基于自抗扰控制技术的PVC反应温度控制

聚氯乙烯(Polyvinyl chloride,PVC)是当前世界上应用最广泛的合成材料之一。聚氯乙烯生产的关键是聚合反应过程,PVC聚合反应温度控制精度直接影响产品质量。由于PVC聚合反应过程具有大时滞及时变非线性的特点,传统的PID控制精度通常难以满足生产需要。研究了自抗扰控制技术在PVC反应温度控制中的应用,通过和IMC-PID的控制仿真对比,验证了自抗扰控制技术适应工况变化的能力。针对实际的PVC生产过程,在DCS上进行了自抗扰控制器组态,并应用于实际PVC生产过程。实际控制结果证实了自抗扰控制技术应用于PVC反应温度控制的可行性和有效性。

化工仪表检测技术在反应器温度控制中的应用研究

化工行业生产设备中的反应器,其温度调控的精确程度对产品素质与生产效益具有举足轻重的影响。依托现代化工仪表检测技术,本课题针对反应器温度的调控问题进行了全面深入的探讨。在反应器的温度管理中嵌潜着众多问题。融入了先进的化工仪表检测技术,实时监测反应器的温度并进行有效调控。持续使用温度传感器用以实时监测,将模拟信号经由数据采集卡转化为数字信号,并引入温度调控器实现闭环控制,以此实现反应器的精确温度管理。因此,化工仪表检测技术在反应器温度控制中具有重要的实用价值。本研究对于今后相关领域的研究提供了宝贵的理论支持。

淤浆法HDPE装置聚合反应温度的影响因素与控制方法

对影响三井油化淤浆法HDPE装置聚合反应温度的因素进行了分析,提出了从循环风量、循环水量、催化剂量、原料气质量、聚合釜搅拌、溢流管线方面对聚合反应温度进行了有效控制的方法。

聚乙烯装置中反应器温度控制方案

聚乙烯(PE)装置反应器温度控制对产品的质量和生产的稳定性具有举足轻重的作用,同时其控制过程具有精度要求高,时间滞后等特点。通过对调温水流量控制的反应器温度回路的分析,从仪表选型和控制算法实现等方面进行综合的讨论,并给出反应器温度控制方案及实施过程。

混合模糊PID的半微量相平衡反应控制仪

针对半微量相平衡反应实验系统对容器环境的严格要求,提出了一种基于模糊和PID混合算法控制的半微量反应容器环境的自动控制系统,根据提出的算法设计了反应环境自动控制的样机。并利用设计的样机进行了半微量相平衡反应实验,实验结果表明,所提出的模型能够根据需求准确控制反应容器温度,该系统能够在15~60°设定环境温度控制点,温度控制精度在±0.2°以内,且保持连续48 h整个反应过程的稳定运行,以准确完成半微量相平衡系统的完整反应,非常适合实验室和工程应用,同时也为同类型的化学反应环境的自动化控制提供了良好的参考范例。

汽油加氢脱硫装置DCS中两个复杂控制回路的实现

介绍某225万t/a催化汽油加氢脱硫装置,采用HONEYWELL Experion PKS系统,实现轻汽油抽出和选择性加氢反应器入口温度两个复杂控制回路的非常规控制模块的实现方案。

基于改进型PID控制算法实现对反应釜温度的精确控制

从改进型PID控制算法在当前工业自动化领域的发展趋势与应用前景入手,介绍了改进型PID相比于常规PID在控制算法上的升级改进,阐述了改进型PID控制算法在工业反应釜控制领域的广泛应用前景,提出了一种基于反应釜温度控制的PID控制算法。

LTAG催化裂化柴油加氢装置设计及应用总结

LTAG技术是一种将芳烃含量高、燃烧性能差的劣质催化裂化柴油进行多环芳烃选择性加氢饱和后,再经催化裂化回炼转化为高辛烷值汽油或轻质芳烃的技术,选择性加氢脱芳反应是该技术中的重要环节。主要介绍了LTAG柴油加氢装置反应器及加热炉等设计特点及应用情况。加氢脱芳反应的反应热远高于常规加氢精制反应,故LTAG柴油加氢的设计与常规加氢精制装置略有不同。某公司新建LTAG柴油加氢装置,采用2台反应器串联、部分循环流程,设置反应开工加热炉,两串联反应器间设置换热器,由该换热器管侧、壳侧出口温度控制两反应器入口温度。该设计方法能有效节约冷氢、降低能耗。

Improved Generalized Predictive Control Algorithm with Offline and Online Identification and Its Application to Fixed Bed Reactor

An improved generalized predictive control algorithm is presented in thispaper by incorporating offline identification into online identification. Unlike the existinggeneralized predictive control algorithms, the proposed approach divides parameters of a predictivemodel into the time invariant and time-varying ones, which are treated respectively by offline andonline identification algorithms. Therefore, both the reliability and accuracy of the predictivemodel are improved. Two simulation examples of control of a fixed bed reactor show that this newalgorithm is not only reliable and stable in the case of uncertainties and abnormal disturbances,but also adaptable to slow time varying processes.

Comparison of Two Types of Control Structures for Benzene Chlorine Reactive Distillation Systems

The ＂neat＂ operation of the two-reactant reactive distillation column has Oetter steady-state economics, while It presents a challenge for design, optimization, and control of the process. Based on the optimal economic design, the dual-composition control structure and dual-temperature control structure are designed respectively for the benzene chlorine consecutive reactive distillation process. The effectiveness and robustness are analyzed comparably for the disturbance resistance in terms of changes of production rate and feed composition. Results show that dual-temperature control with propose selection of tray temperatures and the optimal profile of the set point can provide better transient process performance than the composition control structure.

Controllable preparation of ZnO porous flower through a membrane dispersion reactor and their photocatalytic properties

Three dimensional (3D) flower-like basic zinc carbonate constructed by multilayered nanoplates were rapidly prepared at room temperature through the direct precipitation method coupled with membrane dispersion technology, and porous ZnO with similar structures could be obtained after calcining the precursor. The structural properties of the products before and after the calcining process were characterized by SEM, TEM and XRD.The supersaturation of the reaction system due to the membrane dispersion played an important role in the formation of uniform Zn_5(CO_3)_2(OH)_6 precursors. A plausible mechanism was proposed for the formation of the flower-like ZnO assembled by nanoplates composed of nanoparticles. The obtained ZnO microspheres showed excellent photocatalytic properties, which could be attributed to the open structure and remarkable amount of porous nanoplates.

Dynamics and Predictive Control of Gas Phase Propylene Polymerization in Fluidized Bed Reactors

A two-phase dynamic model, describing gas phase propylene polymerization in a fluidized bed reactor, was used to explore the dynamic behavior and process control of the polypropylene production rate and reactor temperature. The open loop analysis revealed the nonlinear behavior of the polypropylene fluidized bed reactor, jus- tifying the use of an advanced control algorithm for efficient control of the process variables. In this case, a central- ized model predictive control （MPC） technique was implemented to control the polypropylene production rate and reactor temperature by manipulating the catalyst feed rate and cooling water flow rate respectively. The corre- sponding MPC controller was able to track changes in the setpoint smoothly for the reactor temperature and pro- duction rate while the setpoint tracking of the conventional proportional-integral （PI） controller was oscillatory with overshoots and obvious interaction between the reactor temperature and production rate loops. The MPC was able to produce controller moves which not only were well within the specified input constraints for both control vari- ables, but also non-aggressive and sufficiently smooth for practical implementations. Furthermore, the closed loop dynamic simulations indicated that the speed of rejecting the process disturbances for the MPC controller were also acceotable for both controlled variables.

时间比例算法在流程工业现场的应用

本文以中控U6-200一体化PLC与C3900多功能智能控制器在流程工业现场控制中的成功应用为例,阐述了整体实施过程中的控制思想和整体配置及解决方案,同时介绍了实施步骤、应用案例等。

Design and control of a p-xylene oxidation process

The p-xylene(PX) oxidation process is of great industrial importance because of the strong demand of the global polyester fiber.A steady-state model of the PX oxidation has been studied by many researchers.In our previous work,a novel industrial p-xylene oxidation reactor model using the free radical mechanism based kinetics has been developed.However,the disturbances such as production rate change,feed composition variability and reactor temperature changes widely exist in the industry process.In this paper,dynamic simulation of the PX oxidation reactor was designed by Aspen Dynamics and used to develop an effective plantwide control structure,which was capable of effectively handling the disturbances in the load and the temperature of the reactor.Step responses of the control structure to the disturbances were shown and served as the foundation of the smooth operation and advanced control strategy of this process in our future work.

Flowering responses to light and temperature

Light and temperature signals are the most important environmental cues regulating plant growth and development. Plants have evolved various strategies to prepare for, and adapt to environmental changes. Plants integrate environmental cues with endogenous signals to regulate various physiological processes, including flowering time. There are at least five distinct pathways controlling flowering in the model plant Arabidopsis thaliana: the photoperiod pathway, the vernalization/thermosensory pathway, the autonomous floral initiation, the gibberellins pathway, and the age pathway. The photoperiod and temperature/vernalization pathways mainly perceive external signals from the environment, while the autonomous and age pathways transmit endogenous cues within plants. In many plant species, floral transition is precisely controlled by light signals(photoperiod) and temperature to optimize seed production in specific environments. The molecular mechanisms by which light and temperature control flowering responses have been revealed using forward and reverse genetic approaches. Here we focus on the recent advances in research on flowering responses to light and temperature.

Temperature Control of Bench-Scaled Batch Reactor Equipped with a Monofluid Heating/Cooling System

An advanced control concept, Predictive Functional Control （PFC）, is applied for temperature control of a bench-scaled batch reactor equipped with monofluid heating/cooling system. First principles process models are developed. Based on achieved models, significant process variables, which are difficult or impossible to measure online, are estimated from easily measured variables, and cascade PFC control strategy has been projected and implemented in Matlab RI 4. The dynamics of individual subunits is explicitly taken into consideration by internal model in the control algorithms, and model uncertainty, various process disturbances are compensated by modifi- cation of internal model. The experimental results present an excellent capability of tracking the set point, and the success of PFC technique as a process control paradigm is illustratively demonstrated.