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Explosibility of Coal Dust

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Explosibility of Coal Dust DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEOKGE OTIS SMITH, DIRECTOR BULLETIN 425 THE EXPLOSIBILITY OF COAL DUST BY GEORGE S. RICE WITH CHAPTERS BX J. C. W. FRAZER, AXEL LARSEN, FRANK HAAS, AND CARL SCHOLZ WASHINGTON GOVERN M E N T P K I N T IN G OFFICE 1910 CONTENTS. Page. Introd uctory statement...................................... ............ 9 The coal-dust, problem................................................ 9 i Acknowledgments.................................................... 10 Historical review of the coal-dust question in Europe ....................... 11 Observations in England prior to 1850................................. 11 Observations by French engineers prior to 1890........................ 12 Experiments in England between 1850 and 1885........................ 12 Experiments in Prussia............................,.............:..... 14 Experiments in Austria between 1885 and 1891......................... 16 Views of English authorities between 1886 and 1908.................... 17 German, French, and Belgian stations for testing explosives............ 19 Altofts gallery, England, 1908......................................... 21 Second report of Royal Commission on Mines, 1909...................... 21 Recent Austrian experiments.......................................... 22 Historical review of the coal-dust question in the United States.............. 23 Grahamite explosions in West Virginia, 1871 and 1873.................. 23 Flour-mill explosion at Minneapolis, 1878.............................. 23 Explosion at Pocahontas mine, West Virginia, 1884.................... 24 Explosion at Pekay mine, Iowa, 1892.................................. 25 Proposed remedies for dust.........'................................... 26 Results of shooting off the solid....................................... 26 Great disasters of 1907.................. .............................. 27 Inaccurate reports of accidents ........................................ 28 Fatalites in 1908...................................................... 28 Inquiry by the United States Geological Survey ....................... 28 Coal dust and its origin and distribution. .................................. 29 Definition of dust .......................... I......................... 19 Ignition and propagation............................................... 30 Coal-mining methods and dust production ............................. 30 .Dust from hand and from machine undercutting........................ 31 Agencies that distribute coal dust ..................................... 33 Experiments with explosible coal dusts.................................... 34 Effect of quantity or density of dust................................... 34 Character of dust used............................................ 34 Method of procedure.............................................. 35 Method of taking samples......................................... 36 Results.......................................................... 36 Coked dusts produced by explosions............................... 38 Effect of degree of' coarseness of dust................ ^................. 38 Results of tests................................................... 38 Method of screening.............................................. 39 Distribution of dust.............................................. 40 Discussion of results............................................... 40 Character of coke produced....................................... 41 3 4 CONTENTS. Experiments with explosible coal dusts Continued. Page. Effect of chemical composition ........................................ 41 Past experiments................................................. 41 Investigations in the United States by Chamberlin................. 42 . Experiments of Bedson and Widdas ............................... 42 Investigation in France by Taffanel................................ 43 Comparison of Taffanel's methods with those used at Pittsburg gallery. 44 Informal tests at Pittsburg station ................................. 45 Informal tests with road dust ..................................... 48 Experiments at Pittsburg with coal dust............................... 49 Use of coal dust for tamping ...................................... 49 Experiments with coal dust in humidified air ...................... 50 Humidity of mine air..................................................... 54 Natural principles.................................................... 54 Saturated air at different temperatures............................. 54 Amount of moisture in mine air..................... I .............. 56 Effect of seasonal changes of temperature on mine air............... 57 Instruments for measuring atmospheric moisture ....................... 57 Sling psychrometer............................................... 57 Hygrometer used by the Geological Survey ........................ 58 Stationary hygrometer............................................ '58 Principle of wet and dry bulb thermometer ........................ 59 Method of making hygrometric observations in mines .................. 60 Relation of moisture content to temperature and pressure of mine air .... 61 Remedies for coal dust.................................................... 66 Review of remedies proposed ......................................... 66 Loading and cleaning up dust ; ......................................... 66 Sprinkling from water cars............................................. 67 Calcium chloride and other deliquescent salts .......................... 68 Sprinkling and washing down with hose and nozzle .................... 73 Permanent sprinklers................................................. 74 Humidifying by steam jets..........................i................. 76 Quick-naming explosives.............................................. 78 Kockdust ........................................................... 80 Brick or concrete linings and. wet zones......:...... '. .................. 82 Tentative conclusions on the dust problem................................. 83 Factors affecting explosibility ......................................... 83 Volatile combustible matter.............................. _ ......... 83 Structure and size............................. .................... 83 Density.......................................................... 84 Moisture ........................................................ 84 ish content ..................................................... 85 Outward conditions .............................................. 85 Conditions affecting propagation of explosions.......................... 85 Amount of dust.................................................. 85 Moisture in dust and in air.... .................................... 86 Mixture with inert substances..................................... 87 Advantages and disadvantages of proposed remedies.................... 87 Force sprinklers in cars................................... ........ 87 Chemicals ....................................................... 87 Cleaning up dust washing down walls............................ 88 Permanent sprinklers zonal linings... '. ........................... 88 Use of exhaust steam sprays ...................................... 88 Stone dust r- ^ - -r ........,.,,, r .,-. TT , r ...,,.,. T ..., r ... r . r .. r .,. 91 CONTENTS. 5 Page. Observations on manifestations of coked coal dust in mine explosions........ 92 Character of coked dust............................................... 92 Position of coked dust after an explosion............................... 94 Special features in dust explosions......................................... 97 Laboratory investigations of the ignition of coal dust, by J. C. W. Frazer.... 99 Introductory statement............................................... 99 Early experiments of Galloway....................................... 100 Ignition of dust falling on flame....................................... 100 Experiments of Vital................................................. 101 Experiments of Hall and Clark....................................... 104 Experiments of Abel................................................. 105 Experiments of Mallard and Le Chatelier.......................... ... 105 Later experiments by Galloway....................................... 110 Experiments of Thorpe............................................... 110 Reduction of pressure following explosion wave........................ 112 Experiments of Engler ............................................... 113 Lecture experiment of Bedson and Widdas............................. 113 Experiments of Holtzwart and Meyer.................................. 114 Laboratory experiments of Bedson and Widdas ........................ 117 Experiments at Lidivin, France........................................ 121 First series of experiments at Pittsburg testing station................... 124 Second series of experiments at Pittsburg testing station................ 128 Significant points in experiments...................................... 132 Coal-dust investigations at European testing stations, by Axel Larsen........ 133 Protective measures under study ...................................... 133 Apparatus and methods at Altofts and Li6vin.......................... 135 General statement................................................. 135 Instruments at Altofts........................."................... 135 Calculation
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