磷酸活性炭自燃过程反应动力学研究

为研究磷酸活性炭的自燃危险性,以自制的磷酸活性炭(活化温度为300,500和700℃)为考察对象,利用同步热分析仪(STA)对活性炭氧化放热动力学进行试验研究.根据在2,5,10和20℃/min等4种不同升温速率下得到的活性炭DSC/TG曲线,结合Friedman-Reich-Levi动力学方法对反应过程中可能存在的反应机理进行初步判断.研究表明,随着活化温度的升高,活性炭的起始放热温度和最大放热温度随之升高;活性炭整个氧化反应过程中,活化能随着转化率的改变呈现一定规律性变化;碳氧化学反应和气体扩散共同影响活性炭氧化过程,且在不同阶段对氧化的贡献不同.     

多点法测定可燃物质自燃特性的可靠性研究

多点法是一种新提出的自热反应动力学分析方法。采用实验研究和理论分析相结合的方式对多点法的操作过程以及实验结果的可靠性展开研究。通过构建一维导热系统、采用不同形式的热电偶布设方式,对烟叶粉末的自燃临界环境温度、活化能以及反应热与指前因子的乘积等参数进行了测定。研究表明:所构建的一维系统能较好地模拟一维导热;热电偶的分布方式对测量结果有较大影响,对称分布状况下,温度结果与经典的F-K对称模型一致;多点法相比于传统方法省时省力,测定结果有较好的线性拟合相关度,求解的动力学参数较为可靠。     

硫铁矿石热自燃机理研究及其探讨

硫铁矿石自燃是矿山开采中面临的重大灾害之一。矿石自燃不仅会造成巨大的资源浪费和经济损失,还将引发一系列的安全与环境问题。通过研究硫铁矿石自燃的化学热力学机理,掌握了导致硫铁矿自燃的主要原因。利用DSC曲线对硫铁矿自燃过程的氧化特性进行研究,通过对比不同粒径的热流曲线及特征温度点的变化趋势,分析硫铁矿自燃特性的变化规律。应用热分析动力学方法计算了硫铁矿的活化能,比较不同粒径下矿样的活化能大小,为判断其自燃可能性和自燃特性研究提供依据。     

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.     

模糊综合评判法在煤炭自燃预测中的应用

运用模糊综合评判法预测煤炭自燃。在分析煤炭自燃影响因素的基础上,从煤体的氧化放热性能、供氧条件和煤体蓄放热环境三方面确定了模糊综合证券的因素指标,提出了确定评判指标属性值和权重值的方法,并将模糊综合评判法成功应用于矿山煤炭自燃的预测。     

基于活化能指标的硫铁矿石自燃倾向性研究

在硫铁矿石自燃及热分析动力学基础上,结合永鑫黄铁矿3种矿样,运用热重分析手段对矿石从常温到燃点之间的氧化过程进行研究,用不同动力学模型对热重数据进行相关性分析.结果表明,硫铁矿石氧化热解过程符合一级反应动力学机制.运用热分析动力学方法求出矿样在不同升温速率下的活化能,发现随着升温速率的增加,矿样的活化能逐渐增大,自燃倾向性减小;但随着含硫量的增加,矿样的活化能逐渐减小,自燃倾向性增大.     

基于CRITIC法与TOPSIS法的硫化矿自燃倾向性评定

现有的硫化矿自燃倾向性综合评价方法多样,且无统一的标准。以矿样的常温氧化增重率、自热点和自燃点3项指标为关键判定因子,结合CRITIC权重分析法和TOPSIS综合评价法,对硫化矿自燃倾向性进行综合判定。采用CRITIC权重分析法,综合考虑指标内的变异性和各指标间的冲突性,得到3项指标的权重,通过TOPSIS综合评价法计算评价对象与理想对象间的距离,对硫化矿自燃的危险性进行排序。运用该判定方法对国内某金属矿山的10个代表性矿样的自燃倾向性进行综合判定,比较了多个硫化矿矿样的自燃危险,得出10个矿样自燃倾向性从大到小为10#、2#、6#、1#、7#、3#、5#、4#、8#、9#,评价结果与实际情况相符,说明该方法是可行的。     

碱性水对煤自燃特性影响实验研究

为了研究碱性水对煤自燃特性的影响,选取葫芦素煤矿102工作面煤样作为实验煤样,利用STA-449C型同步热分析仪进行热重实验,研究加入PH=8 NaOH的煤样与原煤以及加入蒸馏水煤样在空气氛围中燃烧失重、放热量、特征温度点等变化规律,并根据Coats-Redfern积分模型计算了3种煤样燃烧反应动力学参数（活化能、指前因子）。研究结果表明:加入碱性水的2号煤样失重量较1,3号少,燃烧失重速率更低;2号煤氧化燃烧温度区间缩短,着火温度点升高,放热量少,比1,3号煤分别少485.0,480.4 J/g;3种煤样反应机理基本遵循一级化学反应函数,2号煤各段活化能高于1,3号煤,但2号煤失水活化能小于3号,表明碱性水具有抑制煤自燃效应。     

基于活化能指标硫矿石自燃倾向性的研究

硫矿石的自燃由它内在的机理因素和外在的影响因素决定,在实验室中研究硫矿石的自燃主要是通过研究矿氧复合的机理来确定和预测其自燃的倾向性.利用动力学求解矿石在不同的粒度和不同的升温速率条件下的活化能,来判定硫矿石的自燃倾向性,为硫矿石自燃的防治提供理论依据.     

基于BP神经网络的煤层自燃预测

在全面分析影响煤层自燃因素的基础上,建立了煤层自燃预测的人工神经网络模型.应用该模型对某煤田的多个煤层样本进行了训练和预测,网络经过10次训练后,误差达到设定的最小值,6次预测测试中最大误差仅为0.027 8,最小的为0.000 1.研究表明,该模型精度较高,可用于预测煤层自燃的实际应用.     

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.     

Mechanisms of high-pressure hydrogen gas self-ignition in tubes

This paper describes a numerical and experimental investigation of hydrogen self-ignition occurring as a result of the formation of a shock wave. The shock wave is formed in front of high-pressure hydrogen gas propagating in a tube. The ignition of the hydrogen–air mixture occurs at the contact surface of the hydrogen and oxidant mixture and is due to the temperature increase produced as a result of the shock wave. The required condition for self-ignition is to maintain the high temperature in the mixture for a time long enough for inflammation to take place. The experimental technique employed was based on a high-pressure chamber pressurized with hydrogen, to the point of a burst disk operating to discharge pressurized hydrogen into a tube of cylindrical or rectangular cross section containing air. A physicochemical model involving gas-dynamic transport of a viscous gas, detailed kinetics of hydrogen oxidation and heat exchange in the laminar approach was used for calculations of high-pressure hydrogen self-ignition. The reservoir pressure range, when a shock wave is formed in the air that has sufficient intensity to produce self-ignition of the hydrogen–air mixture, is found. An analysis of governing physical phenomena based on the experimental and numerical results of the initial conditions (the hydrogen pressure inside the vessel, and the shape of the tube in which the hydrogen was discharged) and physical mechanisms that lead to combustion is presented.     

Self-ignition and explosion during discharge of high-pressure hydrogen

The phenomenon of self-ignition and explosion during discharge of high-pressure hydrogen was investigated. To clarify the ignition conditions of high-pressure hydrogen jets, rapid discharge of the high-pressure hydrogen was examined experimentally. A diaphragm was used to allow rapid discharge of the high-pressure hydrogen. The burst pressure was varied from 4 to 30 MPa. The downstream geometry of the diaphragm was a flange and extension pipes, with the pipe length varying from 3 to 300 mm. The diameter of the nozzle was 5 or 10 mm. When short pipes were used, the hydrogen jet did not ignite. However, the hydrogen jet showed an increasing tendency to ignite in the pipe as the length of the pipe became longer. At higher burst pressures, a diffusion jet flame was formed from the pipe. The blast wave from the fireball formed on self-ignition of the hydrogen jet resulted in an extremely rapid pressure rise.     

Detection of incipient self-ignition process in solid fuels through gas emissions methodology

The aim of this study is to propose an experimental methodology to detect incipient self-ignition processes in solid fuels. This methodology is based on the gases emissions of different solid fuels, varying the degree of compaction and the grain size of the materials. To achieve this goal, a procedure for the collection and analysis of the gases emitted by samples of various fuels has been developed, analysing the temperatures at which these emissions begin. The results obtained for different materials show that it is possible to detect incipient spontaneous combustion processes using measurements of CO and CO₂ emissions during heating process, and then to set alarm thresholds based on the concentrations of these gases. Those results have been compared with results from conventional thermogravimetry and differential scanning calorimetry tests and it is shown that the proposed methodology detect the self-ignition process start point in advance.     

Self-ignition in stone wool insulation contaminated with fatty acid (fundamentals,case study,analysis methodology)

A combination of a residual film of flammable organic substance, air and porous structures like insulation material (e.g. stone wool) may result in a fire. The initiating self-heating process depends on the substance (reactivity, volatility), amount of accumulated liquid, volume and temperature. Specific information is given for application and extension of the Thomas criterion with a 2nd order reaction. The experimental part includes new experimental techniques to determine heat transfer and formal reaction kinetic data. The applied self-ignition temperature (SIT) simulation model relies on liquid film volume and not on liquid film surface reaction. As a further result of the studies detailed working procedure of three simplified methodologies for estimation of SITs in technical scale are presented. New techniques to determine parameters necessary for SIT prediction, especially in combination with Methodology III, have the power to reduce the costs for estimating the SIT up to 80%.     

大型气相化学动力学软件包CHEMKIN及其在燃烧中的应用

燃烧化学反应动力学是计算燃烧学中的重要内容之一。本文介绍了处理气相化学动力学的大型软件包ＣＨＥＭＫＩＮ的结构和不同版本的特点,并描述了它在燃烧问题中的应用。最后通过一个算例对Ｈ２／Ｏ２／Ｎ２均相绝热等压燃烧体系进行了处理和计算,以具体说明该软件包的应用效果。