【作者】 罗漩；

【导师】 黄克谨；

【作者基本信息】 北京化工大学 ， 控制理论与控制工程， 2009， 硕士

【摘要】 当前世界能源形势不容乐观,越来越多的研究人员因此开始致力于化工过程的节能研究。作为化工生产过程中最为耗能的单元操作之一,精馏过程的节能研究一直是广大研究人员关注的热点之一。基于内部热耦合技术开发的内部热耦合精馏塔(heat-integrated distillationcolumn,HIDiC)是这些研究中比较引人注目的一个研究成果。HIDiC控制方案研究是其转化到实际应用中的关键。温度控制因为其可靠性高,维护成本低廉,响应快等优点已经被广泛应用于化工过程的控制中。但是,在对HIDiC控制方案的研究文献中却鲜有其温度控制方面的讨论。除此之外,常规的温度控制方案在抑制非平稳扰动(如进料流量或进料成分)方面的表现不是很令人满意,因为此时塔顶和塔底产品成分中都存在较大的稳态余差。为此,本文提出了两种用于减小HIDiC双温度控制时产品质量中存在的稳态余差的方法:温度推断补偿器和浓度推断补偿器。减小稳态余差的关键在于如何准确地感应操作条件的变化,然后适当地调节每个温度控制回路的设定值。在第一种方法中,推断信号是从塔板温度中获得;而在第二种方法中,推断信号是从产品成分中获得。根据来自不同的塔板,第二种方法又可分为推断信号来自进料板的温度和来自两端塔板的温度(也就是两端产品的温度)两种。文中以分离二元等摩尔苯和甲苯混合物的理想HIDiC为研究对象,分别对提出的两种改进方法进行了深入的研究。结果表明它们都能有效地减小产品质量中存在的稳态余差,与此同时第一种方法还能在一定程度上改善双温度控制系统的动态特性。文中还对推断信息来自两端塔板的温度这一方法推广到常规精馏塔中的应用进行了探索,得到了良好结果。这两种方法原理简单、效果明显,且在过程建模方面只需相对较小的改动即可实现。这些特点都为这两种方法在不同类型的双温度控制精馏塔中得到广泛应用创造了良好的条件。更多还原

【Abstract】 In the current world energy situation, more and more researchers have been focusing their attention on the development of energy-saving related technologies. As one of the most energy-consuming unit operations in the chemical process industry, distillation process has always been the target for such kind of studies. Heat-integrated distillation column (HIDiC) is one of the most attractive apparatus that can offer great potentials of energy savings.Effective control of the HIDiC is a key for its practical applications. Temperature control (i.e., indirect composition control) is generally preferred to direct composition control because temperature measurements offer more advantages than composition measurements in aspects of reliability, immediacy and maintenance cost. However, the research about the temperature control of the HIDiC is relatively rare. In addition, conventional temperature control fails to suppress the non-stationary disturbances from feed flow rate and composition as there are large static offsets occurring in the top and bottom product qualities.In this paper, two kinds of methods are proposed for the reduction of the static offsets in the composition of both top and bottom products. They are called as temperature-based inferential compensator and composition-based inferential compensator respectively. The key to achieve this purpose is to sense the non-stationary changes in operation conditions and make corresponding adjustments to the set-points of the dual-temperature control loops effectively. The first method is based on the inferential signals extracted from the stage temperatures and the second method from the composition of products. The temperature inferential signals can be obtained through two ways. One is from the feed stage and the other from the two end stages (i.e., the temperature of products).All the above philosophies are intensively studied through the operation of an ideal HIDiC separating a binary equi-molar mixture of benzene and toluene. It is found that they could work effectively to decrease the static offsets in the product qualities. Moreover, the temperature-based inferential compensator could also improve the dynamic performances of the dual-point temperature control system. Applications of the first method to conventional distillation columns are also explored in this work and similar results have been achieved. The two methods are characterized by simplicity in principle, definite effect in implementation, and relatively small effort in process modeling, thereby allowing wide applications in the operation of various distillation columns with a dual-point temperature control scheme.更多还原