The S-Cape project (Shelter and Escape in the Event of a Release of CO2 from CCS Transport Infrastructure) ran from February 2015 to March 2017 and was a collaboration between the University of Strathclyde and Newcastle University.
Why did we do this project?
Pipelines are acknowledged as one of the safest, efficient and cost effective methods for transporting large volumes of various fluids over long distances and consequently are also considered for the transportation of CO2 in CCS schemes. In the UK, part of the route selection and design process for any high pressure pipeline requires that a Quantitative Risk Assessment (QRA) is conducted along the route. The purpose of the QRA is to assess the risks posed by a pipeline failure to people in the vicinity and to ensure that consistent levels of risk are applied along the pipeline route. The risk levels are normally calculated along a transect drawn perpendicular to the pipeline. These levels are then compared with defined acceptance criteria to determine the safety zone around the pipeline i.e. the distance from the pipeline within which the risk to the public from a pipeline failure is considered to be unacceptable.
What did we do?
In this project we developed two models to predict the CO2 concentration profile within a building that is engulfed by a cloud of CO2. The first model is an analytical model that is based on fundamental principles of ventilation and describes how the CO2 from outside the building would infiltrate into the building. The advantages of the analytical model are that it is quick and easy to run and the level of information that is required about the buildings along the route can be fairly generic. This makes it a more useful tool for pipeline designers. However, it has to be ensured that the output from the analytical model is consistent with experimental data and with the output of more sophisticated Computational Fluid Dynamics (CFD) models. We therefore also built a CFD model that we could compare against experimental data and then use to develop the analytical model further. Once we had the models developed for a simple single storey room, we went on to look at the effect of different heights of clouds, partitions within the building and different atmospheric conditions.
What did we achieve?
We have shown that the effects of shelter should be considered during the QRA of a CO2 pipeline and we have developed two models that allow designers to determine the toxic dose received by an individual within the building compared to individuals outside.
We have shown that undertaking measures such as closing windows and locating upstairs can reduce this toxic load and the models have been developed to allow these effects to be quantified.
We have compared our model results against experimental data for a high flow rate experimental release with good agreement. However, at lower flow rates there is less agreement between the predictions of the analytical and the CFD models and we will continue our work to try and address this gap.
Where can you find out more?
You can find out more by following our submissions and publications in the UKCCSRC datastore. We are also presenting the findings at the UKCCSRC biannual meeting in Sheffield on the 12th September 2017.
We would like to thank……
We would like to acknowledge the support of National Grid in carrying out this research by enabling the data from the COOLTRANS project to be used in this study, particularly for the validation of the models. We would also like to thank DNV-GL for the provision of the dispersion input data for the study.