基于软测量技术的先进控制在精馏塔上的应用

In this paper, the control of a butadiene distillation column is discussed and improved. At first, a neural network soft-sensor instrument of product quality was built based on abundant on-the-spot data collected by DCS and simulated data obtained by a theoretical model. Then, an inferential control scheme based on the soft-sensor was designed. By increasing logic and expert controllers in the inferential control arithmetic, the robustness of the system was enhanced. The practical application showed that the scheme could run smoothly over a long period and realized close-loop control of product quality.     

FEEDFORWARD CONTROL OF A BINARY HIGH PURITY DISTILLATION COLUMN

Feedforward and PID-SISO feedback control are compared on a pilot plant scale distillation column which is operated in the LV-configuration. For the rejection of disturbances in the feed concentration, a simple empirical feedforward control algorithm is presented. Final steady-state values of the manipulated variables are computed from quadratic equations in x_F, which are easily fitted to simulation or plant data. Experimental results for PID- and feedforward control are compared. The need for dynamic filtering of manipulated variables is demonstrated. While direct setting of the manipulated variables may disturbe the system unnecessarily, second order filtering achieves very fast disturbance rejection. The impact of errors in the disturbance measurement on the control performance is investigated. The feedforward algorithm is intentionally kept simple, to allow easy implementation on a standard decentralized control system     

梭式窑烧成曲线的控制

通过对几种烧成曲线控制算法的分析 ,认为应用AI人工智能工业调节器实现梭式窑温度控制可以得到比较好的效果。     

CLOSED-LOOP DATA RECONCILIATION FOR THE CONTROL OF A BINARY DISTILLATION COLUMN

Data reconciliation is a procedure that makes use of process models along with process measurements to give more precise and consistent estimates for process variables. Data reconciliation has been traditionally used to provide a more representative set of data to calculate steady-state inventories and process yields. For dynamic systems, the use of data reconciliation is relatively nascent. This article examines the potential use of data reconciliation in closed-loop control as a filter to attenuate the noise in measurements of the controlled variables so that the controllers can access more accurate sets of data. Data reconciliation filters were implemented in simulations of a PID control system for a binary distillation column. Results showed that data reconciliation could efficiently reduce the propagation of measurement noise in control loops, so that the overall performance of the controller is enhanced.     

APPLICATION OF MULTIVARIABLE GENERALIZED PREDICTIVE CONTROL TO A PACKED DISTILLATION COLUMN

The present work deals with the application of Multivariate Generalized Predictive Control (MGPC) systems to a packed distillation column. The steady-state and dynamic behaviour of the system have been simulated using two film plug flow model. The model solutions have been obtained employing orthogonal collocation on finite element. The Jacobi polynomials within the finite element procedure was tested to determine the phase flow rates, the liquid and vapour composition profiles and the temperature profiles. All the theoretical results were compared with experimental data obtained from a pilot-plant packed distillation column distilling methanol-water mixture. Decoupling and MGPC control of overhead and/or bottom compositions were examined. Perturbation in feed composition and, reflux ratio and the reboiler heat duty were utilized as the disturbance and the manipulated variables respectively. Performance of these systems was tested by using an integral square of error (ISE and IAE) criterion.     

DIRECTIONS OF DISTURBANCES AND MODELING ERRORS ON THE CONTROL QUALITY IN DISTILLATION SYSTEMS

The effect of directions of disturbances and modeling errors on the control quality was studied with the aid of singular vectors. It is shown that the material balance type of control structure can handle larger size of set point changes than the conventional type of structure in almost all the directions of set point changes. On the other hand it is shown that the latter can handle larger size of feed disturbances than the former in large portion of the directions

The effect of modeling errors in the relative volatility and the stage efficiency on the robustness was discussed focusing on their directions. It is shown that the column with the high condition number of 57 remains stable even when both parameters were 10^° in error

Computer simulations were carried out to ascertain the results obtained.     

裂解炉过热蒸汽温度控制的影响因素和控制算法的探讨

主要阐述了裂解炉过热蒸汽温度控制的影响因素和控制方案，并对蒸汽温度约束条件的非线性化问题解决方案做了初步探讨。     

注塑机温度控制方法研究

针对传统注塑机温控系统存在的超调量大、调节时间长等缺点,提出了变参数自调整的模糊比例积分(FUZZY-PI)控制器设计思路,阐述了该控制器的设计方法及温控系统的软硬件设计方法。通过仿真实验说明,该系统实现了精密注塑机料筒温度和喷嘴温度的准确控制,依此可以取代传统的开关控制及比例积分微分控制,大大提高塑料制品的质量。     

IDENTIFICATION OF THE TEMPERATURE-PRODUCT QUALITY RELATIONSHIP IN A MULTI-COMPONENT DISTILLATION COLUMN

In this paper, we show that in finding a mathematical expression to predict the relationship between temperatures measured inside a multi-component distillation column and the quality of the produced product at the top of the column, the application of a recently developed systematic procedure to identify Wiener nonlinear systems [20], supports the user in retrieving from the data accurate information about both the structure and initial parameter estimates of the model to be identified with iterative parameter optimization methods. This property enables the user to improve his prior knowledge instead of being dependent on it for getting parameter estimates as is the case in most existing parametric identification methods, A consequence of this dependency is that wrong prior information leads to models with poor prediction capability on one hand, and very little information on the other hand on how to modify the model structure in order to get improved results. The latter often results in very time consuming “trial-and-error” approaches that furthermore may yield poor results because of the possibility of getting stuck in local minima. The outlined approach has the potential to overcome these drawbacks. One common source of the use of wrong prior knowledge in the identification of multi-component distillation columns is the presence of a static nonlinearity of exponential type that can be removed by taking the logarithm of the measured product quality. It is shown that this “trick” to linearize the system decreases the accuracy of the predicted producted quality. The outlined approach is also compared to a simple NARX neural network black-box identification method that have the potential to approximate general nonlinear input-output behaviours. This comparison shows that the neural network approach easily requires twice as much observations compared to the Wiener identification approach applied in this paper when the variance of the predicted product quality needs to be the same.

The real-life measurement used in this paper were collected at a refinery of the Dutch State Mines (DSM).

Finally, in order to use the model obtained with one (training) data set under other operational conditions, that is to extrapolate the model a simple observer design is discussed and validated with real-life measurements.     

ON THE DESIGN OF ROBUST CONTROL SYSTEMS FOR DISTILLATION COLUMNS

The distillation column dynamics is very nonlinear, especially at high purity. Multivariable control system designs, which are essentially linear, may not be able to perform well at different operating conditions. This paper looks at three different multivariable design techniques—decoupling control, optimal state feedback and pole assignment as applied to distillation column control. Robustness of these techniques are analyzed by looking at the performance of these controllers at different operating conditions. Some interesting results are obtained.     

燃气比对低温干馏方炉温度场的影响研究

利用计算流体动力学(CFD)软件,采用标准k-ε模型、组分传输模型、多孔介质模型以及P1辐射模型对内热式低温干馏方炉内温度场进行了数值模拟.研究表明,改变燃气比时,燃气入口处温度分布趋势不变,低温干馏炉内达到的最高温度受燃气比影响较大,当燃气比为0.6时,最高温度可达到1 870℃.根据低温干馏原理,并结合炉内煤层温度分布的模拟结果,确定了最优的燃气比为1.8.     

EXPERIMENTAL APPLICATION OF GENERALIZED PREDICTIVE CONTROL OF THE TEMPERATURE IN A POLYSTRENE POLYMERIZATION REACTOR

The performance of generalized predictive control (GPC) was examined and compared with conventional control applied to the temperature of as free radical solution polymerization of styrene in a jacketed batch reactor. Optimal conditions were obtained at different initiator concentrations by applying Lagrange's multiplier to the relevant polymerization reactor. The use of the polynomial ARIMAX model related with reactor temperature and heat input was emphasized. Model parameters were determined using the Kalman algorithm. A pseudo random binary sequence (PRBS) signal was employed in order to operate the system. The GPC control method was based on the ARIMAX model. The performance criteria of GPC in evaluating the temperature control results were the required monomer conversion and molecular weight.     

降温速率对坯、釉适应性的影响

通过对坯、釉热膨胀—应力曲线的讨论,用新的数学模型说明了陶瓷烧成制度中若冷却速度不当会引起釉裂的原因     

辊道窑温度监控系统分析与展望

对现有主要的辊道窑温度监控系统作了概括，分析了其构建原理和特点及其应用情况。指出分布式温度监控系统是当前发展的主流，基于现场总线的辊道窑温度监控系统是未来的发展方向，提出了利用工控组态软件和通用计算机开发辊道窑温度监控系统的新思路。     

REVIEW OF SIMULATION METHODS OF THE DISTILLATION COLUMN AND THERMODYNAMIC MODELS IN THE HI DECOMPOSITION SECTION OF THE IODINE-SULFUR PROCESS

The iodine-sulfur thermochemical water-splitting process (I-S process) is one of the most promising and efficient mass hydrogen production methods without greenhouse gas emissions. To a large extent, distillation in the HI decomposition section of the I-S process affects the efficiency of the entire process. This article summarizes the simulation methods for HI distillation in the iodine-sulfur process, including thermodynamic models, design schemes, and parameter analyses. The performance of the thermodynamic models and heat duties of different flow sheets were compared, and the preferable model and flow sheet are recommended. This study can provide a reference for the selection of thermodynamic models and it is also meaningful for the design and simulation of the HI distillation column.     

基于数据融合技术的陶瓷窑炉温度智能控制

根据陶瓷窑炉控制的特点，研究了应用于陶瓷窑炉温度控制系统的数据融合基本方法，以解决测量噪声干扰下参数估计问题。提出了多传感器数据融合与陶瓷窑炉温度智能控制相结合的结构，最后将数据融合方法应用于陶瓷窑炉的温度智能控制系统。应用结果表明，基于数据融合技术的陶瓷窑炉温度控制比采用单一的传感器控制效果有明显的改善。     

RADIAL TEMPERATURE PROFILE IN THE MODELLING OF AN INDUSTRIAL METHANOL REACTOR

The significance of the radial temperature profiles is investigated in industrial reactor simulation. With 2-nd order approximation of the temperature distribution, a radial effectiveness factor is introduced, and a one-dimension model is proposed. It well approaches the solution of the two-dimension one. The radial temperature profiles substantially affect the methanol production rate only in the run away state. At the hot spot the one-dimension model is satisfactory to test the significance of the radial temperature distribution.     

蓄热室温度偏低的原因及解决办法

介绍了烘烤马蹄焰窑炉时蓄热室温度偏低的原因及解决办法.     

有限差分法确定石墨电极中的温度分布

采用有限差分的方法,根据实测处于正常工作状态时电极中的温度分布、热传导的基本方程以及有关边界条件建立的石墨电极从炉内撤出不同时间后电极中的温度场。结果表明,当电极从炉内撤出以后,电极中的温度分布将发生显著的变化,电极表层和端都附近的温度梯度在刚撤出后迅速增大,特别是表层温度梯度远大于正常工况下的温度梯度。     

PP化学降解中助剂、温度和分子量的影响

用直接化学降解法讨论ＰＰ化学降解过程中的添加剂、加工温度和原始分子量对ＰＰ熔体流动性变化的影响。结果表明：ＰＰ中添加的少量防紫外与抗热氧老化阵解等助剂对化学降解剂如过氧化物二叔丁基（ＤＴＢＰ）等活性反应基团有一定的抑制作用。加工温度选择是有效利用化学阵解剂来改善ＰＰ熔体流动性的重要条件之一，同时ＰＰ分子链与化学活性基团的降解现象是有温度依赖性的。另外，在相同的化学降解条件下，不同原始分子量ＰＰ熔体流动性变化有较大的差别。