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The results of studies to ameliorate acid mine drainage by retarding the rate of oxidation of pyrite at source are discussed. In the transpassive region, pyrite oxidizes by reactive dissolution, mass transfer through the product layer and diffusion in the bulk solution. One can decrease the rate of pyrite oxidation by inhibiting either oxidation reactions or cathodic reactions. It is demonstrated in this study that some surface active reagents extend the passive region by affecting both the anodic and cathodic processes. The extension to higher potentials occurs by inhibition of the anodic dissolution process whereas to lower cathodic potentials through decrease in the rate of reduction of molecular oxygen and/or ferric ions. To retard the oxidation of pyrite by ferric ions, which is considered to be the dominant oxidant under conditions of acid mine drainage, it would be necessary to restrict mass transfer or promote complexation of ferric ions at the surface. Imidazoline based reagents were found to be most effective in meeting this goal.

Jan 1, 1994

By P. L. Dunn

Automatic control of fine coal cleaning circuits has traditionally been limited by a lack of sensors. Although several nuclear-based analyzers are available, none have seen widespread acceptance. In this investigation, image analysis is used for on-line determination of ash content in fine coal slurries. The ash content of a flotation tailings stream is correlated to the mean gray level of the slurry. Based on a 90% prediction interval, an analysis of sensor performance indicates an accuracy of 73 ± 4% ash over a range from 65-90% ash. While this result is comparable to existing nuclear-based analyzers, the video-based system is only a fraction of the cost. The sensor is currently installed at the Middle Fork preparation plant owned by Pittston Coal Company.

Jan 1, 1997

By J. F. T. Agapito

Experience at Energy West Mines in the Wasatch Plateau Coal Field, Utah, has shown that longwall face bursts occur mostly near the tailgate when extracting the third adjacent longwall in a panel section where depths exceed 610 m (2000 ft). It is believed that this is due to a combination of cover depth and side abutment stresses created by the widening of a pressure arch formed by interlocking and bridging of large blocks of" very competent strata. The 60-m-thick (200 ft) Castlegate Sandstone probably plays a key role in pressure arching. This paper presents a back-analysis of the location and magnitude of the stresses associated with face bursts that occurred when mining the 7th Right Longwall at the Deer Creek Mine. Improvement of these conditions may be achieved by widening the longwalls to attain critical subsidence width sooner while mining the second long-wall, and to reduce stresses at the face. Wider longwall faces, however, increase the chance of sandstone channel interception often associated with bursts. Satisfactory mitigation of face bursts beyond cover depths of 610 to 670 m (2000 to 2200 ft) may be difficult without using destressing techniques. The hydraulic fracturing/liquid infusion technique seems to offer the best possibilities for application in longwall mining.

Jan 1, 1997

Strainburst phenomena, generally characterized by a sudden release of energy in a volume of highly stressed rock, are often encountered in such situations like crown pillar bursts in cut-and-fill mining, face bursts at development headings and floor bursts in deep shaft sinking. This paper describes a simple FE modeling approach which leads to the calculation of the energy release rate (ERR) and the total energy storage rate (TESR) in the rock mass around the openings. The merits of using such energy parameters in the analysis of strainburst problems to identify areas of high energy release/storage are discussed. However, much site-specific back analyses are needed to better understand how strainbursts and energy parameters are inter-related.

Jan 1, 1998

By T. M. Needham

Increasing ore hardness led to a gradual reduction of mill throughput rates. This, combined with declining head grades and low gold price, prompted a review of milling practice at Kidston. Plant trials and computer simulation of the grinding circuit indicated the potential to increase mill throughput by up to 451 by reducing SAG mill feed size. Secondary crushing and additional ball milling capacity were installed. Commissioning was carried out successfully in September/October 1992. Design, operation and problems of the expanded circuit are discussed, and recent operating results are presented.

Jan 1, 1994

By Don Runge, John T. Zeni

Cuprex Limited is currently developing a small gold mining operation in Central Australia in the Tennant Creek field. In February 1984, the company undertook a feasibility study on the project and operations commenced in August 1984. Ore reserves are located between 230 and 280 metres (755 ft and 919 ft) below surface and ore extraction required the establishment of a shaft network for access, ore hoisting and ventilation. Zeni Drilling Company from West Virginia, U.S.A. was contracted to blind drill two shafts for the project. Blind drilling was selected for various reasons, including timing which related to cost efficiency. The blind drill shaft technique has proved successful in this application and with enthusiastic and innovative support from the mining industry, will prove an efficient and cost effective means of accessing and operating underground mining projects of all sizes in the future.

Jan 1, 1987

By Caibin Wu, Chengfang Yuan, Jiaqi Tong, Zhilong Cheng, Ningning Liao, Chong Zeng

In a series of Julius Kruttschnitt size-dependent breakage models, the cumulative percentage passing 1/10 of the initial size is used as a fineness indicator for scientific research and the selection of grinding equipment. However, in industrial practice, it is quite customary to use the mass percentage passing 75 μm as the indicator. In this paper, based on the energy-particle size model, quartz and calcite, two materials with distinctly different hardness, were used as test samples in a conical ball mill. At the same specific energy, the value of the cumulative percentage passing 1/10 of the initial size decreased while that of the mass percentage passing 75 μm increased with finer feed size. The experimental test values of the mass percentage passing 75 μm have a good linear relationship with the model predictions, which suggests that the particle size energy relationship of the mass percentage passing 75 μm and Ecs can be used instead of the cumulative percentage passing 1/10 of the initial size and Ecs. By building family curves, when particle size x < 300 μm, the family curve can be well fitted, and the fine particle size distribution of the whole product can be reconstructed.

Dec 22, 2022

By Peter C. Finlayson

Rapidly rising gas and oil prices and the falling quality of coal is forcing energy users in many parts of the world to consider the application of low grade fuel, particularly coal, for steam raising and power generation. However, the use of such low grade coal is normally resisted by the consumer because of operational problems associated with high ash content, sulfur emission and, in some instances, slagging problems caused by low melting temperature constituents in the ash. Recently developed technology involving &apos;fluidized bed combustion&apos; offers a potential solution to these operational problems. Much of the early work was conducted in Britain, where rig tests were commenced during the early 1960&apos;s. This has led on to the successful conversion and operation of a fluidized bed fired industrial boiler at the Renfrew works of Babcock & Wilcox Ltd. Orders for the first commercial boilers incorporating this technology have recently been announced. Significant development work on fluidized combustion is now being undertaken in various parts of the world, in particular North America, Germany and Japan, and the first large scale units are under construction or being commissioned. This paper concentrates on the development of the technology in Britain, outlines the reasons for applying fluidized bed combustion and de-scribes its application at atmospheric pressure for steam raising and at elevated pressure for power generation . Coal Processing Consultants is a Partnership between the National Coal Board and Babcock & Wilcox Ltd. of Britain and has been established in order to provide technical advice and economic evaluations on all aspects of coal processing and utilization. In view of the involvement of its Parents in the development and exploitation of fluidized bed combustion technology, Coal Processing Consultants has been retained by clients in various parts of the world to provide expert advice on the application of fluidized combustion for particular coals and project situations.

Jan 1, 1978

By Jeffery L. Kohler

The research and development of a pattern recognition system which can predict incipient failures and safety hazards in the mine power network is described. An examination of mine electrical safety hazards revealed they are often related to the electrical equipment down-time experienced on mine sections. Based on this, a method is proposed that can improve both production and safety, without compromising either. Equipment failure modes are examined to illustrate how the ultimate failure can be predicted for enough in advance to allow a convenient and safe repair, followed by a discussion of actual monitoring system performance. Finally, the paper is concluded by projections of the system&apos;s utility to industry.

Jan 1, 1977

By G. S. Adisoma

To address the problem of grade estimation in a general three-dimensional shape and the uncertainty associated with the estimate, the technique of jackknifing/block kriging short-cut is proposed. A new estimator called jackknife kriging is introduced first. Through the jackknife variance, a confidence limit for the reserve grade estimate can be calculated. Unlike the kriging variance, which is more a measure of data configuration and is independent of data values, the jackknife variance reflects the true variability of the data. This approach provides a simple way to set a confidence level for global estimation of resources.

Jan 1, 1995

By E. De Souza

Rockbursts and rockfalls cause very large safety and productivity losses in underground mines. One of the major unsolved problems of safe, economical rock support in underground mining has been that of maintaining anchorage during dynamic rock loading conditions or seismic related occurrences. It is recognized that the large displacements and high strain rates in excavation walls and underground structures cannot be countered by increasing the strength of stiff rock-reinforcing systems but must be accommodated by introducing yieldability into the support elements. This paper introduces a low cost yieldable support system which provides viable solutions to dynamic support loading. Such system should not only provide a feasible and more effective rock mass stabilization strategy but improve mine safety and reduce losses.

Jan 1, 1998

By B. E. Davis

A fundamental study of the mechanisms involved in the conditioning of coarse Florida phosphate has led to some interesting discoveries. Studies by the Bureau of Mines have shown that conditioning time and mixing intensity greatly affect the grades and recoveries of the phosphate minerals and quartz in the rougher concentrate. In particular, as the conditioning time or mixing intensity increased, the phosphate recovery remained constant while the amount of quartz floated decreased. This phenomenon is contrary to conventional wisdom and could lead to a more efficient coarse flotation circuit.

Jan 1, 1993

By D. W. H. Su

"This paper presents the results of a comprehensive study conducted by CONSOL Energy, Marcellus Shale Coalition, and Pennsylvania Coal Association to evaluate the effects of longwall-induced subsurface deformations on the mechanical integrity of shale gas wells drilled over a longwall abutment pillar. The primary objective is to demonstrate that a properly constructed gas well in a standard longwall abutment pillar can maintain mechanical integrity during and after mining operations. A study site was selected over a southwestern Pennsylvania coal mine, which extracts 1,500-ft-wide longwall faces under about 600 feet of cover. Four test wells and four monitoring wells were drilled and installed over a 125-ft by 275-ft centers abutment pillar. In addition to the test wells and monitoring wells, surface subsidence measurements and underground coal pillar pressure measurements were conducted as the 1,500-ft-wide longwall panels on the south and north sides of the abutment pillar were mined by. To evaluate the resulting coal protection casing profile and lateral displacement, three separate 60-arm caliper surveys were conducted. Prior to the longwall panels being mined by, a number of 3D finite element simulations were conducted to estimate subsidence at the surface, coal pillar pressure increases, the resulting coal protection casing profile and displacement, and the vertical and horizontal displacements in the four monitoring wells. Comparisons of the pre-mining 3D finite element simulation results and the surface/subsurface/underground instrumentation results show that the measured test well and IPI casing deformations and profiles are in reasonable agreement with those predicted by the 3D finite element models, and that the measured surface subsidence and pillar pressure are in excellent agreement with those predicted by the 3D models, which serves to validate the 3D finite element models. Parametric studies employing the validated 3D finite element models demonstrate that larger coal protection casing thickness is expected to have little effect on the lateral deformation, although it may reduce the magnitude of casing plastic deformation, and under deeper cover (~1,100 feet), lateral casing deformation is expected to be smaller, although larger plastic casing deformation may be present near the seam level. Also, evaluation of various casing and cementing designs using the validated 3D models clearly indicates that, when all casings are grouted to the surface except the intermediate and production casings, the intermediate and production casings show little deformation and no plastic strain. This research represents a very important step and initiative to utilize the knowledge and science obtained from mining research to improve miner and public safety as well as the safety and health of the oil and gas industries"

Jan 1, 2017

By A. G. Naguib

In essence, any magnetic separator operates on the basis of imparting a preferential magnetic force on particles of higher magnetic susceptibility which are to be separated from particles of lower magnetic susceptibility. A certain amount of directional deviation to the particles takes place thus allowing for collecting each category of particles separately. The forces in action on particles in a wet magnetic separator of the established designs can be analyzed in a simple manner as shown in Figure 1.

Jan 1, 1972

The heat of immersion of coals in different immersional liquids is measured as a function of particle size and moisture content. Decrease in particle size shows a concomitant increase in the heat of immersion. The heat of immersion is dependent upon the nature of immersional fluids. In addition the nature of moisture present in coal influences the heat of immersion.

Jan 1, 1993

By F. Kitzinger

The possibility of increasing the efficiency of mineral processing plants by means of computer control has prompted metallurgists to examine their flowsheets more critically in order to develop practical control strategies. Control schemes in use to date generally rely on the automation of traditional and previously manually regulated control loops, for instance the addition of reagents to maintain a constant assay or a constant pH. This approach is predicated on the availability of well-established primary sensors such as pH electrodes or on-stream analyzers. Noranda Research Centre, in cooperation with Noranda Group concentrators, has developed a froth level monitor and a pulp density meter susceptible of application in this type of control. Although some of the basic principles on which they are based have been known for some time, their incorporation into the design of reliable, direct-reading instruments which can be interfaced with a computer, is be-lieved to be novel*.

Jan 1, 1977

By QU Hong-lue, YANG Lin-han

Aiming at the subjective impact caused by subjective weighting method in the establishment of rockburst risk attribute identification and prediction model, the combined weighting method was introduced to eliminate the influence of unreasonable weight of each index. Eight discriminant indexes affecting the risk of rockburst were selected. Through the literature review, relevant rockburst cases were collected and 8 index rockburst sample sets were established. A variety of machine learning methods were used to analyze the feature importance of discriminant indexes in the samples, and then to determine the objective weight values of different methods. Combined with the subjective weights determined by the Analytic Hierarchy Process, the combination of weights were successively carried out. Based on the attribute recognition theory, the combination weights with different objective weight methods were established to identify the rockburst risk attributes, and verified by the confidence criterion. The results show that the objective weight value determined by the feature importance analysis of machine learning reduces the subjectivity of the weight of Analytic Hierarchy Process method, improves the prediction accuracy, and makes the prediction result closer to the fact.

Apr 26, 2022

By Jean-Michel Rendu

In most circumstances, the traditional methods of. ore reserve estimation for large undulating sedimentary deposits, such as coal and iron formations, do not allow the accurate prediction of grade for mining blocks. The problem is Particularly accute when the mining blocks are small with respect to the thickness of the geological zones in the deposit, and when there are significant grade changes between the foot-wall and hanging-wall of these zones. A simple geostatistical model has been developed, which takes into account the grade changes not only in the direction of the geological strata, but also in the direction normal to these strata. The genesis of sedimentary deposits and the resulting geological properties of these deposits were considered in the development of the model. The model has been successfully applied to the evaluation of a large coal deposit. Eventhough some practical difficulties have been encountered, for example when part of a geological zone was missing or had not been sampled, these difficulties have been .resolved. Both the theory and its practical application are presented in this paper.

Jan 1, 1979

By M. Hancer

The sign of the surface charge of selected potassium soluble salt minerals namely KClO4 , K2SO4 , KNO3, and KCl was determined from nonequilibrium electrophoresis measurements and found to be negative for each of the salt. Dodecylamine flotation of these salts revealed that the concentration of amine required for flotation increases in the order KClO4< K2SO4< KNO3<KCI. Precipitation of the amine collector colloid was not required for flotation of the oxyanion salts and in this case it appears that adsorption of the dodecylamine cation is sufficient to create the hydrophobic surface state. The order for flotation is explained in terms of surface hydration of these respective potassium salts based on contact angle measurements and FT Raman spectroscopic characterization of water structure.

Jan 1, 1999

By James R. Runkle

Studies in eastern Ohio, northern West Virginia, and southwestern Pennsylvania determined whether subsidence caused by longwall mining influences soil moisture and tree growth. Soil moisture was measured both over new longwall panels and over an unmined control area throughout the growing seasons of 1990, a wet year when the panels were excavated, and 1991, a dry year. No significant effects of mining could be detected. Tree growth was studied in two pairs of woodlots. In each pair, one woodlot was located over a longwall panel excavated about 1980 and the other over an unmined area. Differences in tree growth between mined and unmined areas were neither significant (for most species) nor consistent in direction. The above results imply that if mining does have impacts they are likely to be highly site-specific and localized such as by disruptions of springs or soil slippage.

Jan 1, 1986