Internal corrosion of CO2 transport pipelines for CCS purposes

2017-02-28T04:17:08Z (GMT) by Sim, Samson Yeat Son
The research reported in this thesis focuses on the fundamental understanding of carbon steel corrosion as relevant to the internal corrosion of pipelines intended for Carbon Capture and Storage (CCS) applications. The CCS process appears to be imminent in AustraliaI, as evidenced by current initiatives such as Carbonet, and supercritical CO2 pipelines represent the anticipated mode of CO2 transport from the capture to storage sitesII. A thorough literature review was conducted, which includes studies of the corrosion mechanism related to supercritical CO2 during transport, and the recent contributions from a dynamic field that is continuing to evolve throughout the course of this project. An empirical approach was used in this project to determine the effect of various input variables, including salt and acid impurities, temperature and pressure, on the subsequent corrosion rates of steel in the likely CCS relevant stream chemistry. A high throughput methodology was developed to screen a range of electrolyte chemistries in atmospheric (aqueous) conditions, and supplemented by tests in supercritical CO2. For this, a high pressure autoclave was also used to simulate the high pressure (>7.5MPa) during supercritical CO2 transport. This enabled an empirical model to be developed, in order to predict the expected corrosion rate as a function of electrolyte chemistry – serving as a platform for benchmarking CCS pipeline durability. The techniques in this study include potentiodynamic polarisation tests, weight loss tests, scanning electron microscopy, and optical profilometry. Generally, corrosion rates obtained from the presence of acid impurities and in the presence of an aqueous phase, were high. Corrosion attack was typically localised, with potential for severe attack in cases where co-speciation of acids with carbonic acid could occur. Experiments with increasing water concentration and pressure showed increased corrosion rates attributed to the increased solubility of CO2 in water and the behaviour of the corrosion product (iron carbonate). A correlation was also observed between experiments conducted in aqueous conditions compared to supercritical CO2, which gives merit to experimentation using high throughput methods. __________________________ I IIJ. Mack, B. Endemann, "Making carbon dioxide sequestration feasible: Toward federal regulation of CO2 sequestration pipelines", Energy Policy, 38 2 (2010): p. 735-743