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By Louis C. McCabe

The control of dusts and fumes of submicron size is involved in many process industries. This paper presents in tabular form the quantitative data from a number of metallurgical operations and discusses allowable discharge in terms of effluent-weight ratio. Typical installations for recovery of stack effluents are cited. THERE are many sources of smoke, fumes, gases, and dusts that may cause undesirable contamination in an industrial area. Fumes and gases are the result of chemical action or volatilization, while dusts are produced in processes of disintegration and dispersion. Commonly, smokes are suspended particles formed by combustion or destructive distillation. Methods for controlling smoke are generally known, and great improvements have been made in equipment for removing fine dusts and fumes from gases. In most of the industrial centers of the country, the chief duty of the air-pollution abatement agency is the elimination or reduction of emissions resulting from improper combustion. Correct methods of firing, proper fuel selection, and installation of properly designed equipment may accomplish this. It is becoming more widely recognized that much of the contamination of an industrial atmosphere is caused by dusts, fumes, and gases that are not related to the process of combustion. As such emissions are usually a functional part of plant operation, they rarely can be prevented even by better design and careful operation. When dusts, fumes, and gases are an integral part of the operation, mechanical equipment must be designed to remove these emissions. Most of the dusts and fumes that should be controlled are less than 1 micron in size. Control of such small particles is largely a new and untried field in many industrial areas. However, where conditions have been critical, effective control equipment for dusts, fumes, and gases has been in operation for many years. The problem is not one of smoke abatement and requires an entirely different set of standards for effective solution. Identical standards need not be applied to all industrial areas because of differences in meteorology, physiography, plant location, plant density, and nature of stack effluents. In this paper, discussion of control of atmospheric contamination by industrial plants refers specifically to the Los Angeles area, but the method of approach is applicable to any area where similar problems are encountered. Quantities of particulate matter reported in analysis of stack effluents indicate the need for standards of emission. Many types of dusts and fumes that contribute materially to the air-pollution problem are discharged into the atmosphere at a lower rate than 0.40 grain per cu ft at standard conditions. On the other hand, some stacks discharge at a higher

Jan 1, 1951

By Orville R. Lyons

CENTRIFUGAL force has been utilized for the dewatering of fine coal for over 50 years by means of machines commonly called centrifugal dryers. In any centrifuge the coal and water are subjected to a spinning action which usually inctedtocreases in intensity as the coal progresses through the machine. This spinning action, or the centrifugal force that it induces, tears water away from coal particles and produces a dewatered coal. The effectiveness of the dewatering action for any particular machine is governed by the size-consist of the coal and the centrifugal force imparted to the water on the coal. Four makes of centrifuge are currently being used to dewater fine bituminous coal in the United States. These include the vertical, basket-screen C.M.I. (Centrifugal and Mechanical Industries) Carpenter, Reineveld, and the horizontal solid-bowl Bird. The C.M.I. and Reineveld centrifuges are similar in construction and are variations of the Elmore centrifuge, varying principally in the slope of the basket, operating speed, size of perforations in the basket, and diameter of the basket. The same operating description suffices for both. These centrifuges are made up of two rotating elements, an outside conical screen frame and an inside solid cone which carries spiral pusher blades. The screen frame is supported by a hollow shaft, and the solid cone by a spindle shaft passing through the hollow shaft. Both the screen frame and the solid cone rotate at high speeds; the solid cone, with its scraping flights, rotating somewhat more slowly than the screen. The wet coal enters the machine at the top, falls on the cone, and is thrown against the screen by centrifugal force. The coal slides down the screen until it meets the upper end of the flights, where it is moved slowly along the flights until discharged at the bottom. The elfluent passes through the sieve basket or screen and discharges into a launder. The Carpenter centrifuge consists of a conical rotating element with a vertical axis, built up of three rows of perforated stainless-steel plates or stainless-steel wedge-wire or round-wire sections cut and rolled to conform to the surface of the cone. Wet material is delivered to a conical hopper inside the centrifuge casing and is distributed in a thin, even layer over the inner surface of the cone by a disk mounted on the rotor shaft. Impacting of the coal against the screen and the centrifugal force exerted as the material moves downwards creates a dewatering effect. The moisture is forced through the coal bed and then through the perforated plates of the basket, collecting in a circular trough built into the centrifuge. The effluent is conducted from the trough through the centrifuge casing by outlet pipes. The dewatered coal is discharged over the inside bottom edge of the rotor. The Bird centrifuge consists of a tank or truncated conical shell, which is revolved at the desired speed by means of a drive sheave. A screw conveyor rotates inside the cone or bowl at a slightly lower speed in the same direction of rotation. The feed entrance, in the center of the large end of the truncated cone, is high enough to allow formation of a pool of slurry. Adjustable effluent-discharge ports are located in the large end of the bowl so the level of the liquid can be regulated. The solids are moved forward by the screw conveyor as fast as deposited and carried above the level of the pool for an interval before leaving the bowl. In the past these four makes of centrifuge could be compared only by indirect means. The author published a rough comparison method in 1949' but

Jan 1, 1952

By Harlan W. Nelson, James B. Purdy

The great majority of stokers used in residential heating installations are of the clinkering type. Because of inherent characteristics of the underfeed combustion process as it occurs in these small stokers, and because of the wide range of operating conditions encountered in residential heating schedules, not all bituminous coals can be used successfully in residential underfeed units. The problem of providing consumer satisfaction has been attacked by the joint efforts of the stoker manufacturers and the coal industry; the stoker manufacturers have been concerned with improving their product to permit the use of a wider range of coals, and coal operators have made every effort to market selected and better prepared coals. In view of the wide range of physical characteristics and chemical properties of bituminous coals, the problems are real and are receiving increased attention. Some twelve years ago a laboratory method was developed at Battelle Memorial Institute for the relative evaluation of coals for use in residential underfeed stokers. The method was developed in conjunction with work being done at that time for Bituminous Coal Research, Inc., and for individual coal producers, to obtain information on the characteristics of coal that determined the successful performance of the small stoker. Details of the equipment and test procedure were given by R. A. Sherman1 in a paper presented at the University of Illinois Fifth Short Course in Coal Utilization. During the past several years, the evaluation of over forty different coals has been determined by investigations sponsored at Battelle by coal operators in the eastern producing districts. The purpose of this paper is to compare the results and conclusions derived from the various tests with marketing experiences of the operators, and to discuss briefly the relationship of test results to standard laboratory determinations. Equipment Used in Tests Fig 1 shows schematically the equipment used in the evaluation tests. The stoker is a commercial model of conventional design, having a nominal feed rate of 30 Ib per hr. A special laboratory furnace is used, which is tightly sealed to prevent the entrance of secondary air. The complete stoker-furnace assembly is mounted on platform scales which permits the measurement of combustible weight losses occurring during the test. The furnace stack, in which are a thermocouple, flue-gas sampling tube, and smoke meter, is connected to the laboratory exhaust breeching through a friction-less connection. Through use of an auxiliary blower system, provision is made for the measurement of the air delivered by the stoker fan to the windbox. A water seal in the duct work eliminates inter-

Jan 1, 1950

By Harlan W. Nelson, James B. Purdy

A study of data obtained during laboratory tests to determine the suitability of bituminous coals for use in residential underfeed stokers of the clinkering type has led to the following general conclusions: 1. Performance data obtained during the test furnish useful and practical information upon which to judge the performance of stoker coals. 2. Conclusions derived from the results of evaluation tests are in general agreement with use experience of the coals in the field. The method is of practical use in this regard. 3. Few direct relationships were found between data furnished by the evaluation test and determinations by standard laboratory tests. This is particularly true with regard to coke formation and clinker formation, two of the most important factors in determining the degree of satisfaction to be obtained in applications of the small underfeed stoker. It has not been the intention in this paper to prescribe this evaluation test as the best method for the evaluation of coals for use in residential stokers. That there are other test methods having similar objectives serves to point out the necessity for full-scale laboratory tests. At the present time, a standard test procedure for the evaluation of coals for use in residential stokers is not available. For the past several years a joint committee, appointed from the membership of the Residential Stoker Committee of Bitulninous Coal Research, Inc., and from the Engineer- ing and Research Committee of The Stoker Manufacturers Association, has been working to develop a standard procedure for testing and evaluating bituminous stoker coals. This procedure has been completed to the extent that it has been drawn up in tentative form. It is now planned to install the equipment in several laboratories and to run check tests, using portions of identical lots of coal, to determine the degree of reproducibility offered by the method. Completion of this standard test procedure should greatly facilitate the evaluation of coals for use in residential stokers. Acknowledgments The cooperation of coal operators sponsoring the coal evaluation tests, in granting permission to use data and results from their tests, is gratefully acknowledged. Acknowledgment is also made to Carroll F. Hardy, Chief Engineer, Appalachian Coals, Inc., for his interest and timely suggestions on the preparation of this paper. Special thanks are due to Ralph Sherman, Assistant Director, Battelle Memorial Institute, who was largely responsible for development of the evaluation procedure, for helpful suggestions and advice. References I. H. A. Sherman: The Evaluation of Coal for Use in Domestic Stokers. Univ. of Ill., Eng. Experiment Station, Circular No. 39 (1939). 2. . Q. Shotts: The Relation of Free- swelling Indexes to Other Characteristics of Some Alabama Domestic Stoker Coals. TP 2314, Coal Tech., (Feb. 1948); Trans. AIME (1948) 177, 502. 3. . J. Helfinstine and C. C. Boley: Correlation of Domestic Stoker Combustion with Laboratory Tests and Types of Fuels 11. Combustion Tests and Preparation Studies of Representative Illinois Coals. Ill. State Geol. Survey, Re1. of Zntlestigations No. 120 (19467 ) p. 35. DISCUSSION E. R. Kaiser*—AS a former fuel engineer assigned to residential stokers at Battelle, the writer has read with considerable interest the paper by Messrs. I'urdy and Nelson. It is gratifying to note that earlier test techniques have been developed and that criteria found important in the years 1935 to 1938 are still important in judging the performance of stoker coals for residential heating. The authors have plotted a number of the primary coal data singly against performance data of the stoker in an effort to establish relationships. Unfortunately, wide scattering of points usually resulted, which did not illustrate what experience generally indicates to be the case. For example, Fig 3 indicates almost no trend in the percentage of released ash converted to clinker with change in ash-softening temperature. Other factors, such as fuel bed temperatures and zones of heat release must have influenced the results. In the present state of our knowledge, we cannot explain all of the reasons why suitable stoker coals perform satisfactorily, nor why one satisfactory coal may be better than another. It would therefore

Jan 1, 1950

By J Price, M. R. Geer, H. F. Yancey

COAL mine operators recognize coal as an abrasive material, because the wear of drilling, cutting, and conveying equipment is reflected as a cost item for replacement of parts. Similarly, industrial consumers of coal experience abrasive wear on all coal-handling equipment. Operators of pulverized fuel plants are doubtless most keenly aware of the abrasiveness of coal, because under the high contact pressures developed between coal and metal in pulverizers, abrasive wear is increased many fold. Moreover, experience in operating pulverized fuel plants has demonstrated that some coals are much more abrasive than others. Hardgrove' stated that maintenance costs entailed by the wear of grinding elements is often a more important variable than the cost of the power required to pulverize different coals. Craig2 also reports that one coal may cause pulverizer parts to wear several times faster than another. It is apparent, therefore, that those concerned with pulverizing coal could profitably employ a method for estimating the abrasiveness of different coals, just as they utilize standard tests for thermal value, grindability, and ash-fusion temperature to assist in selecting the most suitable and economical coal to use in a particular plant. The objective of this investigation was to develop a test procedure that would be suitable for general use in estimating the abrasiveness of coals. However, few, if any, of the standard tests now used for evaluating the properties of coal are the product of a single investigation or the result of a single investigator's efforts. Rather, in each case, a testing procedure was devised by one investigator, used by others on a wider variety of coals, and finally refined completely as the result of the joint efforts of a number of interested people. Thus, the test procedure for estimating abrasiveness developed in the course of this work may not be refined sufficiently in its present form for general use, but it may serve as the starting point from which an acceptable test procedure can be developed. The method has been used thus far on only about a dozen coals, and there has been no opportunity to attempt a correlation between experimental results and actual plant experience. Only wider use of the procedure by other investigators and correlation with plant experience can determine to what extent the method will have to be modified to render it suitable for general application. Test Method Although the literature contains no record of an attempt to devise a method for estimating the abrasiveness of coal that could be used industrially, several investigators have tested properties of coal that are closely related to its abrasiveness. The abrasiveness of a material generally is considered to be related to its hardness, and hardness tests for coal have been employed by Heywood,' O'Neill," and Mathes. Also, the resistance of coal to abrasion, a property that presumably is related to the abrasiveness of coal, was measured by Heywooda and by Simek, Pulkrabek, and Coufalik.2 11 these investigators tested only individual pieces of coal. Since coal is a heterogeneous material having components of varying properties, tests of this type can yield results having little more than academic interest. Only a test method that utilizes a representative sample of coal can give results that are useful industrially. The abrasion tests used for various other materials have been considered for adaptation to testing the abrasiveness of coal. The tests used for metals,7-9 paving and flooring,'" and rubber," cannot be used because coal is not sufficiently abrasive.~ The present experimental work was begun before World War II and was conducted by three research fellows"'" working under a joint agreement between the University of Washington and the Bureau of Mines. After a great deal of preliminary work with a variety of apparatus and materials, a test procedure was developed which consisted of rotating a test disk 2Yz in. diam in a steel mortar containing the coal sample. The shaft carrying the test disk at the lower end and a 100-lb load on the upper end was free to move vertically. The bed of coal in the mortar was kept fluid by low-pressure air admitted through a port near the bottom of the mortar. Measurable wear on an Armco iron disk could be obtained in this test procedure, but, despite extensive efforts to eliminate them, several major disadvantages remained in this test method. First, with most coals the amount of wear on the iron disk did not exceed a few milligrams. Second, a single type of disk was not applicable for all coals. A smooth iron disk gave satisfactory results with both bituminous and sub-bituminous coals, but hardly any wear with anthracite or coke. A disk having studs or projections gave more satisfactory abrasion losses with anthracite and coke and presented no operating difficulties with free-burning bituminous and sub-bituminous coals. It could not, however, be used with caking coals because these coals formed a

Jan 1, 1952

By D. S. Choi, R. Stefanko

There are a number of complex factors that influence the effectiveness of anchorage to maintain tension in rock bolts. However, a plastic analysis of the anchorage site employing certain simplifying assumptions with application of the Mohr-Coulomb criterion appears to explain the observed phenomena. Such an analysis has been made and a correlation sought with field and laboratory tests. Field tests were made in an anthracite mine in eastern Pennsylvania and included pull tests and long-term tests of a variety of anchorage devices in two basic lengths, 30 and 42 in. in two widely differing seams. Performance is reviewed for wedge, expansion shell, and resin anchorage. Laboratory tests duplicated many of the field conditions but in addition compared the performance of shells with normal and reversed serrations. This performance was compared with the predicted results from the plastic analysis. One of the major problems in conducting long-term underground tests is the selection of suitable instrumentation. All installed bolts were fitted with spherical and hardened washers to insure the best possible torque wrench readings. In addition, commercially available load cells were used. Finally, the performance of a specially developed strain-gage-equipped ring cell is viewed. Rock bolting as a method of support continues to increase with applications in many other industries in addition to mining. Nevertheless, with nearly 55,000,000 roof bolts installed in coal mines alone last year, this remains as the single greatest use. While bolts have frequently supported ground where conventional timbering could not, there are relatively few design criteria; and trial-and-error procedures prevail. Furthermore, there has been a lag in development of suitable instrumentation that is simple to install and read out, sensitive, durable, reliable, safe, and economical in evaluating the effectiveness of a bolt over long periods of time. Therefore, the pull test continues to be the most popular method of evaluating the applicability of a certain type of roof bolt under specific installation conditions. At The Pennsylvania State University in the Dept. of Mining, research has been conducted for a number of years to measure bleed off in carefully controlled laboratory experiments as well as in underground investigations."-' Unfortunately, most of the instrumentation developed has been primarily suitable only for research purposes, not possessing all of the aforementioned characteristics desirable for routine underground use. Other groups also have met with restricted success. Therefore, while relatively crude, the torque wrench continues to remain as the most widely used load measuring device. While both field and laboratory tests continue to be con- ducted, analytical analyses are attempted to discover the more important design parameters in order that more efficient anchorage might be devised. Bolts are being used for a greater variety of purposes in mining. Suspending wire sideframe belt conveyors from roof bolts is a common application. The suspension of a monorail transportation system presents yet another. One such system has just been installed in a recently reopened anthracite mine and is presently being evaluated under production conditions. Preliminary studies revealed that a considerable cost reduction was possible by suspending the monorail on bolts anchored in the top. The monorail was to be installed under two widely differing conditions—a competent sandstone above the Buck Mountain seam and a softer shale top above the Skidmore. The type of anchorage device, length of bolt, and long-term performance, consistent with economy and safety, had to be established for the installation once the decision was made to suspend the system on rock bolts. This paper describes some of the testing procedures leading to a final selection. Theoretical Analysis of Expansion Shell Anchorage A detailed look at an expansion shell assembly might shed some light on the factors involved in the design of a suitable shell, Fig. 1. When a bolt is rotated, the tapered plug is forced downward, expanding the leaves laterally to grip the sides of the hole. Two friction surfaces are present: (1) the interface of the plug and leaf and (2) the interface between leaf and rock. The relationships of these friction planes, geometry of expansion shell, and properties of the rock are important in the design of an expansion shell. Therefore, an analysis assuming the rock to behave as a rigid plastic material with its yield governed by the Mohr-Coulomb criterion was made." Furthermore, the effect of friction between the leaf and rock produced by serrations was analyzed.

Jan 1, 1971

By S. C. Sun, John A. L. Campbell

Objective of the ittvestigation was to determine the electrokinetic differences, if ally, of anthracite lithotypes and thus establish the feasibility of making a coqlstituent separation by froth flotation or other surface-dependent processes. The elec-trokinetic properties were determined by streaming potential methods. In addition, chemical and physical analyses of the lithotypes were made to establish nonsubjec-tive parameters for their diflerentiation. Electrokinetic results indicate a difference in the characteristics of the lithotypes. The isoelectric points of 4 anthracites and 12 lithotypes were obtained. It was suggested that the relative flotation rates of the lithotypes were pH dependent and that the maximum flotation rate of anthracite occurs in an acidic circuit. Although there has been an increased interest in the electrokinetic properties of coal,' research on the subject is still in an early stage of development."' To the authors' knowledge, no electrokinetic studies have been made on coal lithotypes, particularly anthracite litho-types. This paper presents the results of an investigation of the double layer properties displayed at the anthracite/water interface (whole coal and lithotypes) as determined by streaming potential methods. It is hoped that this investigation and related future investigations will provide correlations from which the surface properties of any coal can be predicted and then related to surface-dependent processes such as froth flotation and flocculation. Another aspect of this research, undertaken to determine the physical and chemical parameters necessary for anthracite lithotype differentiation, was previously published.? The number of parameters involved, lithologic, organic and inorganic, and the wide divergence of these parameters within an individual coal limits the practical utilization of the results; however, the result? are of value and of interest in guiding theoretical developments. Keeping the limitations in mind, the results are analyzed in terms of their application to froth flotation processes and are used to indicate the feasibility of making a lithotype separation by flotation. Experimental Procedure Prior to discussing the experimental work per se, it would be of value to establish an understanding of anthracite lithology. Anthracite Lithology: Coal seams display two different modes of variation, rank and type. A coal's position in the continuous series ranging from peats through anthracites determines its rank. The rank of the material under consideration is anthracite. The different bands of coal which constitute a coal seam are distinctly contrasted in regard to physical properties and chemical composition. These megascopic bands are the coal types and are termed lithotypes., A megascopic examination of 11 anthracites revealed three distinct, homogeneous, lithotypes. The classic description of bituminous coal lithotypes as proposed by Stope" was found to be quite adequate for recognizing the three lithotypes in anthracite, namely vitrain, durain, and fusain. The term vitrain describes the brilliant constituent of coal; durain describes dull coal; and fusain is the term applied to fossil charcoal. The anthracites studied were generally found to contain 60-80% vitrain, 10-30% durain, and 1-10% fusain. A complete description of the physical characteristics and chemical composition of the studied lithotypes can be found in a previous publication.' Sample Preparation: Nine of the anthracites used in the investigation were from Pennsylvania, one was from Russia, and one from Wales. Table 1 shows the various designations and sources of the employed anthracites. The letter V, D, or F added to the whole coal designation indicates respectively the vitrain, durain or fusain lithotype of that coal. The samples were carefully collected to avoid contamination. To insure against oxidation, the samples were obtained as fresh as possible and stored under nitrogen or water. Generally a representative sample of the seam and samples containing high concentrations of one or another of the petrographic constituents were secured for each coal. Pure lithotypes were prepared by manual separation and selection. The pure lithotypes and representative samples were ground to —35 mesh and screened to 35 x 48 mesh. The 35 x 48-mesh fraction was then passed over a magnet to remove iron contamination, washed with doubly

Jan 1, 1971

By J. A. Harrison

The physical composition of coal and the distribution of its physical constituents will partially determine the efficiency of the process chosen for coal preparation. Distribution and concentration of coal macerals will, to a degree, be controlled by preparation processes. A number of preparation processes have been evaluated to determine this interrelation. These evaluations will help provide information needed for the production of coal that meets definite petrographic composition specifications. etrographic composition and degree of coalifica-tion of coal can determine the choice of cleaning processes and equipment used in coal preparation. The purpose of this paper is to present data on studies of the preparation processes of breakage, sizing, cleaning, and blending and to show the effect coal's petrographic composition has on these processes. Herrin (No. 6) and Danville (No. 7) Coals from Illinois were used in these tests. Nomenclature used herein is that approved in the Glossary of the International Committee for Coal Petrology,' based primarily on the Stopes-Heerlen system of classification2 and used in coal petrography laboratories throughout the world. BREAKAGE TESTS Breakage tests of Illinois coals related to petrographic composition have been conducted at various times at the Illinois State Geological Survey. These tests have been classified under two headings -impact tests and compression tests. Impact tests, as the name implies, consisted of breaking the coal by a sharp, sudden force. Impact tests were further divided into fall tests and block tests. Compression tests consisted of applying a constant pressure on a piece of coal until the coal fractured.

Jan 1, 1963

By J. R. Lewis, J. H. Hamilton, V. D. Hanson, K. W. Heinlein, J. M.194-000-000-006 Vonfeld, J. P. Denny

TWO overfeed drum-type separators using a suspension of magnetite in water as the separating medium have been installed in the Champion NO. 1 preparation plant of the Pittsburgh Coal Co., Division of the Pittsburgh Consolidation Coal Company. A simplified flow diagram of the Champion No. 1 coarse coal circuit is shown in Fig. 1. A railroad car rotary dump, capable of handling 20 cars per hr, discharges the coal into a hopper. Coal is fed from the hopper of the rotary dump to a 60-in. belt conveyor by two reciprocating pan-type feeders. The belt conveyor feeds the run of mine coal onto the main raw coal screen. The first deck is fitted with 3 in. round hole perforated plate which removes the 3x0-in. coal. The second deck of the screen is equipped with 6-in. lip screens which separate the remaining coal into +6 in. and 6x3 in. The +6 in. coal is transferred to a shaking picking table and then discharged onto the loading boom. The 6x3-in. coal is fed to the No. 2 dense medium vessel for cleaning. The clean coal from this unit flows to a vibrating screen where the medium is removed and the coal sized into 6x4 in. and 4x3 in. The 6x4-in. coal is transferred to the loading booms and the 4x3-in. is conveyed to the clean coal classifying screens to remove degradation. The 3x0-in. raw coal is blended in a system composed of three storage bins having a total capacity of 400 tons. From these bins the coal is fed onto a 48-in. flight conveyor by three reciprocating feeders. This flight conveyor delivers the coal to the Rheo plant. The 3x0-in. coal is then cleaned in two 48-in. Rheolaveur launders each equipped with two Rheo boxes. The first set of boxes removes a primary refuse and the second set produces a middling product which is recirculated in the launders. The cleaned coal and water overflows from the primary launders to two sizing and dewatering shaker screens where the water and — -in. coal are removed for further cleaning in the Rheo fine coal plant. The 3x3h-in. clean coal is combined with the 4x3-in. coal from the No. 2 vessel, sized into 4x2 in., 2x1 34 in., and 1'/4x in., then sent to the loading booms. The 3x0-in. refuse from the primary launders is normally fed to the No. 1 dense medium circuit, but any portion or all of this material can, as an alternate, be processed in the Rheo rewash launder. The primary refuse when fed to the dense medium circuit is screened into YSXO which is cleaned in the fine coal plant and 3x for cleaning in the No. 1 vessel. The clean coal from this vessel is passed over a vibrating drainage and rinse screen, then sluiced to the rewash sizing shaker where it is dewatered and sized for loading. The installation of a pilot plant separating vessel using a suspension of magnetite in water was pro-

Jan 1, 1953

By J. H. Hamilton, J. R. Lewis, K. W. Heinlein, V. D. Hanson, J. M. 194-000-000-006 Vonfeld, J. P. Denny

TWO overfeed drum-type separators using a suspension of magnetite in water as the separating medium have been installed in the Champion NO. 1 preparation plant of the Pittsburgh Coal Co., Division of the Pittsburgh Consolidation Coal Company. A simplified flow diagram of the Champion No. 1 coarse coal circuit is shown in Fig. 1. A railroad car rotary dump, capable of handling 20 cars per hr, discharges the coal into a hopper. Coal is fed from the hopper of the rotary dump to a 60-in. belt conveyor by two reciprocating pan-type feeders. The belt conveyor feeds the run of mine coal onto the main raw coal screen. The first deck is fitted with 3 in. round hole perforated plate which removes the 3x0-in. coal. The second deck of the screen is equipped with 6-in. lip screens which separate the remaining coal into +6 in. and 6x3 in. The +6 in. coal is transferred to a shaking picking table and then discharged onto the loading boom. The 6x3-in. coal is fed to the No. 2 dense medium vessel for cleaning. The clean coal from this unit flows to a vibrating screen where the medium is removed and the coal sized into 6x4 in. and 4x3 in. The 6x4-in. coal is transferred to the loading booms and the 4x3-in. is conveyed to the clean coal classifying screens to remove degradation. The 3x0-in. raw coal is blended in a system composed of three storage bins having a total capacity of 400 tons. From these bins the coal is fed onto a 48-in. flight conveyor by three reciprocating feeders. This flight conveyor delivers the coal to the Rheo plant. The 3x0-in. coal is then cleaned in two 48-in. Rheolaveur launders each equipped with two Rheo boxes. The first set of boxes removes a primary refuse and the second set produces a middling product which is recirculated in the launders. The cleaned coal and water overflows from the primary launders to two sizing and dewatering shaker screens where the water and — -in. coal are removed for further cleaning in the Rheo fine coal plant. The 3x3h-in. clean coal is combined with the 4x3-in. coal from the No. 2 vessel, sized into 4x2 in., 2x1 34 in., and 1'/4x in., then sent to the loading booms. The 3x0-in. refuse from the primary launders is normally fed to the No. 1 dense medium circuit, but any portion or all of this material can, as an alternate, be processed in the Rheo rewash launder. The primary refuse when fed to the dense medium circuit is screened into YSXO which is cleaned in the fine coal plant and 3x for cleaning in the No. 1 vessel. The clean coal from this vessel is passed over a vibrating drainage and rinse screen, then sluiced to the rewash sizing shaker where it is dewatered and sized for loading. The installation of a pilot plant separating vessel using a suspension of magnetite in water was pro-

Jan 1, 1953

By G. H. Kennedy, H. E. Criner

CYCLONE thickeners are "hydraulic centrifuges" designed either to produce a maximum practical separation between the water and solids of a feed slurry or to classify the slurry solids according to particle settling rate. The possibilities of utilizing the thickener to "close" plant water circuits have been investigated. Since the thickener becomes an integral part of the plant water circuit when installed, the basic means by which the solids content of all circulating water systems must be controlled is reviewed. All coal not separated from the circulating water by means of dewatering screens or settling devices must be bled from the plant at the same rate as they are being fed or created by degradation. If this were not true, the circulated volume would finally be completely filled with solids. If the rate of bleed is low, the solids concentration in the bleed and circulating water generally will be high. To keep a reasonable circulating water concentration, large amounts of fresh water must be supplied and the bleed rate must be high. These conditions are usually undesirable because of the difficulty in securing fresh water, the loss of large quantities of coal, and the pollution of nearby streams. Thickeners are the primary stage in the separation of the water contained in the bleed from the coal. Since a thickener, when operating with reasonable efficiency, usually cannot be expected to deliver an underflow containing less than 50 pct water, secondary dewatering devices such as a slurry screen or vacuum filter must be used to separate additional water from the bleed. The surface area required by the filter or screen will be nearly proportional to the total water which must be handled, and therefore the thickener becomes necessary to hold down the original cost. The water separated from the coal is then returned to the plant circuit to maintain the water balance and thus becomes the source of fresh water. It is not necessary to return clear water to the plant to maintain control of the circulating water concentration. It is only necessary that the bleed dewatering devices remove coal in all sizes at a rate equal to that at which these sizes are entering the circulating water. However, practically speaking, in order to maintain low solids concentration, it is usually necessary that the thickener have good recovery characteristics on bituminous coals in those sizes down to 400-mesh. The thickener can remove the smaller sizes from the closed-circuit system at the "solids in" rate and prevent their "build up" in the circulating water as shown in Fig. 1. With the portion of the feed water going directly to the underflow, comes the very fine solids not concentrated by the cyclone. All the larger solids are removed from the feed and delivered in a concentrated condition at the underflow. To apply thickeners with some reasonable assurance that operating requirements will be met, it is necessary to know the rate at which solids of all sizes must be removed from the circulating water and to know the thickener characteristics. The required removal rate of fine solids not recovered by other dewatering devices may be estimated from the size distribution and tonnage of the plant feed with a reasonable allowance for degradation in the circulating water system. A more reliable estimate may be secured by sampling the plant bleed water during a constant load period.

Jan 1, 1952

By W. J. Parton

The efficient recovery and preparation of small sizes of anthracite called No. 4 Buckwheat (3/32 by 1/32 in.) and No. 5 Buckwheat (1/32 in. by 0), pre-sent a difficult problem to the anthracite operators. In many instances preparation of these sizes, particularly No. 5 anthracite, is extremely inefficient. In many of the older preparation plants, inadequate facilities, and often none at all, were provided as an integral part of the plant for cleaning this fine anthracite. Consequently, much of the material smaller than 3/32 in. was discarded. As the demand for these sizes increased, facilities for preparing the fine sizes were often crowded into existing structures with consequent sacrifices of capacities and efficiency. In addition to this condition, the methods of preparing the finest sizes are being developed in an attempt to improve their efficiencies. Because the demand for small sizes of anthracite still is increasing, many operators would benefit by investigating and improving the cleaning equipment employed on these sizes. The object of this paper is to de- scribe a stationary screen device from which the underflow is restricted by orifices, called a launder screen, along with operating results of several applications of this screen; a settling tank in which two classified products are produced by the installation of a cylindrical partition of smaller diameter than the original tank, one product being recovered from the small tank created by the partition and one product from the space between the inner and outer tank walls; a small pocket classifier or hydraulic trap for use in removing high ash particles from a sludge flow; the classification or segregation of sludge solids occurring in a 16 in. diam pipe flow by analysis of samples procured at different zones; and the operating results of a Fahrenwald sizer, as well as the performance of the concentrating tables handling the classified products. These simple devices were employed at the collieries of the Lehigh Navigation Coal Company Incorporated, Lansford. Pa., in order to improve preparation results on the fine sizes of anthracite. Launder Screens The launder screen is a screening and dewatering device which probably could be used advantageously in the flow diagram of many fine coal plants. Fig 1 shows that it consists of a stationary screen constructed by placing 6 in. high partitions every 6 in. along a launder. Holes are then drilled on 6-in. centers across the bottom of the launder to receive pipe bushings of the desired diameter. The screen cloth is tacked on top of the partitions. When water and solids are fed to the screen, only a small portion of the total water is removed through the orifices in each compartment so that the water in the feed is distributed evenly over the whole length of the screen. The screening action which results is very efficient because the solids are kept in a fluid condition for the full length of the screen. Blinding of the screen can be minimized by the use of screen cloth

Jan 1, 1950

By W. J. Parton

D. R. MITCHELL*—The Chairman mentioned that we have had many papers on cleaning of fine coal and treatment of wash water solids. There are, of course, two reasons for that. One is that we have legislation, particularly in the east. that is making us go into these things whether we want to or not. It just so happens at the present time that I have four plants that are going up under my general direction, three new and one rehabilitation job, and in all of them, we have these problems. Therefore, I was very happy to be able to listen to these papers, because some of the things that are in them are going to help me solve some of the problems that I am facing. Of course, the second reason why we are concerned about fine coal recovery is the fact that coal has become a luxury item in a good many places, particularly in the anthracite region, so that we cannot afford to have it go to waste like we did in former years. There is a third minor reason, and that is that we are finding how to handle and use the extremely fine sizes that we did not know how to use in former years. Now, I have a couple of questions that I would like to ask. First, what are the maximum solids that you could have in a pulp going to one of these launder screens? I realize that it would be for anthracite. Second, of course the life of these screen surfaces is not very long— with brass or bronze, I believe it is a week, and with stainless steel, a month. Would it be possible to use screen surfaces like the Bixby-Zimmer round rod for the small sizes and possibly increase the life? Have you experimented with that? Another point that I would like to bring out, both in Mr. Parton's paper and in some of the others, in studying cyclones and any settling apparatus where we use orifices, the life of the orifices is very short, and that is a problem that still has to be solved. The capacity of the cyclone seems to be small, and if you have a bat-

Jan 1, 1950

By H. M. Chance

The present value of most coal properties resides largely in the cod remaining to be mined, which thus constitutes the most important asset. The object of this paper is to discuss methods commonly used in computing the value of minable coal. To distinguish clearly between such coal values and the values of other property, the several kinds of property values should be divided into classes; so as to avoid the unintentional omission of items of importance. Value op Coal Reserves Judicial decisions prescribe, and appraisers commonly accept, current sales value as the preferred means for determining the value of transferable property. With few exceptions a property is worth the sum that can be realized from its sale by a willing seller to a willing buyer, a sale in which compulsion urges neither party, and between whom there is no community of interest to fix a value; or it is worth at least as much as a responsible buyer will offer for it. Actual sales of like property or bids from responsible buyers for the property, or for substantially like property, are the best established methods for determining values. Only in the absence of such sales or bids can valuations by other methods be entertained, and only for reasons of weight can sales values be set aside. Valuation Based on Royalties Sales of coal in the ground, as customarily carried out through lease under royalty agreements, are therefore the most trustworthy means available for determining the value of coal reserves. The constantly rising value of high-grade coal in the United States can most readily be shown by the increasing royalties per ton that can be obtained for such coals under leasehold. The rising value of land containing such coal can also, of course, be proven by the price at which such properties are actually sold as compared with prices obtainable for lands containing coal of the same grade in the past. It is exceedingly difficult, however, to establish values by the prices paid for coal

Jan 1, 1927

By R. W. Stahl

Employees and dollars are necessary to all enterprises and any force, such as fire, which destroys either, can bring very serious consequences, including business failure. Since everyone acknowledges the necessity of conserving human life, we will devote most of our paper to the economic factors involved. A coal-mine fire is considerably more difficult to combat than a fire in a surface building because of the combustible surroundings in the mine, the explosive gases emitted from the coal, the suspension of explosive dust when mine timbers burn and the unsupported roof falls, the limited space in which approach to the fire can be made, and the limited avenues of escape. A survey of coal-mine-fire protection indicated that a rather low value was being placed on property and equipment. This prompted comparison with other industries. The comments made in this comparison are not intended as an indictment of the coal industry, since we do have mines that are well protected against fire, but the comments on conditions at the mines visited are factual and may help others to improve similar conditions. SURVEY PROCEDURES Plants of the steel, aluminum, rubber, chemical, and petroleum industries were surveyed, and all facets of the fire-protection scheme were covered. The industrial plant invariably had four times as much water readily available for instant use than the mine. In many mines where water is available, no equipment for applying it is provided, such as hose, nozzles, and adapters, so that time is lost in collecting this equipment. (See Table I.) EXTINGUISHERS Many more and generally larger portable extinpishers are available at the plant as compared to the mine. The extinguishers are generally placed nearer to sources of danger. In addition, respiratory protective equipment is always available at strategic points in plants but only in a few mines. (See Figs. 1 and Table 11) INSPECTING AND TESTING EQUIPMENT Plant water facilities are checked weekly and flushed at 6-month intervals, and hose is pressure-tested at least yearly; some mines check water yearly, but hose is not tested unless used. Fire extinguishers are inspected weekly in plants and completely overhauled yearly; one mine had monthly checks and overhauls only after use. FIRE BRIGADES AND TRAINING Every plant had designated fire-fighters and some complete full-time brigades; at one mine a chief mechanic was designated as being in charge of fires, and other depended entirely upon officials who might not be familiar with the equipment. COST OF FIRES AND PERCENTAGE OF CAPITAL INVESTMENT IN FIRE PROTECTION The direct cost of recent mine fires ranged from $128,000 to $240,000; indirect costs, such as lost tonnage, idled equipment, lost orders, and the like might run the cost to over $500,000. (See Figs. 2 and 3).

Jan 1, 1961

By J. C. Rengel

Why and how the nuclear industry entered the electric power generation business is discussed in terms that nuclear energy was an undoubtedly additional energy resource and that it had promise of becoming a virtually inexhaustible generating power if breeder reactors could be devised. The growth of nuclear power, its total generation capacity, are related to the need of increasing energy requirements. The use of atomic energy for power generation will grow if it can compete economically with other fuels. The rate of growth, the time scale and direction of technical development is dependent on ore supplies. It is predicted that by 1980, 50% of all new power installations will be nuclear stations. INTRODUCTION Ten years ago, the nuclear industry was virtually unborn, the Atomic Energy Act of 1954 had just been signed, and peaceful applications of atomic power was little more than a phrase. Serious discussion of the practical application of nuclear energy to electric utility installations in the West was highly unlikely. The questions: Why and how did the nuclear industry enter the electric power generation business at all?; What is the predicted growth of nuclear power?; What technological changes do we predict?; How will the above changes affect the utilities? will in part be answered by this paper. WHY NUCLEAR POWER? The only justification for the West as for any other section of the country for atomic power is economics. Whatever energy source will provide the lowest generation cost will prevail; the only electric utilities which have shown an interest in nuclear power are those to whom it means lower generation costs. It is true that the Government sponsored the development of this technology long before there was any evidence of better economics; but a Government must take a very long-range view and it is the only type of organization that can afford to look more than twenty or thirty years into the future. The Government looked at projections such as shown in Fig. 1, which shows various rates of energy consumption, and matched these against estimates of fossil fuel resources. This showed that we will exhaust our low-cost fossil fuel supplies within 75 to 100 years and our total known fuel supplies within 150 to 200 years. The decision to invest in nuclear energy rested, therefore, on two arguments: a) It was undoubtedly an additional energy resource; and b) It has promise of becoming a virtually inex-haustable resource if breeder reactors could be devised if, while generating power, the reactors would produce more fissile materials than they consumed. This decision produced an unexpected bonus: nuclear power became competitive with fossil power much earlier than had been expected and, as shown in Fig. 2, forced the coal industry to take a hard look at its own position. I believe that the drop of coal prices shown here is the direct result of the entry of nuclear power into the energy supply business. At this point, it ought to be explained why and under what conditions nuclear power can be cheaper than fossil power. Fossil fuel cost to the utility is composed of two factors: a) Mining; and b) Transportation. As a result, the cost of fossil fuel to the utilities varies from 126, 106 Btu to 306, 106 Btu and higher. Nuclear energy is highly concentrated and the transportation factor becomes insignificant. Today the cost of nuclear fuel to the utility ranges between 156

Jan 1, 1967

By J. G. Balkestein, J. W. R. Baerts

During an attempt to develop a method for accurate, rapid, continuous analysis of ash content of wal, the Dutch State Mines Laboratory found that the absorption coefficient for X-rays was related to ash content. This relationship was utilized in the development of an apparatus called CendreX, used to measure the absorption and in turn the ash content. The principle, procedure, accuracy, and applications of the CendreX automatic determination of ash in coal are discussed in detail. Until recent years coal preparation research was concentrated on the possibilities and efficiency of preparation equipment. Ever increasing demands for quality in coal, however, have caused researchers to become concerned with quality control. One of the characteristics strongly influencing quality (calorific value) and, consequently, the price of coal is ash content. Both customer and producer require that the ash content be controlled. To make this possible it is necessary for the producer to collect samples from the coal stream in the washery and to determine their ash content. On the strength of the results obtained the production process can then be adjusted, if required. Until recently incineration was the only method for determining ash content. When coal is incinerated with oxygen, it takes at least 15 min to determine the ash content. Even then some time may be lost in passing on the data. Therefore, this discontinuous and time-consuming method does not make a suitable starting point for checking, re-adjusting, or modifying the production process. Since it was not possible to accelerate incineration by mechanization and automation, another type of rapid continuous analysis had to be found. This would have to depend on some coal characteristic closely linked with ash content. At the Central Laboratory of Dutch State Mines, Dijkstra and Sieswerda found that the absorption coefficient for X-rays was suitable for this purpose. An apparatus based on the measurement of this characteristic was developed. Named CendreX,* this patented equip- *A Stamicarbon N. V. registered trademark. ment, used in combination with a sampler and conditioning apparatus, permits continuous determination of ash content with satisfactory exactness to within 3 min.t At the American Mining Congress meeting of May 1961, Log A. Updegraff, surveying aspects of continuous analyaia, reported on the CendreX appartus (Mining Congress Journal, August 1961). Since the first Condition for correct ash determination, whatever the method used, is always a sample taken in the right way, some practical aspects of sampling will be discussed first. SAMPLING In coal handling operations, each grain has its characteristic properties. In both the cross-sectional and longitudinal direction of the product stream the mixture of these grains is imperfectly blended. The elimination of the factor of segregation between the cross-sections from the direction of the stream is the principal aim of continuous analysis. Therefore, the samples to be analyzed are withdrawn in various places from the segregated product stream in such a way that they form a semi-continuous flow. In order to be truly representative of the product stream, the sample flow must fulfil two conditions: 1) The sample flow must be sufficiently large to insure that adventitious differences between the composition of the product stream and sample flow will be as small as possible. 2) All grains through the entire cross section of the product stream must have an equal chance to get into the sample flow. Since there is always a segregation through the cross section the sample flow will have a bias if the sampler collects only part of this section. In order to prevent the volume of the sample flow from becoming too large, the cross sections are taken discontinuously. However, this discontinuity gives rise to the adventitious differences that arise between the composition of product stream and the sample flow, and these differences become greater and are more deranging as the fluctuations follow each other more quickly. Moreover, the intervals between the morrnents of sampling mean a delay in the analysis. The aim will, therefore, be to collect small samples, or in other words thin cross-sectional increments, taken at sufficiently high frequencies. The following points should also be taken into account: 1) The smallest dimension of the openings in the sample collector must be equivalent to at least 3 d in

Jan 1, 1962

By C. D. Allman

Specifications for coal at the Grand Lake thermal electric station read in part: "Coal will be Rom Minto Bituminous (strip operation). Maximum lump 3x3x4 ft. Very corrosive, abrasive and when damp, sticky. Coal may consist of frozen lumps of coal, snow and ice." To maintain quality control it was necessary to develop an automatic sampling system capable of: 1) sampling from one 10-ton truckload every 1½ min; 2) permitting an operator to automatically take a sample from each truckload; 3) depositing the sample in a pre-selected container, one of a possible 10; and 4) performing the sampling operations in accordance with latest ASTM specifications for sampling coal with an ash content of 35%. This paper tells how these and other problems were resolved and describes the equipment used. The New Brunswick Electric Power Commission issued detailed specification No. 5351-5009 outlining the scope of work and general requirements for a mechanical coal handling system to be installed at the Commissions Grand Lake Generating Station. The thermal station is located at Newcastle Creek, some 40 miles east of Fredericton, N.B. Canada, on the shore of Grand Lake. This particular location is immediately adjacent to the Minto strip mining coal area of New Brunswick. Contained in the specifications, but not detailed specifically was an automatic coal sampling system. The system outlined, was to be designed and specified by the individual equipment tenderers. In conjunction with the Hardinge Co., the Barber-Greene Co. designed a sampling system which was contained in the general contract proposal. The system as designed originally, however, presented certain limitations to a continuous coal handling system and was ultimately changed. However, it was only through preliminary study and design that problems created by the specifications were determined, and these problems discussed and finally negotiated with the NBEPC engineering staff created the subsequent sampling system now being installed by Barber-Greene. It must be considered that where the original specifications did not detail the mechanical equipment, it was necessary to present a system which would correspond to the intent of specification and for which Barber-Greene would be responsible as to function, but remain in a competitive position with regard to the tender considered primarily on a price basis. The system now being installed, contains basically all the components which were detailed originally, with the exception of the holding bin arrangement, which was changed to allow a continuous operation of the entire coal handling system. SPECIFICATIONS The specifications covering the sampling system follow. 4.5 Sampler: An automatic sampling system shall be installed capable of sampling one-truck load of coal every 1½ min. When the coal is dumped into the receiving hopper, the operator shall push a button and the sampler shall automatically take a sample of that particular coal when it reaches the sampler. Then the sample taken shall be crushed and reduced in quantity to a workable sample and deposited in a pre-selected container, one of a possible ten. All samples and sampling operations shall be in accordance with the latest edition of ASTM designation 492 for sampling coal with an ash content of 35%. The coal for the initial sample shall have maximum sized lumps of about 3/4 in. and the final sample shall be adjustable from 2 to 5 lb per sample and capable of passing through a sieve with 1/8-in. diam openings. It should be noted that, because of the time delay between the time the sample is requested and when it is actually taken, the operator may call for one or two additional samples from different coal before the first sample is completely refined and in the final sample can. Coal is received from a number of different suppliers on the same day, therefore, the system shall be designed so that there is no possibility of mixing or contaminating the coal from the different suppliers. All coal rejected from the sample shall be returned to the main conveyor. All chutes, hoppers, etc. shall be designed in accordance with Section 4.6 of these specifications. 4.6 Chutes, Hoppers, etc. All chutes and hoppers

Jan 1, 1963

By W. J. Verner, J. R. Lucas

Billions of tons of bulk solid materials are processed through our industrial plants each year, and the tonnage is steadily rising. It has been estimated that for every dollar spent in industry as a whole, approxinlately 30 cents is consumed in the handling of bulk solid materials. It is in this category that tremendous savings are possible through the use of improved techniques. Since World War 11, the mining, steel, chemical, and grain industries, among others have made use of increased materials-handling automation in order to gain some of these savings. However, in a chain of automatic operations, every link must be completely reliable, for if there is a single failure, the whole system immediately becomes ineffective. Only too often the weak link in the chain proves to be the flow of bulk solids from bins. To contribute to the fundamental knowledge in this area, a research study has been continuing at The Ohio State University. The principal objective of the investigation has been to study the internal stresses existing in confined bulk solids. LITERATURE SURVEY Literature studies have revealed that many outstanding people have made contributions to the field of bulk solids. For instance, C. F. Jenkin,1 suggested: a. The pressure on a bin wall is not directly proportional to the depth beneath the surface of material in the bin. b. The vertical pressure distribution on the base of a bin is not actually uniform but is a variable. c. Arches form in bins as a result of very small deformations of the material in the bin. This deformation causes a series of gaps to appear, and consequently causes the disappearance of diagonal forces that cannot act across these gaps. The removal of the diagonal forces causes horizontal forces to be introduced which seem to be the chief cause of arching. 11. A. Janssen,4 in 1895 in connection with his experiments on bins, derived a differential equation to describe both the lateral and vertical pressure in bins with vertical sides. This represents a significant contribution to bulk solid theory, and thus its solution is reproduced as follows: L = KV = RW/U' [l-e -U'KY/R] I where L is the lateral pressure of the bulk solid in psf., V is the vertical pressure of the bulk solid in psf., K is the ratio of the lateral pressure to the vertical pressure at any point, R is the hydraulic radius of the bin in feet, W is the density of the bulk solid in lbs. per cubic feet, U' is the coefficient of friction between the stored material and the bin wall, and Y is the head of material above the point in question in feet. In 1903, Jamieson,6 in an elaborate series of experiments on full sized bins measured vertical and lateral pressures by hydraulic diaphragms. He determined many values for mediums of corn, wheat, peas, and flaxseed. In 1951, Caughey, Tooles, and scheer3 measured both lateral and vertical pressure in deep bins by using strain guages on steel bands. Values were calculated for cement, gravel, sand, soy beans, shelled corn

Jan 1, 1961

By W. R. Kube, W. H. Oppelt

Five low-rank coals, including two lignites, a steam-dried lignite, and two subbituminous coals, were carbonized at 940°F, in a bench-scale carbon-ize~ with a nitrogen and hydrogen atmosphere, or both, using pressures from atmospheric to 1000 psig. Coking characteristics were observed, and yields, composition, and distribution of products from thermal degradation were determined. The influence of pressure on yields from coal carbonization, as well as on modification of coke structure, has long been of interest. One of the first attempts at pressure carbonization was that of Capps and Hulett1 who in 1917 investigated the effects of pressure ranging from 1 to 20 atm on yields at 600° C for bituminous and subbituminous coals. High-pressure carbonization has not been used commercially for coke production. More recently, carbonization at relatively high pressure in the presence of catalysts and hydrogen has been proposed for the production of metallurgical-grade coke from low-rank fuels.' Another approach involves carbonization at high pressure in a hydrogen atmosphere to produce heating gas and a solid residue that is gasified with oxygen and steam to produce the hydrogen required for hydro-genation 3-4 or, alternatively, is burned to raise steam. Recently it has been proposed to carbonize coal under pressure, burn the gas in a gas turbine to produce power, and use the solid residue as fuel in a conventional steam-power plant.5 Our primary interest in pressure carbonization stems from an attempt to determine the influence of pressure on the coking characteristics of lignite to design a high-pressure slagging gasifier using oxygen and steam. At atmospheric pressure, North Dakota lignite is generally considered to be non-coking. However, lignite and subbituminous coals have been reported to show increased agglomeration properties in steam, hydrogen, or carbon-dioxide atmospheres at elevated pressures, although no strong coke was formed at pressures up to 3000 psig.6 If lignite would agglomerate seriously under gasification conditions, proper flow of charge through the gasifier could not be maintained without installing a mechanical stirring device or destroying the caking properties of the coal before gasification. Data on the caking properties of lignite or other gasification fuel, as well as on yields of products under conditions simulating the carbonization process in the pregasification zone, were required in the preliminary design stage of the gasifier. No information was available concerning the influence of pressure and type of atmosphere on North Dakota lignite. To provide this basic data, the U. S. Bureau of Mines investigated the effect of pressure and a hydrogen or nitrogen-rich atmosphere on the yield of products and on coke formation in a bench-scale pressure carbon-izer. SCOPE OF INVESTIGATION Five coals were tested at 940°F in nitrogen and hydrogen atmospheres, at pressures from atmospheric to 1000 psig. Yields and composition of solid, liquid, and gaseous products were determined as a function of the process pressure, and attention was given to the physical appearance of the solid residue. Percentage of carbon converted, sulfur retained in char, and thermal balances were calculated. In this paper, primary consideration is given to carbonization in a nitrogen atmosphere and to data concerning the solid phase. The effect of pressure in hydrogen is presented in detail for only one lignite. More complete information on the response of the other coals in a hydrogen atmosphere will be published in a USBM Report of Investigations. DESCRIPTION OF EQUIPMENT Details of the bench-scale pressure carbonizer are given in Fig. 1. The body of the carbonizer was

Jan 1, 1961