Modelling the impact of stream impurities on ductile fractures in CO2 pipelines

This paper describes the development, validation and application of a fully coupled dynamic boundary fracture model for predicting ductile fracture behaviour in CO2 pipelines. The application of the model to an hypothetical but realistic CO2 pipeline reveals the profound effects of the line temperature and the types of impurities present in the CO2 stream on the pipeline's propensity to fracture propagation. It is found that the pure CO2 and the post-combustion pipelines exhibit very similar and highly temperature dependent propensity to fracture propagation. An increase in the line temperature from 20 to 30 degrees C results in the transition from a relatively short to a long running propagating facture. The situation becomes progressively worse in moving from the pre-combustion to the oxy-fuel stream. In the latter case, long running ductile fractures are observed at all the temperatures under consideration. All of the above findings are successfully explained by examining the fluid depressurisation trajectories during fracture propagation relative to the phase equilibrium envelopes. (C) 2012 Elsevier Ltd. All rights reserved.