Understanding dense phase CO2 corrosion problems

Increased carbon emissions from the world's energy sector have brought carbon capture and storage (CCS) issues to the forefront. Concerns about pipeline materials corrosion, corrosion deposition, elastomers decomposition and hydrate formation play a significant role in pipeline development projects for CCS. Impurities, temperatures, pressures from the source facility (power plant) to the reservoir via on and off-shore pipelines all pose environmental risks and health concerns for operators to consider when planning their operating scenarios: compression and decompression. Therefore it is important to understand the corrosion mechanisms to prevent or mitigate transport fluid challenges. This study focuses on high pressure dense phase CO2 corrosion problems
The dense phase flow loop facility* at Cranfield is the largest/unique of its kind in the UK, and is capable of running several thousands of hours in flow mode. This development has comprised a number of process equipment, including, high pressure observation window, infrared sensors and monitoring temperature, pressure, and also addition of materials up to 2 inch in diameter and up to 1 m in length for corrosion exposure.
This paper specifically deals with transporting engineering challenges when carbon dioxide occurs in the dense phase (saturated with water) via pipelines and discusses the efforts to put in place proper testing facilities to understand the behavior of the carbon steels (X60, X70 & X100) and elastomers (Buna N, Ethylene Propylene, Neoprene and Fluorocarbon) when exposed to the mixture of CO2 with SO2 as impurity (500 ppm) under realistic conditions For the tests carried out as part of this work, we exposed approximately 30 specimens of different geometry for varying time periods (50 h, 200 h, 400 h, 700 h and 1100 h) during the course of the 1100 hour test period, using CO2+SO2 mixture and the corrosion behavior was investigated via a weight loss method. Surface analyses using ESEM and XRD were applied to understand the morphology and chemical composition of the corroded/deposited sample surface. Initially just after 50 h of exposure, very low quantities of corrosion product covered the specimen's surface, but over time, this was gradually increased to thick uniform product film after an extended period of corrosion (1100 hours). The corrosion product film mainly composed of FeSO3 trihydrate. This study suggests that the corrosion data obtained to date in this process could be used to provide the short term and long term strategies for CCS solutions.