Dissertations / Theses: 'Chemical process control'

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Wang, Chuangnan. "Ultrasonic technique for chemical process control." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24442.

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Ultrasound has found application in chemical processing control using both low power, high frequency monitoring techniques and high power, low frequency process enhancement approaches. In many cases, standard ultrasonic systems are retrofitted to a process and while these produce efficiency improvements, the design of bespoke systems may offer more potential. In particular, this Thesis has considered two techniques used in the biomedical field; harmonic imaging and high intensity focused ultrasound (HIFU) and has translated these into ultrasonic transducers for use in an industrial process control system. Traditional ultrasound monitoring techniques are based on operation in the linear domain and are used to monitor chemical processes by measurement of material acoustic velocity, attenuation or based on spectral analysis. Both active and passive methods have been reported for application in this industrial sector. One issue is the presence of multiple reflections in the received ultrasonic signal which can mask the signals of interest from the load medium. This Thesis has considered a new ultrasonic monitoring approach using a combination of both linear and nonlinear spectral components. This was applied to high-throughput products and a dual frequency transducer designed and fabricated to acquire the ultrasonic backscattered signals in both the fundamental and second harmonic frequency regimes. The additional information provided by the harmonic device enabled discrimination between shampoo and conditioner products with the same density, but different molecular weights. HIFU transducer array designs are then considered for high power, low frequency chemical process enhancement applications. Typical applications of high power ultrasound use single or multiple discrete transducers to insonify a process. These are effective, but inflexible in the delivery of the ultrasonic field. The application of a HIFU array would provide control of the high power focal region in the load medium, which offer advantages to industry. Two transducer array approaches have been considered in this Thesis based on piezoelectric composite configurations. Three HIFU arrays based on the 1-3 piezocomposite have been fabricated to operate between 200-400kHz and fully characterised to evaluate their high power performance. A second transducer configuration was based on a novel 2-2 piezocomposite with a 2 layer stacked configuration. Simulation of this transducer design illustrated its potential for high power applications, although a number of fabrication issues resulted in the manufactured array not operating at full capacity. Importantly, the transducer configurations developed in this Thesis are shown to induce cavitation through the standard aluminium foil test.

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Fien, Gert-Jan A. F. "Studies on process synthesis and process integration." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-08032007-102242/.

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Papazoglou, Michael. "Multivariate statistical process control of chemical processes." Thesis, University of Newcastle Upon Tyne, 1998. http://hdl.handle.net/10443/408.

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The thesis describes the application of Multivariate Statistical Process Control (MSPC) to chemical processes for the task of process performance monitoring and fault detection and diagnosis. The applications considered are based upon polymerisation systems. The first part of the work establishes the appropriateness of MSPC methodologies for application to modern industrial chemical processes. The statistical projection techniques of Principal Component Analysis and Projection to Latent Structures are considered to be suitable for analysing the multivariate data sets obtained from chemical processes and are coupled with methods and techniques for implementing MSPC. A comprehensive derivation of these techniques are presented. The second part introduces the procedures that require to be followed for the appropriate implementation of MSPC-based schemes for process monitoring, fault detection and diagnosis. Extensions of the available projection techniques that can handle specific types of chemical processes, such as those that exhibit non-linear characteristics or comprise many distinct units are also presented. Moreover, the novel technique of Inverse Projection to Latent Structures that extends the application of MSPC-based schemes to processes where minimal process data is available is introduced. Finally, the proposed techniques and methodologies are illustrated by applications to a batch and a continuous polymerisation process.

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Paulson, Joel Anthony. "Modern control methods for chemical process systems." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109672.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 301-322).
Strong trends in chemical engineering have led to increased complexity in plant design and operation, which has driven the demand for improved control techniques and methodologies. Improved control directly leads to smaller usage of resources, increased productivity, improved safety, and reduced pollution. Model predictive control (MPC) is the most advanced control technology widely practiced in industry. This technology, initially developed in the chemical engineering field in the 1970s, was a major advance over earlier multivariable control methods due to its ability to seamlessly handle constraints. However, limitations in industrial MPC technology spurred significant research over the past two to three decades in the search of increased capability. For these advancements to be widely implemented in industry, they must adequately address all of the issues associated with control design while meeting all of the control system requirements including: -- The controller must be insensitive to uncertainties including disturbances and unknown parameter values. -- The controlled system must perform well under input, actuator, and state constraints. -- The controller should be able to handle a large number of interacting variables efficiently as well as nonlinear process dynamics. -- The controlled system must be safe, reliable, and easy to maintain in the presence of system failures/faults. This thesis presents a framework for addressing these problems in a unified manner. Uncertainties and constraints are handled by extending current state-of-the-art MPC methods to handle probabilistic uncertainty descriptions for the unknown parameters and disturbances. Sensor and actuator failures (at the regulatory layer) are handled using a specific internal model control structure that allows for the regulatory control layer to perform optimally whenever one or more controllers is taken offline due to failures. Non-obvious faults, that may lead to catastrophic system failure if not detected early, are handled using a model-based active fault diagnosis method, which is also able to cope with constraints and uncertainties. These approaches are demonstrated on industrially relevant examples including crystallization and bioreactor processes.
by Joel Anthony Paulson.
Ph. D.

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Alici, Semra. "Dynamic data reconciliation using process simulation software and model identification tools." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3025133.

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Chokshi, Nirav N. "Holonic process control : a distributed, collaborative approach to the control of chemical process operations." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615021.

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Mulder, Pieter. "Statistical process control of dynamic processes." Thesis, University of Newcastle Upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289209.

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Zhu, Jianye. "Integrated process design and control of chemical processes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0009/NQ34864.pdf.

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Rawlings, Blake. "Discrete Dynamics in Chemical Process Control and Automation." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/862.

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Formal verification has previously been applied to chemical plant control and automation systems to ensure that they operate as intended. This dissertation examines the related objective of proving that a particular control system does not operate as intended. To this end, we present a set of specifications that address certain aspects of the correct operation of a general control system. Some of those specifications, which relate to invariance and reachability of states that satisfy given logical constraints, do not fall within the classes of specifications that have been addressed in previous work related to the falsification of hybrid systems. For a specification from this class, a sound falsification algorithm is presented which can guarantee that a hybrid system does not meet the specification. The algorithm involves abstraction, as a finite-state discrete system, of the infinite-state hybrid dynamical system that arises when discrete control is applied to a continuous process. The falsification result relies on new results that we present which concern the supervisory control of discrete event systems subject to specifications that involve multiple reachability requirements. The methods we present are applied to two industrial case studies, which were provided by The Dow Chemical Company. We also present two software tools which apply the methods that we have developed. The first tool, SynthSMV, is an extension of the model checking solver NuSMV that can solve some supervisory control problems. NuSMV was chosen as the basis for our work in falsification because previous work has shown that its symbolic model checking algorithms can handle models of industrial-scale control systems in the context of verification. The second tool, st2smv, translates industrial control code to a formal model that can be solved using SynthSMV. The approach is similar to what has been done in previous work that focused on model checking and verification, with some extensions to enable the application of our work concerning supervisory control and falsification.

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Botha, Paul Jacobus. "Detecting change in complex process systems with phase space methods." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019/508.

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Sinangil, Mehmet Selcuk. "Modeling and control on an industrial polymerization process." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/10150.

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Lai, Sau Man. "Feasibility and flexibility in chemical process design /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CBME%202009%20LAI.

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Shi, Ruijie. "Subspace identification methods for process dynamic modeling /." *McMaster only, 2001.

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Smith, Taber H. (Taber Hardesty). "Device independent process control of dielectric chemical mechanical polishing." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/87156.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2000.
Includes bibliographical references (p. 157-162).
by Taber Hardesty Smith.
Ph.D.

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Esmaili, Ali. "Control relevant model identification with prior knowledge /." *McMaster only, 2001.

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Liu, Pi-Shien 1960. "Real-time process control and simulation for chemical mix facility." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276673.

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The purpose of this study is to design a real-time control and simulation system for a chemical mix facility. A simulation circuit board and software simulation in an IBM personal computer emulated the real-time chemical mix facility. A second personal computer controlled the plant. The parallel port in the IBM PC computer serves as a communication path between the controlled and controlling system. Results show that the simulation can assist the design of the actual system.

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Koulouris, Alexandros. "Multiresolution learning in nonlinear dynamic process modeling and control." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11376.

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Padley, Mark Andrew. "Incorporating operability measures into the process synthesis stage of design." Phd thesis, Department of Chemical Engineering, 1991. http://hdl.handle.net/2123/5996.

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Nikraz, Magid. "Integration of operational tasks in chemical plants." Thesis, Nikraz, Magid (2007) Integration of operational tasks in chemical plants. PhD thesis, Murdoch University, 2007. https://researchrepository.murdoch.edu.au/id/eprint/741/.

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The overall, coordinated management of different operational tasks in a chemical plant can improve operational efficiency. These operational tasks can be hierarchically categorised, from the lowest to highest level, as: data acquisition; regulatory control; monitoring; data reconciliation; fault detection and diagnosis; supervisory control; scheduling; and planning. Although each of these tasks is responsible for a particular function, they are dependent on each other, which is why an approach wherein all the different tasks can be integrated into a single unified framework is desirable. While integration has important benefits such as a significant reduction in operator workload and improved decision making, its realisation presents considerable challenges. Few previous works have addressed this topic and even fewer have investigated recent computing paradigms which may greatly assist in the development of a unifying framework. Multi-agent systems were introduced and investigated in this study as a possible means for achieving integration of operational tasks in chemical plants. Multi-agent systems are the subject of a sub-field of computing research known as agent-based computing. Agent-based computing represents a relatively recent and powerful high-level computing paradigm. Initially, a number of software applications were developed for the purposes of this study to assist realisation of the operational tasks. To simplify the process of system development and provide guidance for those unfamiliar with multi-agent systems wishing to adopt the proposed technique, an extensive methodology was devised. The operational tasks were then integrated using the proposed methodology to form an integrated multi-agent system, with the pilot plant at Murdoch University being used as a test base for the solution. The results were positive and demonstrated that the proposed agent-based solution was able to effectively account for the pilot plant setting. It was concluded that, in addition to presently available integration techniques and base technologies, the agent-based approach to integration of operational tasks in chemical plants presents a viable alternative solution.

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Nikraz, Magid. "Integration of operational tasks in chemical plants." Nikraz, Magid (2007) Integration of operational tasks in chemical plants. PhD thesis, Murdoch University, 2007. http://researchrepository.murdoch.edu.au/741/.

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The overall, coordinated management of different operational tasks in a chemical plant can improve operational efficiency. These operational tasks can be hierarchically categorised, from the lowest to highest level, as: data acquisition; regulatory control; monitoring; data reconciliation; fault detection and diagnosis; supervisory control; scheduling; and planning. Although each of these tasks is responsible for a particular function, they are dependent on each other, which is why an approach wherein all the different tasks can be integrated into a single unified framework is desirable. While integration has important benefits such as a significant reduction in operator workload and improved decision making, its realisation presents considerable challenges. Few previous works have addressed this topic and even fewer have investigated recent computing paradigms which may greatly assist in the development of a unifying framework. Multi-agent systems were introduced and investigated in this study as a possible means for achieving integration of operational tasks in chemical plants. Multi-agent systems are the subject of a sub-field of computing research known as agent-based computing. Agent-based computing represents a relatively recent and powerful high-level computing paradigm. Initially, a number of software applications were developed for the purposes of this study to assist realisation of the operational tasks. To simplify the process of system development and provide guidance for those unfamiliar with multi-agent systems wishing to adopt the proposed technique, an extensive methodology was devised. The operational tasks were then integrated using the proposed methodology to form an integrated multi-agent system, with the pilot plant at Murdoch University being used as a test base for the solution. The results were positive and demonstrated that the proposed agent-based solution was able to effectively account for the pilot plant setting. It was concluded that, in addition to presently available integration techniques and base technologies, the agent-based approach to integration of operational tasks in chemical plants presents a viable alternative solution.

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Seewoo, Shilpa. "Control of the desupersaturation reactor used in the SPARRO process." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/5985.

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Bibliography: leaves 84-86.
The work described in this thesis focuses on the Slurry Precipitation And Recycle Reverse Osmosis (SPARRO) process. The process was designed to treat calcium sulphate (gypsum) scaling mine waters by encouraging preferentlal crystal growth onto introduced seeds, rather than on the reverse osmosis membranes. The major problem faced by the SPARRO process was the short membrane life span, possibly due to damage caused by contact with gypsum crystals. Gypsum exists in two extreme morphologies, plate and needle-like crystals, which are formed from high (0.2 M) and low (0.04 M) concentration of CaCl2 and Na2SO4 solutions respectively. This research reinvestigated the SPARRO process from a crystallisation perspective with the aims of: • Increasing the level of understanding of fundamental aspects of the SPARRO process. • Developing a technique to quantify the gypsum crystal morphology. • Developing design specifications for a 5 L lab scale desupersaturation reactor. • Developing and defining the critical parameters in controlling production of gypsum of a specified crystal size and morphology in the desupersaturation reactor.

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Pfeiffer, Celaya Carlos Fernando. "Analysis and design of heterogeneous control laws for nonlinear chemical processes /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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Faanes, Audun. "Controllability analysis for process and control system design." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-35.

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Controllability is the ability of a process to achieve acceptable performance, and in this thesis we use controllability analysis in the design of buffer tanks, feedforward controllers, and multivariable controllers such as model predictive control (MPC).

There is still an increasing pressure on the process industry, both from competitors (prize and quality) and the society (safety and pollution), and one important contribution is a smooth and stable production. Thus, it is important to dampen the effect of uncontrolled variations (disturbances) that the process may experience.

The process itself often dampens high-frequency disturbances, and feedback controllers are installed to handle the low-frequency part of the disturbances, including at steady state if integral action is applied. However, there may be an intermediate frequency range where neither of these two dampens the disturbances sufficiently. In the first part of this thesis we present methods for the design of buffer tanks based on this idea. Both mixing tanks for quality disturbances and surge tanks with “slow” level control for flow-rate variations are addressed.

Neutralization is usually performed in one or several mixing tanks, and we give recommendations for tank sizes and the number of tanks. With local PI or PID control, we recommend equal tanks, and give a simple formula for the total volume. We also give recommendations for design of buffer tanks for other types of processes. We propose first to determine the required transfer function to achieve the required performance, and thereafter to find a physical realization of this transfer function.

Alternatively, if measurements of the disturbances are available, one may apply feedforward control to handle the intermediate frequency range. Feedforward control is based mainly on a model, and we study the effect of model errors on the performance. We define feedforward sensitivities. For some model classes we provide rules for when the feedforward controller is effective, and we also design robust controllers such as μ -optimal feedforward controllers.

Multivariable controllers, such as model predictive control (MPC), may use both feedforward and feedback control, and the differences between these two also manifest themselves in a multivariable controller. We use the class of serial processes to gain insight into how a multivariable controller works. For one specific MPC we develop a state space formulation of the controller and its state estimator under the assumption that no constraints are active. Thus, for example the gains of each channel of the MPC (from measurements to the control inputs) can be found, which gives further insight into to the controller. Both a neutralization process example and an experiment are used to illustrate the ideas.

Paper 4 reprinted with kind permission of the Research Council of Norway Paper 8 reprinted with kind permission of Elsevier Publishing, http://www.sciencedirect.com

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Rigopoulos, Apostolos. "Estimation and control of sheet forming processes." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/10215.

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Abbas, A. "The integration of controllability into process design." Thesis, University of Bath, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374607.

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Diez-Lazaro, Alvaro. "Studies in process analysis and control in batch reactors." Thesis, University of Strathclyde, 2002. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21206.

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This work is part of a number of projects dealing with the development of novel techniques for better analysis and control of chemical processes carried out in batch reactors. The problems of pH measurement and sampling, linked to the implementation of NMR and HPLC on-line analysers, are presented as key areas in this development work. Also, part of the engineering work summarised in this thesis assisted the work of other researchers who participated in the project. In the area of sampling, the difficulties associated with the collection of representatives samples from agitated vessels are introduced. Also, the ideas of calibration and modelling of sampling systems are presented. Modelling tests were used to optimise the design and development of a fast sampling loop system to obtain representative samples from stirred vessels. In addition to this, the modelling studies also assisted the work of other researchers in the project who needed the kinetic and heat-exchange parameters for the process of esterification of crotonic acid. The fast sampling loop was shown to be adequate for the implementation of a low-field NMR system for on-line analysis. The development of discrete samplers designed to collect, dilute and deliver representative samples for LC analysis is also covered in this work. A Mark IV prototype of LC sampler was tested and developed to acceptable levels. In the area of pH measurement the advantages and disadvantages of the use of thermally grown iridium-oxide electrodes are introduced. Their response was compared to that of standard glass electrodes and found to be faster, more stable at high temperatures and no alkaline error was observed. However, the problem of drift of the signals was not fully overcome and it is presented as the limiting factor in the use of the sensors for on-line industrial measurements. Finally, a new type of total iridium-oxide probe is presented.

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Peel, Christine. "Aspects of neural networks for modelling and control." Thesis, University of Newcastle upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262989.

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Narraway, Lawrence Trevelyan. "Selection of process control structure based on economics." Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/7949.

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Reeves, Deborah Edwards. "A comprehensive approach to control configuration design for complex systems." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/10207.

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Chiu, Min-Sen. "A methodology for the synthesis of robust decentralized control systems." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/11314.

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Kingsley, Philip John. "Dielectric Monitoring and Control of an Automated Resin Transfer Molding Process." W&M ScholarWorks, 1991. https://scholarworks.wm.edu/etd/1539625663.

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Yan, Ming. "Multi-objective, plant-wide control and optimization of chemical processes /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/9918.

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Park, Cody. "Sliding Mode Control and Electrical Capacitance Volume Tomography for Advanced Control of the Chemical Looping Process." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu153148162698589.

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Mediliyegedara, T. K. K. R. "Intelligent process monitoring and control approaches for electro chemical discharge machining." Thesis, Glasgow Caledonian University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426445.

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Graciano, José Eduardo Alves. "Real time optimization in chemical process: evaluation of strategies, improvements and industrial application." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-12072016-094348/.

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The increasing economic competition drives the industry to implement tools that improve their processes efficiencies. The process automation is one of these tools, and the Real Time Optimization (RTO) is an automation methodology that considers economic aspects to update the process control in accordance with market prices and disturbances. Basically, RTO uses a steady-state phenomenological model to predict the process behavior, and then, optimizes an economic objective function subject to this model. Although largely implemented in industry, there is not a general agreement about the benefits of implementing RTO due to some limitations discussed in the present work: structural plant/model mismatch, identifiability issues and low frequency of set points update. Some alternative RTO approaches have been proposed in literature to handle the problem of structural plant/model mismatch. However, there is not a sensible comparison evaluating the scope and limitations of these RTO approaches under different aspects. For this reason, the classical two-step method is compared to more recently derivative-based methods (Modifier Adaptation, Integrated System Optimization and Parameter estimation, and Sufficient Conditions of Feasibility and Optimality) using a Monte Carlo methodology. The results of this comparison show that the classical RTO method is consistent, providing a model flexible enough to represent the process topology, a parameter estimation method appropriate to handle measurement noise characteristics and a method to improve the sample information quality. At each iteration, the RTO methodology updates some key parameter of the model, where it is possible to observe identifiability issues caused by lack of measurements and measurement noise, resulting in bad prediction ability. Therefore, four different parameter estimation approaches (Rotational Discrimination, Automatic Selection and Parameter estimation, Reparametrization via Differential Geometry and classical nonlinear Least Square) are evaluated with respect to their prediction accuracy, robustness and speed. The results show that the Rotational Discrimination method is the most suitable to be implemented in a RTO framework, since it requires less a priori information, it is simple to be implemented and avoid the overfitting caused by the Least Square method. The third RTO drawback discussed in the present thesis is the low frequency of set points update, this problem increases the period in which the process operates at suboptimum conditions. An alternative to handle this problem is proposed in this thesis, by integrating the classic RTO and Self-Optimizing control (SOC) using a new Model Predictive Control strategy. The new approach demonstrates that it is possible to reduce the problem of low frequency of set points updates, improving the economic performance. Finally, the practical aspects of the RTO implementation are carried out in an industrial case study, a Vapor Recompression Distillation (VRD) process located in Paulínea refinery from Petrobras. The conclusions of this study suggest that the model parameters are successfully estimated by the Rotational Discrimination method; the RTO is able to improve the process profit in about 3%, equivalent to 2 million dollars per year; and the integration of SOC and RTO may be an interesting control alternative for the VRD process.
O aumento da concorrência motiva a indústria a implementar ferramentas que melhorem a eficiência de seus processos. A automação é uma dessas ferramentas, e o Real Time Optimization (RTO) ou Otimização em Tempo Real, é uma metodologia de automação que considera aspectos econômicos e restrições de processos e equipamentos para atualizar o controle do processo, de acordo com preços de mercado e distúrbios. Basicamente, o RTO usa um modelo fenomenológico em estado estacionário para predizer o comportamento do processo, em seguida, otimiza uma função objetivo econômica sujeita a esse modelo. Embora amplamente utilizado na indústria, não há ainda um consenso geral sobre os benefícios da implementação do RTO, devido a algumas limitações discutidas no presente trabalho: incompatibilidade estrutural entre planta e modelo, problemas de identificabilidade e baixa frequência de atualização dos set points. Algumas metodologias de RTO foram propostas na literatura para lidar com o problema da incompatibilidade entre planta e modelo. No entanto, não há uma comparação que avalie a abrangência e as limitações destas diversas abordagens de RTO, sob diferentes aspectos. Por esta razão, o método clássico de RTO é comparado com metodologias mais recentes, baseadas em derivadas (Modifier Adaptation, Integrated System Optimization and Parameter estimation, and Sufficient Conditions of Feasibility and Optimality), utilizando-se o método de Monte Carlo. Os resultados desta comparação mostram que o método clássico de RTO é coerente, desde que seja proporcionado um modelo suficientemente flexível para se representar a topologia do processo, um método de estimação de parâmetros apropriado para lidar com características de ruído de medição e um método para melhorar a qualidade da informação da amostra. Já os problemas de identificabilidade podem ser observados a cada iteração de RTO, quando o método atualiza alguns parâmetros-chave do modelo, o que é causado principalmente pela ausência de medidas e ruídos. Por esse motivo, quatro abordagens de estimação de parâmetros (Discriminação Rotacional, Seleção Automática e Estimação de Parâmetros, Reparametrização via Geometria Diferencial e o clássico Mínimos Quadrados não-lineares) são avaliados em relação à sua capacidade de predição, robustez e velocidade. Os resultados revelam que o método de Discriminação Rotacional é o mais adequado para ser implementado em um ciclo de RTO, já que requer menos informação a priori, é simples de ser implementado e evita o sobreajuste observado no método de Mínimos Quadrados. A terceira desvantagem associada ao RTO é a baixa frequência de atualização dos set points, o que aumenta o período em que o processo opera em condições subotimas. Uma alternativa para lidar com este problema é proposta no presente trabalho, integrando-se o RTO e o Self-Optimizing Control (SOC) através de um novo algoritmo de Model Predictive Control (MPC). Os resultados obtidos com a nova abordagem demonstram que é possível reduzir o problema da baixa frequência de atualização dos set points, melhorando o desempenho econômico do processo. Por fim, os aspectos práticos da implementação do RTO são discutidos em um estudo de caso industrial, que trata de um processo de destilação com bomba de calor, localizado na Refinaria de Paulínia (REPLAN - Petrobras). Os resultados deste estudo sugerem que os parâmetros do modelo são estimados com sucesso pelo método de Discriminação Rotacional; que o RTO é capaz de aumentar o lucro do processo em cerca de 3%, o equivalente a 2 milhões de dólares por ano; e que a integração entre SOC e RTO pode ser uma alternativa interessante para o controle deste processo de destilação.

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Reeves, Deborah Edwards. "Interaction measures for nonsquare decentalized control structures." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/10206.

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Weighell, Michael. "The performance of adaptive multivariate statistical process control schemes in the chemical and process industries." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268433.

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38

Bansal, Vikrant. "Analysis, design and control optimization of process systems under uncertainty." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/8212.

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39

Bakshi, Bhavik Ramesh. "Multi-resolution methods for modeling, analysis and control of chemical process operations." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13203.

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40

Ruedisueli, Robert Louis. "Cyclically optimized electrochemical processes /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10576.

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41

Ekawati, Estiyanti. "The development of systematic controllability assessment for process control designs." Thesis, Ekawati, Estiyanti (2003) The development of systematic controllability assessment for process control designs. PhD thesis, Murdoch University, 2003. https://researchrepository.murdoch.edu.au/id/eprint/62/.

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Abstract:

Chemical process industries are constantly challenged to operate profitably and efficiently, despite the presence of significant uncertainties and disturbances on the operational conditions, and various operational limitations. The capability to meet the challenge relies on the quality of process control design, which should integrate the dynamic controllability characteristics in addition to the traditional economic considerations. The focus of this thesis is the development of a systematic controllability assessment framework for process control design. The framework addresses the controllability aspects in process and controller structures, as well as in time-domain dynamic performances. The aim is to provide clearer relationships between process profitability, controllability, and operational switching strategies in response to variations in the operating conditions. The skeleton of the framework is a mathematical optimisation algorithm. This algorithm considers the structural, operational and economic problems arising in process control design as a progressive, dynamic, and uncertain semi-infinite mixed integer nonlinear programming problem. The algorithm is an iterative, two-level optimisation, which determines the optimum process design and the associated controllability index within an optimisation window. The window progresses along a time horizon, ensuring optimal process design within the window while accommodating the design switching during the course of load variations in a larger time horizon. The controllability index quantifies the design capability to satisfy a given economic objective. Unique to other existing approaches, the process controllability index is computed based on the multi-dimensional geometric representation of the disturbances and uncertainties, measured process dynamics, and feasible operating spaces. These representations account for variable interactions existing in a multivariable process operation, in contrast to separate quantification in traditional single variable assessments. The geometric computation of the index requires the analysis and elimination of redundant measurement variables, which occur in different combinations at different process and controller structures. The redundancy is detected and eliminated based on statistical collinearity among the process data, allowing the assessment to focus on the retained functional variables and the associated critical disturbances and uncertainties. The redundancy analysis is tailored with a dynamic mixed integer nonlinear programming (MINLP) solver, which is dedicated to select the optimum process and controller structure within the design. The solver is developed based on the branch and bound strategy over the design tree, which consists of alternative nonlinear programming (NLP) sub-problems. In addition to the redundancy analysis, the solver is equipped with a compact MINLP formulation, an alternating depth-first and breadth-first search strategy, sub-problems. The tailored strategy ensures fast and efficient convergence of convex problems, as well as superior optimum of non-convex counterparts. Finally, the framework is performed within a time window, which progresses along the time horizon. This strategy provides realistic responses to major variations along greater length of time, by switching between optimum operational modes, while maintaining the optimum process controllability. The performance of the framework is illustrated through several case studies. Each case demonstrates the novelty of addressing various computational features in a concise algorithm. These include the industrial case, which involves the systematic controllability assessment of an industrial five-effect liquor-burning evaporator within an Alumina refinery, which highlights the contribution of this framework in bridging the process design methodologies with the industrial implementation. The thesis consists of eight chapters, presenting the systematic development of the framework. The numerical implementations have been organised in a MATLAB Toolbox, accompanied with the relevant case studies.

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42

Ekawati, Estiyanti. "The development of systematic controllability assessment for process control designs." Ekawati, Estiyanti (2003) The development of systematic controllability assessment for process control designs. PhD thesis, Murdoch University, 2003. http://researchrepository.murdoch.edu.au/62/.

Full text

Abstract:

Chemical process industries are constantly challenged to operate profitably and efficiently, despite the presence of significant uncertainties and disturbances on the operational conditions, and various operational limitations. The capability to meet the challenge relies on the quality of process control design, which should integrate the dynamic controllability characteristics in addition to the traditional economic considerations. The focus of this thesis is the development of a systematic controllability assessment framework for process control design. The framework addresses the controllability aspects in process and controller structures, as well as in time-domain dynamic performances. The aim is to provide clearer relationships between process profitability, controllability, and operational switching strategies in response to variations in the operating conditions. The skeleton of the framework is a mathematical optimisation algorithm. This algorithm considers the structural, operational and economic problems arising in process control design as a progressive, dynamic, and uncertain semi-infinite mixed integer nonlinear programming problem. The algorithm is an iterative, two-level optimisation, which determines the optimum process design and the associated controllability index within an optimisation window. The window progresses along a time horizon, ensuring optimal process design within the window while accommodating the design switching during the course of load variations in a larger time horizon. The controllability index quantifies the design capability to satisfy a given economic objective. Unique to other existing approaches, the process controllability index is computed based on the multi-dimensional geometric representation of the disturbances and uncertainties, measured process dynamics, and feasible operating spaces. These representations account for variable interactions existing in a multivariable process operation, in contrast to separate quantification in traditional single variable assessments. The geometric computation of the index requires the analysis and elimination of redundant measurement variables, which occur in different combinations at different process and controller structures. The redundancy is detected and eliminated based on statistical collinearity among the process data, allowing the assessment to focus on the retained functional variables and the associated critical disturbances and uncertainties. The redundancy analysis is tailored with a dynamic mixed integer nonlinear programming (MINLP) solver, which is dedicated to select the optimum process and controller structure within the design. The solver is developed based on the branch and bound strategy over the design tree, which consists of alternative nonlinear programming (NLP) sub-problems. In addition to the redundancy analysis, the solver is equipped with a compact MINLP formulation, an alternating depth-first and breadth-first search strategy, sub-problems. The tailored strategy ensures fast and efficient convergence of convex problems, as well as superior optimum of non-convex counterparts. Finally, the framework is performed within a time window, which progresses along the time horizon. This strategy provides realistic responses to major variations along greater length of time, by switching between optimum operational modes, while maintaining the optimum process controllability. The performance of the framework is illustrated through several case studies. Each case demonstrates the novelty of addressing various computational features in a concise algorithm. These include the industrial case, which involves the systematic controllability assessment of an industrial five-effect liquor-burning evaporator within an Alumina refinery, which highlights the contribution of this framework in bridging the process design methodologies with the industrial implementation. The thesis consists of eight chapters, presenting the systematic development of the framework. The numerical implementations have been organised in a MATLAB Toolbox, accompanied with the relevant case studies.

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43

Charos, Georgios Nikolaou. "Model predictive constrained control : development, implementation, and decentralization." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/11311.

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44

Haznedar, Baris. "Reduced order infinite horizon Model Predictive Control of sheet forming processes." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/11222.

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45

Nunes, Giovani Cavalcanti. "Design and analysis of multivariable predictive control applied to an oil-water-gas separator a polynomial approach /." [Gainesville, Fla.] : University of Florida, 2001. http://etd.fcla.edu/etd/uf/2001/anp1585/Phd.pdf.

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Thesis (Ph. D.)--University of Florida, 2001.
Title from first page of PDF file. Document formatted into pages; contains viii, 118 p.; also contains graphics. Vita. Includes bibliographical references (p. 115-117).

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46

Williamson, Alex Stewart. "Dielectric Sensor In-Situ Control of the RTM Composite Fabrication Process." W&M ScholarWorks, 1990. https://scholarworks.wm.edu/etd/1539625589.

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47

Pattinson, Thomas. "Optimal sysnthesis of storageless batch plants using the Process Intermediate Storage Operational policy." Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-08272008-125107/.

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48

Wang, Dawei. "Robust system identification and robust model predictive control with applications to chemical engineering processes." Thesis, The University of Sydney, 2001. https://hdl.handle.net/2123/27788.

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This thesis deals with problems in two closely related research areas, system identification (SYSID) and model predictive control (MPC), which are both important in industrial. process applications. The robustness of SYSID and MPC is the main concern of the thesis. The focus of the first part of the thesis is to develop Robust System Identification Strategies that yield effective and robust estimates of system model and characteristics under the uncertainty of a priori knowledge. The incorporation of the techniques taken from classical system identification approaches as well as robust identification design based on Wavelets density estimation will ensure that the estimation of system is “optimal” in all assumptions and supposed operation conditions considered of the process error. The conclusive result has been a robust and effective estimator that is in accordance to the industrial requirements, in regards to practical implementation of these strategies. This method is applied to most system models and estimation algorithms (especially on—line recursive algorithms) and takes the conventional ones as special cases. This approach has many innovative features, one being the design of robust estimator which is insensitive to deviation from the various assumptions about the prediction error. This characteristic makes a robust estimation to be suitable for most error distributions. This methodology would then be capable of solving a large number of difficult problems in relation to modeling a system using contaminated data facing in fields such as industry, science and economics. The second problem addressed in the thesis is to develop Robust Model Predictive Control Strategies that yield effective and robust controller under the mismatch between plant and the models employed to describe the system. A new robust MPC design method is derived from comparison and discussion of the similarity between parameter estimation and MPC. The incorporation of techniques taken from standard model predictive control approaches as well as the robust controller design will ensure that the controller has better performance regarding assumptions on the nominal model and assumed plant-model mismatch. The result will be a robust and effective controller that is in accordance to the industrial requirements. Some properties of the proposed robust MPC design such as closed loop stability and performance tuning are investigated. The innovative feature of the robust MPC design makes the controller insensitive to deviation from the various assumptions about the nominal model, and to be suitable for most plant-model mismatches. The proposed design can take into account the compromise between efficiency, robustness as well as computation load. It is shown that it is an expansion of ' conventional MPC. The practical implications of the proposed robust system identification and robust MPC design methods are shown by means of chemical engineering process examples.

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49

Rogalsky, Dennis Wayne. "Quantifying plant model parameter effects on controller performance /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/9843.

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50

Ingram, Gordon Douglas. "Multiscale modelling and analysis of process systems /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19319.pdf.

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Dissertations / Theses on the topic 'Chemical process control'

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