HIGH TEMPERATURE CARBONIZATION OF COAL 419
During the formation of such compounds hydrogen is evolved in some quantity, and accounts for the high percentage of this gas usually found in the resultant gas from light charges. With regard to the “ free ” carbon deposited, it is interesting to note that Colman considers that with still higher temperatures and with. increase of time the above compounds yield more hydrogen and benzene nuclei of a still more complex nature, leading eventually to carbon itself. The molecule of solid carbon in all probability consists of a very large number of carbon atoms arranged as a honeycomb of Condensed benzene nuclei. These complex substances, still containing some hydrogen, are black and infusible, and their physical properties are very closely akin to those of pure carbon itself.
As regards the extent of free space in the retort with varying types of charges, . G. P. Lewis has given the following figures :—
22 inches by 16 indies cz> retort, 6 cwt. charge ; space in crown = 65 per oent. of volume of retort,
99 99 99 99 8 99 99 99 99 == 55 99 99 99
99 99 99 99 12 ,, 9, ,, ,, = 32 „ „ „
Coke oven 9 feet by 1 foot 6 inches . . . . = 6 „ „
As illustrating the efiect of varying the duration of charge upon the product obtained, Ferguson Bell gives the following comparisons :•—
Duration of charge. Weight of charge. Gas made per ton. Candle-power No. 2 Met. Calorific value per cubic foot.
Hours. Cwt. Cubic feet. B.Th.U. Net.
6 6 10,594 16-31 538-8
8 7f 11,245 15-59 518-9
10 91 11,499 14-53 488-4
12 Hl 11,463 14-77 484-4
The principle of the intermittent heavy charge has recently been carried to further lengths by the installation of large horizontal retorts ha ving a cross-section of 24 inches by 20 inches, and capable of carbonizing about a ton of coal in. twenty-four hours.
To sum up, the merits of the heavy charge as compared with the results from partly filled retorts may be emimerated as follows :—
(1) Considerably curtailed carbonizing costs.
(2) Less degradation, and, therefore, less naphthalene and free carbon,
(3) Few stopped pipes.
(4) More ammonia.
(5) Better coke of a denser nature, and less breeze.
(6) More tar of a better and thinner quality.
(7) Less retort carbon.
(8) Less sulphur in the form of CS2; etc.
Some doubt seems to exist as to the question of fuel. Whilst some authorities