Search Documents

By M. Stuart

The copper-silver-mercury orebody of Gortdrum Mines (Ireland) Limited is located 3 miles north of the town of Tipperary in the Republic of Ireland. A drilling programme from 1964 to 1966 delineated an ore¬body of 4.19 million tons of copper ore assaying 1.19% Cu and 0.75 ozs per ton Ag, which could be mined from an open pit. Testwork having shown that the ore was amenable to conventional flotation techniques, it was decided to build a concentrator of 500,000 tons ore per year capacity. Stripping of the open pit commenced in 1966 and in the autumn of 1967 the concentrator started up. The first shipments of concentrates were made to the smelter in Europe in late 1967. In the spring of the following year, word was received from the smelter that these early shipments contained between 1% and 2% Hg, and that the smelter could not accept further shipments of this quality.

Jan 1, 1973

By Wm. C. Coffin

THE refractory linings of open-hearth steel furnaces above the bath line are subject to severe wear not only from the heat caused by the combustion of the fuel and the reactions of the bath, but also from the melting action of the gases when not controlled and directed, and from the scouring of the oxides, etc. with which the products of combustion are charged. The framework that encases or binds the furnace is made up primarily of an iron or steel pan in which the furnace proper is built, side and end buckstays, and tie-rods. The expansion and contraction are so great and variable that the bindings may be subjected to severe stresses unless the tie-rods are carefully adjusted in heating up the furnace, but they are most affected by direct heat and usually become deformed from that cause when the lining is worn thin and, sometimes, when sections of the lining fall in and expose some of the framework. A deformed framework displaces the skewback of the roof arch and tends to distort or crush the roof. Bent buckstays deform the front wall, causing the door frames to stand away from the lining so that the gases burn between the lining and the frames, destroying both of them. Frequently the frames are attached to the buckstays; then when the latter bend the frames usually break. Preventing the distortion of the framework and maintaining the economy of the refractories are real factors in the cost of steel making. Not only does the cost of general repairs and reconstruction add directly to the cost of steel produced, but the time lost in making repairs cuts clown the steel production and increases the overhead expense of both the furnace shop and its allied foundry or mills. Many years ago water-cooled equipment applied to iron blast furnaces made it possible to increase greatly not only the size and production of the furnaces but also the life of the lining. It also cut down the loss from frequent repairs. The open-hearth furnace is a much later invention, especially as a commercial factor; for though it dates from the Fred Siemens patent of 1856, much more progress was made in the Bes-

Jan 2, 1919

By Andreas Andenæs, Arne Schram Simonsen

"AbstractThe Tresfjord bridge is with its variety in foundation concepts and difficult soil conditions one of the most geotechnically challenging projects in Norway at the time. The project comprises design of large concrete caissons, steel core piles through large rock fills, and closed end steel pipe piles in up to 40m water depth driven in very hard moraine. Test piling has also been conducted to check feasibility of the concept, and PDA measurements have been used to verify sufficient capacity of piles. FactsThe Tresfjord bridge is part of the new export road from Ålesund to Åndalsnes on the North-West coast of Norway built by the Norwegian Road Administration. The bridge will reduce travel time with about 30 min between the cities, see Figure 1. The bridge is planned to open summer 2015.The Bridge crosses the Tresfjord and will be 1290 m long. The bridge is built as a free cantilever bridge and will be resting on a total of 20 nos. of foundations, where two are abutments resting on steel core piles, three are casted directly on bed rock and 13 are foundations resting on steel pipe piles. The last two foundations holding the main span will be concrete caissons resting on bed rock and moraine. Figure 2 shows a 3D model of how the finished bridge will look. Multiconsult AS is responsible for design and pile supervision , while the Joint-Venture Bilfinger-Tresfjordbridge ANS is responsible contractor.Soil ConditionsPercussion soundings and sampling together with coring have been performed in the individual foundations using a small geotechnical equipped vessel. Acoustic and refraction seismic profiling have also been carried out to tie in the layers between the boreholes.The soil conditions are varying over the length, but are in general dominated by a soft top layer (2-4 m) of sediments over very hard moraine with occasionally large boulders. Piles in the two foundations closest to shore on the western side of the bridge are piled to bed rock with penetrations up to about 27 m in soil.Water depth varies from about 10 to 40 m for the piled foundations. Figure 3 show how the topography of the seabed varies over the bridges length."

Jan 1, 2014

By Grant D. Nicholas

This paper compares an integrated evaluation approach to decision-making with more traditional sensitivity analysis and Monte Carlo simulation. The primary objective is to highlight the differences in NPV that can arise from using these evaluation methods in a top down and bottom-up approach. Results from three resource scenarios, derived from sampling a "virtual" ore body (reality) on grid spacings of 75m, 50m and 25m, are analyzed and compared.

May 1, 2007

By Richard P. Curtin, John M. Goris, Lewis A. Martin

Cable bolt supports are being recognized as an effective ground control system in under-ground coal mines in North America, and their use has increased considerably during the past few years. The U.S. Bureau of Mines personnel are conducting both laboratory and field tests to evaluate the performance of these supports under a variety of conditions and to establish realistic design guidelines. This paper describes efforts to evaluate the capability of cable bolts to resist the high shear forces often present in longwall operations. Shear tests were conducted on pairs of 0.025 m3 (0.88 cu. ft) concrete blocks having joint surfaces ranging from rough to smooth. Tests were conducted on blocks both with and without reinforcement with 15.2 mm (0.6 in.) diameter steel cables. During each shear test, the loads and displacements along the normal and shear axes, as well as loads on the cable, were monitored. Cableloads were determined using strain gauges attached to the outside surfaces of the barrel-and-wedge anchors used for pretensioning the cables. Test results show that a cable bolt placed across a joint more than doubled shear resistance of shear blocks having both smooth and rough joints.

Jan 1, 1996

By George Tryon, E. A. Barnard

The importance of the conservation of the waste heat contained in copper reverberatory furnace gases was realized very early by those in charge of operation at Anaconda. The first attempt to utilize it was in preheating the air used for combustion of the coal. This was done by forcing the air through ducts surrounding the flue-gas downtake and continued down beneath the furnace hearth to the firebox. Any small advantage gained by the heat transferred from the flue gases was more than offset by the losses sustained in cooling the hearth, therefore this process, after several trials, was soon discarded. It was first used at the Old Works as early as 1893 and again for a comparatively short time on the original furnaces at the Washoe smelter, or present works. Water-tube boilers came into general use very rapidly after 1890. Their adaptability for waste-heat steam generation, as well as the saving to be effected by the production of cheap steam from this source, was soon recognized. The first waste-heat boiler to be used in connection with a matte furnace at Anaconda was installed in September, 1900, at the "Old Lower Works." It consisted of a 100-hp. "Cook," vertical water-tube boiler. This boiler had 65 small perpendicular tubes arranged in concentric circles around a 10-in. tube in the center. These tubes were expanded into 4 ft. 4 in. inside diameter cylindrical steel top and bottom drums which served as the steam and mud drums respectively. This boiler was set in a cylindrical brick housing into which the furnace gases entered just above the mud drum and thence circulated upward around the tubes and steam drum to the stack. This installation proved unsatisfactory, presumably on account of difficulty with dust, and was soon abandoned. However, the possibilities for steam generation were undoubtedly encouraging for shortly afterwards (December, 1900) a 300-hp. Stirling boiler was installed, to be followed by two more in the spring of 1901. The choice of the Stirling type of boiler for application to copper reverberatory furnaces was particularly fortunate, as the arrangement of the tubes appears to combine to a great extent the maximum contact of the gases with the heating surfaces of the boiler and at the same time

Jan 1, 1934

By Kate Satish

M/s Konkan Railways Corporation are constructing 760 kms long rail road in the Western Coastal Region of India. The rail road encounters 75 tunnels through the Western Ghats of India with a total length of 78.35 kms, the longest tunnel being 6.5 kms long. The tunnels are of horse shoes shape having a cross section of about 37 Sq.meters

Jan 1, 1996

By L. C. Lang

INTRODUCTION The introduction of 165-mm (61/z-in.) holes to underground mining operations has made possible the application of Canadian Industries Ltd's (CIL) vertical crater retreat (VCR) mining method, illustrated in the accompanying sketches. This unique and revolutionary new application of spherical charge technology (see the Appendix), when applied to primary stopes and pillar recovery, eliminates raise boring, slot cutting, and dilu¬tion of ore by backfill; greatly improves fragmentation; reduces labor and time requirements; eliminates uphole drilling and blasting; and minimizes or completely elimi¬nates damages by blasts to the walls and retreating backs of the stope or pillar. If vertical large diameter holes are drilled on a designed pattern from a cut over a stope or pillar to bottom in the back of the undercut, and spherical charges of explosives are placed within these holes at the calculated optimum distance from the back of the undercut and detonated, a vertical thickness of ore will be blasted downwards into the previously mined area. Repeating this loading and blasting procedure, min¬ing of the stope or pillar retreats in the form of horizontal slices in a vertical upwards direction until the top sill is blasted and the mining of a stope or pillar is completed. The VCR method is also applicable to drop raises and has the potential to replace all other raising methods under most circumstances. PILLAR RECOVERY Levack Mine Inco Metals Co., Ontario Div., provided the first opportunity for the method in pillar recovery. The Levack mine's high grade ore pillar No. 4800 on the 975-m (3200-ft) level was used for the production¬scale experiment (Figs. 1 to 3). The pillar was about 49 m (160 ft) long, 6 m (20 ft) wide, and 20 to 26 m (65 to 85 ft) high. The mined area on both sides of the pillar was backfilled with a 1:30 cement:sand mixture. The pillar was removed in two phases. In phase 1, the standard uphole method was used to blast down the 18-m (60-ft) long section of waste from the bottom of the ore into the undercut. From the pillar's top sill, 165-mm (61/a-in.) holes were drilled downward into the pillar, and by measuring the depth of the holes, the results of the uphole blast were determined and roof line 1 was established. The bottom of each hole was plugged, then filled with sand to place the center of gravity of each spherical charge (loaded from the top sill) at a predetermined optimum distance from the horizontal free surface. The charges were then detonated. After detonation, both draw drifts were full of extremely well-broken material. The depth of each hole was measured again, and the plot of these depths re¬sulted in roof line 2. The same blasting procedure was repeated and the resultant new back elevation was marked by roof line 3. The poor results of the initial uphole blast at one location (notice the peak in area 1) appeared to influ¬ence the subsequent new backs. A third blast success¬fully evened the back, and resulted in roof line 4. An unblasted slab averaging 6.3 m (20.9 ft) thick remained below the pillar's top elevation as the final sill. In all three spherical charge blasts fragmentation of the blasted material was extremely fine. The backfill was fully exposed on both sides of the now-blasted pillar. The backfill remained undamaged and the ore was not diluted by sand. The remnants of all the 165-mm (61/2 -in.) holes remained clean and undamaged, and the holes had well-defined bottoms that could be easily measured and plugged. Each blast took down a 3.9 to 4.2-m (13 to 14-ft) thick horizontal slab of ore. Productivity was three times greater than that of the previously practiced cut-and-fill method. Since this was the first such experiment, blasting the remaining 6-m (20-ft) thick final slab was the sub¬ject of some deliberation. If the described method was repeated, we could have ended up with a 1.8-m (6-ft) thick sill unsafe to work on. It was therefore decided to blast the whole sill using two spherical charges prop¬erly placed in each hole, but with the application of

Jan 1, 1982

By Paul R. Bluekamp

The Mather Mine property is composed of a 5.2 sq km (2 sq mile) area within the Cities of Ishpeming and Negaunee which are located in the Upper Peninsula of Michigan. Production in this mine started in 1943; it ran continuously until its closing in 1979, having produced slightly over 55 million tons of iron ore. This mine was a joint venture between several steel companies and The Cleveland- Cliffs Iron Company (CCI), with CCI being the fee holder and operator. For the first 17 years of operation, the ore was shipped in its natural state directly from the mine to the steel mill. By 1960, iron ore pellets were on the market and they proved so superior to the natural soft Mather ore that the latter became difficult to sell except for the coarser portions. It was decided to develop a pelletizing process for the Mather ore, and this was accomplished by 1965 when the first Mather pellets were produced. From this date, all but the coarse fraction of the Mather ore was shipped as pellets. The geological setting is that of a large east-west trending synclinorium which plunges to the west. The lowest member of this trough-like structure is, for the most part, a quartzite-like graywacke, the upper 20 m of which grades into a softer, fine grained slate. Lying conformably on this graywacke footwall member is an iron- formation member which is over 1,300 m in thickness. This iron-formation is cow posed of thin alternate bands of iron oxides and chert and is intruded by a number of diorite sills - some up to 122 rn (400 ft) in thickness. The north limb of this synclinorium dips at approximately 45' and bottoms out at about 1,000 m from surface in the central part of the mine. There are two sets of faults, many of which are intruded by diorite dikes, which trend east-west and southeast-northwest. Displacements are varied, reaching a maximum displacement of 243 m (800 ft). The ore is found lying directly on the slatey footwall and its position is largely controlled by the faults and dikes, with the bulk of the ore being on the upper side of these structures. The ore is composed of soft earthy hematite and martite with vertical thicknesses up to 122 m (400 ft) although the average thickness would be closer to 46 m (150 ft). The ore averaged 60% iron and 7% silica on a dried analysis. The Mather Mine is located on the north limb of the syncline and was worked from two shafts, the deepest of which. was 1,09 7 m. These two shafts are about 2 km apart and serviced a total of 8 working levels between them during the life of the mine. The level spacing was about 61 m (200 ft). The main haulageways were driven parallel to the ore/footwall contact in the hard cow petent graywacke wherever possible. On the lower levels, deeper into the footwall, naked development was common. This material graded into roof bolting ground towards the upper stratigraphic portion. As drifting progressed further into the upper stratigraphic portion of the footwall, progressively stronger steel sets had to be used. From the main haulageway, cross-cuts were turned into the orebody on 61 m (200 ft) centers and extended as far as needed to recover the ore available to that particular cross-cut. The main haulageways and cross-cuts were driven 3 m (10 ft) high, 3 m (10 ft) wide at the top and 4.6 m (15 ft) wide at the bottom. This configuration would accomodate a set composed of a 2.7 m (9 ft) cap on top of two 2.7 m (9 ft) legs angled out at 18'. A sill plate was used under each leg to prevent its sinking into the ore below. The type of steel used was dependent on the expected weight to be experienced. Sets were placed on 1.63 m (5 ft 4 in.) centers; however, in extremely heavy areas, it was sometimes necessary to install sets on 0.8 m (2 ft 8 in.) centers. On the top two levels (5th and 6th), the ore was considerably hard-er and was mined by sub-level stoping and long hole drilling. Very light steel sets were used in the main haulageways and cross-cuts and timber was used in the production drifts. Some con- crete production drifts were installed on 6th level, but proved to be uneconomical. However, as mining reached greater depths, the ore became softer and more massive, reaching its maximum vertical heights on 11th and 12th levels. On levels 7 through 10, yielding steel sets were used extensively in the slusher drifts. While they were satisfactory on 7th and 8th levels, their success diminished with depth and they were

Jan 1, 1981

By Sidney H. Haughton

FOLLOWING the discovery of diamonds in 1870 and the Witwatersrand gold fields in 1886 South Africa changed from a predominantly pastoral country with a scattered white population into a land whose economy came rapidly to be based primarily on mining. The total value of the mineral output of the Union in 1944 was approximately $493,000,000, to which gold contributed 84 per cent. Gold furnished some 33 per cent of the Union Government's total revenue in that year, and approximately half the country's population obtained its livelihood directly or indirectly from the gold mining industry. In any review of the Union's mining activities and in any consideration of the country's future, gold mining must occupy a prominent place. It is generally conceded that the present structure is not properly balanced and that an economy based on a preponderance of a single nonpermanent factor possesses potentialities of serious instability.

Jan 1, 1946

By Bill Morgan

This paper discusses the economic zones of application for several different types of earthmoving equipment: dozers, wheel loaders in load-and-carry applications, wheel tractor scrapers, articulated trucks, rigid-frame trucks and wagons. Only the medium to large pieces of equipment were considered. From this chart (Figure 1), you can see the size range, in tons of carrying capacity, of Caterpillar equipment and the specific models analyzed.

Jan 1, 1994

By Neal I. Rosenberg

There is an old education maxim that a good teacher "first tells 'em what he's gonna tell 'em, then he tells 'em, and finally he tells 'em what he told 'em. I'm sure this says something about me as a teacher, and therefore as a student as well, but I'm going to begin by violating that maxim. The first thing I'm going to do is tell you what I'm not going to tell you. I'm not going to tell you that my company has found the solution to frozen coal problems. I'm not going to tell you that there is a miraculous new formula, and your frozen coal worries are over. Actually, it is really questionable whether there is a single step or process which will provide the answer. On the other hand, I do believe that at Union Electric we have made significant improvements in our ability to deal with frozen coal over the last couple of years, and I propose to describe some of the things we have done, what conclusions we have drawn so far, and the direction in which we are now headed. It would be well here to give a brief picture of the Union Electric system and the frozen coal problems we face. Union Electric is an investor owned electric utility with headquarters in St. Louis, Mo. Total generating capability is on the order of 6800 megawatts, which snakes us 24th or 25th largest in the United States. Power generation is by steam (both coal and oil fired), hydro, pumped hydro, and combustion turbine units. Although that is a diverse power supply, by far the largest source is our four coal fired steam plants. One receives coal exclusively by barge, the other three by rail. It is at these last three plants that the frozen coal difficulties arise.

Jan 1, 1980

Executive SIDNEY J. JENNINGS, Chairman GEORGE D. BARRON J. E. JOHNSON, JR. EDWIN LUDLOW ROBERT M. RAYMOND Membership KARL FILERS, Chairman LEWIS W. FRANCIS J. E. JOHNSON, JR. LOUIS D. HUNTOON ARTHUR L. WALKER Finance GEORGE D. BARRON, Chairman CHARLES F. RAND BENJAMIN B. THAYER Library E. GYBBON SPILSBURY,1 Chairman ALEX C. HUMPHREYS3 GEORGE C. STONE 2 J. H. JANEWAY4 BRADLEY STOUGHTON

Jan 5, 1918

By A E Reschke

The high-shear colloidal mixer is generally recognised as the most efficient method of mixing cement based grouts. Only recently however has this technology been applied to the production of cemented rockfill (CRF) for use in underground mines in North America. Traditionally, paddle type mixers have been used to produce the cement based slurries required for the preparation of CRF. While considerable success has been achieved with these mixers, tremendous advantages are attained with the colloidal mixer. The combined effect of the highly efficient mixing action and the ability to mix low water/solids ratios, allows for reductions in the cement content for a given strength requirement. Cement can also be replaced by cheaper fillers such as flyash, resulting in further cost savings. Although large-scale dedicated CRF hatching plants are typical, there is a growing need for mobile plants capable of operating anywhere underground. The compact size and rapid hatching speed of high-shear colloidal mixers has allowed them to be incorporated into skid mounted systems capable of producing and discharging cement based slurries onto rockfill aggregate for the production of CRF. In many cases run-of-mine development waste can be used as CRF aggregate with these slurry plants thereby reducing the cost of waste rock removal. These relatively low cost portable plants have now allowed several mines to economically rccmer isolated pillars and realise positive returns on their investment.

Jan 1, 1998

By Rita D. Sylvester

"IntroductionThe Bureau of Mines was established in the public interest to conduct inquiries and scientific and technologic investigations concerning mining and the preparation, treatment, and utilization of mineral substances; to promote health and safety in the mineral industries; to conserve material resources and prevent their waste; to further economic development; to increase efficiency in the mining, metallurgical, quarrying, and other mineral industries; and to inquire into the economic conditions affecting these industries. The organic act of the Bureau, as amended by Congress and approved February 25, 1913, made it the province and duty of the Bureau to ""disseminate information concerning these subjects in such manner as will best carry out the purposes of this Act.""In accordance with this directive, the Bureau reports the findings of its research and investigations in its own series of publications and also in articles that appear in scientific, technical, and trade journals; in proceedings of conventions and seminars; in reference books; and in other non-Bureau publications. The number of these reports, the wide range of subjects they cover, and the variety of mediums in which they appear make the kind of list and index presented in this special publication both necessary and valuable. This issue describes reports and articles published during the period January I, 1965, to December 31, 1969. It supplements the 50-year list of Bureau publications issued from July 1, 1910, to January I, 1960;' the 50-year list of articles by Bureau authors published outside the Bureau from July 1, 1910, to January I, 1960;3 the 5-year list of Bureau publications and articles from January I, 1960, to December 31, 1964.' It includes all the material in the four annual lists of Bureau publications and articles from January 1, 1965, to December 31, 1968, as well as the Bureau publications and articles for 1969."

Jan 1, 1970

By W. G. Davenport

This chapter examines three minor influences on flash smelting's industrial oxygen and oil requirements, i.e.: (a) recycle of molten converter slag to the flash furnace (b) gangue oxides and carbonates (e,g, Ah03, CaC03) in the flash furnace feed (c) minor sulfides (e.g. NiS} in the flash furnace feed. It then examines the. sensitivity of our flash furnace calculations to previously ignored aspects of smelting chemistry -Cu, S and Fe304 in slag and 0 in matte.

Jan 1, 2001

By B Besa, E K. Chanda

It has long been recognised that narrow vein mining needs innovative approaches to mine access and mining methods in order to improve the economics of this vital part of the mining industry. The mining equipment used currently requires large openings in narrow vein-type deposits making mining operations uneconomical. In view of this and other shortcomings of the current mining practices, a study was initiated to investigate the potential of using low profile electric loader with mounted conveyor in conjunction with the electric monorail haulage system (EMTS) to load and haul the blasted material, particularly in decline development and main haulages. Computer simulation based on the General Purpose Simulation System/Henrikson (GPSS/H) is used to model the system and evaluate its performance. The results are compared with those for conventional mining using trucks and loaders. The EMTS provides competitive haulage rates in substantially smaller excavations than is currently achievable. According to simulation results, the electric loader in conjunction with the EMTS had the same number of blasts as the conventional system and hence the same advance rate of 3.33 m per 12 hour shift. Furthermore, the total drill-blast-load-haul cycle time was less than the conventional system by one hour.CITATION:Besa, B and Chanda, E K, 2012. Evaluation of low profile electric loader in conjunction with electric monorail haulage system in narrow vein mining, in Proceedings Narrow Vein Mining 2012 , pp 221-228 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 26, 2012

By M Chiquito, R Castedo, P Segarra, L M. López, J A. Sanchidrián, J Navarro

The aim of this work is to assess the performance of different constructive solutions against explosions on the strength of masonry walls. The solutions tested, namely an external metal mesh, a glass fibre film on the external face of the wall and a basalt fibre film located on the inner face of the wall, have low to medium cost and are originally designed for other purposes, like seismic protection. Four cubic boxes 3 × 3 × 3 m were built using each of the solutions and typical masonry blocks. In the tests, a spherical plastic explosive initiated in the centre was placed at scaled distance of 2.9 m/kg1/3, so that moderate damage would be caused on the wall. In order to assess the performance of the explosive, pressure gauges were placed at the wall and at different distances from the explosion. Additionally, vibrations were monitored with seismographs in the far field and a high-speed camera was used to estimate the shock wave velocity during the tests. The resulting damage has been evaluated on 13 points of the external wall of each box using a rebound hammer. Damage maps have been drawn for each wall based on these measurements and damage has been assessed inside the box considering the fragments mass launched during the test. The use of external metal mess leads to a decrease of 34 per cent on damage of the external wall and 38 per cent reduction of spalling. The use of a film in the inner wall provides a strong reduction on spalling.CITATION:López, L M, Segarra, P, Castedo, R, Sanchidrián, J A, Navarro, J, Santos, A P and Chiquito, M, 2015. Performance of different constructive solutions against explosions in full-scale masonry walls, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 819–824 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By A. W. Fletcher

Report of discussion at February, 1971, IMM general meeting (Chairman: M. J, Cahalan President) of a paper published in Transactions/Section C (Mineral Processing & Extractive Metallurgy), vol. 79, December, 1970, pp. C247-52, and contributed remarks. Contributions are included from: Cahalan M.J., giving figures related to leaching Cu from pyrite at Rio Tinto 1880-1910; Noakes F.D.L.; Embling P.M.K.; Bradshaw A.V.; Le Roux N.W.; Kelly D.P.; and Tuovinen O.H. Questions were raised regarding impurity removal, effects of light and ultraviolet light on the bacteria, the economics of solvent extraction and the possibilities for other organisms or other metals

Dec 1, 1971

By M. Pawlik

The rheological properties of mineral suspensions affect the design and operation of transport, mixing, size classification, grinding, gravity concentration, flotation and de-watering systems. In many cases, the rheological properties can be modified to improve processing through the addition of chemical additives. These additives may be either organic or inorganic and generally affect the state of particle aggregation or dispersion. Inorganic modifiers act primarily by affecting the surface charge of mineral particles and thus control the magnitude of electrostatic attraction/repulsion between particles. The action of organic additives (polymers and surfactants) is a combination of electrostatic and steric forces – the latter being related to the molecular weight of these reagents. While low molecular weight polymers are dispersants (viscosity reducers), high molecular weight polymers are likely to induce flocculation and increase yield stress.

Jan 1, 2004