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By R. C. Buehl

[Improvements in refractories for high-temperature service have made possible the use of higher temperature in many processes. Consequently, it sometimes is desirable to use gases heated above 1,600° F., and for moderate rates of gas flow, there gases can be heaters best with pebble heaters. Pebble heaters of the stationary-bed type in which the chanber was lined with mullite brick and pebbles of pure alumina served as the heat-exchange medium have been used recently to heat the air blown into an experimental blast furnace4/ These pebble heaters worked well and made it possible to use air temperature up to 2,500° F. at the tuyere of the furnace. Since little has been published on this type of gas heater, a review of the construction on employed and operating data should assist in selecting applications and designing units.]

Jan 1, 1953

By Michael D. Fenton

Bauxite resources were primarily in Africa, Asia, Oceania, and South America. Only five countries combined, Australia, Brazil, Guinea, India, and Jamaica, contained most of the total world reserves available for extraction under current economic conditions and accounted for nearly 80 % of world production of bauxite. World bauxite and alumina production declined and prices for smelter-grade alumina remained below the $200/mt level during 1993 because of growing aluminum inventories on international markets and declining worldwide demand. The United States imported bauxite primarily from Australia, Brazil, Guinea, and Jamaica. U.S. alumina plant capacity remained essentially unchanged throughout 1993, but apparent capacity utilization decreased by the close of 1993. Chromium Most of the world's known resources and reserves of chromite are located in India, Kazakhstan, South Africa, and Zimbabwe. India, Kazakhstan, and South Africa accounted for 73 % of world production of chromite. The two largest producers of chromite, Kazakhstan and South Africa, were in the process of major economic and political change during 1993. South Africa's production and exports of chromite continued to fall during 1993, because of weak international demand and a flood of cheap metal from the former U.S.S.R. and China into world markets. Despite a significant increase in production, South Africa's ferrochrome producers continued to operate below capacity in 1993. Prior o the dissolution of the U.S.S.R., Kazakhstan was a major internal supplier of chromite ore to the U.S.S.R. consumer, but subsequent decline in demand led to a downward trend of chromite production in Kazakhstan and increasing exports to Europe during 1992 and 1993. The United States consumed, about 10% of world chromite ore production in various forms of imported materials. The United States imported nearly one-half of its required chromium contained in chromite ore and chromium ferroalloys and metal from South Africa; the remainder was from the minor producers Turkey, Yugoslavia, Zimbabwe, and others.

Jan 1, 1995

By Robert R. Stein, Roy C. Bartholomae, William W. Aljoe

This Bureau of Mines report describes in detail the design and operation of a test apparatus for measuring the sound power levels of drills used by the mining industry. The two major components of the test apparatus are a computer-controlled automated drill test fixture (ADTF) and a large (45,000-ft3) reverberation chamber that houses the ADTF. Design specifications and performance capabilities of the ADTF and the reverberation room are given. Initial test results for three types of drills--a pneumatic percussion drill, a hydraulic percussion drill, and a pneumatic rotary drill--are given to illustrate the types of experiments that can be conducted with the test appartus.

By Donald A. Wilson

As part of a continuing effort to maximize metal recovery from domestic secondary resources, the Bureau of Mines investigated a process for recovering the metallic portion of scrap alkaline batteries. A pyrometallurgical method for recovering nickel and cadmium from Ni-Cd scrap batteries previously developed on a laboratory scale, was scaled up to 25-and 43-pound charges. The method employed reduction and/or decomposition in a retort using a minimum of 2.5 percent carbon as a reductant. Metallic cadmium was distilled at atmospheric pressure and a minimum of 900° C. Purity of the recovered cadmium was 99.8 percent minimum and the nickel-iron residue contained less than 0.02 percent cadmium.

Jan 1, 1981

By M. B. Cooke

 An analytical method for the determination of the gum-forming material in gasoline has been developed by the Bureau of Mines, during a study now in progress to determine the best rays for elimination of such constituents from gasoline. This method is similar in principle to that previously described by Smith and Cooke, which involved evaporation of e semple of gasoline in a small glass dish. The evaporation was started on an actively boiling steam bath and completed in an air oven at 105°C. In the improved method described below, the steam bath has been replaced by a steam heated oven in which an inert atmosphere is maintained. Air is ex- cluded from the oven, consequently the precision of the determination is increased. Furthermore, evaporating dishes different from those previously described may be used.

May 1, 1925

Develop an inexpensive, reliable means of quickly detecting and locating trapped miners in underground coal mines, particularly after a mine accident. The Limitations Although the Bureau of Mines has performed extensive research on the use of electromagnetics for locating trapped miners, much of its research trends toward the development of long-range systems designed to locate an underground transmitter from the surface. Such location systems are beneficial; however, there are several limitations regarding their use. Two limitations are weight and cost of the equipment. Most long-range detection systems would be too heavy and cumbersome to be accepted by miners as part of their daily protective equipment. Since such long-range detection systems are usually expensive, it would not be economically feasible for every miner to be provided with a system.

Jan 1, 1984

"There mines are located in out of the way places, where timber is scarce and its price high, the problem of protecting it from fire risk is of considerable practical importance. Scarcity of timber for mining purposes is commonly met with in the more arid parts of the country, where, so, mine timbers are most likely to become dry, and inflammable, and where, therefore, the risk from fire is accentuated. Any effective and cheap method of securing adequate protection of such timber at the lowest possible cost is worthy of careful investigation. The use of magnesite cement has been suggested in this connection.The necessary qualities for any substance for the use suggested above may be summarized as follows: It should be resistant to abrasion, and to impact and structural stresses. It should be durable when subjected to the action of the elements, and stable to any minor derangements of the base on which it is placed. It must be relatively unaffected by changes in temperature, by the action of water, and should adhere to the material on which it is placed, and it should also be free from shrinkage cracks due to setting up the material, Magnesite cement appears to fulfill the various conditions outlined above.The elasticity of such cement is the outstanding quality which makes it desirable for exterior work. It also possesses the ability to adhere to all materials in a marked degree. Its freedom from expansion and contraction after setting is one of the principal reasons for its adhesive quality. It may be applied to old brick or stone walls, even tho they have been repeatedly covered with paint, and the quality of adhearing to wood makes it possible to secure a weather-proof protection to the wooden casings and trim of exterior openings. The quality of adhesion and elasticity is easily proved by applying a 1/2"" layer to a 1"" board which has been first covered with metal lath. Such a board, about 8 feet long, may be repeatedly deflected about 3"" in the center without breaking the bond to the board, or causing any cracks to appear in the magnesia cement. The ability to resist fire as well as the possession of insulating qualities are also desirable characteristics of magnesia cement stucco.Magnesite cement stucco should be applied in two coats, each 1/4"" thick on various surfaces such as wood lath, metal lath, sheathing board, brick, hollow tile, or stone; care being taken as regards the presence of lime, unless the same has been rendered, or become inert as with very old, walls. The first coat made up to a consistency that works easily under the trowel is applied in the usual manner. No water should be added to the liquid chloride as it would alter its density, and injure the work. The second or finishing coat is then applied. The aggregates are different in each, and no other dry material should be added to them as they come to the trade. The cement may be applied in zero weather without damage. Setting is quite slow under such conditions, but the cement ultimately becomes hard. It should always be applied to a dry surface excepting that under certain conditions it is desirable to apply a solution of magnesium chloride before using the stucco."

Dec 1, 1919

By William C. McBee

Prompted by forecasts of a sulfur oversupply, the Bureau of Mines, U.S. Department of the Interior, is conducting research on potentially large-scale uses of this commodity to extend or replace such construction materials as asphalt, cement, and mineral aggregates. Through these efforts, paving materials have been developed in which sulfur replaces up to 50 pct of the asphalt normally present and which can be prepared and placed with existing mixing and paving equipment. Laboratory properties and design methods for this direct mixing process are described along with properties obtained on small-and large-scale field demonstration projects. These properties are compared with those obtained from control materials prepared without sulfur additions. Monitoring for toxic gases during laboratory and commercial mixing and paving operations is discussed also.

Jan 1, 1978

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

APPENDIX E EQUIPMENT USED FOR FIELD TESTING OF MINE SEALING SYSTEM I. Drilling Operation - Equipment supplied by local drilling contractor 1. Mobile drill rig. 2. Flat bed truck, containing 20 lengths of drill pipe. 3. Auxiliary compressor. 4. Pickup truck for small parts and supply of diesel fuel. 5. Bulldozer. 6. Water supply, in this case the nearby stream. 7. Supply of casing, positioned next to the drill rig. 8. Ready mixed cement grout. 9. Drill bits, stabilizer units, cutting and welding equipment, other miscellaneous tools and supplies. II. Sonar Probing Operation 1. 25 foot tower with pulley mounted atop. - FMA 2. Electric winch with 100 feet of 1/4-inch cable, Model No. 100A, City Engineering Co. , Indianapolis, Indiana. 3. 400 feet of 1-1/2-inch-diameter aluminum pipe with alignment holes and coupling grooves. - FMA*

Jan 1, 1973

By D. R. Tesarik, M. K. Larson, J. P. Dunford, E. G. Zahl

Western coal mines are operating under increasingly challenging ground conditions. Researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health are cooperating with mines to evaluate how these conditions affect mine opening stability and related miner safety. A system was developed to monitor rock and coal stresses during mining of an entire longwall panel. The system was designed to generate data in near real time to evaluate rock behavior in roof strata and the onset of hazardous conditions as overburden stress was redistributed over working entries during gob formation. Computer simulations and in-mine evaluations were used to optimize instrument placement. A prototype packer assembly was designed and tested for installing sensitive instruments in a mine roof. This paper provides background information on the stress monitoring concept and focuses on the development of instrument placement techniques and the prototype packer assembly.

By Foster Fraas

In the separation of a component from a mixture , two fractions are obtained , one containing a high - percentage composition of the component and the other a low - percentage composition . The high - percentage fraction is frequently called the concentrate and the low - percentage fraction the tailing . In many separation processes the recovery is not complete , and the composition of the concentrate decreases as the recovery of the component, which is concentrated , increases . It is this particular class of separations to which this paper is confined .

Oct 1, 1942

By C. H. Elder, Fred N. Kissell, S. D. Maksimovic

The Bureau of Mines evaluated the hydraulic stimulation of a gob-degasification borehole to determine if this procedure would aid in degasifying a longwall panel. The stimulated borehole did not degasify the longwall panel as expected either before or after mining of the panel started. It reduced the underground methane emission only 11 pct, considerably less than the reductions effected by two unstimulated boreholes in the same panel. Some probable reasons for the reduced methane flow from the hydraulically stimulated borehole are very low reservoir gas pressure, location of hydraulically stimulated zones within the grouted casing, a casing break caused by lateral shifting, possible vertical movement of rock strata during caving, grouting of a 4-inch pipe blocking three stimulated zones, plasticity of shales, and possible hole damage by swelling of water-sensitive minerals. The borehole was also located between two second-mined areas, which may have allowed partial degasification of the overburden and the coalbed in advance of mining. Finally, a period of 3 months is probably not long enough for the borehole to degasify the overburden before mining.

Jan 1, 1977

By Eric Zahl, John Dunford, Hamid Maleki

Coal bumps are defined as sudden failures of rock and coal near entries that are of such a magnitude that they expel large amounts of material into a mine opening. 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 the National Institute for Occupational Safety and Health have studied mechanisms of violent failure and have identified individual factors that contribute to coal bumps. In an attempt to develop 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 were used to identify the most significant variables contributing to coal bumps (excluding bumps related to fault-slip). Twenty-five geological, geometrical, and geomechanical variables were considered initially. The most important of these variables were then identified as (1) energy as calculated using the mechanical properties of the strata, depth of overburden, and joint density, (2) mining method, (3) pillar factor of safety, and (4) stress gradient and yield characteristics.

By Thomas M. Barczak

The success of longwall mining can largely be traced to the development of powered roof support systems. The most significant improvement in powered support design has been the shield support, which improved kinematic stability and promoted the application of longwall mining in difficult-to- control caving conditions where chock and frame supports were inadequate. The most obvious trend in shield design has been an increase in shield size and capacity. This U.S. Bureau of Mines report examines shield design and operation practices and their consequences for the utilization of high-capacity shield support systems. An optimization goal is to minimize support loading by selecting an active shield setting force that is compatible with strata behavior and shield loading characteristics. Shield stiffness is an important design parameter that is often overlooked. A consequence of increasing shield capacity by incorporating larger diameter leg cylinders is a proportional increase in shield stiffness. Setting forces have also increased in direct proportion to the increase in shield capacity. The increased stiffness and higher setting force cause the available capacity to be consumed more quickly, severely limiting the ability of high-capacity supports to last longer and provide reserve capacity for difficult mining conditions.

Jan 1, 1992

By R. P. Vinson, D. P. Tuchman

The personal dust monitor (PDM) is a sampling device developed for measuring the personal exposure to coal mine dust of mine workers. The device is based on proprietary technology known as the tapered element oscillating microbalance (TEOM) originally developed as a fixed- site environmental particulate mass monitor by Rupprecht and Patashnick Co., Inc., Albany, NY. Currently, the monitoring of exposure to coal mine dust relies on periodic samples taken by traditional coal mine dust sampling units that use a cyclone, filter, pump, and laboratory measurement of the filter mass. Better measurement of mine dust levels has been the goal of industry and labor for nearly two decades. PDM technology offers accurate, end-of-shift and near real time assessment of worker dust exposure. Laboratory and underground tests compared measurements taken by a prototype PDM-2 (a two-piece TEOM) to the average of multiple personal dust samplers monitoring the same space. In the range of mass loadings P between 0.5 and 4.0 mg/m the PDM met a 25% accuracy criterion 95% of the time with 95% confidence. However, some questions still exist about potential bias between types of coal. The prototype two-piece device is in the process of being combined into a single unit that also contains the miners' cap lamp creating a more ergonomic dust sampling system.

Predict the cumulative hydrologic impact of mining on the environment. Approach A comprehensive set of computer models has been developed to predict the impact of mining on ground water. Mine inflows, drawdowns in aquifers, and ground water quality can be predicted. How It Works The Prickett-Lonnquist finite-difference groundwater model was specially modified for the hydrologic problems of mining. This model, developed at the Illinois Water Survey in the 1960's,

Jan 1, 1982

By W. W. Adams

During the calendar year 1927 the United States Bureau f Mines conducted, for the third consecutive year, a safety contest among more than 250 mines and quarries. Aside from its underlying purpose to promote safety, the object of the contest was to learn which mine or quarry had completed the year's work with the smallest proportionate loss of time from accidents to its employees. Competing companies were grouped into five classes, namely, anthracite mines, bituminous teal mines, metal mines, nonmetallic mineral mines, and quarries and open-pit mines. To the winning company in each group was awarded the bronze trophy "Sentinels of Safety," the gift of The Explosives Engineer magazine. The winner in each group was the mine or quarry whose record showed the smallest loss of time from accidents in proportion to the total amount of time worked by 411 employees. This proportion is designated the "accident-severity"3 rate; it indicates the number of days of disability resulting from personal injuries per thousand man-hours of work performed by all employees. Each company's standing was determined by the Bureau of Mines from detailed records furnished by the contestants. Records of the leading companies were made known to a committee of seven men well known to the mining industry but not connected with the Bureau of Mines. This committee selected the winning companies in accordance with rules governing the Competition. According to the contest rules, the competition for the trophy was restricted to mines employing at least 50 men underground and to quarries and open-pit mines employing at least 25 men in the pit. As several plants fell below these figures during the year, their records could not be considered in connection with the award of the trophy. Figures covering these plants are, however, included in the attached tables.

Jan 1, 1928

By R. D. Saltsman

Under contract with the Federal Bureau of Mines, Bituminous Coal Research, Inc., performed a statistical study to find less expensive and time-consuming methods of monitoring the noncombustible content of coal mine dust. Calculations based on thermodynamic considerations verified the reasonableness of Federal rock-dusting requirements. The results of extensive sampling in southwestern Pennsylvania mines indicated that, at the 95-percent confidence level, the present system of sampling at 200-foot intervals may be replaced by sampling at 500-foot intervals, and that a 1-inch scoop floor sampler may replace the standard 6-inch scoop for floor sampling. Further field testing is recommended.

Jan 1, 1975

By John Gross

The modern practice of grinding ores so that often 80 per cent or more of the product is finer than 200 mesh makes it desirable to supplement sieve sizing so as to extend considerably the range of sizing. Moreover, the fact that the material finer than sieve size represents the major part of the work done in grinding emphasizes thick need in can investigation of crushing efficiency. A method based on the settling rate of particles in grater appeared to be most practical for sizing; finely ground ores. There are two possible methods of utilizing this principle: one based on free settling or sedimentation; and the other on separation by means of a rising; current of water, or elutriation. In sedimentation, mechanical entanglement causes material at the start to settle in a mass, and this persists throughout. As this feature is largely eliminated by elutriation, which permits a comparatively clean separation of the various sizes, the elutriation method was adopted.

Jan 1, 1929

By Ann G. Kim

Gas samples containing 02, N2, H2, He, CO2, CO, CH4, and trace amounts of C 2 to C6 hydrocarbons are analyzed by a gas chromatographic method that utilizes both thermal conductivity and flame ionization detectors. A porous polymer support and molecular sieve columns are used with argon as the carrier gas. A column selector valve makes it possible to perform a complete analysis either on one 1-ml sample in 40 minutes or on two samples in 20 minutes, one sample for each detector. Samples are introduced either by on-column injection or through a gas sampling valve. By varying operational parameters, the speed, sensitivity, and accuracy of analysis may be modified to suit a particular situation.

Jan 1, 1974