萃取富集火焰原子吸收法测定香菇棒中的铅镉

用HNO3-HClO4消解香菇茵棒样品，以DDTC为络合剂，四氯化碳为萃取剂萃取消解液，用HNO3-H2O2混合液反萃取，火焰原子吸收分光光度法测定水相中的铅镉，结果令人满意。     

粒子系统算法在建筑火灾可视化研究中的应用

论述了采用粒子系统建立火灾虚拟现实系统火灾现象的可视化表现原理、算法及特殊处理方法 ,为进一步研究火灾虚拟现实系统 ,提供基础理论和技术支持 ,也是培训消防人员技能和公众火灾自救互救、应急逃生能力的科学方法     

阻燃涤棉混纺织物的研究与发展

对阻燃涤棉混纺织物的国内外研究状况、生产和应用中存在的问题,进行了论述,并提出了今后的发展方向。     

Characterization of air emissions and residual ash from open burning of electronic wastes during simulated rudimentary recycling operations

Air emissions and residual ash samples were collected and analyzed during experiments of open, uncontrolled combustion of electronic waste (e-waste), simulating practices associated with rudimentary e-waste recycling operations. Circuit boards and insulated wires were handled separately to simulate processes associated with metal recovery. The average emissions of polychlorinated dibenzodioxins and dibenzofurans (PCDD/PCDFs) were 92 ng toxic equivalency (TEQ)/kg [n = 2, relative standard deviation (RSD) = 98%] and 11 900 ng TEQ/kg (n = 3, RSD = 50%) of the initial mass of the circuit boards and insulated wire, respectively. The value for the insulated wire is about 100 times higher than that for backyard barrel burning of domestic waste. The emission concentrations of polybrominated dibenzodioxins and dibenzofurans (PBDD/PBDFs) from the combustion of circuit boards were 100 times higher than for their polychlorinated counterparts. Particulate matter (PM) sampling of the fly ash emissions indicated PM emission factors of approximately 15 and 17 g/kg of the initial mass for the circuit boards and insulated wire, respectively. Fly ash samples from both types of e-waste contained considerable amounts of several metallic elements and halogens; lead concentrations were more than 200 times the United States regulatory limits for municipal waste combustors and 20 times those for secondary lead smelters. Leaching tests of the residual bottom ash showed that lead concentrations exceeded U.S. Environmental Protection Agency landfill limits, designating this ash as a hazardous waste.     

CGA G-13 large-scale silane release tests – Part I. Silane jet flame impingement tests and thermal radiation measurement

In early 2011, the G-13 Silane Modeling Task Force of the Compressed Gas Association (CGA) proposed a series of tests to better define pyrophoric behavior during unintentional, large-scale releases of silane. The tests were conducted in two phases under the direction of CGA and its guidelines. Phase I took place from June 27 to June 30, 2011, focusing primarily on thermal radiation and the heat transfer from flame impingement due to silane release from a fully open pressure relief device (PRD) on a tonner. Phase II took place on June 19 and 20, 2012, focusing on thermal radiation and explosion overpressure. The results were subsequently utilized to revise CGA G-13 guidelines on the safe handling of silane. In the present two-part papers, the results from the tests are summarized in order to highlight the key findings. The first part of summary described the results of the flame impingement and thermal radiation tests. Three different test series were conducted, including shakedown tests using nitrogen instead of silane, silane flame-impingement tests onto an adjacent target tonner, and heat-flux tests. For comparison with known values in the published literature, thermal radiation of ethylene flame jets was also measured. In addition, metallurgical analyses of the target tonner indicated that the metallurgical properties of the cylinder material were not altered by the flame impingement. The steel surface temperature at the point of impingement was estimated to be below 853.15 K and definitely did not exceed 950.15 K. Thus, the combination of internal pressure and vessel metal temperature was unlikely to exceed the rupture pressure of the ton cylinder.     

Improved electrospray design for aerosol generation and flame propagation analysis

Although the hazards of aerosol fires and explosions have been studied for decades the data for aerosol flame propagation is still scarce. Additionally there is a lack of standard techniques and measurement apparatus, which impedes the development of optimal aerosol hazard mitigation measures. The focus of this study is development of an improved aerosol electrospray device for the generation of high quality aerosol data. The goal is achieved through higher nozzle packing, precise nozzle and mesh hole alignment and adding two ground meshes. In addition to a flat ground mesh, the utilization of a cylindrical ground mesh demonstrated improved confinement and guidance of droplets. Duratherm 600, heat transfer fluid, was examined to demonstrate the modified electrospray device capabilities as compared to previous design. Results show the modified electrospray can produce more uniform droplets, more even test chamber dispersion, smaller droplet size and higher concentration aerosol, which is essential to study aerosol flame propagation. Accordingly, the results of aerosol flame speed tests for the improved design were more reproducible. Moreover, it was found that a traditional propane pilot flame was unable to ignite the smaller aerosol droplet size due to the strong turbulence generated by the open flame. However, by careful modification of the pilot flame length, the turbulence decreased dramatically and the small droplet size aerosol can be tested.     

Experimental study on the influence of flame retardants on the flammability of R1234yf

As an alternative refrigerant, R1234yf shows great environmental friendliness. However, the flammability has a negative impact on its use and promotion. To lower the combustible risk, it's a proper way to mix with nonflammable refrigerants in applications, but the research on the flammability of these blends is still limited. Therefore, the influence of three typical nonflammable refrigerants CO₂, R1336mzz(E) and R1233zd(E) as flame retardants on the flammability of R1234yf was experimentally studied in this paper. With the measurements of flammable limits of R1234yf/CO₂, R1234yf/R1336mzz(E) and R1234yf/R1233zd(E) at different concentrations, the parameters of regression equations for their flammable limits were obtained. The critical suppression concentrations of retardant were determined as 0.575, 0.35 and 0.6, respectively. The results showed that their suppression abilities could be ranked as R1336mzz(E)>CO₂>R1233zd(E). Then the inhibition mechanisms were analyzed, and the differences in flame colors at flammable limits were compared. With the establishment of estimation model for calculating critical suppression concentrations of ternary blends, the critical suppression lines of CO₂/R1234yf/R1336mzz(E) and CO₂/R1234yf/R1233zd(E) were obtained, by which the nonflammable zones of them were preliminarily determined. The results will provide practical guidance for the applications utilizing R1234yf and its blends in safety.     

A sneak peek into the phenomenology of fuel mist explosions: The key role of vapor fractions

The modern world depends greatly on hydrocarbons, which are ubiquitous, indispensable fuels used in nearly every existing industry. Although important, their use may trigger dangerous incidents, whether in their production, handling, storage, or transporting phase, especially when aerosolized. In light of proposing a standard procedure to assess the flammability and explosivity of fuel mists, a new test method was established based on the EN 14034 standards series. For the previous purposes, a gravity-fed mist generation system was designed and employed in a modified 20 L explosion vessel. This test method allowed the determination of the ignition sensitivity of several fuels. In addition, their explosion severity was represented by the explosion overpressure P_ex, and the rate of pressure rise dP/dt_ex, two thermo-kinetic parameters determined with a specifically developed control system and custom software. Nonetheless, a noticeable difference in the ignition sensitivity and the explosion severity was perceived when changing suppliers or petroleum cuts of some fuels. Moreover, sensitivity studies showed that both the droplet size distribution and the temperature of the droplets play a significant role in fuel mist explosion. These parameters can be directly related to the vapor fraction surrounding a droplet during its ignition. Consequently, this study focuses on the influence of varying the composition of three well-known and abundantly used fuels. Different petroleum cuts were introduced in different fractions into isooctane, Jet A1 aviation fuel, and diesel fuel mixtures, which were then aerosolized into a uniformly distributed turbulent mist cloud and ignited using spark ignitors of 100 J. Subsequently, complementary tests were executed in a vertical flame propagation tube coupled with a high-speed video camera allowing the visualization of the flame and the determination of the spatial flame velocity, and a tentative estimation of the laminar burning velocity. The latter was also estimated from the pressure-time evolution in the 20 L sphere using existing correlations. Indeed, the determination of the laminar burning velocity can be useful in modeling such accidents. Finally, highlighting the essential role of the mist and vapor fraction during their ignition has led to a better understanding of their explosion mechanisms.     

Effects of vent layout and vent area on dynamic characteristics of premixed methane-air explosion in a tube with two side-vented ducts

To further elucidate the influence mechanism of side vents on the dynamic characteristics of gas explosions in tubes is helpful to design more reasonable vent layouts. In this paper, 9.5% methane-air explosion experiments were conducted in a tube with two side-vented ducts, and the effects of vent layouts and vent areas on the dynamic characteristics of explosion overpressure and flame propagation speed were investigated. The results demonstrate that under the same condition with a single vent area of 100 mm × 100 mm, when only the end vent is open, the maximum explosion overpressure and the maximum flame propagation speed are the highest among the five vent layouts. When the side vents 1 and 2 and the end vent are open, the maximum explosion overpressure is the lowest, and an unusual discovery is that the flame front changes into a hemispherical shape, finger shape, quasi-plane shape, tulip shape and wrinkled structure. When only side vent 1 is open, a unique Helmholtz oscillation occurs, and a new discovery is that there is a consistent oscillation relationship among the overpressure, flame propagation speed and flame structure. Helmholtz oscillation occurs only when a single vent area is 100 mm × 100 mm–60 mm × 60 mm, and the oscillation degree decreases with decreasing vent area. During the vent failure stage, the maximum explosion overpressure is generated, the flame front begins to appear irregular shape, and the flame propagation speed shows a prominent characteristic peak. After the vent failure stage, the driving effect of the end vent on the flame is higher than that of the side vent on the flame. Furthermore, the correlation equations of the mathematical relationships among the maximum explosion overpressure P_red, the static activation pressure P_stat and the vent coefficient K_v under four vent layouts are established, respectively.