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Mark Twain once observed that "Everyone complains about the weather but nobody does anything about it." Not too long ago, the same observation held true for the problem of air pollution. During the past 25 years, however, the mounting concern over air pollution has spurred industrial and governmental research to find ways and means to combat the menacing situation. But for all the time and money spent in recent years to fight it, air pollution is still a major problem in most industrialized communities in America. At the SME Fall Meeting last September, coal's responsibility for such pollution was aired at an informative panel discussion moderated by Ernst Hall. The many-sided problem of air pollution became readily apparent as five experts, representing industry and government, parlayed over the task of cleaning up dirty air. Their opening comments are reprinted here.

Jan 11, 1964

By Alfred R. Powell

FOR the purposes of this discussion, the direct gasification of coal means the of hydrogen and carbon monoxide by the well-known water-gas reaction. Chemicals or other synthetic products may be made from these constituents of the gas and under such circumstances the gas is called synthesis gas. Or, if the same gas is used as a fuel, it is called blue gas or water gas. This type of gas has usually been made from coke, especially in this country, and has been used both for fuel purposes and for manufacture of chemicals. Recently, natural gas has gained the ascendancy as a source of synthesis gas for manufacture of chemicals because of its relative cheapness. As natural gas becomes less readily available and more expensive, coal will take its place as a raw material for the preparation of synthesis gas. This substitution will probably take the form of direct gasification of the coal rather than the present two-step procedure of carbonization of the coal followed by gasification of the coke. The chief reason for this probability is the intensive research now being carried on by several organizations to develop successful and economical processes for the direct gasification of coal, which is a considerably cheaper fuel than coke. In the following pages an attempt has been made to predict the chemicals that will result from this future production of synthesis gas by the direct gasification of coal. CHEMICAL REACTIONS OF SYNTHESIS GAS Given the proper conditions, there are many chemical reactions leading to production of useful products that can be carried out with this mixture of hydrogen and carbon monoxide. These many reactions may be grouped into three classes: (1) interaction of hydrogen and carbon monoxide, possibly with addition of other reactants; (2) reaction of hydrogen with various substances; (3) reaction of carbon monoxide with various substances. Thus sometimes hydrogen and carbon monoxide are utilized together in the same chemical reaction while in other instances only the hydrogen or only the carbon monoxide is required as a reactant. Fortunately, practical methods are available for securing either hydrogen or carbon monoxide from synthesis gas, some of which are also applicable for changing the ratio of these two constituents in the gas when that is desirable.

Jan 1, 1953

By H. C. Rolseth, R. H. Kohler

Jet channeling made its entry into the granite industry in 1955 and quickly gained acceptance as an economical method of quarrying. Developed by the Linde Division of Union Carbide Corp., this method employs a small rocket-jet burner with a high-temperature, high-velocity exhaust flame that causes granite to disintegrate. It can thus make continuous vertical cuts to free large blocks from granite formations. The Thermal Spalling Process The effect of a thermal device on rock depends upon the rock's spallability. In simplest terms, spalling is the decrepitation resulting from differential expansion of rock crystals due to thermally induced stresses.1 the individual rock properties influencing the spalling characteristic are so numerous and their interaction is so complex that it has so far been impossible to predict with accuracy the reaction of any particular rock to a high-temperature source of heat. Perhaps computers will eventually make such predictions possible, but for the present it is necessary to impose the thermal shock conditions on a sample of the rock to establish its spalling characteristics. The properties most favorable to a high degree of spallability are: (1) Large linear thermal expansion at temperatures below 700º C. (2) High thermal diffusivity at temperatures below 400º C. (3) Equigranular interlocking structure with little or no fine-grained clay or mica alteration products. (4) No significant amounts of soft, low-melting, or elastic minerals or materials which yield after thermal decomposition.

Jan 7, 1969

By J. E. Pollock

IN the oil-refining industry, steel comprises by far the greatest proportion of the materials used in construction work, but with an enormous number of alloy steels and nonferrous alloys available, and a greater knowledge of their properties and corrosion resistance; a substitu-tion first in the "hot spots" and then in locations of moderately severe corrosive conditions will be made as the greater expense can be justified. In new construction work, advantage is taken of the experience already gained and appropriate materials used, whether for high temperatures and pressures demanding additional strength or for corrosive conditions. The locations, however, where equipment in operation constantly requires replacement will soon become evident, as will the necessity for replacement in more resistant materials, if considerable down-time is to be avoided. In what direction and how far to go in the matter of alloys then becomes a question of the highest importance. Obviously, any replace-ment with more costly material must be. justified economically by the promise of longer life, thereby saving both material and installation costs besides the reduction of loss of production. Where the equipment is overcapacity and a regular schedule of cleaning periods is in force, the last item frequently must be ruled out and justification made on the basis of the first two only. Installation of material that will outlast the remainder of the equipment and have no recovery value must also be avoided; this is particularly important in temporary construction or in old equipment that will soon become obsolete.

Jan 1, 1935

By Byron S. Gottfried

This paper describes a comprehensive computer program, developed under the joint sponsorship of the U.S. Environmental Protection Agency and the U.S. Bureau of Mines, that simulates the performance of coal preparation plants. A typical plant configuration may include several different washers, crushers, and screens as well as stream blenders and stream splitters, interconnected in whatever manner the user may specify. The program will predict the mass and energy yields of each unit and the properties of each flowstream (weight, ash, pyritic sulfur, total sulfur, and energy distributions), provided the feed properties and appropriate values for various control parameters are given. The program is used to assess washability characteristics of different coals, to determine the effectiveness of different plant operating conditions, and to compare the performance of various plant configurations. A brief description is given of the methods used to carry out the calculations for each type of unit. Results of some calculations are also presented. These results illustrate the versatility of the program for analyzing both simple and complex plant configurations. The paper concludes with a description of other accomplishments and future plans.

Jan 1, 1977

By Henry Hanson

A STUDY of the ore to be treated should be the first step in deciding on a machine for crushing or grinding. Coarse crushing is practically confined to the jaw and the gyratory crushers, the large-size jaw type being often employed in large installations as a primary crusher, followed by the gyratory type for secondary reduction. In small plants where mine-run ore is reduced in a single step, either of these machines will do the work. In intermediate and fine grinding, various machines are used. The relative merit of the different types will be governed in no small measure by the size of the installation, the character of the ore to be reduced and the final product desired for subsequent treatment. It should be possible, nevertheless, with the data available, if properly classified, to arrive at an approximation of the relative efficiency of these intermediate and fine grinders. It should be possible, also, to determine the economic grinding range of the different machines. With this in mind, it will be the object of this article to indicate, in rough outline, how the data available may be classified, rather than to attempt to discuss any particular practice and compare the results with other practices. Conclusions or generalizations can not be drawn without an exhaustive classification of data; in fact, many vital points will have to be determined by additional experiments which can be carried on most advantageously in the laboratory. The expense en-tailed in such experiments would be worth while if the data obtained should lead to definite conclusions that would aid in standardizing and simplifying grinding practice.

Jan 2, 1923

By J. Amanat, H. J. Siriwardane

A numerical procedure based on nonlinear finite element analysis has been developed for predicting subsidence profile over longwall mine panels. The developed procedure has been verified by comparing predictions with published field observations at several mine panels. This paper presents certain aspects of predicting subsidence profile over mine panels located in hilly terrain. Analysis of four such cases are presented herein.

Jan 1, 1984

By J. Russ, C. L. Clark

For many years attempts have been made to develop a laboratory test that would serve to indicate the proper temperatures to be used in the various hot-working applications to which metals may be subjected as they are being processed from the cast ingot to the desired finished products. That these attempts have not been very successful is indicated by the fact that most of the temperatures in use today in these operations have been developed over a period of years by trial and error. In other words, the selection of the proper temperatures for the hot-working of metals is generally an art rather than a science. Our knowledge with respect to the behavior of metals at elevated temperatures has been greatly extended during the past several years. While most of the work in this field has been done at proposed operating temperatures of equipment, rather than at processing or fabricating temperatures, one outstanding fact has been developed, which is applicable to the entire high-temperature range; that is, that the rate of deformation to which the metal is subjected is of the same order of importance as the temperature. The failure to properly recognize this fact has greatly retarded the development of a suitable laboratory test for determining hot-working temperatures. Influence of Rate of Deformation on High-temperature Properties It is not the intent of this paper to survey all the work that has been done On the effect of deformation rate On the properties of metals. The importance of this factor, however, was shown by Zay Jeffries' as early as 1919, when he called attention to the existence of the so-called equicohesive temperature and to the effect of certain factors on the location of this temperature' Fig. I is a diagrammatic sketch showing the effect of temperature On the relative strength of the crystals and grain boundaries and the type of fracture that will res depnding On the location of the test, or Or temperature with respect to the equicOhesive temperature. Since the type fracture varies, it also follows that at temperatures below the equicohesive temperature the major deformation occurs in the grains: while at temperatures above, the deformation results either from the movement of the grains with respect to each other or recrystallization of the strained material occurs almost instantaneously, producing new crystals at the fracture. As previously indicated, it is an established fact that the position of this equicohesive temperature for any given metal is dependent On the deformation rate' For example, in 0.15 per cent plain carbon steel the location of this temperature under

Jan 1, 1947

By C. L. Clark, J. Russ

For many years attempts have been made to develop a laboratory test that would serve to indicate the proper temperatures to be used in the various hot-working applications to which metals may be subjected as they are being processed from the cast ingot to the desired finished products. That these attempts have not been very successful is indicated by the fact that most of the temperatures in use today in these operations have been developed over a period of years by trial and error. In other words, the selection of the proper temperatures for the hot-working of metals is generally an art rather than a science. Our knowledge with respect to the behavior of metals at elevated temperatures has been greatly extended during the past several years. While most of the work in this field has been done at proposed operating temperatures of equipment, rather than at processing or fabricating temperatures, one outstanding fact has been developed, which is applicable to the entire high-temperature range; that is, that the rate of deformation to which the metal is subjected is of the same order of importance as the temperature. The failure to properly recognize this fact has greatly retarded the development of a suitable laboratory test for determining hot-working temperatures. Influence of Rate of Deformation on High-temperature Properties It is not the intent of this paper to survey all the work that has been done On the effect of deformation rate On the properties of metals. The importance of this factor, however, was shown by Zay Jeffries' as early as 1919, when he called attention to the existence of the so-called equicohesive temperature and to the effect of certain factors on the location of this temperature' Fig. I is a diagrammatic sketch showing the effect of temperature On the relative strength of the crystals and grain boundaries and the type of fracture that will res depnding On the location of the test, or Or temperature with respect to the equicOhesive temperature. Since the type fracture varies, it also follows that at temperatures below the equicohesive temperature the major deformation occurs in the grains: while at temperatures above, the deformation results either from the movement of the grains with respect to each other or recrystallization of the strained material occurs almost instantaneously, producing new crystals at the fracture. As previously indicated, it is an established fact that the position of this equicohesive temperature for any given metal is dependent On the deformation rate' For example, in 0.15 per cent plain carbon steel the location of this temperature under

Jan 1, 1947

By S. F. Ravitz

IN his excellent book on the Principles of Flotation, Wark1 makes the following sig-nificant statement concerning the theory of flotation: Two questions of first-rate importance must be considered . . . First, it must be decided whether the sulfide minerals require a collector in order that they may float, or whether as has been claimed, they possess an inherent float-ability and need no collector. Second, it must be decided whether the xanthate type of col-lector can react with or be adsorbed by the unchanged sulfide minerals themselves, or whether, as many claim, reaction with the collector is dependent upon initial oxidation of the mineral surface. In the theory of flotation there are no two questions of greater impor-tance than these. Ravitz and Porter2 presented evidence that galena can be floated without a col-lector, and even without any reagent, pro-vided oxidation products are thoroughly removed from its surface. They found also that thoroughly cleaned galena floated faster when xanthate was used than when a frother alone or no reagent was used, and that, without a collector, the recovery decreased gradually upon exposure of the mineral to air. Their work, however, has met with considerable criticism. 1(127),3-6 This paper is presented to answer the objections that have been raised, and to present additional data that confirm their results.

Jan 1, 1940

Kaiser Sees Bright Future for Jamaica Kaiser Aluminum Co. has a big stake in the British West Indies, the Island of Jamaica in particular. There, Kaiser is busy developing one of the most promising bauxite finds in recent years. The $12 million operation was officially opened in February. Facilities have a rating of an annual capacity of 2 million tons and will supply Kaiser plants with ore for years. The ore comes across the Gulf of Mexico, up the Mississippi to stockpiles at Baton Rouge. The stockpile at Baton Rouge would throw many an old river boat skipper for a loss. Where no mountain once existed now stands a man-made bluff of bauxite, known as Bauxite Peak.

Jan 6, 1953

By T. Egleston

THERE has always been a-theory among those working placer mines that gold is both found " rusty," and becomes so under treatment, by which they mean, not that gold becomes coated with oxide of gold, bat that it is either coated superficially or alloyed with sortie substanee 'which prevents the ,contact with mercury, and thus precludes the possibility of amalgamation. To such conditions of the

Jan 1, 1881

By Tokio Yanagida

Major parameters relating to the operating of the conventional calcine-charged reverberatory f'ce process such as distribution coefficients of major elements among slag, matte, blister, and gases, temperatures and weights of intermediates, and heat losses of furnaces were measured and determined. A computer program to estimate heat and material balances at the process was prepared utilizing these data, showing a good agreement with actual results.

Jan 1, 1984

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Jan 1, 1938

By Lawrence Addicks

Some three years ago the smelter connected with the Chrome, N. J., refinery of the United States Metals Refining Co. found itself embarrassed by constantly increasing piles of unsmelted blast-furnace flue dust. The charge was fine and 10 to 15 per cent. of it was blown over into the flue. Sulphur was at that time too scarce to make the sintering of the finer part of the charge attractive, and raw-ore smelting in a reverberatory with a partly oxidized charge was not to be thought of. A great many schemes were considered, including leaching, blowing into the converters, and briquetting, the problem finally narrowing down to blast roasting and nodulizing. It was found by experiment that blast roasting would not yield a satisfactory sinter without the addition of coke dust or sulphide fines to augment the fuel value of the flue dust, and on this account, together with the low first cost of a kiln, the latter was decided upon. A couple of tons of flue dust were tried out in the experimental kiln in the laboratory at Yorktown, Va., of J. H. Payne, who acted as consulting engineer in this connection. This kiln was approximately 2 ft. in diameter and 20 ft. long and was fired with fuel oil. A run of several hours yielded excellent nodules. The ki1n showed no tendency to build in and form "nose rings" and gave a fuel consumption of 50 gal, of oil per ton of flue dust. There was no indication of any stack loss. The roasting was strongly oxidizing. A study of what full-size kilns were doing on cement clinker and on nodulizing pyrites cinder indicated that a 60 by 6 ft. kiln would certainly not consume over half of the oil per ton of flue dust shown on the test and as fuel oil at that time was selling around 2 1/2 c. per gallon it was decided to let it go at that. A 60 by 6 ft. kiln was decided on, as that size is standard in cement practice, although fast being replaced by much larger ones with their greater fuel economy, and as it fitted in the building space available. A 6-in. brick lining brought the net diameter down to 5 ft. The inclination

Jan 1, 1915

By C. K. Leith

ManGanese is one of the minerals which is principally consumed in countries other than origin. Nearly 85 per cent. of the world's production is used by the United States, England, Germany and France, and roughly a third of the total is used by the United States alone. On the other hand, over 85 per cent. of the world production comes from Brazil, Russia, India, the Gold Coast of Africa and the Sinai Peninsula. It follows from this fact that practically all manganese moves across international boundaries in raw or alloy form, and much the larger part of this inovement is for considerable distances and is occan bornc. There is no indication that any one of the principal consuming countries can develop even approximately adequate supplies of its own. Under abnormal war conditions, with high prices and changes in metallurgical methods, only 35 per cent. of the needs of the United States was met from local sources, and under our recent tariff only 11 per cent. There are thousands of manganese deposits scattered about the world, but only a very few which can figure largely in supplying requirements on a modern scale. The known reserves, together with highly probable extensions and explorations now under way, indicate no shortage from a world standpoint for many deeades to come. The production and marketing of manganese is going steadily into fewer and stronger hands. The steel industry uses over 90 per cent. of all the manganese mined and is acquiring control of a considerable part of the production in all of the principal fields—the Germans in Nikopol, the English in India and Gold Coast, the Americans in Georgia, India, Gold Coast and Brazil. Some of the controlling companies arc of international scope. Concentration of commercial control is a notable tendency. A natural consequence is the growing uneasiness of smaller consumers the world over about their ultimate supplies and desire to know more definitely how and where manganese supplies will be controlled in the future. The sources of supply are few cnough to warrant the belief that more or less monopolistic elements of control arc not impossible.

Jan 1, 1927

By Dietmar Espig

Very useful general relationships between operating parameters and the operating results for open- and closed-circuit grinding under steady- state conditions are described. The basic idea of the developed methods consists of the introduction of a known reference state. The relations derived from very simple approximations to individual processes allow one to evaluate fineness and mass flow of the desired state after changing the parameters (feed rate, fineness of the feed material, mill length, transport behavior through the mill, classifier characteristics). It was also possible to derive some general relationships, e.g., * an equation for the influence of the operating parameters of the mill on the fineness of the mill output * a criterion to establish if the desired state of a closed grinding circuit is steady state at all * a possibility to substitute the common influence of the transport behavior of the mill and of the classifier by-pass fraction with the coarse stream on the mill outlet product by means of a fictitious worse transport behavior. The applicability of the described methodology to many problems in grinding practice, including questions of controlling grinding circuits, is demonstrated by some examples. In particular, a working diagram of the standard closed grinding circuit has been established.

Jan 1, 1984

Jan 1, 1938

By Alfredo O. Del Campo

Copper concentrate smelting has been the subject of significant improvements during the last three decades. Several new processes are being successfully applied at industrial scale, and probably no new copper smelter will be built with the old-fashioned reverberatory furnace. However, because of financial reasons, the existing reverberatory furnaces, which smelt a significant part of the copper produced worldwide, are likely to last at least another decade. Some improvements have been introduced in reverberatory smelting practice, the best known being the use of oxyfuel burners. However, efforts to optimize the reverberatory furnace operation through automatic control have not been reported. The complex and semi-continuous nature of the process makes it dificult to find a suitable strategy for its automatic control. Many factors, like fuel economy, productivity, boiler capacity, refractory wear, converter slag return, copper losses in discard slag, etc. are interconnected. The chosen control strategy should take into account all these factors to achieve good economic results. A detailed discussion of these problems is presented.

Jan 1, 1984

By A. L. Holley

The intention of this paper is not to discuss this important subject in all its bearings, but merely to point out why mechanical tests of steel, as ordinarily made, are not, alone, of any special value to engineers—certainly not to general mechanical engineers. The agents of the Barrow Hematite Steel Company, one of the largest and most successful Bessemer establishments in England, have recently distributed a report, made by Sir William Fairbairn,