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By H. A. von Schonfeldt, H. Douglas Dahl

INTRODUCTION During the past decade, significant pro¬gress has been made in applying rock mechanics principles to mine design problems by a great number of researchers. Some of these new techniques have found their way into the engineering and planning offices of the operating mine. In spite of these advances, however, the application of rock mechanics in the day-to-day mine planning and design of our domestic coal mines is rela¬tively rare. There are a number of reasons responsi¬ble for this relatively slow progress, not the least of which is the question of how to measure the success or cost effectiveness of a sizable rock mechanics effort in an opera¬ting mine. Firstly, the properties of geologic materials generally vary over a wide range and it is, therefore, difficult to assess whether an improvement in the mining conditions is due to a design change or due to a change in the geologic conditions. A second reason for the slow acceptance of rock mechanics in engineering thinking is the fact that some of the concepts are quite difficult and that physical evidence of their validity to mine design is still rare. Thirdly, com¬munication between research, engineering and applications oriented people appears to function only intermittently. In our view, however, the most important impediment lies in the "state-of-the-art." Exactly how much can rock mechanics help the mine operator? The best that rock mechanics can do at present is determine whether one approach is better than another when weighed against some design objective (stress, strain, deformation). We cannot determine the abso¬lute best ground control design -- only what is better. If ground control is lost, the statement that "it's the best one we looked at" means very little to the harried operator. While the "state-of-the art" has advanced a great deal, it has certainly not been reduced to an engineering matter in that design hand¬books are available -- they are not. The success of a rock mechanics program, there¬fore, can be determined only over a long period of time of continuous effort.

Jan 1, 1977

By Peng Gao

Coal-based reduction followed by magnetic separation is an innovative technology used in processing refractory iron ores. Given that size is essential to the separation of the metallic iron from the gangue, the morphology of metallic iron particles and their evolution during coal-based reduction are investigated in the present work. The size of the metallic iron particle increased from 128.76 µm to 565.70 µm when the reduction time increased from 20 min to 60 min at 1,225° C and C/O (i.e., the amount of coal addition in terms of the gram-atomic ratio of the fixed carbon in the coal added to the combined oxygen in iron oxides) of 2.5. Based on our microstructural and metallographic analysis, the iron ore reduction process can be divided into three stages: (1) metallic iron particle formation, (2) iron oxide reduction and metallic iron assembly and (3) metallic iron particle growth. Almost all iron oxides are reduced to metallic iron in the second stage. These newborn metallic iron particles are energetically active and able to assemble and grow, and are eventually separated from the gangue. The large metallic iron particles benefit the subsequent magnetic separation process.

By Shiou-Chuan Sun

The froth flotation of coal, differing greatly from that of most minerals1-5, is not improved but rather impaired by temperatures higher than room temperature6-10 This phenomenon has long taunted us for an explanation. Gayle and Associates 8,9 reported the lack of relationship between their contact angle measurements and their flotation of American coals under various temperatures. Bailey and Whelan6 stated that the viscosity of flotation reagents, offering some clue for their flotation of British coals at low temperatures, could not be put forward as an explanation either in whole or in part for the effect of temperatures on coal-flotation. In this paper, a froth hypothesis is proposed to explain the flotation behavior of coals under various pulp temperatures. Test work involved the flotation of coals and the frothing of reagents.

Jan 1, 1966

By H. Sevim

The utilization of high sulfur Illinois coal by utility plants has been decreasing since the enactment of 1990 Clean Coal Air Act Amendment. Illinois coal producers can make their coal saleable by offering the choice of taking the combustion by-products from the utility plants and placing them in the abandoned sections of their mines. To be competitive, however, coal producers need to select an environmentally acceptable transportation-handling-placement system through which the cost-per-ton of by-product disposed can be minimized. In this paper, a few such systems are presented. The favorable operating range of each system is determined in terms of distance and tonnage. A case study is given whereby cost analysis is conducted for an underground coal mine receiving by-products from two Illinois utility plants.

Jan 1, 1997

By W. W. Kephart

The glass container industry is the largest producer of glass in the United States. As of this writing, there are approximately 89 active domestic production locations. In 1984, the industry shipped 11.8 million tons of glass containers. Approximately 70% of this production was clear or flint glass, 20% amber, 7% green, and the remainder miscellaneous colors. Although the production of nearly 12 million tons of glass is impressive, anyone following the industry over the last five years is aware that the industry has changed from a pattern of growth in the 1970's to one of maturity in the 1980's. Some observers, less generous, perhaps, have described the 1980's as a period of decline. In 1981, there were 119 production facilities which produced 13.2 million tons of glass the previous year. This equates to a 10% reduction in glass container production from 1980 to 1984, with a corresponding impact on the segment of the industrial minerals producers serving the container glass industry, as shown in Figures 1 and 2.

Jan 1, 1986

By C. E. Capes

The continuous balling? operation whereby a moist particulate mass is tumbled in a horizontal revolving drum with recirculation of the undersize product can be extremely unstable. Product and recycle rates are subject to wide fluctuations. Although the problem seems to be well-recognized, there is little published information or quantitative data readily available, especially in relation to industrial-scale circuits. Probably the best available published results are in the Russian literature, an illustration of which is given in Figure 1. These data, taken from a study') of some of the factors which influence the stabilization of the pelletizing process, illustrate the wide variations in circulating load and circuit productivity which may be encountered over a period of operation. The problems of balling circuit stability may be traced to random seed or nuclei generation and uncontrolled agglomerate growth. The situation is analogous to that in crystallization processes where (4 considerable attention is given to nucleation control. Traditionally attempts have been made to optimize system and operating variables to stabilize the balling process. A supplemental approach which is taken here is to build on the considerable

Jan 1, 1975

By Robert M. Jimeson

The competitive market potential for solvent refined coal is estimated. Market advantages of solvent refined coal are enumerated. Markets are possible in combustion, railroad locomotion, and carbon electrodes. The combustion characteristics are consistent with expected air pollution restrictions on the emission of sulfur and particulate matter. A market potential of sufficient size exists to support the initiation of solvent refining in the United States. The market analysis should help fuel producers determine the advisability of their undertaking the solvent refining of coal.

Jan 1, 1969

By Robert M. Abrams

The passage of an ore pulp through the froth flotation process results in the production, after dewatering, of a finely divided concentrate. This intermediate product Trust be handled to the subsequent process facilities via belt or other types of conveyors, hoppers, bins, chutes and feeders, and the like, Flotation concentrate has some difficult handling properties such as abrasiveness, sluggishness when moist, or fluidity when dry, These characteristics require the judicious selection or design of handling, equipment and the careful engineering of transfer chutes. It is to the special problems which are encountered in this in-plant handling procedure that this paper is addressed. The methods which will be discussed have beer. developed primarily for the handling of the froth flotation concentrates of copper, leap, and taconite iron ores, but may be generalized, with appropriate modifications, to apply to other similar metallic concentrate&. The controlled feeding of concentrates frog: bins and hoppers is covered alone with some of the techniques used to transfer concentrates from ore belt conveyor to another. Methods are described for unloading belt conveyors into bins or storage tiles, The reclamation from storage piles is also treated.

Jan 1, 1976

By Yoginder P. Chugh

Effects of moisture absorption on the behavior of the Dykersburg shale overlying Harrisburg coal seam in Southern Illinois are presented in this paper. Cylindrical samples of the shale 2.5 cm in diameter and 5.0 cm long were studied for weight gain and swelling strains at 90, 95, and 100 percent relative humidity and under immersed water conditions. After attaining equilibrium conditions, the samples were studied for changes in the strength and deformation behavior. The depth of moisture penetration was measured using the Vickers microhardness measurements. Using the basic mass transfer concepts, effective diffusion coefficients were computed for the shale.

Jan 1, 1980

By Daniel C. McLean

Many of the major copper ore bodies throughout the world contain chalcocite (79.9% Cu) as the principal copper mineral, yet the grades of copper concentrates produced from these ores rarely exceeds 25 to 28% Cu and in one known instance went as low as 13%. The low grade has traditionally been attributed to the presence of "activated pyrite" and/or chalcopyrite, and the universal approach has been excessive regrinding with all of its inherent effects-high capital, energy and maintenance costs, excessive sliming, and concentrate filtration difficulties (high moisture content). E. P. Cadwell, former Chief Metallurgist for American Cyanamid Company, did extensive microscopical studies on several of these types of concentrates from South American operations during the 1950's and discovered they all had one common feature--the pyrite particles in the concentrate were all rimmed with thin films of secondary chalcocite or covellite. As far as a flotation bubble or reagent is concerned, a rim of chalcocite is the same as a solid particle of chalcocite, and as long as a rim is present, the particle is going to float. Upon examination of these rimmed particles under the microscope, it becomes quite obvious why regrinding will never solve the problem and why maximum increases in grade by this technique rarely give improvements in grade of greater than 3 to 5% Cu.

Jan 1, 1983

By Thomas W. Turk

The water treatment industry has historically been involved with reducing or inhibiting the inherant scale forming or fouling tendencies of natural waters associated with large industrial cooling water systems. Fouling is an extremely complex phenomenon. From a fundamental point of view, it may be characterized as a combined momentum, heat, and mass transfer problem. Chemical reaction kinetics is involved, as well as the solubility characteristics of salts in water and corrosion technology. It is a routine practice to over size pumps, piping and heat exchangers to compensate for fouling.

Jan 1, 1983

By J. L. Yordan

An induction time apparatus has been constructed in the present work which has a sensitivity limit of 100-150 micro-seconds. The basic unit is similar to the one used by Eigeles and Volova (1960) and Trahar (1983), but it operates with a micro-computer and has a greater sensitivity. Using this apparatus, the flotation chemistry of the quartz-amine system has been studied. It has been found that at a given dodecylamminium hydrochloride concentration, the induction time is at a minimum at approximately pH 10.5. At this pH, the collector hydrolizes to form neutral amine and the flotation recovery reaches a maximumy,suggesting that iono-molecular species are the surface-active species responsible for flotation. This finding confirms the earlier conclusions obtained using the surface tension (Somasundaran, 1976; Finch and Smith, 1973) and contact angle (Smith, 1963) techniques. The induction time measurements have also been conducted as a function of particle size, collector concentration, indifferent electrolyte concentration and temperature. The results are compared with flotation data, and the activation energies for the bubble-particle adhesion have been calculated.

Jan 1, 1986

By H. C. Juvkam-Wold

The design of an aquifer depressurization system is discussed. The system uses a number of wells surrounding a mine shaft to reduce the aquifer pressure in the vicinity of the shaft. The effect of various parameters such as number of wells, wellbore diameter, time and well location is discussed. It is concluded that, with a properly designed depressurization system, the aquifer pressure and the water inflow rate to the shaft may be reduced to less than 15X of their potential values in the absence of wells

Jan 1, 1980

By Richard J. Fantel

This paper addresses the impact of declining world rutile resources upon the production of titanium products and their asso¬ciated costs. Titanium is used primarily for the production of pigments; in its metal form it is considered a strategic and critical material to the U.S. defense and aerospace industries. There are two major mineral sources for titanium: ilmenite and rutile. Both these mineral types can be used to produce titanium pigments. Only high grade titanium concentrates, such as rutile, high-grade ilmenite, and synthetic rutile (which is produced through further processing of ilmenite), can be used in the production of titanium metal. This paper draws upon the data and analyses of a recent Bureau of Mines Minerals Availability Program appraisal that evaluated the international availability of titanium from market economy countries. The paper will show that production from economic rutile mines will decline sometime after the turn of the century and that rutile shortages could be alleviated by production from other high-grade titanium resources such as higher cost rutile deposits and anatase deposits, or through an increase in world synthetic rutile capacity.

Jan 1, 1984

By Robert A. Pimentel

Dust is still a major problem in increasing production from longwall faces. Over the last decade, significant improvements have been made in the development of techniques for reducing dust exposure on conventional and continuous sections. But virtually no improvements have been made in dust control on longwall sections. It is true, that there are many more continuous mining sections than longwall sections in the United States and that the number of workers overexposed on continuous miner sections is much larger than the number on longwall sections. However, the problem on continuous miner sections appears much easier to solve and, in fact, we believe that the techniques are available to get virtually all continuous miner sections in compliance. The problems on longwall sections are much more elusive. Also, the number of longwall sections in the United States is expected to increase during the 1980's. Thus, dust control on longwall sections remains a formidable and important problem. Companies operating longwall sections with a dust problem are faced with the tasks of having to quantify the various dust sources, of selecting proper techniques to reduce the problem, of implementing the techniques and of evaluating their effectiveness.

Jan 1, 1983

By C. H. Cheh

The amount of fines in run-of-mine coal has been increasing and coal quality has been deteriorating as a result of the increased use of mechanized and continuous mining methods. Removing the mineral matter and pyritic sulfur from coal prior to combustion will lower transportation costs, improve power plant performance and reduce sulfur dioxide emissions. Since physical cleaning methods can only remove individual particles of mineral matter and pyrite, it is necessary to crush and grind coal to fine sizes to separate these contaminants so they can be removed by deep cleaning processes. The increased portion of fines in run-of-mine coal together with attempts to increase the mineral matter removal efficiency have stimulated interest in fine coal cleaning technology. However, there are many problems to be solved before fine coal cleaning can be applied to power plant coals. These problems include: 1. coal cleaning plant capacity is reduced when conventional cleaning circuits are modifies to deep clean coals; 2. existing equipment and technology is not suitable for cleaning fine coal; 3. coal recovery is reduced; and 4. fine coal is difficult to dewater, dry, handle, transport and store.

Jan 1, 1982

By Volkmar Niemitz

Approximately 30 miles east of Chicago on the southern shores of Lake Michigan stands Bethlehem Steel's newest fully integrated steelmaking facility - the billion dollar Burns Harbor plant. The initial phase of "green field" construction that began in 1963 was directed to the creation of high quality finishing facilities. In late 1964 the 160" plate mill came "on stream" followed closely by Sheet and Tin and Hot Strip facilities. Unit train shipments of slabs primarily from the Lackawanna plant located near Buffalo constituted the input materials for the new mills. In 1967 a hot metal facilities program was announced for Burns Harbor that at its completion would make the plant fully integrated. Incorporated within the program were: 1. A new high performance 50" x 96" slabbing mill complete with a battery of soaking pits. 2. A two vessel Basic Oxygen Furnace Shop. 3. (1) battery of 6 meter high Coke Ovens with attendant coal handling facilities. 4. A 3800 feet long vessel loading & unloading dock. 5. The first conveyor belt fed Blast Furnace in the United States. 6. An extensive materials handling system for receiving, stocking and reclaiming from storage the raw materials for the Blast Furnace and Coke Ovens operation. The intent of this paper is to provide a detailed description of the functions and components of the materials handling system noted above.

Jan 1, 1970

By Dmitriy A. Malovichko

The general theory for the description of seismic sources is briefly discussed. The effect of excavations on seismic radiation is considered. Expressions for seismic source mechanisms in terms of the geometrical and mechanical parameters of source processes are provided for the following cases: fault slip and shear failure in a confined environment, dynamic stress fracturing around a tunnel, rock fall, landslide and sudden subsidence. A classification of seismic events in mines based on source mechanisms is introduced. The classification separates blast-, slip- and crush-type events. Various approaches of analysis of source mechanisms involving forward modelling and inversion are discussed. The following examples demonstrating the utility of source mechanisms in mining are presented: forensic analysis of damaging seismic events, assessment of the increase in the depth of failure for dynamic stress fracturing around tunnels and its duration, examination of the rockmass deformation regime, assessment of deformation around tunnels using crush-type events, identification and parameterisation of weak geological structures, stress inversion from slip-type events. Finally, the requirements for seismic data to ensure high quality source mechanism solutions are briefly reviewed and future challenges in the interpretation and utilisation of seismic source mechanisms in mines are speculated on.

Apr 26, 2022

By Joseph G. Selmeczi

Lime and limestone-based SO2 scrubbing processes have demonstrated reasonably good success in removing low concentrations of SO2 from flue gases. While most of the operating problems experienced in the early days of scrubbing have been worked out, problems usually increase and removal efficiency drops with increased amounts of SO2 present in the gas stream. In order to overcome these difficulties, yet still taking advantage of lime and limestone as the lowest cost neutralizing agents, a host of so-called double- alkali systems were developed. These processes take advantage of cations such as Na+ and NH4+ capable of forming highly water soluble bases or basic salts, such as hydroxide, carbonate or sulfite, which having been neutralized or acidified by the absorbed SO2 can be regenerated with a lower cost base such as lime.

Jan 1, 1974

By Elmer H. Citron

The Monterey Coal Company, a wholly owned subsidiary of The Carter Oil Company of Houston, Texas, recently awarded a contract to build the Monterey No. 1 Preparation Plant, which will be located near Carlinville, Illinois, to the McNally Pittsburg Manufacturing Corporation. The preparation plant will be one of the most modern jig preparation plants in the State of Illinois. Illinois No. 6 coal will be delivered by a 48" slope belt having 35-degree carrying idlers, operating at 650 FPM and operating on an incline of nearly 17 degrees. The slope belt is driven by two 450 BP motors and will deliver the mined coal at the rate of 1800 TPH to a stationary step-type ' screen having six-inch openings. The overproduct from the stationary screen will discharge into a 10' x 24' McNally Rotary Breaker and the underproduct will bypass the rotary breaker. The rotary breaker is equipped with heavy manganese screens with 6 ½" diameter openings. The sized 6" x 0 coal from the stationary step screen and the rotary breaker will be discharged by gravity to a 4%" raw coal incline storage belt. The 48" raw coal storage belt will deliver the 6" x 0 sized coal at the rate of 1800 T?H to an 8000 ton concrete raw coal silo, 70 feet in diameter and 1x7 feet high. The 6" x 0 sized coal will be drawn from the concrete storage silo by seven (7) 36" wide reciprocating plate feeders. Five feeders are to have constant speed drives at a rated capacity of 145 TPH each. Two (2) feeders will have remote con- trolled variable speed drives, to provide a varying feed.

Jan 1, 1970