Experimental determination of the flame expansion factor

The flame expansion factor (ratio of volumes of flame gases before and after burning) has been determined by mercury vapour introduction. The method is based on the determination of atomic concentration ratio in the flame and the flameless gas jet using the same sample introduction rate. A good agreement has been found between the expansion factors determined by the proposed method and those calculated by the gas law.     

The effect of flow and gas expansion on atom distribution

As the first part of an investigation into the gas flow and flame expansion effects on the atom distribution in air acetylene flames, this study deals with the problems in the extreme case when the sample is introducted into the system in vapor form. Mercury was the element tested. The favorable condition arising from the atomic state of the vapor led to a significant reduction in acting parameters. A simple relationship between the atom concentration and the atom distribution was deduced from the equation of continuity of mass flow and its validity was experimentally proved. By using Hg vapor sample introduction, a simple method of flame expansion factor determination was developed. This method is based on the comparison of absorbance distribution functions in flame and in flameless cases.     

Effects of gas composition and flame sheathing on the spatial velocity profiles of laminar analytical acetylene flames

A recently developed technique has been employed to spatially map the rise velocity pronies (horizontal and vertical) of commonly used laminar analytical flames and to determine the influence on the profiles of fuel-to-oxidant ratio and the presence of a flame sheath. The rise velocities for fuel-rich, lean, and stoichiometric flames were found to differ substantially, the entire profile being greatest for the fuel-rich condition and lowest for the fuel-lean flame. In addition, the change in rise velocity with the addition of a solid (quartz tube) or gas (N₂) sheath was studied. The flowing sheath, at several different flow rates, affected each rise velocity profile principally by altering atmospheric entrainment and thereby changing secondary combustion in the flame. In contrast, a solid quartz tube used as a sheath produces an additional increase in the entire velocity profile of each flame, since it constrains gas expansion to the direction of flame propagation. The degree to which the velocity of each flame is affected by either a flowing N₂ and quartz sheath is strongly influenced by fuel-to-oxidant ratio.     

使用裂解气相色谱对几种阻燃聚丙烯材料热稳定性及阻燃机理的探讨

用裂解气相色谱（PyGC)考察了经三种类型阻燃剂（含磷、含溴、含溴和磷）改性的聚丙烯的热稳定性。利用PyGC-MS法分析不同样品的高温裂角产物,以此来推测阻燃材料受热分解时气相以及凝聚相所发生的反应,推断阻燃机理,分析影响阻燃效果的因素,为阻燃剂的开发提供有益参考。结果证实,它们都影响聚丙烯的热降解。溴系阻燃剂和磷系阻燃剂是分别从气相阻断、凝固相加速成炭实现阻止燃烧的,而磷-溴型阻燃剂同时具备单纯含磷或者含溴阻燃能力。     

Quenching of Flame Propagation with Heat Loss

The steady propagation of a planar laminar premixed flame, with a one-step exothermic reaction and linear heat loss, is studied. The corresponding travelling wave equations are solved numerically. The dependence of the flame velocity on the heat loss parameter is determined and compared with known results obtained by asymptotic expansion and other approximations. Due to the introduction of an ignition temperature the problem can be reduced to a bounded interval (of length L) and the graph of flame speed versus heat loss parameter can be parametrised by L. The numerical method is tested in the case of a step function nonlinearity when the exact solution of the differential equations can also be calculated.     

火焰原子吸收光谱法测定茶叶中的锰

介绍悬浮液进样-次灵敏线火焰原子吸收光谱法测定茶叶中的锰的方法。以琼脂为悬浮剂，将茶叶样品均匀、稳定地悬浮于琼脂溶胶中，直接喷入空气-乙炔火焰中，利用锰280.1nm次灵敏线，以工作曲线或标准加入法测定锰的含量，方法简便、快速，用于测定茶叶和桃叶样品中的锰，结果准确。     

Comparison of methods to enhance flame ionization detector (FID) signals in gas chromatography

The performances of some numerical methods to improve the signal to noise ratio are compared and applied to enhance noisy signals obtained in gas chromatography with capillary columns and a flame Ionization detector. Several methods have been considered: cutoffs In the Fourier transform of the recorded signal; real time numerical filtering; theoretical model curve fitting; and the correlation of a chromatogram recorded from a pseudorandomly injected sample with the pseudorandom injection function. Numerical real time filtering is shown to be the most convenient method when the main periodic component of the noise has been determined by Fourier analysis.     

Correlation between flame geometry and the absorbance of some elements in the presence of organic solvents

The correlation between the changes in flame geometry and the sensitivity of atomic-absorption determination of silver, copper, iron and lead in the presence of various solvents (water, ethanol, n-propanol, methyl acetate, ethyl acetate and acetone) has been investigated. The flame geometry was studied by the Schlieren technique. Organic solvents, allowing a greater rate of introduction of solution, enable a greater sensitivity to be achieved. However, owing to the expansion of the reaction zone, the increase in sensitivity is not as great as expected from the amount of sample introduced into the flame.     

Analysis of polynuclear aromatic hydrocarbons by glass capillary gas chromatography using simultaneous flame ionization and electron capture detection

The possibility of simultaneous application of an electron capture (ECD) and a flame ionization detector (FID) connected to a glass capillary column for analyzing polynuclear aromatic hydrocarbons (PNA) has been investigated. The ECD/FID ratio is determined for 46 PNA compounds. The ratios vary from 0.02 to 117 with relative standard deviations better than 20 percent determined from 10 replicate analyses. The results suggest that the method may be used for obtaining additional evidence in identifying PNA in environmental samples. Impurities and transformation products in the standard were identified by computerized glass capillary gas chromatography/mass spectrometry. Quinones and diones are responsible for the high EC-response determined in some trace components in the standard. An application of the method is shown for PNA from particulates in urban atmospheres.     

Dispersity and stability of foams obtained from poly(vinyl alcohol) solution and the properties of resulting foamed cryogels

Foams have been generated from aqueous poly(vinyl alcohol) solution by two different methods: dispersion (mechanical) method, i.e., by bubbling a gas through a porous medium into the aqueous poly(vinyl alcohol) solution, and the condensation (chemical) method, i.e., by performing a gas-generating reaction directly in the polymer solution. The effect of the formation method on foam stability and dispersity has been studied. The foam produced by the condensation method of foaming the aqueous poly(vinyl alcohol) solution with nitrogen is more stable and finely dispersed and has a higher expansion ratio than that obtained by bubbling the gas through the polymer solution. Foamed cryogels have been formed by freezing-thawing the foam resulting from the chemical reaction in the polymer solution. The values of the elasticity modulus, melting temperature, and thermal conductivity of the cryogels have been determined.     

Highly sensitive determination of haloperidol in human serum by capillary gas chromatography using a surface ionization detector

A method has been developed for highly sensitive determination of haloperidol in human serum involving a simple extraction procedure followed by gas chromatographic separation. Target components were separated from the extracting solvents with a Van den Berg type solventless sample injector before introduction Into a DB-1 capillary separation column. A surface ionization detector (SID), which has highly selective sensitivity for Substituted amines, was employed for quantitation using bromperidol as an internal standard. Chloroform proved to be the best extracting solvent, yielding a quantitative detection limit of 5 ng/ml (S/N = 2). Comparison of the response to target compounds obtained by the SID, FTD (flame thermionic detector), and FID (flame ionization detector) showed the SID to be superior.     

Combustion properties and thermal degradation behavior of polylactide with an effective intumescent flame retardant

An intumescent flame retardant spirocyclic pentaerythritol bisphosphorate disphosphoryl melamine (SPDPM) has been synthesized and its structure was characterized by Fourier transformed infrared spectrometry (FTIR), ¹H and ³¹P nuclear magnetic resonances (NMR). A series of polylactide (PLA)-based flame retardant composites containing SPDPM were prepared by melt blending method. The combustion properties of PLA/SPDPM composites were evaluated through UL-94, limiting oxygen index (LOI) tests and microscale combustion calorimetry (MCC) experiments. It is found that SPDPM integrating acid, char and gas sources significantly improved the flame retardancy and anti-dripping performance of PLA. When 25 wt% flame retardant was added, the composites achieved UL-94 V0, and the LOI value was increased to 38. Thermogravimetric analysis (TGA) showed that the weight loss rate of PLA was decreased by introduction of SPDPM. In addition, the thermal degradation process and possible flame retardant mechanism of PLA composites with SPDPM were analyzed by in situ FTIR.     

气相色谱法测定火焰气体

用自行研制的采样装置和低温气相色谱联用，对甲烷－空气和正己烷火焰气体能迅速精确地进行全分析。     

毛细管气相色谱法分析液化石油气中二甲醚

建立了液化石油气中二甲醚的毛细管气相色谱分析方法.利用丙酮作为溶剂吸收液化石油气中二甲醚,采用HP-1毛细管色谱柱进行分离,以氢火焰离子化检测器检测,外标法进行定量分析.二甲醚的体积分数在0.5%～30.0%范围内与色谱峰面积呈良好线性关系,二甲醚的定量下限为0.2%,测定结果的相对标准偏差为2.3%～7.3%(n=6...     

Determination of urinary beta-phenylethylamine as its N-benzenesulphonamide derivative by gas chromatography with flame photometric detection.

A selective and sensitive method for the determination of urinary beta-phenylethylamine (PEA) by gas chromatography (GC) has been developed. After extraction of the urine sample with n-pentane, PEA was converted into its N-benzenesulphonamide derivative and then determined by GC with flame photometric detection using a DB-1301 capillary column. By using this method, nanogram amounts of PEA in urine could be accurately and precisely determined without any influence from coexisting substances. Analytical results for the determination of PEA in urine samples from normal subjects are presented.     

Rapid analysis of coke oven gas by capillary gas chromatography

A porous layer open tubular (PLOT) column has been used for monitoring the light hydrocarbons and permanent gases produced in coking plants. The method, which offers a simple alternative to traditional multi column techniques, entails a single injection on to a Carboplot 007 capillary column and simultaneous thermal conductivity and flame ionization detection. The simplified approach proposed is restricted to coke oven gas analysis: application to other gas mixtures has not been considered. The reliability of this procedure compares favorably with that of traditional methods; the technique is also much less time-consuming: seven individual gases can be determined on-line every fifteen minutes. Primary and secondary gas standards were used to determine response curves for the gases. The method also facilitates reliable calculation of heat values associated with the burning of the fuel gas mixtures.     

On thermal gas slip

The distribution function of the gas molecule velocities has been determined in Couette's problem in an approximation of three velocity polynomials by the half-range expansion method. Using this function, we have calculated the isothermal heat flux in the Knudsen layer. The coefficient of the thermal gas slip was determined by means of Onsager's symmetry relations of nonequilibrium thermodynamics, the accommodation coefficient of the tangential pulse of molecules being arbitrary. The formula thus obtained coincides with the formula derived by direct method and with the experimental results obtained by Rabinovich and Derjaguin (within the limits of accuracy of the measurements).     

Non-dispersive atomic-fluorescence spectrometry of trace amounts of bismuth by introduction of its gaseous hydride into a premixed argon (entrained air)-hydrogen flame

A method has been developed for the determination of bismuth by generation of its gaseous hydride and introduction of the hydride into a premixed argon (entrained air)-hydrogen flame, the atomic-fluorescence lines from which are all detected by use of a non-dispersive system. The detection limit is 5 pg/ml, or 0.1 ng of bismuth, but the reagent blank found in a 20-ml sample volume was approximately 2 ng of bismuth. Analytical working curves obtained by measuring peak-heights and integrated peak-areas of the signals are linear over a range of about four orders of magnitude from the detection limit. Perchloric, phosphoric and sulphuric acids up to 2.0M concentration give no interference, but nitric acid gives slight depression of the signal. The presence of silver, gold, nickel, palladium, platinum, selenium and tellurium in 1000-fold ratio to bismuth causes pronounced depression of the signal, whereas mercury and tin slightly enhance the atomic-fluorescence signal. The method has been applied to the determination of bismuth in aluminium-base alloys and sulphide ores with use of the standard additions method. The results are in good agreement with those obtained by flame atomic-absorption spectrometry and optical emission spectrometry with an inductively coupled plasma.     

Flame retardant property of nanopowder aerosols toward methane

The flame retardant property of aerosols formed from 18 different nanopowders has been studied. The diameter of nanocrystalline powders was determined by XRD and TEM. The concentration of combustible gas was determined by gas chromatography. It was found that ZrO₂ nanocrystalline powdered aerosol can effectively retard the burning of CH₄. The flame retardation caused by ZrO₂ toward the combustion reaction of methane is through an inhibitory mechanism, which was further confirmed by contrasting it with Halon extinguishing agent and flame retardant property of ZrO₂-aerosol toward CH₃CH₂CH₃ or CO. The type of nanopowder aerosols as anti-explosion and fireproof agents was researched preliminarily in theory, too. The current ZrO₂-aerosol study will find extensive applications in the field of fire-extinguishing and anti-explosion agents used in case of combustible gas.     

干法制备磷-氮膨胀型阻燃剂的研究

以磷酸、五氧化二磷、季戊四醇和三聚氰胺为原料,采用干法(不添加任何溶剂)合成了一种磷-氮膨胀型阻燃剂。IR分析发现合成阻燃剂具有与磷酸酯三聚氰胺盐类似的P=O和P-O-C双环结构。反应温度、时间和原料配比对酯化反应有明显的影响。酯化反应温度宜控制在120-130℃之间,反应时间2.5小时,加入五氧化二磷可以提高酯化反应的转化率,磷酸与五氧化二磷的摩尔比控制在2:1为宜。热重分析表明,该阻燃剂的起始分解温度为190℃左右,700℃时的成炭率约为30%。该阻燃剂受热后膨胀倍数约为30-50倍,SEM分析发现,阻燃剂膨胀炭层外表面连续、平滑、颗粒之间连结紧密,炭层为内部为多孔结构,空隙大小分布均匀,孔径约为150-200μm之间,这样的泡层结构能更好的起到隔热的效果。