苯乙烯本体聚合工艺模拟与分析

利用Aspen Tech Inc.的polymer plus建立了本体聚苯乙烯聚合反应过程模型,利用其灵敏度分析方法对影响产品产量和分子量的引发剂浓度、反应温度等因素进行分析,得出了引发剂量的增加可以提高产量同时分子量下降;链转移剂量的增加使产量和分子量均下降;在首釜温度115℃和107℃出现Mn和Mw的最大值.     

自由基聚合反应分子量分布的模糊控制

平均聚合度、平均分子量、多分散系数等都是描述聚合物分子量分布的重要参数,对于确定单体转化率下的分子量分布,可只用确定的数均聚合度和多分散系数两个参数表示.为了便于分析,可采用瞬时平均分子量链长和多分散系数的时间轨迹去描述分子量分布,选取反应器的温度或引发剂的浓度作为控制分子量分布的操作变量,使用自寻优模糊控制器跟踪已确定的反应器温度的时间轨迹,同时利用前馈控制器补偿外界扰动带来的影响.模拟仿真结果表明,该方法在实际应用中能取得很好的效果.     

基于链节分析法的聚丙烯装置的动态仿真

以某石化企业的Hypol工艺聚丙烯装置为研究对象,对丙烯聚合工段进行了系统分析,选择了合适的反应器模型.并根据丙烯聚合的反应机理,用链节分析法建立了动力学模型,从而使得动态仿真的实时计算大大简化.利用该机理模型对丙烯聚合装置进行了仿真,模拟计算了数均分子量,转化率等聚合物的重要特征信息,与实际生产工艺参数吻合良好.     

Borstar双峰聚合反应产品性质分析及模型建立

通过对Borstar双峰聚合反应过程产品性质实验分析,Borstar双峰聚乙烯技术超临界环管反应器生产聚合物熔融指数相对于分子量呈指数规律变化,气相反应器生产的聚合物熔融指数随分子量增加而呈一定规律的减少,聚合物分子量继续增加聚合物熔融指数减少趋势缓慢;在实验分析的基础上,基于聚合反应机理应用MATLAB软件建立工业装置聚合过程聚乙烯熔融指数及密度等产品性质计算模型和确定模型参数,通过模型拟合值和实际值的比较,模型能够准确预测熔融指数和密度的变化趋势,有关聚乙烯在环管中的熔融指数、在流化床内的熔融指数和密度的质量模型相对平均误差分别为2.4%,0.5%和0.3%。通过产品质量预测模型的推导和分析,环管部分熔融指数主要受温度、[H2]/[C2H4]影响;而气相部分熔融指数既受环管聚合物来料性质影响,又受气相反应器温度和[H2]/[C2H4]和[C4H8]/[C2H4]的影响     

链节分析法在PVC聚合过程仿真中的应用

以氯乙烯悬浮聚合体系为研究对象,根据氯乙烯聚合反应过程的反应机理,选择了合适的动力学方程式,并以此为依据,将"链节分析法"应用于氯乙烯悬浮聚合体系中,对聚氯乙稀聚合过程中的聚合反应进行分析和模拟,建立了PVC聚合反应的机理模型,从而能更真实地模拟PVC的聚合过程.笔者利用该机理模型对氯乙烯悬浮聚合过程进行了仿真,模拟计算了平均分子量、结构信息、转化率等聚合物的重要性能指标,与实际生产的工艺参数吻合得很好.     

聚氯乙烯聚合釜计算机控制

聚氯乙烯(PVC)是由氯乙烯单体(VC)在聚合釜中聚合而成.在聚合过程中,聚合温度是关键,它决定了产品的型号和质量,从而直接影响企业的经济效益.VC单体聚合时的“凝胶效应”其链终止的主要形式是长链游离基向单体VC分子的链转移,这是决定PVC分子量的关键.而链转移的速率与温度有关,温度较高,链转移速率越快,则生成PVC聚合度较小.实践证明,温度相差2℃,平均聚合度相差336,分子量相差23000左右.而PVC相邻型号之间的聚合度仅相差100左右,因此,聚合温度是影响PVC质量的关键参数.     

自由基聚合反应分子量分布的模糊控制

平均聚合度、平均分子量、多分散系数等都是描述聚合物分子量分布的重要参数，对于确定单体转化率下的分子量分布，可只用确定的数均聚合度和多分散系数两个参数表示。为了便于分析，可采用瞬时平均分子量链长和多分散系数的时间轨迹去描述分子量分布，选取反应器的温度或引发剂的浓度作为控制分子量分布的操作变量，使用自寻优模糊控制器跟踪已确定的反应器温度的时间轨迹，同时利用前馈控制器补偿外界扰动带来的影响。模拟仿真结果表明，该方法在实际应用中能取得很好的效果。     

利用Delphi7.0语言+Access数据库开发聚合物物性估算软件

预测聚合物材料的理化性质在化学工程中一直备受关注.基团贡献法是物性估算的一种很有效的方法.本文根据基团贡献的原理,整理和归类聚合物可估算的性质,并利用可视化编程语言Delphi7.0和Access数据库,终于实现估算的程序化.此物性估算软件可以智能地判断聚合物所处的相态,并利用对应相态下的估算模型预测性质,还可以预测性质与温度、分子量的关系.最后,利用软件对可降解材料聚乳酸进行物性估算,性质包括密度、玻璃化温度、熔点、半分解温度、溶解度参数、表面张力、弹性模量和折射率.对比实验值与估算值发现,平均相对误差仅为3.37%.此外,利用软件还可以估算得到聚乳酸玻璃化温度与分子量,以及热容与温度的关系曲线,与实验曲线的趋势基本一致.综上所述,证实该软件有界面友好,操作方便,可同时估算多种聚合物性质等优点,对聚合物的合成和性质测定实验有指导作用.     

间歇液相本体丙烯聚合过程中产品性质的模拟与分析

在25 kt/a间歇液相本体聚丙烯工业装置反应器机理模型的基础上,建立间歇丙烯聚合过程中产品分子量及分子量分布、熔融指数等性质的数学模型.采用BWRS状态方程计算氢在氢.丙烯系统气-液平衡常数,以分析生产中聚丙烯分子量及分子量分布、聚丙烯熔融指数等参数的变化情况及其影响因素.结果表明:氢在液相中的浓度是影响聚丙烯瞬时分子量的主要因素,主要受氧.丙烯系统气液平衡常数和液相固含率影响,氢在液相中的浓度与温度成正比,与液相固含率成反比.聚丙烯熔融指数模型由重均分子量关联得到,二者呈反比关系,熔融指数的变化与重均分子量变化相对应.瞬时分子量和产量是聚丙烯重均分子量和熔融指数的主要影响因素.     

丙烯间歇液相本体聚合模拟

从聚合反应动力学出发,对丙烯间歇液相本体聚合工业装置建立数学模型,采用PR状态方程进行汽液平衡计算。链增长速率常数k_p、链转移速率常数K_t由质均分子量为20万及30万2个品牌的生产条件及产品性质去拟合得到。应用拟合出的参数,对质均分子量为40万的产品的生产工艺条件进行模拟,模拟结果与实际相比为:聚合物的产量误差0.66%,质均分子量误差2.07%,模拟结果与实际较为吻合。并对反应过程中变量随时间变化情况进行分析,得出聚合物质量、氢气浓度、液相体积等随时间的变化规律,对实际生产工艺的开发与改进具有指导意义。     

碳纳米管/聚乙烯界面分子构型的数值仿真

为研究在应力场和温度场作用下碳纳米管/不定型聚乙烯复合材料界面基体分子取向的变化历程,建立对应的复合材料分子模型.利用经典分子动力学的模拟方法,在对不同温度场碳纳米管表面高分子径向分布函数(Radial Distribution Function,RDF)分析的基础上,重点分析温度和拉伸应力对界面处基体分子取向参数的影响规律.结果表明:当温度从600 K降低到50 K时,界面基体分子的径向分布函数值和取向参数值分别提高140%和119%;当温度为50 K时,对复合材料施加0.01 ps-1的应变速率,当应变从0增加到0.24时,高分子链整体取向参数值提高19%.     

Modeling and control of an LDPE autoclave reactor

A two-compartment four-cell model is developed for the adiabetic slim type autoclave reactor for free radical polymerization of low density polyethylene (LDPE). It is possible to determine not only the reactor performance represented by the monomer conversion and the reaction temperature but also the properties of the polymer product characterized by the average molecular weight and the polydispersity. It turns out that the reactor performance predicted is in good agreement with the plant data and the properties of the polymer product are estimated within reasonable ranges of actual values. The steady state multiplicity is found to exist and is examined by constructing the bifurcation diagram. The effects of various operation parameters on the reactor performance and the polymer properties are investigated systematically to show that the temperature distribution plays the central role for the properties of the polymer products. Therefore, it is essential to establish a good control strategy for the temperature in each compartment. The adaptive pole-placement control algorithm is applied to the temperature control of the adiabatic slim type autoclave reactor. The recursive least square method is used for the model identification. To accomplish a satisfactory control, the estimator and controller are initialized during the period of start-up. It is shown that the reactor system can be adaptively controlled by the pole-placement control algorithm, especially when the reactor temperature distribution is changed.     

Polymer Microfabrication for Microarrays, Microreactors and Microfluidics

Polymer microfabrication methods are becoming increasingly important as low-cost alternatives to the silicon or glass-based MEMS technologies. Polymer hot embossing and injection molding are replication methods applicable to microreplication of a diversity of materials and microstructures.

Equipment with high precision control of pressure and temperature for hot embossing of polymer materials is now available commercially. These systems have made possible the replication of chips containing microchannels for capillary electrophoresis (CE) and microfluidics devices, microoptical components and microreactors. Stable and reproducible polymer microstructures have been demonstrated in several types of materials with structural and optical properties meeting other biocompatibility and detection requirements. The process involves few variable parameters and results in high structural accuracy suited for a wide range of microfabrication applications.

After demonstrating equivalent and, in cases, improved performance, the alternative use of plastic as the microdevice material addresses needs for rapid prototyping in product development and provides cost advantages in product commercialization. Thus an increasing number of devices have been reported recently in the literature, fabricated on a variety of polymer substrates and using different fabrication methods such as laser ablation, injection molding, silicone rubber casting or embossing for microfabrication.     

HDPE装置反应系统模型的应用

HDPE装置反应系统稳态及动态模型采用POLYMERS PLUS软件及ASPEN DYNAMICS,Aspen Custom Modeler软件进行开发。该模型可用于优化操作和增大装置生产能力,从而提高产品质量和产量。经验证模型准确,在此模型的基础上,研究了可提产的新工艺流程的可行性以及聚合反应中主要参数之间的相互影响关系,为改扩建方案的实施提供了依据。     

Multivariable control of the polymer molecular weight in emulsion polymerization processes

A multivariable control strategy is developed to control the polymer molecular weight in emulsion polymerization processes while maximizing the reaction rate by manipulating the jacket temperature and the monomer flowrate. In order to take into account the process nonlinearity, input-output linearizing control is considered. A cascade of two nonlinear observers is developed to estimate the heat of the reaction and the number of moles of radicals in the polymer particles. By introducing these estimations and the available measurements into the process model, the polymer molecular weight could be estimated online. The online estimation and control strategy was validated experimentally in seeded emulsion polymerization of styrene for which the model of the molecular weight is well known. It was also validated for the methyl methacrylate monomer where a simplified model was identified.     

德士古水煤浆气化过程的建模与优化分析

根据德士古水煤浆气化工艺的操作特性和装置特点,采集实际工业运行数据,基于Aspen Plus软件平台,建立了气化炉和水洗过程的模型,模拟结果与实际生产较吻合。基于所建立的模型,进行了水煤浆浓度、气化反应温度对气化结果的灵敏度分析,并讨论了过程的节水,分析了高温汽提冷凝液对废水排放与合成气水汽比的影响。结果表明:在现有工况下,提高水煤浆浓度和反应温度,有效合成气收率会提高;适当减少高温、汽提冷凝液,有利于装置的废水排放和提高合成气水汽比。     

不溶性硫磺含量及稳定性研究

采用熔融法工艺制备了不溶性硫磺(IS),优化设计影响IS含量及稳定性的因素,考察淬冷液温度对IS含量及稳定性的影响,并分别建立了一元线性回归模型。结果表明,熔融法制备IS的适宜条件为:使用含0.05%碘的四氯化碳饱和溶液为稳定剂,恒温温度220℃,恒温时间20 min;复合稳定剂SBS(苯乙烯-丁二烯-苯乙烯嵌段共聚物)/碘/四氯化碳稳定效果较好,其用量为0.05%:0.05%:2.5%。随着淬冷液温度的下降,IS含量及稳定性增加,淬冷液温度与IS含量及稳定性之间均呈线性负相关性。     

Analysis of pattern height development in hot embossing process

The pattern height of hot embossing was analyzed based on the polymer power–law material assumption for better controlling product quality. The time development of the polymer substrate height, pattern height and the imprint pressure were obtained. The imprint temperature with respect to the pattern height was discussed. Theory analysis shows that in a constant imprint pressure, the pattern height has a power relationship with the imprint time. At the beginning imprint stage, as for the elastic response of polymer, the pattern height increases rapidly. With the time increasing, the polymer deform is mainly caused by creep and this results in low imprint speed. On the other hand, the increasing friction force between the polymer and the mold will further reduce the imprint speed. The theoretical data were compared with experiments and the results show that this model can well predict the rule of polymer substrate thickness variation.     

Control strategies for reactive batch distillation

A batch reactor may be combined directly with a distillation column by distilling off the light component product in order to increase the reactor temperature or to improve the product yield of an equilibrium reaction. The same amount of the light product should be removed as the amount being formed by the reaction at any time. A linearized model has been developed which describes the process behaviour satisfactorily for control analysis purposes. The controllability of a combined batch reactor/batch distillation column is found to depend strongly on the operating conditions and on the time during the run. In general, controlling only the reactor temperature (one-point bottom control) is difficult since the set-point has to be specified below a maximum value in order to avoid break-through of an intermediate component in the ditillate. This maximum value may be difficult to know a priori. For the example considered in this study, control of both reactor temperature and distillate composition (two-point control) is also found to be difficult due to large interactions in the column. As with one-point bottom control, the reactor temperature has to be specified below a maximum value. However, energy can be saved since the heat duty can be decreased with time. Controlling the temperature on a tray in the column (one-point column control) is found to give good performance for the given process with no loss of reactant and a high reactor temperature, although no direct control of the reactor temperature is obtained.