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By S. A. Elmquist

Research activities performed by Cleveland-Cliffs Research and Hibbing Taconite plant personnel during the last decade have resulted in the development of an improved autogenous mill grinding circuit. Minus one (1) inch autogenous mill trommel oversize material, con-sidered to be a critical size, is magnetically cobbed and then crushed to 100% minus 3/8" prior to reentry into the feed end of the mill. Autogenous mill capacity increases, up to 25%, have been measured in pilot plant tests using this approach and are also anticipated for the Hibbing Taconite concentrator which presently has reached a 15.5% improvement.

Jan 1, 1994

By J. A. Bradbury

N. A. Degerstrom, Inc. has constructed and operated a processing plant approximately five miles north of Soda Springs, Idaho for processing a byproduct phosphate treater dust from Monsanto's elemental phosphorus plant, also located in Soda Springs. The plant is designed to produce agricultural-grade phosphoric acid, gallium, and silver. The design capacity of the plant is 54.4t (60 st) of treater dust per day, which can produce 16,326t (18,000 st) of phosphoric acid, 6,600 kg of gallium, and 6,033 kg (194,000 oz.) of silver per year.

Jan 1, 1993

By B. Bag

Saturated and unsaturated fatty acids are used in the flotation of iron values present in iron ore. Among the several fatty acids, oleic acid and its sodium salt are widely used. To substantiate the flotation results, the quantum chemical calculations of a few such acids have been carried out by adopting the semi-empirical AM1 method. These acids have been further optimized in the presence of an iron atom. The electronic interaction of the polar carboxylic head group of oleic acid with the iron atom is higher compared to the other acids. The numerical results support the flotation behavior of iron ore with oleic acid. Key words: Iron ore, Flotation, Fatty acids, Quantum chemical calculations, Semi-empirical AM1 method

Jan 1, 2009

By B. J. Arnold

Prior laboratory work has demonstrated -that much of the fine ash-forming minerals entering a flotation froth are there as a result of water carry-over from the bulk contents of the flotation cell (Arnold and Aplan, 1986a). Using a bank of four 300 cu ft WEMCO flotation cells cleaning a well-liberated Lower Kittanning seam coal, test results show that the sulfur and ash content of the froth is directly related to the water content of the froth (or inversely related to the percent of solids in the froth). Reagent changes which result in a watery froth produce a higher ash content in the froth. A direct comparison of laboratory and plant results show that the standard laboratory flotation test produces a product higher in sulfur and ash than that produced in the plant. Caution should be exercised when extrapolating laboratory test results to the plant situation. A method of estimating coal flotation product quality in the plant based on laboratory tests is given.

Jan 1, 1990

By C. Mark, D. M. Pappas

From 1999 through 2008, groundfall events resulted in 75 fatalities, 5,941 injuries and 13,774 noninjury roof falls in U.S. underground coal mines, according to the U.S. Mine Safety and Health Administration (MSHA). A comprehensive analysis of these events was conducted to better understand where and why these incidents occurred. The first segment of the study used the MSHA database to evaluate groundfall injury rate trends related to mining method, year, locality, seam thickness, mine size, coalbeds and seasonal effects. In the past decade, roof fall injury rates have dropped 50%, but rib fall injury rates have remained constant. Room-and-pillar mines had a roof fall injury rate that was nearly 2.5 times the longwall rate. High groundfall rates occurred in the Illinois Basin, a finding that correlates with other studies that have shown that roof rock in the Illinois Basin is weaker than that in the central Appalachian coalfields. Finally, noninjury roof fall rates in the eastern and central United States were found to be 50% higher from July through September, possibly because of the changes in humidity levels that may cause shale mine roofs to deteriorate. The second segment of the study evaluated the root causes of failure by reviewing all MSHA groundfall fatality reports for 1999-2008. Pillar recovery was the leading cause of groundfall fatalities (19%), followed by rib falls, roof skin falls and traveling under unsupported roof (16% each). Defining prominent ground control incident trends and hazards will identify areas where additional study is needed and where innovative solutions need to be developed to reduce these severe occupational hazards.

Jan 1, 2011

By Qinghua Tian, Zhipeng Xu, Dong Li, Xueyi Guo, Liu Zhu

A possible process for extracting tellurium and antimony from a residue generated in alkaline sulfide leaching of telluriumbearing alkaline skimming slag was proposed. The central composite design was employed to define the optimal leaching conditions for tellurium and antimony extractions from the residue sample. Using a 23 factorial matrix, the best performance for tellurium and antimony extractions (96.36% and 99.64%) were obtained at 175 g L−1 Na2S concentration for 80 °C during 60 min. The notable degree for influencing tellurium and antimony extractions was leaching temperature, Na2S concentration, and leaching time. The analysis of variance results indicated that the regression model was significant and suitable to be used for the optimization of independent variables within the range. The model was validated under optimal operating conditions based on the experimental design results. Antimony and tellurium in the leach liquor were separated and recovered by H2O2 oxidation followed by Na2S-Na2SO3 reduction. 98.93% of antimony was precipitated selectively during H2O2 oxidation, while 95.06% of tellurium was precipitated during Na2S-Na2SO3 reduction. NaSb(OH)6 and elemental tellurium was obtained as the product.

By Atta Ur Rehman, Kwame Awuah‑Offei

This paper examines the effect of bucket geometry (cutting blade profile, floor profile, and blade thickness), speed, motor power output, and muckpile particle sizes on bucket penetration and draft for rubber tire loaders. The work uses a 1:16 scaled model of a load-haul-dump in full factorial experiments to examine the effect of the variables on penetration and maximum draft. The results show that speed and motor output are positively correlated to penetration and draft; muckpile particle size is positively correlated to penetration and negatively correlated to draft (p < 0.0014). The results show that buckets with a semi-spade cutting nose profile yield the highest penetration (mean 118.30 mm) followed by those with the spade (mean 108.88 mm), which also yield higher penetration than those straight blades (mean 95.19 mm). Bucket floor profile and blade thickness had no significant effect on penetration or draft. Also, we determined that increasing the speed and motor power output, simultaneously, can reduce bucket penetration. Thus, operators should not waste energy for no additional gain or even loss in bucket penetration. Also, the work finds speed and motor power output each combine with muckpile particle sizes to affect bucket penetration. This research furthers our understanding of the effectiveness of different bucket geometries in improving penetration and reducing draft for rubber tire loaders.

Oct 29, 2021

By B. E. Davis

A technique was devised by the Bureau of Nines to recover coarse (plus 1.7 m) North Carolina phosphate now discarded as waste. Concentration utilizes the difference in particle sphericity between the relatively flat calcite and the rounded phosphate pebbles. Sizing, treatment in a continuous hydraulic classification system, and grinding upgraded a 17.0-pct-P205 reject to 24.5 pct P205 with a phosphate recovery of 63 pct.

Jan 1, 1985

By P. Zhang

A 1989 FIPR characterization study of the future phosphate resources in Florida showed that MgO would be a problem with both the pebble and concentrate as phosphate mining moves deeper. Since the ratio of concentrate to pebble will become higher and higher in the future, reducing Mg content in the concentrate by a small margin would allow blending of a large portion of the high-dolomite pebble. This research was conducted based on that logic. The following six approaches were tested for reducing MgO content in the flotation concentrate: (1) Adding a dolomite depressant in the rougher flotation step; (2) Dolomite flotation on the rougher concentrate with and without grinding; (3) Dolomite flotation on the cleaner concentrate with and without grinding; (4) Scrubbing the flotation feed; (5) Scrubbing the rougher concentrate; (6) Scrubbing the cleaner concentrate. Successful methods include adding a dolomite depressant in the rougher flotation, dolomite flotation on the cleaner concentrate with grinding, and scrubbing the cleaner concentrate in quartz sand. These techniques could reduce MgO content in the final concentrate by 20-40%. The flotation process could achieve a concentrate with the lowest MgO content, but it is the most expensive approach. Adding a dolomite is inexpensive and easy, but the effect is limited. Overall, scrubbing may be the most promising technology for this purpose.

Feb 23, 2014

By Gamal Rashed, Zorica Radakovic-Guzina, Khaled Mohamed

"Underground coal mines use mechanical bolts in addition to other types of bolts to control the rib deformation and to stabilize the yielded coal ribs. Limited research has been conducted to understand the performance of the mechanical bolts in coal ribs. Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted this work to understand the loading characteristics of mechanical bolts (stiffness and capacity) installed in coal ribs at five underground coal mines. Standard pull-out tests were performed in this study to define the loading characteristics of mechanical rib bolts. Different installation torques were applied to the tested bolts based on the strength of the coal seam. A typical tri-linear load-deformation response for mechanical bolts was obtained from these tests. It was found that the anchorage capacity depends mainly on the coal strength. Guidelines for modeling mechanical bolts have been developed using the tri-linear load-deformation response. The outcome of this research provides essential data for rib support design.INTRODUCTIONThe design of rib bolting in U.S. coal mines is based on a trial-and-error process, which is insufficient to eliminate injuries and fatalities caused by rib falls. In the last 10 years, rib failures have resulted in 17 fatalities, representing 52% of the ground-fall fatalities in underground coal mines in the United States (MSHA, 2018). Recently, NIOSH researchers surveyed 90 sites in 14 underground coal mines in the Eastern United States and found that 11 mines are bolting coal ribs, with 4 of those mines using the conventional mechanical bolts and the others using fully-grouted bolts. NIOSH researchers are developing an engineering design procedure for rib support. Pull-out test programs for mechanical and grouted rib bolts were conducted to understand the rib control mechanisms of rib bolts. Only the test results of mechanical bolts are presented in this paper.Mechanical bolt (or point-anchored bolt) is a tensioned bolt anchored down the borehole with a mechanical expansion shell or a resin-grouted medium (Peng and Tang, 1984). The mechanical anchor bolt consists of a plug, a shell anchor, a headed bar with the top end threaded, a bearing plate, a hardened washer, and occasionally a friction-reducing washer. The shell anchor can be either standard or bail type (Figure 1). The standard type shell is held in place by a nut, while the bail anchor uses a strap to hold the shell in place (Peng, 2008). The diameter of the bar is generally 16 mm (? in) for the #5 bolt or 19 mm (6/8 in) for the #6 bolt. The diameter of the hole that the bolt is inserted into must be carefully controlled, since an oversized hole can result in poor anchorage (Moss, 1971). The anchorage is obtained by applying torque to the bolt head, which in turn pulls the plug down in the shell and expands the serrated leaves against the sides of the hole-wall. In the resin-grouted anchor, the resin replaces the mechanical expansion shell at the end of the hole. The anchorage is achieved by bonding between the resin, bolt, and the hole-wall."

Jan 1, 2019

By William G. Pariseau, Mark K. Larson, Heather E. Lawson

Rational design based on engineering fundamentals is essential for the layout of safe, stable shafts and tunnels. Shafts and tunnels including winzes, raises, adits, and crosscuts are lifelines to the underground and must be secure. The contribution of this paper describes a significant extension in existing software previously developed for five important design problems in strata-bound mines such as coal, trona, salt, potash, and some large, lead-zinc mines. This extension in software allows analysis to proceed in three easy steps: (1) preparation of a strata properties file, (2) generation of the finite element model, a mesh, and (3) finite element program execution. Circular, elliptical, and rectangular shaft sections are available for a single shaft, twin shafts, and shafts in a row. Spacing of twin shafts and shafts in a row is a free parameter (pillar width). Tunnel shapes are the same as shafts but include the conventional arched back section. Dipping strata of variable thickness, depth and orientation relative to the excavation of choice are allowed. The analyses are three-dimensional. An elastic-plastic material model based on associated rules of flow and an N-type yield condition for isotropic, transversely isotropic, or orthotropic rock are used for all strata. Example analyses from several hardrock mines are provided to illustrate the three-step process including mesh plotting and plotting of selected results. The goal of this software is to advance mine design technology for improved miner health and safety.

By J. E. Urosek

In October, 1990, a fire started in a large underground coal mine in Western Pennsylvania. During fire-fighting activities, an explosion occurred and all personnel were evacuated. Safe re-entry into the mine was not possible and the mine was sealed. Recovery efforts began in January, 1991 and continued until March, 1991, when permanent underground seals were installed between the fire area and the mine openings. This paper describes an extensive atmospheric monitoring program conducted by the Mine Safety and Health Administration (MSHA), Pittsburgh Safety and Health Technology Center (PS&HTC) including the analysis of mine fire gases, natural ventilation, fan pressure and air quantity distribution.

Jan 1, 1993

By H. Reed

The precious metal mining industry in Nevada handles and generates a certain amount of hazardous materials and waste on a regular basis. These products range from processing material additives to wastes from laboratory testing, heap leaching, and hydrocarbon treatment and disposal. The volume of materials and wastes is dependent upon the amount of ore processed. Handling, treatment and disposal is dependent on the type of material handled and the waste generated. Owing to the health and safety concerns and due to the existing regulations that control handling and disposal of hazardous materials and wastes, the mining industry is obligated to comply with all applicable requirements for proper handling of these products. Plus, in an effort to minimize any impacts from this effort, the industry is continually looking for alternative methods to accomplish these requirements and to also minimize costs. This paper will discuss the general, and in some cases the specific conditions, by which the industry is coping with the issue and efforts to minimize any impacts from handling, treatment and disposal for hazardous materials and wastes. The subject of compliance with the Toxic Release Inventory (TRI) requirements and bio-treatment of wastes and other technologies will be discussed.

Jan 1, 2001

By Ronald J. Roman

A mathematical model was developed for the grinding and flotation section of Union Carbide&apos;s Bishop mill and this model was used to indicate how variations in grind, retention time, and calcite and fluorite content effects the mill capacity, tungsten units produced, and the grade and recovery of the scheelite concentrate. A model such as this is a starting point in determining the economic optimum running condition for a mining and milling operation and an example of this is given.

Jan 1, 1969

By A. Haghighat

The Missouri University of Science and Technology?s (Missouri S&T) Experimental Mine is a teaching and research facility which has been excavated in limestone by mining engineering students over almost 100 years. The mine is currently being extended to a second level. Available fans for ventilation are two surface fans of 24 kW and two underground booster fans of 12 kW. The design of a ventilation network in conjunction with multi surface fans and booster fans entails a complex procedure. Ventsim Visual software modeling has been used for network analysis to determine the optimum surface and booster fans locations, blade settings, and speeds. Both natural and mechanical induced ventilation pressures have been taken into account. Three working faces on each level have been designated as target points that minimum air quantities are required. The model has been calibrated against a pressure and quantity survey. Design of ductwork, door/stopping positions and different fans characteristics have been examined. The optimum flow rate at identified working faces, efficiency and minimum energy losses and annual network power cost determine the best scenario. The optimum design has been determined for the ventilation network for the next 100 years. The optimum flow rate across working faces is the key criterion selected.

Feb 23, 2014

By A. H. Kaksonen

Numerous reactor designs for biological sulfate reduction have been reported. Fluidized-bed bioreactors (FBR) can efficiently retain biomass and allow high mass transfer and reaction rates. This work reviews the development of various sulfate-reducing FBR processes for treating acidic metal- and sulfate-containing waters and recovering metals from bioleaching liquors. The FBR process performance was evaluated with continuous flow experiments under various operational conditions: fluidization rates, influent pH values, metal, sulfate and salt concentrations, hydraulic retention times, electron and carbon sources, and temperatures. Substrate utilization and sulfide inhibition kinetics were determined with batch FBR-kinetic experiments. An artificial neural network (ANN) model was used to predict the performance of the FBR. Sulfate-reducing bacteria (SRB) were characterized in FBRs with molecular and culture-based approaches with the aim to gain a better understating of the bioprocesses. Based on the studies, FBRs are well suited for the combined removal of metals, acidity and sulfate from water.

Jan 1, 2010

By R. Brantley Sudderth

There are three broad categories in which most solvent extraction technology can be distributed?: 1) reagents, 2) equipment, and 3) systems. Reagents which are now used in commercial solvent extraction plants are of many chemical types, and each possesses certain properties which make it more economically desirable than another alternative. The equipment which is&apos; used in solvent extraction plants for contacting the organic and aqueous phases and separating the same is varied. Most common to the industry is the mixer-settler unit which in itself, can be of varied design; but many new innovations in contacting and separating equipment have been recently introduced or are :now being studied. Each specific solvent extraction application will often dictate the type of contacting and separating equipment used. Obviously, the trend is toward smaller less expensive equipment which reduces the often expensive organic inventories necessary for most solvent extraction plants. The current thrust of .investigations in ancillary equipment is usually aimed at recovering organic from solvent extraction sludges or from aqueous streams exiting the process.6 This type of equipment helps to reduce the total organic losses from solvent extraction plants and thus reduce the operating costs. The term "systems" in solvent extraction applies to the manner in which a solvent extraction process is carried out. This manner is usually dictated by the properties of the reagent which is used, and it involves a tailoring of the equipment or the process flowsheet. Some of the things which can be tailored are: 1) The aqueous media -whether acidic or basic and what type of acid or base 2) Counter-current or single stage (co-current) contacting 3) EMF or pH control 4) Organic "crowding" alternative 5) Heating or cooling process streams Regardless of the type or extent of tailoring, efforts to do this are usually a result of the low cost of solvent extraction as a unit process.

Jan 1, 1977

By G. Kazonich

The high costs and environmental problems associated with making iron and steel in the United states is driving the development of new technologies to replace the blast furnace. A prototype reactor incorporating rocket technology was designed and built. This rapid rate reactor was operated successfully and consistently made iron metal. Minus 32s-mesh magnetite particles could be reduced to iron metal in less than 50 ms in a high temperature flow through reactor. Iron product was recovered inside the reactor and in a downstream cyclonic separator. The results of typical operation and how parametric changes affected the reduction of iron ore concentrates are discussed.

Jan 1, 1993

By C. M. Goodall

Solids and liquid phase residence time distribution data is reported for a laboratory column flotation cell. The effects of various physical flotation parameters on residence time distributions are reported and analyzed. A plug flow model with recycle is proposed for the froth phase and a tanks in series model for the pulp. By comparison of two and three phase residence time -distribution data it has been shown that the use of liquid residence time distribution data to predict the residence time distribution of the solids in a column is not valid.

Jan 1, 1990

By A. G. Fonseca

The effects of coal cleaning, coal combustion and flue gas particulate removal systems on the partitioning of 12 trace elements were investigated. This study was prepared to help document the fate of trace elements in modern coal preparation plants and coal-fired utility boilers. The coal cleaning data were obtained from several coal preparation plant operations. The CONSOL 1. 5 MM Btu/hr pilot combustion and electrostatic precipitator (particulate removal system) test facility was used to develop the combustion systems data. A comparison with the very limited amount of published data from utility boilers is presented.

Jan 1, 1993