Near-critical CO₂ flow for carbon capture and storage

Handling CO₂ flow rates for the purposes of capture and sequestration necessitates high pressure and low temperature (in order to maximize density and minimize volumetric flow rate) which brings the flow close to the critical point of CO₂ at approximately 74 bar and 31°C. We are presenting a first experimental investigation of several properties of two near-critical CO₂ flows, namely pipe flow and Joule-Thompson throttling. Shadowgraph technique was employed to visualize the pipe flow structure in an optically accessible test section. CO₂ was compressed in a 1-liter hydraulic accumulator using highpressure nitrogen. Downstream of the cylinder was the test section and a needle valve that controlled the mass flow rate. The results indicated a strong sensitivity of the pressure drop in the pipe on inlet conditions near the critical point. Due to the fact that the isothermal compressibility is very large near the critical point it is very difficult to control the density in the vicinity of the critical point.