Search Documents

By Frank Peterson

THE manufacture of gasoline by extraction or precipitation from the natural gases in which it is found, the present status of. the industry, its past development and future extensions; offer a subject which is so broad that to handle it in its entirety would require a voluminous paper. The writer will, therefore, attempt to concentrate the essential matter of the subject for a general presentation, giving some of the most interesting details of the factors that are important to the industry. This industry has drawn liberally on the principles of physics and chemistry, and, to a large extent, has had to adapt such information as is most useful-not from data recorded with reference to petroleum, but from data recorded with reference to general treatment of other materials. Because of the complex character of the petroleum series of hydro-carbons and the fact that data, such as solubilities, vapor pressures, etc., of the different petroleum compounds have not been determined, we are still working by rule of thumb in. some essential phases of the industry. Furthermore, the difficulties of determining such data are almost insurmountable. We have not one,, but two butanes to deal with-not one, but several, pentanes, hexanes, heptanes, and, as we ascend in the series the complexity and multiplication of isomers increases at such a rate as to make the task of isolating and studying their physical characteristics almost beyond the hope of possible attainment. The industry is the connecting link knitting the interests of oil producers and refiners into a much closer relationship than ever existed .prior to its inception and development. The relation between the producer and the refiner of petroleum prior to 1910 was. a rather antagonistic one in a commercial sense. It was to the interest of the producer of crude petroleum to sell it for a maximum consideration; the refiner's interest was to obtain the same product for a minimum consideration; therefore, each side of the business transaction retained within his own hands as far as possible the trade secrets of his business. Each side maintained an attitude of cold-blooded business sympathy only for the other. Cas-

Jan 12, 1917

By Dirk Bleazard

Barrick Goldstrike Mines is improving the reliability of mining and processing equipment through the use of failure analysis and condition monitoring activities. Program results include an increase in equipment capacity and an overall reduction in operating costs. Identifying equipment failure modes and developing associated capital asset management practices can minimize failure consequences. Successful programs have included alterations to management practices, equipment modifications, and/or the implementation of condition monitoring programs. By controlling or minimizing the effects of incipient equipment failures, corrective actions can be taken earlier in the failure cycle. This results in an associated reduction to repair costs and equipment down time. Mining companies invest in their capital assets to provide the capacity necessary to meet operational needs. Over time, functional failures occur that reduce this productive capacity. Diagnostic technologies now exist that allow the condition of equipment to be monitored. Early response to this information minimizes the effects of functional failures and restores equipment re- liability. Reliability is a performance indicator of overall equipment condition. It is most often expressed in terms of mean time between failures. When the established objectives of a capital asset management program include the maximization of this failure interval, trailing indicators, such as availability and operating cost improve. The probability of equipment failure is influenced by engineering design and operating conditions. The performance level resulting from this operating environment is expressed as "inherent reliability." Without maintenance intervention, equipment will ultimately fail to perform its intended function and become less reliable. Therefore, maintenance must be managed as the supplier of reliable operational capacity. Maintenance can only supply equipment performance that approaches the level of inherent reliability. Actually achieving inherent reliability requires that all maintenance decisions are made at the economically optimal time. Enhancing performance levels beyond inherent reliability can only be achieved by altering operating conditions or practices or through physical equipment modifications. An evolution in maintenance management philosophy has been under way since the beginning of the industrial revolution. As equipment has become more sophisticated, so have maintenance practices. At the beginning of the industrial age, equipment tended to be over designed and slow moving. The first maintenance philosophy was one of reactive maintenance. Maintenance intervals were dictated by the operational status of the equipment. As a result, production interruptions were common and capacity needs were met through an investment in redundant capital assets.

Jan 1, 1998

Edgar Archibald Collins was born at Truro, Cornwall, Nov. 16; 1877. He was the fifth (and youngest) son of J. H. Collins, a well known Cornish geologist and engineer, who died in 1916. Edgar Collins spent part of his childhood at Rio Tinto, in Spain, and after returning to England was educated at Alleyne's School at Dulwich, near London. His technical training was acquired by practical experience in Cornwall, supplemented by private study and by his father's teaching. This method of training for the work of a mining engineer was preferred by his father to that of the technical schools then available, and judging by its result, was not unsuccessful. It is,-however, noteworthy that all members of the Collins family who were products of this system later sent, or planned to send, their own sons to technical schools. Edgar Collins came to Gilpin County, Colorado, in 1894, and returned there in 1898, after several intermediate years spent in Cornwall. In Colorado he worked, under his brother Arthur, in the California and other mines of the Gilpin County district, and thereby gained a practical skill and experience as a working miner, and a habit of minute observation of vein phenomena, which proved of the greatest value in later years. In 1899 he went to the Smuggler-Union it Telluride, as general assistant to his brother Arthur, and stood the brunt of 3 years of struggle with the Western Federation, gaining a reputation, for quiet courage and sound work under the most difficult conditions. After Arthur Collins' assassination in the Smuggler-Union office, in November, 1902, Edgar left Telluride, and shortly thereafter entered the employment of a syndicate headed by Arthur Winslow, of Boston, to search for and develop new mines. While so engaged he spent several unsuccessful months near Parral, in Mexico, and later visited and sampled the- newly discovered district of Grandpa, afterward known as Goldfield, in Nevada. This led to the acquisition by the Winslow syndicate of the Combination mine, at first under lease and option; and Edgar Collins was placed in charge. The Combination was really the starting point of Goldfield. It was a profitable mine before the discoveries at the Jumbo were made; and while the Combination, being a "Company-account" mine, controlled by a few responsible men, never attracted the publicity that centered around the sensationally profitable leases on the Jumbo and Mohawk, which publicity was used to further the feverish stock-dealings that characterized the new district. The Combination was really the pioneer mine, made the first shipments of rich ore, constructed the first water-line, and built the first mill (designed by F. L. Bosqui, an old friend and associate); and while it pursued a quiet and unobtrusive. career up to the time of its sale to and incorporation with the Goldfield Consolidated, was probably, in ;proportion to the amount of money risked, the most profitable bonanza in the recent history of gold mining.

Jan 11, 1918

By E. W. Parker

PROBABLY everyone is well aware that from April 1 to September 11, 1922, anthracite production was completely suspended; during those 163 days not one ton of coal was produced in the anthracite region. The production loss was about 30 million tons, and although production is now at its peak, there is no possible way by. which, within any short space of time, that deficiency can be made up. During that time the miners sacrificed in wages something over 100 million dollars. The anthracite companies paid out in cash, keeping their mines in condition to operate when mining should be resumed, something like 30 million dollars without taking in one cent of revenue. The tonnage of domestic sizes included in that lost output was about 21 million tons. The anthracite operators figured that between September 11, 1922, and March 31, 1923, they would possibly be able to produce about 60 per cent. of the tonnage that was mined the preceding year, that is, from April 1, 1921, to March 31, 1922. The problem then arose as to how that tonnage could be distributed equitably throughout the United States and Canada. We had in our records in Phila-delphia the distribution by communities, about 20,000 of them, to which anthracite had been shipped during the last five years, so that we were well posted as to what each community should be entitled to receive. We allotted to each of those 20,000 communities 60 per cent. of the tonnage that it had received during the preceding coal year, and we have endeavored to see that whatever tonnage we have been able to produce should be equitably distributed on that basis. It was a matter simply of voluntary cooperation by the anthra-cite operators who placed the distribution of their tonnage practically in the hands of the Pennsylvania Fuel Commission; the anthracite companies have almost without exception acceded to every request that we have made of them. When communities were reported entirely out of coal, a telegram or letter to the directors obligated to that community has resulted in some anthracite being shipped there, so that we have thus far kept the distribution on a fairly equitable basis. Prior to the suspension of mining operations, pre-liminary negotiations were carried on for the renewal of the wage scale, the operators thinking that it could be adjusted satisfactorily, and that the same method of procedure would be followed as during the 20 years succeeding the strike of 1902. At every termination of the wage agreement since that date, until last year, an agreement had been reached early in the season that mining operations should be continued, with the under-standing that any new agreement should be retroactive to April 1. At the meeting of the committees of anthra-cite operators and miners, on March 21, 1922, the opera-tors were presented with an ultimatum by the miners to the effect that unless an agreement were reached within ten days, mining operations would cease. That was protested against by the committee of operators as being unfair, not only to the operators and the public but to the men themselves. In spite of this protest the suspension occurred and, as you know, continued until September 11.

Jan 4, 1923

By Robert M. Dreyer

Although lateritic ore deposits are relatively flat-lying, surficial ore bodies, the evaluation of lateritic bauxite and nickel deposits is among the most difficult problems confronting an economic geologist. Laterite is a soil formed under tropical conditions resulting in the concentration, within the soil zone, of certain trivalent metals - principally iron and aluminum, but also, locally, nickel and manganese. The soil zone is divided into two parts: (a) the true soil or lateritic zone and (b) the zone of partially altered bed rock or saprolite. Whereas bauxite generally is confined to the lateritic zone, some nickel deposits occur in both the laterite and saprolite zones. The evaluation of bauxite and lateritic nickel deposits thus has both similarities and differences. These ores have been formed by supergene, soil-forming solutions moving downward through zones of widely varying permeability within the weathering rock. Because the permeability varies widely, both vertically and laterally. the extent of weathering may vary greatly within short distances. Because the weathering process varies widely, the degree of metal concentration may also vary widely. It is not at all uncommon for a laterite to change, within a few centimeters, from a virtually valueless rock to a high grade ore. Moreover, the depth of weathering, and hence the depth and form of the ore profile, vary greatly. Obviously, for this type of deposit, a few grab samples or a few drill holes are virtually worthless. The evaluation of such a deposit requires a sophisticated statistical study based on thousands of carefully selected samples. As a rule of thumb, the cost of evaluating a large bauxite or lateritic nickel deposit will be about one cent per ton of ore in the ground. Thus, the cost of evaluating a several hundred million ton deposit may be considerable. The following factors must be considered during the evaluation: Type of Sampling: The best and most reliable samples for the evaluation of lateritic ores are taken along large, vertical channels in hand-dug pits. Where labor costs are high, some form of drilling may be used in place of pitting, but it is always wise to choose a drilling procedure after checking drilling results against a series of pit channel samples. The drilling may not reproduce exactly the results from pit channel samples, but it may be possible to derive a constant correction factor. If the physical character of the laterite varies within the deposit, it may, of course, be necessary to change the type of drilling, the correction factor or both. In some areas, it has been found empirically that augers, chum drills, vacuum drills, rotary drills, or core drills yield satisfactory results. The problem is to find which drilling technique gives results most similar to channel samples through the heterogeneous sequence characterizing the laterite in a given area. In lateritic nickel deposits, the drilling characteristics of the lateritic and saprolitic portions of the deposit are very different. Within the saprolite, the major nickel values are commonly found in weathered zones within less altered boulders - a type of occurrence which makes sampling very difficult.

Jan 1, 1979

By Harold M. Feder, Irving Johnson

Tkermodynamic functions for dilute solutions of uranium in liquid cadmium were obtained from galvanic cell measurements. Deviations from Henvy's law were observed at concentvations down to 2 x 10-3 atom fraction. Unusually large negative values of the pavtial molal relative enthalpy and excess entvopy of uranium, suggestive of the occu,vvenctwe of partial ovdering of cadmium around uranium in these solutions, were found. The negative relative partial molal enthalpy of uranium at the liquidus accounts for the observed retrogvade solubility of metallic uranium between 473" and about 630°C. The standard free enevgy of formation of UCd,, from a-uranium and liquid cadmium is given by F,° THE constitutional diagram of the U-Cd system,' Fig. 1, is unusual in several respects. The near equality of the Goldschmidt atomic radii2 (Cd, 1.52A U, 1.56A) might be expected to give rise to extensive mutual solubility of the elements except for the restrictions imposed by differences in valence and electronegativity.3 The latter factors must be strongly influential because mutual solubilities in the terminal solid phases are probably negligible, and the solubility of uranium in liquid cadmium in the readily accessible range is only about 1 at. pct. Interestingly, the solubility of uranium in liquid cadmium actually decveases slightly with increasing temperature from 473" to about 630°C. Such a retrograde solubility in a liquid phase is a rare phenomenon in metallic systems; no other authenticated examples were found among the nearly 700 binary phase diagrams compiled by Hansen and Anderko.2 These observations suggested the existence of some unusual interaction between uranium and cadmium. Greater insight into the nature of this interaction was sought by measurement of the thermodynamic properties of the system. EXPERIMENTAL PROCEDURE The emf of cells denoted by the scheme was measured. Each cell consisted of two uranium and two alloy electrodes immersed in a molten lithium chloride-potassium chloride eutectic mixture containing uranium trichloride. The physical arrangement is shown in Fig. 2. The potential between any pair of electrodes could be measured with a Leeds and Northrup Type K-3 potentiometer. The measurements were made at points marked in Fig. 1. It should be noted that points on the phase boundaries represent the concentrations of uranium in the saturated liquid phases of heterogeneous alloys. Uranium Electrodes. Uranium, which is not a particularly soft metal, is capable of retaining residual stresses, and its potential may depend upon its physical condition. Electrodes were prepared from 3-mm diam rods of hot-rolled high-purity4

Jan 1, 1962

In-situ leaching of gold deposits has not become an option largely as a result the lack of suitability of cyanide as a lixiviant due to sluggish kinetics and high dependence on the availability of oxygen. A second problem area is the excessive cost of drilling the required number of injection and production wells needed to service a wellfield capable of maintaining any significant throughput or providing and acceptable level of gold production. Well spacing in in-situ leaching operations is limited by solution life, dissolution rate, and the need for solution control. With cyanide the life of an active solution capable of dissolving significant gold is severely limited by the availability of oxygen which cannot be readily replaced while the solution remains underground. The extremely slow gold dissolution rate also necessitates excessive contact periods in order to dissolve coarse gold.

Jan 1, 1991

By Paul H. Price, John P. Nolting

The history of the salt industry in West Virginia dates back nearly two hundred years; howTever, the history of salt as an important raw material for the chemical industry is much more recent. The earliest record of West Virginia salt was in 1753, when a raiding party of Shawnee Indians attacked frontier settlements in Virginia taking captive a number of the pioneers. One of these, who later escaped and returned to her friends, described how the Indians camped at a salt spring on the banks of the Kanawha River and evaporated the water to obtain a supply of salt to take back to Ohio with them. Settlement of the Kanawha Valley began in 1774, that same year the Battle of Point Pleasant ended the Indian's power in the Ohio Valley; and settlement of the Kanawha Valley progressed rapidly with a consequent increase in the importance of the Kanawha Licks as a source of salt. In those days the evaporation of the brine was a family matter for which the family wash-kettle was commandeered. In 1797, Elisha Brooks erected the first salt furnace in the Kanawha Valley. It consisted of two dozen small kettles set in a double row, with a flue beneath, a chimney at one end, and a fire bed at the other. He obtained his brine at a depth of 20 to 30 ft by sinking hollow logs, called "gums" into the salt lick and dipping the brine with a bucket. His production was about 150 lb a day and sold for 8 to 10 cents a pound. In 1806, the Ruffner brothers, David and Joseph, prospected for and drilled the first well in America using a spring pole and steel chisel bit. After several failures they succeeded, in 1808, in drilling to a total depth of 59 ft where they secured a good flow of strong brine. Most standard drilling tools, jars, casing, and practically all the basic oil well drilling machinery now in use, were developed in the drilling of salt wells. To evaporate this brine, the brothers built a wood-burning furnace similar to that of Brooks but with a better arrangement and with more and larger kettles. When production was started they reduced the price of salt to 4 cents a pound. By 1817, there were some 30 salt furnaces in the Kanawha area. It was in this year that bituminous coal first was used as an industrial fuel. David Ruffner again pioneered the way by converting his furnace for the consumption of coal. This year also brought about the formation of the first trust which controlled production and set a price of 1 cent a pound for the salt.

Jan 1, 1950

Andes Copper has an old camp and a new camp, both isolated until recent road improvements. The old camp is at Potrerillos and the new one at El Salvador, 25 road ,miles away. The company was incorporated in 1916 and the first mine, concentrator, leaching plant, smelter and town were built in the succeeding twelve years. The first blister copper was poured on January 24, 1927. Economic conditions determined the long development period but the end result was the design and construction of a mining complex that was all of a piece, unlike the piecemeal additions to El Teniente and Chuqui. The mining episode at Potrerillos came to an end in 1960 when the ore at La Mina became exhausted and the new mine, El Salvador was brought in. Both of these ore deposits come within four hpundred feet of the surface and had they been developed within the last five years might reasonably have been brought in as open pit mines. However, that is conjecture, and as it stands the operation at La Mina was so ideal for the mining method selected, blockcaving, it became a classic for the textbooks. On the other hand, El Salvador has turned out to be a blockcaving mine to test an engineer's skill. In mining the copper deposit at Indio Muerto mountain, there are ground conditions of every conceivable type. Tunneling in one section, the back can cave like sized pea gravel and only spiling can hold it; in another heading only the lifters are shot but often the rest of the round will sit down in one piece; elsewhere the bottom squeezes up and closes the drifts; and contrary to all other locations, there are sections where the block can be undercut without support. Today the scope of operations at Andes extends from mining to electrolytic copper. Ore is mined at El Salvador and the concentrator is also situated there. Concentrates pipelined 14 miles to Llanth, the water decanted, and then it is hauled by rail 40 miles and 5500 ft higher to the Potrerillos smelter and refinery. Potrerillos and El Salvador are respectively 90 and 70 miles from the port of

Jan 11, 1969

By K. L. Clark, Nicholas Kowall

MAXIMUM furnace efficiency and close control of final steel composition demand that the steel melter be able to follow closely the variations in the carbon content of the bath. For many years, the fracture test has been used by melters for estimating carbon, because it requires only a very short time to pour a sample into a chill mold, cool it in water, break it with a sledge hammer, and observe the fracture. After long experience gained from the observation of such fractures, most melters are able to estimate the carbon content of steel with amazing accuracy, particularly in the lower carbon ranges. Notwithstanding the utility of the fracture test, there has been widespread interest in other methods for rapid carbon determination to supplement it and to ensure against possible errors in human judgment. Several methods, based upon measurement of magnetic properties as functions of carbon content, have been described in the literature1-6 and have been found to give reasonably reliable results in plant practice when scrap composition is known and controlled. A difficulty encountered in the use of analyzers of the magnetic type is that alloying elements do change the relationship between carbon content and magnetic properties and it becomes necessary to establish calibration curves for all the expected combinations of alloy residuals that are not oxidized in the bath. The work reported here is of an investigation of a method that is independent of alloying elements normally present in constructional steels, being based upon the relatively well-known fact that in plain carbon and low-alloy steels martensitic hardness is a function of carbon content alone. WORK OF OTHER INVESTIGATORS In 1938, Burns, Moore and Archer published a curve7 that showed that the hardness of martensite is a function of carbon from 0.10 to 0.50 per cent and is independent of grain size or alloy content, at least within the range found in constructional S.A.E. compositions. Some of the deeper hardening types investigated, however, contained carbon to a maximum of only 0.20 per cent. Using this principle, Kern8 developed a method of rapid carbon determination for S.A.E. 43xx steels. His procedure consisted of chill-casting a test bar that was large enough to give a surface that could be prepared for Brinell indentations. The test piece was quenched immediately after solidification was complete and hardness readings were taken, so that the carbon content could be read from an experimentally determined curve giving the relationship between as-quenched hardness and carbon. EXPERIMENTAL WORK Although Kern's work had been done with a relatively deep-hardening steel, it

Jan 1, 1944

By W J. Bruckard, M J. Vaisey

Ashton Mining Ltd (Ashton) and Lynas Corporation Ltd (Lynas) have established a joint venture partnership to develop and process rare earth oxides (REOÆs) from the Mt Weld deposit in Western Australia. The deposit is located in a deeply weathered volcanic carbonatite structure that contains approximately two million tonnes of rare earth oxides at an average grade of 20 per cent REO. As part of the 1999/2000 feasibility study currently being undertaken by Ashton and Lynas, an extensive laboratory beneficiation test program was undertaken by CSIRO Minerals on diamond drill core samples from the Mt Weld orebody. The aim was to develop a flowsheet, based primarily on flotation that could be confirmed at pilot plant scale. The target concentrate grade was 52 per cent REO with a REO recovery of at least 35 per cent. Two main ore types, nominated as CZ (limonitic siltstone) and LI (nodular limonitic ironstone) were identified for separate laboratory evaluation. The lower grade LI-type ore overlies the higher grade and more extensive CZ-type ore. The majority of the work was conducted on the CZ ore; only limited testing of the LI ore was undertaken. The latter contains a clay component that will present difficulties in processing due to its poor filtering and settling characteristics. Two processing options for treatment of CZ ore were presented for pilot plant consideration. One (Option 1) includes gravity concentration prior to flotation while the other (Option 2) includes finer grinding and four stages of open circuit cleaning. The benefits of each scheme are discussed in detail. Neither has been fully optimised and the definitive flowsheet is most likely to be a hybrid of the two schemes, incorporating the best features of each. Typical metallurgical results from each scheme were final concentrate grades of 49 per cent REO, 10-16 per cent Fe2O3 and 3.2-4.8 per cent CaO. REO recoveries were above 35 per cent in both cases. Features of the processes developed by CSIRO were the inclusion of a gravity concentration stage prior to flotation, a modified flotation reagent scheme, a change in the method of feed preparation, and incorporation of magnetic separation to upgrade final flotation concentrates. Metallurgical results obtained from flotation tests on LI ore were much poorer than those obtained for CZ ore. The best rougher/scavenger result, with the limited amount of testing so far completed, was an REO grade of 32 per cent with a recovery of 28 per cent. Further work is needed to develop a viable processing route for this ore type.

Jan 1, 2000

By Scott A

The object of most blasting operations is to destroy the insitu structure of the rock mass so that mechanical equipment can efficiently excavate the rock fragments. In achieving this objective the blasting engineer is also concerned with minimising damage to the adjacent rock which forms the mine structure relied upon to provide support. Damage to this "structural" rock is undesirable but usually occurs as a result of two distinct processes: ò readjustment of stresses around the excavation as a result of the mining process itself ò impact of vibration and high pressure gases from blasting operations. Gross damage to mine structures from either cause is observed as visible alteration to the appearance of the rock structure in the form of cracking, slabbing, back or over break and visible displacement. Recent work at the Julius Kruttschnitt Mineral Research Centre (JKMRC) has shown that significant reduction in the strength of a rock mass can take place well before the onset of these obvious signs of damage. It has been demonstrated that the effect of blast damage on the behaviour of the rock mass can be many times more prominent than the effect of stress redistribution. This offers the blast design engineer the opportunity to significantly reduce blast induced damage to rock structure by modifying blasting practices. This paper introduces the current JKMRC postgraduate research projects investigating the evaluation and control of blast damage.

Jan 1, 1990

The statistical methods described in the previous chapter permit the estimation of the average value p of a deposit, and the calculation of confidence limits for this value. They are based on the assumption of independence of sample values. As soon as a reasonable number of samples has been obtained from a deposit, local valuation, or estimation of blocks of ore within the mineral deposit, becomes necessary. The assumption of independence of values must then be rejected. Local valuation is possible only if there is a relationship between the value of a sample and the value of the surrounding ore, provided this relationship is a function of the position of the sample with respect to the blocks of ore to be valued. Whichever method is used for the valuation of a block of ore, the following assumptions are always made: ? The values of samples located near or inside the block are related to the value of the block. ? The values of the samples located closest to the block are most closely related to the value of the block. These assumptions will hold true only if the following assumption can also be made: ? There exists a relationship between sample values which is a function of the distance between samples. We are saying that the value x (z) of a sample centred at a point z has properties which are functions of this point. A certain spatial structure exists in the sample distribution. We are therefore dealing with a regionalized phenomenon, and we must treat x (z) as a regionalized variable. This can be done statistically by means of a model chosen to represent the spatial structure of the phenomenon. We shall see that the relationship between block values and sample values can be deduced from the relationship between sample values, and all local valuation problems can be solved using the statistical model obtained from the analysis of the sample values. It is important to realize that this statistical model is obtained by analysing the properties of known sample values, and will be used for the estimation of unknown block values. Such a statistical inference is valid only if the model developed represents the properties of both the sampled section of the ore body and the section to be valued: some stationarity conditions must be satisfied, and the model with the least restrictive conditions is preferred. In the following chapters, the most important models used in spatial geostatistics are presented. The models which can be used when there is no significant drift (trends) in values are described in Chapters 3-1 1. These models can also be used to solve some specific valuation problems when a linear drift is present. A general study of the more difficult problem of analysis of an ore body whose values present a drift is described in Chapter 12. Note that the area considered for local valuation of a block of ore is often small enough for any drift which might be present to be ignored.

Jan 1, 1978

By Jose A. Ruiz

INTRODUCTION For heterogeneous non-catalytic solid-gas reactions carried out in fluidized bed reactors, nominal bed temperature is an average value between gas and solid. For highly exothermic reactions, actual particle temperature can be up to hundred degrees above termocouple temperature, since heat dissipate at slower rate than heat generation during some steps of transformation. These micro instabilities at particle level can displace thermodynamic equilibrium from the desired phase to others. This effect is important when relatively narrow range of phase stability exists, like in sulphation roasting of sulphides, where bed discharge contains, in addition to the desired sulphate others metastable phases such as basic sulphate and ferrite. For example, for copper-iron sulphide concentration roasted below 680°C, no cupric ferrite is formed, as shown by Jakob et al., therefore the separate Kellogg's stability phase diagrams Cu-S-O represent the roasting (Fig.l). At temperature above this one, like 760°C for example, phase stability changes from CuSO4 to the basic sulphate Cu0•CuSO4. Solid state reaction between Cu0•CuSO4 and Fe203 also occurs to form cupric ferrite, Cu0•Fe2O3, therefore the Cu-Fe-S-O Kellogg's phase diagram of Fig. 1 (continuous line) represents this condition of roasting. Although both Cu0•CuSO4 and Cu0•Fe2O3 are metastable phases under normal operating conditions of sulphation roasting(1-10% SO2, 1-10% 02 and 680°C, points A and B,Fig. 1) sulphation of these species and particularly ferrite are slow and limited due to diffusional control. This explain why reactors discharge contains several phases: CuSO4, Cu0•CuSO4, CuO•Fe203 plus small amounts of CuS and FeS due to the baclonixed conditions of fluidized bed reactors. The presence of cuprous ferrite due to reducing conditions inside individual particles also occurs, but in very limited extent at the reaction interface, as it is demonstrated by the low soluble iron levels of calcines. On the other hand, the presence of cupric ferrites can be explained only due to the higher temperature achieved by particles, since below 680°C cupric ferrite formation does not take place. [ ] This phenomena also occurs for others non-ferrous metal sulphides concentrates roasted under sulphation conditions, such as 7n, Co and Ni. Therefore the prediction of discharge composition of fluidized beds is not possible based only on kinetics and mechanistics models alone or purely thermodynamical considerations, since all factors should be integrated to describe the overall phenomena. SINGLE PARTICLE TRANSFORMATION Assuming a first order reaction with respect to the gas and zero for solid, such as

Jan 1, 1984

By Daxian Z, Youdi Z, Shucai Y

The Huolinhe surface mine is a very large-scale surface coal mine, located in the north-east area of China with a production rate of 1.2 Mtpa. Its coal haulage system has a large capacity, long transportation line and high degree of automation. The system comprises two crushing plants, many belt conveyors, four surge bunkers, one loading bunker, one coal storage and five end product bunkers. In this paper, the network patterns of semi-continuous systems in surface mines are studied, the reliability calculation methods and a simulation model are established and the software for computing the reliability of a semi-continuous system is worked out. By considering the whole coal haulage system in the Huolinhe surface mine, the authors developed the system reliability-numerical simulation method. The steps and the computing results of this method are described in detail. Through the calculation, we can master the present situation of system reliability and the main factors impairing system reliability, expose the system weak links, put forward the ways of enhancing system reliability and furnish the basis for improving the system and equipment. The way of increasing capacity and methods of enhancing system reliability are further raised.

Jan 1, 1995

By Paul D. Merica, H. Hanemann

The application of other than mechanical methods to the study of the mechanical-physical properties of metals has become in the last few years a topic of investigation of ever-increasing interest, both from the theoretical standpoint and from that of the engineer and constructor. Besides the investigations which have been made of the magnetic properties of ferromagnetic metals, in their relation to the mechanical properties of these metals, which will be discussed more in detail below, there have been made studies of other phenomena in the same relation, and methods for the mechanical testing 'of metals have even been suggested; for example, the microscopic method of Tammann,' and the thermo-electric method of Turnera for determining elastic limits. The application of all such methods, which are based upon the dependence of some physical, crystallographic, or possibly chemical property, upon the mechanical state of the metal, must be preceded by close and careful correlation of these various "test" properties with the known mechanical state of the different metals or materials. It is with this view that the present work, as well as that of many previous investigators of, what may be termed in the interests of brevity, the mechanical-magnetic properties of ferromagnetic materials of construction, has been done. Previous Investigations of Mechanical Magnetic Properties The effect of mechanical stresses and of deformation, elastic or otherwise, oil the magnetic qualities of iron, steel, and other metals, has been studied by a number of investigators from the time of Joule (1841) to the present. It will, however, for the present purpose be sufficient to give an account only of the principal results obtained in the course of these investigations. It was early noticed (Villari, 1865) that if an iron wire is placed in a

Jan 1, 1916

Ventilation challenges are often encountered when an underground mine expands to new zones and it often is the case to make a thorough review of the existing system and assess immediate and future airflow needs at the desired quantity and quality. An unexpected mine plan change that calls for increased development and production from new areas can impose a strain on the existing ventilation system. Budgetary constraints can also demand creativity in design on the mine ventilation engineerÆs part. Since the addition of several mining horizons it had become obvious at the Meikle mine that something had to be done to increase airflow quantity and quality in the old main zones because most of the ventilation resources had been channelled for development in the new mining horizons. An airflow assessment of the existing system had to be performed and it was determined that the airflow quantity had to be increased by at least 30 per cent and the quality of the air had to be improved by reducing nuisance and respirable dust and at the same time reducing the airflow temperature before it was used in a few mining zones. At the conclusion of the airflow assessment it was determined that a third centrifugal fan would be installed on a new 3.05 m diameter borehole from surface to underground. By a careful study of temperature conditions over time it was determined that an evaporative cooling spray chamber would be sufficient to cool the airflow down from the high dry bulb temperatures observed down to saturation at the wet bulb temperature. At the same time excessive nuisance dust generated as a result of the airflow travelling a long way in a haulage drift will be knocked down in the spray chamber resulting in cool, clean air in the mining districts. Expansion of the existing surface ammonia refrigeration plant was out of the question for several reasons. The fact that the airflow was hot and dry meant that evaporative cooling spray chambers could achieve lower working temperatures at a very low cost compared to the expansion of the chilled water plant. The expansion of the ventilation system at Meikle mine and the use of evaporative cooling spray chambers were demonstrated to be very successful and the information presented in this paper can be of benefit to other mines experiencing the same ventilation problems as was the case at the Meikle mine.

Jan 1, 2005

By C. M. Marquardt

Tramp iron and steel moving on a conveyor belt cause small currents to be generated in a coil situated in a strong magnetic field, which are converted to an alternating current and are amplified. The output voltage from the amplifier fires a thyratron with a relay in its anode circuit, which actuates a howler and simultaneously drops a spot of marker material on the belt. THE problem of tramp iron removal from moving ore belts is a long standing one. When heavy ore streams are carried on a belt, magnetic pulleys and strong surface magnets fail to remove tramp buried in the ore stream. Tramp iron buried in the ore stream cannot be pulled from the bed by surface magnets and is carried past the magnetic pulley by the falling ore stream. With the increased use of detachable bits the problem of the detection and removal of tramp has become more necessary and difficult. Several types of tramp detectors have been developed. It would serve no practical purpose here to review exhaustively the literature on the subject. Methods of tramp detection used are: (1) The magnetic method, wherein the small current generated by the magnetized tramp passing a Coil is used. (2) The unbalanced oscillator method wherein the tank circuit of a stable radio- or audio-frequency oscillator is unbalanced causing a change of frequency or a change in plate current due to changes in eddy currents, hysteresis, or dielectric because of the presence of tramp. (3) The bridge methods wherein the impedance of one leg of an alternating current inductive bridge is changed due to the presence of conducting tramp. Each of these methods of tramp detection has its field of usefulness. The second and third methods are excellent for oxide iron ores, coal, sand and gravel, grain, etc. However, these latter methods are not suitable for use on ores that contain rich conducting sulphides, since a large piece of pyrite or galena will cause the same detector response as a piece of tramp iron. At the Caselton, Nevada, plant of the Combined Metals Reduction Co., sulphide ores are treated; therefore, it was necessary that a tramp detector operating on only the magnetic properties of the tramp iron be used. Tramp iron detectors of this type operate on the principle that if a piece of tramp iron moves near a coil in a high intensity, steady magnetic field, the presence of the moving tramp iron causes the magnetic flux lines through the coil to change. This induces a mall current in the Coil. In series with the Coil is generally placed a relay sensitive to currents of 1 to 3 microamp. When the tramp iron passes near the coil the flux linkages change, causing this very sensitive relay to actuate. Since the contacts of such a relay are very small it must actuate a second relay capable of breaking a larger current

Jan 1, 1951

By E. Brunner, E. S. Mardock

A method of measuring oil saturations in cores or sand packs by neutron scattering is described. This method permits local SatUrations to be measured in a core enclosed in a steel pressure vessel without interrupting the flow. calibration data and a saturation distribution measurement obtained with the apparatus are included by way of illustration. Introduction In laboratory flow experiments designed to study the mechanism of oil production it is frequently necessary to measure the oil saturation in a core or sand pack containing Oil, gas, and perhaps brine. It is sometimes desirable that the saturation measurement refer to a relatively small portion of the core, so as to eliminate end effects; that it be made without interrupting the flow, and that it be applicable to a core enclosed in a steel Pressure vessel capable Of withstanding the Pressures encountered in petroleum reservoirs. None of the usual methods of measuring saturation meets all Of these requirements. To measure the gas saturation by observing the apparent compressibility of the gaseous Phase1 would require the interruption of the flow and would give an average saturation for the whole core. An electrical conductivity method is available for measuring brine saturations,2,3 but it is not applicable to oil. A radioactive tracer might be used if a suitable substance could be found that would dissolve in the oil, emit gamma radiation, and not be adsorbed on the sand, the steel core holder, or in an aqueous- phase. The large gamma-ray background from the mass of radioactive oil in other parts of the apparatus might, however, be undesirable. There remain for the saturation measurement methods involving the absorption or scattering of some penetrating radiation produced outside the apparatus. It might be possible to use X-rays or gamma rays; but these radiations would be so much less strongly absorbed and scattered by the oil than by the steel walls of the core holder and by the sand that it seems doubtful that much precision could be attained. In a beam of neutrons, however, there is a radiation that is very penetrating and, moreover, its scattering by substances containing hydrogen, such as oil, is qualitatively different from that occasioned by other materials. It would seem possible, and has proved to be quite practicable, to measure oil saturations accurately under the required conditions by means of neutron scattering. The first, to our knowledge, to suggest neutron scattering as a means of measuring oil saturation were F. Brans and ,. A. Bottema,4 of the Amsterdam laboratories of the Bataafache Petroleum Maatschappij, who made a few preliminary experiments to test the method while they were engaged in exploring the possibilities of neutrons for well-logging purposes. A comprehensive account of neutrons and their behavior will be found, together

Jan 1, 1946

By E. S. Mardock, E. Brunner

A method of measuring oil saturations in cores or sand packs by neutron scattering is described. This method permits local SatUrations to be measured in a core enclosed in a steel pressure vessel without interrupting the flow. calibration data and a saturation distribution measurement obtained with the apparatus are included by way of illustration. Introduction In laboratory flow experiments designed to study the mechanism of oil production it is frequently necessary to measure the oil saturation in a core or sand pack containing Oil, gas, and perhaps brine. It is sometimes desirable that the saturation measurement refer to a relatively small portion of the core, so as to eliminate end effects; that it be made without interrupting the flow, and that it be applicable to a core enclosed in a steel Pressure vessel capable Of withstanding the Pressures encountered in petroleum reservoirs. None of the usual methods of measuring saturation meets all Of these requirements. To measure the gas saturation by observing the apparent compressibility of the gaseous Phase1 would require the interruption of the flow and would give an average saturation for the whole core. An electrical conductivity method is available for measuring brine saturations,2,3 but it is not applicable to oil. A radioactive tracer might be used if a suitable substance could be found that would dissolve in the oil, emit gamma radiation, and not be adsorbed on the sand, the steel core holder, or in an aqueous- phase. The large gamma-ray background from the mass of radioactive oil in other parts of the apparatus might, however, be undesirable. There remain for the saturation measurement methods involving the absorption or scattering of some penetrating radiation produced outside the apparatus. It might be possible to use X-rays or gamma rays; but these radiations would be so much less strongly absorbed and scattered by the oil than by the steel walls of the core holder and by the sand that it seems doubtful that much precision could be attained. In a beam of neutrons, however, there is a radiation that is very penetrating and, moreover, its scattering by substances containing hydrogen, such as oil, is qualitatively different from that occasioned by other materials. It would seem possible, and has proved to be quite practicable, to measure oil saturations accurately under the required conditions by means of neutron scattering. The first, to our knowledge, to suggest neutron scattering as a means of measuring oil saturation were F. Brans and ,. A. Bottema,4 of the Amsterdam laboratories of the Bataafache Petroleum Maatschappij, who made a few preliminary experiments to test the method while they were engaged in exploring the possibilities of neutrons for well-logging purposes. A comprehensive account of neutrons and their behavior will be found, together

Jan 1, 1946