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By Benjamin K. Pocock

When considering alternative equipment choices in mill or process flowsheets, it is important to determine both capital and operating costs of such equipment as well as other possible savings related to downstream operations. This paper presents a few case studies and shows cursory guidelines for the selection of equipment for new installations or in the retrofitting of existing plants. Based upon recent plant experience, suggestions are given to improve the operation of clarifiers, thickeners and vacuum filters.

Jan 1, 1986

By E. A. Metz

Silicon dioxide, silica, is the most common oxide in the earth' s crust. The health effects of silicon dioxide dust have been known since Biblical times. Agricola's book, published in the mid 1500's on occupational medicine, described a lung disease that afflicted miners. He observed a disease in miners that caused shortness of breath, coughing and wasting. Add fever, chest pains and fatigue and we have the current symptom complex of silicosis. As we approached the 21stcentury, the Labor Department began an aggressive campaign to combat silicosis-a preventable disease. Unfortunately, many publications do not clearly differentiate the polymorphs of silica known to mineralogists. Crystalline silica, i.e., alpha quartz, tridymite and cristobalite need to be considered differently from the amorphous forms of silica. Freshly fractured surfaces of the silica and host specific responses will be examined. Recent research focuses on the biologic interactions of free radicals generated by mineral particles. This results in cell injury and DNA damage, in turn leading to fibrogenesis and possibly carcinogenesis. In addition to particle-cell interactions, emphasis is given to lung defense mechanisms.

Jan 1, 1998

By L. Patts, J. Hummer

The use of diesel-powered equipment in underground coal mines has increased substantially during the last ten years in an effort to enhance mine safety and productivity. Pennsylvania and West Virginia are two of a number of states with regulations governing the use of such equipment. These states both developed and promulgated regulations before permitting diesel equipment in their underground coal mines because of concern for miners’ safety and health, especially with regard to the contamination of mine ventilation air with diesel exhaust emissions. The major components of diesel exhaust emissions are combustion gases and diesel particulate matter. The gaseous emissions consist of carbon monoxide, carbon dioxide, oxides of nitrogen, sulfur oxides and unburned hydrocarbons. The diesel particulate matter (DPM) is comprised of solid carbon particles, liquid and solid hydrocarbons, sulfates and moisture. The Federal Mine Safety and Health Administration (MSHA) also promulgated regulations in an effort to control diesel emissions in underground coal mines. MSHA has adopted threshold limit values (TLVs) for all gaseous components of diesel exhaust, which were established by the American Conference of Governmental Industrial Hygienists (ACGIH). MSHA (30 CFR Part 72 Subpart D) has established a tailpipe DPM emissions limit of 2.5 g/hr for diesel engines used in permissible equipment, heavy-duty non-permissible equipment, generators and compressors used in underground coal mines. A tailpipe DPM limit of 5.0 g/hr has been established for light-duty outby diesel-powered equipment. The rationale for the tailpipe emissions limit was that an ambient measurement of DPM in a coal mine was not feasible because there is no established sampling method able to distinguish between coal mine dust and DPM. The stringent tailpipe emissions limit mandates the use of exhaust aftertreatment devices for most diesel engines used in underground coal mines today. One method by which tailpipe DPM can be reduced to MSHA limits involves using an exhaust cooling device in conjunction with a high-temperature, disposable diesel particulate filter.

Jan 1, 2011

By Hugh McMillan

To protect the water supply for the Metropolitan Chicago area, the Illinois legislature, in 1889, created the Metropolitan Sanitary District of Greater Chicago. To insure the quality of the water supply, the Sanitary District collected and diverted the wastes of 750,000 people away from Lake Michigan. Today, the Sanitary District collects and treats the wastes from a domestic population of 5 ¼ million people and an industrial waste load equivalent to 4 ¼ million people. The District serves Chicago and 120 other cities and suburbs in an 858 square mile area. An average of 1300 million gallons of wastewater is treated each day, producing as a by- product about 700 dry tons of solids which contains more than $10,000 worth of plant nutrients when equated to the value of commercial fertilizer purchased in the retail market. The Sanitary District considered several alternatives to past methods for disposing of these solids, and chose land application as a technique to utilize the solids produced by the wastewater treatment process in a beneficial manner.

Jan 1, 1973

By A. K. Sinha

Research shows that continuous mining sections can normally produce around 950 tons per shift in a seam 5 or 6 ft. thick. The shuttle cars as well as the continuous haulage systems are able to match with the continuous miners in capacity. However, in practice both of the two systems seem to be averaging at around 450 to 500 tons per shift in production. Continuous haulage systems are preferred in thin seams particularly where the floor is soft.

Jan 1, 1981

By K. S. Olson

My reaction when first asked to present this paper was; "What could I possibly say that would hold the audience?s attention for 15 minutes? What could I offer that anyone familiar with the Nevada Barite Industry wouldn't already know?" Well, quite frankly I can't. The industry has certainly been anything but exciting for the past 10 years and, in fact, quite depressing. The challenge, for those few of us left in it, has been to keep it alive. At times it has felt like a doctor must feel with a terminally ill patient. All I can do is recap the past ten years, review the present state of the industry, and offer a few personal opinions and observations as to where I think we are headed.

Jan 1, 1993

By S. S. Klima, A. L. Mazzella, J. S. Driscoll, T. W. Beck

Previous testing was performed by researchers at the National Institute for Occupational Safety and Health (NIOSH) to improve longwall dust control using underside shield sprays with a longwall directional spray system. This testing provided encouraging results toward respirable dust exposure reductions for longwall personnel, achieving as high as 99% dust reduction at some sampling locations along the longwall personnel walkway. Additional laboratory testing was conducted to test these underside shield sprays in conjunction with a shearer-clearer spray system located on the longwall shearer body. The purpose of this testing was to determine if the underside shield sprays interacted positively or negatively with the shearerclearer sprays. Results from this testing indicate that while the shearerclearer system influences where the respirable dust particles are directed, underside shield sprays can still lower respirable dust exposure for longwall personnel.

Mar 2, 2022

By A. Wallace Mitchell

Barite deposits in Nevada occur as bedded and vein-types along a north-northeastern -trending zone which parallels the Antler orogenic belt The bedded deposits of Nevada are the most significant economically. They are presently supplying eighty-five percent of the domestic barite production which is used primarily as a weighting agent in the petroleum drilling industry. The ore bodies are controlled both structurally and stratigraphically, occurring along regional and local structural breaks in siliceous eugeosynclinal rocks of mid-Paleozoic age. Evidence for origin of the barite includes sedimentary and hydrothermal features indicating that localization probably took place along fractures in the seafloor.

Jan 1, 1980

By Edgar W. Sawyer

Attapulgite and sepiolite are the clay minerals used to thicken ionically contaminated watzrs in the preparation of drilling fluids. They are nonsweliing clays that can be dispersed and reflocculated by mechanical means to increase the viscosity of fresh water and salt and gypsum contaminated waters. Those gelled in fresh water do not become excessively thick when contaminated with high salt concentrations or polyvalent cations encountered during drilling. Gels formed exhibit thixotropy and yield pseudoplastic rheological behavior due to the particle interactions and mechanical interferences of the flocculated gel structure.

Jan 1, 1983

By Rudolf Fahn

Bentonites are best suited for the preparation of acid activated clays with efficient adsorption properties. They are weathering products of acid volcanic ashes and their natural deposits are world-wide spread. The main constituent of bentonite is the aluminium hydrosilicate nontmorillonite with a high ability to swell. Süd-Chemie owns bentonite deposits in Germany and subsidiaries in Italy, Mexico and Arizona.

Jan 1, 1979

During foundry sand reclamation process development, molds formed from reclaimed chromite sand showed a rapid decline in tensile strength during thermal cycling tests. Because this characteristic could limit reuse of chromite sand in the foundry, the sand was examined in detail. Scanning electron microscopy, x-ray mapping, magnetic susceptibility, and x-ray diffraction were utilized to evaluate processed chromite sand. It was found that process variables such as binder composition, reclamation temperature, and processing method had a significant effect on the chromite sand particle surface. X-ray diffraction indicated a crystallographic change in the processed sands. Magnetic susceptibility also increased after processing. Diffusion of iron to the particle surface and increased surface roughness were identified as potential causes of the decreased tensile strength in the molds.

Jan 1, 1993

By Allan M. Johnson

The Sherwood Mine is being monitored to determine the nature and extent of changes in the mine and its environs which result from the closing and the cessation of pumping. Of particular interest was the possibility of piping-induced subsidence occurring as the mine flooded. Previous experience in the district indicated that this possibility was very real. A monitoring system, including acoustic sensors, extensometers, surface subsidence monuments, and ground water observation wells was installed in July 1978, just prior to the mine closing. Late in 1979, three piping-induced subsidence events occurred. The monitored data, and related laboratory studies are being applied to a quantitative description of piping-induced subsidence.

Jan 1, 1980

By A. Dadgar, R. H. Sergent

Changes in the ore types available and increased environmental concern have created a demand for an alternative technology to cyanide for the extraction of gold from ore. Great Lakes Chemical Corporation (Great Lakes) believes that halogen chemistry, in particular bromine chemistry, is the best available alternative to cyanide for gold extraction. Great Lakes is a Fortune 500 chemical company with sales of approximately one billion dollars per year. Great Lakes extracts elemental bromine from naturally occurring brines in Southern Arkansas. Great Lakes has developed a family of proprietary bromine compounds to aid in the extraction of gold. In addition to proprietary bromine compounds for gold extraction, Great Lakes has developed a method of recycling bromide ion in the leach circuit. Various recovery methods, including ion exchange and solvent , extraction are currently being studied.

Jan 1, 1990

Mines in the Lake Macquarie region of New South Wales, Australia, are faced with the dilemma of having to introduce longwall mining techniques at a time when increasingly large areas of the surface are being used for urban development. Increasing pressures on safety, costs and productivity performance dictate that longwall mining is the method for the future. Construction of surface structures is controlled by a statutory body known as the Mine Subsidence Board (MSB). All surface structures have to be designed to MSB criteria. All mining plans involving secondary excavation also have to be submitted to the MSB for approval. The Board acts as risk assessor in evaluating acceptable levels of surface subsidence vs. the value of the coal resource. Surface repairs are paid for by a levy on all coal producers.

Jan 1, 1995

By William J. Kohan

Milling has traditionally been considered more art than science. In the last 10 years, significant improvements in process equipment have been made and we are finally taking significant steps toward approaching grinding as a science. Two machines have been at the center of this development. These are the roll press and the high efficiency separator. The former can be considered as a new technology or adaptation of existing i.e. roller mill. The latter is clearly an improvement of existing technology. Other machines have been introduced to a lesser degree and later. Among these are the CKP and Horomill. The purpose of this paper is to provide an over- view of the currently available modifications for operating systems and options for new milling circuits with some comments on their application and history.

Jan 1, 1997

By T. A. Jones

The Kelsey Centrifugal Jig is an enhanced gravity concentrator capable of separating fine minerals and/or minerals with relatively small differences in specific gravity. Since the first commercial installation at the Renison Bell tin mine in Australia, development and improvement in hardware has continued, including the introduction of the high-capacity J1800model Kelsey Jig. The Kelsey Centrifugal Jig is widely applicable to fine mineral recovery duties, with key application areas including mineral sands, tin, gold and nickel. Other areas of application include: iron ore, base metals, chromite, PGMs, soil remediation and scheelite. The latest developments on the Kelsey Jig are discussed together with a review of recent installations involving: • Fine gold / sulphide recovery from leach tailings • Magnesium mineral removal from nickel sulphide concentrates • High-grade zircon recovery from plant tailings

Jan 1, 2004

By P. G. Semple, K. W. Major, R. M. Nendick

As free milling oxide gold ore reserves are depleted, more mining companies are having to evaluate the available alternatives for treating refractory deposits. The selection of a treatment process can be very difficult; and, despite the claims of their respective proponents, there is no one process that will continuously prove superior. Selection of the optimum process for an individual deposit is contingent on the size of the deposit, the grade of the deposit and the refractory nature of the ore. Since extensive metallurgical test programs are usually required to determine the optimum extraction process, an inappropriate initial selection may prove costly and time consuming. This paper discusses the steps involved in evaluating a refractory ore in order to expedite the evaluation of the required process through the feasibility study stage.

Jan 1, 1990

By Yuusaku Tominaga, Sukumar Bandopadhyay

A power-series trend curve of elapsed time was estimated by using time series data of measured concentrations of carbon monoxide in the Taiheiyo coal mine, Hokkaido, Japan. The difference between the moving average concentration data and the estimated data from the trend curve showed linear correlation when plotted on a normal probability paper and a correlation coefficient value of 0.99. It is concluded that the estimate of carbon monoxide concentration using moving average values of concentrations compares very well with the results obtained from the trend curve within the three-sigma (standard deviation) range of the distribution. Thus, it is believed the results can be used to monitor and detect abnormal ventilation conditions in a ventilation network such as the occurrence of spontaneous combustion at an early stage.

Jan 1, 2002

By Joachim H. Schubert, David G. Hulbert, Ian K. Craig, Roger G. D. Henning

This paper presents a stabilizing controller for flotation plants which uses a quasi-multivariable technique. The controller monitors all the levels in the plant, and by anticipating interactions between various parts of the plant, is able to stabilize the plant far more successfully than the normal plant control. Once stabilizing control has been achieved, optimization of the process becomes easier and more sustainable. An estimate of the improvement in metallurgical performance is made and a singular value analysis was conducted to verify that the multivariable algorithm will theoretically control better than a collection of individual PID loops. Metallurgical results are presented to show that the improvements are attainable in practice. Control by the Mintek algorithm was alternated with normal plant control, to show that the improvements are statistically significant.

Jan 1, 1995

By B. Huang, H. Sevim, R. Honaker

The use of medium-to-high sulfur coals has been negatively impacted by the 1990 Clean Air Act Amendment (CAAA). In this article, a method is demonstrated that can render these coals competitive and yet compliant with Phase II of CAAA. The method uses strategic mining and optimized preparation plant operation to minimize production costs, and it utilizes advanced coal-cleaning technology and an SO2 allowance to produce a compliant coal. The method is illustrated through an example from southern Illinois. For an annual production of 3.2 Mt (3.5 million st) and with a $150/st SO2 allowance cost, it was possible to produce a competitive coal for $0.84/million Btu. The production and allowance costs were $0.608/million Btu and $0.232/million Btu, respectively.

Jan 1, 2002