The Fiscal Metering of Transported CO2-Rich Mixtures in CCS Operations

Transport of captured CO2 to permanent storage sites plays an important role in the CCS chain. The pressure and temperature conditions during transport of CO2 by pipelines are very close to the critical conditions of CO2-rich mixtures, and therefore, small changes in pressure and temperature can result in significant changes in the physical properties of the mixtures. This can also challenge the fiscal metering of CO2-rich mixtures, where the accuracy requirements of EU ETS for fiscal metering is required to be in the range of ±1.5% by mass. Accordingly, in this work the performance of suitable flowmeters for CCS chain is evaluated.
A Coriolis mass flowmeter (OPTIMASS 6000-S08 provided by KROHNE Ltd) was selected here, as it can directly measure mass as well as density of the transported fluid. A unique flow loop was designed and constructed based on comparing totalized mass flow shown by the flowmeter with the mass measured using high accuracy weighing scale. The set-up has previously been calibrated using pure CO2 both in the gas and dense liquid phases at pressure and temperature ranges representative of CO2 pipelines. The studies showed that the set-up and the selected flowmeter are in good agreement with both the specification provided by manufacturer as well as EU ETS regulations [1]. In this paper, we evaluate the performance of Coriolis meter in the presence of impurities by using CO2 mixtures representative of different capture technologies, i.e. post-combustion, pre-combustion and oxyfuel. The conditions studied include temperatures from 288 to 295 K, pressure ranges 1.5 MPa to 6.1 MPa and flow rates from 0.6 kg/h to 32.1 kg/h with the turndown of 10 to 50. The recorded flow rate measurements were in good agreement with the weighed values, and moreover, within the regulation requirements stated by EU ETS.