A modular approach to distillation column simulation

THE DYNSYS 2.0 computer program for modeling the dynamic behavior of complex chemical plants is described. The application of this modular program to the simulation of some distillation column control schemes is presented. Tree typical column configurations are studied. The startup of the columns is simulated and the effect of some simple control arrangements is shown.

The advantages of a modular program structure are discussed and the flexibility and utility of DYNSYS is illustrated.     

An assessment of vapor compression distillation

The two parts of this paper deal with the saving of energy which may be accomplished through staging of two or more vapor compression plants and with an evaluation of the forced-circulation arrangement for the process. Experiments using a small vapor compressor are presented to exemplify these two modes of operation. Algebraic expressions for compressor work are also presented and the results of calculations are compared with experimental information.     

环己烯-己烷萃取精馏塔系统的改进

采用新型填料塔技术和新的工艺流程,对原环己烯分离塔系统进行改造,改造后环己烯分离塔塔顶环己烯从6.5%下降到4.0%,环己烯回收塔塔顶环己烷从3.5%～4%下降到2.5%,环己烯纯度从95%提高到97%以上。     

A new approach to distillation column at total reflux

For a distillation column at total reflux, a simulation algorithm is presented, which takes into account the nonideality of both the vapor and liquid phases in addition to the pressure drop at each plate. The solution algorithm based on the Newton-Raphson technique is simple, because this algorithm has only one trial loop and no substitution parts and does not require a large portion of a computer's memory requirements. A numerical example shows the effectiveness of the proposed algorithm.     

丙烯腈生产中如何对精馏塔进行模拟优化

本文重点介绍了丙烯腈生产中精馏塔的数学模型的建立和求解过程，从而完成精馏塔的动态模拟优化过程。     

精馏塔回流比探索

叙述了连续精馏塔操作回流比对产品纯度的影响。在调节回流比操作过程中 ,必须注意每一种调节方式的附加条件和适用范围。     

异戊烯装置催化蒸馏塔的工艺优化

从催化蒸馏的工艺操作入手,针对操作过程中出现的催化蒸馏塔内二聚反应的发生及控制、催化蒸馏塔釜TAME含量的控制、催化蒸馏塔内二甲醚副反应的发生及控制等问题,进行探讨、分析并进行优化。     

Evolutionary design of optimum distillation column sequence

Synthesis of the optimum distillation column sequence (DCS), which incorporates a huge search space composed of both conventional and complex arrangements, is a highly complicated combinatorial problem in the field of chemical process design and optimisation. In this study, a novel procedure for the synthesis of optimum DCS proposed by Boozarjomehry et al. [Boozarjomehry et al., Can. J. Chem. Eng. 87, 477–492 (2009)] is expanded to include the complex distillation arrangements. The method is based on evolutionary algorithms, and the total annual cost (TAC) is the main criterion used to screen alternatives. Efficient procedure has been proposed for encoding mechanism to include and classify various complex arrangements together with conventional distillation columns. All columns existing in each DCS alternative are designed using the most recommended short‐cut methods to estimate the TAC of the DCS. Four standard benchmark case studies are carried out to clearly demonstrate the excellent performance of the proposed method. The produced results for these problems indicate that the proposed method outperforms the other existing approaches in terms of flexibility, accuracy and comprehensiveness. © 2011 Canadian Society for Chemical Engineering     

一个用于精馏塔模拟的新模型

A new computational mass transfer model is proposed for simulating the distillation process by solving the fluctuating mass flux for the closure of turbulent mass transfer equation in order to obtain the concentration profile and the separation efficiency of distillation column. The feather of the proposed model is to abandon the conventional way of introducing the turbulent mass transfer diffusivity (dispersion coefficient) to the turbulent mass transfer equation. To verify the validity of the proposed model, a commercial scale packed column and a sieve tray column were simulated and compared with published experimental data. The simulated results were satisfactorily confirmed in both concentration distribution and separation efficiency.     

An experimental application of the inferential control scheme to the binary distillation column control

The inferential control scheme based on a linear estimator was applied to control of top composition of a pilot scale packed distillation column. Experimental and simulation studies were used to evaluate the inferential control scheme and to compare its performance with a conventional single temperature feedback control with proportional plus integral actions. Both digital simulation and experimental verification showed that the top composition control achieved with the inferential control scheme was superior to that achieved with the conventional control scheme.     

Simulation of vapor flows in short path distillation

Based on the direct simulation Monte Carlo (DSMC) method, one- and two-dimensional models of vapor flows in the short path distillation are established. To reflect the reality, molecular rotation is included in this study and a reasonable boundary condition is introduced. The simulations are tested by comparison with the previous experiment, which shows that the distillation rate and composition are closer to the experiment compared to the previous models, and the simulated temperature field is higher than that of the previous models. The agreements between experimental and simulated results show that the models represent well the phenomena that occur in the vapor space of the short path distillatory. Based on the revised model, macroscopic variables related to a particular position in the distillation gap are analyzed in detailed. Furthermore, dependence of the evaporation efficiency on the ratio of condensing area to evaporating area and influence of inert gas on the distillation process are investigated.     

Sampled-data feedback control of a binary distillation column

The design of sampled-data controllers for a binary distillation column was studied for several types of controllers and for various control tray locations, sampling rates and disturbances. Minimal prototype control was superior to continuous PI control under some conditions but, as expected, was only satisfactory for a specified disturbance. dual “A” control scheme that compensates for both setpoint and load disturbances was developed. Two separate algorithms are implemented simultaneously, one receiving its input signal from the setpoint and the other from the measured variable. Dual control is superior to continuous control, particularly when both disturbances are encountered at the same time, and is superior to the “switching” method proposed by Mosler et al.     

双反应段蒸馏塔的动态特性与控制

针对理想两步连续可逆反应,通过开环和闭环仿真研究了双反应段蒸馏塔(RDC-DRS)的动态特性和可控性。开环仿真结果显示:对于调节通道,尽管双反应段的安排使得塔顶产品浓度和回流流量之间的过程增益有所降低,但也减弱了塔顶产品浓度和再沸器之间的相互耦合。相比于单反应段蒸馏塔(RDC-SRS),RDC-DRS的可控性仍有所提高。对于扰动通道,双反应段的安排并没有改变系统对进料流量扰动的灵敏度。闭环仿真结果显示:在进料流量扰动和组分扰动的情况下,相比于RDC-SRS,RDC-DRS表现出更好的抗干扰性能。综合上述结果可知,针对理想两步连续可逆反应的分离操作,RDC-DRS比RDC-SRS具有更优越的动态特性和可控性。     

Control of a distillation column using self-tuning regulators

Self-tuning regulators were applied to the multivariable control of a pilot distillation unit. Both the top and the bottom product compositions were simultaneously controlled. The multivariable interactions were compensated for by different strategies. It was shown that a proper choice of the control variables made it possible to use a regulator with a smaller number of parameters. The evaluation of the results shows that the self-tuning regulator is a valuable tool in multivariable control of distillation columns.     

丁二烯精馏塔过程控制系统优化

采用前馈、串级、均匀控制等复杂控制回路,对某丁二烯精馏塔过程控制系统进行优化,克服了原PID控制方案的不足,提高了装置的自动化水平,在降低能耗、减少溶剂消耗、加强装置高负荷下的运行周期及提高装置盈利能力方面有重要的实用价值.     

The transient response of a distillation column to changes in feed composition

Wilkinson and Armstrong [1] have derived an expression which predicts the response of plate compositions in a distillation column to step changes in feed composition. This theory is valid up to moderate values of time but cannot be used to predict the changes in composition when the column approaches the new state of equilibrium. Following the same approach it is possible to derive considerably simpler expressions which are valid for the initial part of the response. These solutions can then be extended so as to give the way in which the column approaches equilibrium. The theory is compared with experimental results obtained from a pilot distillation column [6].     

Optimal operation of a batch packed distillation column

Optimal policies for a batch packed distillation unit are examined for the cases of variable reflux ratio and variable boilup rates. This work was to act as a follow-up to Converse's work⁽¹⁾ for a batch plate distillation column with variable reflux policy. For the cases studied, it would seem that the boilup rate optimal policy yields better performance for the still than the reflux ratio optimal policy. The results of the present analysis and those of other authors seem to indicate that more effort should in the future be devoted to new modes of operation rather than to various refinements of the model used in the present and past studies. The present exploratory work seems to support the need for further studies using a packed rectifying section with variable boilup policy along with a novel mode of operation such as that considered by Mayur et al,⁽⁶⁾.     

喷射型催化精馏塔构件的流体力学性能

对垂直筛板帽罩内装催化剂构成的新型塔构件进行了实验研究。考察了板孔动能因子、催化剂藏量、床层空隙率对塔构件压降、罩体喷出量以及液泛和漏液速度的影响。结果表明:压降随板孔动能因子和催化剂藏量的增加而增大,随床层空隙率的增加而减小;罩体喷出液体量随着板孔动能因子的增加先增大后减小,随床层空隙率的增加而增大,随催化剂藏量的增加而减小;漏液速度随液体流量、藏量的增加而增大,随空隙率增大而减少;液泛速度随床层空隙率、液体流量的增大而减小,随藏量增加而增大。新型塔构件流体力学性能良好。