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  • Journal article
    Xenos DP, Lunde E, Thornhill NF, 2016,

    Optimal Operation and Maintenance of Gas Compressor Stations: An Integrated Framework Applied to a Large-Scale Industrial Case

    , Journal of Engineering for Gas Turbines and Power-Transactions of the Asme, Vol: 138, ISSN: 1528-8919

    This paper presents a framework which integrates maintenance and optimal operation of multiple compressors. The outcome of this framework is a multiperiod plan which provides the schedule of the operation of compressors: the schedule gives the best decisions to be taken, for example, when to carry out maintenance, which compressors to use online and how much to load them. These decisions result in the minimization of the total operational costs of the compressors while at the same time the demand of the plant is met. The suggested framework is applied to an industrial gas compressor station which encompasses large multistage centrifugal compressors operating in parallel. The optimization model of the framework consists of three main parts: the models of compressor maps, the operational aspects of compressors, and a maintenance model. The results illustrate the optimal schedule for 90 days and an example of the optimal distribution of the load of the compressors for 5 days. Finally, the results show the economical benefits from the integration of maintenance and optimization.

  • Journal article
    Barocio E, Pal BC, Thornhill NF, Roman Messina Aet al., 2015,

    A Dynamic Mode Decomposition Framework for Global Power System Oscillation Analysis

    , IEEE TRANSACTIONS ON POWER SYSTEMS, Vol: 30, Pages: 2902-2912, ISSN: 0885-8950
  • 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.

  • 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
  • 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
    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
    Mehleri ED, Mac Dowell N, Thornhill NF, 2015,

    Model Predictive Control of Post-Combustion CO2 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
    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
    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
    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
    CecĂ­lio 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.

  • Conference paper
    Romero DD, Thornhill NF, 2014,

    Integration, navigation and exploration of plant topology networks using the property-graph model

    , 2014 IEEE/SICE International Symposium on System Integration, Publisher: IEEE, Pages: 743-748

    Understanding the process topology is essential for many process-systems engineering activities. Previous works in this area have explored the extraction of connectivity and causality knowledge (plant topology) from different sources of engineering data by following qualitative and quantitative methods. A few works, however, have focused on how to integrate, store, and visualize models that can represent the interactions among the different items in a chemical plant. This paper proposes a method for integration, navigation and exploration of topology based on property-graphs, which can support the study of disturbance propagation in chemical plants.

  • Conference paper
    Ersdal AM, Fabozzi D, Imsland L, Thornhill NFet al., 2014,

    Model predictive control for power system frequency control taking into account imbalance uncertainty

    , 19th IFAC World Congress 2014, Publisher: International Federation of Automatic Control, Pages: 981-986, ISSN: 1474-6670
  • Conference paper
    Arroyo E, Schulze D, Christiansen L, Fay A, Thornhill NFet al., 2014,

    Derivation of diagnostic models based on formalized process knowledge

    , 19th IFAC World Congress, 2014, Publisher: International Federation of Automatic Control, Pages: 3456-3464, ISSN: 1474-6670
  • Journal article
    Cecilio IM, Ottewill JR, Pretlove J, Thornhill NFet al., 2014,

    Nearest neighbors method for detecting transient disturbances in process and electromechanical systems

    , Journal of Process Control, Vol: 24, Pages: 1382-1393, ISSN: 1873-2771

    Transient disturbances are increasingly relevant in process industries which rely on electromechanical equipment. Existing data-driven methods for detecting transient disturbances assume a distinct amplitude or time-frequency component. This paper proposes a detection method which is more generic and handles any short-term deviation of a measurement from its overall trend, regardless of whether the trend incorporates features such as oscillations, noise or changes in operation level. The method is based on a nearest neighbors technique and builds a vector of anomaly indices which are high for the period with the transient disturbance. The paper includes analyses of the statistical significance of the threshold proposed and of the sensitivity of the parameters, and it also suggests a color map to visualize the detection results. The method is demonstrated on experimental and industrial case studies.

  • Journal article
    Yang Y, Farid SS, Thornhill NF, 2014,

    Data mining for rapid prediction of facility fit and debottlenecking of biomanufacturing facilities

    , JOURNAL OF BIOTECHNOLOGY, Vol: 179, Pages: 17-25, ISSN: 0168-1656
  • Journal article
    Ikram W, Petersen S, Orten P, Thornhill NFet al., 2014,

    Adaptive Multi-Channel Transmission Power Control for Industrial Wireless Instrumentation

    , IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS (open access article), Vol: 10, Pages: 978-990, ISSN: 1551-3203

    The adoption of wireless technology for industrial wireless instrumentation requires high-quality communication performance. The use of transmission power control (TPC) can help address industrial issues concerning energy consumption, interference,and fading. This paper presents a TPC algorithm designed for industrial applications based on theoretical and empirical studies. It is shown that the proposed algorithm adapts to variations in link quality, and is hardware-independent and practical.

  • Conference paper
    Romero DD, Graven T-G, Thornhill NF, 2014,

    Towards the Development of a Tool for Visualising Plantwide Dependencies

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

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