20 THE COLLIERY GUARDIAN. July 5, 1918. BURNING ANTHRACITE SLUSH.* The coal industry, like others, has had its waste problem. This has lain in the disposal of two products —the slate brought out of the mine with the coal and later separated from it in the process of preparation, and the fine coal produced, for which no commercial demand as yet exists. Slate and bone are at present disposed of in various ways, one of the most effectual being the pulverisation of this material and its flushing back into the old workings to insure surface support. For bituminous slack there exists at the present time a strong de- mand. In the past, however, considerable quantities of this material have been dumped on the ground and wasted at no small cost to the mine because there was no market for this fine material. The sizes of anthracite that have been deemed usable have almost steadily grown smaller since the beginning of the industry. At present the only size of this material made which is not considered burnable in ordinary furnaces equipped for steam generation is what is variously known as culm, silt or slush. This is the size that passes through a 3/ 32 in. circular opening, the actual size of the various particles ranging from minute dust to the full-sized opening referred to above. Because of the variation in size of the individual particles the interstitial openings are numerous but minute, and the passages through which air may travel in traversing a bed of any considerable thickness of this coal, as that upon a firegrate, are small and tortuous. The percentage of voids in a bed of this fuel is probably about the same as that in a mixture of fine gravel and sand. The difficulty encountered in the burning of this fuel by ordinary hand-firing methods in boiler furnaces has been the deadening effect of a fresh charge of coal upon a going fire. This arises chiefly from the small air passages previously referred to. Ordinary natural draught, unless caused from a prohibitively high stack, is inadequate to force air through any considerable thickness of this fuel, and as a result where this material is to be burned commercially forced draught must be installed. The coal department of the Delaware, Lackawanna and Western Bailroad Company, at its Nanticoke power plant, is successfully burning this fuel under boilers, thus utilising a product which has heretofore been considered useless except for the manufacture of anthracite briquettes. The fuel used in this particular power plant is made at the washery operated in connection with the Loomis breaker. The slush, or silt, which passes through the smallest opening of the shaker screens drops into a shallow hoppered tank under the shakers. While being treated on the shakers the coal is subjected to water sprays, and this water, of course, finds its way through the screen plates and enters the hopper-shaped tank referred to, along with the coal passing the small mesh. At the bottom of the hopper-shaped concrete tank below the shaking screen the fine coal and a certain portion of the water is drawn off through an ordinary gate valve into a chute below. The greater portion of the water is, however, drawn from this tank at a point considerably above the apex of the hopper, so that little, if any, coal goes off with the bulk of the water. The chute into which the silt and water are discharged from the bottom of the tank leads to a storage bin exactly similar to the bins for storing the other grades of coal. At suitable intervals—that is, when a sufficient amount of this slush has accumu- lated in the storage bins—it is drawn off through regular chutes into a hopper-bottomed railroad car. Of course, throughout this entire process, or until after the coal has been deposited in the railroad car, all of the voids between particles have been thoroughly filled, or a little more than filled, with water. When a car of this material leaves the washery, while the coal is heaped up somewhat above the level of the top of the car, the water is overflowing the sides. In passing the valve and travelling down the chute, and particularly in flowing from the bin to the car through the loading chute, this mixture of fine coal and water behaves much like a thick or viscous liquid. At a short distance away the material in the car more resembles mud than it does coal. So thoroughly fluid is this material when it enters the car that it is necessary, before running the car under the loading chute from the slush or silt bin, to place in its bottom a few hundred pounds of coal of the next larger size in order to prevent the fine material from flowing out of the cracks around the hopper-bottom doors and thus being wasted. In this condition it is run upon the coal tracks of the Nanticoke power plant. These tracks enter the boiler house at one end and extend throughout the length of the building immediately above the coal storage bunkers. The coal is here discharged from the hopper-bottomed cars and passes down into the bunkers through a cast iron grating containing open- ings about 2| in. by 3f in. From the bottom of the coal bunkers chutes lead to the feed hoppers of Coxe chain grate stokers. The fingers of these stokers, which form the actual coal-supporting surface or grate, are of special design and contain openings about 1 /16 in. wide and 3/32 in. in length. Approximately 6 per cent, of the grate surface is made up of these minute air spaces. On the grate of this stoker this fine material, which is carried to a depth of about 4 in., is burned by the aid of forced draught of an intensity of about 1] to 2 in. of water. Considerable care and no small amount of skill must be exercised in handling this fire. The, fire carried in these stokers is by no means as flexible as it is possible to secure with some types of stokers and bituminous coal. The heat developed, however, is intense, as is evidenced by the slag forma- tions produced on the side of the door opening of the furnace. * Coal Age. In this plant ten Babcock and Wilcox boilers, each of 303 horse-power, are in operation, set in batteries of two each. The actual effective grate surface under- each boiler- is 10 ft. wide and 11 ft. 8 in. long. Four more boilers, duplicates of those now in opera- tion (except as to superheaters), are now being in- stalled. Steam is carried at 155 lb. pressure and 150 degs. of superheat. From the boiler plant the steam is conveyed to the engine room, which con- tains as main units two Allis-Chalmers steam turbines direct connected to Allis-Chalmers 4,100 volt, 565 amp., three-phase, 60 cycle generators. These machines operate at 1,800 revolutions per minute. Surface con- densers are employed, and a vacuum of about 28 in. is secured. Cooling water is drawn from the adjoin- ing river and returns to the same source. The power generated is transmitted direct without transforma- tion to eight different collieries of the Lackawanna company. At this and other Lackawanna plants, so far as is known, have been made the only successful attempts to burn an anthracite fuel as fine as that used. This fine material contains from 85 to 90 per cent, as much heat-per pound as do the larger grades; and the question which has confronted would-be users of this fuel, namely, how to get the heat out of this fine coal, would now appear to have been solved by the chain grate stoker and forced draught as employed in the Nanticoke power plant. THE RUSHTON STONE DUSTING MACHINE. A demonstration of this machine was given on Wednesday of last week at the Kermishaw Nook, No. 4 pit, of the Astley and Tyldesley Collieries, before the members of the Manchester Geological and Mining Society. As can be seen from the illustration, the sprayer consists of a straight iron pipe (about 20 in. long and 2 in. diameter) with a bell mouth and pro- vided with an L-leg (some 10 in. in length), which is inserted into the receptacle containing the stone dust. The rear end of the straight pipe is tapered down to | in. diameter and connected to a source of com- ¥ T . -; The Bushton Stone-dustins Machine. pressed air, the force of the air drawing the dust up the L-piece and discharging it as a fine cloud through the bell mouth. The sprayer is simple, easily operated, and will discharge about three tons of stone dust per hour, or sufficient to dust about 900 yards of colliery Electricity from Lignite.—Previous to the outbreak of war, Germans were experimenting in Devon on the utilisa- tion of lignite for generating electrical power. The lig- nite deposit is in the Bovey Tracey basin, and was formerly first worked to supply fuel for the local potteries, but this was practically discontinued when coal became available. In March 1914 Dr. Lambrecht, the leading mineralogical adviser to the German Government, sub- mitted a report to his employers, the Deutsche Bohrgesell- schaft, on the property and works, in which he referred in the highest terms to the results and prospects of generating electrical energy at very low cost. This view is confirmed by an experienced English mineralogist, and though the lignite has the great disadvantage as fuel of being high in sulphur, valuable by-products could be obtained from it. Scholarships at the Wigan Mining College.—Mr. S. C. Laws, M.A., B.Sc., the principal of the Wigan and District Mining and Technical College, announces that the “Alfred Hewlett” Scholarship, value .£52 per annum, and the two College Scholarships, each of the value of £50 per annum, tenable for three years at the full-time mining course at the college, are offered for competition, and will be awarded on the results of an examination to be held at the college on Monday, Tuesday and Wednes- day, July 22 to 24, 1918. The subjects of examination will be mathematics (two papers), general physics and elementary chemistry, together with two selections from the following : heat, mechanics, chemistry, electricity (with magnetism). The candidates sitting for the scholar- ships must have been under 17 years of age on June 1, 1918. The examination syllabuses, together with entrance fees, may be had on application to the principal of the college, and candidates should note that the entrance forms must be returned, duly completed, before Wednesday, July 17, 1918. NEW MAXIMUM PRICES FOR FRENCH COALS. The French Minister of Munitions has issued the following supplementary list* of maximum prices for I he various collieries mentioned. The figures in brackets immediately preceding the prices relate to the average maximum percentage of ash content in the coals. Cie. des Mines de Cessous. Anthracite with 9-10 per cent, of volatiles—Larue, over 90 mm. (20), 65 fr.; large cobbles, 60-90 mm. (20), 70 fr.; cobbles, 30-60 mm. (20), 70 fr.; nuts, 20-30 mm. (18), 60 fr.; small nuts, 10-20 mm. (32), 34fr.; “type chaux,” 8-60 mm. (35), 31 fr.; small, 0-10 mm. (30), 25'50 fr. Cie. des Chemins de Fee de PaeisLyon Meditbreanee (Houilleee de la Chazotte). Coal—Large, over 150 mm. (12), 57 fr.; cobbles, 50-150 mm. (10), 56 fr.; small, 0’50 mm. (18), 40 fr.; slack, 0-10 mm. (18), 36 fr.; washed small, 10-17 mm. (15), 44 fr.; screenings (35), 36 fr. Briquettes (17), 60 fr. Soc. des Mines de Houille de la Ohapelle- sous-Dun et des Moquets. Flaming coal with 35 per cent, of volatiles.—Large, over 80 mm. (18), 51 fr.; cobbles, 50-80 mm. (20), 41 fr.; washed small, 30-60 mm. (18), 50 fr.; washed beans, 15-30 mm. (18), 45 fr.; washed peas, 8-15 mm. (20), 38 fr.; washed small, 0-8 mm. (20), 34 fr.; nuts, 15-60 mm. (25), 35 fr.; small nuts, 0-15 mm. (30), 24 fr. SCHNBIDEE ET ClE. (HOUTLLERES DU CrEUSOT). Coal with 22 per cent, of volatiles.—Large, over 60 mm. (18), 36 fr.; small, 15-25 mm. (15), 38 fr.; smithy small, 0-10 mm. (12), 36 fr. ; washed small, 010 mm. (15), 30'50 fr.; through-and-through, 25 per cent., large (28), 27 fr. Washery products.—Sludge, 19'50 fr.; slaty coal, 16 fr. Cie. des Mines de la Grand’Combe (Mines de Teets). Lignite.—Large, hand-picked (10), 37 fr.; cobbles, 60-120 mm. (12), 36 fr.; nuts, 50-120 mm. (20), 26 fr.; grains, 30-50 mm. (20), 23'50 fr.; slack, 7-330 mm. (28), 19 50 fr.; dust, 0-7 mm. (35), 18 fr.; through-and- through (28), 19'50 fr.; picking belt waste, hand-picked (50) 12'50 fr. Mine de Methamis. Lignite (with 15 20 per cent, water):—Through-and- through, 20 per cent, small on 10 mm. screen (28), 36 fr. (f); through-and-through. 20-50 per cent small on 10 mm. screen (28), 33 fr. (f). [J Pithead price ; free on rail Carpentras, 17 fr. extra.] Soc. Anonyms des Charbonnages de Champleix (Mines de Vendes). Coal—Large, over 25 mm. (25), 60 fr.; large, 25 mm. (25-35), 35 fr.; washed beans, 16-25 mm. (25), 51 fr.; washed peas, 10-16 mm. (25), 49 fr.; washed small, 0-10 mm. (25), 47 fr. ; rough small, 0-25 mm. (25-40), 30 fr. The maximum prices of coal for the undermentioned collieries have been raised provisionally and uniformly as noted for all kinds of coal. However, whilst the average selling prices as fixed by the latest Decree are to be maintained as closely as possible, special regula- tions will be issued to fix for each colliery the actual prices to be charged for the various kinds of fuel, based on commercial quality, size, ash content, and the desir- ability of increasing the output of particular grades. Alais district:—Cie. Nouvelle des Mines de Portes et Senechas, 5 fr. per ton. Marseilles district: — Soc. Anon des Mines de Charbons des Alpes, 4 fr. per ton. Toulouse district: — Charbonnages de Figeac et Charbonnages de la Pourcille et de Bel-Air, 9 fr. per ton. *Colliery Guardian, May 17, 1918, p. 996. French Miners’ Pensions.—Owing to the increase in wages, the French Government has introduced a Bill, raising to 4,000 fr. per annum the wage limit (previously 3,000 fr.) for compulsory contribution to the fund for miners’ old age pensions (100 fr. per annum at the age of 60). In the case of optional contributors, the former wage range of 3,000-5,000 fr. is to be altered to 4,000- 6,000 fr.