Depressurization of CO2 in a pipe: High-resolution pressure and temperature data and comparison with model predictions (original) (raw)
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International Journal of Greenhouse Gas Control, 2021
To design and operate safe and efficient CO2-transportation systems for CO2 capture and storage (CCS), engineers need simulation tools properly accounting for the fluid and thermodynamics of CO2. As the transportation systems evolve into networks, it becomes important that these tools also account for impurities in the CO2, which may significantly affect the thermophysical properties, directly impacting system design and safety. Tube-depressurization experiments provide crucial data to develop and validate models describing transient multiphase multicomponent flow in pipes. In this work, we perform experiments in a new facility with dense and fast instrumentation for both pressure and temperature. One experiment is for CO2 with 1.8 mol % N2, and one has 1.92 mol % He, both starting from 12 MPa and 25 ∘ C. In order to quantify the effect of impurities, the experiments are compared to results for pure CO2 and analysed on the background of simulations. We employ a homogeneous equilibr...
Energy Procedia, 2014
Pressure-release experiments of CO 2 with impurity contents of 10, 20 and 30 mol% nitrogen have been executed. The experimental investigations were performed in a 140 m long horizontal tube with an inner diameter of 10 mm. The initial conditions of the CO 2 -N 2 mixtures were in the supercritical region at approximately 120 bar and 20 °C. The results, which showed a good repeatability, were then compared with numerical data from a homogeneous equilibrium model. The investigations have concentrated on the pressure wave at the start as well as the pressure and temperature development during the pressure release. The model, which has a certain complexity, but still contains several simplifications, gave relatively good results for all three gas mixtures. Although the absolute values for the temperature development showed to be consistently higher in the experimental results compared to the numerical results, the liquid dry-out points were predicted with good accuracy at all measurement points. The numerical results of the pressure development match the experimental results very well, both regarding the absolute and relative values. Regarding the speed of the pressure wave, the numerical results were consistently too high, which is believed to be caused by the EOS overpredicting the speed of sound for our cases. The good results, especially for the pressure, are promising, and further work is suggested to improve the model.
Industrial & Engineering Chemistry Research
Decompression of CO 2 pipelines is studied both experimentally and numerically to provide a partially validated model as the basis for the prediction of the hazards associated with CO 2 solid formation. The pipeline decompression experiments, performed using a fully instrumented 36.7 m long and 50 mm internal diameter test pipe up to a maximum pressure of 45 bar, incorporating discharge orifice diameters of 4 and 6 mm, reveal the stabilisation of pressure and temperature near the CO 2 triple point. Also, video recordings of the decompression flow in the reinforced transparent section of the steel pipe show that initial stratification of the constituent liquid and vapour phases is followed by rapid CO 2 solid formation and accumulation in the pipe. To aid the prediction of hazards associated with solids formation in pipelines, a homogeneous equilibrium pipeline decompression model is developed accounting for the pertinent physical properties of CO 2 in the liquid, vapour and solid states. The model is validated against the experimental data, showing ability to accurately predict the measured pressure and temperature variations with time along the pipe, as well as the time and amount of the solid CO 2 formed upon decompression across the triple point.
Industrial & Engineering Chemistry Research, 2018
Decompression of CO2 pipelines is studied both experimentally and numerically to provide a validated model as the basis for the prediction of the hazards associated with CO2 solid formation. The pipeline decompression experiments, performed using a fully instrumented 36.7 m long and 50 mm internal diameter test pipe up to a maximum pressure of 45 bar, incorporating discharge orifice diameters of 4 and 6 mm, reveal the stabilisation of pressure and temperature near the CO2 triple point. Also, video recordings of the decompression flow in the reinforced transparent section of the steel pipe show that initial stratification of the constituent liquid and vapour phases is followed by rapid CO2 solid formation and accumulation in the pipe. To aid the prediction of hazards associated with solids formation in pipelines, a homogeneous equilibrium pipeline decompression model is developed accounting for the pertinent physical properties of CO2 in the liquid, vapour and solid states. The model is validated against the experimental data, showing ability to accurately predict the measured pressure and temperature variations with time along the pipe, as well as the time and amount of the solid CO2 formed upon decompression across the triple point.
2014
Pressure-release experiments of CO2 with impurity contents of 10, 20 and 30 mol% nitrogen have been executed. The experimental investigations were performed in a 140 m long horizontal tube with an inner diameter of 10 mm. The initial conditions of the CO2-N2 mixtures were in the supercritical region at approximately 120 bar and 20 °C. The results, which showed a good repeatability, were then compared with numerical data from a homogeneous equilibrium model. The investigations have concentrated on the pressure wave at the start as well as the pressure and temperature development during the pressure release. The model, which has a certain complexity, but still contains several simplifications, gave relatively good results for all three gas mixtures. Although the absolute values for the temperature development showed to be consistently higher in the experimental results compared to the numerical results, the liquid dry-out points were predicted with good accuracy at all measurement poi...
Modelling of gas decompression process for CO2 transmission pipeline
2015
The decompression behaviour of CO2 pipelines must be determined accurately in order to estimate the proper pipe toughness for fracture arrest. Anthropogenic CO2 may contain impurities that can modify the fluid decompression characteristics quite significantly. In this thesis, a simulation study of the decompression behaviour of CO2 based mixtures is presented. The current research is aimed at developing a new multi-dimensional gas decompression model using the Computational Fluid Dynamics (CFD) software ANSYS Fluent. The thermodynamic properties of CO2 mixtures must be determined by using an accurate equation of state (EOS). A comparative study between some of widely used equations of state for gas pipelines is conducted. The wide range GERG-2008 EOS is accordingly adopted to provide the thermodynamic properties of CO2 mixtures. Factors that affect the behaviour of decompression wave speed and the arrest toughness such as operating conditions, fluid compositions and the actual pipe ...
International Journal of Greenhouse Gas Control, 2015
The COSHER joint industry project involved the conduct of large scale experiments to provide release and dispersion data under well-defined conditions, studying the full bore rupture of a CO 2 dense phase high pressure underground pipeline at large scale. The data generated are useful for model development and validation as well as for better understanding of the risks due to large scale underground CO 2 pipeline ruptures. In order to simulate the depressurization of a pipeline, a 219.1 mm diameter pipeline loop was fed from both ends by a 148 m 3 reservoir of CO 2. The rig was designed to promote outflow in the liquid phase for as long as possible. About 136 ton of CO 2 were released in 204 s. During the experiments, measurements of the fluid pressure, fluid temperature and wall temperature of the test facility were made together with measurements of the CO 2 concentration contours and temperature within the dispersing gas cloud.
Towards a thorough Validation of Simulation Tools for CO 2 Pipeline Transport
Energy Procedia
In this work the Schlumberger flow assurance tool OLGA and SINTEF Energy Research in-house CFD tool are assessed for their ability to describe depressurization behaviour of CO 2 pipelines. For this purpose, three full-bore experimental depressurization tests with pure CO 2 have been performed at the Statoil's R&D center in Trondheim, Norway. Simulations results are in general agreement with the experiments with the exception of the behaviour at the innermost position of the where OLGA predicts significantly lower temperatures, and SINTEF tool overestimate the temperature. Both models predict liquid dry-out time with an error of a few seconds. The simulation results are sensitive to the pipe outer heat transfer coefficient, used between the pipe surface and the ambient humid air. Reduction of the uncertainty in the heat-flux to the pipe is identified as a key factor for further validation.
Chemical Engineering Research & Design, 2020
Pressurized liquefied gases such as carbon dioxide are transported at a pressure above their saturation pressure. Therefore, if a pipeline transporting this substance ruptures, an abrupt expansion occurs, causing the flashing of the fluid. Computational tools that predict how fast a depressurization develops, help to assess the consequences of potential pipeline rupture scenarios. This paper describes the development of a 2-D full-bore rupture decompression model to simulate the transient depressurization of a pipeline transporting pure liquefied CO 2 , using ANSYS Fluent as CFD software. The scope of work focuses on incorporating non-equilibrium phase transition, while addressing the calculation of properties for metastable liquid. Additionally, it includes the comparison of model predictions when implementing two thermodynamic approaches: the Peng-Robinson Equation of State (EoS), and correlations developed in this work based on the Span-Wagner EoS. It was found that the thermodynamic approach is deemed to have a predominant effect on the arrival time of the decompression wave front at different locations along the computational domain, while the mass transfer coefficient in the source terms (C) governs the phase transition and the pressure plateau representing this phenomenon.
A homogeneous relaxation flow model for the full bore rupture of dense phase CO2 pipelines
International Journal of Greenhouse Gas Control, 2013
The development of an homogeneous relaxation flow model for simulating the discharge behaviour following the full bore rupture of dense phase CO 2 pipelines is presented. Delayed liquid-vapour transition during the decompression process is accounted for using an empirically derived equation for the relaxation time to thermodynamic equilibrium. The flow model's robustness is successfully demonstrated based on a series of hypothetical shock tube tests. Model validation on the other hand is performed by comparison of the predictions against experimental data obtained for the full bore rupture of realistic scale CO 2 pipelines. Within the ranges investigated, it is found that although delayed phase transition effects have negligible impact on the pipeline decompression rate, ignoring such phenomena results in underestimating the transient discharge rate. This is important since the latter governs the minimum safety distances to CO 2 pipelines and emergency response planning in the unlikely event of pipeline failure.