Inhibition characteristics of coal dust explosion at the gasification atmosphere

The risk of coal dust explosion threatens the safety of coal gasification process. To reveal the inhibition of carrageenan dry-water material (CDM) on coal dust explosion, a 20 L spherical explosive device was adopted to compare with SiO₂ and NH₄H₂PO₄ at the atmosphere of coal gasification. The thermal decomposition behavior and chemical structures of the explosion residues were characterized by synchronous thermal analyzer, X-ray photoelectron spectroscopy and FTIR. The results indicate that the CDM showed the optimal inhibiting effect on 300 mesh and the maximum explosion pressure of anthracite coal dust was reduced to 0.02 MPa with the percentage of 97.53%. At the same concentration, the inhibiting effect of CDM on the coal dust explosion was better than that of SiO₂ and weaker than that of NH₄H₂PO₄. Through the residues analysis, the CDM mainly prevented the volatilization of C-H and consumption of oxygen-containing groups and sulfur-containing groups contributing to the inhibition of coal dust explosion.     

Measurements of density and temperature profiles in the middle atmosphere with a XeF lidar

Density and temperature profiles in the 30-70-km altitude range are measured with a XeF lidar system using Rayleigh scattering. With a 16-W XeF laser at wavelengths 351 and 353 nm, density and temperature accuracies of less than +/-3% and +/-10 K are obtained up to 60 km for an observation time of 15 min. The overall performances are now competitive with and superior to those of traditional Nd:YAG SHG lidars at 532 nm.     

Regeneration of information from optical sensors of the dust component of the natural outer atmosphere of a space vehicle

Algorithms for use in processing the information of an optical system for collection of data on the position, velocity vectors, and dimensions of dust particles found in a neighborhood of a space vehicle are considered. Through the use of the system it becomes possible to observe large objects at greater distances and to calculate the parameters of their motion. The formulas presented in the article are studied with the use of a mathematical model of the system and the results that are obtained converge well with the initial data. Translated from Izmeritel’naya Tekhnika, No. 5, pp. 32–35, May, 2008.     

SHIMMER: a spatial heterodyne spectrometer for remote sensing of earth's middle atmosphere

It is well known and demonstrated that interference spectroscopy offers capabilities to obtain passive remote optical sensing spectra of high precision and also achieves economies in size, cost, and ease of deployment compared with more conventional systems. We describe the development of a near-ultraviolet spatial heterodyne spectrometer designed for remote sensing of the global distribution of the hydroxyl radical OH in the Earth's middle atmosphere. The instrument, known as SHIMMER (Spatial Heterodyne Imager for Mesospheric Radicals), is expected to obtain its first OH measurement from space in early 2002 from the Space Shuttle.     

Pressure sounding of the middle atmosphere from ATMOS solar occultation measurements of atmospheric CO(2) absorption lines

A method for retrieving the atmospheric pressure corresponding to the tangent point of an infrared spectrum recorded in the solar occultation mode is described and applied to measurements made by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier-transform spectrometer. Tangent pressure values are inferred from measurements of isolated CO(2) lines with temperature-insensitive strengths by measuring the slant-column CO(2) amount and by adjusting the viewing geometry until the calculated column matches the observed column. Tangent pressures are determined with a spectroscopic precision of l%-3%, corresponding to a tangent-point height precision of 70-210 m. The total uncertainty is limited primarily by the quality of the spectra and ranges between 4% and 6% (280-420 m) for spectra with signal-to-noise ratios of 300:1 and between 4% and 10% for spectra with signal-to-noise ratios of 100:1. The retrieval of atmospheric pressure increases the accuracy of the retrieved-gas concentrations by minimizing the effect of systematic errors introduced by climatological pressure data, ephemeris parameters, and the uncertainties in instrumental pointing.     

Reevaluation of color constancy algorithm performance

The relative performance of color constancy algorithms is evaluated. We highlight some problems with previous algorithm evaluation and define more appropriate testing procedures. We discuss how best to measure algorithm accuracy on a single image as well as suitable methods for summarizing errors over a set of images. We also discuss how the relative performance of two or more algorithms should best be compared, and we define an experimental framework for testing algorithms. We reevaluate the performance of six color constancy algorithms using the procedures that we set out and show that this leads to a significant change in the conclusions that we draw about relative algorithm performance as compared with those from previous work.     

The venting of dust explosions in a dust collector

Pressures generated by dust explosions in a commercial dust collector have been measured. The dust clouds were formed while the collector was operating under normal working conditions, i.e. dusts were dislodged from the filter elements inside the collector by pulsed reversed air jets. The vented explosion pressures measured under these conditions provide a realistic guide to the explosion pressures that the filter may have to withstand in practice. These pressures are low (2 kPa) when the explosion is vented through a vent close to the ignition source. If, however, the vent is remote from the ignition source and flame turbulence is generated, the rate of combustion is increased and the explosion pressures are higher (14 kPa). The vented explosion pressures encountered when the flame becomes turbulent are reasonably well predicted by the K_st nomograph approach. Pressures generated by highly turbulent explosions in a silo-shaped container have also been compared to the K_st homograph predictions. In these experiments, the pressures were always much higher than predicted.     

Volcanism and the atmosphere: the potential role of the atmosphere in unlocking the reactivity of volcanic emissions

Recent measurements of reactive trace gas species in volcanic plumes have offered intriguing hints at the chemistry occurring in the hot environment at volcanic vents. This has led to the recognition that volcanic vents should be regarded not only as passive sources of volcanic gases to the atmosphere, but also as 'reaction vessels' that unlock otherwise inert volcanic and atmospheric gas species. The atypical conditions created by the mixing of ambient atmosphere with the hot gases emitted from magma give rise to elevated concentrations of otherwise unexpected chemical compounds. Rapid cooling of this mixture allows these species to persist into the environment, with important consequences for gas plume chemistry and impacts. This paper discusses some examples of the implications of these high-temperature interactions in terms of nitrogen, halogen and sulphur chemistry, and their consequences in terms of the global fixed nitrogen budget, volcanically induced ozone destruction and particle fluxes to the atmosphere. Volcanically initiated atmospheric chemistry was likely to have been particularly important before biological (and latterly anthropogenic) processes started to dominate many geochemical cycles, with important consequences in terms of the evolution of the nitrogen cycle and the role of particles in modulating the Earth's climate.     

Remote laser probing of hydrocarbons in the atmosphere

A lidar equation for the Raman backscattering of light from molecules of some hydrocarbons was numerically solved. The optimum value of the copper vapor laser wavelength for the probing of hydrocarbons at a distance from 40 m to 4 km was determined.     

On the structure of instantaneous plumes in the atmosphere

Current methods for the analysis and prediction of the concentration fluctuations occurring in substances dispersing in the atmosphere are reviewed parThe results obtained from a series of very high time resolution concentration measurements conducted in neutral conditions over flat terrain using specIt is evident that risk/hazard analyses based on time mean concentrations distributions can at best be misleading and at worst result in serious undere     

Slow magnetohydrodynamic waves in the solar atmosphere

There is increasingly strong observational evidence that slow magnetoacoustic modes arise in the solar atmosphere, either as propagating or standing waves. Sunspots, coronal plumes and coronal loops all appear to support slow modes. Here we examine theoretically how the slow mode may be extracted from the magnetohydrodynamic equations, considering the special case of a vertical magnetic field in a stratified medium: the slow mode is described by the Klein-Gordon equation. We consider its application to recent observations of slow waves in coronal loops.     

Optical path length fluctuations in the atmosphere

The effect of atmospheric fluctuations on measurements of distance has become increasingly important as laser interferometers become more widely used. The present study evaluates the precision with which dimensions can be monitored by interferometry involving optical path lengths in the open air under good atmospheric conditions. The size and time scale of optical path length fluctuations over distances of one meter, and correlations between fluctuations in nearby optical paths, are measured and analyzed.     

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.     

Elementary processes in prebreakdown phenomena in the atmosphere

The effect of negative oxygen ion destruction upon breakdown conditions in atmospheric air is analyzed. It is shown that ozone accumulation due to plasmochemical reactions occurring in ionized air produces a reduction in the breakdown voltage, related to negative O^– ion destruction upon collision with ozone molecules under realistic conditions. A relationship is derived for electric field breakdown intensity and ozone molecule lifetime for the real atmosphere.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 5 pp. 661–664, May, 1992.     

Preparation of microbial dust suppressant and its application in coal dust suppression

To promote the application of microbially induced carbonate precipitation (MICP) technology for coal dust suppression, two urease-producing bacteria (SZS1-3 and SZS1-5) in a coal mine soil were screened. 16 s rDNA sequencing of these bacteria indicated sequences similar to those of Acinetobacter guillouiae CIP 63.46 and Staphylococcus caprae ATCC 35538, respectively. Strains SZS1-3 and SZS1-5 had their largest urease activity at the initial urea concentration of 0.5 mol/L, under slightly alkaline (pH = 9) and neutral (pH = 7) initial pH levels, respectively. Their final mineralized products were vaterite-type and calcite-type calcium carbonate. Although dust suppression results indicated that both bacteria can effectively bind coal dust particles, consolidated coal dust treated with SZS1-5 had a stronger resistance to wind and rain. The screening, mineralization and dust suppression potential analysis of these two urease-producing bacteria can provide reference for the application of MICP technology in coal dust suppression.     

Microwave spectroscopy of the Mars atmosphere

A study of the use of millimeter-wavelength spectral transitions to investigate the atmosphere of Mars is presented. In the model experiments investigated it is assumed that a spectrometer in the frequency range from 100 to 260 GHz looks into a modest-sized telescope of from 30 to 50 cm aperture from a near-Mars orbit. The molecules H(2)O, CO, O(2), O(3), and H(2)O(2) all have intense spectral lines in the Mars atmosphere in this frequency range and in addition are all very important in understanding the water cycle, the photochemistry, and the circularization in that atmosphere. It is shown that the altitude and the zonal distribution of H(2)O can be mapped even in atmospheric columns as dry as 0.25 precipital μm. Ozone can be mapped over the entire planet, independent of solar-lighting conditions, dust loading, or clouds in the atmosphere, because millimeter waves are insensitive to any particles that can be suspended in the Mars atmosphere. Because the signal-receiving techniques use superheterodyne devices and narrow spectral lines, zonal and meridional winds can be measured at altitudes above 10 km with a precision approaching approximately 3 m/s by the use of Doppler shifts. Temperature-pressure profiles can be measured to altitudes of 100 km by the use of CO lines in the limb-sounding mode.     

A model of the turbulence development in the upper atmosphere

The appearance of quasiperiodic solutions of the Korteweg-de Vries equation, describing waves in the upper atmosphere within the framework of the Freeman-Johnson model, is considered. Evolution of these quasiperiodic solutions can lead to stochastization according to the Ruel-Tackens-Newhouse scenario. Increasing reflection of solar radiation from a turbulent atmosphere influences the entropy balance of the Earth considered as an open system.