Multivariate process monitoring and analysis based on multi-scale KPLS

In the paper, a new multi-scale KPLS (MSKPLS) algorithm combining kernel partial least square (KPLS) and wavelet analysis is proposed for investigating the multi-scale nature of nonlinear process. The MSKPLS first decomposes the process measurements into separated multi-scale components using on-line wavelet transform, and then the resultant multi-scale data blocks are modeled in the framework of multi-block KPLS algorithm which can describe the global relationships across the entire scales as well as the localized features within each scale. To demonstrate the feasibility of the MSKPLS method, its process monitoring abilities were tested for a real industrial data set, and compared with the monitoring abilities of the standard KPLS method. The results clearly showed that the MSKPLS was superior to the standard KPLS, especially in that it could provide additional scale-level information about the fault characteristics as well as more sensitive fault detection ability.     

基于多变量预测控制技术的丙烯精馏塔控制系统

精馏是化工中的重要过程,具有强耦合性、不确定性、非线性和大滞后等特征,且存在着苛刻的约束条件,控制难度大,长期以来都是各种先进控制与优化方案的实验对象。预测控制、内模控制、推断控制、模糊控制、神经元控制等多种控制策略都曾应用于精馏过程。选取了丙烯精馏塔作为研究对象,利用APC-Hiecon软件对其进行了基于多变量预测控制的研究。通过先进控制实施效果对比表明,方案实施后,过程变量运行平稳,有效保障了产品质量及精馏过程的稳定,达到了预期控制要求。     

基于INFI-90集散控制系统的煤粉制备过程自动控制

介绍了INFI-90集散控制系统在湿法水泥生产中煤粉制备过程控制的设计应用,从系统的硬件配置和软件设计方面介绍了该控制系统的应用特点,并着重阐述了煤粉制备系统的动态控制特性,以及采用的相应控制策略。     

PTA生产工艺风险分析及控制

PTA工艺流程存在的潜在危险因素有易燃易爆物泄漏引发的外部火灾及向大气排放的有毒或易燃物。运用HAZOP进行风险评估和事故后果分析。根据评估结果,从本质化安全设计和现场的安全管理2个方面对存在的风险进行控制。     

基于鲁棒模型优化的工艺设计与控制系统集成

采用一种基于鲁棒模型优化方法求解工艺设计与控制集成问题,其核心思想是采用参数不确定状态空间模型描述闭环系统的非线性行为,基于该模型以及二次李雅普诺夫函数可估计系统在外部扰动作用下过程变量变化的最大边界,同时也可测试系统的鲁棒稳定性。该方法避免了求解集成优化问题常用的动态优化方法,可将其转化成一个非线性规划问题。该方法应用于CSTR反应过程的集成优化设计中,结果表明在存在外部扰动时,不仅可以保证过程的经济性能和动态性能,也可保证系统的鲁棒稳定性。     

基于多线程运行控制的高效节能型净水工艺

华北地区某净水厂以当地水库水为水源,原水受到有机物污染,水质受季节影响变化较大。为应对上述水质问题采用高密度沉淀池—V型滤池—超滤—臭氧加活性炭吸附的工艺流程,但该工艺流程较长,运行能耗较高。针对季节和水质变化,以供水安全可靠为前提,高效节能为目标,提出了水厂运行的多线程工艺流程。经节能评估,运行改进后可节能23.96%。     

生产过程控制仪表常见故障分析

介绍了在检测与控制过程中仪表系统出现的故障及判断分析步骤。     

基于IMP的注射螺杆参数优化及工艺过程分析

利用注射过程模拟软件IMP(Injection Molding Plastification)及正交试验设计方法,通过正交设计对螺杆参数优化组合,再利用小步长搜索法生成新的正交试验表并进行二次正交试验,得到变深计量段螺杆最优参数组合。在优化参数的基础上,再采用IMP软件分析机筒温度及螺杆背压对变深计量段螺杆出口物料轴向温度的影响。结果表明:变深计量段螺杆与非变深计量段螺杆相比能减小物料PP的轴向温差;提高背压后,物料PC的轴向温差减小,但物料PP的轴向温差改善效果不明显;同时,机筒加料段和计量段温度的设定对改善螺杆轴向温度分布也有非常重要的意义。     

Approximate dynamic programming based approach to process control and scheduling

Multi-stage decision problems under uncertainty are abundant in process industries. Markov decision process (MDP) is a general mathematical formulation of such problems. Whereas stochastic programming and dynamic programming are the standard methods to solve MDPs, their unwieldy computational requirements limit their usefulness in real applications. Approximate dynamic programming (ADP) combines simulation and function approximation to alleviate the ‘curse-of-dimensionality’ associated with the traditional dynamic programming approach. In this paper, we present the ADP as a viable way to solve MDPs for process control and scheduling problems. We bring forth some key issues for its successful application in these types of problems, including the choice of function approximator and the use of a penalty function to guard against over-extending the value function approximation in the value iteration. Application studies involving a number of well-known control and scheduling problems, including dual control, multiple controller scheduling, and resource constrained project scheduling problems, point to the promising potentials of ADP.     

Integrating data‐based modeling and nonlinear control tools for batch process control

A data‐based multimodel approach is developed in this work for modeling batch systems in which multiple local linear models are identified using latent variable regression and combined using an appropriate weighting function that arises from fuzzy c‐means clustering. The resulting model is used to generate empirical reverse‐time reachability regions (RTRRs) (defined as the set of states from where the data‐based model can be driven inside a desired end‐point neighborhood of the system), which are subsequently incorporated in a predictive control design. Simulation results of a fed‐batch reactor system under proportional‐integral (PI) control and the proposed RTRR‐based design demonstrate the superior performance of the RTRR‐based design in both a fault‐free and faulty environment. The data‐based modeling methodology is then applied on a nylon‐6,6 batch polymerization process to design a trajectory tracking predictive controller. Closed‐loop simulation results illustrate the superior tracking performance of the proposed predictive controller over PI control. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

PTA装置雷达液位计假液位故障分析与控制

介绍了雷达液位计的测量原理及特点,以及雷达液位计在精对二甲酸(PTA)装置对二甲苯(PX)储罐液位测量中的应用,分析了雷达液位计液位测量时产生假液位的原因,并提出了相应的改进措施。结果表明:PX储罐内蒸汽在竖直壁面上冷凝而形成17~26 mm的液滴,因液滴尺寸大于雷达液位计发射波波长(12 mm),雷达发射波遇到液滴时产生反射回波,导致假液位的产生;选择频率为6 GHz,波长为50 mm的低频雷达液位计,将雷达天线由喇叭形改为直杆式,同时将PX储罐内温度由16~40℃提高至30~42℃,可有效避免PX储罐竖直壁面液滴产生的反射回波,控制雷达液位计假液位的产生;改进后的雷达液位计假液位故障明显减少,由改进前3次/d减少到改进后的(1~2)次/a,为PTA装置安全稳定运行提供了保障。     

Dynamic operability analysis of nonlinear process networks based on dissipativity

Most modern chemical plants are complex networks of multiple interconnected nonlinear process units, often with multiple recycle and by‐pass streams and energy integration. Interactions between process units often lead to plant‐wide operability problems (i.e., difficulties in process control). Plant‐wide operability analysis is often difficult due to the complexity and nonlinearity of the processes. This article provides a new framework of dynamic operability analysis for plant‐wide processes, based on the dissipativity of each process unit and the topology of the process network. Based on the concept of dissipative systems, this approach can deal with nonlinear processes directly. Developed from a network perspective, the proposed framework is also inherently scalable and thus can be applied to large process networks. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

SCS工艺小四级冷却液位控制回路的改进

SCS工艺用于煤气净化。由于这个工段的小四级冷却部分其液位控制回路存在缺陷 ,直接影响了后续工序的正常运行 ,因此对液位变送器、调节阀和联锁系统进行了改造 ,并取得了成功。     

基于自回热原理的木材干燥过程的热力学分析

针对木材干燥过程能耗高的特点,设计了一种基于自回热(self-heat recuperation,SHR)原理的木材干燥系统。通过能量分析方法对传统热风干燥过程与SHR干燥过程的耗能情况进行对比分析,同时研究了空气流量、压缩机绝热效率、传热温差对自回热干燥系统性能的影响。结果表明:在相同干燥条件下,SHR干燥系统总耗能比传统干燥过程减少了80.1%,能量回收率为75.4%,而传统干燥过程的能量回收率仅为30.3%。对于SHR干燥系统,在干燥速率不变时,系统总能耗随着空气流量增大而升高,随着压缩机绝热效率增大而降低,最佳绝热效率为0.6~0.8。随着传热温差增大,系统总能耗增加,传热面积减小,最佳传热温差约为10℃。     

丙烯酸酯压敏胶基贴片制备工艺中的质量控制

以丙烯酸酯PSA(压敏胶)和乳癖消浸膏共混作为药用PSA基质,考察了载药量、过程水的加入量、环境湿度、存放时间和制备工艺等因素对PSA基质的黏附性、抗老化性能和药物释放度等影响。结果表明:药用PSA基质中,当w(中药浸膏)≈38%(相对于基质总量而言)、w(水)=8%～10%(相对于基质总量而言)且贴片密封保存时,压敏胶基质的抗老化性能得到明显提高,其180°剥离强度为0.1～0.6kN/m,持粘力超过6h,并保持良好的稳定性;以50r/min左右的搅拌速率制取的PSA基质,其贴片的芍药苷12h释放度为83.61%(相对于芍药苷总量而言);当贴片存放时间超过60d时,药物释放度基本趋于稳定。     

A-O工艺污泥上浮的原因分析与控制措施

从DO、COD、pH值、SRT等方面分析了采用A-O工艺的城市污水处理厂在高温季节污泥上浮的原因,得出大量NO3--N流入沉淀池不能及时排出,发生反硝化反应产生N2导致污泥上浮。并提出了减少曝气量,控制硝化反应程度、增大内回流、增大剩余污泥排放量等有效措施,可解决污泥上浮现象。