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By Wu Chao, Wang Pinglong, Meng Tingrang

This paper discusses the research results of sulphide ore properties with respects on self-heating and the assessment techniques on mine spontaneous combustion for several mines of sulphide ores in China. A group of experimental devices for testing the chemical behaviour of sulphide minerals, the geological structures, the rate of oxygen absorption, the initial self-heating temperature, and the ignition point of ore samples, etc. are also described in detail. These methods have been proved to be effective by several sulphide mines which all have the history of spontaneous combustion of sulphide ores. INTRODUCTION A fire disaster from the spontaneous combustion of sulphide ores in a mine can produce large quantities of toxic gases and heat to pollute the working environment, lead to large economic losses and loss of human life, and even compell the mine to be closed. Some mines of copper, lead, zinc, tin and iron in China are of high content of sulphur. It is of great importance to evaluate the potential of spontaneous combustion of sulphide ores before beginning to design and mine the ore deposits. At present, the mechanism of spontaneous combustion accepted commonly is that sulphide ores undergo slow oxidation on exposure to moisture air at ambient temperature, with the evolution of heat, gases and moisture. The heat generated, if not dissipated, gives rise to an increase in the temperature of the sulphide ores. As the temperature of the sulphide ores rises, the rate of oxidation increases. If this is allowed to proceed unchecked it can eventually result in the ignition of the sulphide ores. For pyrite (FeS2), it reacts with oxygen and water according to the following equations.

Jan 1, 1993

By Fred N. Kissell

Work done by Foster-Miller Associates under a Bureau of Mines research contract has developed methods to increase significantly the amount of fresh air that reaches the front of a continuous-mining machine. The emphasis was on removing methane build- ups that occur at the cutterhead. Using a full-scale plywood mockup of a coal mine working face area, the study showed that in many instances only about 20 pct of the fresh air heading towards an exhaust brattice or tubing actually gets to within 1 ft (0.3m) of the face. The key to providing more air at the face is to enhance and move forward the natural airflow pattern. This change in the natural airflow pattern can be accomplished by taking advantage of the air-moving abilities of the conventional water spray. It was discovered that if all the water sprays on the machine were realigned, then ventilation efficiencies of 70 pct or more were achieved regularly. This meant that if 9,000 cfm (4.2 m3/s) was entering the brattice, at least 6,300 cfm (3.0 m3/s) of this was reaching to within 1 ft (0.3m) of the face. This water spray realignment consists of placing a few nozzles on the side of the machine opposite the curtain and also tilting the front sprays slightly towards the curtain side. Recently, two underground tests and two additional independent laboratory tests of the water "Spray Fan" have been completed. In general, they have confirmed the performance of the Spray Fan system, but they also have provided useful information as to its difficulties and limitations.

Jan 1, 1980

By D. L. Schenk

The Navajo Mine is exclusively a multiple-seam surface coal mine located in the northwest comer of New Mexico. The property is situated entirely on the Navajo Indian Reservation. It is owned and operated by the Broken Hill Propriety Co. Ltd., of Melbourne, Australia. The mine began production in January 1963 with a long-term fuel supply agreement with the Four Corners power plant. The 2175 MW nominal generating capacity of the Four Corners powerplant consumes 7.2 Mt to 7.7 Mt/a (8 million to 8.5 million stpy) of coal. The Navajo Mine has estimated reserves totaling 1 Gt (1. I billion st) of strip minable coal. Only about one-third of that total is presently committed to the generating station. As development continued over the years, mining operations advanced into more complex geologic areas to satisfy the utility's demand for coal. To optimize the committed reserve and provide competitively priced coal to the customer, the Navajo Mine began developing a new pit in June 1986. The Dixon Pit boxcut development was completed in April 1987. About 6 hm3 (7.9 million cu yd) were stripped, uncovering 929 kt (1 million st) of coal. Strip ratio was 7.74:1 including 36.8% rehandle of prime yardage. This case study of the fourth production cut highlights a variety of dragline stripping techniques including highwall bench (overburden) side cast, intermediate highwall bench (parting-interburden) side cast and spoilside bench (partings-interburden) stripping methods. The Dixon Pit offers considerable challenges in the surface recovery of up to seven seams of coal within the 1432 m (4700 ft) of total pit length.

Jan 1, 1990

By T. J. Lyman, M. J. Robison, W. A. Ruemmele

INTRODUCTION The first phase of the Los Angeles Metro Rail Project consists of 7.1 km (4.4 miles) of subway and stations running through downtown Los Angeles from Union Station to MacArthur Park. Contract A171, the Wilshire/Alvarado Line, involves tunnel construction beneath 7th/Street from the 7th/Flower Station to the Wilshire/Alvarado Station. The project consists of the excavation and lininig of 3000 m (9900 ft) of twin-bore, 6.7 m (22 ft) excavated diameter, 5.5 m (18 ft) finished diameter subway tunnels. The location of the project is shown in Figure 1. The majority of the excavation passed through weak siltstone/ claystone bedrock; although, portions of each tunnel approaching the 7th/Flower Station passed through fine-grained alluvium. Both tunnels were excavated with a digger shield. The project also included the excavation and lining of 6 cross passages, 2 communication rooms and a sump, all at tunnel grade between the two bores. A program of geotechnical instrumentation and building monitoring was performed to detect and document the response of the ground and adjacent structures and facilities to tunnel excavation. The instrumentation program was also intended to provide information that would permit implementation of remedial measures, when and as required, to prevent damage to structures, facilities and utilities along the tunnel alignment. The purpose of this paper is to discuss the ground response to tunneling on Los Angeles Metro Rail Contract A171. This paper presents a description of the tunnel project, the excavation and support method used in construction, the subsurface geology, and

Jan 1, 1989

By G. Bloomsburg, R. E. Williams, S. D. Vincent

A modeling scheme is developed to simulate the hydrogeologic effects of mine design and development in unsaturated rock. Simulations are conducted using the UNSAT2 finite element computer program and hydrogeologic data from the site of a proposed mined-out waste repository at Yucca Mountain, NV. Results of the simulations are analyzed for: •variations in the direction of ground water flow and in the distribution of pressure head caused by the design of the mined out openings; and •mine design variables that affect the predicted rates of mine water inflow. Evaluating the hydrogeologic impacts of mine design and mine development in unsaturated rock is significant in several respects. Characterization of the preemplacement of wastes along the fastest path ground water flow system at the Yucca Mountain site has been a primary research effort. Ultimately, however, the degree to which waste isolation is achieved will depend largely on the post-mining hydrogeologic environment as altered by the mine design and on the radionuclide inventory and resulting heat effects of the repository. Therefore, an ongoing characterization of the proposed mined-out nuclear waste repository at Yucca Mountain, NV, is recommended. Modeling results indicate that: •mined out openings will affect the movement of ground water, both in rate and direction; •hydraulic effects of mine development depend on the hydrogeologic environment and on mine design geometry; •mine water inflow is possible in the unsaturated zone, even for mines developed in hydrogeologically homogeneous rocks; and •mine water inflow can occur at values of down ward flux that are appreciably less than the saturated hydraulic conductivity of the overlying rocks.

Jan 1, 1991

By Jeong-Heum Kim, Jan M. Mutmansky, Y. J. Wang

The simulation of randomness in a system of components is important in certain types of systems analyses. This paper presents procedures for generating ventilation networks that are random in many of their characteristics and which can be used to study the performance characteristics of various mine ventilation network analysis procedures without introducing undue bias as a result of the nature of the network. Among the parameters of a network that affect the efficiency of a network analysis procedure are: (1) the interconnection pattern of airways, (2) the distribution of resistances in the network, (3) the number and location of fans, (4) the fan characteristic curve, (5) the size of the network (number of branches), and (6) the density of the network (number of nodes compared with the number of branches). In the procedures proposed here, a single fan with a fixed characteristic is used to simplify the problem and eliminate the fan as a source of variation. The resistances of the airways, the pattern of interconnection of the airways, and the fan location are randomly chosen in an attempt to eliminate the bias in the performance characteristics of the network analysis methods caused by these parameters. A method of generating biconnected networks while keeping the "randomness" of these other parameters is suggested. At the same time, the size and the density of networks are controlled to investigate their impacts on the performances of the network analysis procedures. The combination of these two variables has been termed the "level of complexity" of the network in this paper. Finally, a summary and conclusions section outlines some characteristics of the networks generated, using the random generation procedures outlined in the paper.

Jan 1, 1991

By Alexander N. Winchell

"The waters of Lake Superior flow into those of Lake Huron through the St. Mary's river. The rapids in this river are about half a mile wide and three-quarters of a mile long, in which distance the fall amounts to about twenty feet. Since this was the only obstacle to navigation between the west end of Lake Superior and ports on any of the other Great Lakes except Ontario, attempts were made many years ago to permit the passage of small boats from Lake Huron to Lake Superior by means of canals and locks. The first canal was built on the Canadian side of the river by the Northwest Fur Company in 1797-98. The lock was 38 feet long, 8 feet 9 inches wide and had a lift of 9 feet. A tow path was made along the shores for oxen to track the bateaux and canoes through the upper part of the rapids., The lock was destroyed during the war of 1812 by United States troops from Mackinac Island.The first ship canal, known as the State Canal, was built on the American side of the river in 1853-55, about 750,000 acres of land in Michigan having been granted by congress to a private company as a 'concession for its construction. This canal was more than a mile long, 65 feet wide at the bottom and 100 feet wide at the water's surface. It had two locks, each 350 feet long by 70 feet wide, with a lift of about 9 feet. The depth of water in the canal was about 13 feet and in the locks about 11 1/2 feet."

Jan 1, 1920

By C. F. Kaiser

The Broken Hill proprietary company Limited grate kiln pellet plant (1) located at Whyalla in South Australia commenced production on May 13, 1968. During commissioning, about 25,000 long tons of fluxed pellets were produced. Plant performance was satisfactory and acceptable under the plant guarantee. For production reasons, it was necessary to curtail the fluxed pellet run and revert to the production of acid pellets. In 1970, some 250,000 long tons of fluxed pellets were produced under varying operating conditions to determine the requirements for optimum quality pellets at acceptable production rates. In excess of 180,000 long tons of these fluxed pellets were exported to Japan. Problems experienced in production of the fluxed pellets are detailed, and the quality of the fluxed pellets compared to that of normal acid pellets produced at Whyalla. Brief Plant Details Run of mine ore treated was predominantly soft and friable and contained an average of 66 per cent Fe, 1.7 per cent Si02 and 1.8 per cent Al203. The main iron mineral in the ore was hematite with some martite also present. Plant feed was ground dry in ball mills 11 ft in diameter by 29 ft long to a Blaine surface area of 1600 sq.cm/g and the ground ore was wetted in a pug mill. Balling was carried out in balling drums 10 ft in diameter by 32 ft long. Induration equipment included an eighteen windbox grate 12 ft 2 in. wide by 164 ft 1 in. long, a rotary kiln 18 ft 6 in. diameter by 118 ft 8 in. long and an annular cooler 50 ft mean diameter by 7 it wide.

Jan 1, 1972

By Thomas F. Martin, Daniel J. Sieve

In April 1988, the joint venture of Morrison-Knudsen and Paschen Contractors (M-K/P) was the successful low bidder for the Metropolitan Water Reclamation District of Greater Chicago's (MWRD) Contract Number 73-164-2H. This project is yet another in the MWRD Tunnel and Reservoir Plan (TARP) devised to control and treat overflows from combined sanitary and stormwater flows. M-K/P's project, located along the Des Plaines River, consists of 21,569' of tunnel mined to a 35' diameter and two tunnels totaling 14,529' mined to a 12' diameter. All three tunnels will have 12" thick reinforced concrete lining. The path for combined sewer/storm waters to reach the tunnels begins at a connection structure, continues through an approach sewer, a sluice gate structure and down a vertical shaft which is topped by a backflow structure. The purpose of the backflow structure is to prevent water surging to the surface as the system fills rapidly. Backflow preventors represent a change in design after problems developed on earlier constructed portions of the T.A.R.P.. On this project, 14 drop shafts channel flows to the tunnel system. In addition to the drop shafts, contract specifications require an emergency or escape shaft be located not more than 4000 feet from the tunnel headings. Due to long reaches without drop shafts, four access shafts had to be constructed. Thus, the total shafts constructed under this contract will be eighteen plus one 30' finished diameter construction shaft located within Miller's Meadows. Figure 1 shows the overall Des Plaines River System and the M-K/P contract connection to previous and future MWRD projects.

Jan 1, 1991

By G. Wayne Clough

During shallow tunneling in an urban environment, deposits or pockets of saturated soil or fractured, weathered rock are often encountered. Under such conditions, special problems with tunnel support, underpinning of structures adjacent to the tunneling, and/or flow of groundwater into the tunnel occur. If the ground conditions are appropriate, i.e., the soil is sandy, silty or fissured, or the rock is weathered or fractured, the solution to these tunneling problems may be chemical stabilization of the ground. Injection stabilization as an aid to tunneling is practiced extensively in Europe and its use is increasing in the U.S. The advantages of this technique over conventional solutions can be substantial in terms of cost and time, especially in mechanized tunnel boring where even a small zone of soft ground can bring the tunneling to a complete halt. In this paper European practice in using chemical ground stabilization for urban tunneling will be reviewed. In contrast to previous papers which have dealt with specific applications (1,5,8,9) this paper will broadly cover the subject, addressing itself to grouting techniques, costs, the reasons for grouting, philosophy of the users towards grouting, design of grouting solutions (or lack thereof) and methods of quality control. Differences with U.S. grouting practice are also noted. The information presented is derived from several visits to Europe, discussions with European and U.S. grouting personnel, and the available literature (2). The author's most recent European trip was made under the auspices of the U.S. Department of Transportation in conjunction with a research study being performed at Stanford University; a detailed report of this visit is available in reference (6).

Jan 1, 1976

The most important event affecting the United States coal industry in 1993 was the strike by the United Mine Workers of America (UMWA). This was a series of selective strikes, beginning with a strike against four Peabody Holding affiliates on Feb. 2, following unsuccessful contract negotiations between the UMWA and the Bituminous Coal Operators' Association (BCOA). Although that strike ended on March 3, the failure to reach a new contract agreement led to walkouts at several Midwestern mines on May 10. During the summer, the strike expanded to include mines of 13 companies in seven states including Ohio, Pennsylvania, Illinois, Indiana, Kentucky, Virginia and West Virginia. About 17,000 miners were idled during the strike. As the prospects for a settlement diminished, the Secretary of Labor appointed a federal mediator. The mediation resulted in a five-year contract. In addition to increases in wages and pensions, it was agreed that 60% of new job openings would be filled by laid off and active UMWA miners. In return, companies won the right to establish more flexible work rules and scheduling of miners. While some health care benefits were expanded, the agreement established a new health care system that was designed to reduce costs. Preliminary Energy Information Administration (EIA) data indicate that US coal production fell by 5% in 1993, to 859 Mt (947 million st) (Table 1). The strike was one of the primary causes of the decline in production. Another significant cause was a 27% decline in coal exports. Also, a very small displacement of domestic coal production resulted from a rise in coal imports.

Jan 1, 1994

By Ronald E. Heuer

The significance of surface settlement over soft ground tunnels is well recognized. Cracked buildings, streets transformed into lakes, broken utility lines, to underpin or not to underpin--all are familiar problems. The basic causes of surface settlement are recognized. Possibly the most common and troublesome cause is "lost ground" during construction. Lost ground refers to removal of a larger volume of ground (Ve) than is eventually occupied by the final tunnel structure (Vt). A number of sources of lost ground in shield tunneling have been identified, as illustrated in Fig. 1. These include 1) face loss, 2) overcutting loss, 3) annular tail void loss, and 4) loss through the lining. The ground generally does not stand unsupported around the completed tunnel lining as illustrated in Fig. 1, but moves in to fill the lost volume, resulting in subsidence of the overlying ground surface as shown. As suggested in Fig. 1, lost ground and surface settlement associated with overcutting and the annular tail void tend to occur systematically along the tunnel length. This "systematic" lost volume is "limited" in the sense that it is restricted to an upper limit determined by the shield and lining geometry. Partially controlled face loss may sometimes contribute to this systematic loss. This lost volume is commonly a few percent of the nominal tunnel volume. The resulting surface settlement over the tunnel is commonly in the range of a few inches or less and develops over a period of hours to days. Although they may have a significant impact on surface facilities, systematic ground loss and settlement frequently have little adverse effect on tunneling progress.

Jan 1, 1976

By Dewey W. Geary

Nast Tunnel is the first granitic rock tunnel to be excavated by a machine for the U. S. Bureau of Reclamation. The machine has excavated 7500 ft of the tunnel at this writing. There have been a few good performances; 31 ft in 1, 8 hr shift, and 75 ft in a 24 hr period, but generally, progress has been slower than that accomplished in the area with reasonable comparable conditions using conventional excavation techniques. Button cutters, now employed using compression as the means of fracturing the rock, gives an average cutting rate of 3 ft per hr. Disc cutters manufactured by the machine builders were tried briefly but the snap rings holding the discs to the hub failed. However, disc cutting rates of 6 ft per hr were recorded for short periods of time in a competent coarse grained porphyritic granite. The snuck was also considerably larger and more easily handled than that produced by the button cutters. Hughes Tool Co. is working on a disc type cutter and expects to have them on the cutterhead by mid June. LOCATION, DESCRIPTION AND BID OPENING Nast Tunnel is located 2 miles west of the Continental Divide and 39 miles east of the town of Basalt in Pitkin County, Colorado. The outlet portal is in the Fryingpan River Valley at an elevation of 10,000 ft. The tunnel is a 3 mile long, 10 ft diameter gravity flow water conveyance structure and a part of the west slope water collection for the Bureau of Reclamation, Fryingpan-Arkansas Project. The bids were opened July 9, 1970, with 8 contractors submitting proposals. The contractors were given the opportunity to bid

Jan 1, 1997

By Karl H. Bruemmer

1. TRENDS OF DEVELOPMENT IN THE MECHANICAL DRIVING OF UNDERGROUND EXCAVATIONS IN THE GERMAN COAL MINING INDUSTRY The demand for higher advance in underground excavations led, in the past ten years, to the development and application of various mechanical methods in the coal mining industry of the Federal Republic of Germany. Hence, a modern mine cannot operate anymore without tunneling machines for the driving of horizontal and inclined roads and shaft boring machines for the sinking of shafts. In future, boring operations will assume a high positional value in the mining industry, as the development of cutters has kept pace with the development of machines. In the past ten years, about 40 km of roadways have been bored by tunneling machines in the German coal mining industry, further 140 km will be bored by 1990, part of which are already under contract. The idea was tempting to apply the technology of horizontal tunnel borers also to the sinking of vertical shafts. The underground contractors Deilmann-Haniel GmbH of Dortmund and Thyssen Schachtbau GmbH of Mülheim/Ruhr developed already in 1970, together with Wirth of Erkelenz, a shaft boring machine working without drill pipes, capable of sinking shafts following a pilot borehole, according to the downward reaming method (Fig. 1). In the meantime, two such shaft borers are operating in coal mines with diameters of 4.50 m to 6.50 m. Recently an order was placed for a third Wirth shaft borer for diameters up to 8.50 m. Since 1971 about 3.800 m of open or blind shafts have been sunk by the reaming process (Fig. 2).

Jan 1, 1979

By J. H. Desautels

The modern coal mining industry is subject to a vast array of regulations affecting virtually all aspects of its operations. Probably the most significant over-sight role involves the Office of Surface Mining Reclamation and Enforcement (OSH) established by the Surface Mining Control and Reclamation Act, or SHCRA.1 Although complying and coping with SHCRA can be difficult for coal operators, this complex regulatory process has helped insulate the industry from ongoing efforts to extend regulation under the Resource Conservation and Recovery Act, or RCRA, 2 to aspects of the mining industry in general. The Environ-mental Protection Agency (EPA) has struggled with regulation of mining wastes under RCRA since the mid-1970's, but RCRA itself places most coal mining wastes firmly under the control of OSH and SHCRA. Despite the general exemption from RCRA regulation for waste materials that result from extraction and processing of coal itself, there may be circumstances under which coal mining operators could find themselves subject to regulation under RCRA or a number of other statutes administered by EPA. This paper will review briefly the history of mine waste regulation under RCRA, as well as touch on the policy decisions that led to the exemptions from RCRA regulation. The paper will summarize coal waste requirements under SHCRA, and also will review what operations at coal mines need to be controlled, in order to avoid potential liability under RCRA. In addition, it will mention requirements under other federal laws, including CERCLA, or the "Superfund" law,3 and describe how they may impose restrictions or liability on coal operations for waste or other materials commonly found at surface and underground coal mines.

Jan 1, 1993

By M. C. Williams

The dynamic behavior of batch mill, CSTR mill, and a closed grinding network consisting of a mill, sump, and cyclone was analyzed using the dynamic population balance model (PBM). The dynamic solution of the PBM of a batch, CSTR and a closed grinding network consisting of a mill, sump, and cyclone forms the basis of the dynamic analysis presented here. Two numerical dynamic solution approaches were used. These are: 1) providing additional constraints on breakage selection functions or 2) performing the Arbiter-Bhrany (or other) normalization of the selection functions. Actual experimental anthracite batch grinding data was used to obtain the functionality of the batch dynamic mill selection and breakage functions for a real physical system. The Levenberg-Marquardt algorithm for systems of constrained non-linear equations is used to solve the batch dynamic PBM grinding equations to obtain the grinding selection and breakage rate functions. The mill, sump and hydrocyclone were modeled as a CSTR operating at various retention times. Batch dynamic PBM data was used to provide the mill kinetic and breakage selection function data. Different dynamic solutions were obtained depending on the numerical approach used. Each solution approach to a dynamic PBM with transport, while giving the same prediction for a single batch grinding time, gives different solutions or predictions for mill composition for other grinding times. This fact makes dynamic nodal analysis and control problematic. The fact that the constraint solution approach gives a solution may suggest that normalization for closed networks is not necessary. Differences in solutions to the PBM cannot be excused away by inaccuracies in the data used to model the grinding phenomenon.

Jan 1, 1995

By Raphael G. Kazmann

The predicted warming of the earth's surface, presently the subject of much debate, controversy and legislation, is based on what is termed "the greenhouse effect." This is the result of the property of certain atmospheric gases. These gases allow the passage of radiant energy to the earth's surface and reflect back, to the earth, the infrared radiation given out by the heated surface. Physicists have computed that if there were no greenhouse effect the average temperature of the earth, now about 15° C (60T), would be close to -18° C (OT). Just what gases have produced this salubrious effect? Water vapor is the most important. Then come carbon dioxide, methane and a number of minor constituents of the atmosphere, both natural and man-made. Climate change, its cause and its impact on human activities have been the subject of scientific and historical study for more than a century. Recently, some scientists have concluded that if the man-made increase in the carbon dioxide and other greenhouse gases continues, by the late 21st century the earth's global average temperature will rise between 2° to 8° F. This temperature rise would cause the water in the oceans to expand and the massive polar glaciers to melt. In 1980, it was predicted that the sea level would rise 7.6 m (25 ft) by the late 21st century. By 1985, the predicted rise was 1 m (3 ft); and by 1989, it was 0.3 m (1 ft) (Jastrow, Nierenberg and Seitz, 1990). Agricultural scientists have pointed out that an increase in atmospheric carbon dioxide would enhance biological growth including the production of foodstuffs.

Jan 1, 1992

By Frank E. Dalton

BACKGROUND OF TARP The first settlement in Chicago in the 1830's was only 0.61 m (2 ft) above the level of Lake Michigan. The area was flat and swampy with local streams and rivers generally flowing to Lake Michigan. Repeated outbreaks of cholera and typhoid fever in the middle and late 1800's led to the reversal of the river system (away from Lake Michigan to the Mississippi River). As a result of this reversal, the Chicagoland area has had to restrict water withdrawals from Lake Michigan and has had to develop and implement water management programs in compliance with orders set down by the Supreme Court of the United States. In order to comply with restricted lake diversion requirements and to compensate for a natural setting which was essentially hostile to human habitation, it has been necessary to embark on the construction of massive public works which include the world's largest water filtration plants, the world's largest wastewater treatment plants and finally the construction of TARP. The rivers and streams in the Chicago area are the headwaters of the Illinois waterway system. These headwaters are heavily polluted from combined sewer overflows of the area. Present pollution control laws require that combined sewer overflows be eliminated so that the rivers and streams can be used by the citizens of Cook, Du Page and Will Counties and other downstream communities. Fifty-three of the older most densely populated communities including the City of Chicago, covering an area of 971 sq km (375 sq miles), are served by combined sewers. Combined sewers carry both raw sewage and stormwater. Because porous ground surfaces have been covered 1815

Jan 1, 1979

By H. S. Soto

The exact reasons that explain the low recoveries of coarse particles in conventional flotation machines are not clear. Being a concern for only a couple of mineral industries comparatively very few studies have been devoted to the problem of coarse particle flotation. Coarse particles flotation is particularly important in potash and phosphate beneficiation. Potash concentrates with particles larger than 1-2 mm do not require additional compaction or recrystallization and receive a premium price. However, recovery of this size particle in conventional flotation cells is very low, and therefore, the coarse floation tailings have to be reground and refloated to produce, at a higher cost, a less desirable concentrate. In phosphate beneficiation deslimed coarse ore (nominally l4x35 or l6x35 mesh) is normally treated separatedly from the finer (35x150 mesh) ore. Concentration by conventional froth flotation alone yields very low recoveries, and therefore, additional processes such as agglomerate flotation in tables spirals and belt conveyors have to be used ( Moudgil and Barnett 1979). Fatty acids and fuel oil used in phosphate flotation have a moderate level of selectivity but considerable amounts of sand report to the froth product, thus concentrates have to be further upgraded by a double flotation process. Concentrates from the anionic circuit are scrubbed in an acidic media to desorb the collectors and then refloated in a cationic circuit to eliminate the fine silica (Lawver et.al. 1978). In this paper the reasons that explain the low recovery of coarse particles in conventional flotation are discussed. A flotation column modified according to the main conclusions of this discussion is tested with two coarse phosphate samples.

Jan 1, 1989

By Ian S. Ross

The emphasis in this paper is focussed on dry bulk car go or the same cargo converted to slurry form for ease of handling. It is this type of cargo which is of primary interest to the mining industry whose products it represents to a large extent. The design problems associated with the handling of liquid bulk and of unitized cargo are sufficiently different to be treated separately. This paper then will consider the port handling facilities of dry bulk commodities as part of a system consisting of (1) the movement of products to the port area, (2) the movement of products out of the port area and (3) the handling of products within the port area itself. Expanding within these three components of the total transportation system, the paper will discuss the various difficulties encountered concerning the mode of transport into the port area and the method of handling product from transport to stockpile. Secondly, and before discussing the port area itself and in order to complete the conditions under which the port must operate, the movement of products out of the port area will be covered dealing with such items as the accommodation of the ship, problem associated with the very large ships, optimum berthing arrangements and the need to consider the various costs associated with the vessel. Finally the paper will review within the port or interface area such items as stockpiles, method of recovery, inventory control and an outline of the common design difficulties encountered. In all cases the relative influence on the total transportation costs of each of these dry bulk transportation system components will be considered.

Jan 1, 1972