A new method for the prediction of flash points for ternary miscible mixtures

The flash point is one of the most important physicochemical parameters used to characterize the fire and explosion hazard for flammable liquids. The flash points of ternary miscible mixtures with different components and compositions were measured in this study. Four model input parameters, being normal boiling point, the standard enthalpy of vaporization, the average number of carbon atoms and the stoichiometric concentration of the gas phase for mixtures, were employed and calculated based on the theory of vapor–liquid equilibrium. Both multiple linear regression (MLR) and multiple nonlinear regression (MNR) methods were applied to develop prediction models for the flash points of ternary miscible mixtures. The developed predictive models were validated using data measured experimentally as well as taking data on flash points of ternairy mixtures from the literature. Results showed that the obtained average absolute error of both the MLR and the MNR model for all the datasets were within the range of experimental error of flash point measurements. It is shown that the presented models can be effectively used to predict the flash points of ternary mixtures with only some common physicochemical parameters.     

A prediction model for the flash point of binary liquid mixtures

A prediction model based on the partial least squares of the multivariate statistical analysis methods was developed for the flash point (FP) of binary liquid mixtures. Estimation of the FP of flammable substances is important for safety measures in industrial processes. Since experimental FP data of liquid mixtures are scarce in the literature, there have been many researches to estimate the FP of liquid mixtures using physicochemical laws. In this study, the partial least squares (PLS) method using experimental data was used as a prediction model of the FP of binary liquid mixtures. The FPs predicted from the PLS method were also compared to results from the existing calculating methods using physicochemical laws such as Raoult's law and the Van Laar equation.     

混合液体火灾爆炸危险性——闪点预测与实验研究

支持向量机应用核函数技术,已经成为当前国际上一个研究的热点,由于支持向量机具有良好的理论基础和泛化性能,可将其引入到混合液体闪点预测的研究之中,以期建立准确、高效的预测模型。本文建立了一个基于支持向量机的理论模型,用于预测二元互溶混合液体的闪点。根据所研究混合液体的物理性质,选择了纯物质的粘度、表面张力、配比、燃烧下限等物理参数来表征闪点,以这些参数作为输入参数,二元混合液体的闪点作为输出值,应用支持向量机方法对两者之间的内在定量关系进行模拟。结果表明,闪点预测值与实验值符合良好。本方法的提出为工程上提出了一种预测二元互溶液体闪点的有效方法,可应用于评估混合溶液的火灾爆炸危害性及本质较安全设计。     

Flammability hazard analysis of imidazolium-based ionic liquid binary mixtures under high temperatures

Ionic liquid (IL) mixtures are promising because they can optimize the involved properties according to industrial needs. It has already been demonstrated that IL flammability is due mainly to IL decomposition generating flammable substances. Four different ILs, 1-Butylimidazolium tetrafluoroborate ([BIM][BF₄]), 1-butylimidazolium nitrate ([BIM][NO₃]), 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM][BF₄]), and 1-butyl-3-methylimidazolium nitrate ([BMIM][NO₃]), were selected as the parent salts to form the different imidazolium-based IL binary mixtures. These mixtures were tested via isothermal thermogravimetric analyzer (TGA) at different temperatures (120, 150, 180, 210, and 240 °C), then tested by the flash point analyzer after isothermal heating pretreatment at the above temperatures. Results show that the mixtures' flash point values decrease with the heating temperature increase. Vaporization of the IL mixtures’ decomposition products results in a higher concentration of flammable gases and a flash point decrease, which lead to the flammability hazard increasing. Moreover, results show that the flash points of the studied binary imidazolium IL mixtures are more similar to those of the more unstable IL in their parent ILs. Also, the flammability hazard of IL binary mixtures may obviously increase under the high temperature environment for a long time.     

二元混合液体闪点的计算

以混合溶液纯组分易燃液体闪点的饱和蒸气压为基础,应用乌拉尔定律、双液系的气-液相平衡理论,运用Le Chatelier方程和安托因方程导出二元混合液的闪点计算方法。并例举易燃液体与易燃液体组成的理想混合液、易燃液体与易燃液体组成的非理想混合液、易燃液体与不燃液体组成的非理想混合液的计算过程。乙醇溶液闪点的计算结果与现有的文献资料比较,误差在允许范围内。计算数据用Excel处理,快捷准确,用于确定二元混合液体的火灾危险性。     

Flash point of biodiesel/glycerol/alcohol mixtures for safe processing and storage

Mixtures of biodiesel, glycerol, and ethanol/methanol are commonly processed and stored in biodiesel production. In this work, non-ideal models are used to calculate the Flash Points (FPs) of binary and ternary mixtures, using data available from different feedstocks. Despite the fact that biodiesel is considered safer than common diesel fuels, results show a synergistic effect of biodiesel/methanol and biodiesel/ethanol mixtures, resulting in a reduction of the flash point of mixtures to values lower than the ones of pure compounds. Most soluble ternary mixtures were found flammable, the only exception being mixtures with a relatively lower alcohol content (45% mol. ethanol or 42% methanol) at temperature lower than 303 K. Accidental increase in temperature can cause domino effect, due to the higher solubility and the formation of new flammable ternary mixtures.     

易燃液体仓库安全监控系统研究

通过对易燃液体仓库的潜在危险的分析和研究,以及火灾爆炸危险性分析,说明安全监控技术的重要性。在对监测参数进行分析的基础上,给出了对监测易燃液体仓库的安全监控系统和监测点的布置以及采用合适的探测器。     

多元可燃混合溶液的闪点预测

为了预测多元可燃混合液的闪点,建立了一个预测模型,通过二元和三元可燃混合液闪点实测值的试验对比,证实此模型的误差在可接受的范围内。此模型可以在预知可燃混合液组分比例和单组分闪点基础上快速预测混合液的闪点。     

The lower explosion point—A good measure for explosion prevention: Experiment and calculation for pure compounds and some mixtures

It is well known that explosive mixtures can exist at temperatures below the flash point (FP). Experiments show that the difference between the FP and the lower explosion point (LEP) may be up to 15 K and in some special cases even more. Consequently, an industrial process even running a few Kelvin below the FP may operate in an explosive vapour/air-atmosphere. Operating at temperatures below the LEP gives sufficient safety. Calculated LEPs are discussed and compared with experimental results.     

Theoretical and experimental study of the inhibition and inert effect of HFC125, HFC227ea and HFC13I1 on the flammability of HFC32

HFC32 is a potential alternative refrigerant with excellent thermal performance, but the flammability is a main obstacle for its applications. The group contribution method is utilized to analyze the inhibition efficiency of nonflammable refrigerants in binary mixtures. Furthermore, a novel equation of predicting the minimum inerting concentration of nonflammable refrigerants has been proposed by analyzing the variation of the flame propagation velocity and the flammable refrigerant concentration. Experimental studies of the explosion limits of HFC125/HFC32, HFC227ea/HFC32 and HFC13I1/HFC32 were carried out and the ranges of explosion limits were obtained. At the same time, the relationship between the maximum charge of the flammable refrigerants and lower flammability limit (LFL) was analyzed. The result demonstrates that the proposed novel theoretical equation can effectively predict the minimum inerting concentration of nonflammable refrigerants to flammable refrigerants, and the theoretical results have significance on the security application of the binary mixtures.     

Experimental studies of ignition and explosions in cyclohexane liquid under oxygen oxidation conditions

The safe operation of hydrocarbon liquid-phase oxidation by air or oxygen requires the knowledge on the flammability of hydrocarbon/oxygen mixtures in both the vapor space and vapor bubbles. The latter is of particular importance in situation where pure oxygen is used as the oxidant as most bubbles are expected to be flammable and explosive. New experimental findings are presented for ignition and explosion in cyclohexane liquid under oxygen oxidation conditions. A bubble column is constructed and fitted with multiple igniters. Experiments were performed at liquid temperatures between 373.15 and 423.15 K under various flow rates of pure oxygen. Two drastic different ignition and explosion behaviors were observed. The first is a typical bubble explosion from the direct ignition of the flammable bubbles in the liquid. The explosion occurs immediate following the ignition and do not produce significant energy that endanger the system. The other is a remote, delayed ignition and explosion in the vapor space that can produce significant overpressure and endanger the system. The explosion is attributed to the ignition of flammable vapor space by active free radicals from cyclohexyl hydroperoxide decomposition. A mechanism is proposed for the remote, delayed ignition to occur in the oxidation system. It is concluded that explosion in an oxidizing, bubbly liquid is not only a likely scenario but also a severe scenario, and cyclohexane oxidation should not be carried out directly with pure oxygen and without any inerting.     

基于QSPR方法的脂肪醇化合物闪点预测

为提高脂肪醇化合物闪点预测精度,提出基于定量结构-性质关系(QSPR)原理的脂肪醇化合物闪点预测方法。应用Dragon软件计算出91种脂肪醇的分子描述符,利用遗传函数算法(GFA)从1 481个描述符中筛选出3个与脂肪醇闪点关系最密切的分子描述符。分别用多元线性回归(MLR)方法和支持向量机(SVM)方法进行建模,并采用内部验证和外部检验的方式对模型的拟合度、预测性等性能进行验证。结果表明:预测集的MLR方法和SVM方法的平均绝对误差(AAE)分别为2.870 K和2.706 K;均方根误差(RMSE)为3.451 K和3.371 K。SVM模型在精度上略优于MLR模型,而MLR模型更为简单和方便。     

基于人工神经网络的二元液体闪点预测

建立了一个基于人工神经网络的理论模型,用于预测二元混合液体的闪点.根据所研究混合液体的物理性质,选择了相关黏度、表面张力等物理参数来表征闪点,以这些参数作为输入参数,二元混合液体的闪点作为输出值,应用反向传播(BP)人工神经网络方法对两者之间的内在定量关系进行模拟.结果表明,闪点预测值与实验值符合良好,优于传统的计算方...     

When solids meet solids: A glimpse into dust mixture explosions

Mixing an inert solid or a less flammable compound with a combustible dust can be regarded as a direct application of the inherent safety principle of moderation. An experimental investigation was carried out to determine the evolution of the ignition sensitivity and the explosion severity of such various mixtures as a function of their compositions. It demonstrates that the introduction of small amounts of highly combustible powders (such as sulphur or nicotinic acid) to a less flammable dust (such as microcrystalline cellulose or carbon black) can strongly influence the ignition sensitivity as well as the explosion severity.It has notably been shown that the ignition sensitivity of solid/solid mixtures significantly rises up when only 10–5%wt. of highly flammable dust is introduced. Simple models can often be applied to estimate the minimum ignition energy, minimum ignition temperature and minimum explosive concentration of such mixtures. Concerning the dust explosivity, three cases have been studied: mixtures of combustibles dusts without reaction, dusts with reactions between the powders, combustible dusts with inert solid. If the evolution of the maximum explosion pressure can be estimated by using thermodynamic calculations, the maximum rate of pressure rise is more difficult to predict with simple models, and both combustion kinetics and hydrodynamics of the dust clouds should be taken into account. These results were also extended to flammable dust/solid inertant mixture. They clearly show that the concentration of solid inertant at which the ignition is not observed anymore could reach 95%wt. As a consequence, the common recommendation of solid inertant introduction up to 50–80%wt. to prevent dust explosion/ignition should be reconsidered.     

QSPR在混合物典型燃爆特性预测中的研究进展

为全面了解定量结构-性质关系（QSPR）方法在混合物燃爆特性预测中的研究现状，展望其发展趋势，综述其在混合物闪点、爆炸极限与自燃温度预测中的国内外研究进展，分析预测目标参数的选择、数据收集、描述符计算和筛选以及模型建立和验证等方面的不足与研究方向。结果表明:QSPR在混合物燃爆特性预测中尚处于起步阶段，当前研究的首要限制是混合物燃爆特性参数实验数据样本不足，关键点及难点是混合物结构的准确表征，未来研究应关注的重点是大量数据源统一的数据样本的获取方法、非加和性混合物分子描述符的计算方法以及机器学习等非线性建模方法。     

Lower flammability limits of flammable ternary organic mixtures: Synergistic behavior

Organic flammable liquids and their mixtures, which possess high risk of combustion and explosion, are widely used as raw materials and solvents in chemical and pharmaceutical industries. Lower flammability limits (LFL) is one of the most important parameters to characterize the combustion and explosion hazards of combustible gases and liquid vapors. The LFL of various ternary organic mixtures consist of ketone (acetone and butanone), ester (ethyl acetate) and alcohol (ethanol and isopropanol) were tested at 25 °C and atmospheric pressure. The results showed that resulted LFL values of the experiment were always lower than those calculated by volume fraction weighting method when the volume fraction of alcohol was less than 20 vol% but more than 10 vol%. The co-existence of alcohol and ethyl acetate had synergistic effect on reducing the LFL values of ternary organic mixtures and thus increased their explosive risk. The mechanism of synergistic effect was analyzed, and the results showed that the OH· and H· radicals produced by the oxidation decomposition of alcohols and esters accelerated the oxidation process of ternary organic mixtures, which led to the decrease of experimental LFL values and thus corresponding increased of their explosive risk. This study would be expected to provide some guidance for designing or choosing safer and more suitable ternary organic mixtures prior to their applications for engineering.     

Development of machine learning based prediction models for hazardous properties of chemical mixtures

Lower flammability limit (LFL), upper flammability limit (UFL), auto-ignition temperature (AIT) and flash point (FP) are crucial hazardous properties for fire and explosion hazards assessment and consequence analysis. In this study, a comprehensive prediction model set was constructed by using expanded chemical mixture databases of chemical mixture hazardous properties. Machine learning based gradient boosting quantitative structure-property relationship (GB-QSPR) method is implemented for the first time to improve the model performance and prediction accuracy. The result shows that all developed models have significantly higher accuracy than other regular QSPR models, with the 5-fold cross-validation RMSE of LFL, UFL, AIT, and FP models being 1.06, 1.14, 1.08, and 1.17, respectively. All developed QSPR models can be used to estimate reliable chemical mixture hazardous properties and provide useful guidance in chemical mixture hazard assessment and consequence analysis.     

基于BP神经网络的二元混合液体自燃温度预测

为了给工业界提供一种快速预测二元混合液体自燃温度的有效途径,将试验所测不同组分及配比的168个二元混合液体的自燃温度作为期望输出,将基于电性拓扑状态指数(ETSI)理论、引入混合ETSI概念而计算出的9种原子类型所对应的混合ETSI作为输入,采用三层BP神经网络技术建立了根据原子类型混合ETSI来预测混合液体自燃温度的BP神经网络模型,并应用改进的Garson算法进行多参数敏感性分析。经模型评价验证及稳定性分析,得到训练集的决定系数R2为0.965,平均绝对误差MAE为11.892 K,测试集的交叉验证系数Q2ext为0.923,平均绝对误差MAE为15.530 K,发现该模型的预测性能优于已有的多元非线性回归(MNR)模型,表明BP神经网络模型具有较好的拟合能力和预测能力,对烷、醇类混合体系自燃温度的预测精度最佳。     

Explosive properties of selected aerosols determined in a spherical 5-L test chamber

Combustible liquids in the form of aerosols are important for many industrial processes. Therefore the problem of explosion hazards posed by the aerosols becomes increasingly more prominent. To correctly assess the explosion risk and fulfil the requirements of the ATEX directive, it is necessary to obtain information regarding the flammable and explosive properties of the aerosols. Unlike in the case of gases and dusts, no standard procedures aimed at obtaining quantitative information of this type exist. Factors that influence the explosion dynamics of aerosols include: concentration, droplet size, temperature etc. Some of these factors are strongly dependent on the aerosol generation methods. A prototype apparatus was designed and constructed to address that dependence. The apparatus was used in an attempt to determine the basic explosion parameters of liquid flammable aerosols. The device consisted of a 5-L spherical vessel equipped with a pump-injection system that generated aerosols as well as a spark ignition source. A wide variety of injection settings were tested to select the most suitable conditions over a broad range of concentrations and fluid properties. A measurement procedure was developed for operating the device. Prototype tests were carried out with fluids commonly used in industry: isopropanol and kerosene. The tests demonstrated the significant influence of the vessel wall temperature on the result accuracy. Correct temperature control made it possible to obtain relationships between the aerosol concentration and the following explosion parameters: maximum explosion pressure and maximum rate of pressure rise.