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.     

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.     

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.     

非烃气体置换CH4水合物的实验研究

在自行设计的反应装置中,以石英砂和质量分数3.5%的NaCl溶液模拟海底环境,选取南海北部高含N2和高含CO2天然气藏两组气样组成,分别在温度277.15K、初始压强6.37 MPa和温度275.15K、初始压强4.30MPa条件下进行了混合气置换CH4水合物实验,模拟高含非烃组成天然气渗漏对CH4水合物矿藏的影响。结果表明,CO2量变化最大,在置换CH4水合物过程中起主导作用,N2量变化较小。两种气样在不同实验条件下,反应时间140h时的置换效率分别达到8.64%和20.71%。基于实验结果,简单分析了多孔介质体系CO2置换甲烷水合物中CH4的机理。     

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．     

Adsorption and desorption on coals for CO2 sequestration

Adsorption and desorption of carbon dioxide, methane and other gases on coals has been investigated experimentally using representative Zhongliangshan coals. Gas adsorption is one of the major concerns for both CO2 sequestration and methane recovery processes. The experiments were carried out using both single and multi-component mixtures at 25 ℃ and 30 ℃ with the highest pressure of 12 MPa. The coal was under moisture equilibrated conditions. This provides experimental data from which a predictive assessment of CO2 sequestration and/or methane recovery can be conducted. The results show that for pure gasses the CH4 adsorption capacity is higher than the N2 adsorption capacity but lower than the CO2 adsorption capacity. Injection of CO2 or other gases into the coal significantly affects CH4 desorption. This allows the enhancement of CH4 recovery from the coals, thus supplying more clean energy while sequestering significant amounts of CO2 thereby reducing the greenhouse effect from human beings.     

可燃制冷剂爆炸极限及抑制的理论与实验研究

对影响可燃制冷剂爆炸极限的因素进行了讨论分析,指出仅凭测试的爆炸极限来确定可燃工质的爆炸范围是不可靠的,应考虑测试条件和安全系数。用具有阻燃作用的制冷剂与可燃制冷剂组成混合制冷剂抑制可燃制冷剂的可燃性,研制了可燃工质爆炸极限测试装置,对18种抑制后的混合制冷剂爆炸极限进行了实验研究。     

基于人工神经网络的气体定性分析方法

提出将气体传感器阵列与交馈神经模式识别技术相结合,解决气体传感器的“交叉敏”问题,从而完成气体的定性、定量分析;针对常规ＢＰ算法的缺点,构造了基于自适应调整步长和加动量因子的改进ＢＰ算法用于前馈神经网络的训练;通过实验对Ｈ２、ＣＨ４、ＣＯ等三种气体进行了识别,结果表明利用气体传感器阵列和前馈神经网络进行气体定性分析是可行的。     

可燃制冷剂爆炸极限及抑制的理论与实验研究

对影响可燃制冷剂爆炸极限的因素进行了讨论分析,指出仅凭测试的爆炸极限来确定可燃工质的爆炸范围是不可靠的,应考虑测试条件和安全系数.用具有阻燃作用的制冷剂与可燃制冷剂组成混合制冷剂抑制可燃制冷剂的可燃性,研制了可燃工质爆炸极限测试装置,对18种抑制后的混合制冷剂爆炸极限进行了实验研究.     

化工企业动火作业事故直接原因危险度及关联性探究

为有效预防化工企业动火作业事故,应用事故致因“2-4”模型,以2015年至2020年化工企业发生的16起动火作业事故为样本,分析直接原因的危险程度并明确关联性。结果表明不安全动作原因中未分析、检测可燃性气体浓度或检测不到位（UA₅）及未制定有效的气体检测程序（UA₆）的危险性最高R_UA6=0.611,不安全物态原因中形成可燃性气体或者气体达到爆炸极限（UC₇）的危险程度最高R_UC7=0.626。关联分析中不安全动作触发路径最多占总路径的82.98%。关联差异要素最多的不安全动作为“未制止违章作业（UA₁₄）”,不安全物态为“残留的燃爆物质（UC₁）及材料的合规性（UC₅）”,明确了不安全动作原因是事故控制的要点。研究结果可作为动火作业事故预防的主要依据,为针对性管控措施的实施提供理论参考。     

Vacuum chamber suppression of gas-explosion propagation in a tunnel

To control and reduce the harm of a gas explosion, a new method is proposed for suppressing gas-explosion propagation in a tunnel by using a vacuum chamber. We studied the suppression effect on gas explosions by placing a vacuum chamber at dif-ferent positions along the tunnel. The results indicate that: 1) the vacuum chamber can absorb the explosion wave and explosion energy as much as possible at the beginning of the gas explosion, and; 2) when the vacuum chamber is used the closer it is to the ignition source the more significant the suppression effect. In addition, by using the vacuum chamber: 1) the flame propagation velocity decreases from ultrasonic to subsonic; 2) the flame propagation distance is remarkably shortened; 3) the maximum peak value of overpressure (Pro) decreases from 0.34 to 0.17 MPa or less, and; 4) the impulse of the blast wave (/) decreases from 20 to 8 kPa-s or less.     

煤吸附瓦斯过程温度变化的试验研究

在实验室对不同瓦斯（ＣＯ２,Ｃ４,Ｎ２等）吸附过程中煤体温度的变化进行了研究,证实煤体吸附瓦斯的过程是放热过程;煤体吸附不同的瓦斯时,放出的热量不同：吸附ＣＯ２时最大,ＣＨ４次之,Ｎ２最小;煤对其吸附能力超强的瓦斯,吸附时放出的热量越大,对于同一种瓦斯,吸附的瓦斯压力越大,即瓦斯附量越大,吸附过程放出的热量越大。     

阻燃木材的燃烧特性分析（二）

根据木材阻燃机理,以磷-氮体系阻燃剂为主进行复配,获得3组配方（质量比）：三聚氰胺∶磷酸∶硼酸=2∶2∶3;聚磷酸铵∶双氰胺=2∶1;尿素∶双氰胺∶磷酸=1∶3∶4。每组配方分别配制浓度为5%,10%,15%的阻燃液,采用浸渍法在恒温80℃下,浸渍24 h处理白杨木材试样。利用锥形量热仪在热辐射功率为50 kW/m2的条件下,对阻燃处理后的木材试样以及空白试样进行燃烧特性分析。实验结果表明,三聚氰胺、磷酸、硼酸组成的配方在增强木材试样的耐火性、抑制试样产烟量和一氧化碳生成率方面效果显著;聚磷酸铵APP、双氰胺组成的配方在控制木材试样燃烧速度和降低总热释放量方面效果显著;尿素、双氰胺、磷酸组成的配方在提高载药量、降低热释放速率、延长点燃时间、抑制二氧化碳生成率方面效果显著;3组配方在降低木材试样的质量损失率和有效燃烧热方面效果相近。综合各项分析结果,确定尿素、双氰胺、磷酸按1∶3∶4的比例（质量比）配制浓度为15%的阻燃液为最佳配方。     

Schiff碱型羧酸开链冠醚的合成

按缩合反应合成了一类端基为羧基的Ｓｃｈｉｆｆ碱型开链冠醚其中,Ｘ＝ＣＨ２ＣＨ２－时,Ｒ＝ＣＯ２Ｈ（Ｈ２Ｌ１）;－ＯＣＨ２ＣＯ２Ｈ（Ｈ２Ｌ３）;－ＯＣＨ２ＣＯ２Ｃ２Ｈ５（Ｌ８）：Ｘ＝时．Ｒ＝ＣＯ２Ｈ（Ｈ２Ｌ２）：－ＯＣＨ２ＣＯ２Ｈ（Ｈ２Ｌ４）测定了配体Ｈ２Ｌ１和Ｈ２Ｌ３的酸的离解常数．     

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。     

用H_2-CH_4气制备碳化铁的合适气相成分

计算了不同温度、压力及N2含量下稳定生成碳化铁理论X（H2／CH4％）最大值．实验结果表明，还原气中的H2含量对还原速度、还原度有较大影响，影响碳化铁的终点转化率．还原气中CH4对铁的碳化生成速度影响较小．合适的还原气成分应为50％H2加50％CH4．还原气中N2的存在降低了还原速度及碳化铁的转化率，还原气中N2含量应小于5％．     

Hydrogen Generation from Plasmatron Reforming Ethanol

Hydrogen generation through plasmatron reforming of ethanol has been carried out in a dielectric barrier discharge (DBD) reactor. The reforming of pure ethanol and mixtures of ethanol-water have been studied. The gas chromatography (GC) analysis has shown that in all conditions the reforming yield was H2, CO, CH4 and CO2 as the main products, and with little C2* . The hydrogen-rich gas can be used as fuel for gasoline engine and other applications.     

Zn掺杂对SnO_2纳米线的气敏性能的影响

为了提高SnO2纳米线基气敏传感器在实际应用中存在着灵敏度低、选择性差等问题,采用物理热蒸发法制备纯SnO2纳米线和不同质量百分比（7%,8%,9%,10%）的Zn掺杂SnO2纳米线,将制得的气敏基料制备成旁热式气敏元件,应用静态配气法对浓度均为500ppm的无水乙醇蒸汽、CO及CH4分别进行气敏性能测试.实验结果显示,Zn掺杂SnO2纳米线相比纯SnO2纳米线的气敏性能有了明显提高（乙醇提高2.46倍,CO提高13.88倍,CH4提高1.43倍）,并得出无水乙醇气敏性能在工作温度为280℃最高,CO,CH4在300℃最好.当Zn的掺杂比例为质量百分含量为9%时,各种比例材料所制成的气敏元件气敏性能最高.     

天然气、CO_2重整催化反应的研究(Ⅱ)──积炭的防止

以前期筛选出的对CH4、CO2转化反应良好的Ni－5、Ni－5PM为催化剂,以天然气代替CH4,考察天然气、CO2反应体系．结果表明：Ni－5、Ni－5PM对天然气-CO2有较高的转化活性,但此体系由于天然气中的高烃高温裂解脱氢在反应管壁产生大量炭,而此炭不能通过催化剂消除,为此通过筛选比较,选择了消炭剂此并主要考察了它对反应体系的影响．     

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.