煤粉高压着火特性及影响因素

高压气化炉内煤粉的着火特性对煤粉烧嘴和气化室的设计与运行调控具有重要意义。笔者采用加压热重分析法对3个煤样的着火特性进行研究,根据升温过程中的能量守恒原理和谢苗诺夫着火理论提出了一种新的处理PTG曲线求取着火温度的拐点法,并与传统经验切线法进行对比;讨论了压力、氧气体积分数、升温速率、挥发分和颗粒粒径对着火温度的影响。研究结果表明,煤粉着火温度区间为从初始着火温度(Ti)到极限着火温度(Tig),环境换热条件所决定的切点位置是唯一定解条件,高温工业炉高加热速率对应的为极限着火温度;与常压条件下相比,加压下固定床煤粉的着火为异相着火,着火温度随挥发分的增加而略有增加;在0.1~1.0 MPa和3~5 MPa的压力范围内,随压力的升高,着火温度下降,且比常压下低很多,虽然在1~3 MPa的着火温度略有增加;氧气体积分数对着火温度的影响规律与常压的类似,随氧气体积分数的增加,着火温度降低;虽然加压条件下煤粉的快速反应,拐点法与切线法得到的着火温度相近,但切线法无法响应环境条件的变化,且常压下,经验的切线法无法给出令人满意的结果。     

带延迟点火部件的发射药点火性能试验研究

为了更好地研究发射药的点火性能,在基于密闭爆发器原理的点火性能测试装置基础上增加了一个延迟点火部件,构建了一个新型点火性能模拟试验装置,根据该装置建立了简单的火药分层点火过程模型,模拟并对比了高能太根-18/1、双芳-3-18/1及NR11-18/1三种发射药的点火性能。结果表明,NR11-18/1发射药较易点火,双芳-3-18/1发射药最难点火,点火时间分别为19和45ms。增加延迟点火部件后,可将点火药的燃烧和发射药的燃烧阶段有效区分,不仅有利于对比点火性能差异较小的发射药之间的区别,还有助于分析发射药低压段的燃烧速度。随着延迟点火部件长度的增加,点火时间也增长。     

发射药初温和热物性参数对点火性能影响的研究

采用点火模拟试验装置，对几种发射药在常，低温情况下的点火性能进行试验，获得了这几种发射药在不同温度下的点火特征曲线及重要参数，得出了这几种发射药在不同温度下的点火性能差异，并结合火理论作数值计算，分析了发射药初温对点火性能影响的内在原因，为进一步研究低温下发射药膛内的点火特性及燃烧过程提供依据。     

Ignition of various wood species by radiant energy

The ignition of various wood species by exposure to the radiation of a DKsR-10000 xenon lamp was investigated. Time dependences of ignition delay on the radiant energy intensity were obtained for various wood species: cedar, larch, pine, birch, and aspen. The effect of the initial temperature and moisture content of wood on the ignition time was studied. The ignition temperature of pine and birch wood for various radiant energy intensities was determined by an optical method. It is shown that the ignition time of pine wood decreased by a factor of 1.5–2 as the initial temperature of samples was increased by 100 degrees. It was found that the ignition temperature of wood increased with increasing radiant flux density and depended on the wood species. Increasing the wood moisture content by a factor of 10 increased its ignition time by more than 50%.     

Ignition of the Gas–Coal Dust Mixture. Pointwise Approximation

A mathematical model of ignition of a gas mixture with dust particles is constructed by methods of mechanics of reacting heterogeneous media. Some qualitative feature of the model are studied, which allow one to identify different characteristics variants of thermal dynamics of the mixture: heterogeneous ignition by means of oxidation of coke residue, homogeneous ignition caused by oxidation of volatiles in the gas phase, and hybrid ignition due to simultaneous action of surface and volume reactions. The model is verified using available experimental data on ignition delays of suspended coal particles in air and in oxygen in reflected shock waves.     

一种新型LOVA发射药点火性能的研究

采用点火模拟试验方法，对新型LOVA发射药的点火性能进行了研究，提出了一种预估发射药点火难易的方法。结果表明：在相同的试验条件下该LOVA发射药较单基药难点燃；在密闭爆发器实验中延迟时间短的发射药相应地在点火实验中较容易点燃。     

硼烷合乙二胺的点火、燃烧及热解特性

为探索高氢含量硼烷合乙二胺储氢材料在空气中的燃烧性能,使用气相合成方法制备了硼烷合乙二胺(EDAB)微米颗粒。通过连续激光点火实验,测试了其点火和燃烧参数;通过在氮气和空气中的热解实验,研究了其燃烧过程机理。结果表明,硼烷合乙二胺的燃烧具有点火延迟时间短、点火能量低的特点,在常温常压静止空气流中,点火功率密度为10~9 W/m~2量级时,微米级硼烷合乙二胺的点火延迟时间为0.000 2~0.000 9s,最小点火能量仅0.000 1J;其连续激光点火燃烧过程分为两个阶段,分别产生亮蓝色与黄色火焰。结合材料在氮气及空气中的热解行为,推测该材料燃烧第1阶段蓝色火焰对应其热解释放氢气的燃烧,第2阶段的黄色火焰对应其骨架高温裂解所生成挥发物的燃烧。     

Non-plasma ignition of lead styphnate by a semiconductor bridge and its comparison with plasma ignition

The process of non-plasma ignition of lead styphnate by a silicon-based semiconductor bridge is studied. Discharge characteristics with plasma and non-plasma ignition are analyzed. It is demonstrated that non-plasma ignition is characterized by a low energy and can be applied in cases with fine-grain energy materials.     

The autoignition of polymers

A consistent and relatively simple method is presented for studying the unpiloted ignition of polymeric materials in contact with hot air. The ignition behavior of a particular polymer as determined by its bulk properties may be characterized by the relationship between sample mass and ignition time at constant area for a series of furnace temperatures. Extrapolation of this linear relationship at a given furnace temperature to zero mass results in an intrinsic ignition time which represents the rate of the ignition process when the time required to heat the sample to its decomposition temperature has been eliminated, i.e., the sample is brought to its decomposition temperature instantaneously. The temperature dependence of this intrinsic ignition time shows an Arrhenius relationship with an apparent activation energy of 8–10 kcal/mole for all but one material investigated. This indicates that the mechanism controlling the kinetics of such an ignition process is a physical one, most likely the diffusion of combustible gaseous products into the heated air surrounding the sample.     

韶钢热电厂140 t/h流化床锅炉点火启动技术分析

初步分析了韶钢热电厂140t/h鼓泡流化床锅炉焦炉煤气床上整床点火失败的情况，详细介绍了木炭分床点火的成功方法。     

煤粉富氧燃烧着火温度预测的优化随机森林(GA-RF)模型

二氧化碳排放是造成温室效应的主要原因之一,富氧燃烧作为一种有效的碳减排与封存技术具有广泛的研究前景。在燃煤电厂中煤粉富氧燃烧的着火温度是燃烧器设计和运行安全的重要指标,并且与煤粉组成成分、煤粉粒径以及燃烧氛围都有复杂的相关性。因此,对煤粉富氧燃烧着火温度的预测模型研究意义重大。采用滴管炉分别测量了5种煤粉在O2体积分数为30%、35%、40%、50%、60%、70%、80%、90%、100%富氧条件下的着火温度,分析了氧气体积分数和煤粉的组成成分与着火温度之间的关系。研究发现,随着氧气体积分数分数的增加,5种煤样的着火温度均显著下降,且挥发分越高的煤,下降幅度越大。将45组试验着火温度数据与其他研究者采用同样方法测得的69组着火温度数据组成机器学习样品库,以煤粉的元素分析、工业分析、煤粉粒径及氧气体积分数为输入条件,以着火温度T为目标输出,构建了遗传算法优化的随机森林模型(GA-RF模型),准确预报了煤粉富氧燃烧的着火温度,其预报精度为:R2>0.99,RMSE<16,MAE<8。通过模型参数重要性分析发现,氢组分超过5%后,着火温度出现阶跃式上升,现有煤粉着火数据也证实了该现象。     

Selecting an ignition criterion methodology for use in a radiative fire spread submodel

Research is ongoing to increase the functionality of the fire zone modeling software BRANZFIRE, by converting it from a deterministic to a probabilistic model. One component of this work is the development of a radiative fire spread submodel for which a suitable ignition criterion method is needed. This paper provides details of that ignition criterion procedure and its implementation into the submodel. A list of requirements that the ignition methodology had to satisfy was established. Of the many different piloted ignition models available, the Flux–Time Product technique, and its associated ignition criterion, was selected to be incorporated into the fire spread submodel. This method provides a practical engineering approximation of when a secondary fuel item that is subjected to incident radiation will ignite that is commensurate with the accuracy of the overall model. Primarily to demonstrate the use of the technique in the submodel, a series of ignition experiments were conducted on a single example of upholstered furniture using the Cone Calorimeter apparatus, with specimens tested in both the horizontal and vertical orientation, under piloted and auto ignition conditions. The experimental incident radiation and time‐to‐ignition data, for the piloted ignition mode, was analyzed using a modified Flux–Time Product correlation procedure. To deal with the auto ignition mode, an empirical approximation, based on the modified Flux–Time Product procedure, is proposed. Data for use in the submodel was therefore also derived for the auto ignition mode, based on an experimental determination of the minimum ignition flux. Copyright © 2010 John Wiley & Sons, Ltd.     

Do open flame ignition resistance treatments for cellulosic and cellulosic blend fabrics also reduce cigarette ignitions?

Mattresses/bedding and upholstered furniture are subject to ignition by cigarettes (smoulder) and open flames leading to injuries, fatalities and property damage. There are mandatory and voluntary cigarette ignition standards in the USA for mattresses (16 CFR 1632) and upholstered furniture (UFAC voluntary standards) as well as open flame ignition standards in California (TB 117) and the UK (BS 5852). Open flame ignition standards are being considered/developed for these products. Some suggest that fire retardant (FR) treatments to prevent/reduce open flame ignitions also reduce cigarette ignitions. Some reports suggest that the smoulder ignition propensity of some cellulosic fabrics can be affected adversely by open flame ignition resistance treatments. Ignitions caused by cigarettes and open flames result from different types of combustion that are retarded by different mechanisms. Flaming combustion is a gas phase reaction and occurs when heat causes degradation of the polymer releasing volatile products that undergo rapid oxidation in the air, whereas smouldering combustion is a direct oxidation of either the polymer or its char. The results of textile/fibre industry studies with FR treated upholstery fabrics and a critical review of the available published literature indicate that cigarette ignition propensity of cellulose fabrics is complicated and affected by many factors and that smoulder ignition resistance of these fabrics can be affected adversely by open flame ignition resistance treatments. Copyright © 2004 John Wiley & Sons, Ltd.     

IGNITION BEHAVIOR OF A FUEL SPRAY FLOWING IN A TUBE

The ignition behavior of a spray flowing in a tube is numerically investigated. The ignition process is initiated by a localized heat source or a flame kernel. An hybrid finite-difference scheme is used to solve the two-phase equations. A consistent ignition criterion is obtained, which is shown to provide a sufficient ignition condition for all the cases considered. Results indicate the existence of an optimum droplet size and an optimum equivalence ratio for the minimum ignition energy. The optimum values vary with the mixture conditions such as droplet size, equivalence ratio, and fuel volatility. This is a significant result since the conclusions of earlier studies for the initially quiescent sprays are validated for the flowing situations.     

不同气氛对铝粉点火燃烧特性的影响分析

为了研究流化气体对粉末推进剂点火燃烧性能的提高作用,采用CO_2激光点火器和光纤光谱仪相结合的实验方法,研究了不同气氛条件下Al粉的点火燃烧特性。采用光谱信号拟合测温法计算了Al粉在不同气氛环境中的点火温度。结果表明,常压环境下,粒径1μm的Al粉在N_2O和空气氛围下的点火延迟时间分别为10ms和359ms,从点火成功过渡到全面燃烧的时间分别为829ms和1 579ms,说明Al粉在N2O环境中点火阶段的表面异相反应速率与燃烧阶段的反应速率均快于在空气中;粉径1μm的Al粉在N2O和空气环境下的点火温度分别为1 550~1 650K和1 450~1 500K,两者相近,但都明显低于毫米级Al粉的点火温度(2 300K),说明Al粉的点火温度受粒径影响较大。     

焦载热褐煤气化试验装置点火试验研究

介绍了褐煤温和气化及热半焦连续高温气化工艺流程及其扩大试验装置，着重研究了该装置的燃烧点火设备和点火过程．根据点火试验升温曲线，将点火过程分为加热、着火和燃烧３个阶段并作了讨论，最后对点火试验本身进行了评述．     

Ignition of porous, solid radiation source

Asymptotic analysis of the ignition of a semiinfinite porous body by a radiant heat flux yields a critical condition dividing ignition from inert heating. For the case of ignition, the temperature field in the body prior to ignition and the time characteristics of the process are determined. The dependence of the ignition time on the system parameters is analyzed. Tomsk State University, Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 6, pp. 5–13, November–December, 1995.     

An experimental study of biomass ignition

An experimental study has been conducted to determine the ignition temperature of biomass at 21% O₂, both under pulse ignition conditions and under thermogravimetric conditions. In the pulse ignition experiments, samples of about 2 g wheat straw were placed in an isothermal reactor. The ignition temperature was determined from the transient CO and CO₂ profiles to approximately 255 °C at a superficial gas velocity of 14 cm/s (STP). The ignition temperature increased for decreasing superficial gas velocity.Thermogravimetric experiments at 20% O₂ and heating rates of 5 °C/min with finely milled biomass indicated ignition temperatures of approximately 220 °C for wheat straw, 235 °C for poplar wood, and 285 °C for eucalyptus wood. These values are significantly lower than values obtained for coal under similar conditions and confirm the relationship between volatile matter content and ignition temperature previously reported for coal.A mechanistic model for ignition of biomass is proposed. We believe that the ignition process is initiated by oxidation reactions on the straw surface. These reactions raise the surface temperature above that of the surrounding gas and promote ignition of the volatiles. Once ignited, the volatiles may form a homogeneous diffusion flame away from the particle surface. The superficial gas velocity affects the particle heating rate as well as the transport of oxygen to the surface. For this reason the ignition process is not entirely controlled by kinetics at low temperatures.     

Ignition Characteristics of Steady and Dynamic Release of Pure Silane into Air

Dynamic and steady release tests have been performed to uncover the precise condition for pure silane ignition upon its release into air. Two regimes (dynamic and steady) are studied. In dynamic tests, silane is released from a vessel with a known pressure. It is found that prompt ignition is not observed even with the source pressure down to 0.15 MPa. In steady flow tests, a reproducible critical exit velocity is found above which silane can be released indefinitely into air without any ignition. With the aid of the laminar boundary layer theory, it is found that ignition always occurs in a well-defined mixture fraction called the most reactive mixture fraction. The critical exit velocity and the most reactive mixture fraction suggest that silane release without prompt ignition is most likely caused by flow strains or by scalar dissipations, which prevent chemical reactions of silane oxidation.     

Ignition of a layer of combustible forest materials

Theoretical and experimental studies of the ignition of forest combustible materials by real ignition sources, which are modeled by a reference source, are reported. The time of ignition by the reference source is determined. The critical ignition energy is estimated, and its variation under real conditions is analyzed. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 6, pp. 14–22, November–December 1998. The paper is reported at the 2nd International Conference on Forest Fires (Irkutsk, 10–15 June, 1997).