板式精馏塔开工动态过程的研究

本文从描述塔板上物料衡算的差分-微分方程出发,导出了在全回流封闭操作条件下,当塔顶、塔板和塔底均有存料时开工过程的数学模型并求出其解.根据数学解还证明了板式精馏塔在开工过程中存在着恒浓度点.在一个具有七块塔板,直径为0.17m的筛板塔上对水-乙酸物系进行了开工过程的实验.本文公式的计算值与实验数据较好的吻合并证明了塔内恒浓度点的存在.     

Comparison of Energy Usage for the Vacuum Separation of Acetic Acid/Acetic Anhydride Using an Internally Heat Integrated Distillation Column (HIDiC)

Abstract

Energy savings for an internally heat-integrated distillation column (HIDiC) and a vapor recompression column for the vacuum separation of acetic acid/acetic anhydride was theoretically analyzed and compared to the simulation of a reference column configuration of the Eastman Chemical Company using ASPEN Plus. In these simulations, the design and operating variables were defined and optimized to minimize total energy used. The effects of design variables such as quantity and location of the heat integration stages, reflux ratio, and rectifying section absolute pressure on energy consumption and product purity revealed that one HIDiC configuration had 62% energy savings over the reference column. The distillation column using vapor recompression was evaluated as a benchmark for comparing the HIDiC configurations and the reference column. The VRC column simulation predicted both increased product purity and an energy savings of 91% over the reference unit.     

Experimental study on pressure drops in a dividing wall distillation column

Previous studies in the fields of process design and process control [1] have shown the potential benefits that can be achieved through the implementation of thermally coupled distillation sequences, in particular, the dividing wall distillation column. The dividing wall distillation column meets important goals of process intensification, including energy savings, reduction in carbon dioxide emissions and miniaturization. In this paper, an experimental study on the hydrodynamic behavior of a dividing wall distillation column is presented. Several different values for gas and liquid velocities were tested in order to measure pressure drops and identify operational regions; the air/water system was used as the basis for the experimental setup. Results regarding pressure drops (fitted to the model of Stichlmair et al.) provide operational limits for the operation of the packed dividing wall distillation column. According to the results, the experimental dividing wall column can be operated at turbulent regime that is associated to proper mass transfer.     

精馏塔γ射线扫描故障诊断技术

传统精馏塔故障诊断方法停车时间长,造成巨大的经济损失。γ射线扫描技术利用一束γ射线穿过精馏塔,并沿塔高方向移动,检测穿过射线的强度,得到全塔或部分塔段的射线吸收图谱。射线吸收图谱反映了塔内密度变化,即反映了塔内流体状态,从而为精馏塔的故障诊断提供可靠依据。γ射线扫描可以判断塔内件损坏、液泛、漏液、雾沫夹带、气液分布不均等故障及具体位置;也可为确定精馏塔负荷瓶颈位置、提高产能,以及为安排计划停车提供科学依据。γ射线扫描诊断时,无需停车,具有快速、直观、准确等优点。拜耳技术服务研制开发了全自动γ射线扫描系统,控制精确,操作安全,该系统为拜耳上海一体化基地近百座精馏塔的维护和检修发挥重要作用。     

Profit maximization of the normal hexane recovery process through a thermal integration method

We developed a separation process that can minimize utility consumption in order to obtain normal hexane from crude raffinates for electronic-grade reagents. For the separation of normal hexane from the crude raffinate mixtures, a two-column configuration was selected. The first distillation column removes lighter constituents than normal hexane as a column top product, after which heavier constituents containing normal hexane are put into the middle of the second distillation column. This allows normal hexane with a purity of 95.5 wt% to be obtained from the top of the second distillation column by removing the constituents that are heavier than normal hexane as a second column bottom product. When both distillation columns are operated at approximately atmospheric pressure, it requires about 5.2 tons of steam per hour both for the reboiling heating source. However, when the operating pressure of the second distillation column is increased, the vapor stream coming out of the top of the second distillation column can be used as a heating medium for the reboiling source of the first distillation column. In this way, steam of only 3.1 tons per hour is required, potentially reducing the amount of steam used to 59.6% of the original amount.     

间歇减压精馏分离2-甲基吡啶/2-羟乙基吡啶

采用间歇减压精馏法实现了2-甲基吡啶和2-羟乙基吡啶这一热敏性混合物的分离,并考察了投料组成与操作压力对减压精馏过程的影响。结果表明,高真空条件降低了塔釜温度从而避免了物料在塔釜中受热变性,对于热敏物料2-羟乙基吡啶,减压精馏过程中压力应控制在4325 Pa以下,此时塔釜产品2-羟乙基吡啶的质量分数均能大于97%,同时收率能保持在86%以上。在压力为1325 Pa时,不同投料组成下塔顶产品2-甲基吡啶的质量分数和塔釜产品2-羟乙基吡啶的质量分数均高于98%,两者的收率也均在85%以上,能够很好地满足工业生产要求。     

常减压蒸馏装置减压深拔技术设计

依据常减压蒸馏装置减压深拔现状及研究动态,结合8.0 Mt/a常减压蒸馏装置设计实例,分析了为实现减压深拔目标减压系统所采用的工艺技术,包括较高的加热炉出口温度、减压炉防结焦、减压塔塔顶高真空度和全塔低压降、微湿式带汽提操作、减压塔塔底防结焦等工艺,并重点讨论了过气化油流程设置对减压深拔的影响。     

A novel process integrating vacuum distillation with atmospheric chlorination reaction for flexible production of tetrachloroethane and pentachloroethane

In this paper,we developed a novel process integrating vacuum distillation with atmospheric chlorination reaction (VD-ACR) to realize the flexible production of tetrachloroethane (TeCA) and pentachloroethane (PCA)from 1,2-dichloroethane (DCA).During the simulation,the distillation column and reactors were operated for separation and chlorination respectively under variable pressures and temperatures.It is interesting to note that VD-ACR processes producing pure TeCA or PCA can exhibit the similar configuration parameters after optimization,which enables the flexible production of TeCA and PCA with different molar ratios via changing operating parameters.The molar ratio of TeCA/PCA can be fine-tuned within the range of 0.9∶0.1-0.1∶0.9 through adjusting the amount of chlorine pumped into side reactors,giving rise to the increase of the heat duty of reboiler by five times.A pilot-scale experiment was then operated based-upon this VD-ACR process and the result matched well with the simulation.Therefore,the VD-ACR model presented in this study will be beneficial for the industrial-scale flexible production of TeCA and PCA from DCA.     

多晶硅生产中三氯氢硅精馏节能工艺

简述了多晶硅行业概况和差压耦合蒸馏节能技术。详述了一种高纯三氯氢硅差压耦合精馏工艺,利用高压塔塔顶蒸汽作为低压塔塔釜再沸器热源,实现了能量的集成与过程优化。运用化工模拟软件PRO/Ⅱ8.1模拟了两塔高纯三氯氢硅差压耦合精馏工艺和三塔高纯三氯氢硅差压耦合精馏工艺的设计参数。结果显示,两塔耦合三氯氢硅一次收率为92.0%,理论节能50.1%;三塔耦合三氯氢硅一次收率为92.0%,理论节能66.7%,效果更好。该技术已成功实现工业化,可使精馏单元实际能耗平均降低40%～60%,同时大幅减少了设备投资。     

START-UP PROCESS DYNAMICS OF PLATE DISTILLATION COLUMNS

A mathematical model for discribing the start-up period of a plate distillation column operating undertotal reflux is presented.Based on the differential-difference equation expressing the material balance onthe trays in a complete column with holdups in the reboiler,trays and condenser,the present model isderived and an analytical solution is obtained.The existence of a constant concentration point during thestart-up period is proved mathematically.Experimental work on start-up period is carried out in a seven sieve tray distillation column of 0.17meter in diameter with a water-acetic acid system.Good agreement is found between the experimentaldata and the calculated results.The experimental results also show the evidence of a constant concentra-tion point in the column during start-up period.     

变压精馏分离甲醇-丙酮的工艺模拟及优化

采用Aspen Plus软件,以塔釜能耗为目标,以甲醇、丙酮纯度为约束函数,对双效变压精馏分离甲醇-丙酮工艺过程进行模拟。分析了操作压力、理论板数、回流比、进料位置和进料温度等参数对精馏过程的影响。确定了最优工艺参数：减压塔操作压力40 kPa,理论板数37,回流比2.4,进料塔板数26,进料温度25 ℃;常压塔理论板数30,回流比4.2,进料塔板数23。减压塔所得甲醇质量分数为99.0%,常压塔所得丙酮质量分数为99.7%。对比变压精馏和萃取精馏过程,变压精馏更容易得到高纯度丙酮产品,节能约13.4%。模拟结果对工业设计和设备改造具有一定指导意义。     

Liquid-holdup regions research of novel reactive distillation column for C5 fraction separation

Recent advances in technologies of reactive distillation (RD) offer various design concepts for chemical processes. For separation of cracking C5 fraction, one of the main challenges is improving the conversion of cyclopentadiene (CPD) and the recovery of isoprene (IP). In the current work, a novel reactive distillation column with several liquid-holdup regions was designed, since it allows long residence time and provides flexibility for narrowing the efficiency gap between reaction and distillation. By use of Aspen Plus, a corresponding mathematic model was established and verified to be accurate. Following that, comprehensive studies were carried out for the design of liquid-holdup regions position. Details and principles about the separation performance with the liquid-holdup regions were revealed and optimized parameters were determined with 100 theoretical plates, feed position of 35th plate, and four liquid-holdup regions at 25th, 60th, 75th and 90th plate. The designed RD column could wellmeet the technical requirement, and influence of other important factors including residence time, operating pressure and reflux ratio was further investigated.     

Undergraduate design of experiment laboratory on analysis and optimization of distillation column

A two-level full factorial design and/or a central composite design are used to optimize the operation of a distillation column by manipulating three variables: the feed flow rate, the reflux ratio and the steam flow to the reboiler. The response variable of interest is a profit function where the objective of this experiment is to examine the effect of each of the three factors and their interactions on this profit function. This is accomplished in a sieve tray type continuous distillation column operated at ambient pressure to separate a methanol–isopropanol mixture. Students were asked to determine the significant variables and the optimal operating conditions for steam rate, reflux ratio and feed rate such that the profit is maximized. As a result, this experiment not only exposes students to an industrially relevant unit operation but it also helps complement the classroom teaching on design of experiment concepts.     

Multiple Analysis in a Reactive Distillation Column for the Synthesis of tert‐Amyl Methyl Ether

tert‐Amyl methyl ether (TAME) is produced via reactive distillation. A simulation is set up and controlled on Aspen HYSYS v 8.0 for generating the highest purity of TAME. This simulation includes a plug‐flow reactor and a reactive distillation column. Emphasis was put on finding the optimal operating conditions of the reactive distillation column in order to get the maximum purity of TAME. The operational parameters were reflux ratio, number of reactive stages in the distillation column, and condenser pressure. The results indicated the optimal reflux ratio and condenser pressure which could be adapted to industrial scale.     

新型规整填料及塔内件在润滑油减压塔中的应用

列举了常减压蒸馏装置润滑油型减压塔的实际操作、标定及原始设计等方面的详实数据,并通过工业时间进行了较为系统、科学地对比分析和深层次研究。同时,重点介绍了新型规整填料及塔内件在大型润滑油减压塔中的实际应用。     

ON THE DESIGN OF ROBUST CONTROL SYSTEMS FOR DISTILLATION COLUMNS

The distillation column dynamics is very nonlinear, especially at high purity. Multivariable control system designs, which are essentially linear, may not be able to perform well at different operating conditions. This paper looks at three different multivariable design techniques—decoupling control, optimal state feedback and pole assignment as applied to distillation column control. Robustness of these techniques are analyzed by looking at the performance of these controllers at different operating conditions. Some interesting results are obtained.     

从抽余油中分离甲基环戊烷

研究了从芳烃抽余油中分离甲基环戊烷的方法和流程,首先用Aspen Plus软件模拟了精馏法提取甲基环戊烷的分离结果。通过模拟计算得到了最优的设计参数、操作条件、各塔冷凝器、再沸器的热负荷。在此基础上,还模拟了用甲醇作共沸剂共沸精馏分离得到甲基环戊烷的结果,获得了最优的设计参数和操作条件。     

A review on process intensification in internally heat-integrated distillation columns

Internally heat-integrated distillation column (HIDiC) is the most radical approach of a heat pump design, making efficient use of internal heat-integration: the rectifying section of a distillation column operating at a higher pressure becomes the heat source, while the stripping part of the column acts as a heat sink. Remarkably, a HIDIC can bring up to 70% energy savings compared to conventional distillation columns. This is highly appealing regarding the fact that distillation is one of the most energy intensive operations in the chemical process industry accounting for over 40% of the energy usage. This review paper describes the latest developments concerning this promising but difficult to implement process intensification technology, covering all the major aspects related to the working principle, thermodynamic analysis, potential energy savings, various design configurations and construction options (ranging from inter-coupled or concentric columns, shell and tube and plate–fin heat exchanger columns to SuperHIDiC), design optimization, process control and operation issues, as well as pilot-scale and potential industrial applications. Further advancement, i.e., development of HIDiC technology for multi-component mixture separations is an extremely challenging research topic, especially when HIDiC becomes associated with other technologies such as dividing-wall column (DWC) or reactive distillation (RD).     

闪蒸二相流模型在减压转油线改造中的应用

减压转油线的结构设计对减压蒸馏单元的正常操作和减压拔出率的提高有很大影响。为使转油线设计更加优化,文中将前期工作中建立的描述多组分混合物的闪蒸二相流数学模型应用于转油线的结构改造,提出了一种新的转油线结构。针对某工业实例,对2种结构转油线的压降、温降和气化率模拟结果进行了对比。结果表明,减压转油线的结构改进可减小气液二相流动压降并提高转油线出口气化率。