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By Gordon Lewis

The Penjom Gold Mine is one of the world's worst preg-robbing gold ores, yielding very low recoveries from traditional CIL methods. Gold recovery from the cyclone underflow was targeted to recover as much gold as possible in the absence of the fine preg-robbing carbon. Gold is recovered by intensive cyanidation and tabling of a gold concentrate produced by gravity from the cyclone underflow. The circuit was designed together with Gekko Systems and uses their InLine Pressure Jig and InLine Leach Reactor technology to reject the preg-robbing carbonaceous material and obtain high recoveries from the gravity concentrate before over grinding the carbon and sulphides. The gravity and intensive cyanidation circuit now recovers almost 50% of gold in new mill feed, with unit recovery in intensive cyanidation of up to 90%, the highest unit recovery in the plant. Operating costs for the gravity and intensive cyanidation circuit are under US$2.50 per oz, while the cost to recover gold from the cyclone overflow is -US$200 per oz. (not including common costs of milling, stripping and electrowinning). Figure 1 shows the increase in gold recovery due to the gravity and ILR circuit coming on line at Penjom.

Jan 1, 1999

By Tony Weeks, J. Loah, Ian Mcgaffin

PT Newmont Minahasa Raya (PT NMR) operates a 700,000 tonne per annum open cut gold mine in the Minahasa region of North Sulawesi. The operation commenced production in the second quaiter of 1996 and is expected to produce an average of 150 000 to 180 000 ounces of gold per year for the mine life. The deposit is predominately refractory in nature and requires a complex treatment route incorporating dry milling and whole ore roasting followed by conventional cyanidation and adsorp­tion of the gold onto activated carbon. Gold is eluted from the carbon to produce <lore bars assaying approximately 94 percent gold. A scrubbing system for the removal of mercury from the roaster off gases was commissioned in late 1997. Due to the location of the operation, close to the coast and in seismic region with high rainfall submarine tailings placement (STP) was the preferred method of tailings disposal. Prior to dis­posal into the ocean the tailings from the CIP plant are detoxified in a three stage detoxification circuit to treat cyanide, arsenic and mercury. This paper reviews some of the design and operational fea­tures of the whole ore treatment process employed at the Minahasa Gold Mine.

Jan 1, 1998

By G. Brofas

The reforestation potential of bauxite mining spoils by seeding was examined on this research work. The experimental plot was established on the location Strofi Koukouvista 5, Ghiona Mountain. The experiment consists of 3 species (Pinus nigra, Robinia pseudoacacia, and Spartium junceum) with 4 sowing treatments and 2 sowing seasons (autumn and spring). The treatments were: (1) broadcasting; (2) broadcasting and soil cultivation; (3) broadcasting with straw mulching and straw binding with asphalt emulsion; (4) broadcasting with soil cultivation, straw mulching and straw binding with asphalt emulsion. Third year results show that spring is better than autumn as a sowing season. Only the Spartium junceum species were found to germinate and survive in autumn. The results are better for all the species on the spring seeding. The most effective treatments for Robinia pseudoacacia and Pinus nigra are 3 and 4 while for the Spartium junceum even simple broadcasting shows good results although the best ones are achieved with treatments 2, 3 and 4. The paper?s findings show that reforestation by sowing could be effective for some species but further experimentation with other species is recommended. Concerning Robinia pseudoacacia, testing of different seed preparation treatments is needed in order to maximize the germination of seeds.

Jan 1, 2002

By C. A. Fleming, C. J. Ferron, E. S. Makande, P. Mason

Several small mines are producing refractory gold concentrates in Zimbabwe and, owing to the small scale of most of these operations, their output is processed in a central custom roaster in Kwekwe. Owing to the wide variations in the feed to the roaster, the efficiency of the old Edwards roaster is deemed unsatisfactory with gold recovery from concentrate as low as 70%, and alternative processes were evaluated to improve this situation. Various processes for oxidizing refractory arsenopyrite/pyrite concentrates to liberate gold prior to cyanidation are known. In practice, only two have to date met with wide industrial acceptance, pressure oxidation and roasting. Owing to the ·high arsenic and antimony levels of some concentrates in Zimbabwe, the only viable roasting alternative would be two-stage air-roasting of concentrates in two reactors, as practiced at Giant Yellowknife, Campbell Red Lake and New Consort. This process, however, creates an arsenic disposal problem, and produces gas of fairly low SO2 content, requiring a large gas handling system for acid production. On the other hand, there are currently four commercial pressure oxidation plants treating refractory gold ores (McLaughlin, Mercur, Getchell and Goldstrike) and three treating concentrates (Sao Bento, Porgera, Campbell). One other concentrate oxidation plant is being constructed (Con), and several more are being considered.

Jan 1, 1992

By W. Baguley, L. P. H. Greenhalgh, R. P. Riley

The traditional impeller system for aeration and suspension of slurries, e.g. in bacterial oxidation plants, is the vertical flat blade turbine (VFBT) . This type of impeller is energy-intensive, which results in a heavy-duty design of shaft, gearbox and drive. The Mixtec BX04 agitator development programme is designed to evaluate the use of the new generation of hydrofoil impellers which consume less power and thus have potential for capital and operating cost savings as well as being possibly less damaging to the bacteria. The early tests on pyrite oxidation in a 300 litre laboratory pilot tank using the Thiobacillus ferro oxidans bacteria, showed that hydrofoil impellers had superior characteristics to the VFBT impeller and to air-agitated pachucas, with lower energy input. The geometry of the air sparge ring was found to be very important in optimizing the system. These early successes resulted in a prototype impeller and sparge ring beinq tested in a 9m3 tank where oxygen uptake in water, impeller cavitation at different impeller speeds and air flows were evaluated. Resulting from this work was the supply of an agitator unit to an operating bacterial oxidation plant where it has been successfully evaluated. This paper describes the development work so far carried out

Jan 1, 1992

By J. A. Eisele, G. E. McClelland, M. D. Wroblewski

The Bureau of Mines is conducting research at its Reno Research Center to develop a staged agglomeration-heap leaching system and to electrowin the dissolved precious metals from the pregnant leaching solution. For direct electro- winning to be successful, the pregnant solutions generated during the Initial stages of leaching must be higher grade than obtained by conventional heap leaching. The precious metal concentration of the pregnant solution can be Increased by agglomeration pretreatment with cyanide solution which starts the leaching process during the curing period, by leaching with small volumes of solution and by cycling the leaching solution through more than one heap in a staged manner. The resulting pregnant solution is passed directly through an electrowinning circuit. The barren solution from electrowinning is recycled to the leaching circuit. Bench-scale research on the development of the staged leaching system and on the development of an efficient electrowinning cell are described. The Bureau of Mines developed agglomeration- heap leaching technology. This technology was readily adopted by the mining Industry for heap leaching crushed ores and mine wastes. Current research involves the application of this technology to finely ground feed materials such as precious metal-bearing milled tailings. Tailings agglomeration-heap leaching has also been used commercially.

Jan 1, 1984

By Richard Hogg, Erol Kaya, Jan M. Mutmansky

Characterization of the size, shape, chemical composition, and mineralogical content of mine airborne dusts generally requires a larger mass of dust particles than is typically collected using traditional sampling devices. In this paper, the general design of a passive dust collector is described and the field results are presented. The collector was constructed of galvanized sheet metal duct with a resin-coated honeycomb to provide an elutriation-type system for particle collection. Several versions of the collector were used in the field portions of the research. The dust samples collected from underground coal mines were found to possess angular particle shapes, relatively consistent size distributions, and elemental compositions that showed relatively little variation, at least for the more prevalent elements. In addition, the distributions of particles sizes obtained from the passive dust collector appear to be similar to those of samples collected at the same time in a conventional personal sampler except that the passive device seems to collect a larger quantity of coarse, non- respirable particles. Conclusions on the suitability of this dust collector for collecting characterization samples are presented. In addition, the potential for using such a dust collection system for supplying dusts for biomedical research is discussed.

Jan 1, 1993

By Lindsay Norman

To many who for years have scrutinized the US mineral supply picture, recent, often strident debate on present-day security of many critical mineral supplies echoes sentiments repeatedly expressed in the past decade by the minerals industry. At no time since the last world war has such a flurry of public concern been expressed for the economy&apos;s mineral sector. Where once mineral availability problems were relegated to the newspaper&apos;s business section or not reported at all, today comprehensive analyses of our international mineral posture are discussed in detail by some of the nation&apos;s most respected and widely read periodicals. In past years, disinterest was also experienced whenever the mining industry attempted to carry its message to Congress, the public, and the government&apos;s executive branch. Among minerals professionals, the past decade was a time of particular frustration clue to serious erosion ill US ability to competitively produce the vast array of raw materials vital to the economy acid national defense. Fervent calls for immediate attention were simply not answered. These professionals have understood that mining and agriculture are the primary sources of wealth, fulfilling virtually all needs and creating and sustaining jobs. Why then has it been so difficult to raise the consciousness of the American public, and even more surprisingly, of the government and national leadership? The answer to this question is perhaps endemic to how government functions, but pore important, it begs that mining professionals capitalize on the opportunity and the attention now at hand. Carefully conceived and implemented actions by both private and public sectors are needed more than ever before in the past 35 years. To this end, it is vitally important to seek out and resolve the root causes of supply problems and not dwell on superficial solutions. The following discussion attempts to establish a simple framework to view this process. It does not presume to be an exposition of cause and effect, but hopefully identifies some needed steps. Growing Awareness in the 1970s Of all events stimulating current concern, certainly the OPEC oil embargo has left the deepest impression. It was inevitable that after such a shock, man. Americans would begin asking whether the US was as vulnerable to cutoffs of minerals as it was to oil cutoffs. Then, when serious trade security questions surfaced in sonic mineral-rich nations in Africa and the Persian Gulf, the ominous term &apos;&apos;resource war" began to be heard. Countries such as South Africa, Zaire, Zambia, and Zimbabwe have suddenly become key areas for testing our national security resolve. As the US witnesses the influx of Marxist influence in many sub-Saharan exporting nations and the rising threat to free world access to critical materials and energy, the assurance of adequate supplies is becoming a national issue at last. The US is now learning that self-sufficiency for many vitally important mineral commodities has vanished. Of course, it did not vanish overnight; it had been leaking away for years, and the trend was noted by industry and a few in government. Within the minerals community, suspected weaknesses in America&apos;s resource posture were sought and found. As a result, the country&apos;s heavy reliance on foreign sources fur more than a score of minerals, many extremely vital to security, has been forcefully documented and the case for drastically altering the supply unbalance hits been proposed. The renewed concern for national defense is central to almost all proposals for minimizing US foreign mineral dependence. It is not surprising that many of the voices heard today on the dependency issue are active members or alumni of the militate establishment. Unfortunately, their almost total focus on the security aspects of dependency has tended to obscure important underlying issues which are not directly defense-related. Some of the proposals advanced might mitigate the deeps-dency problems, but they still fall short of curing the underlying problems that have led to a steady loss in mineral self-sufficiency. In almost all instances these problems call be traced to increasing government influence on the free market minerals economy. Some national security proponents seek to attain total self-sufficiency in minerals. Such arguments must he tempered by existing realities. It is easy to demonstrate that the US obtains substantial quantities of sonic essential minerals from potentially insecure sources abroad. That the US will continue to do so in the foreseeable future is not in doubt Uncertainty begins, however, when we try to interpret the significance of these facts. It is important to understand that mineral dependency does not irrevocably lead to vulnerability. Unlike oil, no mineral commodity combines the same degree of universal indispensibility and centralized foreign control of supplies. Moreover, although many US-required minerals are produced by fewer countries than export oil, those minerals cannot approach petroleum in economic or industrial importance. Finally, most foreign supplies come front friendly, secure nations such as Canada, &apos;Mexico, and Brazil. This, aid more, constitutes a vital element in US economic health as a world trading nation. The Cost of Interruption The US is currently stronger and more resilient than many expected after absorbing the oil embargo shock and subsequent price increases. Nevertheless, major worldwide

Jan 6, 1981

By Ian Hutchison, Michael C. Salmon

TRC'S INNOVATIVE EXIT STRATEGIES™ FOR MINE CLOSURE , MINE "EXIT STRATEGIES™", WHAT IS AN EXIT STRATEGY™?

Jan 1, 1998

By F. H. Muge

The problem of how to handle heterogeneous populations in an ore reserve global estimation arises in many geostatistical studies. In some cases it is possible to split data into different significant types of ore in such way that non-overlapping subpopulations are obtained, and a separate study is possible. In other cases the subpopulations are intermingled and a set of nested structures may model the spatial variability of the ore. Finally, one of the populations, consisting of a small proportion of high grade values of economical meaning, may disturb the structural analysis. In this paper, some methods are proposed to cope with these kind of problems and typical case studies are presented.

Jan 1, 1986

By William R. Bond, Jim V. Rouse, Laura L. Damon

As noted by Damon (1990), "The time that a heap (of gold ore) is on the reusable leach pad is of critical economic importance." The Interim Neutralization Study, conducted by Brohm Mining Corporation (Brohm), at the request of the South Dakota Department of Water and Natural Resources and reported by Damon indicated that improvements could be made in leaching and pointed out the need for a better understanding of the gold ore leach procedures. To provide data on an actual heap, personnel from Brohm and GEOCHEM installed a series of pressure/vacuum lysimeters in an active Brohm heap, and conducted subsequent testwork to evaluate the efficiency of leaching. The objectives of the testwork included efforts to:

Jan 1, 1992

By K. Komnitsas

This paper presents the main environmental assessment techniques and indicators that can be used a) for the establishment of a sustainable development framework and b) for the evaluation of the environmental performance within the mining sector. Reference is made to techniques as environmental risk and impact assessment, life cycle assessment, cost benefit analysis and best practical environmental option assessment that can be used as tools to assess environmental impacts of processes, activities and products in the mining sector. In addition, the issue of environmental indicators, covering operational, management and environmental areas, that provide valuable information regarding both the environmental performance of a mining company and its efforts to influence this performance towards sustainability is discussed.

Jan 1, 2003

By D. Royston, D. Denlay

Pulp lifters are used to discharge ground pulp from non-overflow grinding mills. In straight-radial channel pulp lifters, discharge is often incomplete and back-flow down the pulp lifter can occur. Leading-curve channel pulp lifters can be used to ensure complete discharge, especially at high mill rotational speeds. The complex motion of solid materials in pulp lifters has been modelled mathematically for both straight-radial and curved pulp lifters in order to make comparisons between the two types. The model is supported by practical observations of the performance of curved pulp-lifters in a commercial 24ftSAG Mill as well as observations of the discharge from several commercial straight-radial pulp-lifter AG/SAG Mills.

Jan 1, 1999

By M. Stoica

Bioremediation is a complex process which involves mass transfer, chemical and biochemical phenomena. In particular, the adsorption kinetics of a substance by biomass may by model by taking into account: - Enzymatic kinetics type; - Combined kinetics - enzymatic kinetics at the same time with the Monod type biomass growth; - Chemical kinetics for substance adsorption according to Freundlich and Langmuir ad-sorption isotherms; - New empirical kinetics models based on experimental data. In this paper modelling of kinetics of bivalent lead ions on live vegetal biomass (aquatic plant Pistia stratiotes) as well as of hydrocarbons on dead vegetal biomass (pyrolysed nuts) is studied (Stoica, 2004). Modelling was carried out using experimental data and relative equations with an error of 5%.

Jan 1, 2006

By E. Varouchakis

Spartan Spatial Random Fields (SSRF?s) provide a new geostatistical framework (Hristopulos, 2003) with applications targeting environmental risk assessment and natural resources estimation. SSRF?s have the ability to incorporate constraints based on physical laws in the statistical description and have proved to be computationally fast in the analysis of synthetic data sets. This paper presents an application of a specific SSRF model and a new local-error spatial estimator (Hristopulos, 2005) in the mapping of environmental pollutants using a real data set. A detailed comparison of the local SSRF estimator with a classical kriging method is presented. It is shown that the SSRF approach provides a competitive alternative for spatial estimation.

Jan 1, 2005

By R. Gehauf

Magnetic separation using rare earth rolls (RER) and rare earth drums (RED) have seem tremendous development and use in recent years. While the process of magnetic separation is understood, the principles affecting the separation, the specific application and the optimization of RERs and REDs are less well known. This paper offers practical insight into the basic operation, selection and optimization of RERs and REDs. It is a guide for the engineer who must design a test series and select the proper equipment for that application. It provides the engineers and line operators who control the daily operation of the equipment a basic understanding of the dynamics of operation and the principles that govern the optimization of RERs and REDs.

Jan 1, 2004

By Werner Hofmann

INTRODUCTION The attempt to interprete lung cancer incidence caused by inhaled radon decay products in items of radiation dose raises the question of the relevant dose. The various dosimetric approaches published by now are characterized by an increasing complexity in the structure of the models used. Ranging from organ doses to microdosimetric specific energy distributions in the cells at risk, a significant trend from the macroscopic to the microscopic scale can be observed. Since tumors originate preferentially in the basal cells of the lobar and segmental bronchial epithelium, these cells are regarded as the critical target for inhalation carcinogenesis. The evaluation of basal cell doses is, therefore, the main objective of lung dose assessments. Various dosimetric models have been published in the past (Altshuler, Nelson and Kuschner, 1964; Haque and Collinson, 1967; Harley and Pasternack, 1972; Hofmann, Steinhäusler and Pohl, 1979, 1980; Jacobi, 1964; Jacobi and Eisfeld, 1980; James , Greenhalge and Birchall, 1980). Due to incertainties of physical and biological parameters involved and the application of different anatomical and physiological models the claculated doses are varying up to one order of mangitude. Independent of the choice of these dosimetric models applied to the calculation of lung doses, deposition, clearance and resulting dose are affected essentially by the properties of the inhaled aerosol as well as by personal characteristics. Both the properties of the exposed individual as well as of the inhaled environmental atmosphere have to be considered in radiation protection. It is the main objective of this paper to illustrate the influence of both parameter sets on basal cell doses by varying the above parameters. PERSONAL CHARACTERISTICS Though it might be more convenient for radiation protection calculations, the biological "man" cannot be represented by a uniform standard man. In Tab. 1 these personal characteristics which cause the variability of man are listed together with the region of their effectiveness. In the following the influence of these parameters will be discussed with regard to lung dose assessments. Besides these factors the great biological variability of all anatomical and physiological parameters involved as well as pathological alterations due to lung diseases cause additional variations in lung dosimetry. [ ] Age Age can be considered as the most important personal factor influencing the anatomical structure of the lung between birth and about 15 years of life. This period is characterized not only by an enlargement of already existing respiratory units but also by structural changes. Besides these anatomical alterations deposition is strongly dependent also on respiration parameters, such as tidal volume (TV) and respiratory frequency (RF). Whereas RF decreases with progressing age in an exponential manner, TV increases significantly resulting finally in a growth of the respiratory minute volume (RMV). Also mucus clearance in the infant might be more effective than in the adult, though no reliable experimental data are available. Superposing all these age-dependent changes mean basal cell doses are higher for children by about a factor of 2 than for adults living in the same radioactive environment (Hofmann, 1981). In the adult the following alterations of respiration standards with age are reported: total lung capacity diminishes with age, functional residual capacity is unchanged or increases with age and the dead space rises slightly with age (ICRP, 1975). The influence of these lung capacities on deposition, however, can be regarded as insignificant. Due to the ageing process mucus velocities my be considerably smaller in older people. This effect can also be superposed by the simultaneous influence of ciliatoxic effects of cigarette smoke and air pollutants or other bronchial diseases. Since the lower age limit for occupational exposure is about 18 years, age can be disregarded in the uranium mining industry for the determination of radiation doses, though lung cancer induction is significantly dependent on age.

Jan 1, 1981

By Paul L. Russell

Numbers, arithmetic, mathematics. Where did it all come from? Who needs it? We all do, but many school children would not agree. Engineers, physicists, accountants, tax collectors, and most of the general public are well aware that modern society in large part is founded on mathematics and could not exist without it. Mathematics developed over thousands of years as part of the everyday life of man. No one area, tribe, or race can claim discovery. In fact, from the records that do exist, it is evident that many facets of mathematics were discovered independently of others who made similar discoveries. While proof may be lacking, the earliest concepts of mathematics may be some 250,000 to 300,000 years old. The first use of numbers as written records is unknown. However, a bone of a young wolf deeply cut with 55 notches-arranged in two rows, one of 25 notches, the other of 30-was found in Czechoslovakia. Dated to be about 30,000 years old, it is perhaps an early record of some kind of counting system. It is assumed that mathematics was developed as an answer to man&apos;s practical needs, but anthropological studies suggest that the art of counting may have developed in connection with the needs of primitive religious ceremonial rites. Fingers probably were first used to designate sets of from one to five objects. Using both hands, up to 10 items could be indicated. As civilization developed, so did the need for more flexible systems to record items of trade, measure land, and figure taxes. Aristotle noted that the development of the decimal system comes from the fact that most people are born with 10 fingers and 10 toes. In spite of this obvious fact many early civilizations used binary, ternary, and quinary systems while vigesimal systems (with 20 as a base) and even sexagesimal systems (with 60 as a base) were used by others. A form of writing was in use in both the Mesopotamian and Nile valleys as early as 3000 to 4500 B.C. In Mesopotamia, wedge-shaped marks were impressed upon soft clay tablets that were hardened in ovens or by the sun. Many thousands of such tablets have survived. When the tablets were finally deciphered, some were found to be records of items shipped in trade, inventories, tax accounts, and mathematics exercises for teaching. Mesopotamia is also the source of an interesting board game dating back to about 2500 B.C. Its buttonlike men and triangular dice were apparently used with squares of shell, inlaid with lapis lazuli and red sandstone. Unfortunately, rules of play were not found. In Egypt, record preservation was somewhat better. Discovery of the Rosetta Stone in 1799 eventually led to deciphering the Egyptian hieroglyphics that included a numbering system at least 5,000 years old. These records show a competence in counting and numbering. A calendar of good accuracy may have been in existence as early as 4,200 years ago. Mathematics, as practiced today, developed when the Greeks added logic and proof to arithme-

Jan 12, 1982

By John A. Kaufman, Terry D. Vandell

Recent mining regulations have increased the need for detailed engineering and environmental information pertaining to the hydrogeologic environment in mining areas. The cost of obtaining such hydrogeologic information has also increased. After mineralization of potentially economic grade ore and tonnage has been identified, and after completing preliminary mining feasibility studies (suggesting that development is merited), a second exploration phase can incorporate a simple, cost-effective baseline hydrogeologic data reconnaissance program that is limited but useful. Using exploration drill holes only, this program can provide a direct indication of where ground water is encountered. Also, reasonable estimates can be made on the relative production of water from various water-bearing strata, a composite potentiometric surface map can be prepared, and the general chemistry of the ground water can be characterized. This article outlines what typical baseline hydrogeologic data are needed and describes how it can be easily obtained during exploration drilling. Introduction Major engineering and environmental ground water parameters can be identified early in a project by using, drill hole data obtained from a mineral exploration program, designed by the mine geologist and hydrogeologist. Most importantly, data obtained in the exploration drilling program can be used to design a logical, defensible, and cost-effective baseline ground water data reconnaissance and monitor well program, which would be required for mine design and ultimately for mine permit approval. Drilling Where possible, exploration drill holes should be drilled with conventional rotary drilling equipment using air or, if necessary, water as the drilling fluid. Rotary air or water drilling generally allow good delineation of the first major saturated or water-bearing zone. If mud must be used during drilling, distinct hydrogeologic zones can still be defined, although the task may be considerably more difficult. Water Levels Static water levels can be obtained from selected exploration drill holes at specific depths while additional boreholes are drilled. Such measurements should not, however, be conducted until the hole has been developed with air (no water) and has stabilized at each of the depths to be measured. Such water-level information can be particularly useful when more than one aquifer exists. Where mine development is eminent, the hydrogeologist should install 50-100 mm (2-4 in.) diameter PVC casing in select drill holes. The PVC should be slotted, gravel packed, and properly sealed so additional hydrogeologic data can be collected for specific hydrogeologic zones at a later date. Such data could include water level information, permeability estimates based on injection and /or pumping tests, and water quality data. Where casing is not installed in drill holes, or when the drill holes are abandoned, the holes should be properly grouted and back-filled to the ground surface to prevent potential future ground water contamination. Monitoring Air Lift Water Production Estimates of the relative production from various water-bearing strata can be obtained from selected exploration drill holes. If ground water is encountered, its air lift (ground water flow) production can be measured at distinct intervals using a surface water flow measuring device, such as a portable Parshall

Jan 2, 1983

By Ammar Henchiri

INTRODUCTION A current need of the phosphate industry is the development of process technology for treatment of high carbonate content ore. About 75 to 80 percent of the world phosphate reserves (1) are associated with carbonate gangue, which is not amenable to treatment by the existing techniques. Numerous laboratory and pilot plant studies have been devoted to carbonate-phosphate separation. Different techniques were involved (washing, sieving, attrition, flotation, calcination, and leaching). For technical and economical considerations, flotation appears to be an efficient process for this problem. Separation of carbonates (calcite and dolomite) from igneous phosphate is applied in industrial plants in Brazil, Finland, and South Africa. But, for sedimentary phosphate, no industrial realization exists at this time, with the possible exception of some plants in China. The main problems with sedimentary phosphates are: • high substitution by CO3-2 and F- for P04 -3 in the apatite lattice. • larger surface area of the phosphate particles because their surface is porous and irregular. • tendency of sedimentary minerals to produce more slimes in conditioning than the crystalline minerals, hence, larger dosages of collectors are required for sedimentary minerals. Investigations reported in the literature indicate that most processes developed for sedimentary carbonate-phosphate separation involved inverse flotation of carbonates using fatty acids as collectors (2), (3) associated with phosphoric acid (4), monosodium phosphate (5), F- (6), or SiF6 -2 (7) as phosphate depressants. Later investigations, conducted by A. Henchiri and G. Baudet (8), (9), (10), (11), (12), (13) in the BRGM technology department, of phosphoric esters revealed that these reagents are selective collectors for carbonate-phosphate separation. The above investigators developed a process which used phosphoric esters to collect carbonate minerals and sulfuric acid or sodium fluorosilicate as depressants for phosphate. Extensive comparative tests for different processes on the same phosphate sample show that the process developed at BRGM is one of the most promising methods proposed for sedimentary phosphate-carbonate separation. It should be pointed out, however, that phosphoric esters make abundant froths. The handling of these excessive froths will be a problem in an industrial-scale plant. This paper outlines test work performed in order to optimize and to improve the efficiency of the flotation process on a sedimentary phosphate ore selected from the Sra Ouertane orebody. The Sra Ouertane flotation process, illustrated on Figure 1, first removes carbonate minerals by inverse flotation and then recovers phosphate as a froth product, leaving quartz as a cell product.

Jan 1, 1993