Leakage Accidents Research Articles

Experimental study on combustion characteristics of mixed sodium fire in a well-ventilated environment compared with confined space

The accident caused by the leakage and combustion of liquid sodium is common and frequent in the operation of the sodium-cooled fast reactor. In the actual situation, sodium fire caused by sodium leakage accidents often take place in a well-ventilated environment due to the need for fire ventilation, and multiple types of fire often occur simultaneously. In this paper, an experiment of mixed sodium fire in a well-ventilated environment was carried out. The data of temperature, pressure and oxygen concentration were collected and analyzed, and compared to those in the sodium fire experiments conducted in confined space to study the influence of the well-ventilated environment on the combustion characteristics of mixed sodium fire. It is found that the main combustion product in a well-ventilated environment is sodium peroxide, rather than sodium oxide in confined experiments. During the columnar and spray fire stage, the combustion region limits in the vicinity of the axis, and the peak temperature is close to that in the confined experiments, while the corresponding time is much earlier and it has less effect on the temperature of the distant region. In the later stages of combustion, the pool fire would last a much longer time, and the space temperature was higher due to sufficient oxygen, while the peak temperature was relatively lower due to continuous environmental air. This study could provide technical support for simulation research and prevention measures of sodium fire.

Research on natural gas leakage and diffusion characteristics in enclosed building layout

There are many people in urban construction areas, and natural gas leakage can potentially cause serious accident consequences. Predicting the consequences of gas dispersion is important to react rapidly and adequately in the event of an incident. Currently, computational fluid dynamics (CFD) models are an important tool to predict gas dispersion. However, in most cases, considering computational cost, the building layouts is ignored, so the flow field influence near the building area cannot be considered. In this research process, a realizable k-ε turbulence model is used to simulate the natural gas leakage process in a typical building layout (enclosed building layout), while focusing on wind speed and the leakage position. The validity of realizable k-ε turbulence model is verified by experimental data. The results show that under conditions of high wind speed (wind speed≥ 6 m/s), the reverse vortex formed by the shear flow of wind can cause the natural gas cloud to sink. When the leak hole is located in the influence area of the turbulent vortex, it easily induces R-H instability. When combined with the stronger K-H instability at high wind speeds, natural gas clouds may accumulate. This then leads to serious leakage accidents, knowledge of which may be the key component of emergency management during an accidental natural gas leakage. The research results can guide the building layout plan and gas pipeline construction to prevent accidents.

Self-sealing polyurethane coatings containing high oil-absorption resin for storage facility and fuel pipelines

Fuel leakage accidents of storage facilities and pipelines are one of greatest threats to the environment, life safety and economics. Appling self-sealing coating to pipe surface is an economical and effective method to prevent the fuel leakage. In this work, the high oil-absorption resin was designed and synthesized by suspension polymerization. The oil-absorption performance and oil-absorption volume expansion ratio of the high oil-absorption resin for gasoline, kerosene, and diesel were characterized, respectively. The saturated absorption rate of the high oil-absorption resin for gasoline reached 11.14 g/g, and the volume of the high oil-absorption resin expanded to 6 times when the absorption was saturated. The outstanding oil/water separate property of the high oil-absorption resin illustrated the adsorptive selectivity and the potential application of them for pipelines protecting in ocean. The high oil-absorption resin, as a functional filler to the polyurethane resin, exhibited excellent expanding in volume performance to seal the hole of the composite coating. The composite coating with 25 wt% of the high oil-absorption resin sealed a hole of 1.5 mm in diameter in 1 min. As the bottle with filled by kerosene was perforated by a needle with 3 mm in diameter, the composite coating with 25 wt% of the high oil-absorption resin was successfully instantaneous sealed the leak.

CFD analysis and calculation models establishment of leakage of natural gas pipeline considering real buried environment

Different from the above ground pipeline, the soil characteristics and ground conditions have a great impact on the risk of leakage accident for buried natural gas pipeline. In this paper, the effects of ground conditions and soil characteristics on methane leakage and diffusion were studied by using numerical simulation. The two processes of methane leakage and diffusion, the methane leakage rate and the methane diffusion Early Warning Boundary (EWB) were investigated. Finally, based on the least square method and multiple regression theory, the calculation models of methane leakage rate and EWB were established. The results showed that: Compared with Unhardened Surface Ground (UHSG) condition, Hardened Surface Ground (HSG) increased the distribution of pressure, velocity and methane concentration in soil. The viscous resistance coefficient and inertial resistance coefficient of soil had a great influence on the methane leakage rate, while the ground conditions did not. Both ground conditions and soil characteristics had a certain impact on the EWB of methane diffusion. The average error of methane leakage rate direct calculation model was 4.48%, and the average error of EWB calculation model under HSG and UHSG condition was 3.59% and 7.77% respectively. The methane leakage rate and the EWB calculation models suggest the soil characteristics as independent variables and can provide the rapid calculation of leakage rate and EWB under any soil characteristics without the help of computer iterative solution. The methane leakage rate direct calculation model makes up for the vacancy of calculation method of leakage rate of buried pipeline under different soil characteristics.

Amount, composition and sources of macrolitter from a highly frequented roadway

Many researches mention the need to identify the land-based sources of riverine macrolitter but few field data on litter amount, composition and sources are available in the scientific literature. Describing macrolitter hotspot dynamics would actually allow a better estimation of fluxes in the receiving environments and a better identification of the more appropriate mitigation strategies. This study provides new insights in roadway macrolitter production rates, typologies and input sources (i.e. deliberate or accidental). The macrolitter from an 800 m portion of a highly frequented roadway (around 90,000 vehicles per day) was collected during almost one year. Typologies were defined using the OSPAR/TGML classification. Results show high annual loads of macrolitter (42.8 kg/yr/ha), suggesting significant contributions of the road runoff to the litter fluxes in urban stormwater. Over the course of a year, 88.5 kg of debris were collected, including 53.2 kg (60%) of plastic debris. In total, 36,439 items were characterized, of which 84% were plastics. The macrodebris collected present a low diversity of components with Top 10 items accounting for 92% by count and a majority of small and lightweight items like plastic fragments (31%) or cigarette butts (18%). Input sources were estimated for 43% of the mass collected in which 37.2% were deliberately littered and 62.8% were accidental leaks, illustrating a major contribution of uncovered trucks and unsecured loads. The accumulation rates show a linear correlation with the road traffic. Such data are of prime interest since they enable to determine the potential contribution of road traffic to plastic fluxes to the environment.

Superhydrophobic porous polyvinylidene fluoride monolith with outstanding environmental suitability for high-efficient continuous oil/water separation under harsh conditions

The actual cleanup of oil spill and chemical leakage is usually implemented in harsh environments, thus oil absorbents possessing excellent environmental suitability are urgently required for high-efficiency oil/water separation. Herein, a novel three-dimensional porous polyvinylidene fluoride (PVDF) monolith with multi-environmental tolerance was facilely prepared via thermally impacted nonsolvent-induced phase separation method. In view of its unique pore structure and low surface energy, the PVDF monolith owned super-hydrophobicity (water contact angle = 154°) and super-oleophilicity (oil contact angle = 0°) without any modification. As an oil absorbent, the porous monolith exhibited outstanding oil/water separation performance for various oils/organic solvents, such as preeminent separation efficiency, high saturation absorption capacity (21.3 g g−1) and rapid absorption speed (reaching saturation state within 15 s). More importantly, the monolith revealed stable and prominent oil/water separation capability under harsh conditions involving intense ultraviolet radiation (72 h), rapidly alternating temperature (−20 to 65 °C), extreme pH, oil-water emulsion, strongly turbulent water, suspended solids (sand and tea leaf). It is worth noting that the monolith was capable of continuously and efficiently separating oil/organic solvent from water by a simple pump-assisted system (soybean oil flux reached 3520 L m−2 h−1 at 0.06 MPa). A small piece of PVDF monolith (0.132 g) was able to continuously separate at least 16,000 times its own weight of soybean oil and could be reused for 5 cycles. Based on the superior environmental suitability and continuous oil/water separation capability, the porous PVDF monolith has a tremendous potential to clean up large-scale oil contaminants in leakage accidents.

Buckling behavior of buried pipe crossing stratum subsidence area

Stratum subsidence is one of the important factors threatening the pipe safety. Buckling phenomenon occurs on the pipe crossing subsidence area that may cause leakage accidents. The pipe soil coupling numerical model was established in this paper, buckling behavior of buried pipe crossing stratum area was investigated. The effects of subsidence displacement, radius-thickness ratio, internal pressure, buried depth and stratum on buried pipe’s mechanical behavior were discussed. The results show that buckling appears on the pipe when subsidence displacement is large. With the increasing of subsidence displacement, diameter-thickness ratio and buried depth of pipe, the buckling phenomenon becomes more serious. When the internal pressure of pipe increases, the buckling mode changes from concave fold to convex wrinkle gradually, and it is more serious with the increasing of internal pressure. The pipe in rock stratum is more dangerous than that in clay stratum and sand stratum. Those results can be used for the evaluation and maintenance of gas or hydrogen pipes.

Atmospheric Dispersion of Gaseous Amine Emitted from Absorption-Based Carbon Capture Plants in Saskatchewan, Canada

Carbon capture and storage (CCS) is a key strategy to reduce carbon dioxide (CO2) emissions from industrial point sources. Gas absorption into aqueous amine solutions is an immediate technology for carbon capture that has been tested in many demonstration plants. One concern of using the amine-based carbon capture process is the environmental impacts and health risk caused by emissions of gaseous amines from the process to the atmosphere. This work applied the knowledge of air dispersion modelling to map out the atmospheric dispersion and resulting ground surface level concentration of gaseous amine, namely Monoethanolamine (MEA), from a coal-fired power plant (with a carbon capture unit) and in surrounding areas, in case of an accidental leaking of amine from the CCS system to the atmosphere. The chosen study area was centered on a coal-fired power plant in the province of Saskatchewan, Canada. The Environmental Protection (EPA) approved air pollution model (CALPUFF), together with meteorological and geophysical data were used for gaseous amine dispersion simulation. The results were presented, and the ground amine concentrations were found to vary with wind patterns (wind direction and wind speed). The maximum ground surface amine concentrations standard is 15.2 µg/m3. However, the results showed that when using the water wash unit, the MEA concentrations were well below the standard level, compared to those without the water wash unit. It is essential for CO2 capture plants located in highly populated areas to be equipped with water wash units.

Evacuation route optimization under real-time toxic gas dispersion through CFD simulation and Dijkstra algorithm

Evacuation route optimization plays an important role in safe evacuation for toxic leakage accidents. We propose an approach for route optimization under real-time toxic gas dispersion by combining computational fluid dynamics (CFD) code and the Dijkstra algorithm. CFD code is used to simulate the toxic gas dispersion to predict the spatial-temporal distribution of concentrations, which is related to the calculation of the inhaled dose. Taking the dose as the weights of arcs, the concentrations predicted by CFD are embedded into the modified Dijkstra algorithm to calculate the optimal route with minimal total inhaled dose. The results show that the time before evacuation affects the evacuation route optimization, and the death probability exhibits an “S”-shaped growth as time increases. The optimal route may vary with wind direction dominating the direction of toxic gas dispersion because of the change of weights of arcs. Workers wearing protective equipment are allowed to pass through areas with high-concentration toxic gas, and the length of the optimal evacuation route decreases with the level of safety protection. The proposed methodology with appropriate modification is suitable for evacuation route optimization in fires.

User Authentication Method via Speaker Recognition and Speech Synthesis Detection

As the Internet has been developed, various online services such as social media services are introduced and widely used by many people. Traditionally, many online services utilize self-certification methods that are made using public certificates or resident registration numbers, but it is found that the existing methods pose the risk of recent personal information leakage accidents. The most popular authentication method to compensate for these problems is biometric authentication technology. The biometric authentication techniques are considered relatively safe from risks like personal information theft, forgery, etc. Among many biometric-based methods, we studied the speaker recognition method, which is considered suitable to be used as a user authentication method of the social media service usually accessed in the smartphone environment. In this paper, we first propose a speaker recognition-based authentication method that identifies and authenticates individual voice patterns, and we also present a synthesis speech detection method that is used to prevent a masquerading attack using synthetic voices.

Methane leakage source location based on a near-infrared off-axis integrated cavity output spectroscopic ppbv-level sensor and an optimized inverse model

Accurate location of methane (CH4) leakage source is essential for reducing air pollution and implementing effective countermeasures. A leakage source location method was proposed based on a near-infrared off-axis integrated cavity output spectroscopic parts-per-billion in volume (ppbv)-level CH4 sensor and an optimized inverse model. The CH4 sensor was developed for real-time, in-situ atmospheric CH4 monitoring in mobile measurement, which reveals an Allan variance of ∼7.99 ppbv and a response time of ∼8 s. The inverse model combines an improved particle swarm optimization (IPSO) algorithm with a gas turbulent diffusion model. To better solve the local optimal solution and premature convergence problems, optimizing the velocity of particle was presented in the IPSO algorithm. Through comparison, simulation results show that the location precision was increased by 69.14%, 61.43%, 36.61% and 69.81% under different source locations, wind speed, wind direction and moving speed, respectively. Also, five sets of field experiments were conducted to verify the performance of the IPSO, and the location precision was improved by 73.20%, 81.73%, 77.27%, 76.57% and 91.18%, respectively. Both simulation and field experiment results show that the IPSO algorithm has high precision and good robustness in source location. The proposed optimized inversion model provides a reference for the formulation or adjustment of emergency response strategies for gas leakage accidents.

Identification of airborne pollutant sources within a slot ventilated porous enclosure depending on backward model and downwind scheme

Identification of pollutant source, depending on the inverse computational fluid dynamics (CFD) methodology, within a slot-ventilated porous enclosure has been proposed in this paper. The whole fluid flow system is assumed to be two-dimensional, laminar and porous-saturated. As the inverse CFD modeling was ill-posed, a downwind scheme is employed to discretize the convection term to improve the accuracy and the corresponding time step range is derived to achieve numerical stability. Afterward, the downwind scheme simplifies the discretization process and its direct inversion algorithm. The effects of the Reynolds number (), the Darcy number (), the Schmidt number () and locations of pollutant source on the backward time CFD simulations are investigated, respectively. Results show that the temporal size/step is a critical factor of computational stability. In addition, the thickness of velocity or concentration boundary layer directly impacts the sensitivity of the inverse CFD simulation. The present research could aid in the safety of gas-supplying pipe network and relevant pollutant leakage accidents. Highlights Identification of prior-unknown sources was proposed regarding gas-supplying network. Original transport equations were maintained to enhance the accuracy and generality. The downwind convection scheme was implemented to enhance backward CFD procedures. Diverse influencing factors were numerically tested to recover pollutant sources. The proposed new algorithm was validated thoroughly by experiments and benchmark solutions.

Water supply network modeling and pipe burst analysis based on WaterGEMS

In recent years, the water supply task of urban water supply pipe network is more and more heavy, and leakage accidents of pipe network often occur, among which the most serious leakage accident is pipe burst accident. To solve this problem, this study uses WaterGEMS software to establish the topological structure of water supply pipe network, adopts the water supply pipe network model and computer technology to carry out dynamic analysis on pipe burst accident of pipe network, and uses golden section method to predict the water leakage caused by pipe burst accident state.

Leakage source estimation by retrospective search for high concentration points in infrared gas concentrarion images

In recent years, there has been a concern about the occurrence of gas leakage and fire accidents in plant facilities due to damage caused by aging deterioration of gas piping. However, conventional gas leakage source estimation methods require prior teacher data or calculated data of gas clouds to be compared, which requires large computation time and may not be applicable under unexpected circumstances. Therefore, this study proposes a method to estimate the source of gas leakage by visualizing the leaking gas cloud using an infrared camera and performing an inverse problem analysis based on the concentration information without the need for prior teacher data or calculation data. It is found that the leakage source can be estimated by retrospective search from the gas concentration distribution to the location where the infrared absorption is large. In addition, the leak source estimation is achieved with high accuracy by removing the initial search position data and using only the position data near the leak source in the retrospective search.

Tamponage of massif by modern polymeric materials for isolating mined-out areas in the coal seams prone to spontaneous ignition

The causes of endogenous fires and methods to prevent coal spontaneous ignition were analyzed. Rational parameters of rock massif tamponage with different polymeric chemical compositions for stabilization of its stress-strain state and isolation of mine workings from methane penetration and fresh air leakage were investigated by the mine experimental methods. The dependences of the nominal pressure of injection of the chemical composition into the rock massif were established with taking into account coefficients of influence of rock type and stress concentration in the zones unloaded from rock pressure, in zones of geostatic pressure and in stress concentration zones. In order to control any accidental leaks of chemical composition through the main cracks, the stress-strain state of the rock massif in the mined area is taken into account for calculating the volume of substance to be injected. The parameters of methods for the rock massif cementation and tarring around the isolating bulkhead are substantiated. The method is developed for constructing a double isolating bulkhead in difficult mining and geological conditions to isolate the mined-out areas in the coal seams prone to spontaneous ignition.

Grid Computing Method for Bioaerosol Concentrations Coupled with Human Health Risk Values in the Application of Vaccine Enterprise Layout and Site Selection to Reduce Environmental Risks Caused by Bioaerosol Leakage: A Case Study of Leakage Accident in Zhongmu Lanzhou Biopharmaceutical Plant of Gansu Province, China

Grid Computing Method for Bioaerosol Concentrations Coupled with Human Health Risk Values in the Application of Vaccine Enterprise Layout and Site Selection to Reduce Environmental Risks Caused by Bioaerosol Leakage: A Case Study of Leakage Accident in Zhongmu Lanzhou Biopharmaceutical Plant of Gansu Province, China

A Novel Method for Source Tracking of Chemical Gas Leakage: Outlier Mutation Optimization Algorithm.

Chemical industrial parks, which act as critical infrastructures in many cities, need to be responsive to chemical gas leakage accidents. Once a chemical gas leakage accident occurs, risks of poisoning, fire, and explosion will follow. In order to meet the primary emergency response demands in chemical gas leakage accidents, source tracking technology of chemical gas leakage has been proposed and evolved. This paper proposes a novel method, Outlier Mutation Optimization (OMO) algorithm, aimed to quickly and accurately track the source of chemical gas leakage. The OMO algorithm introduces a random walk exploration mode and, based on Swarm Intelligence (SI), increases the probability of individual mutation. Compared with other optimization algorithms, the OMO algorithm has the advantages of a wider exploration range and more convergence modes. In the algorithm test session, a series of chemical gas leakage accident application examples with random parameters are first assumed based on the Gaussian plume model; next, the qualitative experiments and analysis of the OMO algorithm are conducted, based on the application example. The test results show that the OMO algorithm with default parameters has superior comprehensive performance, including the extremely high average calculation accuracy: the optimal value, which represents the error between the final objective function value obtained by the optimization algorithm and the ideal value, reaches 2.464e-15 when the number of sensors is 16; 2.356e-13 when the number of sensors is 9; and 5.694e-23 when the number of sensors is 4. There is a satisfactory calculation time: 12.743 s/50 times when the number of sensors is 16; 10.304 s/50 times when the number of sensors is 9; and 8.644 s/50 times when the number of sensors is 4. The analysis of the OMO algorithm’s characteristic parameters proves the flexibility and robustness of this method. In addition, compared with other algorithms, the OMO algorithm can obtain an excellent leakage source tracing result in the application examples of 16, 9 and 4 sensors, and the accuracy exceeds the direct search algorithm, evolutionary algorithm, and other swarm intelligence algorithms.

Risk assessment of hydrogen leakage in diesel hydrogenation process

Hydrogen, the raw material of diesel hydrofining process, is flammable and explosive. Once the leaking hydrogen is exposed to ignition sources, it will cause huge losses to people's health and property safety. In this paper, a dynamic risk assessment method of hydrogen leakage based on Dynamic Bayesian Network is proposed to analyze the uncertainty and dynamics of hydrogen leakage risk in the diesel hydrogenation process and to make up for the shortage of dynamic risk assessment of diesel hydrogenation process nowadays. Through the case study of diesel hydrogenation process, the applicability and advantages of the proposed method are proved. The dynamic changes of hydrogen leakage probability, the critical risk factors and safety barriers of hydrogen leakage accident are obtained, and possible accident consequences in two years are identified. Meanwhile, the corresponding measures which provide theoretical guidance for the safety production of petrochemical enterprises are proposed to further reduce the risk of hydrogen leakage in the diesel hydrogenation process.

Intermediates formed during natural attenuation of C9 aromatics under simulated marine conditions: Identification, transformation pathway, and toxicity to microalgae

C9 aromatics — benzene hydrocarbon containing nine carbon atoms among — leakage accident has caused serious damage to the marine ecology near Quangang District, Fujian Province, China. The ecological restoration of the accident sea area is basically realized through natural attenuation. To determine whether the natural attenuation of C9 aromatics in the marine environment will generate highly toxic intermediates, and thus cause more serious harm to marine ecology, the intermediates of C9 aromatics (n-propylbenzene, isopropylbenzene, 2-ethyltoluene, 3-ethyltoluene, 4-ethyltoluene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, and indene) in the process of natural attenuation were studied under the marine conditions simulated by a microcosm. The acute toxic effects of 12 intermediates with longer residual time on Phaeodactylum tricornutum were also ascertained. Twenty natural attenuation intermediates of C9 aromatics were identified. These products primarily include the derivatives of phenols, aromatic alcohols, aromatic aldehydes, aromatic ketones, and aromatic acids, as well as an aromatic lactone compound. No intermediates of 1,3,5-trimethylbenzene and indene during the attenuation process were determined. The indirect photooxidation initiated by hydroxyl radical might play an essential role in the formation of intermediates of C9 aromatic. Based on the 96-h EC50 values for P. tricornutum, the toxicity of the 12 intermediates, in descending order, was: 4-ethylphenol, 2-methylacetophenone, 2,3-dimethylbenzyl alcohol, 4-methylacetophenone, 3-methylacetophenone, 1-phenyl-1-propanol, 1-(2-methylphenyl) ethanol, 2-phenyl-2-propanol, 3,4-dimethylbenzoic acid, 2,4-dimethylbenzoic acid, 2,5-dimethylbenzoic acid, then 4-tolylacetic acid. The 96-h EC50 values of the intermediates of C9 aromatics to P. tricornutum ranged from 8.4 to 199.1 mg/L, which were lower than that of their corresponding parent compound. The findings provided essential fundamental insights for the assessment of marine environmental risk of C9 aromatics leakage accidents, and subsequent emergency disposal countermeasures.

A risk assessment framework considering uncertainty for corrosion-induced natural gas pipeline accidents

Corrosion degradation is one of the main causations of natural gas pipeline failure, which poses a severe threat to human life, assets, and the environment. This paper develops a methodology to assess the risk of corrosion-induced natural gas pipeline accidents considering the uncertainties in incident escalations. This approach can capture both the uncertainties in corrosion failure likelihood and the impact of pipeline leak accidents. A pair of limit state functions are established to estimate the corrosion failure probability of the pipeline. The pipeline accident from gas release to vapor cloud explosion (VCE) is modelled using empirical models. Subsequently, the uncertainties in gas pipeline corrosion failure accidents, reflected by some uncertain parameters, e.g., basic pipeline parameters, corrosion defect and environmental conditions et al., are identified. These identified parameters are discretized and described using a set of probability density functions. Eventually, Monte Carlo (MC) method is utilized to solve the established models. Besides, sensitivity analysis is conducted to study the effect of uncertain parameters on the likelihood and impact of a pipeline accident. A practical case is used to test the methodology, proving a valuable tool for risk assessment of corrosion-induced natural gas pipeline accidents.