无累积罐循环全回流操作的模拟研究

间歇精馏循环全回流操作是一种具有前景的新型操作方式。文中在循环全回流操作的基础上,首次提出了无累积罐循环全回流新操作方式。通过数学模型对其进行模拟,模拟计算比较了新方式、恒回流比间歇操作和塔顶储罐一次全回流操作3种操作方式。模拟结果表明:无累积罐新操作方式的全回流阶段时间由2个因素决定,全回流开始时精馏塔内的浓度梯度情况和精馏塔内持液的平均浓度。随着全回流-全采出操作的进行,后续循环中的全回流阶段的时间增加,全采出阶段时间减少。当进料浓度低时,新操作方式的分离效率比恒回流比方式高26.4%—30.1%,并通过模拟揭示了新操作方式的特点。研究表明:无累积罐循环全回流操作方式是一种新型高效的分离操作。     

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.     

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.     

多储罐动态全回流分离方法

多储罐间歇精馏是新型操作方式,目前仅用于多组分混合物分离.为了扩大多储罐间歇精馏塔的应用,将其用于2组分物系的分离,提出了多储罐动态全回流分离方法.其特点是可分为全回流提浓和倒罐采出阶段,这2个阶段交替进行,直到分离结束.建立了该过程的数学模型,并与常规恒回流比方式比较,结果表明:动态全回流方法省时.进一步通过乙酸-水...     

无累积罐循环全回流间歇精馏三温控制操作

提出了通过塔顶、塔中上以及塔中3个温度控制进行操作状态转换的无累积罐循环全回流间歇精馏控制方法,并以理想物系--乙醇-正丙醇混合物为分离物系进行了实验研究。通过实验确定了温度控制条件为当塔顶温度稳定后且塔顶和塔中上温差为0.3 ℃时变全回流为全采出操作,当塔中温度升高1.0 ℃时停止全采出转为全回流操作。同时还考察了在不同乙醇投料浓度条件下这种操作的运行情况,发现不同投料浓度对塔顶产品平均纯度的影响并不显著,基本能保持在0.99。最后在相同的投料浓度和操作条件下,对比了这种新型控制方式和双温度控制方式,结果表明三温度控制方式比双温度控制方式操作时间减少了23.3 min,分离效率提高了23.95%,产品浓度提高了1.06%,产品收率提高了1.08%。     

分批精馏中全回流操作的研究

为了研究采用全回流操作完成一定分离任务时所应达到的平衡程度,提出了平衡程度系数概念,并采用乙醇-异丙醇-正丙醇物系对全回流过程中各组分的平衡程度系数在塔内各处的变化及全回流操作终点适宜的平衡程度系数进行实验研究,结果表明,虽然同一时刻不同组分及不同板上的接近平衡程度不同,但实际应用中可只考虑塔顶处关键组分的接近平衡程度,全回流操作终点适宜的平衡程度系数的选取应综合考虑塔板数及操作时间这两方面因素。     

恒全回流塔顶累积间歇精馏过程的研究

提出了一种过程始终为全回流操作的间歇精馏新型操作方式,其特征在于沿塔身不同高度设置有多个中间累积罐,操作中整塔始终处于全回流状态,每隔一段时间将下一级储罐内的液体转移至上一级储罐,塔顶储罐内液体作为产品转移到产品储槽。建立了该流程的数学模型并采用Matlab软件进行模拟,当目标产品浓度相同时,新操作方式的可以节省操作时间,在最优化的中间累计罐密集程度下,可节省50%左右,与具体操作参数相关;最后采用乙酸-水二元物系对该操作方式进行了试验验证,且整塔运行稳定易于操作控制。     

精馏过程中回流比调节方式的讨论

比较了精馏过程中双流量计式、单流量计式、电磁式、机械式等回流比调节系统的应用情况。着重论述了新型机械式回流调节系统。该系统具有计量精确、投资小、操作简便、跑冒滴漏少、应用面广等优点。     

Investigation of the effect of delayed reflux on PVC grain properties produced by suspension polymerization

The effects of the condenser operation on properties of polyvinyl chloride (PVC) particles produced by suspension polymerization process were investigated in a pilot scale reactor. It was observed that delaying reflux operation increased the cold plasticizer absorption of the final resin. Both bulk density and K‐value of the PVC powder decreased by increasing time delay in the reflux operation. It was also found that commencement of refluxing before 20% conversion resulted in bimodal particle size distribution (PSD), while monomodal PSD was obtained for longer delays in refluxing. SEM micrographs showed that surface of produced particles were rough and smooth when reflux started before and after 20% conversion, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

二元多段恒回流比常规间歇精馏的讨论

介绍在理想操作条件下,二元优化多段恒回流比常规间歇精馏的数值计算方法。通过实例计算,比较常规多段恒回流比与优化多段恒回流比常规间歇精馏能耗,得到等气化量多段的能耗接近于优化多段恒回比的结论。     

The futility of raffinate reflux revisited

The role of reflux in equilibrium separation processes has been examined from a mechanistic viewpoint. The raffinate reflux — presaturation of solvent with raffinate in a separate unit (presaturator) — has been demonstrated to be futile in the past, considering the stages to be ideal. We have examined the utility of raffinate-like reflux in all the equilibrium separation processes. The nature of mass transfer in these processes with and without presaturator and its implications in the design and analysis have been presented.     

二元混合物“全回流”间歇精馏的能耗

介绍了在理想操作条件下，“全回流”间歇精馏二元理想混合物量纲1最小操作总时间的数值计算方法.通过举例计算，比较了在理想操作条件下，“全回流”与部分回流间歇精馏二元理想混合物的能耗，得到了“全回流”间歇精馏适合于相对挥发度小、原料中轻组分的浓度低、塔顶产品中轻组分收率要求高而浓度要求低的分离任务的结论.     

Minimum reflux calculation for multicomponent distillation in multi-feed,multi-product columns: Mathematical model

Multi-feed, multi-product distillation columns are ubiquitous in multicomponent distillation systems. The minimum reflux ratio of a distillation column is directly related to its energy consumption and capital cost. Thus, it is a key parameter for distillation systems design, operation, and comparison. In this series, we present the first accurate shortcut based algorithmic method to determine the minimum reflux condition for any general multi-feed, multi-product (MFMP) distillation column separating any ideal multicomponent mixture. The classic McCabe-Thiele or Underwood method is a special case of this general approach. Compared with existing techniques, this method does not involve any rigorous tray-by-tray calculation, nor does it require guessing of key components. In this first part of the series, we present the mathematical model for a general MFMP column, derive constraints for feasible separation and minimum reflux condition, discuss their geometric interpretations, and present an illustrative example to demonstrate the effectiveness of our approach.     

Foam fractionation with reflux

This paper shows that the foam drainage characterisation of Stevenson (2006a) provides a useful basis for the modelling of foam fractionation systems with and without reflux following the conceptual approach first proposed by Lemlich (1968a). Furthermore, the paper shows that surfactant transport between the rising and falling streams during foam fractionation with reflux can be characterised by a simple mass transfer coefficient. A set of non-dimensionalized process parameters is proposed and, using these, it is shown that this approach enables the whole operating regime of a foam fractionation device to be mapped out from a small number of relatively simple experiments to measure the surfactant adsorption isotherm, foam drainage characteristics, bubble size and mass transfer coefficient.The validity of this approach was demonstrated experimentally for a foam fractionation system continuously separating cetylpyridinium chloride (CPC) from a solution of constant concentration under total reflux. The dimensionless mass transfer group appeared to be invariant for this system, with a mean value of 3.7, over the studied range of rising gas to liquid flux ratio. It was shown for this case that the operation could be summarised in a small number of simple heuristic rules which gave valuable insight into the design and operation of this foam fractionation system.     

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.     

不同回流比对UBAF脱氮性能的影响

对上向流曝气生物滤池(UBAF)前置反硝化工艺处理城市污水的脱氮性能进行了试验研究,探讨了在不同回流比下,系统对COD、TN、NH3-N的去除效果。试验结果表明:当回流比从100%增加到300%时,对COD和NH3-N的去除率有着缓慢的增加,但当回流比增加到400%时,COD和NH3-N的去除率开始下降;回流比对TN的去除影响显著,在一定范围内增大回流比有利于TN的去除,当回流比为200%时,对TN的去除效果最好;在最佳回流比200%下,系统对COD、NH3-N和TN平均去除率分别为92.53%、93.50%和79.79%,出水COD、NH3-N和TN的平均质量浓度分别为17.70、2.12和11.36 mg/L,均能达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)的一级标准。     

带有内部热集成的多储罐间歇精馏全回流操作

鉴于间歇精馏热力学效率低的缺点,提出带有内部热集成的多储罐间歇精馏全回流操作(IHIMVBD)分离二元混合物的新型操作方式。在该操作中,多储罐间歇精馏塔被同轴的夹套式再沸器环绕,利用安装在再沸蒸汽管线上的压缩机使精馏塔的操作压力高于夹套式再沸器,使热量通过精馏塔壁面从高压的精馏塔传向低压的再沸器,实现热量的内部集成。为了进一步提高热力学效率和经济效益,将塔顶蒸汽再压缩技术应用于IHIMVBD,构成强化的内部热集成多储罐间歇精馏全回流操作(Int-IHIMVBD)。该操作能额外利用被压缩的塔顶蒸汽的潜热供给塔釜料液再沸,实现塔顶蒸汽与塔釜料液的热集成。通过模拟分离乙醇-正丙醇的实例表明,相比MVBD和IHIMVBD,Int-IHIMVBD能显著提高分离过程的热力学效率和经济效益。     

Optimal stationary states in thermalhydraulics: Total reflux condensation

Reflux condensation in a weakly fluctuating stationary mode can be classified with dissipative. pattern-forming structures. In those states which possess a single phase region topping the two-phase region the steady state conservation equations do not uniquely determine the length of the two-phase column. This degeneracy can be removed in accord with the principle of maximum path probability by optimizing the rate of entropy production. Models of reflux condensers with one and several cooling jackets which possess a maximal state are presented. The model predicts the general features of the experimental data without recourse to empirical correlations.     

Application of internal reflux in the raffinate phase for membrane extraction in cross-flow rectangular modules

The effect of internal reflux in the raffinate phase for membrane extraction through a cross-flow rectangular module was investigated. Theoretical analysis of mass transfer in cross-flow devices with or without recycle was analogous to heat transfer in cross-flow heat exchangers. In contrast to a device without reflux, considerable improvement in mass transfer is achievable if cross-flow membrane extractors are operated with reflux which provides the increase of fluid velocity, resulting in reduction of mass-transfer resistance. It is concluded that reflux can enhance mass transfer, especially for large flow rate and feed-concentration solution operated under high reflux ratio.     

回流法制备TiO2微球及其结构和催化性能研究

采用回流法制备了介孔TiO2微球催化剂,利用XRD、FE -SEM、BET等方法对所制备的催化剂进行了表征,并与溶剂热法制备的样品进行比较,研究不同制备方法对TiO2结构、彤貌及催化性能的影响.结果表明,回流法制备的样品为锐钛矿单相微球,晶粒间堆积形成介孔结构,比表面积大;而溶剂热法制备的介孔样品含金红石和锐钛矿两相.以EtOH/HCl为回流溶剂制备的样品孔径约为5nm,孔径分布窄,比表面积可达496 m2/g,光催化去除Cr(Ⅵ)反应速率快,去除率达到99％.