Coal dust

“ After treating of methods of collecting and analyzing the gases found in mines, of investigations as to the rate of liberation of gas from coal, and of studies on coal dust, this bulletin discusses such factors as the restraining influence of shale dust and dampness on coal-dust explosions. It then takes up practical considerations as to the danger of explosions, including the relative inflammability of old and fresh coal dust. ”

“ The last great danger to which we have here to make reference, is the explosive action of a quantity of coal-dust in a dry condition. It is only now commencing to be fully recognised that this is really a most dangerous explosive. As we have seen, large quantities of coal are formed almost exclusively of lepidodendron spores, and such coal is productive of a great quantity of dust. Explosions which are always more or less attributable to the effects of coal-dust are generally considered, in the official statistics, to have been caused by fire-damp. ”

“ Miners and coal-heavers are not troubled with consumption. Moreover, if the filings were the cause, all the artisans would suffer, when all breathe the same atmosphere. Secondly, while it is true that discoloured lungs have been observed in some miners, it has not been observed in all, or in many; whereas, it has been observed in men not miners, not exposed to any unusual amount of coal-dust. Thirdly, and most conclusively, experiment has shown that the coal-dust cannot penetrate to the lungs. ”

“ Miners in coal have a surprisingly low mortality, when accidents are excluded from the calculation; except in South Wales, where it is slightly higher than for all males in the same district. Coal dust is relatively free from sharp angles, and is therefore not so irritating to the lungs as metallic dust. Consumption is relatively rare among miners.
The Fur-dyer is very prone to suffer from the dust of the dyed furs, great irritation and disease resulting in many cases. ”

“ Experiments lately made in France show that air laden with coal-dust is highly explosive. Several cases of explosion in coalmines have been traced to the action of suspended coal-dust when no fire-damp was present. ”

“ It is true also that the dust of bituminous coals is much more liable to be explosive than the dust of anthracite. No well authenticated instances of coal dust explosions have been reported from the anthracite regions, while in mining soft coals they have undoubtedly occurred. ”

“ It is colorless because it is full of coal and no change of weather brings amelioration. When the sun fills the air with a blinding glare and palpitating heat waves (as it occasionally does) , each step raises a cloud of coal dust, and when the tropical rain falls in a steady downpour (as it usually does) , [55] the whole world seems covered with coal mud, as if about to dissolve into some carboniferous slime. ”

“ Important points connected with dust of organic origin are its inflammability and its liability to explode when mixed with air. The property of explosiveness was forcibly illustrated in the destruction of six flour-mills by this cause in Minneapolis, Minn., in May, 1878. Coal-dust in coal-mines is a cause of accident from explosions which has been closely investigated in England, Germany, and other mining countries. ”

“ Many varieties of coal produce a quantity of fine dust which settles in the roadways, on roof, and sides, and floor. For many years there has been a controversy as to the relative importance of gas and dust in producing explosions, and the question is still one which gives rise to a lively difference of opinion. But there is no doubt that a mixture of coal-dust and air is explosive, and that even if an explosion is started by gas the disturbance creates clouds of dust which gives rise to secondary explosions and spread the disaster over a wider field than was originally affected. ”

“ He, therefore, considers the argillite objects of the Trenton gravels to be true palæolithic implements.
Disease from Coal-Dust.—M. Paul Fabre has published some observations on the part which coal-dust plays in the pathology of coal-miners. The effects which result from the accumulation of dust in the respiratory passages are obvious and need no particular description. Coal-dust does not exert any special action on the skin. ”

“ The ‘breeze’ is the most valuable portion of the dust, and it rises or falls in value according to the amount of building going on and to the rate of its production; in the summer, but little, comparatively, is made. Coal-dust, it must be remembered, is entirely a distinct refuse from road-dust, which also possesses a certain value, as we shall show by-and-by. When all the finer refuse has passed through the sieve, the larger and coarser articles remain upon the top. ”

“ There is no probability of a dangerous explosion being produced by the ignition of coal dust by a naked light or ordinary flame.
Danger arising from coal dust is best guarded against by systematically sprinkling or watering the main roads leading from the working faces to the shaft, where the dust falling from the trams in transit is liable to accumulate. This may be done by water-carts or hose and jet, but preferably by finely divided water and compressed air distributed from a network of pipes carried through the workings. ”

“ It has been supposed by many that this carbonaceous affection was caused by inhalation of coal-dust. Now, when it can be proved, that there is as much coal-dust at one coal-work as at another, the question comes to be, why should colliers, labouring at one coal-work, be subject to the disease; while those engaged at another, escape? For instance, there is as much coal-dust at Penston and Huntlaw, where there has never been black spit, as there is at Pencaitland, Preston-Hall, and Blindwells. ”

“ Again, those who labour as coal-bankers at the mouth of the shaft, are obliged to inhale much coal-dust in shovelling and arranging the coal received from the pit, and have the sputum tinged to a certain extent by it—which resumes its natural appearance when the collier leaves the labour producing it. They are not subject to the miners' cough, nor is there carbonaceous infiltration found in the lungs of such labourers after death. ”

“ A study of this subject has been made by the United States Department of Agriculture, and various recommendations have been published with a view to preventing the occurrence of sparks in the neighborhood of these dangerous dusts. Coal dust in mines likewise causes numerous explosions. Preventive measures include wetting the dust, moistening the air, and powdering the walls, roof and floor of the mine with a nonexplosive rock dust, which has the effect of stifling an incipient fire or explosion. ”

“ So, too, the enormous hills of anthracite-coal dirt, that in the coal regions of our State have for years borne silent but eloquent testimony to the crudity and wastefulness of our methods of mining coal, now bid fair soon to disappear beneath boilers supplied with ingenious dust-burning devices, or in the form of lumps of artificial fuel. ”

“ Some 40,000,000 tons of valueless coal-dust, lying in the vicinity of the coal-mines and depots of Pennsylvania, have been thus gradually utilized. In some American factories they have found it cheaper and more advantageous to burn only coal-dust or pea coal. A furnace or grate bar has been specially devised for the purpose of burning this kind of fuel, and there is no doubt, with its increasing uses, but that other convenient devices will be supplied for making it of more practical benefit. The utilization of this waste in the coal-regions of the United States is now a decided success. ”

“ This force, acting on the air, throws the finest particles of coal dust into the circulating current, in a finely divided state, with orbid motion, thereby causing each particle of coal dust to be surrounded with air, and359 these particles of dust in this condition coming in contact with the flame of a shot, are easily ignited. ”

“ The charred appearance of the wood-work in coal-mines after explosions is ascribed to the deposition of a crust of scorched or melted coal-dust upon it. The fine dust generated in some of the processes employed in flouring-mills has been recognized lately as a very dangerous source of explosions, and attention has been directed to the contrivance of improvements in machinery to mitigate the perils to which the workers in tens of thousands of mills are exposed from it. ”

“ In connection with this may be mentioned the fact that under certain conditions coal dust may become violently explosive. When it is mixed with air, with or without the presence of fire damp, and is set into sudden and intense vibration by a heavy powder blast, a fall of roof, or other means, it may explode with greater destructive force than even fire damp is capable of. Happily such explosions are not frequent, all the conditions necessary being rarely present at the same time. It is obvious, moreover, that an accident of this kind could occur only in a very dry mine. ”

“ The air is black with coal dust, and the roar of the crushers, screens and rushing mill-race of coal is deafening. Sometimes one of the children falls into the machinery and is terribly mangled, or slips into the chute and is smothered to death. Many children are killed in this way. Many others, after a time, contract coal-miners asthma and consumption, which gradually undermine their health. ”

“ The burning of coal is the principal source of these, not only when the coal is burned with the production of smoke, but also when smokeless, and even when the coal is first converted into gas and burned in the most perfect forms of combustion. It results from this that while in the air over the uninhabited parts of the earth and over the ocean the number of particles is small, being principally produced by natural causes or carried from distant lands, they are much more numerous in inhabited areas, especially in those where much coal is burned. ”

“ Yet the smoke itself, including as it does all the many impurities which exist in coal, is not only evil in itself, but is evil in its influences. Dr Siemens has said:—"It has been shown that the fine dust resulting from the imperfect combustion of coal was mainly instrumental in the formation of fog; each particle of solid matter attracting to itself aqueous vapour. These globules of fog were rendered particularly tenacious and disagreeable by the presence of tar vapour, another result of imperfect combustion of raw fuel, which might be turned to better account at the dyeworks. ”

“ Is it one wid this you'd be, Yank—black smoke from the funnels smudging the sea, smudging the decks—the bloody engines pounding and throbbing and shaking—wid divil a sight of sun or a breath of clean air—choking our lungs wid coal dust—breaking our backs and hearts in the hell of the stokehole—feeding the bloody furnace—feeding our lives along wid the coal, I'm thinking—caged in by steel from a sight of the sky like bloody apes in the Zoo! ”

“ In coal mines, too, coal may fill the air with a dust so fine that explosions take place, with serious loss of life. In Austria it has been found that the fineness of the dust has more to do with the violence of such explosions than has the chemical composition of the particles. ”

“ Where forests of oak once stood, only black charred roots and columns of dressed granite now remain, to tell the tale of a well-to-do Miao-tzŭ peasantry in hand to hand conflict with better-armed opponents.
COAL-DUST AS FUEL.
How to utilize coal-dust as fuel has always been a fruitful topic of discussion where coal mines are worked. I notice that the most recent invention in England is the admixture of pitch with the dust. Here and elsewhere in China, clay is the ingredient used ”

“ Every improvement which results in the better ventilation of a coal-mine tends to leave the dust in a more dangerous condition. The air, as it descends the shaft and permeates the workings, becomes more and more heated, and licks up every particle of moisture it can touch. Thorough ventilation results in more greatly freeing a mine of the dangerous fire-damp, but the remedy brings about another disease, viz., the drying-up of all moisture. ”

“ The mining engineering field force of the Geological Survey, at the head of which is Mr. George S. Rice, an experienced mining and consulting engineer, has already made great progress in the study of underground mining conditions and methods. Nearly all the more dangerous coal mines in the United States have been examined; samples of gas, coal, and dust have been taken and analyzed at the chemical laboratories at Pittsburg; extended tests have been made as to the explosibility of various mixtures of gas and air; as to the explosibility of dust from various typical coals ”

“ This causes a cloud of black dirt, and the front of your house suffers. Then coal must be shovelled up into scuttles; often it is necessary to break up the large lumps. The scuttles are then carried about the house, coals up, ashes down; grates are cleaned and the room is powdered with dust in the process. Grates, fenders, fireirons, and coal-boxes must be cleaned, and fashion ordains that they are generally made, wholly or partly, of polished metal. The weather is cold and a servant is rung for and more coal is demanded. One day the wind blows and the fire will not light. ”

“ Municipalities became affected with the incineration fever. Steam was necessary to drive the electric plant which had been acquired. Why not cut down the coal-bill by making use of the fuel properties possessed by household refuse? The contents of the domestic dust-bin are so varied, ranging from waste-paper, grease-laden bones, fragments of fat, cinders, rags and vegetable odds and ends as to present, in the aggregate, a readily combustible mass possessing distinct calorific value. By utilizing the garbage, which has to be collected, in this manner, the coal-bill might be reduced by so much. ”