规整填料在高压精馏条件下的传质性能

Performance of Mellapak 250Y and 350Y corrugated structured packing in distillation applications at pressures ranging from 0.3 to 2.0MPa is analysed by using HTU-NTU method.These data are obtained in distillation column with 0.15m diameter operated with n-butane/n-pentane system at total reflux.In considering the axial backmixing effects.the height of an overall gas phase transfer unit,HTUOG,is divided into two parts.One part represents the height of an overall gas phase transfer unit,without backmixing, designated as HUTOG,and the other part,designated as the height of a backmixing unit(HBUO),accounts for the backmixing effects.The HTUOG is evaluated from the measured concentration profile of n-butane in liquid phase.The HBUO obtained experimentally is correlated in terms of the properties of the materials being separated and the equivalent diameter of the structured packing.Our result shows that HBUO varies from 0.12 to 0.34m as pressure increases from 1.0 to 1.9MPa.It indicates that the overall efficiency of the structured packing decreas gradually at high pressure,as a result of the vapor backmixing.     

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     

加压下填料塔中液相轴向反混的研究

Liquid phase axial mixing was measured with the tracer technique in a packed column with inner diameter of 0.15m,in which the structured packing,Mellapak 350Y,was installed.Tap water as the liquid phase flowed down through the column and stagnant gas was at elevated pressure ranging from atmospheric to 2.0MPa.The model parameters of Bo andθwere estimated with the least square method in the time domain.As liquid flow rate was increased,the liquid axial mixing decreased.under our experimental conditions,the effect of pressure on Bo number on single liquid phase was negligible,and eddy diffusion was believed to be the primary cause of axial mixing in liquid phase.     

规整填料内气液两相流动与传质的计算传质学模型

Detailed investigation of flow behavior in structured packing distillation columns is of great importance in accurate prediction of process efficiency and development of more efficient and optimal equipment internals. In this study, a three-dimensional two-phase flow model based on VOF method for simulating the hydrodynamics and mass-transfer behavior in a typical representative unit of the structured packing is developed. In the proposed model, the model is used for the closure of turbulent mass transfer equation. By solving the proposed model, the velocity distribution, phase fraction profile and concentration field are obtained. Using these data, the total liquid holdup, the wetted area and the separation efficiency [height equivalent to a theoretical plate (HETP)] are estimated. For testing the model validation, the simulated HETPs are compared with our previous experimental data obtained in a 150 mm-diameter column containing Mellapak 350Y operating at the pressures of 0.6-1.8 MPa. The compari-son shows that they are in satisfactory agreement, with an average absolute deviation (AAD) of 25.4%.     

LIQUID AXIAL BACKMIXING IN MULTISTAGE BUBBLE COLUMN

The characteristics of a staged bubble column can be described by a multi-stage backmixing model,provided: (1) Each stage can be considered as a perfect mixing reactor,and (2) The backmixing coeffi-cients do not vary with time and reactant concentrations.Experimental results indicate that the first conditionis approached under certain conditions,while the second assumption is correct.Studies were made using steady state chemical tracer method to determine the backmixing coefficientsof each plate between stages.The fluid flow through the holes of perforatcd plates is a stochastic process.From the statistical point,the experimental data could be correlated by semicmpirical equation developed.This equation can also be used to correlate the data reported by Nishiwaki for bubble column with plateshaving high percentage of opening area and large size holes between stages.Continuous oxidation of unsaturated sulfur compounds (mainly in the form of thiosulfatc and also somein polythionate form) in nickel ammonium carbonate solution were carried out in bubble columns with heightof 3400mm and diameters of 36 mm and 100mm respectively.The oxidation has to be taken in a multistagebubble column for high degree of oxidation.The axial concentration of unsaturated sulfur compoundsalong a multi-stage bubble column can be calculated from the backmixing model and the kinetic equationof oxidation.Results of calculation agree with the data taken along the column height.Equation was alsodeveloped to calculate the optimum temperatures of oxidation which agree favorably with the experimentalresults.     

Influence of phase ratio on packing efficiency in columns for mass transfer processes

The phase ratio has been found to affect the packing efficiency in packed columns.To ac-count for the effect,a model is set up to correlate the height of a mass transfer unit with the phaseratio with reasonable accuracy.Proposed also is a correlation that allows to predict the efficiency inquestion at any given liquid-gas ratio using the knowledge of other efficiency values at other liquid-gas ratios.     

Soft-sensing modeling and intelligent optimal control strategy for distillation yield rate of atmospheric distillation oil refining process

It is a challenge to conserve energy for the large-scale petrochemical enterprises due to complex production process and energy diversification. As critical energy consumption equipment of atmospheric distillation oil refining process, the atmospheric distillation column is paid more attention to save energy. In this paper, the optimal problem of energy utilization efficiency of the atmospheric distillation column is solved by defining a new energy efficiency indicator — the distillation yield rate of unit energy consumption from the perspective of material flow and energy flow, and a soft-sensing model for this new energy efficiency indicator with respect to the multiple working conditions and intelligent optimizing control strategy are suggested for both increasing distillation yield and decreasing energy consumption in oil refining process. It is found that the energy utilization efficiency level of the atmospheric distillation column depends closely on the typical working conditions of the oil refining process, which result by changing the outlet temperature, the overhead temperature, and the bottom liquid level of the atmospheric pressure tower. The fuzzy C-means algorithm is used to classify the typical operation conditions of atmospheric distillation in oil refining process. Furthermore, the LSSVM method optimized with the improved particle swarm optimization is used to model the distillation rate of unit energy consumption. Then online optimization of oil refining process is realized by optimizing the outlet temperature, the overhead temperature with IPSO again. Simulation comparative analyses are made by empirical data to verify the effectiveness of the proposed solution.     

翅片导流板填料应用于旋转填料床的特性

For an alcohol/water system and with fin baffle packing, continuous distillation experiments were carried out in a rotating packed bed (RPB) system at atmospheric pressure. The effects of the average high gravity factor (β), liquid reflux ratio (R) and feedstock flux (F) on the momentum transfer and mass transfer were investigated. The gas phase pressure drop of RPB increased with the average high gravity factor, liquid reflux ratio and feedstock flux, which was 13.55-64.37 Pa at β of 2.01-51.49, R of 1.0-2.5, and F of 8-24 L&;#8226;h－1 for a theoretical tray in the RPB with fin baffle packing. The investigation on the mass transfer in the RPB with different packings showed that the number of transfer units of RPB with a packing also increased with the average high gravity factor, reflux ratio and feedstock flux. It is found that the fin baffle packing (packing III) presents the best mass transfer performance and lowest pressure drop for the height equivalent to a theoretical plate (HETP), which is 6.59-9.84 mm.     

反置式间歇蒸馏塔的设计程序(Ⅰ)多组分理想物系

Inverted batch distillation column(stripper) is opposed to a conventional batch distillation column(rectifier). It has a storage vessel at the top and products leave the column at the bottom. The batch stripper is favourable to separate mixtures with a small amount of light components by removing the heavy components as bottom products. In this paper, we are presenting a shortcut procedure based on our earlier work for design and simulation of the inverted batch distillation column, which is equivalent to the Fenske-Underwood-Gilliland procedure for continuous distillation. Given a separation task, we propose to compute the minimum number of stages(Nbmin) and the minimum reboil ratio(Rbmin) required in a batch stripper,which are the stages and reboil ratio required in a hypothetical inverted batch distillation column operating in total reboil ratio or having an infinite number of stages,respectively. Then, it is shown that the performance of inverted batch columns with a finite number of stages and reboil ratios could be correlated in Gilliland coordinates with the minimum stages Nbmln and the minimum reboil ratio Rbmin.     

合成气制二甲醚三相淤浆床反应器的数学模型研究

A mathematical model for a bubble column slurry reactor is presented for dimethyl ether synthesis from syngas. Methanol synthesis from carbon monoxide and carbon dioxide by hydrogenation and the methanol dehydration are considered as independent reactions, in which methanol, dimethyl ether and carbon dioxide are the key components. In this model, the gas phase is considered to be in plug flow and the liquid phase to be in partly back mixing with axial distribution of solid catalyst. The simulation results show that the axial dispersion of solid catalysts, the operational height of the slurry phase in the bubble column slurry reactor, and the reaction results are influenced by the reaction temperature and pressure, which are the basic data for the scale-up of reactor.     

规整填料塔中精馏过程的三维模拟(Ⅱ)模型的验证及液相分布和混合行为对精馏过程的影响

用简化三维混合池模型对Gorak所做精馏实验作了实例计算。模型的计算结果与Gorak实验数据符合良好,以简化三维混合池模型为工具,用数值计算的方法研究了规整填料塔中液体流动分布和混合对精馏过程的影响。结果表明：液相轴向返混对精馏有着显著的不利影响;当液体流动分布为严重壁流分布（严重沟流分布）时,必须用三维模型描述才不会产生较大偏差;横向混合系数的增大有利于填料塔分离效率的提高,但不能完全抵消液相严重不均匀分布对精馏过程的不利影响。     

规整填料在加压精馏中的传质性能

高压精馏是现代过程工业中十分重要的分离过程 ,例如炼油工业中轻烃的分离 ,石油化工中乙烯、丙烯等低碳烃类的分离 ,都是经过高压精馏完成的 .高压精馏效率一般较在常压下有所降低 ,其中填料塔较板式塔下降更明显 ,故通常认为采用板式塔比较好 .但规整填料由于其大通量、低压降等优点 ,已经开始涉及高压领域 ,因此对规整填料在高压下的性能需进行测定和研究 .目前 ,对规整填料在高压下传质性能的研究 ,国外ＦＲＩ[1] 近年已开始进行 ,但其实验数据较少 ,在国内目前还属空白 .本文在国家重点精馏分离实验室高压热模精馏实验塔上进行了一系列…     

孔板波纹填料的结构参数对其性能的影响

在内径Φ30 0mm的填料塔中研究了孔板波纹填料的结构参数对液相轴向混合特性、流体力学和传质性能的影响 .研究结果表明 ,轴向返混参数随开孔率、倾角的增加及盘高的减小而增加 ,填料层压降随开孔率、盘高的增加及倾角的减小而降低 ,传质单元高度随倾角的增加、盘高的减小而降低 ,开孔率对传质单元高度的影响有一个适宜值 .通过对实验数据的回归分析得出了轴向返混参数、填料层压降及传质单元高度的关联式 .该研究结果对孔板波纹填料的开发与设计具有参考价值     

加压下板波纹规整填料塔中液相混合行为

采用脉冲示踪法测量了在0．3MPa、0．5MPa和0．6MPa压力下以及在一系列液速和气速下250Y型孔板波纹规整填料内液相的混合行为。应用时域最小二乘法由实验数据得到了液相的轴向返混系数和轴向有效流速等参数,并以y=aReL^e10^cReG10^dp的形式对轴向Peclet准数进行了关联。本研究补充了目前缺乏的加压操作下规整填料液相混合行为的数据。     

从浓度分布评价填料塔性能

精馏塔性能的优劣通常可以用在塔顶和塔底取样,然后计算其分离效率的方法来判断,但这种方法只可以判断出精馏设备效率的高低,却几乎无法找出造成设备效率不够理想或低效的原因．不良初始分布、壁流、沟流和溪流、端效应以及气相或液相返混等现象都可以造成填料塔效率的下降,而     

0.7～1.9MPa下Mellapak 350Y填料传质性能的测定

引　言最近十几年以来 ,规整填料已广泛应用于新建的蒸馏塔以及老塔的改造中 .在常、减压操作中 ,与板式塔相比 ,在相同的分离效率下填料塔具有压降更低和处理能力更大的优点 .但在高压蒸馏操作中 ,液体的喷淋密度非常大 ,其范围在 2 0～ 10 0ｍ3·ｍ- 2 ·ｈ- 1,单位塔截面积上液体负荷的增加使得填料对液体的自分布能力减弱 ,液体易产生偏流、沟流等不均匀流动 .随着压力增大 ,充了气的液相、高的汽液相密度比值、高的汽液相黏度比值等因素都会使填料床层的持液量加大 ,空隙率降低 ,其结果使规整填料处理能力受到制约 .在高压条件下 ,规整…     

无返混动态累积分批精馏过程

动态累积操作是提高分批精馏效率的一种有效方法 ,但在塔顶累积罐内存在的液相返混限制了分离效率的进一步提高。本文提出了塔顶累积罐无返混动态累积操作过程。研究了塔板和塔顶存液量对分离效率的影响。模拟计算和实验结果均表明 ,降低塔顶返混可显著提高动态累积操作的分离效率     

Liquid phase mixing in trayed bubble column reactors

The compartmentalization of conventional bubble columns by perforated trays constitutes a very effective method to reduce the liquid backmixing. The effect of tray design and operating conditions on the overall liquid mixing was studied in a bench-scale trayed bubble column. The extent of liquid backmixing in the column was investigated in light of liquid-phase tracer response experiments. In average, a three fold reduction in the liquid backmixing was achieved in the trayed column as compared to the column without the trays. Moreover, the tray open area and the superficial liquid velocity were found to have the strongest effects on the liquid backmixing. The N-CSTR with Backmixing Model was found to match the experimental tracer response curves better than the Axial Dispersion Model.     

Development of mixture composition maldistribution in a distillation column with structured packing

The distribution of the composition of a mixture of Freons R-114 and R-21 over the cross section of a distillation column filled with structured packing is experimentally studied. Results on the efficiency of Freon mixture separation, the pressure drop in the packing, and the distribution of the local concentration of the low-boiling component throughout the cross section and height of the structured packing are presented. The vapor phase load factor was varied over a wide range up to hydraulic flooding. According to the experimental results, the large-scale maldistribution of the mixture composition occurs inside the packing over the column cross section, even though the overall separation performance of the column is excellent. Maldistribution is observed throughout the total height of the column. The location of the large zones of maldistribution significantly depends on the liquid and vapor flow rates.