液相物性对规整填料内气液二相流的影响

运用商用流体计算软件FLUENT6.3,建立基于Navier-Stokes方程和VOF方法相结合的CFD分析模型,湍流结构模拟采用RNG k-ε模型,研究了液相物性参数对规整填料内气液二相流体动力学特性的影响。采用文献实验测试结果对该模型进行了验证。重点研究了在一定逆向气流速度条件下液相密度和黏度等物性参数对液膜流动的影响。结果表明:在分析的液相物性参数变化范围内,填料表面均能形成一层稳定的液膜流,气相流场分布也基本一致。液相密度增加,界面液相速度均值增大,沿界面速度值波动幅度降低,填料持液量减小。液相黏度增大,界面液相速度均值减小,持液量增加。2个物性参数改变时,有效界面传质面积均保持在一定值范围内波动。     

规整填料表面液膜流动特性的数值模拟

精馏过程气液两相流运动分布特征对分离效率具有重要影响。为研究规整填料表面液膜流体动力学特性建立了基于VOF方法的CFD分析模型,并基于文献试验结果进行了验证。对液膜随时间和空间的演化分布特征、速度场分布和液相流量影响进行了模拟分析。液膜在波纹顶部下沿聚集形成凸起状波峰,在波纹底部波峰消失,而到达下节波纹上沿时,波峰重新形成;瞬态液膜厚度随时间波动,且沿填料表面液膜平均厚度先减小后保持稳定;发现液相聚集及形成液滴坠落容易导致出现干板区。不同位置液膜速度分布存在明显差异,沿填料表面液膜平均速度先增后减或保持稳定;液膜绕过波纹顶部时会加速,在波纹底部和上沿处会减速。液相流量增大,液膜平均厚度和速度均有所增大。     

加压下规整填料塔内气液两相轴向返混实验研究

An experimental study of the extent of axial backmixing in both gas and liquid phases was conducted in a 150 mm ID column packed with Mellapak 250Y corrugated structured packing. The column was operated at pressures ranging from 0.3 MPa to 2.0MPa with nitrogen and water flowing countercurrently through the packing. The amount of axial backmixing was experimentally evaluated by the pulse response techniques using hydrogen in gas phase and an aqueous solution of NaCl in liquid phase as inert tracers. The response of the tracer was monitored by means of thermal conductivity in the gas phase and electrical conductance in the liquid phase. The experimentally determined residence time distribution (RTD) curves were interpreted in terms of the diffusion-type modei. The results indicated that the axial backmixing in the gas increased notably with gas flowrate and slightly with operating pressure and liquid flowrate. The liquid-phase axial backmixing was an increasing function of both gas and liquid flowrates an     

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…     

逆向气流对规整填料表面液膜流体动力学特性的影响

为研究气相流量对规整填料内气液两相逆流流动情况下流场结构及界面行为的影响,建立了基于分离涡模拟(DES)方法与VOF模型相结合的CFD分析模型,VOF控制方程离散采用显示差分格式,体积分数离散采用界面重构方法。计算域整体采用结构化曲线网格(贴体网格)划分,并对局部进行了细化。结果表明,气相F因子较小时(F≤1.354 Pa^0.5),液膜自由表面及其纵向速度分量(v_y)均呈周期性规律分布,波动幅度基本一致,而v_y均为负值。F=3.386 Pa^0.5时,液膜自由表面波动出现紊乱,幅值差异明显增大,而界面液膜v_y值仍基本呈周期性规律分布,在液相波峰下沿出现v_y >0的情况。F=5.418 Pa^0.5时,出现液相返混,气相和液相内均出现大小不等的回流区并随液相返混过程发展演化,同时局部液膜出现整体向上流动特征。F≥6.772 Pa^0.5后,填料下部出现干板区,底部出口不再有液相流出。随气相F因子增大,持液量和有效界面传质面积均先增后减。     

晃动对填料塔动持液量影响研究

浮式液化天然气装置(FLNG)的研究已成为行业热点,为探索FLNG上设备在海上的适应性成为了重难点。填料塔是FLNG重要的处理设备,其稳定工作对天然气预处理具有重要意义。填料塔持液量能够使塔内达到平稳操作,不易引起产品质量的剧烈变化,具有一定的缓冲作用。文中利用冷模实验装置,探究海上晃动条件对填料塔(规整填料)动持液量的影响规律。实验结果表明:任意单一晃动工况下,其恒持液量区的动持液量均小于静止;摇摆+摇摆、摇摆+平荡2种耦合晃动工况下,在较高喷淋量时载液区动持液量大于静止。文中研究内容为FLNG上填料塔流体力学性能研究提供参考。     

液体黏度对CO_2吸收塔规整填料传质性能的影响

为了有效提高CO2捕集过程中的传质效率,需要测量规整填料在不同溶液体系下的传质性能。在氢氧化钠水溶液-空气-CO2体系的基础上,通过向液相加入甘油的方法,使液相黏度由0.001 Pa·s最高增加至0.002 5 Pa·s。这一改变使实验体系更加接近真实的CO2吸收体系,如乙醇胺、二乙醇胺水溶液等。利用此改进后的体系,在直径为200 mm、填料高度为800 mm的填料塔中,测量了波纹倾角为45°、齿顶角为90°、波纹峰高为9 mm的金属板波纹规整填料在不同操作条件下的有效传质面积。实验结果显示:黏度的改变直接影响到填料在同等条件下的有效传质面积。在实验的基础上,将黏度参数关联到新的关联式中,可以有效预测在不同黏度体系下的有效传质面积,计算值与实验值吻合较好。     

气液并流填料塔的持液量

本文提出用静持液准数E对文献及本试验静持液数据进行关联;在受力分析基础上得到单相持液的半经验关系式,使用范围及精度均比文献值有所提高。对脉冲流区后的动持液量提出了单独的经验关联。     

新型垂直板规整填料流体力学及传质性能

采用氧解吸实验,在直径190 mm的有机玻璃塔内,液相喷淋密度10～38 m³·m^-2·h^-1,F因子0.2～3.2 m·s^-1·（kg·m^-3）^0.5的实验条件下测定了一种新型垂直板规整填料的流体力学及传质性能。实验结果表明：垂直板填料的操作压降及传质性能均显著优于商业波纹填料。通过与几种经改进的250型波纹填料相比发现,两者泛点F因子整体上相当;在较高液体喷淋密度下,垂直板填料传质性能及压降均高于改进250型波纹填料;在低喷淋密度下,垂直板填料可实现压降低于改进250型波纹填料,而两者传质性能相当。此外,对填料结构改进对其性能的影响进行了单因素考察。     

Experimental investigation of liquid holdup in structured packings

Liquid holdup is an important hydrodynamic parameter for characterizing the gas/liquid flow pattern in packed beds. In this paper, a study of liquid holdup in 3 different structured packings: Mellapak 2X from Sulzer, Koch-Glitsch Flexipac 2Y HC, and Montz-Pak B1-250M is presented, using air/water, air/water/sugar solutions with liquid viscosity up to 12 cP and air/30 wt% MEA in a 0.5 m ID absorption column with a packing height of 5 m. As expected, at a given liquid load, the liquid holdup was close to constant as a function of gas flow, with an increase at high gas velocities. In general, the Sulzer packing had a higher liquid holdup than observed in the two other packings. A possible explanation for this could be the lack of enhanced draining of liquid as seen with the modifications of the end-section of the Koch-Glitsch and Montz packings. Liquid holdup was found to increase with increasing liquid viscosity. The influence was higher at high liquid load than at low liquid load. Our results indicate a higher dependency at high liquid load and a lower at low liquid load. There was a reasonable agreement between our results and the data found in the literature.     

Reactive distillation: Non-ideal flow behaviour of the liquid phase in structured catalytic packings

Reactive distillation, the combination of chemical reaction and multistage distillation, is one of the most important industrial applications of the multifunctional reactor concept. The most promising column internals for reactive distillation are the so-called structured catalytic packings that combine favourable characteristics of traditional structured packings and heterogeneous catalysts. The non-ideal flow behaviour of the gas and the liquid phase is a fundamental aspect in multiphase reactor design since it has a strong influence on the reactor performance. In this study, liquid phase residence time distributions for the catalytic structured packing MULTIPAK^® were measured by means of conductivity measurements under different liquid and gas flow rates and evaluated with differential models.     

Hydrodynamics of gas-liquid counter-current flow in solid foam packings

Solid foam materials combine high voidage and high surface area. These two properties are advantageous for use in chemical reactors due to the low frictional pressure drop and relatively high surface area that may be used for catalyst deposition. Hydrodynamic parameters such as liquid holdup, pressure drop, and flow regimes similar to those for packed beds, have been obtained for the gas and liquid flows through these solid foam packings. The open-celled solid foam packings used were in the range of 5-40 pores per linear inch (ppi). The regimes studied are two high liquid holdup regimes and a low liquid holdup regime (trickle flow regime). Also the flooding points for counter-current flow have been determined.     

槽式孔板的低含液率气液两相流测量特性

槽式孔板是一种新型气液两相流量传感器,目前尚未发现能够应用于槽式孔板的两相流压降相关式,结合空气/水两相流实验数据,比较了五类典型的标准节流元件两相流压降相关式对槽式孔板测量数据的计算结果,分析了这些相关式的适用范围和误差原因。基于不同的建模思想,综合考虑洛—马参数、介质压力、气相流量等参数的作用,建立了三种相对准确的槽式孔板两相流压降相关式,并将其应用于低含液率的凝析天然气计量技术研究,计算结果表明三种相关式均能达到工业计量的精度要求。     

微通道内气液两相流行为研究进展

综述了微通道内的气液两相流行为及传质特性。在微通道内流型一般分为泡状流、弹状流、环状流和弹状-环状流,没有分层流。气液传质效率比常规尺度中的提高了2～3个数量级。讨论了气泡对气液两相流的影响及其生成、生长和聚并规律。介绍了微通道内气液两相流的计算机模拟结果。从实验、理论和数值模拟3个方面对微通道内气液两相流的研究和应用前景进行了展望。     

规整填料塔的壁流研究

以新的观点分析了填料塔内壁流产生、发展且最终达到平衡的过程。通过数学推导，得到了一个三参数壁流模型，并在实验基础上，进行模型的参数估计，从而求得了八种规整填料的壁流曲线。研究认为，壁流量的大小是填料塔内诸多因素综合影响的最终结果，而填料自身的几何形状和加工精度，是其中最重要的影响因素。通过实验，测取了这些填料的平衡壁流量，其中某些大于４８％。     

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。     

A study of gas and liquid distributions in structured packings

This study describes the gas and liquid distributions in a column with structured packings. The column is 0.5 m in diameter. It is equipped with a total of 1289 detectors in the top and bottom cross-sections. These detectors provide a detailed picture of the gas and liquid flows through elements of only 25 × 25 mm². The maldistribution in the gas bulk flow is negligible. Only the observed wall can contribute to malperformance. The gas flows in parallel to sheet orientation, thus introducing a radial transport. Together with the change in the orientation of subsequent packing elements, this results in good gas mixing. It was observed that the liquid wall flow rate decreases when the gas velocity exceeds 1.7 m/s. Up to the loading point, the maldistribution of the liquid is constant. Above this point, the equality of the distribution deteriorates rapidly, due to the occurrence of large-scale liquid segregation.     

基于临界分流理论的气液两相流均匀分配器

提出了一种新型气液两相流分配器,主要由旋流叶片、整流器、分流喷嘴以及分配腔室组成。通过采用“流型调整”与“临界分流”控制相分离。为研究不同分流比下的分配特征,设计了2喷嘴和4喷嘴两种分配结构。建立了气液两相流数值模型,模拟了气液两相流在分配器内流动特性。在气液两相流实验环道上进行了测试,气相折算速度范围为5.0～25.0 m·s^-1,液相折算速度范围为0.012～0.14 m·s^-1,实验中出现的流型包括波浪流、段塞流以及环状流。结果表明,在临界分流条件下,气液相分流系数主要取决于与侧支管相连通的分流喷嘴数目与总喷嘴数目的比值,不受流型、气液流速等参数波动的影响。对于2喷嘴分配器分流系数接近理论值0.5,对于4喷嘴气液分流系数约为0.25。