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By L. W. Kelly

The purpose of this paper is to describe several methods that have been employed in successfully recovering roof bolts in Indiana, Illinois, and western Kentucky coal mines, the States where successful roof-bolt recovery was started. As far as is known, the first bolts were recovered in a mine in western Kentucky in January or February 1951. In April 1951 a meeting was held at that mine to discuss the recovery of roof bolts. The meeting was attended by A. D. Sisk, former Chief, Kentucky Department of Mines and Minerals; and L. W. Kelly, Federal Bureau of Mines; and officials of the coal company. Inasmuch as roof bolting was in its infancy, the thinking regarding roof bolts at that time was on the problem of getting them in, not getting them out; consequently, the thought of recovering them was revolutionary. The subject was discussed at length from all angles, and it was finally agreed that, if certain safeguards were taken, no agency represented at the meeting would oppose the practice. That this decision was sound has been proved, as thou-sands of bolts have been recovered in the Middle West without a lost-time accident. Recovering roof bolts is a simple operation; consequently, no complicated equipment had to be designed or built for this purpose. However, about 5 years ago, officials of the Traux-Traer Coal Co. conceived the idea and constructed a mechanical device for recovering bolts that has been very successful and has been copied widely in this area. This device will be discussed in detail in part II of this paper.

Jan 1, 1958

By N. P. Gallagher

The U.S. Bureau of Mines investigated a hydrothermal sulfidation (HTS) and chloride leaching procedure to recover lead and silver from plumbojarosite. The plumbojarosite, generated during pressure-oxidative leaching of zinc concentrate in a commercial operation, contained, in percent, 25.4 Pb, 18.8 Fe, 1.4 Zn, 29.5 sulfate (S042.), 3.2 elemental sulfur (SO), 13.4 total S, and 7.4 tr oz/st Ag. The HTS was conducted in an autoclave and converted the plumbojarosite into amorphous iron oxide and liberated the Pb and Ag as sulfides (S2) The best operating conditions were 50 g of plumbojarosite and 7 pct So (2.04 g So added) in 500 mL of 2.0-mol/L NH3 at 150° C for 1 h. The sulfidation product contained, in percent, 37 Pb, 28 Fe, 2 S042., 7 total S, and 11.2 tr oz/st Ag. Flotation of the sulfidation product was conducted at pH 3 with 15-pct pulp density and 2.4lb/st of isopropyl xanthate as collector. The flotation concentrate contained 43 pct Pb, 25 pct Fe, and 13 tr oz/st Ag. FeCl3 leaching of the sulfidation product in a resin kettle extracted 98 pct Pb and 97 pct Ag from the sulfidation product, and HCI-Oz leaching in a shaker glass bottle extracted 99 pct Pb and 98 pct Ag. Both leach residues met the Environmental Protection Agency's Toxicity Characteristic Leaching Procedure (EPA-TCLP) standards for nonhazardous wastes. The HTS and chloride leaching procedure is a potentially effective method for detoxification of plumbojarosite-bearing residue from the zinc pressure-leaching circuit.

Jan 1, 1989

By Dennis A. Long

"The size of off-highway trucks has increased substantially over the last decade, bringing about a radical change in truck maintenance practices and procedures. As a result, surface mine maintenance mechanics today are faced with the increased hazards of working with larger and heavier tools and components and doing repairs at greater heights, thereby exposing them to a high potential for serious injury or death. Not surprisingly, the number of accidents involving truck maintenance mechanics is significantly increasing.The Bureau of Mines has assessed the haulage truck maintenance safety problem, analyzing maintenance-accident data over the 7-yr period, 1978- 84, in terms of personnel, job activities, truck components and systems, tools involved, and truck design. This assessment, based on the review and interpretation of 1,225 haulage truck maintenance accident reports, identified major factors contributing to these accidents. Overall, young, inexperienced workers are involved in most accidents. A typical maintenance accident involves a male mechanic under 33 yr old, with less than 5 yr job experience. INTRODUCTIONOver the past decade, surface mine maintenance and repair operations have changed radically. The number of maintenance personnel has grown along with the hazards of working with larger and heavier components at greater heights and with larger and heavier tools. Furthermore, transfer of skills from over-the-road vehicle mechanics is not as feasible as it once was, because of the ever increasing size of mining equipment and the complexity of its design. In short, surf ace mine equipment maintenance and repair has become increasingly sophisticated as well as labor intensive, necessitating further research and evaluation in terms of both safety and efficiency (1, 7-8) 2"

Jan 1, 1986

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

A computer model of an existing mine ventilation system can be executed using data developed from ventilation survey results. This model can then be used to analyze and evaluate proposed modifications to the system. The acquisition of field measurements during a ventilation survey and the corresponding development of this information into computer input data have been discussed in detail in the preceding chapters. In this chapter, the data are used in computer-oriented analysis of the mine ventilation system. The PSU/MVS was selected for use because of its advanced capabilities. MINE DESCRIPTION The mine chosen for this application is located in Western Pennsylvania. The Pittsburgh coal seam, having an average height of 5-1/4 to 6-1/2 ft, is mined under approximately 300 to 500 ft of cover. The mine preparation plant and shipping facilities are located at the seam outcrop along a river; mining has progressed from the outcrop to an area about 10 miles from the pit mouth so that there are extensive worked-out areas through which access is maintained to the current mining area. Coal haulage is by conveyor to an underground transfer point, located four miles from the pit mouth, and then by high speed rail haulage to the preparation plant. The rail haulage link is scheduled for replacement by a conveyor in the near future. Mining at the present time is limited to the room and pillar method using continuous miners. Longwall mining had been attempted in the past with only limited success; as a result, several panels originally laid out for longwall mining are currently being extracted by room and pillar work. The

Jan 1, 1977

SCOPE AND APPLICATION The rules cover the installation and use of electrical equipment in coal mines.- For generating stations, substations, lines, and equip¬ment aboveground, reference is made to existing rules covering such locations, viz, the National Electrical Code and the National Electrical Safety Code and any existing State or municipal regulations. The purpose of the rules is to set forth methods for safe electrical installation. In preparing the rules five basic measures for safe¬guarding the use of electricity in mines have been followed, viz 1. Remove the contributory causes of accidents or danger. 2. Remove from the vicinity of electrical apparatus all elements susceptible to the influence of electricity. 3. Keep the electric current where it belongs, if possible; if not, limit the area of its activity by protective devices. 4. Use a. large factor of safety in the selection, installation, and in¬ spection of equipment. 5. Have full control of the operation of electrically driven machines. Each rule that is given is proposed as necessary or helpful to the accomplishment of one or more of these measures. DEFINITIONS OF TERMS USED Alive.-See definition of " live." Approved.-The term " approved " means accepted as suitable by a competent committee, board, or organization designated by those adopting the rules. Authorized person.-The term " authorized person " means a per¬son appointed or permitted by the official designated by the State mining laws as the one in charge of the operation of the mine to carry out certain duties incident to the generation, transformation, and distribution or use of electric energy in the mine, such person be-

Jan 1, 1926

By Lloyd A. Morley, Robert Stefanko

A major difficulty encountered during the research was that nation¬al countries (almost world-wide) are in the process of revising their electrical hazard reduction standards. Their principal goal is to align their standards with the International Electrotechnical Commission (IEC) Recommendations Publication Series 79. (31-37) Additionally, CENELEC is requiring all Common Market countries to harmonize their standards. (85) However in the coal mining industry some hazard re¬duction techniques are not being accepted because some systems may not be applicable. Therefore, past literature might not directly relate a country's current feeling about explosion-proof standards. An authority in the United Kingdom (which has been a leader in hazard reduction mainly through work at the Safety in Mines Research Establishment) brought up an additional point. (15) He hopes that since revising British standards BS229 into BS4683, with the intention of corresponding with the IEC 79 series, the recent CENELEC harmoni¬zation process will also follow IEC. (8, 9, 10) The past trend in other major Common Market countries prior to CENELEC's requirement results in the authors' speculation that the standards will be pattern¬ed after the IEC Publications. (5,17,60,84,102) Several letters were sent to the East Block countries but, disa¬ppointingly, replies were dispatched only from the USSR and Poland. Recent Polish standards (1973) were received, and a very close match to the IEC Publications has been noted. (76,77) Because of their economic community, it is extremely logical to assume that the East Block stand¬ards are therefore in concurrence with the IEC. Japanese specifications also appear to be compatible with the IEC Recommendations. (42,43)

Jan 1, 1974

By Deno M. Pappas, Christopher Mark, Eric R. Bauer

During 1998-99, groundfall incidents resulted in 27 fatalities and were responsible for over 70% of all deaths in U.S. underground coal mines. To obtain a better understanding of where and why these incidents occurred, a comprehensive analysis of ground fall injuries and fatalities was conducted. The first portion of the study examined various factors associated with roof and rib fall injuries and reportable roof fall noninjuries that occurred during 1995-98. The study found that the room-and-pillar mining method has twice the groundfall incident rate than the longwall method. Mine locations with high groundfall rates seem to correlate to regions where there is a higher concentration of problematic coalbeds. For example, the Illinois Basin has very high groundfall rates, which can be traced back to several key coalbeds-Kentucky No. 13, Herrin/No. 6/Kentucky No. 11, and Springfield No. 5/Kentucky No. 9. High rib fall rates were found in mines located in thick seams. Groundfall rates were found to be 30% to 40% higher during the months of July through September, possibly due to high humidity that may cause the shale mine roof to deteriorate. The second part of the study examined the root causes of failure by reviewing all groundfall fatality reports for 1996-99. Primary and secondary hazard factors were assigned to each groundfall incident. The primaryf actors resulting in these groundfall fatalities were pillar extraction, traveling under unsupported roof, skin failure, construction, longwall faces, intersections, and geologic discontinuities. Defining prominent ground control incident trends and hazards will identify areas where additional study is needed and where innovative solutions need to be developed to reduce these severe occupational hazards.

Jan 10, 2000

By Douglas D. Reynolds, Tarek Deeb, Qunli Liu

Landmines are a great threat to military vehicles and their occupants. Mine blasts can completely destroy vehicles and kill all the occupants or disable the vehicle and leave the occupants severely injured. Injuries sustained during a landmine blast come from fragmentation that enters the vehicle through a hull breach, hot gasses expanding through the vehicle, or shock created from the extreme pressure of the blast (Lafrance, L.P. 1998). Mitigating the high acceleration experienced by the occupants during survivable mine blasts is the focus of the research being addressed in this paper. Method The objective of the project reported in this paper was to prove the feasibility that pneumatic seat technologies that employ light-weight, foam-filled, inflatable air bladder seats and seat backs can be used to protect the crews of lightweight combat vehicles against the detrimental and injurious effects of mine blasts. This protection includes reducing the shock energy experienced by seated vehicle crews during mine blast initiation and at vehicle slam-down to below potentially injurious levels. Figure 1 shows a schematic representation of the proposed lightweight, foam-filled, inflatable mine blast attenuating seat. It will consist of specially designed interconnected seat and seat back lightweight, foam-filed, air bladders that are supported by a rigid frame. [ ] Results Air gun tests and finite element analyses were conducted to determine the effectiveness of a light-weight, foam-filled, inflatable air bladder seat shock isolation system in isolating a vehicle occupant from the injurious effects of a mine blast. Figures 2 through 5 show analytical and experimental results associated with a 65.8 kg mass resting on an inflatable air bladder that is exposed to a shock input.

Jan 6, 2006

By Barbara Fotta, Lynn Rethi

Within the Mine Safety and Health Administration's (MSHA's) classification of metallnonmetal (MAM) mining, the number of independent contractor' employees has increased significantly in recent years. In 1985 independent contractor employee hours reported to MSHA accounted for 4.5% of all M/NM mining employee hours (excluding office workers); by 1994 that proportion had doubled to 9.0%. As a result, these workers now account for an increasingly significant proportion of fatal and nonfatal mining accidents. According to MSHA's statistics, annually computed fatality incidence rates (the number of fatalities per 200,000 employee hours) for independent contractors working in M/NM mining are consistently higher than those for operator employees. Over the five-year period from 1990 through 1994, 53 independent contractor employees were fatally injured while working on M/NM mine property (See Table 1). More than one third of these fatalities (36%) were due to accidents involving powered haulage; 21% were machinery accidents; and 11% percent were falling material accidents. Combined, these three accident classifications accounted for 68% of all independent contractor fatalities occurring on M/NM mine property during these years. Clearly, current efforts to increase the safety of the mining workforce must also address the safety of the independent contractor employee. This report is a preliminary attempt to identify trends in the employment and safety of independent contractor workers by identifying which segments of M/NM mining are experiencing the greatest increases in the number of independent contractor employees and by examining changes in the rates and types of accidents in which these employees are involved. The employment and accident data used in this report were obtained from the MSHA database. [ ]

By J. L. Ellenberger

The National Institute for Occupational Safety and Health (NIOSH) has continued the research role of the former US Bureau of Mines (USBM) to engineer techniques that will reduce the hazards in the mining workplace associated with coal bumps. Recent research focused on a longwall coal mine in Utah with overburden greater than 750 m (2,500 ft) containing several massive sandstone units. The primary field instrumentation at the site was three-dimensional, full waveform, autonomous microseismic arrays placed underground and on the surface in order to surround the active multi-panel longwall district. The purpose of these arrays was to help investigate the strata mechanics associated with the redistribution of stress and the associated gob formation of the longwall. Specifically, the seismic arrays were used to determine the timing and location of the failure in the strata surrounding the active mining. Overall 13,000 seismic events were detected and located with on-site processing during the five months the panel was being mined, including a magnitude (ML) 4.2 event. Of these, a smaller subset of 5,000 well-located events was selected during post-processing to form a consistent data set for analysis in this paper. From this data set, it was observed that the seismic events generally occurred in advance of the longwall face, both above and below the panel, consistent with failure of the strata in the forward stress abutment zone. Also, the occurrence of the ML 4.2 seismic event within 150-180 m (500-600 ft) of a deep cover longwall face with no associated bump caused a re-evaluation of the nature of the connection between seismic activity and coal bumps.

Jan 1, 2002

By John W. Buch

"INTRODUCTION The Ruhr coal basin is estimated to cover an area of more than 1,000 square miles. Here, the total thickness of the coal bearing formation (Carboniferous) is 10,500 feet, and drilling-hole have revealed 92 coal beds with a total thickness of 262 feet. 6/ Beds pitch from 0 to 90 degrees and about 70 percent of the wartime production came from beds that pitched less than 30 decrees. 5/For example at the Minisiter Stein mine, there are 24 minable coal beds ranging from 80 centimeters. (2 ft., 7 1/2 in.) to 250 centimeters (8 2 1/2 in.). The vertical thickness of the measures is 1,000 meters (3,200 ft.), and at this mine the deposits are covered with 150 meters (500 ft.) of surface wash. The cross section (fig, 1) at Fritz mine; Hoesch, A.G., Essen, Ruhr, is characteristic, The mines have been developed and worked to vertical depths of 2,000 to 2,500 feet by vertical shafts; main-level intervals are 500 to 700 feet apart. Haulage roads are straight, driven in rock, and centered as nearly as practical between property boundaries. Levels are sectionalized by driving crosscuts at right angles to the main haulage road on 800- to 900-foot centers. The roads are the main transportation arteries for the use of trolley or Diesel locomotives. A plan of the sixth main level (fig. 2) at the Bruchstrasse mine; Gelsenkirchener A.G., Bochum, illustrates main-level development and,sectionalizing with crosscuts. The cross section in figure 3 is that of the fourth crosscut west at the same mine."

Oct 1, 1946

By Eric G. Zahl, John P. Dunford, Hamid Maleki

Coal bumps are influenced by geologic conditions, the geometric design of coal mine excavations, and the sequence and rate of extraction. Researchers from private industry and government agencies around the world have studied mechanisms of violent failure and have identified individual factors that contribute to coal bumps. To develop predictive tools for assessing coal bump potential, the authors initiated a comprehensive study using information from 25 case studies undertaken in U.S. mines. Multiple linear regression and numerical modeling analyses of geological and mining conditions were used to identify the most significant factors contributing to stress bumps in coal mines. Twenty-five factors were considered initially, including mechanical properties of strata, stress fields, face and pillar factors of safety, joint spacings, mining methods, and stress gradients. In situ strength was estimated in 12 coal seams where uniaxial compressive strength exceeded 2,000 psi. Allowances were made for favorable local yielding characteristics of mine roof and floor in reducing damage severity. Pillar and face factors of safety were calculated using displacement-discontinuity methods for specific geometries. This work identified the most important variables contributing to coal bumps. These are (1) mechanical properties of strata, including local yield characteristics of a mine roof and floor, (2) gate pillar factors of safety, (3) roof beam thickness, joint spacing, and stiffness characteristics, which influence released energy,(4) stress gradients associated with the approach of mining to areas of higher stress concentrations, and (5) the mining method. By combining the strength of both analytical and statistical methods, new capabilities were developed for predicting coal bump potential and for building confidence intervals on expected damage.

Jan 5, 1999

By R. V. Ramani, B. K. Belle

The increased effectiveness of a two-phase spray system (TPSS) over a single-phase spray system (SPSS) for dust suppression is reported in several laboratory studies. The dust collection efficiencies of SPSS and TPSS were studied in a model experimental longwall gallery facility at Pittsburgh Research Laboratory at NIOSH (USA). The experimental design consisted of two factors: pressure, and airflow. Each factor had three levels. SPSS experiments were conducted at only one pressure (1035 kPa) which is nearly 1.5 times higher than the highest air and water pressure for TPSS experiments. The results of the study are presented in this paper. While it appears that TPSS performed better than SPSS, the data is not sufficiently conclusive on this aspect. The differing spray characteristics of the chosen TPSS and SPSS nozzles did not allow a direct comparison of the two systems. In the TPSS arrangement, considerably greater turbulence in airflow is created around the shearer; it is likely that at least in the immediate vicinity of the tailgate drum, there is a roll back of the dust/mist cloud into the walkway. Therefore, positioning of the personnel upwind of the tailgate drum is necessary to avoid high dust exposures. The rate of decrease in concentration with TPSS is higher than that with SPSS. This may be due to the greater atomization of the water. The test set-up did not allow the study of conditions when coal is cut from tail to head where the potential for personal exposure is high. Changes in the experimental design are necessary to overcome some of the reasons expected for the inconclusive results.

By J. Ankrum, T. Xia1, D. Wilder, K. Spratt

The human lumbar spine is inherently an unstable structure and requires sophisticated neuromuscular control to maintain its stability and for performing physical tasks. As a consequence, it is important to understand the potential health effects on human operators of mechanical stimuli such as shock and vibration.1 Impact applied to a vehicle operator combines the risk of sudden, unexpected load with the mechanical stress of the seated posture.2 Because many work environments contain the potential for multiple, unexpected impacts, it is important to understand how the trunk muscles respond to complex conditions. We believe the results have implications for isolation design and standards development. Methods Muscle activity was recorded during simple and complex impacts, applied randomly and without warning, while subjects sat on an air-suspension truck seat located on a man-rated 6-DOF motion platform (Rexroth-Hydraudyne). Simple (single) impacts consisted of 100 ms quarter-sine jolts in the side-to-side (L and R) and vertical upward (V) directions with peak amplitude at 0.4 g. Complex impacts consisted of combinations of two simple (single) impacts in sequence (LV, RV, VL, VR), separated by 100 ms. Twelve right-handed males (23.7 ± 7.8 years old) were tested without a blindfold under 2 posture conditions (supported while leaning back and unsupported, sitting upright) and 2 seat suspension conditions (present or absent). Each type of impact was repeated three times under each posture and suspension condition, resulting in 84 impacts in total. Surface EMG signals from the left and right erector spinae (ES), rectus abdominis (AR), external obliques (EO) and internal obliques (IO) were recorded and transformed to 25ms RMS values. The response time, defined as the time the muscle activity exceeded the mean + 2 STD of the pre-impact resting period, peak response amplitude, and time were then derived. A mixed-model repeated measures analysis of variance was used to evaluate statistical significance, where type I error rate was set at .05. Results One question we asked of these data was whether there were differences in responses related to simple single strike impacts (L, R, or V) and complex, double-strike impacts (LV, RV, VL, VR). There are 21 possible combinations of comparisons of simple and complex impacts to each other. The differences found are listed in Table 1.

Jan 6, 2006

By R. Hogg, T. F. Dumm

"It is generally agreed that dust characteristics play a role in the development of Coal Workers' Pneumoconiosis (CWP). Unfortunately, there is a serious lack of information on what the characteristics of mine dust actually are and how they vary among different mining regions, coal seams, etc. This paucity of data can generally be attributed to the serious problems encountered in collecting sufficiently large quantities of dust for conventional analytical procedures.Personal samplers are widely used in coal mines for regulatory and enforcement purposes. Generally, these provide information only on the total (respirable) dust loading in the mine atmosphere and on the mineral matter (primarily quartz) content of the respirable dust. A procedure has been developed by which samples collected with a slightly modified personal sampler can be analyzed for particle size distribution, total mineral matter content and elemental composition, in addition to the standard mass and quartz measurements. These analyses could readily be performed on a routine basis. Shape analysis by Scanning Electron Microscope (SEM) could easily be included if appropriate shape criteria are established. Extension of the procedure to include the determination of complete size/specific gravity (composition) distributions is quite straightforward provided sufficiently large samples (at least 10 mg) can be collected. Typical sample sizes for a personal sampler carried by a miner for one shift range from about 0.5 to 2 mg.The basic procedure was developed and evaluated using synthetic mine dust prepared in the laboratory. Field tests in three working mines in Pennsylvania and West Virginia have confirmed the applicability of the approach to the real world. Particle size distribution measurements on mine dust collected in the modified personal sampler were found to agree closely with the results of simultaneous in situ measurements obtained using cascade impactors."

Mar 1, 1989

By Joseph J. Wallace, Lloyd Williams, D. A. Reynolds, James J. Dowd, R. F. Abemethy

"SUMMARY AND CONCLUSIONS1. The investigation shows that the most important beds in Allegany County, from the standpoint of known recoverable reserves are: Lower Bakerstown, Upper Freeport, Upper Bakerstown, Upper Kittraing - less important beds are: Sewickley, Waynesburg, Pittsburgh, and Barton. 2. Known measured and indicated reserves in all beds, based on a minimum thickness of 14 inches and 1,800 tons per acre-foot of coal in place, are estimated to be 556 million short tons, as of January 1, 1951. Of this total, 304 million short tons is in beds 23 inches and more thick. Areas in each bed were omitted from the estimate because available data relative to the bed characteristics are too meager to permit making an estimate that conforms with the definitions of measured and indicated coal adopted for this study. Should future drilling or development prove reserves in these areas, such reserves should be added to the total eat ted reserves.3. Recoverable reserves of coal have been estimated in beds 28 inches and more thick. This thickness is about the minimum now being mined by hand-loading onto conveyors in the Appalachian region. The weighted average recovery for all beds in Allegany County, as determined by this investigation, is 49.8 percent. This percentage is based on the total thickness of coal (less partings 3/8 inch or more thick) in the bed rather than on the thickness of the coal mined. Based on the weighted average percent recovery for all beds in Allegany County, the recoverable reserves are estimated to be 152 million short tons as of January 1, 1951.4. The Allegany County coals are low-volatile bituminous in rank.5. The Allegany County coals are strongly coking."

May 1, 1953

By Ernest R. Rodriguez, Allen D. Look

"INTRODUCTION The underground mine of the Miami Copper Co. has operated since 1927 without a fatality from blasting or the handling of explosives. To improve safety and efficiency, electrical blasting has been used exclusively since 1934. During the period January 1, 1934, to December 31, 1948, inclusive, over 4,000 tons of explosives were used to produce 60,925,071 tons of ore with 896,760 feet of development footage and 2,591,788 square feet of undercut area.The purpose of this paper is to recount the company's precautions to insure safe handling of explosives at this operation, where safety involves careful planning rather than ""trial and error.""GENERAL INFORMATIONThe Miami Copper Co. operates on underground mine in a large, low-grade, Porphyry copper deposit near Miami, Ariz. The deposit contains numerous fractures and planes of weakness, which contribute to ease of working the ore bodies by the block-caving method of mining.An individual stope-caving method is used with stoles 150 feet by 200 to 300 feet and 30- to 50-foot pillars between stapes. After the stope is undercut, the ore is drawn through the draw raises on the grizzly level, and thence through the transfer raises to the ore chutes on the haulage level.Access to the mine is by four active shafts, three of which are primarily for ventilation. No. 5 shaft is used for both hoisting and service. There are four operating levels in the mine. The elevations of the grizzly levels are governed by the contour of the bottom of the ore body and therefore vary in different locations in, the mine.Grizzly levels are on the 850, 900, and 975 levels. The 1,000 level is the haulage level. This mine operates in very low-grade ore and requires economical handling of large tonnages safely and efficiently."

May 1, 1950

By Isaac A. Zlochower

This paper presents data on the limiting (minimum) oxygen concentration (LOC), in the presence of added N2, of methane (CH4), propane (C3H8), ethylene (C2H4), carbon monoxide (CO), and hydrogen (H2), and some of their binary mixtures. It also addresses the issue of the flammable concentration (flammability) limits of these pure gases in air. The study is based on spark ignited explosions in large, spherical laboratory vessels (120-L and 20-L) using a 7% pressure-rise criterion for explosion propagation. The results of the study are compared with the older values which used long flammability tubes with a diameter >5 cm together with visual evidence of substantial upward propagation. They are also compared to results reported recently using a 12-L spherical flask with a visual flame propagation criterion. Finally, they are compared to results reported in Europe using more modest flammability criteria and smaller chambers. The findings reported here show excellent agreement between the 120-L and 12-L results, good agreement with the 20-L results, and reasonable agreement with the earlier flammability tube values for the lower flammability limits. They disagree, however, with the more conservative European values. These results and those from the 12-L experiments also feature lower LOCs than are given by traditional flammability tubes. A model for the LOCs of such fuel mixtures based on the Le Chatelier mixture rule for lower flammable limits is seen to reasonably fit the observed results on binary mixtures and can accommodate more complex mixtures as well. One such set of ternary mixtures containing CH4 and 1:1 CO:H2 is well fitted by the model.

Jan 1, 2009

"There is considerable evidence that all mine dusts do not present the same health hazard. Rank of coal and composition, especially silica content of the mine dust, shape, and surface charge are risk factors that affect the incidence and severity of CWP. Current efforts of Center researchers involve characterization of:•,size/shape/composition•,surface and functional groups•,particle interactions.Work is underway to prepare and characterize respirable coal dust samples, and to develop and evaluate techniques and procedures for the characterization of respirable dust. A suite of standard samples including anthracite, medium volatile and high volatile bituminous coals, quartz, clay, and rock dust have been prepared and thoroughly characterized with respect to the distributions of particle size and compositions. A comparison of the morphology of the standard dust particles with similar particles collected in an underground coal mine is given in Figure 43. Samples of these characterized (Standard) dusts have been distributed among various research groups associated with the Center.The aerodynamic diameter of a particle is a particularly important characteristic since this parameter determines the point of deposition in the human respiratory tract. A 3-dimensional numerical model for theoretically determining the equivalent aerodynamic diameter of irregular shaped particles has been developed and used to analyze coal dust particles and a particle shadowing technique has been developed for .experimental 3-dimensional shape analysis (Figure 44). In the theoretical technique, the equivalent aerodynamic diameter of the particle is numerically determined from computation of the fluid drag on the particle. This allows the aerodynamic diameter of any regular or irregular shaped particle to be determined as a function of the particle's orientation or as an average over all particle orientations. The technique is quite accurate in that the aerodynamic diameter of several coal dust particles have been numerically determined to be within 5% of experimentally measured values."

Nov 1, 1988

By M. R. Geer, H. F. Yancey

"INTRODUCTION The increased use of coal as pulverized fuel has focused attention on the grindability of coal and on the necessity of evaluating this property by a method suitable for use in the usual coal-testing laboratory. Without some knowledge of how various coals behave in the grinding operation, that is, how their use affects mill capacity and power requirements, the selection of coals for pulverized-fuel plants cannot be made on the same critical basis used in selecting coals for other types of burning equipment. The grindability of a coal, serves principally as an indication of the mill capacity attainable in grinding it - not as a direct index of the total cost of grinding. Although the grindability of coal may play a minor role at some plants, it is a decidedly important factor where pulverizer capacity limits the ability to carry high loads.Purpose Standardized tests for determining the grindability of coal are relatively new, so that the information now available on the grindability of various coals is limited in comparison, for example, with that available on proximate analyses. Published information is restricted to determinations on many important Eastern coals by the Fuel Engineering Co. of New York, 4/ a bulletin giving the results of numerous tests by the Babcock and Wilcox Co. 5/, and a comprehensive report on. Alabama coals by the Bureau of Mines. 6/This report presents the results of grindability tests of 34 samples of coals from Illinois, Kentucky, Pennsylvania, Utah, Virginia, Washington, West Virginia, and British Columbia at the Northwest Experiment Station of the Bureau of Mines, Seattle, Wash., in cooperation with the College of Mines of the University of Washington. In the future, as the laboratories of the Bureau make grindalility tests of other coals, additional reports will be issued."

Jul 1, 1938