Читать книгу Description of the Process of Manufacturing Coal Gas - Friedrich Christian Accum - Страница 9
Outline of the new art of procuring light by means of coal gas, and Theory of the production of Gas Lights.
ОглавлениеAll substances, whether animal, vegetable, or mineral, consisting of carbon, hydrogen, and oxigen, when exposed to a red heat, produce various inflammable elastic fluids, capable of furnishing artificial light.
The gases thus obtained are called carburetted hydrogen; they produce, from their combustion, water and carbonic acid. The species of carburetted hydrogen, procured from pit-coal, has of late been called coal gas.
We perceive the evolution of this elastic fluid, during the combustion of coal, in a common fire. The coal, when heated to a certain degree, swells and kindles, and frequently emits remarkably bright streams of flame. And after a certain period these appearances cease, and the coal glows with a red light.
The flame produced from coal, wood, turf, oil, wax, tallow, or other bodies, which are composed of carbon, hydrogen and oxigen, proceeds from the production of carburetted hydrogen gas, evolved from the combustible body when in an ignited state.
It must have been noticed at the same time, that in the common mode of burning coal in a fire-place, or stove, nearly the whole of this inflammable gaseous matter is lost. We often see a flame suddenly burst from the densest smoke, and as suddenly disappear; and if a light be applied to the little jets that issue from the bituminous part of the coal, they will catch fire and burn with a bright flame. The fact is, that the greater part of the carburetted hydrogen gas, capable of affording light and heat, continually escapes up the chimney, during the decomposition of the coal, whilst only a small part is occasionally ignited, and exhibits the phenomena of the flame.
If coal instead of being burnt in the way now stated, is submitted at a temperature of ignition in close vessels, all its immediate constituent parts may be collected. The bituminous part is melted out in the form of coal tar, there is disengaged at the same time a large quantity of an aqueous fluid, contaminated with a portion of oil, and various ammoniacal salts. A large quantity of carburetted hydrogen, carbonic oxide, carbonic acid, and sulphuretted hydrogen also makes their appearance, and the fixed base of the coal, alone remains behind in the distillatory apparatus, in the form of a carbonaceous substance called coke. An analysis of the coal is thus effected by the process of destructive distillation. The products which the coal furnishes may be separately collected in different vessels. The carburetted hydrogen, or coal gas, when freed from the foreign gases may be propelled in streams out of small apertures, which when lighted may serve as a flame of a candle and then form what we now call Gas Lights.
It is in this manner that from pitcoal a production of our own soil, we procure a pure, lasting and brilliant light, which in other cases must be derived from materials in part imported from abroad.
In order to apply this mode of procuring light on a large scale as now practised with unparalleled success in this country, the coal is put into vessels called retorts and furnished with pipes connected with reservoirs to receive the distillatory products. The retorts are fixed into a furnace, and heated to redness. The heat developes from the coal the gaseous and liquid products, the latter are deposited into receivers, and the former are conducted through water in which quick lime is diffused by which the carburetted hydrogen gas is purified. The sulphuretted hydrogen and carbonic acid which were mixed with it, become absorbed by the quick-lime, and the pure carburetted hydrogen is stored up in a vessel called the gas-holder, and is then ready for use.
From the reservoir in which the gas has been collected, proceed pipes, which branch out into smaller ramifications until they terminate at the place where the lights are wanted and the extremities of the branch pipes are furnished with stop-cocks to regulate the flow of the gas into the burners or lamps.
The production of gas-lights, is therefore analogous to that of flame produced from tallow, wax, or oil. All these substances possess, in common with coal, the elements of certain peculiar matters, which are capable of being converted into inflammable elastic fluids by the application of heat.
The capillary tubes, formed by the wick of a candle, or lamp, serve the office of the retorts, placed in the heated furnace in the gas-light process and in which the inflammable gaseous fluid is developed. The wax tallow or oil, is drawn up into these ignited tubes, and is decomposed into carburetted hydrogen gas, and from the combustion of this substance the illumination proceeds. In the lamp as well as in the candle, the oil, or tallow, must therefore be decomposed before they can produce a light, but for this purpose the decomposition of a minute quantity of the materials successively, is sufficient to give a good light. Thus originates the flame of a candle or lamp.
Nothing more therefore is aimed at in the gas-light process, than to separate the immediate products which coal affords, when submitted to a temperature of ignition in a close vessel; to collect these products in separate reservoirs, and to convey one of the products, the inflammable gas, by means of pipes and branching tubes, to any required distance, in order to exhibit it there at the orifice of the conducting tube, so that it may be used as a candle or lamp.
The whole difference between the gigantic process of the gas light operation, and the miniature operation of a candle or lamp, consists in having the distillatory apparatus at the gas-light manufactory, instead of being in the wick of a candle or lamp. In having the crude inflammable matter decomposed previous to the elastic fluid being wanted, and stored up for use, instead of being prepared and consumed as fast as it proceeds from the decomposed oil, wax or tallow; and lastly, in transmitting the gas to any required distance, and igniting it at the burner or lamp of the conducting tube, instead of burning it at the apex of the wick. The principle of the gas-light manufacture is therefore rational, and justifiable by the general mode in which all light is produced.
It only remains to be observed that while the new and important use to which pitcoal may thus be applied, affords a strong confirmation of what has been well observed, that of all subterraneous combustible substances, coal is in this country by far the most important natural production.[2] “It is connected not only with the necessities, comforts and enjoyments of life, but also with the extension of our most important arts, our manufactures, commerce and national riches.
[2] Davy on the Safety Lamp.
“Essential in affording warmth and preparing food, it yields a sort of artificial sunshine and in some measure compensates for the disadvantages of our climate.
“By means of it metallurgical processes are carried on, and the most important materials of civilized life furnished, the agriculturist is supplied with a useful manure and the architect with a necessary cement. Not only manufactories and private houses, but even whole streets and towns are lighted by its application, and in furnishing the elements of activity in the steam-engine, it has given a wonderful impulse to mechanical and chemical ingenuity, diminished to a great extent human labour, and increased in a high degree the strength and wealth of the country.”