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The temporal and cross‐sectional distributions of particles in a 127 mm diameter fluidized bed have been obtained using a new generation, high‐speed electrical capacitance tomography. Two planes of eight electrodes were used and mounted at 160 and 660 mm from the gas distributor which was a 3 mm thick porous plastic plate (maximum pore size of 50‐70 μm). 3 mm diameter, nearly‐spherical polyethylene granules made up the bed. Experiments at sampling frequencies of 200‐2000 cross‐sections per second and gas superficial velocities from just below the minimum fluidization to 83% above minimum fluidization velocities were used. The time series of the cross‐sectional average void fractions have been examined both directly and in amplitude and frequency space. The last two used probability density functions and power spectral densities. The information gathered shows that the fluidized bed was operating in the slugging mode, which is not surprising given the size of the particles. It has been found that an increase in the excess gas velocity above the minimum fluidization velocity resulted in an increase in the mean void fraction, an increase in the length and velocity of the slug bubbles as well as the bed height, and a slight decrease in the slug frequency. The results are presented in a level of detail suitable for comparison with later numerical simulation. [ABSTRACT FROM AUTHOR]

Petrographic studies are commonly used to categorize the potential utilization of coals. Eleven coal samples from the Jharia coalfield (JCF), India, were studied using petrographic techniques to investigate maceral content, reflectance, and textural characteristics. Multiple test samples of each coal were slowly oxidized under controlled laboratory conditions from an ambient temperature of 30°c to 300°c to investigate the morphology of oxidized coals. The petrographic characterization of coals before and after oxidation showed significant changes in both morphology and vitrinite reflectance. The oxidation of coal particles produced three predominant textural changes: particles with homogeneous change of reflectance (HCv), particles with oxidation rims (ORv), and particles with no changes were observed (Uv), respectively. These textural characteristics were used to indicate how particles had interacted with oxygen at low temperatures during the early stages of oxidation. The morphological classification developed provides an alternative method to confirm the susceptibility of a coal to spontaneous combustion. Conventional thermal parameters such as crossing point temperature (CPT) were unable to identify the coals prone to spontaneous combustion. However, certain petrographic parameters could be combined with CPT values to provide a much more accurate measure for susceptibility to spontaneous combustion. [ABSTRACT FROM AUTHOR]

In recent years, there has been significant research effort to investigate the use of plume dispersion models to assess the environmental impact of fugitive dust emissions from surface mining operations. In particular, the results of these studies have identified challenges to the use of traditional Gaussian plume dispersion models to satisfactorily reproduce fugitive dust dispersion and deposition experienced from low elevation release heights within complex topography. This paper presents a discussion of the results of a preliminary series of modelling studies that have employed the UK-Atmospheric Dispersion Modelling System (ADMS) model to investigate the dust dispersion and deposition from a former mining site currently undergoing remediation. The remediation site is located within a valley in south-western Sardinia that may be considered an aerodynamically complex terrain. A series of field measurement surveys were conducted along the length of an unpaved surface haul truck roadway to measure the PM2.5 and PM10 dust fractions within the emitted plumes. To investigate the potential effects that the surrounding topography may have on the atmospheric dispersion and deposition experienced a series of UK-ADMS dispersion models were solved for a range of meteorological stability conditions typical of the area under investigation. A preliminary analysis of the results of these simulations concludes that there was a strong influence of the surrounding terrain on the dispersion and deposition phenomena predicted. [ABSTRACT FROM PUBLISHER]