Determination of the Plastic Stress–Strain Relationship of a Rupture Disc Material with Quasi-Static and Dynamic Pneumatic Bulge Processes

Rupture discs, manufactured using a hydraulic or pneumatic bulge process, are widely used to protect vessels from over-pressuring. The stress–strain relationship of the material in the bulge process plays a major role in understanding the performance of rupture discs. Moreover, both the theoretical analyses and numerical simulations of rupture discs demand a reliable stress–strain relationship of the material in a real bulge process. In this paper, an approach for determining the plastic stress–strain relationship of a rupture disc material in the bulge process is proposed based on plastic membrane theory and force equilibrium equations. Pressures of compressed air and methane/air mixture explosions were used for the bulge pressure to accomplish the quasi-static and dynamic bulge processes of tested discs. Experimental apparatus for the quasi-static bulge test and the dynamic bulge test were built. The stress–strain relations of 316L material during bulge tests were obtained, compared, and discussed. The results indicated that the bulge height at the top of the domed disc increased linearly with an increase in bulge pressure in the quasi-static and dynamic bulge processes, and the effective strain increased exponentially. The rate of pressure rise during the bulge process has a significant effect on the deformation behavior of disc material and hence the stress–strain relationship. At the same bulge pressure, a disc tested with a larger pressure rise rate had smaller bulge height and effective strain. At the same effective stress at the top of the domed disc, discs subjected to a higher pressure rise rate had smaller effective strain, and hence they are more difficult to rupture. Hollomon’s equation is used to represent the relationship between the effective stress and strain during bulge process. For pressure rise rates in the following range of 0 (equivalent to quasi-static condition), 2–10 MPa/s, 10–50 MPa/s, and 50–100 MPa/s, the relation of stress and strain is σe = 1259.4·εe0.4487, σe = 1192.4·εe0.3261, σe = 1381.2·εe0.2910, and σe = 1368.4·εe0.1701, respectively

Flow characteristics and dispersion during the vertical anthropogenic venting of supercritical CO2 from an industrial scale pipeline

Pressurized pipelines represent the most reliable and cost effective way of transporting captured CO2 from fossil fuel-fired electricity generation plants for subsequent sequestration. Leakage of CO2 through a small puncture is the most common form pipeline failure during normal operation; such failures could lead to fracture. The study of pipeline depressurization and inventory dispersion behavior is of paramount importance for assessing the possibility of fracture propagation and the impact of CO2 pipeline releases on the surrounding environment. A large-scale fully instrumented pipeline (258 m long, 233mm i.d.) was constructed to study the pressure response, phase transition and dispersion of gaseous, dense and supercritical phase CO2 during vertical leakage through a 15 mm diameter orifice. The fluid pressures and temperatures in the pipeline were recorded to study the pressure response and phase transition inside the pipeline. Video cameras and CO2 concentration sensors were used to monitor the formation of the visible cloud and the gas concentration distribution in the far-field. There was a “two cold, intermediate hot” phenomenon during the vertical release in the dense and supercritical release due to the dry ice particle accumulation near the orifice. The intersection of the jet flow and settling CO2 mixture resulted in complex visible cloud forms in dense CO2 release

Under-expanded jets and dispersion in supercritical CO2 releases from a large-scale pipeline

Long-distance CO2 pipelines will be widely applied to transport captured CO2 from fossil fuel fired power plants for subsequent sequestration. In the event of pipeline failure a large mass of the inventory may be discharged within a short time, this represents a significant hazard if leaks continue undetected. An important result of the risk assessment for a CO2 pipeline is the safety distance. At present the lack of knowledge concerning near-field source terms and the far-field dispersion behavior of CO2 leaking from pipelines can make the calculation of safety distances imprecise. Study of near-field source terms and dispersion behavior is therefore necessary and of paramount importance for assessing safety distances and the impact of CO2 pipeline releases on the surrounding environment. In order to study CO2 pipeline leakage, a large-scale pipeline set-up with a total length of 258 m and an internal diameter of 233 mm was constructed to study the near-field characteristics and dispersion behavior of supercritical CO2 during sudden releases. The dynamic pressure near the orifice and CO2 concentrations and temperatures within the downstream dispersion region were measured together with the pressures inside the pipeline. The under-expanded jet flow structure and phase transitions in the near-field were studied for supercritical CO2 released though different orifice diameters (15 mm, 50 mm and Full Bore Rupture). The formation of the visible cloud, the distribution of cloud temperatures and CO2 concentrations in the far-field were analyzed using the measured data, photographs and video recordings. The safety distances along the horizontal direction for 5% CO2 concentration for each of the three orifice diameters were determined from the lower limit for adverse human effects

Pressure response and phase transition in supercritical CO2 releases from a large-scale pipeline

Running fractures in long-distance CO2 pipelines are considered catastrophic pipeline failures and can result in the rapid tearing of the pipeline for several hundred metres and the release of massive amounts of inventory within a short time. The prediction of inventory pressure response and phase transition in the event of accidental pipeline rupture is of paramount importance to determining fracture behaviour in a CO2 pipeline. In order to simulate an actual CO2 pipeline, a large-scale experimental pipeline with a total length of 258 m and the inner diameter of 233 mm is developed to study the fluid dynamic behaviour of CO2 pipeline blowdown. High frequency transducers were used to measure the evolution of fluid pressure after rupture. Thermocouples on the top and bottom of pipeline were installed to monitor the temperature distributions inside the pipeline. The pressure responses and phase transitions of supercritical CO2 were studied following pipeline rupture with three orifice diameters (15 mm, 50 mm and Full Bore Rupture). The waveform characteristics of the pressure response and the pressure change rate were studied in supercritical leakage with different orifice diameters, which could be applied to ascertain the leakage location and the leakage diameter size in the real-time monitoring of CO2 pipeline

Capture of pure toxic gases through porous materials from molecular simulations

<p>In the last three decades, the air pollution is the main problem to affect human health and the environment in China and its contaminants include SO_2, NH_3, H₂S, NO₂, NO and CO. In this work, we employed grand canonical Monte Carlo simulations to investigate the adsorption capability of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) for these toxic gases. Eighty-nine MOFs and COFs were studied, and top-10 adsorption materials were screened for each toxic gas at room temperature. Dependence of the adsorption performance on the geometry and constructed element of MOFs/COFs was determined and the adsorption conditions were optimised. The open metal sites have mainly influenced the adsorption of NH₃, H₂S, NO₂ and NO. Especially, the X-DOBDC and XMOF-74 (X = Mg, Co, Ni, Zn) series of materials containing open metal sites are all best performance for adsorption of NH₃ to illustrate the importance of electrostatic interaction. Our simulation results also showed that ZnBDC and IRMOF-13 are good candidates to capture the toxic gases NH_3, H₂S, NO₂, NO and CO. This work provides important insights in screening MOF and COF materials with satisfactory performance for toxic gas removal.</p