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By Chris T. Vild

"ABSTRACT NOT AVAILABLEPRESENTATION SUMMARYIntroductionToday, light gauge aluminum scrap is melted in sidewell furnaces using natural gas reverberatory burners. The scrap is introduced into the sidewell adjacent to the combustion chamber through a submerged archway. Super-heated metal is then pumped into the sidewell where it aids in melting the scrap. From the sidewell, the flow is returned to the combustion chamber through a second submerged archway at some lower temperature. Normally, the burners are set at a designed high fire level and the scrap is introduced at a rate to attempt to mat.ch the burner input. A thermocouple in the bath is programmed to throttle back the burners to low fire if a high temperature limit is exceeded.Jn many cases the thermal efficiencies of these furnaces can be very low. With inadequate circulation, air and natural gas furnaces run at a dismal 18% thermal efficiency. If a circulation system· is added, the efficiency can jump to 28%. For a $100 million lb/yr recycling facility, and natural gas prices reaching $4.50 per million Btu, fuel cost at 18% efficiency can reach $1 million per year. A 10% increase in thermal efficiency saves $350,000 a year in fuel costs.With an increase in thermal efficiency, furnace utilization also increases. A 10% increase in thermal efficiency would result in a 20 million Btu furnace producing 12,000 lb/hr up from 8,000 lb/hr or 35 million lb more produced per year. This is a 33% increase in output.Most current furnace development has focused on burner technology using oxy-fuel, regenerative burners, etc. However, thermal efficiency is also largely effected by the molten metal circulation rate and how well the scrap is mixed into the superheated metal. Therefore, the flow dynamics should be optimized first, before installing of more thermal power.Jn an effort to understand the effect of these variables, a series of computer models were made and the critical factors studied with the goal of demonstrating an increase in thermal efficiency and production. Large-scale graphical representations of these models will be presented."

Jan 1, 2000

By R. A. Spitz, R. Leiby, M. Bricker

Electrochemistry plays a significant role in minimizing wastes at East Penn's secondary lead smelter. East Penn has been recovering spent battery acid for reuse in new batteries since 1992. East Penn also produces a fertilizer feedstock from sulfur dioxide in the smelter stack gases. The success of these processes is, in large part, due to the installation of electrochemical cells. The cells in the acid recovery plant allow the waste from this process to be concentrated into less that 10% of the original spent acid. The cells in the fertilizer plant treat the solution to remove dissolved metals prior to sale to fertilizer manufacturers.

Jan 1, 2000

By R. Elias

Botswana is a mining-dominated sub-Saharan country. Workforces are characterised by poorly educated operators and front line supervisors, with equipment and management to 1st World standards. Poor communication, ignorance of business objectives, inability to meet targets, and lack of problem-solving capacity are the norm. Training leads to high expectations and is of concern to management as a source of dissatisfaction, despite the long-term benefits higher skills have for mine viability. The aims of a technical training programme are presented with various models and approaches being implemented at operations in Botswana. These are used to construct a series of guidelines for technical training initiatives.

Jan 1, 2000

By J. R. Hart, V. C. Smith, V. P. Babarovich-Hansen, J. H. Schubert

"An introduction and case study of Mintek's latest generation of Milling Circuit controller, the MillStarTM with IES (Interpreting Expert System) is presented. This paper also describes as a case study its installation on a Southern African base metals concentrator plant which has demonstrated improved operation, greatly reduced variation in product quality, as well as increased capacity and availability of the circuit.In this case study, the MillStarTMw as installed along with several other enhancements, including hydrocyclone underflow monitoring, product particle size estimation and flotation circuit stabilisation. MillStarTM utilised the particle size measurement to control grind to within 2% of setpoint, all the while ensuring sump level control, density control as well as mill power optimisation. Mintek' s expertise in the modelling of tumbling mills allowed the development of a specialised optimising controller that ensured the mill was kept in the most efficient operating region.MillStarTM augments the automatic control with useful user interface features, such as on-line trends of any logged variables, historic data warehousing and retrieval and production summary reports.A novel feature that distinguishes the MillStarTMi s the IES (Interpreting Expert System). This is a feature of the software that works with the automatic control code to generate explanations for control actions made by the controller. Often complex control systems are mysterious in nature, reducing trust and eventually resulting in them being switched off. The IES method of exposing the heart of the controller has proved popular and is seen to have potential as a training tool. 314"

Jan 1, 2000

By A. V. Tarasov, S. D. Klushin

493 The most common method for minimizing the copper content of residual slag in the process of autogenous smelting of sulfide raw materials is treatment of molten slag in an electric furnace, with optional addition of solid reducing agents, such as coke, and/or sulfiding agents such as pyrite. A drawback of this technique is the fact that the final slag produced still contains 0.5% or more Cu. We have tested a method for treating molten slag obtained as a result of autogenous smelting by a gaseous mixture of sulfur dioxide and methane at a ratio of. SC:SO2 = 0.75 :1.0 in the presence of oxygen. Interaction reaction within the SO2-O2-CRi system proceeded at a high rate at 1373 to 1573 K to form reducing and sulfiding agents: H2S, S, COS, CO, CO2, H2, H2O. The gas mixture requirement was about 100 to 150 Nm3 per 1 tonne of slag. A decrease in the ferric iron concentration (Fe3+) from 10-15% down to 2-3% resulted in lower solubility of copper in slag, and agitation of the melt with gas stream accelerated. the separation of the sulfide phase and slag. Removal of copper from slag was performed in a pilot unit within the second V anyukov furnace zone where slag arrived with a copper content of 0.8-1.3%. The temperature of molten slag was maintained within 1523 to 1573 K. The copper content of the final slag was at a level of0.12 to 0.14%. The matte sent to converting was a mixture of bottom matte from the smelting zone and the slag treatment zone. It had a copper content of about 50 to 55%. Process gases from both furnace zones were combined and sent to the acid plant for sulfur recovery. This process was offered for commercial use at two copper smelters in Russia and CIS.

Jan 1, 2000

By Randall Wheeler, R. Frank Chiappetta

2000 HIGH-TECH SEMINAR Blasting Technology, Instrumentation. and Explosives Applications - Orlando, Florida, USA July 24 - 27,200O 2000 BAI - PROTECTION AGAINST LITIGATION WITH GOOD PRE-BLAST SURVEYS, DAMAGE INSPECTIONS AND RECORD KEEPING 1 of 65 Good Record Keeping is Essential for: 1 ) Compliance with any prevailing Local, State or Federal Regulations, ordinances and permits. 2 ) Protection against potential litigation. 3 ) Balancing explosive consumption, use & costs. 4 ) Use in blast designs.5 ) Blast diagnostics & troubleshooting good/bad shots.

Jan 1, 2000

By R. M. Corn

The Non-Time Critical Forest service CERCLA Action at Mansfield Canyon, Santa Cruz County, Arizona designated previous locators of unpatented mining claims as owners/operators of the Hazardous Waste Facility, retroactively liable for all reclamation costs including reclamation of mines acquired by the Forest Service. The CERCLA Action is based on non-existent tailings, a non-existent permanent resident, inaccurate and unreliable data and did not review or consider prior USGS and USBM data. The consequences of the Forest Service action include(1) reduced exploration, (2) loss of credibility, (3)public disillusionment and distrust.

Jan 1, 2000

By Keizo Uematsu, Kumiko Sanda, Nozomu Uchida

"Full understanding of mechanical properties is the most important assignment in ceramics. Establishment of defects-property relationship is crucial for fulfilling the assignment. This study reports detailed characteristics of defects and their relevance to the mechanical properties for alumina ceramics made through a typical industrial processing. Novel characterization methods were applied to evaluate their defects. A very simple direct correlation was successfully found between defects and properties in ceramics. This result is a great epoch in the field of ceramics. IntroductionThe ceramic materials are used in refractoriness, corrosion resistant materials and structural materials. The low fracture toughness and scatter of strength are very important problems in ceramics. The toughness of ceramics is lower than metal and polymer materials, and the allowed defect size is small. Very small internal defects (pore, crack, huge particle) can be a fracture origin in the brittle fracture. The characteristics of defects such as size, distribution and shape change markedly by process condition, which cause the scatter of strength. This study conducts quantitative evaluation and direct observation of the sizes, shape and a number of internal defects with a light microscope, and discusses the relationship for mechanical properties and defect sizes"

Jan 1, 2000

As has been the case since the early Phoenician traders, the minerals used by modern man come from deposits scattered around the globe. The price received is more and more being set by worldwide supply and demand. Thus the price component in the profit equation:Profits = Material sold (units)x(Price/unit û Cost/unit) is largely determined by others. The recent price history for two of the major metals, copper and iron, are given in Figures 1 and 2, respectively. As can be seen there has been a steady decline in the prices (when expressed in constant dollars) over the 20 years which have lapsed since the first of the International Conferences on Mass Mining, æDesign and Operation of Caving and Sublevel Stoping MinesÆ was held. If one would look back over the entire 20th century this would also be the trend. Cost containment/reduction through efficient, safe and environmentally responsive mining practices is serious business today and will be even more important in the future with increasing mining depths and more stringent regulations. A failure to keep up is expressed very simply as: Profit This, needless to say, is unfavourable for all concerned (the employees, the company, and the country or nation). The mining companies have had to look at ways of reducing the expense part of the profit equation while maintaining safe, environmentally conscious operations. Table 1 summarises the rules for working in todayÆs economy.

Jan 1, 2000

By Axel Preusse

This paper shows basic considerations about the prognosis and prediction of surface subsidence and other ground movements in the German hardcoal industry. The following case studies describe experiences collected in projects between university and industry.

Jan 1, 2000

By Hanjie Chen

Mining experiences have shown that in a pitching seam, roof behavior is significantly different from a flat seam. Uphill mining usually experiences more roof problems than downhill mining. Based on a case study at RAG American Coal Company, Willow Creek Mine, this paper presents the roof control problems experienced in a high pitching seam. Then, finite element modeling is conducted to analyze the roof stress distribution for an entry developed in different directions relative to the seam strike. The results shows that seam inclination has a significant effect on roof stability in terms of tensile stress. Uphill mining experiences higher tensile stress than downhill mining. The modeling technique utilized in this analysis presents a first of kind methodology.

Jan 1, 2000

Introduction The objective of the design and operation of a mine is to make as much money as possible within certain reasonable and responsible constraints. The imposition of constraints on the objective of maximizing profits can result in an optimum mine design. This paper deals with the maximization of profits. Optimization will be discussed in a future paper. In the mining industry, it is generally accepted that the maximum economic recovery is defined by identifying the reserves and the sequence of mining that results in maximum net present value (NPV) or discounted cash flow-rate of return (DCF-ROR), as indicated in Fig. 1 (see Lemieux, 2000). Current parametric analyses techniques, such as varying the mining costs; profit reservation; sales price or metal content, to define pit limits and mining sequence technically referred to single, double or triple parameterization, do not assure that the curve in Fig. 1 will be maximized. In defining the sequence, the first material to be mined should be the first grouping of recoverable mineral that has the highest after-tax unit value and that forms a feasible mining unit. The assumed mining of the first pit should be followed by the assumed mining of the second most profitable and practical pit or pit expansion. If this process of grouping and sequencing is followed until the profitability approaches zero, the general sequence required to extract the maximum economically recoverable reserve is identified. The curve in Fig. I is constructed by calculating the NPV for a series of sequences, each assuming operations are terminated on successively lower profit pits. If the operation ceases on a pit with too high of a profit, opportunity is lost, and the NPV is lower than the maximum. The NPV curve peaks and then starts to decline before the zero-profit pit is assumed mined. This occurs because the money invested in advanced stripping would have produced a greater return if it was invested at the dis¬count rate. The maximum economically recoverable reserve is defined by the pit limit corresponding to the maximum NPV or DCF-ROR. Pit and phase definition The real challenge of reserve definition is identifying the phasing and after-tax profit per ton, so that the curve in Fig. 1 can be plotted. The after-tax profit cannot be properly addressed until after the pits are designed, the production is scheduled and the cash flow is estimated. Throughout the years, many investigators have ad¬dressed this problem. A major thrust of the famous paper in which Lerchs and Grossman (1965) presented their algorithm was to identify a sequence that would produce a result similar to that identified in Fig. 1. Whittle's (1988) four-dimensional analysis is designed to address this issue. The author addressed this same issue in a paper presented to the 1968 Canadian Institute of Mining national convention (Lemieux, 1968). Without a relatively simple methodology to con¬struct the curve in Fig. 1, the number of iterations in a trial-and-error method becomes prohibitively burden-some. The pit designer seeks a simple pit-planning parameter that will serve as a proxy for the after-tax profit per ton used in defining the curve in Fig. 1. The designer's goal is to apply this pit-planning parameter using standard pit-wall location techniques to design a series of pits that will provide a guide to the sequencing. Common techniques used to position pit walls are strip-ratio limits, highwall incremental analysis, floating-cone methods or "maximizer" applications1. Costs, revenues, noncash charges, taxes and profits are usually structured on a unit basis for use in the pit-wall location analysis. Application of the proxy parameter using the pit-design tools should, ideally, result in the definition of pits and sequences that will maximize the curve in Fig. 1. 1 The pit-design tool frequently referred to in the literature as an "optimizer" defines a pit boundary that maximizes the value contained within based on the input parameters and the safe pit-wall angle. The optimization of the pit design involves selection of rate of production, cutoff grade, product quality and other considerations. These considerations constrain the maximization of value. Therefore, pit-design tools that maximize value should be called "maximizers."

Jan 1, 2000

By A. L. Anderson, J. T. Rybock

Lime, soda ash and similar precipitants have been the industry standard for treatment of acid rock drainage (ARD) because of their proven ability and low per-gallon operational cost. However, these methods carry serious environmental drawbacks and high life-cycle costs. KEECO’s Silica Micro Encapsulation (SME) technology has all the positive characteristics of conventional ARD-treatment systems but none of the drawbacks. SME achieves highly effective treatment in a single step, provides options for ARD prevention and recovery of metals, requires lower capital expenditures, generates smaller volumes of higher-density sludge, consistently passes leach tests, and eliminates long-term liabilities associated with potential metal remobilization and hazardous waste landfilling.

Jan 1, 2000

This paper is in two parts. The first part provides background to coal in New Zealand, information on Solid Energy the Company and details of the resources, mines and products of the company. This part of the paper is intended for people who have limited knowledge of the New Zealand coal scene. The second part of the paper focuses on developments underway in New Zealand and discusses planned or possible changes and opportunities. This paper was first presented at the Coaltrans Asia Conference in June 2000.

Jan 1, 2000

By R. T. Dec

A review is undertaken of existing mathematical models of compaction process in roll press. The example of plane-strain, plane-stress model is presented together with comparisons between computed and experimentally recorded pressure distribution in roll nip region. Next, the discrepancies between predicted and measured values are discussed and practical method based on experimental optimization of compaction process using laboratory roll press is proposed. Examples of the selection of optimum roll press operating parameters for calcium oxide fines, sodium chloride and iron oxide dust are presented to illustrate advantages of the method. Finally scale up procedure is discussed for estimating the performance of commercial size roll press based on the data collected on laboratory size equipment.

Jan 1, 2000

By S. M. Pickering, L. T. Gregg

Appraisal of industrial minerals beneath privately owned land requires a different approach and mindset from valuation of base and precious metals or energy minerals, and from valuation of government-owned mineral lands. First, is it the value of inground minerals or of mining rights that is being sought? Second, value to whom, the mining company, a potential investor, the mineral landowner, a lending institution, the property tax assessor, or a condemnor? Third, how should mineral value be apportioned between the land and mineral owner, and a mining company with limited years of lease-hold interest? These and many other questions must be addressed before a valuation method and Discount Rate are selected. For various reasons the Income Method is most often used, with Net Present Value calculations made for long term predicted mining income. Choice of an appropriate Discount Rate is critical.

Jan 1, 2000

By Robert Hopler

The literature of explosives and blasting consists of a great variety of printed materials. These materials include technical papers, books, and articles by individuals and organizations; manufacturer’s product catalogs and brochures; handbooks offering guidance for the field blaster; complete encyclopedias on the subjects, and short entries in general-interest encyclopedias; government publications; proceedings of organizations devoted to the subjects; magazines specific to the subjects; articles in general circulation magazines; and other miscellaneous sources. In short, there is a multitude of literature on the subject, some well indexed for retrieval, but most not. This presentation will be a broad-brush look at some of the most important or interesting literature on the subject, since in no way can all the various references be mentioned, much less covered in depth. To illustrate the presentation, interesting materials from the author’s collection will be shown.

Jan 1, 2000

By James C. Foley, David K. Rehbein

"In-situ characterizations of green state part density and sintering state have long been desired in the powder metal community. Recent ·advances in non-contact electromagnetic acoustic transducer (EMAT) technology have enabled in-situ evaluations of the acoustic attenuation and velocity as sintering proceeds. Pure aluminum (99.999%) and aluminum alloy powders were prepared with high-pressure gas atomization (HPGA). The powders were pressed in a uniaxial die and examined with acoustic waves for changes in velocity and attenuation during sintering. The changes in acoustic properties were correlated with sample microstructures and mechanical properties. Evolution of the acoustic echo train during sintering is shown to provide information on the state of sintering as well as having the potential for detection of interior flaws.IntroductionThe versatility of powder metalallurgy (PIM) technology in the manufacture of complex shapes has enabled an increasing amount of wrought and casting production capacity to be converted to PIM technology. However, ultrasonic inspection of green components produced using PIM techniques remains a challenge and is not generally practiced [1]. Inspection of PIM components in the green state is highly desirable, because the green part can be reclaimed with only accepted components being subjected to further costly processing. Another potential benefit is characterization and greater understanding of the sintering process itself. An increased scientific understanding of the sintering process enables intelligent process control, greater reliability of the production process and a lower rate of rejection of the finished product. In order to realize these potential benefits, it is necessary therefore that accept/reject criterion be based on real time nondestructive evaluation of the green-state components and the sintering process.Most current nondestructive inspection techniques suffer from their inability to perform inspections below the near-surface region with the exception of X-ray and to some extent pulsed eddy current [2]. X-ray inspection requires extensive shielding of production personnel and expensive film and film processing. While development of pulsed eddy current techniques have lessened the impact of the well-known skin effect, the depth of penetration of the induced eddy currents remains somewhat of an issue [2]."

Jan 1, 2000

By Taiping Lou

The coarsening process of precipitates in non-equilibrium systems was studied, and then a physical model of coarsening was proposed. The coarsening process of CaO'TiO2 in MgO-TiO2-Al2O3-SiO2-CaO-CaF system was investigated. It is shown that the coarsening process by the model predicting is agreed with the experimental results.

Jan 1, 2000

By Thomas L. Vandergrift

With the inevitable expansion of homes, businesses, and infrastructure in coal mining regions, the potential for future subsidence above abandoned mines is of increasing concern. Of particular concern are areas underlain by room-and-pillar coal mines. Unlike areas above longwall mines, where total extraction causes subsidence in a predictable and timely manner, subsidence above room-and-pillar mines is difficult to predict and may be active for many decades. As part of a geotechnical assessment of a water pipeline replacement project, NSA Engineering recently performed an evaluation of tong-terns subsidence potential along the proposed alignment due to time¬dependent failure of underlying room-and-pillar workings. The alignment of the replacement pipeline closely follows an existing concrete pipeline, which lies 150 11 to 300 fl above workings that both pre- and post-date the pipeline. Annual surveys along the existing alignment indicate that some subsidence has occurred, primarily from partial pillaring performed in the early 1980's, but that this subsidence is not active. Using the boundary-clement code LAMODEL as the primary analysis tool, NSA followed a three-step approach to estimate future subsidence impacts on the replacement pipeline. First, historical information for the mine was compiled, allowing for calibration of models to actual field conditions. Then, numerical models of workings directly under and adjacent to the proposed alignment were nun, with model input parameters varied until resulting loading patterns matched historical data, and subsidence in the model approximated that measured along survey lines. Finally, time-dependent deterioration of coal pillars was simulated by decreasing the coal strength in the calibrated model until a realistic "worst-case" condition (stability of barriers, but Yielding of production pillars and pillar remnants) was attained. Subsidence from the previous calibrated model was then subtracted from that of the worst case model to estimate future subsidence and related ground movement parameters that slay occur along the proposed alignment. The replacement pipeline design, incorporating couplings capable of withstanding the ground movements predicted, is now being finalized.

Jan 1, 2000