GRAPHICAL PROCEDURE FOR REACTIVE DISTILLATION SYSTEMS

In this paper we analyze a ternary reactive distillation system, where an equilibrium chemical reaction occurs in the liquid phase. By using a set of transformed variables proposed by Barbosa el al. (1988b) and well known graphical procedures for non-reactive systems; the minimum reflux ratio, minimum number of equilibrium stages, mass and energy balances for a reactive column and flash can be easily obtained. The procedures developed in this paper are applied to ISOBUTYLENE-METHANOL-MTBE system.

The main objective in developing this model is to obtain, as much as possible, rigorous information for the analysis of one reactive distillation column in a Process Simulator with capability of handling this type of new operation.     

SIMULATION OF STEADY DISTILLATION PROCESS ACCOMPANIED WITH MULTIPLE CHEMICAL EQUILIBRIUM REACTIONS BASING ON TRANSFORMED VARIABLES

The equations describing the steady state operation of distillation column with simultaneous equilibrium chemical reactions have been transformed into a new set or MESH equations by introducing transrormed composition, flow rate and enthalpy variables. The new set of equations are similar to equations describing traditional non-reactive distillation, and it is general when one or several reactions occur and inert components are present.

An algorithm combining relaxation method and modified Newton-Raphson method is proposed to solve the new equations, the relaxation method is used to estimate initial values, while the modified Newton-Raphson method is used to set solution. The reactive distillation processes of MTBE synthesis with n-butane and the separation of meta- and para-xylene are simulated as numerical examples     

反应精馏工艺流程的合成

反应精馏工艺是近年来倍受重视的研究领域之一,但反应精馏工艺流程的选择目前仍然靠人们的经验和实验探索．本文通过对传统化工工艺流程的理论分析,阐明了传统工艺流程与反应精馏工艺流程的相互关系,从而提出了一种反应精馏工艺流程的构成方法．     

DESIGN AND IMPLEMENTATION OF STATE OBSERVERS IN REACTIVE DISTILLATION

This study demonstrates that state observers can be developed and applied to infer the composition profiles of reactive distillation columns from noise-contaminated temperature measurements. The design and implementation of a Kalman filter (KF) and a Luenberger observer (LO) are carried out, and their performances are quantitatively assessed. The reliability, accuracy, and robustness of the two designs method are examined and compared quantitatively. The design and implementation of a Luenberger observer are simpler and easier to carry out than those of a Kalman filter. On the other hand, a Kalman filter is found to be more robust to a noisy measurements, erroneous initial estimates, and model uncertainties. A Luenberger observer could be used for composition estimation of reactive distillation when an ideal model of the system can reasonably approximate the real system; otherwise, a Kalman filter is recommended to be applied in more practical situations.     

DESIGN AND IMPLEMENTATION OF STATE OBSERVERS IN REACTIVE DISTILLATION

This study demonstrates that state observers can be developed and applied to infer the composition profiles of reactive distillation columns from noise-contaminated temperature measurements. The design and implementation of a Kalman filter (KF) and a Luenberger observer (LO) are carried out, and their performances are quantitatively assessed. The reliability, accuracy, and robustness of the two designs method are examined and compared quantitatively. The design and implementation of a Luenberger observer are simpler and easier to carry out than those of a Kalman filter. On the other hand, a Kalman filter is found to be more robust to a noisy measurements, erroneous initial estimates, and model uncertainties. A Luenberger observer could be used for composition estimation of reactive distillation when an ideal model of the system can reasonably approximate the real system; otherwise, a Kalman filter is recommended to be applied in more practical situations.     

CLASSIFICATION OF REACTIVE DISTILLATION PROCESSES BY DIMENSIONLESS NUMBERS

In the present paper a comparative consideration is given for the physico-chemical phenomena involved in homogeneously and heterogeneously catalyzed reactive distillation processes (RDP). The processes are classified qualitatively by dimensionless parameter groups derived from the balances for vapor, liquid and solid phases according to the principles of irreversible thermodynamics. The groups are applied to analyze industrial processes and experimental data for esterification, etherification and alkylation regarding different catalysts, operating conditions and configurations of plants. The mathematical models published until today and the experimental results are contrasted taking the parameter groups as a basis. This gives a discrimination of the models and some recommendations for their applicability.     

精馏过程的动态模拟

在各类典型精馏过程稳态模型的基础上,建立了6类典型非稳态精馏模型,并对动态精馏过程的开环响应进行了模拟计算.计算结果表明,实际精馏塔内存在的非平衡效应和惯性效应对非稳态精馏的动态响应过程有很大影响,其中惯性效应的影响更为突出.本文建立的三维非平衡混合池动态精馏模型充分地考虑了精馏过程中的非平衡效应和惯性效应,因此相信能够更适合于模拟实际的动态精馏过程.     

一种改进的多元精馏塔动态模型

综合了精馏塔的物料及能量平衡、塔板水力学方程、塔板效率及再沸器动态特性,给出一种改进的非理想多元物系精馏塔通用动态数学模型.增加了汽液平衡计算,从而弥补了文献[1]所提出的动态模型的缺陷,提高了其精度和通用性.模型仿真算法采用Gear积分方法,稳定性好,对解刚性比很高的精馏塔微分方程组十分有效.通过对某丙烯腈萃取精馏塔的仿真表明,该动态模型能够较好地反映对象的动态形为.     

反应精馏制苯甲酸苄酯的研究

研究开发了由对苯二甲酸二甲酯生产过程中副产物粗苯甲酸甲酯酯交换制备苯甲酸苄酯的反应精馏工艺。在酯过量情况下,通过正交实验,确定了最佳工艺条件,并考察了催化剂用量、酯醇比和反应温度三因素对苄酯收率的影响。与间歇釜式反应相比,反应精馏技术用于苯甲酸甲酯醇解制苯甲酸苄酯大大提高了酯过量下的反应收率。     

DYNAMIC SIMULATION OF A DISTILLATION COLUMN SEPARATING A MULTICOMPONENT MIXTURE

In this work, a dynamic model was developed to simulate the transient behaviour of a pilot scale, continuous, siagewise, 15 plate distillation column separating a mixture of ethanol, iso-propanol and isobutanol. The accuracy of the predictions was assessed by transient response data collected during experiments under step changes in reflux ratio, feed flow rate and feed composition.

Results demonstrated the feasibility of simulating multicomponent distillation under unsteady state conditions with fairly good success. Further improvements were suggested for a better accuracy     

A REACTIVE DISTILLATION PROCESS FOR AN AZEOTROPIC REACTION SYSTEM: TRANSESTERIFICATION OF ETHYLENE CARBONATE WITH METHANOL

A reactive distillation process is proposed for manufacturing dimethyl carbonate (DMC) through the transesterification reaction of ethylene carbonate (EC) with methanol. Modeling and simulation of the reactive distillation column have been carried out to study the effects of operating conditions, such as the reflux ratio, the number of theoretical plates, the feed ratio, the top effluent, the liquid holdup, and the feed location, on EC conversion and product composition at the top of the reactive distillation column. The calculated results show that a complete EC conversion can be achieved. The model reliability is analyzed under different Murphree tray efficiencies, showing no considerable difference between the equilibrium and nonequilibrium models for this system. And the calculated results are verified by experimental data and commercial operation of a dimethyl carbonate plant of 10,000 tons per year.     

A REACTIVE DISTILLATION PROCESS FOR AN AZEOTROPIC REACTION SYSTEM: TRANSESTERIFICATION OF ETHYLENE CARBONATE WITH METHANOL

A reactive distillation process is proposed for manufacturing dimethyl carbonate (DMC) through the transesterification reaction of ethylene carbonate (EC) with methanol. Modeling and simulation of the reactive distillation column have been carried out to study the effects of operating conditions, such as the reflux ratio, the number of theoretical plates, the feed ratio, the top effluent, the liquid holdup, and the feed location, on EC conversion and product composition at the top of the reactive distillation column. The calculated results show that a complete EC conversion can be achieved. The model reliability is analyzed under different Murphree tray efficiencies, showing no considerable difference between the equilibrium and nonequilibrium models for this system. And the calculated results are verified by experimental data and commercial operation of a dimethyl carbonate plant of 10,000 tons per year.     

多元精馏过程的非平衡级动态模型

提出了-种通用的多元精馏过程非平衡级动态模型。模型中采用传质、传热速率方程表征实际塔板上的传递过程,避免了级效率的计算。通过引入“分离效率函数”提出一种简洁适用的仿真模型和求解算法,分析了速率模型与“平衡级一级效率”模型之间的内在联系。在两个工业精馏塔上进行了仿真计算和实验检验,结果表明,非平衡级动态模型能够准确预测实际塔板上的动态行为。     

伴有多反应的精馏过程数学模拟

<正>在伴有多个反应的分离过程数学模拟中,反应量的存在使模型变量增多,非线性增强.文献[1～3]在普通精馏的基础上,提出了不同的算法来改进收敛性.他们对各种反应类型,均以动力学计算反应量,迭代变量多,算法也较复杂.Doherty针对平衡反应过程,提出了变换组成变量的概念计算反应相平衡.本文引入此概念,并对流率、焓等物理量进行了相应的变换,使变换后的反应精馏过程数学模型在形式上与普通精馏过程的模型完全一致.并以修正的Newton-Raphson法对对二甲苯和邻二甲苯的反应精馏过程进行了计算.     

START UP AND DYNAMIC PROCESSES SIMULATION OF A DISTILLATION COLUMN

A new dynamic non-equilibrium mixing-pool model for simulating start-up and dynamic re-sponse of a distillation column is reported.The proposed model is established on the basis ofconsidering the two dimensional flow/mixing behavior of actual trays in a distillation column.Com-parison is made among the computed results of the start-up time and the dynamic response time bythe proposed and five other typical models.It is found that the computed time for both dynamicprocesses is longer by the model which considers any flow/mixing pattern than by the model withoutsuch concern.The inertia effect of flow/mixing seems to be important and can not be ignored inmodeling the transient process of distillation.The proposed model,which is believed to be suitableto large column,seems somewhat useful in predicting industrial distillation dynamics.     

内部热耦合精馏塔的初步设计(I) 模型化和操作分析

引　言将热量从精馏段传到提馏段来实现节能是精馏过程节能的一种有效方法 ,即二次回流和蒸发[1](ＳＲＶ) .内部热耦合精馏塔 (ＩＴＣＤＩＣ)的热耦合机理仍是ＳＲＶ方法 ,但去掉了再沸器和冷凝器 ,具有较大的节能潜力 .它的研究只有近 1 0年的历史[2 ,3],目前 ,还没有见到详细的操作分析和设计优化的文献报道 ,只有一些较为相关的文献[4 ,5 ].本文对理想热耦合精馏塔进行了建模和操作分析 .1　模型化图 1是ＩＴＣＤＩＣ的示意图 .精馏段和提馏段被分为两个塔 .热耦合通过两段之间的热交换器来实现 .为了提供传热必须的推动力 ,精馏段将在较…     

循环流化床中流动结构的动态变化

采用激光相位多普勒粒子分析仪（ＰＤＰＡ）测量了二维循环流化床中局部颗粒运动行为及流动结构．通过将ＰＤＰＡ采集的数据进行动态图形化处理，研究了稀、密相的结构以及颗粒聚团的形成和分解．研究结果表明：在循环流化床中不仅存在稀、密两相的不均匀流动结构，而且密相和稀相自身内部也存在不均匀性；颗粒聚团的形成和分解是一个动态过程，颗粒间不同速度造成颗粒相互碰撞，密相能够分解形成稀相，稀相能够合并成为密相．在流动过程中稀相、密相及介于稀、密相间的乳相以动态的形式存在和分解，形成复杂的动态流动结构．     

小波在分析流态化系统多尺度动态行为中的应用

利用小波分解方法,对用激光相位多普勒颗粒分析仪（ＰＤＰＡ）、光纤探针及压差传感器同时测得的二维循环流化床中的信号进行了分解,并对分解信号和三种原始信号进行了比较．研究表明：将动态过程分解为三种尺度是合理的,ＰＤＰＡ信号包含了循环流化床所有尺度的全部信息．分解后三种尺度信号均具有混沌性态,但可预测性比原始信号好,为增加对动态过程的认知和建立较好的动态表达模型提供了途径．     

酚醛树脂基球形活性炭对苯蒸气动态吸脱附性能的研究

采用热重法研究了酚醛树脂基球形活性炭（PHSAC）对苯蒸气的动态吸脱附性能。结果表明PHSAC对苯蒸气有良好的吸脱附性能,其动力学曲线可分为三部分随着比表面积的增大和吸附温度的降低,苯蒸气平衡吸附量增加。再生后,吸脱附性能没有明显变化。     

Attainable regions of reactive distillation—Part III. Complex reaction scheme: Van de Vusse reaction

The main underlying principle behind the application of reactive distillation (RD) for selectivity enhancement is to facilitate the separation of selected components and favorably manipulate the composition profiles in the reactive zone to expedite the desired reaction. In this paper, a geometric approach of attainable region (AR), which is already developed for conventional reactor network, is extended further to include few representative RD configurations. We define new RD building blocks and the corresponding composition vectors that indicate a need of networking of RD units among themselves and with conventional reactors to enlarge the set of attainable compositions. A model reaction scheme of van de Vusse type ) is studied as an illustrative example and an algorithm is developed to obtain the attainable region for the given kinetics, feed composition and relative volatilities. In almost all the different cases, which are studied by varying the kinetics and volatility pattern, network consisting of RD units performs better than the conventional reactor network.