Coriolis Metering Technology for CO2 Transportation for Carbon Capture and Storage
Highly reliable and accurate Coriolis meters have been proposed for metering carbon dioxide in carbon capture and storage (CCS) operations to provide accurate flow measurements. However, there is a lack of calibration studies to quantify Coriolis measurement uncertainty for liquefied CO2. In this study, a first-of-its-kind apparatus was designed, built, and used to calibrate an industrial-scale Coriolis meter using CO2 in the liquid phase. The standard uncertainty of the meter was evaluated within the temperature range 290 to 293 K and at a pressure of 6.5 MPa.
Keywords: CCS, CO2 metering, Coriolis meter, uncertainty, carbon dioxide
Over the last two decades, there has been growing public concern [1, 2] about increasing CO2 emissions  and the consequences in terms of climate change. Approximately 26 % of global CO2 emissions were contributed from fossil fuel power generation [3, 4]. Therefore, carbon dioxide capture and storage (CCS) has been proposed as a short-term solution to significantly reduce CO2 emissions . CO2 captured from power stations will be injected
into geological reservoirs to reduce these emissions [5-7]. Unfortunately, CCS has been slow to develop and achieve commercial success due to a lack of business models. Since accurate flow measurements are required for both commercial and regulatory purposes, a proven metering technology is required to accelerate CCS commercialization. Additionally, the UK Advanced Power Generation Technology Forum (APGTF)  has clearly stated that research and development for CO2 accounting is needed to develop techniques for fiscal metering of CO2 with impurities to an accuracy of ±2 % in the gas phase and liquid phases. However, there are no published studies of accuracy in metering CO2 in the liquid phase. Accordingly, in this study, a calibration system was designed and built to evaluate the uncertainty of metering liquefied CO2.
Material and experimental apparatus
A Coriolis meter was selected for this work, as it can directly measure mass and is expected to be hardly affected by temperature and pressure conditions . The experimental method developed was based on a gravimetric calibration [10, 11]. Temperature, pressure, and flow rate of the tests in this study were at a temperature from (290 to 293 K), pressure at 6.5 MPa, and flow conditions between (0.5 and 0.65 L/min). In this study, 99.9995 vol% of certified supercritical CO2 from BOC was used. A calibration system was designed and built to determine the measurement uncertainty of Coriolis’s mere use for liquid CO2. The smallest industrial-scale Coriolis meter (Krohne, OPTIMASS 6000-S08) with a U-tube design was selected to quantify its uncertainty.
A pressure transducer (GE, UNIK 5000) with 0.1 % standard uncertainty and a thermo sensor integrated with a Coriolis meter were used to monitor pressure and temperature during measurements. The calibration system was controlled via a data acquisition unit with data logged in automatically. Density, temperature, and mass/volume flow rate from the Coriolis flow meter were recorded by An XFC 300 Data logger supplied by Krohne. Finally, the mass flow rate recorded by the Coriolis flow meter during calibration was compared with that determined by the designed rig.
Results and discussion
Two calibration runs were conducted under different flow rates (0.5 and 0.65 L/min), temperature (290 to 293 K), and pressure at 6.5 MPa. Furthermore, during an experiment, the completely constant temperature of the system was difficult to maintain due to friction heat generated by a piston pump head, leading to a temperature fluctuation of 2 K. However, the uncertainties evaluated were hardly affected because the measured mass flow based on the gravimetric calibration method is independent of temperature and pressure conditions . Fig. 1 shows typical physical characteristics of the calibration run at a pressure of 6.5 MPa with a pressure fluctuation of ± 0.1 MPa, temperature between (290 and 292
K) and flow rate at 0.5 L/min. Also, In Fig.1, all of the densities of CO2 recorded from the CO2 Metering Technology in the test runs are above 800 kg/m3 which indicates the calibration system was successful to remain measuring CO2 in the liquid phase without any phase transition during a calibration.
In addition, the measured error of the Coriolis flow meter, u, was calculated using the following equation
Where Mc is the mass flow rate measured from the CO2 Metering Technology and m ref is the mass of CO2 pumped through the Coriolis flow meter. This was recorded by the high-precision weight scale. m ref is calculated
Where m cylinder is the mass of CO2 injected in the storage cylinder and m pipeline is mass of CO2 collected in the collection vessel. The measurement errors, u, are presented in Table 1. The measurement errors obtained in this study are -0.14
% and 0.04 % at temperature from run 1 and run 2, respectively, where 0.025 % is due to the measurement uncertainty of the weight scale.
Table 1. Operating parameters and uncertainties measured using pure CO2 in this study
|Run||Temperature (K)||Pressure (MPa)||flow rate (L/min)||Measurement error, u (%)|
|1||290-292||6.5 ± 0.1||0.5 ± 0.05||0.04 ± 0.029|
|2||291-293||6.5 ± 0.1||0.65 ± 0.05||-0.14 ± 0.021|
A calibration system for evaluating the measurement uncertainty of a Coriolis metering C02 that is and has been designed and built. In addition, The physical parameters monitored in the calibration runs indicate that CO2 successfully remained in the liquid phase without phase transition during calibration.
Accordingly, the system was tested and validated to be able to determine the uncertainty of the Coriolis meter using liquefied CO2. Also, the maximum uncertainty obtained in this study is 0.14 %, which is far less than the required uncertainty of 2 % stated by APGTF.
Furthermore, further measurements needed to be conducted over a wide range of temperatures and pressures representative of CCS operation conditions to quantify more reliable, consistent measurement uncertainty of the Coriolis metering CO2 in the liquid phase.
The authors would like to acknowledge funding received for Project Comet – CO2 Metering Technology in Transportation by Pipeline for CCS under the DECC Carbon Capture Storage Innovation Competition.
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