和利时MACS V控制系统在450t/h循环流化床锅炉中的应用

以浙江嘉化能源化工股份有限公司兴港热电厂背压热电机组节能技改项目（6#锅炉、汽机）为背景,结合循环流化床锅炉的运行特点及控制要求,介绍和利时MACSV系列分散控制系统的应用及实现的功能.     

轧钢冷床上卸钢系统改造

介绍运用变频、PLC、液压技术对轧钢冷床上卸钢系统进行改造。     

Research on graphite powders used for HTR-PM fuel elements

Different batches of natural graphite powders and electrographite powders were characterized by impurity, degree of graphitization, particle size distribution, specific surface area, and shape characteristics. The graphite balls consist of proper mix-ratio of natural graphite, electrographite and phenolic resin were manufactured and characterized by thermal conductivity, anisotropy of thermal expansion, crush strength, and drop strength. Results show that some types of graphite powders possess very high purity, degree of graphitization, and sound size distribution and apparent density, which can serve for matrix graphite of HTR-PM. The graphite balls manufactured with reasonable mix-ratio of graphite powders and process method show very good properties. It is indicated that the properties of graphite balls can meet the design criterion of HTR-PM. We can provide a powerful candidate material for the future manufacture of HTR-PM fuel elements.     

乙炔法氯乙烯合成固定床反应器的建模及分析

针对我国广泛应用的乙炔法氯乙烯合成固定床反应器,结合氯乙烯合成的反应动力学、催化剂的失活动力学,同时引入了传热方程,建立了完整的列管式氯乙烯合成固定床反应器的数学模型。将该模型用于工业生产,模拟了传热系数沿管长的变化,列管内反应温度沿管长的变化并与生产数据对比,验证了模型的正确性。最后分析了乙炔空速、冷却水温度对管内温度分布和乙炔转化率的影响。     

核电站堆芯温度场软测量方法研究

核电站堆芯内部温度是反应堆安全运行的重要参数,由于受到测点安装条件的限制,无法直接测量。为解决该问题,在现有压水堆堆芯功率模型的基础上,结合稳态传热热量守恒方程,构建堆芯温度场的计算模型,推算出堆芯内部温度。并通过数值模拟计算结果与堆芯出口实测值的比较,运用数据不确定度作为判断依据,验证了方法的可行性,得到了堆芯内部不同截面的二维温度分布图,为堆芯内部温度的实时监测提供了理论依据。     

核电站数字化反应堆保护系统停堆响应时间分析

为了评价出核电站数字化反应堆保护系统停堆响应的最大时间,根据数字化反应堆保护系统结构,分析出保护系统的响应过程须经过AI输入、IO总线通讯、CPU运算、网络通讯、DO输出处理。并基于DCS定周期扫描的运行方式,得出了各处理过程所需最大响应时间的计算方法,DCS停堆响应时间的评价值就是各部分最大响应时间的累加。最后提出了可缩短响应时间的改进方法。     

Evaluation of neural networks-based controllers in batch polymerisation of methyl methacrylate

The importance of batch reactors in today's process industries cannot be overstated. Thus said, it is important to optimise their operation in order to consistently achieve products of high quality while minimising the production of undesirables. In processes like polymerisation, these reactors are responsible for a greater number of products than other reactor types and the need for optimal operation is therefore greater.

An approach based on an offline dynamic optimisation and online control strategy is used in this work to generate optimal set point profiles for the batch polymerisation of methyl methacrylate. Dynamic optimisation is carried out from which controller set points to attain desired polymer molecular end point characteristics are achieved. Temperature is the main variable to be controlled, and this is done over finite discrete intervals of time.

For on-line control, we evaluate the performance of neural networks in two controllers used to track the derived optimal set points for the system. The controllers are generic model control (GMC), ([P.L. Lee, G.R. Sullivan, Generic model control, Comput. Chem. Eng. 12(6) (1998) 573–580]) and the neural network-based inverse model-based control (IMBC), ([M.A. Hussain, L.S. Kershenbaum, Implementation of an inverse model based control strategy using neural networks on a partially simulated exothermic reactor, Trans. IchemE 78(A) (2000) 299–311]). Although the GMC is a model-based controller, neural networks are used to estimate the heat release within its framework for on-line control. Despite the application of these two controllers to general batch reactors, no published work exists on their application to batch polymerisation in the literature. In this work, the performance of the neural networks within each controller's algorithm for tracking and setpoint regulation of the optimal trajectory and in robustness tests on the system is evaluated.     

Decentralised control of chromatographic simulated moving bed processes based on wave front reconstruction

The behaviour of chromatographic simulated moving bed processes is described by the movement of concentration profiles through a circle of separation columns. A closed-loop control manipulates the profiles in order to meet demands concerning specified product purity and disturbance attenuation. If steep wave fronts of the concentration profiles occur, the controlled variables undergo fast changes in case of a transient of the process. In this case, a reconstruction of the wave fronts is necessary for a successful control.A simple and effective decentralised controller structure is proposed based on cascaded discrete-time PI controllers. On-line product purity measurements and the reconstructed wave fronts are used for control purposes. Two kinds of process models are used: a rigorous model for dynamic simulations, and strongly simplified plant models for the design of the wave front reconstruction and the controller. The latter models are identified based on experimental step tests with the reference plant and numerical simulations. The performance of the control system is evaluated by numerical simulations.     

明式有束腰罗汉床的曲线美

明式家具不论是在选材用料、造型设计、榫卯构成,还是在加工制作和装饰手法等方面的造诣直至今天还为人折服,人们认识到其价值的同时,也在不断的仿制明式家具的风格。文章通过具体分析明式家具中罗汉床的曲线造型这一点,使明式罗汉床的特点更明确化、具体化。希望通过分析,为现代家具设计师,特别是罗汉床的设计能提供一个清晰准确的定位。