用虚拟混合法计算二元精馏最小回流比

对多进料二元体系精馏分离，介绍一种虚拟混合求算最小回流比的新方法。与其它方法相比，其不仅适用于理想或非理想二元体系，而且比较简便。     

Extractive distillation of binary azeotropic mixtures

The conditions have been determined under which an azeotropic binary mixture can be separated by extractive distillation and under which separation into almost pure components is impossible at any amount of the extracting agent. A general algorithm is suggested for analysis of special manifolds in order to see whether extractive distillation is efficient.     

Batch extractive distillation under constant reflux ratio

The process of batch extractive distillation may provide the advantages of both batch and extractive distillation. So far this process has not been applied at all probably due to its complexity. An algorithm and a computer program were developed for simulating the experiments of a batch extractive distillation process (separation of acetone and methanol on a pilot-plant column containing 32 bubble cap trays applying water as solvent, the reflux ratio is kept constant) on a PC/AT/486. For the integration of the set of nonlinear differential equations (component material balances) the Runge-Kutta method was used. For saving computation time a 2-D linear interpolation method was applied for the ternary mixture when calculating VLE. The experimental and calculated results are compared. Thqe influence of the operational parameters on the process was studied by simulation. Calculations were carried out for another (nonazeotropic, low relative volatility) mixture with a new professional program “PROSIM BATCH”.     

Special distillation regime involving an infinite reflux ratio and an infinite number of separation stages

Distillation at an infinite reflux ratio in combination with an infinite number of trays has been investigated.     

Selecting extracting agents for separation of biazeotropic binary mixtures by extractive distillation

Basic diagram structures for extractive distillation systems are considered. The mutual arrangement of α = 1 lines and pseudoideal lines is analyzed for the case in which the mixture to be separated is biazeotropic. The diagram structures allowing the separation of the mixture in the presence of a particular extracting agent are determined.     

Estimation of minimum reflux in distillation and multipoint boundary value problems

The problem of estimating the minimum reflux ratio is treated as a non-linear multipoint boundary value problem in difference equations. If the problem has a solution, the minimum reflux ratio and the compositions in the column are obtained simultaneously by quasilinearization iteration. With very rough initial approximations or starting values, only nine iterations are needed to obtain a four digit accuracy in concentration. A three digit accuracy in distillate rate is obtained in seven iterations.     

Optimal reflux rate policy determination for multicomponent batch distillation columns

This paper describes a procedure to obtain optimal reflux or optimal distillate rate policy for multicomponent batch distillation columns using the Pontryagin's continuous maximum principle. For application to multicomponent systems, a reduced order model is used using short-cut procedure developed specifically for analysis and design of batch columns.     

精馏过程中回流比调节方式的讨论

比较了精馏过程中双流量计式、单流量计式、电磁式、机械式等回流比调节系统的应用情况。着重论述了新型机械式回流调节系统。该系统具有计量精确、投资小、操作简便、跑冒滴漏少、应用面广等优点。     

Consideration of irreversibility factors for binary distillation

Irreversibility factors affecting the energy consumption in the separation of a mixture in a binary distillation column are considered. The additional energy consumption related to fixed column productivity is estimated from below and compared with the consumption following from relations of equilibrium thermodynamics.     

New equipment for the determination of virial coefficients of pure substances and binary mixtures

A new equipment for the measurement of virial coefficients of pure substances and binary mixtures is described. It consists of an improved modification of the set-up proposed by Eucken and Meyer in 1929. The development is based on a critical review of the existing methods particularly with respect to adsorption effects. In order to reduce the influence of adsorption on the accuracy of virial coefficients, an optimum range for gas density is recommended. The accuracy of the virial coefficients is better than 20 cm³ mol^?1. The set-up was employed for the measurement of virial coefficients of acetone and hexane in the range from 352.95 to 393.85 K. The results are in excellent agreement with data published in literature. Furthermore, cross-virial coefficients of the binary system acetone/hexane were measured and interpreted.     

旋转填料床间歇精馏恒回流比操作性能研究

为寻找强化间歇精馏过程的有效途径,在三角形螺旋填料旋转床中,以乙醇-水为实验物系,进行间歇精馏恒回流比操作性能研究。通过改变转速n、回流比R和进料质量分数wF,考察产品纯度和回收率的变化规律。研究结果表明:产品纯度wD和回收率η均随n增加先增大,后减小,即存在最佳转速nopt;随R的增大缓慢增大;产品纯度随wF的增加而增大,回收率η随wF的增加先增大后减小。在旋转填料床中的间歇精馏应在较小回流比和最佳转速条件下操作,且适合处理较高质量分数的原料。     

Optimal organization of binary distillation

The limiting potential of binary distillation is considered for conventional heat supply to the column bottom and heat removal from the refluxer and for heat supply and removal distributed over the column height. For either case, the limiting column capacity and the minimum heat consumption are related to the external stream compositions and to the heat and mass transfer coefficients.     

The minimum fluidisation velocity,bed expansion and pressure-drop profile of binary particle mixtures

The total bed pressure drop, the pressure-drop profile, bed expansion and bed voidage have been measured for a variety of binary particle mixtures over a wide range of gas velocities.Apparent minimum fluidisation velosities have been defined for segregating systems, and the addition of dense particles of lower minimum fluidisation velocity can cause a decrease in apparent minimum fluidisation velocity of the mixture in a very similar fashion to the addition of finer particles to larger ones of the same density.The measured u_mf s are compared with presently derived simplified theoretical equations and with equations from the literature. It is clearly shown that because of the sensitivity of u_mf determination to voidage, such relationships cannot be used with confidence. However, the empirical equation of Cheung on average follows the shape of the experimental curves well, includig those for binary systems of different density, provided the bed is in a well-mixed condition.Bed pressure-drop profiles are related to the mixing/segregation state and to the amount of fluidisation of the bed and may offer a simple indirect method of determining these conditions in practice.     

Mapping the pattern of distillation trajectory bundles for multicomponent mixtures

A procedure for determining all singular points (their coordinates and types) for a dynamic multicomponent system is reported. The procedure is illustrated by examples of thermodynamic and topological analysis of the dynamic systems of three-component zeotropic mixtures.     

An approximate model for binary azeotropic distillation design

A simple analytical model has been developed for representing vapor-liquid equilibrium data in binary azeotropic mixtures. The method treats the azeotrope as a new pure component and considers the mixture to be composed of two independent binary subsystems; component 1 + azeotrope and azeotrope + component 2. After suitable variable transformations, each subsystem can then be represented by a constant relative volatility type model. The resulting vapor-liquid equilibrium models have been used to derive design equations for binary azeotropic distillation columns.     

无累积罐循环全回流操作的模拟研究

间歇精馏循环全回流操作是一种具有前景的新型操作方式。文中在循环全回流操作的基础上,首次提出了无累积罐循环全回流新操作方式。通过数学模型对其进行模拟,模拟计算比较了新方式、恒回流比间歇操作和塔顶储罐一次全回流操作3种操作方式。模拟结果表明:无累积罐新操作方式的全回流阶段时间由2个因素决定,全回流开始时精馏塔内的浓度梯度情况和精馏塔内持液的平均浓度。随着全回流-全采出操作的进行,后续循环中的全回流阶段的时间增加,全采出阶段时间减少。当进料浓度低时,新操作方式的分离效率比恒回流比方式高26.4%—30.1%,并通过模拟揭示了新操作方式的特点。研究表明:无累积罐循环全回流操作方式是一种新型高效的分离操作。     

Effective Kawakita parameters for binary mixtures

Despite the fact that many industrial processes use mixtures of powders with different physical and mechanical properties, most fundamental studies of powder compression have focused on single-component systems. There is thus an obvious need for an improved understanding of the compression behaviour of mixtures of particulate and granular solids. In this contribution, we show that the Kawakita equation may be particularly useful in this regard. The reason for this is that the degree of compression (i.e., the ratio between the volume reduction and the initial powder volume) for sufficiently high compression pressures P is a linear function of 1 / P. For ideal mixtures, for which the volume of each component may be determined independently of the others, this linearity implies that effective Kawakita parameters for the mixture may be readily expressed in terms of the parameters of its components. In order to validate the proposed approach, binary mixtures of mm-sized spherical agglomerates prepared by wet granulation followed by extrusion and spheronization were investigated experimentally. Predicted and measured Kawakita parameters were generally in good agreement, indicating that the assumption of ideal mixing behaviour is valid for this type of systems.     

Synthesis of flowsheets for extractive distillation of azeotropic mixtures

An algorithm for synthesizing extractive distillation flowsheets for separation of complex ternary azeotropic mixtures with different vapor-liquid equilibrium patterns is proposed.Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 1, 2005, pp. 19–26.Original Russian Text Copyright © 2005 by Ivanova, Timoshenko, Timofeev.