Ultrasonic measurement of liquid carbon dioxide

In recent years, CCS has gained additional attention as a possible means of meeting our climate improvement goals. With CCS demonstration projects under development, there is a need to focus on the widespread deployment of CCS and the technologies needed to make it viable. Upscaling CCS requires the construction of industrial clusters and the development of more complex transportation networks. Such large-scale systems demand reliable and accurate metering of CO₂ for fiscal, commercial, and regulatory purposes. Accurate measurement of CO2 streams is crosscutting along the CCS value chain and is an enabler for CCS business. Recent benchmarking studies agree that the CCS industry could benefit from the measurement capabilities fostered and developed in the oil and gas industry, where numerous metering techniques coexist. Ultrasonic flow meter technology is promising for CCS given the ability of such meters to handle large volumetric flow rates through large pipe sizes using a single metering unit. To date, verification tests of the ultrasonic technology for measuring liquid CO2 have been limited to enhanced oil or gas recovery (EOR or EGR) operations or extraction of CO₂ -rich natural gas, where the uncertainty of the actual flow rate is already quite high. The potential use of ultrasonic meters for CCS has yet to be fully tested and confirmed. Panametrics, a Baker Hughes business, and SINTEF have collaborated to address some of the most relevant knowledge gaps relating to ultrasonic meter performance: Sound attenuation through liquid/dense CO₂. The present theoretical work looks to estimate the vibrational relaxation time of pure CO₂ considering its characteristic temperature of different vibrational modes. The theoretical estimations are contrasted against ultrasonic measurements performed in a physical liquid CO2 testing rig using a four-path ultrasonic flow meter. The results presented here constitute a stepping stone towards understanding the implications of sound attenuation in CCS streams for ultrasound technology.