Supercritical Fluids

Supercritical CO2 System shown with automated control features.

A supercritical fluid is any substance at a temperature and pressure above its critical point. It can diffuse through solids like a gas and dissolve materials like a liquid. Near the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties of a supercritical fluid to be “fine-tuned”. Supercritical fluids are suitable as a substitute for organic solvents in a range of industrial and laboratory processes. Carbon dioxide is one of the many commonly used supercritical fluids. Applications that involve supercritical fluids include extractions, nano particle and nano structured film formation, supercritical drying, carbon capture and storage, as well as enhanced oil recovery studies. Parr has provided systems at one time or another for all the aforementioned applications. The supercritical fluid extraction system pictured above and diagramed below incorporates a 1.2 liter vessel rated for use at 4300 psig (300 bar) at temperatures to 300 °C. The system includes an automated inlet valve and an air piloted back pressure regulator which is used to facilitate a controlled pressure release at the end of the test. The vessel is heated with a 1500W flexible mantle heater. The feed system (not pictured) includes a pump capable of delivering up to 1.5 gallons per minute (5.7 lpm) of liquid carbon dioxide at pressures up to 4000 psig (275 bar).