1 Acid reactions in hub systems consisting of separate non-reactive CO 2 transport lines. Bjørn H. Morland 1,2 , Morten Tjelta 1 , Truls Norby 2 , Gaute Svenningsen 1 1 Institute for Energy Technology, PO box 40, NO-2027 Kjeller, Norway 2 University of Oslo, Department of Chemistry, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway Abstract Corrosion in carbon steel pipelines is a major threat for safe CO2 transport, and there have been several projects studying the corrosivity of impurities which could be found in captured CO2. Often only two or three of these impurities have been present while performing the experiments. Although these experiments have delivered valuable knowledge, there are still questions of what happens when all impurities are present together. Furthermore, several transport pipelines may deliver CO2 to a main pipeline through a hub system for storage or utilization, and while these streams may be safe individually, the blend in the main pipeline could create components that are hazardous for carbon steel. The present study used a novel experimental setup to realistically simulate a CO2 hub. Three individual “pipelines” were joined inside a glass tube in a transparent autoclave. The three “pipelines” were connected to three different reservoir pumps, simulating different capturing sources with dissimilar types of impurities. This gave a mix of low (ppmv) levels of oxygen (O2), sulphur dioxide (SO2), hydrogen sulphide (H2S), nitrogen dioxide (NO2), and water (H2O). Three different experiments were performed with concentrations ranging from 5 to 35 ppmv of the impurities and a total pressure of 100 bar at 25 °C. All impurities were measured before and after the streams were mixed in the autoclave. The experiments revealed that reactions between certain species were occurring even at concentrations as low as 5 ppmv, but the reaction products were not considered harmful. If the impurity concentrations were increased to about 35 ppmv, acids and solids were produced, and the situation became unacceptable for carbon steel. Keyword: CCUS, CO2, transport, CO2 hub, impurities, specification test, H2SO4, HNO3 1 Introduction Carbon capture and storage is needed to meet the goal set by the International Energy Agency (IEA) [1] and the Intergovernmental Panel on Climate Change (IPCC) [2]. This will involve CO2 capture, transportation, and permanent storage, and it is essential that the cost of the overall processes is kept as low as practically possible. Carbon steel is the only material that is economically feasible for long transport pipelines. However, the captured CO2 may contain small amounts of additional components (called impurities in the present paper), which may be corrosive to carbon steel or cause operational problems. A quality specification for the CO2 to be transported is therefore crucial to