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By L. Yuan, J. Soles, W. Tang, R. Thomas

Lithium-ion battery pack fires pose great hazards to the safety and health of miners. A detailed experimental study has been conducted at the National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) to investigate the effectiveness of different fire suppression systems on Li-ion battery pack fire extinguishment. Tests were conducted in a well-ventilated container. Two sizes of battery packs (12V, 24V) were heated by heater strips to trigger thermal runaway and fire. Water mist with different flow rates, ABC powder, type D dry chemical, and water mist with F500 additives were used as the fire suppression agents. Multiple thermocouples were installed on the battery packs to measure the temperature evolution during the tests. The results indicated that the water mist with F500 additives is the most effective suppressant among the agents tested. Dry chemicals, however, do quench the fire for a moment, but cannot prevent re-ignition of the battery since they do not provide enough cooling. The findings of this paper can be used to develop safer battery fire suppression techniques in mining environments.

Feb 1, 2023

By K. Thirumalai

The Bureau of Mines has developed and tested a new concept of combining thermal and hydraulic energy processes for hard rock cutting. The study shows that this novel combination method overcomes the fragmentation limitations of the thermal process in nonspalling rocks and the cuttability limitations of the hydraulic process in high-strength rocks. The method effectively cuts hard rocks at moderate hydraulic pressures (below 30,000 psi). Theoretical predictions of the rock damage process are made and are correlated with experimental results obtained by using both single pulse and continuous water jet hydraulic systems. Traversing point heating and line heating techniques were used for heating rocks preceding the continuous jet impingement. Heating induces structural weakness of the rock material and assists fragmentation by the water jet impingement. The thermohydraulic process is effective if the significant depth of heat penetration induced by the surface heating exceeds the cutting depth produced by the jet impingement. Hydraulic specific fragmentation energy values reduce by about an order of magnitude using the combination technique. The process efficiency and the rate of themohydraulic hard rock cutting increases significantly by increasing the intensity and duration of heating.

Jan 1, 1973

By K. T. Brashear

Since the MINER Act of 2006, the minimum static load of in-situ underground mine seals has been increased from 20-psi to either 50-psi if monitoring is conducted or 120-psi if left unmonitored. These minimum strength requirements in seals must be designed, built, and maintained throughout the lifetime of the seal. Due to this, it has become necessary to assess the effectiveness of non-destructive testing (NDT) technologies to determine seal integrity, which in this case, are explored using sonic waves and tracer gases. Through both small and large scale testing, two NDT methods will be evaluated for their abilities to determine integrity of the seal. A sonic wave technique to observe a change in wave velocity to identify faults within the seal material. As a NDT method, tracer gases may be used as a potential indicator of a connection between both sides of the seal material through a series of faults and cracks within the material itself. This paper reviews the history of underground mine seals and discusses the overall assessment of sonic waves and tracer gases to serve as NDT methods for estimating the integrity of these seals.

Feb 23, 2014

By P. W. Finck

Detailed mapping, using a large diameter diamond-drill in conjunction with high resolution reflection seismics, has increased known resources of kaolin clay and glass-grade silica sand from scattered deposits generally < 1 km2 to large areas of Cretaceous valley fill up to 130 m thick. Detailed chemical and physical analysis of drill core is presently underway. Silica sand deposits intersected in this study are up to 99.4 % SiO2 without beneficiation. Light grey to white kaolin clays identified by XRD and DT A have concentrations values (without beneficiation) up to 47.28% SiO2, 37.44% Al2O3, 0.45% Fe2O3, 0.49% K2O, 0.07% Nap, 0.07% CaO and 0.39% MgO.

Jan 1, 1996

By M. S. Celik

The principal impurities in some feldspar ores are titanium and iron which impart color and in turn degrade the quality of the ore. The mineralogical investigations indicate that titanium element originates from mainly rutile with small amounts of sphene. Conventionally, fatty acids and particularly sodium oleate are extensively used in the flotation of colored minerals from feldspar ores with reasonable success. In this study, new reagents, oleoyl sarcosine and hydroxamate have been used to float colored impurities before and after magnetic separation. Oleoyl sarcosine is found to exhibit better results compared to fatty acids and hydroxamate. The mechanism of the action is elaborated on the basis of experimental data.

Jan 1, 1999

By W. H. W. Husband

Rock salt has been mined by the solution method for many years in many countries. Attempts have been made in the past in Canada and various other countries to produce potash by the&apos; same method. However, only Kalium Chemicals Limited (1) has been successful, possibly because the conditions in Saskatchewan are the most favorable conditions to be found so far for the development of a solution mining method for potash. There are significant differences in solution mining of rock salt and solution mining of potash. First, rock salt deposits are relatively pure in respect to soluble minerals, whereas potash is never found in the pure state and contains Substantial amounts of other soluble minerals, particularly rock salt. In comparison to rock salt, much less potash is dissolved and brought to the surface for the same amount of water circulated through the orebody. The amount of water to be evaporated per unit weight of product is a major difference. Much greater amounts of water must be evaporated when producing potash and the treatment of the brine is more complicated because other dissolved salts have to be separated. Secondly, the rock salt deposits, particularly the domes, are much thicker. Bed thickness is of prime importance because it determines the yield of a well and consequently the economics of the process. Furthermore, as rock salt provides a strong roof structure, larger cavities can be developed and this prolongs the life of the rock salt well.

Jan 1, 1971

Laboratory tests were conducted to evaluate the silica collection efficiency of flooded-bed scrubbers with six different filter panel designs and at two operating velocities. Test results indicated that reductions in filter density negatively impacted respirable dust collection. Silica collection efficiency for the least dense filter was as much as 33 % lower than the collection efficiency of the densest filter. At the low operating velocity, the least dense filter allowed over 40% of the respirable silica dust in the scrubber intake air to pass through the unit, where it would be discharged back into the mine environment. Operation of the scrubber at the higher test air velocity increased silica collection efficiency, regardless of the filter panel tested. The density of the filter panels also impacted the quantity of air that is moved through the scrubber, with higher density filters reducing scrubber airflow. For each filter, the relationship between dust collection efficiency and air moving capacity must be considered to determine overall effectiveness for specific mine applications.

Jan 1, 1998

By Jim V. Rouse

Adverse water-quality impacts of uranium mining and milling activities on both surface- and ground-water resources in the Grants Mineral Belt have recently been documented.1 In some cases, the impacts resulted in violation of existing regulations and license conditions and have endangered public health. Unfortunately, industry-sponsored ground-water monitoring programs do not adequately record the actual impacts of mining and milling on ground-water quality.

Jan 1, 1976

By K. Kim

An analysis was conducted to determine the effects of blasting on slope stability and downstream comminution processes. To investigate these effects, the extent of blast-induced rock damage and the magnitude of induced stress were examined. This analysis showed that damage may extend up to 500 meters (1MPa, tensile strength) in the rock mass, a distance that is sufficient to impact the pit-scale slope over the long term. In addition, the damage zone was calculated using the reasonable assumption that compressive waves are the primary agent in microfracturing during blast fragmentation. The calculated damage zone ? up to 5.6 meters (30MPa, 30% of the compressive strength) ? indicates that microfracturing can occur throughout the entire rock mass in the blasting area. Finally, an economic analysis was conducted by comparing two reasonably assumed blasts in a copper mine. The change in energy required for crushing and grinding was demonstrated using Bond?s law after increasing the blast energy from 180kcal/t to 350kcal/t. A total cost saving of 13.3% ($9.4M) was achieved with the increase. An optimal blast design should consider both slope stability (safety) and downstream comminution energy (production).

Feb 23, 2014

By Faruk Oksuz, Dave Schiemann, Miguel Sanchez, Patrick Jensen

"The McCook Main Tunnel connects Chicago’s Tunnel and Reservoir Plan (TARP) Mainstream Tunnel to the McCook Reservoir. The tunnel system consists of a 10 m (33 ft) finished diameter and 490-m (1,600-ft) long hard-rock tunnel constructed from a 27.5-m (90-ft) diameter and 92 m (300 ft) deep main gate shaft. The gate shaft houses six high-head 4.4 x 9 m (14.5 x 29.5 ft) wheel gates installed in the bifurcated and steel-lined section of the tunnel. The tunnel also includes portal and energy dissipation structures as it daylights into the reservoir. Construction of the McCook Main Tunnel in live flow conditions was a challenging task for the McCook Main Tunnel Project participants, the project owner U.S. Army Corps of Engineers (USACE), local sponsor Metropolitan Water Reclamation District (MWRD) of Greater Chicago, designer Black & Veatch and contractor Kiewit Infrastructure Co. (Kiewit). Once completed in two stages in 2017 and 2029, the McCook Reservoir will hold 38 billion L (10 billion gal) of combined sewer overflows (CSO) and flood waters from the city of Chicago and 36 surrounding communities in Cook County, IL The construction of the tunnel system was divided into two contracts. The first contract for the gate and construction access shaft was completed in August 2011. The second contract included tunnel excavation and concrete and steel lining that was completed in September 2014; installation of gates and hydraulic cylinders that was completed in June 2017; and the last major construction activity was the removal of a temporary concrete plug (bulkhead) and lining that tunnel section to bring the overall tunnel and gates system online before Dec. 31, 2017.This article focuses on the installation, testing and commissioning of the high head wheel gates. Live tunnel connection details to TARP Mainstream Tunnel were addressed in a previous paper submitted at the World Tunneling Conference in 2016."

Mar 1, 2019

By R. Hogg

A standard procedure for determining size-specific gravity distributions of fine coal (including the -400 mesh fractions) by sieving and centrifugal sink-float separation is described. The significance of using a centrifugal sink-float technique and the effect of the magnitude of the centrifugal force on the separation of fine coal are confirmed in the present study. The relative merits of cumulative versus incremental sink-float are discussed. The procedure is evaluated quantitatively using data obtained for the products of froth flotation of -100 mesh coal.

Jan 1, 1994

By R. Srikanth

Dust control in high production longwalls is a major problem requiring, among other things, careful attention to the design of operating practices, and ventilation schemes. Several studies have shown that the shearer is the major source of dust on a longwall face. Support movement has not been regarded as a major source of dust in U.S. longwalls; yet under certain conditions, 31 percent of the shearer operator&apos;s dust exposure can be due to support movement. Several methods have been developed for the control of shield-generated dust. Yet the need for better methods is apparent. In this paper, the amount of airborne respirable dust generated per shield move is estimated from specially designed experiments on longwall faces. A total of ten experiments were conducted in five longwall faces in four different mines. Each experiment involved one face visit and lasted three to six hours. The contribution of shield movement to the airborne respirable dust concentration immediately downwind of the shield moved, varied between 0.12 and 1. 75 mg/m3 in the five longwall faces. The mass of airborne respirable dust generated by shield movement was found to vary between 39 and 386 milligrams per shield move. The results from this study reveal that control of dust from longwall shields requires a combination of approaches involving alternative operating practices, reducing shield dust generation rate, increasing face air flow, and decreasing personnel exposure.

Jan 1, 1994

By D. G. Hartley

The major copper loss at Mount Lyell is in the coarsest particles presented to flotation. An analysis of data collected from the five primary and six secondary ball mill circuits showed that grinding was limited by low breakage rates in secondary mills, possibly due to oversize balls. For 5 months, the make-up ball size for one secondary mill was reduced from 50 to 30 mm. Frequent steady-state tests indicated that overall average breakage rates could be increased by about 70% using smaller balls. A mathematical simulation of the whole circuit with increased breakage rates showed that the resultant finer grind was likely to improve copper recoveries by about 22.

Jan 1, 1981

By Emily Sarver, Cigdem Keles, Jonathan Gonzalez, Nishan Pokhrel, Lizeth Jaramillo

This paper presents a case study of respirable dust characterization in a thin-seam coal mine in southern West Virginia. Samples were collected in various locations within the mine and analyzed using scanning electron microscopy with energy-dispersive X-ray (SEM-EDX), thermogravimetric analysis (TGA), and Fourier transform-infrared (FT-IR) spectroscopy. The study found high non-carbonate mineral content, particularly aluminosilicates and silica, in the dust. The results indicate that fine aluminosilicate particles may interfere with SEM-EDX analysis, leading to an underestimation of coal content. The findings highlight the importance of using multiple analytical methods to accurately characterize respirable coal mine dust.

May 5, 2022

By Vas P. Srinivasa

This paper examines the role of the heavy media separator in the mineral industry. Procedures used in selecting the separating vessel, developing the process flowsheet, and designing a heavy media circuit are discussed. For comparative purposes, the capital investment and operating costs of different types of operation are included.

Jan 1, 1981

By J. R. Patts, J. P. Rider, J. A. Organiscak, A. B. Cecala

"NIOSH recently completed a 15-month study at an underground limestone mine crusher booth which evaluated three research parameters: (1) the effectiveness of a single-filter filtration and pressurization system for improving the air quality inside the operator booth, (2) comparing the effectiveness of ? > 99 and ? > 95 experimental prototype filters in the system, and (3) evaluating the use of three different pressure monitoring devices to determine the performance of the filtration and pressurization system over time. The protection factor was quantified monthly using particle counters in the respirable dust range (0.3–10 µm), and gravimetric dust samples were gathered at the beginning and end of the overall study. Under static conditions and after outlier removal, the single-filter filtration unit installed offered a protection factor between 8 and 216, depending on the filter type and loading condition. The particle counting analysis shows that the ? > 95 filter offers a protection factor greater than 4-times that of the ? > 99 filter when evaluated over 60 minutes. The booth pressure monitors provided data that proved to be a valid indicator of system performance over time. INTRODUCTION Designed and installed correctly, enclosed cabs, operator booths and control rooms offer mine workers protection from physical hazards, such as flying rock, debris, and noise, as well as a more comfortable environment in regards to temperature and humidity [1]. But while it may be easier to quantify whether the A/C unit is working (measuring the temperature) or observe whether the cab offers protection from flying debris, it can be somewhat more difficult to quantify its performance in reducing respirable dust hazards. For over 15 years, NIOSH has been conducting applied research to improve the air quality inside of enclosed cabs of mobile equipment [2-5]. This work has led to the identification and mathematical modeling of enclosed cab filtration systems [6]. The same principles that govern the performance of filtration systems on mobile equipment are applicable to stationary enclosures such as operator booths and control rooms [1, 7]. Stationary enclosures are similar to enclosed cabs; however, the volume of the work area can be significantly larger. In addition, workers who perform their duties in stationary enclosures tend to stay within the room for a greater percentage of the day, as opposed to workers on mobile equipment who may enter and exit frequently. Structural integrity can be easier to maintain as well, as there is typically less vibration and stress placed on these compartments as compared to mobile equipment. In addition to offering protection from dust and flying debris, enclosures must ensure that workers have a healthy supply of fresh air to avoid elevated levels of CO2, which are known to cause headache and dizziness, impairing cognitive function. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) states that enclosures should have no more than 1,100 ppm of CO2 when outside levels are 400 ppm [8]. In addition, the American Society of Agricultural and Biological Engineering (ASABE) recommends a minimum airflow for enclosed cabs of at least 42.5 m3/hr (25.0 cfm) per person [9] to ensure an acceptable level of CO2."

Jan 1, 2017

By M. Fofana

The use of a laboratory-scale magnetic fluid-based separator for coal separations was examined. A Frantz laboratory magnetic separator was modified by fabricating new pole pieces of the appropriate geometry to provide the proper magnetic field gradients. Two separation chambers, which were constructed out of Plexiglas, were designed to fit between the pole pieces. A commercially available, water-based, ferro-magnetic fluid was used as the separating medium. The separating density was changed by varying the intensity of the electromagnet. Both batch and continuous separations were made using 0.59x0.50 and 0.18x0.15 mm coal. The results are compared to those obtained using organic liquids.

Jan 1, 1996

By J. P. Rider, T. W. Beck, J. A. Organiscak

"The National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Mining Research Division (PMRD) has recently developed a series of models utilizing computational fluid dynamics (CFD) to study gas distribution around a continuous mining machine (CM) with various fan-powered flooded bed scrubber discharge configurations in an exhaust curtain working face. CFD models utilizing species transport model without reactions in FLUENT were constructed to evaluate the redirection of scrubber discharge toward the mining face rather than behind the return curtain. The study illustrates the gas distribution in the slab (second) cut. The following scenarios are considered in this study: 100% of the discharge redirected back towards the face on the off-curtain side of the continuous miner; 100% of the discharge redirected back towards the face, but divided equally to both sides of the machine; and 15% of the discharge redirected toward the face on the off-curtain side of the machine, with 85% directed into the return. These models were compared to a model with a conventional scrubber discharge where air is directed away from the face into the return. The models were validated based on experimental data and accurately predicted sulfur hexafluoride (SF6) gas levels at four gas monitoring locations. One additional prediction model was simulated to consider a different scrubber discharge angle for the 100% redirected, equally divided case. This paper describes the validation of the models based on experimental data and the gas distribution results of the CFD models. INTRODUCTION To control methane gas and dust concentrations on continuous mining operations, it is important to provide sufficient quantity of fresh air from the end of tubing or curtain to the active face. In this region, operating machine-mounted water sprays and fan-powered, flooded bed scrubbers can significantly increase the amount of airflow reaching the face [1-3]. However, when an entry is large, especially in higher coal seams, the water spray configuration and the scrubber capacity may not be adequate to maintain sufficient forward airflow to confine the dust cloud to the face. Dust can roll back toward the machine operator as a result [4]. Currently, several coal mines having negligible gas emissions in higher coal seams (2.4 to 3.0 m [8 to 10ft.] thick) with exhaust tubing systems redirect the scrubber discharge back towards the face in an effort to improve dust collection. NIOSH studied the redirected scrubber exhaust techniques for dust and gas control in a full scale CM gallery to assess its potential for industry-wide application [5]. For a CM face, previous studies have concluded that the behavior of gas and respirable dust is a complex process. The distribution/dispersion and transport of gas and respirable dust after they are liberated at the face are governed mainly by their mass properties, the movement pattern of the ventilation air, and interactions with the mining machine and water droplets created by the external water spray systems used for dust control [6-10]. To understand these behaviors in a complex CM environment and to evaluate the effectiveness of various control techniques, numerical modeling has become a necessary supplement to laboratory experiments and field studies."

Jan 1, 2017

By M. S. Klima, M. Fofana

The use of a laboratory-scale magnetic fluid-based separator for coal separations was examined. A Frantz laboratory magnetic separator was modified by fabricating new pole pieces of the appropriate geometry to provide the proper magnetic field gradients. Two separation chambers, which were constructed of Plexiglas, were designed to fit between the pole pieces. A commercially available, water-based, ferromagnetic fluid was used as the separating medium. The separating density was changed by varying the current intensity of the electromagnet coil. Both batch and continuous separations were made using 0.59 x 0.50-mm and 0.18 x 0. 15-mm coal. The results are compared to those obtained using organic liquids.

Jan 1, 1998

By G. Bylapudi, A. Spearing, J. Weber, K. Mondal

U.S. National Institute for Occupational Safety and Health (NIOSH) reports state that about 100 million rock anchors are installed annually in U.S. coal mines (Tadolini et al., 2006), and rock-related safety remains an issue. The majority of these coal mines have conditions that make corrosion probable in the longer term. Despite this, very little research has been performed to analyze corrosion and its effects on rock anchors in coal mines. To further evaluate the effects of corrosive conditions in coal mines on rock anchors, three different experiments were conducted during an initial Illinois Clean Coal Institute (ICCI)-funded project from 2008-2009. The results of these experiments were further studied, with additional tests, in the extended ICCI-funded project during 2011-2012. The experiments were destructive testing, electrochemical testing (potentiodynamic polarization tests) and open circuit potential (OCP) testing, conducted in order to study corrosion in environments similar to those found in Illinois coal mines with a focus on major rock anchor types typically installed underground. Destructive test results showed highest reduction in peak strength at higher pH and temperature. From the destructive test results, epoxy-coated and galvanized anchors were observed to be better when compared to uncoated. Electrochemical testing was performed to find the corrosion potential and corrosion rates of ASTM A615 steel grades 40, 60 and 75 in four different solutions of varying sulfur content at ambient temperature. The effect of temperature and pH levels on corrosion potential and corrosion rates of steel grades were also evaluated with additional electrochemical testing, where an increase in temperature with all other constant conditions caused a significant increase in the corrosion penetration rate. OCP data indicated higher corrosion potential values (-mV) for rock anchors in wet areas, when compared to those from the dry areas. OCP test results of the rock anchors from the laboratory corrosion chambers were similar to those measured in the sampled coal mines.

Jan 1, 2013