Gas emission

“ 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. ”

“ We may prevent smoke, though we cannot cure it, and this prevention depends upon how we supply air to the gas which the coal gives off when heated, and upon the condition of this gas when we bring it in contact with the air by which its combustion is to be effected. We must always remember that coal when its temperature is sufficiently heated, whether in a gas retort or fireplace, gives off a series of combustible hydrocarbon gases and vapors, and all we have to do in order to obtain smokeless fires is to secure the complete combustion of these. ”

“ Let us take a Bunsen burner, in which the air and gas are freely mingled before they enter into combustion. If the air and the gas be properly proportioned, the combustion is so perfect that though a great deal of heat is produced there is but little light. The gas burned in this experiment ought to be the ordinary gas of our mains, which depends for its illuminating power on the circumstance that the hydrogen, of which the gas is chiefly composed, is largely charged with carbon. The illuminating power of the gas may indeed be measured by its available richness in carbon. ”

“ 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. ”

“ As the proportion of light given out by the flame of a gaseous compound of carbon and hydrogen, is in common circumstances in proportion to the quantity of carbon present; it is evident that the gas which contains a greater proportion of olifiant gas, or supercarburetted hydrogen than coal gas, will yield a better and brighter light on combustion. ”

“ The fuels for gas-lighting are natural gas, carbureted water-gas, and coal-gas obtained by distilling coal, but there are different methods of producing the artificial gases. Coal-gas is produced analytically by distilling certain kinds of coal, but water-gas and producer-gas are made synthetically by the action of several constituents upon one another. Carbureted water-gas is made from fixed carbon, steam, and oil and also from steam and oil. Producer-gas is made by the action of steam or air or both upon fixed carbon. ”

“ I want almost—not quite—actual flame to fire coal gas. But here is another gas, about which I may have to say something directly, called marsh gas (the gas of coal-mines) . This requires a much higher temperature than even coal gas to fire it. I want you to understand that although all gases require heat to fire them, different gases ignite at very different temperatures. Bisulphide of carbon gas, e. g., ignites at a very low temperature, whilst marsh gas requires a very high temperature indeed for its ignition. You will see directly that this is a very important fact. ”

“ If seven bulbfuls of air be mixed with one bulbful of gas, an explosive mixture of 1 to 7 is produced, this being 294 the proportion commonly employed for street-gas. For producer-gases the preferred proportion is 1 to 1, oxygen being often added to the air in order to insure complete combustion. ”

“ Natural gas occurs in very large quantities in the United States, where it is conveyed through pipes under pressure for hundreds of miles, and distributed among factories and houses for driving machinery, heating, and cooking. In England and Europe the petroleum engine and coal-gas engine have been most utilised; but of late the employment of smelting-furnace gases—formerly blown into the air and wasted—and of "producer" gas has come into great favour with manufacturers. ”

“ Intermittent processes, in which carbon is first heated to incandescence by an air blast, and then, the air blast being cut off, superheated steam is blown in until the temperature is reduced to a point at which the carbon begins to fail in its action, when the air is again admitted to bring the fuel up to the required temperature, the process consisting of alternate formation of producer gas with rise of temperature, and of water gas with lowering of the temperature. ”

“ But the means of preventing such an occurrence in the common application of gas-lights, are so simple, easy, and effectual, that it would be ridiculous to dread danger where there is nothing to be apprehended. In speaking thus of the safety of the gas-light illumination, I do not mean to deny that no possible circumstances may occur where the coal-gas may be the cause of accident. It is certain that the gas, when suffered to accumulate in large quantities in close and confined places, where there is no current of air, such as in cellars, vaults, &c. ”

“ To obtain the full heat value of a liquid fuel it must be provided with sufficient air to complete the combustion, it must be in a very finely subdivided state, or in the form of a vapor at the time of ignition, and it must be thoroughly mixed with the air so that every part of the oil is in contact which its chemical equivalent of oxygen. Failure to comply with any of these conditions will not only result in a waste of fuel but will also be the cause of troublesome carbon deposits and soot, which eventually will interfere with the operation of the burner. ”

“ The gas from the gas-works is the hydrogen of the coal separated from the carbon. When we heat it with a match to set it to uniting with oxygen, we have nothing but a flame. You know the coal is heated in air-tight retorts; it is heated hot enough to burn, but it can't burn because there is no oxygen for it to unite with; but the heat causes the hydrogen to separate from the carbon, and then it finds its way out through the opening in the retort into the pipes, and when it reaches the air at the end of a pipe, you can heat it a little with a match, and it will begin to unite with the oxygen. ”

“ The art of purifying coal gas, has at length however, been carried to such a perfection, that every possibility of a disagreeable odour arising from its combustion has been wholly removed, in all cases where attention is paid to the perfect combustion of the gas, by keeping the flame of the same of a proper magnitude. ”

“ The extent to which the working medium is expanded depends not only upon the change of temperature but also on its composition.
In all practical heat engines, the heat energy is developed by the process of combustion, which is a chemical combination of the oxygen of the air with certain substances, such as coal or gasoline, known as “fuels.” The heat producing elements of the fuels are generally compounds of carbon and hydrogen, which when oxydized or burnt by the oxygen form products that are unlike either of the original components. ”

“ The resulting water gas contains 60% of hydrogen and 20% of carbon monoxide, both of which are combustible gases. The proportions of the gases evolved can be varied at will by admitting more steam or using an excess of carbon ”

“ Thus, in order that gas may give the best illumination, we must increase the yellow or white space of carbon particles at a white heat, and a burner that will do this, and at the same time hold the balance so that unconsumed particles of carbon shall not escape in the way of smoke, will give the most successful illuminating results. With this end in view the addition of albo-carbon to a bulb in the gas-pipe has proved very successful, and the incandescent gas-jet is constructed on exactly the same chemical principle. ”

“ It is necessary, in consequence of the abundance of charcoal in solution, to supply the gas when burning with plenty of atmospheric air, for as there is more combustible matter in a certain volume of it, than in an equal volume of coal gas, it of necessity must have more oxigen for its consumption. ”

“ The rapid chemical action would raise the temperature of these gases, and thus increase their bulk immensely, which would produce an irresistible expansive force, which would increase the pressure against the sides of the cavern in which the gases were generated, and the ignition of the hydrogen would be a necessary consequence. Such an immense volume of gas being ignited, and confined, would produce such a degree of heat, as rapidly to decompose or melt the substances in its neighborhood, and set at 63 liberty a vast quantity of other gases ”

“ This may be effected by causing a current of air to rise up perpendicular from the bottom of the chimney glass, and to pass out again through the contracted part, or upper extremity of the chimney; but no other current of air should ever be permitted to come near the gas-flame, or enter the glass chimney which covers or defends the light; for if more air be permitted to mix with the flame than is sufficient for the compleat combustion of the coal-gas, it necessarily diminishes the heat, and consequently reduces the quantity of light. ”

“ 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. ”

“ The gases so formed vary in proportion with the temperature of the generator and the amount of steam, but generally contain 32 to 38% of combustible gas, the remainder being the residual nitrogen of the air and carbon dioxide. These gases enter the combustion chamber around the retorts at a high temperature, and are there supplied with sufficient air to complete their combustion, this secondary air supply being heated by the hot products of combustion on their way to the exit flue. ”

“ The illuminating power of the flame of coal gas is, on the contrary, impaired, when, by admixture with other species of gas which precipitate no carbon, its own ignited particles are diffused over a greater surface. This happens when it is mixed with hydrogen, carbonic oxide, carbonic acid, and nitrogen gases, and the diminution of the light is proportional to the dilution of the coal gas. ”

“ When the flame is suffered to rise beyond the standard height, the combustion of the gas becomes imperfect, part of the gas passes through the flame unburnt, and occasions the source of the offensive odour alluded to, which the gas lights never produce when the combustion of the gas is complete. ”

“ The tubes formed by the wick serve the same office as a retort placed in a heated furnace through which the inflammable liquid is transmitted. The oil is drawn up into these ignited tubes, and is decomposed into carburetted hidrogen gas, and from the combustion of this gas the illumination proceeds. See p. 15. What then does the gas-light system attempt? Nothing more than to generate, by means of sufficient furnaces and a reservoir of sufficient capacity, desired quantities of the gas, which is the same material of the flame of candles or lamps ”

“ At first sight it appears absurd, useless, and paradoxical to lose nearly one-third of the heat which fuel can develop, by turning it into gas. Actually the advantage is enormous, especially for producing high temperatures, as is already seen from the fact that fuels rich in oxygen (for instance, wood) when damp are unable, with any kind of hearth whatever, to give the temperature required for glass-melting or steel-casting, whilst in the gas-producer they furnish exactly the same gas as the driest and most carbonaceous fuel. ”

“ In the manufacture of gas, coal is raised to a high temperature, and the gases are driven off by roasting the coal in an oven from which air, i. e., oxygen, is shut out. The gases are conducted away, cooled, purified, and stored for future use in a gasometer; the combined carbon and mineral residue, being non-volatile, is cooled down before being exposed to the air, and is sold as coke. Here we have a striking proof of the fact that high temperature in fuel does not of itself involve combustion. ”

“ There is no escape of combustible matter unconsumed, which is so great a nuisance [101] in all our common lights. The products of the combustion are water and carbonic acid gas [21] . The accurate and elegant experiments of Dr. W. Henry have shewn in the most satisfactory manner, that considerably less carbonic acid is produced by the flame of coal-gas, than by that of oil, tallow, or wax [22] , which [102] sufficiently refutes the absurd notions that have been circulated respecting the pernicious effects of gas-lights. ”

“ Hydrogen is an invisible gas, and the lightest known body in the world, being many times lighter than oxygen. It is combustible and gives out much heat. In our gas establishments it is made in large quantities and combined with carbon for illuminating streets, shops and dwellings. It is the source of all common flame. When united with sulphur in coal mines it becomes explosive. By passing a current of steam through a hot iron tube partly filled with filings, hydrogen gas is given off and burns with a pale yellow flame. ”