碱消解法测定固体废物中六价铬的研究

用碱性消解液对固体废物进行预处理,所得消解溶液用火焰原子吸收光谱法进行测定。结果表明:该方法在0.00~8.00mg/L范围内呈良好线性关系,检出限为2.00mg/kg(样品以计2.5g计)。实际样品测定的RSD为1.37%~9.35%,加标回收率为85.5%~125%。消解溶液同时用二苯碳酰二肼分光光度法进行测定,结果显示,两种方法测定的结果没有显著差异,进一步说明了采用火焰原子吸收光谱法测定固体废物中Cr6+的准确性与可靠性。     

高压击穿电弧作用下开关柜内典型阻燃绝缘件引燃特性的实验研究

高压开关柜内的绝缘件失效故障,易引发火灾事故、区域停电甚至影响电网系统的稳定运行。基于高压击穿电弧模拟与材料引燃机理综合模拟实验平台,针对4 mm厚支柱绝缘子和固封极柱,开展了15 kV击穿电弧作用下的系列引燃实验研究。结果表明,高压电极横向击穿后,电弧迅速上翻形成自上而下“夹持”样品的倒“U”形弧柱,弧根与弧顶首先炭化或引燃。阻燃绝缘件样品顶部形成火焰后,随着燃烧的进行,逐渐从顶部形成穿透样品的内部击穿电弧,该电弧易诱发剧烈燃烧的水平喷射火焰。内部击穿电弧位置向下移动呈“2阶段”特征:在初始阶段较慢,支柱绝缘子和固封极柱样品内击穿点下移速度分别约为2.55 mm/s和1 .74 mm/s,而在第2阶段分别增大至78.50 mm/s和35.03 mm/s。此外,高压起弧瞬间,在紧邻电极上方的绝缘材料表面,升温速率可达180 ℃/s。研究结果可用于高压开关柜各类阻燃绝缘件的科学选型与优化设计,为开关柜防火安全性能的提升提供科学依据。     

Experimental study on water sealing of fire barriers and explosion venting of large-scale pipeline with low-concentration gas

Low-concentration gas transported in pipelines may lead to explosion accidents because gas with a concentration of less than 30% is prone to explode. To reduce the incidence of gas explosions, water sealing of fire barriers is implemented, and explosion venting devices are installed along the pipeline. To investigate their suppression effect on low-concentration gas explosion, experiments using methane–air premixed gas under different conditions were implemented on a DN500 pipeline test system. The effects of three types of explosion venting forms (rupture disc, asbestos board, and plastic film) on explosion overpressure and flame were compared and analysed. Results show that the rupture disc, asbestos board, and plastic film can achieve adequate explosion venting, causing the peak decay rates of explosion overpressure to reach 82.37%, 81.72%, and 90.79%, respectively. The foregoing indicates that the greater the static activation pressure of the explosion venting form, the higher the peak explosion overpressure at each measurement point. Moreover, the shorter the explosion flame duration, the greater the flame propagation velocity. The research results provide an essential theoretical foundation for the effective suppression of gas explosion accidents in the process of low-concentration gas transportation.     

Behavior of flames propagating through lycopodium dust clouds in a vertical duct

The structure of flame propagating through lycopodium dust clouds has been investigated experimentally. Upward propagating laminar flames in a vertical duct of 1800 mm height and 150×150 mm square cross-section are observed, and the leading flame front is also visualized using by a high-speed video camera. Although the dust concentration decreases slightly along the height of duct, the leading flame edge propagates upwards at a constant velocity. The maximum upward propagating velocity is 0.50 m/s at a dust concentration of 170 g/m³. Behind the upward propagating flame, some downward propagating flames are also observed. Despite the employment of nearly equal sized particles and its good dispersability and flowability, the reaction zone in lycopodium particles cloud shows the double flame structure in which isolated individual burning particles (0.5–1.0 mm in diameter) and the ball-shaped flames (2–4 mm in diameter; the combustion time of 4–6 ms) surrounding several particles are included. The ball-shaped flame appears as a faint flame in which several luminous spots are distributed, and then it turns into a luminous flame before disappearance. In order to distinguish these ball-shaped flames from others with some exceptions for merged flames, they are defined as independent flames in this study. The flame thickness in a lycopodium dust flame is observed to be 20 mm, about several orders of magnitude higher than that of a premixed gaseous flame. From the microscopic visualization, it was found that the flame front propagating through lycopodium particles is discontinuous and not smooth.     

Experimental study on the fractal characteristic of methane explosion flame

In this paper flame microstructures and propagation characteristic of methane explosion are studied by high speed schlieren photography technique. By experiment it shows that flame front surface and inner flow field of methane explosion has distinctly fractal characteristic, the effect of the wrinkle of flame front surface and inner reactants on flame propagation can be directly reflect by fractal dimensions. Fractal dimension has a direct relation to flame structure and flame propagation characteristics, and it is the important parameter to scale the flame propagation velocity and flame temperature.     

萃取富集—火焰原子吸收法测定环境水中痕量砷

联合应用高效雾化器、缝式石英管火焰原子吸收法,采用萃取富集技术测定砷,使砷的灵敏度改善267倍,同时消除了大量盐类的干扰,避免了钠、铝等对石英管的损坏。考察了溶液酸度、碘化钾用量、共存离子等因素对实验的影响。该方法的线性范围为0～25μg／L,检出限为。3μg／L,相对标准偏差为3．2％,回收率为97．8％～101．0％,用于环境水样中痕量砷的监测,结果令人满意。     

聚苯胺和氮化硼协效阻燃棉布的制备及性能研究

使用聚苯胺(PANI)与氮化硼(BN)作为阻燃体系,采用一步法对棉布进行阻燃改性,研究了PANI与BN的配比对Cotton-PANI-covered BN复合材料形貌的变化以及对阻燃性能、热稳定性的影响。由扫描电镜(SEM)和全反射傅里叶红外(ATR-FTIR)测试结果可知,PANI成功生长在棉布纤维表面。另外由于PANI的粘附性,BN能被粘附在棉织物表面,从而形成更为致密的包覆结构。研究发现,PANI和BN的存在,能大大提高棉布的热稳定性和成炭性。当PANI的浓度为2.7 wt%,BN的浓度为5.9 wt%时,改性棉布的残炭量能达到8.9%,比纯棉布(0.6%)增加了约14倍。同样,垂直燃烧实时图像能看出PANI/BN改性的棉布的残炭量更高,炭层也更完整,表明PANI和BN具有优良的阻燃效果。     

基于三维图像分析的浮力扩散火焰几何与辐射特性研究

火焰几何特性和辐射特性是刻画火灾规模及其危害的重要参量。利用三维火焰重构技术,获取了丙烷浮力扩散火焰的火焰高度、表面积、体积和火焰面元视角系数的变化规律。结果表明,三维重构的火焰能够表征真实火焰形态的动态变化。平均火焰表面积和体积均可较好地拟合为热释放速率的幂函数,火焰表面积热释放速率随火焰热释放速率的增加趋于常数。平均火焰高度、表面积和体积与火焰外部平均辐射热流之间具有较好的幂函数关系,且拟合指数随着与火源距离的增大而减小。此外,将点源、圆柱辐射模型和火焰面元积分方法得到的辐射计算值与辐射测量值进行比较,发现火焰面元积分方法能够更好地预测火焰外围的瞬时和平均辐射热流分布。     

不同坡度对正庚烷流淌火燃烧特性的影响

针对液体燃油储运过程中泄漏引发的火灾爆炸事故,设计并搭建流淌槽坡度可调式液体燃油流淌火燃烧试验平台,开展连续泄漏正庚烷流淌火试验。选择水平表面(0°)流淌试验作为基准,改变流淌槽的坡度(0.5°,1°和3°),研究分析不同泄漏速率下连续泄漏正庚烷流淌火的燃烧面积、燃烧速率等燃烧特征参数的变化规律。结果表明:1)连续泄漏正庚烷流淌火燃烧特征参数均随泄漏速率增加而明显增加;2)坡度对连续泄漏正庚烷流淌火燃烧特性影响显著,即使流淌槽坡度增加0.5°,其燃烧特性即发生明显改变;3)连续泄漏正庚烷流淌火的平均稳定燃烧速率随流淌槽坡度的增加反而减小。     

Effect of flame propagation regime on pressure evolution of nano and micron PMMA dust explosions

Experiments using an open space dust explosion apparatus and a standard 20 L explosion apparatus on nano and micron polymethyl methacrylate dust explosions were conducted to reveal the differences in flame and pressure evolutions. Then the effect of combustion and flame propagation regimes on the explosion overpressure characteristics was discussed. The results showed that the flame propagation behavior, flame temperature distribution and ion current distribution all demonstrated the different flame structures for nano and micron dust explosions. The combustion and flame propagation of 100 nm and 30 μm PMMA dust clouds were mainly controlled by the heat transfer efficiency between the particles and external heat sources. Compared with the cluster diffusion dominant combustion of 30 μm dust flame, the premixed-gas dominant combustion of 100 nm dust flame determined a quicker pyrolysis and combustion reaction rate, a faster flame propagation velocity, a stronger combustion reaction intensity, a quicker heat release rate and a higher amount of released reaction heat, which resulted in an earlier pressure rise, a larger maximum overpressure and a higher explosion hazard class. The complex combustion and propagation regime of agglomerated particles strongly influenced the nano flame propagation and explosion pressure evolution characteristics, and limited the maximum overpressure.