双溢流立体传质塔板上液相流场CFD研究

采用计算流体力学方法对直径为2 600 mm的工业规模双溢流立体传质塔板板上气液二相流动进行了模拟研究。计算了不同工况下收缩流和扩张流2种流型的液相流场分布,得到了双溢流塔板收缩流和扩张流2种流型的板上气液二相流场分布规律。通过将清液层高度的CFD结果和经验公式的计算结果进行对比,验证了所建模型的正确性。模拟计算结果表明:边降液管收缩流板面液相流动较均匀,近似于均匀的收缩流,不存在回流区;中降液管扩张流板面液相流动不均匀,靠近塔板中心流速较快,塔板弓形区存在着回流现象;板孔处的帽罩区液层较其他地方小,液相体积分数较其他地方低,扩张流受气相的影响较收缩流大。     

分流式降液管的流体力学性能研究

用分流式降液管以空气和水进行了塔盘冷模实验,研究了板压降、板上清液层高度和泡沫层高度、降液管泡沫层高度等流体力学性能,并在相同条件下与无分流式降液管进行了对比实验。结果表明:在相同的操作条件下,分流式降液管的塔板压降比无分流式降液管的塔板压降平均降低了39.3%,分流式降液管能有效降低塔板的溢流强度,提高了塔板的处理量。     

DJ型碳丙脱碳和热钾碱脱碳的扩能设计与应用

合成氨生产中常采用碳丙或热钾碱脱除合成气中的二氧化碳，它们的共性是塔内液体流率都比较大，气液流动参数都高达2以上，都属于加压下的高液气比操作。对于板式塔，在扩能改造中往往是塔板的降液管成为瓶颈，易发生降液管液泛现象。DJ塔板具有多根矩形降液管，溢流周边比常规塔板长2－5倍，可通过更大的液量，已在脱塔扩能设计中获得成功的应用。     

降液管长度对分散降液筛板性能的影响

探讨了分散降液筛板塔的降液管,通过计算分析设置了降液管的管径和长度,以"氧气-空气-水"为体系,研究了降液管长度对分散降液筛板的流体力学性能和传质性能的影响,结果表明降液管长度对分散降液筛板的性能具有重要的影响,且降液管长度为20mm的分散降液筛板综合性能较好。     

弓形降液管两相流动的CFD模拟

采用欧拉两相流模型,模拟了弓形降液管内的空气一水两相流动,得到了与弓形降液管堰长垂直截面上的气含率分布与两相的速度分布.结果表明,降液管底部气含率低,中部的气含率增加显著,上部的气含率较高.液相对气相有很强的夹带作用,同时气相的浮力对于液相流动也有一定的阻碍作用.将模拟结果与文献进行对照,两者吻合较好,说明提出的模型对于降液管内流体流动状况的模拟是合适的.     

读者信箱

<正> 一问:什么是无降液旋流板,它有什么特点?答:无降液管旋流板是对有降液管旋流板的改进。取消了降液管,利用塔板和锥体之间的环隙,作为液相通道,大大增加了流通面积,减少了塔板阻力,并在锥体内表面气、液进行膜式吸收,提高了塔板效率。我院在塔板上又设置了溢流堰,克服了原塔型气硫走短路的缺点。因此,该塔具有结构简单,制作方便,阻力小,弹性大,脱硫效率高的特点。二问:贵院设计的无降液管脱硫系统的主要技术参数是什么?     

竖直管降膜蒸发器流动与传热过程的数值模拟

针对竖直管降膜蒸发器的技术特点,在计算流体力学和传热学理论分析基础上,采用FLUENT软件,运用自定义函数(UDF)编写传质源项,对降膜蒸发器的加热管内液体沿壁面呈膜状下降流动并受热汽化过程进行了三维数值模拟研究,模拟采用Mixture两相流层流模型,Simple算法。模拟结果以3D形式表现了液体沿运动方向在管壁发展成膜的过程,并将模拟得到的液膜厚度与理论计算得到的液膜厚度进行了比较。模拟结果表明,竖直降膜蒸发器加热管具有液膜薄,均匀性好的特点,管表面容易形成柱状流,液膜厚度为1.0 mm。     

一次液泛事故的原因分析及处理措施

0 引言 直径一定的精馏塔可供气、液两相自由流动的截面是有限的.气、液两相之一的流量若增大到某个限度,降液管内的液体便不能顺畅流下,当管内的液体达到上层板的溢流堰顶时,便要漫到上层板,产生不正常积液,最后可导致两层板之间被泡沫充满,这种现象称为液泛,亦称淹塔.精馏塔液泛的原因有：塔内气体流量过大,压差过高,溢流液体无法以自身重力通过降液管流动到下一层塔盘,从而在塔盘上形成积液,导致液泛;过量液沫随气流夹带至上层塔盘,致使上层塔盘液层变厚,加厚的液层又引起更多的液沫被夹带至上层,从而引起液泛.精馏塔液泛将导致塔内压差上升,分离效率降低,馏出组分不合格.     

垂直上升气液两相弹状流模型

基于等效弹单元思想,改进了预测垂直上升管中充分发展气液弹状流流动特性的模型。 模型中考虑了界面切应力对液膜运动的影响;并在液弹空隙度预测中引入临界气体夹带速度的概念,以此来描述弹状流中大气泡尾部的混合特性。本文提出的模型还考虑了管径对液弹空隙度的影响。弹状流模型的计算结果得到本文及其他作者实验数据的验证。     

液液水力旋流器场特性与分离特性研究（四）——锥角变化对压力损失的影响

对液液水力旋流器的压力损失分布情况进行了简单的介绍，分别研究了液液水力旋流器大、小锥角变化对其底流压力损失及溢流压力损失的影响，并对其影响程度进行了分析。     

Flow Regime Maps for Flow of Liquid Through Downcomer in a Turbulent Bed Contactor

The provision of a downcomer to classical turbulent bed Contactor (TBC) increases the gas treating capacity of the equipment. When the downcomer is provided, it is expected that all the liquid passes through the downcomer only without any liquid flow through the distributor. In the present study, the operational regime for the flow of liquid only through the downcomer is experimentally evaluated for various geometric parameters and particle characteristics. It is observed that the preferred operational regime without dumping and weeping increases with an increase in Archimedes number and downcomer diameter, and decreases with an increase in static bed height and downcomer weir height. Correlations are proposed to satisfactorily predict experimentally observed operational regime.     

板式塔降液管的机械消泡研究

研究开发了板式塔降液管机械消泡板组件。在降液管中加设特制的新型消泡板组件,该组件由数列若干块相互平行的倒V字形波纹板垂直排列组成,倒V字形波纹板的开口端向下。消泡板组件半浸于降液管泡沫层中,越堰的泡沫液与波纹板碰撞,以及波动的泡沫层不停地与波纹板摩擦,都加速泡沫的破裂,促进降液管内气液分离,降低了泡沫层高度。开口端向下的倒V字形波纹板还对降液管内液体产生向下的作用力,降低了降液管清液层高度。试验结果表明,对易起泡物系,降液管机械消泡板组件能降低泡沫层高度13.1%—36.2%,降低清液层高度10.5%—32.5%。对不易起泡物系,消泡板组件能降低泡沫层高度7.1%—33.2%,降低清液层高度5.1%—24.6%。因此,该消泡板组件可以起到降低降液管液层高度和延缓降液管液泛的作用,具有良好的消泡效果。     

高通量塔板悬挂式降液管击穿漏气的气液相研究

采用空气-水物系,在直径为500mm的有机玻璃塔中对底部分别开有8个和12个液流孔的悬挂式降液管的漏气进行了研究,并在假设漏入降液管的气体产生的压降与板压降相等的基础上建立了击穿漏气模型.结果表明,当塔内的气体流量逐渐增大,漏入的气体以气柱的形式连续进入降液管时,降液管液层被击穿,降液管无法正常操作.根据实验数据得到了击穿漏气模型的关联式,关联式的计算值与实验值吻合较好.开有12个液流孔的降液管在液流孔的真实漏气气速为1.40 m/s时,漏入的气体会击穿降液管液层.     

多管气升式环流反应器的液体循环

A multi-tube air-lift loop reactor (MT-ALR) is presented in this paper. Based on the energy conservation, a mathematical model describing the liquid circulation flow rate was developed, which was determined by gas velocity, the cross areas of riser and downcomer, gas hold-up and the local frictional loss coefficient. The experimental data indicate that either increase of gas flow rate or reduction of the downcomer diameter contributes to higher liquid circulation rate. The correlation between total and the local frictional loss coefficients was also established.Effects of gas flowrate in two risers and diameter of downcomer on the liquid circulation rate were examined. The value of total frictional loss coefficient was measured as a function of the cross area of downcomer and independent of the gas flow rate. The calculated results of liquid circulation rates agreed well with the experimental data with an average relative error of 9.6%.     

Flow regimes in a turbulent bed contactor

Experiments were conducted in a turbulent bed contactor (TBC) with and without downcomer operating in Type I and Type II modes to obtain the flow regime maps. The variables include flow rate of the gas and liquid phases, size and density of the particles, bed height, free open area of the supporting grid, and diameter and weir height of the downcomer. Static, partially fluidized, completely fluidized, flooding and annular regimes are identified depending on geometric and operating conditions. The effect of these variables on flow maps is discussed and correlations are proposed for delineating the flow regimes.     

Liquid-phase mixing in external-loop airlift bioreactors

Mixing time, circulation time and downcomer linear liquid velocity were measured in two sizes of external-loop airlift bioreactors with Newtonian and non-Newtonian fluids. The mixing time increased as a result of an increase of non-Newtonian characteristics. However, the liquid circulation time was affected only slightly by non-Newtonian flow behaviour. A semi-empirical correlation for circulation time in external-loop airlift bioreactors was proposed. The proposed correlation was compared with the present experimental results and those in the literature. Reasonable agreement was obtained between the predicted and experimental values of circulation times. The downcomer liquid velocity was almost independent of the downcomer-to-rise cross-sectional area ratio. The correlation based on the concept of an eddy diffusivity predicted downcomer liquid velocities in Newtonian and non-Newtonian fluids.     

A new streamlined bubble-cap distributor for high gas–liquid ratio and the liquid distribution mechanisms

The bubble-cap distributor is the most commonly used and critical internal for trickle bed reactors but holds the inherited disadvantage of liquid central aggregation when operating at a high gas–liquid ratio. A new bubble-cap distributor with a streamlined downcomer was developed in this paper to counter back the liquid aggregation and improve its comprehensive performance. The effect of the streamline parameters of the new distributor on liquid distribution was systematically explored by the coupled Euler–Euler-population balance equation (PBE) model. Compared with the classical and polyline converging–diverging structures, the results showed that the streamlined downcomer was a key to generating radial velocity of two-phase flow and reducing the liquid central aggregation for the bubble-cap distributor. The mechanism of well-distribution was explored for the new distributor. Lower converging and diverging angles enhance the distribution performance. A downcomer with a small converging angle and a 30° diverging angle was recommended for dispersing the central aggregated liquid column and acquiring the high distribution uniformity and spray covering circle. These data would be helpful to the optimal design and scale-up of the bubble-cap distributor in further industrial applications.     

数控扫描-γ射线透射技术用于研究塔板两相流体性状的测试

本文用所开发的数控扫描—γ射线透射技术很方便地研究了浮阀塔板的诸流体力学参数,并考察了板上的两相接触状态.     

用纤维光学技术测定液体混合程度对筛板塔效率的影响

本研究采用纤维光学技术及以任意方式注入示踪剂、两点检测之激励-响应手段,实测了普通筛板和大孔径筛板的液相涡流扩散系数.通过对试验数据的回归分析,在较宽的操作条件范围内,得到了涡流扩散系数与堰高、液流强度及空塔气体动能因子的关联式,并发现普通筛板和大孔径筛板可用同一关联式很好地关联.本文关联式所预测的板效率与实测的板效率相比相当符合.     

高液通量DJ塔板的合理设计和工业应用

高液通量塔板在工业上有很大需求。为了通过高液量,塔板设计的关键是降液管结构,尺寸和布置。ＤＪ塔板系列具有独特的降液管型式,其结构和性能适用于高液通量操作;已成功地应用于炼油,石化和化肥的吸收,精馏装置中。