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By Nestor M. Fillip

INTRODUCTION The Advisory Conference on Tunneling held in Washington, D.C. in 1970 under the auspices of the organization for Economic Cooperation and Development (OECD) forecast that $54 billion would be expended by member countries on underground construction in the 1970s. Construction activity since the Conference indicates the forecast may have been conservative. Statistics in the report indicated a vast increase in tunneling projects for mass transit, hydro-electric development, railroad tunnels, sewer and sewage retention reservoirs and water tunnels. Development of equipment is required to meet the demands for high speed excavation and provide tunnel driving systems with maximum efficiency and capability to sustain high speed advance rates. BORING MACHINE CAPABILITY During the last decade, use of Tunnel Boring Machines (TBMs) has increased. Where ground conditions and limits of machine design criteria permit, circular tunnel sections are either the only section , or an alternate sections specified in the documents: a TBM is either required or is an acceptable alternate means of tunneling. The evolution and acceptance of the TBM has had an impact on the construction and to a lesser degree on the mining industry. The traditional drill-blast-muck or "hand" mine

Jan 1, 1974

By Peijian Zhang, Yansheng Liu, Yuusaku Tominaga

The directions for ventilation control are often given in linguistic styles such as "if the airflow rate measured is small, a high value of rotation on a local fan should be chosen." In order to control the underground climate using a computer instead of a human being, both the reliability of data values measured underground and the application of human recognition of data values are required. The efficiency of data transmission is dependent on a method of checking a signal which is changed by mixing noises resulting from cases of electrical and mechanical damage to cables. In the study, fuzzy reasoning is adopted to choose a checking method for underground conditions from a normally operating state to an emergency. Fuzzy reasoning is applied to control airflow rate under the linguistic control rules given. It is shown that an effective series of linguistic control rules derived by fuzzy-sets theory is available in ventilation control when used in conjunction with an air velocity sensor, a computer and a local fan with thyristor control. Moreover, a system to make an optimum series of linguistic control rules for ventilation control is introduced.

Jan 1, 1987

By W. A. Crosby, A. Bauer

The recent increase in size of open-pit mining operations has resulted in major improvements in efficiency that are beneficial to the mining industry. Higher bench heights, larger diameter blast-holes, and more powerful explosives have played an important part in reducing mining costs. These measures have, however, resulted in increased energy concentrations in the blast area, which can result in severe backbreak problems for final pit walls. If backbreak is not controlled, a decrease in the overall pit slope angle will ultimately be necessary, and consequences, such as decreased recoverable ore reserves and increased waste-to-ore ratios, will result. Greater amounts of loose face rock will be produced, and planned safety berms will be less effective or nonexistent. Hazardous working conditions can also result. Remedial measures, such as scaling large areas and using wire mesh or other artificial support, are very expensive and difficult to implement. There must be a trade-off between the money saved by using larger blasts, and the time spent to maintain pit wall quality. The best approach is to control blasting effects so the inherent strength of pit walls is not destroyed. Presplit and trim blasting are two control blasting techniques used to accomplish this. Both techniques are designed to create a low explosive energy concentration per unit of wall area at the perimeter of the pit. Energy concentration of the main production blast must also be controlled to avoid damaging the final pit wall. A low-energy concentration at the final wall can be obtained by decoupling charges, decking charges, using less powerful explosives, decreasing blasthole diameters, and changing the burden and spacing. Rock properties-fragmentation and the final state of the pit wall-influence the success of a blast. The most important properties to consider are: in situ rock strength, and the nature, frequency, and orientation of structural features. Since these variables cannot be controlled, they must be evaluated by suitable field tests, and then a control blast can be designed using controllable variables, such as spacing, burden, and hole diameter, so the blast will be successful for appropriate rock conditions. One main thrust of this article is to show how control blasts can be successfully designed for larger hole sizes, up to 381-mm-diam. While efforts to produce a good control blast in shovel/truck pits have been ongoing for some time, recent use of a modified presplit technique in dragline operations has helped reduce water problems, improve safety, and increase dragline productivity in a number of surface coal mines. This article presents examples on designing and using presplit and trim blasting for large hole operations in both shovel/truck and dragline mines. Presplit Blasting As introduction to presplit blasting, Fig. 1 illustrates a typical presplit blast layout using 102 mm-diam presplit holes for 381¬mm-diam production holes. For this type of blast, presplit holes would normally be drilled first, ahead of main production holes. The choice can then be made between loading and firing the presplit line or infilling the main blast. In the latter case, the presplit line would be fired instantaneously 100-150 milliseconds before the main blast. As shown in the figure, the presplit line is formed ahead of the main

Jan 2, 1982

Conveyor belting-Dunlop Belting Division has published a manual on its Starflex plied conveyor belting. The design section of the manual contains advice on the calculation of tensile strength and horsepower needs while the section on belt selection offers helpful recommendations. Circle 200 on reader service card Hydrostroke feeders-A pamphlet from Kone Corp. highlights the uses and operating principles of its hydrostroke feeders. Circle 201 on reader service card Electric cylinders-A 24-page catalog from Raco International Inc. describes applications for its electric linear actuators in addition to the electronic options for computer - controlled operation. Circle 202 on reader service card High torque drives-T. B. Wood's Sons Co. offers a 56-page booklet providing features and specifications on its high torque drives. Information includes a step-by-step drive selection proce¬dure. (HTD) Circle 203 on reader service card Sludge depth meter-The model 600 sludge-depth meter that locates the sludge bed in clarifiers and settling tanks is described in a four-page bro¬chure from Markland Specialty Engineering Ltd. (600-84) Circle 204 on reader service card Cavity pumps-An eight-page bulletin is available from Robbins & Myers Inc. It features the application of Moyno progressing cavity pumps in handling composite slurry fuels. (400) Circle 205 on reader service card Roller chain-A roller chain catalog shows heavy duty drive chains and other specialty conveyor chains. It is available from Peer Chain Co. (PC200) Circle 206 on reader service card Belt filter-Phoenix Process Equipment Co. has available a pamphlet detailing its belt filter press. The unit is designed to dewater refuse and clean coal, yielding easily handled dry filter cakes. Circle 207 on reader service card Capabilities - Literature from International Mineral Services Ltd. highlights its services and capabilities to the mining industry. Circle 208 on reader service card Motor analysis - How to select the proper electric motor by comparing life cycle costs, power costs, rate of return, and other factors, is described in a brochure from Westinghouse Electric Corp. (SA-11376) Circle 209 on reader service card Cavity pumps - A product application data sheet is available from Robbins & Myers Inc. It details the use of Moyno positive-displacement, progressing cavity pumps in handling ground limestone slurry. (PC-21) Circle 210 on reader service card Dust collectors - "Dust Collector Selection Guide," from American Air Filter, describes dry mechanical collectors, wet collectors, fabric collectors, and electrostatic precipitators. (CAD-1-901G) Circle 211 on reader service card Wet scrubber - A 12-page bulletin from The Ceilcote Co. provides a comprehensive description of its ionizing, wet-scrubber system. (12-19) Circle 212 on reader service card Metric o-rings-Simrit Corp. has published a 16-page brochure detailing its full line of standard metric o-rings. Information includes graphics and dimensional charts, and specific data on materials and application ranges. Circle 213 on reader service card Hearing protection - A 16-page catalog from Cabot Corp., EAR Division, provides information on its hearing protection devices and noise control products. Circle 214 on reader service card Toxic gas detection - Sensidyne Inc. is offering a guide for toxic gas monitoring. A description of the electrochemical sensors, as well as ranges, complete specifications, and interference charts are included. Circle 215 on reader service card Hydraulic bolting systems - Ingersoll-Rand Co. is offering a brochure on its line of hydraulic bolting systems. These systems, hydraulic wrench and power console, are designed for heavy duty bolting applications. Circle 216 on reader service card Temperature monitoring - A brochure describing the Ramsey Engineering Co.'s micromonitor temperature monitoring system is available. Three types of switches are available for monitoring bearing temperatures. (80.300) Circle 217 on reader service card Product catalog - Shadbolt & Boyd Co. has published a product catalog. Among items described are hoist slings and cranes; compressors; hydraulics; wire rope, chains, and fittings; and materials handling and shop equipment. Circle 218 on reader service card Cylinder controls - A 12-page booklet presenting Hanna Corp.'s line of electrical controls for cylinders is available. It features proximity and limit switches for hydraulic and pneumatic cylinders, and standard and 3-amp reed switches for pneumatic cylinders only. (550) Circle 219 on reader service card Slurry pump - Pettibone Corp. has published a 24-page booklet covering its heavy duty pumps made with 'diamond alloy' materials for handling slurries of abrasive materials. Circle 220 on reader service card

Jan 9, 1985

By Peter J. Szabo

The mining executive works in a cyclical industry. His employment is subject to the vagaries of the marketplace. Boom and bust has always been the industry's story. "Big oil" failed in its mining effort. This left emotional and financial scars on many mining families. One must remember that mining executives always play a high-stakes game. Given the cyclical nature of the mining industry, mining executives need to take care of their own financial security. The mining executive that does not plan for his financial security in this cyclical business is playing Russian Roulette with his future. Take a look at those people who have reached their later years with the mining industry. One usually finds three categories of people. Those few in the first group have been fortunate enough to have worked for one company. They have survived the winnowing process of cyclicality, political problems, and takeovers. They have reached normal retirement age. For them, the retirement years are usually comfortable. People in the second group have worked for those same mining companies. But these people have been forced out by early retirement. Or they have been laid off for cyclical, takeover, or political reasons. The third group includes those who have held many positions in the mining industry. Probably not until their later years are they fully vested, if at all, in a pension program. The first small group, then, is the exception. The others, unless they have taken care of their financial security, are doomed to later years of financial problems, stress, and unhappiness. Too late in life, many realize the harsh realities of failure to plan and implement a personal financial program. Mining executives go to some of the world's leading mining schools, to learn how to make money. The curriculum is technically strong. Most mining graduates are familiar with the intricacies of discounted cash flow, present value, and the Hoskold formula. But few of these same mining schools require courses on personal financial planning. Such courses could give mining students a realistic foundation and the mechanisms with which to cope with their cyclical profession. An executive has only three sources of money. He can make money at work. He can put his money to work. Or he can get money from charities, such as government programs. Of these three sources of money, money at work has the best chance of providing financial security in later years. The mining executive must think of the day when he will be too old to work and contribute to the market place. At this point, the quantity and quality of his investments will determine whether his later years will be secure. Along with the Mining Engineering Handbook, two key books should be included in the mining executive's library. These are Venita Van Caspel's The Power of Money Dynamics and Benjamin J. Stein's Financial Passages. These books contain the basic concepts of personal financial planning so critical to an individual's financial survival. Venita points out the simple formula that is the key to financial independence: Time + Money + American Free Enterprise (Rate of Return) = Opportunity to Become Financially Independent Chart 1 shows that this is not a trite formula. The chart shows the dramatic effects of compounding over time. The chart also shows at various yields what a $2000 a year Individual Retirement Account (IRA) contribution will accumulate. Chart 1 (from Money magazine) is based on the future value of an ordinary annuity. It shows that the key to amassing a small fortune by the time a person reaches his 50s is starting to save methodically in his 20s. This, coupled with the highest yields consistent with safety of principal will ensure financial security. There are significant effects from compounding money over time. Every year the decision is put off to save for later years will cost a person dearly by the time he reaches his 50s. For example, consider the decision to put off for one year a $2000 IRA investment at a 12% return. Starting it at age 31 instead of 30 will cost the executive almost $100,000 by age 65. What if the executive waits until age 35 to get started with his $2000 a year investment? He will then lose nearly $400,000 by age 65. Stated another way, the executive costs himself this $400,000 simply because he did not invest $167 a month for five years. $167 a month - that's less than an inexpensive second car payment. This $400,000 pool of money could provide the executive a $40,000 a year income at age 65, assuming a 10% return on invest-

Jan 11, 1985

By A. E. Desrosiers, R. L. Kathren, D. L. Haggard, J. M. Selby

INTRODUCTION The radiological health significance of thorium-230 stems from its tendency to separate from the uranium238 parent, concentrate in bone tissues, and to subsequently irradiate the radiosensitive tissues lining the bone surfaces and the bone marrow. Indeed, thorium-230 may be the radionuclide which contributes the major dose following intake of natural uranium (Hartley and Pasternack 1979). This is reflected by the most recent recommendations of the International Commission on Radiological Protection, which specify the limits shown in Table I for the annual intake of radionuclides by occupationally exposed workers (ICRP 1979). TABLE 1. Occupational Annual Intake Limits (microcuries per year) for Selected Uranium Nuclides and Daughters (ICRP 79) [Radionuclide Ingestion Inhalation] [Uranium-238 200 0.05 Uranium-235 200 0.05 Uranium-234 200 0.03 Thorium-234 300 200 Thorium-230 3 0.02 Radium-226 2 0.5] Clearly, the relatively low annual limit of intake for thorium-230 shows it to be of greater radiological concern than its parent radionuclides. Because of the greater toxicity and different metabolism of thorium-230, monitoring only for uranium-238 does not satisfactorily identify the possible hazard from thorium-230 nor does it provide any real indication of the metabolism or biodynamics of these two radionuclides. Thorium-230 has a half-life of 80,000 years and can be detected by direct counting of the alpha particles or photons emitted during its transformation to radium-226. The 4.69 and 4.62 MeV alpha particles are distinctive and specific indicators of thorium-230 and are emitted with abundances of 76% and 24%, respectively. The principal photon, a 68 keV gamma ray, is emitted in only 0.37% of the transformations and is, therefore, not useful for low level measurements. The other photons emitted have even lower yields, or, in the case of radium L x-rays, are non-specific and, hence, useless for quantification. High sensitivity measurements of thorium-230 currently are usually accomplished by wet washing of the sample substrate, quantitative chemical separation of thorium atoms, and, finally, direct measurement of the alpha particles emitted from a massless deposition. This procedure is complicated, expensive, and time-consuming, and subject to interferences from uranium, other actinides, and other thorium isotopes. Recently, the feasibility of low-level measurement of thorium-230 by neutron activation analysis (NAA) was demonstrated (Kathren, Desrosiers and Church 1980). Two principal variations of the NAA method were used in this study: 1) instrumental NAA technique and 2) post-irradiation radiochemical separations (RCS). Instrumental NAA procedure is a nondestrucive technique which is preferred because of its simplicity. The procedure is as follows: after irradiation with a known neutron fluence, the samples are transferred to a clean container and quantitative gamma spectroscopy performed. With the radiochemical separations procedure, the sample is initially treated as in the instrumental technique. However, after irradiation, a known amount of "carrier" is added to the sample. The element(s) of interest are then separated from the rest of the matrix by distillation, precipitation and extraction techniques. The resulting sample, now free of interferring elements, is then ready for gamma-ray analysis. The use of a "carrier" is to determine the loss of element-of-interest during the chemical separations process. The neutron activation cross section of thorium-230 has an epicadmium resonance value of 1,010 barns (Mughahghab and Garber 1976) and a thermal neutron cross section of 23 barns. The 25.52 hr thorium-231 produced releases two photons of significance: an 84 keV complex, (6.5% yield) and 25.6 keV (15% yield) (Lederer and Shirley 1978). The 84 keV complex is particularly useful for quantification since neither natural uranium, thorium, their daughters, or activation products emit photons in this region. However, the higher yield of the 25.6 keV photon may result in increased sensitivity if there are no other photons of similar energy emitted by other radionuclides in the sample. PRELIMINARY STUDIES Thorium-230 standard stock solution was prepared from a pure sample of the oxide purchased from Oak Ridge National Laboratory. From this stock solution a series of samples were prepared for irradiation in the TRIGA Mark I reactor at Reed College. Various dilutions were prepared as well as thorium-230 spiked urine samples. Irradiation times varied from 1 to 54 minutes in a neutron fluence rate of 1.84 x 1012 n/ cu m-sec. The neutron spectrum was abundant in thermal neutrons, having a Cd ratio of approximately 10. Treated urine samples were also analyzed by the NAA instrumental method. Analysis of untreated urine samples was not possible due to the high background

Jan 1, 1981

By Neil E. Izatt, M. Andre de Ruijter, Ronald L. Bruening, Wesley Young

IBC Advanced Technologies, Inc. has developed ligands, ?amed SuperLig®, which have specific applications in the gold mdustry. These ligands use molecular recognition technology (MRT). One ligand has been developed to selectively recover gold and silver from tailings solutions and from pregnant Merrill-Crowe solutions. Another ligand removes free cyanide, _ th10cyanate, other cyanide species, as well as copper and other base metal cyanide complexes from leached gold-ore solutions. The development of these "species selective'' SuperLig® prod­ucts allows for the more efficient operation of gold recovery processes and opens up the possibility of the economic devel­opment of high-copper gold ores. The resulting gold eluate is a high grade and a high purity stream which will simplify the need for further refming. Engineered systems based on MRT consist of a few unit operations utilizing standard equipment and mate­rials of construction. The process is simple to operate, thereby lending itself to automated modular design, which is both eco­nomic to manufacture and to operate. Test results for the gold and cyanide-copper systems are presented in order to demonstrate the high selectivity and effi­ciency of MRT technology in recovering these species from solution. . IBC Advanced Technologies, Inc. (IBC) and Fluor Daniel, Inc. formed a strategic alliance in late 1994. The goal of the alliance is to combine IBC's scientific expertise in the MRT field with Fluor Daniel's engineering capabilities in the metal­lurgical industry. IBC has its headquarters in American Fork, Utah, USA, where research, development and manufacturing are conducted. Fluor Daniel is an international engineering and construction firm with head offices in Irvine, California, USA. Engineering efforts for the alliance are centered in the Fluor Daniel Mining and Metals Operating Company office in Vancouver, B.C., Canada.

Jan 1, 1996

By Ronald J. Searle, Howard S. Latham

In April 1964 the Bureau of Reclamation awarded the first contract for rapid machine excavation of a water conveyance tunnel . Since then the Bureau has excavated seven tunnels with a total length of over 190,000 feet utilizing rapid excavation tunneling machines. Tunnel bored diameters have varied from 9' 0" to 20' 10" (See Table #1) and tunnel lengths from 5,000 feet to 67,000 feet. Driver and cutter units varied from 43 rolling teeth and eight rolling discs mounted on a rotating head driven by five 200 HP 23,000 volt electric motors to 20 discs and one tricone unit mounted on a rotating head driven by two 100 HP 440 volt motors. All tunnels were driven with a laser beam guidance system governing both line and grade. Trailing conveyors and rail haulage systems were used to dispose of the excavated material. Approved Bureau of Mines diesel locomotive engines for waste trains were prevalent power sources supplemented by battery units on some projects. Sandstone, conglomerates, agglomerates, siltstone, shale, and granite were the geological formations encountered, with sandstone and shale the preponderant material . Tunnel support systems utilized were structural steel ribs; rock bolts and metal plates; and shotcrete, or combinations of these. Progress varied from 51-1/2 feet to 154 feet per working day for three shifts, depending on rock material and supports required. One contractor established a record rate of advance of over 400 feet in one day, 1,905 feet in one week, and 6,848 feet in one month. Such diversified experience in underground machine excavation methods presented an excellent opportunity to observe, analyze, and evaluate associated environmental health problems. Also, to develop measures for controlling

Jan 1, 1997

By Sheldon P. Wimpfen

Man is a short time resident of the planet Earth. He does not have the memory to fully comprehend just what is going on. His span of knowledge can be related to the life of the world to see that this is the case. A museum at Grand Canyon features a geologic clock that compresses Earth's age of 4.5 billion years into 24 hours. Man's estimation of the earth's age has changed radically in the past half century. In 1930, one prominent geologist asserted that the age of the Earth was ". . . at least 600 million years." Later, physicists used radioactive clocks to conclude that the Earth's age was 1.6 billion years. More recently, geologists have found rocks in northwestern Australia estimated to have formed 4.5 billion years ago. As we learn more about what is underfoot, the estimate of Earth's age might change again. The Grand Canyon's 24 hour clock shows that the dinosaurs were the dominant life form for 165 million years. Then an event occurred that wiped them out about 65 million years ago. The prevailing theory is that an asteroid struck the Earth and generated enough dust to wipe out the vegetation upon which most dinosaurs fed. During Earth's existence, there have been at least 12 such mass extinctions - the worldwide disappearance of diverse animal groups. On a planet that has been around for 4.5 billion years and that may continue to exist for another 4.5 billion, it seems reasonable to expect that further mass extinction's will occur. According the Grand Canyon's 24hour clock, the 165 million year reign of the dinosaurs amounted to about five minutes. On that 24 hour clock, the world has been dinosaur free for almost two minutes.

Jan 1, 1993

By Edwin J. Connell, O&apos

Investment in mining and related process facilities will be more costly and complex in the 1980s than ever before. Interest rates and inflation are soaring; regulations are expanding; and in order to achieve economies of scale, plant facilities and mines are getting larger. As the pace quickens, the time/cost circuit closes around the resource owner or developer. Larger modern projects cost more money and take more time to build. The longer it takes to bring a project onstream, the more it costs in interest, escalation, and lost production. One solution to the time/cost squeeze is to take advantage of systems developed by major contractors serving the mining industry. These contractors have been serving clients in planning and executing large and small projects for many years. They have developed systems which, if applied at an early point in the project's life, can be a significant benefit in development of mineral resources. The systems involve performance of feasibility studies, economic evaluations, and the project installation itself. First the Feasibility Study Feasibility studies can minimize risk through systematic evaluations while progressing toward the ultimate objective-an operating plant. Normally, studies are initiated with a minimum amount of specific information and a maximum number of as¬sumptions. Through the course of the study program, assumptions are continuously confirmed, refined, or rejected by facts until a sound basis for decision is available. High on the list of cost effective tools for evaluation is the use of a geostatistically derived sampling program that provides a highly accurate ore reserve estimate for economic evaluation. When a predetermined sample of data from the drilling program and bench-scale or pilot-plant tests are received, a detailed feasibility study may be started. This study can involve design of the mine,

Jan 10, 1980

By Eugene A. Lang, William R. Archibald

Early in 1972, Rocky Mountain Energy Company approached MARCONAFLO with a unique request for assistance. They controlled a series of scattered ore deposits in a remote section of Wyoming which had become increasingly valuable despite their relatively small size, great depth and low grade. At the time, MARCONAFLO was in the process of developing a tailings reclaim system which was based on the use of submersible capsules. It appeared that this basic concept might be adapted to slurry uranium ores and pump them to the surface through a bored hole. This presentation will review for you the development of this unique and potentially very important application of MARCONAFLO technology. This first slide (SLIDE 1) depicts the total mining concept envisioned by MARCONAFLO and Rocky Mountain Energy Company. A series of six self-contained mining units would be positioned through boreholes into the ore strata. An oscillating MARCONAJET would direct a high pressure jet stream into the orebody and put it into a slurry which would flow back to a slurry pump. The slurry would then be pumped to the surface and to a collection tank from which it would be transferred to processing. Both the MARCONAJET and the slurry pump would be actuated and controlled by means of a hydraulic power console mounted on the trailer behind the service tower. By means of a high pressure water pump also mounted on the trailer, return water from processing would be delivered to the MARCONAJET to slurry the ore. Tailings would be returned to a backfill unit for redepositing in the mined-out cavities. A drill rig would precede the mining, and it was estimated that this configuration would represent an optimum system for most effective equipment utilization.

Jan 1, 1976

By O. Ozcan, J. D. Miller, Z. S. Nickolov

The production of soda ash from trona (sodium sesquicarbonate, Na2CO3•NaHCO3•2H2O) resources has completely displaced the production of synthetic soda ash in the USA. Further, the utilization of other trona resources is under consideration in China, Turkey, etc. Recent research has been concerned with the development of flotation technology for the trona industry. In this regard studies on the flotation behavior of sodium carbonate salts: trona, sodium carbonate monohydrate and decahydrate, as well as the flotation behavior of sodium bicarbonate, are reported for both cationic (dodecyl ammonium hydrochloride) and anionic (sodium dodecyl sulfate) collectors. It has been found that strong flotation of sodium bicarbonate (NaHCO3) can be achieved with 100% recovery, while the other sodium carbonate salts do not float well. These results have been explained by FTIR analysis of aqueous solutions of Na2CO3and NaHCO3in a range of concentrations from very dilute to saturated conditions. The changes in the shape of the O-H stretching band of water are correlated with the flotation behavior of Na2CO3salts and NaHCO3. In addition, the absorption band of the carbonate ion at ca. 1385 cm-1is used to monitor its interactions with water and/or other ions in solution. The infrared results demonstrate thatNa2CO3acts as a water structure maker, leading to an extensively hydrated surface that accounts for the poor flotation of most sodium carbonate salts. In contrast, NaHCO3does not have this characteristic and consequently complete flotation is possible with both cationic and anionic collectors. These results support the previous water structure analysis for soluble salt flotation of alkali halides and other oxyanion salts.

Jan 1, 2003

By John A. Lombardi

The solutions used in the heap biooxidative treatment of sulfidic refractory Au ores and concentrates generally load free mineral acid and metals and, in time, become bacteria activity inhibiting due to increased acid and/or metals concentrations. The metals­acid loaded, bacteria action inhibiting, solution must then be: (a) processed, prior to re-use, to reduce its metals and/or free acid mineral acid components to bacteria activity compatible levels; or (b) neutralized prior to discharge. The most common solution processing method to adjust acid-metals contents is liming to effect the precipitation of dissolved metals and neutralization of acid sufficient for solution discharge or re-use. The lime treated solution is high in suspended, colloidal precipitates and requires clarification before reuse. Most often the "bleedstream" of biooxidation solution that is lime treated is discharged and req­uisite volumes of fresh water added to the process inventory. Depending on the level of bacterial action in a heap and the acid consumption characteristics of the ore/concentrate being biooxi­dized, the bleedstream taken from the circulating, irrigation on­off, solution, can be large (e.g., 10%-20% and sometimes as much as 50% of the daily solution flow requires treatment-dis­charge). The lime charge for bleedstream treatment is commen­surately large and represents a major operating cost of the bioox­idation process. The patented HW Process Technologies (HWPT) Engineered Membrane Separation (EMS™) method is an alternative biooxi­dation bleedstream treatment method. EMS™ processing removes the multivalent base metals ions in an acid solution to a small volume EMS™ "concentrate" (typically 25% of the feed­stream volume). The EMS™ method coincidentally makes a "clean acid" EMS™ "permeate" (typically 75% of the feed­stream volume). In general, EMSTM processing enables 75% of the bleedstream volume to be recycled; allows up to 2/3 of the bleedstream acid to be recovered as a 10% solution; and delivers dissolved metals in a highly concentrated stream suited to a. metals recovery or b. reduced cost lime neutralization for a given metals precip­itation relative to full bleedstream neutralization (typically a 30% lime use savings). Implicit in the recovery of process water for re-use and reduced reagent addition requirement for metals precipitation is a significant reduction in wastewater-sludge dis­posal facility size.

Jan 1, 1998

By Raja V. Ramani

The importance of adequate mine ventilation for good health and safety conditions has been recognized since miners first ventured underground. All over the world, governmental actions on mine health and safety are directly connected with mine atmospheric environments, their assessment and control. These governmental actions have been, and continue to be, motivated by the repeated experience that potential threats from inadequate control can evolve, either suddenly or in the long-term, into unpleasant reality, with catastrophic health and safety consequences. These governmental actions are also an indication of the remarkable professional progress being made in the field of mine ventilation. Surely, no developed country allows underground mines to operate without strong measures for the control of ventilation under legislation specific to the mining industry. In the United States, the federal government's responsibility for mine safety has evolved over the years through a series of legislative actions beginning in 1865 and continuing through 1910, 1941, 1947 and 1952. The passage of the Federal Metal and Nonmetallic Mine Safety Act of 1966 (the 1966 Metal Act), the Federal Coal Mine Health and Safety Act of 1969 (the 1969 Coal Act) and the Federal Mine Safety and Health Amendments Act of 1977 (the 1977 Mine Act) are the most important milestones in this long legislative history. The 1977 Mine Act adopted many of the stronger features of the Occupational Health and Safety Act of 1970, perhaps the most significant piece of legislation on workers' occupational health and safety in US history. It is worthwhile to ask, "How far has the United States come in mine ventilation since the enactment of the 1969 Coal Mine Health and Safety Act?" This Act and its associated regulations defined in great specificity many standards for healthful and safe operation of a mine and, in some cases, what constitutes good ventilation practice. Since 1969, the frequency and severity of disaster-type events in US coal mines has decreased markedly. A primary reason for this achievement is the strength of the Coal Mine Health and Safety Act's regulatory features in such areas as methane concentration control, dust control, intrinsic safety and explosion-proof enclosures, minimum air quantity and quality standards and air distribution and escapeway provisions. These requirements greatly influenced mine ventilation planning, engineering and practice, leading to increasingly safe working conditions.

Jan 1, 1993

By Pierre Mousset-Jones

I wish to submit this discussion item on an article published in the August issue of MINING ENGINEERING by Wala and Altman on the use of canonical diagrams for mine ventilation networks. The advent of computer graphics and plotting has enabled complex underground mine layouts to be displayed and plotted in a variety of three-dimensional formats that very closely represent the actual mine layout. This enables the ventilation engineer, who is familiar with the mine, to display the network pressures, quantities, resistances, and fan locations in a way that can be understood by everyone working at the mine. This is important if the ventilation engineer needs to discuss changes in ventilation with production personnel, or escapeway procedures with union personnel. While I can see some of the potential advantages in the canonical ventilation network diagram described by Dr. Wala, it appears to me that the fact that the diagram has no visual equivalence with the actual mine layout means that most mine personnel will find such a diagram almost incomprehensible. The authors have alluded to certain advantages with the canonical diagram. However, I find it difficult to see that these outweigh the fact that almost everything listed can be duplicated in isometric diagrams, and in a manner that is easily understandable to everyone in the mine from the miner to the mine manager. Perhaps the authors could show a clear example comparing an isometric with a canonical portrayal of a mine network showing the information that is immediately available from the canonical network that is not obvious in the isometric diagram. There is in this country a severe problem with the need for ventilation engineering and expertise to be used and accepted by mine management as a necessary part of mine planning. It seems to me that to introduce the requirement for further explanation so that management can understand a canonical network display will hinder more than help the recognition that ventilation engineering needs at so many mines in this country. However, I can see that the canonical approach does have its place in assisting the practicing mine ventilation engineer, wherever he or she exists in the organization chart for a typical mine. In this case, could the authors please indicate the availability of the computer program to compute and plot the canonical diagram for a mine ventilation network.

Jan 1, 1990

By Pierre Mousset-Jones

I wish to submit this discussion item on an article published in the August issue of MINING ENGINEERING by Wala and Altman on the use of canonical diagrams for mine ventilation networks. The advent of computer graphics and plotting has enabled complex underground mine layouts to be displayed and plotted in a variety of three-dimensional formats that very closely represent the actual mine layout. This enables the ventilation engineer, who is familiar with the mine, to display the network pressures, quantities, resistances, and fan locations in a way that can be understood by everyone working at the mine. This is important if the ventilation engineer needs to discuss changes in ventilation with production personnel, or escapeway procedures with union personnel. While I can see some of the potential advantages in the canonical ventilation network diagram described by Dr. Wala, it appears to me that the fact that the diagram has no visual equivalence with the actual mine layout means that most mine personnel will find such a diagram almost incomprehensible. The authors have alluded to certain advantages with the canonical diagram. However, I find it difficult to see that these outweigh the fact that almost everything listed can be duplicated in isometric diagrams, and in a manner that is easily understandable to everyone in the mine from the miner to the mine manager. Perhaps the authors could show a clear example comparing an isometric with a canonical portrayal of a mine network showing the information that is immediately available from the canonical network that is not obvious in the isometric diagram. There is in this country a severe problem with the need for ventilation engineering and expertise to be used and accepted by mine management as a necessary part of mine planning. It seems to me that to introduce the requirement for further explanation so that management can understand a canonical network display will hinder more than help the recognition that ventilation engineering needs at so many mines in this country. However, I can see that the canonical approach does have its place in assisting the practicing mine ventilation engineer, wherever he or she exists in the organization chart for a typical mine. In this case, could the authors please indicate the availability of the computer program to compute and plot the canonical diagram for a mine ventilation network.

Jan 1, 1989

By N. S. Tanious

Retrievability of emplaced nuclear waste from the geologic repository is a performance objective imposed by Federal Regulations. This requirement is designed to provide confidence in the Department of Energy's repository design by keeping the option of retrieval open if the engineered or natural systems prove inadequate for containment and long-term isolation of high-level nuclear waste. This paper presents a summary of current Nuclear Regulatory Commission Staff thinking on the design of the repository for retrieval, and level of retrievability demonstration that may be required during site characterization. However, this paper does not represent official U.S. Nuclear Regulatory Commission position on this topic.

Jan 1, 1989

By A. Johnson

When are SMART transmitters the smartest choice? To answer this question requires a closer look at SMART transmitter technology. It is necessary to understand this technology in order to recognize how it can best be utilized to give the greatest value for the application. And, once the decision to buy transmitters has been made, it becomes a question of whose SMART transmitter to buy. For, although the under-lying technology is similar, the differences that exist in how the technology has been implemented can make a dramatic difference in the end result. What prudent users of SMART technology do is to analyze their needs by application before making their buying decision.

Jan 1, 1988

By M. Gordon, J. M. Tranquilla

Microwave power, used in conjunction with properly designed applicators, is an efficient and practical energy source for pre treating a wide range of mineral ores and concentrates. Novel processes which take advantage of the unique properties of rapid microwave excitation present many distinct advantages over other pretreatment methods. These include dramatically reduced costs and elimination of all or most of the toxic by-products. A capital and operating cost analysis is presented of EMR's microwave process for treatment of refractory gold ores and con­centrates based on the company's experience using both small and large scale pilot plants. Comparisons are presented between the microwave process and roasters, autoclaves and bio-oxidation.

Jan 1, 1998

By Leonard Harris

Since the end of the cold war following the collapse of communism, enormous amount of funds are pouring into the developing countries including investments by mining companies for the development of gold and silver mines. A great deal of these funds are destined for expenditure in areas riddled with bandits, terrorists and active and latent criminals bent on stealing the mine operators hard earned production on its way from the mines to markets. Brambles Security Services employs experts in the field of safely transporting gold and silver products under various alternatives and aimed at relieving the mine owners of this responsibility. This paper examines the various service options available.

Jan 1, 1997