A model-based scheme for the on-line optimization of a liquid extraction process

The on-line optimization of a liquid extraction process using a model-based scheme is described. Four steady-state process models are first investigated for their ability to predict the process performance; these models are subsequently used in the optimization study. The optimization scheme incorporates a simple model-updating technique and is based on an efficient method for constrained optimization which has been developed as part of this study. Rapid convergence to the true process optimum occurs, provided the predictions of the direction of change of the objective function are locally correct. In a few cases, however, poor model predictions result in failure to converge, or give convergence to a point other than the true optimum.     

离子液体在萃取分离领域的研究进展和应用

综述了近几年来离子液体在石油化工领域中萃取分离的应用,主要包括对于脂肪烃和芳烃的萃取分离、烷烃和烯烃的萃取分离、燃料油中的脱硫脱氮,并概述了离子液体在萃取分离过程中的萃取机理和影响因素。此外,针对离子液体回收难度较大的问题,概述了主要的回收方法,包括减压蒸馏、液液萃取和双水相分离等方法。结合离子液体的优势和存在的问题,对其工业化的应用提出展望。     

Optimisation of drop size in countercurrent flow liquid-liquid extraction columns

Experimental data obtained in a pilot plant rotating disc contactor were used to obtain values of parameters for the hydrodynamic and mass transfer models representing column operation. The unique feature of the data was that drop size within the column did not vary appreciably with vertical position. Column performance measurements were therefore truly representative of the particular drop size generated. The models, with the resulting parameter values, were then used in design mode to determine column dimensions as a function of drop size. An optimum drop diameter of 0.20–0.25 cm is indicated for the toluene-acetone-water system.     

Microprocesses of liquid extraction

The extraction mechanism has been considered and the crucial role of the dynamic interfacial layer has been noted. The microprocesses that take place in extraction systems and are associated with the Marangoni effect, the loss of hydrodynamic stability, partial dispersion, coalescence, flocculation, the Ostwald ripening of drops, chemical reactions, the emergence of a new phase, adsorption, coagulation, the formation of structures, and polymerization have been described. For LnCl₃–H₂O–diluent systems (heptane, toluene, tetrachloromethane), data on the shift in the boundaries of the observed transition region over time have been presented. The mechanism of the transfer of the substance in the transition region of the extraction system has been formulated.     

Enantioseparation of chiral aromatic acids in process intensified liquid–liquid extraction columns

Enantioselective liquid–liquid extraction (ELLE) is a powerful alternative to common technologies for separation of racemic mixtures. The first application of ELLE for aromatic acids in liquid–liquid extraction columns is described. The ELLE is investigated experimentally and theoretically for phenylsuccinic acid (PSA) as a representative for aromatic acids. A racemic mixture of (R/S)‐PSA is separated with hydroxypropyl‐β‐cyclodextrin as selector molecule. The ELLE obtained the highest operative selectivity (α_op = 1.8–2) for low pH‐values and temperatures. Because of the low operative selectivity, a countercurrent process is necessary to separate both enantiomers completely. The countercurrent process is investigated in process intensified extraction columns (Ø_in = 15 mm) with a high number of equilibrium stages. The experiments demonstrate a good symmetric separation with an enantiomeric excess of 60% and yields of 80% for both enantiomers. Finally, the back extraction is investigated to recycle the selector molecule and increase the efficiency. © 2014 American Institute of Chemical Engineers AIChE J, 61: 266–276, 2015     

Modeling and simulation of a sulfolane extraction process

Modeling and simulation for a sulfolane extraction process were performed. The process investigated in the present work consists of two tray columns, one of which is used for extraction and the other one for washing. The modified θ-method was employed for the modeling of the process. The computation of the equilibrium state of a two-phase system is one of the key issues in the modeling and simulation of extraction processes. In the present work the UNIFAC method was used for the computation of related thermodynamic properties and equilibrium states. Results of simulations showed good agreement with actual plant operation data.     

Optimisation of the colour sequence in the process of fabric dyeing

When programming a dyeing machine, a sequence of colours has been established in an attempt to reduce the effects caused by dye residues on the colours that are subsequently applied. In this paper a model is presented that makes it possible to determine the optimum sequence. Using a optimisation method, the sequence that minimises the sum of the photocolorimetric differences between the colours required and those obtained has been determined. In order to estimate the change that each colour undergoes due to the presence of residual dye in the dyeing equipment a computer calculation method has been adopted.     

Counter-current solid liquid extraction in a cascade of batch extractors

An analytical solution and method of calculation is presented for a cascade of N perfectly mixed batch extractors operating counter-currently, for spherical solid particles, with parameters which may vary for each extractor. The results for the case of constant and equal parameters along the complete cascade are presented in dimensionless plots; N varies from 1 through 10. The practical interest of these diagrams lies in their use in design and/or in foreseeing the behavior of a cascade when its parameters undergo variations. A sample calculation is included.     

加压溶剂法提取雷公藤甲素及其条件优化

以雷公藤为原料,采用加压溶剂法提取雷公藤甲素,以1,2-二氯乙烷为溶剂,考察了提取时间、料液比和提取温度等因素对提取工艺的影响,并在单因素试验基础上,根据中心组合试验设计原理采用三因素三水平的响应面分析法进行工艺优化,得到提取过程优化的工艺条件为:料液比1:9.7,提取温度115℃,提取时间80min,雷公藤甲素的实际得率可达0.173‰,纯度为1.21%,与常规回流提取法相比优势明显。     

Mass transfer in packed liquid—liquid extraction columns

The mass transfer characteristics of 3·5, 7·3, 10·16 and 15·6 cm i.d. packed liquid—liquid extraction columns were studied with a variety of packings such as, $\text{3}\text{8}$, $\text{1}\text{2}$ and 1 in. ceramic Raschig rings, $\text{5}\text{8}$ in. stainless steel Raschig rings, $\text{1}\text{2}$ and 1 in. ceramic Intalox saddles, $\text{5}\text{8}$ and 1 in. stainless steel Pall rings, and 1 in. polypropylene Intalox saddles and Pall rings. Some data were also obtained for the co-current mode of operation (up-flow) for packed columns, and without packings. In addition the mass transfer charactersitics of a packed extraction column with film flow were studied.The theory of extraction accompanied by a fast pseudo-first order reaction was employed to measure the values of effective interfacial area. The values of overall (continuous and/or dispersed phase) mass transfer coefficient were measured by the Colburn—Welsh technique. A fairly wide range of physical properties of the two phases was covered.The values of overall (continuous phase) mass transfer coefficient and effective interfacial area for new packings such as Pall rings and Intalox saddles, under otherwise similar conditions, are only about 10 and 35 per cent higher, respectively, than those provided by the conventional packings of the same nominal size. However, the flooding velocities for the newer packings are as much as 80 per cent higher than those for the conventional packings of the same nominal size.     

A new lubricants extraction process

Development of a new process for the solvent extraction of lubricating oils, known as EXOL N, is described. The selection of N-methyl-2-pyrrolidone (NMP) as solvent, the determination of its relevant properties, and its application through engineering and pilot-plant studies are reviewed. This EXOL N process is now employed internationally in over a dozen full-scale lube extraction plants.     

Modeling and simulation of a liquid extraction column with structured packing

In this work mass transfer phenomenon of liquid–liquid extraction process with structured packing was modeled. The model was validated by means of fluid-dynamic and mass transfer tests, for mass transfer from the continuous to the disperse phase with n-butanol/succinic acid/water system. The effect on hold-up and outlet concentration profiles of each phase were evaluated when the incoming flow of the disperse phase was disturbed between 10 and 30%. Surface velocity of each phase and hold-up were considered in the model as functions of time. The continuous phase dispersion phenomenon was also taken into account. Deviation percentage average of 8% between the experimental data and the simulation results of the disperse phase composition in steady state were obtained. For the dynamic model the inclusion of the dispersion effect of the disperse phase and more experimental tests are recommended.     

淫羊藿超声提取工艺优化

目的:优选淫羊藿的超声提取工艺。方法:以淫羊藿苷的提取率为指标,高效液相色谱检测含量,应用正交试验优化淫羊藿的最佳超声提取工艺条件。结果:影响提取的主次因素为ABDC(A:乙醇浓度;B:物料比;C:提取温度;D:提取时间)。最佳提取条件为:超声功率为300W、60%乙醇溶液、液固比25:1、提取时间60min、提取温度50℃。根据优选工艺验证实验表明,有效成分提取率94.88%,重现性较好。结论:优选得到的工艺稳定可行。     

正交实验法优选当归多糖的提取工艺

以当归的多糖得率为评价指标,采用正交实验,运用紫外分光光度法对提取物中相关指标性成分的含量进行测定。结果表明,当归多糖最优提取工艺为12倍用量水,提取时间2 h,提取次数2次,醇沉浓度为70%。     

萃取法回收生产聚苯硫醚废液中的N-甲基吡咯烷酮溶剂的研究

研究了萃取法从生产聚苯硫醚过程中产生的废液(洗液和滤液)中回收N-甲基吡咯烷酮,考察了萃取剂的种类、萃取温度、萃取时间、萃取级数以及原液中N-甲基吡咯烷酮的含量等因素对萃取效果的影响。最佳的工艺条件为:萃取温度30℃、萃取时间2h、溶剂比1∶1、通过三级萃取;萃取后的溶剂可用精馏分离的方法实现N-甲基吡咯烷酮与三氯甲烷的回收,且二者均可重复利用。     

Droplet coalescence and breakage rates in a packed liquid extraction column

Coalescence rates for MIBK (methyl isobutyl ketone) droplets in water in a packed column have been measured directly using a novel colorimetric technique. Second-order coalescence and first-order breakage rate constants were derived from the results using a discrete population balance model and were correlated in terms of droplet diameter and dispersed-phase holdup. It is shown that the rate constants can be used to predict the steady-state droplet-size distribution and coalescence rates. They were also used in a theoretical study of mass transfer for a typical polydisperse system, which showed that repeated droplet coalescence and breakage leads to some reduction in column height.     

膜接触器中乳化液膜脱除Ni2+的研究

研究了以D2EHPA/煤油/HC1形成的微乳液体系在中空纤维膜接触器中萃取NiCl2水溶液中Ni2的过程,考察了D2EHPA和Ni2+浓度、水溶液酸度、两相流速对溶液中Ni2+的萃取率和传质性能的影响.结果表明,用D2EHPA/煤油/HCl形成的微乳液体系能有效萃取NiCl2水溶液中的微量Ni2+,增大微乳液中载体D2EHPA浓度和料液pH都能提高Ni2的萃取率和过程的总质系数,增加料液流速能显著提高Ni2+的萃取率和过程的总质系数,表明过程的传质阻力主要在水溶液相.     

Liquid–liquid extraction of a recombinant protein with reverse micelles

Recombinant cytochrome b₅ was extracted into the reversed micelle phase of an anionic surfactant (AOT) in octane and back-extracted to a final aqueous phase. The extraction of the protein was controlled by an electrostatic mechanism, since it was dependent on the global charge of the protein. This was directly demonstrated by experiments with native and mutant cytochromes obtained by site directed mutagenesis. The back-extraction of cytochrome b₅ to a fresh aqueous phase was decreased by factors that reduced the size of the water pool of the organic phase, such as high salt concentrations (1–2 mol dm^?3 NaCl) and low temperatures (4°C), probably because of an increase in a favourable interaction of this protein with the surfactant at closer distances.