Optimization of liquefaction cycles applied to CO2 coming from onshore pipeline to offshore ship transportation

Abstract

In the field of the CO2 transportation for the Carbon Capture, Utilization and Storage (CCUS) process chain, several analyses show that, for a large-scale CO2 transportation, pipeline transportation is the preferred method on land due to its lower cost. Barges also present a feasible alternative if the capture site is near a waterway. Maritime transport becomes more advantageous than pipelines, particularly over long distances and across ocean. Despite the need to liquefy CO2 and to add temporary storage facilities for loading and unloading onto ships, beyond a certain distance at fixed CO2 transported and plant life, ship transport optimal at pressures of 7 or 15 bar depending on the type of vessel. Impurities in CO2, arising from various industrial processes and variable performances of capture technologies, increase energy consumption during compression and could cause corrosion risks. Specifications for CO2 ship transport limit the concentration of certain impurities with strict thresholds. Methods for purifying CO2, such as the two-flash system and stripping column, have been proposed to meet these specifications. The studied CO2 liquefaction methods show that hybrid cycles, combining open cycle with Joule-Thompson expansion and closed cycle with cooling machine offer reduced energy consumption and improved CO2 recovery compared to open or closed cycles. In the presence of the maximum threshold of impurities in the pipeline, energy consumption can nearly double from 21.8 kWh/tCO2 to 40.9 kWh/tCO2, with the highest recovery rising 98.1 %. This research underscores the importance of optimizing CO2 transport strategies to facilitate the deployment of CCUS technologies.

Keywords

• CO2 transport
• CCUS
• Optimization
• Economic
• Exergetic
• Liquefaction