Search Documents

By D. S. Kingery, D. W. Mitchell

The authors attended the 11th International Conference of Directors of Safety in Mines Research held in France, July 1963. In addition to Conference discussions pertaining to control of coal dust they had the added assignment to study present European practices for neutralizing the coal-dust explosion hazard. Information was obtained through discussions with the Research Directors, by visits to testing stations and observations of operating mines in various countries. This paper tells what the current practice in this field is in Europe, and how effectively coal dust explosions are controlled. The method is rock dust barriers. CONTROL OF COAL DUST DISSEMINATION Experience in Europe indicates that the control of dust production and dissemination by water or foam systems is not successful except during undercutting. Cybulski, Dawes, and DeBraaf - respectively Director, Mines Research Establishment "Barbara", Katowice, Poland; Principal Scientific Officer, Safety in Mines Research Establishment, Sheffield, England; and Chief, Central Mines Research Establishment, Hoensbroek, Treebeek, The Netherlands - believe that wetted dust becomes readily dispersible and abatement measures should be considered only as a temporary means for reducing the health hazard. In an effort to reduce the health hazard, calcium chloride is used on the floor of main haulageways in Dutch mines and water infusion is practiced in Germany in mines where the coal is relatively porous. With respect to wet coal dust, the Belgians, British, Dutch, French, and Russians reportedly have accepted the results of research from the Polish and American experimental mines on the effectiveness of water as an inert in arresting explosion propagation. The Polish use the two test methods proposed by the U.S. Bureau of Mines1 for evaluation of the adequacy of wetness of mine dust; they require that water be added to the wet dust to maintain a minimum of 50% moisture by weight if dependence is placed on water alone. GENERALIZED ROCK DUSTING The general attitude with regard to protection against coal dust explosions throughout Europe is that generalized rock dusting is a vital primary step to inhibit initial ignitions but definite emphasis is also placed upon the efficiency of rock dust barriers. Those exceptions to generalized rock dusting are Germany and Austria where some rock dusting is done but principal reliance is placed upon rock dust barriers. The rock dust used in Belgium, Holland, Russia, and Poland is coarser than that used in the U. S.; 50% of the dust is through a No. 200 sieve (75 microns). Recent research by the Polish indicates that the portion finer than 20 microns is ineffective in arresting explosion propagation, and that the rock

Jan 1, 1964

By A. F. Meger

Coal treatment by oil spraying receives special attention at the Georgetown plant for the dividends it pays in satisfying present customers and attracting new markets. Customer satisfaction requires care, quality control, and use of suitable oils. REPRESENTED here are the ideas and varied experiences of many people in the Hanna Coal CO. who have helped develop, over a number of years, an efficient and flexible method for spraying controlled amounts of oil on coal. Since the Georgetown preparation plant began operations early in 1951, oil treatment of coal has received special attention. It is believed that oil treating will satisfy present customers and also attract new markets. The first step in developing the new method of oil spraying was the construction of a dust cabinet for testing 50-lb samples of treated coal with the available oil sprays on the market. Tests results were tabulated for both indoor and outdoor storage. The graph, Fig. 1, shows results of the original tests made with a 700-sec residual blend and a 500-sec lubricating oil on Georgetown stoker coal of 1¼x3/8-in. size.* The advantages of better price, improperly blended can raise havoc. Some.,pale oils also, although odorless when delivered, give off a sweet sickening odor when atomized under pressure. It is recommended that all products be tested before they are used. There is a specific place for all spraying oils. For example, at a power plant a severe dust condition exists around the stockpile area and in parts of the plant. The cheapest spraying oil made, regardless of odor, will do an excellent job in this case and will save the company 3 to 5c per gal or more. Domestic trade, on the other hand, must be carefully handled to prevent complaints about odor, and the only way to do this is to stay with the proved products after the odor tests have been made. The preparation plant at Georgetown has facilities to handle either tank car or tank truck deliveries. Steam is available at the unloading point if the weather is severe, and there is an indicator at the unloading point to prevent overflowing the 20,000-gal underground storage tank. Systematic test samples are removed from each delivery and sent to the lubrication engineer to insure quality control. Fig. 3 illustrates the chutes in which smaller sizes of coal are treated. Fig. 4 shows the entire spraying system. Buried in the ground is a 20,000-gal tank with immersion heaters grouped around the feeder line to insure adequate gravity flow to the pump under all conditions of weather. Oil flows to a 500-gal preheating tank where the temperature is kept about 150°F by six 1½-kw immersion heaters thermostatically controlled. Hot oil is fed through a self-cleaning disc-type filter to the hydraulic pump. Valves and piping make it possible to transfer oil from one tank to another or to drain the lines for maintenance purposes. All this equipment is below ground level in a covered pump room,

Jan 1, 1955

By Orville R. Lyons, A. C. Richardson

THE Coal Division of Battelle Memorial Institute, during the course of an investigation conducted for a coal producer, carried out extensive sampling of the fine-coal section of a preparation plant. The information obtained during the testing period was used to evaluate the overall plant operation and provided the basis for. recommended changes in the plant flowsheet. Included in the information were data for the results obtained when using a Bird centrifuge to dewater the particular coal being treated. At the completion of the investigation, the coal producer gave Battelle permission to publish the operating data for the Bird centrifuge in order to make this information available to the coal industry. The authors wish to take this opportunity to express their appreciation to this company and its officials for their willing cooperation in the matter of publication. Description of Preparation Plant: The preparation plant on which the data were obtained is primarily a jig plant. The coal being washed is a low inherent moisture, friable, Pocahontus-type. The washed coal from the jig is dewatered and sized at 1/4 in. by a Parrish-type dewatering and sizing screen. The minus 1/4-in. coal and the underflow water from the shaker screen flow to a sludge tank where, after the coal settles, the coal is conveyed by a flight conveyor into a pump sump. The pump, a 300-gpm sand pump, delivers a mixture of fine coal and water to a Bird centrifuge which produces a dewatered cake and an effluent. At the time when the investigation was made, the centrifuge effluent was returned to the sludge tank and the cake product was mixed with a coarser size of coal prior to loading into railroad cars. The semiclarified water from the sludge tank overflowed into a pump sump from which it was pumped to the jig. As originally designed, the preparation plant was intended to operate with a closed water system but it was found, soon after operations started, that for various reasons this could not be done. In order to provide for removal of excess water from the system and to aid in maintaining the desired minimum percentage of solids in the circulating water, the plant was operated to provide from the sludge tank a continuous overflow of water and fine solids that was sent to waste. The centrifuge feed represents approximately 35 tons per hour of minus 1/4-in. coal in the form of a pulp averaging 38 pct solids. Sampling Procedure: In order to obtain basic data for determining the relationships existing in the fine-coal section of the preparation plant, samples were obtained for: (1) the centrifuge feed, (2) the centrifuge cake, (3) the centrifuge effluent, and (4) the circulating water. The sampling was arranged to start on a Monday, in order to begin operations with a sludge tank full of fresh water, and was continued long enough to allow sufficient time for fine solids to build up within the water system or for a two-day, four-shift operating period. All samples were taken at half-hour intervals except when plant stoppages occurred. After a stoppage the plant was

Jan 1, 1951

By Orville R. Lyons, A. C. Richardson

THE Coal Division of Battelle Memorial Institute, during the course of an investigation conducted for a coal producer, carried out extensive sampling of the fine-coal section of a preparation plant. The information obtained during the testing period was used to evaluate the overall plant operation and provided the basis for. recommended changes in the plant flowsheet. Included in the information were data for the results obtained when using a Bird centrifuge to dewater the particular coal being treated. At the completion of the investigation, the coal producer gave Battelle permission to publish the operating data for the Bird centrifuge in order to make this information available to the coal industry. The authors wish to take this opportunity to express their appreciation to this company and its officials for their willing cooperation in the matter of publication. Description of Preparation Plant: The preparation plant on which the data were obtained is primarily a jig plant. The coal being washed is a low inherent moisture, friable, Pocahontus-type. The washed coal from the jig is dewatered and sized at 1/4 in. by a Parrish-type dewatering and sizing screen. The minus 1/4-in. coal and the underflow water from the shaker screen flow to a sludge tank where, after the coal settles, the coal is conveyed by a flight conveyor into a pump sump. The pump, a 300-gpm sand pump, delivers a mixture of fine coal and water to a Bird centrifuge which produces a dewatered cake and an effluent. At the time when the investigation was made, the centrifuge effluent was returned to the sludge tank and the cake product was mixed with a coarser size of coal prior to loading into railroad cars. The semiclarified water from the sludge tank overflowed into a pump sump from which it was pumped to the jig. As originally designed, the preparation plant was intended to operate with a closed water system but it was found, soon after operations started, that for various reasons this could not be done. In order to provide for removal of excess water from the system and to aid in maintaining the desired minimum percentage of solids in the circulating water, the plant was operated to provide from the sludge tank a continuous overflow of water and fine solids that was sent to waste. The centrifuge feed represents approximately 35 tons per hour of minus 1/4-in. coal in the form of a pulp averaging 38 pct solids. Sampling Procedure: In order to obtain basic data for determining the relationships existing in the fine-coal section of the preparation plant, samples were obtained for: (1) the centrifuge feed, (2) the centrifuge cake, (3) the centrifuge effluent, and (4) the circulating water. The sampling was arranged to start on a Monday, in order to begin operations with a sludge tank full of fresh water, and was continued long enough to allow sufficient time for fine solids to build up within the water system or for a two-day, four-shift operating period. All samples were taken at half-hour intervals except when plant stoppages occurred. After a stoppage the plant was

Jan 1, 1951

By Orville R. Lyons, A. C. Richardson

F. X. Ferney—We are pleased that this paper was presented at this meeting and thank Mr. Richardson and Mr. Lyons for their effort and work in preparing it. We agree with the authors that it was unfortunate that more comprehensive data were not available when the paper was prepared, this being particularly true since we had no knowledge that the paper was being written and could not make available data which were in our process files. Further, it is our opinion that because the data are not sufficiently comprehensive the results which are presented are erratic and will lead to false conclusions. As we see it, there are three Specific reasons why the data which are presented cannot be considered accurate. 1. The preparation plant was not at equilibrium while the samples were being taken. This is indicated by the fact that the percent of solids in the circulating water varied from 3.9 pct to 10.7 pct during the period when the plant was sampled. 2. We do not believe that the samples of Bird feed which were taken were representative and could indicatc the true feed to the filter. Evidence of this is shown in the data where the dewatered product leaving the centrifuge contains more coarse material than the feed to it, that is, material which is +6-mesh in size. 3. We question if the data concerning screen analysis in the fine sizes is accurate and would conclude (from the data) that these tests were made by a dry-screen method. We have found that wet screening is always necessary to obtain a true picture of the quantity of —200-mesh fines which is present. The test work described in the Lyons-Richardson paper was conducted some time ago and the tests were carried on during a period when the preparation plant had not ironed out all of their start-up problems. Since that time most of these problems have been corrected and now this is a smooth running, well-operated prep-

Jan 1, 1951

By Orville R. Lyons, A. C. Richardson

F. X. Ferney—We are pleased that this paper was presented at this meeting and thank Mr. Richardson and Mr. Lyons for their effort and work in preparing it. We agree with the authors that it was unfortunate that more comprehensive data were not available when the paper was prepared, this being particularly true since we had no knowledge that the paper was being written and could not make available data which were in our process files. Further, it is our opinion that because the data are not sufficiently comprehensive the results which are presented are erratic and will lead to false conclusions. As we see it, there are three Specific reasons why the data which are presented cannot be considered accurate. 1. The preparation plant was not at equilibrium while the samples were being taken. This is indicated by the fact that the percent of solids in the circulating water varied from 3.9 pct to 10.7 pct during the period when the plant was sampled. 2. We do not believe that the samples of Bird feed which were taken were representative and could indicatc the true feed to the filter. Evidence of this is shown in the data where the dewatered product leaving the centrifuge contains more coarse material than the feed to it, that is, material which is +6-mesh in size. 3. We question if the data concerning screen analysis in the fine sizes is accurate and would conclude (from the data) that these tests were made by a dry-screen method. We have found that wet screening is always necessary to obtain a true picture of the quantity of —200-mesh fines which is present. The test work described in the Lyons-Richardson paper was conducted some time ago and the tests were carried on during a period when the preparation plant had not ironed out all of their start-up problems. Since that time most of these problems have been corrected and now this is a smooth running, well-operated prep-

Jan 1, 1951

By W. Z. Price

The coal lands that the Nemacolin mine is to develop embrace over 8400 acres; the tract is oblong and its eastern edge is along the Monon-gahela river. As shown in Fig. 1, the mine is divided into two parts (the North mine and the South mine) by a 150-ft. barrier, which however, is cut through at intervals by haulageways. Each part is fed from seven main entries—a loaded track, an empty, a manway, and four return air courses. The loaded tracks converge at the shaft bottom but the empty roads maintain their identity throughout their length. With three intakes and four returns on either side, there is ample room for expansion of air and every facility for ventilating is provided. The four south air courses converge into two, crossing the shaft bottom, and then into one at the south side of the air shaft. The four north air courses converge in a similar manner on the west side of the same shaft. This convergence is accomplished by concrete arched

Jan 1, 1927

By Elmer R. Kaiser

Industry Adopts Research: Seventy-Ave years ago Thomas A. Edison began in a modest way and with limited funds to gather about him men of various talents to form the first industrial research laboratory. His laboratory at Menlo Park, N. J., became famous for many discoveries and inventions, but possibly the most important of all may yet be the industrial research laboratory itself. Today, private industry operates 2500 research laboratories in which 135,000 persons' are directly and indirectly creating new processes and products and improving old ones, as well as developing new information to help keep the fountain of knowledge from running dry. In this change-making function, the scientific personnel comprises 41 pct; the technical personnel 26 pct; and the balance, 33 pct, nontechnical. The term "industrial research" has become so broad as to include almost everything beginning with the search for and discovery of the laws governing the properties of matter and energy to the development and testing of processes, methods, and equipment. These classes of investigation commonly merge so that no sharp boundary can be traced between them. The National Research Council therefore defines industrial research as "the endeavor to learn how to apply scientific facts to the service of mankind."' Currently, expenditures for research by industry are variously estimated at between $450,000,000 to $700,000,000 a year,' or about twice the expenditure for 1940. The President's Scientific Research Board" estimated that the national research and development for 1947 (excluding atomic energy) was as follows: A few companies spend as much as 5 pct of their gross receipts for research, but 1% to 2 pct is considered a good proportion by many." Shortages: Commendable as is the record of growth and accomplishment of science in industry, it is only a beginning. America and the rest of the world have merely sampled the fruits of industrial research; most industries have yet to make research the key to their future. A top research consultant, T. A. Boyd, of General Motors, states ". . . perhaps 90 per cent of all companies still have no research laboratories."Y or example, of more than 17,000 manufacturing concerns whose gross sales exceed $500,000 a year, less than 2500 have research laboratories. A still smaller proportion of the 184,230 manufacturing establishments in 161 industriese have or could afford their own research facilities. Yet, the small and mediurn-sized com,panies with less than 250 employees each, produce one half of the dollar volume of manufactured products.' How are these companies to participate in and share the benefits of research? Boyd gives two reasons for the inadequate number of laboratories in industry: Many people still do not appreciate the importance of research, nor understand its tremendous potentiali-

Jan 1, 1951

By Elmer R. Kaiser

Industry Adopts Research: Seventy-Ave years ago Thomas A. Edison began in a modest way and with limited funds to gather about him men of various talents to form the first industrial research laboratory. His laboratory at Menlo Park, N. J., became famous for many discoveries and inventions, but possibly the most important of all may yet be the industrial research laboratory itself. Today, private industry operates 2500 research laboratories in which 135,000 persons' are directly and indirectly creating new processes and products and improving old ones, as well as developing new information to help keep the fountain of knowledge from running dry. In this change-making function, the scientific personnel comprises 41 pct; the technical personnel 26 pct; and the balance, 33 pct, nontechnical. The term "industrial research" has become so broad as to include almost everything beginning with the search for and discovery of the laws governing the properties of matter and energy to the development and testing of processes, methods, and equipment. These classes of investigation commonly merge so that no sharp boundary can be traced between them. The National Research Council therefore defines industrial research as "the endeavor to learn how to apply scientific facts to the service of mankind."' Currently, expenditures for research by industry are variously estimated at between $450,000,000 to $700,000,000 a year,' or about twice the expenditure for 1940. The President's Scientific Research Board" estimated that the national research and development for 1947 (excluding atomic energy) was as follows: A few companies spend as much as 5 pct of their gross receipts for research, but 1% to 2 pct is considered a good proportion by many." Shortages: Commendable as is the record of growth and accomplishment of science in industry, it is only a beginning. America and the rest of the world have merely sampled the fruits of industrial research; most industries have yet to make research the key to their future. A top research consultant, T. A. Boyd, of General Motors, states ". . . perhaps 90 per cent of all companies still have no research laboratories."Y or example, of more than 17,000 manufacturing concerns whose gross sales exceed $500,000 a year, less than 2500 have research laboratories. A still smaller proportion of the 184,230 manufacturing establishments in 161 industriese have or could afford their own research facilities. Yet, the small and mediurn-sized com,panies with less than 250 employees each, produce one half of the dollar volume of manufactured products.' How are these companies to participate in and share the benefits of research? Boyd gives two reasons for the inadequate number of laboratories in industry: Many people still do not appreciate the importance of research, nor understand its tremendous potentiali-

Jan 1, 1951

Filter aids are currently used in many industries to increase filtrate clarity and filtration rates. In other industries filtration could be improved if accept- able filter aids could be obtained cheaply. The present paper describes a simple thermal process for making filter aids from coal, outlines the effects of coal properties and major operating variables, and discusses the properties of satisfactory products. Several possible variations in reactor design have been used experimentally, involving fluidized beds of carbon or inert material, reaction of the particles while entrained in air, and a combination of entrainment and fluidization. The limits imposed on product yields by the composition of the parent coal are considered in relation to a range of Australian coals and one New Zealand coal; and the effects of temperature, residence time, and reactant flow rates have been studied in relation to product yields and characteristics.

Jan 1, 1969

Standard petrographic profiles for many Permian seams from New South Wales and Queensland have been drawn up. The standard profiles of seams of the same age and from one or more coalfields were used to compile an idealized or type seam sequence for those coals in which more than half the seam profiles were similar to one another. A marked similarity existed between at least 7 of the 10 type seam sequences formed. The configurations of the vitrite-plus-clarite contents of the plies of 95 per cent of the seams could be formed from different arrangements of 3 basic sequences: (i) a two-ply sequence with a lower vitrite-rich and an upper vitrite-poor ply; (ii) a two-ply sequence with a lower vitrite-poor and an upper vitrite-rich ply; and (iii) a four-ply sequence of 3 plies with vitrite-plus- clarite decreasing upwards, terminating in a vitrite- rich ply. The third basic sequence was very similar to a succession described for some British Carboniferous coals. Eighty per cent of the Australian Permian coal seams studied began with the first (i) basic type of sequence and are interpreted as originating in peat- forming areas which became progressively drier. More than half the seams were formed in an area with a stable depositional surface level which was subject to oscillations of small amplitude.. Many (30%) were formed in an area with a steadily rising depositional surface level.

Jan 1, 1969

By Diessel C. F K, Ng N

The commonly used Stopes-Heerlen coal petrographic classification and nomenclature has over the years been subject to variable interpretations. This paper discusses the problem with specific reference to the inertinite maceral group. The effect of various interpretations of the Stopes-Heerlen system on maceral analysis is discussed and illustrated by means of comparative analyses conducted by a number of laboratories in Australia. An attempt is made to define the reflectance thresholds used by the authors to subdivide the inertinite group; the genetic and technological significance of these thresholds are compared. The difficulties of distinguishing structured and non-structured macerals of the inertinite group is discussed in terms of possible improvements to the present Stopes-Heerlen system by extending the classification to include transitional maceral types.

Jan 1, 1969

A new test coke oven of seven cubic foot capacity is described. The oven was designed to simulate conditions in a central section of a battery oven and a special feature is the achievement of unidirectional heating from the flues on either side of the charge. The method of charging permits close control of charge conditions'such as bulk density and moisture content. These conditions, as well as coking conditions (e.g. flue temper- atures., coking time) must be varied to simulate conditions in different batteries, The effects of several variables on coke quality are discussed. Using test oven conditions corresponding to those of Newcastle steelworks batteries, good agreement was obtained between strength indices of test oven and battery cokes; for 17 tests, the average A.S.T.M. stability and hardness indices for the test oven coke were 38,5% and 69.7%, while those for the battery coke were 37.1.% and 67.6%.

Jan 1, 1969

When a thin film of volatile matter is deposited under vacuum on a polished coal surface, and the coated surface is examined microscopically in piano--polarized reflected light, colour changes are observed characteristic of the various macerals present. The colour changes appear to be mainly due to interference between light reflected at the upper surface of the film and at the film/coal interface. A variety of source materials for the volatile matter required have been tested, including powdered bituminous coal, coal tars, boron oxide, and certain resins.

Jan 1, 1969

Knowledge of coalfield geology has evolved rapidly over the past few years. Recent advances ranging between exploration, mining geology and seam variation studies have enabled application of geological techniques commensurate with technological changes in the coal industry.

Jan 1, 1969

By Wilson R. G

The Bulli and Wongawilli Seams, the two principal sources of coking coal for the Port KKembla steelworks of Australian Iron and Steel Pty. Ltd., vary in rank and in type over the Southern and -South Western Coalfields. The Bulli Seam, ranging widely in type, produces coke varying from weak to strong. The Wongawilli Seam, more consistent in type, produces coke of more consistent strength, but considerably less strong than that from the best Bulli Seam coal. Plans of seam variation show the regional trends in rank and type for each sear. The strongest coke is derived from coal containing between 45 and 55 per cent vitrinite, m.m.f. This is obtainable from the Bulli Sean in a zone embracing Bulli and Appin Colleries.

Jan 1, 1969

The liquid products of low-temperature carbonisation of coal are of variable composition, very much influenced by the rank and type of coal, and process parameters. In general the tar contains a high proportion of phenols and a low proportion of bases. The neutral oil is more analogous to a thermally cracked petroleum oil than to a high temperature tar. Present practice and possible future trends in the production of chemicals and liquid fuels from low temperature tar are reviewed in the light of recent work on the detailed composition of the tar The phenols and aromatics will probably continue to be of most value, with the bases a useful source of spec- ialty products. However the high aliphatic content of the neutral oil (particularly 1-olefins and n-paraffins) is bound to receive more attention for chemicals as well as for liquid Fuels.

Jan 1, 1969

By Taylor G. H

The proposed classification scheme is based on two primary parameters, one for petrographic composition and the other for rank, both being determined with microscopical techniques. The scheme has been applied to a wide range of Australian coals and found to provide a useful means of relat- ing their inherent properties to properties such as volatile- matter yield, crucible swelling number, and calorific value, which will determine how these coals might be used coimierciallyti,

Jan 1, 1969

By Johnson M. W

Factual data about the sedimentation in the Newcastle Coal. Measures are presented. Data concerning the total coal measure sequence (isopachs, sand /shale ratio and total coal thickness variation), data about three coal seams (Borehole, Dudley and Victoria Tunnel) and data about interseam con- glomerate units are discussed. From this data conclusions are drawn about the coal measure environment. The western edge of the coal basin, the Lochinvar Dome, although a high feature was apparently stable during coal measure time. Despite its height it apparently supplied little sediment to the basin. The northern and north-eastern edge, which was unstable, suppl- ied most of the coarse detritus including the conglomerates to the basin. The conglomerates show patterns of fluvial origin but after a period of "normal" variations in pattern they become restricted to two parallel zones evidently tectonically controlled. Deposition of conglomerates is episodic and separated by periods of coal formation when deformation was apparently slight. Formation of each of the three seams considered followed a rather similar pattern - each shows development of thick coal around the basin edge and poor thin coal in the "axial" region of the present synclinal structure. Evidence of in-situ formation of some areas of the seams is discussed and periodic deformation of the basin during coal measure time is postulated.

Jan 1, 1969

By Sergeant G. D, Norman J. R

The importance of reducing the moisture content of fine coal, the nature of the retained water and the means of its removal are discussed. A statistical technique, using a balanced block design, was used to isolate the significant factors determining water content of a coal filter cake, The most significant factor was particle size distribution. A simplex evolutionary operation (evop) was used to determine the optimal quantities of additives required to produce the lowest moisture content for a selected coal size. For this optimum condition (18.6 lb xÇ20 per 100 lb dry coal), additions of 0.045 lb magnesium ion, 0.0026 lb separan A.P. 30, and 0.098 lb aerosol O.T., per 100 lb dry coal were required. The work illustrated the uses of statistical evop technique for the determination of optimal conditions in industrial research projects.

Jan 1, 1969