含硫油品储罐腐蚀自燃理论及实验研究

含硫油品储罐腐蚀自燃事故是炼油企业安全生产的重大威胁.本文对含硫油品储罐腐蚀进行了实验模拟研究,并对实验结果进行了分析,利用扫描电子显微镜对试样腐蚀表面进行了特征分析,并利用X射线仪对腐蚀产物的组成和结构进行了分析.在实验结果分析的基础上,从理论上分析了含硫油品储罐腐蚀自燃机理,探讨了含硫油品储罐腐蚀的自燃影响因素.研究结果可作含硫油品储罐安全设计和含硫油品炼制工艺改进的重要参考.     

含硫油品储罐中硫化铁自燃引发事故原因分析

通过分析含硫油品储罐中活性硫的主要组成及对油品储罐的腐蚀方式,总结了含硫油品储罐中硫化铁的生成方式、自燃性及其主要影响因素。分析认为,尽管活性硫对设备的腐蚀形式多样,但低温湿H2S腐蚀是活性硫对油品储罐的主要腐蚀方式,腐蚀产物极易自燃而引发油品储罐发生火灾和爆炸事故。建立了含硫油品储罐硫化铁自燃事故的故障树(FTA)图并对其最小割集的分析认为:储罐防腐涂层脱落、水的存在和原油含硫是引起顶事件发生的最重要基本事件。通过故障树分析,探讨了硫化铁自燃事故的主要原因并提出相应的预防措施。     

含硫油品储罐自燃事故鱼刺图分析

储油罐硫腐蚀产物氧化自燃引发的火灾、爆炸事故时有发生。为了预防和控制含硫油品储罐自燃事故发生,依据硫化铁自燃的三个必要条件,采用鱼刺图分析方法对含硫油品储罐自燃事故中的人-机-料-法-环因素进行详细分析,找出发生储罐自燃事故各因素之间的逻辑关系并建立鱼刺图。最后提出有效的预防措施,为含硫油品储罐的安全管理提供科学依据。     

基于ISM和区间数的含硫油品储罐自燃影响因素分析

为系统分析含硫油品储罐自燃的各影响因素,基于解释结构模型(ISM)方法的特点,结合事故致因理论,从人-物-环境-管理4个维度找出16个诱导含硫油品储罐自燃的影响因子,初步建立含硫油品储罐自燃影响因素的4级多层阶梯ISM。采用区间数互反判断矩阵,评估各含硫油品储罐自燃影响因素的大小;引入悲观度指数,改进和优化区间数层次模型,最终确定16个指标的权重。结果表明:影响含硫油品储罐自燃的4个维度,其重要度从高到低依次为管理、人、物和环境,因此,需加强对含硫原油生产工艺的日常监管。     

含硫油品储罐自燃机理及事故原因分析

通过企业现场调研并结合若干事故案例的剖析分析了含S油品储罐自燃事故的发生原因,总结了事故的主要影响因素。在建立含S油品储罐自燃的事故树（FTA）图的基础上,通过最小割集的计算与分析,探讨了事故的主要原因及发生条件,并提出了相应的预防控制措施。     

储罐硫腐蚀产物标志性气体的监测

含硫油品储罐内的腐蚀产物与油品中的活性硫反应生成硫化物,而此类硫腐蚀产物氧化自燃是导致储油罐发生火灾、爆炸事故的重要原因.通过试验考察了氧气体积比对硫腐蚀产物氧化自燃过程的影响,探索了铁锈模拟物在氧化过程中SO2气体的释放规律.结果表明:氧气浓度越高,硫腐蚀产物的自燃危险性越大;随着O2浓度增加,氧化反应中SO2的浓度越大,SO2气体析出速度越快,当氧化反应的温度为40℃时,SO2气体浓度达到最大.     

硫化亚铁氧化自燃倾向性的实验研究

含硫油品储罐腐蚀产物FeS的氧化自燃是引起储罐火灾爆炸事故的主要原因。用同步热分析仪(STA)在30～900℃范围内对FeS进行热重热流分析,从物理吸附和化学反应的角度分析了不同粒径和不同升温速率FeS的自然氧化倾向性,计算了不同升温速率FeS的活化能。结果表明,FeS样品粒径越小,越容易发生氧化自燃反应;升温速率越大,FeS越不容易氧化。同时,不同升温速率条件下的FeS反应机制各不相同。从实验得出的动力学参数看出,FeS的氧化反应较复杂,而非简单的放热反应。     

含硫油品储罐腐蚀产物自燃性的热重分析

含硫油品储罐低温湿H2S腐蚀产物FeS的氧化自燃是引起储罐火灾爆炸事故的主要原因.运用SDT-Q600型同步热分析仪对FeS从室温到1 000 ℃的氧化过程进行了实验研究,用不同的动力学模型对热重实验数据进行了相关性分析处理,计算了不同粒径FeS的活化能.结果表明,FeS的氧化自燃过程符合一级反应动力学机制,活化能可以作为衡量FeS氧化自燃性能的一个指标.FeS样品粒径大小对其氧化自燃性有明显影响,随着FeS粒径的减小,TG曲线上氧化起始温度和氧化终止温度降低,其活化能减小.     

油品储罐区风险评价技术研究

本文通过分析影响储罐安全的五大因素18项指标,系统建立了单个油品储罐的安全评价指标体系,采用层次分析-模糊综合评价方法,实现单个油品储罐的安全状况分级。并结合区域定量风险评价方法,实现对油品储罐区的整体风险评价。以某油品储罐区为例,利用建立的指标体系与区域风险评价方法,给出了单个储罐安全等级以及储罐区个人风险等值线分布图和社会风险曲线。更全面的给出了储罐区单个储罐与罐区整体不同层次的风险状况,为油品储罐区规划,管理及事故预防和应急救援提供依据。     

含硫油品储罐腐蚀产物自燃及其防治理论研究

含硫油品储罐内壁腐蚀产物(Fe2O3、Fe3O4、Fe(OH)3)与H2S反应生成硫化铁,硫化铁的氧化放热是引起储罐火灾的主要原因.实验模拟了油品储罐中硫化铁的生成,研究了在无氧条件下H2S气体与油品储罐内壁腐蚀产物的反应以及生成的硫化铁在自然环境下的氧化自燃性.结果表明,Fe2O3、Fe3O4、Fe(OH)3,以及它们的混合物经硫化后生成的硫化铁具有很高的自然氧化活性,在自然环境中,常温下能迅速和空气中的氧气反应并放出大量的热,热量积聚引起储罐火灾爆炸事故.在实验结论的基础上,提出了一些行之有效的安全防范措施.     

煤炭自燃机理及防治技术分类研究

通过分析国内外学者对煤自燃机理的不同说法,提出了煤自燃过程的3个阶段,即潜伏阶段、自热阶段和自燃阶段,指出煤体要发生自燃必须具备4个条件:具有低温氧化性并以破碎的状态存在,有氧体积分数大于12%的空气连续通过,煤炭氧化所生成热量的速度大于散热的速度,上述3个条件同时存在的时间大于煤炭最短自然发火期等等.根据对煤炭自燃机理的研究,将防治技术措施按其作用机理可分为减漏风供氧、吸热降温和既能隔氧又能降温等3类.对防治煤炭自燃以及选择有效而可靠的技术措施具有积极的指导意义.     

基于神经网络的煤层自然发火的非线性预测

煤炭自燃是一典型的非线性现象。笔者论述了煤炭自燃的危害 ,从非线性理论的角度分析了煤炭自燃的本质特征 ;应用神经网络中BP网络这一高度非线性关系映射建立了自然发火预测模型 ,克服了传统预测方法的不足并在山东枣庄矿业集团公司柴里煤矿进行了预测分析 ,预测结果与验证结果基本吻合 ,取得了满意的效果 ,为解决煤炭自燃的预测提供了一条良好的思路和方法 ,具有较大的理论意义和应用价值。     

Numerical investigation and theoretical prediction of self-ignition characteristics of coarse coal stockpiles

Spontaneous combustion of coarse coal stockpiles in temporary coal storage yards was investigated numerically using COMSOL Multiphysics software. The main purposes of the numerical investigation were to identify the self-ignition characteristics of coarse coal stockpiles and formulate a theoretical model to predict the self-ignition time and locations of coarse coal piles. A mathematical model for self-ignition of coarse coal piles was developed and the process of spontaneous ignition of coarse coal stockpiles was simulated. The kinetic data of low-temperature oxidation reaction was obtained from the laboratory-scale experiments with bituminous coals taken from Jindi Coal Mine of Shanxi Province in China. The influence of moisture was ignored because the studied coal had low moisture content (mass concentration: 1.87%) and both coal and ambient environment were assumed to be saturated with moisture (or ambient environment was assumed to be dry). The effects of five variables (i.e. wind velocity, oxygen concentration, height, porosity, and side slope) on the spontaneous ignition in coarse coal piles were examined. Simultaneously, a theoretical prediction model was formulated in light of variable analyses and a great number of simulations.Compared to self-ignition characteristics of fine-particle coal piles, several self-ignition characteristics of coarse coal piles were identified by numerical investigation. Wind-driven forced convection plays a predominant role in self-heating of coarse coal piles. As wind velocity increases, the self-ignition location in the pile migrates from the lower part which is close to the surface of the windward side to the upper part near to the surface of the leeward side. Wind velocity increase exerts the positive or the negative effect on self-heating, which depends on a critical wind velocity value to sustain balances of both the heat and the availability of oxygen in the coarse coal pile. The behavior of self-ignition is remarkably sensitive to both oxygen concentration and height, and a coarse coal stockpile will not ignite spontaneously as long as one of two critical variable values is satisfied: oxygen concentration of 5% or height of 3 m. The theoretical prediction model suggests when and where countermeasures should be made to prevent the self-ignition in the coal stockpile with engineering accuracy.     

Influence of inert materials on the self-ignition of flammable dusts

Flammable solid bulk materials, including dusts, often undergo spontaneous combustion and the spread of reaction fronts. By addition of inert substances, the ignition and combustion behavior can be influenced. In a series of experiments different types of coal were mixed with inert powders to study the effect of the composition on the self-ignition temperature and on the formal kinetic parameters.Hot storage tests as well as simultaneous-thermal analysis were used as experimental techniques with the latter being coupled to FTIR measurements to analyze the composition of gaseous reaction products.All conducted hot storage experiments led to the conclusion that the self-ignition temperature was increased by admixing inert material if the decomposition temperature of the inert matter was higher than the self-ignition temperature of the combustible component at the sample characteristic length. If (exothermic) decomposition of the inert material occurred before a noticeable growth of reaction rate of the combustible material, even a reduction in the self-ignition temperature could be observed. In addition, significantly higher maximum reaction temperatures were observed for the mixtures than for the combustible material alone.     

Comprehensive evaluation on self-ignition risks of coal stockpiles using fuzzy AHP approaches

Self-ignition in coal stockpiles is a serious economic, environmental and safety problem. Evaluation is an effective way to identify the self-ignition hazards in implicit environment of coal piles and provides a guide for countermeasures against spontaneous combustion in coal piles. In this paper, a comprehensive evaluation system is proposed. The trapezoidal and the triangular extent fuzzy AHP methods are employed to handle the imprecision and uncertainty of the effects of factors. A coal stockpile stored at the Bulk Cargo Logistics of Tianjin Port of China and three coal piles in the Teruel basins of Spain are studied to demonstrate the validity of the index system and the effectiveness of fuzzy AHP approaches. The evaluated results indicate that the proposed evaluation system and approaches are valid and objective for evaluating self-ignition risks of coal stockpiles; compared with the trapezoidal fuzzy AHP method, the triangular extent fuzzy AHP approach is more effective to evaluate self-ignition risks of coal piles for the priorities of factors impacting self-ignition risks are highlighted by their weight comparisons' calculation using the triangular extent analysis. The comprehensive evaluation system is beneficial to manage self-ignition risks of coal piles from a holistic point of view and to establish an early warming system of self-ignition risks of coal piles.     

Determination of spontaneous combustion of thermally dried sewage sludge

The general purpose of this research was the determination of self-ignition tendency of thermally dried sewage sludge. Eight Spanish plants located in Madrid, Barcelona and Málaga were selected to develop this study and ten samples were collected. Three different testing methodologies for studying the self-ignition of dusts have been undertaken. Thermogravimetric techniques, self-ignition temperature analyses and UN Division 4.2 tests were developed. The results of these analyses showed the risk of self-ignition during storage and transportation of these substances.     

煤炭自燃发火危险程度识别研究

对影响煤炭自燃发火危险程度的主要因素进行主观判断，运用逐步聚类分析法，对开采煤层煤炭自燃发火的危险程度进行识别，为判定煤炭自燃发火危险程度提供了一种理论方法     

堆积状态下低品质煤临界自燃着火点测定与研究

为了研究低品质煤炭堆积状态下内部自热理论,采用临界自燃着火点理论和Frank-Kamenetskii 模型研究了煤堆内部热产生与热散失平衡理论以及煤堆表面的换热现象;并应用设计研发的煤堆热扩散率及温度监测实验装置和测定方法来评估低品质煤样（褐煤以及亚烟煤）临界自燃温度。结果表明:煤样堆积状态下临界自燃着火点温度可通过实验室内测定分析不同体积网框在不同环境温度条件下自热曲线得出;同体积条件下,临界自燃着火点随着煤品质的升高而增加;在140 ℃ 环境条件下,1#,2# 和3# 煤样在快速升温的前20 min内,温度变化趋势相似;在60~65 ℃,3种煤样出现温度转折点,升温速率开始减缓;根据煤样临界自燃着火点温度结合F-K热发火边界条件理论得出的堆积体积与着火点耦合关系式可预测大体积煤样自燃倾向性及临界自燃温度。     

The influence of initial conditions on the propagation of smouldering fires in dust accumulations

A mathematical model is presented which allows one to treat the combined phenomena of heat, mass and species transfer by diffusion as they occur within smouldering fires in accumulations of dust or other solid bulk materials. The model was applied to predict self-ignition temperatures of five different dusts, where it could be shown that computed and experimental self-ignition temperatures coincide within an error margin of ±5%.

For smouldering fires, if initiated by either self-ignition or an ignition source, it could be shown that the temperature and the velocity at which the reaction front propagates both depend on the volume of the dust accumulation. In addition, the propagation velocity increases when the initial temperature of the dust accumulation is increased and decreases when the initial moisture content of the dust accumulation is increased.

Comparisons of the numerical model with experiments show that the smouldering propagation is mirrored qualitatively, while the accuracy of the computations strongly depends on the accuracy of the input parameters, namely on the apparent activation energy.     

Self-ignition of dust at reduced volume fractions of ambient oxygen

Experiments were performed to investigate the self-ignition behaviour of accumulations of four different technical dusts at oxygen volume fractions ranging from 1.3 to 21%. For this purpose a laboratory oven used for hot storage testing was modified to allow flushing with the pre-mixed oxygen/nitrogen mixture of the desired composition. It was found that for all sample volumes investigated the self-ignition temperatures were higher the lower was the oxygen volume fraction. In addition, the type of reaction changed obviously, since the apparent activation energy significantly decreased at oxygen volume fractions below 6%. However, it was still possible to observe exothermic effects at oxygen volume fractions as low as 1.3%. A numerical model was established to simulate the process of self-ignition including the coupled heat and mass transfer within the dust accumulation using a finite element solver. The model consists of six balance equations for the heat transfer and the transport of five chemical species. It shows that the model reflects self-ignition in dust accumulations with satisfying accuracy, as long as the input data generated by preceding experiments are reliable.