UKCCSRC Call 2 Project: Measurement of water solubility limits of CO2 mixtures to underpin the safe pipeline transportation of CO2

This Proposal focuses on the determination of the dew point of water (H2O), or “water solubility”, in impure CO2 mixtures (e.g. containing nitrogen, N2, oxygen, O2, hydrogen, H2, or mixtures of N2 + H2). The proposed work is a direct result of new findings in our project under Call 1, where we have obtained highly reproducible data for water solubility in CO2 + N2 using infrared spectroscopy and are well on the way to implementing an independent route using the so-called “Karl-Fischer” titration technique to give independent validation of our results. We have shown that the solubility of H2O is significantly reduced by the presence of even low concentrations of N2, a finding which has direct implications on anthropogenic CO2 transportation pipeline specifications and operation (e.g. internal corrosion). Such data have been identified by the Advanced Power Generation Technology Forum (APGTF) and the priorities specified in the UKCCRC Research And Pathways to Impact Delivery (RAPID) Handbook as being crucial for developing safe CO2 transportation in both the gaseous and dense phase. This Project has been designed to fill gaps in the available data, which are crucial for the safe implementation of Carbon Capture and Storage (CCS) because liquid water is highly acidic in the presence of excess CO2; this acidity can be increased by trace amounts of sulphur dioxide (SO2) and hydrogen sulphide (H2S), and this acidity will greatly accelerate corrosion in transportation pipelines and can cause further problems in sub-surface storage. Keeping water and CO2 in a single phase during transportation will largely avoid these problems. In Call 1, we set out to design and develop two complementary experimental approaches using either Infrared spectroscopy or Karl-Fischer titration. The key is now to understand the major implications for the complex range of CCS mixtures. A further complication is that the phase behaviour is highly dependent on both composition and temperature, therefore in order to fully understand the behaviour of water in the context of CCS requires further measurements. For this project we are targeting the needs outlined by National Grid in their letter for pre-combustion CCS where H2 is a likely contaminant. We have obtained preliminary data for H2 which shows that the effects may be greater than for N2, but this needs full validation. Furthermore, we propose to test the widespread assumption that the behaviour of O2 impurities will mirror that of N2. O2 is important in CCS coupled to the oxyfuel technology. Grant number: UKCCSRC-C2-185.