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By John Durkin, Steven Wirch, Fred N. Kissell, Steven Ruggieri

The Bureau of Mines has developed two expert systems to give advice on coal mine dust control, one for continuous miner sections, and another for longwalls. Prototype versions have been evaluated by coal operators and MSHA. Both systems query the user as to the nature and extent of the dust control problem. Typical questions asked deal with matters such as cutting sequence, current dust standards and characteristics of current dust control techniques. Advice given by the system generally does not focus on a single issue, but may suggest a variety of approaches consistent with the ability of the operator to practically implement what is suggested. Both were written using expert system development software called Insight 2+. The advantages of Insight 2+ for the user are: low cost, IBM-PC compatibility, and the fact that little prior experience with computers is required. For the developer, Insight offers an easy to use production rule language and goal driven structure as well as a wide variety of capabilities.

Jan 1, 1987

By Michael S. Kucker, Robert A. Robinson, Harvey W. Parker

Ground deformations are of major concern during tunneling, especially in downtown environments, since they have a significant impact on the costs and practicality of tunneling. This case history describes soil and groundwater conditions and ground behavior during the construction of twin transit tunnels for the Downtown Seattle Transit Project (DSTP). The tunnels were excavated through complex glacial soils ranging from hard glaciomarine drift to flowing sand. The tunneling process was greatly facilitated by the prediction of soil layer positions to an accuracy of ±0.6 m (2 ft). Tunneling was complicated by the presence of over 500 temporary tiebacks and by disturbed ground overlying an operating railroad tunnel. A variety of ground improvement techniques were used to successfully minimize settlements, which ranged from 1 cm (0.4 in.) in glaciomarine drift to 6 cm (2.4 in.) in flowing sands. Ground improvement techniques included compaction grouting, chemical grouting, jet grouting, and eductor well systems.

Jan 1, 1991

In 1993, the United States' economy grew at a rate of about 3%. The Gross Domestic Product rose to $6.4 trillion. With more than 258 million people - 599,000 in mining including petroleum - the United States has more than 100 million dwelling units and more than 190 million licensed motor vehicles. New private housing starts rose 7% to 1.3 million units, new car production fell 3% to 5.5 million units and truck and bus production rose 21 % to 4.9 million units. The rate of inflation was under 3% and the prime rate of interest 6%. The Producer Price Index (1982 = 100) was unchanged from 1992 for fuels and re¬lated products and power at 80 and met¬als and metal products at 119, while chemicals and allied products rose 2% to 128 and non-metallic mineral prod¬ucts rose 2% to 120. The merchandise trade deficit rose 27% to $116 billion.

Jan 1, 1994

By Maynard O. Serbousek, Melvin E. Poad

Shotcrete, a useful support material in underground openings, is a sprayed concrete, and, when used with fast-setting agents, is immediately self-supporting. Although shotcrete has been used extensively for tunnel support, the technique has not been readily accepted by the mining industry because of the lack of essential information on such basic items as material properties and rock interaction. The Spokane Mining Research Center (SMRC) of the Bureau of Mines has been active in the field for the past 2 years, including research on fibrous reinforced shotcrete. IIT Research Institute, Chicago, under Bureau of Mines contract, is investigating physical properties of shotcrete as affected by (1) type of process (wet or dry) and (2) fast-set agents and controlle-dset cements. Already the contractor has shown the advantage of a regulated-set cement over normal cement and fast-set additives for the dry process. The regulated-set cements can produce high early strengths with no decrease in ultimate strength.

Jan 1, 1997

By John Matthews

During 1982 and 1983, it became increasingly clear that North River No. 1 Mine would have to buy a set of replacement longwall shields. Despite extensive efforts to make improvements, the shields that were in place at that time were incapable of holding the roof. North River Energy had limited experience in specifying and acquiring longwall roof supports, but a great deal of experience with our conditions and needs. We there- fore compiled a shield evaluation method that uniquely responded to our situation. The resulting system emphasized teamwork among operating, maintenance and engineering personnel. The charge from management was threefold: select shields to support maximum expected loads, optimize face operations, and pay attention to detail. Final selection was made objectively, based on all available information. We chose a 5516 KN (620 tons) support with a minimum yield load density of 760 KN/m2 (7.9 tons/ft2). This paper reviews our process of specification, design, prototype testing, and fabrication, and offers some relevant suggestions.

Jan 1, 1986

By V. Nasri, P. Jarast, M. Bakhshi

The Montreal metro Blue Line Extension toward the northeast consists of the construction of five new underground stations. The project includes 6 kilometers of the tunnel which will be constructed using a Tunnel Boring Machine (TBM). In line with the commitment to integrating sustainability best practices, Envision verification is pursued this project. The Envision reference framework was developed to cover all the sustainable development aspects of an infrastructure project and each phase of its life cycle (planning, design, construction, operations and maintenance, and end-of-life). As a part of this endeavor, low-carbon concrete and shotcrete mixtures are proposed for the linings of TBM and SEM tunnels as well as stations and auxiliary structures. The CO2 emission of the low-carbon concrete and shotcrete mixtures were compared with their typical mixtures and the total CO2 emissions reduction related to the tunnel lining is determined. The study is of strategic significance for achieving emission reduction in the tunnel industry.

Jun 13, 2023

By R. A. Jankowski

The US Bureau of Mines (USBM) conducted a series of laboratory tests to investigate the effectiveness of using a flooded-bed scrubber with exhaust ventilation in deep-cut faces. An experimental test program to determine the impact on respirable dust levels resulting from changes in face airflow, curtain-setback distance, operator positioning and operating parameters of the external spray system on the miner was completed. Gravimetric sampling was conducted in the immediate return and at three sampling locations on the off-curtain side of the entry. Statistically significant differences in dust levels, on the order of 0.5 to 1.2 mg/m3, were observed between specific sampling locations and changes in several test parameters. Dust sampling results indicated that a flooded-bed scrubber and exhaust ventilation can be a viable dust-control system for extracting deep cuts up to 12.2 m (40 ft) in length. The impact on methane was not evaluated.

Jan 1, 1998

By John W. Amos, John A. Christophersen

The Deister No. 7, "77" and "88" Coal Washing Tables have been used by the coal industry in the cleaning of finer sizes of coal (-1/2") since washing of coals became necessary. This paper will deal with the in-plant use of the CONCENCO "88" Deister Coal Washing Table, along with a brief description of the Deister Refuse Superscalper. Efficient in-plant operation of the Deister Coal Washing Table can be accomplished by the adjustment of six basic variables. These variables are: 1. Headmotion 2. Feed 3. Riffle Pattern 4. Dressing Water 5. End Elevation Adjustment 6. Side Tilt Adjustment VARIABLE NO. 1 HEADMOTION The reciprocating movement of the "88" Table is developed within the headmotion entirely by rotating eccentric weights. Four parallel shafts each carry pairs of eccentric weights (Figure 1-A). The shafts are geared together with gears of 2 to 1 and 1 to 1 ratios, so that the two shafts in vertical alignment which carry the small eccentric weights operate at twice the speed of the other two shafts. The other two shafts are also in vertical alignment with each other and carry large eccentric weights. As power is supplied to one high-speed shaft, once each revolution the forces produced by the large eccentric weights are reinforced and then opposed by the small eccentric weights in a horizontal plane. The direction of movement of the table decks is reversed much more sharply at the forward end than at the backboard end of the stroke, causing material to move toward the refuse end of the table. Because in the vertical plane all centrifugal forces oppose each other and cancel out, there is no vertical movement and virtually no impact to the support steel. The "88" Coal Washing Table is suspended by wire-rope cables from three overhead steel beams, and operates with a perfectly uniform and exact differential motion curve in every stroke (Figure 1-B). The decks, being attached to the headmotion, are reciprocated in a parallel line from the head- motion to the refuse corner at speeds varying from 260-300 strokes per minute. Both length of stroke and speed are set at the factory for the coal characteristic desired and should not be changed. A 3 HP motor is mounted on the top of the headmotion and uses 3 V-belts to transmit driving power to the headmotion. The headmotion must be kept running on a horizontal plane. Punch marks are provided on the side and end of the main frame for use in leveling the motion (Figure 1-C). In leveling the motion, the work must always be done with two cables. To level the long side of the headmotion both front or both rear cables are raised or lowered to bring motion back to level. To level side to side, both right side cables or left side cables are raised or lowered to bring motion back to level VARlABLE NO. 2 FEED When tabling different size coals, each deck of a "88" DIAGONAL-DECK Coal Washing Table will handle feeds as described in figure 2-A.

Jan 1, 1988

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 L. A. Arrington-Webb

Forty-four states produced clay products during 1994 for a total value of $1.6 billion. This was a 3% increase in total tonnage and a 7% increase in value from 1993. Kaolin Domestic production of kaolin during 1994 was estimated to be 9.3 Mt (10.2 million st), according to the US Bureau of Mines (USBM). Georgia remained the leading producer with 7.5 Mt (8.2 million st), followed by South Carolina with 535 kt (589,000 st). Kaolin used as a paper coating or filler pigment accounted for 51% of domestic consumption. Other uses included grogs (14%), fiberglass (5%) and plastics (4%). A reclassification by an Alabama producer of fire clay to kaolin accounts for the introduction of kaolin used in grogs. This also accounts for the apparent decrease in the use of kaolin in paper from 60% in 1993. However, the actual amount of kaolin used in paper was the same.

Jan 1, 1995

By M. J. Liesveld, D. Liesveld

For a Colorado mountain quarry, the Water Jet Channeling Method is far superior to Burning, Sawing, Drilling, or Shooting with Primer Cord, Water, or Black Powder. Throughout the life of our quarry, which was founded in 1947, we have used all the methods and turned to the Water Jet Channeler, which we invented and patented as our ideal way to remove dimension granite from our quarry. We jet the block on 4 sides and remove the block with plugs and feathers on the backside. The Water Jet uses approx 7.5 l/m (2 gpm) running at310,000 kPa (45,000 psi) to erode the crystals @ 1sm/h (10sf/h).The 0.533mm (.021”) nozzle oscillates back and forth to achieve an approx 5cm (2”) channel. Using the Jet, we do not lose corners or cause cracks in our red fine grain light class 5 granite.

Jan 1, 2004

By Frigyes Egerer, Pál Bárczy

Introduction Charles III, Holy Roman Emperor and King of the Austro-Hungarian Monarchy, established one of the first mining schools in Europe on June 22, 1735, in Selmecbanya (Schemnitz in German and Banska Stiavmica in Slovakian). The old city, built around the ancient gold mines, is shown in a contemporary engraving in Fig. 1. Charles' historical decree consisted of 13 chapters and included: the deed of foundation, the definition of grants, instruction for educational policy and curriculum, disciplinary rules, and the appointment of personnel. The first professor of the school, Samuel Mikoviny, gave his first lecture the same year, in December 1735. The 250th anniversary of the establishment of the School of Mines was celebrated Sept. 2-4, 1985, in Miskolc. It was attended by representatives of other Hungarian and of several foreign technical universities. A silver medallion (Fig. 2) was issued to commemorate the occasion and a series of lectures

Jan 6, 1986

By Jr. Stokowski

Topsoil for revegetation projects is in demand in many urban areas. In this case history, a large aggregate producer manufactured a topsoil from three waste materials. The topsoil was produced in a 200,000 m2 (50-acre) abandoned gravel pit that still had additional gravel under 10 m (30 ft) of overburden uneconomic to strip directly. The topsoil was produced by rotary mixing of sludge, overburden, and a lime admixture; solar drying; and stripping and stockpiling of the product. A major problem was an increase of topsoil drying times for stripping from 40 to over 100 hours when it was rewet by storms. The problem was solved by a research project that evaluated over 50 formulations and over 20 waste materials. . The final formula dried in 15 hours and contained 3-parts sandy mine spoil, 1-part sewage sludge, and 2 % spent-bed, a granular quick-lime produced during power-plant flue-gas desulfurization.

Jan 1, 1988

By Rustu S. Kalyoncu

Rainbow colors of roofing granules, adorning the roofs of buildings from single family units to largest office buildings, have their origin in the roofing shingles as burlap soaked with tar appearing as early as the 1700s. Dusting of talc and mica on the coated surfaces, to keep roofing from sticking to itself in storage, represents an early improvement to the original construction product. Sometimes, colored, natural mineral dusts were added as color pigments within the dusting material, for initial color. Prolonged exposure to sun caused the asphalt to become brittle, and it eventually cracked and leaked. Search for solutions to cracking and subsequent leaking problems eventually led to the use of crushed mineral granules on asphalt coated shingles. This provided the impetus for further growth in the asphalt roofing industry. Application of a layer of crushed mineral on the asphalt coating minimized the coating deterioration from exposure to ultraviolet light, thus significantly improving the shingle life. In the 1900s, screened waste from slate quarries was the most commonly used granule in asphalt roofing products. Records indicate the use of coarse slate screenings for asphalt roofing as early as 1906. As the asphalt roofing industry further developed, other naturally colored minerals, such as silica sand, quartz, mica, feldspar, talc, slag, granite, rhyolite, and oyster shells were used on roofing surfaces. Later on, a number of manufactured granular materials, such as crushed brick and tile, fire clay, and white porcelain were used. The first artificially colored roofing granule was produced in 1914 by running molten slag into a solution of alkaline metal silicate, which was absorbed by the porous slag. Various colors were obtained by adding pigments to the silicate coating and by subsequently heat treating the granules. In 1922, another technique was developed in which green slate granules were saturated with copper sulfate solution and heated to 760°C to form copper oxide. Since then, many other granule coloring processes have been patented, one of the most significant being the sodium silicate coatings introduced around 1975. Granules as used in construction (specifically roofing materials) are defined as natural or synthetic-mineral grains smaller than gravel and larger than sand in particle size. They are used primarily for protective and decorative purposes on the weather- exposed surface of asphalt composition roofing. Development of artificial coloring techniques has made it possible for the roofing industry to provide asphalt roofing shingles in a wide variety of colors complementing the color and style of buildings. Roofing granules, as we see today, are the products of long technological evolution.

Jan 1, 1994

By H. F. Broicher

Introduction In April 1998, AIS Sommer GmbH of Germany delivered the first laser-induced fluorescence (LIF) analyzer to the mining industry. LKAB's Kiruna iron ore mine in Sweden shared the costs and the risk of building the prototype. This marks the beginning of LIF analysis as a technique for quality control in mining and mineral processing. Photoluminescence analysis is well established. In most laboratories, fluorescence spectrometers are standard equipment for quality or pollution control. LIF is being used in several applications, including combustion studies and particle image velocimetry. However, it has mostly been used in laboratory environments. The availability of rugged lasers for industrial use brings this powerful tool to the forefront of production, even in the rough conditions found in mining and minerals processing. Laser-induced fluorescence Basics. Fluorescence of naturally occurring minerals has fascinated man since scientific investigation of this phenomenon commenced about 200 years ago. However, importance in industrial application and peripheral activities. Hand sorting of ore under ultraviolet (UV) lamps is seen as an archaic method. Long gone are the days when geologists set out at night with UV hand lamps to find valuable ore deposits, especially those of tungsten. Today, fluorescent minerals are considered collectors' items and museum exhibits. In the late 1960s (Hemphill, 1968) and during the 1970s, attempts to use lasers for excitation of fluorescence in minerals led to the development of an airborne fluorosensor (Seigel and Robbins, 1980). However, this prospecting technology did not gain industry acceptance and vanished from the market. During the past seven years, ongoing research of the LIF of minerals resulted in new findings that give good reason to revive the interest in fluorescence and its use in the mineral industries (Broicher and Zydek, 1995; Broicher, 1998). Fluorescence is defined as the short-lived form of photoluminescence, in which matter emits visible radiation during and after irradiation with light – the fluorescence generally being of a longer wavelength than the irradiation. Fluorescence of matter is described by: • the absorption spectrum, • the emission spectrum, • the decay curve and • the quantum efficiency. The absorption spectrum shows the fluorescence intensity in a fixed spectral band as a function of the excitation wavelength, while the emission spectrum shows the fluorescence intensity at varying emission wave- lengths for a fixed excitation wavelength (Fig. 1). The decay curves describe the exponential decrease of the fluorescence intensity with time. The quantum efficiency is the ratio of irradiating energy to emitted energy. Re- cent research has found that: the quantum efficiency of minerals can be measured and evaluated,

Jan 1, 2000

By Richard B. Berg

California was a major talc-producing State until the late 1980s when production from the deposits in the Death Valley area ceased because of a number of factors which included pressure to discontinue mining in and around Death Valley National Monument, and health concerns affecting markets for tremolitic talc. The states of Montana and Texas now account for slightly more than half of U.S. talc production. Deposits in an area encompassing southern Death Valley and extending east into the Kingston Range were formed by contact metamorphism of carbonate beds in the Precambrian Crystal Spring Formation next to Precambrian diabase sills. These deposits contain ore ranging from high-purity, fine-grained talc to platy, tremolitic talc with high brightness. Deposits of tremolitic talc and talc schist in the Silver Lake District in San Bernardino County resulted from metamorphism of Precambrian carbonate beds intruded by granitic plutons. Northeast in Esmeralda County, Nevada hydrothermal alteration related to Late Jurassic plutons caused talc replacement of Precambrian to Early Cambrian dolomite. A hydrothermal origin is also indicated for talc deposits in the lnyo Range just north of the Death Valley District where bodies of unusually pure talc occur in Paleozoic lime- stone near Jurassic granitic plutons. Talc is now mined from a deposit in the foothills of the Sierra Nevada Range southeast of Sacramento where quartz-mica schist of the Permian Calaveras Formation has been hydrothermally altered to talc. Replacement of magnesite of the Precambrian Allamoore Formation produced talc deposits mined in the Allamoore District of west Texas. This dark-gray talc of low iron content with carbon- aceous material and dolomite is ideally suited for use in ceramics where it makes a white product when fired. Small bodies of platy light-pink to white talc suitable for use as an extender in paint are also mined in this district. In the Llano District of central Texas talc has replaced impure carbonate rocks and serpentinite. All Montana talc production is from deposits in the southwestern part of the State that formed by Precambrian hydrothermal alteration of dolomitic marble. This alteration produced material with high purity that ranges from very fine-grained, massive talc to coarser grained, foliated talc. Markets include pitch control in paper, paint, cosmetics, ceramics, rubber and plastics. In southwestern and northeastern Oregon, talc has replaced serpentinite in the vicinity of Mesozoic plutons. Soapstone for carving is mined from a southwestern Oregon deposit. Deposits of similar origin occur in central and northwestern Washington.

Jan 1, 1995

By M. Javier

"Mining is the main activity that supports civilization. Actual mining presents contradictory concept to the health of the planet. Its business model is linear, fragmented and characterized by inefficiencies in the utilization of water, energy and mineral resources which generate waste and pollution. Before mining begins, it is critical to determine the vulnerability of the ecosystem and after mining, it is critical to determine the depletion of nature. Attending to these vital matters will require quantifying and measuring them. The purpose of this study is to provide and establish the metric to assess the performance and manage a sustainable future for our existence and that of our planet. This index is defined to measure and control Nature Friendly Sustainability (NFS) based on understanding nature. This index will determine the condition of nature constructed on the measurement of physical, chemical and biological equilibrium. Proposing a new mindset for mining design to satisfy nature’s needs would be to offer the same opportunities to future generations. Hence, sustainability is synonymous with equilibrium under a limited ecosystem. Nature is interconnected. Finally, this index of NFS is readable, standardized and relevant to keep nature’s needs in equilibrium. Establishing and NFS index is the next metric for humanity. INTRODUCTION There are a multitude of definitions of what sustainability is. Most of them are defined in terms of the corporate entity from which they emanate. The classical definition of management states that, “if we do not measure it, we cannot manage it.” Management of ecosystems is the definition of sustainability. Indicators of quantity and quality of sustainability are vital in order to create a metric for sustainability. These indicators will measure the depletion and degradation of nature as they occur through human intervention. The first step is to create a metric of sustainability to simplify its definition. The definition of sustainability is based on whether or not you consider nature to be finite or infinite, which is described in Nature Friendly Sustainability (NFS) [1]. The definition of NFS applies to any anthropogenic activity with an understanding of the equivalent activity in nature. That is to say, human activity with nature requires balance and equilibrium in order to be sustainable. The importance of this equilibrium is quantified in a set of metrics in order to establish measurement and acknowledge indicators for our dependence on nature. Sustainability is synonymous with equilibrium in any ecosystem that is limited and fragile. In the graph is the explanation of sustainability definition. See Graph 1"

Jan 1, 2017

By Keith J. Henley, Nicholas C. Clarke, Paul Sauter

A detailed investigation of the stability in cyanide solutions of native gold and gold-silver tellurides in a flotation concentrate from the Golden Mile, Kalgoorlie, has been undertaken to assess whether leaching under different conditions can be used to quantify the distribution of Au between native gold and gold-silver tellurides, as suggested by, for example, Chryssoulis and Cabri (1990). The leaching was carried out on +20 µm native gold and gold-silver tellurides separated from a high-grade flotation concentrate and then diluted with barren quartz. The material leached assayed 270 ppm Au and 118 ppm Te and the leach conditions used were:- Stage 1: Leaching in dilute cyanide (0 .1 % ) at pH 9 .5 for 24 hours to dissolve native gold but not gold-silver tel­lurides. Stage 2: Leaching the residue from Stage 1 in strong cyanide (2%) and pH 12.5 for 96 hours to dissolve gold-silver tellurides.

Jan 1, 1995

By Ivan Caetano Machado

Good morning ladies and gentleman. During 1995 Prof. R. P. King (University of Utah Comminution Center) presented 2 papers on new horizons in comminution: "Comminution Research in the United States " was presented at the 1995 Meeting of the National Mining Association, while "Comminution: Meeting the Needs of Fundamental Research in the Mineral Industry" was presented at the 2nd SME Research Forum - 1995. In both papers a very interesting graph named "Energy usage for various comminution schemes" illustrated some poignant issues proposed by Prof. King. We do think that some of Prof. King's ideas might very well serve as "warm-ups" for this Comminution Panel Discussion, which are ultimately the goals to be reached by the 3-minute presentations. Thus, we shall be addressing in the sequence Prof. King's most relevant ideas (as well as introducing his graph), intending therefore show how important creative and state-of-the-art Mill Modeling is, if it is to become a Tool to Effective Cost-Saving Optimization Strategies.

Jan 1, 1996

By William H. Mount

INTRODUCTION Effective mine ventilation is required to maintain a healthy underground environment for humans. Without effective ventilation, the environment can become unhealthy or hazardous as a result of the depletion of oxygen, contamination with toxic gases, or the buildup of an excessive amount of particulate matter (dust). Each contaminant has an upper limit of concentration that should not be exceeded within an 8-hr period. This is known as the threshold limit value (TLV). The TLV represents an acceptable level of exposure that should produce no ill effects. Unfortunately, more than one contaminant may be present at any one time and the effects of the individual contaminants may be additive, i.e., the effects of each contaminant must be considered simultaneously to determine the potential danger to miners. Possibly the greatest threat to mine-air quality is the uncontrolled underground use of the diesel engine. The diesel engine was invented in 1892 by Rudolf Diesel. His intention was to develop a power source that could burn coal dust as a fuel, but he was unsuccessful in that attempt and had to resort to liquid petroleum fuels (Johnson, 1975). In 1898, the diesel engine was intro¬duced into the United States by Adolphus Busch, who anticipated using it as a prime mover in factories and generating plants. At that time, the diesel engine was a very large and very heavy engine, designed for fixed installations. By 1919, lighter engines were being developed, and by 1931, Caterpillar was marketing a diesel-powered, track-type tractor (Henderson, 1975). Since 1931, the diesel engine has evolved into an extremely popular prime mover in medium and heavy-duty applications. Efficiencies now are on the order of 40% and improvements such as turbocharging and aftercooling have produced engines capable of generating power at a ratio of 0.3 kW/kg (1.0 hp per 5.0 lb) of engine weight. Although the diesel engine is relatively efficient as a mobile power plant, it is far from efficient in terms of the energy produced from the energy potential of the fuel. About 60% of the heat value of the fuel leaves the engine as wasted heat, with about 50% of that heat being emitted through the exhaust pipe and the other 50% being emitted through the radiator or cooling fins. Perfect combustion in an engine would produce only water vapor (H_0), carbon dioxide (CO_), and nitro¬gen (N2) as the byproducts. Since the diesel is not a perfect engine, each pound of fuel burned generates 5.6 m° (200 cu ft) of exhaust gas, containing about 0.009 m3 (0.33 cu ft) of carbon monoxide (CO), 0.009 m' (0.33 cu ft) of nitrogen oxides (NO, NO2, and NOD), and 0.57 m3 (20 cu ft) of carbon dioxide. The balance of the exhaust emission consists of free nitrogen and water vapor (Hurn, 1975). Contrary to popular belief, the diesel is not inherently dirty. Under normal operating conditions, a well-maintained engine neither smokes nor smells. However, the same well-maintained engine can and does produce toxic emissions. A diesel engine is not inherently safe and constitutes a distinct hazard to personnel. This chapter is devoted to a description of the various toxic substances that may be generated by a diesel engine. Although some of these substances may also be produced by blasting or natural causes, the focus of this chapter is on the relationship between the internal- combustion compression-ignition engine (the diesel) and the quality of the mine air. CARBON MONOXIDE Combustion Process During the combustion process (burning) of organic fuels, each atom of carbon combines with two atoms of oxygen, provided that a surplus of oxygen atoms is available. Thus, the carbon is oxidized to carbon dioxide. Most open flames, such as trash fires, camp fires, gas ranges, etc., produce carbon dioxide. However, with insufficient oxygen, incomplete combustion results as the carbon atoms each combine with one atom of oxygen to produce toxic carbon monoxide. Burning charcoal briquettes produce carbon monoxide because the combustion takes place inside the briquettes where sufficient oxygen is not available to the combustion process. Internal-combustion engines, whether burning gasoline or diesel fuel, also produce carbon monoxide. The only oxygen available to the combustion process is that trapped within the cylinder. If the amount of fuel delivered to the cylinder is excessive, there is insufficient oxygen for complete combustion and carbon monoxide production results. In a normally aspirated (nonturbocharged) diesel engine, the amount of air "sucked" into a cylinder is the same on every intake stroke, resulting in complete combustion only at low levels of engine loading, when small amounts of fuel are injected. Higher levels of engine loading cause larger amounts of fuel to be injected into the same volume of air in the cylinder. Unless the volume of air is increased, the combustion process becomes progressively less complete as the amount of fuel increases. Turbocharged engines are able to compensate some¬what for increased loading and increased fuel consumption. The turbocharger acts as a compressor for the intake air, forcing a larger volume of air into the cylinders as the engine speed increases. Hence the turbocharged engine burns cleaner than a naturally aspirated engine and produces slightly less carbon monoxide (Marshall and Fleming, 1971). Much of the underground equipment used today is powered by turbocharged indirect-injection diesel engines. Although these engines emit fewer toxic contaminants than naturally aspirated engines, they do not eliminate the problem. Since the turbocharger is driven by the exhaust gases, rapid accelerations can cause temporary overfueling of the engine until the turbocharger attains a speed sufficient to restore the correct air-to-fuel ratio. During this "turbocharger lag," the combustion cylinders contain insufficient oxygen, causing severe smoking and an increased output of carbon monoxide.

Jan 1, 1982