稻壳粉尘着火敏感性试验研究

摘 要：为探究稻壳粉着火敏感性,利用激光粒度分析仪和SEM对其粒度进行分析及形貌表征,利用Godbert-Greenwald炉、固体自燃点、粉尘层最低着火温度测试仪对自燃点温度、最低着火温度进行试验研究。结果表明：稻壳粉颗粒越大粒度分布越集中;粉尘云最低着火温度随粒度的减小呈降低趋势;标准试验模式下,粒度D50=52.9 μm的稻壳粉自燃点为225.1 ℃;粒度一定时,粉尘层最低着火温度随模具高度的增大而降低,当高度达到20 mm最低着火温度达到最低,且不再随模具高度的升高继续降低。本试验结果可为工业过程安全提供数据和理论支撑。     

浓度对垂直独头管道玉米淀粉火焰传播的影响

选择真空干燥后的食品级玉米淀粉，利用激光粒度分析仪和扫描电镜分析颗粒的形状和几何尺寸。利用高速摄像机技术，在1.2 m长的垂直独头管道内对玉米淀粉粉尘云的爆炸火焰传播行为进行实验研究，考察有、无障碍物的条件下粉尘云浓度对火焰传播的影响。结果表明：火焰整体上呈先增加再降低的发展趋势。粉尘云浓度和障碍物均对玉米淀粉粉尘云火焰传播形态及火焰速度具有显著影响。随粉尘云浓度增加，粉尘燃烧不充分，导致出现最大火焰速度和火焰亮度均逐渐降低，火焰轮廓不清晰,火焰分段等现象。障碍物的湍流效应会加速粉尘燃烧，增加粉尘火焰传播速度，提高火焰亮度和轮廓清晰度，但粉尘云浓度增加会降低障碍物对火焰传播的加速效应，促使最大火焰速度呈先增加再降低的趋势。     

HDPE粉尘云最小点火能试验研究

为研究高密度聚乙烯(HDPE)粉尘云燃爆的敏感性参数,采用粉尘云最小点火能(MIE)试验装置对HDPE粉尘进行试验研究.首先研究3个单一因素(粉尘粒径、粉尘云质量浓度和喷粉压力)对MIE的影响,然后对一定条件下不同质量浓度的HDPE粉尘云在哈特曼管中燃烧的火焰传播行为进行分析,最后采用正交试验法分析了多因素对MIE的影...     

粒径对中密度纤维板粉尘爆炸特性影响实验研究

为探究粒径对中密度纤维板粉尘爆炸及相关特性的影响,采用20 L爆炸球、粉尘云最低着火温度装置、锥形量热仪和哈特曼管装置,对不同粒径粉尘的爆炸下限、最大爆炸压力、最低着火温度、热释放速率和火焰传播规律进行研究。结果表明,随着粉尘粒径减小,爆炸下限和粉尘云最低着火温度降低,最大爆炸压力逐渐增大;粉尘燃烧过程分为升温、着火、过渡、加剧和熄灭5个阶段,并出现2个峰值,热释放速率变化时间和吸热时间随着粒径减小而增加,热释放速率峰值增大;火焰在管道内的传播随着粒径减小先增强后减弱,管道外“火球”形状更大,火焰消散后火星数量变少,火焰尾端更加细长。     

惰性粉体对铝粉尘层着火影响实验研究

通过构建铝粉尘层底板加热条件下着火燃烧的数值模型,探究铝粉尘层着火燃烧规律,同时结合碳酸钙惰性原理,开展碳酸钙粉体惰化条件下铝粉尘层最低着火温度实验。研究表明,铝粉尘着火燃烧具有加热温度高、燃烧温度大的特征,碳酸钙可以有效提高铝粉尘的点火温度,碳酸钙粉体粒度越小、浓度越大,对铝粉尘层的惰化效果越显著。     

Characterization of PM(2.5) in the ambient air of Shanghai City by analyzing individual particles

PM(2.5) samples were collected simultaneously at three representative areas (central city, industrial area and clean air suburban) of Shanghai City. Their morphologies and elemental compositions were determined by scanning electron microscopy coupled with energy analysis (SEM-EDX). The particles were classified into four groups based on morphology and elemental composition. Soot aggregates and spherical fly ash particles were the two dominant types and they were identified as originating from automobile exhaust, metallurgical industry and coal combustion. The size distribution of the particles showed that most had diameters in the range of 0.2-1.4 microm. Individual particles were measured by synchrotron radiation micro-beam X-ray fluorescence (micro-SXRF) and the micro-SXRF spectra were obtained. Pattern recognition techniques, which took the micro-SXRF spectrum of a single aerosol particle as its fingerprint, were used to identify the origins of the particles. Seven source types were identified. They were: metallurgical industry, vehicle exhaust, soil dust, coal combustion, diesel exhaust, oil combustion and motorcycle exhaust. Metallurgical industry, automobile exhaust, and coal combustion were recognized to be the main pollution sources of PM(2.5) in the air of Shanghai City.     

HMX粉尘云火焰传播规律研究

采用改进的可视化Hartmann装置,研究HMX粉尘云爆炸火焰传播规律,观察不同HMX粉尘云质量浓度及粒度对其粉尘云爆炸火焰传播速度及火焰传播高度的影响。结果表明：HMX粉尘质量浓度从74.1 g/m³变化为185.1 g/m³,火焰传播最大高度从29.97 cm增加为60.81 cm,最大速度从58.91 m/s增加为175 m/s;火焰波动幅度随质量浓度的增加而增大,同时,火焰波动出现的时间明显提前。HMX粉尘粒径从19.02 μm增大为53.56 μm时,火焰传播最大高度由55.45 cm降低为40.02 cm,最大火焰传播速度由181.93 m/s降低为121.28 m/s,火焰波动幅度显著降低,火焰波动出现的时间推迟。     

堆积可燃粉尘自燃温度测定与防控措施

介绍关于堆积粉尘自燃的相关测定方法标准,对比分析标准的应用范围和危险性分级依据。基于堆积粉尘自燃温度测定原理,研制了恒温烘箱测定不同容积堆积粉尘自燃温度的测定装置,给出相应的测定方法、测试条件和自燃现象判断依据。以某褐煤为例,分析不同容积堆积粉尘自燃升温的变化规律,结果表明：体积量越大达到设定恒温的时间越长,随后的升温速率越高。从粉尘温度控制、挥发物探测和储存空间、深位火灾扑救方面给出了预防堆积粉尘自燃的对策措施。     

Heating of indoor dust causes reduction in its ability to stimulate release of IL-8 and TNFalpha in vitro compared to non-heated dust

Dust is a major contaminant of the indoor air environment and may affect human health. Indoor dust accumulates on surfaces including heaters and light fixtures, and will be heated when these devices are used. Heat treatment of the dust may change its biologic properties and in this study we simulated the heat treatment with a dust-heating model (50-250 degrees C). The residual and the non-heated dust from seven samples were tested in cultures of fresh peripheral blood mononuclear cells and in A549 cell culture using the release of TNFalpha and IL-8, respectively, as effect indicators. The endotoxin-content and the particle size distribution of the residual and the non-heated dust suspensions were determined for some of the samples. We found that the residual dust had less ability to induce the release of TNFalpha and IL-8. The cytokine decline pattern was similar for all the dust tested and could partly be explained by the reduction in endotoxin content or possibly by inhibitory decomposition products. No correlation was found between the measured particle size distribution and the decreased cytokine levels. The results in this study suggest that the residual dust promotes reduced cytokine response and thereby a possibly lower inflammation reaction in the airways if suspended and inhaled compared with the non-heated dust. PRACTICAL IMPLICATIONS: Accumulation of indoor dust on electric heaters and light fixtures may produce a bad odor when switched on in the cold season and some people claim respiratory distress during such events. To investigate to what extent the residuals of heated indoor dust represent a health hazard, we measured the effect in cell cultures before and after heat treatment of the dust. The in vitro results imply that the residual dust will cause a lower proinflammatory response in the airways if suspended and inhaled compared with non-heated dust. This is partly explained by heat destruction of inflammatory components in the dust.     

Fractional Aerosol Filtration Efficiency of In-Duct Ventilation Air Cleaners

The filtration efficiency of ventilation air cleaners is highly particle-size dependent over the 0.01 to 3 μm diameter size range. Current standardized test methods, which determine only overall efficiencies for ambient aerosol or other test aerosols, provide data of limited utility. Because particles in this range are respirable and can remain airborne for prolonged time periods, measurement of air cleaner fractional efficiency is required for application to indoor air quality issues. The objectives of this work have been to 1) develop a test apparatus and procedure to quantify the fractional filtration efficiency of air cleaners over the 0.01 to 3 μm diameter size range and 2) quantify the fractional efficiency of several induct air cleaners typical of those used in residential and office ventilation systems. Results show that efficiency is highly dependent on particle size, flow rate, and dust load present on the air cleaner. A minimum in efficiency was often observed in the 0.1 to 0.5 μm diameter size range. The presence of a dust load frequently increased an air cleaner's efficiency; however, some air cleaners showed little change or a decrease in efficiency with dust loading. The common furnace filter had fractional efficiency values of less than 10% over much of the measurement size range.     

Dust explosion in a wool factory: Origin, dynamics and consequences

On 9 January, 2001, at the wool factory “Pettinatura Italiana” in Vigliano Biellese (BI), at 5:50 p.m. an explosion caused the death of three people, the injury of another five, as well as considerable damage to part of the factory.

This paper reports the events leading to the explosion together with the investigation that allowed us to reconstruct the accident's dynamic.

The aetiology of the accident can be traced to an unusual case of the “Domino Effect”: some electrical equipment of the lighting system caused a spark or source of heat which caused minor smouldering or flaming combustion of dust layers; the burning dust caused a cloud of dust to rise and ignite (primary deflagration); finally, the flame front of the primary deflagration ran into and ignited large quantities of dust (secondary deflagration). The explosion involved at least 400–500 kg of flammable vegetal and wool fibers, not counting moisture and inert particles. The dust was a by-product of the removal of burr from wool during the carding phase. Since large quantities of such dust were present throughout the ground floor and its equipment, it is surprising that no explosion had occurred during the previous decades. The reason for this is possibly the absence of an appropriate ignition source.     

Errors in the Compilations of Minimum Explosion Concentration Values for Dust Clouds

Database tabulations of minimum explosion concentration MEC for dust clouds often contain data values that are extremely low, i.e., 30 g m^?3, or lower. Such values invariably represent measurement or analysis errors, often due to inadequate dust uniformity in the test vessel. There are only two organic vapors with MEC values below 30 g m^?3, and it is physically implausible that either stationary or randomly moving dust clouds would be more efficient in combustion than vapors. Combustion of dust clouds will have all of the types of heat losses that occur with burning of vapor clouds, but have additional sources of heat losses, particulate radiation and endothermic pyrolysis, not present for vapors (dusts of unstable chemicals are not considered in this paper). Thus, MEC values for dust clouds necessarily have to be higher than for vapors. Other sources of error for dust cloud MEC values have also been identified. These include incorrect data analysis, unrealistic pressure-rise criteria for what constitutes an explosion, and excessive igniter energies used in some apparatuses. German data based on VDI 2263-1 should be post-corrected for statistical treatment errors. But no specific correction exists for low reported MEC values due to mixture nonuniformity or inappropriate pressure criteria. It is recommended that any reported MEC values below 65 g m^?3 for cellulosic agricultural dusts, below 35 g m^?3 for any other organic dusts, and below 55 g m^?3 for dusts of metals or non-metallic elements be expunged as likely to be incorrect. Even at higher MEC values, there is likely to be a systematic bias in the data and this needs to be considered in longer-range research. ASTM E1515 offers more reliable testing and data analysis procedures than does VDI 2263-1 and is preferred.     

超细水雾抑制甲烷-煤尘复合爆炸的实验研究

为掌握瓦斯-煤尘复合爆炸机理,通过可视化爆炸装置进行了密闭空间的超细水雾抑制甲烷-煤尘复合爆炸实验,探究了不同浓度的超细水雾对爆炸超压、压力上升速率、火焰传播速度的影响;研究了超细水雾作用下的火焰传播特征和爆炸不同阶段的抑爆机理。测定了不同煤尘粒径、浓度下的临界抑爆浓度。结果表明：超细水雾使爆炸超压延迟上升;爆炸火焰经历了点火焰、局部强发展火焰、连续不光滑火焰以及稳定分层火焰4 个发展阶段,抑制局部强发展火焰的出现是抑制爆炸的关键;随着超细水雾浓度的增加,压力的二次加速上升现象逐渐消失,放热速率与火焰锋面的燃烧速率的相关性增强;水雾的临界抑爆浓度随煤尘浓度的增加先增后降,随煤尘粒径的增加而降低。     

市政污泥热干化过程的燃爆风险研究

摘 要：为预防市政污泥热干化过程发生安全事故,利用相关仪器设备研究了污泥在堆积状态和分散状态下的燃爆性质,并结合污泥热干化车间的工艺和设备系统分析了污泥热干化过程存在的安全风险。结果发现：污泥在140 ℃存放24 h未发生自热,当温度升至170 ℃以上时存在放热现象,且在200~220 ℃会发生自燃,这说明当薄层干化工艺系统内部温度大于170 ℃时,发生污泥放热和自燃的可能性较高,而常温堆积储存干污泥的安全风险较低;当污泥粉尘与空气形成混合物时,会发生粉尘爆炸,且爆炸压力随污泥粒度变小而变大,这说明在污泥除尘器内部存在发生污泥粉尘爆炸的危险;污泥被干化时会产生氨气、硫化氢、甲烷等可燃气体,这使得在封闭的干化系统内存在发生气体燃烧或爆炸的危险。这些结果,可以为污泥干化技术发展及设备本质安全设计提供安全技术支撑,同时,对市政污泥干化生产安全管理具有指导意义和参考价值。     

典型堆积可燃粉尘自燃特性实验研究

以标准堆积粉尘自然温度测定实验装置,开展堆积状态下典型褐煤、木粉的自燃特性实验研究,分析其在自然通风条件下堆积自燃的温度与时间变化特征,明确了堆积粉尘自燃现象的判断依据和测定方法。结果表明：依据测定堆积粉尘体积量的自燃温度可以预测较大体积量粉尘的自燃温度,堆积体积量越大,自燃温度越低;同一温度下,体积量越大堆积粉尘不稳定。该研究可为堆积粉尘自燃火灾防控和事故调查提供实验数据支撑。     

The relationship between the mass concentrations of sulphate and sulphur dioxide in air polluted with cement dust

The relationship between the mass concentrations of sulphate and SO2 in air was studied over a 1-year period in an area polluted by cement dust. The relationship is described by the equation y = axb, where y is the percentage of sulphate sulphur in total sulphur (sulphate and SO2) and x is the mass concentration of the total sulphur content of the air. According to our previous results, coefficients a and b are characteristic of urban and industrial areas. In the investigated area polluted by cement dust, coefficients a and b characteristic of industrial areas were obtained only during the summer period when cement dust particles predominated. In the winter and over the 1-year period, the influence of other particulate components, which were probably products of fuel combustion, predominated. They were detected because the measuring site was located about 1 km from urban settlements.     

Combustion of crude oil on water

Large-scale test burns on the combustion of crude oil on water completed in a 2 m i.d. test pan to simulate large-scale crude oil fires. Data on burning rate, composition changes, thermal radiation, and the effect of heat addition, indicate combustion may be a viable method for mitigating oil spills on open waters. With the exception of thermal radiation data, the data are presented in this paper. The combustion mechanism appears to be described by equilibrium flash vaporization (EFV) followed by a limited amount of entrainment. In addition, burning rate for the crude oils tested was found to be a weak function of heat addition and to be relatively independent of specific gravity.     

The impact of particle size on the cumulative process of street dust migration

Street dust is a carrier of various pollutants widely distributed in the urban road environment, and has obvious particle size effect on environmental pollution. In this paper, the effects of particle size distribution on dust accumulation, heavy metal pollution and cleaning conditions are mainly discussed. Based on the particle size effect of street dust, the future research and control of non-point source pollution are given a breakthrough.     

碳酸钙、磷酸二氢氨与二氧化硅对面粉爆炸的抑制作用

以面粉为研究对象,采用20 L 爆炸球和哈特曼管测试系统,分别测试了碳酸钙、磷酸二氢氨、二氧化硅和碳酸钙与磷酸二氢氨复合对面粉最大爆炸压力、压力上升速率、火焰传播速度等特性参数的影响。对比分析了4 种惰性粉体的抑制效果及机理。结果表明：磷酸二氢氨除物理吸热外还通过化学分解抑制面粉燃烧和爆炸,其抑爆效果优于二氧化硅和碳酸钙;碳酸钙与磷酸二氢氨两者间会发生抑制燃烧爆炸的附加反应,二者复合比单一惰化粉体有更高的惰化效能。     

TDR技术在石灰炉渣加固土中的应用

石灰炉渣和水泥炉渣常用于加固路基土。石灰炉渣含有除石灰以外的其它化学物质,因此,石灰炉渣加固土的性质比石灰加固土更加复杂。本文试验研究了石灰炉渣加固土的电学特性和强度增长的规律,应用TDR技术测得加固土的电导率随土中化学反应进行的变化规律,提出用双曲线模型反映不同掺入量的加固土电导率的变化与强度增长的规律。与传统的测试方法相比,TDR技术有助于了解石灰炉渣与土之间的化学反应对加固土性质的影响,对于控制压实质量非常有效。