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By S. Horton, F. L. Stanley, P. J. Bethell

Introduction The McClure River Processing Plant is located at McClure in Dickenson County, VA. The plant was originally constructed in 1979 as a 600 st per hour facility. The plant is fed by coals from numerous mines in the area as well as a major longwall mine onsite. Coal is processed predominantly for the metallurgical coal market. The original plant was comprised of three separate processing circuits incorporating a heavy medium vessel for the coarse material (+10 mm). Intermediate sized material (10 x 0.6 mm) was beneficiated in heavy medium cyclones, with the remaining fines (0.6 mm x 0) passing to froth flotation for upgrading. The products from all three circuits were combined prior to thermal drying and then stored in silos or ground storage prior to shipment to the metallurgical coal markets. A middlings heavy medium cyclone circuit was also present to rewash the vessel and primary heavy medium cyclone rejects. The original circuit is as shown as Fig. 1 (Editor's note: All figures are reproduced at the end of this paper.) In reasonably close proximity to the McClure Plant is the much older, less efficient Moss 1 Plant, (Chance cone, table, water only cyclone, froth flotation, Fig. 2), which prior to the McClure Plant expansion was processing considerable tonnages of coal. At that time, the McClure River Plant was processing coal at the maximum possible feed rate, and the Moss 1 Plant was finding increasing difficulty in maintaining the stringent quality specifications on its major metallurgical coal accounts. Given the fact that many of the feeder coals to Moss 1 could be moved with minimal difficulty and cost to McClure, an exercise was conducted to evaluate the potential of expanding the McClure Plant. This would result in transferring coals from Moss 1, thereby increasing yield, reducing operating costs, and enabling customer specifications to be met more easily. After evaluating many possible ways of expanding the McClure Plant, we eventually settled on an approach based on the idea of Gallagher at German Creek in Australia (Gallagher, 1986). Our objective was to increase plant capacity by removing the coarser size fractions (0.60 x 0.15 mm) from froth flotation and at the same time eliminating the finer fractions (1.25 x 0.6 mm) from the heavy medium cyclone circuit, thereby allowing these circuits and therefore the plant as a whole to increase its capacity. These size fractions (0.60 x 0.15 mm from froth flotation and 1.25 x 0.6 mm from the heavy medium cyclone circuit) would be treated in a new spiral circuit. After desired evaluation of the various circuit capacities, including desliming screen, clean coal filter and thermal dryer capacities, etc., it was concluded that we should be able to maintain high levels of processing efficiency in the existing circuitry while at the same time expanding plant feed rate from a nominal 600 st per hour to 1000 st per hour, thereby achieving the objectives The circuit that was finally settled on is shown in Fig. 2. Several unique features were incorporated in this circuit in an attempt to maximize processing efficiency and reduce maintenance costs. First, the idea of a single-stage spiral circuit was abandoned in favor of a two-stage circuit incorporating rewashing the primary spiral middlings in a secondary spiral (Bethell, 88). The spirals selected were Mineral Deposits Model LD4 units. It was felt, after much previous testing, that spiral middlings rather than being a true middling gravity fraction were in fact a combination of true middlings with a preponderance of misplaced light coal and high-density rock. Consequently the insertion of this material directly into either clean coal or refuse streams (per normal practice) would only lead to loss of efficiency. The operating philosophy behind the design of the circuit was to produce the purest coal and rejects possible by adjusting the spiral splitters. Misplacement of refuse into the clean coal and vice versa would be minimized by taking a fairly large middlings cut. By reprocessing this material (10%-15% of primary spiral feed) in a secondary bank of spirals the misplaced material in the primary middlings would be reprocessed and its probability of reporting to the correct stream greatly enhanced. To minimize fines loading on the spirals, fine aperture sieve bends were to be included. A further novel feature of the circuitry is the desliming/ dewatering system. A philosophy of accepting inefficiency but forcing it to work in our favor was developed. The dewatering screens (Linatex Combis) were chosen not for their ultimate screening efficiency but for their ability to remove slimes (tolerating a fair quantity of oversize in the effluent) and their enhanced maintenance characteristics. Any oversize passing into the effluent, together with the fine coal centrifuge effluent, would pass to classifying cyclones, the objective of which was to reject to overflow (and hence froth flotation) as many fines as possible (-150 µm) without running the risk of losing coarse (1.25 x 0.15 mm) material to oversize. Hence, by a process of producing a "slime free" screen product coupled with a "coarse free" cyclone overflow, sizing efficiency could be maximized. Obviously, recirculating load had to be factored into the Combi Screen design capacity. The spiral circuit as shown in Fig. 2 was installed at McClure River in January 1988. The spiral circuit efficiency was very high immediately, and, after the normal debugging, plant capacity has been increased to the point at which we are currently processing of the order of 1100 st per hour. Test program The performance of the spiral circuit has been evaluated by two major samplings of the entire new circuit, coupled with routine bi-monthly tests on all other major components of the plant circuitry.

Jan 1, 1992

By Carl E. Schubert

The application of geophysical technology relative to the exploration, planning, and operation of coal mines is expanding. This is due to the trend of the industry to increase the size of operations, use of mechanized equipment and mining of more difficult coals, where unforeseen conditions can affect mine profitability. Coal is a good geophysical target because of its lower density, higher electrical resistivity, lower seismic wave velocity, and lower magnetic susceptibility in comparison to typical country rock. The more important techniques are well logging, high resolution seismic reflection, seam wave velocity, and radar. These methods can be used to map coal horizons, determine the physical properties of the coal, and identify mining hazards. The methods are not a pancrea however. Their use should be based on a careful assessment of their expected success and cost benefit analysis in comparison with conventional technology, primarily drilling, which none of the techniques presented should entirely replace. In general, the level of technology developed for geophysics surpasses their current level of application to coal problems. In some cases, identifying hazards in advance of mining using seam wave seismic in particular, the state of the art has been developed in Europe and is awaiting fruitful application in the United States.

Jan 1, 1982

By S. E. Phifer

The Haile gold mine was the largest gold producer east of the Mississippi River before 1942. It was the first gold mine in the Southeast to reopen following deregulation of the gold price by the United States Government. The Haile mine was also the first gold mine in the Southeast to use heap leaching and carbon recovery for gold production. Current production involves mining and heap leaching about 1.8 kt/d (1600 stpd). Carbon is used as a recovery medium. Due to the clay and excessive fines in the oxidized ore, agglomeration using portland cement is required before leaching. Agglomerated ore ranges in screen size from 50 mm (2 in.) to less than 75 µm (200 mesh). The agglomerating step combined with certain other conditions has enabled Piedmont Mining Co. to achieve recoveries of about 90% or better.

Jan 1, 1987

By Lewis L. Oriard

INTRODUCTION In recent years, there has been a trend in the direction of larger drilling equipment and larger diameter blastholes. Although this change has improved the efficiencies and reduced the costs in many operations, it has increased the potential for damage to underground openings. In addition, in many instances one now finds more sophisticated delicate instruments, automated control facilities, and a large variety of structures in proximity to blasting activity. The combined effect of larger-scale blasting activity and its proximity to various features of interest is such that there is an increased need for a more refined analysis of blasting effects and their control. BLASTING EFFECTS ON ROCK SURFACES The Breakage Mechanism In order to develop techniques for controlled blasting, one must first understand the features of the mechanisms by which blasting causes rock breakage to occur. These features have not been easy to demonstrate, mostly due to the difficulty in making tests and observations at the high stress levels and short time durations involved. When an explosive charge is detonated, the material surrounding the charge is subjected to a nearly instantaneous, very high pressure [on the order of 1.4 to 13.8 GPa (0.2 to 2.0 X 106 psi), depending on the explosive]. If the charge is coupled to "average" rock, this pressure will pulverize the surrounding rock for a distance on the order of 1 to 3 charge radii in hard rock, and to a greater distance in softer rock (this is also dependent on the type of explosive). As the pressure wave passes into the rock, high tangential stresses cause radial cracks to appear, and the nearly discontinuous radial stress zones gen¬erated by the shock front may cause tangential cracks to appear. The extent of these cracks depends on the energy available in the explosive, how quickly the energy is transmitted to the rock, and the strength properties of the rock. The discontinuous shock front is quickly dis¬sipated, but the expanding gases generate a longer-acting pressure. A compressive pulse travels to the nearest face or internal rock boundary where it is reflected in tension. The tensile strengths of most rocks are roughly 40 to %o of their compressive strengths, so the rock may now fail in tension whereas it may have been able to support the diminished compressive phase without failure. The ten¬sile deflection typically produces a failure described as tensile slabbing or scabbing. Laboratory experiments and field experience have pretty well established that several mechanisms are involved. These include (1) the classical case of tensile parallel slabbing when the pressure pulse is reflected at a free surface; (2) failure under quasi-static compressive loading (the shape is normally irregular due to discontinuities in the rock); (3) radial cracking under the action of tangential stresses at the periphery of the expanding pressure pulse; (4) peripheral cracking at the discontinuous shock front which is quickly dissipated; and (5) additional mass shifting due to the venting of the explosive gases. The first three items have received much attention in the laboratory and the literature. The complex effects of gas venting are difficult to test in the laboratory because of the difficulty in reproducing the many weak planes and discontinuities typical of most field conditions, which play such a prominent role in determining the behavior of the rock mass subjected to blasting. Unfortunately, gas venting effects can be pro¬jected to significant distances under certain field conditions, and are sometimes difficult to control. It is not unusual for gas venting to be the overriding factor in determining the final geometric shape and physical condition of the finished excavation. Sources of Damage For the purposes of this discussion, damage includes not only the breaking and rupturing of rock beyond the desired limits of excavation but also an unwanted loosening, dislocation, and disturbance of the rock mass the integrity of which one wishes to preserve (such as mine pillars, underground openings, etc.). The sources of damage include, of course, all those physical features of the rock breakage mechanism. Each of these effects must be limited to the desired zone of breakage and excavation if the integrity of the remaining rock mass is to remain undiminished. The primary zone of rock breakage usually can be controlled in the normal process of field experimentation to determine proper charge sizes and location for primary excavation. However, it frequently happens that there is damage from sources which are more difficult to account for in the design process, which are often overlooked. These are (1) the overbreak due to poor drilling control, (2) dislocation of rock (mass shifting) due to venting of explosive gases, and (3) loosening or dislocation due to the influence of seismic waves (ground vibrations). CONTROL OF ROCK BREAKAGE Importance of Geometry In studying the rock mass and blasting design con¬siderations, it is important to keep in mind the geometric relationships among charge size, shape, and position, and the physical features of the rock mass to be preserved. The features of principal interest are the external shape and position of the rock mass relative to blasting, and the position and attitude of any weak planes in the rock mass. The Sequence of Blasting and Excavation Events Unfortunately, there are too many times when the task of preserving delicate rock is considered hopeless, and because of this attitude, no further effort is ex¬pended towards caution or control. In such cases there is often a failure to recognize the importance of the se¬quence of the procedures. Attention to this can greatly reduce unwanted effects at minimum cost. Perimeter Control The requirements for perimeter control are highly dependent on the special needs of each particular proj¬ect. The desirable degree of control is a highly variable

Jan 1, 1982

By S. Behl

In the selective flocculation process, polymers with specific functional groups can yield highly selective adsorption and, therefore, high separation efficiency. Selectivity in polymer adsorption may also be attained by specific additives that inhibit the adsorption of the flocculant on some solid surfaces but not on others. Generally, these additives have a different chemical nature than the flocculant. In this study, the lower molecular weight fraction of the flocculant was successfully evaluated as a site blocking agent, leading to higher separation efficiency than obtained otherwise.

Jan 1, 1993

By Y. Ye

Induction times for a variety of minerals have been measured at a particle bed. Electrostatic repulsive forces between bubble and particle generally are of secondary importance in determining the hydrophobic state; nevertheless, the shortest induction times are measured at the isoelectric point of the solid. More importantly, the study shows that the film-rupture mechanism at a polished surface might be different from that at a particle bed. The induction time measured at a particle bed, besides being dependent on the surface chemistry of the system, shows a definite relationship to particle size and density. Theoretical analysis suggests that such a measured induction time at a particle bed should properly be defined as an attachment time which consists of the induction time and the film-displacement time. Thus one portion of the measured attachment time is the induction time, the time required to thin the water film between the particle surface and the gas bubble to a critical thickness so that rupture of the film takes place ('1)' The other portion of the measured attachment time is the time required for the film to be displaced to such an extent that the attachment is stabilized with respect to the upward motion of the bubble and the downward gravitational force acting on the particle ('2)' Further, the present study illustrates that '2 is related to the hydrophobic character of the surface, the rate of film displacement after rupture, the upward velocity of the captive bubble, and, most importantly, the particle size and density.

Jan 1, 1988

By Peter Krag, Rob Henson

It is well known that titanium and zirconium alloys offer superior corrosion resistance in the oxidizing sulfuric acid environments present in sulfide pressure leaching operations. The use of these materials is limited, however, due to their pyrophoricity; several accidents attributed to titanium equipment have been described in technical literature, and other, minor incidents·occur regularly1 • We describe an application of a commercial titanium alloy, Nb-55 Ti, with suitable mechanical properties, corrosion resistance similar to Grade 2 Ti, and featuring a significantly reduced field of ignition conditions

Jan 1, 1992

By H. L. Ford

Flocculant testing should be initiated for economic or performance reasons. When the decision has been made to test, the laboratory can provide valuable information concerning the various products under consideration. Properly conducted laboratory tests can determine: 1. If two flocculants are needed to achieve clarity or density. 2. Ease of mixing. 3. How quickly the material goes into solution. 4. Stability of prepared f locculant solution. 5. Stability of the floc formed. 6. Amount of mixing required for proper floe formation. 7. Optimum flocculant concentration. 8. Optimum pulp density. 9. Approximate location of the point of addition. 10. Single or multiple addition points. When a flocculant shows promise in the laboratory, a plant test should be scheduled. During the plant trial, arrange for normal conditions and start testing with a crew that is most familiar with the unit operation where the flocculant will be applied.

Jan 1, 1986

By Robert A. Irvine

Traditionally, cost effective gains in the capacity of material handling systems were a result of increases in equipment size. In general, the use of maximum capacity components in a system optimizes the production "costs per ton." The trend-"Bigger is Better" will continue in material handling equipment. Since it is rare for plant operators to lament an over abundance of screening capacity, one can safely predict that vibrating screens will follow this trend. Large Vibrating Screens - The Challenge Large vibrating screens represent a unique challenge for Manufacturers, Plant Designers, and Plant Operators. The inherent mode of operation for vibrating screens is self-destructive. More often than Manufacturers admit, Designers plan for, or Operators staff for, a vibrating screen succeeds and self-destructs. This is a problem. It can magnify with larger vibrating screens.

Jan 1, 1983

By RICKARD HANSEN

Vehicle fires in underground mines pose a certain risk for which measures to prevent or mitigate the fires are highly important. Fire protection measures can be divided into active and passive measures, where active measures require an external power to work in the event of a fire, and passive measures could include an existing partition preventing fire spread. As passive fire protection does not rely on activation, it is expected to provide high reliability and a robust solution, and should be considered during the design process. This paper investigates passive fire protection measures that could be implemented in the design of mining vehicles. It was found that passive fire protection should include the use of several measures simultaneously to ensure fire protection throughout the different phases of a fire. Threshold distances for fuel components were calculated, and it was found that combining hydraulic hoses and electrical cables resulted in larger threshold distances. A pool fire along the underside of a vehicle will pose a certain risk, and passive measures should be focused on ignition prevention, making high demands on the insulation/shielding along the underside. Any occurring tire fire may pose a challenge, and the priority should be on preventing ignition. Potential measures include shielding the wheelhouse and applying fire-resistant sealings.

By N. Parra, M. N. Herrera, T. Vargas, B. Escobar, C. Gonzalez

originally published May 1998, Vol. 15, No. 2, pp. 15-1 9 Discussion by G. Rossi, University of Cagliari Reply by T. Vargas, University of Chili

Jan 1, 2000

By E. Valdiviezo, J. F. Oliveira

Adsorption of residual flotation reagents onto equilibrium fluid cracking catalysts is a promising method of purification of flotation process water. In the present paper, adsorption of sodium dodecyl sulphate (SDS), dodecyl ammonium chloride (DAC) and sodium oleate onto a spent catalyst from petroleum industry was studied by analysing the residual concentration of the surfactant after contact with the zeolite catalyst. The adsorption of the DAC was rather low but SDS and sodium oleate presented a high affinity for the catalyst surface. The loading capacity was 4.2 kg/ton for SDS and 5.5 kg/ton for oleic acid. After the treatment of the loaded catalyst with a HCI 1 N solution these surfactants are desorbed and the catalyst may thus be regenerated. This would be an additional advantage to its low cost, not to mention its condition as a discarded product and its availability in large tonnages.

Jan 1, 1995

By Christopher D. Henry

Environmental geologic maps of the Wilcox and Jackson-Yegua lignite belts of the Texas Coastal Plain delineate land areas on the basis of their natural characteristics. Criteria used to define map units include substrate, soil, topography, geologic process, vegetation, and land use. The maps are useful in planning and reclamation of lignite mines and in meeting the requirements of State and Federal surface mining laws. Specific applications include identification of land capability, recharge areas and geometry of aquifers, flood-prone areas, areas that may qualify for prime farmland status, and other areas sensitive to lignite mining.

Jan 1, 1982

By Ian P. G. Hutchison

12.1 INTRODUCTION This chapter deals with the tools required to design leach operations to minimize spillage from leach pads and ponds and erosion damage during flood events or prolonged wet periods. It outlines methods used to design for prolonged dry periods when water shortage can be a problem. Seasonal operational aspects such as winter shutdown and coping with spring snowmelt periods are also discussed. General criteria useful when designing pregnant and barren solution ponds are also outlined. The aim of these notes is to provide designers and operators with a simp1ified approach to developing design parameters which make effective surface water management easy to achieve without resorting to extensive or elaborate analyses. Section 12.2 briefly outlines the types of problems associated with wet climates and floods, as well as dry periods. Determination of flood design parameters is discussed in Section 12.3. Circuit water balance and pond sizing are outlined in Section 12.4. Pond design considerations are included in Section 12.5. Worked examples are included in Section 12.6. 12.2 RAINFALL/RUNOFF PROCESSES There are two types of rainfall-runoff processes that are important when designing heap leach facilities. The first of- these is the short-term, intense rainfall or snowmelt events that occur over a period of a few minutes or hours, causing flooding that can lead to erosion damage and overtopping of ponds and containment dikes. Specific problems that can manifest themselves during these events include: • Washout of access roads; • Damage to containment dikes; • Flood water contamination of circuit water; • Damage to process water ponds by perimeter erosion or overtopping and erosion; • Loss of process circuit fluid due to breaks in containment dikes or process water ponds; and • Erosion of leach pile and consequent sediment contamination of process fluid. Other types of rainfall -runoff processes that could cause problems are the long-term-(generally months-long) wet or dry periods. Extended wet periods

Jan 1, 1988

By Philani Larrance Ngwenyama, Ronald CW Webber-Youngman

The survival chances of trapped miners in underground mines depend on how quickly they can be located and rescued post-accident. During entrapments, emergency rescue is highly desired but can be hindered by the lack of positioning information when a fit-for-purpose missing-person locator system is not available. Various types of missing-person locator systems are available to aid search-and-rescue operations. From the wide range of the available systems, selecting the most suitable one becomes the next challenge. The available systems have not been measured if they are fit-for-purpose or not, and to what situation. This study proposes user requirements that can be used as a guideline to facilitate the system selection process. These user requirements provide a framework for the design and development of a fit-for-purpose missing-person locator system. The user requirements can also be used for evaluating the performances of a particular system, predict its success, and also drive future research toward developing new technology to enhance the capabilities of the current systems.

Apr 1, 2024

By J. Wesley Atkins

In considering the importance of lease management and administration, I have decided to approach the topic, Lease Default and Eviction: Action or Reaction, as a three phase presentation dealing with mineral lease administration and management, past, present and future. Though the title may border on the dramatic, it illustrates the real consequences of alternative approaches to property management viewed from my experience in the evaluation, development and implementation of a number of such systems and services in my current position as president of Talco Group Corporation. First, though, let's take a moment and set the stage by giving a few actual examples of why a pragmatic approach is needed in this particular area.

Jan 1, 1983

By William F. Brandom

INTRODUCTION Cross, et al. (1974), produced a retrospective study of standard setting for underground miners. This report had two distinct components; i) criteria of importance for the protection of the miners, and ii) economic considerations for standard setting. The methods for setting radiation safety standards reviewed were: dose calculations and consensus methods; epidemiology; pathology; bioassay; animal experiments; sputum cytology; chromosome aberrations; and, the Mantel-Bryan Model. By looking back, the authors intended to enable officials to look ahead in making future decisions based on reasonable conclusions. Now it may be time to consider underground miners' protection from another perspective: are there miners who may be especially susceptible to toxic environments?; and if so, are there any biomedical assays that might be indicative of exceptional sensitivities to toxic substances? The human population is genetically very heterogeneous. The data of Saccomanno, et al. (1973), reveal great variability in individual response to radon daughter exposure and only a small portion of the miner population subject to toxic inhalants develop squamous cell metaplasia (Saccomanno, et al., 1970). The majority of the miner population is either not susceptible or is resistant to the toxic agents. This information suggests the existence of a small subpopulation with increased sensitivity or reduced resistance and underscores the need for indicators from biomedical assays that might prove of value for the detection of such individuals. The heightened awareness of the contribution of pollutants in the environment for the potential induction of mutations and carcinogenesis lead to a profusion of short-term bioassays to circumvent the high cost and time-consuming large toxicity animal studies. Over 100 bioassays across taxa from microbes to man are at various stages of use or development (Hollstein, et al., 1979). Less than a dozen tests currently offer early promise for application to[ in vivo] effect studies of man. Many are still in early development, lack the sensitivity needed for a retrospective or prospective study at current permissible exposures, are impractical to conduct in the field, or are not cost effective. The purpose of this paper is to review some of the bioassays that may now, or in the near term, prove applicable for the detection of individual underground miners with increased susceptibility to toxic agents. Throughout this statement, it is assumed that any single test may give false negatives or false positives and, therefore, a tier of tests should be investigated. The possible tests are in various stages of development; some tests better proven than others with a firmer data base and, therefore, with greater probability of usefulness. Some of the less proven assays are not ruled out if they have practical or theoretical promise as indicators. Table I summarizes the assays critiqued for their potential to monitor the effects of [in vivo] exposure to genotoxic substances. POTENTIAL INDICATORS OF HIGHLY SENSITIVE MINERS Assays of Body Fluids It is desirable to have data on the agent(s) to which subjects are exposed when humans are monitored by biomedical effects. Obviously, to varying intensity, the underground mining environments are monitored for radon daughters and it is recognized that the miners are also exposed to other pollutants, most notably, uranium ore dust and diesel fumes. Further testing for the metabolites of the pollutants can be done on body fluid, urine. [High Performance Liquid Chromatography (HPLC)]: This is a very sensitive method for the detection of mutagenic metabolites in urine. The urine is treated with the enzyme sulfatase and beta-glucuronidase to permit identification of substances that are made nonmutagenic by conjugation as glucuronides. The sample is then passed through an XAD-2 resin column and the absorbed organic molecules eluted with acetone. The sample is then split and evaporated to 1 ml and used for direct chemical analysis using HPLC. One drawback to the test is the inability to measure cumulative exposure, but multiple samples can be obtained and comparison to baseline (control) and exposure samples can reveal qualitative differences as a consequence of exposure to mutagens. [The Ames/Salmonella Microbiological Assay]: The Ames/Salmonella microbiological mutagen test is the most extensively used short-term bioassay, with over 2,600 chemicals having undergone testing by this method (Hollstein, et al., 1979). The method, thoroughly worked out and tested for 10 years, consists of taking the second split urine sample from the HPLC preparation, evaporating to dryness and dissolving in dimethylsulfoxide (DMSO). The sample is then applied directly to

Jan 1, 1981

By Theodore M. Gurr, James J. Bartels

Phosphate produced fertilizers provide the phosphorous nutrients required by plant life to sustain significant growth, thus improving the production of food for the world's population. Phosphorous replenishment of soil currently can be obtained efficiently by no other means than by direct application of phosphate fertilizer to the soil. Phosphate products are also utilized in animal feeds, detergent, and various industrial processes. Thirty-three countries are presently mining phosphate rock for the production of fertilizers, and its process byproducts. The major phosphate rock producers are the United States, the former Soviet Union, Morocco, and China [(Table 1)]. Phosphate rock is generally defined as a rock material that contains phosphate minerals which are sufficient for commercial usage. Phosphate minerals are found in sedimentary igneous and metamorphic rocks. Economic resources of phosphates are primarily developed from sedimentary rock sources. The apatite mineral family comprises the majority of phosphate constituents from both sedimentary and igneous rocks. Igneous phosphate rocks are generally composed of fluroapatite whereas sedimentary rocks are generally composed of carbonate fluroapatite, or chlorapatite. Phosphate rock is mined by a multitude of processes, including surface and underground mining. The mined rock requires mechanical and chemical processing to liberate the phosphate for utilization as fertilizer. Approximately 85% of the world's phosphate production uses sulfuric acid, with the remaining processes utilizing nitric and phosphoric acids. Ammonia is also introduced in the manufacture of liquid fertilizer, ammonium phosphate and ammonium polyphosphate. GEOLOGY Mineralogy and Chemical Properties Phosphate most commonly is derived from the mineral apatite, which is chemically described as CA5(F,Cl,OH)(PO4)3. Apatite is also broken up into the composite apatite minerals which are fluroapatite Ca5F(PO4)3, chlorapatite Ca5Cl (PO4)3 and hydroxyl-apatite Ca5(OH)(PO4)3. Carbonate CO3 can substitute for PO, forming carbonate apatite, called francolite. The guano phosphate (bird excrement) mineralogy commonly occurs as brushite CaHP04.2H20, monetite CaHPO4, whitlockite Ca3(PO4), and dahlite Ca10(PO4)6(OH)2. Apatite minerals form from igneous sources where they are developed deep in the earth's crust; and the cooling processes are slow, producing long, hexagonal prismatic to tabular crystals. The termination of the crystal can be basal plans or pyramids. In some instances, the crystals are bipyramids. Faster cooling, or sedimentary derived apatites are more commonly cryptocrystalline. Collophane is a name given to cryptocrystalline apatite found in phosphate rock in fossil form. Apatite minerals are relatively soft and are used to describe the 5 hardness on the Mohs scale. Cleavage is poor and develops along the C(0001). The color of apatite minerals varies from colorless, to violet, and blue, but are predominantly green or brown; luster is vitreous to subresinous. Collophane's physical appearance is often opaline, dense, with colloform structure and sometimes concretionary, nodular or pulverulent. Phosphate Bearing Materials Origins Phosphate deposits of igneous and metamorphic origins have been well defined. Sedimentary origins have been defined, but with a greater degree of uncertainty. Research in the 1980s proved out some of these processes through studies of real time deposition in Chile, Peru, and Australia. Igneous intrusive alkali rock and associated contact metamorphic rocks, provide approximately 20% of the world's phosphate. Fluorine containing apatite minerals are the most common materials containing phosphorous. Fluorapatite occurs in most igneous rocks. Fluorapatite and fluorine hydroxylapatite, together with carbonate varieties of these, are important members of the group. Where an essentially pure chlorapatite, carbonate apatite, and hydroxylapatite are rare and restricted in occurrence, the fluorine containing types occur in most all igneous rocks as early formed accessory mineral, usually in microscopic crystals, and may occur as extremely large bodies as magmatic segregations from alkalic igneous rocks. Apatite is also found crystallized in pegmatitic faces of both acidic and basic types of igneous rocks. More specifically, apatite is associated with magnetite deposits, in hydrothermal veins, especially those formed at relatively high temperatures, and in veins of the Alpine type. Apatite is common in both regionally and contact metamorphosed rocks, especially in the crystalline limestones where it is associated with sphene, zircon, pyroxine amphibole, spinel vesuvianite, phlogopite, talc, chloride schists, and as a contact metamorphic mineral.

Jan 1, 1994

By Biswajit Samanta, Pranjal Pathak

A multimine mineral value chain (MVC) consists of multiple mines in the upstream supplying raw materials to multiple destinations in the downstream. The short-term mine production scheduling problem of a multimine MVC aims to determine the optimal extraction sequence and destination allocation of blocks from all the mines collaboratively to meet the quality and quantity requirements of all the processing plants in each period, subject to all relevant technical and operational constraints of the mining system. It is carried out at shorter scales of days/weeks/months under the purview of long-term production scheduling. An optimal short-term production schedule for MVC involving multiple mines that share the same infrastructure (processing units, stockpiles and waste dumps) requires coordination across the network of mines. Optimizing the short-term production schedules independently at each mine fails to capture the benefit of collaboratively generating schedules for all the mines, resulting in suboptimal schedules. Additionally, in short-term production scheduling, the operations are modeled in greater detail with additional decision variables and constraints to model the more complex multimine MVC situations. This makes the large-scale instances of the problem computationally intractable for standard mixed-integer programming (MIP) solvers. This work presents a customized genetic algorithm (GA)-based heuristic approach to obtain near-optimal solutions to the industrial-scale instances of the short-term production scheduling problem of multimine MVC within a reasonable computation time.

Oct 1, 2022

By Ross W. Smith, Salim Akhtar

Flotation of oxide minerals, particularly silicates, with cationic collectors differs substantially from classic flotation of sulfide minerals using sulfhydryl collectors. In the case of cationic flotation of these minerals, in general: 1. There is a greater importance of electrostatic interaction between mineral and collector. 2. Longer-chained collectors are required; as a rule at least 10 carbons must be present in the hydrocarbon chain. 3. Moderate concentration of collector is required. 4. Attachment between collector and mineral appears to be less strong even though the system may exhibit a large contact angle. 5. Required conditioning time before flotation is usually relatively short. 6. There is sensitivity to slimes. 7. The collectors usually possess frothing power. 8. Selectivity of cationic collectors for specific minerals is usually poor. Almost any of the oxide and silicate minerals may be floated using cationic collectors. However, specific response to these collect- ors varies with mineral type. The following classes and minerals are

Jan 1, 1976