Skip to main content

Quantitative Failure Consequence Hazard Assessment for Next Generation CO2 Pipelines

Final Report Summary - CO2PIPEHAZ (Quantitative Failure Consequence Hazard Assessment for Next Generation CO2 Pipelines)

Executive Summary:

It is widely accepted that without a clear understanding of the hazards associated with the failure of CO2 pipelines, Carbon Capture and Storage (CCS) cannot be considered as a viable proposition for tackling the effects of global warming.

In the CO2PipeHaz project, state of the art multi-phase heterogeneous discharge and dispersion models are developed and experimentally validated for the accurate predictions of the fluid phase, discharge rate and the subsequent atmospheric dispersion of CO2 during its accidental release from pressurised transportation pipelines to be employed as part of large scale CCS chain. The above allow the quantification of all the hazard consequences associated with CO2 pipeline failure, forming the basis for emergency response planning and determining the minimum safe distances to populated areas.

A cost/benefit analysis is performed for a post-combustion CO2 plant in the Laiohe Oil field in China in order to determine the optimum level of impurities in the captured CO2 stream.

Given the very different hazard profiles of CO2 in the gas and solid states, special attention is paid to the accurate prediction of the fluid phase during the discharge process. A numerical package incorporating reliable and computationally efficient equations of state is developed to determine the pertinent thermo-physical and transport properties of CO2 and its various mixtures.

The CO2 outflow and dispersion models developed are extensively validated using unique small and large scale pipeline rupture test facilities constructed during the course of the CO2PipeHaz project.

Safety and risk assessment tools for evaluating the adequacy of controls in CO2 pipelines, with best practice guidelines are also developed. The usefulness of the tools developed is demonstrated based on a case study involving the failure of an hypothetical but nevertheless realistic CO2 pipeline.
Project Context and Objectives:
As part of the challenge to reduce the impact of global warming, pressurised pipelines are considered to be the most practical option for transporting captured CO2 from fossil fuel power plants for subsequent sequestration. This has significant implications for Europe given its heavy reliance on coal fired power plants for its electricity generation and the inevitable routing of CO2 pipelines near populated areas.

Two key areas that need to be demonstrated to gain public acceptance of CO2 pipelines are that such mode of transportation is safe, and the environmental impact in the unlikely event of a pipeline failure is limited. Central to this is the prior knowledge of the time-dependent release rate and the dispersion behaviour of the escaping CO2. Such information is pivotal to quantifying all the hazards associated with the failure of CO2 pipelines, including emergency response planning and determining the minimum safe distances to populated areas.

The CO2PipeHaz project is focused on the development and validation of mathematical models and decision support tools for hazard assessment of CO2 transportation pipelines to be employed as an integral part of the CCS chain. The main objectives as outlined in the Description of Work (DoW) are to:

1. Define an optimum level of impurities in the CO2 stream based on safety, environmental and economic analysis;
2. Develop a computationally efficient multi-phase heterogeneous outflow model for the accurate prediction of the time variant release rate and the physical state of escaping CO2 following pipeline failure, based on a reliable equation of state for CO2 and CO2 mixtures;
3. Develop multi-state dispersion models for predicting the subsequent concentration of the released CO2 as a function of time and distance from the release, both in terms of a detailed near- and far-field modelling capability;
4. Conduct small and large scale experimental validations of the models developed;
5. Provide a detailed understanding of the hazards presented by CO2 releases through experimentation and, using the data generated, validate the outflow and dispersion models developed;
6. Embody the understanding and predictive capabilities developed in decision support tools, assessing and improving existing safety, risk assessment methods, tools for CO2 pipeline application, and producing refined best practice guidelines;
7. Demonstrate the usefulness of the tools developed through their application to possible CO2 pipeline designs.

The main technical developments are carried out in three Work Packages:

WP1: ACCIDENTAL DISCHARGE PHENOMENA
The development of the mathematical models required for predicting the transient discharge rate and dispersion behaviour are encapsulated in WP1. Based on a cost/benefit analysis, the composition and level of impurities to be transported in the CO2 pipeline are determined in WP 1.1. WP1.2 concentrates on the development of the equations of state for CO2 and its mixtures. This work provides the thermodynamic and physical properties data needed for the multiphase discharge model to be developed under WP1.3 and WP1.4. The results of the outflow simulations based on the model developed in WP1.3 serve as the source data for prediction of the near-field (WP1.4) and far-field (WP1.5) dispersion of the released CO2 cloud.

WP2: EXPERIMENTAL DATA
WP2 involves experiments that provide a basic understanding of these complex flows, as well as data toWP assist in the formulation and validation of the outflow and near-field dispersion models. In particular, the experimental data obtained from small-scale release experiments in WP2.1 serve for validation of the outflow and dispersion models in WP1.3 and WP4. Measurements of CO2 concentration in the large-scale release tests in WP2 provide the main data for validation of the far-field dispersion model in WP1.5.

WP3: DECISION SUPPORT
WP3 utilises the knowledge gained in WP1 and WP2 to refine the currently available safety and risk assessment methodologies for CO2 pipelines, together with the development of best practice guidelines for the performance of quantitative risk assessment for CO2 pipelines.

Project Results:

Please find the description of the main S & T results/foregrounds in the PDF file attached.

Potential Impact:

THE POTENTIAL IMPACT

The key impact of this work is to allow the safe and commercial deployment of CCS. The Kyoto Protocol, an international agreement linked to the United Nations Framework Convention on Climate Change, sets binding targets for 37 industrialized countries and the European community for reducing greenhouse gas (GHG) emissions. This amounts to an average of five per cent against 1990 levels over the five-year period 2008-2012. The Special IPCC Report on Carbon Capture and Storage identified CCS as the “single best technology to reduce CO2 emissions rapidly on a global scale”. CCS has the potential for near zero emission power stations even though those power stations burn fossil fuels. Indeed, CCS has the potential to allow exploitation of fossil fuel reserves, including coal, in Europe and the rest of the world without adding to greenhouse gas emissions. It will be an important strategy for maintaining energy supplies and allowing increases in energy production in the developing world, whilst mitigating against climate change.

In China, 70% of its energy is produced from burning coal, which is much higher than the average level of coal usage within the international energy structure (~30-40%). The coal in China is mainly used in power plants and ore-refining furnaces and, as a result, CO2 emissions have increased significantly from 2.3 billion t/a in 2001 to 5.3 billion t/a in 2005. China is now the world’s largest emitter of CO2 and is under significant pressure to reduce its CO2 emissions. To this end, China has recently started a tendering process for CO2 capture and storage technology.

In terms of market size for CCS worldwide, there are currently in excess of 5000 large-scale CO2 sources, in the power industry alone, responsible for emitting approximately 10.5 billion tons of CO2 per annum. IEA studies have shown that, if the world continues on its current path, global CO2 emissions from energy production and use are likely to increase to over 42 billion tons a year by 2030. It is imperative therefore for Europe and the rest of the world that any barriers to the uptake of CCS technology worldwide are resolved. This will be necessary not only to facilitate the export of CCS technology from Europe to the rest of the world, but also to safeguard energy production and other CO2 emitting industries within Europe so that employment prospects and quality of life are maintained and improved.

In achieving these goals, the safety of CO2 pipelines is a serious potential barrier to the uptake of CCS and therefore needs to be resolved. Pipelines will be the most viable and economic means by which to transport large quantities (and flow rates) of CO2 at high pressure from the capture plant to the point of injection. In many cases such pipelines will need to be routed through areas that are densely populated.

Safe transportation of CO2 by pipeline requires an understanding of the effect of catastrophic events. This project provided methodologies for the estimation of hazard ranges and risk in the event of pipeline rupture, which currently do not exist in a suitably validated form and promote the uptake of CCS by removing uncertainty and providing solutions for safe design and operation. The results provide information on safest routing and location of pipelines, safe design of pipelines, and suitable and realistic planning for emergencies. It will also provide information that can be used to provide public reassurance.

All new technologies require public acceptance in order to be successfully introduced. It is very important to address safety from the outset so as to prevent any disasters involving CO2 pipelines. Major events of this kind would attract considerable media attention and the technology would become perceived as dangerous – which could seriously affect the uptake of CCS on global scale.

Developers of CCS projects need as much certainty as possible about the design requirements so that costs can be estimated accurately. This is important in gaining financial investment and approval for new projects. It is also extremely important to be able to calculate hazard ranges from CO2 pipelines, which will be used to ensure that the pipeline is routed in a safe manner, which is acceptable to the planning authorities and other regulators.

Safety and environmental regulators and planning authorities need an understanding of catastrophic releases from pipelines so that there is no unnecessary delay in the approvals process for new CCS projects.

This project provided an understanding of, and a modelling capability for, catastrophic releases from CO2 pipelines. Current models and methodologies for other hazardous substances are not fully applicable to CO2 due to the unique thermodynamics and physical properties of CO2.

The outputs of the project include best practice guidelines for the design and operation of CO2 pipelines, together with validated models for accidental discharge, hazard ranges and levels of risk. The project therefore filled a major gap in current knowledge. It also addressed some of the needs described above of CCS project developers/designers, investors, safety and environmental regulators, land-use planning authorities, and the public.

The project consortium has extensively disseminated the project’s results so as to maximise the impact. This has already led to undertaking a number of consultancy projects for major stake holders and newly funded major collaborative research programmes.

Examples of consultancy projects include:

i) using the outflow model developed in WP2 to test the suitability of the current stock of UK natural gas pipelines for transporting captured CO2

ii) performing Front End Engineering Design Studies in support of one the two shortlisted UK £1bn Carbon Capture and Storage Commercialisation Programme Competition winners (https://www.gov.uk/government/news/preferred-bidders-announced-in-uk-s-1bn-ccs-competition) to build a fully operational CCS unit for capturing 90% of the CO2 from a new super-efficient coal-fired power station at the Drax site in North Yorkshire, before transporting and storing it in a saline aquifer beneath the southern North Sea

iii) predicting pipeline fracture toughness requirements for the transportation of the captured CO2 generated from Brazil's offshore oilfields followed by injection at ultrahigh pressures (>200 bara) for enhanced oil recovery in order to boost oil reservoir productivity and reduce CO2 emissions

Examples of major collaborative research programmes funded as a direct result of the CO2PipeHaz project include:

i) FP7 CO2QUEST project (http://www.co2quest.eu/) coordinated by the UCL team involving a consortium of 12 industry and academic partners undertaking a Techno-economic assessment of the impact of CO2 stream impurities on its capture, transportation and storage

ii) Multiphase flow modelling for hazard assessment of dense phase CO2 pipelines containing impurities funded by the UK Carbon Capture Research Centre.


In terms of the make-up of the project, no individual participant in this project, nor single European country, possessed the expertise to undertake all the work described. The requirement for collaboration between partners therefore arose naturally out of the work proposed since in terms of the fundamental research envisaged, and the decision support tools developed and demonstrated, experts in their various fields are required, and these experts are only available at a European level. The work programme was also more cost effectively undertaken as a collaborative effort at a European level. Were this proposal to undertaken at a national level, there would be a requirement for the development of expertise that already exists elsewhere, and the significant duplication of existing expertise with a consequent increase in overall cost. The proposal was therefore in the spirit of collaboration encouraged by the EC in FP7. The involvement of our Chinese partner also added significant value to the project given the access it gives to an actual CO2 capture and transport facility belonging to the China National Petroleum Corporation.

List of Websites:

Project website address: http://www.co2pipehaz.eu/

Contact details of the project co-ordinator:
Professor Haroun Mahgerefteh
Chemical Engineering Department
University College London
Tel: +44-2076793835
Fax: +44-2076793835
E-mail: h.mahgerefteh@ucl.ac.uk