Integrity considerations for dehydration of carbon dioxide

Abstract

Carbon capture, sequestration, and utilisation is widely considered to be one of the key enablers to decarbonising the economy. Transportation of carbon dioxide (CO₂) is a key focal area in any carbon capture and storage project. While dehydration of natural gas for transportation is well understood and regulated, the same cannot be said for CO₂. This is due to its immaturity relative to natural gas and due to properties of CO₂ being radically different to those of hydrocarbons. One of those physical properties is the ability of CO₂ to saturate with water. Excessive water in CO₂ transportation and injection systems can cause integrity and operability problems such as corrosion, blockages from hydrates and water ice, and slugging due to liquid water dropout. Contaminants present in the CO₂ stream such as methanol and hydrogen can also have a significant impact on the phase envelope. Therefore, to mitigate these issues, dehydration specifications need to be selected based on phase envelopes and other important project parameters such as corrosion, ambient temperatures, and hydrate formation. For every individual project, a selection needs to be made to determine the applicable CO₂ dehydration specification, considering both the normal and transient operating conditions. Based on the selected specification, the most suitable method for implementing dehydration should be selected, along with the optimum location of the dehydration equipment in the multi-stage pressure-boosting plant. This study explores these challenges and presents a methodology for overcoming them.