Hydrocarbon

“ In solid fuels, such as coal, a portion of the compound consists of free carbon and the remainder of a compound of carbon and hydrogen known as a HYDROCARBON. In liquid fuels there is little, if any, free carbon, the greater proportion being in the 29form of a hydrocarbon compound. ”

“ In the latter condition—the hydrocarbons—hydrogen is protected from the all-devourer, oxygen, and enters into innumerable uses. As the inflammable ingredient of wood, of bituminous coal, of petroleum and other vegetable and animal oils, we have it sealed up by Providence, as it were, for a temporary and portable fuel, pending the full development of man's proper authority over the elements—temporary, for it has long been a source of anxiety to economists that the resources of forests and coal-fields are so finite and their prospect of exhaustion so definite. ”

“ In addition to the hydrocarbons, which are the chief constituents of petroleum, the following substances may be present: Sulphur, nitrogen, hydrogen sulphide, carbon disulphide, arsenic, and phosphorus. The carbon percentage may vary from 79.5 to 88.7 per cent.; the hydrogen from 9.6 to 14.8 per cent.; the sulphur from 0.7 to 2 per cent., and in rare cases even 3 per cent.; nitrogen from 0.008 to 1.1 per cent. The hydrocarbons of all crude petroleums fall either into the paraffin or olefin group, those of America belonging chiefly to the first and those of Russia to the second group. ”

“ Compounds of carbon with hydrogen,—the hydrocarbons. Carbon unites with hydrogen to form a very large number of compounds called hydrocarbons. Petroleum and natural gas are essentially mixtures of a great variety of these hydrocarbons. Many others are found in living plants, and still others are produced by the decay of organic matter in the absence of air. Only two of them, methane and acetylene, will be discussed here. ”

“ OIL-GAS. A mixture of several gaseous hydrocarbons, obtained by passing common whale fat, resin, the heavy petroleum or shale oil, or the tarry residues left after the distillation of these two latter substances, or other cheap animal oil, through red-hot tubes, or by allowing it to fall in drops on red-hot stones or bricks arranged in an iron retort, or other suitable apparatus. The gas has great illuminating power, requires no purification, and is quite free from the ammoniacal and sulphur compounds which vitiate coal-gas. ”

“ From this it will be seen that, with the increase of temperature, the hydrocarbons—the olefines and marsh gas series—gradually break up, depositing carbon in the crown of the retort, and liberating hydrogen, the percentage of which steadily increases with the rise of temperature.
The tar formed is affected to an even greater extent than the gas by alterations in the temperature at which the destructive distillation takes place. ”

“ The substances thus formed by a weak union of carbon with hydrogen are called hydrocarbons. They comprise nearly all the highly inflammable vegetable substances. Their being combustible means simply that they have a great disposition to resume their union with oxygen—combustion being nothing other than a more or less violent return of a substance to a union with oxygen or some other such substance, usually one from which it had formerly been separated by force—giving out again by its return, in the form of heat, the force by which the original separation had been effected. ”

“ When coal is heated to redness out of contact with the air, the more volatile constituents, water, hydrogen, oxygen, and nitrogen are in great part expelled, a portion of the carbon being also volatilized in the form of hydrocarbons and carbonic oxide,—the greater part, however, remaining behind,Caking coals. ”

“ In carburetting poor coal gas with hydrocarbons from mineral oil it must be borne in mind that, as coal is undergoing distillation, a rich gas is given off in the earlier stages, but towards the end of the operation the gas is very poor in illuminants, the methane disappearing with the other hydrocarbons, and the increase in hydrogen being very marked. ”

“ But with gases so rich in hydrocarbons as those developed from oil it is excessively difficult to get the necessary air intimately and evenly mixed with the gas in sufficient proportion to bring about the desired result. ”

“ These heated hydrocarbons rise and are heated to a higher temperature as they ascend. They are accordingly decomposed with separation of carbon in the higher parts of the flame, giving the region of bright yellow luminosity. There remains a central core in which neither is there any oxygen for combustion nor a sufficiently high temperature to cause carbon separation. ”

“ Such hydrocarbons are present in coals in small quantities, but they have positive and negative heats of combination, and in coals these appear to offset each other, certainly sufficiently to apply the formula to such fuels. ”

“ Here the hydrogen and hydrocarbons react upon each other, producing a permanent gas, which is purified as usual. The resulting gas is of uniform quality, very pure, and the saving in labor and materials is about 35 per cent. over coal-gas (Scientific American, January 8, 1876) .
As regards the use of petroleum for fuel, it has always been found difficult to secure the complete combustion of the oil, so as to avoid smoke ”

“ We must content ourselves with saying that most modern producers are of the form of a tower in which a thick bed of fuel is partially burnt and partly gasified under the action of a blast of air mixed with steam. The chemical actions that take place are complicated, but the final result is the production of a gas containing from 2 to 8 or 10 per cent. of carbonic acid, 10 to 20 per cent. of hydrogen, 8 to 25 per cent. of carbonic oxide (CO) , 1 to 3 per cent. methane (CH4) , and 45 to 60 per cent. of nitrogen, with varying quantities of moisture, tarry matter, and ammonia. ”

“ Carbon and hydrogen the chief elements in fuel. Carbon and hydrogen make up the larger part of almost every substance that is used for fuel, including gas, gasoline, wood, and soft coal; alcohol, crude oil, kerosene, paper, peat, and the acetylene used in automobile and bicycle lamps. Hard coal, coke, and charcoal are, however, chiefly plain carbon. Since burning is simply the combining of things with oxygen, it is plain that when the carbon of fuel joins oxygen we shall get carbon dioxid (CO2) . When the hydrogen in the fuel joins oxygen, what must we get? ”

“ When the intensity of the heat has reached a certain degree, a part of the carbon unites with part of the oxigen and produces carbonic acid, which by means of caloric is melted into the gazeous state and forms carbonic acid gas; at the same time, part of the hidrogen of the coal combines with another portion of carbon and caloric, and forms the carburetted hidrogen gas, which varies considerably in its constitution, according to the circumstances under which it is produced; a portion of olifiant gas, carbonic oxid, hidrogen, and sulphuretted hidrogen, is also produced during the process. ”

“ At this point let us note how a gas, suitable for an engine, is manufactured at least cost, the outlay being much less than in the case of illuminating gas which represents but one third of the coal placed in the distilling retorts. Instead of this process of distillation, “producer” gas is due to a modified combustion which gasifies all the fuel. In a producer of standard type, atmospheric oxygen comes into contact with the glowing carbon of the coal or wood, forming carbon dioxide, CO2. The heat generated by this union is taken up by the carbon dioxide and the nitrogen of the supplied air. ”

“ Similarly with coal and air: the hydrogen and carbon of the coal have affinities or attractions toward the oxygen of the air, and when I bring them together at a high temperature (of which more hereafter) they rush into one another's embrace to form carbonic acid and water, while their energy is given off as heat or motion of the surrounding bodies. We might have whole minefuls of coal at our disposal; but if we had no oxygen to unite with it, the coal would be of no more use than so much earth or stone. ”

“ I said that there was carbon or charcoal in all common lights, so there is in every common kind of fuel. If you heat coal or wood away from the air, some gas comes away, and leaves behind coke from coal, and charcoal from wood; both carbon, though not pure. Heat carbon as much as you will in a close vessel, and it does not change in the least; but let the air get to it, and then it burns and flies off in carbonic acid gas. This makes carbon so convenient for fuel. But it is ornamental as well as useful, uncle. The diamond is nothing else than carbon. ”

“ When heated in close vessels much more gas is obtained than when burnt in the open air. If moistened charcoal be put into an earthen retort and heat be applied till the retort becomes ignited; gas will be evolved, consisting partly of carbonic acid, and partly of carburetted hidrogen. A gas of similar properties is obtained by causing steam to pass through a tube filled with red-hot charcoal; by passing spirit of wine, or camphor, through red-hot tubes; by distilling oils, wood, bones, wax and tallow, or any animal or vegetable body whatever. ”

“ Wood consists mainly of compounds of carbon, hydrogen, and oxygen. The composition of coal and the fuel gases has been given. Since these fuels are composed principally of carbon and hydrogen or their compounds, the chief products of combustion are carbon dioxide and water. The practice of heating rooms with portable gas or oil stoves with no provision for removing the products of combustion is to be condemned, since the carbon dioxide is generated in sufficient quantities to render the air unfit for breathing. ”

“ Ellisen, of the Paris gas-works, have shown that the gases rich in carbon, such as defiant and acetylene, are developed chiefly during an interval of time, beginning half an hour after the commencement and terminating at half the whole period of distillation, while during the remainder of the time, marsh gas and hydrogen are chiefly developed, which, while possessing little illuminating power, are most advantageous for heating purposes. ”

“ For fuel a pound of coal is about equal to two pounds of wood, and a pound of gasoline to three pounds of wood in heating value, so there would be a great loss in efficiency and economy if the world had to go back to a wood basis. But when that time shall come, as, of course, it must come some time, the wood will doubtless not be burned in its natural state but will be converted into hydrogen and carbon monoxide in a gas producer or will be distilled in closed ovens giving charcoal and gas and saving the by-products, the tar and acid liquors. ”

“ A certain quantity of carbon enters into chemical union with a definite quantity of oxygen, and, as an incident in the process, a definite quantity of heat is liberated. So much coal, for instance, requires for complete combustion so much air, and, granted a sufficiency of air, the union of the carbon and hydrogen in the coal will give out a certain quantity of heat which may be conveniently expressed by the number of pounds of water which that heat would suffice to transform into steam. ”

“ The inflammable gas, which lights our streets, churches, shops, &c., is procured chiefly from coal, burnt in furnaces for the purpose the gas being passed through metal pipes, conveyed underground to the places where the light is required: escaping at the orifice prepared for it, it is lighted when wanted, and burns with, a brilliant flame. This gas consists of hydrogen and carbon; and the oxygen of the air, combined with the hydrogen, causes light as long as hydrogen and oxygen exist and combine. ”

“ The condensable vapours are principally hydro-carbon compounds which become deposited in the form of oil, and amongst a variety of deleterious substances may be mentioned as the chief: ammonia, carbonic acid, carbonic oxide, and sulphuretted hydrogen, but the value of coal-gas principally depends on the presence of bicarburetted hydrogen, and the greater proportion of this the higher will be its light-giving properties. ”

“ Gas thus produced is intensely hot; and as usually it contains sulphur, dust, dirt, and other admixtures, their removal by water in a scrubber would involve a waste of about 30 per cent. of the fuel heat. This loss is much diminished by sending into the producer not only air but steam, to be decomposed into oxygen and hydrogen; the oxygen combines with carbon to form more carbon monoxide, while the hydrogen is the most valuable heating ingredient in the emitted stream of gases. Were only air sent through the producer, the outflowing gases would contain nitrogen to the extent of 65 per cent. ”

“ The manufacture of water-gas differs entirely from that of coal or naphtha gas. It involves the production, first, of a non-illuminating gas from steam, and, second, of petroleum, naphtha, or cannel gas, to furnish the illuminating power. ”

“ More important, however, than the elements are the carbohydrates or compounds of carbon, oxygen and hydrogen, which form the bulk of the natural fuels, wood, peat and coal, as well as of their liquid and gaseous derivatives—coal-gas, coal-tar, pitch, oil, &c., which have high values as fuel. Carbon in the elementary form has its nearest representative in the carbonized fuels, charcoal from wood and coke from coal. ”

“ From an engineer’s standpoint the main constituents of all coal are carbon and hydrogen; in the natural state of coal these two are united and solid; their respective characters and modes of entering into combustion, are however essentially different. The hydrogen is convertable into heat only in the gaseous state; the carbon, on the contrary, is combustible only in the solid condition. It must be borne in mind that neither is combustible while they are united. ”