Distributions of dusts in the plasma column sheath

Dust crystal and void were simulated with a two-dimensional fluid model and a three-dimensional molecular dynamic model. The distributions of dust particles are obtained and these distributions are one-layer or two-layer dust crystals, conversely cone-shaped, and formulation of a cylindrical dust void without ion drag is complex. It is due to a gentle potential bump in the central region of the electrode caused by the cylindrical geometry. It can be concluded that it is the potential well of the central region of the electrode bottom established by lower ion density that contributes to the formation of dust voids.     

Reducing aluminum dust explosion hazards: case study of dust inerting in an aluminum buffing operation

Metal powders or dusts can represent significant dust explosion hazards in industry, due to their relatively low ignition energy and high explosivity. The hazard is well known in industries that produce or use aluminum powders, but is sometimes not recognized by facilities that produce aluminum dust as a byproduct of bulk aluminum processing. As demonstrated by the 2003 dust explosion at aluminum wheel manufacturer Hayes Lemmerz, facilities that process bulk metals are at risk due to dust generated during machining and finishing operations [U.S. Chemical Safety and Hazard Investigation Board, Investigation Report, Aluminum Dust Explosion Hayes Lemmerz International, Inc., Huntington, Indiana, Report No. 2004-01-I-IN, September 2005]. Previous studies have shown that aluminum dust explosions are more difficult to suppress with flame retardants or inerting agents than dust explosions fueled by other materials such as coal [A.G. Dastidar, P.R. Amyotte, J. Going, K. Chatrathi, Flammability limits of dust-minimum inerting concentrations, Proc. Saf. Progr., 18-1 (1999) 56-63]. In this paper, an inerting method is discussed to reduce the dust explosion hazard of residue created in an aluminum buffing operation as the residue is generated. This technique reduces the dust explosion hazard throughout the buffing process and within the dust collector systems making the process inherently safer. Dust explosion testing results are presented for process dusts produced during trials with varying amounts of flame retardant additives.     

一种实验室粉尘处理新方法的研究与设计

粉尘是广泛存在于生产过程中，且严重危害人们身心健康的有害物质，如何快速、高效处理粉尘，减少污染，是广大科技人员追求和研究的课题。在室内粉尘治理的探讨和研究中，将合粉尘的空气用集气罩集中收集、风道中喷水雾化、泥浆入池、超细雾珠纱网拦截等措施，达到了对粉尘的有效治理。该方法安装简单，投资节省，是室内粉尘污染区和地质类实验室制样车间内粉尘治理的一个好方法。     

Carboxymethyl chitosan/poly(ethylene oxide) water soluble binder:Challenging application for 5V LiNi_(0.5)Mn_(1.5)O_4 cathode

Carboxymethyl chitosan/poly(ethylene oxide)(CCTS/PEO) composite is firstly reported as a water soluble binder for the application of 5V LiNi_(0.5)Mn_(1.5)O_4 cathode in Li-ion batteries. Both CCTS and PEO show a high electrochemical oxidation potential of above 5.0 V(vs. Li/Li+). The electrochemical performances of LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathodes with CCTS/PEO composite binders of different mass rates are investigated, it is found that LiNi_(0.5)Mn_(1.5)O_4 cathode with an optimized CCTS/PEO(85/15, w/w) composite exhibits a slightly better cycling performance than that of polyvinylidene fluoride(PVDF), retaining 81.4% capacity as compared with 79.8% for PVDF at 0.5C rate after 200 cycles. LNMO with PEO/CCTS(85/15,w/w) exhibited the better rate capability than that of PVDF. These results demonstrate that CCTS/PEO composite can be potentially used as a water-soluble binder for 5 V LNMO cathode.     

拆除爆破水幕帘降尘技术研究

粉尘污染是城市拆除爆破工程中的一大危害 ,它直接影响拆除爆破在城市改造中的推广应用。在贵阳市第一商场和新华书店两座建筑物爆破拆除中 ,根据对粉尘产生根源的分析和一些现场试验 ,研究并采用了水幕帘降尘技术。爆破前 ,在各爆点悬挂水袋 ,各层楼的地面建水池灌水、顶部悬挂水桶 ,对建筑物和解体构件预定倒塌的区域进行充分洒水。实践证明 ,采取了这些综合措施后 ,取得了显著的降尘效果。与一般不采取降尘措施的拆除爆破相比 ,爆后粉尘减少 80 %以上     

Removal of dust produced in the roadway of coal mine using a mining dust filtration system

Dust particles, which are produced both on the ground and in underground workspaces, significantly affect the human body and the atmosphere. In fact, underground dust hazards are more serious, especially in the heading face of coal mines. People who work in the heading face are exposed to a high concentration of fine particulate matter. Traditional methods such as water sprays, dust removal by ventilation and foam technology, cannot completely solve the problem of dust pollution. Therefore, a mining dust filtration system was designed for removing dust produced in the roadway of coal mines. The study on eight frequently used air duct arrangements indicates that the mining dust filter achieved the best dust collection efficiency when the inlet of the extraction air duct and the outlet of the forced air duct were 3?m and 13?m away from the heading face, respectively. Under the optimum condition, the dust concentration can be significantly reduced in the rear of the dust exhaust hood and gradually decreased along the direction of the roadway. The system proposed in the study reduced the dust concentration to below 3?mg/m³ in the rear of the extraction fan and greatly improved the environment in the roadway of coal mines.     

Improved design of dust test chamber for uniform distribution of dust sedimentation rate

Soiling problems are always encountered for equipment installed in outdoor environments, such as headlamps of automobiles, air conditioners, solar collectors, and so on. How to prevent soiling problems on this equipment is one of the challenges for the design of their external layouts. Thus, evaluations of the dust sedimentation quantities on the surfaces of such equipment are necessary. Outdoor testing is usually straightforward but it takes a long time to experience various environmental parameters, such as dust-laden air, wind speed, wind direction, and so on. Indoor tests, performed in a dust test chamber, are instruments for controlling various environmental parameters independently. The conventional design for a dust test chamber is aimed at providing for a test under extreme environmental conditions. The uniformity of dust sedimentation rate within the chamber is not rigorously controlled. Nevertheless, some applications such as the effect of dust sedimentation on the glazing of solar collector require uniform distribution of dustfall in the test chamber for the indoor (laboratory) test. An improved design for a conventional dust test chamber is proposed. Performance tests done with the remodeled dust test chamber based on the improved design show that the normalized standard deviation of the dustfall concentration can be controlled within 2.41% ± 1.29%.     

Dust explosions-cases, causes, consequences, and control

Dust explosions pose the most serious and widespread of explosion hazards in the process industry alongside vapour cloud explosions (VCE) and boiling liquid expanding vapour explosions (BLEVE). Dust explosions almost always lead to serious financial losses in terms of damage to facilities and down time. They also often cause serious injuries to personnel, and fatalities. We present the gist of the dust explosion state-of-the-art. Illustrative case studies and past accident analyses reflect the high frequency, geographic spread, and damage potential of dust explosions across the world. The sources and triggers of dust explosions, and the measures with which different factors associated with dust explosions can be quantified are reviewed alongside dust explosion mechanism. The rest of the review is focused on the ways available to prevent dust explosion, and on cushioning the impact of a dust explosion by venting when the accident does take place.     

膨化硝铵炸药粉尘爆炸性的初步实验研究

膨化硝铵炸药是一种常见的工业炸药,该文通过20L爆炸球对其粉尘爆炸的危险性进行了试验研究,并和玉米淀粉粉尘进行了比较。研究结果表明,膨化硝铵炸药发生粉尘爆炸的可能性很小,在50～1100g／m^3的浓度范围均未发生粉尘爆炸;玉米淀粉有着粉尘爆炸的危险。所得结果为它们的生产及使用安全提供了必要的参考。     

Removal of lead ions from solution by phosphosilicate glass

A new, selective and sensitive on-site spectrophotometric method for the determination of antimony at trace level in water, soil and dust samples of Central India has been demonstrated. It is based on the color reaction of Sb(III) with I⁻ ions in the presence of a cationic surfactant cetylpyridinium chloride (CPC) in acidic media, and subsequent extraction of the complex with N-phenylbenzimidoylthiourea (PBITU) into chloroform to give a yellow colored complex. The value of apparent molar absorptivity of the complex in the terms of Sb is (7.84) × 10⁴ l mol⁻¹ cm⁻¹ at 440 nm. The detection limit of the method is 5 ng ml⁻¹. In addition, the present method is free from interferences of all metal ions that are associated during the determination of antimony in environmental samples.     

Filtration of dust in a circulating granular bed filter with conical louver plates (CGBF-CLPs)

A novel circulating granular bed filter with conical louver plates (CGBF-CLPs) was designed to remove dust particulates from the flue gas stream of a coal power plant. The purpose of this investigation was to evaluate the performance of the CGBF-CLPs. Dust collection efficiency and pressure drop data were analyzed to determine better operating conditions. The effect of solid mass flow rate, collector particle size and dust/collector particles separator types on the dust collection efficiency and pressure drop in the CGBF-CLPs were investigated in this study. The solid mass flow rate (B) varied from 15.59+/-0.44 to 20.36+/-0.68 g s(-1) and the initial average collector particle sizes were 1500 and 795 microm, respectively. Two types of separators, a cyclone and an inertial one, for separating the dust and collector particles were used in the CGBF-CLPs system. An Air Personal Sampler (SKC PCXR8) was used to determine the inlet and outlet dust concentrations. A differential pressure transmitter and data acquisition system were used to measure the pressure drop. Experimental results showed that the highest dust collection efficiency was 99.59% when the solid mass flow rate was 17.08+/-0.48 g s(-1) and the initial average collector particle size was 795 microm with the cyclone type separator. The results showed that the attrition fines of the original collector particles returning to the granular bed filter (GBF) reduced bed voidage. This phenomenon significantly increased the dust collection efficiency in the CGBF-CLPs. As a consequence, a bigger bed voidage creates a lower dust collection efficiency in the GBF.     

单点除尘器的应用与分析

本文详述了单点除尘器在承钢的应用情况，分析了单点除尘器虚用中存在的问题和解决途径，指出单点除尘技术是是集中除尘系统的良好补充，是物料转运过程中粉尘治理的一个理想选择，特别是对于距离集中除尘设施较远的分散点位除尘，有明显的环境和经济效益优势。     

Chemical mass balance source apportionment of PM10 and TSP in residential and industrial sites of an urban region of Kolkata, India

Daily average PM(10) (particulate matter which passes through a size selective impactor inlet with a 50% efficiency cut-off at 10 microm aerodynamic diameter), TSP (total suspended particulate matter) and their chemical species mass concentrations were measured at residential and industrial sites of an urban region of Kolkata during November 2003-November 2004. Source apportionment using chemical mass balance model revealed that the most dominant source throughout the study period at residential site was coal combustion (42%), while vehicular emission (47%) dominates at industrial site to PM(10). Paved road, field burning and wood combustion contributed 21%, 7% and 1% at residential site, while coal combustion, metal industry and soil dust contributed 34%, 1% and 1% at industrial site, respectively, to PM(10) during the study period. The contributors to TSP included coal combustion (37%), soil dust (19%), road dust (17%) and diesel combustion (15%) at residential site, while soil dust (36%), coal combustion (17%), solid waste (17%), road dust (16%) and tyre wear (7%) at industrial site. Significant seasonal variations of the particulate matters have been observed during the study period. In the monitoring sites total carbon, organic carbon and iron were found to be the marker species of road dust, while organic carbon, total carbon, chloride and sulfate have been observed as the marker species of soil dust in TSP.     

Investigation of lag on ignition of coal dust clouds under varied experimental conditions

Lag on ignition (LOI) of coal dust cloud greatly influences the initiation and propagation of coal dust explosion. This paper investigates the effects of coal dust particle size, dust concentration, ignition temperature, and dust dispersion pressure on LOI of coal dust clouds using Godbert-Greenwald furnace along with a high-speed camera. LOI of coal dust cloud significantly decreased by 1/13 times from 959 to 77 ms with increase in the ignition temperature from 600 to 1000 °C, demonstrating greatest influence of ignition temperature on LOI. LOI increased by 60% with increase in dust concentration from 500 to 4000 g/m³. Optimum dust dispersion pressure at which LOI was found minimum is determined 70 kPa. Empirical relations are established between LOI of coal dust cloud and particle size, ignition temperature, dust concentration, and dispersion pressure. The results are analysed in terms of the occurring physical processes, which led to a better understanding of the variation of LOI, ignition behavior, and explosion propagation of coal dust clouds at varied experimental conditions.     

An upgraded high-velocity dust particle accelerator at Concordia College in Moorhead, Minnesota

In 1975, Concordia College in Moorhead, Minnesota acquired a 2 MeV dust particle accelerator from NASA/GSFC that was used to test the lunar ejecta and micrometeorite (LEAM) experiment flown on Apollo 17. This high-speed dust particle accelerator is still fully functional and is currently being upgraded. Improvements to the electronic detection system have been undertaken including a computer-based, data acquisition system and new particle detection sensor electronics. These sensors have additional amplifiers that extend the range of charge detection to 1×10⁻¹² C allowing for the detection of larger particles. Improvements to the vacuum system have also been made. The accelerator beam line is now pumped with an oil-free, turbomolecular pump reducing possible problems with hydrocarbon contamination. In this work, we describe the facility, and outline some of the recent improvements to the dust particle accelerator and discuss its capabilities and limitations. We also summarize some of the recent experiments conducted using the facility.     

Research on wet-type swirl dust collection technology and its application in underground excavation tunnels

Wet-type dust collectors are widely used in underground excavation tunnels to control dust pollution. Nozzles and filter screens easily blocked by deposited scale and sticky dust, however, are usually a challenging problem for traditional wet-type dust collectors. This increases the cleaning workload and reduces the service life of the equipment. To address this issue, a wet-type swirl dust collection method without using spray nozzles and filter screens is proposed, and a novel wet-type swirl dust collector is designed. Experiments and field application of the wet-type swirl dust collector were carried out. Experimental results showed that the optimum water intake of the dust collector was 1.0 m³/h at 1480 r/min^?1 impeller speed; the dust suppression efficiency of the dust with particles size less than 75 μm was 93%, and that of dust with particles size of 180–250 μm was 95.2%. The field application in China's Tongqing Mine indicated that the respirable dust at the roadheader driver was reduced to 6.9 mg/m³, with a dust removal rate of 92.0%. The wet-type swirl dust collector effectively improves the dust collection efficiency and makes up for the problem of nozzles and filter screens being easily blocked in underground excavation tunnels by the traditional methods.     

Experimental investigation of the performance of a novel foam generator for dust suppression in underground coal mines

Dust in underground coal mines is a serious threat to workers’ health and safety. Foam is used as an efficient means of dust suppression in these confined workplaces. A novel foam generator has been designed to overcome the problem of bottlenecks due to the complex operation and high cost of existing foam technology. Experimental performance testing and evaluation showed that a 20–40 m³/h gas source for generating foam is produced by a small 0.4–0.6 m³/h flow-rate jet, and the device consumes as little as 4–6 kg/h of foaming agent. It requires only a normal pipeline water pressure, eliminating the need for a compressed air supply (compressor, pipelines and/or hoses). Its simplified structure combines the advantages of safe, reliable and convenient operation with compact size. The marked reduction in the consumption of water and foaming agent significantly reduces foam production cost. The foam generator was tested at a coal face and successfully controlled dust produced by a longwall double-drum shearer.     

梧桐树粉尘爆炸特性研究

以梧桐树粉尘为例,研究了可作为工业粉状炸药添加剂的木粉粉尘的爆炸特性。运用哈特曼管测试了粉尘云的最小点火能,得出样品1#、样品2#和样品3#的最小点火能分别为70、90 m J和150 m J。将响应面法中的Box-Behnken试验设计应用于粉尘爆炸压力的测试,用20 L爆炸球进行试验,并从试验结果中拟合回归方程,由此判断出粉尘浓度对爆炸压力的影响最大,其次是点火能量,再次是粉尘粒径。对爆炸压力的试验条件进行优化,试验测得压力值为0.795 9 MPa,试验值与预测值之间的误差仅为1.28%,证明了该模型非常有效。     

Origins of PM10 determined by the micro-proton induced X-ray emission spectra of single aerosol particles

The micro-proton induced X-ray emission (micro-PIXE) spectrum of a single aerosol particle (SAP) was considered as its fingerprint for tracing its origin. A proton microprobe was used to extract fingerprints of SAPs. Environmental monitoring samples of PM(10) were collected from a heavy industrial area of Shanghai and were analyzed by proton microprobe for finding their pollution sources. In order to find the sources of SAPs collected from environmental monitoring sites, a fingerprint database of SAPs collected from various pollution sources was established. The origins of samples collected through environmental monitoring were identified by comparison of the micro-PIXE spectra of SAPs with those of SAPs in the fingerprint database using a pattern recognition technique. The results of this study show that most of the measured PM(10) is derived from metallurgic industry, soil dust, coal combustion, automobile exhaust, and motorcycle exhaust. The study also shows that the proton microprobe is an ideal tool for the analysis of SAPs. The unidentified particles of PM(10) are classified into seven classes by hierarchical cluster analysis based on the element peak intensity in the spectra.     

巡检司电厂除灰中心站的爆破拆除

被拆除的除灰中心站爆破环境非常复杂,采用毫秒微差爆破和预处理措施,确保了除灰中心站的顺利倒塌和周围建筑物的绝对安全.介绍了该次爆破的爆破方案选择、爆破参数、安全防护技术及爆破效果.