Supercritical CO2 Pipelines Research Articles

Synergistic effect of O2 and SO2 gas impurities on X70 steel corrosion in water-saturated supercritical CO2

The synergistic effect of O2 and SO2 on the corrosion behavior of X70 steel was evaluated in water-saturated supercritical CO2 using weight loss analysis and surface analysis techniques. Corrosion experiments were conducted at 40°C and 100bar to simulate typical CO2 transportation conditions. Results indicate that the synergistic effects of O2 and SO2 enhance or inhibit the corrosion rate, depending on the concentration variation of impurities. SO2 had the highest corroding influence on X70 steel, with the corrosion rate of 1.10 mm/year with the addition of 500 ppmv SO2. The presence of SO2 changed the corrosion mechanism and the final products of corrosion consisted mostly of FeSO3. Low concentrations of O2 increased the corrosion rate (0.09 mm/year) primarily by destroying the integrity of the FeCO3 product film in the absence of SO2. However, the corrosion rate of X70 steel progressively decreased to 0.03 mm/year as the concentration of O2 increased to 1000 ppmv, due to high concentration of O2 causing the steel substrate to enter the passivation zone. This study is important for a number of industrial applications, as it provides a theoretical basis for corrosion control of supercritical CO2 pipelines.

含杂质超临界CO 2 输送管线腐蚀的研究进展

A range of impurities may exist in supercritical CO2 stream of transmission pipelines for carbon capture and storage (CCS) process, which are the potential corrosive factors to induce opera- tional risks of the supercritical CO2 transmission pipeline. The impurities induced inner side corro- sion of supercritical CO2 pipelines may become the bottleneck restricting the development and ap- plication of CCS. This paper reviews the recent research progress on the corrosion behavior of pipe- lines for supercritical CO2 transmission. The potential corrosion risks and the impact factors on cor- rosion are analyzed. The influence of impurities on the phase behavior, water chemistry characteris- tics, corrosion scales and the corrosion mechanism of transmission pipelines is also discussed. The shortcomings in the present investigations and the key scientific problems for further research are

The Influence of Impurities on the Chocking Process of Supercritical Carbon Dioxide Pipeline

Transportation safety of supercritical CO2 pipeline is a key aspect of Carbon Capture and Storage(CCS). For reducing the high pressure in supercritical pipeline when accidental cases arise, man-made release will be applied using chocking process. The downstream parameters of chocking process can be predicted based on the adiabatic process assumption. The presence of SO2 as an impurity is helpful for increasing the downstream temperatures through the chocking device to prevent the frozen hazard, whereas the presence of N2 as an impurity indicates a lower downstream temperature. The higher initial temperature can prevent the dry ice formation at the outlet of vent pipe when the multistage chocking is applied. Keywords—CCS, carbon dioxide, pipeline transportation, impurity, chocking process

Numerical Investigation of the Leakage Flow from a Pressurized CO2 Pipeline

The accidental release of supercritical CO2 is one of the main risks during the pipeline transportation for carbon capture and storage and enhanced oil recovery. The leakage of high pressure CO2 involves phase transition and complex changes of the pressure and temperature fields in the pipelines. A mathematical method for simulating the leakage flow through a crack in a pressurized CO2 pipeline is presented. The validated and accurate method has been employed to simulate the flow inside the pipe, while the leakage flow through the crack was calculated using a capillary tube assumption. In the numerical simulation, a real gas equation of state was employed instead of the ideal gas equation of state. Moreover, results of the flow through the crack and measurement data obtained from laboratory experiments of pressurized CO2 pipeline leakage are compared for the purpose of validation. The pipeline pressure and the leakage flow rates are analysed, which reveal the complex nature of the leakage flow of supercritical CO2 pipeline transport.

Safety Control on the Chocking Process of Supercritical Carbon Dioxide Pipeline

Transportation safety of supercritical CO2 pipeline is a key aspect of carbon capture and storage (CCS). For reducing the high pressure in supercritical pipeline when accidental cases arise, man-made release will be applied using chocking process. The downstream parameters of chocking process can be predicted based on the adiabatic process assumption. In the critical chocking process, the critical velocity at outlet is sonic. A chocking pipe can be designed for buffering between different chocking orifices according to the length of turbulence area produced by jetting momentum. For the effect of noise hazard produced by large jetting velocity, a muffler can be applied at the outlet of final stage orifice to atmosphere. For the influence of impurities on the chocking process of anthropogenic CO2 pipeline, the presence of SO2 as an impurity is helpful for increasing the downstream temperatures through the chocking device to prevent the frozen hazard, whereas the presence of N2 as an impurity indicates a lower downstream temperature. The higher initial temperature can prevent the dry ice formation at the outlet of vent pipe when the multistage chocking is applied.

The influence of impurities on the transportation safety of an anthropogenic CO2 pipeline

Transportation safety is a key aspect of carbon capture and storage (CCS), which is a major technology used to reduce greenhouse gas emissions. Supercritical CO2 pipelines have been certified as an optimised choice for CO2 transportation. The results of this study show that the Peng–Robinson (PR) equation of state is recommended for analysis of the properties of supercritical CO2. The influence of nonpolar and polar impurities on the two-phase region and the location of the sharp discontinuity in the density are found by analysing the ternary phase equilibrium and physical parameters using the PR equation of state. A transitional area between the supercritical phase and the dense phase, where the density changes abruptly, is defined as the quasi-critical region. This study describes the functional relation between the temperature and the pressure that defines the quasi-critical line by calculating the partial derivative equations and then determines the effect of impurities on the quasi-critical region of transported CO2. Operational recommendations for pipeline transportation of flue CO2 are developed using a pipeline operated by Sinopec as an example, demonstrating the influence of impurities in flue CO2 on saturation pressure for control and prevention of fractures in CO2 pipelines.

A risk assessment methodology for high pressure CO2 pipelines using integral consequence modelling

This paper presents a risk assessment methodology for high pressure CO2 pipelines developed at the Health and Safety Laboratory (HSL) as part of the EU FP7 CO2Pipehaz project. Until recently, risk assessment of dense phase and supercritical CO2 pipelines has been problematic because of the lack of suitable source term and integral consequence models that handle the complex behaviour of CO2 appropriately. The risk assessment presented uses Phast, a commercially available source term and dispersion model that has been recently updated to handle the effects of solid CO2. A test case pipeline was input to Phast and dispersion footprints to different levels of harm (dangerous toxic load and probit values) were obtained for a set of pipeline specific scenarios. HSL's risk assessment tool QuickRisk was then used to calculate the individual and societal risk surrounding the pipeline. Knowledge gaps that were encountered such as: harm criteria, failure rates and release scenarios were identified and are discussed.

Aqueous Corrosion Testing and Neural Network Modeling to Simulate Corrosion of Supercritical CO2 Pipelines in the Carbon Capture and Storage Cycle

A database was constructed from tests in aqueous electrolytes simulating the damage that may occur to ferrous transport pipelines in the carbon capture and storage (CCS) process. Temperature and concentrations of carbonic acid (H2CO3), sulfuric acid (H2SO4), hydrochloric acid (HCl), nitric acid (HNO3), sodium nitrate (NaNO3), sodium sulfate (Na2SO4), and sodium chloride (NaCl) were varied; the potentiodynamic polarization response, along with physical damage from exposure, was measured. Sensitivity analysis was conducted via generation of fuzzy curves, and a neural network model also was developed. A correlation between corrosion current (icorr) and exposure tests (measured in the form of weight and thickness loss) was observed; however, the key outcome of the work is the presentation of a model that captures corrosion rate as a function of environments relevant to (CCS) pipeline, revealing the extent of the threat and the variables of interest.

Design Overview of High Pressure Dense Phase CO2 Pipeline Transport in Flow Mode

In open literature, there is little information available with regards to the engineering and technological issues for material corrosion, in relation to high pressure supercritical CO2 pipeline transport from single point sources, such as the power industry. A typical CO2 pipeline is designed to operate at high pressure in the dense phase. However, it is evident that although there is considerable experience of testing materials in lower pressure gaseous CO2 in the oil and gas industry, there is little understanding of the behaviour of pipeline materials when in contact with impure CO2 captured either from power plants or the oil and gas industry.In this particular project development, a dynamic dense phase CO2 corrosion rig has been built (conditions: ∼85bar, 40°C and up to 5l/min flow rate) in flow mode, to understand the effect of impurities (SO2, O2, H2, NO2 & CO) present in captured CO2 on the pipeline transport materials. This unique facility in the UK was developed via the MATTRANS project funded by the E.ON-EPSRC strategic partnership (EP/G061955/1). The test rig includes different metallic materials (X grade steel: X60, X70 and X100) to assess the corrosion of pipelines, and different geometry components (tubes, plates, charpy and tensile coupons), to assess ageing and decompression behavior of polymeric seals (Neoprene, fluorocarbon, ethylene and Buna N) under water-saturated dense phase CO2 with different impurity concentrations (0.05mol % SO2; 4mol % O2; 2mol % H2; 0.05mol % NO2; 1mol % CO). The dynamic data generated from this dense phase CO2 corrosion rig will give vital information with regards to pipeline suitability and lifetimes, when operating with dense CO2.

The upper limit of moisture content for supercritical CO2 pipeline transport

A systematic method was established to determine the upper limit of moisture content for supercritical CO2 pipeline transport. In the corrosion experiments, the weight-loss method was applied to measure the corrosion rate of X70 steel exposed to a supercritical CO2/SO2/O2/H2O mixtures for different relative humidity, aiming to explore the critical relative humidity point for X70 steel corrosion under such conditions, which is a crucial point for setting the upper limit of moisture content. The critical relative humidity was estimated to be between 50% and 60% on the basis of the experiment results. The microstructure and chemical composition of the corrosion products were examined employing SEM and XRD. Based on the estimated critical relative humidity combining with the solubility consideration of H2O in CO2 at various temperatures and pressures, the pipeline thermodynamic model was used to determine the upper limit of moisture content for supercritical CO2 pipeline transport.