| Gas. | ||||||
| Blast Furnace. | Producer. | Mond. | Mixed (Fichet). | Water (Stache). | Wood (Riché). | |
| Nitrogen and oxygen | 60 | 59 | 42 | 50 | 5 | 1 |
| Carbon monoxide | 24 | 25 | 11 | 20 | 40 | 29 |
| Carbon dioxide | 12 | 5 | 16 | 7 | 4 | 11 |
| Hydrocarbons | 2 | 2 | 2 | 3 | 1 | 15 |
| Hydrogen | 2 | 9 | 29 | 20 | 50 | 44 |
| 100 | 100 | 100 | 100 | 100 | 100 | |
| Calorific value in calories. | 950 | 1,100 | 1,400 | 1,300 | 2,400 | 2,960 |
| Average weight of a cubic meter in kilos | 1.30 | 1.1 | 1.02 | 1.05 | 0.680 | 0.824 |
| Or of a cubic foot in pounds | 0.008 | 0.007 | 0.006 | 0.0068 | 0.0042 | 0.0051 |
Blast-furnace gas has been used for generating power by means of gas-engines for about ten years. At the present time it is used in engines of very high power, a discussion of which engines more properly belongs to a work on metallurgy, and has no place, therefore, in a manual such as this.
Producer-gas, in the true sense of the term, is generated in special apparatus either under pressure or by
suction in a manner to be described in the following chapters.
Mond gas is produced in generators of the blowing or pressure type from bituminous coal, necessitating the employment of special purifiers and permitting the collection of the by-products of the fractional distillation of the coal. Mond gas plants are, therefore, rather complicated and can be advantageously utilized only for large engines. More exhaustive information can be obtained from the descriptions published by the builders of Mond gas generators.
Mixed gas is generated in apparatus arranged so that the retort is kept at a high temperature, thereby producing a gas richer in hydrogen than that made by producers. It should be observed that in practice the generators at present used yield a producer-gas, the calorific value of which fluctuates between 1,000 and 1,400 calories per cubic meter (3,968 to 5,158 B.T.U. per 35.31 cubic feet); and the composition varies accordingly, in the manner that has already been indicated in the tables for producer-gas and mixed gas. There is no necessity, therefore, for drawing a distinction between these two qualities of gas.
Water-gas should theoretically be composed of 50 per cent. carbon monoxide and 50 per cent. hydrogen, resulting from the decomposition of steam by incandescent coal. In practice, however, it contains a little nitrogen and carbon dioxide. The gas is obtained from generators in which air is alternately blown in to fan the fire and then steam to produce gas. Water-gas
is employed in soldering on account of its reducing properties and of the high temperature of its flame. The great quantity of carbon monoxide which it contains renders it very poisonous and exceedingly dangerous, because it is generated under pressure. From the economical standpoint, its generation is more expensive than that of producer-gas, for which reason its employment in gas-engines is hardly of much value.
Wood-gas, the composition of which has already been given, is generated in apparatus of the Riché type, the principle of which consists in heating a cast retort charged with any kind of fuel, namely wood, and vertically mounted on a masonry base.
This apparatus should be of particular interest to the proprietors of sawmills, furniture factories, and the like, since it offers a means of using the waste products of their plants.