Abstract
Carbon Capture and Storage (CCS) is a promising technology that stops the release of CO2 from industrial processes such as electrical power generation. Accurate measurement of CO2 flows in a CCS system where CO2 flow is a gas, liquid, or gas-liquid two-phase mixture is essential for the fiscal purpose and potential leakage detection. This paper presents a novel method based on Coriolis mass flowmeters in conjunction with least squares support vector machine (LSSVM) models to measure gas-liquid two-phase CO2 flow under CCS conditions. The method uses a classifier to identify the flow pattern and individual LSSVM models for the metering of CO2 mass flowrate and prediction of gas volume fraction of CO2, respectively. Experimental work was undertaken on a multiphase CO2 flow test facility. Performance comparisons between the general LSSVM and flow pattern based LSSVM models are conducted. Results demonstrate that Coriolis mass flowmeters with the LSSVM model incorporating flow pattern identification algorithms perform significantly better than those using the general LSSVM model. The mass flowrate measurement of gas-liquid CO2 is found to yield errors less than ±2% on the horizontal pipeline and ±1.5% on the vertical pipeline, respectively, over flowrates from 250kg/h to 3200kg/h. The error in the estimation of CO2 gas volume fraction is within ±10% over the same range of flow rates.
Highlights
Accurate measurement of CO2 is essential in the practical deployment of the carbon capture and storage (CCS) technology
Since the accuracy of the instrument is the dominant component affecting the measurement uncertainty under two-phase flow conditions, this paper focuses on the accuracy evaluation of the instrument (Coriolis mass flowmeter) in terms of relative error
For the Coriolis mass flowmeter in horizontal orientation, NRMSE is reduced from 2.82% to 1.05% and 0.80% by using least squares support vector machine (LSSVM) model and FP_LSSVM model, respectively
Summary
Accurate measurement of CO2 is essential in the practical deployment of the carbon capture and storage (CCS) technology. The measurement of CO2 flow in CCS pipelines is more challenging than metering the oil, gas or multiphase flow in the air and gas industry due to the readily varying physical properties of CO2. The phase boundaries in the CO2 phase diagram are close to each other and under ambient conditions In this case, unstable temperature or pressure of CO2 flow may result in significant variations in the CO2 physical characteristics (Hunter and Leslie, 2009). Application of Coriolis mass flowmeters to the measurement of single-phase gas/liquid CO2 flow have been conducted (Adefila et al, 2015; Adefila et al, 2017; Lin et al, 2014). Significant challenges are to overcome for the direct flow measurement techniques to achieve 1.5% measurement uncertainty specified in the European Union − Emissions Trading Scheme under all expected CCS conditions (TUV NEL, 2009)
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