带多个中间贮罐的新型分批精馏塔的研究

多罐分批精馏塔由多个分批精馏塔依次连接而成，它只在第一个塔的塔釜加热，在最后一个塔的塔顶设冷凝器。采用恒摩尔持液模型对多贮罐的新型分批精馏塔的研究结果表明：多罐分批精馏塔具有可同时获得多个高纯度产品、无过渡馏分、产率高、操作简单及节能的特点。对多罐分批精馏塔和常规分批精馏塔进行出较的结果显示：采用多罐分批精馏塔分离产品可获得的年利润远高于采用常规分批精馏塔。     

Analysis of the Start‐up Process for Reactive Distillation

The start‐up procedure of a distillation column is a time‐ and energy‐consuming process. Further, the products during the start‐up time are off specification and cannot easily be recycled as for conventional distillation but must costly be disposed of. In this paper, a process model to simulate the barely analyzed start‐up procedure for a reactive distillation from the cold and empty state to steady state is presented. The start‐up of a reactive distillation column has been modeled with gPROMS. The advantage of a cold and empty start‐up is the consistent and reproducible initialization. Commercial simulators do not give the opportunity to start form a cold and empty state, e.g., a column modeled with Hysys must be shut down from a steady state to be able to model the complete start‐up process, which is not possible, for example, for a batch process. Also, a change in the describing equations and discontinuities in process variables is difficult to handle within the simulation. In this paper, the start‐up strategies normally used for distillation without reaction are examined and applied to reactive distillation. It will be shown that the widely used strategy of total reflux is not suitable for reactive distillation. A simplified model to derive a time constant which describes the influence of parameter setting changes, like heating power, reflux ratio and feed composition on the start‐up time, is introduced and validated.     

三氯氢硅歧化反应精馏生产硅烷的模拟简

The reactive distillation process for producing high purity monosilane via trichlorosilane redistribution reaction was simulated. Rigorous RadFrac block was employed in Aspen Plus simulation package. Accurate results could be given when the chemical kinetics was taken into account in the equilibrium stage model. A single column process was used for the verification of previous studies. The results showed that 99.9% purity monosilane could be achieved in the reactive distillation. A pumparound block was employed to reduce the condenser duty with inexpen- sive coolant. The effects of operating pressure, feed stage location, liquid holdup per stage and pumparound loca- tion were also investigated. The energy consumption was limited, but the refrigerant temperature was too low, which is the fatal disadvantage. Therefore, a double columns process was developed to increase the condenser tem- perature. The simulation results demonstrated that a reasonable temperature could be achieved by varying the recy- cle stream location.     

基于(火用)损失分析的反应精馏塔板上反应体积的优化设计

针对以选择性为主要目标的反应精馏塔设计中反应段塔板上反应体积或催化剂的分配问题,提出一种基于热力学(火用)损失分析和流程模拟计算相结合的优化设计策略。为了深层次分析反应精馏塔板上(火用)损失的原因并为制定调优方向提供理论依据,将塔板上的总(火用)损失区分为物理(火用)损失和化学(火用)损失两部分并分别进行计算。在此基础上,将建立的(火用)损失计算方法和流程模拟技术相结合,将反应段塔板上的反应体积的分配和对应的(火用)损失分布相关联,以再沸器热负荷最小为目标,通过建立的方法对反应体积的分配逐步调优,可实现反应精馏塔的优化设计。方法的有效性通过环氧乙烷水合制乙二醇反应精馏体系进行了验证。结果表明,与普遍采用的塔板上等反应体积分配的设计方法相比,通过本文建立的优化分配方法,可使系统的能耗降低18%以上,同时结果优于文献值。     

考虑水力学可行性的反应精馏塔板持液量设计及优化

以筛板塔为塔板基础构型,以原料转化率最大为目标,以塔径和出口堰高为主要调节参数,以塔板水力学可行性为约束条件,建立了一种可优化塔板液相持液量的塔板结构设计方法. 塔模拟计算在Aspen Plus平台上进行,化学反应采用动力学方程表达,塔板水力学计算采用Cup-Tower软件. 结果表明,本设计方法应用于DPC反应精馏过程,在满足流体力学可行性条件下,塔板上液相持液量比基础设计提高了1.39倍,苯酚转化率提高了33.6%.     

分壁式精馏塔精制丁二烯流程模拟

丁二烯是一种重要的石油化工烯烃原料,由于其生产过程能耗高,因此节能降耗成为丁二烯生产工艺的研究热点。利用Aspen Plus模拟软件对丁二烯精制工艺的两套流程进行了模拟研究,考察了分壁式精馏塔(DWC)中内部互连物流连接位置、预分离塔气液相流量和回流比对分离效果和热负荷的影响,对比了相同分离条件下DWC分离流程和传统顺序分离流程的能耗,并根据两套分离流程中塔内液相丁二烯浓度分布情况,分析DWC的节能原因。结果表明,当主塔理论板数105,预分离塔理论板数56,进入预分离塔气相流量1020kmol/h,液相流量890kmol/h,回流比7800时,DWC分离效果最好,丁二烯质量分数可达99.7%,这为DWC精制丁二烯工艺的工业化提供了理论依据。由于DWC有效减少了精馏过程中的返混效应,提高了能量利用率,使其冷凝器可节能29.36%,再沸器可节能29.19%,存在明显的节能优势。     

反应精馏过程中的多稳态分析

Reactive distillation processes for synthesis of ethylene glycol （EG） and ethyl tert-butyl ether （ETBE） were modeled with the simulation package ASPEN PLUS. The input multiplicity and output multiplicity were discussed with the method of sensitivity analysis for both cases. In EG production process, steady state multiplicities were studied in terms of effective liquid holdup volume and boil-up ratio. In ETBE synthesis process, the user kinetic subroutine was supplied into ASPEN PLUS firstly, and then the composition, temperature and reaction-rate profiles within the reactive distillation column were presented in detail. A set of stable solution branches based on distinct initial guesses for a range of boil-up ratio were found in EG synthesis. Input multiplicities were observed for a range of reboiler duty at several values of reflux ratio for ETBE synthesis process. These results can be used to avoid excessive energy consumption and achieve optimum design of reactive distillation column.     

Feasible separation regions for distillation I: Structure

A feasible separation region is determined for only four special combinations of a saturated vapor/liquid feed and total/partial condenser or reboiler. This work addresses the construction of a feasible separation region for a general case where the feed is a mixture of vapor and liquid in equilibrium and where the column is equipped with a partial/total condenser and reboiler. The analysis reveals that the product composition sets (which are defined for various reflux and reboil ratios and a fixed number of stages in each column section) are the main elements of the feasible separation region. The application of the geometric model of the column in combination with the shape of the distillation line led to the conclusion that the feasible separation region is the union of two product composition sets for both enriching and stripping columns both with an infinite number of stages. The boundary of the feasible separation region consists of several curves related to specific types of operating modes in the column. Some of these curves create a well‐known product composition multitude, whereas other curves form a generalized distillation limit. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

带有中间热集成的精馏塔序列及其性能

提出一种带有中间热集成的精馏塔序列(IHISDC)的流程,针对三组元混合物分离的简单塔直接序列,对该流程进行了分析。与传统热集成精馏序列(HISDC)相比,提出的IHISDC通过中间换热器将高压塔的精馏段与低压塔的提馏段进行局部热集成,使能量集成精馏塔之间的压力差更小,进而使能耗费用下降。同时发现,IHISDC中的高压塔再沸器热负荷和低压塔冷凝器热负荷增加,由于换热器数量的增加,IHISDC的投资费用较大。为了进一步降低IHISDC的年度总费用,需要对其设计参数进行优化。     

与换热网络热集成的精馏塔压优化

调整精馏塔的操作条件是节省塔能耗的有效途径之一，然而在对已有装置进行用能优化时，需同时考虑精馏塔操作条件对塔能耗和换热网络能耗的影响。基于装置所有流股的冷热复合曲线，针对跨夹点的精馏塔，同时考虑了精馏塔的再沸、冷凝以及过程流股，分析了塔压变化对装置公用工程消耗的影响，并对某连续重整装置汽提塔进行了案例分析。结果显示，塔压降低可使冷凝器能耗增加，再沸器能耗减小，而对于塔顶塔底出装置流股，塔压降低可节省冷却公用工程但增加加热公用工程。装置总体的节能效果为塔顶冷凝器、塔底再沸器和塔顶塔底出装置流股节能效果的综合作用。对某连续重整装置汽提塔分析表明，塔压降低200.0 kPa时，其加热公用工程用量将减少577.5 kW。     

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…     

Heat integration of distillation columns into overall processes

There are many well-known schemes for better energy efficiency in distillation. Examples are thermal coupling, multiple effect, heat pumping, etc. Usually these schemes are discussed for individual columns in isolation, independently from the overall process they are a part of.This paper puts the design of individual distillation columns into context with the heat integration for the overall process. An insight is discussed wGenerally, the paper defines good integration as a column not crossing the heat recovery pinch of the process and either the reboiler or the condenser     

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%.     

Feasible separation regions for distillation II: A generalized distillation limit

The boundary of the feasible separation region consists of several curves that are related to specific types of operating modes of the column. Some of these curves create a well‐known product composition multitude, whereas other curves form a generalized distillation limit. The generalized distillation limit demarcates the sloppy splits (i.e., separations in which the composition of at least one product lies inside the composition space) from regions not accessible by distillation and depends on the thermodynamic state of the feed (a mixture of vapor and liquid in equilibrium or saturated vapor/liquid) and column equipment (total/partial condenser and total/partial reboiler). The mathematical equations describing the generalized distillation limit are obtained based on the relationships between the curves (which form the generalized distillation limit) and specific types of operating modes of the column as well as the material balances for the enriching and stripping columns. Furthermore, the vapor and liquid pinch‐point curves, which go through the feed composition point, are not dependent on the thermodynamic state of the feed and column equipment. In addition, an algorithm for determining the generalized distillation limit is obtained. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

苯乙烯装置塔系热集成

精馏作为过程工业中最重要和最常用的分离手段, 是耗能最大的单元操作。精馏塔一般从再沸器输入热量, 从冷凝器取走热量, 利用某些塔高温位的冷凝热加热其他塔的再沸器, 并将单塔节能技术与过程集成相结合, 实现塔系的热集成, 可充分挖掘系统内部的节能潜力, 达到减少公用工程消耗的目的。本文通过对某化工厂的苯乙烯装置精馏塔系的分析, 通过各个塔的温焓图之间的关系, 提出了精馏塔系内部热集成的措施, 包括直接热集成、调压热集成和双效精馏与间接热集成耦合等3种方案。对于后两个热集成方案, 采用Aspen Plus模拟改造后精馏塔的变化并验证了方案的可行性。结果表明, 苯乙烯装置采用该热集成措施能明显节省高品位蒸汽的消耗, 降低能量费用。     

Energy saving and thermodynamic efficiency of a double-effect distillation column using internal heat integration

The existing internally heat-integrated distillation column with the problem of utilizing a compressor is modified to propose a new heat-integrated distillation column without the compressor. Two identical columns of a conventional binary distillation are implemented to the heat integration. The energy used in the reboiler is recovered by the internal heat integration between the stripping section of one of the columns at lower pressure and the rectifying section of the other higher pressure column. The heat integration is similar to double-effect distillation, but internal heat integration requires less pressure elevation. The performance of energy saving and thermal efficiency improvement of the proposed system is evaluated with the two examples of the benzene-toluene and methanol-ethanol processes. The performance comparison indicates that the proposed system requires 17.4% less of reboiler duty for the benzene-toluene process and 15.8% less of heating duty for the methanol-ethanol process. The thermal efficiencies are 16.3% and 23.8% for the benzene-toluene and methanol-ethanol processes, respectively. Elimination of the compressor makes the column operation easy and the separate reboilers and condensers for the two columns in the proposed system provide flexible control, when the controllability of the proposed system is compared with that of the existing internally heat-integrated distillation column.     

分批蒸馏优化策略与微机控制的研究(Ⅱ)——分批蒸馏的设备与微机控制

本文为前文(Ⅰ)的继续.文中报道了塔釜无存料分批蒸馏塔新结构以及应用微型计算机对三个实验进行四个闭环回路系统的控制,并在此控制系统上取得大量试验数据,证实了理论计算的正确性与微机控制系统的可靠性.     

内部热耦合精馏塔的操作性能与模拟

对同轴式内部热耦合精馏塔的操作性能和节能效果进行了研究,考察了全回流操作条件下,压缩比对回流量、冷凝器负荷和再沸器负荷的影响。结果表明,随着压缩比的增大,回流量、冷凝器负荷和再沸器负荷均降低。通过实验数据计算得到了该塔的理论板数和两塔间的传热量,精馏段为9块理论板,提馏段为4块理论板,当压缩比为2.2:1时,两塔间传热量为9.98kW。连续操作条件下,对内部热耦合精馏塔的节能效果进行了分析,通过与常规精馏塔的比较,内部热耦合精馏塔可节约52.3%的冷量,输入的再沸器和压缩机总负荷可节约20.34%。另外,基于实验数据,对该内部热耦合精馏塔进行了动态模拟,经连续操作下的实验验证,该内部热耦合精馏塔可在2h后达到稳定操作。     

Exergy analysis of distillation processes

Distillation is a unit operation in which two main processes are involved: heat transfer for vaporizing and condensing and mass transfer for the separation of the mixture. A distillation unit can be described as an exergy converter: that is a unit which converts thermal exergy into chemical exergy. To obtain a complete graphical representation of mass, enthalpy and exergy balances in a fractional distillation, we propose the use of a diagram: the specific enthalpy (in KJ/ Kg of mixture) is plotted against the Carnot factor θ to show the heat and mass transfer effects simultaneously. The application of the methodology to the distillation of an ammonia-water mixture is presented. Conventional fractional distillation consumes a lot of exergy. We propose a new type of distillation in which the reboiler and the condenser normally located at the bottom and at the top of distillation column, are replaced by two heat exchangers integrated in the column itself. The exchanger integrated in the bottom of the column inputs heat to the column, and the other exchanger located in the upper part of the column removes heat. This arrangement minimizes the creation of entropy in the column and therefore maximizes the exegetic effectiveness. This new process, called:“diabatic” or “quasi-reversible” distillation should bring important improvement to conventional distillation, not only from the point of view of energy use (large reduction in the consumption of heat carriers fluids for heating and cooling), but also in terms of capital investment as the cost of fitting a heat exchanger in the destillation column will probably be less than the cost of reboiler or condenser and reflux head.     

Synthesis of complex thermally coupled distillation systems including divided wall columns

The design of thermally coupled distillation sequences explicitly including the possibility of divided wall columns (DWC) is described. A DWC with a single wall can be considered thermodynamically equivalent to a fully thermally coupled (FTC) subsystem formed by three separation tasks (a Petlyuk configuration in the case of three‐component mixtures). It is shown how to systematically identify all the sequences of separation tasks that can produce configurations that include at least a DWC. Feasible sequences that explicitly include DWCs are enforced through a set of logical relationships in terms of Boolean variables. These logical relationships include as feasible alternatives from conventional columns (each column must have a condenser and a reboiler) to FTC systems (only one reboiler and one condenser in the entire system). A comprehensive disjunctive programming formulation for finding the optimal solution is presented. The model is based on the Fenske, Underwood Gilliland equations. However, the disjunctive formulation allows easily the use of any other shortcut, aggregated or even rigorous model without modifying much the structure of the model. Two illustrative examples illustrate the procedure. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1139–1159, 2013