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By E. Nejati, S. Khoshkooei, V. Firouzdor, M. Akbari, F. Khomamizadeh

In this study the effects of Si content on mechanical and thermal fatigue properties of Al-Si casting alloys were investigated. Repeated heating and cooling cycles were applied on the samples at 230°C to develop thermal fatigue cracks. Crack growth mechanisms and microstructural influences were investigated by optical and scanning electron microscopy. Thermal fatigue behaviors were improved successively by increasing of silicon content up to 7wt%. However, addition of more than 9wt% silicon decreased the thermal shock resistance of the alloy. Silicon contents of about 9wt% presented the best mechanical and thermal fatigue resistance in the alloy.

Jan 1, 2006

By LEONARD S. AUSTIN

THE works of The Boleo Mining Co. are situated at Santa Rosalia, Lower California, on the opposite side of the Gulf of California from Guaymas, the, nearest railroad town. The copper deposits were discovered in 1868, and the name Boleo arose from the fact that the ore particles were agglomerated as little balls of carbonate or oxychlorides of copper. When worked on. a small scale, only ore carrying 20 to 25 per cent copper was mined; this was shipped to Europe for reduction In 1884 The Boleo Mining Co. was organized and,-the mine put in condition. Even then, due to the low price of copper, only the richer ore continued to be shipped. To operate the mine successfully the company made radical changes in the methods of development and spent money freely for construction of adequate plants for the treatment of low-grade ore. Finally, the owners of the various adjacent mining claims combined their interests and formed a joint enterprise attractive to French capital.

Jan 1, 1929

By G. Thorsen

An alternative way to the normal practice of precipitation of jarosite, goethite, or hematite for removal of iron from zinc sulphate process liquors/ is to employ the techniques of solvent extraction. The process presented avoids the addition of any external alkali for the extraction of iron by integrating the leaching and solvent extraction steps in a hydrometallurgical zinc plant. By starting the leaching of zinc from the solid zinc calcine material with an organic solution of an acid liquid cation exchanger, the organic phase is loaded with the organic zinc salt from the direct reaction with zinc oxide. The residue from the organic leaching is transferred to a hot acid leach circuit where the remaining zinc oxide and the zinc ferrites will dissolve form¬ing an aqueous sulphate solution of zinc and iron. In the subsequent solvent extraction of iron from this aqueous leach solution, iron is exchanged with zinc from the organic phase. The commercial carboxylic acid Versatic 10 (Shell) is highly efficient for this integrated process of leaching and solvent extraction. The resulting iron-loaded organic phase is heated to 150-200 C in the presence of water whereby the iron will be directly precipitated from the organic phase as iron oxide of high purity and the regenerated organic acid is recycled to the organic leaching step for reloading with zinc.

Jan 1, 1980

By Minghui Li

China is the largest coal producer in the world. In 2012, the coal production in China is 3.65billion tonnes, accounting for approximately 49% of global coal production. The raw coal production in 2012 was 3.8% more than the year 2011. 56% of total raw coal has been washed. The increase in raw coal production also promotes technology to be developed and brings separation capacity become larger and larger in coal processing in China. At present, over 40 extra-large scale coal preparation plants (each plant has capacity of more than 10 Mtpa) are in operation in China, the largest one is 32.5 Mtpa. Heavy medium separation are widely used in new built coal preparation, the washing limit for thermal coal feed lower and lower, the equipment selection tends larger which brings the whole washing system simplified, the local equipment developed and manufactured are more and more used. By discussing designs of several typical thermal coal preparation plants and coking coal preparation plants in China, this thesis introduces the current design of China?s extra-large coal preparation plants, and sums up the prevailing design features and trends of extra-large coal preparation plants.

Aug 1, 2013

By Bi Zongyue, ZhangYongqing, NiuTao, Guo Aimin

Over the past twenty years, significant advances have been made in the field of microalloying steels and associated applications, among which one of the most successful application cases is development and application of heavy-gauge X80 coil with high temperature processing HTP practice used for China's Second West-East pipeline, the longest X80 pipe in the world. During this process, HTP design concept has been sucessfully applied to develop 18.4mm X80 coil with demanding low-temperature fracture toughness requirements. In the meanwhile, China's metallurgical workers have further optimized HTP design concept with the aid of powerful rolling mill and coiling equipment, and made it possible to develop 21.4mm X80 coil used for Russia-China East line. In the paper, we would simply review the development history of high-strength pipeline steels, and then give more priority to the fundamental points for sucessful development of 18.4mm X80 coil and SSAW pipe, which paved the way for subsequent development of 21.4mm X80 coil and SSAW pipe. Finally, we would present the test results of mass production and burst tests, and dispel the suspicion that SSAW pipes made of X80 coil are more qualified to resist ductile fracture.

Oct 1, 2019

By E J. B van Etten

This paper reports on the results of several years of monitoring rehabilitation at a silica sand mine on the Swan Coastal Plain, south of Perth. Mining here occurs below the regional watertable and leaves a post-mine landscape of dredge pond voids (pit lakes) with surrounding battered slopes. The restoration we recommended was to develop the pit lakes as wetlands of regional analogue and value. Several different restoration techniques have been applied to re-vegetate pit lake slopes over many years which have enabled an evaluation of reasons for success/failure of different restoration approaches. Learning acquired clearly showed the benefits of using fresh topsoil for restoration over topsoil that has been stockpiled for several years. Most topsoil used in restoration was from seasonal wetlands and consequently restoration was most successful in the riparian zone from the edge of pit lakes to about 2 m vertically above the water table. Topsoil restored areas above this level remained poor in plant species and cover. Conversely, remedial seeding/planting proved largely unsuccessful. Permanently and seasonally flooded pit lake margins recolonised relatively quickly and successfully with native sedges and rushes. Development of rehabilitated upper slope plant communities over time was evident with loss of typical wetland species and greater growth and survivorship of upland and dampland plant species on mid to upper rehabilitated slopes. Plant communities of lower slopes showed a converse pattern of development, with a shift towards a more typical wetland composition. We believe matching topsoil to site and development of topographic profiles similar to natural wetlands of the region are the keys to optimising restoration success of sand mines with shallow water tables.

Oct 5, 2011

By R West

The Olympic Dam smelter facility processes copper concentrate feed using direct-to-blister smelting technology to support the current site production rate of 225 000 t/a copper. The metallurgical control of the Olympic Dam smelter is largely managed from a single central control room. Control room operation and management is therefore a key function in ensuring safe and reliable operation of the smelter, including identifying and initiating control of abnormal events. As part of a consolidated smelter reliability improvement program, a team consisting of process and control system engineers was formed. The teamÆs charter was to address and resolve the alarm flooding issues being faced by the control room technicians and the lack of an up-to-date base of supporting functional documentation. The project was successfully resourced with WorleyParsons metallurgists, Citect PLC technicians and the on-site technical team. Implementation was conducted over a 12 month period with the goal of achieving best practice alarm levels. The goal was achieved through a systematic process of alarm design review that analysed every configured alarm versus best practice design standards. Innovative concepts such as group-based alarms, first-up interlock displays, graphic only alarming, alarm help and alarm shelving were developed and implemented in conjunction with improved alarm masking. Total configured alarms were reduced from 20 000 to 5000 while the alarm rates were reduced from in excess of 200 alarms per hour per controlling technician to best practice levels of less than 12 alarms per hour per controlling technician. Completion of this program has provided a firm foundation for implementing further control optimisation and was a key activity in supporting sustained smelter reliability levels.

Jan 1, 2005

By S. A. Swensrud

REPORTS from smelters show that all were so occupied with the in- creased production called for during the first half of the year that little time was devoted to metallurgical developments. Improvements which have been made such as gas-firing and other alterations ill the reconstructed Hayden smelter, will require time for reporting. The labor situation at all plants held the most prominent place and put all other problems in the background. Coming events of considerable importance concerti the construction of two new smelters. The Chino unit of Nevada Consolidated which has long had its concentrate smelted at the El Paso plant of the American Smelting and Refining Co. is constructing its own smelter at the property in New Mexico. The newest Phelps Dodge development of the Clay ore body at Morenci, Ariz., will call for another new smelter.

Jan 1, 1938

ICMM’s vision is ‘a viable mining, minerals and metals industry that is widely recognised as essential for modern living and a key contributor to sustainable development’. The ICMM Sustainable Development Framework provides the basis for achieving this vision by assisting the industry to improve its performance. Two years on from the first SDIMI conference, significant progress has been made in further developing and implementing the Framework. To fulfill their commitment to implement and report performance against the ten sustainable development principles in the Framework, ICMM’s corporate members have committed to report ‘in accordance’ with the GRI 2002 Sustainability Reporting Guidelines and the Mining and Metals Sector Supplement, developed by the GRI and ICMM. While much remains to be done, development of the Supplement and the commitment to reporting mark an important milestone for ICMM and the sector.

Jan 1, 2005

The number of employees required to operate a continuous operation was determined. The fixed and variable costs of the operation were separated, generally along the lines of labour and stores components. Proprietary `MicroPlanner' scheduling software was used to assess resource utilisation under the constraints generated by seven-day operation to determine the level of resources required and ensure that the maximum use was being made of all resources. The mine economic model was used to account for both the fixed and variable costs of the various task to determine the cost and net revenue of the various scenarios. The analysis indicated that mine output could be increased while reducing the unit production cost. Several eight- and 12-hour, seven-day rosters were sourced and ranked for their potential to improve production and communication, and for their effect on employee health and lifestyle.

Jan 1, 1995

By F. L. Wilke, J. Fabian, D. Oravec

The task of production planning in ore mining is primarily con¬cerned with the removal of ore blocks within planning periods spread over the life of the mining operation. The investigation of this problem in the past resulted in the introduction of computer based optimizing techniques for production scheduling and se¬quencing. Although these techniques succeed in computing an "optimal" mine output for one planning period, they usually fail in composing a practical and feasible mine plan over the periods in concern. This paper describes conventional production planning based on operations research and the capabilities of a knowledge-based approach. An example of a planning system for the Slovak under¬ground iron ore mine Nizna Slana will be presented. By combina¬tion of these two techniques this system should improve the qual¬ity of planning procedures.

Jan 1, 1996

By C. W. Schulties, W. J. Mallio, L. J. Petrovic, J. A. L. Campbell

Roof control comprises about 35% of direct and indirect underground mining costs. In addition, difficulties in estimating roof control costs for new areas lead to the greatest uncertainties when negotiating coal contracts. And obviously, coal cannot be mined if the roof can't be held. Accordingly, there are strong incentives to attack this problem on as many fronts as possible. One successful geological modeling technique for predicting future roof conditions was recently applied at Peabody Coal's Simco mine No. 5, located in Coshocton, Ohio. Benefits derived from it included: - A better identification of areas where poor safety conditions may be encountered. - Improved roof control cost estimates for contract negotiations. - Estimates of time-duration while mining in bad roof areas. - Labor and materials cost predictions in an existing mine. - Productivity increases through prior knowledge of areas to avoid.

Jan 10, 1975

By D. A. Dukelow

By using the U. S. Steel oxygen sensor to measure the oxygen content of the steel, deoxidation practices have been developed for silicon-killed fine-grain steel produced by the basic oxygen process. Measurements of oxygen content taken at final turndown are related to the amount of the aluminum addition to the ladle necessary to obtain the desired aluminum analysis for proper grain refinement. In comparison with heats deoxidized by the standard approach, which is based on carbon content, the heats deoxidized according to the oxygen-sensor-based schedule showed a 25 percent decrease in variability from the desired aluminum content. As more heats of a particular grade are made, it is expected that improved quality will result in decreased rejections and better analysis control. Sensor-based deoxidation schedules are also being developed for semikilled, rimmed, and capped steels.

Jan 1, 1972

By S. P. Hansen

Gravity sedimentation is one of the most widely used processes for separating solids from liquids whether it be for ore and mineral processing or for treating municipal sewage or industrial wastes. Investment in sedimentation equipment can represent a significant portion of the total capital costs associated with a processing or treatment facility. In spite of the importance of sedimentation, little attention has been devoted in recent years to improving this equipment by applying the basic principles involved in sedimentation. In the water and waste treatment field, design criteria established one half-century ago is still the accepted standard and in reflection of this lack of progress, sedimentation and thickening equipment has remained virtually unchanged. The primary purpose of this paper is to present and describe a new innovation in gravity sedimentation which has been applied to water and wastewater treatment and could definitely have application in the field of ore and mineral classification. A secondary object is to introduce the mixed media filter which has been widely used to treat municipal drinking supplies, industrial process water and to provide tertiary treatment of sewage and industrial wastes. The tube-type clarifier was developed primarily to be applied in the field of water and waste treatment where it was found that it could be used to considerably reduce the size and cost of clarification facilities. A logical extension of the tube clarifier would be to the area of minerals classification, ore separation, and for treating waste water associated with these activities. In water treatment practice, most clarification processes are followed by a filtration step to provide further polishing of the water prior to use. This paper will also discuss the mixed media filter which is graded from coarse to fine in the direction of filtration and is capable of operating at high filtration rates and with greater applied suspended solids loading than other filter designs while providing a high qualify filtrate.

Jan 1, 1970

By Thomas L. J

A series of tests on rock stress measurement devices used with the overcoring method indicated that improvements could be made in their construction. A prototype inclusion cell was developed with strain gauge rosettes bonded to a 0.05 mm thickness stainless steel sheet which was formed into a cylinder around two end pieces. The finished diameter was slightly larger than previous cells so that the thinner plate and the reduced annulus of Araldite cement in the installation borehole gave a better response in the laboratory than the other cells tested, especially in simulated bedded rock. It was less affected by inhomogeneity and temperature changes. Its high sensitivity should make it suitable for both absolute stress measurement and field monitoring. A table of comparative readings is given for the new cell and for four other devices used in simulated in-situ rock conditions.

Jan 1, 1992

By Michel Ruel, Ali Soltanzadeh

This paper describes how to make advanced control choices when difficult processes need improvement. The decision-making process involves choosing between a rules-based approach and a model-based approach as well as weighing benefits and drawbacks, complexity and simplicity, investment and results. This paper will present briefly each solution: basic control, advanced regulatory control, model predictive control and expert systems such as fuzzy logic controllers and neural networks. Three examples are presented: ARC (Advanced Regulatory Control) on pH in a comminution circuit, MPC (Model Predictive Control) for combustible management and FLC (Fuzzy Logic Control) on a Semi Autogenous Mill. The article then proposes a decision tree for selecting the most appropriate approach. A table will compare usage, development, commissioning, maintenance and lifecycle costs for each approach. Finally, conclusions and suggestions will summarize the methodology.

Jan 1, 2014

By Tucker A. J

An overburden blast utilising horizontal blast holes was successfully attempted at the Ulan Coal Mines during December 1991. The blast reduced operational problems and costs and improved dragline productivity in an area of that contains poorly consolidated sands and clays overlying very hard Permian strata.The fan shaped shot consisted of seven 250 mm diameter holes between 80 and 95 metres long drilled into the highwall face. The holes were loaded with ICI Powergel Gold 25606 bulk Emulsion explosive. The design powder factor was 0.15 kg/bcm for the total shot of 180 000 bcros and 0.44 kg/bcm for the competent Permian strata into which the holes were drilled. Fragmentation from the horizontal blast was comparable to areas conventual blasted. Following the success of this shot further shots are planned for this area.

Jan 1, 1992

By J. J. Schwoebel, M. J. Mavor

Rapid coal extraction techniques in gassy mines may strain a ventilation system if a degasification approach is not utilized. Design of mine ventilation systems requires estimates of gas emission rates from unmined coal into the existing mine workings. A degasification system for a specific property can be properly engineered to improve mining economics if the proper geologic and reservoir information is collected. This paper describes methods to determine the degasification rates for horizontal boreholes and vertical (stimulated and unstimulated) wells and the rate of gas emissions into the mine workings. The methodology is demonstrated by a specific example. Horizontal boreholes drilled in advance of mining are demonstrated to be the most effective means of coal seam degasification and reduction of gas emissions into mine workings. The significance of the paper is that few published methods for these estimates are available

Jan 1, 1991

By W. W. Adams

Coal mining in the United States established a good safety record in 1939. The death and injury rates per man-hour of exposure to risk were favorable compared with most previous years, and the number of persons killed or injured in proportion to the quantity of coal mined was also lower than in any other year for which figures are available. Moreover, productivity per man-hour was higher than ever before. The number of man-hours of work performed increased 9 percent over 1938, but there was a slight decrease in the number of men employed. Reports from operating companies showed 539,375 men employed during the year, and the period of operation averaged 179 workdays per man. Man-hours of work numbered more than 678 million. Accidents to the workers resulted in 1,078 fatalities and 54,015 nonfatal disabling injuries, causing disability of the employee for more than the remainder of the clay on which the accident occurred. For each million man-hours of exposure of the employees to mining hazards the fatality rate was 1.59 compared with 1.78 for 1938, and the injury rate was 79.65 compared with 82.61 for 1938. Production of coal averaged 0.661 ton per man-hour compared with 0.637 ton in 1938. The weighted average length of the workday was 7.03 hours or virtually the same as the previous year's average of 7.04 hours. Measured in man-hours, the average period of employment per man was 1,257 hours in 1939 and 1,147 hours in 1938.

Jan 1, 1942

By Edgar S. Cook

At the close of the Bethlehem Meeting, the writer was experimenting with large fuel-charges, 4000 Ibs. basis, as compared with 2000 Ibs., hot had not made sufficient progress to draw any safe conclusions. Previously me had always used 2000 Ibs. fuel, the ore-burden being proportioned to this as a basis. I could never persuade myself that there was any advantage to be derived from following the more popular method of larger fuel-charges. Our men were accustomed to the old way of filling ; and we did not care to run the risk of the errors likely to follow any alteration in routine work, particulary as I could not, by my course of reasoning, discover ally compensating gain. Nevertheless, after reading Mr. Gordon's discussion of Mr. Birkinbine's paper, '' Operations of Warwick Furnace from August 27th, 1880, to September 1st, 1885" (Transactions, xiv., 833), I determined to test by actual experiment the value of large fuel-charges : the change was made in the week commencing March 28th, 1886, and continued until July 25th, about four months. The fuel and ores remained during the trial the same as had been used before, and have been used since. For the first two weeks, the furnace worked with great regularity, giving excellent results, exceeding those of the two weeks immediately preceding. But for my remembrance that the furnace had on former occasions worked with equal uniformity for longer periods without any apparent reason, I should doubtless have concluded that this improvement was due to the different method of filling and congratulated myself that a means had at last been found to prevent inconvenient "dirt" accumulations. Before abjuring my previous skepticism, however, I resolved to pursue the trial further. The fourth meek developed the peculiar conditions that had prevailed previous to the change; and these continued with more or less frequency during May, June and July. At last, finding no improvement over the smaller charges—no change in fact for better or for worse—I commenced filling the 2000 lbs. fuel-charge in the latter part of July, and have continued it up to present writing, September 4th.

Jan 1, 1887