搅拌反应器中计算流体力学数值模拟的影响因素研究进展

回顾了搅拌反应器中计算流体力学（CFD）数值模拟方法的研究历程,包括搅拌桨叶边界条件法、内外迭代法、滑移网格法、多重参考系法、快速照相法等方法;结合各种模拟方法的特点,对机械搅拌反应器数值模拟过程中的挡板的存在、尾涡的消除、复杂桨叶类型的模拟、网格精度的影响、湍流模型的选择、离散格式的差异等几个因素的影响作了分析。提出了搅拌反应器的CFD数值模拟仍有待深入研究。     

搅拌反应器内计算流体力学模拟技术进展

综述了计算流体力学(CFD)技术应用在搅拌反应器的进展情况。重点对搅拌反应器内流动场模拟的各种处理方法,包括"黑箱"模型法、内外迭代法、多重参考系法和滑移网格法,进行了介绍与评价,指出了各种方法所具有的特点及存在的问题。阐述了搅拌反应器内CFD技术的发展方向,并就国内的研究现状进行了简单概述。     

基于FLUENT软件的管式搅拌反应器流场的数值模拟

运用商业计算流体力学(CFD)软件FLUENT对一种新型管式搅拌反应器进行流场模拟,用GAMBIT建立流场实体模型,采用标准k-ε湍流模型以及多重参考系法(MRF)处理搅拌桨区.结果表明,计算所选模型能较准确地预测搅拌反应器的速度场、压力场及湍流动能分布,考察流量为1 m3/h时不同搅拌转速对反应器内部混合的影响,此时对应的最佳搅拌转速为50 rpm左右.模拟结果将为实验研究提供适当的操作参数,对搅拌反应器的优化和放大具有一定参考价值.     

搅拌生物反应器混合特性的数值模拟与实验研究

以工程流体计算软件CFX-4.4为工具,对不同规模的机械搅拌生物反应器的混合特性进行数值模拟,研究了不同操作条件下反应器混合时间的变化规律. 采用pH电极在位监测[H+]的方法实验测定混合时间. 模拟结果与实验测定值之间的误差随反应器容积增大而逐渐减小,对容积为25 m3的反应器误差小于11.6%.     

侧进式搅拌反应器内流场的数值模拟

采用计算流体力学(CFD)技术对某钢铁厂烟气脱硫吸收塔底部浆液池的侧进式搅拌流场进行了数值模拟,研究了搅拌转速和搅拌桨安装角度等因素对3维流场的影响规律.结果表明,在5股流体的相互作用下,反应器内存在一个顺时针的整体大循环流动,相邻搅拌桨之间存在两个小漩涡.随着搅拌转速的增大,中心线上底部的速率迅速增加,当转速大于等于...     

管式搅拌反应器停留时间分布的数值模拟

对一种新型管式搅拌反应器的停留时间分布(RTD)进行了实验研究,运用商业计算流体力学(CFD)软件FLUENT进行流场模拟及RTD计算,证实管式搅拌反应器的停留时间分布受搅拌转速及入口流量等因素影响,带搅拌装置的管式反应器适当增加转速能使RTD曲线变窄,改善流型和抑制返混;转速过大会使RTD曲线变宽,导致死区的产生,不利于反应器的混合.RTD曲线的数值模拟计算结果与实验结果基本稳合.     

连续搅拌釜式丙烯聚合反应器的模拟：（Ⅱ）的反应器的动态模拟

建立了丙烯液相本体聚合搅拌釜式反应器的动态数学模型，通过计算机模拟，研究了进夹套冷却水流量、丙烯蒸汽冷凝量、催化剂浓度及进料温度４个变量在矩形波和阶跃两种干扰方式下反应器的动态行为，为反应器控制系统的设计提供了定量依据。     

连续搅拌釜式丙烯聚合反应器的模拟：（I）反应器的定态模拟

以实验工业装置为背景，建立了丙烯液相本体聚合连续搅拌釜式反应器的定态数学模型，通过模拟计算，考察了诸工艺参数－－进料温度、进料流量、夹套冷却水入口温度和流量、丙烯汽冷凝量、催化剂浓度以及反应器中的氢浓度对聚合反应釜反应结果的影响，并对其定态操作行为作了理论上的解释和分析。     

大型搅拌反应器封头顶部结构优化设计

针对某大型搅拌反应器封头上搅拌法兰的偏转量过大的问题,提出了在封头顶部设置筋板以满足法兰偏转量的设计要求。采用ANSYS Workbench有限元分析软件,对筋板高度与长度的变化进行了参数化建模,得到了筋板的高度、长度与其最大应力之间的变化规律。结果发现筋板高度越低,其最大应力越小。而筋板的长度变大,其最大应力则先增大后逐渐减小,当长度达到某一值时最大应力趋于平稳,最终确定了筋板优化的高度和长度尺寸。     

多相流搅拌反应器研究进展

综述了近五年冷态气液固三相搅拌反应器的研究成果,阐明近期研究热点已转为热态多相流搅拌反应器的流体力学行为。概述了热态气液两相体系中通气功率、混合时间、局部及总体气含率的研究结果。指出今后研究重点应为热态的固液悬浮、气液传质过程及其机理,同时说明用计算流体力学（CFD）对气液固三相搅拌反应器的数值模拟仍属起步阶段。     

Differentiation criteria study for continuous stirred tank reactor and plug flow reactor

All reactors in reality are not ideal plug flow reactor (PFR) or ideal continuous stirred tank reactor (CSTR). They are difficult to differentiate. This study was to investigate the reactor analysis of PFR and CSTR through tracer response curves, residence time distributions (RTD) and several hydraulic performance indexes. We set up the differentiated value of each index. The tracer response curve showed that our lab-scale CSTR was close to ideal CSTR and got 99.9% recovery. In the RTD curves, the results could significantly recognize the PFR nature of high rate pond (HRP). With hydraulic performance indexes study, every selected index demonstrated that the studied HRP was closer to PFR than the studied CSTR. Based on the lab-scale study results, this study established the cutting point between the PFR and CSTR in each index; we were looking through the different types of reactors in literature and we confirmed the criteria with all literature reactors with the “graphic method”. The method helped us to establish those important values to help us to differentiate the reactor types in practice and to understand the designs better.     

连续搅拌反应釜的自适应神经网络控制

基于神经网络的逼近特性,针对一类包含未知函数的串级连续搅拌釜式反应系统,提出了一种自适应控制算法。由于所考虑的反应系统具有非线性特性以及未知函数存在于各子系统的方程中,因此,该系统是复杂和难于控制的。为了克服困难,神经网络逼近系统中的未知函数,新奇的递归设计方法用于消除系统中的互联项,同时,需要定义特殊的被逼近非线性函数。利用李雅普诺夫稳定性分析方法,提出的控制算法保证了闭环系统的所有信号是有界的和系统的输出收敛到零的邻域内。仿真例子表明提出的控制算法是有效的。     

连续搅拌釜式反应器的鲁棒最优控制

针对一类带不确定性的连续搅拌釜式反应器,提出基于滑模控制理论的鲁棒最优控制算法。输入输出线性化方法用于线性化对象模型,假设系统的不确定因素有界,滑模面采用积分型滑模面以确保系统稳态误差为零,将线性二次型理论用于等效控制律的设计中,保证了系统的性能指标最优,自适应滑模切换控制增益的选取在降低系统抖振的前提下补偿了系统的不确定因素及外部扰动,实现了控制器的鲁棒最优。通过仿真实验表明,提出的控制器对匹配的不确定性因素及外部扰动具有鲁棒性,且闭环系统的性能指标最优。     

连续搅拌反应釜系统的非线性鲁棒控制

基于非线性鲁棒控制理论,针对一类单输入单输出连续搅拌反应釜（CSTR）模型设计了具有高增益观测器的非线性鲁棒控制器（ONRC）,并提出了一种简单的控制器参数整定方法。与非线性鲁棒控制器（NRC）和滑模控制方法（SMC）的仿真结果比较表明,ONRC对系统不确定性和干扰具有更好的抑制作用,通过Monte-Carlo试验检验显示,ONRC在模型参数摄动时具有更好的性能鲁棒性。     

Modeling and control of continuous stirred tank reactor for thermal copolymerization

A mathematical model is developed for solution copolymerization in a continuous stirred tank reactor. For the thermal copolymerization of styrene and acrylonitrile (SAN), the kinetic rate expression for thermal initiation is derived by applying the pseudo-steady-state hypothesis to the intermediates, and the kinetic parameters are estimated by experimental investigation. The moment equations of living and dead polymer concentrations are derived by applying the pseudokinetic rate constantmethod. The model is used to calculate the conversion, the copolymer composition, the weight-average molecular weight, and the polydispersity. It is demonstrated that this model can predict the industrial data very well under various operating conditions. The dynamic analysis of the reaction system enables us to determine the polymer properties against the changes in the operation parameters. It is noticed that the monomer conversion is controlled to some extent by the reaction temperature and the feed monomer fraction. The monomer conversion control of a solution copolymerization reactor is treated with different control algorithms. The fuzzy/proportional–integral–derivative controller shows satisfactory performances for both setpoint tracking and disturbance rejection and can be easily applied to continuous polymerization processes. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:921–931, 1998     

超声场下搅拌槽内微观混合

以醋酸锌、氯乙酸乙酯和氢氧化钠的平行反应为研究体系,考察了较高物料浓度时超声场下搅拌槽内的微观混合情况。结果表明:搅拌和超声波振荡对微观混合有明显的强化作用,在不同超声功率下,存在搅拌速率N对微观混合影响的临界搅拌速率Nc。当N>Nc时,搅拌速率对微观混合的影响可以忽略;N相似文献   

Performance of an adiabatic controlled cycled stirred tank reactor

A set of general differential equations was used to describe the dynamics of an adiabatic controlled cycled stirred tank reactor (CCTR). Exothermic reaction between sodium thiosulfate and hydrogen peroxide was carried out in a CCTR under several conditions. The observed dynamic and pseudo steady state behavior agreed very well with predictions from theory. Complete information about the system could be thus ascertained from measurement of tempe only. Conversion and capacity for the three types of reactors, CCTR, CSTR and PFR, were also compared for the model reaction used here.     

Calcium carbonate precipitation in a continuous stirred tank reactor

The precipitation of calcium carbonate, brought about by mixing aqueous solutions of calcium nitrate and sodium carbonate in a continuous reactor, has been studied. The pH (8.5-10.0), reagent concentration (0.25-1.7 N), temperature (15-60°C), residence time (1-3 min), and mixing speed (100-500 rpm) were chosen so that the effects of agglomeration could be examined The presence of agglomerates was confirmed by microscopy. Precipitate size distributions were log normal, and the geometric mean diameters, ranging from 5 to 13 p.m, were extremely sensitive to pH. Large precipitates were obtained under conditions favouring a high agglomeration rate; namely high temperatures, concentrations, and mixing speeds. The effect of residence time was minimal. The geometric standard deviation increased with the mean size of the precipitate. The solids recovery decreased with increasing temperature, but was not significantly affected by the other parameters