Effect of CO2 on explosion limits of flammable gases in goafs

In order to reduce the number of accidents due to explosions of flammable gases in the goaf of coalmines,the conditions for explosion of flammable gases and their explosion limits,affected to a considerable extent by COz,are explored.With the use of our experimental equipment suitable for the study of explosion of polybasic explosive gas mixtures,we investigated the effect of CH4/H2=10/1 and CH4/C2H4=10/1 gases mixed with CO2 on their explosion limits.The results indicate that after adding CO2,the explosion limit of the CH4/H2 (or C2H4) = 10/1 gas mixtures decreased markedly with increasing amounts of CO2.When the amount of CO2 exceeded 25%,the CH4/C2H4=10/1 flammable gas mixture did not lead to explosions.Similar results were obtained when the amount of CO2 exceeded 23% in the CH4/H2=10/1 flammable gas mixture.We also compared the explosion limits and the explosion suppression effect of N2 or CO2 on the explosion limits of the CH4+CO and CH4+C2H4 dual explosive gas mixtures.Along with the increases in the amounts of CO2 or N2,the area of the explosion limits of gas mixtures decreased.Under the same conditions,the explosion suppression effect of CO2 was greater than that of N2.CO2 has clearly the better suppression effect on the explosion of flammable gases in goafs.     

Effect of CO_2 on explosion limits of flammable gases in goafs

In order to reduce the number of accidents due to explosions of flammable gases in the goaf of coalmines,the conditions for explosion of flammable gases and their explosion limits,affected to a considerable extent by CO2,are explored.With the use of our experimental equipment suitable for the study of explosion of polybasic explosive gas mixtures,we investigated the effect of CH4/H2=10/1 and CH4/C2H4=10/1 gases mixed with CO2 on their explosion limits.The results indicate that after adding CO2,the explosion limit of the CH4/H2(or C2H4) =10/1 gas mixtures decreased markedly with increasing amounts of CO2.When the amount of CO2 exceeded 25%,the CH4/C2H4=10/1 flammable gas mixture did not lead to explosions.Similar results were obtained when the amount of CO2 exceeded 23% in the CH4/H2=10/1 flammable gas mixture.We also compared the explosion limits and the explosion suppression effect of N2 or CO2 on the explosion limits of the CH4+CO and CH4+C2H4 dual explosive gas mixtures.Along with the increases in the amounts of CO2 or N2,the area of the explosion limits of gas mixtures decreased.Under the same conditions,the explosion suppression effect of CO2 was greater than that of N2.CO2 has clearly the better suppression effect on the explosion of flammable gases in goafs.     

烷烃气体对甲烷爆炸下限影响的实验研究

为确定烷烃类混合气体中甲烷的爆炸极限,设计了混合气体爆炸实验系统.在实验系统中,采用高精度计算机配气系统配气,其所得到的混合气体含量误差小于1%,从而使气体爆炸下限更加精确.运用该实验系统研究了丙烷、异丁烷混合气体对甲烷爆炸下限的影响.实验结果表明：当混有丙烷的体积分数达到0.60%时,甲烷的爆炸下限可以降到1.35%;当异丁烷的体积分数约为0.30%时,甲烷的爆炸下限可降到1.80%.研究结果对煤矿瓦斯监测的可靠预警具有重要意义.     

Explosive limits of mixed gases containing CH4, CO and C2H4 in the goaf area

The explosive gases CO and C2H4, released mainly flammable gases during the process of coal self-ignition, are of the most important ingredients of the multi-component gases in goaf areas, along with CH4. We have determined some of the parameters of explosive properties of the one-component gases CH4, CO and C2H4 using an explosive trial device of polybasic explosive gas mixtures and emphasized particularly the effect on the limits of explosive concentration of the binary explosive mixed gases CH4+CO, CH4+C2H4, as a function of the amount of CO, C2H4 and inert flame resisting gases (N2, CO2). The experimental results show that the effect of inert gases on the explosive limits of mixed gases, given the property of explosive gas, is obvious: the inert gases (N2, CO2) possess some inhibitory effects on the explosion of the multi-component explosive gas mixtures. The results will provide some experimental support to suppress the occurrence of the gas explosions in goaf areas and provide some directions for designing explosion-proof electric equipment and fire arresters.     

氮气对人工煤气抑爆技术的实验研究

在理论分析及大量实验的基础上,通过向爆炸场加入惰性介质氮气用以改变可燃气体爆炸极限的方法对多元爆炸性混合气体人工煤气抑爆技术进行了实验研究．结果表明,惰性介质氮气可以缩小人工煤气爆炸极限的范围,提高爆炸下限,降低人工煤气的可燃性;当惰性介质氮气达到一定的浓度后,可将人工煤气惰化为不可燃气体,抑制其爆炸的发生,从而解决了人工煤气的安全问题．     

固体氧化物燃料电池的气体检测特性

以变压器油中溶解的H2,CO,CH4,C2H6,C2H4和C2H2故障气体为例,通过化学热力学理论计算了固体氧化物燃料电池(SOFC)的理想输出电压,证明了SOFC对多种故障气体的可检测性.分析温度和压强对SOFC输出电压的影响,结果表明:SOFC的工作稳定性取决于高精度的温度控制系统.利用电化学动力学理论建立气体物质的量与输出电压之间的关系,通过计算发现气体物质的量与输出电压包络之间存在线性关系,从理论上证明了SOFC对故障气体的线性检测特性.设计了基于SOFC和色谱柱的实验平台,实验结果验证了SOFC检测器具有良好的重复性和线性检测特性,基线稳定,C2H2最小检测体积分数为0.08 μL/L,并可同时检测多组份可燃气体.     

隔爆型电气设备最大允许结构间隙值的确定

目的　为隔爆电气设备的制造提供理论依据 .方法　利用间隙隔爆原理 ,对可燃气体 (或蒸气 )的最大试验安全间隙值进行测定 .结果　得到了与 IEC79标准接近的测试数据 .结论　考虑一定安全裕度 ,隔爆型电气设备最大允许结构间隙值应小于此最大试验安全间隙值 .     

ZIF-8体系富集回收炼厂干气中C2H6+C2H4

炼油工业作为一个能量密集型工业,对炼厂干气中轻烃组分气体进行有效回收且利用,将同时解决其一直面临的节能及环保两大难题。采用吸附法以及吸附⁃水合法分离含有C2（即C2H6+C2H4）的模拟炼厂干气M1:C2H6(11.55%)+C2H4(12.46%)+CH4(29.15%)+N2(27.02%)+H2(19.82%),且将分离混合气M2作为二级分离的原料气,完成ZIF⁃8材料对混合气M1的两级分离过程。结果表明,一级分离采用吸附⁃水合分离法使C2组成摩尔分数降低至9.90%;由于原料气M1中C2摩尔分数较高,较吸附分离法,吸附⁃水合法在平衡气相中y_(C_2 )降低幅度和吸附量MC较大;由于C2组分摩尔分数较低,二级分离过程不易形成水合物,因此采用吸附分离法,规避湿ZIF⁃8水分对分离及吸附量造成的负面影响。经过二次分离过程,可以将原料气M1中C2摩尔分数由24.01%降低至2.90%,有效回收了炼厂干气中C2组分。     

湍流的诱导及对瓦斯爆炸火焰传播的作用

对巷道面积突变和巷道分叉对瓦斯爆炸过程中火焰传播速度的影响进行了试验研究。并利用加速环研究了巷道支架对瓦斯爆炸传播规律的影响，在此基础上对湍流的形成过程进行了理论分析。研究结果表明，管路分叉，面积突变对瓦斯爆炸过程中火焰传播规律有重要影响，导致产生附加湍流，使瓦斯爆炸过程中火焰的传播速度迅速增大；在管道内装加速环，将使瓦斯爆炸过程中湍流度加剧，火焰的传播速度更大，激波生成的位置。最大点位置前移。强度增大，研究结果对指导现场防治瓦斯爆炸和减轻瓦斯爆炸的威力具有重要作用。     

不同温度下环保型HFO-1234ze(E)/CO2混合气体分解机理

由于SF6气体的温室效应,以C4F7N、C5F10O、C6F12O和HFO-1234ze(E)等气体为代表的新型环保替代气体得到了广泛的关注,但对于这些气体分子在局部过热或放电状态下导致设备内部温度升高时的分解机理还缺乏研究,为了进一步探究新型环保气体替代SF6气体的可行性。本文以HFO-1234ze(E)分子为例,基于ReaxFF反应分子动力学方法和密度泛函理论,从微观层面模拟研究了HFO-1234ze(E)分子和不同温度下20%HFO-1234ze(E)/80%CO2混合气体的分解现象。结果发现：HFO-1234ze(E)分子存在着7种不同的分解路径,且CO2中的C=O会最先分解,而HFO-1234ze(E)中的C-F键和C=C双键焓值较高,断裂较为困难,随着温度的升高,发生分解的时间也越早;当温度低于2000K时,HFO-1234ze(E)/CO2混合气体几乎都不会发生分解,但当温度为2000K时,HFO-1234ze(E)分子不会发生分解,但CO2分子会迅速发生分解,2600K以上时,温度每上升2000K,HFO-1234ze(E)就会多分解5个左右,CO2就会多分解35个左右,直到最后基本完全分解。混合气体主要分解产生CO、O2、C2O2、HF、CF4、C2F6、C3F6和C3H3F3等各类自由基,其中CO为有毒气体、HF为强腐蚀性气体,应采取措施对其含量进行监测,其他分解产物的化学性质均较为稳定且对环境无害,并仍然具有一定的绝缘能力,表明20%HFO-1234ze(E)和80%CO2混合气体在一定程度上可以完全替代SF6气体,这也为进一步研究其他新型环保混合气体提供了理论依据和工程指导。     

Numerical simulation for explosion wave propagation of combustible mixture gas

A two-dimensional multi-material code was indigenously developed to investigate the effects of duct boundary conditions and ignition positions on the propagation law of explosion wave for hydrogen and methane-based combustible mixture gas. In the code,Young’s technique was employed to track the interface between the explosion products and air,and combustible function model was adopted to simulate ignition process. The code was employed to study explosion flow field inside and outside the duct and to obtain peak pressures in different boundary conditions and ignition positions. Numerical results suggest that during the propagation in a duct,for point initiation,the curvature of spherical wave front gradually decreases and evolves into plane wave. Due to the multiple reflections on the duct wall,multi-peak values appear on pressure—time curve,and peak pressure strongly relies on the duct boundary conditions and ignition position. When explosive wave reaches the exit of the duct,explosion products expand outward and forms shock wave in air. Multiple rarefaction waves also occur and propagate upstream along the duct to decrease the pressure in the duct. The results are in agreement with one-dimensional isentropic gas flow theory of the explosion products,and indicate that the ignition model and multi-material interface treatment method are feasible.     

瓦斯爆炸运动火焰生成压力波的数值模拟

从三维N-S方程出发，用TVD格式，对瓦斯爆炸过程中火焰产生压力波的过程进行了数值模拟，在此基础上，模拟了氢氧燃烧驱动的破膜过程以及破膜前后压缩波、稀疏波对火焰阵面的影响，同时，也研究了瓦斯爆炸过程中，压力波、火焰与障碍物的相互作用，数值模拟结果与理论分析吻合较好，从而进一步验证了该程序能处理含有化学反应和复杂管道的预混可燃气体爆炸问题。     

有机可燃气体爆炸极限的推荐计算方法

提出一种利用氧气系数计算纯净有机可燃气体和由多种有机可燃气体组成的混合气体爆炸极限的计算方法,对目前常用的经验公式进行了整合与修正,简化了对混合气体爆炸极限的计算,也提供了对复杂组成的混合有机可燃气体爆炸极限的快速估算,估算结果与实测值能较好吻合.     

Floor dust erosion during early stages of coal dust explosion development

An ignition of methane and air can generate enough air flow to raise mixtures of combustible coal and rock dust. The expanding high temperature combustion products ignite the suspended dust mixture and will continue to propagate following the available combustible fuel supply. If the concentration of the dispersed rock dust is sufficient, the flame will stop propagating. Large-scale explosion tests were conducted within the National Institute for Occupational Safety and Health (NIOSH) Lake Lynn Experimental Mine (LLEM) to measure the dynamic pressure history and the post-explosion dust scour depth. The aim of this effort is to provide quantitative data on depth of dust removal during the early stages of explosion development and its relationship to the depth of floor dust collected for assessing the incombustible content most likely to participate in the combustion process. This experimental work on dust removal on is not only important for coal mine safety but also for industrial dust explosions.     

Spatial context in the calculation of gas emissions for underground coal mines

The prediction of gas emissions arising from underground coal mining has been the subject of extensive research for several decades, however calculation techniques remain empirically based and are hence limited to the origin of calculation in both application and resolution. Quantification and management of risk associated with sudden gas release during mining(outbursts) and accumulation of noxious or combustible gases within the mining environment is reliant on such predictions, and unexplained variation correctly requires conservative management practices in response to risk. Over 2500 gas core samples from two southern Sydney basin mines producing metallurgical coal from the Bulli seam have been analysed in various geospatial context including relationships to hydrological features and geological structures. The results suggest variability and limitations associated with the present traditional approaches to gas emission prediction and design of gas management practices may be addressed using predictions derived from improved spatial datasets, and analysis techniques incorporating fundamental physical and energy related principles.     

秸秆致密成型块压缩密度对层燃反应性的影响

为了研究秸秆致密成型块压缩密度对其层燃反应性的影响,在DZL2-0.8/160-AII型工业链条锅炉上进行了试烧.结果表明,链条锅炉燃烧秸秆致密成型块时,随着压缩密度的增加,排烟过量空气系数和排渣可燃物含量降低,排渣温度升高.但是当压缩密度超过某一限值时,就会导致排渣可燃物含量和排烟可燃气体含量迅速增加.结论:燃煤链条锅炉燃烧的秸秆致密成型块,其压缩密度大约不应超过950 kg/m3.     

瓦斯事故类型影响严重程度的灰关联分析

煤矿瓦斯事故是煤矿事故防治的重点.在瓦斯事故中,瓦斯爆炸、瓦斯窒息及中毒、煤与瓦斯突出事故往往会造成严重的人员伤亡和财产损失.在所有的瓦斯事故中,由瓦斯爆炸事故引起的死亡人数最多,这和历年的瓦斯事故死亡人数情况相符合.作者基于灰色系统理论,对瓦斯事故类型的影响严重程度进行了灰色关联分析,从灰关联角度验证了煤矿瓦斯事故防治的重点应是:防治瓦斯爆炸、瓦斯窒息及中毒、煤与瓦斯突出事故.     

解决石嘴山市惠农区煤气气源短缺方案

针对惠农区焦炉煤气气源短缺状况，提出了4套解决方案，即新建一组煤气发生炉，当焦炉气供应紧张时，启动煤气发生炉，以发生炉煤气进行补充；新建液化气混空气站，以液化气掺混空气作为补充；新建天然气混空气站，以天然气掺混空气作为补充；以混空气天然气掺混焦炉煤气作为新气源，提高日供气能力．分析了各个方案的特点，最终确定用天然气与空气掺混，然后再以该混合气与焦炉煤气掺混，并严格控制其掺混比例，调整好最终混合气的爆炸极限和其他参数，从而解决惠农区气源短缺状况，提高供气能力，产生了良好的经济效益和社会效益．     

瓦斯事故类型影响严重程度的灰关联分析

煤矿瓦斯事故是煤矿事故防治的重点.在瓦斯事故中,瓦斯爆炸、瓦斯窒息及中毒、煤与瓦斯突出事故往往会造成严重的人员伤亡和财产损失.在所有的瓦斯事故中,由瓦斯爆炸事故引起的死亡人数最多,这和历年的瓦斯事故死亡人数情况相符合.作者基于灰色系统理论,对瓦斯事故类型的影响严重程度进行了灰色关联分析,从灰关联角度验证了煤矿瓦斯事故防治的重点应是：防治瓦斯爆炸、瓦斯窒息及中毒、煤与瓦斯突出事故.     

Effect of variation in gas distribution on explosion propagation characteristics in coal mines

In order to investigate the effect of variation in the distribution of gas on explosion propagation characteristics in coal mines, experiments were carried out in two different channels with variation in gas concentration and geometry. Flame and pressure transducers were used to track the explosion front velocity. The flame speed (Sf) showed a slight downward trend while the methane concentration varied from 10% to 3% in the experimental channel. The peak overpressure (Pmax) dropped dramatically when com-pared with normal conditions. As well, the values of Pmax and Sf decreased when the methane concentration dropped from 8% to 6%. The flame speed in the channel, connected to a cylinder with a length varying from 0.5 to 2 m, was greater than that in the normal channel. The peak overpressure was also higher than that under normal conditions because of a higher flame speed and stronger pressure piling up. The values of Pmax and Sf increased with an increase in cylinder length. The research results indicate that damage caused by explosions can be reduced by decreasing the gas concentration, which should be immediately detected in roadways with large cross-sections because of the possibility of greater destruction caused by more serious explosions.