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By F. B. Micheli

Introduction and Historical Background Although both sluices and devices using a simple flowing film are among the oldest known methods of concentration, they are still extensively employed in a variety of situations where they are not only efficient but also have a low operating cost. More particularly, they are valuable for making a bulk concentrate of high specific gravity minerals from alluvials and beach sand and in upgrading low value ores. The antiquity of some of the basic concepts can be seen in the fact that they are found in Agricola's De Re Metallica which was published at Basic in 1546, while in 1602, Carew114 gave a fairly clear account of tin ore dressing in Cornwall in which grass turves were used to catch the cassiterite. This is perhaps one of the forerun¬ners of the blanket strake. The planilla of Mexico, the lanchute of Malaysia and the old Cornish box huddle are also descended from these early strakes. In fact, a sluice with holes in the bottom for concentrate discharge was shown by Agricola, not unlike the principle used in the plane table and the lamflo sluice. The convex huddle for the treatment of sandy material appeared about 1848 and the concave form eight to ten years later. For the treatment of "slime" sizes, wooden dead frames which were manually worked were used in Cornwall for many years but gave way to the automatic water-operated type in 1860, and even a mechanically tilted frame was described by Henderson115 in 1857. Theoretical Considerations The behavior of solid particles in suspension depends to a great extent upon the pulp density and the size of the suspended particles. In a fairly dilute suspension, such as that normally used when dealing with small particle sizes, the behavior of particles in a flowing film results from two effects. These are the lateral displacement, which is determined by the time taken for each particle to penetrate the flowing film and reach the solid surface, and the resistance offered by each particle to further displacement after it has reached this surface. The initial penetration through the flowing film depends on the size and specific gravity of the particle and the thickness and viscosity of the film. As a result the smaller particles will migrate further before their movement is retarded relative to larger particles of the same specific gravity. The behavior on reaching the solid surface de¬pends on whether there is a single particle layer or, as is more often the case, a multiple layer or thin bed of material which is sufficiently dilated, permits the penetration of higher specific gravity grains. Thrust of Flowing Films. When a thin film of liquid flows over a plane solid surface, the layer next to the surface remains at rest but the velocity of the film increases with the distance from the surface and becomes a maximum near, but not quite at, the free surface. Therefore, a particle in suspension in such a film is acted upon by a greater force near the upper part of the film than at the lower part, resulting in an overturning effect. After a particle reaches the separating surface or an accumulated densely packed bed of other particles, the liquid flow causes it to move downstream by rolling, sliding, or by a movement involving alternating suspension and deposi¬tion (saltation). In rolling and sliding, which are brought about by a substantially noneddying stream, the large submerged particles are acted upon to the greatest extent and they move more rapidly than smaller ones, notwithstanding their greater mass. When two particles of the same size but of different specific gravity are considered, the higher density one moves more slowly by reason of its greater mass. As a result the particles tend to become arranged in the manner shown in Fig. 29. If any particle is so large as to stand above the water surface, the transporting force on such a particle, although the maximum available, will have less effect than that on a submerged one. Such large grains are therefore carried a lesser distance. Fluid Velocity in a Flowing Film It can be shown that if y is the distance within the flowing film from the interface, the fluid velocity v' at this point is given by IIn this equation p' is the fluid density, g the acceleration due to gravity, a the viscosity, a the angle made by the film to the horizontal, and 0 the film thickness (in cgs units). Furthermore, the volume Q of fluid per unit time and unit width is related to the film thickness and can be calculated, since which upon integration gives Consideration of the velocity v' (Eq. l) and the terminal falling velocity µ derived from Stokes law enables the horizontal travel dz in time dt to be calculated as follows: Again integration and substitution of Eq. 3 gives In this equation, z is the distance travelled before a particle of density p at the top of the fluid film has settled on the concentrating surface. From these expressions it can be seen that the depth of the flowing film varies as the cube root of the volume of fluid and inversely as the cube root of the sine of the plane surface inclination. Similarly the distance a particle can travel before reaching the surface is directly related to the quantity of fluid and its viscosity. The viscosity of pulp is greatly increased by the presence of near colloidal particles and consequently the penetration of the somewhat larger grains through the flowing film is retarded, resulting in them being carried further across the concentrator deck. Obviously this effect can be reduced by prior removal of some or all of the ultra¬fine particles. The detrimental effect of kaolin on the separation of fine ferrosilicon from quartz has also been demonstrated by Johnston,116 the relationship between viscosity and efficiency of separation being shown in Fig. 30. The pH value also has a very marked influence on the viscosity and the use of acid mine water, for example, can increase viscosity materially and thereby result in lower efficiency. Dilation of Multi-Particle Systems Except during washing (when a single particle layer may exist) concentration usually takes place in a bed of particles which is partially dilated or stirred by eddy currents. The extreme case is seen in various forms of the sluice where the flow of water and the presence of riffles combine to create a fluid bed in which reverse classification takes

Jan 1, 1985

By Joseph E. Worthington

Increases in the price of gold starting about five years ago, and rapid fluctuations since then, have caused a substantial popular interest in the noble metal. Gold prospecting had been at low ebb since the end of World War II in most of the United states except for a flurry of activity in Nevada occasioned by the Carlin and Cortez discoveries. The last five years, however, have seen a great awakening of interest in gold exploration as well as an opportunity for education for many explorationists in the geology and other vagueries of gold deposits. The present writers have participated over the last few years in a search for gold deposits throughout the United States. This search was greatly influenced by the geologic studies of Dr. Wm. Spence at the Haile Gold Mine in South Carolina as reported in a companion paper. Spence's studies resulted in definition of a geologic model that has proven useful in a number of other geologic environments in the united states. These programs were all carried out under the auspices of Cyprus Mines Corporation and permission by Cyprus to present these results is gratefully acknowledged. The writers, however, reserve for themselves all responsibility for the results and conclusions. The exploration program to be described began in the southeastern United States. Spence's studies provided a reasonable basis for interpreting and understanding the geology of the Haile deposit and also provided a means for predicting additional occurrences. This concept was then expanded to other gold occurrences in the Piedmont and became an effective tool for evaluating other prospects. Finally it became evident that the concept could be applied in some western gold districts. The following discussion will then include descriptions of other Piedmont examples and a few western districts that also appear to fit the pattern.

Jan 1, 1978

By E. L. Smith

The development of larger size flotation machines, which started in the 1950's and 19601s, is still proceeding. The largest mechanical flotation machines available today have unit volumes in the range of 38 to 42 m3 (1,350 to 1,500 cft). In fact, the motivating forces of increasing capital and energy costs and decreasing ore grades, which created the need for large flotation cells, not only still exist, but are becoming more critical. This paper reports the development of an improved mechanism for these large flotation machines. The starting point in the development of a new mechanism was the identification of design and performance features of existing machines where improvements were desirable. The result of this work was a mechanism which is an improvement over existing designs. This new design is characterized by an efficient overhung stator and a vortex profile rotor. The overhung design of the stator removes unnecessary and undesirable baffling in the lowest parts of the tank, while maintaining a quiescent froth layer. This results in lower power consumption and better pulp circulation and solids suspension. The vortex profile rotor acts as an efficient pump, with higher pulp recirculation rates as evidenced by the increased air dispersion capabilities, good solids suspension, and low power consumption.

Jan 1, 1982

By F. B. Brost

In 1976, a decision was made by Anamax Mining Company to install an unusual conveying system to transport ore 10.3 km (6.4 mi) from the new Eisenhower Mine to the Twin Buttes concentrator. The system, supplied by Cable Belt Limited of the United Kingdom, represents a radical departure from conventional belt conveyors. The driving tension is applied through two endless wire ropes driven by a single 2 240 kw (3 000 HP) drive while the belt acts only as the ore carrying medium. Full production was begun in January, 1979. Start-up problems hampered production for several months but were resolved by a joint Anamax-Cable Belt effort. The system has been operating at design capacity for 4-1/2 years, and has proven itself as a reliable, low cost ore transportation system.

Jan 1, 1984

By Larry D. Patts

Section 317(e) of the Federal Coal Mine Health & Safety Act of 1969 directed the Secretary of the Interior to prepare standards under which all working places in a mine shall be illuminated by permissible' lighting while persons are working in such places. Section 317(e) further provides that such Working places shall be illuminated within 18 months after such standards are promulgated. In accordance with this section of the Act, there was published in the Federal Register for December 31,1970 a notice of proposed ru1emaking which prescribed the illumination to be provided in the working p1 aces of underground coal mines. In 1ight of written comments, suggestions, and objections to this proposed ru1emaking, the proposed standards were with-drawn and reproposed in the Federal Register for Wednesday, October 27, 1971. In light of further comments, suggestions, and objections, a public hearing was held on April 4, 1974 and standards were again reproposed and published in the Federal Register for April 1, 1976. Promulgation of the final lighting standards took place on October 1, 1976 which means that the underground coal mining industry must comply with face illumination requirements by April 1, 1978. As mentioned previously, the first proposed ru1emaking for illumination of underground coal mines was published in the Federal Register on October 27, 1971. In early 1972, Consolidation Coal Company (Consol) and the United States Bureau of Mines agreed to a cooperative study of underground face illumination; Conso1 felt that expertise in this field would become increasingly important. Conso1's initial efforts in illumination were aimed at investigati.ng practical lighting systems for underground face equipment. We were concerned with installing unobtrusive lights which provided sufficient face illumination for safety, but at the same time were readily maintainable, electrically reliable, and physically sheltered from damage.

Jan 1, 1977

By S. Gopalakrisbn, J. D. Miller, M. Misra

Pilot-scale tests indicate that effective concentration of fine gold from Colorado River sands can be achieved by flotation with the air-sparged hydrocyclone. The fine sands (55% -400 mesh and 0.01 opt*) from gravity concentration were processed with a 5-cm air-sparged hydrocyclone (capacity ~1.0 t/h dry solids). Concentrate grades as high as 5.0 opt were produced in a single stage at a recovery of 75%. The separation efficiency was significantly better than that achieved in conventional batch flotation experiments.

Jan 1, 1987

By R. A. Matuszak

U.S. Government sponsored studies proclaim large reductions in surface mine productivity. Consulting studies place a large share of the blame on increased governmental regulatory activities and on inexperienced, improperly train people. Union rules, which allow indescriminate bidding for job openings, seem to be a major factor causing the lack of experience in spite of elaborate training programs.

Jan 1, 1982

By E. A. Noble

In the Western Coal Region, successful reclamation of surface-mined areas includes the protection of groundwater sources. To accomplish this, a complete understanding of the geohydrology of the affected area is imperative. Successful mine design also calls for careful attention to geohydrology. Because the Western Coal Region is semi-arid land used mainly for farming and grazing, groundwater is a particularly sensitive topic. It is especially sensitive where the lignite scheduled for mining is itself the aquifer supplying the farms and ranches. Such is the case throughout much of the Western Coal Region, particularly where there are no near-surface sand and gravel aquifers that are commonly found in the glaciated portions of the Region. Just as mining can adversely affect groundwater supply, so can groundwater adversely affect mining. Mine flooding and highwall instability are examples of this. But, mine operators must realize that procedures they use to remedy geohydrologically-related mining problems can have a dramatic effect upon ground- water conditions in areas adjacent to the mine. A logical precaution is to require the acquisition of complete baseline data prior to making the first cut. We recommend that the mining plan not only incorporate the reclamation plan, but that they be developed as one plan.

Jan 1, 1976

By Francis X. McCullough

After OSHA published a Notice of Proposed Rulemaking on August 5, 1983, to revise its standards for Underground Construction, many contractors and their representative associations became concerned by the sweeping changes in the proposed rule. After reviewing all of the evidence and testimony on file with OSHA, the contractors presented extensive written and oral testimony to the Department of Labor in Washington, D. C. to help insure that the final published rule would be effective without jeopardizing the economic viability of the industry. The results of those efforts, the entire OSHA rulemaking process, and the opportunity for the construction industry to participate in that process will be discussed.

Jan 1, 1985

By Adam Bezuijen, Tiago Gerheim Souza Dias

"The construction of mechanized tunnels in soft ground has evolved significantly over the last 20 years, especially in the control of the face pressure and the closure of the soil-lining void to reduce the induced settlements. On the other hand, several mechanisms of the TBM excavation cycle are still not taken into account for routine design calculations, such as the increment of water pressures in front of the tunnel face, the flow of excavation fluids around the shield, the dynamic equilibrium between the grout pressures and the excavation convergence, among others. This paper discusses specifically the issue of face pressures and how several mechanisms, which are routinely not considered, can be easily verified and incorporated into the state-of-practice of design. INTRODUCTION The stability of underground excavations is traditionally assessed through analytical solutions based on the lower bound theorem of plasticity (Atkinson and Potts 1977; Mühlhaus 1985) or the limit equilibrium method (Anagnostou and Kovári 1994; Messerli et al. 2010). These methodologies depend on the tunnel geometry, certain ground parameters and the support pressure. When conventional construction methods are used, the internal support pressure is an abstract representation of the combined effects of partial excavation, ground reinforcement, and the different support elements. The use of closed-face tunnel boring machines (TBM) changed this perspective, as the magnitude of pressures acting on the excavation boundary could be controlled in a more direct way. In front of the TBM the ground is excavated as the cutterhead rotates and the cutting tools scrape the ground from the tunnel face while additives are injected to condition the material. Water, polymers, bentonite, and foam can be used as additives under different conditions (Thewes et al. 2012). The loosened ground with additives, herein referred to as the mixture, flows through the openings at the cutterhead and into the excavation chamber. This mixture is kept pressurized to support the face."

Jan 1, 2016

By Michael Gay

Right in the heart of Boston Harbor lies Deer Island, where a ten-year, 6 billion dollar sewage treatment plant is under construction. The 9.5 mile long, 25.5' diameter Effluent Outfall Tunnel is the center piece of this program. A Robbins double-shielded TBM is currently driving this challenging tunnel some 400 feet below sea level. This paper will discuss the set-up and operation of this Tunnel Boring Machine in driving the longest single heading tunnel ever built in North America.

Jan 1, 1993

By Bernard Y. Saltie

The White Pine orebody is characterized by a high lateral stress or highly faulted and joined conditions. Because of these difficult conditions roof support has always been a main concern. Mechanical bolts were widely used in the early seventies; however, it became apparent that major improvements in ground control were required if safe operation at White Pine was to be continued. The first step was taken in 1973-1974 with the testing of resin bolting. Record of caves and roof-falls with either type of support demonstrated superiority of resin bolting versus mechanical bolting - Safety was dramatically improved which was the absolute first consideration; however resin bolting was still more expensive than mechanical bolting. In order to generalize resin bolt installation, the second step was therefore to acquire special roof bolters compatible with resin bolting. The machine was to enhance the safety of the operation. This was achieved by the acquisition of the Secoma bolting machine equipped with an automatic bolting turret. Being a "hands off" operation the safety of the operator is total. Using a fixed taped attachment of the drill steel on the chuck a front guide and an automatic regulator torque thrust on the steel drilling in small diameter was possible. Being a fully automatic process only one operator is required per machine versus two operators with the conventional machines. The two main objectives were reached enabling the extension of resin bolting to the whole mine.

Jan 1, 1980

By A. Patrick Ryan

To many people, the word cartel implies illegality. However, although it is illegal in the US, cartels are an effective and legal way to conduct business elsewhere in the world. But be-fore we continue, what is a cartel? The American Heritage Dictionary defines a cartel as "a combination of independent business organizations formed to regulate production, pricing, and marketing of goods by the members." However, that definition does not fit many of the "cartels" we are examining today. The International Tin Council is an organization of both consumer and producer nations--no individual companies are represented. The buffer stock is used by the ITC to provide protection for both producers and consumers, and has only been in effect since 1955. (Earlier tin producers groups date back to 1921 when the Federated Malaysia States and the Netherlands East Indies formed the first intergovernmental tin agreement, known as the Bandoeng Pool, which only lasted three years.) The International Bauxite Association only dates back to 1974 when seven nations--Australia, the Dominican Republic, Ghana, Guinea, Guyana, Haiti and Jamaica--agreed to three main objectives: 1) to promote the orderly and rational development of the bauxite industry; 2) to secure a fair and reasonable return on the raw material for the benefit of the nations' citizens; and 3) to safeguard the interests of member countries in relation to the international bauxite industry. 1 Again this organization is composed of nations, not separate firms. This generally follows the pattern that the oil producing countries (OPEC) chose since the nations' mineral product-ion is controlled and often owned by the state. However, the group I am going to discuss fits the more classic mode of a cartel. The informal lead-zinc producers' cartel can be dated as far back as to Roman times when Romans are said to have imposed a quota system on British lead production to safeguard their Spanish lead mines. Also, the lead-zinc producers group is composed only of individual companies, not do not include any lead-zinc consumers. Finally, the activities of the group are not open to public scrutiny, and details are only now available due to a leak in the Australian government. At this point, it is necessary to split the two metals since while many of the members of the cartels produce both lead and zinc they do have different histories and marketing arrangements.

Jan 1, 1978

By J. Groppo, W. Zhang, R. Honaker

"Rare earth elements (REEs) found in coal are in the form of minerals, ion-substitution with clays and organically bound. Rare earth minerals (REMs) such as monazite exist in coal and have a grain size less than 5 microns. Froth flotation was successful in concentrating REMs existing in a thickener underflow material derived from Fire Clay seam coal which contained around 300 ppm of rare earth elements (REEs). Conditioning with fatty acid followed by processing using multiple stages of conventional flotation produced a final concentrate containing 2300 ppm REEs. Using a laboratory flotation column, a concentrate containing around 4700 ppm of total REEs was produced equating to an enrichment ratio of 10:1. INTRODUCTION Rare earth elements (REEs) are becoming increasingly important and have been widely used as raw materials for the production of phosphor, metal catalysts, magnets, and batteries [1, 2]. REE recovery from alternative sources such as coal and coal by-products has the potential to stabilize the economic viability of coal mining operations while providing a dependable supply of critical materials. The average REE content of the world coal is around 60-70 ppm [2]. There are many well-known coal beds with high contents of REEs such as those in the Far East coalfields in Russia (300-1000 ppm), the Fire Clay coal seam in eastern Kentucky (500 ppm), and the Sydney Basin in Nova Scotia, Canada (72-483 ppm) [3-6]. The occurrence of REEs in coal and coal by-products can be classified into three types, i.e., rare earth minerals such as monazite and xenotime, ion exchangeable REEs in clays, and REEs associated with organic matrix. The particle size of the rare earth (RE) minerals in coal and coal by-products is very small and normally in the micron and/or nanometer scales. The flotation technique, which is based on the surface chemistry difference, has been widely used to treat fine rare earth industrial minerals such as monazite, xenotime, and bastnaesite [7-11]. As such, flotation is a promising method for the concentration of REEs from coal and coal by-products. In the current study, rare earth flotation was conducted using the fine coal refuse generated at an operating coal preparation plant treating coal from the Fire Clay seam. REE concentration by flotation required an appropriate amount of grinding and control of the pH value while using typical collectors. Prior to RE concentration, release tests were conducted to evaluate the floatability of the recoverable coal and the REE distribution in the flotation fractions in the fine refuse. Mineralogy of the REE was studied using SEM-EDX."

Jan 1, 2017

By Leonard Bronitsky

The construction mineral aggregates industry--the largest industry on a tonnage basis--is threatened with large shortages in the near future. Ironically, these common minerals which include sand, gravel, and stone are among the most plentiful in the earth's crust. However, as these minerals are low in value and used in large volumes, they are extremely sensitive to transport cost, e.g., a haul of 20 miles doubled the delivered cost of mineral aggregates. Consequently, these minerals must be located close to points of demand to have economic usefulness. But the development of new deposits is virtually impossible near many urban areas for legal, sociological and economic reasons. The spector of unfinished urban transport systems, curtailed residential construction, and a general deterioration of the physical urban plant, looms as a direct consequent of future mineral aggregate shortages in the U. S. metropolitan areas. The shortages of mineral aggregates in the Greater New York Metropolitan Area (G.N.Y.M.A.) are prototypical of the shortages faced by the U. S. Metropolitan areas. This paper presents an economic analysis of the consequences of not considering the broad aspects of conservation economics as a major component of resource management. The needless annual cost for the G.N.Y.M.A. is shown to be $30 million.

Jan 1, 1974

By J. J. Kellar

Researchers have long speculated regarding the adsorption state of collectors on mineral surfaces. Only recently have analytical techniques become available which allow direct in-situ analysis of adsorbed layers. Fourier transform infrared spectroscopy coupled with internal reflection spectroscopy (FT-IRJIRS) with reactive internal reflection elements allows for unobtrusive investigation of the adsorbed layer (Harrick, 1979). This technique has been used both for the in-situ identification of adsorbed species and for the direct calculation of collector adsorption density in real time from infrared spectral data (Miller and Kellar, 1988). The reactive mineral IRE serves both to internally reflect the infrared light and to act as a substrate at which collector adsorption can be monitored. Shown in Figure 1 is a schematic of light being internally reflected in an IRE. As the light is totally reflected at the interface, an evanescent wave propagates a short distance (typically a few microns) away from the IRE, and sampling of the interfacial region occurs. Because of multiple internal reflections, great sensitivity can be obtained. Flotation systems for which this method has been demonstrated include CaF2/oleate, Al2O3/ dodecyl sulfate, CaCO3/oleate, ZnS/xanthate, and KCl/octylamine (Miller and Kellar, 1988; Kellar et al., 1989, 1990; Miller et al., 1990).

Jan 1, 1992

By Roger S. Dewey

1.1. INTRODUCTION Despite indications of a general economic recovery in the U.S. during the mid-19801s, mine operators have not generally shared in the benefits of these reported better times. Budgets have not rebounded, borrowing is tougher, parent companies' pockets are not as deep as in previous years, and margins are not any better -- if there is any left over at all. Managing capital equipment budgets is always a challenge, and the last five years of stretched equipment lives make these decisions more tenuous. Delays and avoidance of replacements due to tough times inevitably makes those decisions increasingly difficult and usually more expensive The purposes of this paper are to present. a brief refresher outline of the fundamentals of equipment replacement analysis, to suggest a number of papers where analysis methods are explained in greater detail. and to recommend the use of a widespread microcomputer software capability (1-2-3) as the easiest path to a much-needed solution for a very difficult, and usually under-supported management decision problem 2. REPLACEMENT DECISION POLICY Investments in equipment replacements must compete for capital with all other investment alternatives. Capital for replacements of ten represents a greater commitment than do the new projects which a company might handle in a given year. But. sadly, formal policies for standardized analysis of replacements rarely exist, even in major companies. Yet this policy can be very significant in determining the competitiveness of a firm. Whereas many replacement decisions are based on cost minimization, economists and financial analysts agree that wealth maximization or return on investment is the superior criterion. Though the difference may seem slight, agreement on a firm's financial objective is vital. Replacement policy should be straight- forward. have a logical basis, and a proper level of sophistication. There are several reasons to develop a policy for replacement decision-making: [I] 1 - equipment's optimal economic life is nearly always shorter than its physical life; 2 - mine life often exceeds equipment life, so management must face these decisions routinly 3 - replacement capital costs, on an undiscounted basis, can run 25 to 75% of original capital 4 - technological changes may result in a newer machine or system which can operate more efficiently, more safely. or less expensively 5 - estimates should be made consistently in the fundamental areas of life expectancy, availability, utilization. price escalation, taxes 6 - long-term and short-term budgeting without decent data and analytical capability is nearly impossible, or at least ineffective Policy development assumptions which must be considered include: the planning horizon, cost patterns, interest rates, availability of capital, replacement vs. expansion, technology advances.

Jan 1, 1987

By Robert B. Fulton

Staurolite, an iron aluminum silicate mineral, is used industrially as a high value-in-use sandblasting agent, as a premium-grade foundry sand, and as the source of aluminum in portland cement manufacture in areas where the aluminum constituent is not economically available from shale or argillaceous limestone. Staurolite is produced by E. I. duPont de Nemours and Company as a coproduct of titanium mineral production in Florida, where it was first recovered on a commercial scale in 1952 from the Pleistocene sand deposit known as Trail Ridge. At this deposit it comprises about one-fifth of the heavy mineral suite, the principal other heavy minerals being ilmenite, leucoxene, rutile, zircon, kyanite, sillimanite, and tourmaline. Staurolite and other nonconductive silicate heavy minerals are separated from the conductive titanium minerals on high-tension electrostatic separators. The silicates are then separated from one another magnetically, the staurolite being relatively magnetic. In the total process, 200 t of raw sand yield 7 t of heavy mineral concentrate from which about 1 t of staurolite is recovered. The staurolite concentrates have the characteristics given in Table 1. Staurolite concentrates are sold in three grades having the size distribution of subrounded grains shown in Table 2. All three grades are used in sandblasting for cleaning metal, for paint removal, and for cleaning masonry buildings. Staurolite compares favorably with lower priced abrasives, such as boiler slags and silica sand, in applications where the abrasive is used only once and is not recovered and recycled. Because it is hard, fine, clean, and dense it can reduce blasting time, and less material is required to clean a specific area. Compared to higher priced abrasives such as aluminum oxide and garnet, which are recycled, staurolite costs significantly less per kilogram and cleans at equal or faster rates. Its breakdown factor, which is a measure of recycling performance, is intermediate between those for aluminum oxide and garnet. [ ] [Tables 3 and 4] show the blast cleaning performance of the three staurolite grades compared to other abrasives. [Table 5] compares the longevity of premium priced abrasives during recycling. [Table 6] shows a cost comparison between silica sand and staurolite. Fringe benefits claimed for staurolite's use as an abrasive are: 1. Good flow properties and freedom from the lumps or slivers found in silica sand or boiler slag abrasives. 2. Low dusting affords good visibility, permits faster working, and reduces cleanup problems. 3. Heated storage is not required during freezing conditions, because the mineral is nonhygroscopic.

Jan 1, 1994

By Cong Zhang, Huaying Wang, Yixin Wei

"Water inrush is a serious geological accident in underground coal mines. This paper focuses on the method of the bow tie analysis based on fuzzy reliability to assess the risk of water inrush in coal mines. First, post failure probability and repair probability of initiating events are divided into 5 levels. Then triangular fuzzy numbers are adopted to quantify experts’ language and to acquire the reliability rate which close to the actual values by defuzzification and calculation. According to dynamic bow-tie analysis model, using the method of moments to fit the reliability time of events by Weibull distribution and offering the random sampling rule of failure and repair time for illustrating the feasibility of fuzzy reliability evaluation. To demonstrate the effectiveness of the proposed assessment approach, bow tie analysis model of water inrush in coal mines is taken as an example.Introduction Dynamic bow tie (DBT) analysis is composed of dynamic fault tree and dynamic event tree analysis, and considers the impact of the time factor upon risk assessment of a system. There are many algorithms applied to calculation of the probabilities of node accident and accident consequence of dynamic bow tie analysis: Hidden Markov Model, Bayesian Network (Khakzad et al 2013), Integral Algorithm (Amari et al 2003) and Monte Carlo Simulation (Kim et al 2016). In terms of simulated time and practicability, the Monte Carlo Simulation has an advantage over other methods. DBT requires mass data in quantitative analysis, including the failure rates and the repair rates of the basic events of the Fault Tree (FT) and the subsequent events of the Event Tree (ET) at different time points, i.e., the distribution of failure time and repair time. In practical analysis, it is hard to obtain a large amount of exact historical statistical data, which is a major problem of risk assessment. Due to the difficulty of obtaining the exact data and historical failure data of the basic events and the subsequent events, the FT and ET analysis is stuck with the study of minimal cut sets, minimal diameter sets, structural importance and qualitative analysis (Liu and Zhang 2010, Yan et al 2012, Wang et al 2009, Li and Wang 2011). This paper will use fuzzy numbers and the defuzzification method to transform the experts’ language into the failure rates and repair rates of basic events and subsequent events, solving the problem that it is difficult to obtain a large amount of historical statistical data, and will use the method of moment to conduct Weibull fitting of the reliability time to provide the random sampling criteria of event failure and repair time in Monte Carlo simulation."

Jan 1, 2017

By O. M. S. Rodrigues

The kaolinite presence in bauxite ores increases caustic soda consumption during the digestion step in the Bayer process. Depending on the kaolinite content, the utilization of the ore in the Bayer process may be unfeasible. This investigation addressed the variables involved in kaolinite flotation through microflotation experiments in a Hallimond tube and zeta potential determinations. The tests were performed with a pure sample of kaolinite (96%). Five collectors were tested: Duomeen T (DT), cetyl pyridinium chloride (CPC), cetyltrimethylammonium bromide (CTAB), dodecylamine (DDA) and Flotigam EDA (EDA). Four of them performed well as collectors, at a concentration of 1x10-4 mol/L: CPC, CTAB, DDA and EDA. The kaolinite isoelectric point (IEP) was determined at pH = 4.6. The IEP was shifted towards higher pH values in the collectors? presence, indicating specific adsorption onto the mineral surface.

Jan 1, 2011