Last data update: Apr 29, 2024. (Total: 46658 publications since 2009)
Records 1-6 (of 6 Records) |
Query Trace: Seaman CE[original query] |
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Design of a water curtain to reduce accumulations of float coal dust in longwall returns
Seaman CE , Shahan MR , Beck TW , Mischler SE . Int J Min Sci Technol 2020 30 (4) 443-447 Accumulation of float coal dust (FCD) in underground mines is an explosion hazard that affects all underground coal mine workers. While this hazard is addressed by the application of rock dust, inadequate rock dusting practices can leave miners exposed to an explosion risk. Researchers at the National Institute for Occupational Safety and Health (NIOSH) have focused on developing a water curtain that removes FCD from the airstream, thereby reducing the buildup of FCD in mine airways. In this study, the number and spacing of the active sprays in the water curtain were varied to determine the optimal configuration to obtain peak knockdown efficiency (KE) while minimizing water consumption. |
Calibration of the cloud and aerosol spectrometer for coal dust composition and morphology
Barone TL , Hesse E , Seaman CE , Baran AJ , Beck TW , Harris ML , Jaques PA , Lee T , Mischler SE . Adv Powder Technol 2019 30 (9) 1805-1814 The cloud and aerosol spectrometer (CAS) was calibrated to enable CAS sizing of coal dust for studies on flammable dust control. Coal dust sizes were determined by light-scattering theories for irregular particles that account for particle composition and morphology in computing coal dust diameters. Coal dust size computations were compared with test dust that was generated by cyclone separation and air-jet sieving and characterized by aerodynamic particle sizer (APS) and computer-controlled scanning electron microscopy (CCSEM) measurements. For test dust in the range of 0.5–32 μm, coal dust size distributions were consistent with cyclone-separated and sieve-segregated sizes. For the 3–20 μm size range, the coal dust size distribution had a mass median diameter that was 14% larger than that of the APS. This difference was reasonable considering that the basic calibration for glass spheres had 13% uncertainty. For the 20–32 μm and 32–45 μm test dusts, mass median diameters differed from CCSEM measurements by only 4% and 5%, respectively. Overall, the results suggest agreement between test dust sizes and computations for coal dust. Alternatively, using conventional Mie theory computations for spheres, coal dust mass median diameters were 35% and 40% larger than APS and CCSEM measurements, respectively. |
Open-air sprays for capturing and controlling airborne float coal dust on longwall faces
Beck TW , Seaman CE , Shahan MR , Mischler SE . Min Eng 2018 70 (1) 42-48 Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce the risk of coal-dust-fueled explosions. The goal of this U.S. National Institute for Occupational Safety and Health study is to determine the potential of open-Air water sprays to reduce concentrations of airborne float coal dust, smaller than 75 microm in diameter, in longwall face airstreams. This study evaluated unconfined water sprays in a featureless tunnel ventilated at a typical longwall face velocity of 3.6 m/s (700 fpm). Experiments were conducted for two nozzle orientations and two water pressures for hollow cone, full cone, flat fan, air atomizing and hydraulic atomizing spray nozzles. Gravimetric samples show that airborne float dust removal efficiencies averaged 19.6 percent for all sprays under all conditions. The results indicate that the preferred spray nozzle should be operated at high fluid pressures to produce smaller droplets and move more air. These findings agree with past respirable dust control research, providing guidance on spray selection and spray array design in ongoing efforts to control airborne float dust over the entire longwall ventilated opening. |
Comparison of the CAS-POL and IOM samplers for determining the knockdown efficiencies of water sprays on float coal dust
Seaman CE , Shahan MR , Beck TW , Mischler SE . J Occup Environ Hyg 2017 15 (3) 0 Float coal dust, generated by mining operations, is distributed throughout mine airways by ventilating air designed to purge gases and respirable dust. Float coal dust poses an explosion hazard in the event of a methane ignition. Current regulation requires the application of inert rock dust in areas subjected to float coal dust in order to mitigate the hazard. An alternate method using water sprays, which have been effective in controlling respirable dust hazards, has been proposed as a way to control float coal dust generated on longwall faces. However, the knockdown efficiency of the proposed water sprays on float coal dust needs to be verified. This study used gravimetric isokinetic Institute of Occupational Medicine (IOM) samplers alongside a real-time aerosol monitor (Cloud Aerosol Spectrometer with polarization; CAS-POL) to study the effects of spray type, operating pressure, and spray orientation on knockdown efficiencies for seven different water sprays. Because the CAS-POL has not been used to study mining dust, the CAS-POL measurements were validated with respect to the IOM samplers. This study found that the CAS-POL was able to resolve the same trends measured by the IOM samplers, while providing additional knockdown information for specific particle size ranges and locations in the test area. In addition, the CAS-POL data was not prone to the same process errors, which may occur due to the handling of the IOM filter media, and was able to provide a faster analysis of the data after testing. This study also determined that pressure was the leading design criteria influencing spray knockdown efficiency, with spray type also having some effect and orientation having little to no effect. The results of this study will be used to design future full-scale float coal dust capture tests involving multiple sprays, which will be evaluated using the CAS-POL. |
Characterization of airborne float coal dust emitted during continuous mining, longwall mining and belt transport
Shahan MR , Seaman CE , Beck TW , Colinet JF , Mischler SE . Min Eng 2017 69 (9) 61-66 Float coal dust is produced by various mining methods, carried by ventilating air and deposited on the floor, roof and ribs of mine airways. It deposited, float dust is re-entrained during a methane explosion. Without sufficient inert rock dust quantities, this float coal dust can propagate an explosion throughout mining entries. Consequently, controlling float coaf dust is of critical interest to mining operations. Rock dusting, which is the adding of inert material to airway surfaces, is the main control technique currently used by the coal mining industry to reduce the float coal dust explosion hazard. To assist the industry in reducing this hazard, the Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health initiated a project to investigate methods and technologies to reduce float ooal dust in underground coal mines through prevention, capture and suppression prior to deposition. Field characterization studies were performed to determine quantitatively the sources, types and amounts of dust produced during various coal mining processes. The operations chosen for study were a continuous miner section, a longwall section and a coal-handling facility. For each of these operations, the primary dust sources were confirmed to be the continuous mining machine, longwall shearer and conveyor belt transfer points, respectively. Respirable and total airborne float dust samples were collected and analyzed for each operation, and the ratio of total airborne float coal dust to respirable dust was calculated. During the continuous mining process, the ratio of total airborne float ooal dust to respirable dust ranged from 10.3 to 13.6. The ratios measured on the longwall face were between 1B.5 and 21.5. The total airborne float coal dust to respirable dust ratio observed during belt transport ranged between 7.5 and 21.8. |
Opto-dielectrometric sensor for measuring total incombustible content in underground coal mines
Mahdavipour O , Jain A , Sabino J , Wright P , White RM , Shahan MR , Seaman CE , Patts LD , Paprotny I . IEEE Sens J 2017 17 (9) 6443 - 6450 Coal dust produced during underground coalmining, i.e. float dust, which deposits throughout the coal mine can be feedstock for coal dust explosions. To prevent these explosions, inert rock dust (limestone dust) is applied to roof, floor, and ribs areas of a coal mine. The ratio of incombustible mass (rock dust + incombustible content of coal dust) divided by total mass of the deposited dust is defined as the Total Incombustible Content (TIC) of the deposited dust within the mine. Regulations require that a minimum TIC ratio (80%;) to be maintained for safe working conditions inside the mine. This paper presents design, fabrication and experimental results for a real-time sensing module which uses continuous optical and dielectrometry methods to measure the TIC of the deposited float dust/rock dust. The optical sensor determines the TIC of the deposited dust based on optical reflection which is described by modified Beer Law. We present an extension of the Bouguer-Beer-Lambert Law to find the relation between the reflectivity of a layer of known thickness (obtained by interdigital dielectrometry sensor) of a dust mixture to the ratio of each constituent. We also present the experimental results from testing the sensor prototypes in a realistic laboratory test bed that is subjected to the deposition of the coal dust/rock dust mixture. The sensor performance and stability at different humidity levels is evaluated and the accuracy of the results are compared to the currently established best practices for measuring TIC in underground coal mines. |
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