Abstract
With about 195 countries signing the Paris (climate) Agreement and world leaders uniting for the planet after the United States’ notification to pull out of the agreement, many carbon capture and storage (CCS) projects are expected to be executed worldwide. Captured CO2 is not pure and may contain several impurities, which affect the flow dynamics of the CO2 fluid in pipelines. To design efficient CO2 pipeline transportation systems, it is imperative to understand the effect of these impurities on the flow behaviour. Aspen HYSYS (V10) and HydraFlash were used to study the behaviour of 90 mol % CO2 and 10 mol % single impurity (N2, CH4, H2, H2S, SO2, Ar, CO, NH3, O2 and H2O). The Peng-Robinson equation of state (EoS), which has the lowest average absolute deviation (AAD) among cubic EoS for predicting CO2 fluid properties, was used in Aspen HYSYS. Three different 50 km pipelines were simulated; one horizontal pipeline and two pipelines with +300 and -300 m in elevation between inlet and outlet respectively. The mass flow rate is 266,400 kg/h and the internal and external diameters of the pipelines are 0.289 m and 0.324 m respectively. All impurities changed the parameters of the flowing fluid. H2 impurity caused the most pressure loss for horizontal pipelines but may cause the least pressure loss for pipelines at high inclination angles. H2 and H2S formed the widest and narrowest two-phase regions, respectively. The results also show that H2 impurity resulted in the most heat loss while H2O and SO2 impurities had the lowest heat losses. Pipeline elevation change also affects the effect of each impurity on pressure changes. The difference in pressure drop between the impurity with the highest effect, H2, and that with the least effect, SO2, is 0.44 MPa for inclined pipelines, 0.77 MPa for horizontal pipelines and 1.44 MPa for declined pipelines. H2S had the mildest effect followed by NH3, H2O, SO2, CO, Ar, CH4, O2, N2 and H2.
