Evaluating the Influence of Noncondensable Impurities on Multiphase CO₂ Flow Behaviour in Pipelines

Carbon capture, utilisation and storage depend on the reliable transport of carbon dioxide through pipelines, yet captured streams commonly contain noncondensable impurities that can alter flow behaviour and compromise transport efficiency. This study investigated the influence of these impurities on multiphase carbon dioxide flow via steady-state compositional simulations in PIPESIM. Two pipeline models were developed underrepresentative operating conditions: a baseline case containing pure carbon dioxide and an impurity-laden mixture containing nitrogen, oxygen, argon, hydrogen, methane, carbon monoxide, light hydrocarbons and water. The thermodynamic behaviour was modelled with the Peng‒Robinson equation of state, whereas the hydraulic performance was evaluated through phase behaviour, pressure profile, pressure gradient and Reynolds number analyses. The results show that impurities expand the phase envelope and reduce the stability of dense-phase transport, increasing the likelihood of two-phase flow. Compared with pure carbon dioxide, the impurity-laden stream exhibited a nonuniform pressure decline, localised pressure gradient spikes and greater fluctuations in the Reynolds number, indicating more complex hydraulic behaviour despite remaining in the turbulent flow regime. These findings demonstrate that impurity composition significantly influences carbon dioxide transport performance and should be explicitly incorporated into pipeline design and flow assurance assessments for future carbon capture, utilisation and storage infrastructure