Mixture Of Dust Research Articles

Considerations regarding test methods against dust and water ingress protection for Ex equipment

The explosion danger in all industries where explosive atmospheres generated by the mixture of combustible dusts or flammable gases with air may form, must be treated as a major hazard, as the explosions that may occur can seriously affect both health and safety people, as well as the environment. It is therefore necessary to assess the explosion risk and to establish appropriate measures to reduce it to acceptable levels in accordance with the requirements of the European Directives. An essential element in the assessment of the explosion risk for electrical and non-electrical equipment intended for use in potentially explosive atmospheres is the way in which an appropriate normal degree of protection is provided through the equipment housing (protection against touching of dangerous parts inside the equipment housing and protection against the ingress of dust and water inside it). The aim of the paper is to highlight compliance with the requirements of the ATEX Directive, given that this protection is a basic requirement for explosion protection and to present the important elements to be considered for the assessment of the normal degree of protection and the development of harmonized test methods with the requirements of European standards.

Physical and mechanical characterization of marble Dust/Wheat straw fiber filled polymer composites

The purpose of this work is to discuss about the feasibility of fabrication of hybrid composites that are filled with a mixture of marble dust and biodegradable short natural fibers i.e., wheat straw. In today’s world need of composite is growing in a variety of fields. There is a need of lightweight, strong, wear resistive yet cost effective composite materials to match the competition in the market. Therefore, many research works are carried out in this field to identify the potential reinforcing capacity of materials. One of these materials is marble dust. This waste can be used a potential filler material in polymer composite upon mixing it with appropriate materials like short wheat straw fibers. Epoxy-based composites are prepared with keeping marble dust content constant to 10 wt% and different weight proportions wheat straw fiber varying from 0 to 4 wt%. Physical and mechanical properties have been studied of these composites. It is observed that tensile strength, flexural strength and micro-hardness of marble dust filled composites increase with increase in the wheat straw fiber content. The enhanced properties of these composites make them suitable for a wide range of product ranging from industrial to household uses.

Self-reducing pellets composed of wastes from steelmaking production for their recycling

This paper presents a study about the recycling of a mixture of EAF filter dust and mill scale; and slag, in the form of self-reducing pellets. At first, chemical and morphological characteristics of the material were investigated. Pelletizing was carried out manually, with the use of graphite 100% fixed carbon and molasses as binder with moisture. The results of reduction tests under the temperature of 1200 ºC for the wastes could be analyzed according to the use of different contents of reducing agent, time and mass loss. It was found that 20% of the carbonaceous material was the best configuration for a maximum mass loss, for both wastes. Furthermore, the pellets composed of stainless steel slag, added to the metallic bath presented a chromium recovery of around 95%, indicating its potential reuse.

Вплив герметизації контуру нового безпечного конфайнмента на поверхневе забруднення зовнішніх поверхонь покрівель об’єкта «Укриття» та оцінка можливості їхньої дезактивації

After the sealing of the enclosing perimeter of the New Safe Confinement — Shelter object (NSC-SO) complex (at the end of 2017), unorganized emissions of radioactive aerosols from the Shelter object were dispersed in the environment. Currently, in the closed volume under the NSC arch, a significant amount of dust is settling and accumulating, which is characterized by a high content of radionuclides. In particular, these processes are manifested on the roofs of the Shelter object, where the mass of dust has already reached 15 g/m2 . At the same time, since the sealing of the containment circuit of the NSC-SO complex, the density of total surface contamination by the sum of alpha- and beta-active nuclides has increased by 9.3 times, and the non-fixed form of surface contamination has increased by 5.7 times. According to our data, the formation of dust is the result of the deposition of a construction dust mixture, as evidenced by its significant content of calcium — up to 72% and heavy metals — up to 28% by mass, as well as radioactive aerosols of unorganized emissions from the SO. Currently, the activity of dust on the surface of the roof structures of the Shelter object is up to 580 kBq/kg of α-active, as well as up to 19,300 kBq/kg of beta- and gamma-active nuclides, which allows it to be classified as medium-active radioactive waste. It was established that the use of a vacuum cleaner (dust suction power ≥13 kPa) for the dry decontamination of the surfaces of the metal structures of the SO roofs allows removing from 79 to 98% of the activity of nonfixed surface pollution, which can provide a significant improvement in the radiation situation during the dismantling work of unstable constructions of the SO. At the same time, it is advisable to use autonomous models of vacuum cleaners for decontamination of places where metal structures are cut. For decontamination of arge surface areas of structural fragments that will be transported to the storage site, models of vacuum cleaners with high production capacity are needed to perform this operation as quickly as possible, which will ensure a reduction in the dose of exposure to the working personnel.

Innovative ways to control dust and explosion safety of mine workings

Ensuring dust and explosion safety during underground coal mining is one of the most important tasks of industrial safety and labor protection departments. The main method of preventing explosions of coal dust settled in mine workings is to process them with stone dust (rock dusting). The traditional methods of quality control of rock dusting include radioisotope, optical and chemical methods. To implement them, the devices are equipped with environmentally harmful radioactive elements, expensive optical sensors, desiccants and replaceable flasks with chemical reagents, which increases the cost of analysis and its duration. The measurement error of these devices is 10 % or more. The main purpose of the study is to develop and substantiate a new method for monitoring the dust and explosion safety of mine workings, which will be devoid of the disadvantages of the methods mentioned above. It is proposed to evaluate the quality of rock-dust distribution by a fundamentally new way – thermogravimetric. The method was tested on the dust of coal mines in Kuzbass and the Vorkuta basin, including dust samples taken in mines with actual explosions. The article presents the results of experimental studies of the processes of thermal destruction of coal and stone dust mixtures. The non-overlapping intervals of the thermogravimetric reaction are identified: moisture yield (35-132 °С); volatile matter yield from coal (380-580 °С); thermal degradation of limestone with carbon dioxide yield (650-850 °С). Methods and mathematical dependencies for processing significant and qualitative identification characteristics of thermogravimetric curves in determining the content of non-combustible components in a sample of mine dust are considered.

Reclamation of cutting oil waste to refuse derived fuel: A life cycle assessment approach for a waste-to-energy system

Reclamation and reuse of spent oil waste are preferable resource management practices that provide energy and environmental benefits. This study aims to have a comprehensive understanding of the environmental benefits and tradeoffs regarding the reclamation of cutting oil waste to refuse-derived fuel (RDF) for steam generation through a life cycle assessment (LCA) approach, with special attention given to pollution characteristics during steam generation. Our results confirmed that majority of the environmental impacts associated with the reclamation process (approximately 78.9%) could be attributed to the electricity consumption involved in the process, which could be offset by the energy savings from the avoided oil waste disposal. Thus, the involvement of RDF in steam generation may enhance the environmental performance of the waste-to-energy system from two aspects, including a reduction in global warming potential (22.2%–99.6%) from decreased fossil fuel consumption and a reduction in toxicity impacts (68.2–71.5%) from minimized pollutant emissions under improved combustion efficiency compared to other tests. The global warming potential for generating 1 ton of steam was found to be the lowest at approximately 0.15 kg CO2 eq using a mixture of RDF and wood dust and the highest at approximately 41.18 kg CO2 eq using a mixture of coal and wood dust. Additionally, pollutant emissions from steam generation were identified as a significant contributor to the overall impacts, in which terrestrial ecotoxicity was found to be the most sensitive impact to the reduction of pollutant emissions in all runs. Future practical efforts for waste oil-to-energy systems are suggested to focus on the implementation of pollution control measures that minimize their associated impacts while maximizing their benefits.

Efficacy of combined treatments of abamectin with three inert dusts for the control of Callosobruchus chinensis on cowpea seeds

The insecticidal efficacy of abamectin (AB) and three inert dusts, diatomaceous earth (DE), zeolite (ZE) and kaolin (KA), was evaluated alone and in binary mixtures as stored cowpea protectants against Callosobruchus chinensis. Inert dusts (DE, ZE and KA) were tested at 100, 500 and 1000 mg/kg (ppm), and abamectin was applied at 0.1, 0.25 and 0.5 mg/kg (ppm). Adult mortality of C. chinensis was evaluated after 3 and 7 days of treatment, while progeny production and cowpea seed weight loss were recorded for all tested treatments after 60 days. The mortality of adults in the binary treatments was higher than the individual treatments of inert dusts or AB. Combined treatments of AB at 0.5 mg/kg with DE, ZE or KA at 500 and 1000 mg/kg led to 100% mortality after 7 days of treatment. Moreover, combined treatments of AB (0.25 mg/kg) with KA (1000 mg/kg), AB (0.25 mg/kg) with ZE (1000 mg/kg) and AB (0.5 mg/kg) with KA (100 mg/kg) caused 100% mortality of adults after 7 days of treatment. After 3 days, the binary mixture of AB (0.5 mg/kg) with KA (1000 mg/kg) was the only treatment inducing 100% adult mortality. All treatments with inert dusts, AB, and their binary mixtures caused significant decrease in progeny production of C. chinensis after 60 days of exposure. In particular, treatments with high concentrations induced strong progeny reduction and led to complete protection of cowpea seeds against weight loss and damage caused by C. chinensis after 60 days. Furthermore, no adverse effect on germination was observed in cowpea seeds treated with the highest application rates of inert dusts, AB, and their mixtures. Our findings demonstrated that binary mixtures of inert dusts with abamectin could be successfully used as potential protectants for cowpea seeds against C. chinensis.

Effectiveness of two inert dusts in conjunction with carbon dioxide for the control of Callosobruchus maculatus and C. chinensis in stored cowpea seeds

The insecticidal potential of two inert dusts, zeolite (ZE) and kaolin (KA), and carbon dioxide (CA) and their binary combinations was evaluated against Callosobruchus maculatus (F.) and C. chinensis L. (Coleoptera: Chrysomelidae: Bruchinae). The inert dusts were applied on cowpea seeds at 100, 500 and 1000 mg/kg, and CA was tested at 10 and 20% for 12 h. The adult mortality was counted after 1, 3 and 7 days of treatment, and progeny production and weight loss of cowpea seeds were examined after 60 days. The adult mortality of both insect species exposed to cowpeas treated with individual and binary treatments increased with the increase of concentration and exposure time. In general, the adult mortality was higher in binary treatments than individual treatments. The full adult mortality (100.0%) was observed in combined treatment (ZE (1000 mg/kg) + CA (20%)) after 1 and 3 days in the case of C. chinensis and after 3 days in the case of C. maculatus. Similarly, the combined treatments of CA (20%) with three rates of ZE (100, 500 and 1000 mg/kg), and CA (20%) with three rates of KA (100, 500 and 1000 mg/kg) induced 100% mortality of both insect species after 7 days except for CA (20%) + KA (100 mg/kg) against C. chinensis. Progeny of C. maculatus and C. chinensis was significantly reduced in individual and binary treatments compared with untreated cowpea seeds. The highest application rates of the binary mixtures of inert dusts with CA induced strong progeny reduction and complete protection of cowpea seeds against damage caused by both insect species for 60 days. Our results indicated that the binary treatments of inert dusts (ZE and KA), with CA seems to be a promising alternative to synthetic insecticides for the control of bruchid insects on stored legumes.

Methods to predict variations of lower explosion limit associated with hybrid mixtures of flammable gas and dust

In order to study variations of the lower explosion limit associated with hybrid mixtures of flammable gas and dust, four hybrid mixtures of methane/lycopodium, methane/polyethylene, ethylene/lycopodium, and ethylene/polyethylene with various concentration ratios were constructed. The lower explosion limits of these mixtures were measured in a 20 L spherical explosion vessel. According to the experimental results, it was obtained that the lower explosion limits of these hybrid mixtures were decreased by increasing the flammable gas concentration. The two-dimensional coordinate system was divided into explosion area and non-explosion area using the lower explosion limit curve. For different hybrid mixtures, the proportions of the explosion area were different in the two-dimensional coordinate system. The larger the proportion, the greater the explosion sensitivity. Based on this proportionality relationship, a dimensionless parameter called sensitivity index was defined as the ratio of the explosion area to the non-explosion area. The greater the sensitivity index, the greater the explosive sensitivity of the hybrid mixture. According to the relationship between the sensitivity indices of different hybrid mixtures, the influencing factors for the sensitivity index were established, including combustion heat of the flammable gas and dust, chemical reactivity of the flammable gas, as well as dimensionless parameters of dust decomposition characteristics. Considering these influencing factors, a calculation method for the sensitivity index was established using maximum explosion pressure as well as explosion indices of the flammable gas and dust. Through this comprehensive study, a new predictive approach for determining variations of the lower explosive limit of hybrid mixtures with the newly proposed sensitivity index was established. The predictive performance of this newly developed approach was verified using data from other hybrid mixtures.

Influence of pre-ignition pressure rise on safety characteristics of dusts and hybrid mixtures

For the determination of the safety characteristics of dusts it is necessary to disperse the dust in the oxidating atmosphere (usually air). In the standard procedures for dusts this is realized by a partially evacuated explosion vessel (20L-sphere) in which the dust gets injected from a dust chamber pressurized with air. Shortly after that injection (60 ms) the dust cloud gets ignited under turbulent conditions, that are otherwise seen as almost ambient with 20 °C and about 1 bar (abs). While there has been a lot of research about the influence of the ignition delay time and the level of turbulence in the recent years little attention was paid to the pre–ignition pressure rise and the allowed variations in the standards. In the following work we showed that the allowed ranges for the pressures in the different dust standards influence the safety characteristics of dust alone severely.Even though hybrid mixtures are an emerging risk problem in an interconnected industry there is no standard for the determination of their safety characteristics. In this work it is shown that especially for the preparation of hybrid mixtures of flammable dust and gas the pressures after injection of the dust and the mixing procedure have a large influence on the composition of the tested mixtures and therefore on the safety characteristics. Considering both effects, wrong concentration of gas and wrong initial pressure, the discrepancy of safety characteristics from different facilities will be too big to applicable. The methods to overcome these weaknesses are also presented.

A Strategy for Field Evaluations of Exposures and Respiratory Health of Workers at Small- to Medium-Sized Coffee Facilities.

Coffee production is a global industry with roasteries throughout the world. Workers in this industry are exposed to complex mixtures of gases, dusts, and vapors including carbon monoxide, carbon dioxide, coffee dust, allergens, alpha-diketones, and other volatile organic compounds (VOCs). Adverse respiratory health outcomes such as respiratory symptoms, reduced pulmonary function, asthma, and obliterative bronchiolitis can occur among exposed workers. In response to health hazard evaluations requests received from 17 small- to medium-sized coffee facilities across the United States, the National Institute for Occupational Safety and Health conducted investigations during 2016–2017 to understand the burden of respiratory abnormalities, exposure characteristics, relationships between exposures and respiratory effects, and opportunities for exposure mitigation. Full-shift, task-based, and instantaneous personal and area air samples for diacetyl, 2,3-pentanedione and other VOCs were collected, and engineering controls were evaluated. Medical evaluations included questionnaire, spirometry, impulse oscillometry, and fractional exhaled nitric oxide. Exposure and health assessments were conducted using standardized tools and approaches, which enabled pooling data for aggregate analysis. The pooled data provided a larger population to better address the requestors' concern of the effect of exposure to alpha-diketones on the respiratory heath of coffee workers. This paper describes the rationale for the exposure and health assessment strategy, the approach used to achieve the study objectives, and its advantages and limitations.

Late Holocene dust provenance at Siple Dome, Antarctica

Compositions of mineral dust in ice cores serve as tracers of paleo-atmospheric circulation patterns, providing linkages between sources and sinks. Here we document the geochemical makeup of dust reaching continental West Antarctica, on late Holocene samples from the Siple Dome A ice core (spanning ∼1030–1800 C.E). The Nd–Sr isotope signature is unusual for Antarctic ice core dust samples. Siple Dome data are characterized by low Nd isotope ratios (as low as εNd = −16.3) along with low Sr isotope ratios (highest 87Sr/86Sr = 0.7102) compared with other Antarctic dust signatures. A well-defined inverse correlation between Sr–Nd isotope ratios indicates two primary mixing sources. The low εNd-values indicate involvement of ancient (Archean-to-early Proterozoic) continental crust, as either the direct source or as a precursor of the source, and the low Sr-values require low Rb/Sr ratios that often reflect high-grade metamorphism. The known Antarctic terrane with these characteristics is parts of Enderby Land, nearly at the opposite end of Antarctica. The isotopic signature of the second end-member is compatible with West Antarctic volcanoes or Patagonia in South America. The Sr–Nd isotopes and trace element abundances are also chemically compatible with mixing between volcanic material from Gaussberg, a small lamproite volcano in Kaiser Wilhelm II Land in coastal East Antarctica whose source is ancient lithospheric mantle, with dust from Patagonia or material from West Antarctic volcanoes. We assess these potential mixing scenarios and conclude that Siple Dome's unusual geochemical signature can best be explained by a mixture of Patagonian dust and a Gaussberg-like source, with additional minor contributions from old eroded Archean-to-early Proterozoic bedrock sources such as those in Enderby Land. Moreover, Siple Dome dust compositions are distinct from dust deposited on Taylor and Clark Glaciers in the McMurdo Dry Valleys of the western Ross Sea, precluding the Dry Valleys as a late Holocene dust source to this region of the eastern Ross Sea.

Biochar as soil amendment: Syngas recycling system is essential to create positive carbon credit

Biochar utilization is accepted as the most cost-effective practice to mitigate global warming via increase in soil C stock. However, its utilization effect on greenhouse gas (GHG) fluxes was evaluated only within land application without considering industrial processes. To evaluate the net effect of biochar utilization on global warming within whole system boundary, swine manure-saw dust mixture was pyrolyzed under four different temperatures, and GHG fluxes were characterized under with/without syngas recycling systems. To determine GHG fluxes from biochar amended soil, 40 Mg ha‐1 of biochar was mixed with soil and incubated under flooded and dried soil conditions. Finally, the effect of biochar utilization was generalized using net global warming potential (GWP) from industrial process to land application. Under without syngas recycling system, huge amounts of GHGs were emitted during pyrolysis, and GHG fluxes highly increased with increasing pyrolysis temperature, due to direct and indirect GHG emissions from feedstock combustion and electricity, respectively. However, syngas recycling system removed most of GHGs, except for direct N2O and indirect GHG emissions from electricity. Biochar application was very effective to mitigate GHG emissions within soil system boundary, and biochar produced at higher pyrolysis temperature showed higher effectivity in decreasing GHG fluxes. Within the whole system boundary from pyrolysis to soil application, without the installation of syngas recycling system, fresh manure application was more effective than biochar to reduce GHG emissions, regardless of soil water conditions. However, with the installation of syngas recycling system, biochar application was much more effective than fresh manure to decrease GHG fluxes. Biochar produced at higher temperature had higher effectivity to mitigate global warming impacts. In conclusion, to functionally mitigate global warming in soils, biochar should be produced in pyrolysis reactors equipped with syngas recycling system under higher temperature.

Influences of methane and propane on the explosion characteristics of polymethyl methacrylate and acrylonitrile butadiene styrene dusts

AbstractPolymethyl methacrylate (PMMA) and acrylonitrile butadiene styrene copolymers (ABS) are widely applied to industrial production, with the risk of explosion mixed with combustible gas increasing gradually. A 20 L spherical explosive device was used to study the variation pattern of the explosion characteristics of four gas–dust mixtures: methane/PMMA, methane/ABS, propane/PMMA, and propane/ABS mixtures. The results showed that despite adding methane and propane, PMMA and ABS dusts within the range of minimum explosion concentration are still likely to explode. The comparative analysis shows that propane is more chemically reactive than methane and PMMA and ABS dusts mixed with propane are more dangerous than those mixed with methane. Meanwhile, it was found that as the concentration of methane and propane increases, the maximum explosion pressure Pmax, maximum explosion pressure rise rate (dP/dt)max, and explosive index K of the dusts rise as well, but the increasing trend remains steady. The single‐phase methane and propane have higher maximum explosion pressure and explosive index than the gas–dust mixture, with the lowest maximum explosion pressure and explosive index found in the single‐phase PMMA and ABS dusts. With methane and propane mixed, the explosion hazard of PMMA and ABS dusts is intensified from St1 to St3. This study reveals the explosion characteristics of PMMA and ABS dusts, providing a basis for ensuring a safe working environment, preventing and controlling explosion accidents, and reducing the destructiveness of accidents.

Effect of turbulence intensity on flame propagation and extinction limits of methane/coal dust explosions

Methane/coal dust explosions pose a serious threat to the safety of coal mining. Since the flow field in the tunnel is unsteady, the effect of turbulence on flame propagation is essential for the disaster risk assessment and safety protection. In this study, the effect of turbulence intensity (u′) on flame propagation characteristics and extinction limits of methane/coal dust explosions is investigated. The turbulence parameters of the flow field and the turbulence-flame interaction are estimated by Particle Image Velocimetry. Luminous flame (raw image) and reaction front (OH radical image) of methane/coal dust mixture are captured. The results reveal that the flame propagation velocity increases by 78–200%, when the u′ increases from 1.86 to 2.66 m/s. The acceleration of flame propagation velocity is due to the increase of the release of volatile matter and the flame folded regions caused by the turbulence. When the characteristic time of the turbulence disturbance becomes shorter than that of the chemical reactions, the heat sink effect of turbulence will dominate the combustion process. In this case, the extinction limits of CH4/coal flames increase with the u′. When the u′ increases from 1.86 to 2.66 m/s, the extinction limits of CH4/coal flames increase by 14–60%.

Some Geotechnical Properties of Plastic Soil Enhanced with Cement Dust

Plastic soil exhibits unfavorited geotechnical properties (when saturation), which causes negative defects to engineering structures. Different attempts (included various materials) were conducted to proffer solutions to such defects by experimenting in practical ways. On one hand, these attempts aimed to improve the engineering characteristics of plastic soil, and on the other hand, to use problematic waste materials as a stabilizer, like cement kiln dust, and to reduce environmental hazards. This paper explored the shrinkage, plasticity, and strength behavior of plastic soil enhanced with cement dust. The cement dust contents were 0%, 5%, 10%, 15% and 20% by dry weight of soil. An experimental series of shrinkage and plasticity tests and unconfined compression tests were carried out to explore the effects of cement dust on the quantitative amount of shrinkage, plasticity characteristics, and shear strength experienced by plastic soil. The effects of curing on soil strength were also investigated. The finding of this paper showed that the critical behavior and plasticity of plastic soil could be reduced by mixing the soil with 15% or 20% of cement dust. The undrained shear strength, cu, of plastic soil-cement dust mixtures increased with the increasing dust content up to 20%. In fact, this strength was affected by the curing period. The best enhancement was attained when the content of cement dust was 20%, and the undrained shear strength was increased more than three times at this content.

Quasi-static dispersion of dusts for the determination of lower explosion limits of hybrid mixtures

Knowledge of the explosion limiting concentration of explosible materials is necessary for the design of explosion protection measures. Currently employed methods of testing the minimum explosible concentration (MEC) of a dust cloud or the lower explosion limit (LEL) of a hybrid mixture are based on arbitrary assumptions and possess technical limitations that often lead to values of MEC/LEL, which are unrealistically low or poorly reproducible.This contribution presents an improved method for the experimental determination of the MEC of a combustible dust cloud or the LEL of a flammable gas or a hybrid mixture. The new set-up operates under laminar conditions and allows a uniform suspension of dust particles in an open top acrylic glass tube. Dust concentration is measured with the help of infrared sensors installed a few centimeters above and below the ignition source.In order to evaluate the dependence of MEC on flow front velocity, MEC of lycopodium was determined at four flow velocities. The results show that the flow field intensity does not significantly influence the MEC of lycopodium for the flow ranges tested in this work. Moreover, LEL of hybrid mixtures of lycopodium and methane was also tested at flow velocities of 4.7 cm/s, 5.8 cm/s, 7 cm/s and 11 cm/s and compared with the values obtained from other sources. The results suggest that the requirement of high energy pyrotechnical igniter may be relinquished, provided that a truly homogeneous suspension of dust particles could be achieved.Moreover, the effect of relative amount of dust and gas, on the course of ignition and flame propagation in hybrid mixtures at their LEL, was studied by the help of high speed videos. For hybrid mixtures of carbonaceous dusts (like lycopodium) at their LEL, ignition occurs in the gas phase, however, flame propagation is only possible through a two-way interaction of dust and gas during the course of combustion.

Закономерности возгорания метана и угольной пыли от электрического источника в горных выработках

Fires and explosions pose the greatest threat in underground mines that use high-voltage electrical grids. The paper presents data on explosions of combustible methane and coal dust mixtures in Russian mines. It is shown that there always exists a high risk of fire resulting from a malfunction in the electrical grid. The research aims at determining the type and parameters of an electric arc, spark or open flame generated at the breaking points of electric conductors which initiate the ignition of a combustible medium. It was found that the commonly known ionic and thermal theories of ignition do not match the present state of knowledge. The methodology consisted in investigating patterns of electric charge generation and transfer up to the point of the mains failure. Regularities of energy processes in the atomic and molecular structure of the conductor material are presented. For the first time ever the concept of transformation of the electromagnetic energy generated in the alternator into photon packets of high-frequency energy is justified. An electron of the conductor atom absorbs a quantum of the generated energy, converts the generated frequency into a high-frequency photon packet and radiates it into the electric grid. It has been found that an electric arc or a spark, acting as a source of ignition for a combustible medium, is an electromagnetic emission of energy in the visible range.

Profiling of Dust and Urban Haze Mass Concentrations during the 2019 National Day Parade in Beijing by Polarization Raman Lidar

The polarization–Raman Lidar combined sun photometer is a powerful method for separating dust and urban haze backscatter, extinction, and mass concentrations. The observation was performed in Beijing during the 2019 National Day parade, the particle depolarization ratio at 532 nm and Lidar ratio at 355 nm are 0.13 ± 0.05 and 52 ± 9 sr, respectively. It is the typical value of a mixture of dust and urban haze. Here we quantify the contributions of cross-regional transported natural dust and urban haze mass concentrations to Beijing’s air quality. There is a significant correlation between urban haze mass concentrations and surface PM2.5 (R = 0.74, p < 0.01). The contributions of local emissions to air pollution during the 2019 National Day parade were insignificant, mainly affected by regional transport, including urban haze in North China plain and Guanzhong Plain (Hebei, Tianjin, Shandong, and Shanxi), and dust aerosol in Mongolia regions and Xinjiang. Moreover, the trans-regional transmission of natural dust dominated the air pollution during the 2019 National Day parade, with a relative contribution to particulate matter mass concentrations exceeding 74% below 4 km. Our results highlight that controlling anthropogenic emissions over regional scales and focusing on the effects of natural dust is crucial and effective to improve Beijing’s air quality.

Experimental study to assess the explosion hazard of CH4/coal dust mixtures induced by high-temperature source surface

The explosion accident caused by the spontaneous combustion surface of coal after the coal dust is rolled up by the gas gushing from the goal seriously threatens the safety of coal coal mining. Based on this hazard, self-developed gas explosion equipment is used to detonate the CH4/coal dust mixture by high-temperature source. The process and mechanism of gas/coal dust explosion induced by coal spontaneous combustion in goaf were simulated, and its risk was evaluated. It is of great significance to understand the initiation mechanism of gas-solid mixture through coal spontaneous combustion in goaf. The results show that the explosion pressure (Pgd), explosion temperature (Tgd), rate of pressure rise ((dP/dt)gd), and explosion index (K) of CH4/coal dust mixtures are closely related to the temperature of high-temperature source and volatile content. The role of coal dust volatiles in homogeneous and nonhomogeneous reactions was revealed. Combined with three explosion parameters (Pgd, Tgd, K), the most dangerous explosion combination concentration of the selected CH4/coal dust mixture is (9.5 %, 500 g/m3), (9.5 %, 400 g/m3), and (8.5 %, 500 g/m3) at 1073 K ignition temperature. The involvement of coal dust leads to a lower explosion limit for CH4/air. The Jiang model has better applicability to the prediction of lower explosion limits for CH4/coal dust mixtures induced by the high-temperature source surface.