Ethylene Oxide (EO), a crucial derivative of ethylene, involves process conditions of high temperature and pressure as well as flammable, explosive, and toxic materials. This complexity predisposes its production to severe industrial accidents. To systematically identify the risk factors that may lead to EO accidents, this study conducted an integrated analysis by leveraging a Knowledge Graph (KG), a Bayesian Network (BN), and Computational Fluid Dynamics (CFD) simulation. First, the key risk factor nodes leading to leakage were identified by using KG. Subsequently, BN was constructed, which enabled the clarification of typical EO leakage scenarios. Then, for the identified typical leakage scenarios, a CFD geometric model was developed. This model was employed to simulate the dispersion patterns following an EO leak under different conditions. Finally, by integrating the results from the BN and CFD analyses, the working conditions with the highest risk level were identified. The results indicated that leakage caused by chemical corrosion or physical erosion of reactors or pipelines presented the highest quantified risk value. This scenario exerts a significant impact on the safe production of EO, necessitating prioritized and focused inspection. Through the integrated KG-BN-CFD methodology, this study has effectively elucidated the disaster-causing mechanisms and evolution patterns of EO leakage accidents. It thereby provides a theoretical foundation and practical guidance for the precise identification of risks, the formulation of targeted prevention and control measures, and the enhancement of inherent safety levels in EO production facilities.
- Article type
- Year
Open Access
Research Article
Just Accepted
Open Access
Research Article
Issue
Underground substations are characterized by complex internal structures and confined spaces. In the case of fires, heat can easily accumulate to form a concealed fire, which significantly increases the difficulty of fire suppression. This study established a full-scale high-pressure water mist fire suppression experimental platform and combined it with computational fluid dynamics (CFD) simulations to investigate the effects of the obstacle height and blockage ratio on the effectiveness of water mist fire suppression. Key parameters such as the fire suppression process, mist flux distribution, suppression time, and gas concentrations were systematically analyzed. The results show that the obstacle height and blockage ratio influence the surrounding flow field in the burning area. The mist flux reaching the burning zone can be significantly reduced, which affects the efficiency of water mist fire suppression. The obstacle height is negatively correlated with the suppression time, whereas the blockage ratio is positively correlated with the suppression time. The fire suppression mechanism of water mist is based primarily on the coupling effects of cooling and oxygen displacement. The oxygen concentration during successful fire suppression ranged from 18.4% to 19.1%. However, water mist promotes the production of CO, with higher CO concentration peaks observed as the suppression time increases. These findings provide valuable insights for optimizing the design of high-pressure water mist fire suppression systems in underground substations and offer theoretical and practical guidance for fire prevention and control in confined spaces.
High-pressure water mist fire suppression systems have been widely used for liquid fuel storage fire in China. In the event of a leakage and subsequent fire accident involving liquid fuels, the fire can rapidly spread owing to the heat feedback within confined spaces. High-pressure water mist fire suppression systems are favored for their energy efficiency, environmental protection, efficient cooling, and rapid smothering; however, their effectiveness in extinguishing liquid fuel fires requires further investigation.
This study explored the impact of high-pressure water mist at different flow rates on fire suppression for different types of oil pool fires through full-scale experiments. An experimental platform was designed and built specifically for high-pressure water mist fire suppression in confined spaces, focusing on transformer oil and gasoline pool fires to investigate the extinguishing effects of water mist on these fires. Cold spray experiments were carried out to assess water mist flux using a measuring cup collection method, which provided crucial data for fire suppression tests. Simultaneously, fire extinguishing experiments were carried out, with thermocouples arranged near the experimental oil pools and on the walls to analyze variations in key parameters such as plume temperature, oil temperature, and wall temperature. Cameras were also installed to record the combustion process and flame morphology.
The experimental results indicate the following: (1) Under identical flow rates, high-pressure water mist is far more effective at extinguishing transformer oil pool fires than gasoline pool fires. For gasoline pool fires, the water mist can control the fire's spread within the confined space; however, even after five minutes of continuous application, complete extinguishment is not achieved. Despite a decrease in the burning area, flame height, and oil temperature, combustion continues. (2) Cold spray experiments reveal that water mist flux in the protected area increases directly with the flow rate of the high-pressure water mist. (3) The effectiveness of fire extinguishment is closely linked to the water mist flow rate. For transformer oil pool fires, higher water mist flow rates significantly shorten the extinguishment times. For gasoline pool fires, increased flow rates strengthen suppression effects but fell short of fully extinguishing the fire. (4) High-pressure water mist can provide continuous cooling to oil and surrounding walls, with cooling efficiency improving as water mist flow rate increases.
The findings of this study provide valuable insights into the application of high-pressure water mist for fire suppression in confined spaces. This research offers important technical support for designing fire protection systems in critical areas of confined spaces, emphasizing the need to consider factors such as fuel type, water mist flow rate, and cooling efficiency.
In recent years, the development of the economy in plateau areas has resulted in the increase in the flights in plateau areas, resulting in a large demand for aviation kerosene. However, the occasional aviation kerosene pool fire that occurs in plateau areas poses a great threat to the safe storage of aviation kerosene. The burning behavior and the corresponding characteristics of liquid fuels, such as aviation kerosene, are different because of the influences of sub-atmospheric pressure and oxygen amount. Moreover, the available reports in the literature concerning sub-atmospheric pressure are mainly based on small-scale experiments, which are greatly affected by heat convection and heat conduction. Furthermore, the burning characteristics are far from the practical fire conditions in plateau areas, which are mainly controlled by heat radiation. Thus, the burning characteristics of liquid fuel pool fires at large scales remain unclear. This study aims to clarify the difference between the burning characteristics of aviation kerosene pool fire under sub-atmospheric pressure and that under atmospheric pressure as well as develop the corresponding prediction models under sub-atmospheric pressure.
A series of pool fire experiments using aviation kerosene with different pool diameters under sub-atmospheric pressure (69 kPa) were carried out. The burning behavior during the whole burning process was analyzed. Moreover, the evolution of some important parameters (including mass burning rate, flame height, and radiative fraction) with the pool diameter were measured and analyzed in detail, and the corresponding prediction models were proposed.
The results showed that the burning rate of aviation kerosene under sub-atmospheric pressure was lower than that under atmospheric pressure for the same burning scale and that the ratio of the rate under sub-atmospheric pressure to that under atmospheric pressure was about 0.58. This result is primarily the result of the heat radiation and heat convection feedback between flame and fuel surface under sub-atmospheric pressure being lower than those under atmospheric pressure. Furthermore, a prediction model of the burning rate was proposed based on the heat feedback. The flame height under sub-atmospheric pressure was higher than that of the same burning scale under atmospheric pressure, primarily because the net oxygen content in the air under sub-atmospheric pressure was reduced and more air was required for fuel burning. In addition, based on the flame entrainment theory, a prediction model of the dimensionless flame height of aviation kerosene under sub-atmospheric pressure was obtained. The radiative fraction decreased slightly with the increase of pool diameter under sub-atmospheric pressure. And at the same burning scale, the radiative fraction under sub-atmospheric pressure was slightly lower than that under atmospheric pressure, primarily because of the reduction of soot particles generated during fuel burning under sub-atmospheric pressure. Subsequently, a prediction model of radiative fraction was developed by modifying the key parameters.
The evolution of the burning characteristics of radiation-dominated aviation kerosene pool fires under sub-atmospheric pressure with pool diameter was found to be consistent with those under atmospheric pressure; however, the values of different burning characteristics changed substantially. The results enrich the large-scale aviation kerosene pool fire data under sub-atmospheric pressure and have practical significance for ensuring the use and storage safety of aviation kerosene in plateau areas.
In recent years, floating-roof tanks have been widely used for liquid fuel storage in China. However, these tanks suffer from a considerable fire risk owing to the accumulation of highly flammable fuel vapors when the liquid fuel level is low. The risk of pool fires, confined by ullage heights, seriously threatens fuel storage and transportation. Furthermore, the flame characteristics, including burning rates and flame heights, are notably affected by ullage heights. However, the research on pool fires with different ullage heights is few. Hence, this study aims to experimentally study the pool fires for different ullage heights and analyze the key parameters (burning rate and flame height). Additionally, a correlation based on dimensionless analysis is proposed to predict the down-reaching flame height.
This study investigates the effect of ullage heights on pool fires. A series of pool fire experiments were conducted using a transparent quartz glass tray and heptane fuel. Different ullage heights (ranging from 3 cm to 50 cm, measured as the vertical distance from the tank top to the liquid fuel surface) were considered. The burning rate was measured using a Sartorius balance and video cameras were installed to record the burning process and flame heights. Flame heights were calculated by converting the flame videos into binary images. Subsequently, the key parameters were analyzed.
The experimental results reveal the following: (1) The ullage height considerably affects the burning process, particularly at the initial and steady stages. At the initial stage, the burning rate sharply increases for cases with a low ullage height, while a burning rate decrease trend is observed after the rapid increase for cases with a large ullage height. This is mainly caused by the continuous uplift of the flame base, moving away from the fuel surface. (2) At the steady stage, the burning rate first decreases and then increases, followed by a final decrease with the increase of the ullage height. The increase in the distance between the flame base and the fuel surface results in this burning rate decrease trend. The burning rate increases because the flame base enters the tray. (3) Based on the flame shape in cases with a large ullage height in the steady stage, total flame height can be divided into the upper flame height outside the tray and the down-reaching flame height inside the tray. The experimental data demonstrates that the upper flame height decreases as the ullage height increases, whereas the down-reaching flame height shows an opposite trend. (4) A correlation is developed using the experimental data and dimensionless analysis to calculate down-reaching flame height with different ullage heights, in which the characteristic tray diameter is revised by considering the influence of ullage heights and air entrainment.
The findings of this study will contribute to the understanding of the burning behaviors of fires at different ullage heights, with practical implications in providing guidance for quantitative risk assessment in tank fires.
京公网安备11010802044758号