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  • Conference paper
    Cecílio IM, Ottewill JR, Thornhill NF, 2015,

    Determining the propagation path of a disturbance in multi-rate systems

    , 9th IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes SAFEPROCESS 2015, Publisher: Elsevier, Pages: 784-789, ISSN: 1474-6670

    Several methods to derive the propagation path of a disturbance in process plants are applicable only to systems whose measurements are all available with the same sampling rate. This paper proposes a multi-rate method to identify the propagation path when measurements have different sampling rates. This is relevant for including in the analysis fast-sampled measurements from electromechanical equipment. The method is based on non-linear mutual prediction, which yields the directionality in the relationship between two time series. The method was demonstrated and validated, giving the expected outcome in an experimental case study, in which the root cause and propagation path of the disturbance were known.

  • Conference paper
    Leng D, Thornhill NF, 2015,

    Process Disturbance Cause & Effect Analysis Using Bayesian Networks

    , 9th IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes SAFEPROCESS 2015, Publisher: Elsevier, Pages: 1457-1464, ISSN: 1474-6670

    Process disturbances can propagate over entire plants and it can be difficult to locate their root causes from observed effects. Bayesian Networks offer a way to represent unit operations, processes and whole plants as probabilistic models which can be used to infer and rank likely causes from observed effects. This paper presents a methodology to use deterministic steady-state process models to derive Bayesian Networks based on alarm event detection. An example heat recovery network is used to illustrate the model building and inferential procedures.

  • Journal article
    Xenos DP, Kopanos GM, Cicciotti M, Thornhill NFet al., 2015,

    Operational optimization of networks of compressors considering condition-based maintenance

    , Computers and Chemical Engineering, Vol: 84, Pages: 117-131, ISSN: 1873-4375

    The paper presents a mixed integer linear programming model which deals with the optimal operation and maintenance of networks of compressors of chemical plants. This optimization model considers condition-based maintenance which involves the degradation of the condition of the compressors. The paper focuses on online and offline washing, two different cleaning procedures which reduce the extra power used by the compressors due to fouling. The state-of-the-art has demonstrated the optimal schedule of the maintenance of a single compressor neglecting the interactions between operation and maintenance of more than one compressor. The suggested optimization model studies a compressor station with multiple compressors and provides their optimal schedule and the best decisions for their washing. Different case scenarios examine the influence of different types of washing methods on the total costs of operation and maintenance. The paper demonstrates the benefits of the optimization and demonstrates that maintenance and operation have to be examined simultaneously and not separately, in contrast to common industrial practice and previous approaches in the literature.

  • Conference paper
    Noor IM, Thornhill NF, Fretheim H, Thorud Eet al., 2015,

    Quantifying the demand-side response capability of industrial plants to participate in power system frequency control schemes

    , IEEE Eindhoven PowerTech, PowerTech 2015, Publisher: IEEE

    Efficiency and sustainability considerations have propelled changes in power and process industries. These changes, which include the increased electrification of process industries, are causing concerns about the reliability of future electricity supplies, and therefore motivate the need for a Smart Grid on an industrial scale. This paper presents a method by which process automation engineers can assess the suitability of an oil and gas plant to participate in power system frequency control services. This paper discusses the necessary specifications for an automated system that enables effective variable operation by analysing the safe operating envelope of the plant. To do that, this paper proposes a methodology to characterise the appropriate actuators, variables and limits of set-point change. This methodology is applied to a case study representing an oil processing facility. The resulting analysis indicates demand-side response capability that the facility can provide without jeopardising operations on-site.

  • Conference paper
    Budinis S, Thornhill NF, 2015,

    Control of centrifugal compressors via model predictive control for enhanced oil recovery applications

    , 2nd IFAC Workshop on Automatic Control in Offshore Oil and Gas Production OOGP 2015, Publisher: Elsevier, Pages: 9-14, ISSN: 1474-6670

    This paper proposes a control system for integrated pressure and surge control of centrifugal compressors for enhanced oil recovery application. The proposed control system is based on linear model predictive control. A fully validated non-linear dynamic model was developed in order to simulate the operation of the compressor at full and partial load. The model of the compression system includes a main process line with the compressor and a recycle line with the antisurge recycle valve. Different disturbance and control tuning scenarios were tested and the response of the model predictive controller was analysed, evaluated and also compared with a traditional control system. Temperature effects have been taken into account in the model of the process and in the constraint formulation of the MPC optimization problem. The results show that the proposed control technique is able to meet the process demand while preventing surge and also minimizing the amount of gas recycle.

  • Conference paper
    Mechleri E, rivotti P, mac Dowell N, thornhill Net al., 2015,

    Flexibility issues and controllability analysis of a post-combustion CO2 capture plant integrated with a natural gas power plant

    , 8th Trondheim Conference on CO2 Capture, Transport and Storage (TCCS-8)
  • Journal article
    Xenos DP, Cicciotti M, Kopanos GM, Bouaswaig AEF, Kahrs O, Martinez-Botas R, Thornhill NFet al., 2015,

    Optimization of a network of compressors in parallel: Real Time Optimization (RTO) of compressors in chemical plants - An industrial case study

    , Applied Energy, Vol: 144, Pages: 51-63, ISSN: 0306-2619

    The aim of this paper is to present a methodology for optimizing the operation of compressors in parallel in process industries. Compressors in parallel can be found in many applications for example in compressor stations conveying gas through long pipelines and in chemical plants in which compressors supply raw or processed materials to downstream processes. The current work presents an optimization framework for compressor stations which describe integration of a short term and a long term optimization approach. The short-term part of the framework suggests the best distribution of the load of the compressors (where the time scale is minutes) and the long-term optimization provides the scheduling of the compressors for large time periods (where the time scale is days). The paper focuses on the short-term optimization and presents a Real Time Optimization (RTO) framework which exploits process data in steady-state operation to develop regression models of compressors. An optimization model employs the updated steady-state models to estimate the best distribution of the load of the compressors to reduce power consumption and therefore operational costs. The paper demonstrates the application of the RTO to a network of parallel industrial multi-stage centrifugal compressors, part of a chemical process in BASF SE, Germany. The results from the RTO application showed a reduction in power consumption compared to operation with equal load split strategy.

  • Conference paper
    Yang Y, Velayudhan A, Farid S, Thornhill Net al., 2015,

    Rapid ranking of high-concentration monoclonal antibody formulations using manufacturability indices

    , Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
  • Conference paper
    Yang Y, Farid S, Thornhill N, 2015,

    Facility fit prediction and debottlenecking of antibody purification facilities

    , Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
  • Journal article
    Kopanos GM, Xenos DP, Cicciotti M, Pistikopoulos EN, Thornhill NFet al., 2015,

    Optimization of a network of compressors in parallel: operational and maintenance planning - the air separation plant case

    , Applied Energy, Vol: 146, Pages: 453-470, ISSN: 1872-9118

    A general mathematical framework for the optimization of compressors operations in air separation plants that considers operating constraints for compressors, several types of maintenance policies and managerial aspects is presented. The proposed approach can be used in a rolling horizon scheme. The operating status, the power consumption, the startup and the shutdown costs for compressors, the compressor-to-header assignments as well as the outlet mass flow rates for compressed air and distillation products are optimized under full demand satisfaction. The power consumption in the compressors is expressed by regression functions that have been derived using technical and historical data. Several case studies of an industrial air separation plant are solved. The results demonstrate that the simultaneous optimization of maintenance and operational tasks of the compressors favor the generation of better solutions in terms of total costs.

  • Conference paper
    Zhang Y, Larsson M, Pal B, Thornhill NFet al., 2015,

    Simulation approach to reliability analysis of WAMPAC system

    , 2015 IEEE PES Innovative Smart Grid Technologies Conference (ISGT), Publisher: IEEE, Pages: 1-5

    Wide are monitoring, protection and control (WAMPAC) plays a critical role in smart grid development. Since WAMPAC frequently has the tasks of executing control and protection actions necessary for secure operation of power systems, its reliability is essential. This paper proposes a novel approach to the reliability analysis of WAMPAC systems. WAMPAC system functions are first divided into four subsystems: the measured inputs, the communication, the actuator and the analytic execution subsystems. The reliability indices of the subsystems are computed then using Monte Carlo approach. A sensitivity analysis is also described to illustrate the influence of different components on the system reliability.

  • Conference paper
    Ikram W, Jansson N, Harvei T, Aakvaag N, Halvorsen I, Petersen S, Carlsen S, Thornhill NFet al., 2015,

    Wireless Communication in Process Control Loop: Requirements Analysis, Industry Practices and Experimental Evaluation

    , 19th IEEE International Conference on Emerging Technology and Factory Automation (ETFA), Publisher: IEEE, ISSN: 1946-0740

    Wireless communication is already used in process automation for process monitoring. The next stage of implementation of wireless technology in industrial applications is for process control. The need for wireless networked control systems has evolved because of the necessity for extensibility, mobility, modularity, fast deployment, and reduced installation and maintenance cost. These benefits are only applicable given that the wireless network of choice can meet the strict requirements of process control applications, such as latency. In this regard, this paper is an effort towards identifying current industry practices related to implementing process control over a wireless link and evaluates the suitability of ISA100.11a network for use in process control through experiments.

  • Conference paper
    Budinis S, Thornhill NF, 2015,

    Supercritical gas recycle analysis for surge control of centrifugal compressors

    , 12th International Symposium on Process Systems Engineering (PSE) / 25th European Symposium on Computer Aided Process Engineering (ESCAPE), Publisher: ELSEVIER SCIENCE BV, Pages: 1583-1588, ISSN: 1570-7946
  • Conference paper
    Xenos DP, Lunde E, Thornhill NF, 2015,


    , ASME Turbo Expo: Turbine Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
  • Conference paper
    Zhang Y, Larsson M, Pal B, Thornhill NFet al., 2015,

    Simulation Approach to Reliability Analysis of WAMPAC System

    , 2015 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT), Publisher: IEEE
  • Conference paper
    Akinmolayan F, Thornhill N, Sorensen E, 2015,

    A Detailed Mathematical Modelling Representation of Clean Water Treatment Plants

    , 12th International Symposium on Process Systems Engineering (PSE) / 25th European Symposium on Computer Aided Process Engineering (ESCAPE), Publisher: ELSEVIER SCIENCE BV, Pages: 2537-2542, ISSN: 1570-7946
  • Conference paper
    Mehleri ED, Mac Dowell N, Thornhill NF, 2015,

    Model Predictive Control of Post-Combustion CO<sub>2</sub> Capture Process integrated with a power plant

    , 12th International Symposium on Process Systems Engineering (PSE) / 25th European Symposium on Computer Aided Process Engineering (ESCAPE), Publisher: ELSEVIER SCIENCE BV, Pages: 161-166, ISSN: 1570-7946
  • Conference paper
    Yang Y, Velayudhan A, Thornhill NF, Farid SSet al., 2015,

    Manufacturability Indices for High-Concentration Monoclonal Antibody Formulations

    , 12th International Symposium on Process Systems Engineering (PSE) / 25th European Symposium on Computer Aided Process Engineering (ESCAPE), Publisher: ELSEVIER SCIENCE BV, Pages: 2147-2152, ISSN: 1570-7946
  • Conference paper
    Romero DD, Graven T-G, Thornhill NF, 2015,

    Linking process, electrical and logical connectivity for supported fault diagnosis

    , 12th International Symposium on Process Systems Engineering (PSE) / 25th European Symposium on Computer Aided Process Engineering (ESCAPE), Publisher: ELSEVIER SCIENCE BV, Pages: 965-970, ISSN: 1570-7946
  • Journal article
    Cecílio IM, Ottewill JR, Fretheim H, Thornhill NFet al., 2014,

    Multivariate Detection of Transient Disturbances for Uni- and Multirate Systems

    , IEEE Transactions on Control Systems Technology, Vol: 23, Pages: 1477-1493, ISSN: 1558-0865

    This paper presents a method to detect transientdisturbances in a multivariate context, and an extension of thatmethod to handle multirate systems. Both methods are basedon a time series analysis technique known as nearest neighbors,and on multivariate statistics implemented as a singular valuedecomposition. The motivation for these developments is thatthere is an increasing industrial requirement for the analysisof data sets comprising measurements from industrial processestogether with their associated electrical and mechanicalequipment. These systems are increasingly affected by transientdisturbances, and their measurements are commonly sampledat different rates. This paper demonstrates superior resultswith the multivariate method in comparison with the univariateapproach, and with the multirate method in comparison toa unirate method, for which the fast-sampled measurementshad to be downsampled. The method is demonstrated onexperimental and industrial case studies.

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