矿井火区封闭进程中瓦斯爆炸危险性的数值模拟分析

为分析火区封闭过程瓦斯爆炸危险性,本文采用热平衡法对封闭过程中烟气影响条件下的甲烷爆炸危险性开展了研究,建立了CO2与CO影响下甲烷爆炸危险性变化数学模型和封闭过程中火区气体组分演化数学模型,并采用FLUENT软件对封闭过程中的主要气体体积分数变化进行了数值分析,在此基础上分析了封闭过程中甲烷爆炸的危险性,得出了甲烷爆炸危险区域位置分布规律和易爆炸时间节点.结果表明:封闭过程中由于受多组分烟气存在的影响,甲烷爆炸下限受CO体积分数的影响较大,而甲烷爆炸上限对CO2体积分数变化较为敏感;火区封闭过程中,火源燃烧状态由富氧燃烧变为富燃料燃烧后甲烷爆炸危险区域大范围增加,得出封闭过程中瓦斯爆炸危险区域主要分布在靠近火源位置和采空区回风侧,其中采空区火源位置的爆炸危险区域持续时间更长,爆炸危险度更大.     

受限空间内气体爆炸惰化泄爆实验研究

为研究惰化条件下受限空间内部混合气体爆炸及泄爆过程中的压力变化规律,对侧面带有泄爆口的球形容器在不同惰性气体浓度条件下密闭爆炸及泄爆过程进行了实验研究.结果表明:容器内初始压力越大,气体爆炸压力及压力上升速率越大,且容器内压力峰值与初压呈线性增加;密闭爆炸时惰性气体占甲烷-空气混合气体的比重越高,容器内的最大压力越低,压力上升速率越小,从点火到达最大压力所用的时间越长,容器内的最大压力与惰性气体的体积分数呈近似线性关系;泄爆与惰化联合作用对容器内的压力峰值及压力上升速率影响都较显著,破膜之前压力缓慢上升,破膜之后快速下降;当惰性气体的浓度达到临界体积分数10%时,泄爆膜一打开,容器内的压力立即下降,使非平衡泄爆转化为平衡泄爆.     

流动态可燃气体爆炸极限的试验研究

利用自行建立的可燃气体动态爆炸特性试验装置,通过试验研究了甲烷、液化石油气(含杂质)和氢气的动态爆炸极限.测试数据表明,甲烷的动态爆炸上限为5.25%,动态爆炸下限为17.05%;液化石油气(含杂质)的动态爆炸上限为2.55%,动态爆炸下限为12.85%;氢气的动态爆炸上限为4.35%,动态爆炸下限为76.05%.通过比较发现这3种可燃气体在动态条件下的爆炸下限值比静态时的爆炸下限高,动态条件下的爆炸上限值比静态时的爆炸上限低,说明动态条件下的爆炸极限范围比静态爆炸极限范围小.     

氢气的生成及对瓦斯爆炸的影响

利用痕量氢气测定方法,对煤氧化过程产生的氢气进行测定,借助20L球形爆炸实验装置,研究氢气对瓦斯爆炸特性的影响．实验结果表明当煤温升高到200～250℃时就可以检测到氢气,之后随温度升高氢气浓度呈指数上升,当煤温升至280℃,φ（H2）最高可达0．479／5．煤样粒径对氢气的生成影响不大,而煤种对氢气的产生却有较大的影响．煤变质程度越低,析出氢气的温度也越低,析出氢气量越多．氢气的存在会大幅度降低甲烷的爆炸下限,并增加甲烷的爆炸威力．φ（H2）为0．5％时,φ（CH4）为2．4％的混合气体就会发生爆炸．     

石油炼厂气与煤共转化制合成气基础研究——丙烷在煤焦及石英砂上裂解实验研究

基于石油炼厂气与煤共转化制合成气,采用小型石英管固定床反应装置,在850～1 000℃时对炼厂气中的丙烷在空床、彬县煤焦以及石英砂上的裂解反应进行了实验研究,结果表明:丙烷裂解产物包括氢气、甲烷、乙烯、碳和微量乙烷,反应温度越高,裂解越完全,生成的氢气和碳越多.850～1 000℃时,丙烷在空床与在彬县焦平衡点和石英砂上裂解转化率及生成产物的量接近,转化率为100%,即丙烷无需催化剂即能完全裂解.丙烷在新鲜彬县煤焦上的裂解更为彻底,但随着焦的催化活性由于裂解生成炭的沉积而逐渐丧失,更容易生成甲烷和乙烯.     

高频介质阻挡放电产生臭氧的实验研究

实验研究了在不同气源条件下高频正弦介质阻挡放电法产生臭氧时电压、体积流量、相对湿度的变化对臭氧体积分数的影响.实验结果表明,当气源分别为空气和氧气时,臭氧体积分数随气体体积流量的变化呈不同的变化趋势,为空气源时臭氧体积分数随气体体积流量的增大先升高后降低,而为氧气源时臭氧体积分数不断下降.气源为氧气时,实验中当电压为较低电压3 064 V,体积流量为30 L/h时,臭氧体积分数高达55 000×10^－6,从而即产生了高体积分数的臭氧又保证了整个系统的安全,降低了成本.     

渐缩微喷管内氢气掺混甲烷预混燃烧实验研究

在出口直径为1.6 mm的石英渐缩喷管中进行预混燃烧实验,研究不同当量比(实际供给的空气量与理论上可完全燃烧需要空气量之比)以及混合比R（甲烷体积与燃料总体积比）下氢气/甲烷/空气在微尺度喷管内稳燃范围、输出推力、壁面温度分布等特性.通过实验发现,混合比越大,对应的稳定流速下限越小,当量比越大,对应的稳定流速下限越大,其中Φ=0.7,稳燃流速范围最大.当Φ=0.6时,壁面最高温度随着R的增大而减小,但是当Φ=0.9时,壁面最高温度几乎没有变化.壁面最高温度出现在Φ=0.7时,为761 ℃.火焰分为2层,内层颜色基本为淡蓝色,表明燃烧中氢气被点燃.当输入功率（由氢气和甲烷的热值与各工况体积流量计算获得）Q=13 W时,Φ=1.0时得到的比冲最大,效率最高.     

低浓度甲烷流向变换催化燃烧

以水铝石和改性过的γ-Al2O3为原料制备了铝溶胶涂层,考察了不同涂层固含量对催化剂比表面积的影响.以贵金属Pd作为催化剂活性成分,研究了催化剂在不同Pd含量和还原条件下催化活性的变化规律,并考查了催化剂预热温度、系统换向周期对反应系统床层温度的影响.结果表明:涂层固含量20%、Pd负载量占涂覆层质量分数1.5%为催化剂最佳制备条件;当催化剂预热温度为450℃、空速为15 000 h-1、换向周期为10 min、甲烷体积分数为0.2%时,甲烷转化率最高可达85%.     

多元混合气体对CH4爆炸影响的反应动力学模拟

为深入研究多元混合气体对CH4爆炸的影响和作用机理,选取C2 H6,C2 H4,CO,H2典型可燃气体,采用CHEMKIN软件构建零维封闭均相反应器模型,研究其对CH4爆炸反应过程的影响,模拟分析以CO为主导的混合气体对CH4最大爆炸压力、最大爆炸温度和爆炸过程中关键自由基(H,O,OH)的影响,同时对H+OH自由基最大体积分数变化规律进行分析,并与理论当量状态下各单一气体对CH4爆炸过程的影响规律作对比.结果表明:混合气体的添加对CH4最大爆炸压力和最大爆炸温度有明显促进作用;爆炸过程中H自由基最大体积分数持续增加,O和OH自由基最大体积分数变化与CH4体积分数有关;多元混合气体对CH4的最大爆炸压力和最大爆炸温度影响与单一H2或CO对其影响规律相似,对关键自由基(H,O,OH)的影响规律与CO更为接近.通过敏感性分析获得了影响CH4爆炸过程的关键反应.     

一株高效甲烷氧化细菌生长条件优化研究

通过对5种不同土壤样品进行甲烷降解实验筛选出甲烷降解率最高的稻田土壤样品,并从土壤样品中分离、筛选出一株具有高效降解甲烷能力的甲烷氧化细菌L08.通过对菌种接种量、pH、培养温度、培养方式等条件的研究,得到菌株的最优生长条件：培养温度35 ℃,pH 7.0;菌液接种量4.0 %（体积分数）,甲烷含量为10 %（体积分数）,测定其生长曲线,为甲烷氧化细菌降解甲烷研究提供基础数据.     

Explosion limits for combustible gases

Combustible gases in coal mines are composed of methane, hydrogen, some multi-carbon alkane gases and other gases. Based on a numerical calculation, the explosion limits of combustible gases were studied, showing that these limits are related to the concentrations of different components in the mixture. With an increase of C4H10 and C6H14, the Lower ExplosionLimit (LEL) and Upper Explosion-Limit (UEL) of a combustible gas mixture will decrease clearly. For every 0.1% increase in C4H10 and C6H14, the LEL decreases by about 0.19% and the UEL by about 0.3%. The results also prove that, by increasing the amount of H2, the UEL of a combustible gas mixture will increase considerably. If the level of H2 increases by 0.1%, the UEL will increase by about 0.3%. However, H2 has only a small effect on the LEL of the combustible gas mixture. Our study provides a theoretical foundation for judging the explosion risk of an explosive gas mixture in mines.     

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.     

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．     

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.     

Methane absorption and application of mixed organic aggregate prepared from Span80 and alkaline salt

The water-based materials for mine gas absorption and explosion suppression were prepared, in which the mixed organic aggregate of Span80 and alkaline salt can be used as methane absorbent. Methane was used as a model of mine gas, and the absorptions of methane with different complex materials were studied using head space gas chromatography. Then the state of aqueous material was characterized with laser light scattering instrument and the effects of different complex materials on explosion suppression were preliminarily studied in explosion chamber which can simulate mine gas explosion. The research results showed that complex material could absorb methane and there was some correlation between the mean diameter of organic aggregate in aqueous material and the absorption effect. Additionally, the aqueous material could suppress the methane explosion to some degree. The material can absorb mine gas in atomization condition, therefore, degrease mine gas concentration and influence the distribution of mine gas in the space, and then suppress the mine gas explosion to some extent.     

低碳烃在ZSM-5催化剂上芳构化技术的研究进展

在概述国内外低碳烃芳构化工艺的基础上,着重对低碳烷烃芳构化的技术进展和现状进行了系统的评述。通过对甲烷、乙烷、丙烷和丁烷的芳构化反应的详细阐述,探讨了低碳烃在ＨＺＳＭ－５及其金属改性的沸石分子筛上芳构化的催化作用和反应机制,评价了金属改性ＺＳＭ－５催化剂在芳构化反应中的优缺点,同时给出了反应条件、芳烃收率和选择性,提出了今后芳构化发展的新方向,为综合利用低碳烃资源和开辟新的生产芳烃原料来源探索了新的途径。     

凝析气藏注气过程中露点压力变化特征研究

在凝析气藏循环注气和注气吞吐解除近井带反凝析堵塞的注气过程中,凝析气流体的露点压力变化较大,而在目前的凝析气藏开发过程中,对凝析气露点压力变化考虑较少.作者利用Nemeth.L.K和Kennedy.H.T.的露点压力计算经验公式,研究了向凝析气中注入N2、甲烷、CO2和丙烷等介质的过程中露点压力变化规律,并分析了衰竭式开发和注气过程中凝析气井近井带露点压力变化特征.结果表明,注甲烷使露点压力有较小幅度的减小;注入CO2和丙烷均可使凝析气露点压力有较大幅度降低;而注入N2将使露点压力升高.在凝析气藏衰竭式开发过程中,当近井带压力下降至露点压力以下时,距井筒越近,凝析气中重质组分含量越低,露点压力也越低.在注气吞吐的焖井阶段,反蒸发作用会引起凝析气中重质组分增加,露点压力将升高.     

Analysis of vacuum chamber suppressing gas explosion

In order to suppress the harm of gas explosion, the current study researched on the body of vacuum chamber. The previous studies verified that it could obviously lower the explosion overpressure by reasonably arranging vacuum chamber on pipe. That is to say, the vacuum chamber has the effect of absorbing wave and energy. To further deeply analyze the vacuum chamber suppressing gas explosion, this research designed the L-type pipe of gas explosion, and compared the experimental results of gas explosion with vacuum chamber and without vacuum chamber. Besides, using the gas chromatograph, this study also investigated the gas compositions in the pipe before and after explosion. The results show that: (1) without vacuum chamber, the maximum value of explosion overpressure is 0.22 MPa, with 60 ms duration, and after explosion, the concentration of oxygen drops to 12.07%, but the concentration of carbon monoxide increases to 4392.3 × 10^?6, and the concentration of carbon dioxide goes up to 7.848%, which can make the persons in danger suffocate and die; (2) with vacuum chamber, explosion overpressure drops to 0.18 MPa, with 20 ms duration or less, and after explosion, the concentration of oxygen still remains 12.07%, but the concentration of methane is 7.83%, however the concentration of carbon monoxide is only 727.24 × 10^?6, and the concentration of carbon dioxide is only 1.219%, at the this moment the concentration ratio of toxic gas drops by more than 83% in comparison to be that without vacuum chamber. Consequently, the vacuum chamber can guarantee that most methane does not take part in chemical reaction, and timely quenches the deflagration reaction of gas and oxygen. Because of the two points mentioned above, it reduces the explosion energy, and lowers that the overpressure of blast wave impacts and damages on the persons and facilities, and also decreases the consumption of oxygen and the production of the toxic gas. Therefore, it is safe to conclude that the vacuum chamber not only absorbs wave and energy, but also prevents and suppresses explosion.     

Time-varying diffusion characteristics of different gases in coal particles

Based on the analytical solution of gas diffusion in spherical coal particles with a constant diffusion coefficient, a calculation method of time-varying diffusion coefficient is proposed by constructing objective function. The time-varying diffusion behavior of methane, nitrogen and carbon dioxide in the coal particles was studied. The results show that with the increase of diffusion time, the diffusion coefficients of methane, nitrogen and carbon dioxide gas in the coal particles exhibit an attenuation characteristic, eventually approaching a limit value individually. The diffusion coefficient of carbon dioxide is larger than methane, and the diffusion coefficient of nitrogen is smallest. Significant phenomenon of limited diffusion was observed for coal of strong adsorption capability. Through the analysis of the diffusion coefficient of gases at different diffusion time, a mathematical model describing the time-varying diffusion characteristic of gases is obtained. The implementation of mixed gases to replace coal bed methane has a very important practical significance.