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By M. A. Reyes, L. Yan

Heat and humidity buildup withn refuge alternatives (RAs) may expose occupants to physiological hazards such as heat stress. The Mine Safety and Health Administration (MSHA) regulations require RAs in underground coal mines to provide a lifesustaining environment for miners trapped underground when escape is impossible. RAs are required to sustain life for 96 h while maintaining an apparent temperature (AT) below 95 °F (35 °C). The National Institute for Occupational Safety and Health (NIOSH) tested a 10-person tent-type RA, a 23-person tent-type RA, and a 6-person metal-type RA in its underground coal mine facilities to investigate the thermal environment over a 96-h period. The test results showed that mine air and mine strata temperatures surrounding an RA occupied by simulated miners (SMs) increased over the 96-h test period. The test results suggest that RA manufacturers should consider this increase in temperatures when calculating and evaluating RA components during surface and laboratory tests. The findings can equip stakeholders with additional considerations for calculating the interior heat and humidity temperature profiles for occupied RAs not tested in situ.

By James E. Friant

The technology applied to shaft sinking has lagged far behind other construction activities. While surface oriented construction and mining have made great strides with new processes and equipment, the majority of shafts sunk currently still follow a drill, blast and muck-out cycle developed in the 16th century. Today, in 1979, the shaft sinking industry is in the midst of its own private industrial revolution. Millions of dollars are being spent annually by industry and government alike to spring the art of shaft sinking into the 20th century. The objective of this paper is to review a few of the newest mechanized schemes for shaft sinking. This is not a theoretical review, however, but a practical one, and deals only with hardware and projects which are currently on jobsites. Figure 1 shows the equipment. On the left is the 241SB 184, a 24 foot diameter blind shaft borer. This machine is currently at about 200 feet, constructing a coal mine shaft in Alabama. It is built and utilized in a manner similar to a tunnel borer. In the upper center is the 1211SR, a 12 foot diameter blind shaft reamer. This machine follows a 6 foot pre-drilled blind pilot hole, and is at work in Chicago. On the upper right is the 121BR, a powerful new blind drill. Just below it is the conical drill head for the 121BR which can utilize either carbide or standard disc cutters. At the center bottom is an expandable back reaming head which can be used to enlarge a drilled shaft up to a maximum of 16 feet diameter, or can be used to produce a shaft having several diameter changes. This equipment is also in use in Chicago.

Jan 1, 1979

By Jida Wu, Zhenqian Wang, Chusheng Liu, Wenqiang Qiu, Mengqi Zou, Wei Zhao

During the dry screening, the hole plugging is a serious problem for most traditional screening equipment sieving the moist fine coal. It would lead to the low preparation efficiency and the low screening efficiency. The flip-flow screen is a new kind of screening equipment by using flip-flow motion of elastic screen surfaces to implement the separation of material. With the remarkable advantages of the extraordinary vibration intensity of screen surface, the hole is difficult to be plugged, and the screening efficiency is improved. In this paper, a kind of centralized forced flip-flow screen (CFFS) was proposed based on the crank rocker mechanism. The flip-flow motion of elastic screen surfaces is achieved by the periodical reversed motion of inner and outer screen boxes driven by crank. The advantages of the CFFS include considerable deformation of the screen surface, stable flip-flow quantity, low working noise, low vibration influence on environment, etc. The principle and construction of the CFFS were introduced, and the modal analysis and harmonic response analysis of key components (the crank and the linkage) were implemented based on finite element method (FEM), respectively. The first six orders of natural frequency and vibration modes were obtained. The maximum equivalent stress and strain under working and resonance frequency were achieved. The results illustrate that the resonance frequency is much higher than the working frequency, and the stress and strain are all within the safe limit of the material. The prototype was manufactured, and the sieving experiment demonstrates that the CFFS perform steadily, and screening efficiency is over 80%. The new feasible method of the dry screening was proposed by the CFFS. The corresponding numerical simulation and the experiment provided a reliable basis for the future promotion of similar product design and research.

Jan 1, 2017

By J. H. LaVerne Palmer, W. (Bill) C. Cox, Lorant B. Geller

An erector transporter (ET) has been designed and built to lift, carry and erect heavy machinery components, in particular the components of a 7.6 m diameter tunnel boring machine (TBM), within the access tunnels of a submarine coal mine in Eastern Canada. The ET is capable of manoeuvring within a 7.6 m tunnel while precisely positioning components as large as 6 m in diameter and weighing up to 27 tonnes each. The unit can negotiate 20% grades while carrying loads of 30 tonnes. The major design features, verification tests and performance trial results are presented. The versatility of the ET is such that many other applications are possible.

Jan 1, 1985

By G. G. Marino, Z. R. Widup

Marino Engineering Associates, Inc. (MEA) was asked to determine the effects of mining beneath a proposed roadway structure. In order to determine the subsidence potential and the magnitude of the mine stabilization costs it is important to know whether underground mining is present, and if so, to what a real extent. The site investigated had the potential to have mining in three different coal seams. To determine where mining was present MEAÕs borehole radar system was used. In summary, the borehole radar subsurface investigation validated that the available mine map in the most shallow coal seam was fairly accurate despite its age (1888), found no mining in the underlying coal seam and detected an area of unknown mining at a depth of about 300 ft in the lowest coal seam which was verified by subsequent drilling.

Jan 1, 2004

By M. Kumral

The in-situ mineral characteristics of a deposit are simulated by sequential co-simulation and averaging the simulated characteristics within specified block volumes creates a three-dimensional block model. This model is then submitted to optimal open pit and production scheduling algorithms. As the market values of industrial minerals depend on the satisfaction of predetermined blending criteria rather than metal content, a Linear Programming (LP) scheme has been used to identify all blocks that can be included in the blend without violating the grade requirements. The Lerchs-Grosmann algorithm using the blocks identified by the LP program determines optimal pit limits. All blocks that lie outside the optimal pit are removed from the system and the blocks within the optimal pit are submitted to the production-scheduling algorithm. Production scheduling optimisation is done in two stages: Lagrangean parameterisation, resulting in an initial sub-optimal solution, and multi-objective simulated annealing (MOSA) improving the sub-optimal schedule further.

Jan 1, 2002

By R. J. Cornelius

Gold with minor associated copper mineralization in the area of what is now the Bougainville porphyry copper deposit has been known since the 1920s and was probably known in German colonial times, pre- 19 14, although no records persist other than a reference by Stanley (1922) to copper specimens from Kieta that he saw in Rabaul. Stanley did not at the time believe that they came from Kieta. Gold was first discovered at Kupei by Jack Comb in 1929 and the Kieta Goldfield was proclaimed in May 1930. In December 1932, the Tapu Reward Claim at Moroni - the site of the Bougainville Copper concentrator, was pegged by C.W.M. Evans who prospected up river from the West Coast. The Pumkuna (Panguna) Reward Claim on the site of the subsequent porphyry copper deposit was granted in February 1934 to G.A. Myers. n May 193 1, the Kupei Reward Claim was transferred to Bou- gainville Gold Options NL and later reverted to Jack Comb and then the Bougainville Syndicate, as did the Pumkuna and Moroni claims. Most of the interested parties had come from the Edie Creek rush on the New Guinea mainland. In 1935, N.H. Fisher, the geologist in Rabaul for the New Guinea administration who later became director of the Australian Bureau of Mineral Resources in Canberra, reported on the three gold areas. Norm Fisher described the gold and copper mineralization and its habit in great detail and this report had a major influence on the events leading to the discovery in the 1960s. Gold production up to the Japanese invasion probably did not exceed $50,000 in value. Half a ton of copper-gold ore from Kupei was sent to O.T. Lempriere's in Sydney for assay in the early 1930s.

Jan 1, 1991

By B. J. Swenty, J. L. Hubbard, R. L. Peyton

Based on the results of the National Program of Inspection of Nonfederal Dams conducted by the US Army Corps of Engineers during 1977-1981, Missouri was found to have the highest number of "unsafe" dams in the nation. Many of the dams classified as unsafe in Missouri were tailings dams.

Jan 1, 1987

By D. B. Stephens

Assessing the occurrence of natural ground-water recharge at mine and mill waste disposal sites may be crucial to addressing regulatory agency concerns regarding the potential impact of waste seepage on ground-water resources. Recharge has been shown to occur even in semi-arid areas where annual lake evaporation exceeds precipitation. Permanent storage of waste seepage in the unsaturated zone is not to be expected if recharge occurs under natural conditions. Establishing the direction and rate of fluid movement in the vadose zone by field measurements is an important element that should be included in the site selection process.

Jan 1, 1987

By A. M. Raichur, K. Keltner, M. Misra

The removal of oxyanions of arsenic present in mine process water and drinking water to a regulatory level (i.e. below 50 ppb) is a challenging problem. Conventional water treatment methods presently used for controlling arsenic have several drawbacks and limited success. A new adsorbent (LS™) developed at the University of Nevada, Reno, has strong specificity for both arsenate and arsenite species present in process waters. The adsorbent in very selective to oxyanions of arsenic and competition of other indifferent ions is minimum. Water samples from different sources were tested and arsenic was successfully removed to below 50 ppb. This paper describes both batch and packed column tests conducted in the laboratory as well as at the plant sites using LS™.

Jan 1, 1997

By M. Li, J. D. Miller

It has been discovered that water insoluble alcoholic solutions of alkyl hydroxamic acids serve as selective collectors for the flotation of phosphate mineral resources (Miller et al., 2000). The effectiveness of the new collector chemistry has been demonstrated by the results from single stage bench scale flotation experiments for feed material from plants in Florida, North Carolina, and Utah. In the best case, from experiments with low grade (5% P20,) coarse feed (16 x 35 mesh), a single stage phosphate recovery of 95% was achieved with a concentrate grade of 31% P20,. Such a separation efficiency could not be achieved using the traditional fatty acid/fuel oil collectors as is evident from a comparison of the respective grade/recovery curves.

Jan 1, 2002

By R. M. Imhof, M. J. G. Battersby, J. V. Brown

There is a plethora of former industrial sites where coal mining operations have left large slurry impoundments. These contain raw washed fines, which have previously been too expensive to process to requisite grades for commercial use. New technology has been developed for fine material processing, namely the Imhoflot pneumatic flotation G-Cell. This froth flotation technique is a highly efficient means of concentrating coal and is particularly appropriate to the nature of materials encountered in tailings ponds. The high volumetric throughput resulting from the vastly reduced residence time in the cell allows for drastically reduced equipment sizes when compared to conventional flotation cells. This means the process, when combined with innovative pre treatment and filtration equipment can be developed as a mobile plant concept. This is seen as a minimum requirement when re-treating and rehabilitating fine coal ponds.

Jan 1, 2003

By John L. Shafer

A process for the conversion of stibnite (Sb2Sj) concentrates, crude antimony oxide, or metal to a pure cubic antimonous oxide (senarmontite) has been developed on a laboratory scale. The conversion of stibnite to senarmontite has been piloted. The high purity of the final product is the result of forming antimony trichloride as a low temperature distillable intermediate. To obtain the antimony trichloride the stibnite, or crude oxide is slurried in molten antimony trichloride and reacted with gaseous hydrogen chloride. Antimony metal is oxidized to the trichloride with chlorine. The hydrogen sulfide produced from the hydro- chlorination of stibnite can be upgraded to a strength of 95% or greater for further treatment. The crude antimony trichloride is separated from the gangue by a preliminary evaporation and then is fractionally distilled and the trichloride distillate has less than 50ppm of arsenic and lead combined (the most troublesome impurities in antimony processing). The purified antimony trichloride is then hydrolyzed with sodium or ammonium hydroxide to produce the cubic form of antimonous oxide (senarmontite) to the exclusion of the rhombic form (valentinite) which is photosensitive. The advantage of this process is the ability to treat a wide range of antimony ores, concentrates, and metal to yield a high purity oxide in a controllable range of particle sizes.

Jan 1, 1975

By P. N. Bradbury

The coal companies of today have to make all of their in-the-field managers MAINTENANCE PRODUCTION MANAGERS. By using a computer application to monitor all aspects of the daily production as well as the maintenance, a company can immediately effect a cost reduction by studying the down-time and delay trends on an everyday basis. This paper will outline how a company can use a program to not only put a stop to the increasing supply and maintenance costs but start trimming each of these cost centers while actually increasing the efficiency and productivity of the current work force.

Jan 1, 1991

By J. E. Carr

A bewildering number of continuous thickeners and clarifiers are used in mineral industries and other heavy industries. General types are: 1. Conventional Thickeners (Fig. 1). 2. Thickeners with Flocculating Feedwells (Fig. 2). 3. Solids Contactors (Fig. 2). 4. Tray Thickeners (Fig. 3). 5. Lamellas (Fig. 4). 6. Conventional Thickeners with Lamellas 7. High Flow, Fluid Bed Thickeners (Fig. 5). These units must be adapted to varied applications. They must provide operating flexibility to meet process needs. Such factors multiply the decisions which must be made prior to the selection of a thickener. The seven types of thickeners listed above, with their variations, share design concepts which limit their application and which can be used to evaluate their performance. Some of these are listed: 1. Feed velocities must be limited and/or controlled. 2. Natural or reagent flocculation is necessary. 3. Horizontal settling area is the basis for capacity. 4. Overflow velocities must be limited and/or controlled. 5. A controlled underflow is necessary. Applying these needs to the basic process concepts is thickener selection. The basic function of a thickener in the minerals industry is the separation of a thickened sludge containing fine solids from water. To this primary separation function are frequently added others to give a list as follows:

Jan 1, 1977

By Nikhil Dhawan, Veeranjaneyulu Rayapudi, Singh Rahulkumar Sunil

The ever-increasing demand for steel and the subsequent depletion of high-grade ores requires the massive utilization of low-grade iron ores. In the present study, an iron ore slime sample containing 56.1% Fe was investigated using physical beneficiation, carbothermal reduction, and a microwave-assisted process; however, physical beneficiation and microwave exposure were found to be inefficient as they yielded lower iron recovery. Using coconut shell as an alternative reductant was found to be promising and does not lead to the formation of higher iron oxides, such as fayalite and wustite phases. The microwave-assisted carbothermal reduction was found at par with conventional reduction, saving time and heating. The optimum magnetic concentrate obtained in both carbothermal reduction routes (microwave and muffle furnace: Fe grade, Fe recovery, and yield of 64.3, 97, and 84%, and 67, 99, and 83%, respectively) are suitable for alternative iron-making or blast furnace units.

By Patricio A. Riveros

Various types of commercial ion exchange resins were evaluated with respect to their ability to extract gold from cyanide leach solutions. Large differences were found among the various resins in terms of selectivity and gold loading. The hydrophi­licity and the charge density appear to be the main factors that determine the resin characteristics. Polystyrene weak-base resins, such as Dowex MWA-1, exhibited the best all-round performance.

Jan 1, 1990

By C. J. Bise

Safety training requirements differ from mine to mine due to changes in the demographic characteristics of the workers or changes in job and organizational characteristics. Accordingly, a microcomputer-based procedure has been developed to assist mine trainers is determining if undesired worksite performances result from lack of knowledge or skill, which are trainable categories, or from categories that are considered to be non-trainable (such as equipment limitations or management procedures). A special effort was made to understand the psychology of worker behavior by analyzing worker reactions to various organizational and job characteristics.

Jan 1, 1995

By W. T. Gorton

Bonds are required by state and federal law to address reclamation when the permittee defaults. Under various principles of law, a bonding company may propose to perform the obligations of the permittee, however, the negotiations with the regulatory agencies, surface and mineral owners and other interested parties can create a very complicated scenario that requires an understanding of the law regarding environmental protection, bankruptcy and surety ship, along with technical expertise in land reclamation. This paper presents the engineering professional with a framework regarding areas of law that pertain to surety reclamation projects and negotiations with state and federal agencies and related parties. Though presented in the context of the coal industry, the principles discussed are generally applicable to the mining industry as a whole.

Jan 1, 2003

By David Corkum, David Hatem

Subsurface construction projects are risky ventures and the decision to deliver a project using the Design-Build model does not eliminate those risks. Differing site conditions, inadequate design, and delays will continue to plague some projects. The Design-Build procurement model, however, presents a broad opportunity to allocate those risks much differently than in the familiar Design-Bid-Build model. Starting with a philosophical approach to risk and reward, this paper discusses the continuum of possible risk allocation strategies. It concludes with a proposed optimum strategy in terms of the project’s overall economic efficiency, and points to the dispositive contractual provisions that serve to contour the risks.

Jan 1, 2003