Search Documents

By Oliver Bowles

THE ADVERSE CONDITIONS that have gripped industry during recent years have to some extent submerged technical developments under the more pressing demands of economic problems. Progressive operators, nevertheless, have given attention to improvements in processes and equipment even when sales were at a low ebb. The array of facts relating to technical advancement here presented, although doubtless incomplete, is sufficient to indicate that the spirit of inquiry and research has not been quenched by adversity. During the latter part of 1933 a new element has focused interest more fully on improved methods of quarrying, mining, and preparation of nonmetallic minerals. Codes established under the NRA have fixed minimum wages, reduced working hours, and tended to establish selling prices .on a basis of reasonable profit. Labor adjustments will in many instances increase the cost of production, and stabilization of selling prices will tend to emphasize quality and service rather than price as sales arguments. These new conditions point to a growing necessity for improving technique in the interest of reducing cost of production and improving the quality of products. Thus, technology is linked with economics more firmly than ever.

Jan 1, 1934

By A. C. Rice

Aminopolyacetic acid chelating agents were added to separatory-funnel-scale solvent-extraction systems to determine the effect on separating rare-earth elements. Average values for separation factors between adjacent elements obtained with Primene JM-T2 increase 36 percent when EDTA is added to the aqueous phase. Adding HEDTA or DCTA also improves separation factors for certain rare-earth elements. Percentage of extraction and the separation factors exhibit marked sensitivity to concentrations of amine, chelating agent, and hydrogen ion. The chelating agents improved separation in Primene JM-T, BHDA, and Primene 81-R extraction systems.

Jan 1, 1963

Plant survey data has shown that gold recovery through a specific copper concentrator was significantly lower than copper recovery. Size-by-size analysis revealed that this was due to poor recovery of+75 µm and ?23 µm gold containing particles. In order to further investigate the nature of the gold losses, experiments were conducted at laboratory scale. Gold deportment studies on the laboratory flotation products revealed that coarse gold (+75 µm) reporting to the rougher tailing was predominantly associated with non-sulphide gangue. Further grinding of the plant rougher tailing improved recovery of gold and copper, while not affecting iron recovery, due to improved liberation of gold from non-sulphide gangue in coarse size fractions. EDTA extraction to remove surface contaminants showed a similar improvement for fine, liberated gold flotation.

Jan 1, 2003

By James R. Wickens, David La Rosa, Robert E. McIvor, Adrian Dance

"The comminution circuit at Barrick Cortez Gold Mine uses an open circuit primary jaw crusher followed by a standard SABC grinding circuit. The grinding circuit incorporates a 26’Ø x 11’ SAG mill, an Omnicone 1560 pebble crusher and a 16’Ø x 28½’ ball mill. Both mills are driven by 4500 HP motors.In 2007, several comminution circuit studies were performed to assess circuit performance and map a course for improvement. This paper discusses the results of those studies including an analysis of mine-to-mill opportunities, grinding work index efficiency, and ball mill functional performance. Subsequently, improvements to the circuit were made to enhance operating efficiency. Specifically, improvements to the pebble crusher liner configuration, advanced process control system (expert system) and ball mill classification and ball charge are discussed. In addition, other current and future improvement opportunities are discussed.INTRODUCTIONThe Barrick Cortez property is expanding to include the new Cortez Hills open pit and underground mines. Ore from these new mines will be processed in the existing Pipeline mill facility. In conjunction with ore characterization work, performance of the comminution circuit needed to be quantified. Thus, in 2007, the comminution circuit was surveyed and opportunities for improvement identified.Figure 1 below shows the Pipeline mill flowsheet. It is a standard SABC grinding circuit using an open circuit primary jaw crusher followed by a 26’Ø x 11’ (7.92m Ø x 3.35m) SAG mill, in closed circuit with a Omnicone 1,560 pebble crusher, and a 16’Ø x 28½’ (4.88m Ø x 8.69m) ball mill. Both mills are driven by 4,500 HP (3,357 kW) motors. The SAG discharge screen aperture is 5/16” (8 mm) x 1-1/16” (27 mm) slots. Ball mill circuit classification is done with Krebs D20B cyclones."

Jan 1, 2009

By B. Prof. Silliman

THE experiments detailed by Dr. Hunt,* having demonstrated the fact that the copper contained in the "clay ore" of Jones's Mine, was rendered completely soluble in the bath of ferrous chloride, used in the Hunt and Douglas process, after heating in contact with carbonaceous matter in a close vessel, I set myself to devise a form of muffle furnace adapted to the treatment of large quantities of these and similar ores by a continuous process. The result is shown in the diagrams on Plate X, reduced from the working drawings, after which this furnace was built early in 1876, at Phoenixville, by the Chemical Copper Company on their works at this place. The peculiar character of this ore determined the form, dimensions, and position, with reference to charging and discharging of these muffles. The ore arrived from the mine with from 20 to 25 per cent. of moisture, and when dried at 212° F., or more slowly at lower temperature, it falls to a light incoherent powder, with occasional lumps of undecomposed rock. In this condition it is readily mingled with coal-dust or any like reducing agent, and requires no other preparation for the muffle than the use of the shovel, to mix it well with the reducing agent. As it is a remarkably good non-conductor of heat, it was obvious that the mass, to be heated through in a reasonable time, must not be too thick, while the weight of the mass must be sustained in a way to avoid undue strain upon the walls of the muffle. These walls must be as thin as practicable, to favor the more rapid transmission of heat, and must, therefore, be so con¬structed as to admit of being stayed on the sides at frequent intervals to resist the lateral thrust of the very mobile mass of pulverulent ore, which, for obvious reasons, must be charged at the top and drawn from the bottom of each chamber. These considerations led to the form adopted, viz., two vertical muffles, standing upon very strong bridge tiles, seen in longitudinal section, on the line E, F, and in plan in Fig. 3, on the same plane. (Plate X.) The vertical section of the muffle is seen in Fig. 4, drawn in the plane G, H, of the longitudinal section, Fig. 6, which is the key to all sections. The walls of the muffles are built of the best firebrick, very care- * See paper by Dr. Hunt, page 325.

Jan 1, 1876

By Richard J. Robbins

Raise and shaft drilling, a continuing development RICHARD J. ROBBINS* (Visitor) Although the past decade has witnessed many improvements in large-diameter drilling machinery for the boring of raises, there is still room for improvement both in operational use and in the design of equipment. Some of the available machines are described and illustrated, and it is concluded that the possibilities of new systems and designs should continually be re-assessed since the factors that determine their feasibility, such as bore diameter, cutter costs, and penetration rates, are changing rapidly.

By C. W. Sheng

In this paper conventional construction procedure is briefly described for the installation of stone columns in soft ground in China. A viewpoint concerning the mechanism of ground improvement by use of stone columns is presented for discussion. Based on the information obtained from field measurement and observation three important problems relating to the construction and design of stone columns are discussed. Finally, a case history is given to show that short stone columns floating within the weak soil layers may in some instance be used to improve the weak strata of great thickness.

Jan 1, 2010

By Masanobu Morita, Koichi Kurokana, Kenji Hashimoto, Yoji Tasaki, Yukio Iida

"It has been the long desire of blasting engineer to realize the automatization of tunnelblasting to improve the safety and efficiency. As for bore hole drilling, the automatizationhas been achieved by the improvement of drilling machine. However, the firing process isstill depending on the hand-operation. We developed the wireless initiating system using amacrowave power as a step for automatization of tunnel blasting operation. In this paper,we present the outline of the wireless initiating system and the results of experimentalstudy of the wireless detonator which is key component of the system."

Jan 1, 1993

By Yasumasa Hattori

Fluid flow in a flash furnace concentrate burner was investigated quantitatively in order to improve burner performance. Computational fluid dynamics was utilized for researching fluid flow in a burner port mathematically then its results were reviewed in the commercial flash furnace burner and its calculation results were found to be in good agreement with the actual measurement results. Based on those results, a mathematical fluid flow model for the Sumitomo flash furnace concentrate burner has been developed so as, to improve premixing and combustion efficiency of concentrate in the reaction shaft.

Jan 1, 2002

By Gerald H. Luttrell, Roe-Hoan Yoon

Flotation columns are becoming increasingly popular due to their ability to improve selectivity and to reduce operating costs. Unfortunately, these advantages are not often realized because of poor operating practices and difficulties associated with design and maintenance. This article provides guidelines for the operation and design of columns. The discussion will focus on designing proper wash water systems for improved selectivity, maximizing throughput by increasing the bubble surface area rate, and minimizing operating and maintenance costs. It is suggested that the design of the air sparging system is the most critical element in column flotation.

Jan 1, 1993

By Jukka Pukkila, Pekka Särkkä

Intensive co-operation between mining industry and mining machine manufacturers during an eight year program Intelligent Mine™ led to a new concept for applying automation technology in mining to improve the productivity and safety of mines. 'The results of the program are now implemented in several mines in Finland and with similar ideas as well elsewhere in the world. The degree of optimal automation of an intelligent mine depends on several technical and economical factors. The basic precondition for the approach is a clear improvement in total economy of the mine.

Jan 1, 2002

The Bureau of Mines has conducted considerable research to improve life support technology for underground mining applications. This proceedings volume presents several new developments that may help increase the chances of mine workers in surviving underground disasters. Several papers address the performance of present self-contained self-rescuers (SCSR's) and provide proposed guidelines for the design and testing of a second-generation SCSR. Improvements In the safety and effectiveness of mine rescue and recovery operations are described, including the design of a low-profile rescue breathing apparatus and a rescue team helmet.

Jan 1, 1987

By L. M. Kaas

Production planning techniques, particularly a production scheduling model are proposed for use in taconite mining in Minnesota. Applications of the scheduling model, on a two-year mine plan, which evaluates the equipment involved, are detailed. Data and tables are included. INTRODUCTION Fifty years ago Walter Swart, a mining engineer investigating the Minnesota taconites for the Jackling interests, made this report: "There is no doubt in my mind that this taconite mining is a game worth playing and that it can be played to a successful finish. It seems now only a question of men, money, methods and details."' The prosperous industry envisioned by Swart and other taconite pioneers is today a reality. Its growth has been spurred by technological advances in mining and beneficiation, depletion of natural ore reserves, and improvement of the economic climate. However, the massive problems that were solved to make this development possible are only a foreshadowing of the questions of "men, money, methods and details" that will be encountered in the future. The increasing demands for higher quality taconite pellets have already forced producers to examine better methods of quality control for their operations. THE NEED FOR PRODUCTION SCHEDULING The maintenance of fairly constant crude ore characteristics is of major importance to mill quality control. Through careful mixing of ore from storage bins, the concentrator staff can partially reduce the deviations of the feed analysis from the analysis desired. However, the limited effectiveness of bin mixing systems has caused some mining companies to utilize large capacity blending piles to reduce grade variations. Although the analysis of material being reclaimed from such a pile is relatively uniform, raw materials still must be scheduled from the mine into the pile in such a manner that the average analysis of all material is close to the feed analysis prescribed by the mill. PRODUCTION SCHEDULING MODEL Minnesota taconite mining companies have used three analyses to estimate how a certain ore will react to concentration. These factors are the crude magnetic iron content of the ore, the iron content of the plant concentrate produced from the ore at a standard grind, and the grindability index of the ore. The actual laboratory tests used to determine these factors have been described by Apuli.2 These data are obtained from analysis of diamond drill cores, and are the established criteria used by mine planning engineers to formulate taconite production schedules. Variations in the grade of mine output should be controlled by any production scheduling system. However, to be truly practical, production scheduling methods must also consider many of the less tangible variables that affect mine operation. These include pit layout, available equipment, and ownership of ore leases. The number and scope of the variables inherent in this type of mine planning suggested that a computer simulation could be used to solve the problem. The preparation of information for use with a computer simulation program was the initial phase of this project. Meaningful data was developed from logs of diamond drill cores. Analyses were related to their respective areas of influence by means of mine maps, Fig. 1. The three assay variables and tonnages for each area were punched on cards. In addition to these values, a location code number was punched in the first eight columns of the cards. This code is explained as follows: Column 1 Bench number Column 2 Quadrant location as determined by mine reference lines Columns 3-5 East-west coordinate Columns 6-8 North-south coordinate The heart of any simulation techniques is a well engineered mathematical model. To develop a model for taconite production scheduling, the relationship between the three assay variables had to be established. Because changes in each analysis factor affect the mill circuits in different manners, a weighting system was used to determine the relative im-

Jan 1, 1967

By F. Khomamizadeh

In this study, deep cryogenic treatment was applied to A319 cast aluminum samples. Although the cryogenic treatment didn't have any significant effect on mechanical properties of the well degassed and fluxed samples, but the tensile strength of the samples containing a considerable amount of gas and shrinkage defects was improved surprisingly, This improvement was attributed to the strengthening of the a-aluminum matrix which slows down the propagation of the existing defects. There was no significant increase in the hardness after cryogenic treatment, The abrasion resistance of the alloy was improved after cryogenic treatment, by developing a homogeneous protector shield, composed of abrasive grains penetrated into the soft aluminum matrix and kept tight.

Jan 1, 2005

By J. W. Walkiewicz

The U.S. Bureau of Mines has conducted studies using microwave energy to stress-crack iron ores. In a microwave chamber which simulates a continuous throughput operation, the Bond grindability of a taconite sample was improved by 13 pct at a bulk temperature of 197? C. To further improve the economics of microwave fracturing, higher powers up to 16 kW were used to rapidly heat samples to relatively low temperatures in a continuous belt-fed applicator. A significant enhancement of grindability was obtained with a minus 1.9-cm taconite rod mill feed. At a sample temperature of 130? C, the grindability was improved a maximum of 26.1 pct over the non-microwaved sample.

Jan 1, 1993

By Dean S. Rogers

The conventional role of exploration, development and grade control is examined in this paper within the context of the many and varied types of gold occurrences which are found at the Dome Mine. The account endeavours to trace the development of the total ore evaluation process, from diamond drilling through the exploration and drifting stage, to the stope development and planning phase of the operation, with an emphasis on sampling techniques and assaying procedure. The concept of ore reserve calculations is developed and the practice of grade control is described. In summary, the role of the geological, the engineering and the mining department is presented in relation to the contribution each has to make in the evaluation and exploitation of ore from one of the world's classic Archean gold deposits.

Jan 1, 1985

Electronic Detonators have made significant strides over the last few years, both in quality of product and performance in different blast applications. The precision and flexibility of the SMARTDET units provides the mines with a powerful means of controlling blast results, giving both cost and productivity improvements. The SMARTDET Electronic Detonator System, robust and easy to use, has been successfully deployed over the last 18 months in improving mine productivity and creating safer working conditions in both quarrying and long-hole stoping. The key to the improvements has been the precision and flexibility of the electronic timing, and the ability of the mine personnel to grasp the concept quickly and use it effectively.

Jan 1, 1999

By Ronald O. Harma

Iron ore pellets made from concentrates produced from low grade iron ores are the primary iron bearing feedstock for iron making in North American blast furnaces. Steelmakers are demanding increasingly higher quality to provide for improved blast furnace productivity, efficiency, product quality and environmental compliance. Unfortunately, this higher quality iron ore product must be produced from the vast deposits of low grade iron ores that are becoming increasingly poorer in quality with regard to mineral liberation and ease of concentration. Since some of these low grade iron ores require grinding to as fine as 90% -500 mesh (25 microns) for liberation and since more of the silicious gangue and other minor undesirable constituents must be removed to provide the higher quality, we have come to depend on flotation to do the added work. Flotation technology and other preflotation unit operations must improve to meet these increasing demands. In many cases, flotation equipment, reagents and circuit operating performance have improved little during the last two to three decades. Mechanical flotation cells have grown from 14 cubic meters (500 cubic feet) to over 84 cubic meters (3000 cubic feet) to help reduce capital and operating costs; however, flotation metallurgical performance has not improved, Column flotation has only recently shown promise in improving metallurgical performance for iron ore rougher flotation. Previous column flotation success was mainly in scavenger and cleaner flotation steps for treating minerals other than iron ore. Although some new flotation chemicals have been developed for removal of silica and other minor constituents under widely varying mineralogical scenarios, recovery of iron mineral has not improved. The operation and control of flotation circuits have become more challenging because of the increasing workload on flotation. Better sensing, process control and operation of flotation circuits are essential as we go forward. Iron ore upgrading by flotation can be classified into either anionic or cationic methods. Anionic flotation of either iron oxide or silicious gangue is accomplished by collector type, pH control and selective chemical activation . Similarly, cationic flotation of silica or iron oxides is accomplished by collector type, activation and/or pH control. Removal of other minor constituents is achieved by using specialty chemicals under controlled conditions for preflotation, co-flotation or post flotation steps. Generally, anionic flotation is used for floating cleanly liberating crystalline oxidized iron ores such as hematite, specularite and martite. Earthy and hydrated oxides such as hematite and geothite can be upgraded with either anionic or cationic collectors after controlled dispersion of slimes or prior removal of slimes. Anionic flotation of silicious waste can be achieved by calcium activation of silica. For magnetic iron ores small amounts of locked silica particles (middlings) can be removed by cationic silica flotation, which is the only method in commercial use in North America today. Historically the efficiency of these iron ore flotation processes has been restricted by the loss of fine iron particles (minus 500 mesh) to the tailings product. New technology is required to overcome this loss and improve overall flotation performance. Development of technology for more selective separation of silica and other minor undesirable constituents from iron ore will provide both quality and cost benefits to the iron and steel producers. Development of future iron ore production in North America will face stiffer technical challenges. These new and undeveloped iron ore deposits are largely oxidized (non-magnetic) and by nature contain more slimes and other undesirable constituents. Unless other new technology evolves, flotation will be the major treatment process required to upgrade these difficult low grade iron ores.

Jan 1, 1993

By A. B. Holland-Batt

Following a relatively static period in the 1960s and 1970s when incremental development rather than innovation was the norm for gravity separation, the last 15 years has seen a number of new developments in this area. The paper briefly reviews the traditional gravity separation techniques and then examines the newer developments such as centrifugal separators. Particular emphasis has been placed on novel devices or improvements that offer either better control or improved performance.

Jan 1, 1998

By Roshan B. Bhappu

Although the economic importance of recovering copper by leaching of mine work dumps from open-pit operations has been realized for some time, serious attempts to understand and to improve such operations through scientific research has been made only in recent years. This progress report covers the results of chemical, physical, and biological studies pertaining to the dump leaching process and discusses salient features and parameters that may be helpful in improving such operations.

Jan 1, 1968