二氧化硅对膨胀型阻燃聚乙烯的性能影响研究

利用锥形量热仪(CONE)、裂解气相色谱仪(PyGC)、示差扫描量热仪(DSC)等先进的分析测试手段,研究了二氧化硅对膨胀型阻燃聚乙烯阻燃性能的影响、各阻燃剂之间的协同性以及阻燃机理。实验结果显示,阻燃剂的加入可延缓PE的降解过程,降低材料的热释放速率,降低基材在升温过程中的放热量,使基材具有良好的阻燃性;SiO2的适量加入可改善膨胀碳层的耐热性,当SiO2的添加量为6％时,协同阻燃效果最佳。     

Experimental study on vented deflagration of hydrocarbon fuel-air mixtures in a 20-L semi-confined cylindrical vessel with a slight static activation pressure

The overpressure peaks and flame propagation characteristics of hydrocarbon fuel-air mixtures vented deflagration in a 20-L cylindrical vessel with a slight static activation overpressure (P_ST = 2.5 kPa) and five vent opening ratio were studied by a series of experiments. The experiments focused on the effect of vent opening ratio on the overpressure peaks and flame propagation characteristics of hydrocarbon fuel-air mixture vented deflagration. The internal overpressure-time profiles and high-speed photographs of flame propagation processes were obtained. The results showed that three overpressure peaks were distinguished in the internal overpressure-time profiles, caused by the burst vent cover (p_burst), the acceleration of burnt gas (p_fv), and the fierce external deflagration of vented unburned fuel (p_ext), respectively. The changing of the vent opening ratio had almost no effect on the value of p_burst and (dp_burst/dt). With increasing vent opening ratio, the values of p_fv, p_ext, (dp_fv/dt) and (dp_ext/dt) showed a decreasing trend while the values of p_burst and (dp_burst/dt) were nearly constant. The flame presented a hemispherical shape before the vent cover ruptured then developed as a mushroom shape after accelerated to external field. There were three flame speed peaks during flame propagation process, resulted from venting flow acceleration, external deflagration, and axial heat flux formed by internal combustion. With the increase of vent opening ratio, all of the maximum flame speed, external average flame speed, maximum flame distance and external flame duration showed a downward trend, excepting for the internal average flame speed almost remained constant.     

水中总铁两种测定方法的比较

环境监测实验室常使用不同方法进行重复检测作为检测结果质量保证的手段之一。据此对测定水中总铁的两种方法 -邻菲啰啉分光光度法和火焰原子吸收法在校准曲线和检出限、方法精密度和准确度等进行了全面比较,得出两者校准曲线相关性均较好,检出限均为0.03 mg/L,精密度RSD均小于5%,加标回收率均在90%～105%。两者的测定结果无显著性差异。     

火焰原子吸收光谱法测定水中银

采用硝酸消解样品,氘灯背景校正技术消除非特征吸收和光散射影响,火焰原子吸收光谱法测定水中银,方法简便可靠,检出限为0.010 mg/L,RSD为0.9%～6.6%,加标回收率为93.0%～101%.     

采用火焰传感器的高速抑爆响应系统测试研究

为实现主动抑制瓦斯爆炸,研制了高速抑爆响应系统。选用尺寸为150mm×150mm×1 600mm的有机玻璃管道,在CH4体积分数为9.5%的条件下进行响应系统测试实验。系统采用火焰传感器进行爆炸火焰探测,通过所设计的程序自主判定瓦斯爆炸的发生并输出控制电信号,以继电器或MOS管为电路控制开关,通过电磁阀控制抑爆剂的喷出。实验结果表明,火焰传感器探测、信号采集、爆炸判断、输出电信号的总平均耗时为22ms,抑爆剂开始释放的平均时刻为59.8ms,抑爆剂释放到管道顶端的平均时刻为79.8ms。而爆炸火焰传播到达喷头所在1.0m处平均时刻为176.2ms。实验表明该系统具有高速主动抑爆响应功能和良好的稳定性、可靠性。     

Effect of concentration and ignition position on vented methane–air explosions

Experiments were conducted in a 1 m³ vessel with a top vent to investigate the effect of methane concentration and ignition position on pressure buildup and flame behavior. Three pressure peaks (p₁, p₂, and P_ext) and two types of pressure oscillations (Helmholtz and acoustic oscillations) were observed. The rupture of vent cover results in p₁ that is insensitive to methane concentration and ignition position. Owing to the interaction between acoustic wave and the flame, p₂ forms in the central and top ignition explosions when the methane–air mixture is near–stoichiometric. When the methane–air mixture is centrally ignited, p₂ first increases and then decreases with an increase in the methane concentration. The external explosion-induced P_ext is observed only in the bottom ignition explosions with an amplitude of several kilopascals. Under the current experimental conditions, flame–acoustic interaction leads to the most serious explosions in central ignition tests. Methane concentration and ignition position have little effect on the frequency of Helmholtz and acoustic oscillations; however, the Helmholtz oscillation lasts longer and first decreases and then increases as the methane concentration increases for top ignition cases. The ignition position significantly affects the Taylor instability of the flame front resulting from the Helmholtz oscillation.     

超高效液相色谱-串联质谱法同时检测溴代阻燃剂

采用Acquity BEH C18色谱柱,以甲醇-乙腈混合液和水为流动相,辅以电喷雾正离子模式多反应监测(MRM)进行定性定量分析,建立了一种同位素稀释超高效液相色谱-串联质谱(UPLC-MS/MS)同时检测四溴双酚A(TBBPA)、三-(2,3-二溴丙基)异氰脲酸酯(TBC)和3种六溴环十二烷(HBCD)异构体的方法。水样通过固相萃取进行净化,回收率达到85.3%~96.1%。土壤和底泥样品经加速溶剂萃取后,采用酸性硅胶和中性硅胶柱进行净化,回收率达到81.5%~102.7%。该方法对TBBPA、TBC、α-HBCD、β-HBCD、γ-HBCD在水和土壤中的检测限分别为1.0、1.2、2.0、0.8、1.2 ng/L和0.10、0.12、0.20、0.08、0.12 ng/g。     

Determination of total chromium by flame atomic absorption spectrometry after coprecipitation by cerium (IV) hydroxide

A method for the preconcentration of the total chromium based on coprecipitation with cerium (IV) hydroxide is proposed for determination of chromium by flame atomic absorption spectrometry. Different factors including carrier element amount, pH, sample volume and matrix ion effects for the precipitation were examined. The detection limit of the total chromium (k = 3, N = 15) was 0.18 μg l⁻¹. The presented method was applied for the determination of chromium in the wastewater samples from Kayseri and Nigde Organized Industrial Region-Turkey and in drinking water from our laboratory, Kayseri with satisfactory results (relative standard deviations below 8%, recoveries 95%). The analytical results obtained by the proposed method for certified copper sample was in good agreement with the certified value.     

共存碱金属离子在火焰发射分析中的干扰及消除

研究了采用火焰发射法测定K、Na、Ca、Mg,通过调节火焰状态和适量加入某些盐类来消除碱金属离子存在的干扰,使实测样品获得满意的结果。K、Na、Ca、Mg的方法检出限分别为0．005mg/L、0.01mg/L、0.10mg/L、0.01mg/L;样品回收率分别为93％、106％、84％、112％。     

油池边沿高度对池火燃烧特性影响的实验研究

研究了油池边沿高度(h)对池火燃烧特性的影响,开展了内径(d)为10 cm的不同h和不同油盘材料(石英、不锈钢、铝和铜)的正庚烷池火实验。结果表明,正庚烷池火的燃烧速率、火焰高度和脉动频率均随着边沿高度的增大而减小,且随着油盘材料的热导率增大,边沿高度的影响逐渐减弱。基于量纲分析分别修正了火焰高度和脉动频率模型,结果能够较好地符合实验值。