Experimental evaluation of density meters using liquid CO₂ and their effect on volumetric to mass flow conversion for CCS

CO₂ capture and storage (CCS) is an important technology for reducing atmospheric CO₂ emissions. Urgent climate targets require widespread implementation of CCS. CCS commands the deployment of measurement technology that enables accountability, process control, and reporting of the stored mass of CO₂ to regulatory bodies. The metering needs through the CCS value chain encompass as a bare minimum mass flow rates and stream composition. Most CCS-suitable flow metering technologies measure volumetric flow rates; thus, density knowledge is needed for volumetric-to-gravimetric flow rate conversion. Mass flow measurement, or mass derived from combined volume and density measurements, is fundamental in all nodes where custody transfer occurs. In this work, three off-the-shelf density measurement technologies were tested. The technologies encompass a Coriolis meter, a Gamma-ray densitometer and a torsional resonator. Densities calculated using the Span-Wager equation of state were used as reference. To assess the capabilities of each technology, the experimental campaign encompasses a broad operation envelope relevant to CCS applications. The gamma-ray meter, calibrated in situ, presented the least deviation from the reference density. The Coriolis measurements were highly repetitive, suggesting that calibration with CO₂ would improve the performance. Density measurements exhibited a high sensitivity to temperature; thus accurate reference temperature is required in the vicinity of the fiscal meters when deployed in the field.