OPTIMAL DESIGN AND OPERATION OF BATCH PROCESSES

The economical design of continuous chemical processes to produce commodity products has reached an advanced state of development. Modern computer tools are used routinely to simulate and optimize these processes. This is not the case, however, for the manufacture of speciality products which must be made in batch operations. The continuing shift towards the production of higher value-added specialty products by the CPI has stimulated efforts aimed at developing good computer assisted design strategies for batch processes.

This paper discusses the formulation of the problem for the optimal design and operation of batch processes. The batch problem differs from the continuous one in a number of important ways. First, batch plants do not operate at steady state. There are important trade-offs between the processing time and the severity (intensity) of processing in single units. Cycle time and performance trade-offs also exist among the various units in the process. Second, batch plants produce multiple products in many cases. There is often a competition for shared resources (labor, utilities, and equipment) among the various products. This paper presents a hierarchical solution approach for the design and optimization of a batch process. The approach is demonstrated by solving an example problem which illustrates the fundamental economic trade-offs.     

SOME COMMENTS ON THE OPTIMAL OPERATION OF BATCH CRYSTALLIZERS

Ajinkya and Ray (1972) discussed the optimal operation of crystatlizers and computed the optimal temperature policy for a specific example using numerical techniques. The analytic solution for the general case is obtained here. It allows interesting physical interpretations and practically useful comparisons of the optimal control law with commonly used cooling policies.     

用夹紧区原理确定多元恒回流比分批精馏最小回流比

夹紧区是精馏塔内出现的浓度几乎不变的区域,对于三元物系来说,根据夹紧区在塔内出现的位置可分为：上、中和下加紧区.在无穷板数和任一瞬时釜浓下选择不同的回流比可使分批精馏处于不同夹紧区下操作.文中讨论了三元恒回流比分批精馏过程中夹紧区的演变,在Rayleigh方程的基础上建立了应用夹紧区原理确定多元恒回流比分批精馏最小回流比的方法.该方法并不要求相对挥发度为常数,并且能准确计算顶浓,克服了通常所采用的Underwood公式法的缺陷,为多元分批精馏的简捷设计奠定了基础.     

间歇蒸馏的新设计法

本文提出间歇塔的一种新的设计方法——序列稳态塔法。用此法可同时求出间歇蒸馏塔的理论板数、最佳操作回流比、塔釜组成和温度随时间的变化;导出釜液温度与最佳操作回流比的关系,实现由釜液温度前馈控制整个间歇蒸馏过程;以及求出整个间歇蒸馏过程所需的时间。计算速度快,其结果可满足工程设计的需要。     

分批精馏中的持液作用

分批精馏中持液影响塔内的动态过程,因此许多学者一直致力于分批精馏过程中持液作用的研究,但由于研究缺乏系统性,持液的作用一直是学术上争论的热点.本文提出用全过程分离难度系数关联各参数对分离过程的影响,并建立了分批精馏的恒摩尔持液模型,用全过程的分离难度系数研究了分批精馏的持液作用,结果表明：塔顶持液对分离不利,但塔身持液在一定条件下增多可使所需回流比降低;塔内持液量与釜液量之比为一个因子,当q<0.7时,确定的分批精馏塔存在最佳投料量.采用甲苯-乙苯二元物系对最佳投料量进行了实验验证,实验结果与模拟结果吻合较好.     

SELECTION OF MULTICOMPONENT BATCH DISTILLATION SEQUENCES

As in continuous distillation systems, the design of batch distillation begins with the selection of a sequence of separations. This paper considers the usual case where the column processes multicom-ponent mixtures with the recycle of intermediate cuts. It is proved that this cyclic operation does converge to a “steady state” balance. This permits to model batch distillation with recycle as a function of the steady state variables, i.e. without the need of successive simulations to obtain the steady state. Furthermore, we use simplified analytical models which permit a quick approximation to the optimal design of a given sequence, thus aiding the designer in the screening of alternative separation sequences, to preselect one, or a small set of good sequences.     

分批精馏模拟技术

综述了当前分批精馏模拟技术的研究进展。介绍了作为目前快捷（ｓｈｏｒｔｃｕｔ） 模型主流的ＦＵＧ快捷模型和ＩＳＣ 快捷模型。与严格模型相比,ＦＵＧ模型和ＩＳＣ 模型具有适应性强、计算量小、计算精度较高的独特优点。     

动态累积分批精馏过程研究（I）─—操作方法及实验

提出了动态累积分批精馏过程，选用两种不同物系进行了动态累积操作实验。结果表明：与传统分批精馏方法相比，动态累积法既利用了全回流高效率浓缩，又消除了飞轮效应，所以分离效率明显提高，在实验中分别缩短操作时间２５％和４０％。     

间歇精馏塔启动过程的模型化

引　言在以往的研究中 ,间歇精馏塔的模型大部分建立在平衡模型的基础上[1] ,系统初值的选取基于伪热初始状态 ,即每层塔板上有足够的积液量 ,塔板温度在泡点温度以上的汽液平衡状态 .多数间歇精馏过程的仿真模拟软件中使用伪热状态作为初始状态[2 ] ,例如 ,ＨＹＳＹＳ Ｒ○ (Ｈｙｐｒｏｔｅｃｈ )、ＢＡＴＣＨＦＲＡＣＴＭ (Ａｓｐｅｎｔｅｃｈ )和ＣＣ -ＢＡＴＣＨ Ｒ○(ＣＨＥＭＣＡＤ) .它们都是通过稳态和平衡计算为微分代数方程组提供了满足一致性要求的初始值 .间歇精馏过程的一个特点就是精馏塔频繁地从冷状态启动 ,初始状态会因再…     

DESIGN OF BATCH DISTILLATION COLUMNS FOR BINARY MIXTURES

In this note analytical equations are presented that describe the separation obtained for binary batch distillation. Formulas are obtained for both the constant distillate composition and constant reflux methods of operation. The results are strictly for distillation with an infinite number of stages ( corresponding to minimum reflux) however, it is shown that the equations derived closely describe the operation with a small finite number of stages.     

DYNAMIC OPTIMAL CONTROL OF BATCH CRYSTALLIZATION PROCESSES

The estimation of the solids circulation rate in a dual fluidized bed gasifier is essential as it influences the gasification performance. However, such estimation requires experimental data input, which is often not available during the design phase of a fluidized bed. In this work, a correlation was developed based on literature and experimental data (from a cold model dual fluidized bed gasifier) to estimate the solids circulation rate at high solids-to-gas density ratios. The correlation was then validated with literature data from a dual fluidized bed steam gasifier under hot conditions, yielding maximum discrepancies of ±25%.     

DYNAMIC OPTIMAL CONTROL OF BATCH CRYSTALLIZATION PROCESSES

This work applies an on-line optimal control strategy developed by Zhang (2001) to two cooling batch crystallization processes. The algorithm initially finds the optimal crystallizer temperature and subsequently uses a feedback control system in order to achieve the desired final product quality of the crystals expressed in terms of the final crystal size distribution. In both batch processes, it is shown that the on-line optimal control approach provides better final product quality as compared with a simplified optimal cooling policy. The improvement is especially noticeable in the presence of plant/model mismatch or errors in the initial conditions.     

间歇反应精馏过程的模拟及其刚性问题

本文修正了Boston等人用于间歇精馏过程的数学模型,使之能适用于间歇反应精馏过程;提出了用解离法完成间歇反应精馏过程模拟的计算步骤;比较了SIRK,GEAR和EPISODE等软件在间歇精馏过程刚性微分方程数学模型积分中的有效性;并以醋酸丁酯用乙醇转移酯化反应精馏过程为例说明了方法的应用。     

带中间贮槽的间歇精馏塔的模拟计算

带中间贮槽的间歇精馏塔由２个分离段及其中间的贮槽组成。假定液体持液量和待分离的体系的相对挥发度均保持不变,建立了该塔的一个简化的模型,由此得到各组分在整个塔中的分布情况。在此基础上,又考察了各个操作参数对分离效果的影响。     

DYNAMIC OPTIMAL CONTROL OF BATCH RICE DRYING PROCESS

The drying of paddy rice may result in quality degradation, expressed as a head kernel yield, leading to significant commercial depreciation of the product. A mathematical model of the drying and of the quality degradation process was combined with a dynamic optimization algorithm to determine the drying conditions (air temperature and relative humidity as functions of time) that ensured the highest possible final product quality for a specified drying time and a specified final moisture content. The robustness of the optimal drying strategy with respect to the initial state of the product, to the model parameters and to the initialization of the optimization algorithm was verified. The compromise between the highest achievable final quality and the allowed total drying time was studied. The combination of simulation and optimization yielded a new insight in the rice drying process and in the quality preservation strategies.     

三元醇类间歇精馏模拟和实验

在ASOG相平衡理论的基础上,利用托马斯法（Thomas）模拟三元醇类间歇精馏过程,用精确校正法防止模拟结果的失真现象.实验结果证明了数学模型的正确性及计算方法的可靠性.定义了单位时间经济效益目标函数,并讨论了回流比和理论板数对单位时间经济效益的影响关系,得出了在给定条件下的最佳回流比为5.5,最佳操作理论板数为20的结论.     

单产品间歇过程最优化设计

首先对附属设备和主体设备构成网络的间歇过程最优化设计问题进行了初步的研究,根据间歇操作的特点,提出了过程设计的一般数学模型,并用于本室开发的对二氯苯间歇结晶过程最优化设计,采取可变容差法与枚举法相结合,建立了相应的最优化设计的软件,为实际生产过程设计提供了依据。 此外,本文针对间歇过程设计问题的最优化算法做了进一步的研究,提出了一种比较有效的算法。其优点是:单维搜索,运算速度快。适用于较大维数的最优化设计问题的计算,在此基础上有可能进一步开发出通用的软件。     

SENSITIVITY ANALYSIS OF OPTIMAL CONTROL POLICIES FOR BATCH PROCESSES

The computation of optimal control policies for batch processes, critically depends on the process model employed. The real process may deviate from the assumed model due to external signal or model parameter variations. In this paper we examine the effects of these variations on

(a) the value of the objective function, when the nominal optimal policy is applied

(b) the optimum value of the objective function.

We present quantitative relations between the perturbed and the nominal problems and demonstrate their use through a number of examples.     

间歇恒沸精馏法从异丙醇水溶液中回收异丙醇

采用单塔间歇恒沸精馏法将异丙醇与水分离,从含水１２．６％左右的醇溶液可制得含水小于０．５％的异丙醇产品,醇的回收率达９７．０％。对恒沸剂选择、用量,流程和操作要点作了推荐及说明