锂离子电池安全性特点及热模型研究

锂离子电池的安全问题越来越受到重视.本文从锂离子电池热安全性特点着手,分析了锂离子电池的着火、爆炸和电解液泄漏等安全事故特点.简单介绍了锂离子电池主要材料的产热特性、相互反应产热特性.讨论了锂离子电池热模型建立的两种途径,即量热仪途径和化学反应途径,通过这些热模型的建立,来指导锂离子电池的安全设计和管理.     

储煤筒仓系统爆炸危险因素分析

结合火力发电厂输煤系统运行状况，分析了储煤筒仓系统的爆炸危险因素，并作出了具体的预防及应对措施，对相关企业的安全工作有较好的参考价值。     

Systems thinking in a gas explosion accident – lessons learned from Taiwan

On July 31, 2014, at around 23:57, several huge explosions occurred that lasted for 2 h in Kaohsiung City, Taiwan. As a result of a gas leak from a ruptured underground pipeline, the catastrophic incident destroyed more than 6 km of roads, killed 32 people, injured 321 people, and damaged 3259 buildings. Pipeline explosions have been reported as a repeatedly occurring problem, indicating that (1) complex systems are difficult to manage and control, and (2) humans are unable to effectively learn from experiences of accidents. Initial analyses results reveal that root causes of this incident were a combination of a series of complex chain reactions, which eventually led to propylene leakage and explosion. This is a systematic problem, which can hardly be investigated or analyzed by traditional research approaches. Based on the investigation reports and “systems thinking” method, this study develops causal loop diagrams for the Kaohsiung gas explosion to explore the root causes of the disaster. The research results indicate that (1) this pipeline explosion incident was the result of the chain reactions and was the output of a complex system; (2) the mental model of “production first” and “experience gap” were the root causes of the disaster; and (3) to achieve a higher safety standard, continuous education to improve the mental model of “safety first and safety over production” are essential. The findings of this study may contribute toward the improvement of the standard operating procedure for disaster management and preventing similar incidents in the future.     

Effects of particle thermal characteristics on flame microstructures during dust explosions of three long-chain monobasic alcohols in a half-closed chamber

To reveal clearly the effects of particle thermal characteristics on flame microstructures during organic dust explosions, three long-chain monobasic alcohols, solid at room temperature and similar in physical-chemical properties, were chosen to conduct experiments in a half-closed chamber. In the experiments, the dust materials were dispersed into the chamber by air to form dust clouds and the hybrids were ignited by an electrical spark. A high-speed optical schlieren system was used to record the flame propagation behaviors. A fine thermocouple and an ion current probe were respectively used to measure the flame temperature profile and the reaction behaviors of the combustion zone. Based on the experimental results, combustion behaviors and flame microstructures in dust clouds with different thermal characteristics were analyzed in detail. As a result, it was found that the dust flame surfaces were completely covered by cellular structures that significantly increased the flame frontal areas. Flame propagated more quickly and the number of the cellular cells increased as increasing the volatility of the particles. On the contrary, maximum temperature and the thickness of the preheated zone decreased as increasing the volatility of the particles. According to the ion current profile, the particles in the preheat zone were pyrolyzed to intermediate radicals and the radicals' fraction in the higher volatile dust flame was higher than that in the lower volatile dust flame.     

A product analysis-based study on the mechanism of inflammable gas explosion suppression

To study the mechanism of the suppressing effect of Expanded Aluminium (EA) on the premixed gas explosion, premixed methane-air and propane-air gases were undergone explosion reaction in the presence of EA in a self-designed closed pipeline with the overpressures and the compositions, rates and sensitivities of products analyzed. The results showed that the 9.5% methane-air and 5% propane-air explosions produced peak pressures decreased by 79.3% and 65.6%, and residual methane and propane contents increased by 270% and 560% respectively than without EA. In addition, the results revealed that the explosions of propane in the presence of EA produced less methane and carbon oxides contents, but more ethylene and propylene contents. The simulation showed that H, O, and OH are the key factors affecting the rate of products. The product compositions, together with other parameters, suggested that EA decreased temperature, inhibited chain initiation and propagation reaction, but facilitated chain termination reaction by advancing and accelerating the gas phase and wall destruction reaction of radicals, especially collisions and concentration of key free radicals. This new research method based on the analysis of explosion products can be used for in-depth research into gas explosion features and shed light on the suppressing mechanism of EA in flammable gas explosion.     

基于人工神经网络的气体泄爆最大超压预测研究

为解决传统经验公式在预测气体泄爆中最大超压出现时的较大偏差或过于保守的问题，提出使用人工神经网络预测气体泄爆最大超压。基于124组实验数据，采用BP与RBF神经网络，通过优化算法计算与迭代循环对泄爆样本中的影响因素进行降维与选择，并确定2类神经网络本身在学习与计算气体泄爆样本时的相关参数。结果表明:PCA（主成分分析法）在当前样本条件下的降维效果较差，而通过迭代对比确认气体泄爆样本中的5类特征全部保留时神经网络的训练模拟效果最好；通过对124组实验数据进行随机挑选训练集与测试集的训练模拟结果发现，神经网络对气体泄爆中最大超压的预测效果较好；通过对比Molkov提出的和经Fakandu等改进的NFPA 68经验公式以及2类神经网络的预测结果表明，神经网络相比于传统气体泄爆经验公式具有明显优势。     

Inherent thermal runaway hazard evaluation method of chemical process based on fire and explosion index

Thermal runaway hazard assessment provides the basis for comparing the hazard levels of different chemical processes. To make an overall evaluation, hazard of materials and reactions should be considered. However, most existing methods didn't take the both into account simultaneously, which may lead the assessment to a deviation from the actual hazard. Therefore, an integrated approach called Inherent Thermal-runaway Hazard Index (ITHI) was developed in this paper. Similar to Dow Fire and Explosion Index(F&EI) function, thermal runaway hazard of chemical process in ITHI was the product of material factor (MF) and risk index (RI) of reaction. MF was an indicator of material thermal hazards, which can be determined by initial reaction temperature and maximum power density. RI, which was the product of probability and severity, indicated the risk of thermal runaway during the reaction stage. Time to maximum rate under adiabatic conditions and criticality classes of scenario were used to indicate the runaway probability of the chemical process. Adiabatic temperature rise and heat of the desired reaction and secondary reaction were used to determine the severity of runaway reaction. Finally, predefined hazard classification criteria was used to classify and interpret the results obtained by this method. Moreover, the method was validated by case studies.     

Study of the influence of melamine polyphosphate and aluminum hydroxide on the flame propagation and explosion overpressure of aluminum magnesium alloy dust

When aluminum magnesium alloy dust floats in the air, a certain ignition energy can easily cause an accidental explosion. To prevent and control the occurrence of accidental explosions and reduce the severity of accidents, it is necessary to carry out research on the explosion suppression of aluminum magnesium alloy dust. This paper uses a vertical glass tube experimental device and a 20 L spherical explosive experimental device to carry out experimental studies on the suppression of the flame propagation and explosion overpressure of aluminum magnesium alloy dust with melamine polyphosphate (MPP) and Al(OH)₃. With increasing MPP and Al(OH)₃ concentrations, the flame brightness darkened, the flame velocity and propagation distance gradually decreased, and P_max and (dp/dt)_max decreased significantly. When the amount of MPP added reached 60%, the flame propagation distance decreased to 188 mm, which is a decrease of 68%, and the explosion overpressure decreased to 0.014 MPa, effectively suppressing the explosion of aluminum magnesium alloy dust. The experimental results showed that MPP was more effective than Al(OH)₃ in inhibiting the flame propagation and explosion overpressure of the aluminum magnesium alloy dust. Finally, the inhibitory mechanisms of the MPP and Al(OH)₃ were further investigated. The MPP and Al(OH)₃ endothermic decomposition produced an inert gas, diluted the oxygen concentration and trapped active radicals to terminate the combustion chain reaction.     

Effect of pyrolysis and oxidation characteristics on lauric acid and stearic acid dust explosion hazards

The effect of pyrolysis and oxidation characteristics on the explosion sensitivity and severity parameters, including the minimum ignition energy MIE, minimum ignition temperature MIT, minimum explosion concentration MEC, maximum explosion pressure P_max, maximum rate of pressure rise (dP/dt)_max and deflagration index K_st, of lauric acid and stearic acid dust clouds was experimentally investigated. A synchronous thermal analyser was used to test the particle thermal characteristics. The functional test apparatuses including the 1.2 L Hartmann-tube apparatus, modified Godbert-Greenwald furnace, and 20 L explosion apparatus were used to test the explosion parameters. The results indicated that the rapid and slow weight loss processes of lauric acid dust followed a one-dimensional diffusion model (D1 model) and a 1.5 order chemical reaction model (F1.5 model), respectively. In addition, the rapid and slow weight loss processes of stearic acid followed a 1.5 order chemical reaction model (F1.5 model) and a three-dimensional diffusion model (D3 model), respectively, and the corresponding average apparent activation energy E and pre-exponential factor A were larger than those of lauric acid. The stearic acid dust explosion had higher values of MIE and MIT, which were mainly dependent on the higher pyrolysis and oxidation temperatures and the larger apparent activation energy E determining the slower rate of chemical bond breakage during pyrolysis and oxidation. In contrast, the lauric acid dust explosion had a higher MEC related to a smaller pre-exponential factor A with a lower amount of released reaction heat and a lower heat release rate during pyrolysis and oxidation. Additionally, due to the competition regime of the higher oxidation reaction heat release and greater consumption of oxygen during explosion, the explosion pressure P_m of the stearic acid dust was larger in low concentration ranges and decayed to an even smaller pressure than with lauric acid when the concentration exceeded 500 g/m³. The rate of explosion pressure rise (dP/dt)_m of the stearic acid dust was always larger in the experimental concentration range. The stearic acid dust explosion possessed a higher P_max, (dP/dt)_max and K_st mainly because of a larger pre-exponential factor A related to more active sites participating in the pyrolysis and oxidation reaction. Consequently, the active chemical reaction occurred more violently, and the temperature and overpressure rose faster, indicating a higher explosion hazard class for stearic acid dust.     

受限空间内惰性气体对CH4爆炸抑制特性研究

N2和CO2是常用的惰性抑爆气体,为研究两种气体的抑爆特性,采用20L球形爆炸试验装置,分析了不同浓度配比条件下N2/CH4/空气以及CO2/CH4/空气混合气体的爆炸压力,同时采集爆炸后的气体样品,对比分析爆炸后残留气体的主要成分。结果显示:随CH4浓度从5%增加至12.5%时,完全抑制CH4爆炸需要的惰性气体最小量先增大后降低,CH4浓度在6.5%~7.5%之间时,抑爆需要的惰性气体的量最大;在同一CH4浓度条件下,抑爆需要N2的量大于CO2,并且CH4浓度在5%~6.5%时,抑爆需要两种惰性气体的量值差别最大;当CH4浓度一定时,随着加入惰性气体量的增大,爆炸最大超压逐渐降低,惰性气体浓度和爆炸超压之间基本呈线性关系;在同样条件下,相对于N2,CO2为抑爆气体时,爆炸后腔体内残留的CH4浓度较高。研究成果为惰性气体抑爆技术提供技术支撑,同时为揭示惰性气体抑爆机理有一定作用。