Design and control of an olefin metathesis reactive distillation column

This paper considers the design and control of a reactive distillation column in which one reactant is consumed and two products are formed (A?B+C). The volatilities are α_B>α_A>α_C, i.e. the reactant is intermediate boiling between the two products. The metathesis of 2-pentene is considered as the demonstrative example. The column has a single feed of the intermediate boiling reactant. The distillate contains mostly light component and the bottoms mostly heavy.Three designs are considered: the base case (low-conversion/low-pressure), a low-conversion/high-pressure case and a high-conversion/high-pressure case. The base design is obtained from the literature, and the other two steady-state designs are optimized with respect to the total annual cost. All the designs are found to be openloop stable. Five control structures are studied for the base design. Then the best two structures are applied to the remaining two designs. This category of reactive distillation exhibits less challenging problems than other categories since it uses a single feed, which eliminates the need for the control structure to perfectly balance two fresh feeds.Simulation results demonstrate that effective dynamic control is provided by a control structure that uses two temperatures to maintain the purities of both product streams. No internal composition measurement is required. This structure is found to be robust and stable and rejects loads and tracks setpoints very well.     

Evaluation of a two-temperature control structure for a two-reactant/two-product type of reactive distillation column

Several different control structures have been proposed for reactive distillation columns. The appropriate control structure depends on the flowsheet and on the type of reactions occurring in the column. If two reactants are involved and if it is desirable to operate the process without any excess of reactant, it is necessary to manage the fresh feed streams so that the stoichiometry is exactly balanced. A composition analyzer that measures an internal composition in the column is often required. However, if two products are produced, it is possible to avoid the use of an analyzer by using two temperatures in the column to adjust the two feed streams. This type of structure was proposed by Roat et al. [Roat, S., Downs. J., Vogel, E., Doss, J., 1986. Integration of rigorous dynamic modeling and control system synthesis for distillation columns. In: Chemical Process Control—CPC III. Elsevier, Amsterdam.] for the ideal reaction A+B↔C+D in one of the earliest papers dealing with reactive distillation control.The purpose of this paper is to explore the effectiveness of this two-temperature control structure for various column designs (number of reactive stages) to quantify the impact of design on controllability. We also discuss the issues of the selection of the trays whose temperatures are to be controlled and the tuning of the two interacting temperature controllers. Disturbances in production rate and fresh feed compositions are made to examine the rangeability of this control structure. Both an ideal reaction system and the methyl acetate system are studied. One of the main conclusions is that the locations of the temperature control trays should be made such that the two temperature controllers both have direct action (an increase in temperature increases feed), which requires negative openloop process gains for both loops.     

多组分间歇精馏工艺计算探讨

介绍用“微元时段”计算多组分间歇精馏的方法。     

精馏塔静态仿真：Ⅰ.静动态混合数学模型的应用

本文为了克服精馏塔静态仿真不易收敛和初值难以给定等难题，巧妙地利用隐含数值积分方法的特点，将稳态与动态数学模型耦合起来，用以求解高难度的非理想精馏塔静态仿真问题。所得静动态混俣模型大大提高了精馏塔静态仿真的鲁棒性，对于高度非理想精馏塔的仿真尤为有效。通过对某丙烯腈萃取精馏塔的静态仿真，充分证明了这种混合模型化方法的可行性。     

从120号溶剂油中提取正庚烷并回收甲基环己烷的研究

总结了国内外正庚烷的生产状况和市场行情，分析了中小型石化企业生产正庚烷的可行件，提出采用萃取精馏分离正庚烷的方法．在间歇精馏塔塔顶温度为91-101℃、塔釜为103-110℃的条件下，可以得到58％以上正庚烷和甲基环己烷的混合液．根据物质相关性质，初步确定有关萃取溶剂，利用单级循环汽液平衡釜对初选的萃取剂进行实验研究，选定乙二醇作为萃取剂，为进一步实验研究提供依据．     

真空蒸馏脱硒的研究

本文从理论上分析了真空蒸馏脱Se的影响因素时间和温度,并通过实验给予验证,提出了最佳条件,对工业采用真空蒸馏脱出含Se物料中的Se具有一定的指导性。     

超纯汞生产新工艺的技术研究

本文着重介绍了超纯汞生产新工艺的基本原理的理论探讨及生产工艺过程的控制。     

F2.4微孔膜的制备及在膜蒸馏过程中应用的初步研究

采用相转化法制备了F2 4的疏水微孔膜 ,并对F2 4和PVDF微孔膜的机械性能以及疏水性等方面进行了对比 .结果表明 ,F2 4微孔膜在拉伸时的应变以及断裂伸长率约为PVDF微孔膜的 6～ 9倍 ;其接触角 (77 4°)也大于PVDF膜的接触角 (6 6 7°) .尽管膜蒸馏的数据显示F2 4微孔膜的蒸馏通量尚不及PVDF膜 ,但通过调节各项制膜参数 ,F2 4可能具有良好的应用前景     

New strategies for separations through reactions

Separations through reactions can provide reliable and economically viable alternatives to established methods of separation, particularly for close boiling substances. New strategies in ‘Dissociation Extraction’ and ‘Dissociation Extractive Crystallization’ for separation of close boiling acidic/basic mixtures have been highlighted. Separations with aqueous solutions of hydrotrope and aqueous micellar solutions have been brought out. Separations by membranes with facilitated transport is potentially attractive. This paper is dedicated to Dr L K Doraiswamy on his sixtieth birthday.     

Characteristics of the reactive distillation column with a novel internal

A new catalyst loading method, in which catalyst particles are packed in a reactor with a novel internal, has been studied by measuring pressure drop, RTD, liquid holdup and mass transfer. It can be inferred from experimental results that the internal changes the conventional gas and liquid counter-current flow into a new cross-current flow, so the problems of excessive pressure drop and “flooding” are avoided. When pressure drop, liquid holdup, RTD and mass transfer coefficient are similar, the catalyst loading fraction of the new method is much higher than that of conventional methods. Furthermore, the reactive distillation reactor with the novel internal has advantages such as simple structure, low operating cost, and convenience for installation and removal of the catalyst.