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With the advent of COAG reforms in the late 1990s requiring full commercial return from æpublic infrastructureÆ, and the tightening regulatory compliance for any project that involves the development or modification of any natural resource, it has become increasingly difficult for the private sector to contemplate development and/or ownership of new large-scale water supply infrastructure. The hurdles that must be overcome often seem insurmountable even before a detailed understanding of the project challenges can be developed. Australia has prospered over the last 50 years in an environment where regional development, including mining, has been encouraged by high commodity prices, a well-trained and available labour force and abundant spare capacity in the necessary infrastructure, in particular rail, power and water. Unless future infrastructure is created in advance of, or closely following, demand, this prosperity may be in jeopardy. This paper presents a snapshot of todayÆs project development challenges, and with reference to some recent case histories, argues that owing to their unique background, culture and status, water utility government owned corporations (GOCs) are well-suited to fulfilling the demand for new water infrastructure.

Jan 1, 2006

By J. Goldfield

Asbestos fiber, before it can be used commercially, is separated from the rock in which it is naturally found. Johns-Manville Corp. is currently constructing a 12-story fiber mill, of which the first half is completed and in operation. The mill will be the largest in the world, producing about 30 pct of the world's fiber. It was engineered and constructed by a cooperative effort of the engineers of the Canadian Johns-Manville Fibre Div. and the general plant engineering dept. Detailed design work on all phases of the job was done by Surveyer, Ninniger & Chenevert of Montreal. A series of crushing, screening, air aspirating and air separating processes will separate the fiber from 10 tons of rock per min. But to process this amount of ore about 90 tons of air per min will be handled in the aspirating and dust-collecting systems. To express this in more common units, 2.5 million cfm of air will be required. All this air will pass through a bag-type continuous automatic filter and will be expelled to atmosphere in summer or returned to the mill for heating during the winter months.

Nov 1, 1955

By Charles Catlett

Much has been done of late years to facilitate preliminary stratigraphical investigations, and for examination at considerable depths and in a certain character of material the diamonddrill, in its general forms, certainly stands pre-eminent among the tools for such work. But there are large classes of deposits —indeed, I may say the larger proportion in which ordinary. prospecting is done—which lie near the surface and are interbedded with soft and fine material. The method usually employed for prospecting these is by means of small shafts. These are sunk with considerable slowness and at considerable expense, depending largely upon the character of the material encountered, and are greatly interfered with by water. In this region the smallest are 3 by 4 feet, but they are usually considerably larger. Having had occasion during the past year to do a large amount of prospecting work, I have found the use of a hand-auger and drill of immense value in this respect, and in my practice it has largely superseded, and always preceded, the other forms of investigation. I believe that the information desired mas

Jan 1, 1898

By J. Poijärvi, J. Rastas

Recently, when increasing attention has been paid to mercury for environmental reasons, the interest of several plants is directed to the removal of mercury from roaster and smelter gases. When Outokumpu Oy built its zinc plant at Kokkola in 1969, intensive development work was started to find an efficient and economic method for mercury removal from roaster gases. A process was developed, after laboratory research and pilot plant tests, to eliminate and completely recover mercury from the roaster gases. The process was commissioned in 1970. The behaviour of mercury in the roasting process and several possible methods of removing it from gases are discussed in this paper. Theoretical investigations and empirical tests show that the removal of elemental mercury from gases by sulphatization is very efficient. Further, it is stated how the technical process was built on this idea. The zinc sulphide concentrates contain small quantities of selenium, chlorine and fluorine. The role of selenium in the process is described. Similarly, the behaviour of chlorine and fluorine in the roasting, sulphatizing and scrubbing units has been discussed. Finally, the recovery of purified mercury and selenium from the precipitates is described.

Jan 1, 1973

By Graham Daws

State of the Art Room and Pillar mining techniques have been employed at two coal mines in the UK in the last two years. This paper describes the design of pillars and rockbolted support systems for Room and Pillar mining operations in these collieres. Within the last year, rock mass classification systems have been used in the design process of a room and pillar mining layout at one of these collieries. In particular, the roofbolt support system was detailed using these techniques and the support system was linked with operational aspects such as depth of cut. The depth of cut was initially estimated using rock mass classification systems and then verified by a stand up trial which was monitored remotely. The stand up time has a direct influence on the operational aspects of the mine and this is described. The design was verified by performance monitoring and the results are discussed. The importance of understanding the role of rockbolting is emphasised along with some examples of accurately determining in-situ bolt performance. The paper also recommends some modifications to rock mass classification systems when applied to underground coal mining operations.

Jan 1, 1998

By Charles Behre

THIS paper deals with recent geologic studies in the slate belt of Northampton, Lehigh and Berks counties, Pennsylvania. The work was conducted under the auspices of the Pennsylvania Topographic and Geologic Survey. Three years have now been spent in detailed consideration of the economic geology of this region. In the field, particular attention was paid to the bearing of geology on quarry development and property valuation and the object of this paper is to summarize the results from that viewpoint. Excellent studies of a somewhat similar nature have already been carried out by Bowles,1 but with the emphasis upon the details of quarrying and fabricating methods, rather than upon the geologic relations. THE NORTHAMPTON-LEHIGH-BERKS DISTRICT Location The region here discussed lies in east-central Pennsylvania and extends southwestward from Delaware River, on the New Jersey line, to the Schuylkill in north-central Berks County. It is an elongated belt occupying the northern sections of the three counties mentioned and lying along the southern edge of Blue Mountain. Its length is about 50 miles and its average width five or six, though in places it attains a maximum of 10 miles.

Jan 1, 1928

By S. V. Bogdanov, S. I. Grishaev

"The article presents the materials about the appropriateness of the use of rental indices to assess the effectiveness of the use of deposits of rare earth elements (REE). The authors suggest from the standpoint of rent payments to rate for the owner the possibility of using the anticipated rental income as the indicator for the analysis of preferences and economic significance of enrichment of extracted raw materials in the emerging field of rare earth metals (REE). Usually from ore mined at the fields, for flotation technology to produce concentrates with collective REE, then they are subjected to chemical-metallurgical processing of the received products are divided into pure oxides, chemical compounds or isolated from them pure metals and alloys. This commercial product is shipped to the buyer. REE were a non-renewable natural resources, so the calculations for determining differential and specific rent showed that during the development of the technologies of mineral processing of a specific field it is necessary to consider what the expected rental income depends on the magnitude of differential rent is related to the volume of production of REE for the whole planned period of exploitation of natural resources. This income is determined by the amount of stock field. For long-term exploitation of the deposit is observed in almost direct proportional dependence between the annual differential rent and the rental income. The decrease in rents in the long run is determined by the change in the composition of ores included in the extracted raw materials and the balance between light and heavy REE. The largest 70% reduction of the rent projected for ""cerium"" fields, while for ""yttrium"" these losses are considerably smaller. Tomtor, Chuktukon and Katuginskoye Russian deposits are characterized by a level of rent that is comparable to the mastered foreign sources of REE. Thus, the enrichment of minerals with REM in the domestic deposits is quite competitive at the world level. INTRODUCTION Deposits of rare earth metals (REE) are non-renewable resources that should be developed and used so that it would be possible to provide a reduction due to payment of appropriate resources for future generations. This compensation, due to the reduction of natural resources, can be carried out both in natural and in economic terms (1). When analyzing economic compensation options, particular attention should be paid to rental income in assessing the attractiveness of using different REE deposits. It is known that absolute and differential rents are summands when calculating the value of natural rents. The value of the absolute natural rent is proportional to the unit price of the product obtained from mineral raw materials and sold on the commodity market. Limitations, as well as the use in production processes and business, contribute to the gradual reduction of natural resources, which increases their consumer value and affects the price of commodity products from primary raw materials."

Jan 1, 2018

By Branagan D. F

The geology of the area studied is briefly described, together with the prospecting methods used in the search for copper, lead, zinc and uranium ore bodies.Four prospects, Mt. Corella, Yanasinga, Lawlor's and Greenmount, which were diamond-drilled, are described in detail and geochemical results are discussed in relation to the mineralization found. Copper anomalies were found wherever intrusive rocks were mapped, and showed a much closer relation to geology and mineralization than did the predominantly lead and zinc anomalies.Geochemical prospecting aids in the overall mineral search programme because of its speed and economy, as it helps to pinpoint areas worthy of detailed geological examination. Geochemical anomalies are a guide to favourable zones but may not indicate the presence of ore.INTRODUCTIONDuring 1953-55 the National Lead Company of New York carried out a search for minerals in an area south and west of Cloncurry (Fig. 1) in rocks of Precambrian age. After reconnaissance mapping, a number of prospects were chosen for closer examination by detailed geological mapping and geochemical sampling, and from these prospects, five sites were selected for drilling.This paper records the salient features of the exploration programme and discusses the geology and geochemistry of four of the prospects-Mt. Corella, Yanasinga, Lawlor's and Greenmount. Practically all the prospects examined showed high zinc "anomalies" or "dispersion" trains. Greta, Mt. Corella and Lawlor's prospects showed some copper anomalies and, to a lesser extent, lead anomalies. In particular, Greenmount exhibited striking copper anomalies.

Jan 1, 1960

By N. S. Stoloff, R. G. Davies

The annealing behavior of a heavily cold-worked FeCo-V alloy has been studied at temperatures both above and below Tc, the critical temperature for ordering. It was found that re crystallization and grain growth can take place below Tc in the ordered state and that, in agreement with results for fcc alloys, order retards grain growth. The activation energy for pain growth is -55 kcal per mole in the disordered condition; it was not possible to assign a value to the activation energy for grain growth below Tc because the degree of order is changing rapidly over the temperature interval investigated. Precipitation of an fcc y phase was observed upon annealing the cold-worked alloy at temperatures of 675°C and below. SINCE it is known that diffusion constants are greatly affected by long-range order,' it is not unreasonable to anticipate that order will influence the diffusion-controlled phenomena of recrystallization and grain growth. In the course of a study of strain aging of ordering alloys around the composition Ni3Fe Vidoz, Lazarevic, and cahn2 noted that a disordered cold-worked alloy annealed at a temperature T1 just below Tc will order but not recrystallize; Tc is the critical temperature for order. The same alloy annealed at a temperature T2 just above Tc, or an alloy of different (nonordering) composition annealed at either T1 or T2, will recrystallize after equivalent amounts of cold work. Initially Selisskii and coworkers,3,4 who examined a series of cold-worked and annealed bcc Fe- Co alloys, reported that alloys forming the B2 FeCo super lattice could not be recrystallized below Tc. However in a later paper5 it was shown that FeCo ordered alloys could be recrystallized below Tc. Thus the first question to be answered by the present investigation was whether or not a heavily cold-worked Fe-Co-V alloy could be recrystallized below Tc. When it was found that the alloy would indeed re-crystallize below Tc, the influence of long-range order upon subsequent grain growth was studied. EXPERIMENTAL PROCEDURE The grain-growth measurements were made upon FeCo-2 pct V wire of 0.031 in. diam; the alloy was the same as that used in an earlier study of the mechanical properties of FeCO-v.6 The wire was produced by cold swageing and drawing a rod 0.125 in. diam that had been quenched into iced brine from 850°C to disorder the alloy; the initial grain size was 0.05 mm. Rates of grain browth were measured after isother-mally annealing the wire in the temperature range 675° to 825°C; T, is -720°C. Grain diameters were measured on the transverse cross section of the wires. The line-intercept method of determining the grain diameter was used; conventional light photomicrographs were taken when the grain size was greater than 10 . Carbon replicas were produced and examined in the electron microscope if the grain size was less than Dislocation configurations after recrystallization anneals were studied by electron transmission microscopy of foils produced by cold rolling a 0.125-in.-thick strip of the quenched material to 0.012 in. The foils, after heat treatments similar to the wire samples, were thinned by electropolishing in a chromic-

Jan 1, 1967

By F. B. Eiseman

IT is desired -to determine the effect of the extent of bank repairs on the final slag volume in acid electric steel-melting practice. It is understood that the repairs stud- TABLE I-Summary of Effect of Bank Repairs on Slag Volume [ ] ied here are necessary and the amount of sand added is that needed to maintain hearth and banks in a satisfactory condition. In this way the effect of repair materials on the amount of slag tapped would be found with a reasonable degree of accuracy. Ten heats were made for this study with careful attention to a uniform charge. The steel was the usual grade B and melting was carried out in a 3 1/2-ton top-charge Lectromelt furnace. Melting practice in all cases was the same-complete oxidation, with recarbonization by means of low-silicon pig iron.

Jan 1, 1947

By J. L. Rodrigues Bravo

The aim of this paper is to show the results of the study that relate the variations of the bismuth content in the Caraíba Metais' electrolytic copper with the main electrolysis' process variables as electrolyte flow rate and temperature, anode's impurities content, electrolyte composition, current density, etc and their combinations and factors like cathode washing, blend of materials entering rod plant's furnace, analytical methods, shot-circuit inspection, etc. Also, the methodology considered arsenic, bismuth and antimony mass balance in the electrolysis and their electrolyte's molar ratio relations as well as bibliographic references of refineries that operate in similar conditions. The results showed the circumstances with the major probability of causing bismuth content increasing in the electrolytic copper and the main operating conditions that have to be fixed for having less bismuth variation and lower content in the electrolytic copper.

Jan 1, 2007

By D. M. Cregger, J. L. Rosenblad, R. E. Ranken

The construction of a large span, high-walled underground opening in a low strength shale rock is unprecedented. The feasibility of constructing a pumped storage project with several tunnels and a large underground powerhouse in low strength shale rested largely on the feasibility of building stable openings large enough to accommodate the required equipment. Because of the lack of experience with large openings in shale, the decision was made to excavate a test adit and test chamber and conduct a multi-faceted geotechnical evaluation program designed to yield pertinent in-situ data on the ability of the shale to accommodate a large underground opening. Factors considered in the shape, size, orientation, and location of the test chamber were: (1) similarity to the anticipated powerhouse chamber, (2) nature of the most important data to be obtained, (3) feasibility of construction, and (4) economics.

Jan 1, 1983

By Milton E. Wadsworth

Cost effectiveness in gold and silver leaching has centered mainly on reducing or preventing excessive use of lixiviants. In cyanide leaching practice, the active reactants, cyanide and oxygen, present different problems. The activity of cyanide may be adjusted at cost, but oxygen from air, has a fixed, low activity with an equilibrium concentration of ~7 ppm. Consequently, the use of air in agitation and heap leaching presents distinct kinetic problems. The refractory ores are either high consumers of oxygen or tend to immobilize dissolved precious metal-cyanide complexes. Commercial treatment of refractory ores involves oxidation by pressure leaching, roasting or biooxidation prior to cyanide leaching. Chemical reactions important in preoxidation of refractory sulfide ores by pressure leaching and biooxidation are considered. Major emphasis is given to the role of oxygen in heap leaching of oxidized ores.

Jan 1, 1995

By R. E. Miner, J. K. Jackson, D. F. Gibbons

Internal-friction measurements were made during isothermal aging treatments of 18 pct Ni maraging-steel wires between 420° and 612°C. A sharp initial drop in the internal-friction level was interpreted in terms of a rapid dislocation recovery reaction. The rate of the recovery was found to be independent of temperature. Truncation of the recovery reaction was apparent in those systems that exhibited the rapid age-hardening characteristics of the maraging steels. It is proposed that this initial hardening response is the result of a low activation energy preprecipitation reaction involving molybdenum. A gradual rise in the internal-friction level at longer aging times was associated with the precipitation of a molybdenum-containing precipitate. CONSIDERABLE research effort has recently been devoted to the mechanisms responsible for the high strength and toughness of 18 pct Ni maraging steels. These bcc martensitic alloys are found to harden during aging at temperatures between 400° and 600°C. The aging response is very rapid with more than half the total hardness increase occurring within the first few minutes of aging, Fig. 1. Precipitate particles have been observed in the later stages of aging by a number of investigators.'-' While the identity of the precipitates remains the subject of some controversy, one or more of the intermetallic compounds, Ni3Mo, Ni3Ti, and Fe2Mo, are almost certainly involved. Heterogeneous nucleation of precipitates at dislocations has been noted8 and cobalt is believed to enhance the formation of fine, homogeneously distributed particles by lowering the solubility of the alloying elements in the martensitic matrix.3,7 Transmission electron microscopy studies of the initial hardening behavior have not been fruitful. Strengthening mechanisms based on atomic ordering have not been generally supported by X-ray and neutron-diffraction experiments.9 In the present investigation, the aging reaction was studied using isothermal-aging internal-friction measurements. The marked sensitivity of internal friction to short-range diffusion and precipitation processes has provided a convenient tool for the elucidation of the strengthening mechanisms operative in the maraging steels. EXPERIMENTAL PROCEDURE An upright torsion pendulum was used to measure the internal friction of several maraging steels during isothermal aging. The pendulum was placed in an atmosphere of helium at a pressure slightly less than atmospheric. To permit measurement of internal friction during the first minutes of aging, the specimens were rapidly heated by passing a current through them in a manner similar to that described by Ang and Wert.10 Thermal gradients in the specimen were largely eliminated by using specially designed specimen grips11 which produced temperature variations of less than 1 pct over 90 pct of the specimen length and less than 3 pct over the entire length at aging temperatures up to 620°C. A proportioning strip-chart program controller was employed to maintain constant specimen temperature during treatments of up to 36 hr duration. A number of vacuum-melted laboratory heats having compositions near that of a typical commercial 18Ni-7Co-5Mo-0.4Ti alloy were investigated. The amount of cobalt was varied from 0 to 7 wt pct in five of the heats. Either molybdenum or titanium was omitted in the remaining two heats. The alloy desig-

Jan 1, 1967

By L Lorenzen, C Aldrich

In this paper, a neurofuzzy model is proposed for the development of an explanatory model of an industrial gold leach circuit based on historic plant data. A regression tree was used to partition the data in the predictor variable space and the structure of the tree was used as a basis for the derivation of fuzzy rules that could be integrated into a fuzzy expert system useful for operator decision support or process control. The position and shape of the membership functions were optimised with a backpropagation algorithm in a neural network framework. The approach yielded a significantly better explanatory model of the gold losses in the plant than comparable linear models. Although a regression tree could perform somewhat better in accounting for the variance of the dissolved gold losses, the tree was less robust than the fuzzy model.

Jan 1, 2007

By K. L. Whitehead, R. A. Jankowski, N. I. Jayaraman

Most continuous miner sections utilizing flooded-bed scrubbers also use blowing face ventilation. Blowing ventilation, however, interferes with dust capture and minimizes scrubber effectiveness. To enhance the efficiency of the scrubber system and reduce dust concentrations, the Bureau of Mines tested various combinations of operating parameters. Experiments for system efficiency took place in a full- scale model mine at 3.05 m roof height. In general, higher values for scrubber and face airflows resulted in lower dust concentrations. In addition, optimum dust controls would include a face ventilation to scrubber airflow ratio of one. When the airflow ratio was either less than or greater than one, the dust levels in the return and at the operator locations increased. No single dust control technique was the most effective one at all locations due to mutual interaction among techniques.

Jan 1, 1992

By A. E. Jenkins, L. A. Baker, N. A. Warner

Rates oj decarburization of levilated Fe-C droplets conlaining 5.5 to 0 pct C have been measured at 1660°C. Gas mixtures of 1, 10, and 100 pct 0, with helium diluenl were used at velocities of 12.5 and 62.5 cm per sec. Rates were independent of carbon concentration in the mell and in good agreement with the calculated rule of oxygen diffusion through the gas boundary layer. The effects of flow rale and total pressure are as predicled and the rates are approxitnalely 2.5 times those with CO2 as oxidant. The mass-transfer correlation used incorporaled the efject of natural convection as well as forced conrection. Graphile spheres are shown to oxidize at the same rate as Fe-C droplets under the same experimental codlions. It is concluded that, for high carbon concentrations in the melt, the rate of- decarburizalion is controlled wholly by the rate of gaseous diffusion. Rate measurements with pure CO, are reported for low carbon concentrations where CO bubbles nucleate within the droplet. Under these circumstances the decarburi-zation decreased with carbon concentration and it is proposed that carbon diffusion is significant in conlrolling the decnvburization rate. In an earlier paper1 decarburization rate measurements were reported for levitated Fe-C alloys at 1660°C but with CO2 as the oxidant. The decarburization rate was found to be independent of carbon concentration in the melt but slightly affected by total pressure. The authors were unable to explain the slight pressure effect but in all other respects the results were consistent with control by diffusion in the gas boundary layer. Subsequent work has been directed at finding the reason for the slight pressure effect and whether the kinetics with oxygen as oxidant parallel those with CO2. Recently Ito and Sano2 have shown that with water vapor-argon atmospheres the decarburization rate is gaseous diffusion controlled until an oxide film appears on the surface. In this work the melts were contained in crucibles. MASS TRANSFER IN THE GAS PHASE In the earlier analysis1 only forced-convection mass transfer was considered. Subsequent recognition of the existence of some free-convection mass transfer explained the observed small effect of total pressure on the decarburization rate. Steinberger and Treybal3 and Kinard, Manning, and Manning4 have developed correlations involving the linear addition of the contribution of radial diffusion, free and forced convection. Steinberger and Treybal&apos;s correlation was chosen as the most applicable to the present work since it correlated most of the data available in the literature and handled the low Reynolds number region exceptionally well. The correlation for (Gr&apos;Sc) < 108 is where Nu&apos; is the Nusselt number for mass transfer based upon the total surface of a sphere in an infinite medium, G&apos; is the mean Grashof number for mass transfer defined by Eq. [2], Sc is the Schmidt number (µ/pDAB)f, Re is the sphere Reynolds number (dpu,pf/µf), p is the viscosity of the gas (poise), p is the density of the gas (g cm-3), Dab is the binary diffusivity for the system A-B (sq cm sec-&apos;), dp is the sphere diameter (cm), u is the approach velocity of the gas (cm sec-I), and subscript f denotes the property value is computed at the film temperature Tf defined by Tf = +1/2(To + Tr) where To is the specimen temperature and T, is the approach gas temperature (oK). Natural convection occurs when inhomogeneities exist in gas density. These may be caused by concentration gradients, temperature gradients, or both. In the present work the temperature gradient between the sphere and the bulk gas was very large and in some cases, for example the runs with pure oxygen, the concentration gradient was also appreciable. The Grashof number defined by Mathers, Madden, and piret5 was used since it took account of both temperature and concentration gradients: where Gr&apos; is the Grashof number for mass transfer (p2fgd3|-yA-yA|/µ2f), Gr is the Grashof number for heat transfer (p2f gd3p|To - T,]/µ2fTf), Pr is the Prandtl number (cpµ/k)f, g is the acceleration due to gravity (cm sec-&apos;f, a is the concentration densification coefficient (1/p)(ap/ayA)T, yA is the mole fraction of component A at the gas-metal interface, yA is the mole fraction of component A in the bulk gas stream, cp is the heat capacity of the gas per unit mass at constant pressure (cal g-I OK-&apos;), and k is the thermal conductivity of the gas (cal cm-&apos; sec-1 OK-1). Mathers et al. tested this combined Grashof number

Jan 1, 1968

By Elmer R. Kaiser

COMBUSTION of coal and transfer of heat from flames and gases to boiler surfaces continue to be of great interest to engineers here and abroad. Numerous investigations have been in progress to improve furnace and boiler performance and economy. The importance of better understanding of the processes and opportunities for improvement is apparent when it is remembered that heat from at least 500 million tons of coal a year the world over is being transferred to boiler water at efficiencies ranging mostly between 50 and 90 pct. Even slight gains in efficiency, economy, and labor saving become very significant when multiplied by the enormous quantity of fuel consumed. Also the competitive position of the large coal, oil, and gas industries in satisfying the fuel consumers is greatly affected by the achievements made through technical progress with each fuel. This paper is part of a continuing activity of Bituminous Coal Research, Inc., to extend the knowledge of coal utilization for steam generation and to seek promising directions for future research and development in cooperation with others. Particularly in the latter regard, numerous interviews were held during the last three years to seek the experience and advice of boiler and combustion-equipment manufacturers, electric-utility executives, and fuel engineers. A wealth of published information was also reviewed, which together with the interviews pointed to the advisability of further work on ash and sulphur control. For the present purpose a number of factors important to efficient heat liberation and recovery have been grouped as follows: 1—combustion, temperatures, and rates of heat liberation; 2—radiation, convection, and furnace and boiler configuration; 3—sponge ash, slag, and hard-bonded deposits; 4— low-temperature deposits and corrosion (cooling flue gas below dew point and air-pollution control); 5—the limitations of coal cleaning and boiler size and cost as related to fuel characteristics; 6—future possibilities and conclusions. The development of combustion apparatus for power boilers is progressing at a lively pace. There has been no letup in improvements in design of pulverized-coal-fired boilers, and there is a strong trend at present toward improving dry-bottom units. Spreader stokers with overfire jets and dust collectors as standard equipment are gaining favor. Less than 10 years in commercial use, cyclone burners are going into numerous installations here&apos; and abroad.&apos; Underfeed and traveling-grate stokers have long since been developed for heavy-duty operation, yet new developments in overfire jets and humidification of air blast have improved their performance. A water-cooled vibrating-grate stoker of German origin is being introduced into the United States and Canada." The primary objectives of an ideal coal combustion device are: capacity to burn the variety and sizes of coals likely to be economically available during the life of the unit; capacity to burn the coals automatically for a wide load range and rapid load fluctuations and to burn the coals completely to CO2, H2O, and SO2, which means without smoke and cinders, or carbon in the refuse; capacity to control and discharge all the ash in final granular form without ash adhesion to walls or tubes, and without flue dust; minimum furnace volume; minimum labor and maintenance; low initial and operating cost. Regardless of the method of burning, the gaseous products of coal combustion are N2, CO2, O2, H20, and SO?. By way of illustration, the coal analyses in Table I is assumed from an installation described by E. McCarthy.&apos; When coal is burned with 20 pct excess air (theoretical air, 9.23 lb per lb of coal), the quantities of combustion gas shown in Table II are produced. In addition, the gases carry particles of fly ash, unconsumed cinders, soot particles, and small but significant amounts of vaporized oxides and sulphates of sodium, potassium, lithium, phosghorous, iron, and other metals. In recent years, germanium, one of the rare metals found in coal, has been shown to oxidize and vaporize at combustion temperatures and to be concentrated by reconden-sation at lower temperatures." Pulverized coal and cyclone flames" have peak temperatures of 3000&apos; to 3500°F. Temperatures in fuel beds of large underfeed stokers reach maxima of 3000°F, sufficient to fuse almost any ash and to volatilize some of it. These peak temperatures are above the optimum necessary for rapid combustion, but they hasten heat transfer for ignition as well as boiler heat absorption. Furnace and gas temperatures increase with combustion air preheat. Low excess air has the same effect. Fine coal pulverization and highly turbulent combustion shorten the distance for fuel burnout, increase flame temperature, and speed up heat transfer. Rates of combustion of pulverized coal exceeding 200,000 Btu per cu ft per hr have been demonstrated in atmospheric gas-turbine combusters,

Jan 1, 1955

By Carl A. Zapffee

FOR a number of years a puzzling phenomenon of brittleness in Class II ferritic stainless steels, developing in the temperature range near 475C, has received increasing attention, but its nature remains essentially unknown. During an investigation of the fractographic structures in stainless steels, conducted in the author&apos;s laboratory the past several years, principally under sponsorship of the Office of Naval Research, some observations of a new kind were found for "475 °C embrittlement." While the details of the study cannot be given here,&apos; three fractographs will suffice to carry the

Jan 1, 1952

By Mike Koehler

An underground mine that produces aggregate limestone was in operation for approximately eight years when geological changes resulted in dangerous rock falls. The roof in the mine was not bolted; therefore, the drilling and blasting program was called upon to maintain roof integrity. Drilling and blasting were analyzed and modifications were adopted to stabilize the roof. Initial changes were made in the drilling equipment, drill pattern, explosive type, and timing. Any amendments made, after the initial phase, were made individually so it would be easy to discern which changes worked.

Jan 1, 2002