Research on the Effect of Extinction Characteristics of Coal Dust on Visibility

Abstract

A good knowledge of the reduction mechanism of visibility is fundamental to developing preventive strategies in coal mines. In this work, the Mie theory was selected for investigating the absorption and scattering of coal dust. A prediction model for evaluating the visibility was developed based on the extinction characteristics of coal dust. The optical properties have been discussed to simplify the model and clarify the relationships among the different wavelengths and diameters. Additionally, the variety of extinction coefficients can be reasonably used in guiding the calculated visibility under different conditions. The experimental results demonstrated that the reduction of visibility was attributed to the synergistic effect of the extinction of coal dust and droplet. For the field application of this prediction model, the relative errors of the calculated and measured visibility were 9.8 and 7.1% from models I and II, which reflected the small deviation between the two methods. The prediction model can accurately describe the visibility in mines due to coal dust pollution. The exploration results provide a significant reference for the development and application of air cleaning technology for increased visibility.

A Wavelength-Dependent Visible Light Communication Channel Model for Underground Environments and Its Performance Using a Color-Shift Keying Modulation Scheme

“…In contrast, our proposed channel model considers Mie (and not Rayleigh) scattering and absorption effects in both LOS and NLOS links. The exclusion of the Rayleigh regime can be justified by looking at the ratio of the size of the spherical particles to the wavelength, α = πD/λ [30], where D is the diameter of the particle. If α 1, then the Rayleigh scattering model is valid.…”

“…When wavelength and particle size are comparable, Mie scattering theory is more accurate, and when α 1, then geometric scattering theory is used [30]. The particle size distribution of airborne particles in underground mines varies depending on the extractive activity, mineral composition, and geology of the mine, but a generalization can be made by looking at several studies conducted in underground coal mines in the United States [31,32], China [30,33], and the former Soviet Union [34] and underground gold mines in Alaska, Nevada, and South Africa [35], all of which show that the particle sizes of coal and silica dust particle sizes are in the order of 1 µm to 100 µm. Taking into account the wavelengths in the visible spectrum, this range of particle sizes implies that α takes values in the order of 1 to 10 3 : that means that Mie theory is the preferred regime for describing the scattering and absorption phenomena in underground mines.…”

“…The attenuation of optical channels in non-ideal environments is usually modeled by the Beer-Lambert law, e.g., underwater optical channels [14,36,37], outdoor optical channels degraded by rain and snow [38] and sandstorms [39], and UM-VLC channels attenuated by coal dust [5,30]. The transmittance function T(λ), according to the Beer-Lambert law, is given by [30]:…”

“…This extinction coefficient takes into account the loss of optical power due to scattering and absorption by dust particles. In Mie regime, B ext can be expressed as [30,40]:…”

“…The Rosin-Rammler (R-R) distribution is widely used in the literature to model the particle size distribution of dust that results from the crushing of solids such as coal, rocks, and other materials and has been empirically validated numerous times [41]. The authors in [30] use the R-R distribution in their calculations of the extinction coefficient of coal dust in underground mines. The authors in [34] also argue that mine dust is best described by the R-R method.…”