Showing that the average of the South Lancashire and Cheshire coals is inferior in rapidity and in efficiency of evaporation to both of the other coals, and that though the best of the South Lancashire coals has a greater evaporative efficiency than the others, the rapidity of evaporation was less. This comparison is corroborative of the deductions made from Delabèche and Playfair's analysis and trials of coals from the several districts (see page 413). EVAPORATIVE PERFORMANCE OF NEWCASTLE COALS IN A MARINE BOILER, AT NEWCASTLE-ON-TYNE, 1857.1 These experiments were made to test the evaporative power of the steam-coal of the Hartley district of Northumberland. The experimental boiler was of the marine type, 10 feet 3 inches long, 7 feet 6 inches wide, and 10 feet high; with 2 internal furnaces, 3 feet by 3 feet 3 inches high, and 135 flue-tubes above the furnaces, in 9 rows of 15 each, 3 inches in diameter inside, 5% feet long. The dead-plates were 16 inches long, and 21 inches below the crown of the furnace. As the result of many preliminary trials, two standard lengths of fire-grates were fixed upon-4 feet 9 inches, and 3 feet 21⁄2 inches, with a fall of 1⁄2 inch to a foot; and the fire-bars were cast 1⁄2 inch thick, with air-spaces from 5% to 3/4 inch wide. The fire-doors were made with slits 1⁄2 inch wide and 14 inches long, for the admission of air. The chimney was 2 feet 6 inches in diameter. A water-heater was applied at the base of the chimney, in the thoroughfare; it contained 76 vertical tubes, 4 inches in diameter, surrounded by the feed-water. Total area of fire-grates, 4 feet 9 inches long, 281⁄2 square feet. Do. Do. do. 3 ", 22 194 Heating surface of boiler (outside), 749 square feet. water heater,.....320 Ratio of larger grate-area to heating surface of boiler, 1 to 26.28 Do. smaller do. do. I to 38.91 Two systems of firing were adopted, as "standards of practice:"-First, ordinary or spreading firing, in which the fuel was charged over the grate, and the whole of the supply of air was admitted through the grate. Second, coking-firing, in which the fuel was charged, I cwt. at a time, upon the dead-plate, and subsequently pushed on to the grate, making room for the next charge; and air was admitted by the doorway as well as by the grate. Four systems of furnace were tried, of which Mr. C. W. Williams' was adjudged by the experimentalists to have rendered the best performance. According to this system, air was admitted above the fire at the front of the furnace, by means of cast-iron casings, having apertures on the outside, with slides, and perforated through the inner face, next the fire, with numerous 5/8-inch and 1⁄2-inch holes, having a total area of 80 square inches, or 5.33 square inches per square foot of grate. Alternate firing was adopted by Mr. Williams. The general results of the experiments are given in table No. 274. 1 The author has derived the particulars of those trials from the Report of Messrs. Longridge, Armstrong, & Richardson to the Steam Collieries Association of Newcastle-on-Tyne. 1857. Table No. 274.-NEWCASTLE COALS (OF THE HARTLEY DISTRICT OF NORTHUMBERLAND)-RESULTS OF EVAPORATIVE 1857. (Compiled from the Report of Messrs. Longridge, Armstrong, and Richardson to the Steam Collieries Association of Newcastle-on-Tyne.) NOTES TO TABLE.-1. When the temperature was 600° in the uptake of the boiler, it was reduced by from 40° to 50° after having passed through the water-heater. 3. The experimentalists reported that Mr. Williams' plan gave the best results, and they concluded: "Ist. That by an easy method of firing, combined with a due admission of air in front of the furnace, and a proper arrangement of fire-grate, the emission of smoke may be effectually prevented in ordinary marine multitubular boilers whilst using the steam-coals of the Hartley district of Northumberland. 2d. That the prevention of smoke increases the economic value of the fuel and the evaporative power of the boiler. 3d. That the coals from the Hartley district have an evaporative power fully equal to that of the best Welsh steam-coals, and that, practically, as regards steam navigation, they are decidedly superior." These gentlemen made a trial of Aberaman Welsh coal, and they found that its practical evaporative power, when it was hand-picked, and the small coal rejected, was at the rate of 12.35 lbs. of water per pound of coal, evaporated from 212°; this may be compared with the best result from Hartleys coal, large and small together, in table No. 274, which was 12.53 lbs. water from 212° per pound of coal, or with another result of experiment, with Hartley coal, not given in the table, showing 12.91 lbs. water per pound of coal. As a check on these results, they ascertained the total heat of combustion of the two coals here compared, by means of an apparatus constructed by Mr. Wright, of Westminster, so contrived that a portion of coal is burned under water, and the products of combustion actually passed through the water, which absorbs the whole heat of combustion. The following are the comparative values: The experimentalists also point out the "elasticity of action" of the Hartley coals: they burned them at rates varying from 9 to 371⁄2 lbs. per square foot of grate per hour without difficulty, and without smoke. The Welsh coal, burned at the rate of 341⁄2 lbs. per foot per hour, melted, it is said, the fire-bars after an hour and a half's work. TRIALS OF NEWCASTLE AND WELSH COALS IN THE MARINE BOILER AT & Taplin. 1858. Messrs. Miller & Taplin, representing the Board of Admiralty, conducted, in 1858, a series of trials at Newcastle, with the same marine boiler as was employed by Messrs. Longridge, Armstrong, & Richardson, the object of which was to investigate the comparative evaporative power and other properties of Hartley coal and Welsh steam-coal, and the merits of Mr. Williams' plan of smoke-prevention. The fire-bars were 14 inch in thickness, and had 5%-inch air-spaces. The feed-water was passed through the heater, except when otherwise stated. Mr. Williams' apparatus was constantly in action when Hartley coal was burned without smoke; and it was closed when this coal was tried for smoke making, also when Welsh coal was burned. Table No. 275.-NEWCASTLE AND WELSH COALS:-RESULTS OF EVAPORATIVE PERFORMANCE IN THE SAME MARINE (Compiled from the Report of Messrs. Miller & Taplin to the Board of Admiralty.) 1858. Remarks on the Prevention of Smoke, &c. per grate. Hour. Grate per Hour. from 60° per Hour. 212° per Grate per Hour. Pound of Coal. sq. feet. cwt. lbs. cub. feet. cub. feet. lbs. 42 6.0 16.00 89.84 2.14 9.65 Long grates, air-passages fully open. No smoke. 9.14 Do. do. do. 6.8 18.13 94.46 2.25 8.96 6.0 20.36 86.24 2.61 9.25 No smoke. Trial of small broken coal. Trial with slow combustion. Damper in chimney closed to an area of 250 sq. ins. Grate raised 5 ins. Bars 5 in. thick, spaces 1⁄2 in. No smoke. These trials were made to compare the efficiency of coal brought direct from the collieries with that of the same coal after having been carried about and transshipped. But there was a doubt whether the coal from the dockyard was Buddle's or another quality. Test for bituminous or highly smoky coal. No smoke. West Hartley.. Do. Do. 29 30 Do. 223 Dense Do. Forced draught by steam jet in chimney. Air-passages above fire, closed. black smoke. 5.29 26.92 84.31 3.83 10.27 No smoke. 5.30 26.98 82.21 3.73 9.98 Do. 7.0 35.64 102.76 4.67 9.46 31.56 6.2 78.78 3.58 8.19 { Air-passages above the grate closed, with Welsh coal. 38 { Blaengwarn Merthyr, sent from Woolwich Dockyard.. 22 4.55 23.18 74-35 3.38 10. II I 3 4 5 67 2 No smoke, except light brown when firing. 8 NOTE. The quantities in column 7 have been recalculated.-D. K. C. |