内部热耦合精馏塔的初步设计(II) 控制分析和参数优化

引　言研究表明[1,2 ],控制和设计优化往往是节能方法实际应用中的主要困难 .关于二次回流和蒸发(ＳＲＶ)、Ｐｅｔｌｙｕｋ、热交换网络 (ＨＥＮ)等方法的控制设计已经有了大量的研究[3,4].这些研究方法可以借鉴到内部热耦合精馏塔 (ＩＴＣＤＩＣ)的控制研究上[5 ].本文对理想ＩＴＣＤＩＣ进行了自由度分析、暂态分析和ＰＩＤ控制研究 ,并进行了设计参数的优化和分析 .目前 ,尚未见到设计优化的文献报道 .1　自由度分析对于理想二元混合物 ,ＩＴＣＤＩＣ动态系统由6.5ｎ 1 0个独立方程 (ｅ)、 6.5ｎ 2 7个变量υ构成 ,系统的自由度为 ｆ =…     

Nonlinear wave modeling and dynamic analysis of internal thermally coupled distillation columns

Internal thermally coupled distillation column (ITCDIC) is a frontier in the energy saving distillation research. It is well known for the complex dynamics, which challenge the establishment of an excellent reduced model for further control strategy design greatly. In this article, a physical approach of the ITCDIC process based on nonlinear wave theory is explored, where it is first discovered that traditional wave theory in conventional distillation columns (CDIC) could not be directly applied in ITCDIC, due to: First, the internal thermal coupling results in mole flow rates varying evidently over each stage, which not only makes the wave modeling of the wave phenomenon in ITCDIC more difficult but also makes wave dynamics greatly different between ITCDIC and CDIC; Second, an interesting wave phenomenon of ITCDIC is discovered that waves located in the rectifying section and stripping section travel under opposite tendencies when the steady state is disturbed by the step change of thermal condition q, one sharpens and the other is likely to spread synchronously, it means the movement of wave profiles in ITCDIC could not be simply described by shock wave velocity, which is usually used in wave modeling of CDIC; more seriously, shapes of the self‐sharpening wave profiles in ITCDIC change obviously during the traveling processes, which further reveals that shape influence on wave velocity has to be considered in the wave modeling of ITCDIC. A rigorous wave velocity and a natural wave velocity are derived, respectively, based on which, the detailed analyses of traveling wave characteristics are carried out. A novel wave velocity, based on the profile trial function which has been well developed by Marquardt, is further derived to consider the obvious change of profile shape. And a completed nonlinear wave model of ITCDIC is thereby established by combining the proposed wave velocity with thermal coupling relations and material balance relations. The benzene‐toluene system is illustrated as an example, where component concentration prediction and distinct dynamic characteristics are carried out in detail based on the proposed nonlinear wave models. The research results reveal the accuracy and validity of the proposed nonlinear wave model of ITCDIC. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

内部热耦合精馏塔基于非理想物系的最优评价

Internal thermally coupled distillation column(ITCDIC) is a frontier in energy saving distillation research. In this paper, the optimal assessment on the energy saving and the operating cost for ITCDIC of nonideal mixture is explored. An evaluating method is proposed, and the pertinent optimization model is then derived. The ethanol-water system is studied as an illustrative example. The optimization results show that the maximum energy saving in ITCDIC process is about 35% and the maximum operating cost saving in ITCDIC process is about 30%,as compared with a conventional distillation column(CDIC) under the minimum reflux ratio operating; the optimal operating pressure of the rectifying section is found to be around 0.25 MPa; the effects of the feed composition,operating pressure and the heat transfer rate on operation are also found and analyzed. It is revealed that ITCDIC process possesses high energy saving potential and promising economical prospect.     

内部热耦合精馏塔的初步设计(I) 模型化和操作分析

引　言将热量从精馏段传到提馏段来实现节能是精馏过程节能的一种有效方法 ,即二次回流和蒸发[1](ＳＲＶ) .内部热耦合精馏塔 (ＩＴＣＤＩＣ)的热耦合机理仍是ＳＲＶ方法 ,但去掉了再沸器和冷凝器 ,具有较大的节能潜力 .它的研究只有近 1 0年的历史[2 ,3],目前 ,还没有见到详细的操作分析和设计优化的文献报道 ,只有一些较为相关的文献[4 ,5 ].本文对理想热耦合精馏塔进行了建模和操作分析 .1　模型化图 1是ＩＴＣＤＩＣ的示意图 .精馏段和提馏段被分为两个塔 .热耦合通过两段之间的热交换器来实现 .为了提供传热必须的推动力 ,精馏段将在较…     

基于内部热耦合精馏塔非线性wave模型的高纯控制

首先建立内部热耦合精馏塔（ITCDIC）的非线性波动降阶模型,并将非线性波动理论（wave）应用到ITCDIC控制问题中,实现一般模型控制（GMC）方案.与传统控制方案相比,基于波动理论的一般模型控制（waveGMC）不再采用ITCDIC的近似线性模型,更好地解决了高纯控制过程中的非线性问题,通过对波形的速度和位置控制能够在短时间内使系统达到稳定.苯-甲苯物系的实例研究表明,ITCDIC波动模型在高纯控制过程中能够精确反映ITCDIC的动态特征,waveGMC控制方案较传统控制方案更加稳定可靠.