Separation of Homogeneous Azeotropic Mixtures by Pressure Swing Distillation – Analysis of the Operation Performance

The complex separation of a homogenous azeotropic mixture by pressure swing distillation is analyzed based on a rigorous dynamic model considering the system acetonitrile/water. The model is validated with our own experimental data. Investigations showed that the process can be operated in a very stable and robust manner even when large disturbances set the feed concentration to the other distillation region.     

间歇共沸精馏分离乙醇一水体系的改进研究

间歇共沸精馏是分离共沸物的一种方法,适用于化工、制药、溶剂回收、天然产物提取等产量小、品种多的行业,因此间歇共沸精馏近年来已成为非常活跃的研究和开发热点.对已有的常规间歇共沸精馏的操作方式作了改进,即共沸剂改为在塔釜回流,以正己烷为共沸剂,对分离乙醇-水共沸体系进行了改进研究,并与常规间歇共沸精馏的实验结果进行比较.结...     

非均相共沸间歇精馏模拟

提出了非均相共沸间歇精馏过程计算模型。将共沸精馏塔分为再沸器，塔体，冷凝器和液相分层器几部分，用Newton-Raphson法与泡点法结合对这4个部分进行迭代计算。经实例模拟表明，操作条件指定合理，本模型只需要用很简单的初值，能以较快的速度收敛到正确解。本模型对间歇精馏操作具有一定的指导作用。     

丙酮-甲基异丙基酮-水三元非均相共沸物精馏研究

用剩余曲线图(RCM)方法对丙酮-甲基异丙基酮(MIPK)-水三元非均相共沸物系进行分析,提出通过利用中间液-液分离器,在一个塔中实现丙酮、MIPK、水的分离。结合残余曲线、蒸馏边界线、精馏段和提留段浓度轮廓线、中间液-液分离器相平衡线等曲线对提出的丙酮、MIPK、水三元物系非均相共沸精馏过程进行了详细的分析,对非均相共沸精馏过程的设计和操作都将会起到重要的作用。以MIPK生产中的分离过程为例,建立了节能型精馏流程,结果表明,该流程可以节省设备投资,简化操作,降低生产成本。     

Scheduling Model for a Multi‐Product Batch Plant Using a Pre‐Ordering Approach

A scheduling model for a multi‐product, multistage batch plant with parallel units is presented. The objective is to maximize the weighted completion times of orders in every processing stage while imposing a penalty on the slower orders. The proposed model uses the continuous‐time representation mode and describes the allocations of tasks, units and stages by a set of binary variables. In order to reduce the model size and provide a more effective solution to the model, a pre‐ordering approach that sorts the processing sequence of orders is developed. The pre‐ordering approach identifies the infeasible assignments through which the number of binary variables is significantly reduced. Illustrative examples are provided to show that the size of the proposed model is small, and therefore, needs much less computational effort in comparison with the existing models in the literature.     

Design and Control of Heterogeneous Azeotropic Distillation for Separating 2‐Methylpyridine/Water

In industrial processes, 2‐methylpyridine/water mixtures can be separated via the conventional heterogeneous azeotropic distillation (HAD) using benzene as entrainer. 2‐Methylpyridine and water can form a heterogeneous azeotrope by themselves, based on which an improved HAD process is proposed. This allows for reducing the total operating cost and total annual cost (TAC) by more than one‐tenth compared with the conventional HAD process. Two different control structures were established for the enhanced HAD process. The results indicate that applying the feedforward ratio controllers to the control structure can handle the feed disturbances and maintain product purities with smaller transient deviations and shorter settling times.     

Recrystallization of Salicylamide using a Batch Supercritical Antisolvent Process

Recrystallization of the nonsteroidal anti‐inflammatory drug salicylamide was investigated using a batch supercritical antisolvent (SAS) precipitation process. Carbon dioxide was used as the antisolvent, and acetone, ethanol and ethyl acetate were used as solvents. Particle morphology determined by SEM showed that particles with a regular shape were obtained from the SAS process. The crystal structure analyzed by XRD showed that the intensities of specific peaks were modified. No decomposition or deterioration was confirmed by DSC measurements where the melting temperature remained the same after SAS recrystallization. The effects of process parameters were investigated with acetone as the solvent. At a higher pressure of 110 bar, a higher saturation concentration of 90 %, and a lower temperature of 293 K, the length of the rectangular particles decreased to 50 μm. This showed a significant change from the irregular and broken particle shapes with particle sizes up to 200 μm before processing by SAS.     

非均相共沸精馏分离乙二醇及1，2一丙二醇的研究

由于乙二醇及1,2一丙二醇的沸点相近,采用常规精馏方法难以分离。本文通过非均相共沸精馏的方法采用乙苯、混合二甲苯、异丙苯三种共沸剂进行实验,结合共沸剂的选择性和共沸物的共沸点来确定共沸剂。通过实验结果分析发现混合二甲苯能明显提高乙二醇及1,2一丙二醇的挥发度,是分离乙二醇及l,2一丙二醇良好的共沸剂。     

离子液体萃取精馏分离丙酮-甲醇共沸体系过程模拟

使用Aspen Plus过程模拟软件,模拟了离子液体1-甲基-3-甲基咪唑磷酸二甲酯([MMIM][DMP])作为萃取剂,萃取精馏分离丙酮和甲醇共沸物的过程.分析了全塔理论板数、原料进料位置、回流比、塔顶产品产出量等因素对分离丙酮和甲醇共沸物分离效果的影响.获得的最佳工艺条件为:萃取精馏塔的全塔理论板为40块,原料进料...     

非均相恒沸精馏分离回收正丁醇的模拟与优化

针对青岛某染料厂现有中性染料母液正丁醇回收率低、废水排放量大和不达标等问题,提出了改进的工艺,以原料水为自夹带剂的非均相恒沸精馏回收正丁醇,用 PRO/II模拟软件考察了各操作参数对冷却水和蒸汽用量的影响,确定了适宜的工艺条件,使回收率由95%提高至98%,废水达标排放,模拟结果与试验值吻合,可用于指导工业生产与设计。     

Batch Liquid‐Liquid Extraction of Phenol from Aqueous Solutions

The aim of this work is the study of batch liquid‐liquid extraction of phenol from aqueous solutions in a bench‐scale well‐mixed reactor. The influence of the ratio of phase volumes, temperature, and rotational speed on phenol removal (0.72–1.1 % w/w) was investigated using methyl isobutyl ketone as an extracting solvent. For this purpose, the ratio of phase volumes were set at 0.1 and 0.2, the temperature at 10, 20, and 30 °C, and the rotational speed at 300, 400, and 500 rpm. A physical model based on the material balance of the phases as well as the equation of mass flux between the phases allowed the estimation of the overall coefficient of mass transfer coupled with the superficial area. Moreover, it proved to fit, satisfactorily well, the experimental data of residual phenol concentration in the organic phase versus time under all the conditions investigated.     

氯乙酸甲酯减压间歇精馏分离工艺研究

采用减压间歇精馏技术从氯乙酸甲酯/甲醇/水三元组分中分离氯乙酸甲酯,考察了操作压力、回流比和精馏时间对减压间歇精馏过程的影响,得出了较佳的间歇精馏条件:操作压力为8 k Pa,回流比为3∶1,回收产品中氯乙酸甲酯质量分数为99.84%,氯乙酸甲酯回收率为77.42%。     

间歇精馏脉动馏出方式的研究

对间歇精馏脉动操作在产品馏出段的产品进行了研究,通过实验证可知,所建立的数学 可以较好地描述该操作过程各参数的变化规律。提出了一种以过程分离因子为基础的目标函数,可方便地用于衡量二元间歇精馏不同操作策略产品馏出段的分离效果。     

Total Reflux Operation of Multivessel Batch Distillation for Separation of Binary Mixtures

Multivessel batch distillation （MVBD） is mainly used to separate mixtures with more than two compo-nents. In this article, a new operation mode with MVBD is proposed for separation of binary mixtures under total reflux. A mathematic model is setup for the simulation. The proposed operation policy and the regular operation with constant reflux are compared theoretically and experimentally. The results show that the new operation mode has great advantages in time saving and operation flexibility. MVBD presents great potential for separation with high efficiency.     

MD Simulations of Diffusivities in Methanol‐n‐hexane Mixtures Near the Liquid‐liquid Phase Splitting Region

Molecular Dynamics (MD) simulations have been carried out to determine the self‐diffusivities in binary mixtures of methanol and n‐hexane with varying compositions at four different temperatures of 303.15 K, 307.7 K, 310.7 K, and 313.15 K. The Darken relation was used to determine both the Fick diffusivity and the Maxwell‐Stefan diffusivity. The values of the Fick diffusivity obtained from the simulations are in very good agreement with published experimental data of Clark and Rowley [17]. These diffusivities approach zero near composition regions where liquid‐liquid phase splitting occurs. On the other hand, the Maxwell‐Stefan diffusivity is well‐behaved and appears to be practically insensitive to the complex thermodynamics.     

间歇精馏分离2，4－和2，6－二甲基硝基苯

在内径２Ｏ毫米，高１２００毫米的填料精馏柱内，采用间歇精馏的方法对间二甲苯的硝化产物进行了分离实验。实验中考察了回流比和柱顶温度对馏出物组成的影响。实验结果在明：当柱顶压强为０．００２兆帕时，采用回流比７～９，可以分别从柱顶和釜内得到含量大于９８％的２，６－和２，４－二甲基硝基苯。     

Theoretical Investigations on the Quaternary System n‐Butanol,Butyl Acetate,Acetic Acid and Water

Reactive distillation has been established for different processes, for example, the production of MTBE and TAME. Numerous publications have shown experimental and theoretical results of such etherification processes. The present paper deals with a theoretical background for an esterification process. The investigations will be carried out with the quaternary system consisting of n‐butanol, butyl acetate, acetic acid and water. For this system, not often used in literature, the chemical equilibrium constant and a suitable reaction kinetic has to be found. The different singular points will be checked and the kind of singularity will be determined. Residue curve maps will show the shape of simulations from different starting points. The differences between a simple distillation process and a reactive distillation process will be demonstrated.