Dynamic modelling and predictive control for the sequential collaborative reactors of cobalt removal process under time‐varying conditions

The accuracy of the process model directly affects the performance of the model‐based controller. In zinc hydrometallurgy, the overall dynamics of the cobalt removal process can hardly be described by a fixed model since there are a series of interconnected reactors working together under time‐varying inlet and reaction conditions. In this study, an interacting continuously stirred tank reactors (ICSTR) model is developed to describe the cooperative relationship of these cascaded reactors. Considering the time‐varying inlet and reaction conditions, the reaction surface conversion coefficient is defined and incorporated into the ICSTR model, and the kernel partial least squares (KPLS) is employed to update the dynamic model online. The effectiveness of the time‐varying ICSTR model is validated using industrial data. Based on the proposed time‐varying ICSTR model, a predictive controller is designed to realize the optimal operation of the cobalt removal process. Simulation results indicate that compared with conventional predictive control and manual manipulation, the time‐varying ICSTR model‐based predictive control method can not only maintain the outlet cobalt ion concentration but also reduce the zinc dust dosage.     

搅拌反应器中反应热的实时监测Ⅱ模拟放热反应过程的状态及参数估计

在自制的５Ｌ规模反应量热实验装置中，以热平衡为基础建立了搅拌反应器的动态热传递模型，应用扩展Ｋａｌｍａｎ参数估计和状态估计的方法在线得到模型参数和模拟反应的放热速率、累积反应热。实验数据和模型估计值比较，预测误差在±７％以内     

Model predictive control for the reactant concentration control of a reactor

The reactant concentration control of a reactor using Model Predictive Control (MPC) is presented in this paper. Two major difficulties in the control of reactant concentration are that the measurement of concentration is not available for the control point of view and it is not possible to control the concentration without considering the reactor temperature. Therefore, MIMO control techniques and state and parameter estimation are needed. One of the MIMO control techniques widely studied recently is MPC. The basic concept of MPC is that it computes a control trajectory for a whole horizon time minimising a cost function of a plant subject to a dynamic plant model and an end point constraint. However, only the initial value of controls is then applied. Feedback is incorporated by using the measurements/estimates to reconstruct the calculation for the next time step. Since MPC is a model based controller, it requires the measurement of the states of an appropriate process model. However, in most industrial processes, the state variables are not all measurable. Therefore, an extended Kalman filter (EKF), one of estimation techniques, is also utilised to estimate unknown/uncertain parameters of the system. Simulation results have demonstrated that without the reactor temperature constraint, the MPC with EKF can control the reactant concentration at a desired set point but the reactor temperator is raised over a maximum allowable value. On the other hand, when the maximun allowable value is added as a constraint, the MPC with EKF can control the reactant concentration at the desired set point with less drastic control action and within the reactor temperature constraint. This shows that the MPC with EKF is applicable to control the reactant concentration of chemical reactors.     

Influence of the process parameters on temperature conditions and productivity of multitubular reactor for methanol to formaldehyde oxidation

The results of the parametric analysis of the methanol oxidation to formaldehyde on the basis of the kinetic model of reactions on an iron-molybdenum oxide catalyst and the two-dimensional model of a multitubular reactor were reported in the paper. The results of kinetic experiments on an industrial Fe-Mo granular catalyst were given. Calculation results were compared with industrial data. The possibilities of controlling the methanol oxidation to formaldehyde in multitubular reactors at varied plant unit productivity with consideration for process restrictions were theoretically studied. The effect of parameters on the temperature and concentration conditions in reactors at different ratios of catalyst and inert material loads was studied.     

基于改进状态转移算法的串级平推流反应器动力学参数估计

实际化工过程反应系统通常由若干个相互关联的平推流反应器串级构成，要建立其机理模型，并估计其动力学参数，就必须反复求解大规模非线性微分方程组，计算代价较高。针对智能优化算法在求解昂贵优化问题时计算成本过高，而工业过程模型往往只需要找到一组满意解即可的特点，提出了一种基于改进状态转移算法的串级平推流反应器动力学参数估计方法。该算法在保留标准状态转移算法全局寻优能力和快速收敛能力的同时，利用对立算子优化初始种群，并根据误差阈值判定满意解中止条件，可有效节约计算时间。以实际炼油企业的加氢裂化装置为研究对象，采用所提方法对其反应系统的动力学参数进行估计，仿真结果表明了所提方法的有效性。     

UBF-BAF处理羧甲基纤维素冷凝液特性

采用UBF-BAF组合工艺对多效蒸发食品添加剂羧甲基纤维素(CMC)产生的酸性冷凝液进行生物降解,考察了UBF-BAF组合工艺参数,构建了基于化学需氧量(COD)去除的UBF反应动力学模型,并对UBF和BAF反应器生物膜中的生物学特征进行了解析,初步揭示出UBF-BAF处理CMC冷凝液的特性. 其适宜的运行参数为：UBF的水力停留时间24 h,BAF的水力停留时间5 h,温度20~40℃,pH=6.5~7.5,BAF反冲洗周期5~7 d. 当进水COD浓度为2388~4000 mg/L时,UBF反应器对COD的去除率高于84.26%,BAF反应器对COD的去除率高于80.53%,最终出水达到《污水综合排放标准(GB 8978-2002)》一级排放要求.     

AN OPTIMAL EXTENDED KALMAN FILTER DESIGNED BY GENETIC ALGORITHMS

A Geno-Kalman filter is utilized for state estimation of a bench-scale batch reactor that handles an exothermic reaction between H₂O₂ and Na₂S₂O₃. This reaction system includes three different states including the concentration of reactants as well as the temperature of the reactor. All of the states are measured during the process. The proposed procedure is to run an optimal extended Kalman filter by which the Kalman design parameters, Q and R, are obtained by genetic algorithms. The extended Kalman filter is initially designed by trial and error and used as a baseline in this study. Then an optimal white-bound extended Kalman filter design is obtained through an optimization on the baseline estimator, using genetic algorithms. The results show a significant improvement in the performance of the estimator. Moreover, a color-bound extended Kalman filter was also designed to allow a dynamic linear trend for the change in nonzero elements of the process noise covariance matrix.     

偶氮染料在气-液-固循环浆态光催化反应器中的降解脱氮

偶氮染料废水是一种集中量大的重要污染物,其中的偶氮键可被环境微生物降解生成具有毒性的芳香胺类化合物。本文从光量子效率、脱氮速率、脱氮能耗等方面,对比研究了一种新设计的气-液-固循环浆态光催化反应器和环隙式光催化反应器对偶氮染料降解脱氮的性能。结果表明,由于空气的引入,使气-液-固循环浆态光催化反应器的量子收率有一定程度下降,同时造成单位数量级脱氮能耗也有一定增大,但偶氮染料脱氮速率比在环隙式反应器中的情况有大幅度提高,表明气-液-固循环浆态反应器在偶氮染料废水光催化降解脱氮方面具有较大应用前景。     

Optimal hybrid modeling approach for polymerization reactors using parameter estimation techniques

The dynamics of polymerization catalytic reactors have been investigated by many researchers during the past five decades; however, the emphasis of these studies was directed towards correlating process model parameters using empirical investigation based on small scale experimental setup and not on real process conditions. The resulting correlations are of limited practical use for industrial scale operations. A statistical study for the relative correlation of each of the effective process parameters revealed the best combination of parameters that could be used for optimizing the process model performance. Parameter estimation techniques are then utilized to find the values of these parameters that minimize a predefined objective function. Published real industrial scale data for the process was used as a basis for validating the process model. To generalize the model, an artificial neural network approach is used to capture the functional relationship of the selected parameters with the process operating conditions. The developed ANN-based correlation was used in a conventional fluidized catalytic bed reactor (FCR) model and simulated under industrial operating conditions. The new hybrid model predictions of the melt-flow index and the emulsion temperature were compared to industrial measurements as well as published models. The predictive quality of the hybrid model was superior to other models. The suggested parameter estimation and modeling approach can be used for process analysis and possible control system design and optimization investigations.     

苯乙烯连续搅拌釜式本体聚合工业过程模拟

采用了机理分析建模法对苯乙烯工业本体预聚过程进行了模型化研究，并通过对流体在反应器中混合模式的分析，表明预聚釜可视作全混流（CSRT）反应器模型，此外对热聚合机理中的引发级数和终止反应进行了考察，利用预聚釜的工业数据确立了三分子引发，同时考虑偶合和歧化终止以及向溶剂链转移的反应机理模型，并选取了合适的动力学参数，然后利用工业装置采集的数据进行了模拟，从宏观转化率，平均分子量和微观分子量分布两个方面对模型进行了验证，模拟结果和工业数据符合得较好，该模型方程不仅能模拟稳态，非稳态预聚过程，同时也为装置开发新产品，改造扩建，优化操作方案等提供了理论基础。     

Feasibility Study of a Solar Reactor for Phenol Treatment by the Photo‐Fenton process in Aqueous Solution

Solar reactors can be attractive in photodegradation processes due to lower electrical energy demand. The performance of a solar reactor for two flow configurations, i.e., plug flow and mixed flow, is compared based on experimental results with a pilot‐scale solar reactor. Aqueous solutions of phenol were used as a model for industrial wastewater containing organic contaminants. Batch experiments were carried out under clear sky, resulting in removal rates in the range of 96–100 %. The dissolved organic carbon removal rate was simulated by an empirical model based on neural networks, which was adjusted to the experimental data, resulting in a correlation coefficient of 0.9856. This approach enabled to estimate effects of process variables which could not be evaluated from the experiments. Simulations with different reactor configurations indicated relevant aspects for the design of solar reactors.     

Safety aspects in modelling and operating of batch and semibatch stirred tank chemical reactors

Safety aspects in modelling of batch and semibatch stirred tank reactors as well as a model based safety analysis have been considered. Applicability of two basic types of models – i.e. the perfectly mixed reactor model and the CFD model, both formulated for laboratory scale as well as pilot plant scale reactors – has been discussed. A formulation of the appropriate reactor model, which is adequate to the considered case study has been demonstrated and tested experimentally. Particular attention has been devoted to the formulation of robust CFD models employed to simulate a performance of the stirred tank reactors. It has been found that models for perfectly mixed reactors may have quite wide range of application, while the CFD models should be definitely used in case of fast reactions, high viscosity of the reacting mixture as well as of failure leading to stopping of the impeller. The CFD models are able to predict a dynamic behaviour of reactors at any circumstances, so they can play a significant role in safety analysis carried out for industrial scale reactors, for which experimental safety tests are expensive and dangerous.     

Estimation of catalytic activity using an unscented Kalman filtering in condensation reaction

The catalytic activity of cation exchange resins will be continuously reduced with its use time in a condensation reaction for bisphenol A (BPA). For online estimation of the catalytic activity, a catalytic deactivation model is studied for a production plant of BPA, state equation and observation equation are proposed based on the axial temperature distribution of the reactor and the acetone concentration at reactor entrance. A hybrid model of state equation is constructed for improving estimation precision. The unknown parameters in observation equation are calculated with sample data. The unscented Kalman filtering algorithm is then used for on-line estimation of the catalytic activity. The simulation results show that this hybrid model has higher estimation accuracy than the mechanism model and the model is effective for production process of BPA.     

乙炔加氢反应器二维非均相机理动态建模及分析

乙炔加氢反应器具有非线性、慢时变的特点,当前用于预测控制的模型过于简化,使得对反应器长期运行的控制效果难以达到最佳,因此有必要建立精确的模型作为乙炔加氢反应器的实验室虚拟装置,研究更加有效的控制方法。通过机理分析的方法建立了乙炔加氢反应器严格的二维非均相动态数学模型,并且考虑了催化剂失活的问题。基于动态流程模拟软件gPROMS分析了重要模型参数对反应器稳态模拟的影响,为不同的装置选择参数提供了依据,并且针对本文模拟的实际对象提供了一组数据。模拟分析了催化剂失活对于系统长期运行的影响。对所建立的动态数学模型进行了动态模拟,结果基本反映了实际生产情况。将动态机理模型线性化,得到动态机理模型在不同操作点上的线性状态空间模型特征值,以此进行稳定性分析。动态模拟和稳定性分析的结果表明,在反应温度控制开环的条件下,所研究的反应器在大范围的操作点是稳定的。     

Enhancing dynamic data reconciliation performance through time delays identification

In order to improve the performance of data reconciliation methods, an efficient Genetic algorithm (GA) for determining time delays has been developed. Delays are identified by searching the maximum correlation among the process variables. The delay vector (DV) is integrated within a dynamic data reconciliation (DDR) procedure based on Kalman filter through the measurements error model. The proposed approach can be satisfactorily applied not only off-line but also on-line. It was firstly validated in a dynamic process with recycles and feedback control loops. Then, the methodology was successfully applied to a highly non-linear and complex challenging control case study, the Tenessee Eastman benchmark process, demonstrating its robustness in complex industrial problems. This case study required to implement an extended Kalman filter to deal with the existing non-linearities.     

间歇化学反应温度先进控制系统

由于间歇化学反应器中动力学参数的不确定性和时变性,使其成为先进控制算法工业应用的主要对象。本文对以预测函数控制算法（PFC）为核心并结合PID控制的先进控制算法进行了研究,针对间歇化学反应器的温度跟踪控制问题,提出了包括PFC在内的四种控制方案的先进控制策略。并在SUPCON－JX300集散控制系统上开发了间歇反应温度跟踪先进控制软件包,工业现场运行取得了很好的结果。     

The bifurcation behavior of continuous free-radical solution loop polymerization reactors

The bifurcation behavior of continuous free-radical solution loop polymerization reactors is analyzed in this work. A mathematical model is developed in order to describe the impact of the recycling pump and other external reactor parts upon the process dynamics and stability. Stability analysis is performed using bifurcation theory and continuation methods. It is shown that under certain operational conditions as many as seven steady states are predicted for the loop polymerization reactor. Oscillatory behavior is observed for a wide range of process parameters and onset of oscillations is observed during the transition from operation without material recycling to operation with partial recirculation of the polymer solution. Besides, at certain constrained range of operation conditions, complex dynamics can be observed, including the onset of chaotic behavior. It is also shown that the thermal parameters of the reactor and recycling pump exert a profound effect upon the process stability. For this reason it is shown that oscillatory behavior is very unlikely to occur in actual industrial reactors.     

湿法炼锌中除钴工艺现状研究与发展

对湿法炼锌硫酸锌溶液净化除钴工艺作了简要介绍,分别介绍了目前工业上应用的两大类方法:一类为加有机试剂(黄药、β-萘酚)除钴;另一类为锌粉置换除钴。并对新的除钴方法进行了介绍。分析比较了各种方法的优缺点。     

Experimental study and model simulation of a two-stage continuous polymerization process for polystyrene

Free radical solution polymerization of styrene in two stage polymerization process has been studied using a binary mixture of symmetrical bifunctional initiators. The continuous reactor system was composed of two reactor units; a prepolymerization reactor (e.g. stirred tank reactors) and a filled tubular reactor packed with static mixers. When the stirred tank reactor was used as a prepolymerizer, a feed stream to the filled tubular reactor was more viscous than the monomer/solvent mixture. It was of interest to investigate how the performance of the filled tubular reactor has been investigated by the feed of viscous prepolymer solution. A dynamic model of the continuous two stage polymerization process was presented by experimental data and model simulation. A reasonably good agreement between the model and the experimental data was obtained without using any adjustable parameters. The experimental results of the two stage polymerization were compared with the results without prepolymerization reactor. It was found that the addition of a prepolymerization reactor has almost no effect on the performance of the filled tubular reactor.     

Removal of zinc ions from aqueous solution using a cation exchange resin

The present study is concerned with the mass transfer and kinetics study of zinc ions removal from aqueous solution using a cation exchange resin packed in a rotating cylindrical basket reactor. The effect of various experimental parameters on the rate of zinc ion removal, such as initial zinc ion concentration, packed bed rotation speed and temperature has been investigated. In addition to find a suitable equilibrium isotherm and kinetic model for the zinc ion removal in a batch reactor. The experimental isotherm data were analyzed using the Langmuir, Freundlich and D–R equations. The equilibrium data fit well in the Langmuir isotherm. The experimental data were analyzed using four sorption kinetic models, pseudo-first and second-order equations, the Elovich and the intraparticle diffusion model equation, to determine the best fit equation for the biosorption of zinc ions onto purolite C-100 MH resin. Results show that the Elovich equation provides the best correlation for the biosorption process.