Evaluation of a 38 L Explosive Chamber for Testing Coal Dust Explosibility

Coal dust explosions are the deadliest disasters facing the coal mining industry. Research has been conducted globally on this topic for decades. The first explosibility tests in the United States were performed by the Bureau of Mines using a 20 L chamber. This serves as the basis for all standardized tests used for combustible dusts. The purpose of this paper is to investigate the use of a new 38 L chamber for testing coal dust explosions. The 38 L chamber features design modifications to model the unique conditions present in an underground coal mine when compared to other industries where combustible dust hazards are present. A series of explosibility tests were conducted within the explosive chamber using a sample of Pittsburgh pulverized coal dust and a five kJ Sobbe igniter. Analysis to find the maximum pressure ratio and Kst combustible dust parameter was performed for each trial. Based upon this analysis, observations are made for each concentration regarding whether the explosibility test was under-fueled or over-fueled. Based upon this analysis, a recommendation for future explosibility testing concentrations is made

Explosion Testing of a Polycarbonate Safe Haven Wall

The MINER Act of 2006 was enacted by MSHA following the major mining accidents and required every underground coal mine to install refuge areas to help prevent future fatalities of trapped miners in the event of a disaster where the miners cannot escape. A polycarbonate safe haven wall for use in underground coal mines as component of a complete system was designed and modeled using finite element modeling in ANSYS Explicit Dynamics to withstand the MSHA required 15 psi (103.4 kPa) blast loading spanning 200 milliseconds. The successful design was constructed at a uniform height in both half-width scale and quarter-width scale in the University of Kentucky Explosives Research Team\u27s (UKERT) explosives driven shock tube for verification of the models. The constructed polycarbonate walls were tested multiple times to determine the walls resistance to pressures generated by an explosion. The results for each test were analyzed and averaged to create one pressure versus time waveform which was then imported into ANSYS Explicit Dynamics and modeled to compare results to that which was measured during testing for model validation. This paper summarizes the results

Understanding the Connection between Blasting and Highwall Stability

Surface mines continue to implement highwalls for several reasons, such as increasing recovery, improving margins, and justifying higher stripping ratios. Highwall stability is a complex issue that is dependent upon a variety of mining and geologic factors, and a safe design is necessary for a successful surface operation. To improve highwall stability, it is important to understand the connection between local geology and blasting. Explosives are employed throughout the mining industry for primary rock breakage. There are a number of controlled blasting techniques that can be implemented to improve highwall stability. These include line drilling, smooth wall blasting, trim blasting, buffer blasting, air decking, and presplitting. Each of these techniques have associated advantages and disadvantages. Understanding local geology is necessary for selecting the appropriate controlled blasting technique. Furthermore, understanding the limitations and conditions for successful implementation of each technique is necessary. A discussion of the impact of geologic conditions on highwall stability is provided. Additionally, discussion is provided for the successful incorporation of the controlled blasting techniques listed above, and the associated mining and geologic factors that influence the selection and design of controlled blasting plans. Finally, a new methodology is proposed

Transitions in coral reef accretion rates linked to intrinsic ecological shifts on turbid-zone nearshore reefs

Nearshore coral communities within turbid settings are typically perceived to have limited reef-building capacity. However, several recent studies have reported reef growth over millennial time scales within such environments and have hypothesized that depth-variable community assemblages may act as equally important controls on reef growth as they do in clear-water settings. Here, we explicitly test this idea using a newly compiled chronostratigraphic record (31 cores, 142 radiometric dates) from seven proximal (but discrete) nearshore coral reefs located along the central Great Barrier Reef (Australia). Uniquely, these reefs span distinct stages of geomorphological maturity, as reflected in their elevations below sea level. Integrated age-depth and ecological data sets indicate that contemporary coral assemblage shifts, associated with changing light availability and wave exposure as reefs shallowed, coincided with transitions in accretion rates at equivalent core depths. Reef initiation followed a regional ∼1 m drop in sea level (1200–800 calibrated yr B.P.) which would have lowered the photic floor and exposed new substrate for coral recruitment by winnowing away fine seafloor sediments. We propose that a two-way feedback mechanism exists where past growth history influences current reef morphology and ecology, ultimately driving future reef accumulation and morphological change. These findings provide the first empirical evidence that nearshore reef growth trajectories are intrinsically driven by changes in coral community structure as reefs move toward sea level, a finding of direct significance for predicting the impacts of extrinsically driven ecological change (e.g., coral-algal phase shifts) on reef growth potential within the wider coastal zone on the Great Barrier Reef

Evaluation of the 20 L Dust Explosibility Testing Chamber and Comparison to a Modified 38 L Vessel for Underground Coal

The phenomenon of combustible dust explosions is present within many industries. Tests for explosibility of dust clouds per ASTM E1226 use a 20 L explosive chamber that places the combustible dust directly below the dispersion nozzle which generates a thorough mixture for testing purposes. However, in the underground coal mining industry, there are a number of geologic, mining, and regulatory factors that change the deposition scheme of combustible coal dust. This causes the atmosphere of a coal mine to have a variable rock dust-coal dust mixture at the time of ignition. To investigate the impact of this variable atmosphere, a series of lean explosibility tests were conducted on a sample of Pittsburgh Pulverized coal dust. These explosibility tests were conducted in a 38 L chamber with a 5 kJ Sobbe igniter. The 38 L chamber generates a variable air-dust mixture prior to ignition. The test results indicate that the 38 L chamber experiences reduced explosive pressures, and lower explosibility index values when compared to the 20 L chamber

Explosive Dust Test Vessel Comparison using Pulverized Pittsburgh Coal

Explosions of coal dust are a major safety concern within the coal mining industry. The explosion and subsequent fires caused by coal dust can result in significant property damage, loss of life in underground coal mines and damage to coal processing facilities. The United States Bureau of Mines conducted research on coal dust explosions until 1996 when it was dissolved. In the following years, the American Society for Testing and Materials (ASTM) developed a test standard, ASTM E1226, to provide a standard test method characterizing the “explosibility” of particulate solids of combustible materials suspended in air. The research presented herein investigates the explosive characteristic of Pulverized Pittsburgh Coal dust using the ASTM E1226-12 test standard. The explosibility characteristics include: maximum explosion pressure, (Pmax); maximum rate of pressure rise, (dP/dt)max; and explosibility index, (Kst). Nine Pulverized Pittsburgh Coal dust concentrations, ranging from 30 to 1,500 g/m3 , were tested in a 20-Liter Siwek Sphere. The newly recorded dust explosibility characteristics are then compared to explosibility characteristics published by the Bureau of Mines in their 20 liter vessel and procedure predating ASTM E1126-12. The information presented in this paper will allow for structures and devices to be built to protect people from the effects of coal dust explosions

Management intensive grazing on New England dairy farms enhances soil nitrogen stocks and elevates soil nitrous oxide emissions without increasing soil carbon

Management intensive grazing (MIG), also known as rotational grazing or multi-paddock grazing, is purported to sequester carbon (C) in soils compared to other agricultural management systems. Prior research examining the potential for MIG to enhance soil C has been inconclusive, and past investigations have not addressed whether higher nitrous oxide (N2O) emissions may accompany increases in soil C stocks. Here we examined linkages among MIG, soil C accumulation, and N2O emissions in cool-season, organic pastures of the northeastern United States. We found that pastures under MIG increased soil C concentrations by 11% from 0–15 cm depth but that soil C stocks at all sampled depths did not differ between hayed and grazed fields. We observed a divergent response in soil N to MIG, where both N concentrations and stocks significantly increased and the soil C:N ratio significantly decreased in rotationally grazed pastures. Our results also demonstrated that during the second year of the study, N2O emissions were on average 33% higher in grazed fields and compared to hayed fields. These elevated N2O fluxes in MIG fields may have offset any soil C gains achieved under MIG, as demonstrated by similar climate forcing values (as CO2-equivalents) for hayed and grazed pastures over a 100-year time horizon. The significant variation we detected among farms in soil C and N stocks, soil microbial activity, plant biomass production, and soil greenhouse gas emissions demonstrates that MIG does not have uniform effects across the landscape. Overall, our study demonstrates that care should be taken when promoting management practices that may have unintended climate consequences

Swarm UAVs for Area Mapping in GPS-denied Locations

Utilizing small Unmanned Aerial Systems (SUAS) in mapping and cartography applications holds transformative potential, particularly in challenging and GPS-denied environments. Traditionally, mapping involved manual efforts using diverse tools, but there has been a fundamental shift towards autonomous vehicles capable of achieving efficient results in less time and with reduced human effort. Autonomous mapping typically relies on single a UAV employing Simultaneous Localization and Mapping (SLAM) or photogrammetry alongside GPS. This research project seeks to leverage swarm robotics to map intricate landscapes and rugged terrains using SUASs with a faster, more accurate, and precise approach, eliminating dependence on GPS for global positioning. The mapping scope encompasses hard-to-access locations like cliffs, abandoned structures, and forests, as well as areas impractical for manual surveying, such as construction sites and expansive indoor spaces like warehouses, factories, or historical buildings resistant to modifications for survey purposes. The swarm will exhibit an emergent-like behavior to map any location efficiently, ensuring collision-free navigation among sUAS and ground objects

Energy Efficient Microlith-Based Catalytic Reactor and Recuperator for Air Quality Control Applications

Precision Combustion, Inc. (PCI) and NASAs Marshall Space Flight Center (MSFC) have been developing, characterizing, and optimizing high temperature catalytic oxidizers (HTCO) based on PCIs patented Microlith technology to meet the requirements of future extended human spaceflight explorations. Previous efforts focused on integrating PCIs HTCO unit with a compact, simple recuperative heat exchanger to reduce the overall system size and weight. Significant improvement was demonstrated over traditional approaches of integrating the HTCO with an external recuperative heat exchanger. While the critical target performance metrics were achieved, the thermal effectiveness of PCIs recuperator remained a potential area of improvement to further reduce the energy requirements of the integrated system. Using the same material combinations and an improved recuperator design, the redesigned prototype has experimentally demonstrated 20 30% reduction (flow dependent) in steady state power consumption compared to the earlier prototype without compromising the destruction efficiency of methane and volatile organic compounds (VOCs). Moreover, design modifications and improvements allow our redesigned prototype to be more easily manufactured compared to traditional brazed plate-fin recuperator designs. The redesigned prototype was delivered to MSFC for validation testing. Here, we report and discuss the performance of the improved prototype HTCO unit with a high efficiency recuperative heat exchanger based on testing at PCI and MSFC. The device is expected to provide a reliable and robust means of disposing of trace levels of methane and VOCs by oxidizing them into carbon dioxide and water in order to maintain clean air in enclosed spaces, such as crewed spacecraft cabins