Numerical Analysis of Explosion Characteristics of Vent Gas From 18650 LiFePO_(4) Batteries With Different States of Charge

The combustion and explosion characteristics of lithium-ion battery vent gas is a key factor in determining the fire hazard of lithium-ion batteries.Investigating the combustion and explosion hazards of lithium-ion batteries vent gas can provide guidance for rescue and protection in explosion accidents in energy storage stations and new energy vehicles,thereby promoting the application and development of lithium-ion batteries.Based on this understanding and combined with previous research on gas production from lithium-ion batteries,this article conducted a study on the combustion and explosion risks of vent gas from thermal runaway of 18650 LFP batteries with different states of charge(SOCs).The explosion limit of mixed gases affected by carbon dioxide inert gas is calculated through the“elimination”method,and the Chemkin-Pro software is used to numerically simulate the laminar flame speed and adiabatic flame temperature of the battery vent gas.And the concentration of free radicals and sensitivity coefficients of major elementary reactions in the system are analyzed to comprehensively evaluate the combustion explosion hazard of battery vent gas.The study found that the 100%SOC battery has the lowest explosion limit of the vent gas.The inhibitory elementary reaction sensitivity coefficient in the reaction system is lower and the concentration of free radicals is higher.Therefore,it has the maximum laminar flame speed and adiabatic flame temperature.The combustion and explosion hazard of battery vent gas increases with the increase of SOC,and the risk of explosion is the greatest and most harmful when SOC reaches 100%.However,the related hazards decrease to varying degrees with overcharging of the battery.This article provides a feasible method for analyzing the combustion mechanism of vent gas from lithium-ion batteries,revealing the impact of SOC on the hazardousness of battery vent gas.It provides references for the safety of storage and transportation of lithium-ion batteries,safety protection of energy storage stations,and the selection of related fire extinguishing agents.

Model analysis for combustion characteristics of RDF pellet

Fundamental studies of the combustion characteristics and the de HCl behavior of a single refuse derived fuel(RDF) pellet were carried out to explain the de HCl phenomena of RDF during fluidized bed combustion and to provide data for the development of high efficiency power generation technology using RDF previously. For further interpreting the devolatilization and the char combustion processes of RDF quantitatively, an unsteady combustion model for single RDF pellet, involving reaction rates, heat transfer and oxygen diffusion in the RDF pellet, was developed. Comparisons of simulation results with experimental data for mass loss of the RDF samples made from municipal solid waste, wood chips and poly propylene when they were heated at 10K/min or put into the furnace under 1?073?K show the verifiability of the model. Using this model, the distributions of the temperature and the reaction ratio along the radius of RDF pellet during the devolatilization process and the char combustion process were presented, and discussion about the inference of heating rate on the combustion characteristics were performed.

Thermogravimetric Analysis of Effects of High-Content Limstone Addition on Combustion Characteristics of Taixi Anthracite

Combustion characteristics of Taixi anthracite admixed with high content of limestone addition were investigated with thermogravimetric analysis. The results show that limestone addition has a little promoting effect on the ignition of raw coals as a whole. The addition of limestone is found to significantly accelerate the combustion and burnout of raw coals. The higher the sample mass is, the more significant the effect will be. The results also show that the change of limestone proportion between 45%-80% has little effect on ignition temperatures of coal in the blended samples. Increasing limestone content lowers the temperature corresponding to the maximum weight loss. Although higher maximum mass loss rates are observed with higher limestone content, the effect is found not ascribed to changing limestone addition, but to the decrease of absolute coal mass in the sample. The change of limestone proportion has little effect on its burnout temperature. Mechanism analysis indicates that these phenomena result mainly from improved heat conduction due to limestone addition.

气道及燃烧室对米勒循环发动机性能的影响

基于CONVERGE软件对比分析了中、高滚流比进气道及挤气结构对缸内流场及燃烧特性的影响,仿真与试验变化趋势较为一致,结果表明,在2500rpm 1.2MPa工况下,相比高滚流气道,中滚流比气道及挤气方案缸内流场的变强,燃烧特性变好,油耗分别降低0.5%、2.13%;在6000rpm 1.5MPa工况下,中滚流气道流场及燃烧变差,功率降低2.2%,而挤气方案流场降低幅度相对较小,且流场分布相对较好,爆震倾向变好,燃烧相位提前,功率提高4.17%。

淮南矿区典型煤样自燃特性热重-红外联用实验研究

为降低煤矿安全事故发生风险,针对煤自燃氧化出现紧急危险性等问题,研究淮南矿区典型煤样的自燃特性。以淮南张集煤矿6、8、11-2和13-1煤样为例,通过热重-红外(TG-FTIR)联用技术分析煤样在升温氧化过程中的质量变化和气相产物析出特性。实验结果表明:四种煤样的升温氧化过程均可分为5个阶段,包含6个特征温度点;燃烧阶段各煤样反应活化能按由大到小排序为6煤、8煤、11-2煤、13-1煤;主要气相产物吸收峰强度按由高到低排序为13-1煤、11-2煤、8煤、6煤;根据活化能大小和主要气相产物吸收峰强度判断各煤样自燃风险按由高到低排序为13-1煤、11-2煤、8煤、6煤。本文结果可为类似矿区矿井火灾防治提供基础理论支撑。

西藏三种木材生物质的燃烧特性及动力学分析

为了探讨西藏地区丰富的藏川杨、高山松和川滇高山栎3种木材生物质在燃烧过程中的反应机理,采用热重分析了三种木材的燃烧特性,通过Coats-Redfern积分法研究了其动力学特性。结果表明:3种木材生物质燃烧过程总体趋势一致,可分为失水干燥、生物质燃烧、焦炭燃烧和生物质燃尽共4个阶段,其中挥发分燃烧阶段失重占比最大。根据综合燃烧特性指数,川滇高山栎的燃烧特性最好,其次是藏川杨、高山松;随着升温速率增大,木材生物质的综合燃烧特性指数增大,燃烧速率增大,DTG曲线峰值增大,峰形变宽;藏川杨、高山松和川滇高山栎的最佳反应级数分别为1、2、2,相关系数均大于0.95。燃烧反应活化能从低到高分别为:藏川杨46.10 kJ/mol、高山松70.05 kJ/mol、川滇高山栎85.59 kJ/mol;频率因子从低到高依次为:藏川杨2.25×10^(4)min^(-1)、高山松3.99×10^(6)min^(-1)、川滇高山栎2.14×10^(7)min^(-1),该研究为优化燃烧过程和提高能源利用效率提供了理论依据。

中药渣水解炭燃料特性及热解燃烧动力学分析

中药渣因含水率高而处理困难,将中药渣经水热处理后有较好的应用前景。以中药渣为研究对象,采用水热处理获取中药渣水解炭,通过工业分析及元素分析、热重分析及动力学分析研究了水热处理对中药渣水解炭特性的影响。结果表明:随着水热处理温度升高,中药渣水解炭的固定碳及元素C含量、燃料比(水解炭的空气干燥无灰基固定碳与挥发分的质量比)及高位发热量增加,挥发分、元素H及元素O含量明显降低,n_(O)/n_(C)及n_(H)/n_(C)逐渐降低,水解炭性质接近一般动力煤性质。热重分析发现热解过程中,280℃下形成的水解炭在160℃~300℃和300℃~500℃出现较明显的双峰失重峰,其余水热处理温度下形成的水解炭仅在275℃~400℃出现一个极明显失重峰。随着水热处理温度的升高,水解炭热解活化能由69.56 kJ/mol降至40.55 kJ/mol。水解炭燃烧过程主要经历四个阶段,180℃~295℃主要是小分子挥发分热解阶段,其活化能为63.65 kJ/mol~105.02 kJ/mol;295℃~390℃主要是小分子挥发分主要燃烧阶段,其活化能为10.78 kJ/mol~35.76 kJ/mol;390℃~410℃主要是大分子挥发分析出与燃烧阶段,其活化能为117.08 kJ/mol~201.61 kJ/mol;410℃~520℃主要是固定碳与焦炭的燃烧以及少量矿物与无机化合物的热分解阶段,其活化能为22.18 kJ/mol~92.10 kJ/mol。随着水热处理温度升高,水解炭燃烧同一阶段的指前因子与活化能变化趋势一致。水解炭的可燃性指数、着火指数以及综合燃烧指数随着水热处理温度升高、水热时间增加以及固液比的增大而减小,固液比为1 g:15 mL且在220℃下水热1 h获得水解炭的燃烧性能较好,综合燃烧指数为3.55×10^(-10)/(min^(2)·℃^(3)),可为高湿固废水热燃料化的应用提供参考。

兰炭燃烧特性

利用热重分析法探究兰炭的燃烧特性,考察兰炭粒径、4种助燃剂[MnO_(2)、Fe_(2)O_(3)、柠檬酸钠、Ca(OH)_(2)]、w(柠檬酸钠)对兰炭燃烧特性的影响。结果表明,减小兰炭粒径有助于改善其燃烧特性;柠檬酸钠能够有效降低兰炭的着火温度、50%有机质燃尽温度,其着火温度由461.9℃降至409.5℃、50%有机质燃尽温度由626.3℃降至584.9℃;w(柠檬酸钠)<3.0%,兰炭的着火温度、50%有机质燃尽温度下降明显,其燃烧速率也基本保持不变,但随着w(柠檬酸钠)增多,兰炭的各项特征温度下降缓慢,燃烧速率下降明显,表明适量加入柠檬酸钠有利于改善兰炭的燃烧特性。

市政污泥的热解与燃烧特性及动力学

市政污泥的合理化处理可有效防治生态环境污染与水资源浪费,研究其热解处理技术对指导市政污泥的科学处治具有十分重要的意义。利用热重分析法分析了重庆5种典型市政污泥在不同升温速率下的热重法(thermogravimetric,TG)和微商热重法(derivative thermogravimetry,DTG)曲线演变规律,剖析了热解和燃烧条件下的挥发分析出特性指数D、综合燃烧特性指数、活化能、指前因子等参数的分布特征,揭示了其热解与燃烧特性及动力学规律。结果表明:5种市政污泥的挥发分和灰分的含量较高,而固定碳含量较低;随着升温速率的增加,不同污泥的综合热解性能和综合燃烧性能均越来越优异;综合所有升温速率下的热解和燃烧特性参数,土主和鱼洞污泥的综合热解性能最优,而唐家桥污泥的综合燃烧性能最佳。经过动力学分析,鱼洞污泥的热解过程平均活化能相比其他4种污泥更低,为112.34 kJ/mol,唐家桥污泥的燃烧过程平均活化能相比其他4种污泥更低,为67.46 kJ/mol,说明了鱼洞和唐家桥污泥分别具有优异的热解和燃烧特性。

RP-3航空煤油/O_(2)的简化反应机理优化与验证

采用RP-3航空煤油的简化反应机理对多工况条件下RP-3航空煤油/氧气混合物的氧化、着火延迟与层流燃烧特性进行了数值计算,并与相应试验数据进行了对比验证;同时,采用敏感性分析方法对该简化反应机理中燃料相关骨架反应机理中的基元反应进行了敏感性分析;采用遗传算法,对重要的基元反应速率常数进行优化,形成了优化后的RP-3航空煤油/氧气混合物的简化反应机理.结果表明,大部分工况条件下初始简化反应机理对RP-3航空煤油/氧气混合物氧化过程中主要组分浓度、着火延迟时间以及层流燃烧速度的预测值与相应试验值存在较大误差.同时,优化后的简化反应机理对多工况条件下RP-3航空煤油/氧气混合物氧化过程中的主要组分浓度、着火延迟时间及层流燃烧速度的预测值与相应试验值吻合较好.

煤泥微观结构及燃烧特性实验研究

为了掌握煤泥微观结构和燃烧特性,采用扫描电子显微镜、傅里叶红外光谱测试及热重分析的实验方法,研究了彬长矿区煤泥的表观特征、官能团种类及燃烧特性。采用动力学分析方法,得到了不同升温速率的动力学参数变化规律。结果表明:煤炭在洗选过程中分离出的矿物杂质以堆积或与煤互相渗透为一体的形式赋存于煤泥结构中,隔绝了煤泥与空气接触,影响了其表面性质;煤泥中存在大量矿物质基团,这是煤泥难以利用的重要原因之一;煤泥在不同升温速率下的氧化过程呈分阶段特性,且随着升温速率的增加,TG-DTG-DSC曲线均呈现滞后现象。高升温速率延长了煤泥热解燃烧的反应过程,使得煤泥的特征温度、着火特性指数Ci和燃烧特性指数S随升温速率的增加呈现增大趋势。煤泥的活化能E和指前因子A与升温速率呈负相关,但效果并不明显。研究结果对煤泥资源化利用具有重要意义。

甲醇/正庚烷混合燃料自燃特性实验与数值模拟研究

为了理解甲醇/柴油双燃料机的自燃特性并为燃烧计算所需骨架机理提供理论依据,以正庚烷作为柴油替代物,应用快速压缩机对宽广实验条件下甲醇/正庚烷混合燃料的自燃特性进行了研究。实验条件覆盖了甲醇/柴油双燃料机的典型工况。实验研究结果显示,随着压力升高、甲醇比例减少或当量比增大,混合燃料滞燃期变短。根据实验数据验证了爱尔兰国立大学(National University of Ireland,NUI)的正庚烷详细机理对甲醇/正庚烷的适用性,并利用该机理在CHEMKIN PRO软件中进行了化学动力学分析。结果表明,甲醇与正庚烷竞争羟基(hydroxyl,OH)从而抑制系统氧化过程。敏感性分析结果显示,超氧化氢(HO_(2))反应生成过氧化氢(H_(2)O_(2))是燃烧过程中最敏感的反应,抑制系统氧化过程的进行。本研究可为获得适用于甲醇/柴油双燃料机燃烧计算的骨架机理提供理论依据。

氨纶防黄剂粉尘的着火特性分析

为研究氨纶防黄剂粉尘的燃烧特性,采用粉尘云最低着火温度标准实验装置和同步热分析技术,分别研究了典型防黄剂HN-150粉尘云最低着火温度(MITC)的分布特性和粉尘热解过程,根据实验结果进行燃烧特性和动力学分析。研究结果表明:粉尘粒径越小,MITC越低;喷尘压力增大,MITC升高;粉尘云质量浓度增大,MITC先降低后稳定,且当粉尘云质量浓度大于2 096 g/m^(3)时,MITC稳定在270℃,小于150 g/m^(3)时,不会发生着火;粉尘云质量浓度对MITC的影响最大。随着粒径的增大,粉尘的着火温度、峰值温度、燃尽温度呈上升趋势,最大燃烧速率、平均燃烧速率、可燃性指数和综合燃烧特性指数呈下降趋势;随着升温速率的增大,粉尘的燃烧特性参数均呈上升趋势。随着粒径的减小,粉尘的平均活化能减小,越容易发生燃烧。MITC和热解过程中的着火温度相对应,这与燃烧特性和热分析动力学结果一致。因此该基础研究可为防黄剂的安全生产提供参考依据。

煤粉锅炉掺烧气化灰渣适应性分析及预测

近些年,国内煤化工项目出现较多采用粉煤加压气化工艺,生产过程中会副产大量高水分、低热值的气化灰渣。考虑到气化灰渣具有热值可供回收,因此采用合理方式重新利用气化灰渣是此类项目实现节能降耗的新型途径,也是实现煤炭高效清洁利用的有效措施。具体针对某煤化工项目煤粉锅炉拟掺烧气化灰渣的各燃料燃烧特性进行预测和分析,用于对锅炉实际掺烧提供理论指导,达到气化灰渣有效利用和锅炉掺烧稳定运行的目的。

基于小波包分析的内燃机曲轴轴承故障特征识别

传统内燃机曲轴轴承故障特征识别方法直接进行阈值降噪未进行多传感器信号采集,造成传统方法识别效果较差,提出基于小波包分析的内燃机曲轴轴承故障特征识别。对内燃机曲轴轴承故障多传感器信号进行采集,提高信号处理的效率和准确性,基于小波包分析进行阈值降噪,设计故障特征识别流程,实现基于小波包分析的内燃机曲轴轴承故障特征识别。设计对比实验,实验结果表明,该研究方法故障特征识别效果更好。

藏东南典型生物质及其掺混样品燃烧特性及动力学分析

为给西藏农村经济建设和生态文明建设提供能源支持,采用热重分析方法研究了藏东南地区牛粪、玉米秸秆及其掺混样品的燃烧特性,采用Coats-Redfern积分法研究其动力学特性。结果表明,牛粪和玉米秸秆生物质燃烧过程总体趋势一致,共分为4个阶段,生物质挥发分析出与燃烧是主要燃烧阶段,失重占比最大;提高升温速率会使生物质燃烧速度增大,失重峰值增大;采用TG-DTG联合定义法对牛粪、玉米秸秆及其掺混生物质燃烧特性进行分析,根据综合燃烧特性指数,玉米秸秆的燃烧特性好于所有掺混样品且大于牛粪;各样品燃烧反应活化能从低到高分别为:牛粪52.19 kJ/mol、牛粪占比75%样品为47.70 kJ/mol、牛粪占比50%样品38.70 kJ/mol、牛粪占比25%样品35.23 kJ/mol、玉米秸秆33.09 kJ/mol。该研究为西藏地区多类型生物质能源燃烧利用效率提供了理论依据和技术支持。

基于不同水质边界下油池火燃烧特性的实验研究

为解决使用原位燃烧法(ISB法)处理漏油时,不同水质边界对燃烧效率、除油效果产生的问题,分别对6~20 cm圆形直径油池火的燃烧特性进行实验研究。通过对3种水质边界下柴油池火的燃烧速率、火焰温度、火焰高度的对比分析,结果表明:不同水质边界下柴油池火燃烧可分为3个阶段:引燃阶段、稳定燃烧阶段和熄灭阶段。针对稳定燃烧阶段,由于水质边界的成分与相态不同,燃烧速率各有差异,其中海水边界下池火的燃烧速率最快,而冰边界远小于前两者,针对该现象建立传热模型进行分析,建立了适用于3种水质边界条件下预测火焰高度的数学模型。

Experimental Studies on Combustion Characteristics of Mixed Municipal Solid Waste

In our country, municipal solid wastes (MSW) are always burnt in their original forms and only a few pretreatments are taken. Therefore it is vital to study the combustion characteristics of mixed waste. In this paper, thermogravimetric analysis and a lab scale fluidized bed facility were used as experimental means. The data in two different experimental systems were introduced and compared. It took MSW 3-3.5 min to burn out in FB, but in thermogravimetric analyzer, the time is 20-25 min. It can be concluded that, in general, the behavior of a mixture of waste in TGA can be expressed by simple combination of individual components of the waste mixtures. Only minor deviations from the rule were observed. Yet, in Fluidized Bed, it was found that, for some mixtures, there was interference among the components during fluidized bed combustion.

Combustion Characteristics and Kinetics of Anthracite Blending with Pine Sawdust

The combustion characteristics and kinetics of anthracite,pine sawdust and their blends were investigated under combustion condition by thermogravimetric analysis,respectively.The fractions of pine sawdust in the blended samples were set to be 30%,50%,and 80%.The results showed that the ignition and burnout temperatures of pine sawdust were lower and the maximum combustion rate was higher than those of anthracite.With the increase of pine sawdust content,the ignition temperature and burnout temperature of the blends decreased,while the maximum mass loss rate and the combustible index of the blends increased;that is,the comprehensive combustion property became better.The kinetic parameters for the blends combustion under air condition were calculated based on experimental results using Coats-Redfern model.When the pine sawdust content varied in the range of 30%-80%,the combustion processes of these blends could be divided into two stages and the combustion reactions belong to the first-order reaction.The values of apparent activation energy at two individual stages decreased from 68.78to47.28kJ·mol-1 and from 113.53 to 46.43kJ·mol-1,respectively.

多元低热值煤混合燃烧特性热重实验研究

为了实现风化煤、煤矸石、煤泥的大规模利用,通过热重分析研究了多元低热值煤在不同升温速率、掺混比例下的着火特性和综合燃烧特性,并采用改良Coats-Redfern方法分析其动力学特性。结果表明:提高升温速率可以改善低热值煤的燃烧特性;煤泥、风化煤比例的增加有利于混煤的燃烧,随着二元混煤中风化煤比例由10%增至90%,混煤综合燃烧特性指数由1.73×10^(-8)增至1.41×10^(-7);随三元混煤中煤泥比例由20%增至80%,混煤综合燃烧特性指数由8.77×10^(-8)增至1.57×10^(-7)。与煤矸石相比,混煤的活化能更低、综合燃烧特性指数更高,具有更好的燃烧特性。研究结果可为多元低热值混煤在循环流化床中的大规模利用及其工业装置的设计与运行提供参考。