Conceptual Design of Double‐Feed Reactive Distillation Columns

The feasibility and feasible range of operating parameters for double‐feed reactive distillation columns are evaluated, based on the combination of pinch point map analysis for the middle‐section in the compositional space and the feed angle method as an efficient shortcut design method. Limiting bounds for operating parameters are determined where the properties of singular points change. The existence and values of such bounds may vary in double‐feed reactive distillation columns depending on the nature of the system under study. The methodology is illustrated by production of methyl acetate and ethyl acetate. An efficient method is described to identify the most promising candidates of double‐feed reactive distillation columns and to study the design flexibility in terms of operating parameters.     

精馏塔的故障诊断方案设计

本文简单地介绍了精馏塔故障诊断的必要性。主要讨论了精馏塔的故障诊断专家系统和故障诊断的具体步骤(其中主要包括建立设备档案、确定检测方法、检测周期及维修时间和性能预测及档案管理)。只有将维修技术、故障诊断技术和计算机远程监测技术有机的结合，才能有效地预防和避免事故、优化操作条件和延长操作周期，为企业取得更大的经济效益和社会效益。     

氟代碳酸乙烯酯精馏工艺及其塔器设计

精馏是生产高纯度氟代碳酸乙烯酯(>99.95%)的重要工艺之一。本文分析了氟代碳酸乙烯酯提纯工艺的特点,根据实验数据,确定了合适的操作压力和理论板数;利用Aspen Plus物性估算模块,估算了FEC物性数据,并进行了塔器设计,推荐了塔的结构形式、填料高度和塔径。     

反应精馏过程图解设计法研究进展

反应精馏是伴有化学反应的精馏过程 ,具有设备紧凑、能量集成等优点。文章总结介绍了 80年代中期以来国内外有关反应精馏过程设计的研究进展 ,重点分析了图解设计法理论研究的现状和局限性 ,指出了反应精馏过程图解设计法的发展方向。     

Effects of Liquid Holdup in Condensers on the Start‐Up of Reactive Distillation Columns

Compared with start‐ups in conventional distillation columns, those in reactive distillation (RD) columns are much more time and energy consuming, and generate a large amount of by‐products which are not easy to deal with together. For several years, researchers have been trying out different methods to shorten the time required to lower the cost of the start‐up. In this work, a rigorous dynamic model in the ChemCAD simulator is applied to model the start‐up process for the esterification of ethyl acetate in a reactive distillation column. In the model, two sets of equations are employed: one for the fill‐up and heating stage and the other for the equilibration process which follows. In the fill‐up and heating stage, fluctuation curves of the reboiler temperatures with respect to time which are similar to those for conventional distillation columns are observed, while in the equilibration process it is found that the increase of the liquid holdup volume in the condenser reduces the time required to reach steady state for the reactive column and decreases the liquid holdup volume in the reboiler at the equilibrium state. This shows that the liquid holdup volume in the condenser has an important effect on the start‐up of reactive distillation columns.     

反应精馏过程的研究进展

反应精馏是化学反应和精馏过程耦合为一体的单元操作，已成为当今的重要研究领域。本文综述了反应精馏过程的模拟计算和设计方法，介绍了过程控制中的多定态问题，总结了反应精馏的工业应用情况，指出了研究中应注意的重要因素，并指出了未来的研究方向。     

Thermodynamic Fundamentals of Reactive Distillation

Reactive distillation means the simultaneous implementation of reaction and distillation in a counter currently operated column. The effective phase equilibrium is very complex since the chemical equilibrium is superimposed on the vapor liquid equilibrium. The paper focuses on the calculation and presentation of this equilibrium using so called reactive distillation lines. This leads to a clear explanation for the existence of reactive azeotropes and to a simple method for the determination of the concentration of these azeotropes. The effectiveness of this method is demonstrated on several mixtures with different reaction mechanisms.     

Control of Ideal Heat Integrated Distillation Columns

The operation of an ideal heat integrated dlstillation columan (HIDiC) is addressed .Five Kinds of control configurations, i.e. single-loop control, multi-loop control, multivariable internal model control (IMC), modified multlvariable internal model control (MIMC) and nonlinear process model-based control (NPMC), are designed and applied to the process. Simulation results demonstrate that all of the above control confaguratloam ere valid for product quality control. NPMC control configuration is found to be the best one among all the alternatives. It can readily realize setpoint transitions and conduct effectively against external disturbance. MIMC control configuration ranks second in the row for its regulatory responses to feed composition disturbances with relatively extended setting time, Next comes from the multi-loop control configuration, which is moee or lees handicapped by its greater deviations and overshootings. IMC control configuration can not compete with the multi-loop control configuration because it is extremely sensitive to operating condition changes. Single-ioop control configuration is the worst one among all the mentioned control configurations. Its responses for the uncoutrolled end products are extremely sluggish.     

Retrofit of Distillation Columns Using Thermodynamic Analysis

Abstract

Thermodynamic analysis provides the column grand composite curves and exergy loss profiles, which are becoming readily available for a converged distillation column simulation. For example, the Aspen Plus simulator performs the thermodynamic analysis through its Column–Targeting tool for rigorous column calculations. This study uses the column grand composite curves and the exergy loss profiles obtained from Aspen Plus to assess the performance of the existing distillation columns, and reduce the costs of operation by appropriate retrofits in a methanol plant. Effectiveness of the retrofits is also assessed by means of thermodynamics and economics. The methanol plant utilizes two distillation columns to purify the methanol in its separation Section. The first column operates with 51 stages, has a side heat stream to the last stage, a partial condenser at the top and a side condenser at stage 2, and no reboiler. The second column operates with 95 stages, has a side heat stream to stage 95, a total condenser, and high reflux ratio. Despite the heat integration of the columns with the other Sections and a side condenser in column 1, the assessment of converged base case simulations have indicated the need for more profitable operations, and the required retrofits are suggested. For the first column, the retrofits consisting of a feed preheating and a second side condenser at stage 4 have reduced the total exergy loss by 21.5%. For the second column, the retrofits of two side reboilers at stages 87 and 92 have reduced the total exergy loss by 41.3%. After the retrofits, the thermodynamic efficiency has increased to 55.4% from 50.6% for the first column, while it has increased to 6.7% from 4.0% for the second. The suggested retrofits have reduced the exergy losses and hence the cost of energy considerably, and proved to be more profitable despite the fixed capital costs of retrofits for the distillation columns of the methanol plant.     

反应精馏过程图解法设计策略研究

从反应精馏过程图解法设计的理论研究出发,探讨了反应空间、转换组成变量以及剩余曲线等应用范围和局限性;通过分析反应精馏操作线方程的变化,提出了图解法设计反应精馏过程的策略;（1）用奇异点判断法结合实验数据可判定应用反应精馏过程的可行性;（2）借助反应空间可判断该过程能否在单塔中得到完全分离;（3）图解法设计的多种设计结果及相应对策。采用实例验证了该策略的可行性。     

Control System Design for a Single Feed ETBE Reactive Distillation Column

Reactive distillation (RD) is advantageous for the Ethyl Tert‐Butyl Ether (ETBE) synthesis. The steady state model of an ETBE reactive distillation column created using the simulator HYSYS is analyzed to synthesize effective control structures. Since the column exhibits input multiplicity with the dual process objectives of ETBE RD (isobutene conversion and ETBE purity), inferential variables are selected. A control structure that organizes a sensitive tray temperature in the stripping section using the reboiler duty and maintains the temperature difference of reactive trays using the reflux flow, is found to be most suitable. A decentralized PI controller and constrained Model Predictive Controller (MPC) are implemented, and performances are compared for set point tracking and disturbance rejection. MPC control algorithms are implemented in MATLAB and interfaced with HYSYS. Constrained MPC (CMPC) is found to be effective for load disturbance rejection, which frequently occurs in the single feed configuration.     

Efficiency of Distillation Columns Containing Packed Sieve Trays

Abstract

The Murphree efficiency of the fifth tray in a six-sieve tray distillation column, 7.8 cm in diameter and 85 cm high, was increased from 37.5 to 90% when three disks of a wire mesh pad, 9 cm high, were placed on the tray. An acetone-methanol test system was used in this investigation. The pressure drop across the tower corresponding to this packing increased by 33%. Nine disks of Raschig rings of similar height increased the tray efficiency to 75% and the pressure drop by 16%. A model was used for the azeotropic system, and the overall tower efficiency was found to increase by about 20% due to the presence of packing on a single tray.     

填料塔在高压蒸馏中的应用

高压蒸馏与真空和常压操作相比,填料塔中的气液均匀分布变得更加困难,并导致气相返混增加,填料分离效率下降,但经过适当的设计,填料塔不但可以提高高压蒸馏的生产能力,而且效率也得到提高。文中介绍高压蒸馏填料塔的特点和近年来的研究进展,并总结了国内外高压蒸馏填料塔新塔设计和老塔改造的成功经验。     

自回流式精馏塔在轻组分精馏中的优势及操作特性

深入分析了自回流式精馏塔与传统精馏设备的区别以及在轻组分精馏中的优势,同时分析了其在生产过程中的操作特性。     

多组分精馏计算的新方法

本文应用Newton-Raphson技术求解精馏计算的三对角线物料平衡方程组.提出了一种新的块状三对角线矩阵法.本方法具有程序简单,对初值的选择要求不高,占用计算机内存少,计算偏导数少和快速稳定收敛等特点.