浮阀塔板上两相接触状态及相状态转变规律的探讨

本文作者对锥心浮阀塔板上气液两相的接触状态进行了实验研究,认为主要有喷溅、混合泡沫和完全泡沫三种状态.在正常的气液负荷范围内系混合泡沫状态.文中探讨了两相接触状态的转变规律与塔板入口端的清液层高度以及塔板上的雾沫夹带率有良好的对应关系,从而确定了有两个转相点.此外,还对两相接触状态的转变机理作了初步分析,得出了计算相状态转变点的准数关联式.     

宝塔罩型塔板性能研究

开发了一种宝塔罩型塔板。该塔板是在塔板上设置数个由板孔、升气筒、塔型罩、进液孔所构成的豆塔罩单元，在单元内气液呈喷射状态接触，实现两相传热传质。流体力学性能和传质性能研究证明：该塔板压降、氧解析效率、漏液等性能与新型垂直筛板相当，但雾沫夹带要比新型垂直筛板低。因而该塔板具有较大的生产处理能力和较宽的稳定操作范围。     

新型矩形垂直筛板的研究

研究了一种矩形垂直筛板.该塔板是在塔板上设置数个由板孔、升气筒、矩型罩、底隙所构成帽罩单元,在单元内气液呈喷射状态接触,实现两相传热传质.流体力学性能和传质性能研究证明该塔板压降、漏液等性能与新型垂直筛板相当,但雾沫夹带要比新型垂直筛板低.因而该塔板具有较大的生产处理能力和较宽的稳定操作范围.     

二元系分批式闪急蒸馏的计算

闪急蒸馏亦称为平衡蒸馏,是将一批液体中的一部分汽化,并使所发生的全部蒸气与留剩的全部液体保持密切接触,俾蒸馏终了时,蒸气与液体互成平衡,然后再将蒸气抽出而冷凝之。因此,在蒸馏终了时,气液二相组成间的关系,应如平衡图上所示,且与汽化的程度有关。此三者间的关系式如下:     

组合导向浮阀塔板的雾沫夹带实验及CFD模拟

对组合导向浮阀塔板进行了水力学实验，测定了2块直径1m、不同浮阀排布的组合导向浮阀塔板的雾沫夹带和相关水力学数据。根据实验塔板的结构和尺寸参数建立几何模型，采用Fluent 6.3.26软件对板上气液两相流动进行CFD模拟，考察了塔板上的气液两相流动状况。清液层高度和雾沫夹带的模拟结果与实验结果吻合较好，验证了模拟的准确性。对两块不同浮阀排布的组合导向浮阀塔板的雾沫夹带和板上液体反向流进行了分析，结果表明在适当位置用导向能力更强的梯形浮阀代替矩形浮阀可有效降低雾沫夹带率和液体反向流比例，雾沫夹带率的实验值和模拟值分别降低了13.4%和10.6%，液体反向流比例降低了12.8%。研究结果表明，通过CFD模拟可望指导两种浮阀的合理排布和塔板的优化设计。     

精馏塔塔板两相流理论及实验研究

塔板上气液两相的流动状况尤其是液相的流速分布对塔板效率有重要影响。针对塔板上的气液两相流动 ,研究者提出了许多理论及实验方法 ,以期准确模拟和测量塔板上液相的流动分布。文中介绍并评价了塔板两相流动计算的各种理论模型以及两相流动测量的各种实验方法     

组合导向浮阀塔板多相流的数值模拟

为了深入了解组合导向浮阀塔板的流体力学性能,在阀片全开状态下,利用计算流体力学(CFD)方法对700 mm中试规模的组合导向浮阀塔塔板上的气液两相三维流场进行模拟研究,采用欧拉-欧拉非稳态模型(Eulerian),考虑气液两相间的动量传递现象,将清液层高度作为衡量非稳态流场收敛的判别标准。通过关联实验数据,得出适合组合导向浮阀塔板的清液层高度关系式,并与模拟结果进行对比。模拟结果表明,组合导向浮阀塔板的液面梯度和弓形区域回流面积小,具有良好的流体力学性能。     

泡沫法——化工新成就之一

一、引论在化学工业中,经常碰到气体和液体直接接触的传热或传质,或同时进行传热和传质的过程。此外,气体的湿法清净也是通过气、液两相的直接接触来进行的。目前在工业上进行气、液两相直接接触所用的设备,按照两相之间接触的情况可以分为两类:     

立体连续传质塔板板上清液层高度实验研究

对立体连续传质塔板( LLC - Tray)的板上清液层高度进行了测量.结果表明:LLC -Tray板上清液层高度随液体流量的增加而增加,随堰高的增加而增大,气速对清液层高度的影响很小.     

计算塔板板效率的局部贡献法

<正>引言 塔径较大的塔板上液体流动的不均匀性对板效率的影响早已引起了人们的注意,在大型塔板上,由于气液两相的剧烈湍动,致使不同区域液体的流动各不相同,如果只采用单一形式描述塔板上液体的运动特点,未免有失普遍性。因而,本文将在分析塔板上液体运动特点的基础上,提出一种新的计算模型,力求更好地符合实际情况。1 实验现象 塔板上流体力学的测定是在前已述及的装置上进行的,用热膜风速仪直接测定了塔板上气液两相流场的分布,发现不仅塔板弓形区存在返混,而且塔板入口堰附近一段距离内,液体也存在返混,其具体长度随液流强度、气相负荷以及出口堰高度等因素而异。采用逐步回归分析方法对实验数据进行回归,得到入口堰返混段长度关联式     

带有侧线采出回流的部分透热精馏的节能优化

以正丙醇-异丙醇体系为例，研究了带有侧线采出回流的部分透热精馏操作。在该操作中，精馏段侧线采出气相，经塔外冷凝后回流至塔内采出板上方；提馏段某塔板被同轴的夹套式中间再沸器环绕，侧线采出该板处的气相回流至塔内采出板上方。通过单因素分析和响应面法对精馏段和提馏段操作的相关工艺参数分别进行了模拟优化，并对相应操作的热力学性能和分离性能的变化进行了分析。最终优化结果表明：达到规定的分离效果，带有侧线采出回流的部分透热精馏相较于绝热精馏有效能损失降低了26.5%。带有侧线采出回流的部分透热精馏操作通过合理分配能量、降低对热剂和冷剂的品位要求和提高能量利用率，最终达到节能目的。     

混合池模型推算气液返混对精馏效率的影响

精馏操作过程中 ,气液返混现象对精馏传质效率有重要影响。为预测其影响规律 ,文内针对含有错流塔板且气相预混合的精馏塔 ,提出了气液返混发生时计算精馏效率的混合池模型。所得计算结果与实验数据的比较说明模型是可靠的。在此基础上 ,根据计算结果 ,探讨了不同情况下气液相返混对精馏效率的影响 ,发现气体返混和液体返混的发生均导致板效率下降 ,且过程的汽提因子和点效率越大 ,板效率随返混的发生而下降的速度越快。     

汽—液—液三相与汽—液两相塔板效率比较

本文通过小型精馏塔及600×150 mm~2矩形模拟塔的实验,对比研究了气(汽)-液两相和气(汽)-液-液三相的塔板效率。并就物系性质(表面张力梯度、液体粘度或分散粘度),两液相体积比,气速及操作工况对传质的影响进行了研究。提出三相传质和两相传质差异的主要因素,得出估算三相精馏塔板效率的关联式。     

塔板上流型变化对板效率影响的计算传质学

利用能够描述塔板上气液两相错流过程的流体力学模型,建立了同时模拟气液两相流动与传质过程的数学模型;通过对气液两相传质方程和流体力学模型方程的联立求解,计算得到了塔板上液相速度分布和气液两相浓度分布的数值解,考察了气相完全混合和气相部分混合两种条件下塔板上的气液两相浓度分布,同时考察了气相完全混合时流型变化对塔板效率的影响.     

Overall efficiency evaluation of commercial distillation columns with valve and dualflow trays

The main objective of this work is to establish appropriated ways for estimating the overall efficiencies of industrial distillation columns with valve trays with downcomer and dualflow trays. The knowledge of efficiencies has fundamental importance in the design and performance evaluation of distillation columns. Searching in the literature, a tree of alternatives was identified to compose the tray efficiency model, depending on the mass transfer models, the liquid distribution and vapor flow models on the tray, the liquid entrainment model, the multicomponent mixture equilibrium model, the physical properties models, the height of froth on the tray model and the efficiency definition. In this work, different methods to predict the overall efficiency of distillation columns with valve and dualflow trays were composed and compared with data from three commercial distillation columns under different operating conditions. The models were inserted in the Aspen Plus 12.1 simulator, in Fortran language, together with tray geometrical data, fluid properties and operating data of the distillation columns. For each column, the best thermodynamic package was chosen by checking the temperature profile and overhead and bottom compositions obtained via simulation against the corresponding actual data of industrial columns. A modification in the fraction of holes evaluation that is jetting parameter of the Garcia's hydraulic model of dispersion above the tray was proposed. This modification produced better results than the original model to predict the fraction of holes that are jetting and in the efficiency of dualflow trays and similar results to Garcia model in the efficiency evaluation of valve trays. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

精馏塔的压降测量研究(英文)

Pressure drops are of major importance for distillation/absorption columns. This paper mainly discusses how to correctly measure, interpret and use pressure drop data. The possible causes of incorrect pressure drop measurements are studied including the effects of pressure tap dimensions, locations, and vapor condensation etc. The effect of the static head of vapor on the pressure drop data and column pressures is evaluated. Variations of sec-tional pressure drops along the column are investigated based on the experimental data obtained from commercial size distillation columns at Fractionation Research, Inc. (FRI). For a packed column, it is found that the spacing between the liquid distributor and the top of the bed affects the overall pressure drop measurements, which is con-firmed by a fundamental fluid dynamics analysis.     

考虑气相影响的塔板流速场模拟

引言用计算机对塔板上液相流速场的模拟对于准确地预测塔板的分离效率具有重要意义．但塔板气液两相错流流动问题比较复杂,迄今未得到很好解决．李建隆提出零方程单流体塔板流场计算模型,对涡流粘性系数采用代数估值的方法求解其模型,模型中考虑了气体的阻力作用,模拟计算结果未能给出常见的回流区．张敏卿提出考虑垂直气相流阻力作用的K－ε湍流模型,即在标准K－ε湍流模型的动量输运方程中引入一气体阻力项,其它方程及方程中的系数不变．此模型在某些工况下可模拟出部分回流区．袁希钢等从Elghobashi的两相流双流体模型出发,在推…     

蒸馏塔板上汽液传质系数的确定——非平衡池法(Ⅰ)模型的建立及求解

本文提出一种确定蒸馏塔板上汽液传质系数的新方法——非平衡池法.该法将塔板沿液流方向分为适当数目的串联非平衡池,通过联立求解每一池各相的物料衡算、能量衡算、相平衡和传质传热速率方程,可从塔板入口组成得到出口组成.调整汽液传质系数使计算的出口组成与实测值相等,从而可确定出两相传质系数.方程组用混合牛顿法求解.     

The second law optimal state of a diabatic binary tray distillation column

A new numerical procedure to minimize the entropy production in diabatic tray distillation columns has been developed. The method was based on a least square regression of the entropy production at each tray. A diabatic column is a column with heat exchangers on all trays. The method was demonstrated on a distillation column separating propylene from propane. The entropy production included contributions from the heat transfer in the heat exchangers and the mass and heat transfer between liquid and vapor inside the distillation column. It was minimized for a number of binary tray distillation columns with fixed heat transfer area, number of trays, and feed stream temperature and composition. For the first time, the areas of heat exchange were used as variables in the optimization. An analytical result is that the entropy production due to heat transfer is proportional to the area of each heat exchanger in the optimal state. For many distillation columns, this is equivalent to a constant driving force for heat transfer. The entropy production was reduced with up to 30% in the cases with large heat transfer area and many trays. In large process facilities, this reduction would ideally lead to 1-2 GWh of saved exergy per year. The most important variable in obtaining these reductions is the total heat transfer area. The investigation was done with a perspective to later include the column as a part in an optimization of a larger process. We found that the entropy production of the column behaved almost as a quadratic function when the composition of the feed stream changed. This means that the feed composition is a natural, easy variable for a second law optimization when the distillation column is a part of a process. The entropy production was insensitive to variations in the feed temperature.     

CFD and experimental studies of liquid weeping in the circular sieve tray columns

Sieve trays are widely used in fractionating devices like tray distillation towers existing in separation and purification industries. The weeping phenomenon that has a critical effect on the efficiency of tray towers was studied by a numerical model and some experiments. The experiments were carried out in a pilot scale column with the diameter of 1.22 m that includes two test trays and two chimney trays. Weeping rates and some hydraulic parameters were measured in sieve trays with the hole area of 7.04%. Furthermore, the total weeping rate and weeping rate in inlet and outlet halves of the test tray were determined. It was also used an Eulerian–Eulerian computational fluid dynamics (CFD) method for the present study. The model was able to predict the dry tray pressure drop, total pressure drop, clear liquid height, froth height, and weeping rate simultaneously. Furthermore, the obtained CFD results were in a good agreement with the experimental data in terms of pressure drop and the model properly predicted several hydraulic parameters like the liquid weeping behavior along the tray.