Coal measure

“ In the hope of remedying in some measure the evils thus distinctly ascertained to arise from the undue thickness of the masses of coal subjected to the distillatory process, there have not been wanting manufacturers who have had recourse to experiments on a large scale, to ascertain with certainty whether they might not be gainers by suffering the distillatory process, when the retorts are charged with two bushels of coal, to proceed only for the space of six hours, instead of eight. ”

“ The number of workable seams and consequent thickness of coal in every division of the coal-area are in proportion to the thickness of the carboniferous rocks. Beginning at the base of the coal-measures, and reaching up to the height of 400 feet, to the base of the barren measures, there exist, in the bituminous regions, 3 feet of coal for every 50 feet of strata. The next 400 feet are generally barren of workable coal ”

“ Taking the coal measures of South Wales and Monmouthshire, we have a series of accumulations in which the coal-beds become not only more anthracitic toward the west, but also exhibit this change in a plane which may be considered as dipping south-south-east, at a moderate angle, the amount of which is not yet clearly ascertained, so that in the natural sections afforded, we have bituminous coals in the high grounds and anthracite coals beneath. ”

“ Aside from the coal-measures below the sandstone, there have been found above the sandstone, north of Pine Mountain, 1650 feet of coal-measures, containing nine beds of coal of workable thickness, and between Pine and Cumberland mountains there is a greater thickness of coal-measures, containing twelve or more workable beds. Some of these are coking coals of great excellence. Cannel-coals are found in sixteen of the counties in the eastern coal-fields. Two of them at least are of unexampled richness and purity. The value of a cannel-coal is determined by its volatile combustible matter. ”

“ In the coal regions of Rhode Island the disturbances affecting the earth’s crust have been very violent. The motion, heat, and compression have been so great as to give the rocks associated with the coal measures a true metamorphic or crystalline structure, and to transform the coal itself into an extremely hard anthracite; in some places, indeed, it has been altered to graphite. The flexures of the coal formation are very abrupt and full of faults, and the coal itself is greatly broken and displaced. ”

“ The coal-measures form an elliptical basin, and are several thousand feet in thickness. Coal is found in three horizons, of which the upper has no less than 82 seams, measuring 180 feet in all. The lowest horizon yields valuable steam and blast-furnace coal. In the north of England the coal-fields of Lancashire, Derbyshire, and Yorkshire are the largest. ”

“ Effect of Rate of Heating of Coal on the Extent of Combustion Space Required.—There is still another factor, a very important one, which, with a given coal and any given air supply, will influence the extent of the combustion space. This factor is the rate of heating of the coal when feeding it into the furnace. The so-called “proximate” analysis of coal is indeed only very approximate. When the analysis shows, say, 40% of volatile matter and 45% of fixed carbon, it does not mean that the coal is actually composed of so much volatile matter and so much fixed carbon ”

“ As far as the gas-making properties of the first three are concerned, the relative proportions of carbon and volatile products are much the same. Everybody knows a piece of cannel coal when it is seen, how it appears almost to have been once in a molten condition, and how it breaks with a conchoidal fracture, as opposed to the cleavage of bituminous coal into thin layers; and, most apparent and most noticeable of all, how it does not soil the hands after the manner of ordinary coal. ”

“ In the great coal-field of South Wales, to which we must look for our main supply of anthracite, we are able to trace the action of heat in producing a whole series of different classes of coal in a single seam, which at one part is highly bituminous—soft, flaming coal, like the Wallsend, then it becomes harder and less bituminous, then semi-bituminous “steam coal,” then less and less flaming, until at last we have the hard, shiny form of purely carbonaceous coal, that may be handled without soiling the fingers, and which burns without flame, like coke or charcoal. ”

“ One of the chief dangers to which workmen in the mines are subject arises from the gases given off by minerals and metals. Though these deleterious gases are commonly found in more or less abundance in the coal mines, and are usually considered in connection with such mines, they are, nevertheless, not confined to the coal measures. ”

“ There is perhaps no subject in the art of manufacturing coal gas, on which practical men are less agreed, than they are on the temperature most economically to be employed for the production of coal gas in the large way. It must be sufficiently evident, that cast-iron retorts, when worked at a low temperature, will last longer, than when exposed to higher degrees of heat. ”

“ Anthracite, another form of carbon, is used as fuel for strong furnaces. It leaves little “ash,” and is smokeless when burned. Coal, in all its forms, is evidently derived from wood. Thousands of years ago vegetable matter must have been embedded in the ground and subjected to carbonization. There are different kinds of coal, all of which come under one or other of the following heads: cubical coal, slate coal, cannel coal, glance-lignite,—the last being, as its name implies, an imperfect development of wood; it is a brown coal. We are not here concerned with coal as a fuel. ”

“ And if we give credit to the assertion of those workmen, whose business it is to manufacture a given quantity of gas by means of a certain quantity of coal delivered to them, it would appear that coal which affords gas abounding in sulphuretted hydrogen, is the kind of coal most easily to be decomposed. This, as far as it regards the decomposition of Scotch Splent or cannel coal, is certainly true. No species of coal affords gas at a lower temperature, and of none is the gaseous product more loaded with sulphuretted hydrogen gas. ”

“ Where thirty or forty seams of coal have been found one below another, we have evidence of land and water thus changing places many times.
When vegetable matter is excluded from air and under great pressure, it decomposes slowly, parting with carbonic acid gas; and is first changed into lignite or brown coal, and then into bituminous coal, or the soft coal that burns with smoke and flame. I have been in a coal-mine where the carbonic acid gas, pouring from a crevice in the coal, put out a lighted candle. ”

“ The investigations include the possibility of making satisfactory commercial fuels from lignite or low-grade coals which do not stand shipment well, the benefiting of culm or slack coals which are wasted or sold at unremunerative prices, and the possibility of improving the efficiency of good coals. Some of the various forms of commercial briquettes, American and foreign, are shown in Fig. 2, Plate XX. After undergoing chemical analysis, the coal is elevated and fed to a storage bin, whence it is drawn through a chute to a hopper on the weighing scales. ”

“ And again we have shown little willingness to dignify coal by seeking to draw out by improved mechanical processes all the stored content of heat in this lump of carbon. Instead we content ourselves by giving it a mere pauper touch, driving off the greater volume of its value into the air. ”

“ The gas which soon comes from the stem of the pipe does not take fire unless a light be applied, when it may be seen to burn with a bright flame, and after the flow of gas has ceased, nearly the whole of the carbon of the coal will be found unconsumed in the bowl of the pipe. This simple experiment illustrates perfectly the first step in the manufacture of coal-gas, namely, the process of heating coal to redness in closed vessels, by which operation the substances originally contained in coal are destroyed, and their elements enter into new combinations. ”

“ The temperature necessary for the decomposition of different kinds of coal, varies. Some species of coal are more readily decomposed, and require a less portion of fuel than others; they yield up their maximum quantity of gas, in an almost equal stream from beginning to end, and no extraordinary increase of temperature is required to terminate the distillatory process. Other kinds of coal require a different treatment ”

“ The loss occasioned by this rapid diminution of the means employed, is serious in every point of view, in regard as well to the quantity of fuel used and time wasted, but it is unavoidable in the operation of decomposing coal in masses or layers from 5 to 10 inches in thickness, and must be a great drawback on the value of the gas-light discovery. ”

“ It must not be thought that in this huge area the coal is all uniformly good. It varies greatly in quality, and in some districts it occurs in such thin seams as to be worthless, except as fuel for consumption by the actual coal-getters. There are, too, areas of many square miles in extent, where there are now no coals at all, the formation having been denuded right down to the palaeozoic back-bone of the country. ”

“ Chemists tell us that coal is chiefly constructed of carbon, compounded with oxygen, hydrogen, and nitrogen. There are many varieties, but all may be classified under two general headings—bituminous and anthracite. Bituminous coal contains a large amount of a tarry substance, a kind of mineral pitch or bitumen, which burns with a brilliant flame and a black sooty smoke, exceedingly rich in carbon. Anthracite coal is hard and stone-like in its texture, burning with scarcely any flame and no smoke. It produces a fire of intense heat when it is once ignited. ”

“ When we consider the before mentioned varieties of coal in an economical point of view, as fuel to be used in the gas-light process, for heating the retorts, it appears from a series of experiments that have been made under my direction, that the second class of coal comprehending those varieties which contain a larger quantity of carbon than bitumen (p. 45,) afford the most economical fuel, they act less on the grate bars, and fire bricks of the furnace than those varieties which take fire easily and burn briskly with a strong blaze. ”

“ Of course the newly-exposed face of the coal would have its initial temperature of 183°; but this is a trivial heat compared to the red-hot radiant surfaces to which puddlers, shinglers, glassmakers, etc., are commonly exposed. Divested of the incumbrance of clothing, with the whole surface of the skin continuously fanned by a powerful stream of air—which, during working hours need be but partly saturated with vapor—a sturdy midland or north-countryman would work merrily enough at short hours and high wages, even though the newly-exposed face of coal reached 212° ”

“ It must be obvious, that in proportion as the mass of coal in the retort becomes carbonized or converted into coke, the exterior surface becomes a gradually increasing obstacle to the action of the heat upon the interior or central part of the coal remaining to be decomposed. The heat required on that account must be more intense, and kept up to no purpose, and the extrication of gas becomes slower and slower, as the operation proceeds. ”

“ Hard coal of good quality has 90 per cent or more of carbon, and burns with little flame. Soft coal contains as much as 18 per cent of flame-making substances, and gives off a heavy smoke. Hard coal is therefore cleaner, but it is more costly than soft coal, because the supply is smaller. The most important anthracite mines are found in the eastern United States, and hard coal is used more in this section than elsewhere. Good hard coal may be recognized by its glossy black color and bright surfaces. It is sold under different names taken often from the locality where it is mined. ”

“ To the poor people who live in the vicinity of the breakers these heaps of refuse coal are an unmixed blessing. Pieces of good coal are always being thrown out inadvertently with the waste, and the bony coal that is discarded is not by any means without value as a fuel; indeed it makes a very respectable fire. So, too, one can obtain, with a screen, from the culm heap quite a little percentage of material that will burn. ”

“ The difficulties in burning bituminous coals with economy and with little or no smoke increases as the content of fixed carbon in the coal decreases. It is their volatile content which causes the difficulties and it is essential that the furnaces be designed to properly handle this portion of the coal. The fixed carbon will take care of itself, provided the volatile matter is properly burned. ”

“ The Bureau of Mines has compiled valuable information on the character and analyses of coal from almost every field in the United States. Information concerning the character and chemical constituents of the coal, together with knowledge pertaining to the equipment of the plant, makes it possible to select a fuel adapted to the equipment, thereby insuring better combustion. Hundreds of boiler plants operate at no greater than 60 per cent efficiency, and it would be a comparatively simple matter to bring them up to 70 per cent efficiency. ”

“ The main use of coal, as we all know, is to produce heat, without which many a paterfamilias would grumble when the dinner-hour came and he had nothing hot to eat. It not only, however, supplies heat, but the beauty of the processes for lighting up our houses is now mainly derived from coal. The immense consumption of coal, among other things, is in the production of the vapour of water—steam, by which our thousands of engines on sea and land are made to perform their various appointed tasks. ”