The Effect of CO 2 Purity on the Development of Pipeline Networks for Carbon Capture and Storage Schemes

One of the key aspects relating to the transportation of anthropogenic carbon dioxide (CO2) for climate change mitigation as part of Carbon Capture and Storage (CCS) schemes is the composition of the CO2 stream to be transported. The specification of this stream has both technical and economic implications and, as CCS schemes start to become realised, the requirement to specify the CO2 stream quality is becoming more important. The aim of this work has been to analyse the effects of the composition of the CO2 stream from post-combustion, pre-combustion and oxyfuel capture processes on the hydraulic network design and the relative costs of the network. Several key conclusions have been drawn to inform the process of specifying the CO2 purity and to guide pipeline operators on the specification of a CO2 stream, for dense phase pipeline operation, on the basis of hydraulic design. The analysis has shown that impurity additions up to 2mol% did not affect the relative cost/km for the networks when compared to a pure CO2 equivalent in terms of the pipeline internal diameter and length. However, the inlet pressure to the network is increased for all of the compositions studied and in this respect, levels of hydrogen in particular should be limited to less than 1mol% to reduce inlet pressure and thereby compression costs. It has been demonstrated that direct connection pipelines from source to sink are the most expensive network options however, when designing a pipeline network, the size of the emitters, the phasing of entry into the network and the stability of the network in the event of interruptions in flow needs to be considered.