Conference papers and presentations


Forthcoming papers

PSE will be presenting papers at the following events.

13th Annual CCUS Conference (Pittsburgh, Pennsylvania, Apr 28 - May 1, 2014)

1. CCS System Modelling: Enabling Technology to Help Accelerate Commercialisation and Manage Technology Risk – A Case Study on the Operation of CCS Networks

Alfredo Ramos Plasencia1, Anatole Weill2, Thierry Moes3, Laurence Robinson4, Frances Harding5, Ian Phillips5, Mario Calado1, Elton, Dias1, Adekola Lawal1, Javier Rodriguez1, Nouri Samsatli1, Gerardo Sanchis1, Mark Matzopoulos1 and Costas Pantelides1, (1) Process Systems Enterprise Ltd, London, UK, (2) EDF Energy, London, UK, (3) Rolls-Royce plc, London, UK, (4) E.ON New Build & Technology Limited, Nottingham, UK, (5) CO2DeepStore, Aberdeen, UK

The commercial implementation of CCS still faces significant challenges arising from need to consider the whole chain as a single system in order to make design and operation decisions that satisfactorily address the commercial imperatives and risk requirements of the various stakeholders along the chain. Even a quick analysis shows that decisions made at the power plant level can have a significant effect on storage providers at the other end of the chain, and vice versa. A systems modelling approach is essential to address this challenges.

In order to address this, a ?3m project was commissioned and co-funded by the ETI and project participants, who comprise E.ON, EDF, Rolls-Royce, CO2DeepStore, Process Systems Enterprise (PSE) and E4tech. The project is aimed at delivering a robust, fully integrated tool-kit that can be used by CCS stakeholders across the whole CCS chain. This tool-kit will be released as a commercially-supported software product.

The tool-kit includes models for conventional generation (pulverised coal and combined cycle gas turbine), new generation (gasification and oxyfuel), solvent-based carbon capture, compression, transmission and injection. Using the system modelling tool-kit it will be possible to look at single areas such as amine plants in detail (e.g. start-up and shutdown studies); investigate partial-chain operations in isolation to evaluate specific safety critical events; or analyse interactions across whole CO2 transmission networks with multiple sources and sinks. The tool-kit also caters for interfacing of external software packages such as E.ON's PROATES, allowing companies to preserve existing workflows where necessary. In addition an advanced custom modelling capability means that it is easy to add models of new processes and combine them with existing flowsheeting components.

This presentation describes the results of a case study for a CCS network comprising capture from a supercritical pulverised-coal and a CCGT power plant, two compression stations and transport to injection in two subsea formations for storage. Both steady-state and dynamic scenarios were considered and results were obtained for different power plant loads, CO2 capture rates and a variety of environmental conditions.

2. Model-based economic optimisation of CO2 compressor train design and operation

Mário Calado, Élton Dias, Javier Rodriguez, Alfredo Ramos, Costas Pantelides, Process Systems Enterprise Ltd, London, UK,

Currently, compressor trains are typically designed using heuristics, in an iterative fashion. This paper describes an approach for determining optimal design parameters of a CO2 compression train for Carbon Capture and Storage (CCS) developed by Process Systems Enterprise (PSE), using rigorous model-based optimisation methods that can take into account time-varying flowrates or delivery pressures.

In this paper, a multi-period optimisation based design methodology was applied to two basic types of rotating equipment for compression of captured CO2 streams (single shaft, "in line" centrifugal barrel compression train and multi-shaft integrally geared compressor train) and the resulting designs analysed and compared.

Optimisation variables can include continuous decision variables such as inter-section/stage pressures, and integer or discrete decision variables, such as number of sections/stages. For the off-design scenarios, the drive speed was optimised in the multi-section centrifugal compression train configurations, while the inlet guide vane (IGV) position was optimised in the integrally geared compressor systems.

Rigorous models of centrifugal as well as integrally geared compressors were implemented in the gPROMS advanced process modelling environment and used to build a superstructure model that contained a maximum-allowable set of inter-connected compressor sections/stages, including recycle loops and intercoolers.

This model was then subjected to a set of optimisations, with an objective function comprising total annualised capital and operating costs. These design calculations involved the solution of a Mixed Integer Non-Linear Programming (MINLP) optimisation problem in gPROMS platform.

The first optimisation determined the optimal number of sections/stages, section/stage diameters, required heat transfer area of the intercoolers and other key design attributes for a given service, based on identical pressure ratios across each section/stage. A second study considered the inclusion of inter-section/stage pressures as additional optimisation variables.

Finally, a third case study applied a multi-period design approach to determine the optimal number of sections/stages for a typical daily load profile that emulated the typical flow of CO2 from a power station following grid demand. This approach makes it possible to accurately determine trade-offs between higher capital expenditure and increased flexibility of service and lower operating costs, thus minimising the overall annualised cost of operation under varying flowrate conditions.

3. An integrated framework for the dynamic modelling of solvent-based CO2 capture processes

Javier Rodriguez, Adekola Lawal, Mário Calado, Nouri Samsatli, Alfredo Ramos, Thomas Lafitte, Javier Fuentes, Costas Pantelides, Process Systems Enterprise Ltd, London, UK,

This work presents a predictive modelling framework for solvent-based CO2 absorption developed by Process Systems Enterprise (PSE), which can be used for testing, screening and designing new solvent blends, and to establish the most suitable process configuration and operating conditions. The modelling framework is made possible by the integration of two components: a) gSAFT advanced thermodynamics and b) a gPROMS library of capture unit models.

gSAFT is a physical properties package that implements some of the most advanced SAFT-based equations of state, as developed by Imperial College London. The Statistical Association Fluid Theory (SAFT) is rooted on statistical mechanics, so SAFT equations of state involve a limited number of parameters, with a clear physical meaning. Hence, these parameters can be fitted to a limited amount of experimental data, and used to predict phase behaviour and physical properties for a wide range of conditions. This is of paramount importance to the screening of novel solvents or solvent mixtures. We have developed a robust methodology for the prediction of the thermophysical properties and phase behaviour of mixed solvent systems, both physical and chemical.

The capture model library is implemented in the gPROMS platform, and comprises gSAFT-tailored high-fidelity dynamic rate-based models of absorption-desorption units for carbon capture. Models of all other relevant units, such as reboilers, condensers, flash vessels and heat exchangers are also included.

Absorption-desorption model units can be quickly configured to simulate their operation with new solvents. Furthermore, since the model library is fully dynamic, analysis of shut-down and restart scenarios can be carried out, providing new insights into the performance of solvents and process configurations. PSE's own model implementations, validated with literature experimental data, include some of the most common chemical and physical solvents, such alkanolamines and their mixtures, chilled methanol or mixtures of DEPG. Additionally, PSE has recently been working with a number of clients, implementing their proprietary solvents within this framework. Relevant results will be presented in this paper.

4. gSAFT: advanced physical properties for carbon capture and storage system modelling

Javier Rodriguez, Mário Calado, Adekola Lawal, Elton Días, Nouri Samsatli, Alfredo Ramos, Thomas Lafitte, Javier Fuentes, Costas Pantelides, Process Systems Enterprise Ltd, London, UK,

Process Systems Enterprise is finalizing the development of gCCS, a commercial system modelling tool for whole-chain carbon capture and storage. One of the many challenges involved in the development of such tool is the provision of accurate physical properties for the compression and transmission subsystems of the chain. There are three main issues that need to be addressed for a physical properties engine for CCS compression and transmission to be suitable: (1) The presence of impurities - physical properties of the CO2 streams being transported will be greatly affected by composition; (2) the engine needs to cover a wide range of conditions, in terms of pressures and temperatures; (3) there is a dramatic lack of experimental data, which exacerbates the difficulty of fitting and validating thermodynamic models.

Molecular-based equations of state (EOS) are a very appealing alternative to more classical approaches. In particular, the Statistical Association Fluid Theory (SAFT) is especially suited for its ability to deal with complex fluids. SAFT-based EOS are rooted on statistical mechanics, so they involve a limited number of parameters, with a clear physical meaning. Hence, they can be fitted to a limited amount of experimental data, and used to predict phase behaviour and physical properties for a wide range of conditions, including those far from the ones employed for parameter estimation.

Process Systems Enterprise's gSAFT is a commercial implementation of one of the most advanced SAFT-based EOS: SAFT - γ Mie EOS, developed by Imperial College. In this work, we illustrate the development of a gSAFT physical property engine for the gCCS tool. The physical properties and phase equilibrium are accurately described for a set of components ¬ and their mixtures ¬ that cover the sort of systems that are likely to be encountered in CCS CO2 transportation. The models are then validated by comparing the predicted behavior of relevant mixtures with experimental data. The performance of the gSAFT physical property engine within the gCCS tool will be demonstrated with a number of case studies that involve typical CCS compression and transmission flowsheets.

5. Hazard analysis of carbon capture and storage systems

Adekola Lawal1, Sam Botterill2, Mark Matzopoulos1 and Alfredo Ramos Plasencia1, (1) Process Systems Enterprise Ltd., (2) Energy Institute, London, UK.

A typical carbon capture and storage (CCS) project will involve multiple operator companies, for instance, the power station or other CO2 source, CO2 capture plant, CO2 transport pipeline and offshore CO2 injection operators. Whilst there is considerable experience in the operation of these individual components, there are various gaps in knowledge with regards their interoperability at a system level. These uncertainties present a significant risk to the safe and flexible operation of CCS projects.

It is vital that the safe operation of integrated CCS systems can be demonstrated in the early stages of project design as safety concerns are often cited in objections to CCS projects going forward. In addition, making further provisions for safe operation can greatly influence the project's commercial viability. Complexity is also likely to increase, as second generation CCS projects will lead to the creation of CO2 transport networks. The safe operation of a CCS system will require close co-ordination between the different stakeholders.

The study has been carried out with a comprehensive system modelling tool-kit specifically built for studying CCS chains, gCCS. The predictive dynamic process models available in gCCS allow rapid and effective exploration of the design and operational performance of whole chain CCS systems.

gCCS was applied to various typical operational scenarios identified as threats to CO2 flow assurance. These scenarios include:

  1. Unplanned shutdown at injection site / loss of storage in a single chain and in a CCS network
  2. Loss of upstream compression
  3. Loss of intermediate compression
  4. Shutdown of CO2 capture plant and in a CCS network with several CO2 sources

Key analyses carried out include:

  • How long would it take before the units upstream or downstream are severely impacted by the above disturbances
  • Which units may require an emergency shutdown in the event of one of the above scenarios
  • How long would operators have before venting of CO2 is required
  • What benefits would intermediate CO2 storage offer
  • How quickly will disturbances in CO2 flow affect enhanced oil recovery operations
  • How quickly does pressure build up in pipelines

10th Global Congress on Process Safety (New Orleans, LA, Mar 30 - Apr 2, 2014)

1. Using dynamic analysis for accurate assessment of pressure relief and blowdown system performance

Praveen Lawrence , James Marriott, Process Systems Enterprise Ltd

Blowdown/flare systems typically provide the last line of defense to prevent loss of primary containment or escalation when a loss of containment or fire has occurred. Sizing of the flare system must be sufficient to ensure timely blowdown of all systems without overpressuring the flare headers or knockout drum. Moreover, recent work by the API-521 committee indicates that blowdown times for thinner-walled vessels may need to be shortened from the original design.

Traditional flare modeling assumes that the header and knockout drum are at steady-state conditions. This can be overly conservative, since it does not take credit for the finite time required to "pack" the flare system. In new designs, this can lead to oversizing. In existing systems that need to be retrofitted with larger blowdown valves to address current practices for blowdown time, this could exaggerate overpressure issues, leading to unnecessary modifications.

A more rigorous, fully dynamic flare model can be used to produce more efficient designs, or to demonstrate the sufficiency of existing systems. This paper details how such a dynamic analysis, using fully coupled process and flare system models, has been applied to a number of oil & gas facilities in Alaska, for which steady-state analysis indicated excessive pressure. It shows how the transient behavior of the flare system can be accurately predicted for blowdown events, avoiding unnecessary modifications.

2. Process Modelling Requirements for the Safe Design of Blowdown Systems – Changes to Industry Guidelines and How This Impacts Current Practice

Praveen Lawrence, James Marriott, Apostolos Giovanoglou, Process Systems Enterprise Ltd.

Safe design of pressure relief and blowdown systems requires that safety valves, relief orifices, flare piping and KO drums are all sufficiently sized, to ensure that the process is protected from over-pressurisation and that emergency depressurisation can be executed rapidly. An essential design step is to ensure that temperatures resulting from auto-refrigeration are sufficient to avoid the risk of brittle fracture in both the process equipment and flare system.

However conventional calculation methods rely on a number of assumptions and approximations. In particular, calculation of safe design temperatures and relieving rates for complex blowdown segments are typically based on analysis of a single pseudo-vessel with simplified representations of the fluids thermodynamics and heat transfer.

Best-practice in engineering and operating companies when assessing risks in pressure relief and blowdown systems now increasingly involves the application of high-fidelity dynamic simulation techniques. For example:

  • rigorous, distributed blowdown system models are used to assess the risks of cold temperature brittle fracture during process depressurisation
  • analytical methods are used when performing pool and jet fire evaluations.

Evolving industry guidelines are likely soon to necessitate a change in the way all Oil & Gas companies approach process safety, in particular the design and analysis of pressure relief and blowdown systems. This presentation discusses how industry practice is beginning to evolve in anticipation of the forthcoming changes.

The 4th Korea CCS International Conference (Jeju Island, Korea, 24-26 February, 2014)

1. Model-Based Economic Optimisation of CO2 Compressor Train Design and Operation

Mario Calado, Elton, Dias, Javier Rodríguez, Alfredo Ramos Plasencia and Costas Pantelides, Process Systems Enterprise Ltd.

Compressor trains are typically currently designed using heuristics, in an iterative fashion. This paper describes an approach for rapidly determining optimal design parameters of a CO2 compression train for Carbon Capture and Storage (CCS) using rigorous model-based optimisation methods that can take into account time-varying flowrates or delivery pressures. Optimisation variables can include continuous decision variables such as inter-stage pressures, and integer or discrete decision variables, such as number of sections. Rigorous models of a single-section compressor were constructed in the gPROMS advanced process modelling environment. These were used to construct a superstructure model that contained a maximum-allowable set of inter-connected compressor sections (arbitrarily set to 8 sections), including recycle loops and intercoolers. This was then subjected to a set of optimisations, with an objective function comprising total annualised capital and operating costs. Execution involved solution of a Mixed Integer Non-Linear Programming (MINLP) optimisation problem using the Outer Approximation / Equality Relaxation / Augmented Penalty (OAERAP) algorithm included in gPROMS platform. The first optimisation determined the optimal number of sections, section diameters, required heat transfer area of the coolers and other key design attributes for a given service, based on identical pressure ratios across each section. The second performed the same optimisation, but with the inclusion of inter-section pressures as optimisation variables. The third case applied a multi-period optimisation approach to determine the optimal number of sections for a typical daily load profile that emulated the typical flow of CO2 for a power station following grid demand. The approach makes it possible accurately to determine trade-offs between higher capital expenditure (e.g. the use of more compressor sections) on the one hand, and increased flexibility of service and lower operating costs (through the application of optimised inter-section pressures), on the other hand, to minimise the overall annualised cost of operation under varying flowrate conditions.

2. gSAFT: advanced physical properties for carbon capture and storage system modelling

J. Rodriguez, M. Calado, E. Dias, A. Lawal, N. Samsatli, A. Ramos, T. Lafitte, J. Fuentes, C. Pantelides, Process Systems Enterprise Ltd.

One of the many challenges involved in the development of such tool is the provision of accurate physical properties for the compression and transmission subsystems of the chain. There are three main issues that need to be addressed for a physical properties engine for CCS compression and transmission to be suitable: (1) The presence of impurities – physical properties of the CO2 streams being transported will be greatly affected by composition. Different combinations of power stations and capture technologies will produce CO2 streams with a varying number and concentration of impurities; (2) the engine needs to cover a wide range of conditions, in terms of pressures and temperatures; (3)There is a dramatic lack of experimental data, which exacerbates the difficulty of fitting and validating thermodynamic models.

For the reasons abovementioned, molecular-based equations of state (EOS) are a very appealing alternative to more classical approaches, such as cubic EOS. In particular, the Statistical Association Fluid Theory (SAFT) is especially suited for its ability to deal with complex fluids. SAFT-based EOS are rooted on statistical mechanics, so they involve a limited number of parameters, with a clear physical meaning. Hence, they can be fitted to a limited amount of experimental data, and used to predict phase behaviour and physical properties for a wide range of conditions, including those far from the ones employed for parameter estimation.

Process Systems Enterprise?s gSAFT is a commercial implementation of one of the most advanced SAFT-based EOS: SAFT–γ Mie EOS, developed by Imperial College. In SAFT–γ Mie, molecules are treated as associating chains of spherical segments that interact via Mie potentials. Hydrogen bonding and association is mediated through short-range off-centre square well association sites.

In this work, we illustrate the development of a gSAFT physical property engine for the gCCS tool. The physical properties and phase equilibrium are accurately described for a set of components and their mixtures that cover the sort of systems that are likely to be encountered in CCS CO2 transportation. Pure component and binary interaction parameters are regressed to publicly available vapour–liquid equilibrium data. The models are then validated by comparing the predicted behaviour of relevant mixtures with experimental data.

The performance of the gSAFT physical property engine within the gCCS tool will be demonstrated with a number of case studies that involve typical CCS compression and transmission flowsheets.

3. CCS System Modelling: Enabling Technology to Help Accelerate Commercialisation and Manage Technology Risk

Alfredo Ramos Plasencia, Mario Calado, Elton, Dias, Adekola Lawal, Javier Rodríguez, Nouri Samsatli, Gerardo Sanchis, Mark Matzopoulos and Costas Pantelides, Process Systems Enterprise Ltd.

The commercial implementation of CCS still faces significant challenges. Many of these arise from the fact that the whole chain and, eventually, whole CO2 transportation network needs to be considered as a single system in order to make design and operation decisions that satisfactorily address the commercial imperatives and risk requirements of the various stakeholders along the chain. Even a quick analysis shows that design and operating decisions at the power plant can have a significant effect on storage providers at the other end of the chain, and vice versa. A systems modelling approach is essential, but there are currently no tools that can satisfactorily provide this capability over the whole CCS chain.

In order to address this, a ?3m project was commissioned and co-funded by the ETI and project participants, who comprise E.ON, EDF, Rolls-Royce, Petrofac (via its subsidiary CO2DeepStore), Process Systems Enterprise (PSE) and E4tech. The project is aimed at delivering a robust, fully integrated tool-kit that can be used by CCS stakeholders across the whole CCS chain that will be released as a commercially-supported software product at the end of the project.

Because of the requirement for many stakeholders to be able to model areas of the chain beyond their own specific processes (for example, a key requirement for power generators is the ability to investigate the effects on their operation of amine and compression systems attached to their plants), the tool-kit will provide process models for the whole chain. This will also allow it to be used by groups who require a whole-chain view, such as engineering companies or government departments who need to quantify policy decisions.

The tool-kit includes models for conventional generation (pulverised coal and combined cycle gas turbine), new generation (gasification and oxyfuel), solvent-based carbon capture, compression, transmission and injection. The individual process models are mostly medium­to­high fidelity: multicomponent streams; rate-based and/or equilibrium methods for vapour-liquid separation; comprehensive compressor models allowing multi­stage, multi­section compressors with manufacturers curves; and distributed pipeline models for construction of pipeline networks that can take elevation into account. The capture models use rate­based techniques for accurate quantification of chemical and physical capture in order to quantify energy penalties accurately and allow meaningful analysis of transient operations.

Using the system modelling tool-kit it will be possible to look at single areas such as amine plants in detail; investigate partial-chain operations for example, power generation, capture and compression; or analyse interactions across the whole chain and eventually the whole CO2 transmission network with multiple sources and multiple sinks. The tool­kit also caters for interfacing of external software packages such as E.ON?s PROATES, in order to simplify interoperability analysis while allowing companies to preserve existing workflows where necessary. In addition an advanced custom modelling capability means that it is easy to add models of new processes and combine them with existing flowsheeting components.

This presentation describes the results of a case study for a whole-chain CCS system including capture from a supercritical pulverised-coal power plant, compression and transport to injection in subsea storage. Both steady­state and dynamic scenarios where considered and results were obtained for different power plant loads, CO2 capture rates and a variety of environmental conditions (ambient and cooling water temperatures).

4. Hazard analysis in carbon capture and storage chains

Adekola Lawal1, Sam Botterill2, Mark Matzopoulos1 and Alfredo Ramos Plasencia1, (1) Process Systems Enterprise Ltd., (2) Energy Institute, London, UK.

A typical CCS project will involve multiple operator companies, e.g. the power station, CO2 transport pipeline and offshore CO2 injection operators. Complexity is likely to increase as second generation CCS projects will lead to the creation of CO2 transport networks with multiple CO2 sources and storage options.

The safe operation of the CCS system will require close co-ordination between the different stakeholders. This study aims to identify and analyse potential hazards by considering typical trip, outage and shutdown scenarios and describing the effects on stakeholders up and down the chain. It will seek to demonstrate how the process can be safely managed in the event of a system failure and suggest a communication procedure based on the best practices currently available across industry. This procedure shall provide clear guidance regarding the course of action in critical safety events and clarify the responsibilities of each party across the chain for various events.

The study has been carried out with a comprehensive system modelling tool-kit specifically built for studying CCS chains, gCCS. The predictive dynamic process models available in gCCS allow rapid and effective exploration of the design and operational performance of whole chain CCS systems. gCCS was applied to various typical operational scenarios identified as threats to CO2 flow assurance. These scenarios include:

  1. Unplanned shutdown at injection site / loss of storage in a single chain
  2. Loss of upstream compression
  3. Loss of intermediate compression
  4. Shutdown of CO2 capture plant

Key analyses carried out include:

  • How long would it take before the units upstream or downstream are severely impacted by the above disturbances
  • Which units may require an emergency shutdown in the event of one of the above scenarios
  • How long would operators have before venting of CO2 is required
  • What benefits would intermediate CO2 storage offer
  • How quickly will disturbances in CO2 flow affect enhanced oil recovery operations
  • How quickly does pressure build up in pipelines

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