浆态相费托合成多级串联CSTR的数学模拟

本文应用数学模拟方法,探讨了多级串联 CSTR 在浆态相 FT 合成工艺中使用的可性能。模拟计算的结果得到了 Rheinpreussen—Koppers 示范厂的实验数据的支持。此外,通过若干参数对反应器性能影响的考察,以及不同流动模型计算结果的比较表明,采用简单易算的多级串联CSTR 模型,只要合理选择反应器级数,可以不同程度地模拟鼓泡塔浆液反应器的性能。     

Control of a non-isothermal continuous stirred tank reactor by a feedback-feedforward structure using type-2 fuzzy logic controllers

A control system that uses type-2 fuzzy logic controllers (FLC) is proposed for the control of a non-isothermal continuous stirred tank reactor (CSTR), where a first order irreversible reaction occurs and that is characterized by the presence of bifurcations. Bifurcations due to parameter variations can bring the reactor to instability or create new working conditions which although stable are unacceptable. An extensive analysis of the uncontrolled CSTR dynamics was carried out and used for the choice of the control configuration and the development of controllers. In addition to a feedback controller, the introduction of a feedforward control loop was required to maintain effective control in the presence of disturbances. Simulation results confirmed the effectiveness and the robustness of the type-2 FLC which outperforms its type-1 counterpart particularly when system uncertainties are present.     

一类干扰有界约束非线性系统的鲁棒模型预测控制

针对一类干扰有界约束非线性系统设计了基于控制不变集切换策略的鲁棒模型预测控制算法.针对非线性系统线性化之后的结果,给出了平衡点的非线性标称系统控制不变集的计算方法.然后在考虑线性化误差和加性有界干扰影响的基础上,构造了平衡点附近最小鲁棒正不变集.结合不变集切换策略和Tube不变集控制方法,提出了干扰有界约束非线性系统的不变集切换策略.最后将该算法应用到一类典型的非线性化工过程连续搅拌反应釜(CSTR)中,仿真结果验证了算法的有效性.     

PID CONTROLLER TUNING FOR UNSTABLE SYSTEMS BY OPTIMIZATION METHOD

Simple Tuning formulae are provided for optimal PID controller settings for unstable first order plus time delay systems. The method is based on minimization of integral squared errors (ISE). A method of calculating the set point weighting parameter is proposed to reduce the overshoot for servo problems. The performances of the proposed PID settings are compared with the settings recently proposed by Huang and Chen (1997, 1999) for both the servo and regulatory problems. The performance of the controller is also evaluated under parameter uncertainty in time delay and separately in process gain. Tuning formulae are given for PI controller along with the set point weighting. The performance of the PI controller is compared with that of Poulin and Pomerleau (1996). Two simulation studies, one on control of an unstable nonlinear bioreactor and a second on an unstable chemical reactor using the proposed PID controller settings, show improved performances both for servo and regulatory problems.     

A study of the effect of drag-reducing surfactants on flow patterns in stirred vessels

The analysis of velocity data in a stirred vessel, obtained experimentally in this work by laser Doppler velocimetry, as well as from the literature, shows that the dissolution of a surfactant with a long alkyl chain - in this work, hexadecyl trimethyl ammonium bromide - and a counter ion with an aromatic group - in this work, sodium salicylate - can modify the mean and r.m.s. velocities of the liquid, a phenomenon similar to the drag reduction observed in tubular flows. The magnitude and importance of this effect depend on the concentration of the surfactant-counterion mixture and on the localization of the element of fluid in the vessel, i.e., in a zone close to the impeller or farther away from it, but not in a monotonic fashion.     

Nonlinearity measures: definition, computation and applications

This paper is the first of two papers treating the quantification of open loop nonlinearity of dynamic systems. A generic definition of a nonlinearity measure is presented on the basis of the “best” linear approximation of a nonlinear system. Generalizing an earlier approach of Allgöwer, the measure can be applied both to the analysis of steady state operating points of continuously operated processes as well as to a trajectory dependent analysis of batch or other transient processes. An approximative computational strategy transferring the original infinite dimensional nested optimization problem into a convex finite dimensional minimization problem is discussed. The applications in this paper focus on operating point dependent analysis. Three continuously operated stirred tank reactor (CSTR) examples are investigated including a benchmark CSTR. The latter is also used to illustrate a computationally efficient lower bound approximation of the proposed nonlinearity measure. The additional difficulties associated with a trajectory rather than an operating point dependent analysis will be discussed in the forthcoming second part of this communication treating transient reaction processes.     

Fuzzy model-based observers for fault detection in CSTR

Under the vast variety of fuzzy model-based observers reported in the literature, what would be the properone to be used for fault detection in a class of chemical reactor? In this study four fuzzy model-based observers for sensor fault detection of a Continuous Stirred Tank Reactor were designed and compared. The designs include (i) a Luenberger fuzzy observer, (ii) a Luenberger fuzzy observer with sliding modes, (iii) a Walcott–Zak fuzzy observer, and (iv) an Utkin fuzzy observer. A negative, an oscillating fault signal, and a bounded random noise signal with a maximum value of ±0.4 were used to evaluate and compare the performance of the fuzzy observers. The Utkin fuzzy observer showed the best performance under the tested conditions.     

玉米秸秆两级CSTR厌氧消化工艺动力学性能研究

文章采用物料衡算模型、微生物衡算模型和一级动力学模型对两级CSTR厌氧消化系统的运行性能进行了研究。研究结果表明:两级厌氧消化系统HRT(20+20)d和HRT(30+10)d的产甲烷系数分别比单级厌氧消化系统HRT40d增加了5.38%和5.99%;HRT(20+20)d和HRT(30+10)d的第一级反应器的一级动力学常数高于HRT40d以及HRT(20+20)d和HRT(30+10)d的第二级反应器的一级动力学常数;HRT40d,HRT(20+20)d和HRT(30+10)d的微生物产率系数分别为0.003 8,0.016 6和0.020 4;在不同有机负荷率下,HRT(20+20)d,HRT30+10d和HRT40d的平均微生物浓度分别为0.221~0.350,0.275~0.447,0.047~0.076 g/L。     

Control-relevant nonlinearity measure and integrated multi-model control

A control-relevant nonlinearity measure (CRNM) method is proposed based on the gap metric and the gap metric stability margin to measure the nonlinear degree of a system once a linear control strategy is selected. Supported by the CRNM method, an integrated multi-model control framework is developed, in which the multi-model decomposition and local controller design are closely integrated, model redundancy is avoided, computational load is reduced, and dependency on a prior knowledge is reduced. Besides, a 1/δ gap-based weighting method is put forward to combine the local controllers. On one hand, the 1/δ gap-based weighting method has merely one tuning parameter and can be computed off-line; on the other hand, it is sensitive to the tuning parameter, flexible and easy to tune. Two continuous stirred tank reactor (CSTR) systems are investigated. Closed-loop simulations validate the effectiveness and benefits of the proposed integrated multi-model control approach based on CRNM.     

反应器操作方式对酶动力学拆分立体选择性的影响

描述了在批式反应器和连续流搅拌反应器（ＣＳＴＲ）中酶动力学拆分对映异构体的不同之处，从宏观反应器平衡角度，推导出了在ＣＳＴＲ反应器中不同于在批式反应器中的一定酶立体选择性（Ｅ）下，底物或产物的对映体过量值与反应的转化率之间关系的定量关系式。并通过商品脂肪酶及芽胞杆菌Ｅ－５３脂肪酶催化的萘普生甲酯的不对称水解反应得到了证实。分别在批式反应器和ＣＳＴＲ反应器中进行萘普生的酶法拆分，在一定转化率下，批式