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.     

拟稳态模型用于间歇萃取精馏的数值模拟

Batch extractive distillation (BED) is a special method used in the distillation process by adding a solvent into the batch distillation column to alter the relative volatility of the components and improve the separation. A comprehensive design and simulation method is required due to the complexity of BED. In this study, a quasi-steady-state model for BED is proposed, the derivation and solution of the model are presented. This shortcut model can be used to simulate the composition and temperature of the reboiler, the top and other plates of the column in a batch extractive distillation operation. The calculated values are in good agreement with the experi-mental data. The results show that the quasi-steady-state model is a practical method because of some advantages such as high precision and fast calculation.     

浓度极稀物中回收微量重组分的精馏操作策略—准间歇精馏

A new operation policy--quasi-batch distillation for recovering infinitesimal amounts species existing in a mixture is presented. In quasi-batch distillation operation, feed is introduced with a constant flow rate onto the feed stage of the column, and the flow rate of the distillate is the same as that of the feed, whereas the bottom product is withdrawn periodically. The behavior of quasi-batch distillation is simulated and analyzed through an example on heavy water separation. Comparing with continuous or batch distillation, the new operation policy is more reliable and efficient to achieve higher recovery of dilute component. This is especially suitable for separating small amount of precious species from large amount of raw material.     

全回流-全馏出与变塔压联合的间歇精馏过程

A novel operation of batch distillation-combination of varying colum pressure and total reflux-total efflux is studied experimentally. In the operation, the product is accumulated at the top of the column under total reflux and then drained off completely, and the column pressure is varying in the whole process. This process has been industrialized successfully with large profits. The conventional mode of batch distillation is improved by this method effectively: the separation eficiency and the yield of product are increased greatly, the operation time is shortened and the production cost is cut down. Moreover, the amount of condensation water is decreased and the over-high reboiler temperature is lowered.     

周期操作全回流间歇精馏的动态模型(英文)

Cyclic total reflux (CTR) batch distillation is a promising mode of the process but lacking of appropriate modeling for the period of filling the reflux drum. A new dynamic modeling method for the simulation of CTR batch distillation is proposed in this work, in which the changes in column holdup and liquid flow rate during the filling of the drum, and the consequent change in valid number of theoretical plates are considered. The effect of drum holdup on operation time is investigated and the optimal drum holdup is obtained from the simulation. The dynamic modeling is compared to the conventional modeling without consideration of change in liquid flow rate. The experimental result shows that the present modeling is more reliable and more accurate, especially for the col-umn with large liquid holdup.     

Effect of thermodynamic parameters on prediction of phase behavior and process design of extractive distillation

Extractive distillation was investigated for separation of the minimum azeotrope of n-propanol/water,via the Aspen Plus simulation platform.Experimental data of n-propanol/water,which could pass the thermodynamic consistency test,were regressed to get suitable binary interaction parameters (BIPs) by the UNIQUAC thermodynamic model.The azeotrope system was heterogeneous in the simulation with built-in BIPs,which was contrary to the experimental data.The study focused on the effect of thermodynamic parameters on the prediction of phase behavior,and process design of extractive distillation.N-methyl-2-pyrrolidone (NMP) and ethylene glycol were used as solvents to implement the separation.Processes with built-in and regressed BIPs were explored,based on the minimum total annual cost (TAC).There were significant differences in the phase behavior simulation using different thermodynamic parameters,which showed the importance of BIPs in the design and optimization of extractive distillation.     

分批精馏过渡段放持液操作方式

The new mode of operation for slop cut withdrawal in batch distillation, i.e., draining Column liquid holdup at the end of slop cut period, was proposed. And the stopping criterion for the operation was investigated, Experiments were carded out with isopropanol-n-propanol binary system and isopropanol-n-propanol-n-butanol ternary system in a distillation column with a liquid collector installed between the reboiler and the column section, Experimental results in a Ф 45mm batch column show that the proposed policy can overcome the flywheel effect caused by column liquid holdup and thus cut down operation time and energy consumption 31%-61%.     

周期全回流间歇精馏中全采出操作时的塔顶浓度平台期(英文)

The total withdrawal operation is an inevitable section in cyclic total reflux batch distillation.In the operation,an interesting phenomenon "overhead concentration platform"(OCP) appears,which is defined as a period of time with high overhead concentrations when the operation is changed from total reflux to total withdrawal.The OCP phenomenon and its influential factors,such as the theoretical stage number,feed concentration,and feed composition,are examined by simulations and experiments.The experimental equipment is a column with random packings.It is shown that the number of theoretical stages influences the OCP more significantly than the other factors.     

三正丁胺络合萃取精馏分离醋酸和水

A new separation method, reactive extractive distillation, was put forward for separating water and acetic acid. The separation mechanism was analyzed through infrared spectra technique. Isobaric vapor-liquid equilibrium (VLE) data at 101.33 kPa for the binary or ternary systems consisting of water, acetic acid and tributylamine were measured. The activity coefficients were correlated by using Wilson, NRTL, and UNIQUAC Equations.The VLE experiment showed that tributylamine could enhance the relative volatility of water to acetic acid. An extractive distillation experiment was carried out and proved that tributylamine was a good extractive solvent.     

模拟移动床改进进料模式提高生产效率的模型化研究(英文)

A new feeding mode for a simulated moving bed(SMB)is proposed.The outlet stream from zone Ⅱ is collected at regular intervals.The concentration of the solution is increased by dissolving raw materials and then fed to zone Ⅲ as the feed stream during the next collection interval. In this feeding mode,the concentration of the stream fed to zone Ⅲ is identical to that of original feed,while in a conventional SMB,the feed is diluted by mixing with the outlet stream of zone Ⅱ before feeding to zone Ⅲ.The new feeding mode increases the inlet concentra tion of zone Ⅲ.A modeling investigation shows that higher inlet concentration of zone Ⅲ increases the height of concentration band in SMB,improving the separation performance significantly.In comparison with the traditonal feeding mode,the new feeding mode increases the productivity by 23.52% and decreases the solvent consumption by 22.56%,so as to increase the raffinate and extract concentrations by 53.17% and 20.38%,respectively.The collection interval for the outlet stream from zone Ⅱ has no effect on the separation performance after reaching the steady state,so that the collection interval can be increased to make the operation more convenient.     

常规间歇萃取精馏分离苯-环己烷的研究

通过一个常规间歇萃取精馏实验装置,考察了不同萃取剂在不同回流比及萃取溶剂加入速率情况下对分离苯-环己烷共沸体系的影响。结果表明,二元混合溶剂能够解决单一溶剂的选择性与溶解性相矛盾的问题;且在同等条件下,综合性能优于单一溶剂;随着溶剂加入速率和操作回流比的增加,产品的产量逐渐提高,尤其重要的是混合溶剂间歇萃取精馏技术与简单溶剂间歇萃取精馏技术相比并不复杂。     

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...     

旋转填料床间歇萃取精馏性能研究

为了寻找强化间歇萃取精馏过程的有效途径,在装填2mm×2mm三角形螺旋填料的旋转床中,以乙醇-水为实验物系,乙二醇为萃取剂,通过考察馏出液组成随时间的变化情况,产品的纯度和回收率随转速、回流比和溶剂比的变化情况,研究了旋转填料床间歇萃取精馏的性能。结果表明,旋转填料床中强大的离心力和高效填料的协同作用极大地强化了间歇萃取精馏过程,具有分离效果好、操作时间短、节能、小设备大生产能力等突出优点;存在最佳转速使产品的纯度和回收率最大;增加溶剂比和回流比均能使产品的纯度和回收率得到提高,但增加溶剂比的效果更显著。旋转填料床是强化间歇萃取精馏过程的有效途径。     

双溶剂进口的双釜间歇萃取精馏

提出了带有塔底回收釜及双溶剂进口的间歇萃取精馏操作方式。在新操作方式中,塔内回流液不流回塔釜,而是流入塔底回收釜,再经简单蒸馏气相返回塔釜,回收后的溶剂返回精馏塔中。以乙二醇作溶剂分离乙醇-水物系的实验结果表明,当间歇操作次数为2时,产品采出率最大,单位产品消耗的新鲜溶剂量最少。新操作方式具有塔釜温度变化平稳,新鲜溶剂用量相对较少等优点。     

混合溶剂间歇萃取精馏分离过程的模拟

由于混合溶剂存在"混合溶剂效应",能够解决简单溶剂选择性与互溶性相互矛盾的问题,因此混合溶剂间歇萃取精馏技术可以大大拓宽传统单一溶剂间歇萃取精馏分离技术的应用空间。文章建立了反映常规混合溶剂间歇萃取精馏过程的恒摩尔持液数学模型,并运用2点隐含法对其求解,结果表明,模拟计算结果与实验结果吻合较好。随后运用该模型探讨了塔身持液量、混合溶剂进料位置等因素对混合溶剂常规间歇萃取精馏的影响。得出以下结论,产品馏出速率随塔身持液量的增大而减小,塔顶馏分产量与塔身持液量的关系不大。另外,混合溶剂进料位置的选定对分离效果也有较大的影响,需要正确选择。     

异丙醇脱水技术研究进展

主要介绍了异丙醇-水分离的几种工艺和新方法。在介绍异丙醇脱水常规工艺的基础上,重点阐述隔壁共沸精馏、间歇萃取精馏、吸附蒸馏和膜分离法等新工艺,具体分析了各种方法的优缺点及研究情况,并展望了异丙醇-水分离工艺的前景。     

乙醇-乙酸乙酯体系的间歇萃取精馏研究

在常规的间歇萃取精馏实验装置中,研究了以N,N-二甲基酰胺(DMF)和二甲亚砜(DMSO)作萃取剂;在间歇萃取精馏塔中分离乙醇-乙酸乙酯体系的过程。对全回流时间、不同萃取剂、恒沸物组成、溶剂和混合物的体积比、加盐及加碱等因素考察,分析萃取精馏分离乙醇-乙酸乙酯共沸体系的影响,从而得出最佳的萃取条件。     

带有中间储罐的间歇萃取精馏的模拟研究

本文提出了带有中间储罐塔间歇萃取精馏过程计算模型,将中间罐看成一块理论板,萃取剂看成第三组份进行建模,利用调节因子和泡点法相结合对整个塔进行迭代计算,经实例模拟表明,本模型只需较简单的赋初值,能以较快的速度收敛,本模型对带有中间储罐间歇萃取精馏操作及模拟具有一定的指导作用。