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By Shiou-Chuan Sun

DISCUSSION shiou-chuan sun (author's correction) - Too late for revision, the author realized that the data on stability of froth presented in this paper were not based on the same height of froth column. It is recommended herein that the stability of froth is better calculated by dividing the time elapsed until the froth disappeared by the volume (in cu cm per sq cm) or height of the froth column, and is expressed in sec per cm. The stability data in Tables I, II, and III of this paper were recalculated, in accordance with this recommendation, and the results are shown respectively in the accompanying Tables VII, VIII, and IX. Compared with Tables I, II, and III of the paper, the stability data of Tables VII, VIII, and IX are more reliable in disclosing the persistence of froth of various frothers having different frothabilities. For example, the conclusion given in the paper that the stability of froth is generally proportional to the volume of froth becomes invalid when the stability of froth is expressed in sec per cm, as shown in Tables VII, VIII, and IX. Table VII shows that both the stability and volume of froth increase with the addition of small amounts of n-hexyl alcohol, and that further additions of n-hexyl alcohol decrease the stability but increase the volume of froth. Table VIII indicates that the stability of different types of frothers is governed by their chemical composition and is difficult to predict from their frothability. Table IX shows that the stability of different frothers with similar nonpolar groups tends to increase with a decrease of the hydro- philic property of their polar groups, and consequently with the decrease of their solubilities. This is further substantiated by the fact that the stability of frothers, as listed in Table IX, is generally lowered by the solvent effect of absolute ethyl alcohol. Table IX shows also that the stability of froth tends to increase with the decrease of the volume of froth* provided the frothers used have similar nonpolar groups and dissimilar polar groups.

Jan 1, 1953

By Shiou-Chuan Sun

DISCUSSION shiou-chuan sun (author's correction) - Too late for revision, the author realized that the data on stability of froth presented in this paper were not based on the same height of froth column. It is recommended herein that the stability of froth is better calculated by dividing the time elapsed until the froth disappeared by the volume (in cu cm per sq cm) or height of the froth column, and is expressed in sec per cm. The stability data in Tables I, II, and III of this paper were recalculated, in accordance with this recommendation, and the results are shown respectively in the accompanying Tables VII, VIII, and IX. Compared with Tables I, II, and III of the paper, the stability data of Tables VII, VIII, and IX are more reliable in disclosing the persistence of froth of various frothers having different frothabilities. For example, the conclusion given in the paper that the stability of froth is generally proportional to the volume of froth becomes invalid when the stability of froth is expressed in sec per cm, as shown in Tables VII, VIII, and IX. Table VII shows that both the stability and volume of froth increase with the addition of small amounts of n-hexyl alcohol, and that further additions of n-hexyl alcohol decrease the stability but increase the volume of froth. Table VIII indicates that the stability of different types of frothers is governed by their chemical composition and is difficult to predict from their frothability. Table IX shows that the stability of different frothers with similar nonpolar groups tends to increase with a decrease of the hydro- philic property of their polar groups, and consequently with the decrease of their solubilities. This is further substantiated by the fact that the stability of frothers, as listed in Table IX, is generally lowered by the solvent effect of absolute ethyl alcohol. Table IX shows also that the stability of froth tends to increase with the decrease of the volume of froth* provided the frothers used have similar nonpolar groups and dissimilar polar groups.

Jan 1, 1953

By K. M. Tait, M. M. McDonald

"An overview of the status of the development and application of Integrated Gasification Combined Cycle (IOCC) power generation is presented. Current projects in North America, Europe and Japan are described, together with the status of plans to apply the technology in Canada. A brief review of the technology is presented, including promising coproduction cycles and hybrid gasification fluid bed processes. The ability of the process to be modified for CO2 to be extracted for enhanced oil recovery or disposal is addressed. The environmental impact of IGCC technology is compared to those of other power generation technologies IntroductionDefinition and HistoryIntegrated Gasification Combined Cycle (IGCC) technology is a concept which has been around for about 50 years but has been generating increasing interest in the last 10 to 15 years. This paper focusses on coal as the feedstock for gasification. Other feedstocks used in gasification systems have included oil, biomass, tires and petroleum coke. IGCC technology integrates coal gasification with generation of electricity by means of a combined cycle system which fires the produced gas in the gas turbine. Figure 1 shows the basic components of an IGCC system which are the gasifier, the gas cleanup system and sulphur recovery plant, the gas turbine/generator set, the heat recovery steam generator (HRSG) and the steam turbine/generator set. The benefits of an IGCC system over a conventional Rankine Cycle pulverized coal (RCPC) fired system for the generation of electricity from coal are that the IGCC system has potential to have higher efficiency and lower emissions of NO., SO and CO2 per unit of power produced than the corresponding RCPC system."

Jan 1, 1994

By Michael J. Peacock

The Powhatan No. 4 Mine is located in southeastern Ohio along the Ohio River in Monroe County. The mine produces approximately 3.2 million tons of steam coal annually from the Pittsburgh No. 8 seam. The Pittsburgh No. 8 seam in this area dips to the southeast in varying amounts from 10-feet to 40-feet per mile. The seam is made up of a main bench coal (4' to 5f' ) containing several thin and variable partings and a rider ("roof") coal (0" to 18") which is separated from the main bench by a parting (0" to 18") that is reasonably consistent in occurrence and position. Strata overlying the seam varies from a bedded to nonbedded calcareous mudstone-claystone (6' to 12') in the north and east regions of the mine to a sandstone (Pittsburgh Sandstone C10' to 40'1 in the south and west regions. The Redstone Limestone (10' to 18' ) overlying the mudstone-claystone in the north and east thins and rises toward the area of sandstone deposition in the south and west. From its opening in April of 1971 until late 1981, primary roof support in the long-1 ived entries at Quarto Mining Company's Powhatan No. 4 Mine had been achieved with 8-foot and 10-foot. 518-inch mechanical roof bolts using a Single expansion shell. These bolts were installed so that the expansion shell achieved a competent anchorage in the limestone. However, as the mine developed westward, the limestone began to trend upward becoming inaccessible as an anchorage medium at the 8-foot and 10-foot horizons. Anchorage achieved in the underlying mudstone-claystone strata was failure-prone due to weathering (after exposure to air and moisture) and inconsistencies in the anchorage horizon, leading to an increase in the incidence of reportable roof falls at the mine. Responding to the threat to safety and productivity posed by the increase in roof falls. Mine Management through its Safety and Engineering Departments, sought solutions to the problem. In seeking a solution to the problem, the safest and en engineering groups examined the reportable roof falls to determine the cause of those failures. Their examination pinpointed two items which were found to be a common link in the majority of those falls; namely, anchor integrity and geologic trends. Analysis of the roof falls indicated that due to effects of air and moisture on the anchoraae zones in the mudstones and clay- itones, the integrity of the anchorage over time could not be maintained. Geologic trends noted included the upward trend of the -main limestone as mining progressed westward, inconsistencies in the amount of roof coal and draw slate in the immediate mine roof and increasing evidence of heavily slickensided immediate mine roof. In the absence of the protective barrier provided by the roof coal, the immediate strata and particularly the draw slate, is susceptible to deterioration due to the weathering effects of air and moisture and thus is prone to "eat out" around the roof bolts and cause roof falls. The presence of heavily slickensided roof creates a need for increased contact surface such as that provided by plank and header blocks to aid in holding up the roof and tends to make the behavior of such roof very unpredictable. Having determined the causes of the roof falls. Mine Management began to identify the kind of roof support which would best solve these problems, while at the same time providing the mine with a safe, cost effective and efficient roof support system. This paper will provide an analysis of how this decision was reached, the background that was researched to aid in forming the decision, the considerations that played key roles in the formulation of the plan, the mechanics of following through and implementing the new roof support system, and an assessment of the resultant gains in safety, productivity and improved costs derived from the implementation of the new roof support system.

Jan 1, 1986

The evolution of mineral sand mine rehab ilitation techniques have been techniqually based. Research and investigations have been carried out by government authorities, mining companies and academic institutions. Protection of the physical and biological environments is a vital part of any mine oper- ation. The Mineral Sands Mining Industry in New South Wales is successfully working within the State's environmental framework and is meeting; community requirements and expectations concerned with the environment and mine rehab- ilitation. Keywords: Environment, mineral sands mining, mine rehabilitation, revegetation.

Jan 1, 1986

By L. H. Munson, D. E. Hadlock, L. F. Munson, R. L. Gilchrist, P. D. Robinson

All uranium mills are required to perform sampling and analysis for radioactive particulates in their gaseous effluent streams and in the environment. Pacific Northwest Laboratory was requested by the U.S. Nuclear Regulatory Commission (NRC) to provide technical assistance to them for their Uranium Mill Health Physics Appraisal Program. In conducting appraisals, air sampling methods used at NRC-licensed mills were reviewed and several deficiencies noted. This paper includes only environmental and effluent particulate sampling although much of the information is applicable to both in-plant and environmental samples. First, the components of a proper sampling program are discussed: program objectives, program design, sampler design, analyses, quality assurance, and data handling. Then the specific deficiencies, or the "pitfalls" from the first 8 mill appraisals are discussed. The first consideration in establishing an air sampling program is defining the objectives of the program. What is air sampling suppose to accomplish? Many of the deficiencies we have observed have resulted because the desired objectives were not clearly established in the minds of the radiation safety staff. PROGRAM OBJECTIVES An environmental air sampling program ought to fulfill the following seven objectives. The first is to: 1) [demonstrate regulatory compliance]. Although a goal of most programs, regulatory compliance, is not well understood. One has not only to comply with the conditions of the source materials licensee, but one must also demonstrate compliance with 10CFR20 and 40CFR190. For example, 10CFR20.106 states: "A licensee shall not possess, use, or transfer licensed material so as to release to an unrestricted area radioactive material in concentrations which exceed the limits specified in Appendix B, Table II of this part .... For purposes of this section, concentrations may be averaged over a period not greater than one year." Even if a mill's license does not require sampling at the site boundary of maximum concentration, a sample may be necessary to demonstrate compliance with 10CFR20. Most mill personnel are painfully familiar with 40CFRl90.10, which states: "Operations.... shall be conducted in such a manner as to provide reasonable assurance that: (a) The annual dose equivalent does not exceed 25 millirems to the whole body.... of any member of the public as the result of exposures to planned discharges of radioactive materials, radon and its daughters excepted... from uranium fuel cycle operations..." This means a licensee's sampling program must give "reasonable assurance" that the member of the general public receiving in the most exposure gets no more than 25 millirems per year. The sampling program necessary to provide that assurance may or may not be a license requirement. However, merely meeting the license requirements and the explicit regulatory requirements does not necessariarly ensure an adequate effluent and environmental air sampling program. The second objective of the environmental air sampling program, is to 2) [identify the source(s) of contaminants]. This will include not only the routine program, but special sampling for verification of sources and nonsources. Only after sampling can a mill operator be assured that roof vents, laboratory hoods, and other localized ventilation systems are not making a significant contribution to environmental releases. An environmental sampling program should also allow the mill operator to fulfill the third objective, to 3) [estimate exposures]. Even before 40CFR190, a sampling program should have provided the mill operator with the information necessary to determine the dose to the "fence post" person, or at least to determine if doses were well below the 10CFR20 limits previously allowed. The program should 4) [detect and measure unplanned releases]. If there is a fire, a scrubber failure, or if a drum of yellowcake breaks open, measured releases will almost always be lower than conservative estimates. Whether or not a system to provide sampling during accidents is needed is almost always a cost-benefit decision. In general, uranium operations do not sample just in case an accident may occur. Yet they may decide on continuous air sampling in lieu of intermittant sampling partially because of the potential for accidents. Another objective of air sampling is 5) [to provide information on the effectiveness of control systems]. This is always a concern with new or modified equipment and may dictate sampling frequency in other situations as well. For instance, if a small leak in a bag filter cannot be detected by other means, then more frequent stack sampling may be indicated. A routine effluent and environmental monitoring program should also fulfill the sixth objective,

Jan 1, 1981

By P. G. Gresse

The Orange-Vaal River system is known to be the primary secondary source for alluvial diamond deposits in the northern Cape and along the west coast of Namaqualand. The higher order sources for diamonds contained within this system are still not defined entirely to satisfaction, but certainly include kimberlite pipes exposed in the catchment regions of these rivers. The focus of alluvial diamond mining along the Orange-Vaal system recently changed from the traditional areas in the upper catchment regions?the Barkly West, Christiana, Bloemhof, Wolmaranstad, Schweizer-Reineke region, and the lower regions near the mouth of the Orange River at Baken, Alexander Bay and Oranjemund, to the area between Douglas and Prieska?the so-called mid-Orange region (Figure 1).

Jan 1, 2003

By Duluth Engineers' Club, Engineers' Club of Northern Minnesota

"Iron ore in Minnesota probably carries a heavier tax burden than any mineral in any other place in the world. The State Tax Commission, created in 1907, originated the system, and with the assistance of the School of Mines is constantly making such adjustments, changes and increases as appear necessary, in order to place mineral reserves on the assessment rolls at their true and full present taxable value. The ore bodies on the Mesabi are so well defined by drilling and underground devel¬opment that it is possible to estimate very exactly the volume on every forty acres of land taken as a unit. This is done by the operating or holding company and reported annually to the Tax Commission, Who check the estimates, having all data, and- proceed to fix the valuation for taxation purposes.The first step is to ascertain a general average selling price in open market, over a period of years ; then the total cost per ton (exclusive of royalty) to produce and market the ore. The difference between the average selling price and producing cost per ton is taken as the future full value per ton. This is then discounted at a rate of interest that represents the present and possible future worth of money, over a period of years that will be required to exhaust the ore body, giving the present full value per ton., Iron ore is taxed at 50 per cent of its full value, while other property is taxed at 33 1/3 per cent and 25 per cent."

Jan 1, 1920

By W. H. Frederic, A. C. Fieldner, W. A. Selvig

"Low-rank coals have a pronounced tendency to disintegrate or ""slack” when alternately dried, and wetted by exposure to the weather. The more readily a coal slacks the greater is its tendency to ignite spontaneously and the more care must be used in its shipment and storage. Lignite slacks very readily when exposed to the weather. Slacking trouble is also experienced in shipping and storing subbituminous coal, but not to the same extent as with lignite. As a rule, bituminous coals are only slightly affected by weathering and in general may be classified as nonslacking coals. The slacking tendency of subbituminous coal is one of the characteristics that is used to distinguish it from bituminous coal. An accelerated laboratory method of test was developed to measure such slacking tendencies. This method was applied to a number of coals, principally from the State of Washington, and the method and the results obtained are given herein.Helpful information concerning slacking tendencies of coal was received from Marius R. Campbell, senior geologist U. S. Geological Survey.Coals that slack readily contain relatively large amounts of moisture. When exposed to the weather such coals lore moisture rapidly. As the coal loses moisture at the surface there is a gradual drift of moisture from the interior of the piece to the surface. If the loss of moisture at the surface proceeds at a faster rate than it is replaced by moisture from the interior of the coal piece, there undoubtedly in greater shrinkage of the coal at the surface as tom-pared to the interior of the piece and stressed are generated in the surface coal.These stresses in the surface coal cause it to crack and disintegrate.Likewise, when the air-dried coal is wetted by rain, the exposed surface of the coal pieces gain moisture more rapidly than the interior of the piece, causing greater expansion in the surface coal and the coal breaks down further. As this process of air drying and wetting is continued when the coal is exposed to the weather, the slacking proceeds and the exposed lumps of coal may disintegrate completely."

Nov 1, 1930

By Lloyd A. Morley

Proposed advantages and disadvantages of low-voltage shielded trailing cables are formulated utilizing the literature and industry sources. A partial analysis of these proposed advantages and disadvantages is completed through a review of the literature. Cable costs are assembled from mine operators, cable and splice manufacturers, and actual cable purchases. To confirm each advantage and disadvantage, an underground test site is established, and testing is performed here and in the laboratory. All testing procedures are completely described. The results of this investigation are reported and used to formulate recommendations attendant to low-voltage shielded cables. Suggestions for installation, handling, and maintenance are presented.

Jan 1, 1977

By H. K. VAN POOLLEEN, W. Hurst, H. C. Bixel

In an earlier publication* I showed the development of the instantaneous point source solution for a well producing at a constant rate at the center of a system of two radial, adjoining sands of different permeabilities. I also showed how a wellbore radius could be incorporated if this were the development required. For the purpose of that paper and the point I wished to make, this solution served. It yielded a simplifying solution of sands in series identified by Eqs. VI-26 and VI-27. (These equations are reproduced in part by Bixel and van Poollen as their Eq. 3, Page 302.) I am well aware that the simplified solutions are approximations. The facts that these Ei-functions satisfy the diffusivity equation and meet the boundary conditions both at the well and at the interface between sands, and that the earliest time considerations yield zero pressure drop, are evidence that the solutions are good approximations. This was the purpose for these formulas, which I interpret that where the permeabilities are of finite order of magnitudes in the respective media, the relations give satisfactory answers. However, from the authors' point of view there are reservations, which leads me to consider their entire generalization as illustrated in their Figs. 1 through 14. What I understand from their storage capacity, relationship Fs, which is the ratio of the product of porosity and compressibility of Sand II to Sand I, that is employed here by the authors as a correlative means of identifying one figure from another, there is nothing in the exact mathematics that supports such a term as a means of correlation. This is taken out of context, unsustained that this applies. Here the mathematics are known, where the true correlation is the diffusivity term of one sand to another. This entails permeability that refers back again to the term M in their paper for the transmis-sibility of fluid from one sand to the other that should have also been a part of this storage capacity. In Figs. 8 through 14, which purported to show the simplified equation following this correlation, there are apparent discontinuities for M equal to or less than 0.1000 that differ from the trends for greater values of M. In this connection there is no reference radius given for this cumulative pressure drop in the paper that would permit me to make these calculations. However, what is clear for M equal to 0.1000 or less we are treated to almost a closed barrier at the interface; a condition entered by the writers without qualification. This across-the-board treatment of these simplified formulas, whatever the motive of the authors, enters into a range of permeabilities that even I as the contributor would have reservations that such could apply. Under comparable conditions I would be looking at a closed reservoir or some facsimile for such. The extent to which the approximation or the exact equations pertain is not evident in the generality offered by Bixel and van Poollen in their paper. Only when they or other writers show the comparison of the pressure distributions within the formations can one be able to judge the rational limits to subscribe to the simplified formulas.

Jan 1, 1969

By F. H. Buttner

Commodity currency intrigues most of us because of the problems it offers to solve for the Third and the First Worlds. What problems might be solved, if commodity currency were to be adopted in the Third World? That is really the question we are probing here right now. It would take a while to think through all their subtle consequences of this question, but, off the top, it might well have at least three important impacts. Most important of these to this audience is relief from unfair Third World competition. Second, it might well liberate Third World economies from financial indebtedness to the First World and give them freedom from the liquidity limitations. The third benefit is that it might help relieve World trade tensions. All three benefits are interrelated. We could start our speculations on the application of commodity currency from anyone of these starting points. But let us use the starting point most important to you, unfair competition to the U.S. mining industry. From there we might wind up with some thoughts on things you, yourselves, can do to improve things.

Jan 1, 1978

By L. J. Olivier

The possible closure and subsequent flooding of South Deep Gold Mine?s (SD) neighbouring Randfontein Estates Limited No. 4 Shaft (REL 4) necessitated the construction of five concrete plugs in the connecting tunnels to prevent the ingress of groundwater into REL4 from flooding SD. This paper describes the proposed controlled flooding of REL 4, the planned in-service monitoring of the five plugs and the water barrier between REL 4 and South Deep Mine, and the long-term maintenance of the plugs and rock mass in the immediate vicinity of the plugs.

Jan 1, 2006

By F. Weinberg, L. MacAulay

DAVIS,' in an investigation of solute redistribution along molten rods of dilute silver in tin, concluded that at horizontal temperature gradients below approximately 5°C per cm very little convective mixing takes place. Cole and winegard2 observed temperature oscillations in horizontal melts of tin, with temperature gradients of several deg per cm. They associated the temperature oscillations with the presence of convective flow in the melt. At temperature gradients less than 1°C per cm they did not detect convective flow. In the present work, direct measurements of con-vective flow in liquid tin have been made using a radioactive tracer technique. The results indicate that extensive convective flow occurs at temperature gradients below those previously reported. The apparatus used to determine the extent of con-vective flow is shown in Fig. 1. The graphite boat Fig. l(a), has two rectangular channels both of which contain molten tin. Radioactive Ag110 in the form of Sn-0.2 pct Ag alloy was introduced at the end of one channel, by rotating the cylinder shown. A series of fixed thermocouples were positioned along the center of the second channel to determine the temperature gradient. It was assumed that the two channels had identical temperature distributions. The graphite boat was inserted into a vycor tube which was surrounded by a multiple winding tube furnace as shown in Fig. l(b). The tin was melted in an argon atmosphere. The distribution of Ag110, as a function of position along the boat at a given time after introduction of the ~g"', was determined with the

Jan 1, 1970

One of the most important goals of the experiments is to determine deformation and strength of the rock specimen under applying triaxial load, the status of failure condition is one of the subjects which can be used in soil mechanic and foundation engineering applications. To investigate the effect of confining pressure on the triaxial test, the rock has been considered as bonded-particles method and has been simulated by particle flow code three dimensions (PFC3D). This model, does not have pre-existing microcracks and all the particles have the same size (2 mm diameter), equal to the real specimen shape. To compare the mechanical behavior and failure pattern of the numerical and experimental results at uniaxial and triaxial tests at the same conditions, the Young's modulus, Possion's ratio as well as maximum axial stress have been considered. On the other hand, the microcracks growth and change of failure pattern at the modelling of the uniaxial and triaxial tests with different confining pressures up to failure point were reported. According to the experimental work, the number density of microcracks decreases from starting value and remains almost constant up to the failure beyond that point. The comparison of the numerical and experimental results of maximum axial stress and the Possion's ratio revealed good accordance. The initial number density of microcracks at the model was zero and increased while microcracking. Also, the sudden increment around the maximum stress was observed which is because of unstable growing of microcracks near the maximum stress. In all uniaxial and triaxial tests with different confining stresses, the number density of microcracks during the failure remains almost constant which can be considered as a proof of failure occurring in the model. The experimental results indicate the similar trend as well.

Nov 25, 2010

By P. W. A Severin

"The Sturgeon Lake deposit, a partly eroded lens of massive sulphides with an underlying sulphide stringer zone, is one of five orebodies that occur in the Sturgeon Lake area of northwestern Ontario within volcaniclastic rocks of the Archean Wabigoon Subprovince in the Superior Province of the Canadian Shield.The Sturgeon Lake Cu-Zn-Pb-A g-Au deposit was discovered in October 1970 as a result of an I.P. survey. Production from this open-pit mine began in March 1974 and continued until the ore was exhausted in March 1980.The Sturgeon Lake property is underlain by basaltic volcanics, minor amounts of mafic lapilli tuff and rhyolite volcaniclastics. A quartz crystal-bearing rhyolite occurs at the top of the felsic volcaniclastics and is ""capped"" by the Sturgeon Lake massive sulphide deposit. The felsic volcanics have been intruded by a crudely layered sill-like, carbonatized mafic intrusion. Recent work suggests that the felsic rocks that underlie the Sturgeon Lake deposit are lateral equivalents of those in the vicinity of the Mattabi Mine and are not correlative with the dacitic volcaniclastics that underlie the Lyon Lake and Creek Zone deposits. Hydrothermal processes that resulted in the formation of the Sturgeon Lake orebody have resulted in a depletion of Na2O, CaO and FeO and an increase in MgO, K2O, copper and zinc. In the vicinity of the sulphide stringer zone, the rhyolites are ""bleached"" due to silicification and sericitization. The rocks lying immediately below the massive sulphides are locally strongly chloritic.The Sturgeon Lake deposit may have formed on a top ographic high which prevented mafic flows and dacitic volcaniclastics that underlie the Lyon Lake and Creek Zone deposits from inundating the Sturgeon Lake fumarolic vent from the west. Continued or resurgent activity from the Sturgeon Lake fumarole may have resulted in the formation of the Lyon Lake and Creek Zones as more ""distal "" deposits in topographic lows. The Sturgeon Lake, Lyon Lake and Creek Zone deposits were subsequently overlain by mafic tuffs and flows."

Jan 1, 1982

By D. A. Bird

Water chemistry data were used to identify the sources of ground-water and surface-water inflow to the IOZ block cave mine. Water samples were collected to obtain vertical and lateral hydrochemical profiles within different levels of the underground workings. Water chemistry data were evaluated in conjunction with geologic and structural information to define controls on locations of ground-water inflows, and to select targets for drilling and interception of water. Drilling has intercepted water-producing zones that were previously unidentified through mapping and drilling. The program has resulted in a reduction in water inflows to the block cave area.

Jan 1, 1998

By J. S. Phipps, D. R. Skuse

"Aqueous slurries of fine particle size calcium carbonate are used in a diverse range of end-use products. In many cases, the end use performance is governed by the fineness of the particle size distribution. In turn, the maximum fineness of the particle size distribution is primarily determined by the efficiency of the dispersants used during the production process. Here we report the sodium polyacrylate mediated dispersion of calcite and kaolin. Firstly, we report a colloid chemical description of the dispersant behaviour and attribute the stabilisation to both steric and electrostatic mechanisms. Secondly, we describe how the understanding developed in the first part of the study can be utilised to produce more effective dispersant systems which allow the preparation of, added value, higher solids and finer particle size calcium carbonate slurry products.INTRODUCTIONConcentrated aqueous dispersions of fine, particulate kaolin and calcium carbonate are used extensively in the coating of paper. Currently more than 10 million tonnes of such dispersions are used annually in North America and Europe alone, and worldwide consumption is growing at around 3% per year.Generally, paper is coated to enhance its visual appearance. Firstly, coatings improve the optical properties of the blank sheet, i.e. its brightness (or whiteness), opacity and gloss. Secondly, they improve the physical properties of the sheet that will influence the quality of the final printed image, such as surface smoothness, porosity, and ink absorption. In order to achieve these aims economically, paper coatings must be applied at high speeds and with minimal drying costs.Kaolin and calcium carbonate pigments are the major components of most paper coating formulations. Particle size distributions are chosen to maximise the optical benefits that they confer, and to allow the production of formulations that can be easily pumped, handled and coated. Coating pigments are generally produced and transported as slurries, and so it is important to obtain dispersions with the highest possible solids content, both to minimise drying costs and the quantity of water transported. This paper examines the dispersant technology that is currently used in the industry and the mechanisms by which it functions, and illustrates ways in which this technology has developed and could be further improved in the future."

Jan 1, 2003

We live in a world in crisis. One where the tides of change run ever faster. Where the only thing we can be sure of is change itself. The challenge we face, therefore, is not how to resist the forces that move us nor even to try to predict where they will lead us, but to harness their energy and use their momentum to find new and innovative solutions to problems that can seem intractable. Indeed, crisis is often the catalyst which energises a business to change its technology and to form a partnership with a company which specialises in pioneering new technology.

Jan 1, 1993

By L. A. Melis, K. S. Fraser

"This paper describes the development of a milling circuit for the complex Midwest orebody, containing a high-arsenic uranium ore typical of that found in northern Saskatchewan. The results of preliminary bench-scale test work are summarized. Data from a pilot-plant program carried out at the Ontario Research Foundation are provided for the selected mill flowsheet. Also described are waste circuits which have been established to produce effluents of acceptable quality. Pilot-plant testing of sub-aerial tailings deposition is also described. The applicability of manufacturers' equipment for the various circuits in the flowsheet is discussed.IntroductionThe Midwest uranium deposit is in northern Saskatchewan, 700 km north of Saskatoon, near the eastern edge of the Athabasca BasinDevelopment work on the project is directed by Canada Wide Mines Ltd., a subsidiary of Esso Resources Canada Limited. Participants in the project are Esso Resources Canada Limited, Numac Oil and Gas Ltd., Bow Valley Industries Ltd ., Mink Mining Corporation and Midwest Mining Corporation.The deposit consists of a series of flat lenses of massive ore overlain by a halo of lower-grade sandstone ore. The massive ore is formed of pitchblende and nickel arsenides, along with clay, and averages about 10% U and 9% Ni, The principal minerals are pitchblende (UO2-UO3), coffinite (U(SiO4)1-x(OH)4x), gersdorffite (NiAsS), niccolite (NiAs) and rammelsbergite (NiAs2). The sandstone ore, a friable clay-rich sandstone with sooty pitchblende, averages about 0.4% U and 0.6% Ni. Typical expected mill feed analyses are given in Table I.A bench-scale development program ore was carried out during the period from August 1978 to May 1981 in the laboratories of Lakefield Research of Canada Ltd. (Lakefield), (Lakefield, Ontario), the Colorado School of Mines Research Institute (CSMRI), (Golden, Colorado) and, to a lesser extent, the Ontario Research Foundation (ORF), (Mississauga, Ontario) and the Saskatchewan Research Council (SRC), (Saskatoon, Saskatchewan). Direction of the development studies was shared by Canada Wide Mines Ltd. and its metallurgical consultants, A.H. Ross and Associates. Input was received from Envirotech, Enviroclear, Interox America, and Knight and Piesold Ltd."

Jan 1, 1983