Estimating the Failure Probability of CO2 Pipeline as Part of Carbon Capture and Storage Chain

This paper presents the development of an analytical method for predicting the Cumulative Distribution Function (CDF) for CO2 pipeline puncture failures based on fitting the Weibull distribution to the failure hole size data in the Pipeline and Hazardous Material Safety Administration (PHMSA) historical database using the Maximum Likelihood Estimator (MLE). The method starts with obtaining the minimum acceptable sample size for acquiring a reliable MLE through assessing the quality of the MLE as a function of the data sample size using the Mean Squared Error (MSE). For low quality MLE, the bootstrapping method is employed to enhance the confidence of the distribution fitting by calculating the 95% Confidence Interval (CI) of the MLE. The minimum acceptable sample size is then compared with the number of the database CO2 hole size data to decide whether the bootstrapping is needed. The results show that the sample data available are far less than what would be required for obtaining a reliable MLE and hence the bootstrapping method is applied to acquire a range of CDFs that may be considered valid for representing the probability distribution of CO2 pipeline failure hole sizes. The resulting CDF range shows that at least 70% of the failure holes are smaller than 0.25 of the pipe internal diameter for CO2 pipelines

Multi-objective economic and environmental assessment for the preliminary design of CO2 transport pipelines

A methodology based on the multi-objective optimisation of economic and environmental aspects is presented to support the preliminary design of CO2 transport pipelines employed as part of Carbon Capture and Storage (CCS) systems. Pareto optimal design solutions are determined for a realistic point-to-point CO2 pipeline using Level Diagrams and choosing the Nominal Pipe Size (NPS) as a decision variable. A quantitative procedure entailing the definition of economic and environmental key performance indicators is defined to allow the identification of an optimum pipeline design. The outcome is compared against the minimisation of single-objective indicators based on the CO2 avoided and carbon pricing concepts. The results of a case-study concerning a 70 km long pipeline transporting 10 Mt yr−1 of supercritical CO2 show that the multi-objective method yields an optimum NPS equal to 30, higher than the NPS 28 deriving from the alternative indexing methods. The proposed multicriteria approach effectively considers case-specific environmental sustainability constraints, which result in determining 46% of the overall performance measure of the identified optimum solution. The results show that conventional single-objective methods underestimate the contribution of environmental factors up to 2.6% of the overall performance index value. A Monte Carlo probabilistic analysis is performed to verify the robustness of the results with respect to the possible uncertainties

A model of the near-field expansion of CO2 jet released from a ruptured pipeline

The transportation of pressurised CO2 using pipelines is a crucial element of the Carbon Capture and Storage chain; for their safe design the ability to accurately predict the consequences of a failure, the jet release and ensuing dispersion is essential. Such phenomena are commonly modelled in stages: jet expansion followed by atmospheric dispersion. For jet expansion modelling, both analytical and Computational Fluid Dynamic (CFD) models are available to predict the fully expanded flow conditions which are subsequently used as inputs in dispersion modelling. Although analytical models are computationally efficient, due to the lack of experimental data, their predictions have yet been verified. In this work, a conservation law based multiphase analytical model is constructed with a rigorous equation of state. The predicted flow variables at full expansion are then compared to those from the Shear Stress Transport k-ω CFD model. The quantitative comparisons between two models provide necessary verification of the application of analytical models in accidental release modelling

Henry’s Law Constants and Vapor–Liquid Distribution Coefficients of Noncondensable Gases Dissolved in Carbon Dioxide

The accurate determination of the solubilities of the typical impurity gases present in captured CO2 in the carbon capture, utilization, and storage chain is an essential prerequisite for the successful modeling of the CO2 stream thermodynamic properties. In this paper, Henry’s law constants and the vapor–liquid distribution coefficients of six noncondensable gases, namely, N2, O2, H2, CH4, Ar, and CO, at infinite dilution in liquid CO2 are derived based on published vapor–liquid equilibrium data at temperatures ranging from the triple point (216.59 K) to the critical point (304.13 K) of CO2. The temperature dependence of Henry’s law constants of the six gases is correlated using approximating functions previously proposed for aqueous solutions. A correlation that provides the best fit for the Henry constants data for all the six gases, with the accuracy (absolute average deviation %) of 4.2%, is recommended. For N2, O2, H2, Ar, and CO, the combined standard uncertainty in the derived Henry constants is less than 6%, whereas for CH4, due to a larger deviation between the utilized data, the uncertainty is less than 18%. Analysis of the temperature variation of the vapor–liquid distribution coefficient at infinite dilution shows that when all the six gases are present in the CO2 stream, separation of N2, O2, Ar, and CO from CO2 can be problematic due to their similar volatilities, while the distinct volatilities of H2 and CH4 at lower temperatures make their separation from CO2 easier

An Integral Model for Pool Spreading, Vaporisation and Dissolution of Hydrocarbon Mixtures

A two-phase or liquid release of flammable or toxic fuel may rainout forming a liquid pool. This represents a major safety hazard as the liquid will evaporate upon contact with the substrate forming a flammable vapour cloud. This paper describes a new robust model for spreading, vaporisation and dissolution of a multi-component pool. The new model is an extended version of the pool model PVAP in the Phast consequence modelling package. The multi-component pool model tracks the mixture composition of the transient pool as a function of time, and employs established mixing rules to estimate overall pool properties. Two distinctive cases for pool vaporisation are studied namely boiling and evaporation. Additionally, the model makes continuous checks for transitions between boiling and evaporation by performing a bubble point calculation at each step of the simulation. The present work introduces for the first time a model for the dissolution of water- soluble chemicals present in a multi-component pool. Predictions using the model are compared against the widely-used HGSYSTEM multi-component pool model, LPOOL, and published experimental data in terms of numerical robustness and accuracy. © 2012 IChemE

Numerical study of the effect of heat transfer on solid phase formation during decompression of CO2 in pipelines

CO"jats:sub"2"/jats:sub" solid phase formation accompanying rapid decompression of high-pressure CO"jats:sub"2"/jats:sub" pipelines may lead to blockage of the flow and safety valves, presenting significant hazard for safe operation of the high-pressure CO"jats:sub"2"/jats:sub" storage and transportation facilities. In this study, a homogeneous equilibrium flow model, accounting for conjugate heat transfer between the flow and the pipe wall, is applied to study the CO"jats:sub"2"/jats:sub" solid formation in a 50 mm internal diameter and 37 m long pipe for various initial thermodynamic states of CO"jats:sub"2"/jats:sub" fluid and wide range of discharge orifice diameters. The results show that the rate of CO"jats:sub"2"/jats:sub" solid formation in the pipe is limited by heat transfer at the pipe wall. The predicted amounts of solid CO"jats:sub"2"/jats:sub" are discussed in the context of venting of CO"jats:sub"2"/jats:sub" pipelines. Document type: Articl

Assessment of Fracture Propagation in Pipelines Transporting Impure CO2 Streams

Running fractures are considered as most dangerous catastrophic mode of failure of high-pressure transportation pipelines. This paper describes methodology for coupled modelling of an outflow, heat transfer and crack propagation in pipelines. The methodology is validated and applied to investigate the ductile fracture propagation in pipelines transporting impure CO 2 streams to provide recommendations for the fracture control. To assess the propensity of pipelines to brittle fractures, the temperature distribution in the pipe wall in the vicinity of a crack is simulated for various conditions of heat transfer relevant to both overground and buried pipelines

A fully coupled fluid-structure interaction simulation of three-dimensional dynamic ductile fracture in a steel pipeline

Long running fractures in high-pressure pipelines transporting hazardous fluid are catastrophic events resulting in pipeline damage and posing safety and environmental risks. Therefore, the ductile fracture propagation control is an essential element of the pipeline design. In this study, a coupled fluid-structure interaction modelling is used to simulate the dynamic ductile fractures in steel pipelines. The proposed model couples a fluid dynamics model describing the pipeline decompression and the fracture mechanics of the deforming pipeline exposed to internal and back-fill pressures. To simulate the state of the flow in a rupturing pipeline, a compressible one-dimensional computational fluid dynamics model is applied, where the fluid properties are evaluated using a rigorous thermodynamic model. The ductile failure of the steel pipeline is described as an extension of the modified Bai-Wierzbicki model implemented in a finite element code. The proposed methodology has successfully been applied to simulate a full-scale pipeline burst test performed by British Gas Company, which involved rupture of a buried X70 steel pipeline, initially filled with rich natural gas at 11.6 MPa and −5 °C. Document type: Articl