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By Dickinson C.

Discussion at the The Midland Counties Institution of Engineers' general meeting held in Nottingham on 6th May 1916, on the paper published in Trans. I.Min.E., vol.XLVIII, 1914, p.400, included brief oral contributions by Bragge G.S. and Hepplewhite W.H. with the author's responses regarding leakage and boring of cement into the coal

Dec 1, 1916

By John Freer

As an innovation on the annual programme, the Excursions Sub-Committee organized a social get together of the Institute's Councillors and their families on Sunday, 27th February, 1983. Asian Mining - change of date The Second Asian Mining Conference, previously announced as being held in Manila, The Philippines, from 5th to 8th November, 1984, will now be held in Manila from 11th to 14th February, 1985.

Jan 1, 1983

By J. E. Wennen

Screens serve several important functions in CIL and CIP processes for gold extraction. One important screen application known as interstage screening allows slurry to be continuously transfered through a series of CIL or CIP tanks while retaining activated carbon in the tank. In some cases, this has been accomplished by using airlifts to carry slurry containing activated carbon to an external screen which separates carbon as oversize and returns it to the tank by gravity. The undersize slurry advances to the subsequent tank. More recently this has been accomplished using launder screens and Kambalda type screens. These are essentially static screens that rely on air blasts or mechanical sweepers to clear carbon away from the screen surfaces.

Jan 1, 1998

By Jim Johnson

The purpose of this paper is to summarize and discuss a variety of site specific conditions which are typically evaluated as part of the engineering design process for heap leach pads, solution control ponds, and associated facilities. The following sections will focus primarily on the topographic, climatologic, hydrologic, and geotechnical evaluations critical to selection of heap leach sites, and selection of a preferred heap leach configuration or method. Other important considerations in the design of a heap leach project, including evaluation of ore properties and leachability, pregnant solution processing requirements, spent ore neutralization/disposal requirements, and other anticipated reclamation requirements are beyond the scope of this paper are not addressed in any detail.

Jan 1, 1998

By Dale Brunton, Robert Adams, Michael Dutton

Tunnels and other underground structures are typically designed using ground-structure interaction models instead of traditional structural analysis programs. This allows for the degree of load sharing etween the two odies to e calculated allowing for a more efcient design. hile modern codes outline the use of limit states with factors on applied actions, limit states are not typically compatible with ground-structure interaction models. Consequently, the engineer is left to develop rational methods for incorporating load factors into their analyses. Several methods can be considered, including the Largest Factor Method, Averaging Method, Subtraction Method, and Split Factor Method. This paper discusses the approaches, compares their effects using a case example, and provides a recommendation for designers.

Jun 23, 2024

By A. B. Hooker, L. C. IlsLey

Several ignitions or mine pa, which might have led to explosions, and at least ona mine fire attributed to heated leg wires of electric detonators, have occm.rred. at rn1::.es in which outside shot firing is practiced. Photographs taken at one mine ind.la.ted. that the wires became red hot during firing. These results having been --i·-led. to the .Lttention of the electrical section of the Bureau of the Mines, ignitions the tests and to reportd aid in herein preventing were made future to trouble determine of if this possible kind, the cause of The investigation, which 1• considered preliminary, included tests to determine the conditions tha.t cause gas ignitions from heated. leg wires of electric and. of detonators, copper leg possible wires, remedies The tor samples such of heating, wire used. and in the the relative test were behavior the of reg\llar ironDa. Pont iron and copper leg wires (No, 22 A,W,G.) C\1t from Du. Pont electric detonators.

Aug 1, 1922

By W. Kemp Wait

Electronic ore sorting is a coarse particle beneliciating process which performs a function which in the past was primarily achieved through the use of hand picking belts. Photometric ore sorting is capable of separating waste from mineral bearing rock having a distinct difference in surface light reflectance levels. This type of ore sorter can be applied to gold and silver ores which are contained in quartz veining. Photometric ore sorting has been used at gold mines in South Africa as well as the Black Pinc silver mine in Montana. A new ore sorter has recently been developed with precious metal ores in mind. This ore sorter is capable of sorting ores on both photometric and conductivity sensing parameters. The first production machine has been installed at a gold mine near Beardmore, Ontario and currently is being used to process low grade waste dumps.

Jan 1, 1998

By Fabian Laumen, Sunny Schoone, Felix Leaman, ELISABETH CLAUSEN

The paper evaluates the attenuation behavior of acoustic emission (AE) signals in four different materials used in marine environments. The study aims to identify materials with the highest and lowest AE signal attenuation, providing insights into wave propagation and structural monitoring in deep-sea mining applications.

Dec 1, 2023

Prof. Henry M. Howe, New York, N. Y. (communication to the Secretary*):—The results presented in Mr. Mathewson's paper are of very great interest. Perhaps the most interesting is that shown in Table I. and Fig. 1, in which the arsenic decreases in 10 min. from 0.22 to 0.07 per cent. This is such a large decrease that it is to be hoped that Mr. Mathewson will verify it by repeating his tests with a matte of similar composition. This is particularly to be desired, because the simultaneous removal of sulphur appears to be very small. All three blows further agree in showing that the removal of arsenic is in the very early part of the blow. The fact that the removal of arsenic then ceases abruptly cannot be explained completely by the fact that the arsenic has fallen so low as by its lowness to resist further removal, because in the first blow the arsenic becomes stationary at 0.06 per cent., whereas in the third blow it does not become stationary until it has fallen to 0.034 per cent. The abrupt ending of the removal of arsenic is more likely to find its explanation in the composition of the slag, and it is to be hoped that Mr. Mathewson will supplement these extremely valuable data with others in which the composition of the slag at the same time shall be given. The sudden rise of arsenic toward the end of the third blow I suppose must be referred to an error in sampling or analysis.

Jan 1, 1908

By Connor Meinke, Shaihroz Khan, Kevin Erwin, Rajiv Chandramohan, Muhammad Usman Siddiqui

A geometallurgy study aims to link metallurgy and geology to reduce technical risk and enhance the economic performance of a mineral-processing plant. It does so by accounting for variability in a deposit to develop cash-flow models with variable throughput rates. High-quality sample selection for metallurgical test work that is representative of the deposit is an essential component of a geometallurgy study, but the large multidimensional data set makes sample selection a daunting task, as classifying the data set while respecting its heterogeneity is difficult. This paper presents a streamlined approach for sample selection, using statistical analysis techniques in Python. It cuts down time to select samples from around 1,200 s per drillhole to about 60 s for data classification and from 12 h to 8 h for handpicking samples from the classified data set, translating to cost savings. The cumulative sum method and k-means clustering method are used in the methodology to elegantly classify the data and select representative samples. The effectiveness of the methodology is demonstrated by presenting data from a prefeasibility study of a copper-iron mine in which 40 samples were selected for flotation test work.

Dec 1, 2024

By Claudia Gasparrini

"The ore microscope and electron microprobe, two common instruments for academic research, have not been used to full advantage in the Canadian mining industry, perhaps because they are not readily available to most mining companies.The present paper gives a description of the two instruments and of the manner in which, when used together, they contribute to the identification and description of mineralogical and metallurgical samples, and reviews the applications, to . date, in the mineral industry.The metallurgical applications can assist in determining the best separation technique for a particular metal or other economically important element, can provide explanations for poor recovery and/or liberation, can be used to determine theoptimum concentrate grade and can indicate environmental problems that may arise from the extraction process.In certain cases, the use of the two instruments may assist in the evaluation of new mineral deposits and in the determination of the origin of mineralization.IntroductionThe ore microscope and electron microprobe, two widely used instruments in universities and other research institutions, have not been exploited to their full potential by the Canadian mining industry.High-magnification, high-resolution ore microscopes, owned by most Canadian universities and government mining branches, are not widely used by mining organizations. The situation is very much the same with the microprobe. The geology departments of several major Canadian universities have easy access to this instrument. Fifteen of them, to the author's knowledge, own one and a few have already acquired or are planning on acquiring a second and later model. The mining branches of the Canadian Government have similar easy access to microprobes, as at least four of these instruments are available to them in Ottawa alone. The mining companies, on the other hand, except for the few larger ones which have their own research laboratories, have not been able to take advantage of electron microprobes in the past.This failure to exploit good ore microscopes and electron microprobes has been mainly due to a lack of expertise in the use of the two instruments for the study of metallurgical problems related to ore mineralogy. Government institutions providing research and test work to the industry are few in number, and are not always equipped with these instruments or are not geologically-oriented. Information provided on a consulting basis by universities and by government mining branches is normally limited, and frequently is not oriented to the needs of the mining company."

Jan 1, 1980

By R. Le Houillier, M. Nagamori, A. J. Plumpton

"Asbestos tailings are a typical serpentine, hydrated magnesium silicate, consisting primarily of antigorite and a few per cent of unrecovered fibrous chrysotile. Serpentine has unique thermal properties in that dehydroxylating calcination at 600 to 700°C can yield an amorphous structure in which most of the magnesia is liberated from the original bond with silica and thereby rendered chemically active. The amount of activated magnesia can be quantified by selective leaching with a weak acid such as acetic acid. Many wet processes have been proposed to extract magnesium values from calcined or natural serpentine by means of various acids and their ammonium salts. However, the only commercial utilization of serpentine today is found in dry processes such as the production of fused magnesium phosphate fertilizer .The present paper reviews the physical chemistry of the dehydroxylation of serpentine and also various wet and dry processes in order to provide a general view regarding the chemical transformation of asbestos tailings.IntroductionAsbestos fibers occur as chrysotile, a serpentine polymorph. More than nine tenths of mined asbestos ores consist of massive non-fibrous serpentine, primarily the polymorph antigorite, which is discarded as tailings after fiber extraction. For many decades, Quebec has been a world leader in the production of asbestos fibers. As a result, colossal tonnages of serpentine have accumulated in the Eastern Townships'!'. Serpentine minerals are found in large deposit s throughout the world, and significant research efforts have been made, particularly in Japan and the USSR, mostly in attempts to extract magnesia or silica values therefrom.The chemical composition of serpentine (chrysotile and antigorite) may be ideally expressed as Mg3Si2Os(OH). which corresponds to 43.7% MgO and 43.3% SiO2. Natural serpentines often contain a few per cent of Ni-bearing magnetite and other impurities, and therefore the contents of MgO and Si02are both about 40% or lower.Serpentine (hydrated magnesium silicate) is virtually insoluble in weak acids. However, when dehydroxylated under controlled conditions, ' it decomposes to an amorphous state in which magnesia and silica are isolated and chemically active. The magnesia so activated is readily soluble in weak acids. This unique characteristic of calcined serpentine, first discovered in 1942,, has since attracted the attention of innumerable researchers, whence many processes have been proposed."

Jan 1, 1980

By Bunting S. Crocker

EBBLE grinding at Lake Shore is not a temporary BlE wartime substitute. The tube milling plant, with a 1000 ton per day capacity, grinds a hard siliceous ore to 90 pct — 325 mesh. The plant, prior to using pebbles, was consuming 4.3 lb of 11/4-in. grinding balls per ton of ore, which amounted to 785 tons of balls per year. At September 1951 prices, $132.60 per ton, this steel cost amounted to $104,400 per year, or $0.285 per ton milled. By the Lake Shore method of substituting screened rock for this steel, all of this cost is saved. This is one of the major economies in Lake Shore mill practice. Regardless of the ultimate price of grinding balls, a change back to steel balls is not considered. The present pebble plant is more flexible than a steel ball plant and equally efficient. For example, if it is desired to change the size of grinding media, the pebble charge in any mill can be changed completely in 4 to 5 days, as against 76 days to change completely a 1-in. steel ball charge. To change pebble size it is necessary only to change two sets of screens and clean out the rock feed storage bin. This will take 8 to 10 days as against 3 to 4 months to clean out the customary supply of grinding balls kept on hand. Also it has not always been possible to purchase all desired sizes of balls at any price. In an analysis of savings effected by the use of the pebble mills, the flexibility of the Lake Shore grinding plant should be discussed, as it has a direct bearing on these savings. The plant has always used several units to handle tonnage rather than sending all the tonnage through a single unit. This principle may result in using small diameter mills, but no objection to that is seen. At no time has any advantage been found in cost per ton ground in large diameter mills. Both the capacity and the power of any mill varies as the diameter raised to the 2.6th power. Consequently large or small mills are equally efficient, and a plant, should be designed to use as many units or combination of units as is consistent with reasonable operating practice. Mills under 5 ft diam are harder to reline, etc. To define the case at Lake Shore, 2600 tons per day formerly were milled in seven 7x6-ft ball mills and twelve 5x16-ft (and two 6x16-ft) tube mills.* This gave an excellent test plant and an extremely efficient one. In this plant the ratio of ball mills to tube mills was 1:2. When the much cheaper pebble mills were substituted for the tube mills, this ratio was changed to one ball mill to four pebble mills to take the greatest possible advantage of the cheaper operating mill, i.e., the pebble mill. This flexibility without loss in efficiency has been an important item in the cost savings. It is interesting to note that the use of pebbles for fine grinding was proved first in the laboratory in a 12-in. ball mill. In fact, since 1934 all testing on — 8 mesh material has been done in this 12-in. mill. Scope of the Tests A paper on fine grinding at Lake Shore Mines was published in July 1940.' This paper covered 7 years of intensive research on fine grinding as well as sizing methods and equipment, plant scale grinding tests on 5x16-ft tube mills with and without grate discharges both with 1-in. and -in. balls, the use of laboratory mills to evaluate plant changes, and several reports on classifiers and classification. In the following July the addendum report2 was added in which the idea of series-circuit grinding was introduced, and the results of running five stages of tube mills and bowl classifiers were shown. Since 1940, the ball milling end of the plant has been altered extensively as a result of tests on the use of 3-in. rods in 7x6-ft mills and the use of the Tyler repulping screen with from 7 to 14 mesh screens. These tests are lengthy and may be covered in a separate report later. The scope of this report is confined to ore ground by rod milling and ball milling until it passed through an 8 mesh Tyler Ty-rod screen. The —8 mesh screen undersize then was pumped to a primary bowl classifier in open circuit and the sands from the bowl sent to the primary pebble mills, see Fig. 1. In the pebble mill circuit the ore is ground to 90 pct —325 mesh (24 pct + 28 microns). In studying the flowsheet, attention should be paid to the efficiency of the classification equipment used. The Tyler repulping screen is an efficient machine on the 8 to 10 mesh separation, and the bowl classifier is equally efficient at the 325 mesh separation. Efficient classification is a necessity for series-circuit stage grinding. The ore is hard siliceous porphyry, 60 pct SiO,, 80 pct insoluble. Its grindability at different meshes has been shown near the top of the list in F. C. Bond's grindability tests.' Lake Shore is not shown, but an adjacent mine with identical ore, Wright-Hargreaves, is. Reasons for the Changeover Since 1936 grinding balls have been rising steadily in price with no sign of stopping. For a mill that used 4.5 to 5.2 lb of grinding balls for every ton of ore ground this rise represented an alarming increase in grinding costs. In many cases the quality of the grinding balls fell off as the scrap steel became more difficult to obtain. The ratio of tube mills to ball mills increased with the use of the Tyler repulping screen in the ball mill circuit. Originally only 3.0 lb of balls per ton were used in the tube mills, and this

Jan 1, 1953

By W. D. Elston, A. E. McLaughlin, G. B. Hampton, W. L. Barham, J. F. Murphy, W. H. Cundiff, J. W. Mulloy, R. G. Breuer, J. W. Shaffer

Introduction Alumina (aluminum oxide) is the material from which all the world's aluminum is produced. In the Western World, all the alumina is made from bauxite by the Bayer process. In the nearly 150 years since aluminum was first isolated by Oersted, the metal has grown from a laboratory curiosity to a position of major importance in the world's commerce. In terms of annual production rates aluminum is first among nonferrous metals. Oersted's discovery-reduction of aluminum chloride with potas¬sium amalgam-was improved on by Ste. Claire Deville, whose so¬dium amalgam reduction of aluminum chloride led to the commercial production of aluminum in France in 1855. Ste. Claire Deville's method prevailed until 1886 when Charles Martin Hall and Paul T. Heroult each invented a process for the production of aluminum by the electrolysis of alumina dissolved in molten cryolite. The inven¬tion by Karl Josef Bayer in 1888 of an economical process for making very pure aluminum oxide (alumina) from bauxite established the necessary link between known ores and the Hall-Heroult reduction process. Bayer's work completed the scientific base-the ore bauxite refined to alumina by the Bayer process (U.S. Patent No. 515,895), the alumina reduced to aluminum in the Hall-Heroult cell (U.S. Patent No. 400,766--upon which today's aluminum industry is founded. Small-scale production of aluminum in the U.S. began in 1888 utilizing the Hall cell. By 1903, bauxite properties and a Bayer process refining step had been incorporated into the production activities. On this base the aluminum industry in the U.S. has grown at an annual compounded rate of 15%. Since 1946 the annual growth rate has been 10%.1 The rapid growth of the industry is the result of many factors among which are the existence of widespread bauxite ore deposits; a sound and economic production technology; and the properties of the metal-lightness, strength, ductility, good electrical and heat con¬ductivity, and pleasing appearance, which lead to ever greater de¬mands for aluminum in an industrializing society. At the inception of the industry, the only market that could be found for aluminum was in the production of cooking utensils. How¬ ever, the rapidly accelerating industrial and technological development of the Western World soon created new needs for aluminum, and today aluminum is marketed in a broad range of industrial, commer¬cial, and consumer applications. The principal uses for aluminum are:' building and construction, 22%; transportation, 18%; electrical, 13%; packaging, 11%; consumer durables, 10%; machinery and equipment, 7%; other, 19%. The 1974 production of primary alumi¬num in the world was 14.5 million short tons, which at an approximate ingot price of 40¢ per lb puts a value of $11.6 billion on the industry product prior to fabrication. While aluminum is widely distributed in the earth's crust and is a major constituent of many rocks and soils, to date no method of extraction of aluminum from such nonbauxite material has been brought to commercial practice in the Western World. In the USSR alumina is produced by the complex processing of nepheline syenite, but elsewhere all commercial production of alumina is from bauxite. A brief discussion of recent developments and other processes for alumina is included in the subsection "Other Processes for Alumina," page 19-15. In early 1973, a major U.S. aluminum producer announced the successful development of processes for the production of aluminum from aluminum chloride. This achievement promises to exert a major influence on the future of the aluminum industry. In the initial com¬mercial application of this new technology, Bayer alumina will be chlorinated, and the aluminum chloride then reduced by electrolysis. Important claims for the new processes are lower energy requirements (one-third less than obtainable in Hall cells) and reduced labor costs. Capital costs are said to be no greater than for conventional plants. While the announced intention is to produce the aluminum chlo¬ride from Bayer process alumina, the new chloride reduction process will eliminate the other raw materials, carbon and fluorides, required by the conventional Hall cells. The electrodes in the chloride cell will not be consumed on the reduction process and the electrolyte will have, as the name indicates, a chloride rather than a fluoride base. 2. Bauxite Definition and Origin. Bauxite is a naturally occurring raw material composed principally of a mixture of one or more of the hy¬drated aluminum oxide minerals gibbsite (Al2O2 3H2O), boehmite (Al2O3 H2O), and diaspore (Al2O, - H2O), and impurities of silica, iron oxide, titania, and other various elements in trace amounts. It is an end or near-end product of chemical weathering. Depending on the amount of iron impurities, the color of bauxite varies from dark red and brown to pink to white. Some bauxite is finely divided, free digging earthy material, while other forms are dense and rocky, requiring explosives in mining. Many gradational forms exist. It is one of the most variable of mineral raw materials in chemical composition and physical appearance. It is generally believed that bauxite deposits resulted from intense chemical weathering of aluminum-bearing rocks or formations under tropical or subtropical conditions with alternating wet and dry sea¬sons. Topographic conditions were favorable for drainage and the in-situ accumulation of aluminum, iron, and titanium oxides. There was low to moderate topographic relief with a minimum of erosion during long quiet periods in earth history.2 The occurrence of bauxite is widespread and it has been found on all continents except Antarctica. Production was reported from 27 countries in 1974, at which time total world production was over 79 million metric tons. Of this production 76% was from seven coun¬tries-Australia, Jamaica, Surinam, Guinea, USSR, Guyana, and Greece-which ranked in that order of production. In Table 1 are shown typical compositions of bauxite from some

Jan 1, 1985

By Bunting S. Crocker

EBBLE grinding at Lake Shore is not a temporary BlE wartime substitute. The tube milling plant, with a 1000 ton per day capacity, grinds a hard siliceous ore to 90 pct — 325 mesh. The plant, prior to using pebbles, was consuming 4.3 lb of 11/4-in. grinding balls per ton of ore, which amounted to 785 tons of balls per year. At September 1951 prices, $132.60 per ton, this steel cost amounted to $104,400 per year, or $0.285 per ton milled. By the Lake Shore method of substituting screened rock for this steel, all of this cost is saved. This is one of the major economies in Lake Shore mill practice. Regardless of the ultimate price of grinding balls, a change back to steel balls is not considered. The present pebble plant is more flexible than a steel ball plant and equally efficient. For example, if it is desired to change the size of grinding media, the pebble charge in any mill can be changed completely in 4 to 5 days, as against 76 days to change completely a 1-in. steel ball charge. To change pebble size it is necessary only to change two sets of screens and clean out the rock feed storage bin. This will take 8 to 10 days as against 3 to 4 months to clean out the customary supply of grinding balls kept on hand. Also it has not always been possible to purchase all desired sizes of balls at any price. In an analysis of savings effected by the use of the pebble mills, the flexibility of the Lake Shore grinding plant should be discussed, as it has a direct bearing on these savings. The plant has always used several units to handle tonnage rather than sending all the tonnage through a single unit. This principle may result in using small diameter mills, but no objection to that is seen. At no time has any advantage been found in cost per ton ground in large diameter mills. Both the capacity and the power of any mill varies as the diameter raised to the 2.6th power. Consequently large or small mills are equally efficient, and a plant, should be designed to use as many units or combination of units as is consistent with reasonable operating practice. Mills under 5 ft diam are harder to reline, etc. To define the case at Lake Shore, 2600 tons per day formerly were milled in seven 7x6-ft ball mills and twelve 5x16-ft (and two 6x16-ft) tube mills.* This gave an excellent test plant and an extremely efficient one. In this plant the ratio of ball mills to tube mills was 1:2. When the much cheaper pebble mills were substituted for the tube mills, this ratio was changed to one ball mill to four pebble mills to take the greatest possible advantage of the cheaper operating mill, i.e., the pebble mill. This flexibility without loss in efficiency has been an important item in the cost savings. It is interesting to note that the use of pebbles for fine grinding was proved first in the laboratory in a 12-in. ball mill. In fact, since 1934 all testing on — 8 mesh material has been done in this 12-in. mill. Scope of the Tests A paper on fine grinding at Lake Shore Mines was published in July 1940.' This paper covered 7 years of intensive research on fine grinding as well as sizing methods and equipment, plant scale grinding tests on 5x16-ft tube mills with and without grate discharges both with 1-in. and -in. balls, the use of laboratory mills to evaluate plant changes, and several reports on classifiers and classification. In the following July the addendum report2 was added in which the idea of series-circuit grinding was introduced, and the results of running five stages of tube mills and bowl classifiers were shown. Since 1940, the ball milling end of the plant has been altered extensively as a result of tests on the use of 3-in. rods in 7x6-ft mills and the use of the Tyler repulping screen with from 7 to 14 mesh screens. These tests are lengthy and may be covered in a separate report later. The scope of this report is confined to ore ground by rod milling and ball milling until it passed through an 8 mesh Tyler Ty-rod screen. The —8 mesh screen undersize then was pumped to a primary bowl classifier in open circuit and the sands from the bowl sent to the primary pebble mills, see Fig. 1. In the pebble mill circuit the ore is ground to 90 pct —325 mesh (24 pct + 28 microns). In studying the flowsheet, attention should be paid to the efficiency of the classification equipment used. The Tyler repulping screen is an efficient machine on the 8 to 10 mesh separation, and the bowl classifier is equally efficient at the 325 mesh separation. Efficient classification is a necessity for series-circuit stage grinding. The ore is hard siliceous porphyry, 60 pct SiO,, 80 pct insoluble. Its grindability at different meshes has been shown near the top of the list in F. C. Bond's grindability tests.' Lake Shore is not shown, but an adjacent mine with identical ore, Wright-Hargreaves, is. Reasons for the Changeover Since 1936 grinding balls have been rising steadily in price with no sign of stopping. For a mill that used 4.5 to 5.2 lb of grinding balls for every ton of ore ground this rise represented an alarming increase in grinding costs. In many cases the quality of the grinding balls fell off as the scrap steel became more difficult to obtain. The ratio of tube mills to ball mills increased with the use of the Tyler repulping screen in the ball mill circuit. Originally only 3.0 lb of balls per ton were used in the tube mills, and this

Jan 1, 1953

By H. W. Hitzrot

Introduction Mechanical classifiers consist of a settling tank with parallel sides and a sloping bottom equipped with a mechanism which continuously agitates the pulp and removes the settled solids. The functions served by mechanical classifiers include the following: (1) allow the particles larger than the desired size to settle in the tank and provide an overflow product with a minimum of oversize particles, (2) produce an overflow product of sufficiently high solids content to meet the requirements of the subsequent processing steps, (3) agitate the pulp and permit separation of the entrapped undersize particles so they can report in the overflow product, and (4) drain and remove the underflow solids from the settling pool. Various types of mechanisms have been used to agitate the pulp and remove the settled solids, which include: (I) endless belt and chain drags, (2) reciprocating rakes, (3) helical flights mounted on a rotating shaft which extends through the settling pool, (4) helical flights inside of a rotating drum which contains the classifier pool, (5) troughed conveyor belts forming the settling pool in the concave curve of the belt closely following the tail pulley, and (6) low-speed impellers agitating the underflow settled in the apex of cone-type mechanical classifiers.23 The principal use of mechanical classifiers has been in closed¬-circuit wet grinding; however, this application has been widely displaced over the past few decades by the hydrocyclone. The hydrocyclone installation, including its feed pump, offers lower capital costs and requires less floor space. Nominally it produces an overflow prod¬uct of higher solids content, compared with a mechanical classifier, for comparable classification size up to 400µm (35 mesh). However, these advantages of the hydrocyclone are being gained at the sacrifice of some of the advantages of the mechanical classifier. The mechanical classifier requires less power and has lower maintenance costs than the hydrocyclone and its feed pump. The underflow product from the mechanical classifier can have a higher solids content and contain less entrapped undersize particles than the comparable product from the hydrocyclone. Consequently, it is capable of operating at a higher classification efficiency. A reduced circulating load24, 25 results under these conditions in a closed-circuit grinding application. Other applications for mechanical classifiers include desliming, dewatering, and washing operations. Sand-slime separation may be achieved using one or more stages of mechanical classifiers. Typical applications would include washing and deslimining of concrete aggre¬gate or sand; glass sand; abrasives; oyster shells; phosphate rock; iron, nickel, and chromium ores; alumina; zeolites; solar salt; and precipitates from chemical processing. As an example for the latter, Bitzer26 recommended the use of mechanical classifiers for countercur¬rent cementation-in-pulp of copper from the leach liquor. Similarly, mechanical classifiers are used in uranium processing27 for separation of the barren sands from the pregnant leach solution. Depending on the particle size and the effectiveness of the sand¬slime separation, the sand product from mechanical classifiers may be drained to solids content approaching 84%. Thus, mechanical classifiers are frequently used as dewatering equipment for various applications, such as: 1) Make a product having suitable solids content for subsequent transport by belt conveyor. 2) Provide a drained product to reduce cost of drying. 3) Provide a drained, washed, heavy sand product for return to the circuit. 4) Recover fine values from dilute plant effluents from coal, sand, phosphate-rock, and iron-ore washing plants and from steel-mill flue¬dust scrubbers. 5) Drain residual reagents of a preceding process stage prior to conditioning with reagents of different characteristics, e.g., cationic¬anionic flotation of phosphate rock, iron ore, etc. Design and Operating Features The proper selection of mechanical classification equipment re¬quires that the properties of the solids and liquid are adequately de¬fined. The following descriptive information regarding the solids is desired: feed rate, chemical and physical composition, density, tem¬perature, size analysis, and desired separation size. For the liquid used, the following data would be needed: feed rate, density, viscosity, pH, and temperature. Settling Area. The pool area required to permit a particle larger than the separation size to settle depends on the density and shape of the particle and on the density and viscosity of the pulp within the classifier pool. These criteria of the solids and pulp determine the settling rate which, in turn, determines the settling area required. Determination of the settling rate by long-tube batch tests can be used to calculate the settling area. A theoretical approach for estimat¬ing the settling area requirements is discussed in Chapter 1, Classifica¬tion Theory. This procedure can be used when neither test data nor empirical data from similar operations are available. Data on settling-area requirements and settling rates have been compiled by the manufacturers of mechanical classifiers. The approxi¬mate settling area required for a particular separation size can be estimated by using the curve shown in Fig. 65. This curve applies for closed-circuit grinding applications. For dilute velocity classification in open circuit, desliming, the length of the overflow weir, W, multiplied by the weir's mean distance from the feed opening, E, is used as the design criterion, instead of the settling area, in sizing the classifier. The area requirements, W X E, for dilute velocity classification can be expressed in terms of volumetric flow, Q, and settling rate, Rs, as follows: W x E = Q/(18.06 Rs) where W and E are feet, Q is gallons per minute, and Rs is inches per second. Overflow Weir. The hydraulic head, and thus the velocity at which the overflow crests the overflow weir, is one of the factors controlling the particle size of classification. Consequently, the length of the overflow weir must be designed to provide the overflow velocity which allows the particles larger than the desired size of classification to settle in the working area of the pool. Obtaining the necessary

Jan 1, 1985

By Jean-Paul Drolet

"The ultimate aim of the Law of the Sea Conference, held under the auspices of the United Nations, is to ensure that all aspects of the use of the sea are covered by international law. The question facing the nations of the world can be stated as: "" Who will control and benefit from the use and the wealth of the sea?""The United Nations Conference on Law of the Sea - known as UNCLOS - which reconvened in New York during the latter part of August 1978 was the third such Conference in the UN's history. The concepts of sovereignty over the territorial sea and freedom on the high seas have remained fundamental to the international law o f the sea until our time. The legal regime based on these two concepts developed initially from state practice meant that the unilateral actions taken by one or more countries were eventually accepted and followed by others.It was not until 1958, during the first Geneva Conference on the Law of the Sea (pursued in a second Conference in 1960) that the Law of the Sea was codified and modified to a certain extent by the then independent nations of the world in the four multilateral conventions on territorial sea and contiguous zone, continental shelf, high seas, and fishing and conservation of living resources.A third Conference got under way many years later when the members of the UN met in New York at the end of 1973 for preliminary discussions . This meeting stemmed largely from the need to fill gaps in existing international legislation which did not cover the new uses of the sea. The Conference was subsequently reconvened a number of times - in Caracas (1974), in Geneva (1975) and twice in New York (1976) for what was called "" substantive negotiating sessions."" A sixth session was held in New York in 1977; a seventh, held in Geneva at the beginning of 1978, recessed and reconvened in New York at the end of August 1978. This is what is referred to, in international jargon, as the seventh session of the Third United Nations Conference on the Law o f the Sea. The following dates are the principal markers of a saga which began some twenty years ago with the purpose of regulating the use of the oceans."

Jan 1, 1981

By Eric Lutz

"Great effort has been expended for more than 40 years to improve the workplace safety and health of surface and underground miners across the United States. When looking at the past decade, withstanding the 2010, Upper Big Branch (UBB) disaster that took the lives of 29 miners, this effort has resulted in a generally decreasing trend from 57 fatalities (22 coal; 35 metal/non-metal) in 2005, to 45 (16 coal; 29 m/ nm) in 2014. Through August of this year, there have been 23 mining-related deaths (eight coal; 15 m/nm). These results reflect continued diligence and perseverance on the part of miners that stay true to our legacy; and demonstrate significant investments from mine-site leadership, mining corporations, and state and federal regulators. However, over the past five years there have been an average of 32 fatalities per year, with a low of 36 (2011 and 2012) to a high of 45 (2014). If we know that there will be somewhere between 30 and 50 mining related deaths next year, which of us will volunteer to be counted as one of the numbered? Clearly, we all agree that one fatality is too many; and as evidenced by changes following UBB, deaths in any sector are deaths reflective of all mining across all sectors.The impact of each miner death touches us all. Miner’s deaths are felt deeply by family and friends, most significantly the children; their communities in which they served, supported, and worshiped; and by society that has lost a hardworking, dependable contributor. Further, to take a slightly cynical, but realistic view, miner fatality events impact the financial vitality of mining and contracting companies and broadly diminish investor confidence. Just as important, these events significantly impact our communities and result in negative public perceptions, which ultimately drive regulatory policy and related compliance pressures. This resulting pressure forces operations to broadly address safety and health gaps in very specific ways (i.e., see U.S. Mine Safety and Health Administration (MSHA) regulations regarding lids for trash cans) minimizing a mine site’s opportunities for operational flexibility. To break this cycle that is the operational reality, mining companies are focusing tremendous efforts on fatality prevention and specifically on dedicated investment to prevent multiple fatality events."

Jan 1, 2015

The plans for the activities of the Petroleum Division for the coming year do not differ materially from those of the past several years. The fall meeting is scheduled for Oct. 12 and 13 and is to be held at Tulsa, Oklahoma. The Division, of course, will take part in the annual meeting of the Institute at New York. A fall meeting will also be held in California at approximately the same time as the meeting at Tulsa. A number of papers are to be presented at the two meetings simultaneously. The various committees are at work arranging the programs. The Division will continue to be active in its various fields of endeavor, such as stabilization, production reviews, and economics, but special stress is to be laid on the engineering and research fields. In the past the Division has served as a forum for open and frank discussion of problems confronting the engineers in the oil industry. It is hoped that it will continue to function in this capacity. Papers presenting original ideas and extending the boundaries of knowledge and understanding in the field of petroleum production will be welcomed. Members who have interesting information to contribute should not wait until called upon by one of the Committees, but should offer a paper at the earliest opportunity. The past year has seen a decided strengthening of the control over production, with prospects of even more rigid control in the future. It is essential that production programs under such control be carefully planned and it is highly desirable that petroleum engineers take an active part in the planning, to insure efficient production of oil and minimize the waste of this natural resource. At a time like this, when it is difficult to keep the production of oil within reasonable limits, it may seem unnecessary to improve the efficiency of production methods, but, as has been aptly said, the trouble is not that we have too great a reserve of oil but that we are producing tomorrow's oil today. Therefore it behooves those who are entrusted with the engineering and scientific phases of production to learn how to get the greatest yield economically possible from the present and future fields in order that we may enjoy the advantages of petroleum products for a long time to come.

Jan 1, 1934

By J. T. Mackenzie

HENRY MARION HOWE, in whose memory we are gathered together, was one of the great thinkers who develop from time to time to whom is given the rare gift of synthesis. Analysis is given to few, but synthesis, the ability to show the relation of all parts to each other and thus to give a clear picture of the whole, is reserved for the very few. Analysis can be achieved by honesty, intelligence, and industry, but synthesis is only given to genius Professor Howe's crowning achievement is the picture of the whole iron-carbon series shown in Fig. I, which places steel, malleable, gray iron, mottled and chilled irons in their proper relation to each other and shows the essential unity of the series. Perhaps his best statement of the case is found on page go of the Metallography of Steel and Cast Iron in these words: "Each member of the gray cast-iron series consists of the metallic matrix approximately equivalent to that member of the steel-white-cast-iron series to which it corresponds in percentage of combined carbon with its continuity broken up-by masses of graphite . . . " Apparently he had taken considerable interest in this idea around the turn of the century, for he refers to a discussion at the Franklin Institute in 1900 in which he said: "Though many others had probably conceived this relation between the steels and cast irons, it was here enunciated for the first time, so far as I know. It was received with great incredulity." The concept was explained in some detail in a paper on 'The Constitution of Cast Iron" presented before the A.S.T.M. in 1902 when Professor Howe was retiring president of that young society. In the discussion Dr. Sauveur stated that he was "very well acquainted with Professor Howe's theory of the constitution of cast iron," and went on to say that while he "shared it to the fullest extent, some foundrymen . . . claim cast iron is a metal entirely different from steel . . . that steel and cast iron have very little in common, and that therefore the knowledge gained in the study of steel is of little or no value in the study of cast iron." Dr. Moldenke, in discussing the same paper, said he had been working on the same theory for 12 years but he laid no claim to publication. Discussing the difference in the micro- structure of the metallic matrix, Professor Howe pointed out that "such minor struc- tural differences are indeed to be expected, because of the difference in the conditions under which these constituents are generated. "One difference in these conditions is that the steel of most micrographs has been either forged or at least treated thermally in such a way as to give a new structure radically different from that which formed during the initial solidification, whereas the cast irons have not. Hence what we see in the steels is a transformation structure, but in the cast irons a solidification structure. By giving the cast

Jan 1, 1944