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1.
Ethyl acrylate (EA) is widely used in industry as a precursor for varnishes, adhesive, and finishes of papers and textiles. This important ester can be produced directly from ethanol (EtOH) and acrylic acid (AA) via esterification reaction with the presence of sulphuric acid as homogeneous catalyst. The proposed design flowsheet of this process includes a CSTR reactor coupled with a rectifier and an overhead decanter. In order to further purify the final EA product, another stripper is needed with its top vapor recycled back to decanter. The simplest and industrial easily applicable overall control strategy will be investigated with only one tray temperature control loop in each of the two columns. The final proposed overall control strategy of this process is found to be different than another similar coupled reactor/columns process published earlier [I-L. Chien, Y.P. Teng, H.P. Huang, Y.T. Tang, Design and control of an ethyl acetate process: coupled reactor/column configuration, J. Proc. Cont. 15 (2005) 435–449]. Both EtOH and AA feed flow rates are used as manipulated variables in the overall control strategy with CSTR heat duty left as throughput manipulator for the overall process. The final EA product with stringent specifications of 0.1 wt% EtOH and 0.005 wt% AA impurities can be achieved with this proposed overall control strategy despite feed flow rate and feed composition disturbances. 相似文献
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Design and control of an ethyl acetate process: coupled reactor/column configuration 总被引:1,自引:1,他引:0
I-Lung Chien Yao-Pin Teng Hsiao-Ping Huang Yeong Tarng Tang 《Journal of Process Control》2005,15(4):435-449
In this paper, design and control of a realistic coupled reactor/column process to produce ethyl acetate is studied. The process design is more complicated because the ethyl acetate product is neither the lightest nor the heaviest component in the system. A search procedure is proposed to obtain the optimum process design and operating condition of this process. The optimum process design is the one that minimize the Total Annual Cost (TAC) of this process while satisfying the stringent product impurity specifications. The optimum overall process design includes a continuous-stirred tank reactor (CSTR) coupled with a rectifier, a decanter, another stripper, and a recycle stream. After the process design is established, the next step is to use dynamic simulation to test the appropriate control strategy for this process. Sensitivity analysis is performed to obtain the suitable temperature control points for the columns. The proposed control strategy is very simple containing only one temperature control loop in each column. This recommended simpler control strategy uses the ratio of acetic acid feed rate to ethanol feed rate to control the 5th stage temperature of the rectifier and uses the stripper reboiler duty to control the 5th stage temperature of the stripper. The proposed control strategy does not need any on-line composition measurements and can properly hold product purity in spite of feed flow rate and feed composition disturbances. For small deviations of the product impurity compositions during disturbances, a slow cascade outer composition loop structure can be implemented using off-line composition measurements from the quality lab. 相似文献
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I-L. Chien C. J. Wang D. S. H. Wong C. -H. Lee S. -H. Cheng R. F. Shih W. T. Liu C. S. Tsai 《Journal of Process Control》2000,10(4)
In this work, a laboratory scale sieve plate distillation column was constructed to investigate the conventional control strategies of an isopropyl alcohol (IPA), cyclohexane (CyH) and water (H2O) heterogeneous azeotropic distillation column. Steady state process analysis showed that the optimal operation point should be located at a critical reflux, a transition point at which the distillation path switches from a route that passes through IPA+H2O azeotrope to one that passes through IPA+CyH azeotrope. At this critical reflux, a high purity IPA product can be obtained with minimum energy consumption and maximum product recovery. However, the steady state is extremely sensitive to feed disturbances. A good control strategy must be able to maintain a steady column temperature profile that shows a plateau near 70°C to ensure passage around IPA+CyH azeotrope. In this study, an inverse double loop control strategy is recommended. Through experimental testing, the proposed control strategy was demonstrated to keep the product IPA purity at the desired high-purity level under all feed disturbance changes while other conventional control strategies fail. 相似文献
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《Control Engineering Practice》2003,11(2):141-159
This paper details a multiple model adaptive control strategy for model predictive control (MPC). To maintain performance of this linear controller over a wide range of operating levels, a multiple model adaptive control strategy for dynamic matrix control (DMC), the process industry's standard for MPC, is presented. The method of approach is to design multiple linear DMC controllers. The tuning parameters for the linear controllers are obtained using novel analytical expressions. The controller output of the adaptive DMC controller is a weighted average of the multiple linear DMC controllers. The capabilities of the multiple model adaptive strategy for DMC are investigated through computer simulations and an experimental system. 相似文献
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由于煮糖结晶过程本身受干扰的因素比较多,如糖浆的锤度、糖浆杂质、真空度以及温度的变化都会影响蔗糖结晶过程,非线性比较强。因此一般的控制策略(比如常规PID)难以凑效,根据煮糖结晶过程的物料平衡、能量平衡和生产过程的各种物性参数的机理解析关系(如晶体生长分散)建立描述被控对象的模型,并以该模型作为预测模型对煮糖结晶过程实施动态矩阵控制(DMC).仿真结果表明该控制算法对煮糖过程的控制是有效的。 相似文献
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Yao-Qing Ren Xiao-Gang Duan Han-Xiong Li C.L. Philip Chen 《Journal of Process Control》2013,23(3):351-358
A multi-variable fuzzy logic controller (FLC) is proposed to control a class of distributed parameter systems (DPSs). When a DPS is transformed into finite-dimensional ordinary differential equations (ODEs) by using time/space separation, each ODE can be considered as a subsystem. According to design strategy of conventional FLC, one FLC should be designed for one subsystem. It will be very complex because there are many subsystems. In order to reduce design complexity, only a MF and a rule base are designed in the controller. For other subsystems or ODEs, their MFs can be designed equivalently by introducing scaling factors. Then, the proposed FLC has ability to control multi-variable processes. At last, the proposed FLC is applied to control a rod catalytic reaction process. The simulation results demonstrate the effectiveness of the proposed fuzzy control strategy. 相似文献
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改进的动态矩阵控制算法在发酵罐温度控制中的应用 总被引:1,自引:0,他引:1
啤酒发酵是一类复杂的生化反映过程,其温度控制具有大时滞特性。由于机制复杂、环境多变,温度对象难以建立精确的数学模型,常规控制方式难以胜任此类系统的控制,并且当存在不可预测的干扰时,控制效果更难保障。针对这一问题,以啤酒发酵罐的温度为控制对象,将动态矩阵控制(DMC)引入该温度控制,基于DMC一步控制的思想,引入时间最优控制对DMC控制量进行改进,形成快速响应的预测控制算法。应用结果表明该算法有效提高了系统对干扰的抑制能力,具有较好的应用价值。 相似文献
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Ball mill grinding circuit is a multiple-input multiple-output (MIMO) system characterized with couplings and nonlinearities. Stable control of grinding circuit is usually interrupted by great disturbances, such as ore hardness and feed particle size, etc. Conventional model predictive control usually cannot capture the nonlinearities caused by the disturbances in real practice. Multiple models based adaptive dynamic matrix control (ADMC) is proposed for the control of ball mill grinding circuit. The novelty of the strategy lies in that intelligent expert system is developed to identify the current ore hardness and then select a proper model for ADMC. Compared with the various nonlinear DMC strategies, the approach can synthesize and analyze as many variables and status as possible to adequately and reliably identify the process conditions, and it does not introduce additional computational complexity, which makes it readily available to the industrial practitioner. Simulation results and industrial applications demonstrate the effectiveness and practicality of this control strategy. 相似文献
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The control strategy of a reactive distillation for synthesis of MTBE is investigated. Although steady state multiplicities occur in the column, a linear control is still possible since a controlled and manipulated variable-pairing scheme that exhibits a sufficiently large range of near linear relations can be found, if we operate at constant reflux ratio. Reboiler duty is used to control the temperature of a stage just below the reaction section and near the top of the stripping section. Stoichiometric balance is controlled by a feed ratio plus internal composition control scheme, using a control valve installed on the C4 feed-line as the manipulated variable. Such a scheme is capable of maintaining the desirable steady state that achieves high product purity and reactant conversion. However, a similar scheme that uses a control valve installed on the methanol feed-line as the manipulated variable shows severe oscillation. It is caused by multiplicity in the interaction between the temperature and stoichiometric control loops. 相似文献
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Decentralized control of the Tennessee Eastman Challenge Process 总被引:3,自引:0,他引:3
N. Lawrence Ricker 《Journal of Process Control》1996,6(4):205-221
A decentralized control system is developed for the Tennessee Eastman Challenge Process (TE problem). The design procedure begins with the selection of the method for production-rate control, to which inventory controls and other functions are then coordinated. Results show that production rate can be maximized at any of the three standard product compositions, even when the feed of reactant A is lost. All specifications of the challenge problem are satisfied despite large disturbances in feed composition and reaction kinetics. Variability in product rate and quality is less than that seen in previous studies. The process can operate on-spec for long periods without feedback from composition measurements. Setpoints for certain variables (such as reactor temperature and concentrations of A and C in the reactor feed) must be chosen a priori, and the effect on operating cost is estimated. The performance of the proposed decentralized control is compared to that of a nonlinear model predictive control (NMPC) developed previously. There appears to be little, if any, advantage to the use of NMPC in this application. In particular, the decentralized strategy does a better job of handling constraints - an area in which NMPC is reputed to excel. Reasons for this are discussed. 相似文献
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图解设计法,可以相对较少的已知数据快速、直观地获得反应精馏塔的结构和操作参数。本文在转换组成变量的基础上,系统地推导了反应精馏塔板组成线方程及设计可行性判据,提出了基于塔板组成线进行反应精馏图解设计的策略,并对理想反应体系进行了实例设计计算。研究结果表明:利用塔板组成线进行反应精馏设计可同时获得多组可行设计方案,比现有精馏线和剩余曲线设计方法更为有效,并有利于设计的优化和经济效益评价。 相似文献
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为了切实解决延迟焦化常规控制出现的问题,在介绍鲁棒多变量预估控制技术(RMPCT)以及焦化工艺的基础上,制定了装置总体控制目标,并根据对焦化装置干扰来源的分析以及联合循环比工作特点的分析,提出了通过引入干扰事件模型克服干扰,通过调节联合循环比提高处理量和降低能耗的控制策略。由于加热炉与分馏塔既有联系又相对独立,因此将控制器范围划分为反应控制器和分馏控制器。工业实践表明,该控制策略和控制器范围划分是合理的,采用RMPCT可以有效抵御焦炭塔切换带来的干扰,装置平稳运行,降低了产品质量波动,增加了装置处理量。RMPCT应用于延迟焦化装置是成功和有效的。 相似文献
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Plant-wide design and control of acetic acid dehydration system via heterogeneous azeotropic distillation and divided wall distillation 总被引:1,自引:0,他引:1
San-Jang Wang Chi-Ju Lee Shi-Shang Jang Shyan-Shu Shieh 《Journal of Process Control》2008,18(1):45-60
Energy-saving plant-wide design and plant-wide control of an acetic acid dehydration system with the feed containing methyl acetate and p-xylene are investigated in the study. A heterogeneous azeotropic distillation using isobutyl acetate as an entrainer is designed to obtain high-purity acetic acid at the column bottom and to keep a small acetic acid loss through the top aqueous draw. The accumulation of p-xylene in the column is avoided by adding a side product stream. The mixture in the aqueous phase of decanter, containing mostly water, methyl acetate, and isobutyl acetate is separated using a divided wall distillation column. The whole acetic acid dehydration system includes a heterogeneous azeotropic distillation column and a divided wall distillation column.The control strategies using temperature loops are proposed for this acetic acid dehydration system. For the heterogeneous azeotropic distillation column, the requirements for acetic acid compositions in both the aqueous phase of the decanter and the column bottom can be satisfied by designing entrainer inventory temperature control and cascade temperature control simultaneously. The stages of controlled temperatures are chosen by singular value decomposition and closed-loop analysis methods based on the criteria of minimum entrainer makeup. For the divided wall distillation column, steady-state analysis methods are used for the selection of proper controlled and manipulated variables and the determination of their pairings. Dynamic simulation results demonstrate that the proposed plant-wide control strategy can maintain product purities and reject external disturbances in feed flow and composition changes as well as internal disturbances such as changes in liquid and vapor splits. 相似文献
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一种新型非线性Hammerstein系统动态矩阵控制算法 总被引:1,自引:0,他引:1
将动态矩阵控制策略(DMC)推广到由一个非线性静态多项式函数和一个线性动态阶跃响应环节组成的非线性Ham-merstein系统,详细地给出了该新型非线性Hammerstein系统动态矩阵控制算法(NLH-DMC).把NLH-DMC应用于一套强非线性pH中和过程,给定值跟踪和抗干扰仿真结果表明,NLH-DMC比线性DMC(LDMC)和过程控制领域常用的非线性PID(NL-PID)具有更好的控制性能.进一步的仿真实验证实,NLH-DMC不仅具有良好的控制响应,而且在存在较大模型误差时仍具有很好的稳定性及鲁棒性. 相似文献