Testing the effects of Supercritical CO2 (scCO2)

Element supports the Energy Industry in managing the challenges of polymeric materials like elastomers, thermoplastics, thermosets, and composites in service in supercritical CO2 environments.

As part of the power generation industry, Carbon Capture Utilisation and Storage (CCUS) requires the containment and transport of supercritical CO2 (scCO2) in large quantities through pipes, valves, compressors, etc, each of which can contain non-metallic components essential for safe and efficient operation. These components can be items such as liners, seals and gaskets, or even composite structural parts and valve bodies.

scCO2 properties and non-metallic materials

Due to its characteristics, scCO2 is used as a non-toxic, recyclable, low-energy solvent in many other industries, including food production, pharmaceuticals, and building materials. Above 31 °C and 73.8 bar, CO2 turns to superritical CO2, showing characteristics of a liquid and a gas. It can permeate as quickly as a gas and be absorbed as much as a liquid. This presents the worst of both worlds in performance terms. The phenomenon results in

• high permeation rates (influencing metal corrosion rates, contamination, pollution, and loss of product durability),
• rapid gas decompression problems (including blistering, leaching out of stabilizers and plasticizers in the polymer)
• and excessive swelling leading to tearing of the material.

Non-metallic components like thermoplastic pipes and elastomeric O-rings are susceptible to swelling in contact with scCO2; the level of swell varies with temperature and pressure. In addition, elastomers are prone to rapid gas decompression (RGD) damage. The latter occurs when external pressure is released quickly, and the pressurized CO2 present in the polymer is unable to leave naturally by diffusion. At standard pressure and temperature, the volume of CO2 absorbed by a small seal can be significant, easily totaling 100 cm3, which means it can suffer irreversible fracture damage and possibly mechanical damage, such as local extrusion in service due to significant swell.

Exposure tests with scCO2

To the oil & gas industry supercritical CO2 has been present as a constituent of hydrocarbon production and for injection for decades. Our experts have significant experience and knowledge of how these materials behave in scCO2; this includes performance aspects such as dimensional stability, chemical aging resistance, RGD resistance, and permeability. Exposure tests to 1000 bar and 200 °C are routine, as are multi-cycle RGD/blister resistance tests and long-term (>1 year) durability tests.

The Element advantage

Element has supported the wider energy industry as it manages the challenges scCO2 presents to non-metallic materials for over 30 years. We have developed novel assessment and inspection techniques specifically to address the potential issues around scCO2 and polymers, allowing us to create and run customized test programs for our customers.
As Element’s Global Center of Technical Excellence for Polymers, the materials testing laboratory in Hitchin has designed a unique visual observation fixture that allows to monitor and measure materials in-situ whilst under pressurized scCO2 conditions. This includes the effect of pressure/temperature changes assessed in-situ, as well as the effect of RGD.

For more information about testing the effects of scCO2 on non-metalics or to request a quote, contact us today.