utilize the high levels of turbulence, improve mixing rates and hence reduce mixing limitations. There are; however, numerous operational problems associated with submerged feed with dip tubes so surface feed is still preferred by operations staff. One alternate way of adding reagents into a stirred tank is to feed at the liquid surface using a high velocity jet. The ability of a high speed jet mixed feed stream to reduce mixing limitations has been investigated in this study. While most previous studies report results in the laminar flow regime (even for mesomixing limited operation), the present investigation presents data for much higher feed velocities.Experiments revealed that with reduced feed time, there is a local maximum in byproduct formation and the product quality initially improves with faster feed once this point is reached. However, other factors (primarily macromixing issues) limit the maximum improvement that can be achieved and in fact at very short feed times the byproduct formation increases again. Analysis of the design based on mixing and turbulent jet constraints shows that it is very difficult to obtain a fully turbulent jet because this leads to very short feed times (and associated convective stoichiometric limitations), very high feed stream velocities (where the feed stream overshoots the impeller) or very small feed pipe diameters (giving a large pressure drop through nozzle). Feed jets at high velocities are difficult to achieve under reasonable operating conditions and do not provide any substantial improvement in performance.     

A Chemical Exchange System for Isotopic Feed to a Nitrogen and Oxygen Isotope Separation Plant

Abstract

A process has been developed to provide isotopic feed to a nitric oxide isotope distillation plant. Central to the process is the isotopic chemical exchange of NO and nitric acid in countercurrent flows in a 3-in. diameter packed column. An isotopically depleted stream of NO is reenriched to natural isotopic abundances by the exchange and is recycled as feed back to the distillation columns. Makeup NO is generated in another column from sulfur dioxide and nitric acid. Multistage gas purifiers reduce condensible impurities in the nitric oxide below 10 ppm. The process operates unattended at flow rates of 0.5 to 2 mol/min. The new NO recycle-enrichment and generation processes have successfully provided the feedstock for the NO isotope separation columns for over 6 years.