汽液液三相精馏总板效率的研究

在Oldershaw精馏塔内,对汽液液三相精馏筛型塔板上的传质特性进行测试,研究了泡沫工况下,汽速、液汽比等操作条件,表面张力梯度、界面张力、乳化液分散粘度等物系性质,以及油水体积比等多种参数对总板效率的影响、对测试数据进行关联,获得了适用于泡沫工况下汽液液三相精馏过程的总板效率估算式,此关联式对设备设计及操作优化有一定的参考价值.     

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。     

汽液平衡数据对精馏塔设计的影响

该文分析了产生汽液平衡数据偏差的原因,井采用一简捷算法用以评估当汽液平衡数据发生波动时对精馏塔设计的影响。文章对相平衡模型的选择;模型参数的不确定性;汽相非理想性的考虑;汽液平衡数据的波动性对精馏塔设计的影响等问题作了论述。     

蒸馏塔内汽-液-液三相的流动及传质

详细的分析了国内外有关蒸馏塔内出现的汽-液-液三相的传质现象,并通过现有的研究成果,一方面总结出了影响塔板效率的多种因素,如流动工况、汽速、油水比、界面张力、表面张力和界面湍动等因素,并着重的阐述了第二液相的存在对塔板效率的影响;另一方面,总结出了汽-液-液三相存在的两种传质途径以及几种合理有效的传质机理;同时总结了蒸馏塔内汽-液-液三相传质的发展现状及前景。     

乙醇脱水塔内两相和三相共沸精馏

研究了乙醇脱水塔内的两相共沸精馏和汽液液三相共沸精馏过程。利用Aspen plus模拟软件对乙醇脱水塔内4种工况的精馏曲线、共沸剂浓度分布、回流量和再沸器能耗进行了分析比较。结果表明,苯做共沸剂时,脱水塔内两相共沸精馏和汽液液三相共沸精馏的精馏曲线、共沸剂浓度分布、回流量和再沸器能耗相近,脱水塔精馏曲线都跨越了精馏边界,并且共沸剂在塔内大多数板上都有较高浓度分布。而环己烷做共沸剂时,两相共沸精馏工况和汽液液三相共沸精馏工况条件下的脱水塔内精馏曲线、共沸剂浓度分布、回流量和再沸器能耗有较大差别。汽液液三相共沸精馏工况条件下,环己烷在塔内大多数板上有较高浓度分布,起到较好的脱水作用,而两相共沸精馏工况条件下脱水塔内共沸剂仅分布在塔顶几块塔板上,塔内多数板上没有起到共沸剂作用。     

汽相分流催化精馏塔中苯氯化工艺实验研究

在一种结构新颖的汽相分流催化精馏塔中,采用不同的催化剂装填方式,进行了苯氯化催化精馏实验;研究了上行汽(气)体的侧线分流比例及压降降低的比例,考察了氯气流量对苯氯化催化精馏结果的影响。在保证最终塔釜氯化液中氯苯含量在 95%以上及苯含量在 1%以下的前提下,得出了适宜的侧线分流的比例为 30%~40%和适宜的氯气通入流量为 600mL?min?1。实测了到达催化精馏终点时的全塔温度分布和浓度分布数据,为今后进行催化精馏塔数学模拟计算及工业连续催化精馏塔的放大设计计算提供参考依据。     

精馏塔全塔效率及板效率测定条件的研究

精馏技术广泛应用于各类精细化学品的生产中,占整个化工生产能耗的大部分.通过测试不同精馏时间和精馏浓度下的全塔效率和板效率来获取最佳全塔效率和板效率.结果表明,浓度为15%,精馏时间为1.7 h时,精馏塔的全塔效率和板效率均为最佳值.     

分批精馏中的持液作用

分批精馏中持液影响塔内的动态过程,因此许多学者一直致力于分批精馏过程中持液作用的研究,但由于研究缺乏系统性,持液的作用一直是学术上争论的热点.本文提出用全过程分离难度系数关联各参数对分离过程的影响,并建立了分批精馏的恒摩尔持液模型,用全过程的分离难度系数研究了分批精馏的持液作用,结果表明：塔顶持液对分离不利,但塔身持液在一定条件下增多可使所需回流比降低;塔内持液量与釜液量之比为一个因子,当q<0.7时,确定的分批精馏塔存在最佳投料量.采用甲苯-乙苯二元物系对最佳投料量进行了实验验证,实验结果与模拟结果吻合较好.     

乙烯精馏塔控制中降液管时滞效应影响分析

在精馏塔动态建模中忽略了降液管容积对液相流动及传质的滞后,导致模型与实际精馏塔存在明显差异。针对某实际乙烯精馏塔,通过机理分析建模,建立理论降液管模型,并在原精馏塔模型基础上构建了考虑降液管时滞效应的乙烯精馏塔动态模型。通过仿真,将该模型与原模型的动态特性进行比较,其差异性说明考虑降液管能够更加准确地把握精馏过程的动态特性。另外,对两种动态模型分别设计控制器,整定得到的控制器参数差别很大,说明忽略降液管的影响造成在此基础上设计的控制器可能不适用于实际装置。因此,在动态建模中考虑降液管能够更加准确地对精馏塔进行分析、控制和优化,具有一定的现实意义。     

气液液三相精馏传质性能研究进展

介绍了气液液三相精馏塔板传质性能研究的进展情况,讨论了气速、液气比等操作条件,表面张力、界面张力、液体的粘度或分散粘度、密度和相对挥发度等物系性质以及油水体积比等多种参数对传质效率的影响,探讨了第二液相的存在对传质的影响,文中的许多观点和建议对于优化精馏塔的设计具有重要的指导意义。     

CALCULATING DISTILLATION EFFICIENCIES OF MULTICOMPONENT i-BUTANE/ n-BUTANE COLUMN

This paper presents experimental data and estimated distillation efficiencies of an industrial scale distillation column separating i-butane and n-butane. The data gathered from plant instruments and laboratory analysis were reconciled and compared to distillation simulations. The simulations were performed with a number of real plates using the point and the Murphree plate efficiency calculation model. This matrix model of efficiency at first estimates the point efficiencies using the two-film and multicomponent mass transfer theory. The point efficiencies are then converted into Murphree plate efficiencies using a liquid mixing model. The whole method is implemented in a computer program to simulate an industrial distillation column with real plates. Finally the calculated product compositions are compared with reconciled measurements. The values of overall, section, point and Murphree plate efficiencies of multicomponent i-butane/n-butane system are also calculated. The results show that point efficiencies are not adequate for large industrial scale columns. The results also imply that the plate efficiency calculation method can be utilized and employed in the design and simulation of industrial scale columns.     

水醇烃体系相平衡模拟及其应用

采用CPA方程模拟了水、醇、烃多组分体系气液液三相平衡,与实验数据比较后可知,CPA方程能够较好地预测极性组分PVT特性和相平衡。并把CPA方程应用于汽提冷甲醇天然气脱水工艺的模拟计算,为工艺设计提供了必要的参考数据。     

Stepwise periodic distillation—I: Total reflux operation

The theoretical predictions of doubled overall efficiency for plate distillation columns operated in the controlled cycling mode have not been confirmed by pilot scale experiments. In an attempt to circumvent the hydrodynamic problems causing this failure, we have found a new periodic operating mode where the liquid flow is manipulated directly, and not indirectly through pulsations of the vapour flow rate (as in controlled cycling).In this paper we present the theory of stepwise periodic distillation, under assumptions allowing a comparison with known results for controlled cycling. We show that the two processes have the same asymptotic efficiencies for large values of the number of trays while periodic stepwise distillation is slightly more efficient than controlled cycling for a finite number of trays     

EFFICIENCY CONSIDERATIONS FOR CHOICE BETWEEN TRAYS AND PACKINGS

Mass transfer efficiency models for plate and packed columns in distillation applications were examined. The influence of operating conditions, hardware parameters and physical properties on the height equivalent of a theoretical plate (HETP) were investigated. Recommendations on the choice of packings or trays were developed for different cases to maximize column efficiency. Some inconsistencies in the efficiency models for plate and packed columns reported in the literature were also discussed.     

Point and Stage Efficiencies in Distillation

Abstract

The definition of Murphree point efficiency in distillation is critically examined. Characteristics of Standart's stage efficiency definition are utilized to define a new point efficiency on a plate in a column. This new definition was shown to be consistent and symmetrical. For crossflow on a plate, the proposed point efficiency was found to be equal to Standart stage efficiency subject to only the assumption of a uniform value of the proposed point efficiency over the whole plate.     

Studies of Controlled Cyclic Distillation: I. Computer Simulations and the Analogy with Conventional Operation

Abstract

Computer simulations of a controlled cycling rectification still were run to determine the theoretical effects of local point efficiency, slopes of the equilibrium and operating lines, amount of liquid dropped during the liquid-flow period, and other parameters on over-all column and individual plate efficiencies. It is shown that, although the Murphree vapor efficiency of a plate at any instant of time is assumed to be constant and equal to the local point efficiency, the effective plate efficiency based on the resulting liquid-phase plate compositions is usually significantly greater than the point efficiency. This leads to the improved separating ability achieved in controlled cyclic operation. The existence of a precise analogy between controlled cyclic distillation and conventional distillation with liquid-phase concentration gradients across the plates of the column is shown. In essence, this analogy reduces to the substitution of time as the independent variable in the former case for distance in the latter case.     

The effect of vapour mixing on efficiency of large diameter distillation plates

Liquid and vapour flow maldistribution has been experimentally detected in large diameter distillation plates. Theoretical models developed to predict plate efficiency taking into account similar phenomena generally assume completely mixed vapour. This paper analyses the effect of vapour mixing on the plate efficiency for different values of stripping factor, point efficiency and liquid mixing degree and shows the remarkable influence of vapour mixing in presence of liquid maldistribution. Moreover a criterion for the prediction of the plate efficiency is suggested.     

塔板沟流及其影响

介绍了塔板上一种特殊的流动不均现象．首次给出了用热膜流速仪在φ1200冷模高弹性浮阀塔板上测定的沟流量数据．并进行了塔板沟流量对塔板效率影响的模拟研究,在计算中采用了新的分区法──将塔板分为传质鼓泡区和沟流区,得出了不同参数条件下塔板沟流量与塔板效率的变化关系曲线。