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By J. G. Nalven

On July 1, 1999, most domestic metal mines will have to report releases of toxic chemicals into the environment for the first time as required by SARA Title 313. Some of these reportable releases will appear huge in relation to reports by other industries. The reasons for the potentially large reportable releases, special considerations for mining operations, and strategies for dealing with the reports are described. Data composited from experience with several mining companies is presented in the context of a typical gold mine.

Jan 1, 1999

By Frank E. McCall, John K. Marshal, Fred Garcia

Since the advent of longwall mining systems in the United States, mine operators are increasingly relying on methane drainage techniques to supplement the ventilation system. The most commonly used technique is the vertical gob borehole. The number and spacing of vertical gob boreholes per panel is generally based on experience and underground conditions. To design a more efficient methane drainage systems, mine operators must accurately determine methane gas produced. Thus, mine operators must monitor gas flow and methane gas concentration on every vertical gob borehole on active panels at least once or twice during each 8-hr shift. As the mine grows, it is possible to have more than one operating longwall and many vertical gob boreholes. Thus, daily visits to each vertical gob borehole site can become very time consuming. During weekends when methane gas concentrations typically drop because there is no mining activity, borehole sites may not be visited. To obtain accurate gas flow data, a gob borehole monitoring system was designed and constructed by the U.S. Bureau of Mines (USBM). Gas flow, methane gas concentration, gas temperature, barometric pressure, and vacuum pressure of the exhaust fan are the parameters collected by the system. The system also includes circuitry for automatic shutdown of the exhaust fan and an alarm system before an unsafe condition is created. Telemetry components were also integrated into the system to allow for transmission of borehole data to the mine office. As a test, the system was installed and operated on a vertical gob borehole for six months. Test results indicated that intermittent measurements with hand-held instruments from vertical gob boreholes were always higher than gas flows measurements made by the gob gas analyzer system. This paper describes the system components, operational characteristics, and the results of the test program.

Jan 1, 1995

By K. C. Kocsis

Underground ventilation systems, which require electricity to operate the fans and fossil fuel for heating in winter, can account for a significant portion of the energy consumption of mines. Recent studies have shown that the ventilation system in deep and highly mechanized metal mines could be responsible for 40 to 60 percent of their overall energy consumption. Presently, underground ventilation systems are designed for peak air volume requirements, which usually occur well into a future stage of the mines’ operating life. As a result, during their early operating stages, the intake air volume of the mines could be well in excess of their true air volume needs. Such ventilation systems could be considered as uneconomic, and to remain competitive the ventilation design needs to improve while the mines are trying to reduce energy consumption and their carbon footprints. This paper introduces a new mine ventilation design method where an underground base-metal mine’s ventilation system is designed by integrating discrete-event mining process simulation (DES) with mine ventilation modeling techniques. Furthermore, based upon the output data generated by means of discrete-event mining process simulations, the air volume requirement for the operating life of the mine is determined for “traditional” versus “activity-based” ventilation requirements. The output data generated through ventilation simulations are then used to quantify the economic and environmental benefits of an activity-based ventilation delivery system.

Jan 1, 2018

By Chin Wei Yang

Linear programming (LP) has proven to be a most effective mechanism for modeling a vast array of practical problems, while the development of LP applications in engineering have been extensive enough to show its advantages and limitations. In this paper: we focus on the properties of the widely-wed linear programming transportation (LPT) model formulated and developed by Koopmans (1) . There have been many models of this type applied especially in the field of energy economics (2-7). Since most of these applications can be linked to the seminal work of Henderson (8), we stall present our discussions based on his work.

Jan 1, 1980

By Palmer C. Sweet

Mining-related wastes, which are increasing, are being utilized more and more as valuable resources in Virginia. The Environmental Protection Agency (EPA) divides mining-related wastes into two categories: those generated from mineral extraction and beneficiation and those generated from mineral processing. Materials from both categories are produced in Virginia, where waste (by-product) materials are present at a variety of mining sites and processing plants; some of which have been exploited for various uses in the past and/or present. These materials include: used concrete recycled for roadbase material; pyrite coated with magnetite for use in portland cement; minor amounts of fly ash for use in concrete block, lightweight aggregate, and flowable structural fills; granite and diabase quarry fines for use as agricultural and asphalt filler; lime kiln dust for use in neutralizing and stabilizing coal refuse; soapstone aggregate for use in terrazzo heat retention panels; kaolin for use as a filler product and as an ingredient in white cement; slate quarry fines used as landcover and combined with aggregate for crusher run and as a filler in asphalt; and coal refuse for use as fuel in a lightweight aggregate plant. There are some materials available that have never been utilized, although several ideas were investigated to turn them into usable commodities. One such material is a high-alumina scrap produced as a by-product at a ferrovanadium processing plant. However, large quantities of waste materials from metal mining, industrial mineral, and fossil fuel operations remain to be disposed of in an environmentally safe and economic manner. In 1989, almost one million tons of fly ash were produced from burning of coal at eight coal-fired power plants in Virginia. Present uses for this waste such as an ingredient in concrete block, concrete aggregate, and in structural fills cannot dispose of all the available material; however, increased use of fly ash as a soil/rock substitute for structural fills and embankments may solve the problem of its disposal. Another waste material is calcium carbonate precipitate paste produced at a lithium carbonate processing plant and presently being used for back filling an on-site inactive underground limestone mine. Flue gas desulfurization (FGD) wastes in the form of CaS04 will probably increase threefold. If this material contains a minimum of 95 percent gypsum and negligible chloride, it may have a value to a wallboard manufacturer as we move toward the year 2000. Thought must be given how this increasing waste can be disposed of in an environmentally safe manner.

Jan 1, 1995

By H. D. Sharma

INTRODUCTION Uranium mill tailings, by-products from the mining and milling of uranium oxide contain all decay products of uranium-238, uranium-235 and all the Th-232. The ore containing all daughter products of the parents U-238, U-235 and Th-232 is ground to approximately 50% under 200 mesh particle size and after extraction of uranium, the residue, described as tailings, is discharged into natural depressions confined by dams. These deposition sites are referred to as tailings ponds. Tailings ponds are located in two mining districts, Bancroft and Elliot Lake in the Province of Ontario, Canada. Some parts of tailings ponds are dry up to a depth of several meters, whereas other parts have a water table very close to the surface and still others are covered with water. The extent to which the daughters of uranium isotopes are in equilibrium with the parents U-238 and U-235 is dependent on the age of the deposit in which uranium occurs and the extent to which the decay products are removed by geochemical processes. In the mining district of Bancroft, the deposit is known to be approximately 1 billion years old, whereas in Elliot Lake, the deposit is considered to be approximately 2 billion years old. The ratio of radiogenic lead isotopes Pb-206 and Pb-207, can provide some estimates concerning the age of the deposits. If the tailings are not affected by geochemical processes, the tailings would contain all the daughters of the 4n+2 and 4n+3 series in equilibrium concentrations. The equilibrium activities of some members of the 4n+2 series are calculated in Table 1. [ ] The amount of radiogenic stable lead isotopes depends on the age of the ore deposits. If the deposit in each district is of the same age, a definite relationship is expected with respect to the activity of Pb-210 and the radiogenic stable isotopes. Approximately 33 million tons of the tailings have been deposited in the early 1960's, approximately 20 years ago. During this period of storage, the segregation of uranium daughters, like radium, the diffusion of gaseous product, Rn-222, and removal of precursors by geochemical processes, can cause dis-equilibrium. Earlier work concerned with the uptake of Ra-226 and Pb-210 by plants (Kalin and Sharma, 1981), indicated that the concentrations of Pb-210,in samples of the tailings taken, were lower than the expected equilibrium. The diffusion of radon from a variety of matrices has been studied (Tanner, 1964). It has been shown that the diffusion coefficient is dependent on the particle size in which its precursor is present, the moisture content and the surface conditions. The direct measurement of radon concentrations in the environment near the ponds is dependent on the metereological conditions. Kramer, Schroeder and Evans, 1964, have examined the variations in the concentration of radon near the ground level with respect to atmospheric variables, such as changes in barometric pressure, precipitation, wind velocities, thermal atmospheric instability. It is difficult to relate the total release of radon from the ponds to the atmosphere over an extended period. Our measurements of Pb-210 and total lead on tailings samples taken from 16 sites indicate that the ratios of the activity of Pb-210 to the mass of total lead can provide parameters which are helpful in the estimation of the total amount of radon and its decay products diffusing from the tailings ponds. In this paper, we present the results of measurements of activities of Ra-226, Pb-210 and total lead in samples from various ponds situated in both mining districts. The measurements were confined to samples taken at 0-25 cm depth from the surface.

Jan 1, 1981

By William Gleason

During the 116th National Western Mining Conference and Exhibition in Denver, CO, the host city was often referred to as world?s mining capital, so it was fitting that the conference looked at the mining industry through a global lens. In the current world economy, the mining industry must keep a sharp focus on such things as commodity prices and global supply and demand as well as local issues that can have a dramatic impact on a mine?s social license to operate. In short, companies should mine locally but think globally. During the three-day conference at the Colorado Convention Center, a range of global and local issues that effect the industry were discussed. A record 1,144 people attended the conference.

By D. McCarthy

This paper discusses the process involved in developing an optimum method of treating and removing heavy metals from water that have leached out from the native rock -prior to discharge back into the environment. Also designed into the system is a manner to stabilize the metals removed as a precipitate, so that they can be disposed of as a non-hazardous waste.

Jan 1, 1992

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. D. Wunderlich

Providing a safe & secure environment for your employees and other company assets is absolutely necessary in our litigeous society. Security hardware is no different than computers or other technical equipment, in that new equipment is developed each year that makes older equipment obsolete. This presentation will help to explain how your existing security system and security procedures can be updated to meet industry standards without the expenditure of a great deal of money. If you are concerned about potential security problems and how to address these problems, this presentation is a must.

Jan 1, 1995

By Steven Keim, Steven Stansfield, Kevin Andrews

Geotechnical, geological, and hydrogeological fieldwork and data collection for the mining industry is often conducted by younger, less-experienced staff members. In many cases, fieldwork personnel are recent college graduates or are otherwise relatively new to the mining industry. Due to busy schedules, staffing shortages, project budgets, and in some cases, poor management, new fieldwork hires often do not receive thorough training. In the past and the present, many workers in the mining industry learn(ed) by “doing.” While this is still considered to be the most practical approach and the easiest way for a company to determine the skill set of an employee, there is always some risk involved in the “feet to the fire” method. The reality is that field personnel are often collecting data on which major operational decisions will be made or on which regulators will base enforcement decisions. Inadequately trained or inexperienced field personnel may collect inaccurate data or fail to recognize key conditions that may influence decisions made by regulators, design engineers, mine managers, and corporate leaders. Even the best engineers may come to incorrect conclusions if they are starting with poor input data. Decisions based on inaccurate data often result in delays, budget issues, unsafe conditions, or even worse consequences. This paper provides numerous mining industry examples of incidences where inaccurately collected field information did, or could have, resulted in major adverse consequences. The paper also offers some simple approaches to minimizing the potential for such problems.

Jul 1, 2023

By S. L. Bessinger

Introduction In the design and specification of a ventilation system for an underground mine, it is necessary to make reasonably accurate estimates of the pressure losses in the various airways of the mine. These estimates can be made with little difficulty for open airways with simple geometric cross-sections, such as those cut by continuous miners or tunnel-boring machines. The situation is much different on a longwall face, where the airway's complex geometric cross section and the presence in the airway of obstructing equipment having a variety of shapes make it difficult, if not impossible, to estimate pressure loss using traditional methods of calculation. Head losses in mine entries are calculated using Atkinson's Equation. [22H= KPLQ (English) H= KP 3Q (SO (1) 5.2AA] where H = pressure loss, in. of H2O (Pa); K = friction factor, lbf•min2/ft4 (kg/m3); P = perimeter, ft (m); L = airway length, ft (m); Q = airflow quantity, ft3/min (m3/sec); and A = flow cross-sectional area, ft2 (m2) In this equation, the friction factor, K, is an empirical constant that describes the aerodynamic roughness of the airway. Typically, the K-factor for a given airway is determined by measuring the factors H, P, L, Q and A in Equation (1) and calculating K. Tables of friction factors calculated in this way are found in textbooks and handbooks that deal with mine ventilation analysis. Unfortunately, very few K-factors have been measured on longwall faces, and the accuracies of those that have been measured are entirely site specific, because of the wide variety of equipment found on longwalls. The development of a technique for prediction without mine-site measurements of the friction factor for any longwall face, regardless of its configuration, will thus be very useful in the design of ventilation systems for mines in which longwall mining is practiced. Calculation of pressure losses using Atkinson's Equation (1) and empirically determined K-factors provides accurate and useful approximations in cases where the airways have relatively simple cross sections. However, a careful analysis using the principles of fluid mechanics shows that such calculations are based on two assumptions that are not strictly correct when there are obstructions in the airway. The first assumption is that the air velocity distribution in the cross section, particularly around the perimeter, is uniform. This assumption results from the fact that the tabulated K-factor values found in the literature are based on field measurements with uniform conditions. Such uniformity does not exist in longwall airflows. The second common assumption is that the K-factor, and corresponding head loss, is independent of the Reynolds Number (NR) for a given flow. In fact, this assumption is not strictly correct, and is particularly erroneous in the case of irregular protuberances into the airflow, such as those found on a longwall face. The errors arising from the assumptions may be avoided by using K-factors calculated by a newly devised method, described below, which takes into account the fundamental principles of aerodynamic drag analysis. This new technique has two advantages: first, it is flexible enough to model any longwall, regardless of equipment configuration; second, it employs terminology and equations familiar to those who perform mine ventilation analysis, using K-factors, for which ventilation engineers have an intuitive understanding, rather than drag coefficients. To provide guidance for development of a longwall drag model, data were taken on two modern longwalls operating in substantially different conditions. Pressure measurements at Mine B were made with 200-foot (61-m) sections of 1/8-in. (3-mm) diameter plastic tubing, attached to a Dwyer Magnehelic gauge. Pressure drops were measured in 200-foot increments down the face, and summed to give the drop for the entire face length. This technique was found to produce small, repeated errors because of the number of segments required to span the longwall. At Mine A this problem was avoided by using a single, continuous, plastic tube for the entire face length. The psychrometric properties of the air were measured for both Mines A and B. A calibrated, standard vane-anemometer was used to measure the airflow on both faces. Finally, numerous dimensions were measured on both faces, and face profile drawings were obtained to allow detailed evaluation of the face equipment geometry. From this information, accurate evaluations of the average wetted perimeter and average area of the longwall face airways were made. Since the airflow is not confined to inside the powered supports at all points along the face, a quadratically weighted average of the airflows measured at various stations along the face was calculated: [n2Qavg =Qi Ii / It(2)i=1] where [Q, avg = average airflow for analytical purposes, ft3/min (m3/sec); Q= airflow at station i, ft3/min (m3/sec); 1= length of segment represented by Q, ft (m); h= length of longwall face, ft (m): and n= number of quantity measurement stations.] The quadratic weighting scheme was chosen because the

Jan 1, 1992

By C. T. Holland

Coal mining has been an important industry in the Appalachian area for many years. This is particularly true in the northern part of the area, namely, in Pennsylvania, West Virginia, and Ohio. Also, in the south a great deal of mining activity has been carried on in Alabama, Kentucky, and southwest Virginia. Some of the by-products of this activity has been the production of mineralized water from the mines in copious quantitites. The southern Appalachians have been somewhat more fortunate in that the water there has had a considerable amount of alkalinity in it, which has to a large extent eliminated some of the more undesirable aspects of mine drainage. Northern Appalachia, including central and western Pennsylvania, the Monongahela basin in West Virginia, and the Appalachian area in eastern Ohio have not been so fortunate in that coals in those areas and the top and bottom rock have, in many cases, shown considerable quantities of pyrite, and the water does not carry the carbonates found farther south.

Jan 1, 1969

By John C. Bowling

Many recent mine developments in North America are located in remote northern regions with extreme winter temperatures in the range of -20oF to -60°F. In addition, many locations are subject to very heavy snowfall. This paper discusses some of the key considerations in the planning and design of mine plant buildings, particularly concentrators, located in these regions. SUMMARY & CONCLUSIONS The subject is considered under three main headings: I. Building Out line and Structural Frame 2. Wall and Roof Materials 3. Foundations The plan outline of a mine plant building will naturally be governed by the scope and layout of the process equipment it contains. The selection of roof profile, on the other hand, will generally depend upon a number of factors extraneous to the process e.g. snow conditions. When these factors are considered for concentrators in cold locations, a flat or stepped roof will usually be more economical and suitable than a sloping roof. The materials normally used for the structural framework of concentrators are the same as used for other industrial buildings, namely steel, concrete and wood. Structural steel, however, is the most commonly used material for concentrators in

Jan 1, 1971

By W. R. Bruce, R. W. Wittkopp, R. L. Parratt

Introduction The Relief Canyon gold deposit is about 24 km (15 miles) east of Lovelock at the south end of the Humboldt Range in northwestern Nevada. The deposit, is in the Relief-Antelope Springs mining district, which has historically produced silver, antimony, and mercury. There is, however, no mention in the literature of commercial gold production. Fluorite prospects at the gold deposit site have had no reported production. At Relief Canyon, the Late Triassic Grass Valley formation overlies and is in fault contact with the Late Triassic Natchez Pass formation. Epithermal disseminated gold mineralization is found within the various types of fault breccia between these two formations. Geology The Natchez Pass formation of Late Middle to Late Triassic age is composed of more than 300 m (985 ft) of massive gray to dark gray locally carbonaceous dolomitic limestone. Some minor beds of shale and siltstone up to 1 m (3 ft) thick are found in the project area. The limestone is locally silty or sandy. The color of this formation below the oxidation base ranges from gray to black and appears to be a function of carbon content. The Grass Valley formation of Late Triassic age is composed of more than 200 m (655 ft) of interbedded units of thinly parted argillite, hard gray to brown quartzite, siltstone, and shale. Within the oxidation zone, these units are olive gray. A few beds within this formation are slightly calcareous and a number of sections, especially those containing shale, are dolomitic. Below the oxidation zone, the quartzite beds are often slightly carbonaceous and the argillite, siltstone, and shale beds are often highly carbonaceous, giving them a black color. Two types of intrusive rocks have been recognized at the Relief Canyon deposit. Both appear to predate mineralization. Fine to moderately fine grained quartz monzonite dikes, up to 3 m (10 ft) thick, were encountered in several drill holes. In a number of intervals, these dikes have undergone either propylitic or argillic alteration. The age of these types of dikes is not known. It appears, however, that they are either Jurassic or Cretaceous. No gold mineralization has been found in this type of dike. Diabase dikes were also encountered in a number of drill holes. These dikes have almost always been propylitically altered. Although the exact age of the diabase dikes is not known, they are probably equivalent in age to the quartz monzonite dikes. Quaternary alluvium is found forming fans at the base of steep slopes and as recent fill in present day drainages. The alluvium is composed of either Natchez Pass limestone or Grass Valley quartzite and siltstone, depending on which unit served as the bedrock source. A significant portion of the Relief Canyon deposit is covered by Quaternary alluvium. Figure 1 shows a generalized geologic map of the Relief Canyon area. At the deposit's site, the Grass Valley formation appears to have been thrust over the Natchez Pass formation. The age of the thrust is probably correlatable with the Nevadan Orogeny, which gives it a Jurassic-Cretaceous age. The general strike of the thrust, referred to as the Relief Fault, is in a northwest direction. The strike of the bedding of both the Natchez Pass and Grass Valley formations roughly parallel the strike of the Relief Fault. The general dip of both the Natchez Pass and Grass Valley formations is in a southwest direction. The general dip of the Relief Fault, in the area of the Relief Canyon gold deposit, varies and has the appearance of a northeast-southeast striking anticline that plunges in a southwest direction. A small fold perpendicular to the plunge of this anticline forms a dome over the southerly portion of the Relief Canyon deposit. A number of northeast and northwest trending normal faults slightly offset the Relief Fault. Because of their small displacement, they are not shown on the generalized map. Gold Mineralization Gold mineralization occurs along the highly brecciated fault contact between the Natchez Pass and Grass Valley formations. Weak gold mineralization often occurs up to 2 m (6.5 ft) above the thrust in the Grass Valley formation. Most of the ore grade mineralization, however, is present below the Grass

Jan 11, 1984

By Anita Wu

"GENERAL BACKGROUND/CONTEXT The £300 million Bond Street Station Upgrade project will provide essential congestion relief and step-free access to an important interchange and destination station in the heart of the London Underground network. In 2010 London Underground (LU) let a design & build contract to Costain Laing O’Rourke (CoLOR), with the works to be completed in early 2017. CoLOR’s lead designer is Halcrow-Atkins JV (HAT). The station upgrade works comprise the following principal elements: •,A new satellite ticket hall on the North side of Oxford Street •,Two additional escalators and stairs providing congestion relief to the Jubilee line platforms •,Four lift shafts to provide step-free access between the different levels of the station •,Additional stairs to Central line platform level •,Tunnelled connection to the Crossrail station immediately to the south •,Connecting passageways, including ten connections to existing station tunnels. To achieve this, an existing property at 354-358 Oxford Street has been purchased and demolished, and the basement deepened to make provision for the new ticket hall. From this basement two circular shafts have been sunk, providing construction access for the tunnelled passages and lift and escalator shafts. The tunneling is principally in the London Clay stratum, which is widely recognized as a favorable tunneling medium, although the deepest parts of the works extend into the Lambeth Group strata which consist principally of stiff clays at this level but also contain water-bearing sands. The majority of tunneling has been carried out using mechanical excavation and sprayed concrete linings but other techniques have been used in areas where SCL is not practicable.A key challenge for design and construction of the works has been spatial constraint, in particular due to: •,The existing underground station layout •,The Limits of Deviation for the works •,The small construction site at 354-358 Oxford Street •,Overlaying Third Party assets including Listed buildings, sewers and water mains."

Jan 1, 2016

By Karl Ingmarsson

Larger mines spend millions of dollars annually on rock drilling tools, but often purchase based on historic consumption. The results vary from excess inventory to acute tools shortages. These lead to emergency sourcing, sometimes mixing products that don’t perform optimally. Boart Longyear analyzed the usage pattern of 96 thousand drill bits at thirteen different underground mining contracts, showing very high variability. The monthly standard deviation on a product level was 42%, with the highest for development and low volume bits. A new rule of thumb is suggested to carry only one month of safety stock for high volume bits, but increase to three months for low volume bits. This balance will reduce the risk of outages with less inventory. The accuracy can be improved by considering the specific conditions at each mine and reclassifying individual bits for a different safety stock level. Root cause analysis and collaborative forecasting between mines and suppliers can lead to further optimization of availability and inventory levels.

Feb 1, 2024

By P. H. Lu, M. J. DeMarco, J. R. Koehler

Beginning in late 1985 and continuing through 1987, US Bureau of Mines personnel investigated longwall chain pillar and entry design in two and three-entry gateroad systems at a deep underground coal mine in central Utah. To evaluate their respective stability characteristics, four chain pillars and two longwall panels within the two separate entry systems were instrumented with Bureau hydraulic borehole pressure cells to continuously monitor vertical and horizontal pillar and panel stresses through adjacent panel retreat. In addition, supplemental entry closure information was obtained from sites located in the vicinity of the instrumented pillars. The findings presented in this report demonstrate the practicality of evaluating mine pillar stability using in situ methods and support three significant conclusions regarding ground control aspects of the investigated two-entry system: (1) Total areal entry loading was considerably less for the two-entry system, as opposed to the three-entry system, (2) a smaller percentage of opened ground in the two-entry system contributed to a marked reduction in rooffalls, and (3) lower areal loading in the two-entry system suggests improved ground conditions when mining the underlying seam.

Jan 1, 1987

By Paul C. Lingo

The title of my talk today might lead you to two logical conclusions: The industry is faced with a problem that requires a solution and after discussing the problem I will offer a solution. The first conclusion is painfully accurate. One need only look at the accident statistics to be aware of the problem. During the eight-year period 1954 through 1962, the United States Bureau of Mines reports that falls of rock and coal accounted for 1,435 of the 2,516 fatal injuries that occurred in underground bituminous coal mines. Some improvement was made during 1962. For the first time since records have been kept, falls of rock and coal accounted for less than 50 per cent of the underground fatal injuries. The 105 deaths recorded in 1962 indicate that a great amount of work remains to be done in this area. As to the second conclusion, let me assure you at the outset that I have no panacean solution; however, I do propose to discuss some aspects of the problem and some possible methods of solution. What methods of solution are now, or have been employed in attempting to solve the problem? More specifically, what methods have you and your associates used? Has it been an orderly well thought out approach to the entire problem, or has it been a somewhat piecemeal approach which tackled the immediate problem and left the total problem for another day? Perhaps a new approach may be in order.

Jan 1, 1964

By D. R. Spears, D. A. Stanley

The US Bureau of Mines investigated the fundamental aspects of shear-flocculation using a rapid, in-situ particle size analyzer. Silica was stirred in the presence of an aliphatic amine to determine the effects of collector coverage, stirring speed and solids concentration on the kinetics of shear-flocculation. The results showed that shear flocculation is a two-stage process. In the first stage, which occurs during the first 1-2 min. of the reaction, the mean particle size increases rapidly, and in the second stage, an equilibrium is set up between the rates of floc growth and floc decay. Collector dosage affected the position of the equilibrium by altering the number of surface sites for particle-particle attachment. A minimum stirring speed was necessary for shear flocculation, which was dependent on solids concentration and collector dosage. This stirring speed was the minimum necessary for particles to overcome the electrostatic energy barrier, and that results in keeping the conditioned particles dispersed. Larger particles flocculated more rapidly. At very high stirring speeds, large flocs became unstable, resulting in a narrowed particle size distribution in the slurry.

Jan 1, 1995