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By K. Rajamani, L. B. Hales

Much of the process control effort in the mineral industry uses proportional-integral-derivative controllers that require periodic retuning. Retuning hundreds of controllers typically employed in a single plant is a formidable task for the control engineer. Adaptive controllers offer an alternative to this problem, since they are designed to tune themselves. Four schemes of adaptive control-gain scheduling, model reference adaptive control, self-tuning regulator, and optimal adaptive controllers-are discussed with process examples. The control of a ball mill circuit with a multivariable self-tuning regulator is illustrated. This controller encompasses the advantages of the other three controllers and is applicable for a wide range of process variability.

Jan 1, 1988

By D. D. Runnells, D. C. Keith, G. A. Doyle, J. Tilk

Until the suspension of conventional operations in 1996, the White Pine Mine was the second-largest active underground copper mine in the United States, underlying an area of approximately 30 km2 (13 sq. miles) in the Upper Peninsula of Michigan. The mine operator intends to initiate in-stope solution copper mining by circulating a solution (lixiviant) of mine water, sulfuric acid and ferric iron through rubblized ore. As planned, the solution would be retired in the mined-out stopes following completion of the solution-mining activities. Investigations into the fate of the retired solution indicated that the solution, through time, would change from an acidic, metal-rich solution to a near-neutral, reducing solution containing much lower concentrations of metals. Investigations included reaction-path modeling (EQ3/6) and laboratory and in-mine tests. The combination of neutralization and reduction will result in precipitation of most metals, primarily as metallic sulfates, chlorides and sulfides.

Jan 1, 1998

By R. L. Bleifuss, S. Zhong, H. E. Geotzman

Microwave heating of iron ore was investigated as an alternative to conventional reduction processes to solve the problem of slow heat transfer. Microwave heating and reduction tests were run on composite green balls made from coal and magnetite concentrate. Benchscale tests were run on both powdered and pelletized feeds using a 15 kW microwave generator. A significant increase in the reduction rate was obtained. With 20% excess stoichiometric carbon in the mix, more than 90% reduction of the iron ore can be achieved in about 10 min at temperatures of around 1,000°C. The reduction of iron ore with coal by microwave heating produces a pure, dust free, high-Btu flue gas that can be used in related thermal operations. Depending on the purity, the reduced iron product could be fed directly to an electric arc furnace for melting. In some cases, the removal of a slag phase may be required to eliminate excess silica and alumina.

Jan 1, 1997

By M. Yavuz

Decision Making (DM) can be defined as a selection process of the best one among the alternatives sets in order to obtain goal, and mostly has an uncertain situation [7]. Every mining engineer is subjected to a number of mining DM problems in daily mining operations. In reality, all stages of mining have its own DM problems. Most of time, engineers do not use scientific methods for DM problems. These problems can mostly be solved by the engineers according to their past experiences and practical studies. Mining engineers often use their intuition in DM process. Experience and intuition have been central to DM because of the frequent lack of quantitative data including geology, grade distribution and ground condition, as well as environmental, social and economic factors [8]. In decision process, linguistic variables become in question and decision makers may not know how these variables are computed [9]. So, the DM process may be qualitative, quantitative or combination of the two. The problem structuring and analysis process is conceptualized in Figure 1 [8]. The qualitative analysis is based primarily on the judgment, knowledge and experience of an expert (or team of experts). In a quantitative analysis, the focus is on facts and the data associated with a problem and a mathematical formulation that encompasses the objectives, variables and constraints of the particular problem. The quantitative analysis has traditionally been the subject of operation research and management science [8].

Jan 1, 2008

By Joseph B. Alberts, David D. DiPonio, Francis B. Manning

From 1996 to 2001, Wayne County and 13 suburban Detroit communities constructed the Downriver Regional Storage and Transport System (DRSTS) to improve area water quality, protect public health and alleviate basement flooding. The project consisted of a 10-mile long storage and transport tunnel, a pump station at the existing wastewater treatment plant, 9 miles of relief sewers (6 in tunnel and 3 in open cut). The work was separated into 10 contracts. Due to hydraulic design requirements and other constraints, the tunnel profile was located generally 65 feet below ground surface within a soft to medium clay strata which skimmed along the top of a very dense glacial till “hardpan” overlaying bedrock. Boulders within the tunnel bore were recognized as a significant, but indeterminate risk. This paper presents a case history of the owner’s contracting strategy for risk assumption and management of the boulder impacts on the project. Actual conditions encountered during construction and contractual adjustments made to address problems are reviewed, and recommendations for future contracts are included.

Jan 1, 2003

By Richard V. Beck, Donald R. East, Jeremy P. Haile

In view of the increasing use of heap leach operations in the mining industry and the critically important performance of the leach pad liner in both the economic and environmental aspects of the design, it has become essential that the designer fully understand the factors affecting the performance of the liner. Minimizing the loss of pregnant solution through the leach pad liner is obviously of paramount importance to the economic efficiency and environmental compliance of the heap leach operation. Losses through the liner are a function of the hydraulic conductivity of the liner material and the hydraulic gradient across the liner. This applies to both natural and synthetic materials. The hydraulic gradient across the liner is a function of the build-up of solution above the liner, which in turn is determined by the permeability of the heap material, the slope of the liner, the drainage path length and the leachate infiltration rate. A relationship incorporating each of these parameters and their effect on the hydraulic head acting on the liner has been developed in terms of the Dupuit criterion, assuming one- dimensional flow with vertical accretion.

Jan 1, 1987

By L. Reyes-Bozo, R. Ginocchio, A. Godoy-Faúndez, C. Sáez

Relationships among mining industry, society and environment have been historically complex due to its environmental impacts. In the Chilean mining industry, repetitive and small spills of fuel during maintenance of machinery have been adsorbed by desert soils and sawdust to control environmental pollution. The froth flotation is the main technology to recover specific mineralogical species from sulphide ores. Flotation reagents are expensive and representing an environmental risks due to its physics properties. Our objective was to investigate the feasibility of applying bioremediation as a cost-effective alternative technology to physical-chemical treatments and to evaluate the efficacy of biosolids as foaming agents. Our results show that the bioremediation is feasible by use of the autochthonous microbial communities and biosolids could be used as new environmental-friendly organic reagents. This research discloses a sustainable bioremediation process and industrial ecology model based on these two successful cases.

Jan 1, 2011

By R. R. Tatiya

The algorithms to model three stoping methods - sublevel, down- the-hole (DTH) and cut and fill stoping have been developed. These algorithms are capable of designing and performing economic analysis for one or more number of stopes in a continuous orebody. The design and economic analysis of each individual stope are first obtained. This is followed by the composite stope design layout and overall economics of the stopes under study. This paper describes only the stope design aspects of these models. The programs have been written using Fortran 77 with Tektronix graphical aids available at Imperial College Computer Centre (ICCC) London and are based on the basic data obtained from Khetri Copper Complex (KCC) and Rajpura Dariba (a zinc mine) in India. Minor modifications, however, may be necessary in some routines when used on other systems and for other mines.

Jan 1, 1989

By J. L. Fuentes

The so called 'SISCOM' is a General Purpose, microprocessor-based Monitoring and Control System, developed by AITEMIN to meet the requirements of Spanish Mining Industry in - the field of automation and data -transmission. Typical applications -are automatic control of pumps, compressors, fans and conveyors, as well as environmental monitoring and production monitoring. In relation with the last, the - System has been succesfully installed in a full section roadheader and in a mechanised steep coal face. In both cases, the main objective is to get information about running times, down times and causes, -and monitoring of other important parameters such as ventilation, methane content, power consumption..etc. Measurements concerning the face behaviour from a geomechanical point of view are also monitored. These are different pressures and stresses. All data is transmitted to the - surface and on-line analysed by a -desk-top microcomputer. The paper shows the system structure and the requirements that have - been considered on its design. Attention is given to the mechanical data acquisition problem, involving special development of some transducers. The information provided by the surface microcomputer is shown and its utility discussed.

Jan 1, 1986

By A. C. Smith

Although it is only utilized in a few U.S. longwall mines, a bleederless ventilation system can be an effective spontaneous combustion control method in mines with a demonstrated history of spontaneous combustion. In order to provide insights for the optimization of bleederless ventilation systems for U. S. underground coal mines, a computational fluid dynamics (CFD) study was conducted to model the spontaneous heating in longwall gob areas with a bleederless ventilation system. A single longwall panel with a bleederless ventilation system was simulated, and typical ventilation data for a longwall mine was used in the simulations. The permeability and porosity profiles for the longwall gob were estimated using a geotechnical model and were used as inputs for the CFD modeling. The effects of gob permeability and resistance of the collapsed entries on the spontaneous heating were studied. The effectiveness of nitrogen injection to prevent spontaneous heating in the gob was also examined. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

Jan 1, 2008

By E. Topuz, M. J. McPherson, J. Banik

This paper summarizes the analyses of ventilation layouts for mines that experience both spontaneous combustion. The major focus is placed on the longwall coal mine layouts used in several countries. Each of the different layouts is modeled in the form of a ventilation network. The gob of a longwall panel is the most critical location for the occurrence of spontaneous combustion. Airflow leakage paths inside the gob are simulated by using a simplified grid-like network. Computer simulations with this model indicates that the W-system of ventilation is most effective in minimizing air leakage into the gob. Homer, the U-system of ventilation, with pressure balancing behind the face support line, is also found promising for longwall panels. The magnitude of air leakage into the gob is observed to change with the advance or retreat of bee, thus requiring appropriate balancing of pressure to maintain the leakage at a minimum.

Jan 1, 1995

By Peter Sullivan, Johan van Heerden

Increased use of continuous miners and roadheaders in the underground coal mining industry in South Africa has led to improved productivity and efficiency of operations. Of major concern, however, is the increased amount of airborne dust generated during mining. Dust is a health hazard in terms of respiratory diseases, can impede productivity and is the major contributor to the potential of underground explosions. The concern of the South African coal mining industry with regard to the underground dust problem has led to the establishment of a Dust Control Section in the Coal Mining Division of COMRO. In the field of dust suppression system evaluation and design, collaborative work has been undertaken by COMRO and FLOSEP. This paper gives a review of the application of Computational Fluid Dynamics (CFD) in evaluating and improving environmental conditions in continuous miner and roadheader sections. A brief history of the development of the CFD model as well as a discussion of a typical application is included.

Jan 1, 1993

By J. Finch, J. Yianatos, N. W. Johnson, R. Espinosa-Gomez

A method of determining the maximum concentrate solids rate or carrying capacity is described for given column operating conditions. The method requires alteration of the feed rate of solids to the column at a fixed residence time by manipulation of the % solid of the column feed pulp or the bias rate. The carrying capacity was measured for five streams at the Mt. Isa Mines Pb/Zn and Cu concentrators. As a potential scale up parameter, the mass of solids per unit time per unit column cross section (Ca, g/min.cm2) is explored. Ca is tentatively related linearly to the 80% passing size (d80) of the concentrate. For d80 < 15 pm Ca was less than 4 g/min.cm2 (8 lb/min.ft2) which makes it a critical consideration in scale-up for such fine feeds. An alternative carrying capacity parameter, mass of solids per unit volume of gas Cg was not as useful as Ca since Cg varied inversely with gas rate.

Jan 1, 1988

By J. Partyka, Trevor R. J. Kelly

This paper presents the results on noise testing of a fan only, as well as the results of a steel silencer and of flexible silencers that were connected directly to a fan. On-site facilities and free-field method set by the British Standards Institution were used to measure and then compare the fan only and different practical silencer configuration setups. In order to determine the fan-silencer combination that would give the maximum noise attenuation, total noise intensity, noise contributed to by the fan motor only, as well as aerodynamical noise created through air interacting with the fan parts were considered to obtain decibel readings for the octave bands. Subsequently, the optimal configuration found was the setup with flexible silencers on the fan inlet and the fan outlet. If only one silencer is used, it should be installed on the fan inlet. The aerodynamic noise affects the low frequencies. The flow noise is then overtaken at 1 kHz by the mechanical noise.

Jan 1, 1995

By F. W. De Vries

A review as of the date of this meeting will cover the writer's perception of eachof the areas indicated in the charts. Changes in many are occurring with enough frequency that a detailed summary would be inaccurate within a few days of writing; for this reason, only an outline is appropriate for advanced preparation.

Jan 1, 1998

By Paul H. Lu

This paper proposes a novel method, "integrity factor approach," of mine-pillar stability evaluation based on in situ triaxial-loading measurement. The pillar integrity factor is defined as the quotient resulting from division of integrated total pillar strength across the critical dimension by the integrated total pillar load across the same dimension. The integrity factor is dynamic, while the conventional safety factor is static. With this approach, the pillar stability can be evaluated at any stage of mining progress during panel operation. It automatically considers the progressive failure of the pillar and post-failure strength without the need to clearly define the boundary between yielded and intact zones of the pillar. Based on two case studies, the integrity factor approach is shown to be a practical, effective technique for evaluating stability of conventionally designed pillars. It is suggested that a more realistic estimate of in situ pillar strength could be made based on the combination of in situ triaxial-loading measurements and laboratory true triaxial compression tests, rather than through the traditional combination of biaxial-loading measurements and conventional triaxial compression tests.

Jan 1, 1986

By F. M. Swain

High-calcium limestones occur in the upper part of the New Market Formation, of Lower Middle Ordovician age, in Franklin and Cumberland Counties, Pennsylvania. The high-calcium facies of the New Market Formation is represented by sublithographic limestone or vaughanite, which probably formed in quiet water; low-energy environments such as intershoal lagoons, or in protected bays similar to the present-day Florida Bay environment. Rapid facies changes are characteristic of the strata. The better grade of stone lies in the upper 100 to 125 feet of the New Market Formation and averages 95-97% calcium carbonate. Silica and magnesia are about equal in amount as impurities. One high-calcium belt extends from the Maryland state line through Chambersburg and Newville to beyond Carlisle. The strata in this belt are structurally complex, which requires careful field study&apos; and core-drilling prior to exploitation. Stone suitable for blast-furnace flux is present in relatively large amounts, but stone for open-hearth use or portland cement requires more selective quarrying.

Jan 1, 1966

By S. L. McGill, P. B. Comba

Many gold producing states are requiring rinsing of spent heaps to render the leached ore compatible with the environment and are placing reatrictiona on effluent pH, cyanide, and metals concentrations. Parameters which may affect efficient rinsing of heaps have been investigated by the U.S. Bureau of Mines in laboratory column studies. Rinse profiles for cyanide, metals, and pH as a function of the volume of water passed through the spent ore are presented. Fresh water rinsing of spent ore in columns showed that rinsing of cyanide was not affected by the rinse solution application rate. Interrupted rinsing with a rest period between applications reduced the volume of water required to meet effluent cyanide concentrations. Chemical oxidation of the effluent with recycle of the rinse solutions reduced effluent cyanide concentrations and the volume of waste solution generated. Water rinsing was not successful in reducing the alkalinity of the cement agglomerated ore. A dilute acid solution had to be applied after cyanide removal to reduce effluent pH levels to specified limits.

Jan 1, 1991

By C. Ceccarini, I. Salvadori, G. Oggiano

GENERAL BACKGROUND The first mention of the presence of bauxite in the mesozoic series of north-west Sardinia (fig. 1) is owed to Oosterbaan, a Dutch geologist, who carried out a geological survey of the area in the ninetten thirties. A more detailed study of the mesozoic series was attempted in the fifties by Pecorini and other, who concentrated particularly upon the stratigraphy of the bauxitic horizons, through examination of the various outcrops. In the sixties a pining company, Monte Amiata S.p.A., turned its attention to a section of the deposit outcropping near Olmedo and, considering it to be of some promise, carried out prospecting works consisting essentially of various trenches, some bore holes, a few adit and a. layout plan for the preparation and execution of trial exploitation. The results, although positive, did not convince the company&apos;s shareholders to continue the exploration. This report, which is intended as a new contribution to knowledge of the Sardinian bauxite deposit, takes into account the information acquired not only from a drilling prospection begun in 1979 in connection with the SOMIT-PROGEMISA joint venture, but also the results of structural studies and numerous chemical, mineralogical and

Jan 1, 1984

By D. Armour, E. R. Bauer, D. R. Zuchelli, T. M. Durr, E. R. Reeves

A team of noise specialists from the National Institute for Occupational Safety and Health (NIOSH), Mine Safety and Health Administration (MSHA), and Joy Manufacturing attempted to evaluate an engineering noise control on a Joy longwall stageloader. The team developed and executed a test plan to evaluate the noise attenuation of the engineering control in an underground coal-mining environment. An evaluation of the long-term noise effects and durability of the engineering control were also a focus of the research effort. Pre- and postcontrol measurements consisting of a combination of worker dosimetry and task observations, tape recordings, and sound level measurements were used to evaluate the engineering control. A description of the engineering noise control, pre- and post-control sound level measurements, and an evaluation of control success is presented. In the end, no evaluation was possible due to mining practices, miner task variations, and inconclusive data.

Jan 1, 2005