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By C. P. Lazzara, F. J. Perzak, C. C. Hwang, C. D. Litton

Fire development and spread along conveyor belts in ventilated ducts were investigated experimentally and theoretically. Various types of conveyor belts used in mining applications were ignited and burned in a full-scale gallery under various flow conditions. The flame spread rates depended strongly on the ventilation air speed. The time-temperature traces of gas and belt obtained at 12 feet from the entrance show that a rapid belt surface temperature change takes place prior to a change in the gas temperature, indicating that radiative heat transfer from the flame to the belt surface plays an important role. Further, anomalies in the flame spread rate in the vicinity of 1.5 m/s air speed (i.e., much greater rate than that observed at either higher or lower speeds) can be explained through the mechanism of flame tilt and the resultant view factor between the flame surface and the belt surface. In order to correlate the fire spread with material properties of the conveyor belts (such as the specific heat, the thermal conductivity, and the pyrolysis temperature) and the fire environment (such as the gas temperature and the ventilation air speed), a theoretical model has been developed. This model is based on the experimental observation that the radiative heat transfer is the dominant mode of energy transfer ahead of the flame front. Agreement between the theory and the experimental results is good.

Jan 1, 1991

By John A. DesLauriers, Hans J. Broennimann

INTRODUCTION The early record of tunnel excavating machines in hard rock tunneling has not been one to particularly brag about. We have all heard the stories of major difficulties when trying to break hard rock with machines at promised advance rates of several times that of conventional drill and blast. Unfortunately, sometimes this has not happened. It has been through this trial of the past generations disappointments that today's TBM's have evolved to their present high level of performance in a wide range of ground conditions. Today's machines offer much increased reliability and durability. This translates into high availability to the tunnel contractor. Although there still are occasional disappointments being reported, the state of the art is that reliable and predictable machine excavation of rock now is both a reality and well founded expectation. The most recent editions of Atlas Copco's MINI/MIDI Fullfacer, we feel, make a strong contribution to the reliable performance of todays TBM's---especially in small-size rock tunnels. This report will, 1.) explain the equipment and effect of rock both on the cutting technique and machine performance; 2.) list advantages of the non-circular shape, during and after construction; 3.) list applications in civil and mining industries; 4.) discuss North American experiences, performance and costs; 5.) list advantages over drill and blast and; 6.) discuss briefly lease arrangements.

Jan 1, 1979

By J. A. Brierley, S. N. McIntosh, C. L. Brierley, E. G. Baglin, E. G. Noble, D. L. Lampshire

The U.S. Bureau of Mines investigated column bioleaching as a means of recovering manganese from a domestic low-grade oxide ore. Manganese was solubilized from the ore using indigenous heterotrophic microorganisms and molasses as the nutrient source. The effects of medium flow rate, molasses concentration, and frequency of medium replacement on the rate of manganese extraction were examined. Results showed that flow rates between 0.4 and 8.1 L/min/m2 had little impact on manganese extraction, while an increase in the total amount of molasses applied during leaching directly affected the extent and rate of manganese extraction. Manganese extractions of more than 90% were achieved in 12 weeks of bioleaching in column tests using 500 g charges of ore. Sugar utilization by the microorganisms and formation of organic acid metabolites were monitored by high performance liquid chromatography (HPLC). Two methods were evaluated to recover manganese from the sugar- depleted bioleaching medium: (1) adsorption onto weak cation exchange resin, followed by stripping and precipitation techniques; and (2) direct precipitation of the manganese as MnCO, using ammonium carbonate. Both recovery methods removed at least 95% of the solubilized manganese from the medium as a carbonate salt. The stripped molasses medium was replenished with fresh molasses and recycled back through the bioleach column, successfully leaching more manganese.

Jan 1, 1993

By K. N. Han, J. J. Kellar, Y. Guan

The adsorption of zinc species onto silica in ammoniacal solutions was studied. The adsorption isotherms indicated that the adsorption of zinc increased with increasing pH. The adsorption density increased as the zinc equilibrium concentration increased up to =3.5x10-4 M. Above this concentration, the adsorption density was independent of the equilibrium concentration, and a maxima adsorption density was reached. Temperature had no significant effect on the adsorption density.

Jan 1, 1995

By Michael Michaylov, Elena Vlasseva

On the basis of well known and widely used in mine practice retreat longwall mining system, physical and mathematical models of air leakage dynamics have been created. Flow is assumed viscous-inertial and considering natural anisotropy of porous media of a gob area. As a result of modeling pressure and leakage distribution and velocity field can be defined. Thus the model presented in this paper can be used as aerodynamical prediction of gob area characteristics.

Jan 1, 1995

By Rex L. Outzen

Houston International Minerals Borealis Project is an open pit heap leach operation. The operation uses open pit mining, two stage crushing, agglomeration, heap leaching, zinc precipitation and induction refining to produce approximately 50,000 ounces of gold per year. Due to the ore being extremely ameanable to heap leach processing techniques, low manpower requirements and efficient management, the operation is one of the lowest cost gold producing operations in the United States.

Jan 1, 1984

By D. V. Ramani, M. M. Kissel, M. T. Ityokumbul

Experiments were carried out to determine the efficacy of bubble column flocculation. An acid-base neutralization method was used to determine the mixing time in a 0.064- by 1.5-m bubble column equipped with a Mottporous sparger. The mixing times decreased as the tracer injection point approached the gas sparger. Preliminary flocculation experiments on two clay samples were carried out. The effects of frother addition and airflow rate are presented and discussed.

Jan 1, 2000

By D. A. Stanley, B. J. Scheiner

The Bureau of Mines, US Department of the Interior, has investigated the use of rheology to provide insight into the mechanism of flocculation. A technique developed by Tattersall has been modified and used to explain the flocculation of calcium montmorillonite with polyethylene oxide. The results indicated that there are two types of bond systems operating during the flocculation sequence. Also, flocculation results are highly dependent on the shear rate and the amount of polymer added.

Jan 1, 1990

By William J. Francart, Gary J. Wirth

Fire detection capability in conveyor belt entries of coal mines has advanced considerably since the passage of the Federal Coal Mine Health and Safety Act. The advances in instrument technology and computer based monitoring have provided better fire detection than ever introduced in the industry. This paper discusses recent belt conveyor fires and detections in mines utilizing CO Monitoring Systems. Data from investigative reports is presented on belt entry fires from 1991 to the present.

Jan 1, 1993

By G. G. O. O. Uwadiale

Starting from a crude ore assaying 45.6% Fe, a fine-grained oolitic iron ore was concentrated by the oil agglomeration technique to 90% Fe recovery and 65% Fe assay. The ore required grinding to minus 5 µm to effect adequate liberation, and the technique yielded optimum results at pH 9. The roles of pH, collector, and bridging liquid concentrations on selectivity and yield of iron minerals in the concentrates are discussed.

Jan 1, 1991

By Arol, A. I., I. Iwasaki

The presence of calcium ion in iron ore pulps causes heterocoagulation of rnontmorillonite on hematite leading to indiscriminate dispersion. Two methods were investigated to control the adverse effect of montmorillonite: a chemical method using such complexing agents as EDTA and sodium tripoly- phosphate, and a mechanical method involving ultra- sonic treatment. Their roles in controlling the adverse effect were investigated by zeta potential measurements, starch adsorption tests, and flocculation and selective flocculation tests.

Jan 1, 1988

By Philip U. Santacroce, James H. Meinholz

One-half of the $607 million Conveyance construction portion of the Milwaukee Metropolitan Sewerage District's Water Pollution Abatement Program is completed or under contract. 12,200 m (7.5 miles) of tunnel boring machine (TBM) driven rock tunnel from 2.5 m (8.0 ft) to 9.9 m (32.3 ft) diameter has been completed. This paper presents a review of TBM performance and a discussion of the pertinent geological conditions of the area.

Jan 1, 1987

By Michael L. Nave

An existing coal mine's raw coal 60 inch conveyor system had become productivity bound by a capacity of 3,500 tph. The existing conveyor drives were fixed speed wound rotor induction motor drives installed in 1983. The fast track upgrade installed variable speed medium voltage variable frequency drives to speed up the conveyor to a capacity of 5, 000 tph. The installation took place over a one week system shutdown during Christmas 2000.

Jan 1, 2002

By Bernard J. Reddy

This paper describes in detail the economic forces affecting cobalt supply, demand, and prices. The major factors that will determine the growth or decline in the use of cobalt in each of its applications are discussed. The flows of cobalt from mine to refinery are described on a company-by-company basis. The paper concludes with a discussion of how the characteristics of the supply and demand sides of market interact to determine cobalt prices.

Jan 1, 1986

By R. P. King

Thermal pretreatment can significantly improve industrial comminution operations by reducing energy requirements and increasing mineral liberation. The effect of pretreatment using conventional and dielectric heating followed by quenching on the fracture characteristics of a number of single and multiphase brittle materials has been investigated using the Ultrafast Load Cell. It has been observed that very significant reductions in both fracture energies and the material integrity (damage) were achieved by heating followed by water quenching.

Jan 1, 1995

By W. A. Steingraber

This paper discusses the application of deep well disposal techniques to the problem of disposing of large volumes of low level radioactive wastewaters generated by the in situ uranium mining industry in Seth Texas. Data is presented on wastewater composition and volumes, geologic and hydrologic parameters of the disposal reservoirs, tell construction techniques, well operation, well monitoring requirements, and critical factors in evaluating the Safety and environmental impact of a deep injection well system.

Jan 1, 1980

By Frank Hagar, George M. L. Robinson

NTRODUCTION The Resource Conservation and Recovery Act and CERCLA (SUPERFUND), in many instances, has had an adverse economic impact on the hardrock mining industry. Over the last few years, many abandoned and active mining operations have been added to the Environmental Protection Agency (EPA) National Priority List (NPL) . When the property is placed on the NPL the operator or EPA is required to conduct extensive environmental assessments to determine if historical mining practices have degraded the existing environmental. If degradation has or will continue, the responsible party is required to implement appropriate remedial action plans. If a responsible party is not identified, the EPA implements a cleanup program. Experience has demonstrated abandoned and active mining operations are subject to RCRA, and possibly Super- fund, if the mine has not adopted appropriate hazardous waste disposal management procedures. If off-site contamination has occurred, the operator will be required to mitigate the impacts and will be required to adopt additional procedures to minimize future impacts. Since the passage of RCRA and Super- fund, many mining operators are adopting management procedures to monitor and inventory hazardous sub- stances and wastes generated, stored and disposed on site. Many operators are in a difficult position because ore, waste rock, process chemicals or other solid waste, in many instances, can be classified as hazardous waste. If the process or other solid waste is deemed to have the characteristics of a hazardous waste, the operator can inventory and adopt appropriate, in- expensive management procedures. However, if the ore or waste rock has hazardous waste characteristics, in- expensive control technologies are impossible to implement. Since existing statutes and regulations require hazardous waste control, the operator will be required to inventory, characterize and monitor all aspects of the mining operations including but not limited to exploration, mining, ore processing and waste disposal. During this process, geological, geotechnical, geochemical, waste and ore volumes, and process materials must be tracked throughout the mining process. To accomplish this task, the most cost effective method to maintain documented and accurate records, is through the implementation of an integrated database management system. The database management system can be used to model and simulate the entire mining operation and if necessary, used to predict whether the operation is in compliance with existing regulations. The developed database can also be used to operating optimize mining and disposal costs.

Jan 1, 1987

By Y. Tao

The features of the teeter bed separator and its application in the coarse slime separation of Chengjiao coal preparation plant were discussed. The relationship between the coarse slime separation efficiency by TBS and the particle size were studied, and the influence of using TBS on dense medium consumption and oil consumption were investigated, it increased the clean coal yield and the comprehensive recovery of the whole plant, and brought huge economic benefits to Chengjiao coal preparation plant.

Jan 1, 2011

By Frederick H. Parkinson, Joseph Fernandez, David E. Westfall

The April 13, 1992, flooding in the freight tunnel network under the city of Chicago had a profound effect on the nearby Chicago Transit Authority (CTA) subway service. This paper provides an overview of the evaluation techniques, mitigation measures, and water control efforts used to maintain the integrity of the subway tubes. Specific topics discussed include visual inspections, inflow monitoring, structure and soil testing and sampling techniques, and the development and implementation of chemical and cementitious grouting programs.

Jan 1, 1993

By R. L. Pozzo, A. S. Malicsi, I. Iwasaki

The electrochemical nature of mineral-grinding media interaction in the wet grinding of one and two sulfide mineral ores was investigated with regard to the flotation behaviors of the minerals. Two iron sulfides (pyrite and pyrrhorite) and mild steel were used to represent the sulfide minerals and the grinding media, respectively. Galvanic currents in two- and three-electrode combinations under abrasive and non abrasive conditions were correlated with the floatabilities of these minerals under corresponding conditions.

Jan 1, 1991