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By Janet Briggs, Michael Vertes, J. F. Shirley, R. E. Cutherbertson, Alexander Sutulov, J. D. Vincent

Molybdenum, the 42nd element in the periodic table, is now a very important metal in industry of the United States and the world. Chemically, it is a very complex element having valences of 0, +2, +3, +4, +5, and +6, and can exist as a mixture of these valences in many compounds. It was discovered and separated by Scheele in 1778. At the present time, molybdenite is the only important commercial source of molybdenum. Molybdenum occurs in some 12-14 different recognized minerals, but practically all of the production is molybde¬nite. As late as 1915, it was considered a rare metal. Germany made extensive use of it during the first world war, which resulted in the establishment of a molybdenum industry in the United States at Cli¬max, Colo., in 1917. It was not until the mid-1920s when its introduc¬tion to steelmaking developed for the US automobile industry that the metal gained important acceptance. The first notable example was the Willis-Saint Claire automobile introduced in 1921 by C. Harold Willis, formerly chief metallurgist for Ford Motor Co. Molybdenum has also been produced in the US from wulfenite (PbMoO4) from Arizona and Nevada, and a small amount of molyb¬denite was produced up to the early 1970s as a coproduct from two molybdenum-bismuth mines in Quebec, Canada. The first byproduct production of molybdenite from a copper con¬centrating operation was achieved at Cananea, Sonora, Mexico, and was followed shortly by the Utah division of Kennecott Copper Co. in the mid-1930s. This section of the Handbook is divided into four main subdivi¬sions: Chapter 2, which deals with the concentration and recovery of molybdenite from primary molybdenum ores; Chapter 3, which deals with the recovery and separation of molybdenite as a byproduct from copper production; Chapter 4, which deals with the conversion practices employed for converting molybdenite to the oxide or metal form; and Chapter 5, which covers the uses of molybdenum in steel¬making, chemicals, pigments, lubrication, catalysts, etc. The Free World molybdenum production, for the past eight years from all sources, is shown in Table 1. 2. Primary Molybdenite Ores General In 1978 there were four primary molybdenite recovery plants in operation: Climax, Endako, Quests, and Henderson. For over half a century the Climax mine has been by far the largest and most important source of molybdenum in the world. During the early 1970s a few primary molybdenite mines in British Columbia were shut down due to adverse economical conditions. The largest of these was British Columbia Molybdenum, formerly owned by Kennecott Copper Corp. The Climax plant and operations are described in detail and the opera¬tions of the other plants are summarized following a general discussion of recovering molybdenite from primarily molybdenite ores. Recovery of molybdenite as a byproduct will be taken up in Chapter 3. Geology Molybdenite production from mines in which it is the sole or preponderantly important mineral is confined to ore bodies in granites or igneous-type rocks or pegmatite dikes. More than one state of mineralization is sometimes present as at Climax, York, Hardy, and Questa. In the case of Climax, important byproduct recovery of tung¬sten, tin, pyrite, and monazite is also attained. The molybdenite is commonly disseminated very finely in the siliceous granitic gangue but does occur in stringers and blebs in silicified mineral solution channels. Treatment of Primary Molybdenum Ores All primary molybdenum ores are low in molybdenite, the content ranging from less than 0.20% MoS2 to a high of about 0.40% MoS2. A high resistance to grinding is a common ore characteristic combined with a habit of very fine dissemination of molybdenite in the siliceous portion of the ore. Because of low MoS2 content, high hardness, and fine dissemination of molybdenite in primary ores, it has been necessary to develop a special mill treatment which yields an accepta¬ble recovery at a reasonably low milling cost. Essentially, the treatment consists of intensive rougher flotation at a relatively coarse grind with production of a low grade rougher froth containing a substantial percentage of the molybdenite in the form of low grade middling particles, followed with multistage regrinding to liberate the locked molybdenite and several stages of flotation cleaning to produce a finished grade concentrate. Rougher flotation on pulp ground to ap¬proximately 35 mesh is common practice, even if complete liberation of molybdenite from siliceous gangue may require regrinding to 200 mesh. The flotation of middling particles with a very low content of molybdenite in the rougher flotation step has been made possible by the application of a combination of reagents first developed at the Climax mill and used with some modification in the treatment of all primary molybdenum ores. The reagents commonly employed and their functions in flotation are:

Jan 1, 1985

By Richard L. Gordon, William A. Vogely

In this chapter, the principles that determine the procedures selected to transform minerals in the ground into usable commodities are re¬viewed.a I argue here that straightforward mod¬ification of the modern general economic theory of production suffices to meet the practical needs of a mineral economist. Therefore, the chapter is largely a review of the general economic theory of production to which is added discussion of the special prob¬lems of the exhaustibility of mineral resources and the economics of finding and developing economically recoverable minerals. In many cases, propositions applicable to all industries are reviewed because they are not treated ade¬quately in prior texts. In the discussion, use is frequently made of basic concepts of differential calculus widely used in economics. However, this is supple¬mented by simpler verbal and graphical treat¬ments, so that those either untrained in the calculus or, as is often the case, whose skills have grown rusty, can still follow the discus¬sion. Where the argument depends critically on the mathematics, this is noted and the justifi¬cation for including the material is provided. In addition, an appendix outlines the critical mathematics and reviews some of the numerous books published that provide the most readable available introduction to the subject. Further¬more, mineral industries examples are used to suggest the relevance of the theory. THE RELEVANCE OF THE ECONOMICS OF PRODUCTION Three basic steps are involved in establishing the relevance of economic analysis to mineral ¬industries decision making. First, the general theory of production must be defined, and its relationship to the simpler models of production stressed in economics textbooks must be noted. Second, the critical modification-considera¬tion of the problems of discovering and devel¬oping mineral deposits-must be developed. It turns out this too involves a special case of the general theory of production. Third, the concept of an economics of exhaustible resources must be explored sufficiently to suggest why its practical relevance is doubtful (or at least far smaller than the numerous writers on the subject seem to believe). The present approach is heavily influenced by post-1945 developments in economic anal¬ysis. Particularly since World War II, economic theory has drastically changed its scope. First, stress has increased greatly upon viewing the economy as a network of intertwined markets known technically as the general equilibrium system.b In this view, not only is the economy viewed as an integrated system, but critical con¬cepts are viewed somewhat differently than was previously fashionable. Specifically, in general equilibrium models, the concepts of supply and demand are rejected as central concepts in favor of a distinction be-

Jan 1, 1985

By Donald Crowell

Due to falling metal prices and depletion of ore reserves, lead-zinc mining in the Leadville, Colorado, area gradually came to a halt in the 1950's. Exploration work continued, however, and by 1969 sufficient ore had been blocked out to warrant sinking a shaft and erecting a new concentrator to treat 700 tpd. The new shaft and concentrator were to be located in Iowa Gulch several miles east of Leadville at an elevation of 11,100 ft. The Leadville project is a joint venture between Newmont Mining Company and ASARCO with ASARCO being the operator. Design work began in the fall of 1969. Engineering was done by Torkelson Engineering Company of Salt Lake City in conjunction with the Central Engineering Department of ASARCO. The plant was constructed by Stearns-Roger Corporation. Construction began in the spring of 1970 and the plant went onstream in April, 1971. Flow sheets and equipment lists are attached. This paper will describe the flow sheet very briefly and discuss in more detail those aspects of the design which may be of interest, particularly the provisions for expanding the capacity of the plant.

Jan 1, 1972

By Fathi Habashi

CRYSTALLIZATION from aqueous solution is a simple and old method for the recovery of metal values from leach solution. Practically all the methods for the recovery of aluminum from clay are based on the crystallization of an aluminum salt from the leach solution. Differences in solubilities may be used to advantage for separating two metals from the same leach solution. The classical method of Marignac (1866), which makes use of the difference in solubilities of K2TaF7 and K2NbOF5 to separate niobium from tantalum, has been used successfully in the manufacture of these metals (Fig. 10-1). The slurry containing the metal oxides is dissolved in 70 % hydrofluoric acid, diluted, and heated near boiling. A potassium salt is added in sufficient quantity to form the complex fluorides of the niobium and tantalum present. The solution is filtered and allowed to cool. At room temperature most of the tantalum salt crystallizes out while the niobium remains in solution.

Jan 1, 1970

By Keat Chuan Chew, Qiao Yue Tung, Teoh Yaw Poh

"1 INTRODUCTION With a land area of 718 square kilometres housing a population of slightly over 5.4 million, as of 2014 (Department of Statistics Singapore 2015), Singapore is a highly urbanised city. Transport infrastructure is critical to keep the country and economy highly connected and functional as the population in Singapore continues to grow. The importance of a robust transport infrastructure is recognised by the Ministry of Transport in Singapore, which is working towards bringing 8 in 10 households within a 10-minute walk of a train station by 2030 (Ministry of Transport 2015). This gives rise to the rapid expansion of the rail network in highly urbanised Singapore, resulting in more tunnelling work having to be carried out in closer proximity to existing buildings. Such tunnelling work is expectedly more challenging and complex, and if not managed effectively, will impose higher risk to the adjacent buildings. Hence, the Building and Construction Authority (BCA) has implemented specific control measures to mitigate such tunnelling risks and to ensure safety of the public. 2 CHALLENGES FACED BY TUNNELLING WORK IN SINGAPORE 2.1 General Challenges of Tunnelling in Singapore With the increasing densification of the rail network in a highly urbanised setting, rail projects in Singapore are faced with several key challenges. One such construction challenge is constrained construction sites brought about by network intensification. Alongside the growth of the rail network, shown in Figure 1, other infrastructure networks in Singapore are also continuously growing. Underground interchange stations between networks become increasingly common, forcing each underground interchange station to be constructed deeper and in closer proximity to existing buildings (Figure 2). Singapore is not alone in facing this issue. The same can be observed in cities like London, in which its myriad network of subway lines pushes new lines and interchange stations to be constructed deeper."

Jan 1, 2016

By T. A. Lloyd

The use of tank cells over the years has provided a means for low cost, space efficient, extra capacity in existing flotation circuits. In some cases, new plants have selected tank cells as the machine of choice. Typical tank cells use high efficiency impellers for mixing, which results in low power draw. Unfortunately, these mixers have poor aerating characteristics that compromise metallurgical performance. This has all changed with Outokumpu's new flotation concepts. Outokumpu has recently developed the HG or High Grade flotation cell that can provide higher recovery with better selectivity while maintaining the simple operation of conventional cells.

Jan 1, 1993

By A. F. Grandt

What is prime farmland? Can such land, once it has been strip-mined for coal, be restored so that it will produce corn, soybeans, wheat, and alfalfa? What methods or practices are necessary to bring about restoration within a reasonable time so that crop yields will be equivalent to or higher than those of unmined prime farmland under high levels of management? These questions concerned land use researchers in Illinois as early as 1948 when the Illinois Agricultural Experiment Station experimented with growing cultivated crops on strip-mined land in St. Clair County (1). This research was done almost 30 years before requirements of Public Law 95-87 were passed by the United States Congress and signed August 3, 1977.

Jan 1, 1980

In cold regions rinsing of spent cyanide leach heaps is stopped during winter and is resumed again after snow melts. The effect of this idle time on the overall cyanide removal process was studied in this work. Samples were collected for rinsing tests from one heap at the Ryan Lode Mine of Citigold Alaska, Inc., near Fairbanks. The material was tested for cyanide removal a large column, 1.22 m high by 20 cm square, and in a small column, 1.22 m high by 10 cm in diameter. The rinse water was analyzed at regular intervals to determine the rate of cyanide removal from the solids. It was found that diffusion plays a major role in the removal of cyanide from the ore particles. Calculations showed that the insulating effect of the snow cover on the heap provides an excellent moderates the interior temperature of the heap, and would be expected to help the progress of the diffusion reaction during winter. The result expected result wil1 be higher cyanide values reporting to the rinse water after snow-melt.

Jan 1, 1993

By L. Cheng

Almost all modern cutting bits use a cemented tungsten carbide tip to provide adequate hit life against wear. Laboratory tests by the US Bureau of Mines have indicated that the number of strikes for ignition increased by a factor of three with a new non-rotating bit impacting a sandstone block when the clearance angle was increased by 10°, and that carbide-tipped bits allowed more strikes before ignition than steel-tipped bits by a factor of 7 to 10. Recent field tests in an operating coal mine indicate a dramatic reduction in the frequency of frictional ignitions and improvement in hit life by using a mushroom-shaped hit cap and a larger initial clearance angle. The latter was achieved by increasing the hit attack angle. Improved hit performance through selection of the grade of tungsten-carbide is a com¬promise between fracture resistance and wear resistance. A large clearance angle should he maintained by various techniques, such as a variable attack angle holder, or a reusable hit that can he reground.

Jan 1, 1990

By G. Deschenes, M. Fulton

The New Britannia Mine processes a qumtz-carbonate gold ore containing 4.63 git Au at a rate of 2,200 tpd. The ore contains approximately 3 .0% arsenopyrite, 2. 7% pyrite and the rest is gangue minerals. Eight to ten percent of the gold is refractory to leaching. Two years ago, New Britannia Mine experienced cyanidation problems. Gold extraction was not stable and occasionally decreased significantly. Preliminary test work, at laboratory scale and in the plant, indicated that lead nitrate addition was beneficial. A laboratory study was initiated to evaluate the level of control of the parmneters (grinding size, dissolved oxygen, pH, free cyanide and lead nitrate) to optimize the efficiency of the process. It was found that lead nitrate addition is required to alleviate the effect of metallic sulphides. This addition causes a significant increase in the gold leaching kinetics and a reduction in the cyanide consumption. The optimum system appeared to be: leaching for 24-30 hours at pH 11.8, 50 git lead nitrate, 250 ppm NaCN and 8 ppm 02. The gold extraction was 89.8% with grinding at 89%-74Fm (leached tail at 0.48 git). Cyanide and lime consumption are 0.40 kglt NaCN and 1.9 kglt respectively. Following the incorporation of lead nitrate, overall gold extraction was increased from 89.2% to 91.1 % but no change was noticed in cyanide consumption. The gross profit is $CDN 988,000 per year.

Jan 1, 1999

By Mark Van Dyke, Ted Klemetti, Jake Beale, Zoheir Khademian, Joe Wickline

In 2016, a 3.7-ML magnitude event caused by mining activity occurred at a longwall mine in southwestern Virginia which was recorded by the United States Geological Survey (USGS) and felt by local residents. The event was the largest of its kind since a global mine design change by the operator was instituted in 2008 following three large events in 2005, 2006 and 2007 (3.4, 4.3, and 3.4, respectively). Two of the three pre-2008 events (2005 and 2007) damaged ventilation controls in the mine which fueled a mine fire. In 2016 the mine’s management requested researchers from the National Institute for Occupational Safety and Health (NIOSH) to access geological data and determine what parameters could possibly lead to events of a magnitude of 1.0 ML or greater. Evaluation of 2,152 geological data points and modeling revealed three major geological factors in common with the majority

By A. Sinha, C. Sawmliana, P. Pal Roy

Using the newly developed and permitted explosive Pentadyne-HP (Gulf Oil Corporation Ltd., Hyderabad), the Blasting Department of the Central Institute of Mining and Fuel Research, Dhanbad experimented at the GDK-5 Incline, RG-1 Area of the Singareni Collieries Company Ltd. (SCCL) to establish one modified angular cut blasting pattern as an alternative to conventional solid blasting in India to obtain longer pull, as well as to achieve at least 40 t of coal in a single blast round for the deployment of diesel load-haul-dump units at the face. This permitted explosive satisfied the statutory requirements of incendivity characteristics applicable to P5 explosives of the regulatory agency Directorate General of Mines Safety (DGMS) of India. The present paper summarizes the development of this new blasting pattern and its possible use in Indian coal mines.

Jan 1, 2010

By McCarthy. Richard E.

The prime movers of the Centralia Project, the surface coal mine and the power plant, private utilities are very aware of public attitudes. They have established and maintain the reputation for leadership in public service and are genuinely concerned that this project initiate the pro-grams and design the hardware to answer the question :What will be the impact of the mine and the plant on the physical environment, i.e., the air, soil and the water." So in the beginning almost as soon as the decision had been made to go ahead with the project, officials of the two private utilities, Washington Water Power and Pacific Power & Light went on record and publicly stated time and again that the overall approach of the Operators would be to do all that was reasonably possible to safeguard the environment. This attitude became part of the thinking of the project planners, part of the design of the power plant and part of the plan for the surface mine. The coal to be mined is from the Skookumchuck formation. The formation is Late Eocene and is made up of poorly consolidated marine and non-marine deposits. The major overburden removal equipment is a bucket-wheel excavator -conveyor system and a 56 yard dragline. Mining of the coal will be done with truck and shovel. The coal is processed, washed and crushed to 1 ¼ " for delivery to the power plant. The muddy water created by the washing process is chemically treated and the solids removed by a thickener-vacuum filter system.

Jan 1, 1971

By Stephen P. Signer

The U.S. Bureau of Mines is developing an intelligent system for roof' control that uses both an expert system and neural networks to improve the capability of mining engineers to evaluate roof support effectiveness for ground control in coal mines. The expert system com- pares roof support capacities with the support requirements estimated to be necessary to maintain entry stability. It does this by evaluating the results of tests on various types of roof support and establishing the maximum allowable load according to anchorage capacity and yield strength of the support. After the user enters geological information (rock properties, geometry of the opening, in situ stresses, bolt pattern parameters, etc. ), the expert system compares the predicted required loading to the roof support capacity and gives the operator advice on the adequacy of the design and how improvements could be made. A good source of the real-time data necessary to allow the expert system to make decisions will come from a roof bolting machine being developed by the Bureau of Mines. Researchers have collected data from a Western coal mine on drill bit position, penetration rate thrust, torque, and rotation rate. Using this information, two neural net- works were developed to identify different types of strata and features in a mine roof such as rock type, rock compressive strength and joint characteristics. The result is a system that can assist a mining engineer with design information that can be constantly updated as mining progresses.

Jan 1, 1992

By T. D. Arnold

The Barrick Bullfrog underground mine was established as an afterthought to the main open pit. As open pit ore dwindles, the underground mining becomes increasingly more important as an ore source, and to the overall economics of the project. This situation is similar to many other mines, and there is a strong move towards underground mining in the United States today. There are inherent problems in starting and operating underground mines in the shadow of any open pit operation, and at the Bullfrog there were several attempts at productive increases that were both successful and unsuccessful.

Jan 1, 1996

By J. L. Heaver

All complete plant foods require phosphorus, nitrogen and potassium. And phosphate rock is the primary source for the phosphorus of the inorganic fertilizers. As more and more world food production is grown with these chemical fertilizers and since the Florida field supplies over 30% of the phosphorus component, let us look at the vital phosphate industry. Mining of phosphate rock in Central Florida began in 1891 and production has continued to grow at a steady pace. In 1965 a phosphate mine was opened in Hamilton County, North Florida and one in Beaufort County, North Carolina in 1966 . Since the beginning of mining in 1891, approximately 700 million metric tons of phosphate rock have been produced of this amount one-half was mined in the last 11 years. While the field was not deliberately "high-graded," the best of the known deposits were mined first. Those now being mined, and those yet to be mined, cost more to operate and the product is of lower grade. The U. S. Bureau of Mines' data for 1977 lists "Florida" phosphate rock production as 40.6 million tons; 86% of U. S. production and 85% of "Florida" capacity. The U. S. Bureau of Mines includes North Carolina production in "Florida" statistics so as not to reveal individual data for the one mine operating there. Approximately one-half of "Florida" production is exported, either as rock or as rock equivalent in upgraded products. Deposits of phosphate rock necessary to support present and future production are catalogued as: reserves, paramarginal reserves and resources. Reserves denote deposits which can be mined at a profit now. Paramarginal reserves are defined by the U. S. Bureau of Mines and the U. S. Geological Survey as: that portion of sub-economic resources that a) borders on being capable of production economically, or b) is not commercially available solely because of legal or political circumstances. The " b)" part of this definition may now be expanded to include environmental controls and requirements. Resources are deposits which cannot be mined at a profit at present. Listed in Table I are reasonable values for each of the three categories of phosphate deposits in the northern and southern parts of Central Florida. North Florida and North Carolina.

Jan 1, 1978

By Harrison R. Cooper

The expanding use of digital control in the metallurgical industry is a significant recent development. From 1970 to 1975, approximately forty metallurgical plants throughout the world have adopted automation techniques based on digital controls (see Table 1). Several recent technical reports have described development of digital control systems in concentrator grinding control, 1,2 flotation,3 and smelter operations.4,5

Jan 1, 1975

By Fred C. Bond

Any improvement in the accuracy of commercial comminution calculations under the Third Theory must be accomplished either by increased precision in energy input measurements, or by a better evaluation of the total new crack length produced, as indicated by the feed and product size distributions. Since at the present time feed and product sizes are approximated solely by the microns 80% passes, the most promising opportunity for increased accuracy lies in consideration of their plotted size distribution characteristics. This paper shows how more accuracy can be obtained over an increased range of feed and product sizes from size distribution studies.

Jan 1, 1962

By M. L. Harris

Explosions in underground mines and surface facilities such as processing plants are caused by confined accumulations of combustible dust and/or flammable gas mixed with air in the presence of an ignition source. Underground explosions can be prevented by minimizing methane concentrations through methane drainage and ventilation, by adding sufficient rock dust to inert the coal dust, and by eliminating ignition sources. The effectiveness of rock dust in arresting explosion propagation was proven by experiment and practice (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11). The precise mechanism by which rock dust (generally pulverized limestone dust) quenches flame has not been fully explained, but is believed to be absorption of thermal energy from the heated gases and absorption of radiant energy, which reduces the preheating of unburned coal particles ahead of the flame front. One measurable aspect of explosibility is incombustible content. In order to determine whether enough rock dust is applied, 30 CFR1 § 75.403, Maintenance of Incombustible Content of Rock Dust, requires at least 80% incombustible content on the roof, ribs, and floor of underground coal mines. 30 CFR § 75.403-1 further defines the incombustible content as follows: ?Moisture contained in the combined coal dust, rock dust and other dusts shall be considered as a part of the incombustible content of such mixture.? In order to determine the incombustible content of the mine dust, samples of deposited dust from specified areas in a mine must be collected, analyzed, and then compared with the minimum standard of 80%. The traditional low temperature ashing (LTA) approach to determine if a coal and rock dust mixture is compliant with the inerting requirement consumes the coal dust and considers the remaining material to be inert. Compliance with the law is then determined by comparing the measured percentage of inert material of the representative band sample with the pre-established requirement of 80%. The incombustible content of the sample includes rock dust, the amount of moisture as received at the lab, and the inherent ash in the coal. The LTA method is not itself a direct measure of explosibility but is a surrogate that calculates a single parameter associated with large-scale Bruceton Experimental Mine (BEM) explosion test results conducted with dry rock dust. This method assumes a homogenous mixture with no layering of rock dust and coal dust. Float coal dust is a serious explosion hazard if it accumulates on top of the rock dust and is not mixed with the rock dust (12). Mitchell and Nagy (13) studied the effectiveness of water as an inerting agent for the coal dust explosion hazard. The study emphasized that surface water evaporates readily from dusts. Thus, in a passageway where the dust is wet, changes in weather or the ventilation system could dry the dust and make it unsafe in a relatively short period of time. Where adequate rock dust has been applied, this drying effect is not a factor. However, if the mine depends upon the moisture content as part of the incombustible content, fluctuations in the dust surface moisture within a mine can render moisture content an ineffective and inconsistent measure of safety. Additionally, if sufficient moisture is absorbed and subsequently relinquished by rock dust, a cake can form and render the rock dust ineffectual. The trend has long been recognized that mine explosions occur primarily during the winter season when the humidity is low for long periods of time (14, 15, 16). In light of this trend and due to the potential variability of the moisture content of the dust, it may not be prudent to include variable surface moisture in the total incombustible content of the sample. Instead, surface moisture should be viewed as an additional safety measure as long as the rock dust is dispersible. However, moisture limits the ability of the rock dust to disperse and can significantly reduce its capacity to effectively inert propagating explosions (2, 13, 17, 18, 19, 20, 21, 22). Given the methods by which the as-received moisture and incombustible content are determined, dust samples from the 2010 MSHA database were assessed to determine the variability of the moisture content throughout a year and how often the measured as-received moisture might have affected the dust explosibility determination if removed. The findings were then verified by observation in laboratory studies and within the NIOSH OMSHR Safety Research Coal Mine (SRCM).

Feb 23, 2014

By S. Mischler, J. Organiscak, S. Klima, C. Seaman

"Researchers at the National Institute for Occupational Safety and Health’s Pittsburgh Mining Research Division (PMRD) performed comparative testing of six hollow cone water sprays from three manufacturers: static swirl chamber sprays from Spraying Systems (BD-3, BD-5) and Steinen-Hahn (SH-3, SH-5), and movable swirl chamber sprays from Repair King (RK-3, RK-5). Water flow testing was completed at three operating pressures (60, 80, and 100 psig) where both sets of sprays (3-series and 5-series) produced similar water flows, deviating less than 8% from the average water flow rate at each pressure. Airflow induction testing was completed at 80 psig using a hot wire anemometer to take air velocity measurements upstream of the spray nozzles. Respirable dust capture efficiency testing was completed in a 14.5-m3 (512-ft3) closed system dust chamber at 80 psig. The dust capture efficiency ranged from 7.2% to 9.9% for the 3-series nozzles, and from 5.3% to 7.1% for the 5-series nozzles. Sprays were also analyzed using a Cloud Aerosol and Precipitation Spectrometer (CAPS), which uses light scattering to count and size the airborne water droplets from each spray. In both cases, Spraying Systems sprays produced the largest mean droplet size, followed by Steinen-Hahn and Repair King sprays, respectively. INTRODUCTION Coal mine worker overexposure to respirable coal dust continues to be a problem in underground coal mining operations in the United States. The U.S. Mine Safety and Health Administration (MSHA) now requires coal mine worker respirable dust exposure to be no more than 1.5 mg/m3 average over the actual working shift (CFR 30-70.100, 2016). Potential overexposure to respirable dust by continuous miner, roof bolter, and shuttle car operators may be prevented if proper safety and health practices are implemented as detailed in the mine’s ventilation plan (CFR 30-75.371, 2016). Water sprays are a necessary component of an underground coal mine ventilation plan. They are important on the continuous mining unit for moving air and removing respirable coal dust from the breathable airstream. MSHA requires underground coal mines to include the number, types, location, orientation, operating pressure, and flow rate of operating water sprays in their mine ventilation plans (CFR 30-75.371, 2016). Water sprays can become clogged, requiring the sprays to be properly checked, maintained, and replaced in order to continue meeting the ventilation requirements described in the mine ventilation plan.In an effort to eliminate the problems with spray clogging, Repair King has developed self-cleaning movable swirl chamber hollow cone water sprays (RK-3, RK-5). The spray’s movable swirl chamber is designed to only open when water pressure is applied to the spray nozzle, preventing the nozzle from clogging. Anti-clogging sprays could improve mine production by reducing the amount of time spent servicing clogged sprays. Also, these sprays could improve health and safety of miners since they would continue to suppress and capture dust and continue to move airflow at the face, while a clogged spray loses this ability until it is cleaned or replaced manually. The objective of this research was to assess the comparability of the Repair King sprays with the most commonly used sprays in underground coal mines using performance criteria. An assessment of the sprays self-cleaning or anti-clogging capability was not conducted."

Jan 1, 2017