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.     

Application of factor method for minimum reflux: Multiple feed distillation columns

Analytical equations for determining the minimum reflux ratio of multiple feed distillation columns are presented by using a factor method. For the method, a factor which converts feed flow to minimum reflux ratio is used. The factor is a function of the feed concentration and thermal condition. The calculation steps for determining minimum reflux ratio of multiple feed columns are summarized. A computer program is available (microcomputer or mainframe). Application of the factor method for minimum reflux ratio is illustrated by several examples.     

Dynamic behaviour of side-stream distillation columns for the separation of binary azeotropes mixtures

In the last years, the interest for dynamic modelling and simulation has increased. However, the studies have been restricted to two-column products. A side-stream distillation column may replace two simple columns for some applications, saving energy and investment. Intuitively, the side-stream should primarily contain middle-boiling point from a multicomponent mixture. Using the residue curves, we can define new separation sequences and new configurations for old processes. The principal proposal of this work is to analyse the dynamic behaviour of side-stream extractive distillation column, a new configuration for extractive distillation process, and to compare it with the conventional one used for the same objective. It is observed that the dynamic behaviour of side-stream column is very fast and the operating performance of the column is nearly the same of the conventional one.     

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。     

二元提馏式间歇精馏的优化操作与最小汽化总量

理想操作条件下二元提馏式间歇精馏优化操作的汽化总量与最小汽化总量的计算是约束函数优化问题。本文采用罚函数法,将此约束函数优化转变为无约束函数优化,并采用固定双步长因子梯度法数值求解该函数的极值。计算表明:固定双步长因子梯度法具有良好的收敛性,同时,降低分段数较多时,数值截断误差积累对计算结果的影响。二元提馏式间歇精馏优化操作较恒残液组成操作的能耗低的原因如下:在理论板数相对较少(接近二元提馏式间歇精馏恒残液组成操作所需的最少理论板)时,优化操作通过控制再沸比提高了能耗效率;在理论板数相对较多时,优化操作通过控制再沸比,在保证过程的能耗效率较高的同时,可尽可能快地将物料移出系统,减少了精馏过程中塔顶贮槽内液体的混合熵产。通过对计算结果的归纳与外推,得到了理想操作条件下理论板数为无穷多时二元提馏式间歇精馏优化操作再沸比的变化方式以及最小汽化总量的计算公式。     

Design and control of pressure-swing distillation for separating ternary systems with three binary minimum azeotropes

The separation of ternary nonideal systems with multi-azeotrope is very important because they are often found in the waste of chemical and pharmaceutical industries, which is much more difficult due to the formation of multi-azeotrope and distillation boundary. We propose a systematic procedure for design and control of a triple-column pressure-swing distillation for separating ternary systems with three binary minimum azeotropes. This procedure involves thermodynamic insights, a two-step optimization method, and effective control strategy. The separation of tetrahydrofuran (THF)/ethanol/water is used to illustrate the capability of the proposed procedure. It is found that the pressure limits in columns can be determined through the analysis of residue curve maps, distillation boundary, and isovolatility curves. The optimal triple-column pressure-swing distillation is generated with the minimum total annual cost (TAC) of $2.181 × 10⁶ in sequence A. The operating conditions are well controlled approaching their desired specifications in an acceptable time when disturbances occur. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1281–1293, 2019     

恒再沸比提馏式间歇精馏的最小再沸流比与能耗分析

通过构造一函数,推导出二元恒再沸比提馏式间歇精馏,在理想操作条件下,理论板数趋向无穷多时,瞬时恒浓区变化方式可由此函数值(>0或<0)来判断,完善了二元恒再沸比提馏式间歇精馏最小再沸比计算方法。推导出二元恒残液组成提馏式间歇精馏,在理想操作条件下的最小汽化总量的计算公式。通过对理论板数趋向无穷多时的能耗分析得到,二元提馏式间歇精馏,要求残液中重组分的收率和平均浓度均高时,相对于恒残液组成操作,采用恒再沸比操作能耗较高,其主要原因是低效总能耗（理论板数趋向无穷多时,直接表现为无效总能耗）在总能耗中占比例较大。     

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.     

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.     

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.