Explosion prevention and mitigation in plants which process, generate and store combustible dusts

Combustible dusts which are present in workplaces are a significant hazard which cannot be ignored by the plant owners, managers and workers. Combustible dust deflagrations and explosions have caused large numbers of deaths and catastrophic property damages in various industries, ranging from pharmaceutical plants to sugar factories. One may say that dust explosions in process industries always start inside process equipment such as mills, dryers, filters. Such events may occur in any process in which a combustible dust is handled, produced or stored, and can be triggered by any energy source, including static electricity, friction and hot surfaces. For any combustible dust type, several important parameters have to be taken into account when designing and using protective systems: i.e. the ease with which dust clouds ignite and their burning rates, maximum explosion pressure, maximum rate of explosion pressure rise. These parameters vary considerably depending on the dust type, their knowledge being a first step for carrying out a proper explosion risk assessment in installations which circulate combustible dusts. The paper presents the main aspects concerning explosion protection which have to be taken into account when designing protective systems intended to be used in explosive atmospheres generated by combustible dusts and the importance of selecting the proper explosion protection technique.

Color Dependence of Planetary Transit Depths due to Large Starspots and Dust Clouds: Application to PTFO 8-8695

Although thousands of exoplanets have now been discovered, there is still a significant lack of observations of young planets only a few Myr old. Thus there is little direct evidence available to differentiate between various models of planet formation. The detection of planets of this age would provide much-needed data that could help constrain the planet formation process. To explore what transit observations of such planets may look like, we model the effects of large starspots and dust clouds on the depths of exoplanet transits across multiple wavelengths. We apply this model to the candidate planet PTFO 8-8695b, whose depths vary significantly across optical and infrared wavelengths. Our model shows that, while large starspots can significantly increase the color dependence of planetary transits, a combination of starspots and a large cloud surrounding the planet is required to reproduce the observed transit depths across four wavelengths.

The radiation properties of burning clouds of metal dust. 3. Modification of the emission spectrum

In this work we studied the emission spectra of the combustion products of low-volume dust clouds (V = 5 L) from aluminum (ASD-4), as well as clouds from mixed compositions of aluminum with inorganic powdery oxidizing agents (NaNO3, NaCl, Na2CO3·10H2O, Sr(NO3)2, Ba(NO3)2, KNO3, CuSO4, CuSO4·10H2O) and combustible (B, AlB2, Cu). This article discusses the possibilities of purposeful modification of the emission spectrum of the base composition using various inert and optically active dispersed additives that shift the maximum of the emission spectrum of the fuel composition to the region of longer waves or cause a local change in the emission spectrum in the corresponding spectral regions. In the course of the experiments, it was revealed that the introduction of additives into the basic composition of dispersed fuel does not significantly change the dynamic characteristics of the suspension. However, the additives lead to a decrease in temperature (by about 100–200°K in the presence of an additive up to 25% by weight) and to a corresponding shift in the maximum of the radiation spectrum. The possibility of a significant local modification of the spectrum in the yellow region with the help of inorganic additives to the fuel of sodium salts with a low decomposition temperature (additives Na2CO3·10H2O) was shown experimentally. Boron additives and boron compounds (B, AlB2) leads to a significant increase in the luminosity of the flame in the green region of the spectrum with a maximum radiation in the range Δλ = 530 ÷ 580 nm. The article presents the lighting characteristics (luminous intensity, light sum) of large clouds (V ≥ 10 m3) of mixed compositions based on PAP-2 aluminum powder. It was found that the introduction of inorganic additives to the base fuel does not lead to a noticeable change in the lighting characteristics, but somewhat increases the time of the cloud glow both in the visible and infrared parts of the spectrum.

Magnetized Dusty Black Holes and Wormholes

We consider the generalized Tolman solution of general relativity, describing the evolution of a spherical dust cloud in the presence of an external electric or magnetic field. The solution contains three arbitrary functions f(R), F(R) and τ0(R), where R is a radial coordinate in the comoving reference frame. The solution splits into three branches corresponding to hyperbolic (f>0), parabolic (f=0) and elliptic (f<0) types of motion. In such models, we study the possible existence of wormhole throats defined as spheres of minimum radius at a fixed time instant, and prove the existence of throats in the elliptic branch under certain conditions imposed on the arbitrary functions. It is further shown that the normal to a throat is a timelike vector (except for the instant of maximum expansion, when this vector is null), hence a throat is in general located in a T-region of space-time. Thus, if such a dust cloud is placed between two empty (Reissner–Nordström or Schwarzschild) space-time regions, the whole configuration is a black hole rather than a wormhole. However, dust clouds with throats can be inscribed into closed isotropic cosmological models filled with dust to form wormholes which exist for a finite period of time and experience expansion and contraction together with the corresponding cosmology. Explicit examples and numerical estimates are presented. The possible traversability of wormhole-like evolving dust layers is established by a numerical study of radial null geodesics.

Revisiting the Most Destructive Earthquake Sequence in the Recent History of Greece: Environmental Effects Induced by the 9, 11 and 12 August 1953 Ionian Sea Earthquakes

The August 1953 seismic sequence comprised the most destructive events in the recent history of Greece. The mainshock on 12 August, and its foreshocks on 9 and 11 August, devastated the southern Ionian Islands. The existing literature emphasized the destructive effects of the earthquakes on buildings, as well as to the emergency response and recovery actions. This resulted in a large gap in capturing the full picture of the earthquake’s environmental effects. The present study aims to fill this gap by reconstructing the most complete picture possible of the primary and secondary effects on the environment of the southern Ionian Islands by the August 1953 earthquakes. This reconstruction is based on all available sources, comprising not only the existing scientific literature, but especially sources that have not been considered to date, including newspapers of local and national circulation. In total, 120 cases of the earthquake’s environmental effects were identified, comprised of 33 cases of primary and 87 cases of secondary effects. In descending order of occurrence, slope failures, co-seismic uplift, hydrological anomalies, ground cracks, tsunami, liquefaction, dust clouds, hydrocarbon-related phenomena, jumping stones and vegetation effects were distributed mainly in Cephalonia Island and secondarily in the Ithaki and Zakythos Islands. The primary effects were mainly detected in eastern Cephalonia, which presented uplift of up to 70 cm, while the majority of the secondary effects were triggered in specific zones with characteristics that made them susceptible to the occurrence of earthquake-related hazards.

Position correction in dust storm forecasting using LOTOS-EUROS v2.1: grid-distorted data assimilation v1.0

When calibrating simulations of dust clouds, both the intensity and the position are important. Intensity errors arise mainly from uncertain emission and sedimentation strengths, while position errors are attributed either to imperfect emission timing or to uncertainties in the transport. Though many studies have been conducted on the calibration or correction of dust simulations, most of these focus on intensity solely and leave the position errors mainly unchanged. In this paper, a grid-distorted data assimilation, which consists of an image-morphing method and an ensemble-based variational assimilation, is designed for realigning a simulated dust plume to correct the position error. This newly developed grid-distorted data assimilation has been applied to a dust storm event in May 2017 over East Asia. Results have been compared for three configurations: a traditional assimilation configuration that focuses solely on intensity correction, a grid-distorted data assimilation that focuses on position correction only and the hybrid assimilation that combines these two. For the evaluated case, the position misfit in the simulations is shown to be dominant in the results. The traditional emission inversion only slightly improves the dust simulation, while the grid-distorted data assimilation effectively improves the dust simulation and forecasting. The hybrid assimilation that corrects both position and intensity of the dust load provides the best initial condition for forecasting of dust concentrations.